Epigenetic alterations in type 1 diabetes and their association with poor glycemic control: the SED1-EPI substudy.

Type 1 diabetes (T1D) is an autoimmune disease characterized by β-cell destruction and insulin deficiency. Circulating microRNAs (miRNAs) are promising biomarkers for disease monitoring and complication risk assessment. This study aimed to describe the epigenetic profile in a multicenter Spanish T1D cohort and its association with clinical variables. We analyzed plasma samples from 125 participants (76 T1D, 49 controls) recruited across nine Spanish hospitals. Eight candidate miRNAs from a prior Asturias cohort study were quantified using RT-PCR. Associations with clinical and biochemical parameters were explored, and enrichment analysis was performed to investigate affected biological pathways. Of the miRNAs analyzed, only hsa-miR-200a-3p was significantly overexpressed in T1D versus controls (p = 0.035). In T1D patients, hsa-miR-200a-3p, hsa-miR-1-3p, and hsa-miR-340-5p showed positive correlations with HbA1c, while hsa-miR-224-5p correlated with body mass index (BMI). Poor glycemic control (HbA1c ≥ 7.5%) was associated with higher expression of hsa-miR-1-3p, hsa-miR-200a-3p, and hsa-miR-340-5p. No significant expression differences were found according to comorbidity or hypertension status. hsa-miR-200a-3p emerges as a potential biomarker for β-cell stress in long-standing T1D, while hsa-miR-1-3p and hsa-miR-340-5p may reflect glycemic control status and vascular risk. These findings support further evaluation of these miRNAs in larger, clinically diverse T1D cohorts.