The link between stress and feeding behaviour.

Exposure to stress is inevitable, and it may occur, to varying degrees, at different phases throughout the lifespan. The impact of stress experienced in later life has been well documented as many populations in modern society experience increasing socio-economic demands. The effects of stress early in life are less well known, partly as the impact of an early exposure may be difficult to quantify, however emerging evidence shows it can impact later in life. One of the major impacts of stress besides changes in psychosocial behaviour is altered feeding responses. The system that regulates stress responses, the hypothalamo-pituitary-adrenal axis, also regulates feeding responses because the neural circuits that regulate food intake converge on the paraventricular nucleus, which contains corticotrophin releasing hormone (CRH), and urocortin containing neurons. In other words the systems that control food intake and stress responses share the same anatomy and thus each system can influence each other in eliciting a response. Stress is known to alter feeding responses in a bidirectional pattern, with both increases and decreases in intake observed. Stress-induced bidirectional feeding responses underline the complex mechanisms and multiple contributing factors, including the levels of glucocorticoids (dependent on the severity of a stressor), the interaction between glucocorticoids and feeding related neuropeptides such as neuropeptide Y (NPY), alpha-melanocyte stimulating hormone (α-MSH), agouti-related protein (AgRP), melanocortins and their receptors, CRH, urocortin and peripheral signals (leptin, insulin and ghrelin). This review discusses the neuropeptides that regulate feeding behaviour and how their function can be altered through cross-talk with hormones and neuropeptides that also regulate the hypothalamo-pituitary-adrenal axis. In addition, long-term stress induced alterations in feeding behaviour, and changes in gene expression of neuropeptides regulating stress and food intake through epigenetic modifications will be discussed. This article is part of a Special Issue entitled 'SI: Central Control of Food Intake'.