Obesity is one of the most prevalent and costly diseases in Western society, and we currently lack effective, non-invasive treatment strategies. The amylin system is a promising target for a pharmaceutical approach to weight loss, as amylin analogs reduce food intake and body weight in humans and animal models. The ventral tegmental area (VTA), a mesolimbic nucleus that is important in the regulation of food intake, was recently identified as a site of action for amylin-mediated control of feeding. However, the mechanisms by which VTA amylin receptor activation reduces food intake are unknown. The main goal of the proposed 5- year research career development plan is to facilitate the applicant's transition from postdoctoral fellow to a fully independent academic scientist. This wil be accomplished by training the applicant in a variety of molecular, neuroanatomical, and behavioral techniques that will be used to identify mechanisms by which amylin acts in the VTA to reduce food intake and promote weight loss. Understanding more about the central nervous system mechanisms engaged by amylin to decrease feeding will provide new insight into putative targets for the development of obesity pharmacotherapies.
Specific Aim I elucidates the intracellular signals engaged by VTA amylin receptor activation and their relevance to amylin- induced suppression of feeding. The studies in this Aim will identify the signaling molecules upregulated and/or activated by VTA amylin and the specific gene and protein expression mechanisms that induce these signals.
Specific Aim II tests the hypothesis that VTA amylin receptor activation reduces food intake in part by modulating dopamine signaling. Behavioral, immunohistochemical, and voltammetric techniques will be used to probe VTA amylin-induced changes in dopamine signaling in the nucleus accumbens, a key mesolimbic site for the control of feeding. The possibility that VTA amylin may impinge on dopamine signaling to other mesolimbic nuclei will also be explored.
Specific Aim III evaluates the role of VTA amylin signaling for controlling intake of palatable macronutrients, specifically carbohydrate and fat. Behavioral analyses will establish the ability of VTA amylin receptor signaling to modulate intake of each macronutrient, as well as the contribution of post-ingestive gastrointestinal feedback to VTA amylin-mediated reductions in fat and/or carbohydrate intake. Additionally, a novel adeno-associated virus (AAV)-shRNA strategy will be used to knock down amylin receptor expression in the VTA. This approach will be used to examine the chronic requirement of VTA amylin signaling for normal energy balance and macronutrient intake. The novel combination of ex vivo and in vivo techniques utilized in the proposed studies will offer complementary data to deepen our understanding of how amylin activates distributed nuclei in the brain to regulate feeding and energy balance, thus providing important information for the development of more effective obesity pharmacotherapies.
The proposed research is designed to evaluate the mechanisms by which the hormone amylin acts at a recently identified brain site-of-action, the ventral tegmental area, to suppress food intake. Furthering our knowledge of the central nervous system functions of amylin may provide new information into mechanisms controlling energy balance, thereby offering insight into potential targets for the pharmacological treatment of obesity.