Diabetes Alters microRNA Expression in Epicardial and Subcutaneous Adipose Tissue from Patients Undergoing Elective Cardiac Surgery

Epicardial adipose tissue (EAT) function may influence the heart, given its metabolic actions and proximity to the heart. We hypothesized that diabetes mellitus (DM) alters miRNA expression across adipose tissue types, and that modifications in EAT may have critical implications for cardiac physiology. To test this, we compared EAT and subcutaneous adipose tissue (SAT) miRNA profiles between patients with and without DM and across tissues within each disease group. Paired biopsies from patients with (<i>n</i> = 18) and without DM (<i>n</i> = 46) undergoing cardiac surgery were analyzed using miRNA profiling and bioinformatics. Among 680 miRNAs screened, 34 were uniquely expressed in EAT, confirming a distinct molecular signature in this fat depot. Notably, miR-155-5p was significantly elevated in EAT from patients with DM, indicating a localized metabolic effect. In SAT, miR-93-3p and miR-223-3p were upregulated in patients with DM and consistently higher than in EAT, regardless of DM status, indicating tissue-specific regulation. miR-324-5p was more expressed in SAT of patients in the NDM group, reflecting combined effects of tissue type and DM. These patterns remained consistent across cardiac disease stratifications. Pathway analysis revealed that miRNAs enriched in EAT target genes involved in cardiomyocyte growth and differentiation. Overall, the findings highlight the unique miRNA profile of epicardial fat and its altered response to DM, supporting its relevance in cardiac physiology.