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Diabetes. 1996 May;45(5):651-8.

Metabolic impairment precedes insulin resistance in skeletal muscle during high-fat feeding in rats.

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Department of Physiology and Biophysics, University of Southern California, School of Medicine, Los Angeles 90033, USA.


To examine whether impairment of intracellular glucose metabolism precedes insulin resistance, we determined the time courses of changes in insulin-stimulated glucose uptake, glycolysis, and glycogen synthesis during high-fat feeding in rats. Animals were fed with a high-fat (66.5%) diet ad libitum for 0, 2, 4, 7, or 14 days (n = 10-11 in each group) after 5 days of a low-fat (12.5%) diet. Submaximal and maximal insulin-stimulated glucose fluxes were estimated in whole body and individual skeletal muscles using the glucose clamp technique combined with D-[3-3H]glucose infusion and 2-[1-14C]deoxyglucose injection. Both submaximal and maximal insulin-stimulated glucose uptake in whole body decreased gradually with high-fat feeding. However, the decreases were minimal and not statistically significant during the initial few days (i.e., 2 and 4 days) of high-fat feeding (P > 0.05). In contrast, insulin-stimulated whole-body glycolysis (both maximal and submaximal) significantly decreased by approximately 30% with 2 days of high-fat feeding and remained suppressed thereafter (P < 0.05). Similar patterns of changes in insulin-stimulated glucose uptake and glycolysis were also observed in skeletal muscle. Insulin-stimulated glycogen synthesis and glucose-6-phosphate (G-6-P) concentrations in skeletal muscle increased significantly during the initial few days of high-fat feeding and gradually returned to control levels by day 14, suggesting that increased G-6-P concentrations were responsible for increased glycogen synthesis. Thus, suppression of insulin-stimulated glycolysis and a compensatory increase in glycogen synthesis (presumably arising from the glucose-fatty acid cycle) preceded decreases in insulin-stimulated glucose uptake in skeletal muscle during high-fat feeding. These findings suggest that the insulin resistance may develop as a secondary response to impaired intracellular glucose metabolism.

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