Leptin: 30 Years Later.

The discovery of leptin as an adipocyte-secreted hormone encoded by the ob gene whose absence produces severe obesity that is corrected by leptin repletion in both mice and humans was a transformative event in metabolic science. Leptin's discovery in 1994 accelerated the identification of central neuronal circuitry responsive to peripheral signals that regulate energy balance as well as metabolic, neuroendocrine, and other vital functions. Leptin's primary physiological role was initially viewed as preventing obesity by its levels rising, but subsequent research has emphasized the key role of falling levels to signal starvation. Resistance to leptin action, though partial, characterizes common forms of obesity. Despite much being learned about leptin signal transduction over 30 years, the precise molecular mechanisms for leptin resistance and common obesity remain unclear. Leptin therapy is effective in rare patients with congenital leptin deficiency and other low leptin conditions but not common obesity. Interestingly, reducing hyperleptinemia may prove useful in treating common obesity.