Cardiovascular Effects of Tibolone: A Selective Tissue Estrogenic Activity Regulator

Oral Therapeutics Post Menopausal Osteoporosis

Osteoporosis affects a significant number of postmenopausal women in the United States. Screening is performed using clinical assessments and bone mineral density scans via dual x-ray absorptiometry. Oral therapy is indicated to prevent pathologic fractures in those deemed at increased risk following screening. Bisphosphonates including alendronate, ibandronate, and risedronate are currently first-line oral therapeutics in fracture prevention following the diagnosis of osteoporosis. Hormonal therapies include estrogen-containing therapies, selective estrogen receptor modulators, and other compounds that mimic the effects of estrogen such as tibolone. Lifestyle modifications such as supplementation and physical activity may also contribute to the prevention of osteoporosis and are used as adjuncts to therapy following diagnosis. These therapeutics are limited primarily by their adverse effects. Treatment regimens should be tailored based on significant risk factors demonstrated by patients, adverse effects, and clinical response to treatment. The most severe risk factors relevant to pharmacological selection involve hormone replacement therapies, where concern for venous thrombosis, coronary artery disease, breast, and uterine cancer exist. Bisphosphonates are most commonly associated with gastrointestinal discomfort which may be mitigated with proper administration. Although adverse effects exist, these medications have proven to be efficacious in the prevention of vertebral and non-vertebral fractures in post-menopausal women. Fracture risk should be weighed against the risk of adverse events associated with each of the regimens, with clinical judgment dictating the treatment approach centered around patient goals and experiences.

Tibolone Improves Memory and Decreases the Content of Amyloid-β Peptides and Tau Protein in the Hippocampus of a Murine Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) affects women more than men and consequently has been associated with menopause. Tibolone (TIB) has been used as a hormone replacement therapy to alleviate climacteric symptoms. Neuroprotective effects of TIB have also been reported in some animal models.

OBJECTIVE

This study aimed to assess the effect of TIB on memory and Aβ peptides and tau protein content in the hippocampus and cerebellum of transgenic 3xTgAD ovariectomized mice.

METHODS

Three-month-old female mice were ovariectomized. Ten days after surgery, animals were divided into four groups: wild-type (WT)+vehicle; WT+TIB (1 mg/kg); 3xTgAD+vehicle; and 3xTgAD+TIB (1 mg/kg). TIB was administered for three months, and memory was evaluated using the object-in-context recognition task. Subsequently, animals were decapitated, and the hippocampus and cerebellum were dissected. Using commercial ELISA kits, these brain structures were homogenized in a PBS buffer for quantifying Aβ40 and Aβ42 and phosphorylated and total tau.ResultsA long-term memory deficit was observed in the 3xTgAD+vehicle group. In contrast, TIB treatment improved long-term memory in the 3xTgAD+TIB group than those treated with vehicle (p < 0.05). Furthermore, TIB treatment decreased Aβ and tau content in the hippocampus of 3xTgAD mice compared to vehicle-treated groups (p < 0.05). No significant changes were observed in the cerebellum.

CONCLUSION

Chronic treatment with TIB showed neuroprotective effects and delayed AD neuropathology in the 3xTgAD mice. Our results support hormone replacement therapy with TIB in menopausal women for neuroprotection.

Validation of housekeeping genes as an internal control for gene expression studies in the brain of ovariectomized rats treated with tibolone

INTRODUCTION

In the central nervous system (CNS), tibolone actions are mainly modulated through its interaction with estrogen, progesterone, and androgen receptors. Several studies have reported the expression of sex hormone receptors in the CNS using the RT-PCR endpoint technique. Although some studies have validated reference genes for rat brain tissue in different experimental conditions, no suitable reference genes have been reported in brain tissue from ovariectomized rats treated with tibolone.

OBJECTIVE

The aim of this investigation was to evaluate the expression of different housekeeping genes in several brain regions in ovariectomized rats treated with tibolone to determine the stability of a single housekeeping gene and a combination of two housekeeping genes under these experimental conditions.

METHODS

Adult female Sprague-Dawley rats were ovariectomized. Seven days after the surgery, animals were administered a single dose of vehicle (water) or tibolone (10 mg/kg/weight). Twenty-four hours later, animals were sacrificed, and the hypothalamus, hippocampus, prefrontal cortex, and cerebellum were dissected. Total RNA was extracted from these tissues, and RT-qPCR was performed to amplify Ppia, Hprt1, Rpl32, and Gapdh housekeeping genes.

RESULTS

Ppia was the most stable gene in the hypothalamus and cerebellum, whereas Hprt1 was the most stable gene in the prefrontal cortex. For the analysis of the combination of two genes, the most stable combination was Ppia and Hrpt1 for the prefrontal cortex and Ppia and Rpl32 for the cerebellum.

CONCLUSION

In ovariectomized rats treated with tibolone, Hprt1 and Ppia genes showed high stability as housekeeping genes for qPCR analysis.

Tibolone as Hormonal Therapy and Neuroprotective Agent

Tibolone (TIB), a selective tissue estrogenic activity regulator (STEAR) in clinical use by postmenopausal women, activates hormonal receptors in a tissue-specific manner. Estrogenic activity is present mostly in the brain, vagina, and bone, while the inactive forms predominate in the endometrium and breast. Conflicting literature on TIB's actions has been observed. While it has benefits for vasomotor symptoms, bone demineralization, and sexual health, a higher relative risk of hormone-sensitive cancer has been reported. In the brain, TIB can improve mood and cognition, neuroinflammation, and reactive gliosis. This review aims to discuss the systemic effects of TIB on peri- and post-menopausal women and its role in the brain. We suggest that TIB is a hormonal therapy with promising neuroprotective properties.

Tibolone Effects on Human Glioblastoma Cell Lines

BACKGROUND

Ovarian steroid hormones are involved in modulating the growth of glioblastomas (the most common, aggressive, and lethal brain tumor) through the interaction with their intracellular receptors. Activation of sex hormone receptors is involved in glioblastomas progression. Tibolone (TIB) is a selective tissue estrogenic activity regulator widely prescribed to treat menopausal symptoms and to prevent bone lost. The effects of TIB on the growth of glioblastoma are unknown.

AIM OF THE STUDY

To evaluate the effects of TIB on cell number, migration, and invasion of two derived human glioblastoma cell lines (U251 MG and U87), as well as the role of this steroid in estrogen and progesterone receptors activity and content.

METHODS

U251-MG and U87 human glioblastoma cell lines were grown with different doses of TIB. The number of cells was determined and migration and invasion tests were carried out. Protein expression was performed by Western blot.

RESULTS

We observed that TIB (10 nM) increased the number of cells by inducing proliferation with no effects on cell migration or invasion. The increase in cell proliferation induced by TIB was blocked by estrogen (ERs) or progesterone receptor (PRs) antagonists, ICI 182, 780 and RU 486, suggesting that these receptors mediate proliferating actions of TIB; TIB also modified the content of ERs and PRs by increasing ER-α, ER-β, and PR-B, while decreased PR-A.

CONCLUSION

Our results suggest that TIB increases cell number and proliferation of human glioblastoma cells through the regulation of ERs and PRs actions and content.

TERT inhibition leads to reduction of IL-6 expression induced by palmitic acid and interferes with the protective effects of tibolone in an astrocytic cell model

Although it has been shown that telomerase has neuroprotective effects, mainly as a result of its non-canonical functions in neuronal cells, its role with respect to glial cells remains unknown. There is growing evidence indicating that telomerase plays an important role with respect to inflammation, especially in the regulation of pro-inflammatory cytokine gene expression. The present study aimed to evaluate the role of telomerase in an astrocyte cell model treated with palmitic acid (PA) and tibolone. Cell death, reactive oxygen species production and interleukin-6 expression were evaluated under telomerase inhibition with the BIBR1532 compound in T98G cells treated with tibolone and PA, using fluorometry, flow cytometry, enzyme-linked immunosorbent assays and the quantitative polymerase chain reaction. The results obtained showed that telomerase protein was increased by PA after 36 hours, alone or in combination with tibolone, and that its activity was affected by PA. Telomerase inhibition reduced interleukin-6 expression and it interfered with the protective effects of tibolone on cell death. Moreover, tibolone increased Tyr707 phosphorylation in PA-treated cells. In the present study, we provide novel findings about the regulation of telomerase by PA and tibolone. Telomerase was involved in inflammation by PA and in protective effects of tibolone. Therefore, we conclude that telomerase could play a dual role in these cells.

Tibolone modulates neuronal plasticity through regulating Tau, GSK3β/Akt/PI3K pathway and CDK5 p35/p25 complexes in the hippocampus of aged male mice

Aging is a key risk factor for cognitive decline and age-related neurodegenerative disorders. Also, an age-related decrease in sex steroid hormones may have a negative impact on the formation of neurofibrillary tangles (NFTs); these hormones can regulate Tau phosphorylation and the principal kinase GSK3β involved in this process. Hormone replacement therapy decreases NFTs, but it increases the risk of some types of cancer. However, other synthetic hormones such as tibolone (TIB) have been used for hormone replacement therapy. The aim of this work was to evaluate the long-term effects of TIB (0.01 mg/kg and 1 mg/kg, intragastrically for 12 weeks) on the content of total and hyperphosphorylated Tau (PHF-1) proteins and the regulation of GSK3β/Akt/PI3K pathway and CDK5/p35/p25 complexes in the hippocampus of aged male mice. We observed that the content of PHF-1 decreased with TIB administration. In contrast, no changes were observed in the active form of GSK3β or PI3K. TIB decreased the expression of the total and phosphorylated form of Akt while increased that of p110 and p85. The content of CDK5 was differentially modified with TIB: it was increased at low doses and decreased at high doses. When we analyzed the content of CDK5 activators, an increase was found on p35; however, the content of p25 decreased with administration of low dose of TIB. Our results suggest a possible mechanism of action of TIB in the hippocampus of aged male mice. Through the regulation of Tau and GSK3β/Akt/PI3K pathway, and CDK5/p35/p25 complexes, TIB may modulate neuronal plasticity and regulate learning and memory processes.

Short-term tibolone does not interfere with endothelial function: a double-blinded, randomized, controlled trial

Objective To evaluate the effect of short-term hormone replacement therapy with tibolone 2.5 mg daily on endothelial function of healthy postmenopausal women, using flow-mediated dilation (FMD) of the brachial artery. Methods We performed a randomized, double-blinded, placebo-controlled study. A total of 100 healthy postmenopausal women were randomly allocated to receive tibolone (n = 50) or placebo (n = 50) for 28 days. Measurement of the FMD of the brachial artery was performed before and after the use of tibolone and placebo. Results A total of 31 women completed the study in the tibolone group, and 32 women completed the study in the control group. The results of the FMD measurements obtained from the women in the two groups before treatment were similar (0.018 and 0.091, for tibolone and placebo, p = 0.57). The values of the FMD in women who used tibolone and placebo, before and after the treatment, were similar in both groups. The numbers of women who presented an increase in the values of the FMD in both groups were also similar. Conclusion Our results demonstrate that the administration of 2.5 mg tibolone to healthy postmenopausal women for 28 days does not promote endothelial-dependent vasodilation, measured by FMD of the brachial artery.

Chronic administration of tibolone modulates anxiety-like behavior and enhances cognitive performance in ovariectomized rats

Hormone replacement therapy (HRT) may be prescribed to prevent the symptoms of menopause. This therapy may include estrogenic and/or progestin components and may increase the incidence of endometrial and breast cancers. Tibolone (TIB), which is also made up of estrogen and progestin components, is often used to reduce the impact of HRT. However, the effect of TIB on the processes of learning, memory and anxiety has yet to be fully elucidated. The aim of this study was to evaluate the long-term effect on learning, memory processes and anxiety in ovariectomized rats caused by different doses of TIB (0 mg/kg, 0.01 mg/kg, 0.1 mg/kg 1.0 mg/kg and 10 mg/kg, administered daily via the oral route for 18 weeks). Two behavioral animal models, the autoshaping and T maze models were employed. The concentrations of acetyl choline transferase (ChAT) and tryptophan hydroxylase (TPH) in the hippocampus were directly measured by Western blot. No significant changes were observed in the autoshaping model and spontaneous activity test. In the T maze, increased latency was observed with TIB doses of 1 and 10 mg/kg compared to the vehicle. We observed that the ChAT content decreased with increasing doses of TIB, whereas TPH content increased with doses of 1 and 10 mg/kg of TIB. These data indicate that high doses of TIB improved emotional learning, which may be related to the modulation of the cholinergic and serotonergic systems by TIB.

Effects of menopause and tibolone on different cardiovascular biomarkers in healthy women

BACKGROUND AND AIM

The effects of tibolone on cardiovascular risk is not yet fully understood today. We designed this study to assess the effect of the menopausal status and tibolone treatment (2.5 mg/day for 3 months) on different biomarkers of cardiovascular risk in healthy women.

METHODS

Blood arterial pressure were measured, and blood samples collected for glucose, lipid profile (total cholesterol, high density lipoproteins, HDL, low density lipoproteins, and triglycerides), inflammatory (C-reactive protein, Interleukin-6, IL-6, tumor necrosis factor alpha, TNF alpha) and oxidative stress (hydroperoxides and antioxidant capacity) evaluation in 15 premenopausal (mean age: 30 +/- 4 years) and 15 postmenopausal (mean age: 52 +/- 3, mean time from menopause 1.4 +/- 0.4 years) women before and after tibolone treatment.

RESULTS

The menopausal status is associated with increased systolic and diastolic pressure (p<0.05), higher IL-6 (p<0.05) and TNF alpha (p<0.01), and lower antioxidants (p<0.01). However, blood pressure (p<0.05), glucose (p<0.05), TNF alpha (p<0.05) and HDL (p<0.05) fell after tibolone, which did not significantly affect levels of the other biochemical parameters.

CONCLUSIONS

As menopause is associated with increased blood pressure, inflammation and oxidative stress, tibolone restores blood pressure and has beneficial effect on inflammation and glycemia without worsening oxidative stress, although it also reduces HDL levels. Such modifications should be taken into account when tailoring menopausal therapies to specific requirements of each woman.

Soy-tibolone combination - effect on lipids in postmenopausal monkeys and women

OBJECTIVES

To determine whether co-administration of soy during tibolone treatment would prevent tibolone-induced dyslipoproteinemia in postmenopausal monkeys and women.

METHODS

Surgically postmenopausal cynomolgus monkeys (n = 18) were assigned randomly to one of four dietary regimens in a Latin Square crossover design, such that all animals received all diets for 14 weeks with a 4-week washout period: (1) casein/lactalbumin (CL); (2) tibolone (Tib, 1.25 mg/day women's equivalent); (3) soy (138 mg isoflavones/day women's equivalent); (4) Soy + Tib. Postmenopausal women on tibolone treatment were randomized to receive soy powder (52 g of soy protein containing 112 mg isoflavones) or placebo (containing 52 g of milk protein) daily in a crossover trial for 8 weeks with a 4-week washout period.

RESULTS

Monkeys given Tib alone had approximately 14% increase in plasma LDL + VLDL-C; whereas those given soy combined with tibolone had significant ( approximately 22%) reductions. Tib treated monkeys had reductions in plasma HDL-C of about 48% vs. no reductions in Soy + Tib. In postmenopausal women using tibolone, soy reduced plasma LDL-C concentrations by approximately 10% from baseline without a change in HDL-C.

CONCLUSIONS

Co-administration of soy during tibolone treatment improved the lipoprotein profile in both monkeys and women; however, the effects were more robust in monkeys.