Metabolic effects of voluntary wheel running in young and old Syrian golden hamsters

To explore the metabolic effects of high volume wheel running in the Syrian golden hamster, 6-week old (YOUNG) and 6-month old (OLD) male animals were randomly divided into sedentary (i.e., YOUNG-S or OLD-S) or running wheel (i.e., YOUNG-RW or OLD-RW) groups (n = 8/group). RW groups had 24-h access to activity wheels while S were housed in standard rodent cages. At the start of wheel exposure, the number of revolutions were similar in both groups, but by day 15 were nearly two-fold higher in the YOUNG vs. OLD. OLD ate more than YOUNG and wheel running increased food intake by approximately 50%. YOUNG-RW maintained the same total body mass as YOUNG-S, while OLD-RW had a transient weight loss of approximately 10 g. Perirenal fat mass was smaller in YOUNG- and OLD-RW groups compared with S groups (45% and 66%, respectively. Plantaris muscle cytochrome c oxidase activity was also approximately 2-fold higher in YOUNG-RW than in YOUNG-S hamsters but was similar between OLD-RW and OLD-S groups. Plasma leptin levels were approximately 60% lower in YOUNG-RW compared with YOUNG-S and correlated significantly with visceral fat pad mass (r2 = 0.58, p = 0.001). Corticosterone levels were lower in YOUNG-RW (13.0 +/- 0.36 ng/ml) than in YOUNG-S (16.4 +/- 0.83 ng/ml) hamsters and higher in OLD-RW (22.62 +/- 0.47 ng/ml) than in OLD-S (15.54 +/- 0.13 ng/ml) hamsters. These observations reveal that the hamster is a suitable model for accelerating the effects of exercise on body composition and metabolic alterations associated with training and that the training adaptations are more pronounced in younger compared with older hamsters, possibly as a result of the higher voluntary wheel activity in the former group.