Macrophages in epicardial adipose tissue and serum NT-proBNP in patients with stable coronary artery disease

Coronary artery disease (CAD) is widely considered a chronic inflammatory disorder, and dysfunction of epicardial adipose tissue could be an important source of the inflammation. Amino-terminal fragment of pro-B-type natriuretic peptide (NT-proBNP) is a known marker of cardiovascular disorders of cardiac origin. Recent studies show that inflammatory stimuli may influence its secretion. Our purpose was to evaluate NT-proBNP serum concentration in relation to immune cell ratios in epicardial adipose tissue (EAT), and cytokine levels in the patients with stable CAD. Patients with stable CAD and heart failure classified into classes II–III, according to the New York Heart Association (NYHA) scale, scheduled for the coronary artery bypass graft (CABG) surgery, were recruited into the study (n = 10; 59.5 (53.0-65.0) y. o.; 50% males). The EAT and subcutaneous adipose tissue (SAT) specimens were harvested in the course of CABG surgery. Immunostaining with anti-CD68, anti-CD45, antiIL-1β and anti-TNFα monoclonal antibodies was performed to evaluate cell composition by differential counts per ten fields (400 magnification). Fasting venous blood was obtained from patients before CABG. Blood was centrifuged at 1500g, aliquots were collected and stored frozen at -40 °С until final analysis. Concentrations of NT-proBNP, IL-1β, IL-6, IL-10, TNFα were determined in serum samples by enzyme-linked immunosorbent assay (ELISA). We have found increased production of IL-1β and TNFα cytokines in EAT compared to SAT. Concentrations of NT-proBNP exceeded 125 pg/ml in 4 patients, and correlations between the CD68⁺ macrophage counts in both EAT and SAT samples (r_s = 0.762; p = 0.010 and r_s = 0.835; p = 0.003, respectively). NT-proBNP levels showed positive relations with CD45⁺ leukocyte counts (r_s = 0.799; p = 0.006), and with IL-1β⁺ cell numbers (r_s = 0.705; p = 0.023) in EAT samples only. As for the serum biomarkers, NT-proBNP levels showed negative correlation with fasting glucose levels (r_s = -0.684; p = 0.029), and positive correlation with serum IL-6 concentrations (r_s = 0.891; p = 0.001). Increased serum concentrations of NT-proBNP in CAD patients correlate with accumulation of macrophages in EAT, which is associated with increased production of IL-1β in EAT and correlates with some metabolic parameters.

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