The potent contraceptive gestodene exerts insulinotropic effects through its a-ring reduced metabolites with intrinsic estrogen-like activity in pancreatic ß-cells.

PURPOSE: The contraceptive gestodene is a potent synthetic progestin used in several low-dose contraceptive formulations. Clinical studies reported a relationship between long-term use of combined oral contraceptives containing gestodene (GDN) and profound alterations in glucose metabolism in women. The observation that contraceptive synthetic progestins exert hormone-like effects other than their progestational activities, prompted us to investigate whether GDN may induce estrogen-like effects, even though GDN does not interact with estrogen receptors. The aim of this study was to investigate whether GDN affect pancreatic ß-cell activity, directly or through its conversion to other bioactive metabolites. METHODS: The effects of GDN and its two derivatives 3ß,5α-tetrahydro-GDN and 3α,5α-tetrahydro-GDN on insulin 2 (Ins II) and glucokinase (Gk) expression and glucose-stimulated insulin secretion were determined in pancreatic islets from female rats. RESULTS: Gestodene did exert significant effects on islet ß-cells activity. The most striking finding was that 3ß,5α-tetrahydro-GDN and 3α,5α-tetrahydro-GDN had greater stimulatory effects on Ins II and Gk expression than that observed with GDN, consistent with their effects on glucose-stimulated insulin secretion. The effects on gene expression induced by GDN-derivatives were abolished by ICI 182,780 and MPP. In addition, the presence of inhibitors of androgen and progestin-metabolizing enzymes eliminated gene expression induced by GDN. These results indicated that GDN is metabolized to A-ring reduced metabolites with estrogen-like activities and through this mechanism, GDN may affect ß-cell activity. CONCLUSIONS: Altogether, the data suggest that 19-nortestosterone-derived contraceptives such as GDN, possess insulinotropic effects through their conversion into metabolites with intrinsic estrogen-like activity in pancreatic ß-cells.

The effect of tibolone treatment on lipid profile in women: A systematic review and dose-response meta-analysis of randomized controlled trials.

Inconsistencies exist with regard to influence of tibolone treatment on the lipid profile. The reasons for these inconsistencies might derive from several factors, i.e., differences in baseline variables, intervention duration, participants' health status or baseline body mass index (BMI). To address these inconsistencies, based on a systematic search in Scopus, PubMed/Medline, Web of Science, and Embase for papers published until 21 December 2020, we conducted the current dose-response meta-analysis of randomized controlled trials (RCTs) to determine the impact of tibolone treatment on the lipid profile. The overall findings were derived from 26 RCTs. Tibolone administration decreased total cholesterol (TC) (weighted mean difference, WMD: -18.55 mg/dL, CI: -25.95 to -11.16, P < 0.001), high-density lipoprotein-cholesterol (HDL-C) (WMD: -9.42 mg/dL, CI: -11.83 to -7.01, P < 0.001) and triglyceride (TG) (WMD: -21.43 mg/dL, CI: -27.15 to -15.70, P < 0.001) levels. A significant reduction in LDL-C occurred when tibolone was prescribed for ≤ 26 weeks (WMD: -7.64 mg/dL, 95% CI: -14.58 to -0.70, P = 0.031) versus > 26 weeks (WMD: -8.84 mg/dL, 95% CI: -29.98, 12.29, P = 0.412). The decrease in TG (WMD: -22.64 mg/dL) and TC (-18.55 mg/dL) concentrations was more pronounced in patients with BMI ≥ 25 kg/m2versus BMI < 25 kg/m2. This systematic review and meta-analysis discovered that tibolone decreases TC, HDL-C and TG levels. LDL-C concentrations are significantly reduced when tibolone administration lasts for ≤ 26 weeks.

The synthetic steroid tibolone exerts sex-specific regulation of astrocyte phagocytosis under basal conditions and after an inflammatory challenge.

BACKGROUND: Tibolone is a synthetic steroid used in clinical practice for the treatment of climacteric symptoms and osteoporosis. Active metabolites of tibolone, generated in target tissues, have an affinity for estrogen and androgen receptors. Astrocytes are direct targets for estrogenic compounds and previous studies have shown that tibolone protects brain cortical neurons in association with a reduction in reactive astrogliosis in a mouse model of traumatic brain injury. Since phagocytosis is a crucial component of the neuroprotective function exerted by astrocytes, in the present study, we have assessed whether tibolone regulates phagocytosis in primary astrocytes incubated with brain-derived cellular debris. METHODS: Male and female astrocyte cell cultures were obtained from newborn (P0-P2) female and male Wistar rats. Astrocytic phagocytosis was first characterized using carboxylate beads, Escherichia coli particles, or brain-derived cellular debris. Then, the effect of tibolone on the phagocytosis of Cy3-conjugated cellular debris was quantified by measuring the intensity of Cy3 dye-emitted fluorescence in a given GFAP immunoreactive area. Before the phagocytosis assays, astrocytes were incubated with tibolone in the presence or absence of estrogen or androgen receptor antagonists or an inhibitor of the enzyme that synthesizes estradiol. The effect of tibolone on phagocytosis was analyzed under basal conditions and after inflammatory stimulation with lipopolysaccharide. RESULTS: Tibolone stimulated phagocytosis of brain-derived cellular debris by male and female astrocytes, with the effect being more pronounced in females. The effect of tibolone in female astrocytes was blocked by a selective estrogen receptor ß antagonist and by an androgen receptor antagonist. None of these antagonists affected tibolone-induced phagocytosis in male astrocytes. In addition, the inhibition of estradiol synthesis in the cultures enhanced the stimulatory effect of tibolone on phagocytosis in male astrocytes but blocked the effect of the steroid in female cells under basal conditions. However, after inflammatory stimulation, the inhibition of estradiol synthesis highly potentiated the stimulation of phagocytosis by tibolone, particularly in female astrocytes. CONCLUSIONS: Tibolone exerts sex-specific regulation of phagocytosis in astrocytes of both sexes, both under basal conditions and after inflammatory stimulation.

Effects of tibolone on fibrinogen and antithrombin III: A systematic review and meta-analysis of controlled trials.

Tibolone is a synthetic steroid with estrogenic, androgenic and progestogenic activity, but the evidence regarding its effects on fibrinogen and antithrombin III (ATIII) has not been conclusive. We assessed the impact of tibolone on fibrinogen and ATIII through a systematic review and meta-analysis of available randomized controlled trials (RCTs). The search included PUBMED, Web of Science, Scopus, and Google Scholar (up to January 31st, 2016) to identify controlled clinical studies investigating the effects of oral tibolone treatment on fibrinogen and ATIII. Overall, the impact of tibolone on plasma fibrinogen concentrations was reported in 10 trials comprising 11 treatment arms. Meta-analysis did not suggest a significant reduction of fibrinogen levels following treatment with tibolone (WMD: -5.38%, 95% CI: -11.92, +1.16, p=0.107). This result was robust in the sensitivity analysis and not influenced after omitting each of the included studies from meta-analysis. When the studies were categorized according to the duration of treatment, there was no effect in the subsets of trials lasting either <12months (WMD: -7.64%, 95% CI: -16.58, +1.29, p=0.094) or ≥12months (WMD: -0.62%, 95% CI: -8.40, +7.17, p=0.876). With regard to ATIII, there was no change following treatment with tibolone (WMD: +0.74%, 95% CI: -1.44, +2.93, p=0.505) and this effect was robust in sensitivity analysis. There was no differential effect of tibolone on plasma ATIII concentrations in trials with either <12months (WMD: +2.26%, 95% CI: -3.14, +7.66, p=0.411) or≥12months (WMD: +0.06%, 95% CI: -1.16, +1.28, p=0.926) duration. Consistent with the results of subgroup analysis, meta-regression did not suggest any significant association between the changes in plasma concentrations of fibrinogen (slope: +0.40; 95% CI: -0.39, +1.19; p=0.317) and ATIII (slope: -0.17; 95% CI: -0.54, +0.20; p=0.374) with duration of treatment. In conclusion, meta-analysis did not suggest a significant reduction of fibrinogen and ATIII levels following treatment with tibolone.

The synthetic progestin, gestodene, affects functional biomarkers in neonatal rat osteoblasts through an estrogen receptor-related mechanism of action.

BACKGROUND: Clinical studies have shown that gestodene (GDN), a potent third-generation synthetic progestin, affects bone resorption. However, its mode of action in bone cells is not fully understood. The aim of this study was to establish whether GDN affects bone directly or through its bioconversion to other metabolites with different biological activities. METHODS: In this study, we investigated the effects of GDN and its A-ring reduced metabolites on proliferation, differentiation, and mineralization of calvarial osteoblasts isolated from neonatal rat and their capacity to displace [3H]-E2 at ER binding sites. RESULTS: In contrast to progesterone, gestodene did exert significant effects on osteoblast activities. The most striking finding was the observation that the A-ring reduced derivatives 3ß,5α-tetrahydro-GDN and 3α,5α-tetrahydro-GDN, though to a lesser extent, had greater stimulatory effects on the osteoblast activity than those observed with GDN. The effects on osteoblast proliferation and differentiation induced by GDN-reduced derivatives were abolished by the antiestrogen ICI 182780, consistent with their binding affinities for the estrogen receptor. In addition, the presence of a 5α-reductase inhibitor or inhibitors of aldo-keto hydroxysteroid dehydrogenases abolished the GDN-induced enhancement of osteoblast differentiation. These results indicated that GDN is metabolized to the A-ring reduced metabolites with estrogen-like activities and through this mechanism, GDN may affect the osteoblast activity. CONCLUSION: Together, the data suggest that synthetic progestins derived from 19-nortestosterone such as GDN, have beneficial effects on bone due to their biotransformation into metabolites with intrinsic estrogenic activity.

A two-centre, open-label, randomised study of ovulation inhibition with three transdermal contraceptive patches, each containing different amounts of ethinyl estradiol and gestodene in healthy, young women.

Here we report the findings of a two-centre, open-label, randomised, Phase IIa study designed to investigate whether an ethinyl estradiol (EE)/gestodene (GSD) patch that has been developed (referred to herein as the 'EE/GSD patch') reliably inhibits ovulation in comparison with patches delivering lower doses of these hormones. The study rationale was to provide justification of the doses of EE and GSD selected for the EE/GSD patch. Healthy women, aged 18-35 years, were randomised to receive treatment with either the EE/GSD patch, a 'reduced-GSD patch' (delivering similar amounts of EE and approximately half the amount of GSD) or a 'reduced-EE/GSD patch' (delivering half the amount of EE and GSD). Treatment was administered for three 28-day cycles (three × 7 patch-wearing days, plus a 7-day patch-free interval). The primary pharmacodynamic variable was the percentage of women with ovulation in at least one of Cycles 2 and/or 3, as indicated by Hoogland score. Pharmacokinetic parameters for EE and GSD were also measured. Results indicated that the EE/GSD patch effectively suppressed ovulation, while patches delivering lower doses of EE and GSD were less effective for this purpose. All three patches showed comparable tolerability.

[INFLUENCE OF ETHINYLESTRADIOL - GESTODENE COMBINATION ON THE FUNCTIONAL ACTIVITY AND EXPRESSION OF P-GLYCOPROTEIN.]

The influence of a combination of ethinylestradiol (6.5 mg/kg) and gestodene (16.5 mg/kg) on the functional activity of P-glycoprotein efflux transporter and its expression in the liver and small intestine was studied on 20 Chinchilla rabbits. P-glycoprotein functional activity was characterized by the pharmacokinetics of its marker substrate - fexofenadine upon single peroral administration. P-glycoprotein expression was investigated by the immunohistochemical method. It was established that 14-day administration of ethinylestradiol - gestodene combination did not influence the functional activity of P-glycoprotein. After 21-day administration of this combination, the maximum concentration of fexofenadine and its area under concentration - time curve were increased and its clearance was decreased. These data are indicative of the inhibition of P-glycoprotein functional activity in the organism. Immunohistochemical analysis showed a reduction in the total expression of P-glycoprotein in the liver and small intestine after joint administration of ethinylestradiol and gestodene for 21 days, which confirmed a decrease in P-glycoprotein synthesis. Correlations between P-glycoprotein activity, its expression in the liver, and estradiol level were revealed.

Effects of estradiol, progestogens, and of tibolone on breast proliferation and apoptosis.

AIM: To study the effects of estrogen therapy, alone or combined with progestogens, and of tibolone on the expression of proliferation and apoptosis markers in normal breast tissue. METHODS: Thirty 250-day-old Wistar rats were castrated and 3 weeks later received one of the following treatments by gavage for 5 weeks: (1) estradiol benzoate; (2) estradiol benzoate + medroxyprogesterone acetate; (3) estradiol benzoate + norethisterone acetate; (4) estradiol benzoate + dydrogesterone; (5) tibolone; (6) placebo. Following treatment, the expression of proliferating cell nuclear antigen (PCNA) and caspase-3 was analyzed by quantitative immunohistochemistry in the breast tissue, and proliferation and apoptosis were analyzed semiquantitatively by microscopic imaging. RESULTS: There was a statistically significant difference among the groups for PCNA, caspase-3 and the caspase-3 : PCNA ratio. Tibolone was associated with the lowest proliferative activity, followed by estradiol benzoate + dydrogesterone; however, estradiol benzoate + dydrogesterone showed the greatest rate of apoptosis. CONCLUSIONS: The various progestogens can have more or less proliferative and pro-apoptotic effects than estradiol alone. Among the treatment schemes analyzed, the estradiol + dydrogesterone combination resulted in a higher apoptosis rate in relation to the proliferation rate and tibolone was associated with the lowest proliferation.

Is expression of rat breast matrix components influenced by estrogen, progestins and tibolone?

AIM: To study the effects of estrogen therapy, alone or combined with progestogens, and of tibolone on the expression of heparanase (HSPE), extracellular matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9), perlecan and proliferating cell nuclear antigen (PCNA) in normal breast tissue. METHODS: Thirty 250-day-old Wistar rats were castrated and 3 weeks later received one of the following treatments by gavage for 5 weeks: (1) estradiol benzoate; (2) estradiol benzoate + medroxyprogesterone acetate; (3) estradiol benzoate + norethisterone acetate; (4) estradiol benzoate + dydrogesterone; (5) tibolone; (6) placebo. Following treatment, the expressions of mRNA for HSPE, MMP-2 and MMP-9 were analyzed by real-time PCR and the protein expressions of HSPE, MMP-2, MMP-9, perlecan and PCNA were quantified by immunohistochemistry. RESULTS: There was a statistically significant difference among the groups for the expression of HSPE mRNA due to high levels in the tibolone group. The groups differed in terms of PCNA, with lower levels found in the tibolone group followed by the estradiol benzoate + dydrogesterone group. A statistically significant positive correlation was observed for PCNA versus perlecan and MMP-9. CONCLUSIONS: There was no difference in the effects of combinations of estradiol and different progestogens on extracellular matrix components, and breast cell proliferation was associated with increases in perlecan and MMP-9.

Antioxidant effect of the active metabolites of tibolone.

Certain steroidal compounds have an antioxidant effect in humans. Our aim was to test whether the synthetic steroid tibolone and its metabolites are also able to display such a property. For this, granulocytes from healthy men and women were incubated for two hours with different concentrations (10(-7), 10(-8), 10(-9 )M) of either estradiol, tibolone, 3α-hydroxytibolone, 3ß-hydroxytibolone, Δ(4)-tibolone, 3α-sulfated-tibolone, 3α-17ß-disulfated-tibolone, 3ß-sulfated-tibolone or 3ß-17ß-disulfated-tibolone. Superoxide anion generation of neutrophils was measured by photometry. Results of different steroids were given as percentages of their controls. A more simple superoxide generating system, the xanthine-xanthine oxidase reaction was also tested. We found that granulocyte superoxide production did not differ from the control using 10(-9 )M of steroids. Using 10(-8 )M concentration: estradiol (80.9 ± 2.5%); 3ß-sulfated-tibolone (83.3 ± 4.7%); 3ß-17ß-disulfated-tibolone (81.0 ± 4.2%) caused a significant decrease in superoxide production, compared to the control. In addition at 10(-7 )M, 3ß-hydroxytibolone and 3α-sulfated-tibolone also showed antioxidant effects. In the xanthine-xanthine oxidase system estradiol (67.4 ± 1.0%), 3α-sulfated-tibolone (85.8 ± 5.3%), 3α-17ß-disulfated-tibolone (71.9 ± 2.5%), 3ß-sulfated-tibolone (73.9 ± 5.0%), and 3ß-17ß-disulfated-tibolone (65.8 ± 3.4%) caused a significant decrease in superoxide production. Conclusively, although tibolone itself did not show significant antioxidant capacity, most of its active metabolites have antioxidant effects.

Effects of tibolone and its metabolites on prolactin and insulin-like growth factor binding protein-1 expression in human endometrial stromal cells.

The effects of the postmenopausal replacement steroid tibolone and its 3α-, 3ß-OH and Δ-4 tibolone metabolites were evaluated on progesterone receptor-mediated classic decidualization markers insulin-like growth factor binding protein-1 (IGFBP-1) and prolactin expression in human endometrial stromal cells (HESCs). Supernatants of conditioned medium or erxtracted RNA from experimental cell incubations of confluent HESCs were subjected to ELISAs, Western blot analysis and RT/PCR, and results were statisically assesed. Over 21 days, specific ELISAs observed linear increases in secreted IGFBP-1 and prolactin levels elicited by tibolone and its metabolites. Cultured HESCs were refractory to E2 and dexamethasone, whereas tibolone and each metabolite exceeded medroxyprogesterone acetate in significantly elevating IGFBP-1 and prolactin output. Anti-progestins eliminated IGFBP-1 and prolactin induction by tibolone and its metabolites. Immunoblotting and RT/PCR confirmed ELISA results. These observations of IGFBP-1 and prolactin expression: (a) indicate the relevance of cultured HESCs in evaluating the chronic effects of tibolone administration to women; (b) are consistent with PR-mediated endometrial atrophy and protection against endometrial bleeding despite the persistence of circulating ER-binding, but not PR-binding metabolites following tibolone administration to women.

The impact of testosterone, tibolone and black cohosh on purified mammary and placental 17ß-hydroxysteroid dehydrogenase type 1.

CONTEXT: Mammary and placental 17ß-hydroxysteroid dehydrogenase type 1 (17ßHSD1). OBJECTIVE: To assess the impact of testosterone, tibolone, and black cohosh on purified mammary and placental 17ßHSD1. MATERIALS AND METHODS: 17ßHSD1 was purified from human mammary gland and placenta by column chromatography, its activity was monitored by a radioactive activity assay, and the degree of purification was determined by gel electrophoresis. Photometric cofactor transformation analysis was performed to assess 17ßHSD1 activity without or in presence of testosterone, tibolone and black cohosh. RESULTS: 17ßHSD1 from both sources displayed a comparable basal activity. Testosterone and tibolone metabolites inhibited purified mammary and placental 17ßHSD1 activity to a different extent, whereas black cohosh had no impact. DISCUSSION: Studies on purified enzymes reveal the individual action of drugs on local regulatory mechanisms thus helping to develop more targeted therapeutic intervention. CONCLUSION: Testosterone, tibolone and black cohosh display a beneficial effect on local mammary estrogen metabolism by not affecting or decreasing local estradiol exposure.

Effect of tibolone on dendritic spine density in the rat hippocampus.

INTRODUCTION: Oestrogen deficiency produces oxidative stress (OS) and changes in hippocampal neurons and also reduces the density of dendritic spines (DS). These alterations affect the plastic response of the hippocampus. Oestrogen replacement therapy reverses these effects, but it remains to be seen whether the same changes are produced by tibolone (TB). The aim of this study was to test the neuroprotective effects of long-term oral TB treatment and its ability to reverse DS pruning in pyramidal neurons (PN) of hippocampal area CA1. METHODS: Young Sprague Dawley rats were distributed in 3 groups: a control group in proestrus (Pro) and two ovariectomised groups (Ovx), of which one was provided with a daily TB dose (1mg/kg), OvxTB and the other with vehicle (OvxV), for 40 days in both cases. We analysed lipid peroxidation and DS density in 3 segments of apical dendrites from PNs in hippocampal area CA1. RESULTS: TB did not reduce lipid peroxidation but it did reverse the spine pruning in CA1 pyramidal neurons of the hippocampus which had been caused by ovariectomy. CONCLUSIONS: Oestrogen replacement therapy for ovariectomy-induced oestrogen deficiency has a protective effect on synaptic plasticity in the hippocampus.

Tibolone prevents oxidation and ameliorates cholinergic deficit induced by ozone exposure in the male rat hippocampus.

Oxidative stress is related to the development of central nervous system diseases involving memory processes. Cholinergic system and memory processes are disrupted by ozone exposure. In rats, ozone induces motor disturbances and memory deficits as well as biochemical changes in brain regions related to memory processes. In this work, we analyzed the effect of chronic tibolone (TIB) administration in central nervous system, specifically the content of choline acetyltransferase, acetylcholinesterase, acetylcholine and oxidative stress markers in the hippocampus of male rats exposed to ozone. Our results reveal a neuroprotective effect of TIB treatment on neuronal damage induced by chronic ozone exposure. Furthermore, we suggest that TIB can prevent memory deficits by providing a protective effect against oxidative stress and the cholinergic system disruption induced by ozone exposure. Together, these findings present a potential neuroprotective effect of TIB in processes linked to memory deficits induced by aging or neurodegenerative diseases.

Effect of tibolone vs hormone replacement therapy on climacteric symptoms and psychological distress.

BACKGROUND: The objective was to elucidate the effect of tibolone vs hormone replacement therapy (HRT) on climacteric symptoms and psychological distress. METHODS: All consecutive women with climacteric symptoms were allocated to receive tibolone (2.5 mg) or estradiol valerate (1 mg) plus medroxyprogesterone acetate (2.5 mg). RESULTS: The improvement in "feeling dizzy or faint" after tibolone treatment was more prominent than that after HRT (-0.7 ± 0.8 vs -0.0 ± 0.9, p = 0.004). In addition, other climacteric symptoms, including anxiety, depression, somatic symptoms, and vasomotor symptoms, and sexual function improved after tibolone and HRT, but there were no between-group differences. Psychological distress assessment demonstrated that somatic complaints, obsessive-compulsive symptoms, depressive symptoms, hostility, additional symptoms, and the General Symptom Index improved after tibolone treatment and HRT, but there were no between-group differences. Personality traits assessment revealed that neuroticism improved after tibolone treatment. CONCLUSION: Tibolone seems more beneficial than HRT in treating symptoms of dizziness and faintness. Both tibolone and HRT could improve psychological distress.

Gonadal hormone deprivation regulates response to tibolone in neurodegenerative pathways.

Gonadal hormone deprivation (GHD) and decline such as menopause and bilateral oophorectomy are associated with an increased risk of neurodegeneration. Yet, hormone therapies (HTs) show varying efficacy, influenced by factors such as sex, drug type, and timing of treatment relative to hormone decline. We hypothesize that the molecular environment of the brain undergoes a transition following GHD, impacting the effectiveness of HTs. Using a GHD model in mice treated with Tibolone, we conducted proteomic analysis and identified a reprogrammed response to Tibolone, a compound that stimulates estrogenic, progestogenic, and androgenic pathways. Through a comprehensive network pharmacological workflow, we identified a reprogrammed response to Tibolone, particularly within "Pathways of Neurodegeneration", as well as interconnected pathways including "cellular respiration", "carbon metabolism", and "cellular homeostasis". Analysis revealed 23 proteins whose Tibolone response depended on GHD and/or sex, implicating critical processes like oxidative phosphorylation and calcium signalling. Our findings suggest the therapeutic efficacy of HTs may depend on these variables, suggesting a need for greater precision medicine considerations whilst highlighting the need to uncover underlying mechanisms.

Progestin effects on cell proliferation pathways in the postmenopausal mammary gland.

INTRODUCTION: Menopausal hormone therapies vary widely in their effects on breast cancer risk, and the mechanisms underlying these differences are unclear. The primary goals of this study were to characterize the mammary gland transcriptional profile of estrogen + progestin therapy in comparison with estrogen-alone or tibolone and investigate pathways of cell proliferation in a postmenopausal primate model. METHODS: Ovariectomized female cynomolgus macaque monkeys were randomized into the following groups: placebo (Con), oral conjugated equine estrogens (CEE), CEE with medroxyprogesterone acetate (MPA) (CEE + MPA), and tibolone given at a low or high dose (Lo or Hi Tib). All study treatment doses represented human clinical dose equivalents and were administered in the diet over a period of 2 years. RESULTS: Treatment with CEE + MPA had the greatest effect on global mRNA profiles and markers of mammary gland proliferation compared to CEE or tibolone treatment. Changes in the transcriptional patterns resulting from the addition of MPA to CEE were related to increased growth factors and decreased estrogen receptor (ER) signaling. Specific genes induced by CEE + MPA treatment included key members of prolactin receptor (PRLR)/signal transducer and activator of transcription 5 (STAT5), epidermal growth factor receptor (EGFR), and receptor activator of nuclear factor kappa B (RANK)/receptor activator of nuclear factor kappa B ligand (RANKL) pathways that were highly associated with breast tissue proliferation. In contrast, tibolone did not affect breast tissue proliferation but did elicit a mixed pattern of ER agonist activity. CONCLUSION: Our findings indicate that estrogen + progestin therapy results in a distinct molecular profile compared to estrogen-alone or tibolone therapy, including upregulation of key growth factor targets associated with mammary carcinogenesis in mouse models. These changes may contribute to the promotional effects of estrogen + progestin therapy on breast cancer risk.

Effects of tibolone or continuous combined oestradiol/norethisterone acetate on glucose and insulin metabolism.

OBJECTIVE: To determine the effects of tibolone or oestradiol (E(2) )/norethisterone acetate (NETA) hormone replacement therapy on glucose and insulin metabolism in postmenopausal women. DESIGN: Single-centre double-blind placebo-controlled randomized clinical trial. SUBJECTS/METHODS: We randomized 105 healthy postmenopausal women to tibolone 2·5 mg daily, continuous combined oral E(2) 2 mg/NETA 1 mg daily or placebo over a 2-year study. We performed intravenous glucose tolerance tests (IVGTT) with measurements of plasma glucose, insulin and C-peptide concentrations and the IVGTT glucose elimination rate, k. Mathematical modelling was performed to determine measures of insulin sensitivity, S(i) , pancreatic insulin secretion and hepatic and plasma insulin elimination. RESULTS: Tibolone decreased S(i) to 53-63% and k to 72-79% of baseline values but increased IVGTT phase 2 C-peptide concentrations 1·6-1·8-fold and pancreatic insulin secretion 2·2-2·4-fold, so overall IVGTT glucose concentrations were unaffected. Similar, but for k, significantly smaller changes in insulin and C-peptide secretion were seen with E(2) /NETA, also with no effect on overall IVGTT glucose concentrations. CONCLUSIONS: Tibolone reduces insulin sensitivity. Healthy postmenopausal women seem able to compensate for this and maintain normal postload glucose concentrations, but it may not be advisable to prescribe tibolone to women with, or at increased risk for, diabetes.

Tibolone induces serotonin, estrogen, and progesterone receptor expression but not contractile response to serotonin in the rat uterus.

Most studies on the effect of tibolone on the uterus have focused on the endometrium dismissing the importance of the myometrium. The aim of the present study was to investigate some estrogen-like actions of tibolone in the uterus assessed by: 1) the expression of estrogen, progesterone, and serotonin receptors, and 2) the myometrial contraction induced by serotonin. Estradiol (250 µg), progesterone (50 mg), or testosterone (25 mg) pellets were implanted to ovariectomized rats. Tibolone (0.5 mg/day) was orally administered. An implanted pellet containing vehicle or an equivalent volume of water p.o., were used as controls. Sixty days after beginning the treatments, rats were killed and uterus removed. One horn was processed to evaluate estrogen-alpha, progesterone A and B, and serotonin-2A receptors expression, and the other one was used for studying contraction to serotonin and 60 mM potassium solution. The present data showed that tibolone-induced expression of estrogen, progesterone, and serotonin receptors, but did not induce uterine contractile response to either serotonin or potassium solution. These findings suggest that, in the uterus, tibolone may exert molecular estrogenic actions such as the induction of receptor expression, but not a physiological response as the estrogen-dependent contraction to serotonin.

The effects of different hormone treatment on endothelial function in healthy postmenopausal women.

We aimed to compare the effects of different types of hormone treatment (HT) on endothelial function by means of brachial artery ultrasonographic examination in postmenopausal women. Sixty-two healthy postmenopausal women were included in this study. Subjects were assigned to one of the five groups receiving 6 months of treatment [estrogen (conjugated estrogen), estrogen (conjugated estrogen) plus progesterone (medroxyprogesterone acetate; MPA), raloxifene, tibolone or control]. Endothelial function was assessed by measurement of flow-mediated dilatation (FMD) and nitrate-dependent dilatation in the brachial artery. At the end of 6 months, FMD values were found to be significantly increased in women with HT use than the control group (p = 0.001). In subgroups, FMD increased significantly in the estrogen [12 ± 7 versus 25 ± 8, p = 0.001] and raloxifene groups [7 ± 5 versus 11 ± 3, p < 0.01] compared to tibolone and estrogen plus progesterone groups. In conclusion, endothelial function is impaired in postmenopausal women. Both estrogen and raloxifene regimens may improve endothelial functions in healthy postmenopausal women. The direct protective effects of these HT on the healthy endothelium may be more remarkable than the favorable effects on lipid profile.