The role of ghrelin in stress and reward-based eating (#59)
Most people experience altered feeding behaviors upon stress. However, the molecular substrates and neuronal circuits that link complex eating behaviors and stress remain mostly unknown. Ghrelin is a hormone secreted from the gastro-intestinal tract, and its receptor, named the growth hormone secretagogue receptor 1a (GHSR), is highly expressed in the brain. Plasma ghrelin concentrations increase upon stress and also under negative energy balance conditions, such as fasting and calorie restriction. Ghrelin is essential for body weight and energy balance regulation, and it is recognized as the only known orexigenic peptide hormone. Ghrelin was initially shown to act at hypothalamic level, where it regulates neuroendocrine axis and stimulates the food intake by activating on homeostatic circuits, which regulates appetite depending on energy availability. Further evidence showed that ghrelin also acts on mesolimbic circuitries and, as a consequence, regulates hedonic aspects of eating that involve behaviors that lead to the consumption of pleasurable foods. Our laboratory has been studying the physiological implications of ghrelin as a signal of stress to the brain and the impact of ghrelin on reward-based eating. In this talk, I will present our studies that have not only highlighted the role of ghrelin as a key player for the control of stress responses and eating behaviors but also have partially defined the neuronal circuitries and targets by which ghrelin regulates these specific responses.