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Insulin time‐dependent effects on the leg exchange of glucose and amino acids in man
Author(s) -
LUNDGREN F.,
EDÉN E.,
ARFVIDSSON B.,
LUNDHOLM K.
Publication year - 1991
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1991.tb01390.x
Subject(s) - medicine , insulin , endocrinology , amino acid , chemistry , biochemistry
. Time‐dependent effects of insulin on the leg exchange of glucose, lactate, glycerol, free fatty acids (FFA) and amino acids were measured in relation to oxygen uptake (leg and whole body) and whole body glucose assimilation including oxidation. Seven healthy males (58 ± 3 years of age) were investigated before operation of uncomplicated inguinal hernia or varicose veins. Euglycaemic glucose clamp investigations with systemic hyperinsulinaemia between 100–120 mU 1 ‐1 were used. Metabolic measurements were performed before and during hyperinsulinaemia at 2 and 6 h following the start of glucose clamp to evaluate the time‐dependency of insulin actions. Whole body glucose uptake increased continuously for up to 6 h (from 4·7 ± 0·7 to 8·0 ± 0·8 mg/kg/min, P <0·01) despite stable plasma concentrations of glucose and insulin. This was also true for glucose oxidation. Whole body oxygen uptake did not change significantly during the clamp while the leg exchange of oxygen uptake did (from 5·9 ± 0·86 μmol/100 g/min to 11·6 ± 2·4, P <0·01). Insulin effect on leg blood flow was time‐dependent and increased two‐fold (2·3 ± 0·4 ml/100 g/min to 4·4 ± 0·9, P <0·001) during clamp. The leg production of lactate increased continuously, accounting for approximately 15% of the glucose uptake across the leg, but the rise in arterial lactate did not reach the level of statistical significance. Plasma FFA concentrations decreased in a time‐dependent manner during clamp, while the leg exchange of FFA switched rapidly to a stable net uptake. Arterial concentrations of amino acids declined with time. The leg release of the sum of all amino acids decreased also in a time‐dependent manner and then switched to a net uptake, mainly depending on an increasing uptake of leucine, valine and methionine. The release of phenylalanine and tyrosine, which are not metabolized in peripheral tissues, were not significantly influenced by prolonged hyperinsulinaemia. The results demonstrate that the euglycaemic glucose clamp procedure is not associated with steady‐state metabolism for glucose assimilation, oxygen uptake, lactate formation and amino acid exchange either measured across the whole body or peripheral tissues. The results also support a recent finding in our laboratory that insulin in itself does not inhibit net degradation in human peripheral tissues including the leg skeletal muscles.