Central Nervous System Delivery of the Antipsychotic Olanzapine Induces Hepatic Insulin Resistance
- Corresponding author: Silvana Obici, .
OBJECTIVE Olanzapine (OLZ) is an atypical antipsychotic whose clinical efficacy is hampered by side effects including weight gain and diabetes. Recent evidence shows that OLZ alters insulin sensitivity independent of changes in body weight and composition. The present study addresses whether OLZ-induced insulin resistance is driven by its central actions.
RESEARCH DESIGN AND METHODS Sprague-Dawley rats received an intravenous (OLZ-IV group) or intracerebroventricular (OLZ-ICV group) infusion of OLZ or vehicle. Glucose kinetics were assessed before (basal period) and during euglycemic-hyperinsulinemic clamp studies.
RESULTS OLZ-IV caused a transient increase in glycemia and a higher rate of glucose appearance (Ra) in the basal period. During the hyperinsulinemic clamp, the glucose infusion rate (GIR) required to maintain euglycemia and the rate of glucose utilization (Rd) were decreased in OLZ-IV, whereas endogenous glucose production (EGP) rate was increased compared with vehicle-IV. Consistent with an elevation in EGP, the OLZ-IV group had higher hepatic mRNA levels for the enzymes glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. Phosphorylation of hypothalamic AMP-activated protein kinase (AMPK) was increased in OLZ-IV rats compared with controls. Similarly, an intracerebroventricular infusion of OLZ resulted in a transient increase in glycemia as well as a higher Ra in the basal period. During the hyperinsulinemic period, OLZ-ICV caused a decreased GIR, an increased EGP, but no change in Rd. Furthermore, OLZ-ICV rats had increased hepatic gluconeogenic enzymes and elevated hypothalamic neuropeptide-Y and agouti-related protein mRNA levels.
CONCLUSIONS Acute central nervous system exposure to OLZ induces hypothalamic AMPK and hepatic insulin resistance, pointing to a hypothalamic site of action for the metabolic dysregulation of atypical antipsychotics.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
- Received March 31, 2010.
- Accepted July 23, 2010.
- © 2010 by the American Diabetes Association.
Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.