IS LEPTIN AN INSULIN COUNTER-REGULATORY HORMONE

Leptin, the product of the ob gene, controls appetite through the hypo thalamus and may affect many other tissues because of the widespread d istribution of its receptors, Leptin is synthesized by white adipose t issue (WAT) under conditions of high energy availability and insulin s timulus, Glucocorticoids enhance this synthesis and catecholamines ham per leptin production, Leptin diminishes insulin secretion by the panc reatic beta cells and induces insulin resistance, In fact leptin hampe rs insulin action on WAT itself in a negative feedback loop, The evide nce acquired in studies on diabetics, starvation, refeeding and insuli n and glucose clamps supports this interpretation, which may also expl ain part of the difficulties encountered by the current postulate that links leptin to WAT mass size signalling to the brain, Leptin may be, essentially, a counter-regulatory hormone limiting the insulin drive to store energy in the form of fat, its effects reaching from a decrea se in food intake to lower insulin secretion and increased resistance to insulin and lower glucose uptake and fat synthesis by WAT.