Research Projects

Novel Sites Of Action For Feeding Related Peptides

Many hormones or neuropeptides that contribute to the regulation of energy balance exert their effects at numerous sites throughout the CNS. The pancreatic hormone amylin reduces food intake, but until recently, its ability to suppress feeding had predominantly been attributed to activation of the area postrema, a hindbrain nucleus. Recently, our laboratory found that the ventral tegmental area, a nucleus in the mesolimbic reward system, is another important site of action mediating the ability of amylin to promote negative energy balance. We are following up on this initial discovery by investigating the intracellular and neuroanatomical mechanisms by which amylin signaling in the ventral tegmental area controls energy balance. Understanding more about the distributed actions of amylin to reduce food intake may shed light onto new potential pharmaceutical approaches for the treatment of obesity.

Reward / Motivated Feeding: Why We Override Our Satiation Signals.

It is clear that the excessive food intake, especially of palatable foods, that contributes to human obesity is not driven by metabolic need alone. While our lab investigates the importance of neuropeptide signaling on vagal afferents and in hindbrain and hypothalamic nuclei for the homeostatic control of food intake, it is also critical to examine and better define the neural basis of non-homeostatic controls of food intake.

Ongoing extensive investigations in our lab are examining the neuroendocrine systems that connect within-meal inhibitory feedback from gastrointestinal satiation signals to nuclei in the mesolimbic reward system (MRS), including the ventral tegmental area and nucleus accumbens. Activation of the MRS by these neuroendocrine

systems is postulated to decrease motivation to continue feeding, leading to meal termination. Thus, current projects are investigating the behavioral, molecular, neuronal and physiological mechanisms by which energy balance-relevant neuropeptides (such as glucagon-like peptide-1, leptin, and amylin) are modulating the non-homeostatic controls of feeding mediated by nuclei in the MRS.

Integrative Systems Neuroscience Of Energy Balance

While the CNS control of energy balance involves redundant and anatomically distributed processing across the CNS, a few nuclei, such as the nucleus tractus solitarius (NTS) of the hindbrain, stand out as essential for the processing and integration of a variety of ascending and descending pathways controlling for food intake and energy balance. It is also very clear that more progress could be made in the treatment of obesity if research focused attention on these specific CNS nuclei that serve as hubs for the neural control of energy balance. Thus, our lab explores the intracellular mechanisms by which multiple neurochemical systems interact and synergize at the level of the NTS to control for energy balance.

From Hunger To Nausea: Points On The Same Spectrum Of Ingestive Behavior.

More than 1.6 million cases of cancer are diagnosed yearly in the United States. The toll on the patient can be life-threatening, and unfortunately the pharmacological- and radiation-treatment options for cancer are commonly accompanied by a host of undesirable side effects (pain, diarrhea, anorexia, nausea, vomiting). The severity of these side effects can cause cancer patients to delay or refuse chemotherapy, in turn leading to increased patient morbidity and mortality. With approximately 80% of chemotherapy patients experiencing chemotherapy-induced nausea and vomiting, there is an urgent need to develop more effective anti-emetic and anti-nausea treatments to improve the quality of life for cancer patients undergoing chemotherapy and/or radiation therapy.

Similar to the widely accepted view of nausea being a major side effect for cancer treatment, nausea and/or vomiting are the primary adverse events (i.e. side effects) reported in many patients receiving pharmacotherapy for Type 2 Diabetes Mellitus (T2DM). Indeed, ~20-50% of T2DM patients maintained on the GLP-1R agonists (liraglutide and exendin-4) report nausea/vomiting, and yet there is very little investigation of the mechanisms mediating the nausea/malaise and virtually no understanding of the significance of nausea/malaise in relation to GLP-1 receptor-mediated suppression of food intake.

Although rodents lack the physiology needed to vomit, behavioral paradigms such as pica (ingestion of non-nutritive substances) and conditioned taste avoidance (CTA) are used commonly in both rats and mice as models for the study of malaise and nausea. Our lab utilizes these well-established rat models of malaise to determine the neural pathways and physiological mechanisms responsible for mediating the nausea/malaise induced by GLP-1 receptor ligands and chemotherapy drugs, as well as to determine whether the nausea/malaise is correlated or causal for the intake-inhibitory effects of GLP-1 receptor-targeting pharmaceuticals.