Isoleucine
Overview:
Isoleucine is an amino acid that is used in the biosynthesis of proteins (ie: converting proteins into usable forms for our bodies). Isoleucine is one of the three branched chain amino acids (BCAAs) alongside both leucine and valine. It is essential in humans, meaning the body cannot create it and must get it from the diet. Isoleucine is critical in regards to increasing glucose uptake into skeletal muscle, a fancy way of saying 'enhancing muscle development'.
Benefits:
Energy production is one of the main benefits associated with isoleucine (and BCAAs in general). The body breaks down isoleucine into a molecule called acetyl-CoA, which is the same molecule made when sugars are converted into energy. Humans then further burn acetyl-CoA to produce carbon dioxide, oxygen and a large quantity of energy. Isoleucine also has antibacterial properties in the intestines and may act as a protectant (references 2, 3, 4).
Synergies:
Biotin, sometimes referred to as Vitamin B7 or Vitamin H, is an absolute requirement for the full catabolism of isoleucine (as well as leucine) (reference 6). With inadequate biotin, the human body will be unable to fully break down isoleucine and leucine molecules. This can lead to numerous physiological issues related to muscle maintenance and protein synthesis, lipid metabolism, and fatty acid metabolism, as well as cognitive issues. Interactions with resveratrol (a common mTOR inhibitor) may increase glucose uptake at the cost of muscle protein synthesis. This result would be benefit diabetics, but be a hindrance for persons wishing to build muscle (references 1 and 5).
Side Effects:
Over consumption may lead to liver disease, excessive urination, and depression.
Dosage:
The recommended dosage range for isoleucine is between 5-10g per day. However, since isoleucine in food products is also bioactive, supplemental doses of isoleucine taken with meals can be lower. The increase in glucose uptake seen with isoleucine appears to occur in animals with maximal efficacy at around 0.45g/kg, and the approximately human equivalent of this dose has been tested in humans and has been noted to reduce glucose spikes following a meal (reference 7).
Further Reference:
1. Doi M, et al Isoleucine, a potent plasma glucose-lowering amino acid, stimulates glucose uptake in C2C12 myotubes . Biochem Biophys Res Commun. (2003)
2. Goldman MJ, et al Human beta-defensin-1 is a salt-sensitive antibiotic in lung that is inactivated in cystic fibrosis . Cell. (1997)
3. Harder J, et al A peptide antibiotic from human skin . Nature. (1997)
4. Fehlbaum P, et al An essential amino acid induces epithelial beta -defensin expression . Proc Natl Acad Sci U S A. (2000)
5. Buller CL, et al A GSK-3/TSC2/mTOR pathway regulates glucose uptake and GLUT1 glucose transporter expression . Am J Physiol Cell Physiol. (2008)
6. "Biotin & Detoxification Needs in Cognitively Delayed Adult - Metametrix Learning Center". Metametrix.com. Retrieved 2013-10-18.
7. Wang B, et al Amino acid mixture acutely improves the glucose tolerance of healthy overweight adults.