Endothelin-1 and nitric oxide levels are related to cardiovascular risk factors but are not modified by estradiol replacement in healthy postmenopausal women. A cross-sectional and a randomized cross-over study.

OBJECTIVE: To evaluate whether in healthy postmenopausal women endothelial substances such as endothelin-1 (ET-1) and nitric oxide are related to cardiovascular risk factors and can be influenced by estradiol replacement. DESIGN: A cross-sectional evaluation and a randomized, double-blind, placebo-controlled study with cross-over. METHODS: In 20 healthy postmenopausal women it was investigated the relation of ET-1 and NOx with age, BMI, 24-h blood pressure, lipid and glucose metabolism, and coagulation parameters. In addition, in the same women, the role played by estrogens on circulating ET-1 and stable derivatives of nitric oxide (nitrite/nitrates) was investigated by administering for 2 months transdermal estradiol (50 microg/day) vs. placebo. RESULTS: ET-1 and NOx were inversely related to each other (r=0.458; P=0.016). Multivariate analysis of regression showed that ET-1 levels were related directly to LDL-cholesterol (r=0.585; P=0.0005) and protein C (r=0.516; P=0.0008), and inversely to insulin (r=0.488; P=0.0065). The ratio NOx/ET-1 was directly related to HDL-cholesterol (r=0.441; P=0.005). The above relations were not influenced by estradiol. Indeed, in comparison to placebo, transdermal estradiol, besides reducing nocturnal systolic (P=0.002) and diastolic (P=0.03) blood pressure, did not modify ET-1 or NOx levels, as well as, any of the parameters considered. CONCLUSIONS: The relation of several cardiovascular risk factors with ET-1 and NOx/ET-1 suggests a primary role for these endothelial products in the determination of the cardiovascular risk of women. The present data do not support a role for transdermal estradiol in modifying ET-1 or NOx levels of healthy postmenopausal women.

Acute modifications in the levels of daytime melatonin do not influence leptin in postmenopausal women.

Melatonin shows a clear circadian rhythm with peak values at night, and may act directly with fat cells. Leptin, the anorexic hormone synthesized mainly by adipocytes, is produced in a circadian fashion, similar to that of melatonin. Accordingly, in the present study, we investigated whether melatonin may contribute to the rise in circulating leptin. The study was performed in postmenopausal women with 2 months of treatment with placebo or estradiol (50 microg/day). Melatonin was administered in doses of 1 mg by mouth versus placebo. In experiment 1, melatonin was administered at 08:30 hr. In experiment 2, at 08:30 hr and 10:30 hr, and in experiment 3 at 15:30 hr. Three blood samples, one every 15 min, were collected prior to the administration of melatonin and 2 hr after the administration of the single melatonin dose or the second melatonin administration (experiment 2). Following its administration, circulating melatonin reached pharmacological levels. In the three experiments, levels of leptin were not modified by the daytime administration of melatonin. These data indicate that, at least in daytime hours, acute modifications in daytime melatonin levels do not influence levels of leptin of postmenopausal women either without or with estradiol replacement. Accordingly, the metabolic, endocrine, reproductive and biological modifications induced by acute daytime melatonin in women do not seem to be mediated by modifications in circulating leptin.

Influence of transdermal estradiol in the regulation of leptin levels of postmenopausal women: a double-blind, placebo-controlled study.

OBJECTIVE: To investigate whether the administration of transdermal estradiol is capable of modifying circulating levels of leptin. DESIGN: Forty postmenopausal women randomly received in a double-blind fashion, a transdermal patch containing either placebo or estradiol (50 microg/day). After 2 months of treatment, they were switched to the alternate treatment for another 2 months. Leptin levels were measured at the end of the placebo and estradiol administration. In a subset of 28 women an evaluation of body composition via bioelectrical impedance and an oral glucose tolerance test (OGTT; 75 g) were also performed at the end of the placebo and estradiol administration. Glucose, insulin, and leptin levels were measured in all OGTT samples. RESULTS: Leptin levels were related directly to body mass index (BMI), fat mass, and insulin, and inversely related to lean mass. In comparison to placebo, transdermal estradiol increased estradiol (from 77.8 +/- 8.4 pmol/l to 183.1 +/- 20.9 pmol/l; p < 0.0001) but did not significantly modify leptin (19.1 +/- 2.4 microg/l vs. 18.6 +/- 2 microg/l) or BMI. Estradiol did not modify fat mass or lean mass, significantly increased intracellular water (31.1 +/- 0.7% vs. 37.2 +/- 2.3%, p < 0.05), and decreased extracellular water (40.5 +/- 0.7% vs. 36.3 +/- 1.7%; p < 0.04). Leptin did not increase during OGTT, but a significant decrease, linearly related to BMI ( r = 0.519; p = 0.0189), was observed at the end of the test. CONCLUSIONS: Low doses of transdermal estradiol exert no influence on fasting leptin levels or BMI. The possibility that different doses of estradiol exert a more pronounced effect on circulating leptin needs to be addressed in comparative studies.