MPO and diabetes mellitus: In DM patients, hyperglycemia may impair several mechanisms of immune defense which result in predisposition to infection and complications, including impaired neutrophil function (e.g., chemotaxis, bacterial killing, phagocytosis, and impaired adherence), impaired myeloperoxidase activity and antioxidant system and micro- and macroangiopathies, and a decrease in cytokine response during leukotriene release in humoral immunity [19–21].