| Leucine: The Anabolic Amino by Jason Budsock, Product Manager |
 The branched chained amino acids (BCAA's) are aptly name because they have a carbon chain which deviates or branches off from the main linear carbon backbone. There are three BCAA's-leucine, isoleucine, and valine. Of these three, leucine appears to be the most important. Several studies indicate that leucine acts as the amino acid that regulates protein metabolism. Leucine is the key amino acid that stimulates protein synthesis and decreases protein breakdown. Let's see why leucine is such an important amino acid. During exercise, protein synthesis decreases, while protein breakdown increases. Although muscle protein synthesis is stimulated during the post-exercise recovery phase, net muscle protein balance remains negative in the absence of macronutrient intake. In the past, studies have shown that whey protein and carbs were needed to stimulate protein synthesis and bring protein degradation to a halt. But recent research now shows that there is an even more efficient way to increase protein sythesis. What's the ticket, you ask? Well, it's the addition of leucine to the mix. Leucine increases muscle protein synthesis to an even greater degree than a mixture of whey protein and carbohydrates or carbohydrates alone. It appears that leucine works directly at the genetic level through non-hormonal means-via translation initiation in skeletal muscle. Leucine's effect on mTOR is synergistic with insulin via the phosphoinositol 3-kinase signaling pathway. Together, insulin and leucine allow skeletal muscle to coordinate protein synthesis with physiological state and dietary intake.1 Leucine has also been shown to work independently of circulating plasma insulin levels, by increasing the phosphorylation (activation) of key proteins involved in the regulation of protein synthesis.2 What this means is that leucine is the major factor for turning on the processes that maxmize protein synthesis-the key to optimizing whole body protein balance. In summary, it appears that the additional ingestion of free leucine in combination with protein and carbohydrate represents an effective strategy to increase muscle anabolism following resistance exercise. The combined ingestion of leucine, protein and carbohydrate in the recovery period from resistance exercise stimulates muscle protein synthesis in several ways. It provides amino acids as precursors for muscle protein synthesis, and the added leucine works to further increases plasma insulin concentrations while at the same time directly stimulating protein synthesis. This additional leucine also affects muscle protein metabolism by decreasing the rate of protein degradation, most likely via increases in circulating insulin, and the phosphorylation of key proteins involved in the regulation of protein synthesis.3 These breakthrough studies have motivated Universal Nutrition to include ample doses of leucine, in its most advanced and readily absorbed forms, into the postworkout beverage sensation Torrent as well as in the reformulation of the non-hormonal anabolic, Animal M-Stak. 1. Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutrition. 2006 Feb;136(2):533S-537S. 2. Anthony JC, Reiter AK, Anthony TG, Crozier SJ, Lang CH, MacLean DA, Kimball SR, and Jefferson LS. Orally administered leucine enhances protein synthesis in skeletal muscle of diabetic rats in the absence of increases in 4E-BP1 or S6K1 phosphorylation. Diabetes 51: 928-936, 2002. 3. René Koopman, et al. Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. Am J Physiol Endocrinol Metab 288: E645-E653, 2005. |