Effects of estrogen on insulin sensitivity in ovariectomized rats

Abstract

Metabolic syndrome is more prevalent in men than in women. However, postmenopausal women became to have its higher incidence. We investigated whether insulin sensitivity is deteriorated in ovariectomized rats, and is improved by chronic estrogen replacement. Female Wistar rats aged 9 weeks were ovariectomized. After 4 weeks, the rats were assigned either to a placebo-treated (P) group (n=8) or a group treated with 17β-estradiol (E2) (n=8), subcutaneously implanted with either placebo- or 17β-estradiol (1.5 mg / 60-day release) pellets. After 4 weeks of estrogen or placebo treatment, the body weight, percent body fat and wet weights of visceral fat were increased in the P compared with the E2 group, while cumulative food intake per body weight was enhanced in the E2 group. During a 1 g/kg intravenous glucose tolerance test, the glucose and insulin responses (incremental areas under the curve) were greater in the P group than the E2 group. Plasma concentration of free fatty acid was marginally lower, and triglyceride was significantly lower in the P group than the E2 group. Plasma levels of leptin and TNF-α were not different between the two groups, but adiponectin was higher in the P group than the E2 group. These results suggest estrogen deficiency increases visceral fat mass, and deteriorates insulin sensitivity. [J Physiol Sci. 2006;56 Suppl:S226]