Subchronic olanzapine treatment decreases the expression of pancreatic glucose transporter 2 in rat pancreatic β cells

The protein kinase D1-mediated inflammatory pathway is involved in olanzapine-induced impairment of skeletal muscle insulin signaling in rats

AIMS

Skeletal muscle insulin resistance (SMIR) contributes to the metabolic syndrome. Mounting evidence has demonstrated that the second generation antipsychotic olanzapine causes SMIR. The present study sought to investigate the molecular mechanisms underlying olanzapine-induced SMIR.

MAIN METHODS

Male rats were given olanzapine (5 mg/kg, by a gavage method) for consecutive eight weeks. Plasma glucose and insulin concentrations were determined enzymatically or by ELISA. Gene/protein expression was analyzed by Real-Time PCR, Western blot and/or immunohistochemistry.

KEY FINDINGS

Olanzapine increased fasting plasma insulin concentration, and decreased glucose clearance during insulin tolerance test in rats. In skeletal muscle, it decreased protein expression of membrane glucose transporter (GLUT) 4, the ratio of membrane to total GLUT4, and total insulin receptor substrate 1 (IRS1). However, it increased protein phosphorylation of Ser³⁰⁷ in IRS1, Y⁶⁰⁷ in phosphoinositide 3-kinase p85α and Ser³⁰⁷ in AKT. These results indicate olanzapine-induced impairment of skeletal muscle insulin signaling. Mechanistically, olanzapine upregulated mRNA expression of TNFα, IL6 and IL1β, and protein phosphorylation of both IκB kinase (IKK)α/β and nuclear factor (NF)κB p65. Furthermore, it increased protein phosphorylation of Ser^485/491 in AMPKα2, whereas it decreased AMPKα2 activity. More importantly, both Western blot and immunohistochemical analyses revealed that olanzapine increased protein phosphorylation of Ser^744/748 in protein kinase D1 (PKD1).

SIGNIFICANCE

The present results suggest that the PKD1-mediated inflammatory pathway is involved in olanzapine-induced impairment of skeletal muscle insulin signaling in rats. Our findings may go new insight into the mechanisms underlying olanzapine-induced SMIR.

Metformin attenuates antipsychotic-induced metabolic dysfunctions in MK801-induced schizophrenia-like rats

RATIONALE

Second-generation antipsychotics are the first-line medications prescribed for schizophrenic patients; however, some of them, such as olanzapine and risperidone, may induce metabolic dysfunctions during short-term treatment. Metformin is an effective adjuvant that attenuates antipsychotic-induced metabolic dysfunctions (AIMD) in clinical practice. Whether metformin can reverse AIMD and whether metformin affects the therapeutic effects of antipsychotics in animal models of schizophrenia are questions that still need to be investigated.

METHODS

In this study, an animal model of schizophrenia was established by consecutive injections of MK801 during the neurodevelopmental period. In adulthood, different dosages of olanzapine or risperidone treatment were administered to the schizophrenia model animals for 14 days. Both therapeutic effects and metabolic adverse effects were measured by behavioral tests, histopathological tests, and biochemical tests. The coadministration of different doses of metformin with olanzapine or risperidone was used to evaluate the effects of metformin on both AIMD and the therapeutic effect of those antipsychotics.

RESULTS

The MK801-treated rats showed schizophrenia-like behavior and variations in the shape and volume of the hippocampus. Both olanzapine and risperidone reversed the MK801-induced behavioral abnormalities as the dosage increased; however, they degenerated the hepatocytes in the liver and influenced the blood lipid levels and blood glucose levels. The coadministration of metformin did not affect the therapeutic effects of olanzapine or risperidone on behavioral abnormalities but attenuated the metabolic dysfunctions induced by those antipsychotics.

CONCLUSION

Metformin attenuated the olanzapine- and risperidone-induced metabolic dysfunctions in MK801-induced schizophrenia-like rats without reducing the therapeutic effects of the antipsychotics.

Exercise Protects Against Olanzapine-Induced Hyperglycemia in Male C57BL/6J Mice

Olanzapine is a widely prescribed antipsychotic drug. While effective in reducing psychoses, treatment with olanzapine causes rapid increases in blood glucose. We wanted to determine if a single bout of exercise, immediately prior to treatment, would attenuate the olanzapine-induced rise in blood glucose and if this occurred in an IL-6 dependent manner. We found that exhaustive, but not moderate exercise, immediately prior to treatment, prevented olanzapine-induced hyperglycemia and this occurred in parallel with increases in serum IL-6. To determine if IL-6 was involved in the mechanisms through which exhaustive exercise protected against olanzapine-induced hyperglycemia several additional experiments were completed. Treatment with IL-6 (3 ng/g bw, IP) alone did not protect against olanzapine-induced increases in blood glucose. The protective effects of exhaustive exercise against olanzapine-induced increases in blood glucose were intact in whole body IL-6 knockout mice. Similarly, treating mice with an IL-6 neutralizing antibody prior to exhaustive exercise did not negate the protective effect of exercise against olanzapine-induced hyperglycemia. Our findings provide evidence that a single bout of exhaustive exercise protects against acute olanzapine-induced hyperglycemia and that IL-6 is neither sufficient, nor required for exercise to protect against increases in blood glucose with olanzapine treatment.

Pathophysiological mechanisms of increased cardiometabolic risk in people with schizophrenia and other severe mental illnesses

Patients with schizophrenia have increased mortality and morbidity compared with the general population. These patients have a 20-year shorter lifespan than peers without schizophrenia, mainly due to premature cardiovascular disease, suicide, and cancer. Patients with severe mental illness are at increased risk for cardiovascular disease related to increased incidence of diabetes, hypertension, smoking, poor diet, obesity, dyslipidaemia, metabolic syndrome, low physical activity, and side-effects of antipsychotic drugs. Some second-generation antipsychotics (eg, clozapine, olanzapine, quetiapine, and risperidone) are associated with an increased risk of weight gain and obesity, impaired glucose tolerance and new-onset diabetes, hyperlipidaemia, and cardiovascular disease. The mechanisms by which schizophrenia and patients with severe mental illness are susceptible to cardiometabolic disorders are complex and include lifestyle risks and direct and indirect effects of antipsychotic drugs. An understanding of these risks might lead to effective interventions for prevention and treatment of cardiometabolic disorders in schizophrenia and severe mental illness.