Chronic voluntary exercise down-regulates Ob-Rb mRNA in the ARC in Wistar rat, but doesn't influence in OLETF rat -an animal model of obesity and hyperphagia-

Abstract

Regular exercise is known to result in reduction of fat tissue mass and serum leptin level followed by an increase in eating behavior. However, the effect of exercise on leptin receptor subtype-b (Ob-Rb) in the arcuate nucleus of the hypothalamus (ARC) has not yet been reported in old Wistar and OLETF rats. The purpose of this study was to investigate the effects of regular exercise on the expression of Ob-Rb mRNA in the ARC.
Male Wistar and OLETF rats were randomly assigned to either the exercise or control group, respectively. At 26~38 weeks, exercising rats housed freely accessible running wheels and all rats were provided with water and chow food ad libitum.
Chronic voluntary exercise remarkably reduced fat tissue mass and blood leptin level in both Wistar and OLETF rats. In Wistar rats, no change was observed with regard to food intake, and this demonstrated leptin resistance. There was a significant decrease in gene expressions of Ob-Rb in the ARC. On the other hand, exercise did not influence the hypothalamic Ob-Rb mRNA expression and resulted in a remarkable elevation of appetite in OLETF rats. The present findings suggest that de-sensitive regulation of leptin induced by long-term exercise might lower the signal of fat volume change to regulate food intake in old Wistar rats, but not in obese and hyperphagic OLETF rats. [Jpn J Physiol 54 Suppl:S239 (2004)]