EFFECTS OF GENETIC SELECTION AND VOLUNTARY WHEEL RUNNING ON GLUCOSE TRANSPORT IN MICE

Abstract

504 The effects of genetic selection and free access to running wheels on skeletal muscle (soleus and extensor digitorum longus, EDL) glucose transport was studied. Selective breeding (selected, S) was done over 18 generations of mice using number of revolutions per day on a running wheel as the phenotype. In previous generations, the total revolutions per day and VO2max was significantly greater for S compared to randomly bred control mice (non-selected, NS) (Swallow et al, JAP, 84:1). For each genotype, we randomly assigned animals to one of three treatments for a period of 8 weeks: 1) continuous access to a running wheel; 2) same as 1, but wheels locked 48 hours prior to experiment; and 3) wheels continuously locked. All animals were removed from wheel cages 4-8 hours prior to sacrifice. Nested two-way analysis of variance demonstrated a significant effect of genotype for both body weight and retroperitoneal fat pad weight/body weight ratio (NS heavier than S). There was no significant treatment effect on body weight, however fat pad/body weight ratio was greater in wheel-locked (treatment 3) compared to treatments 1 and 2. Contralateral muscles were studied in vitro so that basal (no insulin) and insulin-stimulated (100 uU/ml) glucose transport (determined using 2-deoxyglucose) were evaluated from each animal. Despite the treatment effect on body composition as indicated by fat pad/body weight ratio, there was no significant effect of treatment on insulin-stimulated glucose transport in either muscle. A significant genotype effect (S greater than NS) was found for insulin-stimulated increase in glucose transport (insulin - basal) for the soleus and EDL. These results indicate that, in addition to changes in VO2max, genetic selection for wheel running activity elicits changes in body composition and insulin action in skeletal muscle. Supported by - AG10026