Effects of exercise training on energy balance of ovariectomized rats.
The purpose of the present study was to investigate both the respective and interactive roles of exercise training and ovarian hormones on the regulation of energy balance. Female rats were divided into sedentary and exercise-trained groups. Each group thus formed was further divided into a sham-operated group, an ovariectomized group, or ovariectomized estradiol-treated group. Rats were exercise trained on a rodent motor-driven treadmill. After 33 days of treatment, rats were killed and the energy contents of carcasses, feces, and food were determined. Brown adipose tissue (BAT) thermogenesis was assessed through mitochondrial GDP binding. The results show that ovariectomy led to increases in food intake, body weight, and protein gains, whereas estradiol treatment abolished these effects. The results also show that exercise training reduced fat gain. Exercise training interacted with ovariectomy on energy gain; in sedentary rats ovariectomy enhanced the energy gain, an effect that disappeared in exercise-trained rats. However, exercise training was found to alter neither body weight and protein gains nor energy intake. Ovariectomy did not affect energy expenditure when the results are expressed in relative terms (kJ.kg body wt-0.67.day-1). Similarly, exercise training did not modify energy expenditure (kJ.kg body wt-0.67.day-1) once the cost of the training program was subtracted. BAT mitochondrial GDP binding was not affected by any of the experimental treatments. The present results therefore suggest that neither ovariectomy nor exercise training affect energy expenditure through regulatory forms of BAT-mediated thermogenesis.