Meta-analysis of the association between polymorphisms of estrogen receptor α genes rs9340799 and rs2234693 and Alzheimer's disease: evidence from 23 articles

Estrogen receptor beta (ESR2) gene polymorphism and susceptibility to dementia

Strong evidence supports the involvement of sex steroid hormones in the development and progression of dementia. Attention has been largely focused on the association between genetic variants of estrogen receptor alpha (ERα, ESR1) with dementia, although several studies indicate that ERβ is predominantly expressed in the brain. Interestingly, however, a limited number of studies evaluate the role of ERβ (ESR2) in dementia. Therefore, a meta-analysis was conducted to clarify the association between ESR2 genetic polymorphisms and the risk of dementia. All the relevant studies evaluating ESR2 genetic polymorphisms and dementia were identified through online databases. In total, 14 studies including 20,609 subjects were analyzed. Collectively, it was found that a combined data set of ESR2 polymorphisms was not associated with dementia risk. Interestingly, ESR2 rs4986938 polymorphism is significantly associated with dementia in the Asian population (OR = 0.73, 95% CI 0.59-0.91, P = 0.006). The carrier of A allele in rs4986938 exhibits a protective effect against dementia (A vs. G, OR = 0.6633, P = 0.012; AA + GA vs. GG, OR = 0.6499, P = 0.014; GA vs. AA + GG, OR = 0.6672, P = 0.025; GA vs. GG, OR = 0.6617, P = 0.022). In conclusion, our study suggests that ESR2 genetic polymorphisms are not significantly associated with dementia risk. ESR2 rs4986938 may have potential as a genetic marker for dementia in the Asian population. However, further studies need to verify this conclusion.

The Effect of Hormone Replacement Therapy on Cognitive Function in Female Patients With Alzheimer's Disease: A Meta-Analysis

Previous studies have indicated that estrogen may delay disease progression and minimize the cognitive decline in patients with Alzheimer's disease (AD). However, the evidence for an estrogen deficiency in women with dementia and cognitive dysfunction is inconsistent. In the present review, a fixed effect meta-analysis revealed that the hormone replacement therapy (HRT) group exhibited significant improvements in Alzheimer Disease Assessment Scale-Cognitive subscale scores relative to those observed in the placebo group, suggesting that HRT is feasible for treating cognitive decline in patients with AD. However, no significant differences in Mini-Mental State Examination and Clinical Dementia Rating scale scores were observed between the 2 groups. The results of our systematic review indicate that HRT can improve cognitive function in female patients with AD. Due to limitations in sample size and the available literature, further multicenter trials with larger sample sizes are required to support these findings.

Molecular basis of Gender Dysphoria: androgen and estrogen receptor interaction

BACKGROUND

Polymorphisms in sex steroid receptors have been associated with transsexualism. However, published replication studies have yielded inconsistent findings, possibly because of a limited sample size and/or the heterogeneity of the transsexual population with respect to the onset of dysphoria and sexual orientation. We assessed the role of androgen receptor (AR), estrogen receptors alpha (ERα) and beta (ERβ), and aromatase (CYP19A1) in two large and homogeneous transsexual male-to-female (MtF) and female-to-male (FtM) populations.

METHODS

The association of each polymorphism with transsexualism was studied with a twofold subject-control analysis: in a homogeneous population of 549 early onset androphilic MtF transsexuals versus 728 male controls, and 425 gynephilic FtMs versus 599 female controls. Associations and interactions were investigated using binary logistic regression.

RESULTS

Our data show that specific allele and genotype combinations of ERβ, ERα and AR are implicated in the genetic basis of transsexualism, and that MtF gender development requires AR, which must be accompanied by ERβ. An inverse allele interaction between ERβ and AR is characteristic of the MtF population: when either of these polymorphisms is short, the other is long. ERβ and ERα are also associated with transsexualism in the FtM population although there was no interaction between the polymorphisms. Our data show that ERβ plays a key role in the typical brain differentiation of humans.

CONCLUSION

ERβ plays a key role in human gender differentiation in males and females.

Oestradiol level, oestrogen receptors, and mortality in elderly men: The three-city cohort study

CONTEXT

Although endogenous oestradiol, generally considered as the female hormone, has been little investigated in men, it could play a role in men's health, mortality in particular. The influence of oestrogen receptors (ER) genetic polymorphisms on this relationship has never been studied.

DESIGN AND PARTICIPANTS

The Three-City cohort study included (1999-2001) 3650 men ≥65 years who were followed for mortality over 12 years. At baseline, total oestradiol (tE2) was measured and ER genotyped in a random subsample of 472 men without hormonal treatment. Free oestradiol (fE2) was estimated using Vermeulen and Södergard algorithms.

MAIN OUTCOME

Mortality data were obtained from death certificates. We used inverse probability weighted Cox models to examine the association of oestradiol with all-cause and cause-specific mortality and its interaction with ER genetic polymorphisms.

RESULTS

A total of 183 men died over the follow-up (cardiovascular disease (CVD), n = 44; cancer, n = 57; other causes, n = 82). After adjustment, there was a quadratic relationship of all-cause mortality with tE2 and fE2 (P-quadratic = 0.04 and 0.05, respectively), with higher mortality for the top and bottom tertiles compared to the middle one. These associations were stronger for CVD mortality (P-quadratic = 0.01 and 0.02 for tE2 and fE2, respectively) and disappeared for cancer mortality. There was no evidence of an interaction of oestradiol with any ER polymorphisms on all-cause mortality.

CONCLUSION

In elderly men, we showed a nonlinear association of tE2 and fE2 with all-cause mortality. These quadratic relationships were stronger for CVD mortality and did not exist for cancer mortality. ER genetic polymorphisms did not modify this association.

Polymorphisms in sex steroid receptors: From gene sequence to behavior

Sex steroid receptors have received much interest as potential mediators of human behaviors and mental disorders. Candidate gene association studies have identified about 50 genetic variants of androgen and estrogen receptors that correlate with human behavioral phenotypes. Because most of these polymorphisms lie outside coding regions, discerning their effect on receptor function is not straightforward. Thus, although discoveries of associations improve our ability to predict risk, they have not greatly advanced our understanding of underlying mechanisms. This article is intended to serve as a starting point for psychologists and other behavioral biologists to consider potential mechanisms. Here, I review associations between polymorphisms in sex steroid receptors and human behavioral phenotypes. I then consider ways in which genetic variation can affect processes such as mRNA transcription, splicing, and stability. Finally, I suggest ways that hypotheses about mechanism can be tested, for example using in vitro assays and/or animal models.