Central nervous system delivery of the antipsychotic olanzapine induces hepatic insulin resistance.
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.


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 (R(a)) in the basal period. During the hyperinsulinemic clamp, the glucose infusion rate (GIR) required to maintain euglycemia and the rate of glucose utilization (R(d)) 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 R(a) in the basal period. During the hyperinsulinemic period, OLZ-ICV caused a decreased GIR, an increased EGP, but no change in R(d). 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.
Martins
Paulo J F
PJ
Obesity Research Center, University of Cincinnati, Cincinnati, Ohio, USA.
Haas
Michael
M
Obici
Silvana
S
D000818:Animals; D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001569:Benzodiazepines / Q000008:administration & dosage / Q000494:pharmacology*; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D002339:Carotid Arteries / Q000503:physiopathology; D017931:DNA Primers; D015309:Glucose Clamp Technique; D005952:Glucose-6-Phosphatase / Q000187:drug effects / Q000235:genetics; D006946:Hyperinsulinism / Q000503:physiopathology; D007262:Infusions, Intravenous; D007276:Injections, Intraventricular; D007333:Insulin Resistance / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000187:drug effects / Q000235:genetics; D007601:Jugular Veins / Q000503:physiopathology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009479:Neuropeptides / Q000187:drug effects / Q000235:genetics; D000077152:Olanzapine; D000068797:Orexins; D011333:Pro-Opiomelanocortin / Q000187:drug effects / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014404:Tubulin / Q000187:drug effects / Q000235:genetics
D014150:Antipsychotic Agents; D001786:Blood Glucose; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D014404:Tubulin; D001569:Benzodiazepines; D011333:Pro-Opiomelanocortin; D005952:Glucose-6-Phosphatase; D000077152:Olanzapine