Mendelian randomization and multi-omics approach analyses reveal impaired glucose metabolism and oxidative phosphorylation in visceral adipose tissue of women with polycystic ovary syndrome

Study question: What is the significance of visceral adipose tissue (VAT) in the pathogenesis of polycystic ovary syndrome (PCOS) and its impact on the regulation of metabolic disorders in women with PCOS?

Summary answer: We revealed a potentially causal relationship between increased genetically predicted VAT and PCOS-related traits, and found that VAT exhibited impaired glucose metabolism and mitochondrial oxidative phosphorylation (OXPHOS) in women with PCOS.

What is known already: PCOS is a common reproductive endocrine disorder accompanied by many metabolic abnormalities. Adipose tissue is a metabolically active endocrine organ that regulates multiple physiological processes, and VAT has a much stronger association with metabolism than subcutaneous adipose tissue does.

Study design, size, duration: Mendelian randomization (MR) analysis was used to investigate the potential causal association between genetically predicted VAT and the risk of PCOS. Data for MR analysis were extracted from European population cohorts. VAT samples from sixteen PCOS patients and eight control women who underwent laparoscopic surgery were collected for proteomics and targeted metabolomics analyses.

Participants/materials, setting, methods: PCOS was diagnosed according to the 2003 Rotterdam Criteria. The control subjects were women who underwent laparoscopic investigation for infertility or benign indications. Proteomics was performed by TMT labeling and liquid chromatography-tandem mass spectrometry analysis, and targeted metabolomics was performed by ultra-performance liquid chromatography-tandem mass spectrometry analysis. The key differentially expressed proteins (DEPs) were validated by immunoblotting.

Main results and the role of chance: MR analysis revealed a potentially causal relationship between increased genetically predicted VAT and PCOS, as well as related traits, such as polycystic ovaries, total testosterone, bioavailable testosterone, and anti-Müllerian hormone, while a negative relationship was found with sex hormone-binding globulin. Enrichment pathway analysis of DEPs indicated the inhibition of glycolysis and activation of mitochondrial OXPHOS in the VAT of PCOS patients. MR analysis revealed that key DEPs involved in glycolysis and OXPHOS were significantly linked to PCOS and its related traits. Dot blot assay confirmed a significant decrease in glycolysis enzymes PKM2 and HK1, and an increase in mitochondrial Complex I and III subunits, NDUFS3 and UQCR10. Moreover, metabolomics analysis confirmed down-regulated metabolites of energy metabolic pathways, in particular glycolysis. Further analysis of PCOS and control subjects of normal weight revealed that dysregulation of glucose metabolism and OXPHOS in VAT of women with PCOS was independent of obesity.

Large scale data: The mass spectrometry proteomics data have been deposited to the iProX database (http://www.iprox.org) with the iProX accession: IPX0005774001.

Limitations, reasons for caution: There may be an overlap in some exposure and outcome data, which might affect the results in the MR analysis.

Wider implications of the findings: The changes in protein expression of key enzymes affect their activities and disrupt the energy metabolic homeostasis in VAT, providing valuable insight for identifying potential intervention targets of PCOS.

Study funding/competing interest(s): This work was supported by the National Key Research and Development Project of China (2021YFC2700402), the National Natural Science Foundation of China (82071608, 82271665), the Key Clinical Projects of Peking University Third Hospital (BYSY2022043), and the CAMS Innovation Fund for Medical Sciences (2019-I2M-5-001). All authors report no conflict of interest.

Trial registration number: N/A.