Effects of insulin on whole‐body and regional amino acid metabolism

Abstract

~ Effect Tissue References Protein degradation J Ribosome degradation Macromolecule degradation (lysosomal) t Protein synthesis T mRNA transcription T mRNA translation t mRNA stability t Ternary complex formation J AA oxidation and deamination t AA transport Skeletal muscle Fibroblasts Cardiac muscle Liver 1 5 2 7 Skeletal muscle Liver 16,24,33,34, 37,38,40,42,43 Skeletal muscle in fed animals 52 Hepatocytes 56,57,6042, Fibroblasts Skeletal muscle 145,146 AA = Amino acid. in vivo. A m f Physiol 262: E92SE935, 1992. Tessari P, Nissen SL, Miles JM, and Haymond MW: Inverse relationship of leucine flux and oxidation to free-fatty acid availability in vivo. J Clin Invest 77: 575-581, 1986. Beaufrere 8, Chassard D, Broussolle C, Riou JP, and Beylot M: Effect of D-P-hydroxybutyrate and long-and medium-chain triglycerides on leucine metabolism in humans. A m Physiol 262: E26bE274, 1992. Nair KS, Welle SL, Halliday D, and Campbell RG: Effect of P-hydroxybutyrate on wholebody leucine kinetics and fractional mixed skeletal muscle protein synthesis in humans. J Clin Invest 92: 198-205, 1988. Miles JM, Nissen SL, Rizza RA, Gerich JE, and Haymond MW: Failure of infused betahydroxybutyrate to decrease proteolysis in man.

Postprandial hyperaminoacidaemia overcomes insulin resistance of protein anabolism in men with type 2 diabetes

“…Insulin stimulates protein synthesis and suppresses catabolism in vitro [4][5][6][7] and in vivo [8][9][10]. Amino acids, particularly the branched-chain amino acids (BCAA), have effects on protein synthesis that are both independent of [11,12] and synergistic with insulin [8,11,12].…”

Endocrine responses to the oral ingestion of a physiological dose of essential amino acids in humans

“…7 (Prior & Smith 1983). It is interesting to see that the effect of insulin is dose dependant (Tessari 1994) allowing individual clearance of serum AA according to the metabolic needs of the subject. It is notable that the insulin release after the intake of the milk powder solution mimics the course of the AA group.…”

“…The hypothesis was that AA cause a shift towards anabolic processes which is initiated by increased insulin (Fukagawa et al 1986, Tessari 1994 and hGH, and accompanied by a decrease in glucocorticoids (Louard et al 1994). The effect of a single AA bolus on leptin and ghrelin was of particular interest, as kinetic data on the effects of special diets on these two peptide hormones are either controversial (Drewes et al 1997, de Precigout et al 2000 or completely lacking.…”

Effect of Amino Acid Infusion on Human Postoperative Colon Protein Synthesis in Situ

“…It is generally accepted that, compared with the fasting state, IV amino acids stimulate total body protein synthesis. 2 One portion of this stimulation takes place in skeletal muscle tissue where even a short-term amino acid infusion may double protein synthesis in situ. 29 However, the majority of peripherally administered amino acids are being removed in the splanchnic bed.…”

“…1 Potential anabolic actions of amino acids are known to occur in muscle and in splanchnic tissues. 2 At the intestinal tract, amino acid metabolism and protein turnover are particularly important because an efficient formation of new protein is essential for maintaining a high rate of cell division and proliferation and for the production of cellular structure compounds and secreted enzymes. 3,4 Unfortunately, in humans effects of specific substrates have almost exclusively been studied in the whole splanchnic bed, not allowing a differentiation between hepatic and intestinal changes.…”