CLINICAL AND DIAGNOSTICAL SIGNIFICANCE OF ENDOTHELIAL DYSFUNCTION IN PATIENTS WITH CHRONIC KIDNEY DISEASE

ISSN: 2582-4686 SJIF 2021-3.261,SJIF 20222.889, 2024-6.875 ResearchBib IF: 9.948 / 2024 VOLUME-5, ISSUE-12 829 CLINICAL AND DIAGNOSTICAL SIGNIFICANCE OF ENDOTHELIAL DYSFUNCTION IN PATIENTS WITH CHRONIC KIDNEY DISEASE Dauletbaeva Nurjamal Bayramaliyevna 1st year master’s student in internal diseases,Urgench state medical institute, Urgench, Uzbekistan Abstract. Chronic kidney disease (CKD) represents a steadily growing global medical and socioeconomic burden, characterized by progressive and irreversible loss of renal function and a markedly increased risk of cardiovascular morbidity and mortality. Numerous large-scale epidemiological investigations have demonstrated that cardiovascular complications account for more than half of all deaths among patients with CKD, frequently occurring at early stages of renal dysfunction and often preceding the need for renal replacement therapy [1,2]. In recent decades, endothelial dysfunction has been identified as a central pathophysiological mechanism that links impaired renal function with accelerated atherosclerosis, arterial stiffness, vascular calcification, and adverse cardiovascular outcomes. The vascular endothelium is a highly specialized and metabolically active organ that plays a crucial role in maintaining vascular homeostasis by regulating vasomotor tone, inflammatory responses, oxidative balance, hemostasis, and smooth muscle cell proliferation. In the context of CKD, endothelial integrity is progressively disrupted by a complex interplay of uremic toxin accumulation, chronic low-grade inflammation, oxidative stress, dyslipidemia, anemia, and disturbances in calcium–phosphorus metabolism, leading to profound alterations in endothelial phenotype and function [3–6]. The present study was designed to provide a comprehensive evaluation of the clinical and diagnostic significance of endothelial dysfunction in patients with different stages of chronic kidney disease. This observational study was conducted at the Khorezm multidisciplinary medical center and included 120 patients stratified according to CKD stage. Endothelial function was assessed using flow-mediated dilation of the brachial artery, serum nitric oxide levels, endothelin-1 concentrations, and C-reactive protein as an inflammatory marker. The results demonstrated a clear and progressive deterioration of endothelial function with advancing CKD stage, with the most pronounced abnormalities observed in patients with end-stage renal disease undergoing maintenance hemodialysis. A strong correlation was identified between estimated glomerular filtration rate and endothelial dysfunction parameters, underscoring the close interrelationship between renal impairment and vascular endothelial injury. These findings support the concept that endothelial dysfunction is not merely a consequence but a key driver of cardiovascular pathology in CKD and highlight its potential value as an important clinical and diagnostic marker for cardiovascular risk stratification and therapeutic decision-making in this high-risk population. Keywords: chronic kidney disease, endothelial dysfunction, vascular endothelium, nitric oxide, inflammation, oxidative stress, cardiovascular risk, biomarkers; renal function, atherosclerosis Introduction. Chronic kidney disease is currently recognized as one of the most significant noncommunicable diseases worldwide, with a continuously increasing prevalence driven by aging populations, the global epidemic of diabetes mellitus, hypertension, obesity, and metabolic syndrome [1]. CKD is characterized by a progressive decline in glomerular filtration rate, structural kidney damage, and a wide range of systemic complications that extend far beyond the kidneys themselves. Among these complications, cardiovascular disease remains the leading cause of morbidity and ISSN: 2582-4686 SJIF 2021-3.261,SJIF 20222.889, 2024-6.875 ResearchBib IF: 9.948 / 2024 VOLUME-5, ISSUE-12 830 mortality, with CKD patients experiencing a markedly higher incidence of ischemic heart disease, heart failure, cerebrovascular events, and sudden cardiac death compared with the general population [2]. Importantly, traditional cardiovascular risk factors alone are insufficient to fully explain this excess risk, suggesting the involvement of additional, CKD-specific pathophysiological mechanisms [3]. In this context, endothelial dysfunction has emerged as a critical early event in the development of cardiovascular complications associated with chronic kidney disease. The vascular endothelium functions as a dynamic endocrine and paracrine organ that plays a central role in regulating vascular tone, permeability, coagulation, inflammation, and cellular growth through the balanced production of vasoactive substances such as nitric oxide, prostacyclin, and endothelin-1 [4]. Under physiological conditions, nitric oxide exerts potent vasodilatory, anti-inflammatory, antithrombotic, and antiproliferative effects, thereby maintaining vascular homeostasis and protecting against atherosclerosis. However, in CKD, endothelial nitric oxide bioavailability is markedly reduced due to impaired endothelial nitric oxide synthase activity, decreased availability of its substrate Larginine, increased levels of asymmetric dimethylarginine, and enhanced oxidative degradation of nitric oxide by reactive oxygen species [5–7]. Simultaneously, chronic kidney disease is associated with increased production of vasoconstrictive and pro-inflammatory mediators, particularly endothelin-1, which promotes sustained vasoconstriction, vascular smooth muscle cell proliferation, oxidative stress, and inflammation [8]. These alterations lead to increased arterial stiffness, impaired vasodilatory capacity, and structural vascular remodeling, thereby accelerating the development of atherosclerosis and left ventricular hypertrophy [9]. Importantly, endothelial dysfunction develops early in the course of CKD and progressively worsens as renal function declines, making it a potentially valuable marker for early cardiovascular risk assessment and disease monitoring [10]. Despite extensive experimental and clinical evidence supporting its importance, endothelial dysfunction is not routinely evaluated in everyday nephrological practice, particularly in developing regions, underscoring the need for further clinical research in this area. Objective. The objective of the present study was to conduct a comprehensive evaluation of the clinical and diagnostic significance of endothelial dysfunction in patients with various stages of chronic kidney disease, with particular emphasis on its association with renal function decline, inflammatory activity, and the severity of vascular impairment, in order to assess its potential utility as a marker for cardiovascular risk stratification in routine clinical practice. Materials and methods. This observational cross-sectional study was carried out at the Khorezm multidisciplinary medical center in the year 2025 and included 120 adult patients with a confirmed diagnosis of chronic kidney disease. All participants provided written informed consent prior to enrollment, and the study protocol was approved by the local ethics committee. Patients were stratified into four groups based on the stage of CKD as defined by estimated glomerular filtration rate using the CKD-EPI formula. The first group consisted of patients with CKD stages I–II (30 patients), the second group included patients with CKD stage III involved 35 patients and the third group comprised 25 patients with advanced CKD stages IV–V not yet receiving renal replacement therapy and the fourth group consisted of 30 patients with end-stage renal disease undergoing maintenance hemodialysis. Exclusion criteria included acute infectious or inflammatory diseases, active malignancy, severe hepatic dysfunction, autoimmune disorders, and recent cardiovascular ISSN: 2582-4686 SJIF 2021-3.261,SJIF 20222.889, 2024-6.875 ResearchBib IF: 9.948 / 2024 VOLUME-5, ISSUE-12 831 events, in order to minimize potential confounding factors. Endothelial function was assessed using a multimodal approach that combined functional, biochemical, and inflammatory markers. Flowmediated dilation of the brachial artery was measured using high-resolution ultrasound as a noninvasive indicator of endothelium-dependent vasodilation. Serum nitric oxide levels were determined using a spectrophotometric assay as a surrogate marker of endothelial nitric oxide production, while endothelin-1 concentrations were measured by enzyme-linked immunosorbent assay to assess vasoconstrictor activity. In addition, C-reactive protein levels were measured as an indicator of systemic inflammation. Standard laboratory parameters, including serum creatinine, lipid profile, and hemoglobin levels, were obtained for all patients. Statistical analysis was performed using appropriate parametric and non-parametric tests, with results expressed as mean ± standard deviation, and a pvalue of less than 0.05 was considered statistically significant. Results. The analysis revealed a clear and statistically significant progressive deterioration of endothelial function with advancing stages of chronic kidney disease. Patients in the first group exhibited relatively preserved endothelial function, as reflected by higher flow-mediated dilation values and serum nitric oxide levels, whereas patients in the second and fourth groups demonstrated markedly impaired endothelium-dependent vasodilation. The most pronounced endothelial dysfunction was observed in patients with end-stage renal disease undergoing hemodialysis, who exhibited significantly reduced FMD values, profoundly decreased nitric oxide levels, and markedly elevated endothelin-1 and C-reactive protein concentrations (p < 0.001). Correlation analysis demonstrated a strong positive relationship between estimated glomerular filtration rate and flowmediated dilation (r = 0.62), as well as an inverse correlation between eGFR and endothelin-1 levels (r = −0.58), indicating that worsening renal function is closely associated with progressive endothelial injury and inflammatory activation. Discussion. The findings of the present study provide compelling clinical evidence that endothelial dysfunction is a central and progressively worsening feature of chronic kidney disease and plays a critical role in the pathogenesis of cardiovascular complications in this patient population. The observed reduction in nitric oxide bioavailability and concomitant increase in endothelin-1 activity with advancing CKD stages are consistent with previously published studies and highlight the complex imbalance between vasodilatory and vasoconstrictive forces in uremic conditions. Of particular importance is the observation that endothelial dysfunction was already detectable in early stages of CKD, supporting the concept that vascular injury begins long before the development of end-stage renal disease. The severe endothelial impairment observed in hemodialysis patients further underscores the cumulative impact of uremic toxins, oxidative stress, chronic inflammation, and extracorporeal circulation on vascular health, emphasizing the need for early preventive and therapeutic strategies aimed at preserving endothelial function. Conclusion. In conclusion, endothelial dysfunction represents a fundamental pathophysiological mechanism underlying the high cardiovascular morbidity and mortality observed in patients with chronic kidney disease. Its severity increases progressively with declining renal function and is most pronounced in patients with end-stage renal disease receiving hemodialysis. The assessment of endothelial function provides valuable clinical and diagnostic information that may facilitate early identification of high-risk patients, improve cardiovascular risk stratification, and support the development of individualized preventive and therapeutic strategies. Incorporating endothelial ISSN: 2582-4686 SJIF 2021-3.261,SJIF 20222.889, 2024-6.875 ResearchBib IF: 9.948 / 2024 VOLUME-5, ISSUE-12 832 function assessment into routine nephrological practice may therefore contribute to improved cardiovascular outcomes and overall prognosis in patients with chronic kidney disease References: 1. Levin A, Stevens PE. 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