Voluntary whhhl running normalizes insulin resistance and reduces ob mrna expression in adipose tissue ok osborne-mendel rats

1'he purpose of this study was to assess the effects of voluntary wheel running on regional adipose I issue (AT) mass, cell size, fal celi insulin sensitivity, and AI expression of Oh mRNA in rats that are either sensitive (OM) or resistant (S5B/PI) to dietary fat induced ohesit>. Male OM and S5B/P1 rats had ad libitum access to standard rodent chow and water. At 3-5 weeks of age. animals of both strains were randomly assigned to either an exercise or sedentary control group. The exercise groups had 24 hr access to a running wheel. After 8 weeks of training, animals were sacrificed and the following fat depots were dissected and weighed: inguinal, epididymal, retroperitoneal, and perirena! Animals in both OM and S5B/P1 exercise groups ran more in subsequent weeks than the previous week. Oral glucose tolerance tests performed during the 7th week of training revealed a significant reduction in area under the insulin curve for OM, but little change in S5B/P1. Insulin sensitivity for glucose oxidation of epididymal fat cells m vitfi was significant!) increased in both strains with exercise. Inguinal, epididymal. and retroperitoneal fat depots weighed less in the running than in the nonrunning groups of both strains (p < 0.01), but there was a more dramatic shift in the fat cell size distribution (i.e., from larger to smaller cells) in the OM exercisers Kpididymal Ob protein mRNA was measured by Northern Blot analysis using a 520 bP cDNA probe derived by PCR from ral retroperitoneal AT Ob protein mRNA levels in sedentary OM animals were higher than in S5B;PI; however, with exercise training a significant reduction in Ob protein mRNA expression was only observed in the OM animals. These results support the hypothesis that fat cell si/e and insulin sensitivity are important regulators of Ob protein mRNA expression.