Leptin regulates glucose homeostasis via the canonical WNT pathway.

Leptin is a body weight regulatory hormone, but it is arguably even more potent at regulating blood glucose levels. To further our understanding of the molecular mechanisms by which leptin controls glucose homeostasis, we have used transgenic zebrafish models and conditional deletion of beta catenin in the mediobasal hypothalamus of adult mice to show that Wnt signalling in the brain mediates glucoregulatory effects of leptin. In zebrafish, under normal feeding conditions, leptin regulates glucose homeostasis but not adipostasis. In times of nutrient excess, we found that leptin also regulates body weight and size in this species. Using a Wnt signalling reporter fish, we show that leptin directly activates the canonical Wnt pathway in vivo. Pharmacological inhibition of this pathway prevented the leptin-induced improvement in glucose tolerance. In adult mice, conditional deletion of the key Wnt effector molecule, {beta}-catenin, in the mediobasal hypothalamus of male mice confirmed the essential role of the Wnt pathway in mediating leptin action and the neuroendocrine regulation of glucose homeostasis. Adult-onset {beta}-catenin deletion in the mediobasal hypothalamus led to glucose intolerance, exacerbation of caloric intake and body weight gain under high fat diet, as well as resistance to exogenous leptin.