Intestinal Transit and Body Weight Responses to Ovarian Hormones and Dietary Fiber in Rats

A two-part experimental design was used to study the effects of ovarian hormone cessation, hormone supplementation, and dietary fiber composition on body weight, appetite, and intestinal transit. In Part 1, effects of ovarian hormone status on body weight and baseline and stimulated intestinal transit were measured in chow-fed rats. Sprague-Dawley rats were ovariectomized (OVX), then injected daily (22 days) with estrogen (E), progesterone (P), the combination (E + P), or placebo. Controls were sham operated and placebo injected. Among OVX rats, E and E + P had the least body weight gain (9%, 6%); placebo and P had the greatest (36%, 34%). In OVX-P, baseline intestinal transit (measured in anesthetized rats as distance traveled by a charcoal marker) was relatively low, but vagal stimulation via centrally administered thyrotropin-releasing hormone evoked an increase significantly larger than that in other groups. In Part 2, experiments probed the interacting effects of ovarian hormone cessation and dietary fiber composition on body weight and baseline intestinal transit. Caloric intake was measured to determine the contribution of altered appetite. Rats were OVX or sham operated, then fed liquid diets with or without dietary fiber (25 days). OVX fiber-fed rats had significantly higher caloric intake, weight gain, and baseline intestinal transit than other groups. Caloric intake did not fully account for group differences. These results demonstrate modulation of GI function by ovarian hormones and dietary fiber.