Abstract

**Abstract** Oxidative stress and the resulting accumulation of reactive carbonyl species are implicated in the pathogenesis of numerous vascular diseases, yet the differential effects of specific carbonyls on endothelial function remain poorly understood. This study investigated the comparative impact of two major carbonyl stress markers, malondialdehyde (MDA) and methylglyoxal (MGO), on key signaling pathways in endothelial cells. Our objective was to determine how these compounds affect insulin signaling, nitric oxide (NO) production, and the integrity of the endothelial barrier, processes critical for vascular homeostasis. Endothelial cells were exposed to physiologically relevant concentrations of MDA and MGO, and subsequent changes were assessed using Western blotting for insulin pathway components, Griess assay for NO metabolites, and transendothelial electrical resistance (TEER) measurements. The results demonstrate that MDA, but not MGO, significantly impaired insulin-stimulated Akt phosphorylation, a central step in insulin signaling. Furthermore, MDA exposure led to a marked reduction in NO production and a substantial decrease in TEER, indicating a compromise of the endothelial barrier. These findings suggest a specific and potent role for MDA in mediating endothelial dysfunction, potentially through distinct mechanisms of protein modification compared to MGO. This work highlights MDA as a critical target for therapeutic intervention aimed at preserving vascular health in conditions associated with heightened oxidative and carbonyl stress.