Does hyperinsulinemia in ob/ob mice cause an insulin-stimulated adipose tissue?

After a 1-h preincubation to remove endogenous insulin, adipose tissue of obese mice (C57BL/L4 ob/ob) had a lower rate of glucose metabolism than tissue which was not preincubated. In contrast, preincubation did not change the metabolism of adipose tissue from lean mice (C57B1/6J +/+). The preincubation effect was abolished in obese mice which had had their serum insulin levels lowered toward normal by streptozotocin treatment. Injection of anti-insulin serum to obese mice caused adipose tissue removed 15 min after the injection to display a rate of glucose metabolsim lower than that of tissue removed before the injection. No such effect was seen in lean mice. These data are consistent with the hypothesis that hyperinsulinemia in the obese mice causes a chronic state of insulin stimulation of their adipose tissue, possibly contributing to their high rates of lipogenesis and their obesity. Several lipogenic enzymes were measured in adipose tissue of both lean and obese mice, and no single enzymatic abnormality was detected which might explain the hyperlipogenesis. Pyruvate dehydrogenase and acetyl-CoA carboxylase were both insulin-sensitive enzymes in lean and obese mice.