Adverse effects of insulin antibodies on postprandial plasma glucose and insulin profiles in diabetic patients without immune insulin resistance. Implications for intensive insulin regimens.
To assess the possible influence of moderate titer insulin antibodies on diabetic glycemic control, we examined insulin-antibody equilibrium binding characteristics, postprandial glucose tolerance, and plasma free-insulin profiles after subcutaneous injection of both porcine and human insulin (0.15 U/kg) in 12 patients with insulin-dependent diabetes mellitus under conditions stimulating intensive insulin therapy. The patients' antibodies bound porcine and human insulin indistinguishably, and their plasma glucose and free-insulin profiles after ingestion of a standard meal were similar with both insulins. Initial increases in plasma free-insulin levels after injection of both insulins were negatively correlated with both insulin-antibody binding (r = -.55, P less than .006) and postprandial hyperglycemia (peak level r = -.56, P less than .006); the latter was positively correlated with insulin-antibody binding (r = .48, P less than .02). The effects of insulin antibodies on postprandial plasma free-insulin and glucose levels could be accounted for substantially by the association constant of the high-affinity insulin-antibody binding sites (K1); patients in the highest quartile for K1 had significantly slower initial increments in plasma free insulin (0.31 +/- 0.04 vs. 0.46 +/- 0.06 microU/min, P less than .05) and greater postprandial hyperglycemia (peak value 237 +/- 10 vs. 166 +/- 12 mg/dl, P less than .001) than patients in the lowest quartile. We conclude that moderate insulin-antibody titers commonly found in insulin-treated patients can slow the early increase in plasma free insulin after subcutaneous injection and that this impairs postprandial glucose tolerance; such an effect may limit the effectiveness of intensive insulin therapy.