Role of hypothalamic Foxo1 in the regulation of food intake and energy homeostasis.

Insulin signaling in the hypothalamus plays a role in maintaining body weight. Studies suggest that the forkhead transcription factor Foxo1 is an important mediator of insulin signaling in peripheral tissues. Here we demonstrate that in normal mice, hypothalamic Foxo1 expression is reduced by the anorexigenic hormones insulin and leptin. These hormones' effects on feeding are inhibited when hypothalamic Foxo1 is activated, establishing a new signaling pathway through which insulin and leptin regulate food intake in hypothalamic neurons. Moreover, activation of Foxo1 in the hypothalamus increases food intake and body weight, whereas inhibition of Foxo1 decreases both. Foxo1 stimulates the transcription of the orexigenic neuropeptide Y and Agouti-related protein through the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway, but suppresses the transcription of anorexigenic proopiomelanocortin by antagonizing the activity of signal transducer-activated transcript-3 (STAT3). Our data suggest that hypothalamic Foxo1 is an important regulator of food intake and energy balance.