Gender differences in association of plasma adiponectin with obesity reflect resultant insulin resistance in non-diabetic Japanese patients with schizophrenia

Adipose tissues poorly produce adiponectin in the population with increased body fat mass and diabetes mellitus. It was investigated whether hypoadiponectinemia is associated with obesity and insulin resistance in patients with chronically medicated schizophrenia. A cross-sectional study was designed for 73 non-diabetic Japanese patients with schizophrenia. The patients aged <70 years with body mass index (BMI) > or =18.5 were selected. Anthropometrics and blood parameters including fat-derived cytokines were measured, and then the BMI and homeostasis model assessment-insulin resistance (HOMA-IR) was calculated. The variables were compared between the non-obesity (BMI, 18.5-24.9) and obesity (> or = 25.0) groups, and between genders. Plasma adiponectin negatively correlated with BMI (r = -0.554, P < 0.0003) and HOMA-IR (r = -0.380, P = 0.007) in men, but not in women. The obesity group in men, as compared with the non-obesity group, showed significantly lower plasma adiponectin (P = 0.008) and higher HOMA-IR (P < 0.05), but not in women. Plasma leptin showed a significant positive correlation with BMI (r = 0.604, P < 0.0001 in men; r = 0.763, P < 0.0001 in women) and HOMA-IR (r = 0.618, P < 0.0001 in men; r = 0.679, P < 0.0001 in women). The mean plasma leptin in the obesity group was significantly higher than that in the non-obesity group (P < 0.01 in men; P < 0.01 in women). In contrast to plasma leptin, plasma adiponectin showed gender difference in relation to BMI and HOMA-IR.