Effect of experimentally induced diabetes mellitus on serum leptin level and the role of insulin replacement therapy

ABSTRACT

The regulation of circulating leptin concentration is multifactorial and still understood. Therefore, the present study was designed [1] to demonstrate the effect of gender on leptin concentration in intact control rats, [2] to evaluate the relationship between serum leptin concentration, serum insulin level and body weight in control rats and streptozotocin [STZ] diabetic rats [untreated and treated with insulin]. A total number of 48 healthy adult albino rats of both sexes [24males and 24 females] were used in this study. The animals were divided equally into four groups, each group was subdivided equally into -male and female subgroups. Group 1[G1] served as control group, group 2[G2] experimental diabetics group [not treated] and group 3[G3] and group 4[G4] experimental diabetic group treated with insulin for 2 and 21 days. These groups were examined for the following parameters body weight, blood glucose level, serum insulin and leptin concentration. It was found that serum leptin level was significantly higher in female than in male control group. However, this difference could not be detected in between male and female rats in all other studied groups. Moreover, a strong positive correlation was found between leptin concentration and insulin hormone level, and body weight in control male and female rats. STZ-induced diabetes associated with a significant rapid decrease in circulating leptin concentration [G2], this decrease was accompanied with a significant decrease in both serum insulin level and body weight, then, it was rapidly reversed by insulin treatment for 2days [G3] and 21 days [G4]. There was also a positive correlation between serum leptin concentration, body weight and serum insulin level in this diabetic group. However, leptin was found to change in an inverse proportion to the variation in blood glucose concentration in both male and female diabetic groups. The direct relationship of serum leptin concentration to serum insulin concentration and the inverse relationship of leptin concentration to blood glucose level were preserved in both male and female insulin replacement therapy groups. In conclusion, in adult albino rats, several factors are involved in the regulation of circulating leptin level such as gender, body weight, blood glucose level and serum insulin concentration