Diabetes
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Leptin is an adipocyte-secreted hormone important in energy homeostasis and diverse physiological processes. A circulating soluble form of the leptin receptor [soluble leptin receptor (sOB-R)] is the main leptin-binding protein and determinant of free leptin index (FLI), the presumed biologically active form of leptin. We performed observational and interventional studies to elucidate the regulation of sOB-R and FLI in humans. ⋯ Physiological and pharmacological doses of recombinant-methionyl human leptin (rhLeptin) administered to fasted men prevented the fasting-induced increase of sOB-R levels, and pharmacological doses resulted in a decrease in sOB-R levels. These studies provide evidence that sOB-R is regulated by gender, adiposity, hormones, and rhLeptin administration. This may have important implications for the biological activity of leptin in disease states associated with abnormal leptin levels (e.g., obesity and anorexia nervosa).