Desensitization of the insulin receptor at an early postreceptor step by prolonged exposure to antireceptor antibody

Abstract

We have used an adipocyte-like cell line, the 3T3-L1 fatty fibroblasts, to compare acute and chronic effects of autoantibodies directed against the insulin receptor. Acute exposure of the cells in tissue culture to the antibodies resulted in a blockade of insulin binding and stimulation of 2-deoxyglucose transport and glucose oxidation. Maximal acute effects were reached within 30-120 min. Subsequently, the stimulatory response decayed and, after 6 hr in the continuous presence of the antibodies, basal glucose metabolism-had returned to the level observed with unexposed cells and a state of severe insulin resistance prevailed. In contrast to the decay of bioresponse, no change in insulin binding was detectable over the same time period. The mechanism of desensitization seemed to involve events early after insulin binding to receptor because cells exposed to antibody for prolonged periods of time, although unresponsive to insulin and antireceptor antibodies, responded normally to both spermine and vitamin K5, agents that stimulate glucose metabolism independently of the insulin receptor. These data suggest that prolonged or continuous occupancy of the insulin receptor by a ligand, in this case antireceptor antibodies, does not produce a continuous biological response. Instead, there is desensitization at some early step in the pathway for insulin action. These observations have important implications with respect to the mechanism of insulin action andi to other situations in which there is long-term exposure of cells to antibodies that react with membrane components. Antibodies that bind to the insulin receptor have been found in patients with a rare form of insulin-resistant diabetes termed the "syndrome of insulin resistance and acanthosis nigricans type B" (1). These antibodies, which are polyclonal and mainly of the IgG class, block insulin binding (2,3) and, in the presence of a second antibody, can be used to immunoprecipitate solubilized insulin receptors (4). When tested in short-term in vitro experiments, the antireceptor antibodies also have an insulinlike activity. In adipocytes and skeletal muscle, the antireceptor antibodies have been shown to stimulate 2-deoxyglucose transport, glucose incorporation into lipids and glycogen, and glucose metabolism to CO2 (5, 6). In addition, these antibodies mimic insulin's effect on lipolysis, amino acid transport, and enzymatic activity of glycogen synthase and phosphorylase (7,8). These in vitro findings are in contrast to the chronic in vivo effects of these antibodies to produce severe insulin resistance and hyperglycemia.In the present study, we have investigated the effects of the antibodies on insulin binding and glucose metabolism in more long-term experiments, taking advantage of the recently established adipocyte-like cell line, the 3T3-L1 fatty fibroblasts (9-11). As with adipocytes, the antireceptor antibodies inhibit insulin binding and produce acute insulin-like effects in these cells. This insulin-like action, however, is transient; after 6-4...

Clinical disorders associated with autoantibodies to the insulin receptor. Simulation by passive transfer of immunoglobulins to rats.

“…While partially purified Anti-R has insulin-like effects when exposed to cultured cells for short intervals, longer exposure to Anti-R desensitizes cells to the effects of both Anti-R and insulin in vitro (19,20). Therefore, we wished to determine the effect of larger concentrations of Anti-R IgG given repeatedly over longer periods of time on the plasma glucose of our in vivo rat model.…”

Remission of insulin resistant diabetes in two patients with anti-insulin receptor antibodies.

“…If the anti-insulin receptor antibodies act as insulin agonist, it is difficult to explain the reason of occurrence of hyperglycemia. Karlsson et al (1979) elucidated this contradiction, showing that when the chronic exposure of tissue to the antibodies continued, insulin-like activity was lost and the antibodies acted as a competitive antagonist to insulin.…”

Antibody-induced Desensitization of the Insulin Receptor

“…Suspended cells were prepared by incubation of plates in Joklik's spinner medium supplemented with 2 mM EDTA for 30 min at 37°C (22). The cells were washed once in Joklik's spinner medium with 2 mM EDTA and then washed twice in an incubation medium appropriate for the studies to follow.…”

“…Recently, we have used 3T3-L1 cells to develop an in vitro model for the insulin resistance seen in patients with antibodies against the insulin receptor (22). As with other cells, these antibodies rapidly inhibit the binding of insulin and mimic the action of insulin in 3T3-L1 cells.…”