Deciphering the DNA methylome in women with PCOS diagnosed using the new international evidence-based guidelines

Study question: Is there any methylome alteration in women with PCOS who were diagnosed using the new international evidence-based guidelines?

Summary answer: A total of 264 differentially methylated probes (DMPs) and 53 differentially methylated regions (DMRs) were identified in patients with PCOS and healthy controls.

What is known already: PCOS is a common endocrine disorder among women of reproductive age and polycystic ovarian morphology (PCOM) is one of the main features of the disease. Owing to the availability of more sensitive ultrasound machines, the traditional diagnosis of PCOM according to the Rotterdam criteria (≥12 antral follicles per ovary) is currently debated as there is a risk of overdiagnosis. The new international evidence-based guidelines set the threshold for PCOM as ≥20 antral follicles per ovary when using endovaginal ultrasound transducers with a frequency bandwidth that includes 8 MHz. However, current DNA methylation studies in PCOS are still based on the Rotterdam criteria. This study aimed to explore aberrant DNA methylation in patients diagnosed with PCOS according to the new evidence-based guidelines.

Study design, size, duration: This cross-sectional case-control study included 34 PCOS cases diagnosed using new international evidence-based guidelines and 36 controls.

Participants/materials, setting, methods: A total of 70 women, including 34 PCOS cases and 36 controls, were recruited. DNA extracted from whole blood samples of participants were profiled using array technology. Data quality control, preprocessing, annotation, and statistical analyses were performed. Least absolute shrinkage and selection operator (LASSO) regression were used to build a PCOS diagnosis model with DNA methylation sites.

Main results and the role of chance: We identified 264 DMPs between PCOS cases and controls, which were mainly located in intergenic regions or gene bodies of the genome, CpG open sea sites, and heterochromatin of functional elements. Pathway enrichment analysis showed that DMPs were significantly enriched in biological processes involved in triglyceride regulation. Three of these DMPs overlapped with the PCOS susceptibility genes thyroid adenoma-associated protein (THADA), aminopeptidase O (AOPEP), and tripartite motif family-like protein 2 (TRIML2). Fifty-three DMRs were identified and their annotated genes were largely enriched in allograft rejection, thyroid hormone production, and peripheral downstream signaling effects. Two DMRs were closely related to the PCOS susceptibility genes, potassium voltage-gated channel subfamily A member 4 (KCNA4) and farnesyl-diphosphate farnesyltransferase 1 (FDFT1). Finally, based on LASSO regression, we built a methylation marker model with high accuracy for PCOS diagnosis (AUC=0.952).

Limitations, reasons for caution: The study cohort was single-center and the sample size was relatively limited. Further analyses with a larger number of participants are required.

Wider implications of the findings: This is the first study to identify DNA methylation alterations in women with PCOS diagnosed using the new international evidence-based guideline, and it provided new molecular insight into the application of the new guidelines.

Study funding/competing interest(s): This study was supported by the National Key Research and Development Program of China (2021YFC2700400), Basic Science Center Program of NSFC (31988101), CAMS Innovation Fund for Medical Sciences (2021-I2M-5-001), National Natural Science Foundation of China (32370916, 82071606, 82101707, 82192874, and 31871509), Shandong Provincial Key Research and Development Program (2020ZLYS02), Taishan Scholars Program of Shandong Province (ts20190988), and Fundamental Research Funds of Shandong University. The authors declare no conflicts of interest.

Trial registration number: N/A.