DPP4 and diabetes mellitus: After adjusting for HbA1c, BMI, and diabetes duration, patients on insulin therapy (22.8 ± 1.5 ng/mL) showed significantly higher NOX2 levels compared to those on metformin alone (19.8 ± 0.9 ng/mL, p = 0.041) or DPP-4 inhibitors alone (18.9 ± 1.2 ng/mL, p = 0.028).