Dysbiosis of the Saliva Microbiome in Patients With Polycystic Ovary Syndrome Original paper

What Was Studied?

This study investigated the composition, diversity, and diurnal oscillation of the salivary microbiome in women with polycystic ovary syndrome (PCOS) compared to healthy controls. The researchers sought to determine whether salivary microbiota differ in PCOS patients at different time points during the day and to assess how disruptions in these microbial patterns might contribute to metabolic and endocrine dysregulation. Using 16S rRNA gene sequencing, the authors analyzed salivary samples collected every six hours over 24 hours, along with fecal samples, from 10 PCOS patients and 10 age-matched healthy women. They evaluated microbial diversity, taxonomic differences at multiple phylogenetic levels, and predicted metabolic pathway alterations using PICRUSt. A key objective was to identify whether PCOS disrupts the circadian rhythm of oral microbiota, which may contribute to systemic disease processes.

Who Was Studied?

The study recruited 10 women with PCOS diagnosed via the Rotterdam criteria and 10 healthy controls, all aged between 18 and 45, and matched for body mass index (BMI), diet, and lifestyle factors. Participants underwent strict dietary controls before sample collection, and the study excluded individuals with recent antibiotic or probiotic use, hormonal treatment, or oral or systemic diseases. Saliva was sampled at four Zeitgeber time (ZT) points, and stool samples were collected to compare oral and gut microbiota profiles. Blood samples were also taken to assess hormonal and metabolic biomarkers, allowing for correlation with microbial changes.

What Were the Most Important Findings?

PCOS patients showed clear evidence of salivary microbiota dysbiosis. At ZT0, alpha diversity was significantly lower in PCOS participants, indicating reduced species richness and diversity. Beta diversity analysis revealed significant structural shifts in the microbial community at ZT0 and ZT18. Notably, the relative abundance of the phylum Fusobacteria and the genus Fusobacterium was consistently higher in PCOS patients at all time points, while beneficial taxa such as Actinobacteria and Leptotrichia were diminished, particularly at night.

Functionally, PCOS samples exhibited disrupted KEGG pathways. “Methane metabolism” and “butanoate metabolism” were consistently upregulated, both of which have been associated with metabolic disorders and gut permeability. Conversely, pathways related to protein folding, secretion systems, and structural molecule synthesis were downregulated. Critically, the study found that the circadian rhythm of bacterial abundance, observable in healthy individuals for phyla like Proteobacteria, Bacteroidetes, and orders such as Lactobacillales, was largely absent in PCOS patients. This disruption may contribute to both oral health problems and broader metabolic dysfunction via chronobiological misalignment.

While no major differences were detected in gut microbiota composition or diversity between the PCOS and control groups, the oral microbiome showed profound alterations. This suggests that salivary bacteria may offer more accessible and sensitive biomarkers for PCOS-related dysbiosis than fecal bacteria, at least in early or non-obese phenotypes.

What Are the Implications of This Study?

This study provides the first robust evidence that the salivary microbiota in PCOS not only differs significantly from that of healthy controls but also lacks a normal diurnal rhythm. These findings underscore the relevance of the oral microbiome as both a diagnostic window and a potential therapeutic target in PCOS. Clinicians should consider the possibility that microbial timing is as important as microbial composition. Elevated Fusobacterium levels and reduced Actinobacteria may serve as early biomarkers for PCOS-linked dysbiosis, while their functional consequences, such as increased methane production and impaired protein metabolism, suggest mechanistic links to systemic inflammation, insulin resistance, and metabolic syndrome.

From a clinical standpoint, the convenience of saliva sampling, combined with time-sensitive microbial signatures, could facilitate non-invasive PCOS monitoring and risk stratification. This opens the door for chrono-microbiome interventions, timed probiotic delivery, circadian-aligned dietary changes, or salivary microbiome modulation as adjunct therapies. These findings highlight the need for further metagenomic and metatranscriptomic studies to validate and expand the functional understanding of these dysbiotic patterns.