The Effect of Leptin Level Fluctuations by a Repeated Fasting/Refeeding on the Leptin Sensitivity in OLETF Rats

Abstract

Background: Leptin resistance is a common feature in obese subjects and animals, and this is commonly accompanied with hyperleptinemia. We speculated that one of the causes of leptin resistance is a persistently elevated leptin concentration and then we hypothesized that fluctuations of serum leptin would increase leptin sensitivity in the leptin-resistant state. Methods: We used a repeated fasting and refeeding (RFR) protocol to produce fluctuation in leptin levels in 7 month-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats and Long-Evans Tokushima Otsuka (LETO) rats, We then measured the leptin sensitivity following an intracerebroventricular (i.c.v.) infusion of leptin. Results: The OLETF rats exhibited severe visceral fat deposition, hyperleptinemia and leptin resistance. However, in the OLETF-RFR rats, the anorexic effect following i.c.v. leptin infusion was restored. Moreover, the visceral fat mass and serum leptin levels decreased, while the serum adiponectin levels were elevated in the OLETF-RFR rats compared to the OLETF-Control rats. The leptin receptor content in the hypothalamus increased in the OLETF-RFR rats compared to the OLETF-Control rats, and the leptin receptor content in the OLETF-RFR rats decreased compared to that in the the LETO-Control rats. Conclusions: These results suggest that the intermittent suppression of the serum leptin level reversed the leptin resistance in OLEFT rats, and this may have occurred due to an increased number of leptin receptors in the hypothalamus. (J Korean Endocr Soc 23:310~318, 2008)