Causal impact of gut microbiota and associated metabolites on pulmonary arterial hypertension: a bidirectional Mendelian randomization study

Patients with pulmonary arterial hypertension (PAH) exhibit a distinct gut microbiota profile; however, the causal association between gut microbiota, associated metabolites, and PAH remains elusive. We aimed to investigate this causal association and to explore whether dietary patterns play a role in its regulation.

Alistipes (odds ratio [OR] = 2.269, 95% confidence interval [CI] 1.100–4.679, P = 0.027) and Victivallis (OR = 1.558, 95% CI 1.019–2.380, P = 0.040) were associated with an increased risk of PAH, while Coprobacter (OR = 0.585, 95% CI 0.358–0.956, P = 0.032), Erysipelotrichaceae (UCG003) (OR = 0.494, 95% CI 0.245–0.996, P = 0.049), Lachnospiraceae (UCG008) (OR = 0.596, 95% CI 0.367–0.968, P = 0.036), and Ruminococcaceae (UCG005) (OR = 0.472, 95% CI 0.231–0.962, P = 0.039) protected against PAH. No associations were observed between PAH and gut microbiota-derived metabolites (trimethylamine N-oxide [TMAO] and its precursors betaine, carnitine, and choline), short-chain fatty acids (SCFAs), or diet. Although inverse variance-weighted analysis demonstrated that elevated choline levels were correlated with an increased risk of PAH, the results were not consistent with the sensitivity analysis. Therefore, the association was considered insignificant. Reverse Mendelian randomisation analysis demonstrated that PAH had no causal impact on gut microbiota-derived metabolites but could contribute to increased the levels of Butyricicoccus and Holdemania, while decreasing the levels of Clostridium innocuum, Defluviitaleaceae UCG011, Eisenbergiella, and Ruminiclostridium 5.

Gut microbiota were discovered suggestive evidence of the impacts of genetically predicted abundancy of certain microbial genera on PAH. Results of our study point that the production of SCFAs or TMAO does not mediate this association, which remains to be explained mechanistically.