The effect of experimentally induced insulin resistance on the leptin response to hyperinsulinaemia.

Objective: Insulin is thought to be an important regulator of leptin secretion. However, increasing evidence suggests that insulin-mediated glucose uptake rather than insulin per se regulates circulating leptin concentration. Here, we hypothesised that a reduction of insulin sensitivity, ie insulin resistance, will diminish the stimulatory effect of insulin on leptin secretion as a consequence of decreased insulin-mediated glucose uptake.

Short-term treatment with metformin decreases serum leptin concentration without affecting body weight and body fat content in normal-weight healthy men.

A weight-reducing effect of metformin has been demonstrated in obese subjects with and without diabetes. The mechanisms of this action are unclear, which may be partly due to the fact that in obese and diabetic patients the substance's effects result from a complex interaction with the distinct endocrine and metabolic disturbances in these patients. To dissociate primary from secondary action of metformin, we examined effects of the substance in normal-weight healthy subjects.

Vascular endothelial growth factor: a novel endocrine defensive response to hypoglycemia.

Glucose, the most important fuel for the brain, is supplied by the actions of counterregulatory hormones and the sympathetic nervous system. Yet to obtain access to the brain, glucose must pass the blood-brain barrier. Here we show that vascular endothelial growth factor (VEGF), a potent regulator of blood vessel function, is a candidate hormone for facilitating glucose passage across the blood-brain barrier under critical conditions.

Losartan attenuates symptomatic and hormonal responses to hypoglycemia in humans.

Objective: Reduced awareness of hypoglycemic symptoms and compromised hormonal counterregulation increase the risk of severe hypoglycemia in people with diabetes mellitus. Up to the present, angiotensin 1 receptor blockers, which play an important role in controlling diabetic complications, have not been known to increase the risk of hypoglycemia. Nevertheless, we observed 3 cases of diabetic patients complaining of reduced awareness of hypoglycemic symptoms while they were under treatment with losartan in our outpatients clinic.

Hypoglycemia, but not insulin, acutely decreases LH and T secretion in men.

Hypoandrogenemia is frequently associated with hyperinsulinemia in men with the metabolic syndrome. We questioned whether insulin or changes in blood glucose levels influence pituitary gonadotropin secretion or testicular steroidogenesis in healthy men. Also, the relationship between hypoglycemia-induced activation of the hypothalamus-pituitary-adrenal axis and altered steroidogenesis was examined.