The role of melatonin
in human insulin regulation is poorly understood.
To investigate the influence of melatonin
supplementation on glucose and insulin levels and on lipid metabolism in blood serum and the liver.
The acute melatonin
effects on insulin secretion
in male Wistar rats were investigated. In addition, carbohydrate and lipid metabolism was studied. In in vivo experiments, melatonin
was administered subcutaneously in two different doses (0.5 and 1.0 mg/kg body weight, respectively), and animals were decapitated after 1 hour.
The higher dose of the hormone increased insulin level in blood. The applied pancreas perfusion
technique allowed us to confirm a direct mechanism of melatonin
action on the pancreas. The ability of melatonin
to stimulate insulin output was dose dependent. The highest effect was noticed for 100 nmol/L, whereas 1 nmol/L did not influence this process.
treatment in vivo caused many biochemical consequences. The hormone augmented significantly the concentrations of total, free, and esterified cholesterol, as well as high-density lipoprotein cholesterol in blood. Together with the enhanced insulin secretion
observed in the in vivo experiment, the level of free fatty acids in blood decreased and, surprisingly, glucose concentration was significantly elevated.