Type 2 diabetes (T2D) is a metabolic disorder characterized by hyperglycemia and insulin resistance in which oxidative stress is thought to be a primary cause. Considering that mitochondria are the main source of ROS, we have set out to provide a general overview on how oxidative stress is generated and related to T2D. Enhanced generation of reactive oxygen species (ROS) and oxidative stress occurs in mitochondria as a consequence of an overload of glucose and oxidative phosphorylation. Endoplasmic reticulum (ER) stress plays an important role in oxidative stress, as it is also a source of ROS. The tight interconnection between both organelles through mitochondrial-associated membranes (MAMs) means that the ROS generated in mitochondria promote ER stress. Therefore, a state of stress and mitochondrial dysfunction are consequences of this vicious cycle. The implication of mitochondria in insulin release and the exposure of pancreatic β-cells to hyperglycemia make them especially susceptible to oxidative stress and mitochondrial dysfunction. In fact, crosstalk between both mechanisms is related with alterations in glucose homeostasis and can lead to the diabetes-associated insulin-resistance status. In the present review, we discuss the current knowledge of the relationship between oxidative stress, mitochondria, ER stress, inflammation, and lipotoxicity in T2D.

OBJECTIVEDiabetes is associated with oxidative stress and increased mortality, but a possible correlation between leukocyte-endothelium interactions, oxidative stress, and silent myocardial ischemia (SMI) is yet to be confirmed.RESEARCH DESIGN AND METHODSMitochondrial dysfunction and interactions between leukocytes and human umbilical vein endothelial cells were evaluated in 200 type 2 diabetic patients (25 with SMI) and 60 body composition– and age-matched control subjects. A possible correlation between these parameters and the onset of SMI was explored, and anthropometric and metabolic parameters were also analyzed.RESULTSWaist, levels of triglycerides, proinflammatory cytokines (interleukin-6 and tumor necrosis factor-α), HbA1c, high-sensitivity C-reactive protein (hs-CRP), glucose, and insulin, and homeostasis model assessment of insulin resistance were higher in diabetic patients than in control subjects. However, no statistical differences in hs-CRP and insulin levels were detected when the data were adjusted for waist. None of these parameters varied between SMI and non-SMI patients. Mitochondrial function was impaired and leukocyte-endothelium interactions were more frequent among diabetic patients, which was evident in the lower mitochondrial O2 consumption, membrane potential, polymorphonuclear cell rolling velocity, and GSH/GSSG ratio, and in the higher mitochondrial reactive oxygen species production and rolling flux, adhesion, and vascular cell adhesion molecule-1 (VCAM-1) and E-selectin molecules observed in these subjects. Moreover, these differences correlated with SMI. Statistical differences were maintained after adjusting the data for BMI and waist, with the exception of VCAM-1 levels when adjusted for waist.CONCLUSIONSOxidative stress, mitochondrial dysfunction, and endothelium-inducing leukocyte-endothelium interactions are features of type 2 diabetes and correlate with SMI.

Mitochondrial fusion/fission alterations have been evaluated in different tissues of type 2 diabetic (T2D) patients. However, it is not known whether mitochondrial dynamics is disturbed in the leukocytes of T2D patients and whether glycemic control affects its regulation. Anthropometric and metabolic parameters in 91 T2D patients (48 with glycated hemoglobin [HbA1c] <6.5% and 43 with HbA1c >6.5%) were characteristic of the disease when compared with 78 control subjects. We observed increased reactive oxygen species production in leukocytes from diabetic patients, together with a reduced mitochondrial oxygen consumption rate, especially in poorly controlled patients. Mitochondrial fusion was reduced and fission was increased in diabetic patients, and both features were accentuated in patients with poor glycemic control. Furthermore, leukocyte rolling flux rose in parallel to HbA1c levels. The induction of leukocyte-endothelial interactions in diabetic patients was related to reduced mitochondrial fusion and higher mitochondrial fission. Our findings suggest that mitochondrial dynamics could be influenced by glycemic control in leukocytes of diabetic patients, in which there is decreased mitochondrial fusion and elevated fission related to enhanced leukocyte-endothelial interactions. These findings lead to the hypothesis that poor glycemic control during T2D may alter mitochondrial dynamics and could eventually promote leukocyte-endothelial interactions and the onset of cardiovascular diseases. Antioxid. Redox Signal. 25, 108-115.