Grant: Master's Award: Canada Graduate Scholarships

Obesity has emerged as one of the top global health issues posing a major risk for a number of chronic diseases including type II diabetes, cardiovascular disorders, stroke, atherosclerosis, cancer, depression, dementia and Alzheimer's disease. In Canada, more than half the adult population is overweight or obese. Since obesity diminishes the health, quality of life and increases morbidity, it is of utmost importance to determine the underlying mechanism and to identify potential molecular therapeutic targets. Obesity commonly results from excess caloric intake over energy expenditure. Palatable diets high in sugar, salt and/or fat typical of today's western society is thought to override the homeostatic satiety mechanism and promote hedonic feeding. Repeated exposure to palatable diet can cause development of preference and overconsumption of such diet. However, the molecular and cellular mechanism underlying the effect of palatable food on the reward circuitry in the brain is incompletely understood. Food intake is ultimately regulated by the brain. In a preliminary study, we found that local injections of nociceptin/orphanin FQ, an endogenous opioid, into the lateral hypothalamus of rats induced a decrease in palatable sugar pellet intake. Interestingly, after the animals were repeatedly given weekly access to sugar pellets for 9 weeks and acquired a preference for sugar, nociceptin no longer exerted its inhibitory effect. The current study will test the hypothesis that nociceptin is an inhibitory regulator of palatable food intake whose action becomes desensitized as preference for palatable food develops. The results could implicate the regular consumption of palatable foods in offsetting the body's natural mechanisms for food intake control and provide a target for therapeutic intervention.