Abstract
Background and Objectives:Leptin is a peptide hormone secreted by an adipose tissue. It acts as a satiety signal to hypothalamus and informs the central nervous system about the amount of fat mass. Insulin and leptin play important roles in controlling body weight. In this study we assessed the effects of insulin on plasma levels of leptin in diabetic rats.
Materials and Methods: Diabetes was induced in 15 male Sprague Dawley rats with intraperitoneal injection of 50mg/kg streptozotocin (STZ). Then rats were divided into three groups: 1) non-treated, 2) insulin 10u/kg/day treated and 3) insulin 20u/kg/day treated. One blood sample before and three blood samples with one-day interval after induction of diabetes were collected from eye angle of rats.
Results: Analysis of data indicated that: 1) before induction of diabetes there was no significant difference in the mean levels of leptin, insulin and glucose among groups, 2) after induction of diabetes, plasma levels of leptin and insulin was lower significantly in non-treated diabetic rats compared with treated rats (p<0.05), while glucose levels were higher significantly in non-treated rats (P<0.05), 3) insulin treatment maximally after 2 hours produced a significant increase in plasma leptin concentrations, and 4) in 20u/kg/day insulin treated rats plasma levels of leptin and insulin were higher, while glucose was lower significantly (p<0.05) compared with 10u/kg/day insulin treated rats.
Conclusion: In conclusion, this study showed that insulin is one of the necessary factors that may act by transferring of glucose into the adipose cells, so glucose as intracellar signal stimulates leptin secretion from adipose tissue of STZ-diabetic rats. This stimulatory effect of insulin on leptin secretion acted maximally 2 hours after subcutaneous injection of insulin to STZ-diabetic rats.