O estresse oxidativo decorre de um desequilíbrio entre a geração de compostos oxidantes e a atuação dos sistemas de defesa antioxidante. A geração de radicais livres e/ou espécies reativas não radicais é resultante do metabolismo de oxigênio. A mitocôndria, por meio da cadeia transportadora de elétrons, é a principal fonte geradora. O sistema de defesa antioxidante tem a função de inibir e/ou reduzir os danos causados pela ação deletéria dos radicais livres e/ou espécies reativas não radicais. Esse sistema, usualmente, é dividido em enzimático (superóxido dismutase, catalase e glutationa peroxidase) e não-enzimático. No último caso, é constituído por grande variedade de substâncias antioxidantes, que podem ter origem endógena ou dietética. Objetivou-se revisar os principais mecanismos de geração de radicais livres, bem como a ação dos agentes mais relevantes do sistema de defesa antioxidante, ressaltando suas implicações sobre os marcadores do estresse oxidativo. Também serão abordados os principais fatores exógenos moduladores do estresse oxidativo.

Background: The triglyceride-glucose index (TyG index) is a tool for insulin resistance evaluation, however, little is known about its association with coronary artery disease (CAD), which is the major cardiovascular death cause, and what factors may be associated with TyG index. Objective: To evaluate the association between the TyG index and the prevalence of CAD phases, as well as cardiovascular risk factors. Methods: The baseline data of patients in secondary care in cardiology from Brazilian Cardioprotective Nutritional Program Trial (BALANCE Program Trial) were analyzed. Anthropometric, clinical, socio-demographic and food consumption data were collected by trained professionals. The TyG index was calculated by the formula: Ln (fasting triglycerides (mg/dl) × fasting blood glucose (mg/dl)/2) and regression models were used to evaluate the associations. Results: We evaluated 2330 patients, which the majority was male (58.1%) and elderly (62.1%). The prevalence of symptomatic CAD was 1.16 times higher in patients classified in the last tertile of the TyG index (9.9 ± 0.5) compared to those in the first tertile (8.3 ± 0.3). Cardiometabolic risk factors were associated with TyG index, with the highlight for higher carbohydrate and lower lipid consumption in relation to recommendations that reduced the chance of being in the last TyG index tertile. Conclusion: The TyG index was positively associated with a higher prevalence of symptomatic CAD, with metabolic and behavioral risk factors, and could be used as a marker for atherosclerosis. Trial registration ClinicalTrials.gov identifier: NCT01620398. Registered 15 June, 2012