title: Effects of growth hormone on fuel utilization and muscle glycogen synthase activity in normal humans.
abstract: To examine the insulin antagonistic effects of growth hormone (GH), seven healthy subjects underwent, in random order, two 5-h euglycemic clamp studies with moderate hyperinsulinemia. A GH infusion (45 ng.kg-1.min-1) was given throughout one of the studies. GH inhibited the insulin-stimulated glucose disposal by 27% from 4.4 +/- 0.7 to 3.3 +/- 0.4 mg.kg-1.min-1 (P less than 0.02) and raised the nonprotein energy expenditures (NPEE) from 18.7 +/- 0.5 to 20.5 +/- 0.3 kcal.kg-1.24 h-1 (P less than 0.03). Lipid oxidation contributed 71.7 +/- 5.6% of NPEE during the GH infusion as compared with 48.7 +/- 5.2% during the control clamp (P less than 0.02). In skeletal muscle biopsies, insulin binding to wheat germ agglutinin-purified insulin receptors and insulin receptor kinase activity were unaffected by GH infusion. Glycogen synthase activation by insulin was inhibited by 41% during the GH clamp (fractional velocity 14.1 +/- 2.5 vs. 8.3 +/- 1.4%, P less than 0.03). In conclusion, GH 1) increases energy expenditures and inhibits glucose oxidation in favor of an increased lipid oxidation, and 2) inhibits insulin-mediated activation of the glycogen synthase in skeletal muscle biopsies by a mechanism distal to insulin receptor binding and kinase activity.
authors.affiliation: Medical Endocrinological Department III, University Clinic of Internal Medicine, Aarhus, Denmark.
authors.forename: J F
authors.initials: JF
authors.lastname: Bak
authors.forename: N
authors.initials: N
authors.lastname: Møller
authors.forename: O
authors.initials: O
authors.lastname: Schmitz
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004734:Energy Metabolism / Q000187:drug effects*; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D006006:Glycogen Synthase / Q000378:metabolism*; D013006:Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism; D012016:Reference Values
chemical_list: D001786:Blood Glucose; D007328:Insulin; D013006:Growth Hormone; D006006:Glycogen Synthase; D011972:Receptor, Insulin; D005947:Glucose