Olanzapine treatment is associated with reduced high molecular weight adiponectin in serum: a potential mechanism for olanzapine-induced insulin resistance in patients with schizophrenia.

Treatment of schizophrenia with olanzapine and other atypical antipsychotic agents is associated with insulin resistance and diabetes mellitus. The mechanism for this is not understood. Adiponectin is an insulin-sensitizing cytokine secreted by adipocytes. It is present in serum in multimers of varying size. Trimers and hexamers are referred to as low molecular weight (LMW) adiponectin. Larger multimers (12-, 18-, and 24-mers) have been designated high molecular weight (HMW) adiponectin and seem responsible for the insulin-sensitizing action of this adipokine. The aim of this study was to examine total adiponectin and LMW and HMW multimers in serum from patients with schizophrenia treated with either olanzapine (n = 9) or other typical antipsychotics (n = 9) and compare results with 16 healthy sex-, body mass index-, and age-matched controls. The effects of olanzapine on adiponectin protein expression and secretion in in vitro-differentiated primary human adipocytes were also examined. Patients receiving olanzapine had significantly lower total serum adiponectin as compared with those on conventional treatment and controls (5.23 +/- 1.53 ng/mL vs. 8.20 +/- 3.77 ng/mL and 8.78 +/- 3.8 ng/mL; P < 0.05 and P < 0.01, respectively). The HMW adiponectin was also reduced in patients on olanzapine as compared with the disease and healthy control groups (1.67 +/- 0.96 ng/mL vs. 3.87 +/- 2.69 ng/mL and 4.07 +/- 3.2 ng/mL; P < 0.05 for both). The LMW adiponectin was not different between patient groups (P = 0.15) but lower in patients on olanzapine as compared with controls (3.56 +/- 0.85 ng/mL vs. 4.70 +/- 1.4 ng/mL; P < 0.05). In vitro, short duration (up to 7 days) olanzapine exposure had no effect on total adiponectin expression or multimer composition of secreted protein. In summary, this study demonstrates a correlation between olanzapine treatment and reduced serum adiponectin, particularly HMW multimers. This may not be a direct effect of olanzapine on adipocyte expression or secretion of adiponectin. These observations provide insights into possible mechanisms for the association between olanzapine treatment and insulin resistance.

High molecular weight adiponectin correlates with insulin sensitivity in patients with hepatitis C genotype 3, but not genotype 1 infection.

BACKGROUND: Obesity is recognized as a cofactor in hepatitis C (HCV) liver injury. Adipokines may be the link between increasing body mass index (BMI) and disease progression in HCV. Adiponectin is an anti-inflammatory adipokine that is present in serum in a range of multimeric forms that appear to have different metabolic functions. METHODS: We studied 30 male patients with untreated chronic HCV (15 each with genotypes 1 and 3) and 12 controls. The three groups were matched for age and BMI. Total adiponectin and high (HMW) and low (LMW) molecular weight adiponectin multimers were measured. The relationships between adiponectin, BMI, insulin sensitivity, and liver histology were examined. RESULTS: Genotype 3 was associated with greater hepatic steatosis and inflammation than genotype 1. Patients with genotype 1 were less insulin sensitive than genotype 3, who had similar insulin sensitivity to controls. Insulin resistance was associated with a decrease in total and HMW adiponectin in both HCV and controls, while LMW adiponectin was unchanged. When the effect of genotype was examined, this association was present with genotype 3 but not genotype 1 infection. CONCLUSIONS: These data demonstrate that the relationship between insulin resistance and adiponectin is similar in controls and patients with genotype 3 but not genotype 1 infection. The greater degree of insulin resistance in genotype 1 appears to be a genotype-specific effect.