Although serum levels of superoxide dismutase 1 (SOD-1) and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) were not affected by the presence of T2DM, diabetic patients exhibited significant endothelial dysfunction, as evidenced by impaired brachial flow-mediated dilation and altered serum serotonin (5-HT) levels. This evidence concerns the gene SOD1 and type 2 diabetes mellitus.