Hypothalamic Regulation of Hepatic Glucose Production and Glucose Homeostasis

Johns Hopkins University, Baltimore MD

Investigators

Linked publications & trials

Abstract

? DESCRIPTION (provided by applicant): The prevalence of the metabolic syndrome and type 2 diabetes has climbed enormously over the last decades. Nearly 26 million Americans (8.3% of the U.S. population) have diabetes (90% of whom are type 2) and additional estimated 79 million US adults (about 35%) have pre-diabetes according to new estimates from the CDC. Insulin resistance is the main culprit in the development of these disorders. Although our understanding of the molecular basis of insulin signaling and insulin resistance has significantly increased, the therapeutic interventions for insulin resistance/type 2 diabetes remain inadequate. Recent reports have shown the importance of central neural signaling in the control of hepatic glucose production and glucose homeostasis. Using adeno-associated virus (AAV)-mediated manipulation of expression of the orexigenic peptide neuropeptide Y (NPY) in the dorsomedial hypothalamus (DMH) to study the function of DMH NPY in the control of energy balance, we have noted a potential role for DMH NPY in the regulation of glucose homeostasis. Our pilot studies have revealed that knockdown of NPY in the DMH enhanced hepatic insulin sensitivity and promoted insulin-induced suppression of hepatic glucose production independently of the changes in body weight. Given that the brainstem/vagal nerve circuits participate in the control of hepatic glucose production, we hypothesize that DMH NPY signaling affects hepatic glucose production to regulate glucose homeostasis via a descending pathway to the brainstem and through the actions of the vagus nerve. The present research project is aimed at assessing this hypothesis via the following three Specific Aims. In Aim 1, we propose to characterize DMH NPY signaling in the regulation of hepatic glucose production by determining the importance of hepatic vagal signaling in DMH NPY regulation of hepatic glucose production and examining the contribution of neural signaling in the nucleus of the solitary tract and the dorsal motor nucleus of the vagus to the glycemic effect of DMH NPY. Aim 2 focuses on identifying the role of DMH NPY modulation of paraventricular nucleus (PVN) oxytocin (OXT) signaling to regulate hepatic glucose production. We will specifically assess whether alterations in OXT signaling in the brainstem affect the glycemic effect of DMH NPY. In Aim 3, experiments are proposed to ascertain the actions of the neuromodulators such as cholecystokinin and agouti-related protein in modulating DMH NPY signaling in the regulation of hepatic glucose production and glucose homeostasis. Overall, the results from this project will elucidate the potential neural mechanism underlying the control of glucose homeostasis, and provide the neural basis for designing potential intervention strategies for the prevention and treatment of insulin resistance and diabetes.