27. EPIGENOME-WIDE ANALYSIS REVEALS DISTINCT DNA METHYLATION PROFILES FOR OPIOID DEPENDENCE VERSUS OPIOID EXPOSURE

Background The U.S. opioid epidemic represents a serious public health crisis. While epigenetic mechanisms have been linked to opioid use disorder (OUD), more research is needed to identify actionable biomarkers that distinguish opioid exposure from opioid dependence. In this study, we aimed to disentangle the epigenomic signatures of opioid exposure and opioid dependence. Methods Our study cohort included 909 Yale–Penn study participants, including individuals with opioid dependence (OPI-DEP, n = 339), opioid-exposed but not dependent (EXPOSED, n = 165), and opioid non-exposed individuals (NON-EXPOSED, n = 405). Genome-wide DNA methylation using blood-extracted DNA was profiled using the Illumina EPIC array. Quality control was performed using the R packages minfi, ewastools, and ENmix. Epigenome-wide association analysis was conducted using the cpg.assoc function, adjusting for age, sex, estimated cell-type proportions, ancestry principal components, six surrogate variables and other mental health and addictive disorders, including posttraumatic stress disorder, major depression, and cocaine, cannabis, tobacco and alcohol use disorders. Functional enrichment analysis was performed using the Enrichr database to identify overrepresented biological processes and pathways. Multiple testing correction used a false discovery rate (FDR) set at 0.05. Results When comparing OPI-DEP with EXPOSED, we identified eight CpG (cg03609826, cg20062737, cg25565138, cg25019044, cg14873739, cg12212240, cg09265274, cg25581027) sites significantly associated with OPI-DEP, including loci mapped to C1orf25, DLK2, RASA3, TGFA, OSBPL3, and MYCBPAP. Comparing EXPOSED with NON-EXPOSED, cg13476336 was significantly associated with opioid exposure; this maps to NR1D1, a gene involved in astrocyte activation. Differentially methylated genes associated with opioid dependence showed significant enrichment in the ERBB2-EGFR Signaling Pathway (GO:0038134) and Bile Acid Biosynthetic Process (GO:0006699). Discussion Our work helps to differentiate the epigenomic effects of opioid dependence from those of exposure, pinpointing potential targets for biomarker development and therapeutic intervention.