Three weeks of postweaning exercise in DIO rats produces prolonged increases in central leptin sensitivity and signaling

Patterson CM, Bouret SG, Dunn-Meynell AA, Levin BE. Three weeks of postweaning exercise in DIO rats produces prolonged increases in central leptin sensitivity and signaling. Am J Physiol Regul Integr Comp Physiol 296: R537-R548, 2009. First published January 21, 2009; doi: 10.1152/ajpregu.90859.2008. -In rats selectively bred to develop diet-induced obesity ( DIO) 3 wk of postweaning exercise reduces weight and adipose regain for 10 wk after exercise cessation, despite intake of 31% fat high-energy ( HE) diet. To test the hypothesis that this effect is due to increased central leptin sensitivity, 4-wk-old DIO rats were fed the HE diet and left sedentary ( Sed), exercised for 3 wk, and then remained sedentary for 10 additional weeks (Ex/Sed) or continued exercise for a full 13 wk ( Ex). After 3 wk, leptin ( 5 mg/kg ip) induced a 36% decrease in 24-h food intake in Ex rats, while Sed rats had no change in 24-h intake. Ex rats also had 23% more leptin-induced phospho-STAT3 (pSTAT3)-expressing neurons in the arcuate nucleus ( ARC) and 95% and 68% higher I-125-labeled leptin receptor binding in the ventromedial and dorsomedial nuclei than did Sed rats, respectively. At 7 wk after onset, leptin decreased 24-h intake by 20% in Ex and 24% in Ex/Sed rats without altering Sed intake. After a total of 13 wk, compared with Sed rats, Ex and Ex/Sed rats had 58% and 38% less fat, respectively, but leptin failed to decrease food intake in any group. Nevertheless, Ex, but not Ex/Sed rats, still had 32% more ARC leptin-induced pSTAT3-expressing neurons than Sed rats. These data suggest that brief postweaning exercise in DIO rats that are inherently leptin resistant causes a sustained resistance to obesity on HE diet, which is, in part, due to increased central leptin sensitivity.