Leucine

Research Update: Protein and Body Composition
Fitness Management (May 2008)
Over the past few years, a considerable amount of research has been published related to protein supplementation and muscle/strength development. [2, 6, 10, 12] Recent work has documented significantly greater gains in muscle mass and strength when protein is ingested in close time proximity to a resistance-training session. [4, 7] In a 12-week study conducted with previously untrained men, researchers examined the effects of consuming supplemental protein immediately after versus two hours after a strength-training session. Those who consumed protein immediately after their workout gained significantly more muscle size and strength than those who consumed it two hours removed from their workout.

Athletes: Amino Acids Speed Muscle Recovery
Healthnotes Newswire (3-09-2006)
Supplementing with a mixture of amino acids may lead to quicker muscle recovery after exercise and could reduce muscle damage caused by strenuous exercise, reports the Journal of Nutrition. The new study reviewed trials that used an amino acid combination (branched-chain amino acids or BCAAs— including leucine, isoleucine, and valine) over long periods of time to determine its effects on muscle strength and recovery after exercise, and its ability to prevent muscle damage caused by intense exercise. All of the studies used an amino acid mixture containing 14% glutamine, 14% arginine, 30% BCAAs, and seven other amino acids.

Muscle Protein Anabolism In Type 2 Diabetes
Current Opinion in Clinical Nutrition and Metabolic Care 2013 (Jan); 16 (1): 83–88
Muscle protein anabolism in T2DM is resistant to the action of insulin but perhaps not to amino acid supply or exercise. Whether leucine supplementation improves muscle mass and function in persons with T2DM (especially elderly) with reduced protein intake or muscle mass needs to be determined.

Leptin and Leucine Synergistically Regulate Protein Metabolism
in C2C12 Myotubes and Mouse Skeletal Muscles
British Journal of Nutrition. 2012 (Dec 5): 1–9 [Epub ahead of print]
Leucine and leptin play important roles in regulating protein synthesis and degradation in skeletal muscles in vitro and in vivo. However, the objective of the present study was to determine whether leptin and leucine function synergistically in regulating protein metabolism of skeletal muscles.

Co-ingestion of Protein and Leucine Stimulates Muscle Protein
Synthesis Rates to the Same Extent in Young and
Elderly Lean Men
American Journal of Clinical Nutrition 2006 (Sep); 84 (3): 623–632
The progressive loss of skeletal muscle mass with aging is attributed to a disruption in the regulation of skeletal muscle protein turnover.

Potential Importance of Leucine in Treatment of
Obesity and the Metabolic Syndrome
J Nutr. 2006 (Jan); 136 (1 Suppl): 319S–323S ~ FULL TEXT
Whereas total protein is important in providing substrates for gluconeogenesis, leucine appears to regulate oxidative use of glucose by skeletal muscle through stimulation of glucose recycling via the glucose-alanine cycle. These mechanisms produce protein sparing and provide a stable glucose environment with low insulin responses during energy-restricted periods.

Weight Loss Without Losing Muscle Mass in Pre-obese and
Obese Subjects Induced by a High-soy-protein Diet
Int J Obes Relat Metab Disord. 2004 (Oct); 28 (10): 1349–1352 ~ FULL TEXT
This is the first study that evaluates a soy-protein-enriched diet used in different weight reduction programmes with respect to changes in body composition. The simple measurement of body weight is not satisfactory any more, as muscle mass is determining the resting metabolic rate as well as motor competence and daily activity-induced energy expenditure. Therefore, muscle mass changes may be a parameter for long-term efficacy of a dietary programme. The described soy-protein-enriched diet limited in carbohydrates and fat is easy to follow, and apparently more effective in losing fat and preserving muscle mass than a conventional diet.

Dietary Protein Impact on Glycemic Control
During Weight Loss
The Journal of Nutrition 2004 (Apr); 134 (4): 968S–73S
A key element in the diet appears to be the higher intake of BCAA leucine with unique regulatory actions on muscle protein synthesis, modulation of the insulin signal, and sparing of glucose use by stimulation of the glucose-alanine cycle. This review focuses on the contributions of leucine and the BCAA to regulation of muscle protein synthesis and glycemic control.

The Role of Leucine in Weight Loss Diets
and Glucose Homeostasis
The Journal of Nutrition 2003 (Jan); 133 (1): 261S–267S
The branched-chain amino acid leucine is an example of an amino acid with numerous metabolic roles that function in proportion with cellular concentration. This review provides an overview of the current understanding of metabolic roles of leucine and proposes a metabolic framework to evaluate the merits of a higher protein diet for weight loss.