Leptin: the weight-reducing plasma protein encoded by the obese gene.

Leptin, the protein encoded by the recently cloned obese gene, has the properties of a hormone released by adipose tissue, regulating appetite and energy expenditure. Injected leptin reduces body weight and food intake in mice, and in obese, diabetic mice (with a mutated obese gene), it also reduces plasma insulin and glucose. Leptin release is stimulated by insulin; leptin appears to act on the hypothalamus by inhibiting the release of the neuropeptide Y.