Provision of a voluntary exercise environment enhances running activity and prevents obesity in Snark-deficient mice

The present study was performed to investigate the involvement of SNARK in physical activity levels in mice. To examine the acute effect of SNARK deficiency on voluntary running, Snark-deficient mice (Snark(+/-): n = 16) and their wild-type counterparts (Snark(+/+): n = 16) were assigned to sedentary or exercise (1 wk voluntary wheel running) groups. In addition, to clarify the differences in voluntary running activity and its effect between genotypes, mice (Snark(+/+): n = 16; Snark(+/-): n = 16) were also kept in individual cages with/without a running wheel for 5 mo. Unexpectedly, in both voluntary running experiments, running distances were increased in Snark(+/-) mice compared with Snark(+/+) mice. Under sedentary conditions, body and white adipose tissue weights were increased significantly in Snark(+/-) mice. However, no significant differences were observed between the two genotypes under exercise conditions, and the values were significantly less than those under sedentary conditions in the long-term experiment. In the short-term experiment, serum interleukin-6 level in exercised Snark(+/+) mice was the same as that in sedentary Snark(+/+) mice, whereas that in sedentary Snark(+/-) mice was significantly lower than in the other groups. In contrast, serum leptin level was reduced significantly in exercised Snark(+/-) mice compared with sedentary Snark(+/-) mice. The results of this study demonstrated that exposure to an environment that allows voluntary exercise promotes increased running activity and prevents obesity in Snark-deficient mice.