Relationship between blood DNA methylation, diet quality indices and metabolic health: Data from Obekit study

Epigenetic mechanisms, which can be modulated by dietary factors, have been proposed as a possible factor in understanding interindividual differences in disease susceptibility. We aimed to determine the relationships between DNA methylation (DNAm), diet quality, and metabolic health in Spanish individuals. This is a transversal study encompassing 337 male and female participants in the Obekit study. Diet quality was assessed using a validated semiquantitative food frequency questionnaire and seven previously established scores: overall, healthy and unhealthy Plant-Based Diet Index (PDI, hPDI and uPDI, respectively), dietary diversity score (DDS), unprocessed/minimally processed foods (MPF) and ultra-processed foods (UPF) consumption and Mediterranean diet (MD) score. DNAm was analyzed in white blood cells using the Infinium MethylationEPIC v1.0 BeadChip kit. After filtering by a variance >0.36, we have worked with 5,261 CpG sites. We found four false discovery rate (FDR)-significant correlations between nutrients and CpGs sites: cg00167275 (GLUD1) correlated with alcohol, cg05218090 with folic acid, cg16682935 (PAPSS2) with selenium, and cg09821790 (SLC7A6) with fish food. One differentially methylated region (DMR) located at zinc finger protein gene 57 (ZFP57) was closely related to obesity and specific nutrients, food groups, and diet quality indices. The regression models of diet quality based on DNAm demonstrated that the most predictive values were when UPF and hPDI were considered. Also, UPF and hPDI were the best indices for predicting the main cardiometabolic risk factors. Our finding suggests that specific nutrients and diet quality indices may influence the degree of DNAm and putatively, the metabolic health in Spanish individuals.