Schizophrenia Research vol:143 issue:2-3 pages:358-362
BACKGROUND: Second-generation antipsychotics (SGAs) increase the risk of type 2 diabetes. The mechanism is thought to center on drug-induced weight gain, which starts the dysmetabolic cascade of insulin resistance, increased insulin production and pancreatic beta-cell failure. An independent effect of SGAs on insulin secretion has been suggested in animal models, but has not been demonstrated in clinical samples. OBJECTIVE: To determine the post-challenge insulin secretion in patients treated with SGAs. METHOD: We identified 520 non-diabetic individuals treated with clozapine (N=73), olanzapine (N=190), quetiapine (N=91) or risperidone (N=166) in a consecutive, single-site cohort of 783 adult psychiatric inpatients who underwent a comprehensive metabolic assessment. Insulin secretion was measured as the area under the curve (AUC(insulin)) generated by levels recorded at baseline, 30, 60 and 120min after the intake of 75g of glucose. The independent predictors of insulin secretion were determined with regression analysis in the entire sample and separately in patients with normal glucose tolerance (NGT) and prediabetes. RESULTS: The post-challenge AUC(insulin) was independently predicted by AUC(glucose), waist circumference, triglyceride levels and younger age (p<0.0001); non-smoking status (p=0.0012); and treatment with clozapine (p=0.021). The model explained 33.5% of the variance in insulin secretion (p<0.0001). The clozapine effect was present in the NGT group, but not in prediabetics. CONCLUSIONS: Clozapine, but not olanzapine, quetiapine and risperidone, is an independent predictor of post-challenge insulin secretion in non-diabetics, particularly in those with normal glucose tolerance. The findings suggest that the diabetogenic risk of clozapine may persist even after weight reduction.