Figure 1.

The illustration focuses on the regulation of energy homeostasis by the hypothalamus. NPY/AgRP and POMC/CART neurons located in the ARC of hypothalamus project to secondary neurons such as PVN, DMH, VMH, LHA, and secrete orexigenic AgRP or anorectic POMC. The MC3/4R in PVN are activated after binding with the active component a-MSH cleaved by POMC, and the integrated signals are transmitted to the NTS to regulate feeding behavior. Meanwhile, PVN also secretes anorexic neurohormones CRH to suppress food intake. BDNF located in the VMH is the downstream effector of a-MSH, which plays a role in inhibiting food intake. LHA is mainly stimulated by NPY/AgRP neurons in the ARC and secretes orexigenic peptides, orexin and MCH. Peripheral signals from adipose tissue, pancreas or the gastrointestinal tract either enter the hypothalamus through the median eminence, or connect to the NTS in the brainstem via acting on the vagus nerve afferents, and these signals effectively induce activities of the related nuclei, such as ARC and NTS, then influence the second order neurons of PVN, VMH. DMH and LHA.