Table 1 Summary of major microbiome studies involving PCOS

Kelley 2016 [50]

USA

NA

Letrozole-induced PCOS mouse model/placebo

16S rDNA sequencing

V4

↓α diversity

β diversity:

PCoA of the UniFrac distances: a significant shift

↑Lachnospiraceae, Erysipelotrichaceae, Ruminococcacea

↑Allobaculum, Blautia, and Ruminococcus

↓S24–7 and 1 in the family Rikenellaceae, genus Alistipes

Guo Y 2016 [7]

China

NA

Letrozole-treated rats (n = 24)/control (n = 8)

16S rDNA sequencing

V3

NA

↓Lactobacillus, Ruminococcus, and Clostridium

↑Prevotella

Lindheim 2017 [18]

Austria

Rotterdam Criteria

PCOS (n = 24)/control (n = 19)

16S rDNA sequencing

V1-V2

↓α diversity

β diversity:

Unweighted UniFrac analysis: significant clustering

↓Phylum Tenericutes, the order ML615J-28 (belonging to the phylum Tenericutes)

↓Family S24–7 (belonging to the phylum Bacteroidetes)

Liu 2017 [18]

China

Rotterdam Criteria

PCOS (non obese PCOS,n = 12; obese PCOS,n = 21)/controls (n = 9 non obese control;n = 6 obese control)

16S rDNA sequencing V3–4

↓α diversity

β diversity:

CO group was more similar with that of PN and PO groups, rather than CN group

↑LPS-producing bacteria

↓Spore forming species

↓Akkermensia (of the phylum Verrucomicrobia) and Alistipes, Corprococcus, Ruminococcus

Torres 2018 [20]

Poland

Rotterdam Criteria

Women with PCOM (n = 42)/control healthy women

(n = 48)/women with PCOS (n = 73)

16S rDNA sequencing V4

↓α diversity in women with PCOS compared with healthy women

β diversity was correlated with hyperandrogenism

↑Porphyromonas spp., Bacteroides coprophilus, Blautia spp., Faecalibacterium prausnitzii in women with PCOS compared with healthy women

Insenser 2018 [21]

Spain

Rotterdam Criteria

PCOS (n = 15)/16 non hyperandrogenic control women (n = 16) and control men (n = 15)

16S rDNA sequencing V4

↓α diversity in women compared with men

↓β diversity in obese patients with PCOS compared with their lean counterparts

↑Catenibacterium, Kandleria genera

Zeng 2018 [22]

China

Rotterdam Criteria

IR-PCOS (n = 9, PCOS with insulin resistance),

NIR-PCOS (n = 8, PCOS alone), and healthy controls (n = 8)

16S rDNA sequencing V3–4

↓α diversity in IR-PCOS compared to healthy controls

β diversity(weighted UniFrac and PCoA analysis):samples from the HC group can be clearly discriminated from the IR-PCOS group

↑Prevotellaceae in IR-PCOS and NIR-PCOS compared to healthy controls

↑Bacteroides in IR-PCOS and NIR-PCOS compared to healthy controls

Sheman

2018 [84]

USA

NA

Model of prenatal androgen exposure rats/maternal hyperandrogenemia by single-injection of testosterone cypionate or sesame oil vehicle

16S rDNA sequencing

↑α diversity in PNA animals

β diversity:

the PNA animal samples were further apart.

↑Nocardiaceae and Clostridiaceae

↓Akkermansia, Bacteroides, Lactobacillus, and Clostridium

Zhang 2019 [52]

China

NA

PCOS (n = 38)/control (n = 26)

16S rDNA sequencing V3-V4, deep shotgun metagenomic sequencing

β diversity:

weighted and unweighted UniFrac analysis:

significant clustering

↓Faecalibacterium, Bifidobacterium, and Blautia

↑Parabacteroides, Bacteroides, Lactobacillus, Oscillibacter, Escherichia/ Shigella, and Clostridium

Chen 2019 [98]

China

Chinese Criteria

2012

non⁃acne PCOS patients(n = 10), MSA⁃PCOS,n = 10)/ healthy controls (n = 10)

16S rDNA sequencing

V3-V4

↓α diversity

β diversity:

weighted UniFrac analysis:samples from the HC group can be clearly discriminated from PCOS

↑Bacteroides

↓Prevotella, Faecalibacteruim

Zhou 2020 [99]

China

Rotterdam Criteria

obese PCOS (OG,n = 30), non-obese PCOS (NG,N = 30) /healthy women (NC,n = 30) healthy but obese women (OC,n = 11)

16S rDNA sequencing

V3-V4

α diversity: Simpson index of OTU: NG was significantly higher than that in NC

β diversity: No significant difference

↑OG:Lactococcus, Paraprevotella, Alloprevotella

↑NG:Coprococcus_2, Lactobacillus, Prevotella_7

Qi 2019 [53]

NA

PCOS (n = 50)/control (n=43)

Whole-genome shotgun sequencing

α diversity:no significant

difference

↑Bacteroides vulgatus