Metabolismo de proteínas y aminoácidos
METABOLISMO DE PROTEÍNAS Y AMINOÁCIDOS
Enzymes involved in branched‑chain amino acid metabolism in humans
Adeva-Andany, M. M., López-Maside, L., Donapetry-García, C.,
Fernández-Fernández, C., & Sixto-Leal, C. (2017). Enzymes involved in
branched-chain amino acid metabolism in humans. Amino acids, 49(6), 1005-1028
Cañas (2002) Taurine is ubiquitous in nature but its distribution and concentration differs among biological
organisms. Its role as an antioxidant and osmoregulator has been recently recognized.
Synthesis and transport may be different among species and tissues, with implications on the role of taurine in normal and physiologic processes and in pathological conditions. Taurine may be considered as a conditionally essential nutrient in certain circunstances such as parenteral nutrition, haemodialysis and infant formulas where a dietary supplement may be needed to maintain normal levels.
organisms. Its role as an antioxidant and osmoregulator has been recently recognized.
Synthesis and transport may be different among species and tissues, with implications on the role of taurine in normal and physiologic processes and in pathological conditions. Taurine may be considered as a conditionally essential nutrient in certain circunstances such as parenteral nutrition, haemodialysis and infant formulas where a dietary supplement may be needed to maintain normal levels.
Gingras et al (2007) The ability of the skeletal musculature to use amino acids to build or renew constitutive proteins is gradually lost with age and this is partly due to a decline in skeletal muscle insulin sensitivity. Since long-chain omega-3 polyunsaturated fatty acids (LCn–3PUFA) from fish oil are known to improve insulin-mediated glucose metabolism in insulin-resistant states, their potential role in regulating insulin-mediated protein metabolism was investigated in this study.
Experimental data are based on a switchback design composed of three 5 week experimental periods using six growing steers to compare the effect of a continuous abomasal infusion of LCn–3PUFA-rich menhaden oil with an iso-energetic control oil mixture. Clamp and insulin signalling observations were combined with additional data from a second cohort of six steers. We found that enteral LCn–3PUFA potentiate insulin action by increasing the insulin-stimulated whole-body disposal of amino acids from 152 to 308 μmol kg−1 h−1 (P = 0.006). The study further showed that in the fed steady-state, chronic adaptation to LCn–3PUFA induces greater activation (P < 0.05) of the Akt–mTOR–S6K1 signalling pathway. Simultaneously, whole-body total flux of phenylalanine was reduced from 87 to 67 μmol kg−1 h−1 (P = 0.04) and oxidative
metabolism was decreased (P = 0.05). We conclude that chronic feeding of menhaden oil provides a novel nutritional mean to enhance insulin-sensitive aspects of protein metabolism.
Experimental data are based on a switchback design composed of three 5 week experimental periods using six growing steers to compare the effect of a continuous abomasal infusion of LCn–3PUFA-rich menhaden oil with an iso-energetic control oil mixture. Clamp and insulin signalling observations were combined with additional data from a second cohort of six steers. We found that enteral LCn–3PUFA potentiate insulin action by increasing the insulin-stimulated whole-body disposal of amino acids from 152 to 308 μmol kg−1 h−1 (P = 0.006). The study further showed that in the fed steady-state, chronic adaptation to LCn–3PUFA induces greater activation (P < 0.05) of the Akt–mTOR–S6K1 signalling pathway. Simultaneously, whole-body total flux of phenylalanine was reduced from 87 to 67 μmol kg−1 h−1 (P = 0.04) and oxidative
metabolism was decreased (P = 0.05). We conclude that chronic feeding of menhaden oil provides a novel nutritional mean to enhance insulin-sensitive aspects of protein metabolism.
Zhenyukha et al (2017) pathological and physiological conditions increased BCAA plasma concentrations have been described. Elevated BCAA levels predict insulin resistance development. Moreover, BCAA levels higher than 2 mmol/L are neurotoxic by inducing microglial activation in maple syrup urine disease. However, there are no studies about the direct effects of BCAA in circulating cells. We have explored whether BCAA could promote oxidative stress and pro-inflammatory status in peripheral blood mononuclear cells (PBMCs) obtained from health (2011) y donors. In cultured PBMCs, 10 mmol/L BCAA increased the production of reactive oxygen species (ROS) via both NADPH oxidase and the mitochondria, and activated Akt-mTOR signalling. By using several inhibitors and activators of these molecular pathways we have described that mTOR activation by BCAA is linked to ROS production and mitochondrial dysfunction. BCAA stimulated the activation of the redox-sensitive transcription factor NF-κB, which resulted in the release of pro-inflammatory molecules, such as interleukin-6, tumor necrosis factor-α, intracellular adhesion molecule-1 or CD40L, and the migration of PBMCs. In conclusion, elevated BCAA blood levels can promote the activation of circulating PBMCs, by a mechanism that involving ROS production and NF-κB pathway activation. These data suggest that high concentrations of BCAA could exert deleterious effects on circulating blood cells and therefore contribute to the pro-inflammatory and oxidative status observed in several pathophysiological conditions.
aa esenciales y metabolismo proteico
JM Dickinson, BB Rasmussen (2011) The precise cellular mechansims linking amino acids to mTORC1 signaling and muscle protein metabolism are currently not well understood. More defined cellular mechansims are beginning to emerge suggesting a role for several intracellular proteins including hVps34, MAP4K3, and the Rag GTPases. Additionally, specific amino acid transporters may have a role both upstream and downstream of mTORC1. Continued investigation into the precise cellular mechanisms linking amino acid availablity and muscle protein metabolsim will help facilitate improvements in existing therapies for conditions of muscle wasting
aminoácidos ramificados (2020)
Neinast et al (2019) Branched chain amino acids (BCAAs) are building blocks for all life-forms. We review here the fundamentals of BCAA metabolism in mammalian physiology. Decades of studies have elicited a deep understanding of biochemical reactions involved in BCAA catabolism. In addition, BCAAs and various catabolic products act as signaling molecules, activating programs ranging from protein synthesis to insulin secretion. How these processes are integrated at an organismal level is less clear. Inborn errors of metabolism highlight the importance of organismal regulation of BCAA physiology. More recently, subtle alterations of BCAA metabolism have been suggested to contribute to numerous prevalent diseases, including diabetes, cancer, and heart failure. Understanding the mechanisms underlying altered BCAA metabolism and how they contribute to disease pathophysiology will keep researchers busy for the foreseeable future.
GLN en regulación de metabolismo proteico (2011)
Zongyong Jiang (2011) Glutamine is the most abundant free alpha-amino acid in plasma and skeletal muscle. This nutrient plays an important role in regulating gene expression, protein turnover, anti-oxidative function, nutrient metabolism, immunity, and acid-base balance. Interestingly, intracellular and extracellular concentrations of glutamine exhibit marked reductions in response to infection, sepsis, severe burn, cancer, and other pathological factors. This raised an important question of whether glutamine may be a key mediator of muscle loss and negative nitrogen balance in critically ill and injured patients. Therefore, since the initial reports in late 1980s that glutamine could stimulate protein synthesis and inhibit proteolysis in rat skeletal muscle, there has been growing interest in the use of this functional amino acid to improve protein balance under various physiological and disease conditions. Although inconsistent results have appeared in the literature regarding a therapeutic role of glutamine in clinical medicine, a majority of studies indicate that supplementing appropriate doses of glutamine to enteral diets or parenteral solutions is beneficial for improving nitrogen balance in animals or humans with glutamine deficiency.
JM Dickinson, BB Rasmussen (2011) The precise cellular mechansims linking amino acids to mTORC1 signaling and muscle protein metabolism are currently not well understood. More defined cellular mechansims are beginning to emerge suggesting a role for several intracellular proteins including hVps34, MAP4K3, and the Rag GTPases. Additionally, specific amino acid transporters may have a role both upstream and downstream of mTORC1. Continued investigation into the precise cellular mechanisms linking amino acid availablity and muscle protein metabolsim will help facilitate improvements in existing therapies for conditions of muscle wasting
aminoácidos ramificados (2020)
Neinast et al (2019) Branched chain amino acids (BCAAs) are building blocks for all life-forms. We review here the fundamentals of BCAA metabolism in mammalian physiology. Decades of studies have elicited a deep understanding of biochemical reactions involved in BCAA catabolism. In addition, BCAAs and various catabolic products act as signaling molecules, activating programs ranging from protein synthesis to insulin secretion. How these processes are integrated at an organismal level is less clear. Inborn errors of metabolism highlight the importance of organismal regulation of BCAA physiology. More recently, subtle alterations of BCAA metabolism have been suggested to contribute to numerous prevalent diseases, including diabetes, cancer, and heart failure. Understanding the mechanisms underlying altered BCAA metabolism and how they contribute to disease pathophysiology will keep researchers busy for the foreseeable future.
GLN en regulación de metabolismo proteico (2011)
Zongyong Jiang (2011) Glutamine is the most abundant free alpha-amino acid in plasma and skeletal muscle. This nutrient plays an important role in regulating gene expression, protein turnover, anti-oxidative function, nutrient metabolism, immunity, and acid-base balance. Interestingly, intracellular and extracellular concentrations of glutamine exhibit marked reductions in response to infection, sepsis, severe burn, cancer, and other pathological factors. This raised an important question of whether glutamine may be a key mediator of muscle loss and negative nitrogen balance in critically ill and injured patients. Therefore, since the initial reports in late 1980s that glutamine could stimulate protein synthesis and inhibit proteolysis in rat skeletal muscle, there has been growing interest in the use of this functional amino acid to improve protein balance under various physiological and disease conditions. Although inconsistent results have appeared in the literature regarding a therapeutic role of glutamine in clinical medicine, a majority of studies indicate that supplementing appropriate doses of glutamine to enteral diets or parenteral solutions is beneficial for improving nitrogen balance in animals or humans with glutamine deficiency.
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