The long-term effects of tibolone on aortic stiffness and endothelial function

The effect of tibolone treatment on fasting blood sugar, insulin, insulin resistance and endothelial function in postmenopausal women: A meta-analysis of randomized controlled trials

BACKGROUND AND AIM

The menopause is associated in females with the presence of dysglycemia, insulin resistance and with the development of endothelial dysfunction. Tibolone (TIB) is a synthetic steroid compound with selective oestrogenic and, to a lesser extent, progestogenic and androgenic properties prescribed to postmenopausal women to alleviate the symptoms of the climaterium and to prevent the development of osteoporosis. However, the impact of TIB on fasting blood sugar (FBS), insulin, Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) index and flow-mediated dilation (FMD) in women has not been evaluated so far. Thus, to investigate this research question, we conducted the present systematic review and meta-analysis.

METHODS

Two independent reviewers searched the Scopus, Web of Science, PubMed/Medline and Embase databases up to 20 December 2020. The weighted mean differences (WMDs) and the 95% confidence intervals (CI) were calculated using the DerSimonian and Laird random effects models between the TIB and control groups and included in the forest plot.

RESULTS

The overall findings were generated from 12 eligible randomized controlled trials. As compared to controls, TIB administration resulted in a significant reduction of FBS (WMD: -3.06 mg/dL, 95% CI: -5.30 to -0.82, P = 0.007), and of the HOMA-IR index (WMD: -0.61, 95% CI: -1.11 to -0.11, P = 0.01). However, treatment with TIB did not lead to significant changes of the FMD (WMD: 0.78%, 95% CI: -0.20 to 1.77, P = 0.12) or of insulin levels (WMD: -0.10 mIU/L, 95% CI: -2.04 to 1.83, P = 0.91).

CONCLUSION

TIB administration can decrease FBS and the HOMA-IR index in postmenopausal women. However, the use of TIB does not influence insulin levels or FMD.

Effects of tibolone and conventional HRT on the expression of estrogen and progesterone receptors in the breast

OBJECTIVE

There is evidence that long-term hormone replacement therapy (HRT) is associated with an increased breast cancer risk. The aim of this study was to assess the effects of tibolone on estrogen and progesterone receptors in comparison to the effects of conventional HRT in the breast of surgically postmenopausal macaques.

METHOD

Sixty macaques were bilaterally ovariectomized 3 months before hormonal treatment was initiated. The animals were randomized into four treatment groups, including tibolone (TIB), conjugated equine estrogens (CEE), conjugated equine estrogens+medroxyprogesterone acetate (CEE+MPA) and control animals (C). After 2 years treatment, breast tissues were collected, fixed and paraffin embedded. Immunohistochemistry assays with monoclonal antibodies for estrogen receptors (ERalpha and ERbeta) and progesterone receptors (PRA and PRB) were performed.

RESULTS

The expression of ERalpha was markedly decreased in the CEE+MPA group as compared to C and TIB groups. The TIB group was not different from the C and CEE groups. No significant differences were found for ERbeta immunostaining. The expression of PRA was strongly increased in the TIB group as compared to the C and CEE+MPA groups. Immunostaining of PRB was increased in the CEE and TIB treated animals as compared to both C and CEE+MPA groups.

CONCLUSIONS

Tibolone increased the expression of both PRA and PRB, without affecting ERalpha and ERbeta expression in the macaque breast. These findings indicate that the effects of tibolone in breast tissue could be mediated via differential regulation of PRA and PRB isoforms and therefore distinct from those observed with conventional HRT.

Estrogen and tibolone metabolite levels in blood and breast tissue of postmenopausal women recently diagnosed with early-stage breast cancer and treated with tibolone or placebo for 14 days

Unlike estrogens plus progestagens, tibolone, a selective tissue estrogenic activity regulator, does not increase breast tenderness and mammographic density. To elucidate this, serum and breast levels of tibolone and estrogenic metabolites are measured. Postmenopausal women (n = 102) with early-stage, ER(+ve), primary breast cancer received tibolone or placebo for 14 days in an exploratory, double-blind, randomized trial (STEM carcinoma tissue). Baseline and presurgery sera were collected; tumor tissues were obtained at surgery. E(1) (estrone), E(2) (estradiol), E(1)S (estrone-sulfate), tibolone-its nonsulfated, monosulfated, and disulfated 3-hydroxymetabolites-and Delta(4)-tibolone were measured by validated gas chromatography and mass spectrometry and liquid chromatography with tandem mass spectrometry assays. More than 12 hours after the final dose, serum E(1), E(2), and E(1)S levels were unchanged with placebo, whereas tibolone significantly increased E(1)S and the E(1)S/(E(1) + E(2)) ratio. In tumors, E(1) and E(2) levels were higher than in serum, and E(1)S levels were lower, with placebo and tibolone administration. The percentage of E(1)S was about 90% in serum and 16% in tissue. Tibolone did not affect tissue levels of endogenous estrogens. Serum levels of estrogenic 3alpha- and 3beta-hydroxytibolone, progestagenic/androgenic Delta(4)-tibolone, and monosulfate metabolites were low. Serum 3alphaS,17betaS-tibolone and 3 betaS,17betaS-tibolone levels were 250 and 52 ng/mL, respectively. Tumor levels of 3alpha- and 3beta-hydroxytibolone and Delta(4)-tibolone were higher than in serum, but disulfate levels were lower. The percentage of sulfated tibolone metabolites was 99% in serum and 96% in tumor. Serum metabolite patterns of estradiol and tibolone are different from those in tissues and are compatible with neutral effects of tibolone on breast Ki67 expression.