**Abstract**

Type 2 diabetes mellitus (T2D) is characterized mainly by insulin resistance and/or deficiency, presenting risk factors related to aging, hypercaloric diet and sedentary lifestyle. Hyperglycemia, a hallmark of T2D, contributes significantly to the production of reactive oxygen species (ROS), inducing oxidative stress and various cellular and molecular changes in the body. As a consequence, several signaling pathways may be affected, mainly involving biological processes such as inflammation, DNA damage responses, antioxidant defense and metabolic changes. All these processes are relevant for the understanding of the pathogenesis of T2D, and also for the development of diabetic complications in chronic patients. Recently, common characteristics linking T2D to Alzheimer's disease (AD) have been reported. The purpose of this chapter is to highlight the main processes associated with the disease, such as insulin signaling pathways, oxidative stress, mitochondrial dysfunction, DNA damage and repair and antioxidant defense. In addition, the molecular impact of nutritional interventions in patients with T2D will also be addressed, as will the molecular keystones linking T2D and AD. Recently, there is accumulated evidence indicating that the two diseases may share common signaling pathways that may be relevant to the etiopathogenesis of each of them.

**Keywords:** type 2 diabetes mellitus, insulin resistance, hyperglycemia, oxidative stress, DNA repair, reactive oxygen species (ROS), mitochondrial dysfunction, Alzheimer's disease
