Abnormal uterine bleeding in obesity in the reproductive period as a manifestation of the universal hypoxic syndrome

• Marina B. Khamoshina
• Mekan R. Orazov
• Yulia S. Artemenko
• Madina M. Azova
• Leyla V. Tskhovrebova
• Anna V. Aghajanyan
• Irina A. Mullina

Abstract

The aim of the study was to study the prevalence of polymorphic variants of the VEGF-A, eNOS, IL6 and HIF-1α genes and to determine the expression features of CD34⁺ and eNOS angiogenesis markers in the endometrium as manifestations of universal hypoxic syndrome in women with AUB (abnormal uterine bleeding) and obesity.

Material and methods. The study included 159 women at reproductive age with AUB. At the first stage, women were stratified into two groups depending on BMI: 1^st group (n=84) – obese patients (BMI ≥30 kg/m²) and 2^nd group (n=75) – patients with normal weight (BMI 18.5–24.9 kg/m²). The genetic control group was represented by women of reproductive age without a history of AUB (n=59). All patients underwent a molecular genetic study to determine single nucleotide polymorphisms (SNP) of the endothelial nitric oxide synthase gene eNOS T786C [rs2070744], the vascular endothelial growth factor gene VEGF-A C2578A [rs699947], the hypoxia-induced factor gene – HIF-1α C1772T [rs11549465], the interleukin – 6 gene IL6 C174G [rs1800795]. At the second stage, all patients from the main group underwent a pathomorphological examination of endometrial biopsies. Based on anamnestic data and the results of histological conclusions of endometrial biopsies, a group of patients with a verified diagnosis of AUB-E was formed, which was also stratified into two groups depending on BMI: 1^st group (n=20) – patients with obese BMI (≥30 kg/m²) and 2^nd group (n=20) – patients with normal weight (BMI 18.5–24.9 kg/m²). The morphological control group included women of reproductive age without a history of AUB (n=10). All patients underwent immunohistochemical examination of CD34⁺ and eNOS angiogenesis markers in endometrial biopsies taken from women of the main group during an episode of abnormal uterine bleeding by separate diagnostic curettage and in women of the control group taken on the 2^nd–3^rd day of the menstrual cycle by aspiration biopsy. Statistical data processing was performed using the SPSS Statistics 26 software package.

Results. It was found that in the group of women with AUB and obesity, the frequency of occurrence of the TC genotype for eNOS T786C was significantly higher than in normoweight patients and women from the control group (p=0.044). Also, in patients with AUB and obesity, a significantly higher prevalence of the CA genotype for the VEGF-A C2578A gene was found compared to the control group (p=0.001), however, no dependence on the presence of obesity was found (p=0.527). When assessing the occurrence of the HIF-1α C1772T gene polymorphism, it was found that the CC genotype was determined significantly more often in the group of normoweight patients compared to obese women and the control group (p<0.02), however, the CT genotype was more common among obese patients than in normoweight patients (p=0.002), without significant differences from the control group (p=1.000). Calculation of the frequency of occurrence of IL6 C174G gene genotypes demonstrated a significant increase in the proportion of patients carrying the CC genotype in the main group compared to the control group (p<0.001), regardless of the presence of obesity (p=1.000). In contrast, the occurrence of the GG genotype was significantly lower in women with AUB and obesity and normoweight compared to women in the control group (p<0.001), without differences within the cohort of patients with AUB (p=1.000). According to the results of the immunohistochemical study and morphometry, a significant increase in the expression area of angiogenesis markers CD34⁺ and eNOS was revealed in the group with AUB-E and obesity compared to normoweight women and women of the morphological control group (p<0.001).

Conclusion. Thus, it is acceptable to assume that in obese women, the formation and strengthening of a pro-inflammatory profile may contribute to the involvement of the endometrium in the inflammatory process and lead to its morphofunctional changes. This is probably largely due to tissue hypoxia. Probably, the development of hypoxic syndrome occurs due to the activation of the pathological process of neovascularization in the endometrium. New pathogenesis pathways of endometrial dysfunction in AUB allow us to consider the manifestations of AUB-E as a clinical marker of universal hypoxia in obesity and metabolic syndrome in women.

Keywords: hypoxic syndrome; obesity; genetic polymorphisms; angiogenesis; hypoxia; VEGF-A; HIF-1α; eNOS; CD34+

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