The gut microbial composition in polycystic ovary syndrome with insulin resistance: findings from a normal-weight population Original paper

What was studied?

This study examined the gut microbiota composition in normal-weight women with polycystic ovary syndrome (PCOS), with a specific focus on how insulin resistance shapes their microbial profiles. The goal was to identify microbiome signatures—particularly taxa such as Enterococcus, Rothia, and Prevotella—that might distinguish PCOS with insulin resistance from PCOS without insulin resistance and from healthy controls. Using 16S rDNA sequencing of the V3–V4 region, the researchers compared alpha- and beta-diversity, taxonomic composition, and microbe-clinical correlations to better understand how the gut microbiome differs across these metabolic phenotypes.

Who was studied?

The study included 36 women aged 18–35 years, all with normal BMI (18.5–23.9 kg/m²). Fourteen had PCOS with insulin resistance (PCOS-IR), ten had PCOS without insulin resistance (PCOS-NIR), and twelve served as healthy controls. All participants were free from confounders such as hormonal therapy, antibiotics, probiotics, insulin sensitizers, or immunosuppressants for at least three months. Clinical data, metabolic markers, anthropometric measures, and fecal samples were collected for comprehensive phenotyping and microbiome profiling.

Most important findings

The central finding was the distinct enrichment of Enterococcus and Rothia in the PCOS-IR group. Diversity metrics (alpha and beta) did not differ significantly among groups, suggesting that shifts in specific bacterial taxa—rather than overall community complexity—are more relevant in normal-weight PCOS. Enterococcus abundance was highest in PCOS-IR and was positively correlated with waist circumference, hip circumference, diastolic blood pressure, and HOMA-IR. Rothia abundance was similarly elevated in PCOS-IR and positively associated with waist circumference and free fatty acids, suggesting links to abdominal adiposity and lipid metabolism. In contrast, Prevotella, a short-chain-fatty-acid (SCFA)–producing genus, was most abundant in healthy controls and significantly reduced in both PCOS groups, indicating a potential loss of beneficial fermentative capacity. The study also identified Lactobacillus as a distinguishing taxon in PCOS-NIR, hinting at metabolic differences within PCOS phenotypes.

Key implications

These findings highlight targeted microbial signatures relevant for a microbiome database, particularly the strong association of Enterococcus and Rothia with insulin resistance in normal-weight PCOS. Because Enterococcus can degrade GLP-1—an incretin essential for glucose homeostasis—its enrichment may contribute to dysregulated insulin signaling in PCOS-IR. Reduced Prevotella suggests diminished SCFA production, potentially weakening gut barrier function and metabolic resilience. Collectively, these microbial shifts may influence abdominal obesity, lipid dysregulation, inflammation, and hormonal imbalance even in individuals with normal BMI. This study underscores the value of microbiome-based biomarkers for phenotyping PCOS beyond adiposity and supports future metabolomic and interventional research aimed at gut-targeted therapies.

Citation

He F, Li Y. The gut microbial composition in polycystic ovary syndrome with insulin resistance: findings from a normal-weight population.Journal of Ovarian Research. 2021;14:50. doi:10.1186/s13048-021-00799-9