Objective: 

Leptin, a hormone-cytokine mainly produced by the adipose tissue, has pleitropic effects on many biological systems. The aim of this study was to investigate the effects of peripheral leptin on lymphocyte subpopulation.

Methods: 

Initially forty male Swiss albino mice were divided into five groups. Mice in group I (Control) were given serum physiologic (SP) and group L100, group L250, group L500, and group L1000 were given 100, 250, 500 and 1000 mg/kg/day recombinant mouse leptin, respectively. Leptin or SP was injected subcutaneously for the next 6 days. Daily food/water intake was recorded for each group. At the end of the study, whole blood samples (500 ml) were obtained via intracardiac punction in anesthetized mice after 15 hours from the last injections. Leptin levels and lymphocyte subpopulations in blood samples were analyzed.

Results: 

No in vivo dose-dependent effect of leptin was seen on lymphocyte subpopulation count in mice. Treatment of mice with high-dose leptin led to increase only CD4+ cells (P < 0.05). In addition, high-dose leptin slightly increased CD3+ cells but this was not statistically confirmed (P = 0.08). Notably, it was found that leptin caused insignificant changes on body weight and food intake in normal body weight mice.

Conclusions: 

The data support that high-dose leptin has proliferative effect on CD4+ cells in vivo.