Exploring the causal relationship between inflammatory bowel disease and Bell's palsy based on inflammatory proteins: a Mendelian randomization study

Background: The relationship between Inflammatory Bowel Disease (IBD) and Bell’s palsy remains unsubstantiated. This study aims to investigate the causal relationship between IBD and Bell’s palsy. Methods: Using two-sample Mendelian randomization (MR) method to explore the relationship between IBD and Bell’s palsy. We applied Bell’s palsy summary statistics from GWAS statistics for 91 inflammatory proteins and FinnGen R10 and IBD summary statistics from the International Inflammatory Bowel Disease Genetics Consortium. Results: The two-sample MR study indicates a significant positive association between IBD and Bell’s palsy (OR: 1.13, 95% CI [1.03 to 1.23], P = 0.0065) and between Crohn’s disease and Bell’s palsy (OR: 1.10, 95% CI [1.02 to 1.18], P = 0.0088). After applying Bonferroni correction, IBD remained significantly correlated with Bell’s palsy. Subsequently, the causal relationship between circulating inflammatory proteins in Bell's palsy and inflammatory bowel disease samples was reevaluated. The results of MR study between inflammatory proteins among these two diseases suggests that the C-X-C Motif Chemokine Ligand 5 (CXCL5) is a potential protective factor and interleukin_17C (IL_17C) is a risk factor for these two diseases. Conversely, Signaling Lymphocytic Activation Molecule Family Member 1 (SLAMF1) is a protective factor for Bell's palsy and a risk factor for inflammatory bowel disease. Conclusions: The findings indicate that IBD may be a risk factor for Bell’s palsy at the genetic level. CXCL5, IL_17C, SLAMF1 are possible co-acting pathways between Bell's palsy and inflammatory bowel disease. These findings may provide new targets for the treatment of both diseases.