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“Functional properties of whey, whey components and essential amino acids. Mechanism underlying health benefits for active people (Review).”
Abstract
Whey proteins and amino acid supplements have a strong position in the sports nutrition market based on the purported quality of proteins and amino acids they provide. Recent studies employing stable isotope methodology demonstrate the ability of whey proteins or amino acid mixtures of similar composition to promote whole body and muscle protein synthesis. Other developing avenues of research explore health benefits of whey that extend beyond protein and basic nutrition. Many bioactive components derived from whey are under study for their ability to offer specific health benefits. These functions are being investigated predominantly in tissue culture systems and animal models. The capacity of these compounds to modulate adiposity, and to enhance immune function and anti-oxidant activity presents new applications potentially suited to the needs of those individuals with active lifestyles. This paper will review the recent literature that describes functional properties of essential amino acids, whey proteins, whey-derived minerals and other compounds and the mechanisms by which they may confer benefits to active people in the context that exercise is a form of metabolic stress. The response to this stress can be positive, as with the accretion of more muscle and improved functionality or greater strength. However, overall benefits may be compromised if immune function or general health is challenged in response to the stress. From a mechanistic standpoint, whey proteins, their composite amino acids, and/or associated compounds may be able to provide substrate and bioactive components to extend the overall benefits of physical activity.
... Νowadays cheese whey is of particular scientific interest and it seems to possess many applications, especially in food science and technology. More specific cheese whey can be used by creameries in order to produce cheese, known as "whey cheese", or to enrich other dairy products, such as milk, chocolate milk, and yogurts, aming to cover athletes' needs and demands in protein [3]. Whey proteins are of incresed nutritional 2 value (high concentration of essential amino acids) and are used as dietary supplements for muscle growth and enhancing body composition of athletes [3]. ...
... More specific cheese whey can be used by creameries in order to produce cheese, known as "whey cheese", or to enrich other dairy products, such as milk, chocolate milk, and yogurts, aming to cover athletes' needs and demands in protein [3]. Whey proteins are of incresed nutritional 2 value (high concentration of essential amino acids) and are used as dietary supplements for muscle growth and enhancing body composition of athletes [3]. Moreover, it seems to exhibit many functional properties in food industry including, its usage in producing edible films [4,5], encapsulating and delivering bioactive compounds [6], forming gells and foams [1] etc. ...
... The precursor of silver ions [16], AgNO3 concentration ( 3 ) varied in the range 0.1 -2 mM, and Whey concentration ( ℎ ) in the range 0.2 -16.67 % v/v. The sodium hydroxide concentration ( ) 3 spanned the range 0 -50 mM. All synthesis was performed in the dark without stirring, and the the final volume was 2.5 mL unless otherwise stated. ...
Green synthesis of silver nanoparticles (AgNPs) using raw Whey has never been reported. Silver nanoparticle formation involves a reduction reaction of silver salt solution with Whey extract. Extract and metal salt concentrations, and temperature can control this reaction. In this work, incubation period, extract, AgNO3, and NaOH concentrations were used as the independent factors using central composite design under response surface methodology. The aim was to elucidate the influence these factors have on the measured UV-Vis absorption spectra fitted with a Voigt function, and to optimize the conditions for nanoparticle formation. The fitting parameters, peak wavelength (λ0), peak area (A), and Full Width at Half Maximum (FWHM), were the responses. Silver nanoparticle formation was only possible in an alkaline environment (pH 10). The peak wavelength and the FWHM are influenced mainly by extract and AgNO3 concentrations. In contrast, the peak area is influenced by a total of 33.54 % from the interaction terms of AgNO3 and extract concentrations with NaOH. Metallic AgNPs were formed for the following parameter ranges: a) Whey (0.4 – 1.6 % v/v), b) AgNO3 (0.15 – 0.6 mM), c) NaOH (10 – 50 mM), and d) Time (20 – 60 min). Silver oxide nanoparticles were also observed.
... Whey has a high nutritional value and is easily digested and assimilated. It is a rich source of minerals (calcium, phosphorus, sodium, potassium, chlorine, iron, copper, zinc, magnesium), as well as B-complex vitamins [23][24][25]. Table 1 presents the gross chemical composition of sweet and acid whey while Table 2 reports the content of minor bioactive proteins in. Whey proteins represent about 20% of the total protein in milk and the principle fractions are β-lactoglobulin (β-Lg), αlactalbumin (α-La), bovine serum albumin (BSA), immunoglobulins (Igs) while the minor proteins are lactoferrin, glycomacropeptide (GMP), lactoperoxidase, proteose peptone [5,23]. ...
... Moreover, they are the first amino acids used during periods of exercise and resistance training [53]. Whey protein isolates (WPI) in particular, are high in branched-chain amino acids (20-23 g/100 g protein), which increases satiety, protects against muscle-protein loss, enhances muscle-protein synthesis, and improves glycemic control [25,54]. ...
... As a result, whey disposal represents a major problem and, in some cases, a high operational cost [101][102][103][104][105]. In general, the main industrial processing of whey is drying, which is 70% of the annual production of whey [25]. ...
Вивчено закономірності процесу збагачення сироватки молочної магнієм (1,8…4,1 рази) і манганом (1,5…4,2 рази) внаслідок електроіскрового диспергування струмопровідних гранул відповідних металів в технологічному електророзрядному комплексі залежно від три
... Whey protein also plays a function in physiological protection and performance enhancement during various types of aerobic exercise (Huang et al., 2017). 26% of Branched chain amino acids are present as the protein score in whey protein, During protein synthesis leucine plays an important role in protein metabolism as a key signal in the translation initiation pathway and it is also participate in reversible phosphorylation of proteins that maintain the control of 40s subunit of ribosome (Ha and Zemel, 2003) . (Villarreal, 2017) ...
... Runners are more concerned with GIT disorders many of them have diarrhoea in marathon races. Due to decreased blood flow in the intestinal tract created damage in the intestine wall but here the it is directed towards working muscle with nutrient deprivation with high intestinal permeability further damage walls (Ha and Zemel, 2003). This also creates some problems like indigestion of food before the event. ...
... This also creates some problems like indigestion of food before the event. Whey and its components have essential function Gut; toxin binding is inhibited as glycomacropeptides show probiotic effect which stimulates cholecystokinin, for better functioning of digestive tract lactose plays an important role by hydrolysing galactooligosaccharides. Whey is a probiotic vehicle which plays a crucial role in the Gastrointestinal tract here there is plausible mechanism where athlete with GIT dysfunction can get benefitted with the consumption of Whey beverage (Ha and Zemel, 2003). ...
... Each type of protein has a limiting AA, but the kind of limiting AA differs depending on the source of protein [42]. According to Ha and Zemel (2003) [43], Lys is the first limiting AA in many high-protein foods. In products based on both dairy and soy proteins, the reduction in active Lys induced by the Maillard reaction leads to a significant quality loss during storage. ...
... Each type of protein has a limiting AA, but the kind of limiting AA differs depending on the source of protein [42]. According to Ha and Zemel (2003) [43], Lys is the first limiting AA in many high-protein foods. In products based on both dairy and soy proteins, the reduction in active Lys induced by the Maillard reaction leads to a significant quality loss during storage. ...
... However, the EAAI values of tested products were relatively low, ranging between 30.5% and 33% in fresh products, respectively (Table 3) and during storage did not change significantly. Brown and Jeffrey (1992) [43] reported that a protein has high quality when the EAAI value is greater than 90%, moderate quality when the EAAI is between 70% and 89%, and low quality when the EAAI is less than 70%. ...
Novel organic high-protein bars (HPB) were developed and produced from organic ingredients such as prebiotic and pro-healthy additives or whey protein concentrate (WPC-80). The influence of temperature and time on the selected physicochemical parameters and antioxidant activity of three formulations of HPBs when stored (at 4 °C and 22 °C for 3 months) was investigated. The fresh products varied on the basis of available carbohydrates, crude lipids, amino acid profile, and fatty acid profile resulting from the used formulations. A total of 17 amino acids (AA), including 10 essential amino acids (EAA), were identified in HPBs. The concentrations of all essential amino acids determined by EAA scores (AAS), except Histidine (His), were higher than the FAO/WHO/UNU (2007) pattern; for the WPC-80 however, in the case of the developed HPB, the scores were lower (0.21–0.48). The first limiting amino acid in HPB was Val (Valine). The temperature and time of storage significantly affected the proximate chemical composition and an assessment of the products’ antioxidant activity. The amino acid and fatty acid composition of stored products slightly changed. However, stored HPBs had a low content of trans fatty acids (TFAs). The optimal method of storage for the investigated bars was at the temperature of 4 °C for 3 months.
... Because essential amino acids are so vital to our health, it may be better to enrich foods with high levels of them [44]. In comparison to chickpea and mung bean proteins, the digestibility of essential amino acids in A. platensis protein was about 85% in humans [45]. greatly improved (p<0.05) in this study by the addition of A. platensis. ...
... Essential amino acids are so vital to human health. Therefore, foods that are enriched with them are favored [45]. The essential amino acid in the protein of A. platensis was found to be approximately 85% digestible by humans, which is higher than the digestibility of chickpea and mung bean protein [21]. ...
Arthrospira platensis, which is known as the most important food supplement of the future due to its high nutritional value, was the focus of this study. The main objective of this study was to develop a functional cracker enriched with proteins, essential amino acids, and polyunsaturated fatty acids with the incorporation of A. platensis. Therefore, this research aimed to improve the texture (including moisture and firmness) and sensory properties (such as color, taste, and smell) of crackers by adding A. platensis at three different levels (0%, 2.5%, and 5.0%). The sensory attributes of crackers were evaluated by twenty taste testers and thirty consumers, assessing color, odor, taste, crispness, and overall preference. The highest hardness value among the studied trials was observed in trial 14, which contained 5% A. platensis with 577 N. According to the results of the panel test, among the crackers with 5% A. platensis addition, trial 14 had the highest color value. To obtain the optimum formula, dough with 50 mg/g A. platensis, 625 mg/g flour, and 220 mg/g water was recommended. The addition of A. platensis has great potential to improve the nutritional, textural, and sensory properties of crackers.
... Currently, cheese whey serves as a cost-effective protein source with numerous applications in the food industry. 4,9,10 a-Lactalbumin (a-lac) and b-lactoglobulin (b-lg) are the two main components of whey proteins. Whey proteins interact with ionizable polysaccharides and oligosaccharides, resulting in the formation of soluble or insoluble complexes. ...
... Fig. 2(A) shows the ideal charge of the protein as a function of pH represented by a continuous line. The ideal charge of the protein, calculated using eqn (9), represents the charge of the protein considering only the acid-base equilibrium, i.e., without considering the electrostatic environment surrounding each titratable group. At a low pH value, the ideal charge of the protein is close to 19 positive charges. ...
In this study, we conducted a comprehensive computational investigation of the interaction between α-lactalbumin, a small globular protein, and strong anionic oligoelectrolyte chains with a polymerization degree from 2 to...
... According to recent studies, dairy products offer benefits beyond the usual "growing strong bones" benefit. For instance, several elements in milk and dairy products are good for the gastrointestinal system and immune system (Ha et al., 2003). Milk can be fermented by bacteria, yeasts, and filamentous fungi to produce a variety of products such as cheese, butter, and yoghurt. ...
... Some of the components in milk and milk products served roles that are now recognized to be advantageous to the immune system and the gastrointestinal tract one or two generations ago. (Ha et al., 2003). ...
Dairy products have long been recognized as a source of healthy nourishment, a vital part of many people's diets because of the protein, vitamins, minerals, and fatty acids they contain. According to recent studies, consuming dairy products appears to help with muscle growth, lowering blood pressure and low density lipoprotein cholesterol, and preventing tooth decay, diabetes, cancer, and obesity. Organic milk and probiotic microorganisms that use milk products as a vehicle may also provide additional benefits. In addition to the previously mentioned advantages; research demonstrates that dairy products are essential for immune system function and gastrointestinal health. Yogurt, cheese, vinegar, butter, soy milk, lactic acid, and other dairy products are a few of them. Certain texts include in-depth information on the historical manufacturing of certain dairy products as well as the industrial production process, including the metabolic route that breaks down the protein, fat, and carbs.
... Undoubtedly, as an essential constituent of nutrition, amino acids are widely used to produce fertilizers, drugs, medicines, biodegradable plastics, and chiral catalysts. 4−6 The hydrophobic aromatic rings of essential and nonessential amino acids 7,8 such as L-phenylalanine and L-tyrosine have applications in the food, pharmaceutical, and agriculture industries. L-Phenylalanine, primarily utilized in producing food items and traded as dietary supplements, has the breast milk of mammals as its primary natural source. ...
... The hydration number, N h , of the amino acid was evaluated by using the relation 34 (5) Further N h values of L-phenylalanine and L-tyrosine in water were calculated employing the equation earlier used by 35 as follows (6) where the symbols 36 and 308.15 K, 37 respectively. The calculation of V elect values has been done using the relation (7) where intrinsic molar volume, V int o , was obtained by the crystallographic volume 38 V cryst . (8) Table 3 represents the hydration number, N h , stipulating the dehydration of amino acids, i.e., L-phenylalanine and L-tyrosine, in association with the preservative molecules, contributing further to concentration increases of the cosolute. ...
... Otherwise, some proteins such as lactoferrin and a-lactalbumin reduce oxidative stress due to their iron-chelating properties (Abrahão, 2012;Ha & Zemel, 2003). Additionally, it is believed that whey proteins can improve body weight because low-calcium diets induce calcitropic hormones to promote adipose tissue lipid storage, but this effect can be inhibited with high-calcium diets. ...
... Additionally, it is believed that whey proteins can improve body weight because low-calcium diets induce calcitropic hormones to promote adipose tissue lipid storage, but this effect can be inhibited with high-calcium diets. These proteins also participate in body protein synthesis because of their high leucine and other important amino acid contents, which are important in the protein synthesis pathway (Ha & Zemel, 2003). ...
Dairy-derived bioactive components have health-promoting effects due to their large number of biological properties. Although the physiological significance of several of these substances is not yet fully understood, both proteins and bioactive peptides are now believed to be health-enhancing components. Serotonin is a key signalling neurotransmitter for the gut‒brain axis that controls a wide range of physiological functions, highlighting its regulation of neurobiological and intestinal physiology. Here, we discuss the roles and pathways whereby these milk-derived bioactive peptides could modulate serotonergic functions as they are an emerging and potential therapeutic adjuvant for the dietary modulation of gut‒brain axis disorders mediated by serotonin.
... In addition, Glu plays a pivotal role in the quick dividing of cells and is considered substantial through metabolic strain or sickness periods. All essential AAs should be found in each diet at adequate levels to promote the postprandial muscle protein biosynthesis process, where essential AAs are operators that have the capability to catalyze the muscle tissue anabolic pathways (40). As for Samh seeds powder was found to be rich in protein content (20-23%) and contains plenty of His, Met, Tyr, Gly, and Arg acids (16, 17). ...
Objectives
The rising demand for convenient and nutritious food options, especially among young adults with fast-paced lifestyles, highlights the need for quick energy and protein sources during physical activities and breakfast. Consequently, aimed to formulate and evaluate the nutritional, functional, and glycemic properties of high-protein energy balls using Sukkari date paste a variety of the date palm (Phoenix dactylifera L.) paste, Samh seed (Mesembryanthemum forsskalei Hochst) powder, whey protein concentrate, and camel milk powder.
Methods
The nutritional value of the formulated balls was evaluated by assessing their chemical composition, dietary fibers, amino acids (AAs), and fatty acids (FAs). Additionally, antioxidant properties were determined using the DPPH method and reducing power assays. In vitro protein digestibility was also measured. Furthermore, the in vitro glycemic index and glycemic load, as well as the human glycemic response for various samples, were examined.
Results
Samples containing combinations of date paste, Samh seeds, and either camel milk powder (DSC) or whey protein concentrate (DSW) demonstrated high nutritional value, with significant caloric content measured at 352.76 ± 0.125 Kcal/100 g for the first combination and 328.76 ± 0.242 Kcal/100 g for the second. These samples also showed significant (p < 0.05) DPPH radical scavenging activity, with values of 63.78 ± 2.43 μg of ascorbic acid equivalent/g for the date paste and Samh seeds with camel milk powder (DSC) and 59.87 ± 2.61 μg of ascorbic acid equivalent/g for those with whey protein (DSW). Furthermore, the presence of a variety of essential amino acids and fatty acids in DSC and DSW was higher than in the rest of the samples (DS, DW and DC), which is under the current study. Sensory evaluations indicated that all samples were highly accepted. The in vitro study revealed that the degree of protein digestibility was higher in samples that contained both Samh seeds powder and whey protein concentrate or camel milk powder than in the sample that contained Samh alone. Also, all samples exhibited low in vitro glycemic index (<55) and glycemic load (<10). Moreover, the human glycemic response evaluation showed that blood glucose levels gradually declined after 30 min, returning to pre-meal levels by 120 min, indicating no post-meal hyperglycemia, resulting in a normal glycemic response in healthy young adults.
Conclusions
Combining Samh seed powder with dairy proteins to create protein-energy balls using Sukkari date paste results in nutritious snacks that are rich in amino acids, fatty acids, dietary fibers, and antioxidant compounds. These snacks also have a low glycemic response and high protein digestibility in vitro. Therefore, high-protein energy balls made from date paste enriched with Samh seed powder, along with either camel milk or whey protein powders, are recommended as a protein and energy source for healthy young adults who do not experience post-meal hyperglycemia.
... Far beyond their nutritional role, whey proteins are a significant source of biologically active components, including bioactive peptides with various healthpromoting effects, making them the focus of extensive research [11]. The most extensively studied biological functions of these peptides include cytomodulatory, antithrombotic, and opioid-like effects, mineral-binding capability, antihypertensive and cholesterol-lowering activity, and antimicrobial and antioxidant properties, as well as immunomodulatory effects [12][13][14][15][16][17][18]. It is important to note that although several studies have reported on the immunomodulatory properties of milk whey, most of them use whey protein concentrate (WPC) and whey protein isolate (WPI) derived from bovine milk, rather than fresh SW. ...
Sweet whey (SW), a by-product of cheese production, has potential immunomodulatory properties that could be beneficial in preventing inflammation-related diseases. This study investigated the effects of SW derived from bovine, caprine, ovine, or an ovine/caprine mixture of milk on inflammation-related gene expression in THP-1-derived macrophages, both with and without LPS stimulation. Cells were treated with SW-D-P3 (a fraction smaller than 3 kDa produced by in vitro digestion), and the expression of inflammation-related genes was assessed using quantitative PCR. Results showed that the expression of TLR2 and ICAM1 was attenuated in non-LPS-stimulated macrophages treated with SW-D-P3, regardless of animal origin. Moreover, the expression of TLR4, IL1B, and IL6 was decreased and the expression of an NF-κB subunit RELA and CXCL8 was elevated in a subset of samples treated with SW-D-P3, depending on the milk source. In LPS-challenged cells, the expression of CXCL8 was upregulated and the expression of IRF5 and TNFRSF1A was downregulated in SW-D-P3-treated cells, regardless of animal origin. On the other hand, a number of inflammation-related genes were differentially expressed depending on the animal origin of the samples. Moreover, the higher IL10 expression observed in cells treated with ovine/caprine SW-D-P3 compared to those treated with SW-D-P3 of bovine, caprine, or ovine origin suggests an anti-inflammatory response, in which alternatively activated macrophages (M2 polarization phenotype) may participate. Overall, these findings suggest that incorporating SW into the food industry, either as a standalone ingredient or supplement, may help to prevent inflammation-related diseases.
... properties. (36) Whey has been recently touted as a healthful dietary supplement to reduce blood pressure. Antihypertensive peptides have been isolated in the primary sequence of bovine beta-lactoglobulin. ...
Whey, a milk-based protein complex, is being promoted as a functional food with several health advantages. Alpha-lactalbumin, betalactoglobulin, lactoferrin, glycomacropeptide, and immunoglobulins are among the biological components of whey that exhibit a variety of immune-boosting characteristics. Whey can also function as a chelating agent, antiviral, antibacterial, hypolipidemic, antihypertensive, anticancer, and antioxidant. The conversion of the amino acid cysteine into glutathione, a strong intracellular antioxidant, is believed to be the main way that whey works. Whey has been successfully used in several clinical trials as an antibacterial agent and to treat cancer, HIV, hepatitis B, cardiovascular disease, and osteoporosis. Additionally, whey protein has shown promise in improving workout performance.
... BLG is the predominant whey protein in bovine milk, constituting about 50 % of the whey protein [9,51]. It plays a major role in the food and pharmaceutical industries due to its ability to bind hydrophobic molecules and vitamins, like retinol (Vitamin A), enhancing nutrient bioavailability [52][53][54]. Previous studies reported that at a neutral pH, the Tanford transition phase of BLG is of particular interest because it impacts its capacity to interact with both synthetic and natural ligands [10]. ...
Whey protein from bovine milk is highly valued in the food and pharmaceutical industries because of its high protein content and abundance of essential amino acids. The relationship between whey protein and the β-lactoglobulin (BLG) gene has been extensively discussed because BLG is the most abundant whey protein, making up approximately 50 % of the total whey protein in bovine milk. In recent years, researchers have been interested in this gene because of its critical role in healthy milk production, and any genetic polymorphism in this gene may deteriorate the milk quality. In the current study, we identified several deleterious and damaging non-synonymous single nucleotide polymorphisms (nsSNPs) in BLG and analyzed their destabilizing effects using different computational algorithms. Cumulative results from all tools and evolutionary conservation profiles of BLG suggested that four nsSNPs, G17A, W19C, F136S, and C119R, were the most deleterious and could affect the structural integrity of the protein. Detailed molecular dynamics simulation analysis revealed that all variants induced major structural alterations, that affected the ability of the protein to interact with natural and synthetic ligands. Particularly, the G17A, F136S, and C119R variants induced large conformational changes in the EF loop and main α-helix of BLG, which may affect the access of natural and synthetic ligands to the central calyx of BLG. We hope that the suggested nsSNPs will guide future studies and assist researchers in improving the quality of bovine milk.
... These amino acids benefit human health by aiding in the body's repair. 1 WPI are also rich in various bioactive substances and possess good emulsifying, gelling, foaming and other functional properties. Therefore, WPI can be widely used as emulsifiers, thickeners, surface active ingredients and carriers, etc., in the food field. ...
BACKGROUND
Whey protein isolate (WPI) is a high‐quality animal protein resource. The modification of WPI through physical, chemical and biological methods can substantially improve the functional properties of proteins. This study investigated the effect of electron beam irradiation (EBI) on the modification of WPI–xylose glycosylation.
RESULTS
The degree of grafting and browning revealed that EBI promoted WPI glycosylation. The maximum emission wavelength of intrinsic fluorescence was red‐shifted and the fluorescence intensity was reduced, suggesting that irradiation induced the unfolding of the WPI structure, thereby promoting glycosylation. Fourier‐transformed infrared spectroscopy revealed that the covalent binding of the conjugates occurred on the introduction of the hydrophilic groups, resulting in decreased surface hydrophobicity. When compared with conventional wet‐heat glycosylation, irradiation‐assisted glycosylation improved the emulsifying activity of WPI from 179.76 ± 0.83 to 277.83 ± 1.44 m² g⁻¹, and the emulsifying and rheological properties improved.
CONCLUSION
These results confirmed that EBI can increase the degree of WPI glycosylation and improve the functional properties of proteins, thereby laying a theoretical foundation for the further application of WPI. © 2024 Society of Chemical Industry.
... O uso do soro para o desenvolvimento de produtos lácteos mostra grande potencial, por meio tanto da agregação de valor nutricional ao produto diante de seu alto valor biológico, quanto da geração de riquezas e da diminuição do impacto ambiental causado pelo seu descarte inadequado 3,4 . O emprego do soro lácteo na elaboração de produtos é uma boa forma de reduzir os custos de produção, em virtude de seu baixo preço e vasta disponibilidade nas indústrias de derivados lácteos 5 ...
O objetivo da pesquisa foi elaborar uma bebida láctea fermentada saborizada com xarope de cupuaçu adicionada de prebióticos e avaliar sua estabilidade durante o armazenamento. Foi realizada uma análise sensorial de ordenação de preferência para a escolha de duas formulações a ser submetidas a análises de pH, acidez, sinérese, viscosidade, atividade de água, cor (L*a*b*), conteúdo de inulina, cinzas, umidade, proteína, lipídio, determinações microbiológicas de coliformes a 45 °C, Salmonella e fungos filamentosos e leveduras, viabilidade de bactérias lácticas e análise sensorial de aceitação. Na análise sensorial de ordenação de preferência, a formulação que obteve a maior soma de ordens foi a que continha 725 mL de soro de leite e 20 g de inulina, e a segunda foi a formulação com 950 mL de soro de leite, 20 g de inulina e 6 g de farinha de banana verde. O teor de inulina das formulações, ao final dos 28 dias, foi de 1,88 g e 2,09g/100g de produto, respectivamente. A viabilidade de bactérias lácticas encontrou-se em concordância com os parâmetros estabelecidos pela legislação (1,4x108 e 1,2x108 UFC/mL). Na análise sensorial de aceitação, a amostra que apresentou o maior índice de aceitabilidade a todos os atributos sensoriais avaliados foi a que continha 725 mL de soro e 20 g de inulina, com 28 dias de armazenamento. As bebidas lácteas prebióticas adicionadas de xarope de cupuaçu mantiveram-se estáveis ao longo do tempo determinado da vida de prateleira, mesmo sem a adição de conservantes, podendo ser uma excelente opção para o mercado consumidor. Palavras-chave: Inulina. Farinha de banana verde. Theobroma grandiflorum. Derivado lácteo.
... The mTOR kinase serves as a central regulator of muscle protein synthesis, and its activity is significantly influenced by the availability of nutrients-particularly amino acids and growth factors (50). Whey proteins may further enhance antioxidant capacity by providing cysteine-rich proteins, which work in the synthesis of glutathione, a crucial intracellular antioxidant (51). ...
Background
Sarcopenia is associated with oxidative stress. The Oxidative Balance Score (OBS) is commonly used to assess dietary and lifestyle exposure to oxidative stress. However, few studies in the literature have assessed the correlation between sarcopenia and OBS.
Aim
This study aimed to assess the association between OBS and sarcopenia among young and middle-aged adults in the United States using data from the National Health and Nutrition Examination Survey (NHANES).
Method
Weighted logistic regression analysis was used to investigate the association between OBS and sarcopenia based on data from NHANES 2011–2018. Subgroup analyses were performed to observe the consistency of the outcomes, and the stability of the results was tested using sensitivity analyses.
Result
The final sample included 5,525 young and middle-aged American adults. A higher OBS was associated with a lower risk of sarcopenia. In the fully adjusted model, the second (odds ratio [OR]: 0.62, 95% confidence interval [CI]: 0.41, 0.94; p = 0.023), third (OR: 0.50; 95% CI: 0.34, 0.74; p < 0.001), and highest quartiles (OR: 0.18; 95% CI: 0.11, 0.28; p < 0.001) of the OBS were associated with higher risks of sarcopenia when compared to the lowest quartile. This association was consistent across both dietary and lifestyle OBS scores. Our subgroup analysis revealed no significant differences between the subgroups of variables included in the interaction analysis. Sensitivity analyses revealed similar results.
Conclusion
Our study showed that higher antioxidant and lower antioxidant exposure may decrease the risk of developing sarcopenia. Higher OBS scores may indicate greater protection against sarcopenia; however, further clinical studies are warranted to confirm these findings.
... Plant proteins are less digestible in the human GI system (Kårlund et al., 2019;Tomé, 2013), and most of them cannot meet all the requirements of the human body for essential amino acids (Chardigny et al., 2016;Fussell et al., 2021;Gorissen et al., 2018), so animal protein sources are of particular importance in the human diet. Among proteins, animal proteins that contain essential amino acids are of vital value to the human body because these amino acids are not synthesized in the human body (Ha & Zemel, 2003;Kårlund et al., 2019;Lim et al., 2021;Sudhakararao et al., 2019). This protein is significant in providing enough well-balanced nutrition for human health and advancing physical and mental development (Bulus Doka, 2013). ...
In recent years, consecutive research has been conducted on the nutrient requirements of the quails to find an optimum and affordable legitimate growth promoter. Different types of vegetable oil have been tested so far. This study aimed to evaluate the effects of pure corn oil (PCO) on growth performance and live body weight gain in Japanese quails. A total of 80 four-day-old quail chicks were divided into two groups: control (20 checks) and experimental (60 checks). The experimental group was subdivided into three subgroups (G1, G2, and G3) of 20 chicks per group. All the control and experimental group chicks were fed a commercial grower quail diet in all three growth phases. Despite the commercial diet, the G1, G2, and G3 experimental groups were fed 1, 3, and 5% PCO, respectively. The values for live body weight did not significantly change after adding PCO to the quail’s diet. According to the study's findings, adding PCO to the commercial diet of Japanese quails in various amounts had no beneficial effects on feed consumption and growth rate. Additionally, it had an insignificant (p>0.05) detrimental impact on the growth performance of the quails compared to control groups. In conclusion, we can say that adding PCO to quail's commercial diet in the hot months of the year under Afghanistan's climate has no positive impact on growth and further slows down the rate of body weight gain.
... Essential amino acids cannot be synthesized in the body and therefore must be taken in through the diet. Essential amino acids from whey, especially leucine, are necessary to stimulate protein synthesis in muscle and represent a high proportion of amino acids that are necessary to stimulate muscle growth (11,12). The utilization of whey protein in the body is closely related to the cystine / methionine ratio, which is about 10 times higher in whey protein than in casein (1). ...
The values of whey as a healthy and therapeutically useful drink are well known, and in folk medicine it has often been attributed miraculous powers and possibilities. This is nothing new, bearing in mind that in 460 BC, the father of medicine Hippocrates emphasized the value of whey in the treatment of tuberculosis, jaundice, diseases of the liver and digestive system, skin diseases and many other diseases. Whey is obtained during milk processing and cheese production, where it is present in almost 90% of the total mass. The composition of whey is specific. Water makes up to 93% of the composition, the rest consists of sugars and minerals, B vitamins, as well as a great wealth of probiotic bacteria. Whey is the largest source of essential amino acids compared to plant or animal sources. The concentration of amino acids in whey is 43% compared to oats (21%), wheat husk (21%) and wheat (22%), milk 39%, casein 34% and eggs 32%) or meat proteins (38%). Whey proteins contain almost 50% of essential amino acids and about 26% of branched-chain amino acids. Their composition is similar to the amino acid composition of human muscles, which allows their faster absorption than other sources of protein. The share of free amino acids in whey is 4 to 10 times higher than in milk. They have a significant effect on protein synthesis and a very strong anabolic effect in the body. Whey amino acids stimulate skeletal muscle regeneration, reduce fatigue, increase synthesis, and reduce muscle protein breakdown. Whey proteins increase the levels of antioxidant enzymes, especially glutathione and catalase. Positive effect on the reduction of the levels of TBARS (thiobarbituric acid reactive substance) is an important indicator of the decreasing process of lipid peroxidation. Reduction of oxidative stress process in the liver has positive consequences on inflammation and the content of lipids in the liver tissue and atherosclerosis process. Recent research indicates a positive effect on glucose metabolism, improving insulin sensitivity and preventing the development of fatty liver syndrome and type 2 diabetes. It has a positive effect on weight control, so whey proteins are integral parts of healthy medical diets, sport drinks, with approved efficacy in obesity treatments. Essential amino acids also act as neurogenic active substances, and they are also known as precursors of biogenic amines and neurotransmitters, so it is logical that there is a growing interest in researching their potential in psychiatry.
... al., 2007). When leucine is taken with whey protein then, there would be increased stimulation of protein synthesis, which ultimately speeds up the recovery and adaptation to stress (Ha and Zemel, 2003). However, high heat treatment in combination with pasteurization can lead to denaturation of whey proteins; this denatured whey protein was found to trigger hydrophobic interactions with other proteins that ultimately leads to the formation of gel of proteins, while aggregation upon renneting or acidification of milk is not found with the native whey protein (Foegeding et. ...
... Several authors have highlighted the potential application of agri-food by-products in the production of food items, emphasizing their possible implications for human health and sustainability [10][11][12][13][14]. According to recent research, agri-food by-products, including dairy by-products, can be incorporated into various nutritionally enhanced products to boost their bioactive profile, fiber content, and antioxidant capacity, all while maintaining a high level of sensory acceptability. ...
The valorization of milk whey appears to be a promising strategy for managing by-products from dairy food industries, which incur demanding economic costs for treatment and/or disposal. Thanks to its numerous bioactive components, whey is expected to be increasingly incorporated into foods in the future. We investigated the safety of ovine milk whey through in vitro experiments on human primary gingival fibroblast (HGF-1) proliferation and wound healing. Fibroblasts play a crucial role in the repair processes from the late inflammatory phase until the final stages. Cells treated with varying concentrations of ovine whey (0.01%, 0.1%, 1%, and 10%) were able to close wounds more rapidly than vehicle-treated cells. Time- and dose-dependent responses were observed in cell populations exposed to ovine whey. Specifically, wounds treated with 0.1% and 10% milk whey showed better migratory capabilities compared to those treated with 0.01% and 1% milk whey after 24 and 48 h. In addition, ovine milk whey stimulates extracellular matrix deposition, as evidenced by the increasing levels of CD44 antigen density evaluated through FACS analysis, as well as COL1A1 expression measured both via RT-qPCR and immunofluorescence. This phenomenon was particularly evident at concentrations of 0.01% and 10%. Ensuring quality and safety has become a major concern for health authorities in the food industry. Our findings suggest that ovine milk whey is safe and possesses regenerative properties. It facilitates tissue re-establishment following exposure to environmental stress, particularly accelerating gingival wound closure.
... The reasons for consuming whey supplements are to improve muscle mass, enhance performance, shorten recovery time, prepare for competition and maintain overall health. As whey protein contains high-quality protein and is rapidly digested, it is a valuable supplemental source for individuals aiming to increase muscle mass or maximise their recovery from the resistance training exercise (Ha and Zemel, 2003). Our findings were consistent with a few other studies. ...
Background
Gym users are one of the populations who frequently consume dietary supplements. Nevertheless, data investigating the perspective of gym users regarding dietary supplement intake are still lacking. Our qualitative study aims to acquire insights into the perceptions of gym users regarding dietary supplement consumption.
Methods
A total of 10 gym users who have a membership and are actively training at the gymnasium were recruited from Selangor and Kuala Lumpur, Malaysia. In-depth interview was conducted, and all responses were recorded and transcribed verbatim. The data were analysed using the NVivo version 12 software.
Results
All participants consume dietary supplements almost every day, with most of them taking at least three supplements a day. Five themes emerged from these interviews: (1) gym and the use of dietary supplements, (2) reasons for supplement intake, (3) source of information, (4) supplement perceptions and beliefs and (5) health screening experience. Half of the participants did not consult with any nutritionist or dietitian before taking dietary supplements. The reasons for consuming supplements are to improve muscle mass, enhance performance, maintain overall health, fasten recovery time and prepare for competition. Our findings suggest that participants perceived supplements to be beneficial and exceeded the potential adverse effects.
Conclusions
Lack of awareness amongst the recruited gym users in Klang Valley, Malaysia, regarding the potential risk of side effects suggests that there is a need to provide correct information about the benefits and risks of using dietary supplements.
... Nutraceutical strategies have been reported to inhibit an imbalance between angiogenic signals, increase mitochondrial metabolism, and decrease oxidative stress [7,11,16,17]. Nucleotides consist of a nitrogenous base, a pentose sugar, and one or more phosphate groups. They are intracellular compounds that play critical roles in many biological processes [5]. ...
Prolonged inactivity in skeletal muscles decreases muscle capillary development because of an imbalance between pro- and antiangiogenic signals, mitochondrial metabolism disorders, and increased oxidative stress. Nucleotides have been shown to exert a dose-dependent effect on disuse-induced muscle atrophy. However, the dose-dependent effect on capillary regression in disused muscles remains unclear. Therefore, this study investigated the dose-dependent effect of nucleotides on capillary regression due to disuse. For this purpose, Wistar rats were divided into five groups as follows: control rats fed nucleotide-free diets (CON), hindlimb-unloaded rats fed nucleotide-free diets (HU), and hindlimb-unloaded rats fed 1.0%, 2.5%, and 5.0% nucleotide diets, (HU + 1.0% NT), (HU + 2.5% NT), and (HU + 5.0% NT), respectively. Unloading increased reactive oxygen species (ROS) production and decreased mitochondrial enzyme activity, thereby decreasing the number of muscle capillaries. In contrast, 5.0% nucleotide-containing diet prevented increases in ROS production and reductions in the expression levels of NAMPT, PGC-1α, and CPT-1b proteins. Moreover, 5.0% nucleotide-containing diet prevented mitochondrial enzyme activity (such as citrate synthase and beta-hydroxy acyl-CoA dehydrogenase activity) via NAMPT or following PGC-1α upregulation, thereby preventing capillary regression. Therefore, 5.0% nucleotide-containing diet is likely to prevent capillary regression by decreasing oxidative stress and increasing mitochondrial metabolism.
... Las PL han sido uno de los suplementos más usados por los atletas y consumidores de productos de nutrición deportiva para apoyar la hipertrofia muscular y mejorar la condición corporal; estos suplementos se posicionan como fuentes de proteína y aminoácidos de alta calidad y como un medio potencial para mejorar la masa corporal magra junto con el entrenamiento adecuado [53]. Se ha demostrado que estas proteínas estimulan la síntesis de proteínas musculares (MPS) en mayor medida que la caseína y la proteína de soya, tanto en reposo como después del ejercicio, en personas jóvenes y mayores [54]; tras su ingestión, la proteína se digiere rápidamente al estómago por su solubilidad, en estas condiciones ácidas, se hidroliza y sale rápidamente del estómago dando como resultado un aumento pronunciado de aminoácidos en la sangre. ...
Resumen El lactosuero se descubrió hace unos 3,000 años como subproducto de la industria láctea (quesera principalmente) y durante años se consideró como un líquido de desecho, utilizado como alimento para animales o simplemente vertido como residuo a ríos. Sin embargo, hoy en día el aprovechamiento del suero de leche permite reconocerlo como un ingrediente nutricional de alto valor agregado aplicado a muchos productos alimenticios. Dentro de su composición encontramos: lactosa, grasa, proteínas de importante valor biológico, minerales y vitaminas; las proteínas del lactosuero se constituyen como una fuente económica con múltiples propiedades tecno-funcionales, nutracéuticas y nutricionales, útiles para añadir a una amplia gama de alimentos multiplicando posibilidades de desarrollo para la misma industria láctea. Teniendo en cuenta lo expuesto, a lo largo de esta revisión se describirán aspectos relevantes sobre este subproducto lácteo haciendo énfasis en las proteínas que lo conforman y en sus derivados (concentrados e hidrolizados), así como las propiedades moleculares, fisicoquímicas y tecno-funcionales, aspectos que lo posicionan como una materia prima llamativa a nivel industrial además de las bondades que para la salud del consumidor imparte.
... Natural polymers are cost-effective, safe with no obvious side effects, an advantage over synthetic polymers [38]. Whey protein, a milk protein and a valuable by-product from cheese industry, is among the various natural polymers of the organic nanocarriers that are widely used in a variety of food products for health and wellbeing due to its rich source of essential amino acids [39,40]. Generally speaking, proteins are considered ideal materials for nanoparticle preparation because of their high capacity for drug binding through different mechanisms such as electrostatic interactions, hydrophobic interactions and covalent bonds, in addition to their amphiphilicity, which allow them to interact well with both the drug ligand and the solvent. ...
Background
CLA (conjugated linoleic acid)-mediated activation of the schistosome tegument-associated sphingomyelinase and consequent disruption of the outer membrane might allow host antibodies to access the apical membrane antigens. Here, we investigated a novel approach to enhance specific antibody delivery to concealed surface membrane antigens of Schistosoma mansoni utilising antibody-conjugated-CLA nanomicelle technology.
Methodology/Principal findings
We invented and characterised an amphiphilic CLA-loaded whey protein co-polymer (CLA-W) as an IV injectable protein nanocarrier. Rabbit anti-Schistosoma mansoni infection (anti-SmI) and anti-Schistosoma mansoni alkaline phosphatase specific IgG antibodies were purified from rabbit sera and conjugated to the surface of CLA-W co-polymer to form antibody-conjugated-CLA-W nanomicelles (Ab-CLA-W). We investigated the schistosomicidal effects of CLA-W and Ab-CLA-W in a mouse model of Schistosoma mansoni against early and late stages of infection. Results showed that conjugation of nanomicelles with antibodies, namely anti-SmI, significantly enhanced the micelles’ schistosomicidal and anti-pathology activities at both the schistosomula and adult worm stages of the infection resulting in 64.6%-89.9% reductions in worm number; 72.5–94% and 66.4–85.2% reductions in hepatic eggs and granulomas, respectively. Treatment induced overall improvement in liver histopathology, reducing granuloma size and fibrosis and significantly affecting egg viability. Indirect immunofluorescence confirmed CLA-W-mediated antigen exposure on the worm surface. Electron microscopy revealed extensive ultrastructural damage in worm tegument induced by anti-SmI-CLA-W.
Conclusion/Significance
The novel antibody-targeted nano-sized CLA delivery system offers great promise for treatment of Schistosoma mansoni infection and control of its transmission. Our in vivo observations confirm an immune-mediated enhanced effect of the schistosomicidal action of CLA and hints at the prospect of nanotechnology-based immunotherapy, not only for schistosomiasis, but also for other parasitic infections in which chemotherapy has been shown to be immune-dependent. The results propose that the immunodominant reactivity of the anti-SmI serum, Schistosoma mansoni fructose biphosphate aldolase, SmFBPA, merits serious attention as a therapeutic and vaccine candidate.
... BCAAs are vital for athletes because they are the first amino acids consumed during exercise and resistance training. This makes them the first ones to be depleted after intense workouts (Ha & Zemel, 2003). When calories are limited; whey protein is superior to other forms of protein for promoting fat reduction. ...
Whey is produced in huge quantities by the dairy industry as a byproduct, and as non-food leads to serious environmental issues due to its high organic matter content. There has been a lot of research done over the last several decades how to use whey in a more sustainable and cost-effective way. The creation of value-adding goods including whey powders, functional meals, edible films and coatings, lactic acid, alcoholic beverages, sports drinks, and other biochemical, bioplastics, and biofuels is the core objective of sustainable whey management. In recent years, researchers have looked at different ways to use whey in a more affordable and ecologically friendly way, with the main goal of turning undesirable end products into useful materials. It is a source of several bioactive ingredients with various physiological and functional characteristics. It also provides an opportunity to food industries to develop functional foods with potential health benefits. Whey’s active components are advantageous because they offer antibacterial and antiviral activities, boost antioxidant activity, support bone and immune system health, improve athletic performance, and prevent cancer and cardiovascular disease. This chapter describes how to use whey and its components sustainably while using integrated processes and refining techniques to create high-value whey-based products. This is done in accordance with many international initiatives for improved planetary health, such as the EU Green Deal and the Sustainable Development Goals (UN, General Assembly. Transforming our world: The 2030 agenda for sustainable development. 2015).
... Sistein konsantrasyonun yüksek olmasına bağlı olarak glutatiyon üretimini arttıran tek protein peynir altı suyu proteinidir. Glutatiyon, vücudun antioksidan ve bağışıklık savunma sistemlerinin ana maddesidir [30,31]. ...
Türk Gıda Kodeksi peynir tebliğine göre peynir altı suyu; pıhtı kesimi sonrasında pıhtıdan ayrılan ve teleme dışında kalan yeşilimsi sarı renkteki sıvı olarak tanımlanmaktadır. Peynir altı suyu, peynir prosesinin ana yan ürünüdür. Peynir altı suyu yüksek oksijen ihtiyacına sahiptir bu yüzden su kaynaklarına atıldığında çözünmüş oksijeni azaltır ve çevre için risk oluşturur. Peynir altı suyu, farklı düzeylerde laktoz, serum proteinleri (albümin, globülin), vitaminler, mineraller, laktoferrin, laktoperoksidaz gibi minör bileşenler, yüksek amino asit (lösin, izolösin ve valin) içeriğine sahiptir. Peynir altı suyu zengin kuru madde içeriği ile insan sağlığı ve beslenmesi açısından biyolojik değeri yüksek bir atıktır. Peynir altı suyunun gıda ürünlerinde kullanımı, besin değeri zengin gıdaların üretilmesi açısından inovatif, ayrıca atık su arıtma maliyetlerinin düşürülmesine katkı sağlaması ve yanlış bertaraf edilmesinden kaynaklı çevresel zararın azaltılması yönünden büyük ekonomik ve ekolojik değere sahiptir. Muhafaza, taşıma ve depolama kolaylıklarında dolayı peynir altı suyu tozu üretimi ve kullanımı yaygın olarak tercih edilmektedir. Gıda endüstrisinde yoğurtlar, dondurmalar, kekler, şekerlemeler, bebek mamaları, soslar, fırıncılık ürünleri, et ürünleri, çorbalar ve çeşitli içeceklerin gibi gıdaların üretimde kullanılmaktadır. Bunlarla birlikte peynir altı suyu tozundan yemlerle karıştırılarak hayvan beslenmesinde de yararlanılmaktadır. Son yıllarda peynir altı suyunun tek olarak kullanıldığı veya süt, meyve suyu, meyve pulpları vb. ile karıştırılarak ve aynı zamanda probiyotik bakteri ve/veya maya ilaveli birçok inovatif ürün geliştirilmektedir. Özellikle probiyotik mikroorganizmaların büyümesi ve canlılığı için uygun bir besin matrisi sunduğu için fermente peynir altı suyu içecekler ile ilgili araştırmalar artış göstermiştir. Probiyotik fermente peynir altı suyu içeceklerinin, kandaki kolesterol seviyesini düşürücü, laktoz metabolizmasını düzenleyici, kan basıncını düşürücü, antikanserojenik özellikleri ve immun sistem teşviki gibi insan sağlığına olumlu etkiler gösterdiği uzun zamandır bilimsel çalışmalara konu edilmiş ve halen bu konularda çalışmalara devam edilmektedir. Bu çalışmada peynir altı suyu ve farklı probiyotik kültürler kullanılarak üretilen fermente içecekler ile ilgili araştırmalar ürünlerin kalite özellikleri ve insan sağlığına etkileri kapsamında derlenmiştir.
... Whey protein is classified as a high-quality protein with a complete amino acid profile. Amino acids and bioactive compounds isolated from whey also improve immunity and gastrointestinal health [14]. ...
Whey is the largest by-product of the dairy industry. It is a popular dietary protein among athletes and fitness models showing antimicrobial activity and antioxidant capacity. It is important due to its large production and nutritional composition, for which whey can be considered a valuable by-product for food industry applications. This study incorporated liquid whey at different concentrations (0%, 25%, 50%, 75%, and 100%) as an ingredient in bread, substituting water. The increasing addition of whey showed a decreasing formation of acrylamide in bread. Protein and fat content increased significantly on increasing whey addition. Texture profile parameters like hardness, fracturability, gumminess, and chewiness were improved by adding whey. At the same time, springiness is reduced on increased whey incorporation due to increasing protein interactions. Bread with 50% whey showed optimum quality. The results show the application of whey as a potential ingredient in bread and a mitigation strategy for acrylamide formation.
Graphical abstract
... From the diagram, it can be directly observed that the amino acid composition of yak milk is different between geographical regions. From the diagram, it can be seen that the CYS + MET in the milk of Meiren yak is relatively high, in which cysteine can increase glutathione levels, thus showing strong antioxidant properties and helping the body fight various diseases [18]. It can be seen from Table 2 and Figure 1 that there was no significant difference in branched chain amino acids (BCAAs) in yak milk from different regions (p > 0.05), but it was relatively high in Maqu yak milk. ...
This study aimed to investigate the nutritional properties of yak milk in various areas of Gannan. The milk composition analyzer, automatic amino acid analyzer, and flavor analyzer were used to detect the conventional nutrients, amino acids, and volatile flavor substances of 249 yak milks in Meiren grassland, Xiahe grassland, and Maqu grassland (hereinafter referred to as Meiren yak, Xiahe yak, and Maqu yak) in the Gannan area. The results showed that the fat content of Meiren yak milk was significantly higher than that of Maqu yak and Xiahe yak (p < 0.05). The protein content of Meiren yak milk was significantly higher than that of Xiahe yak (p < 0.05), but not significantly different from that of Maqu yak (p > 0.05). The casein content in the milk of Maqu yak was significantly higher than that of Meiren yak and Xiahe yak (p < 0.05). There was no significant difference in the lactose content of yak milk in the three regions (p > 0.05). The content of glutamic acid in the milk of Meiren yak, Xiahe yak, and Maqu yak was noticeably high, which was 1.03 g/100 g, 1.07 g/100 g, and 1.10 g/100 g, respectively. The total amino acid (TAA) content was 4.78 g/100 g, 4.87 g/100 g, and 5.0 g/100 g, respectively. The ratios of essential amino acids (EAA) and total amino acids (TAA) in the milk of Meiren yak, Xiahe yak, and Maqu yak were 42.26%, 41.27%, and 41.39%, respectively, and the ratios of essential amino acids (EAA) and nonessential amino acids (NEAA) were 73.19%, 70.28%, and 70.61%, respectively. In the yak milk samples collected from three different regions, a total of 34 volatile flavor compounds were detected, including 10 aldehydes, five esters, six ketones, four alcohols, two acids, and seven others. The main flavor substances qualitatively obtained from Meiren yak milk were ethyl acetate, n-valeraldehyde, acetic acid, heptanal, and n-hexanal. Xiahe yak milk mainly contains ethyl acetate, isoamyl alcohol, n-valeraldehyde, heptanal, and ethyl butyrate. Maqu yak milk mainly contains ethyl acetate, n-valeraldehyde, isoamyl alcohol, heptanal, ethyl butyrate, and n-hexanal. Principal component analysis showed that the flavor difference between Xiahe yak and Maqu yak was small, while the flavor difference between Xiahe yak, Maqu yak, and Meiren yak was large. The findings of this research can serve as a foundation for the future advancement and application of yak milk.
... Probiotics can be used to regulate microbiota, and they play a significant role in gut health and metabolism [52]. Many products, such as traditional dairy products used in the fermentation industry, the main sources of the fermentation process, these products also serve as vehicles for probiotics, meaning they act as a means of transportation for the probiotic to reach its intended site of action in the body [53,54]. This was confirmed by analyzing the data from the selected articles; among all the formulations used, which were 29 in total, approximately 58.6% were dairy products. ...
As resistance to conventional antibiotics among bacteria continues to increase, researchers are increasingly focusing on alternative strategies for preventing and treating bacterial infections, one of which is microbiota modulation. The objective of this review is to analyze the scientific literature on the immunomodulatory effects of probiotics in bacterial infections. This is an integrative review of the literature based on systematic steps, with searches performed in the databases Medline, PubMed, Scopus, Embase, and ScienceDirect. The most prevalent bacterial genera used to evaluate infectious processes were Salmonella, Escherichia, Klebsiella, and Streptococcus. Lactobacillus was the most commonly used probiotic genus, with Lactobacillus delbrueckii subsp. bulgaricus is the most frequently used species. In most studies, prophylactic treatment with concentrations of probiotics equal to or greater than 8 log CFU/mL was chosen. However, there was considerable heterogeneity in terms of effective treatment duration, indicating that the results cannot be generalized across all studies. This review found that probiotics interact with the immune system through different mechanisms and have a positive effect on preventing different types of bacterial infections.
... Whey milk represents an excellent source of lactoferrin, bovine serum albumin, lactoperoxidase, immunoglobulins, growth factors, bioactive peptides, and galacto-oligosaccharides [10]. Because of the inherent chemical composition, the consumption of isolated whey protein is encouraged to increase physical performance, modulate adiposity, and enhance immune functions in humans [11,12]. So far, only 50% of the whey milk produced worldwide is further processed and valorized for human consumption, despite the fact that whey production from cheese making exceeds 190 million tons per year [13]. ...
This study aimed to recycle whey milk by-products (protein source) in fruit smoothies (phenolic compounds source) through started-assisted fermentation and delivering sustainable and healthy food formulations capable of providing nutrients that are unavailable due to an unbalanced diet or incorrect eating habits. Five lactic acid bacteria strains were selected as best starters for smoothie production based on the complementarity of pro-technological (kinetics of growth and acidification) traits, exopolysaccharides and phenolics release, and antioxidant activity enhancement. Compared to raw whey milk-based fruit smoothies (Raw_WFS), fermentation led to distinct profiles of sugars (glucose, fructose, mannitol, and sucrose), organic acids (lactic acid and acetic acid), ascorbic acid, phenolic compounds (gallic acid, 3-hydroxybenzoic acid, chlorogenic acid, hydrocaffeic acid, quercetin, epicatechin, procyanidin B2, and ellagic acid) and especially anthocyanins (cyanidin, delphinidin, malvidin, peonidin, petunidin 3-glucoside). Protein and phenolics interaction enhanced the release of anthocyanins, notably under the action of Lactiplantibacillus plantarum. The same bacterial strains outperformed other species in terms of protein digestibility and quality. With variations among starters culture, bio-converted metabolites were most likely responsible for the increase antioxidant scavenging capacity (DPPH, ABTS, and lipid peroxidation) and the modifications in organoleptic properties (aroma and flavor).
... Both whey and soy are considered complete proteins, with a high amount of essential amino acids and both are proven to increase muscle building following resistance training. [15][16][17] The current research directly comparing whey to soy protein supplementation following resistance training and its effect on MPS is limited. Much of the existing literature comparing the difference between whey and soy protein is equivocal. ...
The current research directly comparing whey to soy protein supplementation following resistance training and its effect on muscle protein synthesis (MPS) is limited. Existing literature comparing the difference between whey and soy protein is equivocal. The purpose of this review is to examine research directly comparing whey to soy protein supplementation regarding muscle protein synthesis following resistance training. A literature review was performed utilizing specific search terms with inclusion and exclusion criteria. It is suggested that differences between whey and soy protein on MPS with resistance training are apparent in experienced resistance training athletes and when the duration of training is 12 weeks or longer.
... New applications of whey would therefore support SMEs in terms of whey recycling cost (Lavelli & Beccalli, 2022). This clear liquid left over from curdling the milk during the production of cheese or casein is a rich source of nutritional valuesproteins (β-lactoglobulin, α-lactalbumin, bovine serum albumin, immunoglobulins, lactoferrin, lysozyme), minerals (calcium, zinc, magnesium, phosphorus, copper, sodium, potassium, chlorine, iron), vitamins (especially B-complex vitamins), amino acids and lactose (Blažić et al., 2018;Ha & Zemel, 2003;Papademas & Kotsaki, 2020). The presence of these nutrients that are easily digestible for humans means that whey can be viewed as a value-added material and not merely a difficult to utilize waste from dairy processing. ...
The potential of whey from Italian cheese productions to support skin health and anti-ageing mechanism was studied. The effect of whey on dermal and epidermal cells was evaluated. Whey inhibited the activity of elastase and tyrosinase enzymes by 60% and 32%, respectively. Whey cytotoxicity against tested skin cell lines, human fibroblasts (HDFa) and keratinocytes (HaCaT) was not observed. Moreover, the antioxidant activity of the samples was noted, after treatment with whey intracellular ROS level was decreased by 87% in comparison with the hydrogen peroxide-treated cells. Fibroblasts produced a significant amount of extracellular matrix molecules, collagen I, elastin and glycosaminoglycans as a result of treatment with tested whey. In addition, the ability of samples to improve the cell barrier integrity of keratinocytes was proven. The obtained results indicate that pure whey supports skin health and shows potential to be used by the cosmetic industry.
... Supplementation of diet with fermented milk was accompanied by the enhancement of skeletal muscle strength and hypertrophy in response to resistance training (Bridge et al., 2019;Thomas et al., 2011). Non-fermented whey protein supplementation was tested on muscle hypertrophy in various resistance training studies, where findings indicated that specific peptides may provide muscle recovery capabilities, while their antioxidant capacities may also contribute towards recovery physiological responses to exercise (Devries and Phillips, 2015;Ha and Zemel, 2003;Stark et al., 2012). There have been several studies on the improvement of muscle parameters with whey protein supplementation (Andersen et al., 2005), fermented whey proteins on protein digestion and absorption, increment of branched chain amino acids levels, and effects of fermentation on calcium absorption and bone density improvement (Matsuda et al., 2022). ...
The present study evaluated the effects of fermented whey protein using kimchi lactic acid bacteria Lactobacillus casei DK211 on skeletal muscle mass, muscle strength, and physical performance in healthy middle-aged males performing regular resistance exercises. Effective protein supplementation and regular exercise are two important factors for improving muscle health. Therefore, in this study, the effects of consuming fermented whey protein twice a day were investigated and compared with that of non-fermented supplementation. Forty-eight males (average age 44.8) were randomly assigned to two groups: Fermented whey protein supplementation (FWPS) and non-fermented whey protein concentration supplementation (WPCS) groups. Each group ingested 37 g of FWPS or WPCS twice a day for eight weeks. Body composition, muscle strength, and physical performance were assessed pre- and post-intervention. Independent t-tests or chi-square tests for the categorical variables were performed for analyzing the observations. FWPS was effective in promoting the physical performance in dynamic balance measurement and muscle health, indicated through the increment in grip strength (left), upper arm circumference, and flat leg circumference from the baseline. However, similar improvements were not observed in the WPCS group. These results imply that whey protein fermented by L. casei DK211 is an effective protein supplement for enhancing muscle health in males performing regular resistance exercises.
... In addition, whey proteins have health-promoting properties such as antimicrobial, anti-cancerogenic, immune-stimulating, and antioxidant activities; reduction in blood pressure, the risk of cardiovascular disease and osteoporosis; and satiety regulation. Due to these properties, it is a valuable by-product [7][8][9]. ...
Recently, the demand for goat and sheep cheese has increased mainly because of its nutritional and health benefits. As a result, an enormous amount of whey from various animal species is produced as a waste/by-product. The production of functional probiotic fermented beverages from different types of whey protein concentrates (WPC) could be a good way to valorize whey. Meanwhile, reduced environmental pollution and economic sustainability will be provided. In this study, probiotic beverages enriched with 1% kiwi powder were produced from goat, sheep, and cow WPC (15%). Moreover, Streptococcus salivarius subsp. thermophilus and the probiotic bacteria Lactobacillus acidophilus and Bifidobacterium animalis subsp. lactis were used for fermentation. The results showed that WPC significantly increased the protein content and acidity of beverages (p < 0.05). Production with WPC also improved the viability of probiotic bacteria and S. thermophilus, total phenolic compound (TPC), and antioxidant activity of beverages. The highest viability of probiotic bacteria (9.67 log CFU/mL for Bb-12 and, 9.35 log CFU/mL for L. acidophilus) was found in beverages produced from goat WPC. In addition, WPC increased the free amino acid content of beverages, and the highest essential amino acids and branched-chain amino acids were found in beverages produced from goat WPC as 146.19 mg/100 g and 70.31 mg/100 g, respectively (p < 0.05). Consequently, while production with goat, cow, and sheep WPC improved quality compared to the control, beverages produced from goat WPC excelled. The production of a functional probiotic beverage with goat WPC is promising for dairy technology.
Protein plays a crucial role in maintaining and supporting the musculoskeletal system. With advancing age, deterioration of musculoskeletal integrity poses a significant public health challenge, contributing to increased physical disability, reduced quality of life, and heightened mortality risk. A well-balanced diet rich in key nutrients helps prevent musculoskeletal disorders. Among the crucial nutrients, calcium, vitamin D, protein, and magnesium play particularly vital roles. Adequate protein intake is essential for maintaining muscle and bone health in older adults, with varying recommendations across countries regarding protein needs for this demographic. Protein is found in a diverse array of dietary sources, animal-based foods, plant-based foods. Hence, this chapter discusses the crucial role of protein in maintaining musculoskeletal health, specifically in preventing and combating conditions related to protein deficiency in the musculoskeletal system. Additionally, it will explore various sources of protein.
Fat plays a key role in the manufacturing of processed meat products with desired quality characteristics. However, due to the recent concern over the negative health implications of high fat meat products, by various health organizations (WHO/FAO/NHLBI); consumers are very much conscious about their nutrition and health and choose low fat meat products as these are perceived at least by many to be “better for you” than traditional counterparts that contain higher levels of animal fat. Reduction of fat in processed meat products is extremely challenging and poses difficulties in terms of appearance, flavour and texture besides health-conscious consumers continue to look for ways to improve nutritional habits without sacrificing psychological satisfaction. For this reason, a number of substances (such as carbohydrate, protein and lipid based) with high water binding capacity, able to promote the texture, mouth feel and form gels have been examined for their ability to replace fat and are called fat replacers. Fat replacers are substances which structurally may be considered fats, proteins or carbohydrates, that is, designed to replace all or part of the fat in a product, with minimum impact on the organoleptic quality of the food product, yielding fewer calories than fat. This chapter is aimed to summarize the recent approaches for the development of low-fat/reduced-fat processed meat products.
In this study, storage related changes in physico-chemical and sensory properties of non-fat fermented milk drinks that contain soy protein isolate (SPI), pea protein isolate (BPI), wheat gluten (BG) and rice protein (PP) were investigated.
Vegetable protein additives at a level of 0,5% were added to the reconstituted skim milk (10,7% DM) and then this mixture was heat treated for 10 minutes at 90°C. Milks, used in production of yoghurt were inoculated with 3% yoghurt starter culture and incubated at 42±1°C until pH reached 4,6. The yoghurts were stored at 4±1°C for 12 hours and the fermented milk drinks were prepared by diluting the yoghurts (2:1 yoghurt/water). On the 1., 7., 14. and 21. days of storage physico-chemical analysis such as pH, titratable acidity, syneresis, viscosity, dry matter, ash, color (L, a, b values), protein and amino acid contents and sensory properties such as texture, flavor, color, flavor intensity, flavor and overall acceptability were determined.
Addition of vegetable protein additives to non-fat fermented milk drinks have affected pH, titratable acidity%, syneresis, viscosity, dry matter, ash, color (L, a, b values), protein and amino acid contents (p<0,01). During storage, viscosity values of non-fat fermented milk drinks showed an increase. Vegetable protein additives have increased amino acid levels of non-fat fermented milk drinks. The highest rate of essential amino acids was found in SPI-added drinks with major amino acids being lysine, leucine, isoleucine, methionine and threonine. Fermented milk drinks with BPI have a preferred taste than the others. In general vegetable protein additives were found to be effective on sensorial attributes (p<0,01).
In conclusion, the use of vegetable protein additivites in non-fat fermented milk drink formulations was shown to improve the physico-chemical and sensory properties, as well as increase the nutritional value, and therefore, could be an alternative for the development of functional dairy products.
In the category of sports supplements, whey protein powder is one of the popular supplements for muscle building applications. Therefore, verification of the sport supplements as authentic products has become a universal concern. This work aimed to propose vibrational spectroscopy including near infrared (NIR) and infrared (IR) as rapid and non-destructive testing tools for the detection and quantification of maltodextrin, milk powder and milk whey powder in whey protein supplements. Initially, principal component analysis was applied to data for pattern recognition and the results displayed a fine pattern of discrimination. Partial least square discrimination analysis (PLS-DA) and K-nearest neighbours (KNN) were exploited as supervised method modelling classification. This process was done in order to respond to two vital questions whether the sample is adulterated or not and what is the kind of adulteration. PLS-DA showed better classification results rather than KNN according to the figure of merits of the model. Partial least square regression (PLSR) was employed on pre-treated spectra to quantify the amount of adulteration in sport whey supplements. Eventually, it seems vibrational spectroscopy could be implemented as a simple, and low-cost analysis method for the detection and quantification of mentioned adulterants in whey protein supplements.
Background
Malnutrition often occurs in patients with cancer, which eventually leads to decreasing response to therapy and increased morbidity and mortality rate. Oral Nutrition Supplements (ONS) are necessary to provide additional nutritional intervention to prevent and treat malnutrition in cancer patients. Purple sweet potato is a local food that is abundantly available in Indonesia and can be utilized as a basic ingredient for producing a modified ONS formula that is not only high in nutritional value but also has good physical quality.
Objective
This study aimed to evaluate the nutritional value and physical quality of purple sweet potato-based ONS.
Methods
A new local food-based formula was formulated by using purple sweet potato as the main ingredient. This new formula, which was then mentioned as the treatment formula, was subsequently compared with the control formula. The control formula was made from ingredients commonly used for producing ONS in hospitals in Indonesia, such as milk powder, sugar, oil, and other additives such as maltodextrin and creamer. Meanwhile, the treatment formula was labelled into three treatment formulas based on the differences in the proportions of white egg flour and whey protein as a protein source in each treatment formula. The treatment formula was formulated by using local ingredients of purple sweet potato flour and egg white flour by adding whey protein, extra virgin olive oil, omega-3 powder, sugar, and creamer. A proximate analysis was conducted to analyze the nutrient content of the formula and the viscosity and osmolarity tests were conducted to evaluate the physical qualities of the formula. The laboratory analysis results were described as descriptive data, then analyzed by using One-Way ANOVA. The determination of the best treatment formula in the form of effectiveness (Nh).
Results
The results of the proximate test and physical quality showed that the best formula based on the highest Nh value of 0.75 was P3 with 245 kcal energy, 8.8 g (14%) protein, 6.5 g (24%) fat, and 37.8 g (62%) carbohydrate, viscosity 28.1 cP, and osmolarity 492.3 mOsm (iso-osmolar) per serving size (200 ml).
Conclusion
Formula P3 which contains more egg white flour than whey protein is the best formula that has the best nutritional value and good physical quality.
The characteristics of rice protein deamidated (DRP) by choline chloride-citric acid and glucose-citric acid natural deep eutectic solvents (G-C NADES, C-C NADES) at different dilutions were investigated. Compared with the effect of citric acid deamidation on the structural and functional properties of the protein, the DRP from the NADESs led to remarkable differences in the degree of hydrolysis (DH), SDS-PAGE, morphology, surface hydrophobicity, average particle size, intrinsic fluorescence, amino acid compositions, and emulsion activity. The results of SDS-PAGE, DH, and SEM showed the NADESs reduced the occurrence of uncontrolled hydrolysis of protein during acid deamidation. DRP from C-C and G-C NADESs was found to significantly improve solubility. DRP prepared by C-C NADES showed a more than 40% solubility over a wide pH range associated with its higher emulsifying activity (37.62–44.19 m2/g) and emulsifying stability (73.76–86.9 min), as well as a better deamidation effect while lower DH. Thus, these findings showed that acid-based NADESs had great potential as a modified RP product to expand its application.
Global milk production has increased by 59% since 1988, reaching 944 million tonnes in 2023. This surge has resulted in an annual by-product, whey, totalling 200 million tonnes. Despite half of this whey being utilized in the food and pharmaceutical sectors, significant quantities are discarded, posing environmental challenges due to its high biological oxygen demand. Whey proteins and lipids are recovered from whey, and the resultant whey permeate stream is rich in lactose is a viable carbon source for value-added biochemical. D(-)lactic acid (DLA) is a versatile organic acid molecule widely used in the synthesis of thermostable biodegradable polymers viz., polylactic acid (PLA). However, the DLA market faces constraints; downstream demand is unsaturated, and upstream production is restricted, leading to elevated costs and posing challenges to its growth and profitability, which affect PLA manufacturing. This review study addresses a novel techno-economic approach involving strategies for genetic engineering of lactic acid bacteria and process intensification towards efficient valorization of whey permeate into DLA. This review enumerates a circular bioeconomy approach offering both environmental benefits and revenue opportunities for the dairy sector, revolutionizing by-product utilization and enhancing the industry’s sustainability.
Purpose: Research shows the benefits of whey isolate protein powder and casein protein powder supplementation in regard to body composition and resting metabolic rate; however, minimal research exists comparing the effectiveness of whey to casein supplementation. Methods: Eighteen (18) physically trained, healthy individuals (23±3.1 yrs.; 171.7cm; 12 males; 6 females) completed a randomized two condition [Combat 100% Isolate (Whey) versus Combat 100% (Casein)] by two time point [Pre-, Post-] intervention. The intervention consisted of subjects supplementing on either whey or casein in conjunction with resistance training over an 8-week period. Pre and post testing included % body fat and metabolic rate. Results: A 2x2, repeated-measures analysis of variance (ANOVA) demonstrated non-significant (p ≥ 0.05) effects on changes in % body fat and resting metabolic rate following the 8-week intervention. Conclusions: The data concludes no differences in the effects of whey versus casein protein supplementation in physically active, healthy individuals
Whey is a source of protein of high nutritional value. In this work, the effects of block cryoconcentration assisted by centrifugation and vacuum evaporation on the physicochemical properties and in vitro digestibility of whey were determined. In vitro digestibility analysis was performed by evaluating the degrees of protein hydrolysis of the fresh, evaporated and cryoconcentrated whey protein samples from the third cycle. The results showed that the samples after the second and third cryoconcentration cycles had no significant differences in protein or lactose content. The in vitro digestibility analysis indicated that the protein obtained by cryoconcentration showed better gastrointestinal digestibility than that obtained by evaporation, with values of 68.2% and 55.4%, respectively. This study demonstrates that block cryoconcentration assisted by centrifugation is an efficient and novel technique that enables the preparation of concentrated protein solutions of high nutritional and biological value.
Commercial whey protein (CWP) is generally produced in the cheese making process with heat treatment. Recently, native whey protein (NWP) can be obtained through microfiltration without heat treatment. The difference in physicochemical properties of CWP and NWP was confirmed in previous studies; however, in vivo research on the effect on muscle strength and protein synthesis is still lacking. In this study, rats were orally administered 1.56 g protein/kg body weight of lyophilized beverages containing CWP and NWP for 8 weeks. The biological value and net protein utilization in the NWP were significantly higher than in the CWP. Moreover, NWP increased muscle mass and grip strength compared to CWP. NWP also increased the phosphorylation of the mammalian target of rapamycin and ribosomal protein S6 kinase, pivotal proteins for muscle protein synthesis. These results suggest that NWP enhance muscle strength and protein synthesis more effectively than CWP.
Yaşam standartlarının değişmesine bağlı olarak tüketim alışkanlıkları da değişmiş ve insanlar daha çok ambalajlı gıdaların tüketimine yönelmiştir. Genel olarak atıkların ağırlıkça %20‟sini ambalaj atıkları oluşturmaktadır. Sanayi atık miktarları sıralamasında gıda sanayi ikinci sırada yer almaktadır. Bu nedenle gıda endüstrisindeki ambalaj atık miktarının azaltılmasına yönelik yenilebilir özelikteki ambalajların üretimi ile ilgili çeşitli çalışmalar yapılmaktadır. Yenilebilir film kaplama yöntemi ile gıdanın dış yüzeyinde bulunan plastik ambalaj materyal kalınlığı biraz daha inceleceğinden dolayı çevre atık miktarı azalabilmektedir. Ayrıca yenilebilir film kaplama ile gıdaya ekstra fonksiyonel özellik kazandırılmaktadır. Yenilebilir film üretiminde kullanılan karbonhidrat, protein ve yağ bazlı bileşen filmlerin özelikleri ve son ürünün kalitesi üzerine etkilidir. Peyniraltı suyu peynir üretim teknolojisinin mamullerinden birini oluşturmaktadır. Türk Gıda Kodeksi‟ne göre peyniraltı suyundan suyun uzaklaştırılmasıyla elde edilen ve son üründeki nem içeriğinin ağırlıkça en fazla %5 olduğu toz ürüne peynir altı suyu tozu denilmektedir. Peyniraltı suyunun süt proteinlerinin yaklaşık %20 sini oluşturan makro ve mikro protein içermesi bu ürünün besleyici değerinin önemini attırmaktadır. Günümüzde peyniraltı suyu tozu gıda katkı maddesi olarak gıda sanayinde kullanılmaktadır. Peyniraltı suyu tozunun gıda sanayinde içeriğindeki protein miktarı farklılık gösteren peyniraltı suyu protein tozu, peyniraltı suyu protein konsantratı ve peyniraltı suyu protein izolatı gibi formlarında bulunmaktadır. Çalışmamızda yüksek besin değerine sahip peyniraltı suyu tozu içeren yenilebilir filmlerin özellikleri ve son yıllarda yapılan çalışmalar derlenmiştir.
Advances in processing technologies and the accumulation of scientific data on the functional and biological properties of whey components have contributed to the growing commercial valuation of cheese whey over the last decade. New membrane separation and chromatographic techniques have made it possible to fractionate and enrich various components of whey more efficiently than before. The specific properties of these components can now be examined in greater detail and new applications developed accordingly. The utilisation of cheese whey is evolving into a new industry producing a multitude of purified ingredients for numerous purposes. The most significant areas of R&D related to whey proteins include functional foods, the rheological properties of foodstuffs, and biopharmaceuticals.
The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could
affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically 13C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested
as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology.
WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia,
probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not
after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with
the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ± 91 μmol⋅kg−1) than with WP (373 ± 56 μmol⋅kg−1). Leucine intake was identical in both meals (380 μmol⋅kg−1). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect
on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate
the postprandial metabolic response, a concept to be applied to wasting situations.
An epidemiologic study of Los Angeles Marathon (LAM) applicants was conducted to investigate the relationship between self-reported infectious episodes (IE), training data, and LAM participation. Eight days before the LAM, 4926 of 12,200 applicants were randomly selected, and sent a pilot-tested four page questionnaire, which was received 7 days after the LAM. The 2311 respondents were found to be 2.0 yr older and 7.6 min faster than other LAM finishers (p less than .01). Univariate and multivariate analyses (logistic regression) were conducted to test the relationship between IE and km/wk of running (6 total categories). The final model tested controlled for age, marital status, reported sickness in other members of the runner's home, perceived feelings of stress in response to personal training regimens, and the suppressive effect of sickness on regular training. In runners training greater than or equal to 97 vs less than 32 km/wk, the odds ratio (OR) for IE during the 2 month period prior to the LAM was 2.0 (95% confidence interval (CI) 1.2-3.4). A test for trend showed an increase in OR with increase in km/wk category (p = .04) which was largely explained by the increased odds of reported sickness in the greater than or equal to 97 km/wk category. Of the 1828 LAM participants without IE before the LAM, 236 (12.9%) reported IE during the week following the LAM vs 3 of 134 (2.2%) similarly experienced runners who did not participate, OR = 5.9 (95% CI 1.9-18.8). These data suggest that runners may experience increased odds for IE during heavy training or following a marathon race.
We investigated the effects of the nature of the flooding amino acid on the rate of incorporation of tracer leucine into human skeletal muscle sampled by biopsy. Twenty-three healthy young men (24.5 +/- 5. 0 yr, 76.2 +/- 8.3 kg) were studied in groups of four or five. First, the effects of flooding with phenylalanine, threonine, or arginine (all at 0.05 g/kg body wt) on the incorporation of tracer [13C]leucine were studied. Then the effects of flooding with labeled [13C]glycine [0.1 g/kg body wt, 20 atoms percent excess (APE)] and [13C]serine (0.05 g/kg body wt, 15 APE) on the incorporation of simultaneously infused [13C]leucine were investigated. When a large dose of phenylalanine or threonine was administered, incorporation of the tracer leucine was significantly increased (from 0.036 to 0. 067 %/h and 0.037 to 0.070 %/h, respectively; each P < 0.01). However, when arginine, glycine, or serine was administered as a flooding dose, no stimulation of tracer leucine incorporation could be observed. These results, together with those previously obtained, suggest that large doses of individual essential, but not nonessential, amino acids are able to stimulate incorporation of constantly infused tracer amino acids into human muscle protein.
Overexpression of the murine agouti gene results in obesity. The human homologue of agouti is expressed primarily in human adipocytes, and we have shown recombinant agouti protein to increase adipocyte intracellular Ca2+([Ca2+]i) and thereby stimulate lipogenesis. However, since recent data demonstrate that increasing adipocyte [Ca2+]i may also inhibit lipolysis, we have investigated the role of agouti-induced [Ca2+]i increases in regulating lipolysis in human adipocytes. Short-term (1 h) exposure to recombinant agouti (100 nM) protein had no effect on basal lipolysis, although longer term treatment (24 h) caused a 60% decrease in basal lipolysis (P<0.0001). Short-term agouti treatment totally inhibited ACTH-induced lipolysis (P<0.05). Since melanocortin receptors (MCR) are involved in some actions of agouti, we next determined whether agouti's antilipolytic effect is exerted through competitive antagonism of the ACTH receptor (MCR-2). Forskolin (1 microM), an adenylate cyclase activator, induced a 48% increase in lipolysis in human adipocytes (P<0.05); this effect was reversed by 100 nM agouti (P<005), demonstrating that the antilipolytic effect of agouti is distal to the ACTH receptor. To determine the role of [Ca2+]i in the antilipolytic effect of agouti, human adipocytes were treated with KCl or arginine vasopressin to stimulate voltage- and receptor-stimulated Ca2+ influx, respectively. Both agents caused inhibition of forskolin-induced lipolysis (P<0.005). Furthermore, agouti's antilipolytic effect was also blocked by the Ca2+ channel blocker nitrendipine. These data demonstrate that agouti exerts a potent antilipolytic effect in human adipocytes via a Ca2+-dependent mechanism. This effect, combined with agouti-induced lipogenesis, represents a coordinate control of adipocyte lipid metabolism that may contribute to an agouti-induced obesity syndrome.
The nutritional quality of milk proteins, evaluated both in terms of digestibility and postprandial oxidation and retention in human subjects, was investigated in this study. Five healthy adult volunteers were given 480 ml 15N-labelled milk (i.e. 190 mmol N). 15N was subsequently determined at the ileal level, using a naso-intestinal intubation technique, as well as at the faecal level. Plasma and urine were sampled for 8 h after meal ingestion. Dietary exogenous N recovered at the terminal ileum after 8 h reached 8.6 (SE 0.8) mmol while the amount collected in the faeces was 6.5 (SE 0.7) mmol after 5 d. The true ileal and faecal digestibilities were 95.5 (SE 0.4)% and 96.6 (SE 0.4)% respectively. The appearance of [15N]amino acids in the plasma was rapid and prolonged. The measurement of 15N in the body urea pool and in the N excreted in the urine allowed us to calculate the deamination occurring after [15N]milk protein absorption. The net postprandial protein utilization (i.e. NPPU = (Nabsorbed-Ndeaminated)/Ningested), calculated as an index of protein quality 8 h after milk ingestion, was 81.0 (SE 1.9)%. Our data confirm that milk protein has a high oro-ileal digestibility in man and demonstrate that milk protein has a high NPPU, an index corresponding to a period in which the dietary protein retention is maximal.
Oxidative stress contributes to muscular fatigue. GSH is the major intracellular antioxidant, the biosynthesis of which is dependent on cysteine availability. We hypothesized that supplementation with a whey-based cysteine donor [Immunocal (HMS90)] designed to augment intracellular GSH would enhance performance. Twenty healthy young adults (10 men, 10 women) were studied presupplementation and 3 mo postsupplementation with either Immunocal (20 g/day) or casein placebo. Muscular performance was assessed by whole leg isokinetic cycle testing, measuring peak power and 30-s work capacity. Lymphocyte GSH was used as a marker of tissue GSH. There were no baseline differences (age, ht, wt, %ideal wt, peak power, 30-s work capacity). Follow-up data on 18 subjects (9 Immunocal, 9 placebo) were analyzed. Both peak power [13 +/- 3.5 (SE) %, P < 0.02] and 30-s work capacity (13 +/- 3.7%, P < 0.03) increased significantly in the Immunocal group, with no change (2 +/- 9.0 and 1 +/- 9.3%) in the placebo group. Lymphocyte GSH also increased significantly in the Immunocal group (35.5 +/- 11.04%, P < 0.02), with no change in the placebo group (-0.9 +/- 9.6%). This is the first study to demonstrate that prolonged supplementation with a product designed to augment antioxidant defenses resulted in improved volitional performance.
Recent data from this laboratory demonstrate that increasing adipocyte intracellular Ca(2+) results in a coordinated stimulation of lipogenesis and inhibition of lipolysis. We have also noted that increasing dietary calcium of obese patients for 1 year resulted in a 4.9 kg loss of body fat (P<0.01). Accordingly, we tested the possibility that calcitrophic hormones may act on adipocytes to increase Ca(2+) and lipid metabolism by measuring the effects of 1, 25-(OH)(2)-D in primary cultures of human adipocytes, and found significant, sustained increases in intracellular Ca(2+) and a corresponding marked inhibition of lipolysis (EC(50) approximately 50 pM; P<0.001), suggesting that dietary calcium could reduce adipocyte mass by suppressing 1,25-(OH)(2)-D. To test this hypothesis, we placed transgenic mice expressing the agouti gene specifically in adipocytes on a low (0.4%) Ca/high fat/high sucrose diet either unsupplemented or with 25 or 50% of the protein replaced by non-fat dry milk or supplemented to 1.2% Ca with CaCO(3) for 6 wk. Weight gain and fat pad mass were reduced by 26-39% by the three high calcium diets (P<0.001). The high calcium diets exerted a corresponding 51% inhibition of adipocyte fatty acid synthase expression and activity (P<0.002) and stimulation of lipolysis by 3. 4- to 5.2-fold (P<0.015). This concept of calcium modulation of adiposity was further evaluated epidemiologically in the NHANES III data set. After controlling for energy intake, relative risk of being in the highest quartile of body fat was set to 1.00 for the lowest quartile of Ca intake and was reduced to 0.75, 0.40, and 0.16 for the second, third, and fourth quartiles, respectively, of calcium intake for women (n=380;P<0.0009); a similar inverse relationship was also noted in men (n=7114; P<0.0006). Thus, increasing dietary calcium suppresses adipocyte intracellular Ca(2+) and thereby modulates energy metabolism and attenuates obesity risk.
This review focuses on studies of mucosal immunity in elite athletes and specifically addresses the role of mucosal immunity in respiratory illness and associations with the intensity, volume, and duration of exercise. Habitual exercise at an intense level can cause suppression of mucosal immune parameters. Salivary IgA and IgM concentrations decline immediately after a bout of intense exercise and usually recover within 24 hours. Training at an intense level can result in a chronic suppression of mucosal immunoglobulin levels. The degree of suppression is associated with the intensity of the exercise and the duration or volume of the training. Low levels of salivary IgM and IgA, particularly the IgA1 subclass are associated with an increased risk of respiratory illness. Monitoring mucosal immune parameters during critical training periods and establishing personal profiles for individual athletes may provide an assessment of the risk status of an athlete for URTI and allow effective management by the athlete and coach. The nature of the respiratory illnesses in some elite athletes is still uncertain. Recent data indicate viral reactivation may be a significant cause of the respiratory symptoms. Despite suppression of mucosal immune parameters, elite athletes are capable of normal responses to novel oral vaccinations, indicating that mucosal immune mechanisms are intact.
We have demonstrated previously a regulatory role for intracellular Ca2+ ([Ca2+]i) in adipocyte lipogenesis and lipolysis and have recently reported that 1,25-(OH)2-D increases adipocyte [Ca2+]i, which causes increased lipogenesis and decreased lipolysis. We have now tested the hypothesis that suppressing 1,25-(OH)2-D by increasing dietary calcium will suppress adipocyte [Ca2+]i, thereby facilitating weight loss by stimulating lipolysis and inhibiting lipogenesis in calorically (Kcal)-restricted (70% of ad lib) aP2-agouti transgenic (aP2-a) mice. Mice (aP2-a) exhibiting a pattern of obesity gene expression similar to humans were fed a low-Ca (0.4%)/high-fat/high-sucrose diet for six weeks, resulting in a 27% and twofold increase in body weight and total fat pad mass, respectively, with a twofold increase in adipocyte [Ca2+]i pad lib or Kcal-restricted (70% of ad lib) on this diet either unsupplemented (basal) or with 25% or 50% of the protein replaced by non-fat dry milk (medium or high) dairy or supplemented with CaCO3 to 1.2% Ca for six weeks. Adipocyte [Ca2+]i was unaffected by Kcal restriction but was reduced markedly by all three high Ca diets (290 vs. 130 nM, p2+]i and thereby reduce energy storage and increase thermogenesis during Kcal restriction.
To evaluate the importance of protein digestion rate on protein deposition, we characterized leucine kinetics after ingestion of "protein" meals of identical amino acid composition and nitrogen contents but of different digestion rates. Four groups of five or six young men received an L-[1-13C]leucine infusion and one of the following 30-g protein meals: a single meal of slowly digested casein (CAS), a single meal of free amino acid mimicking casein composition (AA), a single meal of rapidly digested whey proteins (WP), or repeated meals of whey proteins (RPT-WP) mimicking slow digestion rate. Comparisons were made between "fast" (AA, WP) and "slow" (CAS, RPT-WP) meals of identical amino acid composition (AA vs. CAS, and WP vs. RPT-WP). The fast meals induced a strong, rapid, and transient increase of aminoacidemia, leucine flux, and oxidation. After slow meals, these parameters increased moderately but durably. Postprandial leucine balance over 7 h was higher after the slow than after the fast meals (CAS: 38 +/- 13 vs. AA: -12 +/- 11, P < 0.01; RPT-WP: 87 +/- 25 vs. WP: 6 +/- 19 micromol/kg, P < 0.05). Protein digestion rate is an independent factor modulating postprandial protein deposition.
Numerous reports established that in skeletal muscle the indispensable branched-chain amino acid leucine is unique in its ability to initiate signal transduction pathways that modulate translation initiation. Oral administration of leucine stimulates protein synthesis in association with hyperphosphorylation of the translational repressor, eukaryotic initiation factor (eIF) 4E binding protein 1 (4E-BP1), resulting in enhanced availability of the mRNA cap-binding protein eIF4E, for binding eIF4G and forming the active eIF4F complex. In addition, leucine enhances phosphorylation of the 70-kDa ribosomal protein S6 kinase (S6K1). These results suggest that leucine upregulates protein synthesis in skeletal muscle by enhancing both the activity and synthesis of proteins involved in mRNA translation. The stimulatory effects of leucine on translation initiation are mediated in part through the protein kinase mammalian target of rapamycin (mTOR), where both insulin signaling and leucine signaling converge to promote a maximal response.
Whole-body and splanchnic metabolism of dietary amino acids derived from casein (CAS) or the corresponding crystalline L-amino acid mixture (AA) were compared. Male adult rats were adapted for 9 d to two isoenergetic, isonitrogenous diets (15 g/100 g protein, 5 g/100 g fat) containing either CAS or AA. On d 10, the rats were fed a single mixed meal (3 g dry mass) containing either intrinsically (13)C-labeled goat casein or the amino acid mixture containing [U-(13)C(6)] leucine and [alpha-(15)N] lysine. Rats were killed before and 1, 3, 5 and 7 h after meal ingestion and samples of plasma, stomach wall and contents, small intestine and liver were collected. (13)C and (15)N enrichments of free and protein-bound amino acids in plasma and tissues were analyzed by gas chromatography-combustion isotope ratio mass spectrometry. Urinary nitrogen excretion was higher (P < 0.05) and weight gain lower (P < 0.05) in rats given the AA diet, indicating a lower whole-body net protein synthesis. Free (13)C-leucine from the AA diet appeared in the intestinal mucosa free pool more rapidly (P < 0.05) than the CAS-(13)C-leucine, probably due to the faster transit through the stomach of the AA group. However, the incorporation of dietary leucine into plasma and liver proteins was higher in the CAS group 7 h after the meal (P < 0.05), whereas lysine incorporation into liver protein was higher in the AA group (P < 0.05). We conclude that whole-body protein homeostasis is better supported by dietary casein-bound than crystalline free amino acids, and that protein-bound leucine, but not lysine, is used more efficiently for liver protein synthesis than dietary free leucine.
We used a previously developed compartmental model to assess the postprandial distribution and metabolism of dietary nitrogen (N) in the splanchnic and peripheral areas after the ingestion of a single mixed meal containing either (15)N-labeled milk or soy purified protein. Although the lower whole-body retention of dietary N from soy protein was measured experimentally, the splanchnic retention of dietary N was predicted by the model not to be affected by the protein source, and its incorporation into splanchnic proteins was predicted to reach approximately 35% of ingested N at 8 h after both meals. However, dietary N intestinal absorption and its appearance in splanchnic free amino acids were predicted to be more rapid from soy protein and were associated with a higher deamination, concomitant with a higher efficiency of incorporation of dietary N into proteins in the splanchnic bed. In contrast, soy protein was predicted to cause a reduction in peripheral dietary N uptake, as a consequence of both similar splanchnic retention and increased oxidation compared with milk protein. In addition, protein synthesis efficiency was reduced in the peripheral area after soy protein intake, leading to dietary N incorporation in peripheral proteins that fell from 26 to 19% of ingested N 8 h after milk and soy protein ingestion, respectively. Such a model thus enables a description of the processes involved in the differential metabolic utilization of dietary proteins and constitutes a valuable tool for further definition of the notion of protein quality during the period of protein gain.
• The aim of this study was to describe the time course of the response of human muscle protein synthesis (MPS) to a square wave increase in availability of amino acids (AAs) in plasma. We investigated the responses of quadriceps MPS to a ≈1.7-fold increase in plasma AA concentrations using an intravenous infusion of 162 mg (kg body weight)−1 h−1 of mixed AAs. MPS was estimated from D3-leucine labelling in protein after a primed, constant intravenous infusion of D3-ketoisocaproate, increased appropriately during AA infusion. • Muscle was separated into myofibrillar, sarcoplasmic and mitochondrial fractions. MPS, both of mixed muscle and of fractions, was estimated during a basal period (2.5 h) and at 0.5-4 h intervals for 6 h of AA infusion. • Rates of mixed MPS were not significantly different from basal (0.076 ± 0.008 % h−1) in the first 0.5 h of AA infusion but then rose rapidly to a peak after 2 h of ≈2.8 times the basal value. Thereafter, rates declined rapidly to the basal value. All muscle fractions showed a similar pattern. • The results suggest that MPS responds rapidly to increased availability of AAs but is then inhibited, despite continued AA availability. These results suggest that the fed state accretion of muscle protein may be limited by a metabolic mechanism whenever the requirement for substrate for protein synthesis is exceeded.
The effects of amino acids on protein turnover in skeletal muscle were determined in the perfused rat hemicorpus preparation. Perfusion of preparations from fasted young rats (81±2 g) with medium containing either a complete mixture of amino acids at five times (5×) their normal plasma levels, a mixture of leucine, isoleucine, and valine at 5× or 10× levels, or leucine alone (10×) resulted in a 25–50% increase in muscle protein synthesis and a 30% decrease in protein degradation compared to fasted controls perfused in the absence of exogenously added amino acids. When the branched-chain amino acids were omitted from the complete mixture, the remaining amino acids (5×) had no effect on protein turnover. The complete mixture at 1× levels was also ineffective. Comparison of the effects of amino acids with those of glucose and palmitate indicated that amino acids were not acting by providing substrates for energy metabolism. The stimulatory effect of amino acids on protein synthesis was associated with a facilitated rate of peptide-chain initiation as evidenced by a relative decrease in the level of ribosomal subunits. This response was not as great as that produced by insulin, and the amino acids did not augment the effect of insulin. Although protein synthesis in preparations from fed young rats (130±3 g) was stimulated by the addition of a mixture of the branched-chain amino acids (5×) to about the same extent as that observed in the fasted young rats, protein degradation was not affected. Furthermore, neither synthesis nor degradation were affected in preparations from fasted older rats (203±9 g) suggesting that the age and or nitritional state of the animal may influence the response of skeletal muscle to altered amino acid levels.
The present study was performed to test the hypothesis that orally administered essential amino acids, in combination with carbohydrate, will stimulate net muscle protein synthesis in resting human muscle in vivo. Four volunteers ingested 500 mL of a solution containing 13.4 g of essential amino acids and 35 g sucrose (EAA). Blood samples were taken from femoral arterial and venous catheters over a 2-hour period following the ingestion of EAA to measure arteriovenous concentrations of amino acids across the muscle. Two muscle biopsies were taken during the study, one before administration of the drink and one approximately 2 hours after consumption of EAA. Serum insulin increased from normal physiologic levels at baseline (9.2 +/- 0.8 microU/mL) and peaked (48 +/- 7.1 microU/mL) 30 minutes after EAA ingestion. Arterial essential amino acid concentrations increased approximately 100 to 400% above basal levels between 10 and 30 minutes following drink ingestion. Net nitrogen (N) balance changed from negative (-495 +/- 128 nmol/mL) prior to consumption of EAA to a peak positive value (416 +/- 140 nmol/mL) within 10 minutes of ingestion of the drink. EAA resulted in an estimated positive net N uptake of 307.3 mg N above basal levels over the 2-hour period. Muscle amino acid concentrations were similar prior to and 2 hours following ingestion of EAA. We conclude that ingestion of a solution composed of carbohydrates to stimulate insulin release and a small amount of essential amino acids to increase amino acid availability for protein synthesis is an effective stimulator of muscle protein anabolism.
Overtraining and long-term exercise are associated with an impairment of immune function. We provide evidence in support of the hypothesis that the supply of glutamine, a key fuel for cells of the immune system, is impaired in these conditions and that this may contribute to immunosuppression. Plasma glutamine concentration was decreased in overtrained athletes and after long-term exercise (marathon race) and was increased after short-term, high intensity exercise (sprinting). Branched chain amino acid supplementation during long-term exercise was shown to prevent this decrease in the plasma glutamine level. Overtraining was without effect on the rate of T-lymphocyte proliferation in vitro or on the plasma levels of interleukin-1 and -6, suggesting that immune function is not impaired in this condition. Given the proposed importance of glutamine for cells of the immune system, it is concluded that the decrease in plasma glutamine concentration in overtraining and following long-term exercise, and not an intrinsic defect in T lymphocyte function, may contribute to the immune deficiency reported in these conditions.
Rates of muscle protein synthesis were measured in vivo in tissues of post-absorptive young rats that were given intravenous infusions of various combinations of insulin and amino acids. In the absence of amino acid infusion, there was a steady rise in muscle protein synthesis with plasma insulin concentration up to 158 mu units/ml, but when a complete amino acids mixtures was included maximal rates were obtained at 20 mu units/ml. The effect of the complete mixture could be reproduced by a mixture of essential amino acids or of branched-chain amino acids, but not by a non-essential mixture, alanine, methionine or glutamine. It is concluded that amino acids, particularly the branched-chain ones, increase the sensitivity of muscle protein synthesis to insulin.
Twenty one healthy subjects were studied after an overnight fast. Muscle tissue obtained by needle biopsy from m. quadriceps femoris was homogenized and precipitated with 4% sulfosalicylic acid. The supernatant material was analyzed for 23 to 28 free amino acids by a modified Moore-Stein technique. Simultaneously obtained plasma samples were precipitated with 6% sulfosalicylic acid and in all other respects were treated in the same way. Extracellular water in the muscle was estimated using a modified chloride method. The extra cellular (EC) and intracellular (IC) concentration and the IC/EC gradient for each amino acid was calculated. The majority of the amino acids showed much higher concentration in intracellular water than in plasma. The concentration gradient was especially high for taurine, glutamic acid, and glutamine. Valine, leucine, isoleucine, phenylalanine, citrulline, and tyrosine had a concentration gradient below 2.0. The rest of the amino acids showed gradients between 5.0 and 10.0. The free amino acid pool in skeletal muscle tissue was calculated in a normal man weighing 70 kg to be 86.5 g without taurine and 121.5 g with taurine. Of the total pool of muscle free amino acids the 8 essential amino acids represent only 8.4%, whereas glutamine, glutamic acid and alanine constitute about 79%.
Mutations leading to ectopic expression of the murine agouti gene (a) result in progressive obesity. To further characterize this model, we analyzed adipose and hepatic mRNA levels for fatty acid synthase (FAS) and stearoyl-CoA desaturase (SCD), two key enzymes in de novo fatty acid synthesis and desaturation, respectively. FAS and SCD mRNA in both tissues of obese (Avy) mice were dramatically increased relative to lean (ala) controls. Excessive expression of these genes in this model could be due to direct effects of the agouti gene product; to test this possibility we treated 3T3-L1 adipocytes in vitro with recombinant agouti protein. Agouti treatment increased FAS and SCD mRNA levels by 1.5- and 4-fold, respectively. In addition, FAS activity and triglyceride content were 3-fold higher in agoutitreated 3T3-L1 cells relative to controls; these effects were attenuated by simultaneous treatment with a calcium channel blocker (nitrendipine). These data demonstrate that the agouti protein can directly increase lipogenesis in adipocytes and suggest that these effects are mediated through an intracellular calcium-dependent mechanism.
Enhanced intestinal permeability has been associated with gastrointestinal disorders in long-distance runners. The primary purpose of this study was to evaluate the effect of running intensity on small intestinal permeability by using the lactulose and rhamnose differential urinary excretion test. Secondary purposes included assessing the relationship between small intestinal permeability and gastrointestinal symptoms and evaluating gastric damage by using sucrose as a probe. Six healthy volunteers [5 men, 1 woman; age = 30 +/- 2 yr; peak O2 uptake (VO2peak) = 57.7 +/- 2.1 ml.kg-1.min-1] rested or performed treadmill exercise at 40, 60, or 80% VO2peak for 60 min in a moderate environment (22 degrees C, 50% relative humidity). At 30 min into rest or exercise, the permeability test solution (5 g sucrose, 5 g lactulose, 2 g rhamnose in 50 ml water, approximately 800 mosM) was ingested. Urinary excretion rates (6 h) of the lactulose-to-rhamnose ratio were used to assess small intestinal permeability, and concentrations of each probe were determined by using high-performance liquid chromatography. Running at 80% VO2peak increased (P < 0.05) small intestinal permeability compared with rest, 40, and 60% VO2peak with mean values expressed as percent recovery of ingested dose of 0.107 +/- 0.021 (SE), 0.048 +/- 0.009, 0.056 +/- 0.005, and 0.064 +/- 0.010%, respectively. Increases in small intestinal permeability did not result in a higher prevalence of gastrointestinal symptoms, and urinary recovery of sucrose did not reflect increased gastric permeability. The significance and mechanisms involved in increased small intestinal permeability after high-intensity running merit further investigation.
Exercise has a profound acute effect on protein metabolism. Whereas reports on whole body responses to exercise have varied results, it is generally agreed leucine oxidation is increased during exercise, thus indicating increased net protein breakdown. Following endurance exercise, whole body protein breakdown is generally reduced from resting levels, while following eccentric exercise, both whole body protein breakdown and leucine oxidation are increased. Whole body protein synthesis, on the other hand, is either increased or unchanged. Much of the disagreement in the results of studies on the response of whole body protein metabolism to exercise may be attributed to the limitations of the available methods. Even if the methodology accurately reflects whole body metabolism, this may not reflect changes in the protein metabolism of muscle. Although endurance exercise has not been studied, muscle protein breakdown is increased following resistance exercise. There is a concomitant, and qualitatively greater, increase in muscle protein synthesis following resistance exercise, which may last for as long as 48 h. Increased muscle protein synthesis is linked to increased intramuscular availability of amino acids, and thus, to increased blood flow and increased amino acid delivery to the muscle, as well as increased amino acid transport. Administration of exogenous amino acids after exercise increases protein synthesis while ameliorating protein breakdown, thus improving net muscle protein balance. While it is clear that muscle protein synthesis and protein breakdown increase in a qualitatively similar manner following exercise, the mechanisms of stimulation have yet to be determined. However, we propose that the intracellular availability of amino acids is the link between these processes.
The effect of dietary protein on the initiation of mRNA translation was examined in rats starved for 18 h and then fed isocaloric diets containing either 20% protein (20P) or no added protein (0P). Feeding the 20P diet, but not the 0P diet, stimulated protein synthesis in skeletal muscle and liver by 38 and 41%, respectively. The stimulation was associated with reduced binding of eukaryotic initiation factor (eIF) 4E to the translational repressor 4E-BP1, increased formation of the active eIF4E-eIF4G complex, and increased phosphorylation of 4E-BP1. In contrast, feeding a 0P diet had no effect on any of these parameters. Feeding a 20P diet resulted in partial dephosphorylation of eIF4E in both tissues. In liver, refeeding a 0P diet also resulted in partial eIF4E dephosphorylation, suggesting that the phosphorylation state of eIF4E is not important in the stimulation of protein synthesis under these conditions. Finally, plasma insulin concentrations were the same in rats fed either diet (14.8 +/- 4.9 vs. 15.5 +/- 4.5 microU/ml for 20P and 0P groups, respectively), suggesting that feeding-induced changes in plasma insulin are not sufficient to stimulate protein synthesis. Instead, a combination of dietary protein and insulin may be required to stimulate translation initiation.
Adequate protein nutrition could be used to limit gradual body protein loss and improve protein anabolism in the elderly.
We tested the hypothesis that an uneven protein feeding pattern was more efficient in improving protein anabolism than was an even pattern.
After a controlled period, 15 elderly women (mean age: 68 y) were fed for 14 d either a pulse diet (n = 7), providing 80% of the daily protein intake at 1200, or a spread diet (n = 8), in which the same daily protein intake was spread over 4 meals. Both diets provided 1.7 g protein x kg fat-free mass (FFM)(-1) x d(-1). Protein accretion and daily protein turnover were determined by using the nitrogen balance method and the end product method (ammonia and urea) after an oral dose of [15N]glycine.
Nitrogen balance was more positive with the pulse than with the spread diet (54 +/- 7 compared with 27 +/- 6 mg N x kg FFM(-1) x d(-1); P < 0.05). Protein turnover rates were also higher with the pulse than with the spread diet (5.58 +/- 0.22 compared with 4.98 +/- 0.17 g protein x kg FFM(-1) x d(-1); P < 0.05), mainly because of higher protein synthesis in the pulse group (4.48 +/- 0.19 g protein x kg FFM(-1) x d(-1)) than in the spread group (3.75 +/- 0.19 g protein x kg FFM(-1) x d(-1)) (P < 0.05).
A protein pulse-feeding pattern was more efficient than was a protein spread-feeding pattern in improving, after 14 d, whole-body protein retention in elderly women.
This study was designed to determine the response of muscle protein to the bolus ingestion of a drink containing essential amino acids and carbohydrate after resistance exercise. Six subjects (3 men, 3 women) randomly consumed a treatment drink (6 g essential amino acids, 35 g sucrose) or a flavored placebo drink 1 h or 3 h after a bout of resistance exercise on two separate occasions. We used a three-compartment model for determination of leg muscle protein kinetics. The model involves the infusion of ring-(2)H(5)-phenylalanine, femoral arterial and venous blood sampling, and muscle biopsies. Phenylalanine net balance and muscle protein synthesis were significantly increased above the predrink and corresponding placebo value (P < 0.05) when the drink was taken 1 or 3 h after exercise but not when the placebo was ingested at 1 or 3 h. The response to the amino acid-carbohydrate drink produced similar anabolic responses at 1 and 3 h. Muscle protein breakdown did not change in response to the drink. We conclude that essential amino acids with carbohydrates stimulate muscle protein anabolism by increasing muscle protein synthesis when ingested 1 or 3 h after resistance exercise.
Dietary protein quality is influenced by several factors and especially amino acid composition as well as the bioavailability of the protein. The method to assess the dietary protein quality recommended by the FAO/WHO (1985, 1990) is based on the ability of the protein to satisfy the indispensable amino acid requirements. The Protein Digestibility Corrected Amino Acid Score (PD-CAAS) has been proposed as a quality index and takes into account both the indispensable amino acid composition and the protein digestibility. This index can easily be used routinely, but some conceptual and methodological limits must be considered, such as the determination of both nitrogen and indispensable amino acid requirements, the bioavailability of dietary protein and the validation of the quality indexes. Another level in the evaluation of protein quality considers more specific activities related to specific protein-derived components. The compounds responsible for these activities include enzymes, immunoglobulins, mediator and hormone-like substances. These actions are linked to native proteins or to peptides cleaved from protein during digestion.
This study was undertaken to determine whether the protein feeding pattern could induce chronic adaptation of protein turnover. After a 15-day adaptive period, elderly (68 yr) and young (26 yr) women received, for 14 days, a diet providing 200 KJ x kg fat-free mass (FFM)(-1) x day(-1), where the daily protein intake (1.7 g protein x kg FFM(-1) x day(-1)) was either spread over 4 meals in the spread pattern or mainly (80%) consumed at noon in the pulse pattern. One day after the end of the dietary treatment, whole body leucine kinetics were measured by use of a continuous [(13)C]leucine infusion, both in the postabsorptive state and in the same fed state. The pulse pattern was able to induce, in young as in elderly women, a lower postabsorptive leucine oxidation and endogenous leucine flux than the spread pattern and improved the responsiveness of nonoxidative leucine disposal during 4-h oral feeding. Thus the pulse pattern was able to induce chronic regulation of protein metabolism in young as in elderly women.
The first approach used to study the utilization of nitrogen in the body was based on the measurement of nitrogen balance. Limitations to this method reside in the difficulty of precisely determining nitrogen losses and, more specifically, miscellaneous N losses. These shortcomings are particularly restrictive when investigating adaptation of the organism to different levels of protein intake. The principal issue is to gain a better understanding of the adaptive processes that occur with high protein intakes and the possibility of producing a net protein accretion by nutritional means in different situations. The investigation of protein metabolism in relation to dietary proteins, with a focus on the postprandial phase of nitrogen diurnal cycling, enables a clearer determination of the metabolic pathways for dietary nitrogen as a function of different factors, which include the habitual protein level and intrinsic protein characteristics. We propose that this in vivo approach in humans should be used to validate simpler indices of the nutritional value of proteins.
This study was undertaken to determine whether a pulse protein feeding pattern was more efficient than a spread pattern to improve protein anabolism in young women as was already shown in elderly women. After a 15-d adaptive period [1.2 g protein/(kg fat-free mass. d)], 16 young women (age 26 +/- 1 y) were given a 14-d diet providing 1.7 g protein/(kg fat-free mass. d), using either a pulse pattern (protein consumed mainly in one meal, n = 8), or a spread pattern (spreading daily protein intake over four meals, n = 8). Nitrogen balance was determined at the end of both the 15-d adaptive and the 14-d experimental periods. Whole-body protein turnover was determined at the end of the 14-d experimental period using [(15)N]glycine as an oral tracer. Nitrogen balance was 17 +/- 5 mg N/(kg fat-free mass. d) during the adaptive period. It was higher during the experimental period, but not significantly different in the women fed the spread or the pulse patterns [59 +/- 12 and 36 +/- 8 mg N/(kg fat-free mass. d) respectively]. No significant effects of the protein feeding pattern were detected on either whole-body protein turnover [5.5 +/- 0.2 vs. 6.1 +/- 0.3 g protein/(kg fat-free mass. d) for spread and pulse pattern, respectively] or whole-body protein synthesis and protein breakdown. Thus, in young women, these protein feeding patterns did not have significantly different effects on protein retention.
There is considerable debate about the human lysine requirement and the consequent nutritional value of wheat protein.
We used a novel [1-(13)C]leucine balance protocol to examine whether adaptive mechanisms to conserve lysine allow wheat to be utilized more efficiently than expected according to current estimates of lysine requirements and wheat utilization.
Wheat and milk proteins were compared in 6 adults infused for 9 h with L-[1-(13)C]leucine in the postabsorptive state (0-3 h), who were fed half-hourly with low-protein (2% of energy, 3-6 h) and isoenergetic higher-protein (12-13% of energy, 6-9 h) meals providing maintenance energy intakes. From acute measurements of [1-(13)C]leucine balance, we predicted nitrogen balance, the metabolic demand for protein, the efficiency of postprandial protein utilization (PPU), and the requirements for wheat protein and lysine.
Leucine balance was higher after the milk than after the wheat feeding because of the greater inhibition of proteolysis by milk. PPU, calculated as the ratio of Deltanitrogen balance to Deltanitrogen intake between the low-protein and higher-protein periods, was 0.68 +/- 0.06 for wheat and 1.00 +/- 0.09 for milk (P </= 0.001). The estimated average wheat protein requirement (0. 6/PPU) was 0.89 +/- 0.08 g*kg(-)(1)*d(-)(1), indicating a lysine requirement of 23.2 +/- 2.0 mg*kg(-)(1)*d(-)(1). The measured PPU for wheat, 0.68 +/- 0.06, was higher than the value calculated from wheat lysine intake and milk protein lysine deposition, 0.26 +/- 0. 02, and higher than predicted by most published estimates of lysine requirements, apart from a value of 19 mg/kg indicated by nitrogen balance studies.
The results show that adaptive mechanisms of lysine conservation allow wheat protein to be utilized more efficiently than expected.
Anecdotal, survey, and epidemiological data suggest that endurance athletes are at an increased risk for upper respiratory tract infection (URTI) during periods of heavy training and the 1 - to 2-wk period after race events. The majority of athletes, however, who participate in endurance race events do not experience illness. Of greater public health importance is the consistent finding of a reduction in URTI risk reported by fitness enthusiasts and athletes who engage in regular exercise training while avoiding overreaching/overtraining. Although it naturally follows that infection risk should in some way be linked to acute and chronic exercise-induced alterations in immunity, attempts thus far to measure this association have been unsuccessful. There is growing evidence that for several hours subsequent to heavy exertion, several components of both the innate and adaptive immune system exhibit suppressed function. The immune response to heavy exertion is transient, however, and further research on the mechanisms underlying the immune response to prolonged and intensive endurance exercise is necessary before meaningful clinical applications can be drawn. Some attempts have been made through chemical or nutritional means (e.g., indomethacin, glutamine, vitamin C, and carbohydrate supplementation) to attenuate immune changes after intensive exercise to lower the risk of infection. No consistent relationship between nutritional interventions, exercise immunology, and alteration in URTI risk has yet been established.
Active persons ingest protein supplements primarily to promote muscle strength, function, and possibly size. Currently, it is not possible to form a consensus position regarding the benefit of protein or amino acid supplements in exercise training. Determination of whether supplements are beneficial has been hampered by the failure to select appropriate endpoints for evaluation of a positive effect. Furthermore, studies focused at a more basic level have failed to agree on the response of protein metabolism to exercise. An additional complication of dietary studies that is not often taken into account is amount of energy intake. Because of these and other complications, studies at the whole body level have not yielded a clear picture of the need for, or response to, dietary protein or amino acid supplements. Consequently, it is necessary to examine this issue at the tissue level. In untrained subjects, both muscle protein breakdown and synthesis are increased in response to exercise. Amino acid intake further stimulates muscle protein synthesis after exercise as a consequence of stimulating amino acid transport into the intramuscular compartment. The stimulatory effect of amino acids after exercise is greater than the effect of amino acids on muscle protein synthesis when given at rest. These data suggest that not only may the exact composition and amount of an amino acid supplement be important, but the timing of ingestion of the supplement in relation to the exercise must be considered in designing future studies to evaluate the efficacy of amino acid supplements.
Both physical activity and diet stimulate processes that, over time, alter the morphologic composition and biochemical function of the body. Physical activity provides stimuli that promote very specific and varied adaptations according to the type, intensity, and duration of exercise performed. There is further interest in the extent to which diet or supplementation can enhance the positive stimuli. Prolonged walking at low intensity presents little metabolic, hormonal, or cardiovascular stress, and the greatest perturbation from rest appears to be from increased fat oxidation and plasma free fatty acid mobilization resulting from a combination of increased lipolysis and decreased reesterification. More intense jogging or running largely stimulates increased oxidation of glycogen and triacylglycerol, both of which are stored directly within the muscle fibers. Furthermore, these intramuscular stores of carbohydrate and fat appear to be the primary substrates for the enhanced oxidative and performance ability derived from endurance training-induced increases in muscle mitochondrial density. Weightlifting that produces fatigue in brief periods (ie, in 15-90 s and after 15 repetitive contractions) elicits a high degree of motor unit recruitment and muscle fiber stimulation. This is a remarkably potent stimulus for altering protein synthesis in muscle and increasing neuromuscular function. The metabolic stress of physical activity can be measured by substrate turnover and depletion, cardiovascular response, hormonal perturbation, accumulation of metabolites, or even the extent to which the synthesis and degradation of specific proteins are altered, either acutely or by chronic exercise training.
Five clinical studies of calcium intake, designed with a primary skeletal end point, were reevaluated to explore associations between calcium intake and body weight. All subjects were women, clustered in three main age groups: 3rd, 5th, and 8th decades. Total sample size was 780. Four of the studies were observational; two were cross-sectional, in which body mass index was regressed against entry level calcium intake; and two were longitudinal, in which change in weight over time was regressed against calcium intake. One study was a double-blind, placebo-controlled, randomized trial of calcium supplementation, in which change in weight during the course of study was evaluated as a function of treatment status. Significant negative associations between calcium intake and weight were found for all three age groups, and the odds ratio for being overweight (body mass index, >26) was 2.25 for young women in the lower half of the calcium intakes of their respective study groups (P: < 0.02). Relative to placebo, the calcium-treated subjects in the controlled trial exhibited a significant weight loss across nearly 4 yr of observation. Estimates of the relationship indicate that a 1000-mg calcium intake difference is associated with an 8-kg difference in mean body weight and that calcium intake explains approximately 3% of the variance in body weight.
HIV infection is characterized by an enhanced oxidant burden and a systemic deficiency of the tripeptide glutathione (GSH), a major antioxidant. The semi‐essential amino acid cysteine is the main source of the free sulfhydryl group of GSH and limits its synthesis. Therefore, different strategies to supplement cysteine supply have been suggested to increase glutathione levels in HIV‐infected individuals. The aim of this study was to evaluate the effect of oral supplementation with two different cysteine‐rich whey protein formulas on plasma GSH levels and parameters of oxidative stress and immune status in HIV‐infected patients.
In a prospective double blind clinical trial, 30 patients (25 male, 5 female; mean age (± SD) 42 ± 9·8 years) with stable HIV infection (221 ± 102 CD4 + lymphocytes L ⁻¹ ) were randomized to a supplemental diet with a daily dose of 45 g whey proteins of either Protectamin (Fresenius Kabi, Bad Hamburg, Germany) or Immunocal (Immunotec, Vandreuil, Canada) for two weeks. Plasma concentrations of total, reduced and oxidized GSH, superoxide anion (O2–) release by blood mononuclear cells, plasma levels of TNF‐α and interleukins 2 and 12 were quantified with standard methods at baseline and after therapy.
Pre‐therapy, plasma GSH levels (Protectamin: 1·92 ± 0·6 μM; Immunocal: 1·98 ± 0·9 μM) were less than normal (2·64 ± 0·7 μM, P = 0·03). Following two weeks of oral supplementation with whey proteins, plasma GSH levels increased in the Protectamin group by 44 ± 56% (2·79 ± 1·2 μM, P = 0·004) while the difference in the Immunocal group did not reach significance (+ 24·5 ± 59%, 2·51 ± 1·48 μM, P = 0·43). Spontaneous O 2 – release by blood mononuclear cells was stable (20·1 ± 14·2 vs. 22·6 ± 16·1 nmol h ⁻¹ 10 ⁻⁶ cells, P = 0·52) whereas PMA‐induced O 2 – release decreased in the Protectamin group (53·7 ± 19 vs. 39·8 ± 18 nmol h ⁻¹ 10 ⁻⁶ cells, P = 0·04). Plasma concentrations of TNF‐α and interleukins 2 and 12 ( P > 0·08, all comparisons) as well as routine clinical parameters remained unchanged. Therapy was well tolerated.
In glutathione‐deficient patients with advanced HIV‐infection, short‐term oral supplementation with whey proteins increases plasma glutathione levels. A long‐term clinical trial is clearly warranted to see if this ‘biochemical efficacy’ of whey proteins translates into a more favourable course of the disease.
Relationships between micronutrients and dairy product intake and changes in body weight and composition over two years were investigated.
Two year prospective non-concurrent analysis of the effect of calcium intake on changes in body composition during a two year exercise intervention.
54 normal weight young women, 18 to 31 years of age.
Mean intakes of nutrients of interest were determined from three-day diet records completed at baseline and every six months for two years. The change in total body weight and body composition (assessed by dual x-ray absorptiometry) from baseline to two years was also determined.
Total calcium/kilocalories and vitamin A together predicted (negatively and positively, respectively) changes in body weight (R2 = 0.19) and body fat (R2 = 0.27). Further, there was an interaction of calcium and energy intake in predicting changes in body weight, such that, only at lower energy intakes, calcium intake (not adjusted for energy) predicted changes in body weight.
Regardless of exercise group assignment, calcium adjusted for energy intake had a negative relationship and vitamin A intake a positive relationship with two year changes in total body weight and body fat in young women aged 18 to 31 years. Thus, subjects with high calcium intake, corrected by total energy intake, and lower vitamin A intake gained less weight and body fat over two years in this randomized exercise intervention trial.
The milk protein, caseinomacropeptide (CMP), is a predominant breakdown product of casein in the human stomach, and may aid in the regulation of food intake. Using a human feeding study design, this project assessed the effects of CMP on satiety and satiation by measuring the amount of food consumed at meal times and through subjective motivation to eat questionnaires. The following beverage treatments were prepared: 0.4% CMP solution, 2.0% CMP solution, vehicle alone, and water containing colorant and clouding agent. Twenty male and 32 female adults were enrolled into the study using a Latin Square randomization. Treatment beverages and ad libitum lunches were consumed on four separate occasions at the Study Center. After lunch, subjects left the Study Center, and completed a standardized questionnaire every hour throughout the afternoon and evening to assess hunger and stomach fullness, and kept track of all food and beverages consumed. Under these experimental conditions, CMP had no effect on energy intake or weight of food consumed at lunch or for the remainder of the day. CMP also had no effect on subjective indicators of satiety. Intake of CMP before a midday meal has no effect on regulation of food intake over a short-term period.
There is increasing commercial interest in the production of functional foodstuffs which have health-promoting properties. Over the last five to ten years, significant progress has been made in the identification and characterisation of bovine milk components that can affect the function of the immune system. This review outlines the major components of bovine milk that have been shown to modulate immune function, and discusses experimental approaches to the identification of various facets of the immune response that are known to be affected by milk-derived proteins.
Milk contains various components with physiological functionality. Peptides derived from caseins and whey proteins including opioid peptides, antihypertensive peptides, casein phosphopeptides, alpha- and beta-lactorphins and albutensin have been shown to possess various bioactive properties. This review considers an overview of the bioactive components in milk proteins and whey and their physiological function.
1. The aim of this study was to describe the time course of the response of human muscle protein synthesis (MPS) to a square wave increase in availability of amino acids (AAs) in plasma. We investigated the responses of quadriceps MPS to a approximately 1.7-fold increase in plasma AA concentrations using an intravenous infusion of 162 mg (kg body weight)(-1) h(-1) of mixed AAs. MPS was estimated from D3-leucine labelling in protein after a primed, constant intravenous infusion of D3-ketoisocaproate, increased appropriately during AA infusion. 2. Muscle was separated into myofibrillar, sarcoplasmic and mitochondrial fractions. MPS, both of mixed muscle and of fractions, was estimated during a basal period (2.5 h) and at 0.5-4 h intervals for 6 h of AA infusion. 3. Rates of mixed MPS were not significantly different from basal (0.076 +/- 0.008 % h(-1)) in the first 0.5 h of AA infusion but then rose rapidly to a peak after 2 h of approximately 2.8 times the basal value. Thereafter, rates declined rapidly to the basal value. All muscle fractions showed a similar pattern. 4. The results suggest that MPS responds rapidly to increased availability of AAs but is then inhibited, despite continued AA availability. These results suggest that the fed state accretion of muscle protein may be limited by a metabolic mechanism whenever the requirement for substrate for protein synthesis is exceeded.
To assess preschool children's food consumption (24-60 months) and relate these findings to body composition at 70+/-2 months.
A longitudinal study of children's dietary intakes for selected nutrients and servings of dairy products.
Fifty-three white children participating in a longitudinal study (2-96 months) of children's food practices and growth.
Using in-home interviews and trained interviewers, 18 days of dietary data and measured height and weight of each child at 6 month intervals were collected. Body composition was determined by dual energy X-ray absorptiometry.
Dietary fat was 30-33% of energy with saturated and monounsaturated fat intakes>10% and polyunsaturated<10%. Adjusting for body mass index (BMI), GLM models to predict percent body fat (%BF) or grams of total fat (gTF) with mean longitudinal calcium intake (%BF: R2=0.51, F=7.88, P<0.0001; gTF: R2=0.51, F=9.84, P=0.0001) or total servings of dairy products (%BF: R2=0.47, F=6.93, P<0.0001; gTF: R2=0.47, F=8.31, P<0.0001) as independent variables gave significant results. Higher mean longitudinal calcium (mg/day) intakes and more servings/day of dairy products were associated with lower body fat. Males had significantly less body fat (P=0.01) than females.
Higher longitudinal intakes of calcium, monounsaturated fat, and servings of dairy products were associated with lower body fat.
Glutamine is a nonessential amino acid that can be synthesized from glutamate and glutamic acid by glutamate-ammonia ligase. Glutamine is an important fuel source for the small intestine. It was proposed that glutamine is necessary for the maintenance of normal intestinal morphology and function in the absence of luminal nutrients. However, intestinal morphologic and functional changes related to enteral fasting and parenteral nutrition are less significant in humans than in animal models and may not be clinically significant. Therefore, it is unclear whether glutamine is necessary for the preservation of normal intestinal morphology and function in humans during parenteral nutrition. It was suggested that both glutamine-supplemented parenteral nutrition and enteral diets may pre-vent bacterial translocation via the preservation and augmentation of small bowel villus morphology, intestinal permeability, and intestinal immune function. However, it is unclear whether clinically relevant bacterial translocation even occurs in humans, much less whether there is any value in the prevention of such occurrences. Results of the therapeutic use of glutamine in humans at nonphysiologic doses indicate limited efficacy. Although glutamine is generally recognized to be safe on the basis of relatively small studies, side effects in patients receiving home parenteral nutrition and in those with liver-function abnormalities have been described. Therefore, on the basis of currently available clinical data, it is inappropriate to recommend glutamine for therapeutic use in any condition.
We reported recently that suppression of the renal 1 alpha ,25-dihyroxyvitamin D-3 (1 alpha ,25-(OH)(2)-D-3) production in aP2-agouti transgenic mice by increasing dietary calcium decreases adiposity. However, it was not clear whether this modulation of adipocyte metabolism by dietary calcium is a direct effect of inhibition of 1 alpha ,25-(OH)(2)-D-3-induced [Ca2+]i. Accordingly, we have now evaluated the direct role of 1 alpha ,25-(OH)(2)-D-3. Human adipocytes exhibited a 1 alpha ,25-(OH)(2)-D-3 dose-responsive (1-50 nM) increase in [Ca2+]i (P<0.01). This action was mimicked by 1 ,25-dihydroxyluministerol(3) (1 alpha ,25-(OH)(2)-lumisterol(3)) (P<0.001), a specific agonist for a putative membrane vitamin D receptor (mVDR), and completely prevented by 1 ,25-dihydroxyvitamin D-3 (1 beta ,25-(OH)(2)-D-3), a specific antagonist for the mVDR. Similarly, 1 alpha ,25-(OH)(2)-D-3 (5 mM) caused 50%-100% increases in adipocyte fatty acid synthase (FAS) expression and activity (P<0.02), 61% increase in glycerol-3-phosphate dehydrogenase (GPDH) activity (P<0.01), and an 80% inhibition of isoproterenol-stimulated lipolysis (P<0.001), whereas 1 ,25-(OH)(2)-D-3 completely blocked all these effects. Notably, 1 alpha ,25-OH)(2)-lumisterol(3) exerted more potent effects in modulating adipocyte lipid metabolism, with 2.5- to 3.0-fold increases in FAS expression and activity (P<0.001) and a threefold increase in GPDH activity (P<0.001). Also 1 alpha ,25-(OH)(2)-lumisterol3 was approximately twice as potent in inhibiting basal lipolysis (P<0.025), whereas 1 ,25-(OH)(2)-D-3 completely blocked all these effects. These data suggest that 1 alpha ,25-(OH)(2)-D-3 modulates adipocyte Ca2+ signaling and, consequently, exerts a coordinated control over lipogenesis and lipolysis. Thus, a direct inhibition of 1 alpha ,25-(OH)(2)-D-3-induced [Ca2+](i) may contribute to an anti-obesity effect of dietary calcium, and the mVDR may represent an important target for obesity.
Strenuous prolonged exertion and heavy training are associated with depressed immune function. Furthermore, improper nutrition can compound the negative influence of heavy exertion on immunocompetence. Dietary deficiencies of protein and specific micronutrients have long been associated with immune dysfunction. An adequate intake of iron, zinc, and vitamins A, E, B6 and B12 is particularly important but excess intakes can also impair immune function. Immune system impairment has also been associated with excess intake of fat. To maintain immune function, athletes should eat a well balanced diet sufficient to meet their energy requirements. An athlete exercising in a carbohydrate-depleted state experiences larger increases in circulating stress hormones and a greater perturbation of several immune function indices. Conversely, consuming carbohydrate during exercise attenuates rises in stress hormones such as cortisol and appears to limit the degree of exercise-induced immunosuppression, at least for non-fatiguing bouts of exercise. Strong evidence that high doses of antioxidant vitamins, glutamine supplementation or echinacea extracts can prevent exercise-induced immunosuppression is lacking.
Exercise increases the use of amino acids for glucose production and stimulates the oxidation of amino acids and other substrates to provide ATP for muscular contraction, and thus the availability of amino acids and energy for postexercise muscle protein synthesis may be limiting. The purpose of this study was to determine the potential of postexercise nutrient intake to enhance the recovery of whole-body and skeletal muscle protein homeostasis in humans.
Primed-continuous infusions of L-[1-13C]leucine and L-[ring-2H5]phenylalanine were initiated in the antecubital vein and blood was sampled from a femoral vein and a heated (arterialized) hand vein. Each study consisted of a 30-min basal, a 60-min exercise (bicycle at 60% VO2max), and a 180-min recovery period. Five men and five women were studied three times with an oral supplement administered immediately following exercise in random order: NO = 0, 0, 0; SUPP = 0, 8, 3; or SUPP+PRO = 10, 8, 3 g of protein, carbohydrate, and lipid, respectively.
Compared to NO, SUPP did not alter leg or whole-body protein homeostasis during the recovery period. In contrast, SUPP+PRO increased plasma essential amino acids 33%, leg fractional extraction of phenylalanine 4-fold, leg uptake of glucose 3.5-fold, and leg and whole-body protein synthesis 6-fold and 15%, respectively. Whereas postexercise intake of either NO or SUPP resulted in a net leg release of essential amino acids and net loss of whole-body and leg protein, SUPP+PRO resulted in a net leg uptake of essential amino acids and net whole-body and leg protein gain.
These findings suggest that the availability of amino acids is more important than the availability of energy for postexercise repair and synthesis of muscle proteins.
A continuous supply of a complete complement of essential amino acids is a prerequisite for maintenance of optimal rates of protein synthesis in both liver and skeletal muscle. Deprivation of even a single essential amino acid causes a decrease in the synthesis of essentially all cellular proteins through an inhibition of the initiation phase of mRNA translation. However, the synthesis of all proteins is not repressed equally. Specific subsets of proteins, in particular those encoded by mRNAs containing a 5'-terminal oligopyrimidine (TOP) motif, are affected to a much greater extent than most proteins. The specific decrease in TOP mRNA translation is a result of an inhibition of the ribosomal protein S6 kinase, S6K1, and a concomitant decline in S6 phosphorylation. Interestingly, many TOP mRNAs encode proteins involved in mRNA translation, such as elongation factors eEF1A and eEF2, as well as the ribosomal proteins. Thus, deprivation of essential amino acids not only directly and rapidly represses global mRNA translation, but also potentially results in a reduction in the capacity to synthesize protein.
We review evidence regarding the influence of dietary fat, fiber, the glycemic index and sugar on energy intake and body weight. Although data from comprehensive long-term studies are lacking, published investigations suggest that the previous focus on lowering dietary fat as a means for promoting negative energy balance has led to an underestimation of the potential role of dietary composition in promoting reductions in energy intake and weight loss. More randomized clinical trials are needed to examine the relative utility of different putative dietary factors in the treatment of obesity.