Causality Between 91 Circulating Inflammatory Proteins and Various Asthma Phenotypes: A Mendelian Randomization Study

Objective
To investigate the causal relationship between 91 circulating inflammatory proteins and Various asthma phenotypes by means of Mendelian randomization.

Methods
Genome-wide association Studies (GWAS) of 91 inflammatory proteins were pooled from the Olink Target platform with 14,824 participants. Various asthma phenotypes were derived from the FinnGen Biobank. Inverse variance weighting (IVW) was used as the main method for MR Analysis, supplemented by Mr-Egger, Weighted median, Simple mode, and Weighted mode. The MR-Egger intercept term test and Cochran’s Q test were used to test the polymorphism and heterogeneity of IVs, and visual analysis was carried out to draw scatter plots, funnel plots, and leave-out-one plots. The FDR correction was performed due to the possibility of a type 1 error.

Results
Genetically predicted IVW results revealed a total of 30 data sets suggesting a potential causal relationship between circulating inflammatory proteins and asthma phenotypes. Among them, 2 results were still strongly positive after FDR correction. The level of CST5 (OR=1.184; 95% CI: 1.075–1.305; P=0.0001; P-FDR=0.028) is associated with an increased risk of non-allergic asthma. LIF-R (OR=0.723; 95% CI: 0.620–0.842; P=0.000; P-FDR=0.003) is associated with a reduced risk of asthma in children. There was no pleiotropy or heterogeneity in the remaining 16 results that suggested a potential causal relationship.

Conclusion
Increased CST5 levels are associated with an increased risk of non-allergic asthma. LIF-R is associated with a reduced risk of asthma in children.