Plasma and cerebrospinal fluid leptin levels are maintained despite enhanced food intake in progesterone-treated rats

Objectives: For adipostatic control, increases in food intake are followed by increased leptin levels that in turn reduce food intake. However, progesterone administration increases both food intake and body weight. The aim of this study was to analyze changes in the white adipose tissue-leptin system in rats with enhanced plasma levels of progesterone. Methods: Female Wistar rats received progesterone chronically by means of subcutaneous implants over 30 days. Results: They showed an increased food intake followed by increased body weight and heavier fat depots. An enhanced ob-mRNA level was detected in inguinal white adipose tissue depot on day 2 of treatment but the increase was transient, disappearing on day 6 of treatment. No changes in ob-mRNA levels were found in parametrial and retroperitoneal white adipose tissue depots. Plasma and cerebrospinal fluid leptin levels were unchanged either during the treatment or between corresponding treated and control rats. Leptin concentrations in cerebrospinal fluid were ten times lower than in plasma (0.2-0.3 ng/ml versus 2-3 ng/ml respectively). Conclusions: These results indicated that progesterone Favours a positive energy balance not only by enhancing food intake but also by inhibiting the concurrent enhancement in plasma and cerebrospinal fluid leptin levels expected from the increased fat mass.