The oxytocin-oxytocin receptors system — a new pathogenetic mechanism in the development of diabetic phenotype of heart failure with preserved ejection fraction in women

Aim . To determine the pathogenetic role of the oxytocinergic system in the development of myocardium structural and functional changes in women with heart failure with preserved ejection fraction (HFpEF) associated with type 2 diabetes mellitus (DM2T) (diabetic phenotype of HFpEF). Material and methods . The study included 60 women aged 67.0±4.9 years with HFpEF stage I-IIA, FC I-III, 30 of them had DM2T who were admitted for elective coronary artery bypass grafting. The development of HFpEF is caused by coronary artery disease (CAD) and arterial hypertension (AH). Prior to surgery, all patients underwent a standard examination, blood levels of NT-proBNP, oxytocin (Ox), echocardiography were determined to find the types of left ventricular (LV) myocardial remodeling and diastolic dysfunction (DD). Myocardium biopsies of the right atrium auricle obtained during coronary bypass surgery were studied by microscopy, morphometry and immunohistochemistry (the expression of oxytocin receptors (OxR), a marker of proliferation ki-67). Results . According to echocardiography, eccentric LV hypertrophy (46.7/36.7%) and DD type 2 (47/17%, p=0.003) prevailed in the group of women with the diabetic phenotype of HFpEF. A higher content of NT-proBNP (480.72±241.87/434.46±282.78 ng/ml, p=0.06) and a lower concentration of Ox (102.11±35.89/320.37±294.71 pg/ml, p=0.0016) in blood serum were established, as well as an increase in the number of cardiomyocytes (CMC) with a high expression level OxR (63.69±19.47/12.16±23.09%, p=0.000) in patients with the diabetic phenotype of HFpEF. Negative associations were determined between the blood level of Ox and the CMC diameter (r=-0.10, p=0.020), the area of their cytoplasm (r=-0.16, p=0.000) and the area of the nuclei (r=-0.11, p=0.015) in patients of both groups. A decrease in Ox concentration in the blood of patients with diabetic phenotype of HFpEF was accompanied by an increase in the number of CMCs with a high level of OxR expression (r=-0.63, p=0.000). Conclusion . The study has shown the important involvement of oxytocinergic signaling pathways in the HFpEF pathogenesis. HFpEF associated with DM2T in women was characterized by more unfavorable structural and functional changes in the myocardium, a significant increase in the number of hypertrophied CMCs with a high level of OxR expression and Ox decrease in blood serum. The mechanisms of the first-established significant increase in the content of Ox in the blood of patients with HFpEF without diabetes and its significant decrease in patients with diabetic phenotype of HFpEF leading to more pronounced structural and functional changes in the myocardium, require further study.