Aim: The level of plasma leptin, just like insulin and glucose, is decreased during fasting and shows an increase after refeding. In addition, insulin is thought to be a hormone regulating the level of leptin. The aim in this study is to explore how insulin and hyperglycemia affect the level of plasma leptin in experimentally induced diabetic rats.

Material and method: Diabetes was induced in rats via streptozotocin (STZ) injection. STZ-induced hyperglycemic rats were injected with insulin daily. In group I, the insulin dosage arrangement have been made in such a way to keep the blood glucose between 150-300 g/dl; and the other group of animals (Group II) was injected with insulin to keep the blood glucose level at 350-600 g/dl.

Results: There was a significant rate of decrease in the level of leptin in the rats with very high blood glucose. However, the amount of leptin has approached to the control values by showing an increase in the rats having relatively high levels of blood glucose after being injected with high dosages of insulin. Only the values of leptin and triglycerides did show a negative but significant correlation in the rats with very high levels of blood glucose.

Conclusion: In conclusion, high dosages of insulin in diabetic rats normalize the reduced leptin levels and probably exert this effect in the existence of hyperglycemia.