The mediating role of circulating inflammatory cytokines in causal associations between plasma metabolites and asymptomatic bile duct and cholecyst calculus: A Mendelian randomization study

Asymptomatic gallbladder and biliary tract calculus may make into symptomatic disease or bring anxiety for patients. The formation of gallstones was associated with genetic risk factors and metabolic abnormalities. Genome-wide association studies (GWAS) data of 1400 plasma metabolites (PMs) and 91 circulating inflammatory cytokines (CICs) were obtained from the GWAS catalog, while the GWAS data of calculus of gallbladder without cholecystitis and calculus of bile duct without cholangitis or cholecystitis were retrieved from the IEU OpenGWAS project. The causalities from PMs or CICs to asymptomatic bile duct or cholecyst calculus were explored by 2-sample Mendelian randomization (MR) analysis. Furthermore, the MR analyses were implemented from the identified PMs to CICs. Following the false discovery rate adjustment, the significant causalities, including 6 CICs and 5 PMs on asymptomatic biliary stone and 5 CICs and 48 PMs on asymptomatic gallstone, were identified. Fibroblast growth factor 19 (FGF-19) and aspartate/mannose ratio were the common protective factors of asymptomatic biliary tract calculus, while Monocyte chemoattractant protein 2 (CCL-2) may serve as a disease-promoting agent. Moreover, Bilirubin degradation product, C17H18N2O4 (1) levels, and Bilirubin (Z,Z)/etiocholanolone glucuronide ratio were associated with FGF-19 level, while aspartate/mannose ratio was related to TNF-related apoptosis-inducing ligand level. Based on MR analysis, we identified the multiple PMs and CICs, especially FGF-19, which may affect the formation of gallbladder and biliary tract calculus. Moreover, the partial CICs could be the downstream mediator of PMs related to asymptomatic gallbladder and biliary tract calculus. These results contributed to supporting previous studies and provided evidence for disease prevention or management.