Fluctuation of serum leptin level in rats after ovariectomy and the influence of estrogen supplement

In order to understand the mechanism of increasing body fat in perimenopaus al and postmenopausal women, an ovariectomy-induced obesity model was used to study the role of leptin. In this investigation, a long-term study laste d for 13 weeks was conducted to monitoring the change of serum leptin level in rats after the loss of estrogen, and also to examine the influence of e strogen replacement. The results showed that three weeks after the removal of ovaries the body weight of Ovx rats was already significantly higher tha n the other two groups, and continued to gain more weight thereafter. Accom panying with the significant weight gain was the changes in the serum lepti n levels. The leptin concentration declined gradually during the first half of experimental period, dropping down to an almost undetectable level at w eek 7 (0.216+/-0.132 ng/ml). Subsequently, its concentration began to eleva te, and by the end of experiment leptin level was significantly higher (3.1 82+/-0.936 ng/ml) than the value before the operation (0.818+/-0.242 ng/ml) . This fluctuation of serum leptin level caused by ovariectomy was eliminat ed by the replacement of estrogen. The present data indicate that ovariecto my-induced weight gain is caused by the early drop in leptin level. The lat er rise in leptin production is connected to the increased body weight prob ably originated from a reduced sensitivity in leptin signal.