Blood levels of glucose and insulin and insulin resistance in patients with schizophrenia on clozapine monotherapy

ObjectiveWe tested the hypothesis that fasting blood glucose and insulin levels are higher in schizophrenic subjects on clozapine monotherapy compared with healthy controls and they correlate with anthropometric measurements, laboratory tests and body composition.MethodsData for 24 subjects with schizophrenia treated with clozapine and 24 age- and sex-matched healthy volunteers was analyzed.ResultsPatients taking clozapine had higher fasting levels of glucose (103.5 ± 31.6 vs. 87.8 ± 11.7 mg/dL, z = −2.03, p = 0.04), there was no difference for insulin concentrations and markers of insulin resistance. In the clozapine group glucose levels correlated with clozapine dose (R = −0.43, p = 0.03), while insulin levels correlated with weight (R = 0.66, p < 0.001), body mass index (R = 0.54, p = 0.007), abdominal (R = 0.53, p = 0.007) and waist (R = 0.43, p = 0.04) circumference, total body fat (R = 0.51, p = 0.01), and uric acid levels (R = 0.50, p = 0.01). In the clozapine group insulin levels were lower in subjects with body mass index <25 kg/m2 (7.0 ± 3.3 vs. 13.4 ± 8.8 μU/mL, p = 0.04) and in subjects without abdominal obesity (6.3 ± 2.4 vs. 13.3 ± 8.6 μU/mL, p = 0.03).ConclusionsWe found higher blood glucose levels in subjects taking clozapine and no differences in blood insulin levels between subjects with schizophrenia and controls. Associations between blood insulin levels and abdominal/waist circumferences support the role of abdominal obesity as an important risk factor of insulin resistance.