Idiopathic Premature Ovarian Failure and its association to the abnormal longitudinal changes of telomere length in a population of Iranian Infertile Women: A pilot study

Causal association between telomere length and female reproductive endocrine diseases: a univariable and multivariable Mendelian randomization analysis

BACKGROUND

The relationship between leukocyte telomere length (LTL) and female reproductive endocrine diseases has gained significant attention and research interest in recent years. However, there is still limited understanding of the exact impacts of LTL on these diseases. Therefore, the primary objective of this study was to investigate the genetic causal association between LTL and female reproductive endocrine diseases by employing Mendelian randomization (MR) analysis.

METHODS

Instruments for assessing genetic variation associated with exposure and outcome were derived from summary data of published genome-wide association studies (GWAS). Inverse-variance weighted (IVW) was utilized as the main analysis method to investigate the causal relationship between LTL and female reproductive endocrine diseases. The exposure data were obtained from the UK Biobanks GWAS dataset, comprising 472,174 participants of European ancestry. The outcome data were acquired from the FinnGen consortium, including abnormal uterine bleeding (menorrhagia and oligomenorrhea), endometriosis (ovarian endometrioma and adenomyosis), infertility, polycystic ovary syndrome (PCOS), premature ovarian insufficiency (POI) and premenstrual syndrome (PMS). Furthermore, to account for potential confounding factors such as smoking, alcohol consumption, insomnia, body mass index (BMI) and a history of pelvic inflammatory disease (PID), multivariable MR (MVMR) analysis was also conducted. Lastly, a series of pleiotropy tests and sensitivity analyses were performed to ensure the reliability and robustness of our findings. P < 0.0063 was considered to indicate statistically significant causality following Bonferroni correction.

RESULTS

Our univariable MR analysis demonstrated that longer LTL was causally associated with an increased risk of menorrhagia (IVW: odds ratio [OR]: 1.1803; 95% confidence interval [CI]: 1.0880-1.2804; P = 0.0001) and ovarian endometrioma (IVW: OR: 1.2946; 95%CI: 1.0970-1.5278; P = 0.0022) at the Bonferroni significance level. However, no significant correlation was observed between LTL and oligomenorrhea (IVW: OR: 1.0124; 95%CI: 0.7350-1.3946; P = 0.9398), adenomyosis (IVW: OR: 1.1978; 95%CI: 0.9983-1.4372; P = 0.0522), infertility (IVW: OR: 1.0735; 95%CI: 0.9671-1.1915; P = 0.1828), PCOS (IVW: OR: 1.0633; 95%CI: 0.7919-1.4278; P = 0.6829), POI (IVW: OR: 0.8971; 95%CI: 0.5644-1.4257; P = 0.6459) or PMS (IVW: OR: 0.7749; 95%CI: 0.4137-1.4513; P = 0.4256). Reverse MR analysis indicated that female reproductive endocrine diseases have no causal effect on LTL. MVMR analysis suggested that the causal effect of LTL on menorrhagia and ovarian endometrioma remained significant after accounting for smoking, alcohol consumption, insomnia, BMI and a history of PID. Pleiotropic and sensitivity analyses also showed robustness of our results.

CONCLUSION

The results of our bidirectional two-sample MR analysis revealed that genetically predicted longer LTL significantly increased the risk of menorrhagia and ovarian endometrioma, which is consistent with the findings from MVMR studies. However, we did not notice any significant effects of LTL on oligomenorrhea, adenomyosis, infertility, PCOS, POI or PMS. Additionally, reproductive endocrine disorders were found to have no impact on LTL. To enhance our understanding of the effect and underlying mechanism of LTL on female reproductive endocrine diseases, further large-scale studies are warranted in the future.

[The dual role of the menopausal hormonal therapy as the enhancer of pleiotropic telomere rejuvenation and the silencer of cellular aging (literature review)]

Present worldwide healthcare researches prove that female patients are more sensitive to the population aging. Menopause or climacteria (climax) - is not as ageing itself, but a physiological unstoppable process. The main task for a physician is to improve life quality for female despite of ageing problems. Menopausal hormone therapy (MHT) due to the estrogen component has an anti-inflammatory, antioxidant effect and promotes the expression of telomerase, which together changes the homeostasis and integrity of telomeres. The use of MHT for five years or more can not only significantly change the quality of life, but also increase its duration. Literature search was carried out in national (eLibrary, CyberLeninka.ru) and international (PubMed, Cochrane Library) databases in Russian and English. The priority was free access to the full text of articles. The choice of sources was prioritized for the period from 2019 to 2021. However, taking into account the insufficient knowledge of the chosen topic, the choice of sources dates back to 1989.

Ovarian Telomerase and Female Fertility

Women's fertility is characterized both quantitatively and qualitatively mainly by the pool of ovarian follicles. Monthly, gonadotropins cause an intense multiplication of granulosa cells surrounding the oocyte. This step of follicular development requires a high proliferation ability for these cells. Telomere length plays a crucial role in the mitotic index of human cells. Hence, disrupting telomere homeostasis could directly affect women's fertility. Strongly expressed in ovaries, telomerase is the most effective factor to limit telomeric attrition and preserve ovarian reserve. Considering these facts, two situations of infertility could be correlated with the length of telomeres and ovarian telomerase activity: PolyCystic Ovary Syndrome (PCOS), which is associated with a high density of small antral follicles, and Premature Ovarian Failure (POF), which is associated with a premature decrease in ovarian reserve. Several authors have studied this topic, expecting to find long telomeres and strong telomerase activity in PCOS and short telomeres and low telomerase activity in POF patients. Although the results of these studies are contradictory, telomere length and the ovarian telomerase impact in women's fertility disorders appear obvious. In this context, our research perspectives aimed to explore the stimulation of ovarian telomerase to limit the decrease in the follicular pool while avoiding an increase in cancer risk.

Telomere length in granulosa cells and leukocytes: a potential marker of female fertility? A systematic review of the literature

In the context of a continuously increased delay of motherhood and of an increase of the incidence of premature ovarian failure, it is of the greatest interest to dispose of a predictive marker of the duration of the fertility window. Unfortunately, current available markers of women’s fertility (hormonal rates or echography count of small follicles) have a poor predictive value of premature ovarian failure. In the last ten years, some studies have suggested that telomere length may be correlated with premature ovarian failure, but the results of these studies are contradictory.

In accordance with guidelines from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), this systematic review of the literature selected studies evaluating telomere length or telomerase activity in granulosa cells and/or in leukocytes as a premature ovarian failure marker.

Five publications (252 premature ovarian failure patients) were included in this review of experimental evidence. Two of them studied telomere length and/or telomerase activity in granulosa cells and 4 in leukocytes in women with premature ovarian failure. For each study, authors determined if there was a positive or a negative correlation between telomeric parameters and premature ovarian failure.

3 studies (178 premature ovarian failure patients) found shorter telomere length in granulosa cells and/or leukocytes and/or lower telomerase activity in premature ovarian failure patients. 2 studies (74 premature ovarian failure patients) presented contradictory results about the correlation of leucocyte telomere length with premature ovarian failure.

Shorter telomeres and diminished telomerase activity in granulosa cells appear to be associated with ovarian insufficiency. However, the number of studies and of subjects within are low and the methodology questionable. The confirmation of these results is essential with more subjects, better defined populations and more adapted methodology, in order to consider telomere length in granulosa cells and/or in leucocytes as an early and reliable marker for the decline of ovarian function.