Primary biliary cirrhosis and rheumatoid arthritis: a comprehensive study combining genetics and transcriptomics.

Observational investigations have discerned a correlation between primary biliary cirrhosis (PBC) and rheumatoid arthritis (RA). The primary objective of this study is to elucidate the disease risk correlation between them in terms of genetics, and to explore the genes and signaling pathways involved. We acquired genome-wide association studies (GWAS) summary data for PBC and RA from distinct repositories: PBC data sourced from the IEU OpenGWAS database, and RA data obtained from the Finnish consortium. Employing a bidirectional two-sample Mendelian randomization (MR) approach, we scrutinized the disease risk correlation of PBC and RA. Subsequent to this analysis, we conducted a series of meticulous sensitivity assessments to gauge the robustness of our MR findings. These evaluations encompassed analyses for heterogeneity and horizontal pleiotropy, outlier identification, Leave-One-Out analysis, and assessments for adherence to normal distribution assumptions. Furthermore, we conducted an in-depth analysis of the genes and signaling pathways potentially involved in the disease risk correlation between PBC and RA. Finally, a difference analysis and receiver operating characteristic (ROC) curve analysis were conducted. The MR analysis conducted in this study revealed a significant positive disease risk correlation between PBC and RA (P < 0.001, odds ratio [OR] 95% confidence interval [CI] = 1.081 [1.036-1.128]). Moreover, reverse MR analysis also demonstrated a significant positive disease risk correlation between RA and PBC (P < 0.001, OR 95% CI = 1.702 [1.422-2.039]). Importantly, the bidirectional MR analysis detected no evidence of heterogeneity, horizontal pleiotropy, or outliers, and the results were not affected by single single nucleotide polymorphisms (SNPs). Additionally, the findings were consistent with a normal distribution. SNP-associated gene mapping was performed, identifying 14 candidate genes. Subsequent pathway enrichment analysis indicated that these genes were predominantly involved in the chemokine signaling pathway, JAK-STAT signaling pathway, and Th1/Th2 cell differentiation. Among them, IL12RB2, CCR6, and MANBA may serve as key mediators in the shared disease risk correlation architecture of PBC and RA. Further analysis of the differences identified a gene (MANBA). The ROC curve demonstrated the potential diagnostic value of MANBA. The findings of this study suggest a bidirectional disease risk correlation between PBC and RA, establishing them as mutually risk factors. In clinical practice, vigilance is paramount among patients diagnosed with RA regarding the potential development of PBC. Conversely, individuals presenting with PBC should undergo systematic screening for the presence of RA. The genes and pathways identified in this study as potentially contributing to the mutual disease risk correlation between PBC and RA provide valuable insights and lay the groundwork for future investigations into the underlying molecular mechanisms.