PCOS without hyperandrogenism is associated with higher plasma Trimethylamine N-oxide levels

Background Polycystic ovary syndrome (PCOS) is an endocrine and metabolic disorder, and its pathogenesis is still under debate. Trimethylamine-N-oxide (TMAO) is a small, organic compound generated by the gut microbiome with a hypothesized relation to insulin resistance (IR) and low-grade inflammation in PCOS. By comparing plasma TMAO levels in non-PCOS participants and PCOS patients without hyperandrogenism (HA), we aimed to determine whether plasma TMAO levels correlate with PCOS without HA and to analyze their relationship with low-grade inflammation and IR. Methods A total of 27 PCOS patients without HA and 23 non-PCOS participants were enrolled in this study and subdivided into “nonobese” and “obese” arms for each group. Levels of plasma TMAO were quantified, and basic clinical characteristics and plasma biomarkers of inflammation were assessed. Results First, plasma TMAO levels, insulin levels and homeostatic model assessment of insulin resistance (HOMA-IR) values were higher in PCOS patients without HA, especially in the obese subgroup. Second, the levels of the inflammatory factors interleukin (IL)-17A, IL-18 and interferon gamma (IFN-γ) were significantly increased in obese PCOS patients without HA. Third, plasma TMAO levels were associated with body mass index (BMI) in the normal-weight groups, and the obese groups had higher fasting plasma insulin (FINS) and HOMA-IR values. Finally, logistic regression showed that the plasma levels of TMAO and luteinizing hormone/follicle-stimulating hormone (LH/FSH) were independent predictors of PCOS and indicated an increased risk of PCOS. Conclusions Elevated plasma TMAO levels may be associated with the pathogenesis of PCOS without HA and correlated with increased systemic inflammation. Further studies are needed to determine the suitability of TMAO as a predictive biomarker and to identify possible therapies for PCOS.