Peripheral Blood DNA Methylation Changes after Omega-3 Fatty Acid Treatment Indicate Anti-inflammatory Effects and Individual Variability

Background Omega-3 or n-3 polyunsaturated fatty acids (PUFAs) are widely studied for health benefits based on potential anti-inflammatory effects. However, the factors involved in mediating the anti-inflammatory responses to n-3 PUFAs are not fully understood; furthermore, many effects from n-3 PUFA treatment are not well characterized in humans. Of interest is the role of DNA methylation (DNAm) in mediating the effects of n-3 PUFAs on inflammation. Objective We aimed to characterize the effects of n-3 PUFA treatment on DNAm in inflammation-related signaling pathways in PBMCs of women at high risk of breast cancer Methods PBMCs of women at high risk of breast cancer were obtained at 0 and 6 months of n-3 PUFA treatment in a previously reported dose finding trial (n=10 matched pairs in the 5 g/day EPA+DHA dose arm).[[53][1]] DNA methylation of PBMCs were assayed using reduced representation bisulfite sequencing to obtain genome-wide methylation profiles on a single nucleotide level. Analyses were performed to investigate the effects of n-3 PUFA treatment on DNAm both genome-wide and within a set of candidate genes. Results A large number of differentially methylated CpGs (DMCs) in gene promoters (24,842 DMCs in 5507 genes) showed significant enrichment for hypermethylation in both the candidate gene and genome-wide analyses. Using these DNAm changes, pathway analysis identified significantly hypermethylated signaling networks after n-3 PUFA treatment, such as the Toll-like Receptor pathway. Based on analyses of data per individual, DNAm changes from n-3 PUFA treatment appear highly variable between study participants. Conclusions Dietary n-3 PUFA supplementation for six months is associated with DNAm changes in PBMCs with potential for anti-inflammatory effects. PBMC DNAm profiles may offer a novel means of assessing individual response to n-3 PUFAs. This observation warrants further investigation in future n-3 PUFA intervention studies. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement M01 RR000034 48 M01 RR000034 48 T32 GM068412 T32 CA221709 ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Institutional Review Board of The Ohio State University All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as [ClinicalTrials.gov][2]. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Processed data is available upon request [1]: #ref-53 [2]: http://ClinicalTrials.gov