Endothelial Dysfunction and Early Renal Injury Biomarkers in Hypertensive Patients After COVID-19

Background: Endothelial dysfunction and renal injury are emerging as a common feature of long COVID, especially in those with hypertension. It is not yet well characterised whether SARS-CoV-2 infection exacerbates podocyte dysfunction, fibrotic signalling and renal hemodynamic remodelling, over and above the effects of hypertension alone and there are no reliable early biomarkers in this population. Methods: We conducted a comparative cross-sectional study with prospective 6-month treatment response follow-up in 120 adult patients (aged 30–60 years) with essential hypertension (Stage I, II or III; n = 40 per stage), at Bukhara Regional Multidisciplinary Hospital. Each stage subgroup was further divided into post-COVID (3–6 months after recovery; n = 20) and non-COVID (n = 20) strata. Patients with diabetes, known chronic kidney disease, previous myocardial infarction or stroke and other major comorbidities were excluded. Serum cystatin-C, creatinine, aldosterone, TGF-β1 and VEGF-A; urinary nephrin and microalbumin; cystatin-C-derived eGFR (CKD-EPI) and oral protein-loaded renal functional reserve (RFR); and renal Doppler indices (Vps, Ved, RI, PI) of the main, segmental and interlobar arteries were assessed before and after 6 months of guideline-based renin–angiotensin–aldosterone system (RAAS) blockade (enalapril 5–10 mg or azilsartan 40–80 mg, ±eplerenone). Comparisons were made by Student’s t-test—associations by Pearson correlation. Results: At baseline, post-COVID hypertensive patients exhibited consistently higher endothelial–podocyte injury markers than non-COVID counterparts. Urinary nephrin was elevated across all stages (Stage I: 126.5 ± 9.1 vs. 91.9 ± 8.3 pg/mL, p < 0.01; Stage III: 203.3 ± 11.2 vs. 164.5 ± 9.7 pg/mL, p < 0.05), as were VEGF-A (Stage III: 286.1 ± 16.4 vs. 223.2 ± 12.6 pg/mL, p < 0.01) and TGF-β1 (Stage III: 186.4 ± 10.1 pg/mL, 1.3-fold higher; p < 0.01). The detection of microalbuminuria was 100% in Stage III post-COVID patients and 85% in non-COVID controls. The post-COVID groups had selective loss of renal functional reserve (7.8 ± 1.1% in Stage III compared to 12.5 ± 1.6% in non-COVID controls, p < 0.001). Nephrinuria correlated strongly with RFR (r = −0.824, p < 0.001), eGFR (r = −0.797, p < 0.001) and aldosterone (r = 0.613, p < 0.001). Six months of RAAS blockade reduced nephrinuria, microalbuminuria and TGF-β1 in both arms but the magnitude of biomarker reduction appeared smaller in the post-COVID group, particularly in Stage III. Conclusions: Long COVID appears to be associated with persistent endothelial dysfunction and podocyte injury in hypertensive patients. These results indicate that nephrinuria, VEGF-A, TGF-β1 and renal functional reserve are potential exploratory markers of endothelial and renal abnormalities in hypertensive patients following COVID-19. Before clinical utility can be determined, larger studies with multivariable modelling, diagnostic-performance analyses and correction for multiple testing are needed. The differences in biomarker response between groups observed in this study need to be confirmed in larger prospective studies with multivariable modelling and formal interaction analyses.