Branched-chain amino acid

A branched-chain amino acid (BCAA) is an amino acid having aliphatic side-chains with a branch (a central carbon atom bound to three or more carbon atoms). Among the proteinogenic amino acids, there are three BCAAs: leucine, isoleucine and valine.[1] Non-proteinogenic BCAAs include norvaline and 2-aminoisobutyric acid.

A chemical structure diagram of leucine
Leucine
A chemical structure diagram of isoleucine
Isoleucine
A chemical structure diagram of valine
Valine

The three proteinogenic BCAAs are among the nine essential amino acids for humans, accounting for 35% of the essential amino acids in muscle proteins and 40% of the preformed amino acids required by mammals.[2]

Research

Dietary BCAA supplementation has been used clinically to aid in the recovery of burn victims. A 2006 paper suggests that the concept of nutrition supplemented with all BCAAs for burns, trauma, and sepsis should be abandoned for a more promising leucine-only-supplemented nutrition that requires further evaluation. [3]

Dietary BCAAs have been used in an attempt to treat some cases of hepatic encephalopathy.[4] They can have the effect of alleviating symptoms, but there is no evidence they benefit mortality rates, nutrition or overall quality of life.[5]

Certain studies suggested a possible link between a high incidence of amyotrophic lateral sclerosis among professional American football players and Italian soccer players, and certain sports supplements including BCAAs.[6] In mouse studies, BCAAs were shown to cause cell hyper-excitability resembling that usually observed in ALS patients. The proposed underlying mechanism is that cell hyper-excitability results in increased calcium absorption by the cell and thus brings about cell death, specifically of neuronal cells which have particularly low calcium buffering capabilities.[6] Yet any link between BCAAs and ALS remains to be fully established. While BCAAs can induce a hyperexcitability similar to the one observed in mice with ALS, current work does not show if a BCAA-enriched diet, given over a prolonged period, actually induces ALS-like symptoms.[6]

Degradation

Degradation of branched-chain amino acids involves the branched-chain alpha-keto acid dehydrogenase complex (BCKDH). A deficiency of this complex leads to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products in the blood and urine, giving the condition the name maple syrup urine disease.

The BCKDH complex converts branched-chain amino acids into Acyl-CoA derivatives, which after subsequent reactions are converted either into acetyl-CoA or succinyl-CoA that enter the citric acid cycle.[7]

Enzymes involved are branched chain aminotransferase and 3-methyl-2-oxobutanoate dehydrogenase.

Claims in Bodybuilding

Bodybuilders make claims about the effectiveness of using BCAAs to aid recovery after a workout.[8] These claims[9] include prolonged mental and physical stamina[10] as well as a decrease in exercise-induced muscle breakdown and inflammation.[11] BCAAs are sold as bodybuilding supplements.[12]

See also

References

  1. ↑ Sowers, Strakie. "A Primer On Branched Chain Amino Acids" (PDF). Huntington College of Health Sciences. Retrieved 22 March 2011.
  2. ↑ Shimomura Y, Murakami T, Naoya Nakai N, Nagasaki M, Harris RA (2004). "Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise". J. Nutr. 134 (6): 1583S–1587S. Retrieved 22 March 2011.
  3. ↑ De Bandt JP; Cynober L (2006). "Therapeutic use of branched-chain amino acids in burn, trauma, and sepsis". J. Nutr. 1 Suppl 136 (30): 8S–13S. Retrieved 22 March 2011.
  4. ↑ Chadalavada R, Sappati Biyyani RS, Maxwell J, Mullen K. (2010). "Nutrition in hepatic encephalopathy". Nutr Clin Pract. 25 (3): 257–64. doi:10.1177/0884533610368712.
  5. ↑ Gluud LL, Dam G, Les I, Córdoba J, Marchesini G, Borre M, Aagaard NK, Vilstrup H. (2015). "Branched-chain amino acids for people with hepatic encephalopathy". Cochrane Database of Systematic Reviews. (2). doi:10.1002/14651858.CD001939.pub2.
  6. 1 2 3 Manuel, Marin; Heckman, C.J. (2011). "Stronger is not always better: Could a bodybuilding dietary supplement lead to ALS?". Experimental Neurology 228 (1): 5–8. doi:10.1016/j.expneurol.2010.12.007. ISSN 0014-4886.
  7. ↑ Sears DD, Hsiao G, Hsiao A, Yu JG, Courtney CH, Ofrecio JM, Chapman J, Subramaniam S (2009). "Mechanisms of human insulin resistance and thiazolidinedione-mediated insulin sensitization". Proc. Natl. Acad. Sci. USA 106 (44): 18745–18750. doi:10.1073/pnas.0903032106. Retrieved 22 March 2011.
  8. ↑
  9. ↑ "BCAA Supplements and Their Benefits". Macrospective. Retrieved 2016-03-23.
  10. ↑ Blomstrand, E.; Hassmén, P.; Ekblom, B.; Newsholme, E. A. (1991-01-01). "Administration of branched-chain amino acids during sustained exercise--effects on performance and on plasma concentration of some amino acids". European Journal of Applied Physiology and Occupational Physiology 63 (2): 83–88. ISSN 0301-5548. PMID 1748109.
  11. ↑ Howatson, Glyn; Hoad, Michael; Goodall, Stuart; Tallent, Jamie; Bell, Phillip G.; French, Duncan N. (2012-01-01). "Exercise-induced muscle damage is reduced in resistance-trained males by branched chain amino acids: a randomized, double-blind, placebo controlled study". Journal of the International Society of Sports Nutrition 9: 20. doi:10.1186/1550-2783-9-20. ISSN 1550-2783. PMC 3395580. PMID 22569039.
  12. ↑

External links

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