A branched-chain amino acid BCAA is an amino acid having an aliphatic side-chain with a branch a central carbon atom bound to three or more carbon atoms. Among the proteinogenic amino acids , there are three BCAAs: BCAAs fill several metabolic and physiologic roles. Metabolically, BCAAs promote protein synthesis and turnover, signaling pathways, and metabolism of glucose. Physiologically, BCAAs take on roles in the immune system and in brain function. BCAAs are broken down effectively by dehydrogenase and decarboxylase enzymes expressed by immune cells, and are required for lymphocyte growth and proliferation and cytotoxic T lymphocyte activity.
Once in the brain BCAAs may have a role in protein synthesis, synthesis of neurotransmitters, and production of energy.
Diets that meet or exceed the RDA for total protein 0. Dietary BCAA supplementation has been used clinically to aid in the recovery of burn victims.
However, a 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. Dietary BCAAs have been used in an attempt to treat some cases of hepatic encephalopathy.
Certain studies suggested a possible link between a high incidence of amyotrophic lateral sclerosis ALS among professional American football players and Italian soccer players, and certain sports supplements including BCAAs. 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.
Blood levels of the BCAAs are elevated in obese, insulin resistant humans and in mouse and rat models of diet-induced diabetes, suggesting the possibility that BCAAs contribute to the pathogenesis of obesity and diabetes. Five enzymes play a major role in the parallel synthesis pathways for isoleucine, valine, and leucine: Isoleucine forms a negative feedback loop with threonine dehydrogenase.
Dihydroxyacid dehygrogenase converts the dihyroxyacids in the next step. The final step in the parallel pathway is conducted by amino transferase, which yields the final products of valine and isoleucine. 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.
Enzymes involved are branched chain aminotransferase and 3-methyloxobutanoate dehydrogenase. While most amino acids are oxidized in the liver, BCAAs are primarily oxidized in the skeletal muscle and other peripheral tissues.
Leucine indirectly activates p70 S6 kinase as well as stimulates assembly of the eIF4F complex , which are essential for mRNA binding in translational initiation. Some phosphorylation of p70 S6 kinase was discovered. When BCAAs were administered following a training session, sufficient phosphorylation of p70 S6 kinase and S6 indicated activation of the signaling cascade.
Advances in Molecular Biology. BCAAs are broken down effectively by dehydrogenase and decarboxylase enzymes expressed by immune cells, and are required for lymphocyte growth and proliferation and cytotoxic T lymphocyte activity. Huntington College of Health Sciences. From Test Tube to Field". The National Academies Press.
In addition to cell signaling, the mTOR pathway also plays a role in beta cell growth leading to insulin secretion. Higher concentrations of leucine cause hyperactivity in the mTOR pathway, and S6 kinase is activated leading to inhibition of insulin receptor substrate through serine phosphorylation.
Both humans and rats were tested for prevalence of BCAA signatures leading to insulin resistance. Human subjects' body mass index was compared to concentration of BCAAs in their diet, as well as insulin resistance level. It was determined that subjects considered obese had higher metabolic signatures of BCAAs and higher resistance to insulin than those lean individuals with a lower body mass index. Metformin is able to activate AMP kinase which phosphorylates proteins involved in the mTOR pathway, as well as leads to the progression of mTOR complex from its inactive state to its active state.
Get Branched-chain Amino Acid essential facts below. View Videos or join the Branched-chain Amino Acid discussion. Add Branched-chain Amino Acid to your Like2do. This book really gives you good thought that will very influence for the readers future.
How to get thisbook? Getting this book is simple and easy.
You can download the soft file of this book in this website. This website is available with pay and free online books. Anticipate for others minutes time until the save is finish. This softer make is serious to interpret in case you aspire.