Disruption of the nitric oxide cycle and oxidative stress in patients with prediabetes: prospects for early correction with quercetin

Prediabetes is linked to early metabolic and vascular issues, with oxidative and nitrosative stress and disruption of the nitric oxide cycle being central. These factors contribute to endothelial dysfunction and higher cardiovascular risk. Finding strategies for early correction of these changes is a critical focus in modern metabolic medicine. Objective — to investigate the characteristics of oxidative stress and nitric oxide production in patients with prediabetes and evaluate the potential for their early correction with quercetin. Materials and methods. Thirty-two patients were examined and divided into a control group (n=15) and a main group (n=17, prediabetes). Prediabetes was diagnosed following ADA recommendations and the National Clinical Protocol. Patients in the main group received quercetin for 20 days. MDA levels, SOD, catalase, cNOS, iNOS, and arginase activity were assessed before and after treatment. Non-parametric statistical methods, correlation analysis, and ROC analysis were applied. Results. Before treatment, patients with prediabetes showed increased iNOS activity, elevated MDA, and altered antioxidant enzyme activities compared to controls. Following quercetin administration, iNOS activity decreased 5.9-fold (p<0.0001), MDA concentration decreased by 31.0% (p<0.0001), SOD activity decreased by 37.8% (p<0.0001), and catalase activity decreased by 21.6% (p<0.0001), while arginase activity increased by 82.0% (p<0.0001). cNOS activity remained unchanged. ROC analysis demonstrated high diagnostic informativeness of MDA, iNOS, and arginase (AUC 0.926 — 1.0). Conclusions. Prediabetes involves increased oxidative and nitrosative stress, along with an imbalance in the nitric oxide cycle. Administering quercetin effectively addresses these issues in their early stages, making it a useful option for preventing the progression of metabolic and vascular complications.