Abstract
BACKGROUND: DNA methylation plays an important role in systemic lupus erythematosus (SLE) pathogenesis by regulating immune cell function and disease progression. Dietary factors, particularly methyl-donor micronutrients such as folic acid and vitamin B12, may influence DNA methylation patterns and autoimmune responses. However, their specific effects in SLE, especially in adipose tissue that is a key modulator of systemic inflammation, remain unclear. Given the high prevalence of obesity in SLE and its impact on disease severity, understanding the interaction between nutritional status, epigenetics, and immune dysregulation is crucial. This study examines whether folic acid and vitamin B12 supplementation modulate adipose tissue DNA methylation in female SLE patients, considering their nutritional status, to uncover potential mechanisms influencing disease progression and therapeutic response. This is a randomized, double-blind, placebo-controlled trial with premenopausal women with inactive SLE, classified as normal weight (NW, n = 23) or excess body weight (EBW, n = 27). Participants received daily supplementation of folic acid (400 mcg) and vitamin B12 (2000 mcg) or placebo for 12 weeks. Phenotypic characteristics and adipose tissue DNA methylation profiles were assessed before and after intervention using the Illumina EPIC BeadChip platform. RESULTS: Supplementation significantly increased serum folic acid and vitamin B12 levels in both groups (p < 0.05), with a greater rise observed in NW patients (p = 0.035). In the NW group, 120 differentially methylated CpG sites (DMCpGs) were identified post-intervention (74 hypermethylated and 46 hypomethylated sites). These genes were linked to autoimmunity, inflammatory metabolism, obesity, and metabolic health pathways. In contrast, no DMCpGs were detected in the EBW group, potentially due to obesity-related chronic inflammation or altered folic acid metabolism associated with excessive adipose tissue. CONCLUSION: Folic acid and vitamin B12 supplementation modulated DNA methylation in SLE depending on nutritional status. Epigenetic remodeling occurred exclusively in NW patients, whereas EBW patients showed no detectable changes. These findings suggest that obesity may create an "epigenetic resistance" to micronutrient interventions, highlighting the importance of precision nutrition strategies in autoimmune disease management. TRIAL REGISTRATION: NCT05097365.