Causality Between Gut Microbiota and Inflammatory Bowel Disease:A Bidirectional Mendelian Randomization Study

The exact relationship between inflammatory bowel disease(IBD)and gut microbiota(GM)is still unclear.This study aimed to explore the cause-and-effect relationship between IBD and GM by Mendelian randomization analysis.The IBD data used in this study were obtained from Genome-Wide Association Studies.The GM data were from the Dutch Microbiome Project and included 207 taxa and 205 microbiota-associated pathways.Multivariate Mendelian randomization analysis was performed to investigate the relationship between GM and IBD.The results demonstrated that susceptibility to developing IBD is negatively correlated with class Clostridia(OR=0.80,P=0.003),family Sutterellacea(OR=0.87,P=0.014),genus Coprobacter(OR=0.90,P=0.009),order Clostridiales(OR=0.80,P=0.003),phylum Firmicutes(OR=0.82,P=0.002)and Coprobacter fastidiosus(OR=0.90,P=0.009).Conversely,the risk of developing IBD was positively correlated with the phosphopantothenate biosynthesis I pathway(OR=1.17,P=0.006),Bacteroides caccae(OR=1.14,P=0.021)and Bacteroides uniformis(OR=1.26,P=0.003).Reverse causality was found between the phosphopantothenate biosynthesis I pathway and IBD(OR=1.03,P=0.04),but not for the remaining specific GM taxa.In conclusion,our study demonstrated a causal relationship between specific GM features and IBD.