Biomolecular Changes in Epicardial Adipose Tissue in Patients Undergoing Cardiac Surgery on Cardiopulmonary Bypass, a Scoping Review

Cardiopulmonary bypass (CPB) is essential in cardiac surgery but is associated with significant postoperative inflammation. Epicardial adipose tissue (EAT), due to its close proximity to the myocardium and vasculature, may play a role in mediating these inflammatory responses. A systematic search of MEDLINE and EMBASE identified five studies that analyzed molecular changes in EAT, subcutaneous adipose tissue (SAT), and/or serum before and after CPB. Outcomes included changes in mRNA expression and protein levels of inflammatory and metabolic biomarkers. EAT demonstrated increased expression of fibroblast growth factor 21 (FGF-21), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) following CPB. Adipokine profiles revealed decreased EAT protein levels of leptin, adiponectin, and adipocyte fatty acid-binding protein (A-FABP), while circulating levels varied depending on patient comorbidities. Mitochondrial electron transport chain (ETC) gene expression significantly decreased in EAT but not in SAT. Endoplasmic reticulum (ER) stress markers including activating transcription factor 4 (ATF4), DNA damage inducible transcript 3 (DDIT3), activating transcription factor 6 (ATF6), and heat shock protein family A (Hsp70) member 5 (HSPA5) showed differential upregulation, particularly in patients with coronary artery disease (CAD). EAT is biologically active and contributes to both local and systemic inflammation following CPB. These biomolecular changes may underlie adverse postoperative outcomes, highlighting EAT as a potential therapeutic target to reduce CPB-associated complications.