Ovarian hormones, but not androgens, mediate running-induced changes in high fat diet choice patterns in rats

Physical inactivity and increased consumption of energy dense, high fat (HF) foods leads to a state of positive energy balance. Regular exercise can facilitate the maintenance of a healthy body weight and mediate changes in dietary selection. Past studies using a two-diet choice (chow vs. HF) and voluntary wheel running paradigm found that upon simultaneous introduction of a novel HF diet and wheel running, male rats show complete and persistent HF diet avoidance whereas the majority of females reverse HF diet avoidance. Ovariectomy (OVX) appears to decrease HF diet preference, bringing it closer to what is observed in male rats. Given that estrogen, but not progesterone, mediates changes in food intake and energy balance, we hypothesized that estrogen signaling is required for the reversal of HF diet avoidance in female rats. Accordingly, Experiment 1 compared the persistency of running-induced HF diet avoidance in males, sham-operated females, and OVX rats with replacement of oil vehicle, estrogen (E), progesterone (P), or both (E+P). Results showed that the number of rats and time point at which wheel running rats reversed HF diet avoidance varied. The reversal of HF diet avoidance in running females and OVX E+P rats occurred more rapidly and frequently than male running rats. E+P, but not E or P, replaced OVX wheel running rats significantly reversed HF diet avoidance. OVX oil rats avoided HF diet to the same extent as male rats for the first 11 days of diet choice and then rapidly increased HF diet intake and began preferring it. This incomplete elimination of sex differences suggests that developmental factors or androgens might play a role in sustaining running-induced HF diet avoidance. Subsequently, Experiment 2 aimed to determine the role of androgens in the persistency of running-associated HF diet avoidance with sham-operated and orchiectomized (GDX) male rats. The results showed that both intact and GDX male running rats persistently avoided the HF diet to the same extent. Taken together, these results suggest that both organizational and activational effects of ovarian hormones play a role in female specific running-induced changes in diet choice patterns. Importantly, the activational effects of androgens are not required for the expression of HF diet avoidance in males.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste