Leucine as a pharmaconutrient in health and disease.
OBJECTIVE
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands. L.vanLoon@maastrichtuniversity.nl
Luc J C
LJ
van Loon
D000596:Amino Acids / Q000494:pharmacology / Q000627:therapeutic use; D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000517:prevention & control*; D019587:Dietary Supplements; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology / Q000627:therapeutic use; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007930:Leucine / Q000494:pharmacology* / Q000627:therapeutic use; D009124:Muscle Proteins / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D055948:Sarcopenia / Q000378:metabolism / Q000517:prevention & control*
D000596:Amino Acids; D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D009124:Muscle Proteins; D012333:RNA, Messenger; D007930:Leucine