D94-05 DNA Methylation Signatures of Oxidative Stress and Inflammation Are Altered by a Mediterranean Diet in Firefighters

Rationale Particulate matter (PM) exposure and metabolic syndrome promote oxidative stress, inflammation, and alterations in DNA methylation. The Mediterranean diet has been associated with anti-inflammatory and antioxidant effects, but its long-term impact on DNA methylation of oxidative stress-related genes in PM-exposed individuals remains unclear. We want to evaluate whether a 6-month Mediterranean dietary intervention (FIREHOUSE randomized controlled trial: Food Intake REstriction for Health OUtcome Support and Education) modifies DNA methylation of genes involved in oxidative stress and inflammation among firefighters with prior PM exposure. Methods World Trade Center-exposed firefighters with lung injury were randomized to either a low-calorie Mediterranean diet (LoCalMed) or usual care (UC). Genome-wide methylation profiling was performed on available paired high-quality samples (baseline vs. 6-month, LoCalMed; n = 34 or UC; n = 33 -Illumina EPIC array). From >850,000 CpGs, 5,846 CpGs related to oxidative stress and inflammation (Gene Ontology, MSigDB; University of California San Diego) were analyzed (“limma” package, paired modeling). Differentially methylated CpGs were defined by |log2FC|>0.25 and FDR<0.05. Enrichment analyses were conducted (KEGG and Ingenuity Pathway Analysis [IPA]). Results There were no significant differences in baseline age (55.9 vs. 52.7 years), BMI (32.4 vs. 33.8 kg/m²), spirometry (FEV1 and FVC), and exposure characteristics between groups. LoCalMed had 65 significantly before-after differentially methylated CpGs, compared to 21 in UC (eight overlaps), Figure 1A-B. In LoCalMed, KEGG enrichment revealed extensive diet-related alterations of inflammatory and oxidative stress pathways, including cytokine-cytokine receptor interaction, reactive oxygen species, and Ras signaling pathway, Figure 1C. IPA identified 79 diet-related genes meeting significance (FDR<0.05). Canonical pathways such as phagosome formation (z-score: -2.67), macrophage activation (-2.44), and IL-10 signaling (-2.2) showed inhibition in LoCalMed, Figure 1D. Predicted inhibition of cell movement (-3.5), recruitment of granulocytes (-2.45), and the MAPKKK cascade (-2.43) were observed in LoCalMed, Figure 1E. In contrast, the UC group showed fewer KEGG-enriched pathways. Mapping of the IL-10 pathway demonstrated overall alterations of IL-10/STAT3 signaling (blue) and concurrent activation of downstream proinflammatory mediators (NF-κB, IL1B, IL6, TNF), suggesting coordinated epigenetic regulation of immune balance, Figure 1F. Of note, there was induction of proinflammatory mediators (orange), which will need to be further explored. Conclusions A 6-month dietary intervention induced DNA methylation changes in oxidative stress and inflammation-related genes, suggesting a systemic epigenetic shift and alteration in redox balance. These findings support diet-driven modulation of the epigenome as a potential mechanism underlying the health benefits of the Mediterranean diet in populations exposed to environmental pollutants.