Effectiveness of estradiol in preventing and reversing obesity induced by ovariectomy and high-caloric diet in female rats.

Abstract

Estrogens have recently been described as being most effective in restraining the food intake and body weight of female rats that face impending obesity. A corollary is that estrogens are more effective in preventing than reversing the body weight gain that accompanies ovariectomy (Ovx). Four experiments examined the effects of estradiol benzoate (EB) on food intake, body weight, ano-nasal length, and body weight to body length ratio (Lee index) of ovariectomized and intact rats maintained on control or high-fat diets, and of Ovx and intact rats that had been reduced by deprivation. Estradiol benzoate was highly effective in preventing the increase in food intake, body weight, and ano-nasal growth after Ovx. It was relatively ineffective in reversing body weight gain after Ovx. However, when ano-nasal length was also considered, EB was effective in returning Ovx rats to an appropriate body weight for their increased ano-nasai length. About 40% of the body weight gain after Ovx appears to be due to skeletal growth and the increased tissue mass necessary to maintain it. Intact rats fed a high-caloric diet did not exhibit an increased rate of ano-nasal growth, which indicates that the skeletal growth that occurs after Ovx is not simply a result of increased food intake. Estradiol benzoate was eventually effective in reducing the body weights of intact rats maintained on a high-fat diet, but it also reduced the body weights of intact control rats. The high-fat diet did not alter the amount of weight gained after Ovx. It is concluded that EB modulates food intake and body weight by multiple mechanisms, one of which is by modulating skeletal growth. The nature of the effect of EB on the body weight of intact rats suggests that this effect occurs by still another mechanism.

Effects of estradiol and progesterone on food intake, body weight, and carcass adiposity in weanling rats

“…In contrast, it is fairly-well established that ovarian hormones given prepubertally do not alter eating (Mueller and Hsiao, 1980;Ross and Zucker, 1974;Sieck, Nance, Ramaley, Tayler and Gorski, 1977;Wade, 1974;Wade and Zucker, 1970b;Zucker, 1972 The period prior to puberty is characterized as a time of rapid somatic and skeletal growth (Kennedy, 1969;Mueller and Hsaio, 1980;Ross and Tarttelin, 1978;Slob, 1972;Widdowson and McCance, 1960): After weaning, rats eat more (in proportion to their body weights), gain weight faster, and increase body length more rapidly than sexually mature animals. Nonetheless, these animals are not obese relative to older animals (Mueller and Hsiao, 1980).…”

“…In adult female rats, ovariectomy (OVX) increases body weight, an effect which can be reversed by estradiol treatment (Mueller and Hsaio, 1980;Wade, 1975). Treatment of OVX rats with progesterone alone has no effect on body weight, but given concurrently with estradiol or to intact rats, progesterone increases body weight (Galletti and Klopper, 1967;Hervey and Hervey, 1976;Wade, 1975;.…”

Adaptation of Feeding and Counter‐Regulatory Hormone Responses to Intermediate Insulin‐Induced Hypoglycaemia in the Ovariectomised Female Rat: Effects of Oestradiol

“…Our recent studies show that reinstatement of physiological levels of the ovarian steroid, oestradiol, in ovariectomised (OVX) female rats prevents intensification of hypoglycaemia and attenuation of central nervous system neuronal activation during multiple dosing with this insulin formation (4). The influence of oestradiol on ad lib feeding is well established (5–8), but the role of this steroid in glucoprivic hyperphagia remains controversial because oestradiol inhibits glucose antimetabolite‐induced consumption when co‐delivered with progesterone (9), but does not modify hypoglycaemic patterns of food intake when administered alone (10). Although oestrogen is reported to suppress regular (e.g.…”