Insulin responsiveness of protein metabolism in vivo following bedrest in humans
- 30 September 1988
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Endocrinology and Metabolism
- Vol. 255 (4), E548-E558
- https://doi.org/10.1152/ajpendo.1988.255.4.e548
Abstract
To test the influence of bedrest on insulin regulation of leucine metabolism, six normal young men were subjected to a five-step hyperinsulinemic euglycemic clamp before and after 7 days of strict bedrest. A primed-constant infusion of [1-13C]leucine at 0.12 +/- 0.02 mumol.kg-1.min-1 was used. Before bedrest, the basal rate of appearance (Ra) of intracellular leucine and leucine oxidation were 2.79 +/- 0.17 and 0.613 +/- 0.070 mumol.kg-1.min-1, respectively. Insulin caused a dose-dependent reduction of the intracellular leucine Ra and leucine oxidation to a minimum of 1.64 +/- 0.08 and 0.322 +/- 0.039 mumol.kg-1.min-1, respectively, in nonbedrested subjects (P less than 0.001). Insulin also caused a dose-dependent reduction of plasma leucine concentration from 95 +/- 4 to 38 +/- 2 mumol/l (P less than 0.001). After bedrest, subjects exhibited decreased glucose tolerance and increased endogenous insulin secretion, but basal and insulin-suppressed intracellular leucine Ra and leucine oxidation rates were not different from control. Magnetic resonance imaging of the back and lower extremities revealed a 1-4% decrease in muscle volume and a 2-5% increase in fat volume secondary to bedrest. Bedrest also resulted in a negative nitrogen balance as compared with the control period, with an average cumulative loss of 6.3 g of nitrogen after 6 days. Urinary 3-methyl-L-histidine excretion was unchanged by bed rest. Thus because negative nitrogen balance and skeletal muscle atrophy occurred in six rested subjects in the absence of changes in the two indices of protein breakdown used in this study (3-methyl-L-histidine release and leucine release), it seems likely that muscle protein synthesis was inhibited.This publication has 29 references indexed in Scilit:
- The effect of indomethacin on the response of protein synthesis to feeding in rats and manClinical Science, 1987
- Decrease in human quadriceps muscle protein turnover consequent upon leg immobilizationClinical Science, 1987
- Insulin-mediated reduction of whole body protein breakdown. Dose-response effects on leucine metabolism in postabsorptive men.JCI Insight, 1985
- 3-Methylhistidine as a Measure of Skeletal Muscle Protein Breakdown in Human Subjects: The Case for Its Continued UseClinical Science, 1983
- Use of a heated superficial hand vein as an alternative site for the measurement of amino acid concentrations and for the study of glucose and alanine kinetics in manMetabolism, 1981
- Muscle and Plasma Amino Acids After InjuryAnnals of Surgery, 1978
- Estimation of Somatomedin-C Levels in Normals and Patients with Pituitary Disease by RadioimmunoassayJCI Insight, 1977
- Effects of immobilization upon various metabolic and physiologic functions of normal menAmerican Journal Of Medicine, 1948
- EFFECT OF PROLONGED PHYSICAL INACTIVITY ON TOLERANCE OF SUGARArchives of Internal Medicine, 1945
- The influence of prolonged muscular rest on metabolismBiochemical Journal, 1929