Neuropeptide signaling in the integration of metabolism and reproduction.

Fertility is gated by nutrition and the availability of stored energy reserves, but the cellular and molecular mechanisms that link energy stores and reproduction are not well understood. Neuropeptides including galanin-like peptide (GALP), neuropeptide Y (NPY), products of the proopiomelanocortin (POMC; e.g., alpha-MSH and beta-endorphin), and kisspeptin are thought to be involved in this process for several reasons. First, the neurons that express these neuropeptides all reside in the hypothalamic arcuate nucleus, a critical site for the regulation of both metabolism and reproduction. Second, these neuropeptides are all targets for regulation by metabolic hormones, such as leptin and insulin. And third, these neuropeptides have either direct or indirect effects on feeding and metabolism, as well as on the secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH). As the target for the action of metabolic hormones and sex steroids, these neuropeptides serve as molecular motifs integrating the control of metabolism and reproduction.