Association between metabolic syndrome and inflammatory bowel disease: a bidirectional two-sample Mendelian randomized study.

Introduction: Epidemiological studies have revealed parallel increases in the incidences of metabolic syndrome (MetS) and inflammatory bowel disease (IBD). Clinical observational studies have shown an association between MetS and a poor prognosis of IBD. However, the causal relationship between MetS and IBD remains unclear. This study used bidirectional two-sample Mendelian randomization to investigate potential causal links between MetS and IBD, including ulcerative colitis (UC) and Crohn's disease (CD). Material and methods: Genetic associations of MetS and its components with IBD were sourced from public databases of European populations. Inverse variance weighting was conducted, with weighted median, Mendelian randomization-Egger (MR-Egger), and Mendelian randomization Pleiotropy RESidual Sum and Outlier (MR-PRESSO) methods used as sensitivity analyses. This process was repeated in the opposite direction. Results: The inverse variance weighted (IVW) method showed that genetic prediction of MetS may be a potential risk factor for CD (OR = 1.34, 95% CI: 1.009-1.779; Conclusions: This MR analysis showed a causal relationship between genetically predicted MetS and CD, and genetically predicted hypertension and UC. Therefore, these patients need to be closely monitored clinically for the risk of CD/UC comorbidities. In patients with IBD, close monitoring of MetS-associated cardiovascular risk is required.