Alterations of bacteriome, mycobiome and metabolome characteristics in PCOS patients with normal/overweight individuals

Beyond the reproductive tract: gut microbiome and its influence on gynecological health

PURPOSE OF REVIEW

The analysis of microbiome in association with female health is today a "hot topic" with the main focus on microbes in the female reproductive tract. Nevertheless, recent studies are providing novel information of the possible influence of the gut microbiome on gynecological health outcomes, especially as we start to understand that the gut microbiome is an extended endocrine organ influencing female hormonal levels. This review summarizes the current knowledge of the gut microbes in association with gynecological health.

RECENT FINDINGS

The gut microbiome has been associated with endometriosis, polycystic ovary syndrome, gynecological cancers, and infertility, although there is a lack of consistency and consensus among studies due to different study designs and protocols used, and the studies in general are underpowered.

SUMMARY

The interconnection between the gut microbiome and reproductive health is complex and further research is warranted. The current knowledge in the field emphasizes the link between the microbiome and gynecological health outcomes, with high potential for novel diagnostic and treatment tools via modulation of the microenvironment.

Alterations in gut and genital microbiota associated with gynecological diseases: a systematic review and meta-analysis

BACKGROUND

Increasing number of studies have demonstrated certain patterns of microbial changes in gynecological diseases; however, the interaction between them remains unclear. To evaluate the consistency or specificity across multiple studies on different gynecological diseases and microbial alterations at different sites of the body (gut and genital tract), we conducted a systematic review and meta-analysis.

METHODS

We searched PubMed, Embase, Web of Science, and Cochrane Library up to December 5, 2022(PROSPERO: CRD42023400205). Eligible studies focused on gynecological diseases in adult women, applied next-generation sequencing on microbiome, and reported outcomes including alpha or beta diversity or relative abundance. The random-effects model on standardized mean difference (SMD) was conducted using the inverse-variance method for alpha diversity indices.

RESULTS

Of 3327 unique articles, 87 eligible studies were included. Significant decreases were found in gut microbiome of patients versus controls (observed species SMD=-0.35; 95%CI, -0.62 to -0.09; Shannon index SMD=-0.23; 95%CI, -0.40 to -0.06), whereas significant increases were observed in vaginal microbiome (Chao1 SMD = 1.15; 95%CI, 0.74 to 1.56; Shannon index SMD = 0.51; 95%CI, 0.16 to 0.86). Most studies of different diagnostic categories showed no significant differences in beta diversity. Disease specificity was observed, but almost all the changes were only replicated in three studies, except for the increased Aerococcus in bacterial vaginosis (BV). Patients with major gynecological diseases shared the enrichment of Prevotella and depletion of Lactobacillus, and an overlap in microbes was implied between BV, cervical intraepithelial neoplasia, and cervical cancer.

CONCLUSIONS

These findings demonstrated an association between alterations in gut and genital microbiota and gynecological diseases. The most observed results were shared alterations across diseases rather than disease-specific alterations. Therefore, further investigation is required to identify specific biomarkers for diagnosis and treatment in the future.

Alterations of gut microbiota biodiversity and relative abundance in women with PCOS: A systematic review and meta-analysis

BACKGROUND

Numerous studies have implicated that the gut microbiota is associated with polycystic ovary syndrome (PCOS). However, a comprehensive data-based summary shown that the effects of the PCOS on the gut microbiota is minimal. We aim to assess the alterations of gut microbiota in women with PCOS.

METHODS

An electronic search of PubMed, Web of Science, Embase, Cochrane Library and Ovid was conducted for eligible studies published from inception to 28 March 2023, without any language or regional restrictions. We used Newcastle-Ottawa Quality Assessment Scale (NOS) to complete the assessment of the risk of bias and Stata 15.1 software to performed meta-analysis.

RESULTS

There were 19 human observational studies in total with 617 women with PCOS and 439 healthy individuals were identified. Compared to the control group, the Chao index (WMD -28.88, 95% CI -45.78 to -11.98, I2 = 100%), Shannon index (WMD -0.11, 95% CI -0.18 to 0.00, I2 = 92.2%); and observed operational taxonomic units (OTUs) counts (WMD - 23.48, 95% CI -34.44 to -12. 53, I2 = 99.6%) were significantly lower in women with PCOS. The relative abundance of Bacteroidaceae was significantly higher (WMD 0.12, 95% CI 0.02 to 0.22, I2 = 9.2%), however there were no statistical differences in Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, Alcaligenaceae, Bifidobacteriaceae, Clostridiaceae, Enterobacteriaceae, Lachnospiraceae, Prevotellaceae, Ruminococcaceae, Veillonellaceae, Bacteroides, Bifidobacterium, Blautia, Dialister, Escherichia-Shigella, Faecalibacterium, Lachnoclostridium, Lachnospira, Megamonas, Phascolarctobacterium, Prevotella, Roseburia, and Subdoligranulum.

CONCLUSION

We demonstrated the alpha diversity of gut microbiota and the relative abundance of Bacteroidaceae in women with PCOS are altered. The results indicates that dysbiosis may be a potential pathogenetic factor in PCOS and provided reliable information to investigate the role of gut microbiota in the development and progression of PCOS.

Alteration in gut mycobiota of patients with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a serious disease characterized by high androgen, insulin resistance (IR), hyperglycemia, and obesity, leading to infertility. The gut mycobiota has been reported to evolve in metabolic diseases including obesity, hyperglycemia, and fatty liver. However, little is known about the gut mycobiota and PCOS. In the current study, we recruited 17 PCOS patients and 17 age-matched healthy controls for community structure and functional analysis of the gut mycobiota. The results showed that PCOS patients have reduced diversity and richness of the gut microbiota compared with healthy controls. β-Diversity analysis showed that the community structure of the gut microbiota of patients with PCOS was significantly different from healthy controls. At the phylum level, PCOS patients have reduced Basidiomycota and increased Ascomycota compared with healthy controls. At the family level, the higher relative abundance of Saccharomycetaceae and lower Trichosporonaceae and Ascomycota_unclassified were detected in PCOS patients than in healthy controls. At the genus level, different microbial compositions were also observed between PCOS patients and healthy controls. In addition, PICRUSt2 showed that patients with PCOS have different microbial functions in the gut compared with healthy controls. LEfSe indicated that Saccharomyces and Lentinula were enriched in the fecal samples of PCOS patients, while Aspergillus was depleted compared with healthy controls. Our finding indicates that PCOS patients have different community structures and functions of the gut mycobiota, which provides new insight into PCOS pathogenesis and intervention. IMPORTANCE It was found that intestinal fungi as well as serum metabolites in PCOS patients were significantly different from those in healthy subjects. However, no studies have been done to show exactly which fungus interacts with which bacteria in humans or which fungus acts alone. As fungal research progresses, it will be possible to fill this gap.

Perturbations in gut microbiota composition in patients with polycystic ovary syndrome: a systematic review and meta-analysis

BACKGROUND

The results of human observational studies on the correlation between gut microbiota perturbations and polycystic ovary syndrome (PCOS) have been contradictory. This study aimed to perform the first systematic review and meta-analysis to evaluate the specificity of the gut microbiota in PCOS patients compared to healthy women.

METHODS

Literature through May 22, 2023, was searched on PubMed, Web of Science, Medline, Embase, Cochrane Library, and Wiley Online Library databases. Unreported data in diversity indices were filled by downloading and processing raw sequencing data. Systematic review inclusion: original studies were eligible if they applied an observational case-control design, performed gut microbiota analysis and reported diversity or abundance measures, sampled general pre-menopausal women with PCOS, and are longitudinal studies with baseline comparison between PCOS patients and healthy females. Systematic review exclusion: studies that conducted interventional or longitudinal comparisons in the absence of a control group. Two researchers made abstract, full-text, and data extraction decisions, independently. The Joanna Briggs Institute Critical Appraisal Checklist was used to assess the methodologic quality. Hedge's g standardized mean difference (SMD), confidence intervals (CIs), and heterogeneity (I2) for alpha diversity were calculated. Qualitative syntheses of beta-diversity and microbe alterations were performed.

RESULTS

Twenty-eight studies (n = 1022 patients, n = 928 control) that investigated gut microbiota by collecting stool samples were included, with 26 and 27 studies having provided alpha-diversity and beta-diversity results respectively. A significant decrease in microbial evenness and phylogenetic diversity was observed in PCOS patients when compared with control participants (Shannon index: SMD = - 0.27; 95% CI, - 0.37 to - 0.16; phylogenetic diversity: SMD = - 0.39; 95% CI, -- 0.74 to - 0.03). We also found that reported beta-diversity was inconsistent between studies. Despite heterogeneity in bacterial relative abundance, we observed depletion of Lachnospira and Prevotella and enrichment of Bacteroides, Parabacteroides, Lactobacillus, Fusobacterium, and Escherichia/Shigella in PCOS. Gut dysbiosis in PCOS, which might be characterized by the reduction of short-chain fatty acid (SCFA)-producing and bile-acid-metabolizing bacteria, suggests a shift in balance to favor pro-inflammatory rather than anti-inflammatory bacteria.

CONCLUSIONS

Gut dysbiosis in PCOS is associated with decreased diversity and alterations in bacteria involved in microbiota-host crosstalk.

TRIAL REGISTRATION

PROSPERO registration: CRD42021285206, May 22, 2023.

The association between gut microbiome and PCOS: evidence from meta-analysis and two-sample mendelian randomization

BACKGROUND

Increasing evidence from observational studies and clinical experimentation has indicated a link between the gut microbiotas (GMs) and polycystic ovary syndrome (PCOS), however, the causality and direction of causality between gut microbiome and PCOS remains to be established.

METHODS

We conducted a comprehensive search of four databases-PubMed, Cochrane Library, Web of Science, and Embase up until June 1, 2023, and subjected the results to a meta-analysis. In this study, a bidirectional two-sample Mendelian randomization (MR) analysis was employed to investigate the impact of gut microbiota on polycystic ovary syndrome (PCOS). The genome-wide association study (GWAS) data for PCOS comprised 113,238 samples, while the GWAS data for gut microbiota were derived from the MiBioGen consortium, encompassing a total sample size of 18,340 individuals. As the largest dataset of its kind, this study represents the most comprehensive genome-wide meta-analysis concerning gut microbiota composition to date. Single nucleotide polymorphisms (SNPs) were selected as instrumental variables at various taxonomic levels, including Phylum, Class, Order, Family, and Genus. The causal associations between exposures and outcomes were assessed using four established MR methods. To correct for multiple testing, the false discovery rate (FDR) method was applied. The reliability and potential biases of the results were evaluated through sensitivity analysis and F-statistics.

RESULTS

The meta-analysis incorporated a total of 20 studies that met the criteria, revealing a close association between PCOS and specific gut microbiota species. As per the results from our MR analysis, we identified six causal associations between the gut microbiome and polycystic ovary syndrome (PCOS). At the genus level, Actinomyces (ORIVW = 1.369, FDR = 0.040), Streptococcus (ORIVW = 1.548, FDR = 0.027), and Ruminococcaceae UCG-005 (ORIVW = 1.488, FDR = 0.028) were identified as risk factors for PCOS. Conversely, Candidatus Soleaferrea (ORIVW = 0.723, FDR = 0.040), Dorea (ORIVW = 0.580, FDR = 0.032), and Ruminococcaceae UCG-011 (ORIVW = 0.732, FDR = 0.030) were found to be protective factors against PCOS. Furthermore, the MR-PRESSO global test and MR-Egger regression indicated that our study results were not affected by horizontal pleiotropy (p > 0.05). Finally, the leave-one-out analysis corroborated the robustness of the MR findings.

CONCLUSION

Both our meta-analysis and MR study indicates that there is a causal relationship between the gut microbiome and PCOS, which may contribute to providing novel insights for the development of new preventive and therapeutic strategies for PCOS.