Association between rs7903146 and rs12255372 polymorphisms of transcription factor 7-like 2 gene and polycystic ovary syndrome: a systematic review and meta-analysis

Association of TCF7L2 genetic variants rs12255372 and rs7903146 with the polycystic ovary syndrome risk: systemic review and meta-analysis

BACKGROUND

A significant overlap in the pathophysiological features of polycystic ovary syndrome (PCOS) and type 2 diabetes mellitus (T2DM) has been reported; and insulin resistance is considered a central driver in both. The expression and hepatic clearance of insulin and subsequent glucose homeostasis are mediated by TCF7L2 via Wnt signaling. Studies have persistently associated TCF7L2 genetic variations with T2DM, however, its results on PCOS are sparse and inconsistent.

METHODS

We performed a comprehensive literature review of the data published till June 2024, on rs7903146, rs12255372, and PCOS in PubMed, Medline, the Cochrane Library, Google Scholar, Science Direct, Scopus, and Web of Science, followed by a meta-analysis to evaluate the association between these genetic variations and the PCOS risk. Using a random effects model, the pooled odds ratio (OR) and confidence intervals (95%CI) were computed using STATA statistical software.

RESULTS

The genotypic data from 3052 controls and 2291 women with PCOS from ten published studies were analysed. The results indicated no cumulative association between the rs7903146 variant and PCOS risk in either the allelic (C vs. T: OR = 1.21; 95% CI: 0.96-1.47, p > 0.05) or genotypic models (CC vs. CT + TT: OR = 1.06; 95% CI: 0.90-1.23, p > 0.05). Similarly, the genetic variant rs12255372 was not associated with PCOS risk both in the allelic and the dominant inheritance model(p > 0.05). Unlike East Asians (MAF < 0.025), both variants are highly frequent across other global populations including America, South Asia, and Europe (MAF ≥ 0.19).

CONCLUSION

Unlike T2DM, our results showed that rs7903146 and rs12255372 variants of the TCF7L2 gene do not modulate the PCOS risk. However, the role of other TCF7L2 variants remains to be studied in future studies.

Association of the endothelial nitric oxide synthase (eNOS) 4a/b polymorphism with the risk of incident diabetic retinopathy in patients with type 2 diabetes mellitus: a systematic review and updated meta-analysis

OBJECTIVE

To conduct a systematic review and updated meta-analysis on the potential association between endothelial nitric oxide synthase (eNOS) 4a/b polymorphism and the risk of developing diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM) and to identify possible clinical biomarkers for early screening of DR.

MATERIALS AND METHODS

A meta-analysis based on case-control or cross-sectional studies was conducted to examine the correlation between eNOS 4a/b polymorphism and DR. Pooled odds ratio (OR) and 95% confidence interval (CI) were used to estimate the association strength.

RESULTS

We included 19 studies, covering 7838 subjects. An association was observed in Caucasians (allelic model: OR = 1.273, 95% CI: 1.006-1.610, p = .045; recessive model: OR = 0.575, 95% CI: 0.371-0.892, p = .014; dominant model: OR = 1.268, 95% CI: 1.052-1.528, p = .013; homozygote model: OR = 1.833, 95% CI: 1.176-2.856, p = .007). Moreover, population-based studies have indicated an association between eNOS 4a/b polymorphism and DR susceptibility.

CONCLUSIONS

The present study showed that intron 4a allele of eNOS 4a/b is a risk factor for DR in Caucasians with T2DM. Thus, eNOS 4a/b may be used as a biomarker for the early screening and diagnosis of DR in Caucasian T2DM patients.Key messagesEndothelial nitric oxide synthase 4a/b gene polymorphism is not associated with the risk of developing diabetic retinopathy in the overall population, Asians, or Chinese Han patients with type 2 diabetes. However, 4a is a risk factor for the development of diabetic retinopathy in Caucasians.Endothelial nitric oxide synthase 4a/b gene polymorphism is not associated with the type of diabetic retinopathy.

Family history of menstrual irregularity or diabetes mellitus enhances the susceptibility to polycystic ovary syndrome among subjects harboring rs7903146 genetic variant of TCF7L2

Purpose

TCF7L2 mediated Wnt signaling cascade regulates glucose homeostasis by orchestrating expression, processing, and hepatic clearance of insulin. Type 2 diabetes mellitus (T2DM) and polycystic ovary syndrome (PCOS) significantly overlap in pathophysiological features with insulin resistance as a central driver. While TCF7L2 is the most potent T2DM locus, studies on the association of TCF7L2 with PCOS are limited and inconclusive. Therefore, in addition to expression profiling, the association of TCF7L2 polymorphic variant rs7903146 with PCOS was evaluated.

Methods

Using Rotterdam-2003 criteria for the diagnosis, 120 PCOS cases, and 120 age-matched controls were recruited. Subjects underwent clinical, biochemical, and hormonal assessment, followed by genotyping for rs7903146, carried out by PCR-RFLP and TCFL2 expression profiling by qRT-PCR. Genotype-phenotype correlation analysis was performed to evaluate any such associations. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were computed by conditional logistic regression.

Results

Higher odds of developing PCOS were observed in the women having a family history (FH) of either T2DM (OR = 3.86, 95% CI:1.90 - 7.83), hirsutism (OR = 4.74. 95%CI: 1.91 - 17.21) or menstrual irregularities (MI) (OR = 3.07, 95%CI: 1.61 - 8.54). The genotypes of rs7903146 did not confer any risk for developing PCOS (OR = 0.46;95%CI: 0.15 - 2.03). However, the elevated risk was seen in the subjects who harbored the variant allele and had FH of either T2DM (OR = 6.71; 95%CI: 1.89 - 23.78) or MI (OR = 9.71; 95% CI:1.89 - 23.78).

Conclusion

TCF7L2 polymorphic variant rs7903146 is not independently linked to PCOS risk, but modulates the risk in the subjects having a family history of either T2DM or MI.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-022-01050-y.

The Genetics of Polycystic Ovary Syndrome: An Overview of Candidate Gene Systematic Reviews and Genome-Wide Association Studies

Polycystic Ovary Syndrome (PCOS) is a complex condition with mechanisms likely to involve the interaction between genetics and lifestyle. Familial clustering of PCOS symptoms is well documented, providing evidence for a genetic contribution to the condition. This overview aims firstly to systematically summarise the current literature surrounding genetics and PCOS, and secondly, to assess the methodological quality of current systematic reviews and identify limitations. Four databases were searched to identify candidate gene systematic reviews, and quality was assessed with the AMSTAR tool. Genome-wide association studies (GWAS) were identified by a semi structured literature search. Of the candidate gene systematic reviews, 17 were of high to moderate quality and four were of low quality. A total of 19 gene loci have been associated with risk of PCOS in GWAS, and 11 of these have been replicated across two different ancestries. Gene loci were located in the neuroendocrine, metabolic, and reproductive pathways. Overall, the gene loci with the most robust findings were THADA, FSHR, INS-VNTR, and DENND1A, that now require validation. This overview also identified limitations of the current literature and important methodological considerations for future genetic studies. Much work remains to identify causal variants and functional relevance of genes associated with PCOS.

Genetic determinants of polycystic ovary syndrome: progress and future directions

The field of the genetics of polycystic ovary syndrome (PCOS) has relatively recently moved into the era of genome-wide association studies. This has led to the discovery of 16 robust loci for PCOS. Some loci contain genes with clear roles in reproductive (LHCGR, FSHR, and FSHB) and metabolic (INSR and HMGA2) dysfunction in the syndrome. The next challenge facing the field is the identification of causal variants and genes and the role they play in PCOS pathophysiology. The potential for gene discovery to improve diagnosis and treatment of PCOS is promising, though there is much to be done in the field before the current findings can be translated to the clinic.