[Causal relationship between relative abundance of gut microbiota and teratozoospermia: A two-sample Mendelian randomization analysis]

Objective: To explore the potential causal relationship between gut microbiota and teratozoospermia.

Methods: We searched the database of Genome-Wide Association Study (GWAS) for gut microbiota- and teratozoospermia-related data. We used gut microbiota as an exposure factor, determined the instrumental variables according to the GWAS data on 18 340 participants released by the MiBioGen Alliance, and derived the outcome variables from the European data on teratozoospermia, with a sample size of 85 716, including 915 cases and 209 006 controls. Using inverse-variance weighting (IVW), MR-Egger regression and the weighted median estimator (WME), we performed two-sample Mendelian randomization (MR) analysis on the retrieved data, and estimated the causal relationship between gut microbiota and teratozoospermia based on the β value.

Results: Two-sample MR analysis indicated that the class Erysipelotrichia, family Erysipelotrichaceae, family Streptococcaceae, genus Coprococcusl, genus Ruminococcaceae UCG009, genus Streptococcus, order Clostridialesm and order Erysipelotrichales were causally related with the increased risk, while the family Porphyromonadaceae with the decreased risk of teratozoospermia.

Conclusion: The class Erysipelotrichia, family Erysipelotrichaceae, family Streptococcaceae, genus Coprococcusl, genus Ruminococcaceae UCG009, genus Streptococcus, order Clostridialesm and order Erysipelotrichales are one of the causes of teratozoospermia, related to the increased risk of the condition, while the family Porphyromonadaceae has a protective effect on sperm morphology, reducing the risk of teratozoospermia.