Metabolic effects of physical training in ovariectomized and hyperestrogenic rats

Abstract

This study was undertaken to evaluate the effects of regular endurance-type exercise on glucose tolerance and glucose-stimulated insulin response (GSIR) in ovariectomized (OVX) rats with and without estrogen replacement. To do that, OVX Sprague-Dawley rats were compared with an OVX estradiol-treated group (OVXE2) and a sham-operated (Sham) group. Each of these groups was subdivided into a sedentary and a treadmill-trained (8 wk) group. Intravenous glucose tolerance tests (0.5 g/kg) were conducted in all rats 48 h after the last training session. Plasma levels of 17beta-estradiol and the uterus weight were significantly (P < 0.05) lower in OVX compared with results in Sham and significantly (P < 0.01) higher in OVXE2 (hyperestrogenic) compared with results in Sham. Body weights were significantly (P < 0.01) different among groups, in the following decreasing order: OVX, Sham, and OVXE2. The average daily food intake was significantly (P < 0.01) increased in OVX rats compared with Sham, whereas estradiol treatment diminished this effect (P < 0.01). Exercise training was found to alter none of the above-mentioned variables in all three experimental conditions. Although the mean integrated area under the glucose and insulin curves was not affected by OVX, training induced a significant (P < 0.01) reduction in the mean integrated area under the insulin curve in all three experimental conditions. It is concluded that the positive effects of physical training on improving GSIR in OVX and hyperestrogenic animals are similar to what has been found in Sham.

Effects of physical training on body composition and organ weights in ovariectomized and hyperestrogenic rats

“…24,25 We recently reported that exercise training in OVX rats results in an improvement of the insulin-resistant condition without any reduction in body weight. 7 From the present data, it may be suggested that a reduction in body fat contributes to the exercise training-induced improvement in insulin sensitivity in OVX rats.…”

“…7 OVX resulted in a significant (P < 0.01) reduction of 17b-estradiol levels (Table 1). However, 17b-estradiol levels in OVX rats were still approximately 75% of those measured in Sham.…”

“…Results of this experiment showing a decrease in glucose-stimulated insulin response in trained rats of all Body composition in ovariectomized trained rats M Shinoda et al three estrogen groups have been previously reported and are not presented in this paper. 7 Five days after the ivGTT, all rats were weighed and their pre-implanted catheters were connected with an extension (PE50) used to anesthetize them (pentobarbital sodium; 20 mg=kg, iv) after an overnight fast. Rapidly after complete anesthesia, the abdominal cavity was opened and approximately 5 ml of blood was collected via the abdominal vena cava ( < 45 s).…”

“…The present data on weight gain and food intake have been presented and interpreted in a recent paper. 7 The main observation was that an 8 week training program does not reduce overall weight gain and increased food intake brought about by an ovariectomy. While this does not mean that body composition was not changed by training, it does mean that any changes related to training cannot be attributed to a change in body weight.…”

“…5,6 In this context, it is of interest to determine whether OVX animals can benefit from an exercise training program. Recent studies have reported that physical training in OVX rats improves glucose stimulated insulin response 7 and increases glucose transporter concentration in skeletal muscle. 8 The only existing study 2 on fat deposition and exercise training reports a reduction in fat gain with training regardless of estrogenic status (sham-operated, OVX with or without estrogen replacement).…”