O9.2. ANTIPSYCHOTIC DRUGS IMPAIR BRAIN GLUCOSE SENSING RESULTING IN WHOLE BODY INSULIN RESISTANCE
Authors: Castellani Laura , Kowalchuk Chantel , Asgariroozbehani Roshanak , Tran Veronica , Brett McIntyre William , Hamel Laurie , Remington Gary , Giacca Adria , Hahn Margaret 
Published: May 2020

Abstract

Background
Antipsychotics (APs) remain the cornerstone treatment for schizophrenia, and are widely used on- and off-label for other psychiatric disorders. However, their use presents a significant risk for serious adverse glycemic effects. Independent of changes in adiposity, APs directly dysregulate whole body glucose metabolism, and this may occur through the central nervous system (CNS). To this end, we have recently demonstrated that the second-generation AP, olanzapine, impairs hypothalamic insulin-action, resulting in dysregulation of whole-body insulin sensitivity. In addition to a critical role of hormones such as insulin in the CNS, glucose-sensing at the hypothalamus is also pivotal for the regulation of whole-body insulin sensitivity. Glucose also represents the primary fuel for brain function, and the hypothalamus represents the key brain center (through glucose sensing neurons) to partition resources to ensure maintenance of key homeostatic systems. In the current study, we set out to examine the effects of a first generation AP (e.g. haloperidol) and second-generation AP(e.g. olanzapine) on hypothalamic-glucose sensing, and subsequent regulation of peripheral glucose metabolism.

Methods
Gold-standard, pancreatic-euglycemic clamps were used to assess changes in glucose kinetics in response to a primed, continuous intracerebroventricular (ICV) infusion of glucose or vehicle solution (2mM, 5μL/hour, into the 3rd ventricle). Male rats were co-treated with an acute injection of olanzapine (3mg/kg, S.C.), haloperidol (10mg/kg, S.C.) or a weight adjusted vehicle solution. Dosing of APs was based on clinical D2 occupancies. Groups included (ICV–peripheral) vehicle–vehicle (n = 6), glucose–vehicle (n = 8), glucose–olanzapine (n = 6), vehicle–olanzapine (n = 6), glucose-haloperidol (n = 6) and vehicle-haloperidol (n = 7). The peripheral glucose infusion rate needed to maintain euglycemia during the clamp was used as a measure of whole-body insulin sensitivity.

Results
As expected and previously demonstrated, ICV (central) glucose infusion caused a significant increase in the peripheral glucose infusion rate of glucose (mg/kg.min) compared to vehicle treated rats (Veh-Veh 3.11±0.73 vs Glu-Veh 8.39±1.61), p&lt;0.05). This effect was mitigated by treatment with both olanzapine (Glu-Veh 8.39±1.61, Glu-Ola 0.63±0.37, p&lt;0.05) and haloperidol (Glu-Veh 8.39±1.61, Glu-Hal 3.01±0.46, p&lt;0.05). In summary, olanzapine and haloperidol both impaired central glucose sensing resulting in whole body insulin resistance.

Discussion
Hypothalamic glucose-sensing is critical for the regulation of peripheral glucose homeostasis. This data, for the first time, demonstrates evidence that both first- and second-generation APs disrupt hypothalamic glucose-mediated regulation of glucose kinetics. Perturbed glucose-sensing in the CNS is expected to have deleterious consequences for metabolic homeostasis, and possibly other brain glucose-dependent functions such as cognition. The study unveils a novel effect of AP treatment to disrupt brain nutrient-sensing, suggesting this may be a mechanism by which these drugs increase risk of type 2 diabetes.