Redox Homeostasis and Antioxidant Response After Bariatric Surgery in Severe Obesity: Insights from a Controlled Clinical Cohort

<i>Background and Objectives:</i> Obesity represents a major public health concern worldwide, particularly in economically challenged regions, and is often associated with metabolic comorbidities such as type 2 diabetes mellitus, hypertension, and metabolic-associated fatty liver disease. Oxidative stress plays a central role in obesity pathophysiology through the accumulation of reactive oxygen and nitrogen species. This study aimed to investigate changes in specific oxidative stress biomarkers in patients with obesity before and one year after bariatric surgery, with a lean control group as reference. <i>Methods</i>: This observational cohort study included 50 patients with morbid obesity undergoing bariatric surgery (laparoscopic sleeve gastrectomy or one-anastomosis gastric bypass) and 50 patients without obesity undergoing other surgical procedures. Plasma levels of malondialdehyde (MDA), reduced and oxidized glutathione (GSH and GSSG), nitrite (NO₂^-), and nitrate (NO₃^-) were measured preoperatively and one year postoperatively in the bariatric group, and once in the control group. Quantification was performed using HPLC-based techniques. <i>Results</i>: Postoperative analysis revealed a significant reduction in oxidative stress markers. MDA levels decreased from 21.58 to 16.62 ng/mL after surgery, while GSH levels increased significantly, although they remained lower than in the control group. GSH/GSSG ratio improved slightly, indicating enhanced antioxidant capacity. Nitrite and nitrate levels showed a marked reduction postoperatively, which may reflect both diminished NO production and complex metabolic adaptations following weight loss. Correlation analysis showed that reductions in BMI were significantly associated with increases in GSH levels and decreases in MDA. <i>Conclusions</i>: Bariatric surgery led to significant improvements in key oxidative stress biomarkers in patients with obesity, supporting the hypothesis that weight loss mitigates oxidative damage. However, the reduction in nitrite suggests potential trade-offs in nitric oxide metabolism that warrant further investigation. Long-term studies are needed to determine the clinical significance and sustainability of these biochemical improvements.