Leucine as a pharmaconutrient in health and disease.
ABSTRACT 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.
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ABSTRACT: Aging is associated with many physiological changes, which may in time lead to numerous pathophysiological outcomes, including adverse vascular events. For example, senescence of the immune system and cellular senescence both contribute to rising inflammation with age, potentially induced by the overall burden of comorbid illness, adipose tissue mass, diet, socioeconomic status, and physical activity. In turn, this chronic inflammation decreases physical and cognitive performance, and promotes sarcopenia and the syndrome of frailty. These events and others decrease the functionality of life as we age and include an increased risk of thrombosis and adverse cardiovascular outcomes. In this review, we aim to overview the aging process primarily as related to functional impairment, and provide evidence for the role of protein, and specifically differential quality protein, in particular whey protein, and timing and distribution of intake, to help reduce some of the morbid effects of aging, including reducing obesity, improving glycemic control, and improving vascular function.Seminars in Thrombosis and Hemostasis 08/2014; 40(6). DOI:10.1055/s-0034-1389081 · 3.69 Impact Factor
Chapter: Milk proteins and human healthMILK 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;
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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; 11:38. DOI:10.1186/1743-7075-11-38 · 3.36 Impact Factor