Leucine as a pharmaconutrient in health and disease
Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
Current opinion in clinical nutrition and metabolic care
01/2012; 15(1):71-7. DOI: 10.1097/MCO.0b013e32834d617a
Amino acids do not merely represent precursors for de-novo protein synthesis, but also function as nutritional signals regulating various metabolic processes. In fact, ample evidence has been generated to show that various tissues respond to changes in amino acid availability via signal transduction pathways that are also regulated by hormones such as insulin, glucagon, and insulin-like growth factor 1.
Amino acids, and leucine in particular, can act as strong insulin secretagogues when administered in combination with carbohydrate. Leucine administration can be applied effectively to improve postprandial glycemic control. Furthermore, amino acids have been shown to stimulate mRNA translation, thereby increasing muscle protein synthesis and stimulating net protein accretion in an insulin-independent manner. These anabolic properties of amino acids have been mainly attributed to the essential amino acids, and leucine in particular. In accordance, the recent in-vivo human studies show that leucine ingestion can augment the blunted muscle protein synthetic response to protein or amino acid ingestion in elderly men.
Leucine has been proposed as a promising pharmaconutrient in the prevention and treatment of sarcopenia and/or type 2 diabetes. Though there are numerous applications for the proposed benefits of leucine in health and disease, the recent long-term nutritional intervention studies do not confirm the clinical efficacy of leucine as a pharmaconutrient.
Available from: Sze Yen Tan
- "Since the subjects in this study were healthy, one of these roles may be the stimulation of muscle protein synthesis. The relative high abundance of leucine in whey with α-lactalbumin protein may be beneficial to stimulate muscle protein synthesis . "
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ABSTRACT: BackgroundProtein quality evaluation aims to determine the capacity of food sources and diets to meet protein and indispensable amino acid (IAA) requirements. This study determined whether nitrogen balance was affected and whether dietary IAA were adequately obtained from the ad libitum consumption of diets at three levels of protein from different primary sources for 12 days.MethodsTwo 12-day randomized crossover design trials were conducted in healthy subjects [n = 70/67 (M/F); age: 19-70 y; BMI: 18.2-38.7 kg/m2]. The relative dietary protein content was lower than [5% of energy (En%)], similar to (15En%), and higher than (30En%) customary diets. These diets had a limited variety of protein sources, containing wheat protein as a single protein source (5En%-protein diet) or 5En% from wheat protein with 10En% (15En%-protein diets) or 25En% (30En%-protein diets) added from whey with α-lactalbumin, soy or beef protein.ResultsThere was a dose-dependent increase in nitrogen excretion with increasing dietary protein content, irrespective of the protein sources (P = 0.001). Nitrogen balance was maintained on the 5En%-protein diet, and was positive on the 15En%- and 30En%-protein diets (P < 0.001) over 12 days. Protein intake from the 5En%-protein diet did not reach the amount necessary to meet the calculated minimal IAA requirements, but IAA were sufficiently obtained from the 15En%- and 30En%-protein diets. In the 15En%- and 30En%-protein conditions, a higher protein intake from the soy-containing diets than from the whey with α-lactalbumin or beef containing diets was needed to meet the minimal IAA requirements.ConclusionProtein intake did not compensate for an insufficient indispensable amino acid intake with a low-protein diet for 12 days.Trial registrationThese trials were registered at clinicaltrials.gov as NCT01320189 and NCT01646749.
Nutrition & Metabolism 08/2014; 11(1):38. DOI:10.1186/1743-7075-11-38 · 3.26 Impact Factor
Available from: Robin Mcgregor
- "However, whey protein contains a greater amount of the BCAAs leucine, isoleucine, and valine than does casein. Of the BCAAs, leucine is thought to be the most potent activator of protein synthesis (Katsanos et al., 2006; van Loon, 2012), although a recent study has shown that high levels of nonleucine BCAAs can induce equivalent protein synthesis when given with a whey protein supplement (Churchward-Venne et al., 2012). Casein in turn contains several essential amino acids (EAAs), including histine, methionine, and phenylalanine in a greater amount than whey protein, and also contains a greater amount of the non-EAAs arginine, glutamic acid, proline, serine, and tyrosine (Hall et al., 2003). "
MILK PROTEINS: FROM EXPRESSION TO FOOD, 2nd edited by H Singh, M Boland, A Thompson, 01/2014: chapter Milk proteins and human health: pages 541-555;
Available from: Robin Mcgregor
- "The effectiveness of whey protein in conjunction with dietary advice to improve adiposity and lean body mass in addition to body weight per se has been assessed in several studies. Whey protein is well established as a driver of skeletal muscle anabolism, with its constituent BCAAs such as leucine driving greater protein synthesis [119,120]. As such, a high dairy protein diet may enhance metabolic health through maintenance of lean body mass during weight loss. "
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ABSTRACT: Epidemiological evidence shows that consumption of dairy products is associated with decreased prevalence of metabolic related disorders, whilst evidence from experimental studies points towards dairy protein as a dietary component which may aid prevention of type 2 diabetes (T2DM). Poor metabolic health is a common characteristic of overweight, obesity and aging, and is the forerunner of T2DM and cardiovascular disease (CVD), and an ever increasing global health issue. Progressive loss of metabolic control is evident from a blunting of carbohydrate, fat and protein metabolism, which is commonly manifested through decreased insulin sensitivity, inadequate glucose and lipid control, accompanied by a pro-inflammatory environment and hypertension. Adverse physiological changes such as excess visceral adipose tissue deposition and expansion, lipid overspill and infiltration into liver, muscle and other organs, and sarcopaenia or degenerative loss of skeletal muscle mass and function all underpin this adverse profile. 'Sarcobesity' and sarcopaenic diabetes are rapidly growing health issues. As well as through direct mechanisms, dairy protein may indirectly improve metabolic health by aiding loss of body weight and fat mass through enhanced satiety, whilst promoting skeletal muscle growth and function through anabolic effects of dairy protein-derived branch chain amino acids (BCAAs). BCAAs enhance muscle protein synthesis, lean body mass and skeletal muscle metabolic function. The composition and processing of dairy protein has an impact on digestion, absorption, BCAA kinetics and function, hence the optimisation of dairy protein composition through selection and combination of specific protein components in milk may provide a way to maximize benefits for metabolic health.
Nutrition & Metabolism 07/2013; 10(1):46. DOI:10.1186/1743-7075-10-46 · 3.26 Impact Factor
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