Anti-insulin receptor antibodies mimic the effects of insulin on the activities of pyruvate dehydrogenase and acetylCoA carboxylase and on specific protein phosphorylation in rat epididymal fat cells.

Previous studies have shown that autoantibodies against insulin receptors found in certain patients with severe insulin resistance stimulate glucose transport and metabolism in fat cell and muscle preparations. The present studies show that preincubation of rat epididymal adipose tissue with 1 : 1000 dilution on one such serum results in a two fold increase in the initial activities of pyruvate dehydrogenase and acetylCoA carboxylase. These increases are similar to the maximum effects of insulin. Incubation of isolated fat cells with the serum at the same concentration also resulted in the increased phosphorylation of three intracellular proteins with subunit molecular weights of 130,000, 35,000 and 22,000 to the same extent as observed with insulin. These findings lend further support to the view that the short term effects of insulin do not involve the entry of the insulin molecule (or part thereof) into cells of target tissues.