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  • Title: Dissociation between fat-induced in vivo insulin resistance and proximal insulin signaling in skeletal muscle in men at risk for type 2 diabetes.
    Author: Storgaard H, Jensen CB, Björnholm M, Song XM, Madsbad S, Zierath JR, Vaag AA.
    Journal: J Clin Endocrinol Metab; 2004 Mar; 89(3):1301-11. PubMed ID: 15001626.
    Abstract:
    The effect of short- (2 h) and long-term (24 h) low-grade Intralipid infusion on whole-body insulin action, cellular glucose metabolism, and proximal components of the insulin signal transduction cascade was studied in seven obese male glucose intolerant first degree relatives of type 2 diabetic patients [impaired glucose tolerance (IGT) relatives] and eight matched control subjects. Indirect calorimetry and excision of vastus lateralis skeletal muscle biopsies were performed before and during hyperinsulinemic euglycemic clamps combined with 3[(3)H]glucose. Clamps were performed after 0, 2, or 24 h Intralipid infusion (0.4 ml.kg(-1).min(-1)). Insulin-stimulated glucose disposal decreased approximately 25% after short- and long-term fat infusion in both IGT relatives and controls. Glucose oxidation decreased and lipid oxidation increased after both short- and long-term fat infusion in both groups. Insulin-stimulated glucose oxidation was higher after long-term as compared with short-term fat infusion in control subjects. Short- or long-term infusion did not affect the absolute values of basal or insulin-stimulated insulin receptor substrate-1 tyrosine phosphorylation, tyrosine-associated phosphoinositide 3-kinase (PI 3-kinase) activity, insulin receptor substrate-1-associated PI 3-kinase activity, or Akt serine phosphorylation in IGT relatives or matched controls. In fact, a paradoxical increase in both basal and insulin-stimulated PI 3-kinase activity was noted in the total study population after both short- and long-term fat infusion. Short- and long-term low-grade Intralipid infusion-induced (or enhanced) whole-body insulin resistance and impaired glucose metabolism in IGT relatives and matched control subjects. The fat-induced metabolic changes were not explained by impairment of the proximal insulin signaling transduction in skeletal muscle.
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