AUTHOR=Raita Yoshihiko , Zhu Zhaozhong , Camargo Carlos A. , Freishtat Robert J. , Ngo Debby , Liang Liming , Hasegawa Kohei 

TITLE=Relationship of Soluble Interleukin-6 Receptors With Asthma: A Mendelian Randomization Study

JOURNAL=Frontiers in Medicine

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2021.665057

DOI=10.3389/fmed.2021.665057

ISSN=2296-858X

ABSTRACT=<p><bold>Purpose:</bold> Emerging evidence suggests a potential role of interleukin-6 pathways—trans-signaling with soluble interleukin-6 receptors—in the asthma pathobiology. Despite the evidence for their associations with asthma, the causal role of soluble interleukin-6 receptors remains uncertain. We investigated the relations of soluble interleukin-6 receptors with asthma and its major phenotypes.</p><p><bold>Methods:</bold> We conducted a two-sample Mendelian randomization study. As genetic instruments, we selected 33 independent <italic>cis</italic>-acting variants strongly associated with the level of plasma soluble interleukin-6 receptor in the INTERVAL study. To investigate the association of variants with asthma and its phenotypes, we used genome-wide association study data from the UK Biobank. We combined variant-specific causal estimates by the inverse-variance weighted method for each outcome.</p><p><bold>Results:</bold> Genetically-instrumented soluble interleukin-6 receptor level was associated with a significantly higher risk of overall asthma (OR per one standard deviation increment in inverse-rank normalized soluble interleukin-6 receptor level, 1.02; 95%CI, 1.01–1.03; <italic>P</italic> = 0.004). Sensitivity analyses demonstrated consistent results and indicated no directional pleiotropy—e.g., MR-Egger (OR, 1.03; 95%CI, 1.01–1.05; <italic>P</italic> = 0.002; <italic>P</italic><sub>intercept</sub> =0.37). In the stratified analysis, the significant association persisted across asthma phenotypes—e.g., childhood asthma (OR, 1.05; 95%CI, 1.02–1.08; <italic>P</italic> &lt; 0.001) and obese asthma (OR, 1.02; 95%CI 1.01–1.03; <italic>P</italic> = 0.007). Sensitivity analysis using 16 variants selected with different thresholds also demonstrated significant associations with overall asthma and its phenotypes.</p><p><bold>Conclusion:</bold> Genetically-instrumented soluble interleukin-6 receptor level was causally associated with modestly but significantly higher risks of asthma and its phenotypes. Our observations support further investigations into identifying specific endotypes in which interleukin-6 pathways may play major roles.</p>