The aim of the article is to examine side effects of increased dietary intake of amino acids, which are commonly used as a dietary supplement. In addition to toxicity, mutagenicity and carcinogenicity, attention is focused on renal and gastrointestinal tract functions, ammonia production, and consequences of a competition with other amino acids for a carrier at the cell membranes and enzymes responsible for their degradation. In alphabetic order are examined arginine, beta-alanine, branched-chain amino acids, carnosine, citrulline, creatine, glutamine, histidine, beta -hydroxy- beta -methylbutyrate, leucine, and tryptophan. In the article is shown that enhanced intake of most amino acid supplements may not be risk-free and can cause a number of detrimental side effects. Further research is necessary to elucidate effects of high doses and long-term consumption of amino acid supplements on immune system, brain function, muscle protein balance, synthesis of toxic metabolites, and tumor growth and examine their suitability under certain circumstances. These include elderly, childhood, pregnancy, nursing a baby, and medical condition, such as diabetes and liver disease. Studies are also needed to examine adaptive response to a long-term intake of any substance and consequences of discontinuation of supplementation.

• MeSH
• Amino Acids adverse effects   metabolism   MeSH
• Arginine pharmacology   MeSH
• Child MeSH
• Glutamine * metabolism   pharmacology   MeSH
• Histidine metabolism   MeSH
• Muscle, Skeletal metabolism   MeSH
• Humans MeSH
• Dietary Supplements * adverse effects   MeSH
• Aged MeSH
• Pregnancy MeSH
• Check Tag
• Child MeSH
• Humans MeSH
• Aged MeSH
• Pregnancy MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Amino Acids MeSH
• Arginine MeSH
• Glutamine * MeSH
• Histidine MeSH

The article shows that skeletal muscle plays a dominant role in the catabolism of branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) and the pathogenesis of their decreased concentrations in liver cirrhosis, increased concentrations in diabetes, and nonspecific alterations in disorders with signs of systemic inflammatory response syndrome (SIRS), such as burn injury and sepsis. The main role of skeletal muscle in BCAA catabolism is due to its mass and high activity of BCAA aminotransferase, which is absent in the liver. Decreased BCAA levels in liver cirrhosis are due to increased use of the BCAA as a donor of amino group to alpha-ketoglutarate for synthesis of glutamate, which in muscles acts as a substrate for ammonia detoxification to glutamine. Increased BCAA levels in diabetes are due to alterations in glycolysis, citric acid cycle, and fatty acid oxidation. Decreased glycolysis and citric cycle activity impair BCAA transamination to branched-chain keto acids (BCKAs) due to decreased supply of amino group acceptors (alpha-ketoglutarate, pyruvate, and oxaloacetate); increased fatty acid oxidation inhibits flux of BCKA through BCKA dehydrogenase due to increased supply of NADH and acyl-CoAs. Alterations in BCAA levels in disorders with SIRS are inconsistent due to contradictory effects of SIRS on muscles. Specifically, increased proteolysis and insulin resistance tend to increase BCAA levels, whereas activation of BCKA dehydrogenase and glutamine synthesis tend to decrease BCAA levels. The studies are needed to elucidate the role of alterations in BCAA metabolism and the effects of BCAA supplementation on the outcomes of specific diseases.

• MeSH
• Diabetes Mellitus metabolism   MeSH
• Isoleucine metabolism   MeSH
• Liver Cirrhosis metabolism   MeSH
• Muscle, Skeletal metabolism   MeSH
• Leucine metabolism   MeSH
• Humans MeSH
• Metabolic Diseases metabolism   MeSH
• Valine metabolism   MeSH
• Amino Acids, Branched-Chain metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Isoleucine MeSH
• Leucine MeSH
• Valine MeSH
• Amino Acids, Branched-Chain MeSH