[A case-control study on the relationship between DNA methylation and occupational noise hearing loss]

Objective: To explore the relationship between DNA methylation and occupational noise-induced hearing loss. Methods: A case-control study was conducted. People with hearing loss induced by occupational noise were recruited as the case group and those with normal hearing but still exposed to occupational noise were recruited as the control group. A total of 60 participants were included, of which 30 participants were in the case group and 30 in the control group. The methylation level was detected by 850k genome-wide DNA methylation chip technology. The significance of differential methylated position (DMP) was tested by R-packet 'Champ'. The differential methylated region (DMR) was analyzed by using Champ's Bumphunter algorithm. Cluster profiler was used to analyze the gene list for GO and KEGG pathway enrichment. Results: There was significant difference between two groups in binaural high-frequency average hearing threshold (P<0.05), but there was no significant difference in age, smoking, drinking, hypertension, physical exercise and cumulative noise exposure. The results of DMP and DMR analysis showed that 713875 sites were detected in the case group and the control group, and 439 methylation sites with significant difference, accounting for 0.06%; 650 regions were detected, and 72 methylation regions with significant differences, accounting for 11.08%. Compared with the control group, the results of GO enrichment analysis showed that the case group had statistically significant differences in four pathways: axogenesis of projection neurons in the central nervous system, neuronal development in the central nervous system, axogenesis of neurons in the central nervous system and neuronal differentiation in the central nervous system. KEGG enrichment analysis showed that there were significant differences in sphingolipid metabolism, aldosterone synthesis and secretion, primary bile acid biosynthesis pathway between the case group and the control group. Conclusion: The occurrence of occupational noise-induced hearing loss may be related to the regulation of gene expression related to axogenesis of projection neurons in the central nervous system, development of neurons in the central nervous system, axogenesis of neurons in the central nervous system, differentiation of neurons in the central nervous system, sphingolipid metabolism, aldosterone synthesis and secretion, primary bile acid biosynthesis and gene methylation related to metabolism.