0.62 METABOLIC AND THERMOGENIC EFFECTS OF AMINO ACID (AA) 1NFUSIOliIN MAN L.S. Brandi, M. Oleggini, S. Bevilacqua, R. Bonadonna, M.A. Giorico, G. Buzzigoli, C. Boni, and E. Ferrannini C.N.R. Institute of Clinical Physiology, Institute of Surgery and 2nd Medical Clinic, University of Pisa, Pisa, Italy AA mixtures are an obligatory constituent of parenteral nutrition regimens; their metabolic interactions with glucose utilisation are not, however, well described. We in- fused, on two separate days, Freamine IIIR or saline into 7 healthy volunteers during a 2-hr, euglycaemic insulin (1 mU.min-l *kg) clamp combined with continuous, computerised indirect calorimetry. The AA infusion rate (0.7 g-kg-',or 0.1 g.kg-l of nitrqgen) was designed to raise blood AA levels 2-3-fold. While plasma glucose was held constant at basal levels in both the saline (4.6kO.l mM) and the AA study (4.6*0.1), plasma insulin concentrations were 60% higher (105+7 vs 64k6 mu/l, PcO.001) during AA infusion. The se- rum C-peptide levels (1.83kO.23 vs 0.68kO.16 ng/ml, P<O.OOl) confirmed the presence of stimulated insulin release. Despite the latter, whole body glucose disposal was impaired by AA administration (24.6k2.0 vs 32.2k2.0 umol.min-l.kg-l, PcO.02). This resulted from an inhibition of both insulin-induced glucose oxidation (8.3kl.O vs 12.2k1.4 umol.min-1. kg-', P<O.O5) and nonoxidative glucose disposal (7.4i2.1 vs 11.5rt2.7umol.min-'*kg-', P< 0.05). On the other hand, both lipid oxidation (u.94kO.21 vs 0.62kO.28 umol.min-l.kg-1, PcO.02) and protein oxidation (as estimated from urinary nitrogen excretion, 0.26kO.04 vs 0.21kO.05 mmol/min, P40.01) were increased during AA infusion. On balance, energy production was markedly stimulated by Freamine III (1.38kO.09 vs 1.16*0.09 kcal/min, PdO.01)' We conclude that Freamine administration (a) stimulates insulin secretion; (b) in- hibits both oxidative and nonoxidative glucose utilisation, thereby sparing plasma glucose and, possibly, glycogen, and (c) strongly enhances energy production. 72

Metabolic and thermogenic effects of amino acid (AA) infusion in man

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Page 1: Metabolic and thermogenic effects of amino acid (AA) infusion in man

AA mixtures are an obligatory constituent of parenteral nutrition regimens; their metabolic interactions with glucose utilisation are not, however, well described. We in- fused, on two separate days, Freamine IIIR or saline into 7 healthy volunteers during a 2-hr, euglycaemic insulin (1 mU.min-l *kg) clamp combined with continuous, computerised indirect calorimetry. The AA infusion rate (0.7 g-kg-',or 0.1 g.kg-l of nitrqgen) was designed to raise blood AA levels 2-3-fold. While plasma glucose was held constant at basal levels in both the saline (4.6kO.l mM) and the AA study (4.6*0.1), plasma insulin concentrations were 60% higher (105+7 vs 64k6 mu/l, PcO.001) during AA infusion. The se- rum C-peptide levels (1.83kO.23 vs 0.68kO.16 ng/ml, P<O.OOl) confirmed the presence of stimulated insulin release. Despite the latter, whole body glucose disposal was impaired by AA administration (24.6k2.0 vs 32.2k2.0 umol.min-l.kg-l, PcO.02). This resulted from an inhibition of both insulin-induced glucose oxidation (8.3kl.O vs 12.2k1.4 umol.min-1.

kg-', P<O.O5) and nonoxidative glucose disposal (7.4i2.1 vs 11.5rt2.7 umol.min-'*kg-', P< 0.05). On the other hand, both lipid oxidation (u.94kO.21 vs 0.62kO.28 umol.min-l.kg-1, PcO.02) and protein oxidation (as estimated from urinary nitrogen excretion, 0.26kO.04 vs 0.21kO.05 mmol/min, P40.01) were increased during AA infusion. On balance, energy production was markedly stimulated by Freamine III (1.38kO.09 vs 1.16*0.09 kcal/min, PdO.01)'

We conclude that Freamine administration (a) stimulates insulin secretion; (b) in- hibits both oxidative and nonoxidative glucose utilisation, thereby sparing plasma glucose and, possibly, glycogen, and (c) strongly enhances energy production.