The adipoinsular axis: effects of leptin on pancreatic beta-cells

The prevalence of obesity and related diabetes mellitus is increasing world wide. Here we review evidence for the existence of an adipoinsular axis, a dual hormonal feedback loop involving the hormones insulin and leptin produ ced by pancreatic beta-cells and adipose tissue, respectively. Insulin is a dipogenic, increases body fat mass, and stimulates the production and secre tion of leptin, the satiety hormone that acts centrally to reduce food inta ke and increase energy expenditure. Leptin in turn suppresses insulin secre tion by both central actions and direct actions on beta-cells. Because plas ma levels of leptin are directly proportional to body fat mass, an increase of adiposity increases plasma leptin, thereby curtailing insulin productio n and further increasing fat mass. We propose that the adipoinsular axis is designed to maintain nutrient balance and that dysregulation of this axis may contribute to obesity and the development of hyperinsulinemia associate d with diabetes.