FIGURE 1.

Determinants of hypothalamic weight regulation. This schematic overview focuses on energy homeostasis and feeding centrally regulated in two subsets of neurons within the arcuate nucleus of the hypothalamus. The anorexigenic acting peptide leptin is secreted from adipocytes in proportion to body fat (long-time regulation). Stimulation of the anorexigenic system by leptin leads to satiety achieved through expression of POMC peptides like α-MSH, which acts on melanocortin receptors (MC3R and MC4R), whereas the appetite-activating (orexigenic) system is repressed. Neuropeptide Y (NPY) and agouti-related peptide (AgRP) expression by ghrelin results in appetite stimulation and the initiation of food intake. Ghrelin concentration in the blood fluctuates throughout the day and therefore permits short-time regulation of appetite and food intake. MC3R bridges between the regulatory networks of both feeding systems as well as the different time frames.