We sought to determine a role for NPY overexpression in the dorsomedial hypothalamus (
DMH) in
obesity etiology using the rat model of adeno-associated virus (AAV)-mediated expression of NPY (AAVNPY) in the
DMH. Rats received bilateral
DMH injections of AAVNPY or control vector and were fed on regular chow. Five-week postviral injection, half the rats from each group were switched to access to a high-fat diet for another 11 weeks. We examined variables including
body weight, food intake, energy efficiency, meal patterns,
glucose tolerance, fat mass, plasma
insulin, plasma
leptin, and hypothalamic gene expression. Rats with
DMH NPY overexpression had increased food intake and
body weight and lowered metabolic efficiency. The
hyperphagia was mediated through increased meal size during the dark. Although these rats had normal
blood glucose, their plasma
insulin levels were increased in both basal and
glucose challenge conditions. While high-fat diet induced
hyperphagia,
obesity, and
hyperinsulinemia, these effects were amplified in rats with
DMH NPY overexpression. Arcuate Npy,
agouti-related protein and
proopiomelanocortin expression was appropriately regulated in response to positive energy balance. These results indicate that
DMH NPY overexpression can cause
hyperphagia and
obesity and
DMH NPY may have actions in
glucose homeostasis.