The role of antioxidants in the chemistry of oxidative stress: A review.

Oxidative stress and chronic inflammation are known to be associated with the development of metabolic diseases, including diabetes. Oxidative stress, an imbalance between oxidative and antioxidative systems of cells and tissues, is a result of over production of oxidative-free radicals and associated reactive oxygen species (ROS). One outcome of excessive levels of ROS is the modification of the structure and function of cellular proteins and lipids, leading to cellular dysfunction including impaired energy metabolism, altered cell signalling and cell cycle control, impaired cell transport mechanisms and overall dysfunctional biological activity, immune activation and inflammation. Nutritional stress, such as that caused by excess high-fat and/or carbohydrate diets, promotes oxidative stress as evident by increased lipid peroxidation products, protein carbonylation and decreased antioxidant status. In obesity, chronic oxidative stress and associated inflammation are the underlying factors that lead to the development of pathologies such as insulin resistance, dysregulated pathways of metabolism, diabetes and cardiovascular disease through impaired signalling and metabolism resulting in dysfunction to insulin secretion, insulin action and immune responses. However, exercise may counter excessive levels of oxidative stress and thus improve metabolic and inflammatory outcomes. In the present article, we review the cellular and molecular origins and significance of ROS production, the molecular targets and responses describing how oxidative stress affects cell function including mechanisms of insulin secretion and action, from the point of view of possible application of novel diabetic therapies based on redox regulation.

Molecular mechanisms of ROS production and oxidative stress in diabetes.

Oxidative stress is the result of the imbalance between reactive oxygen species (ROS) formation and enzymatic and nonenzymatic antioxidants. Biomarkers of oxidative stress are relevant in the evaluation of the disease status and of the health-enhancing effects of antioxidants. We aim to discuss the major methodological bias of methods used for the evaluation of oxidative stress in humans. There is a lack of consensus concerning the validation, standardization, and reproducibility of methods for the measurement of the following: (1) ROS in leukocytes and platelets by flow cytometry, (2) markers based on ROS-induced modifications of lipids, DNA, and proteins, (3) enzymatic players of redox status, and (4) total antioxidant capacity of human body fluids. It has been suggested that the bias of each method could be overcome by using indexes of oxidative stress that include more than one marker. However, the choice of the markers considered in the global index should be dictated by the aim of the study and its design, as well as by the clinical relevance in the selected subjects. In conclusion, the clinical significance of biomarkers of oxidative stress in humans must come from a critical analysis of the markers that should give an overall index of redox status in particular conditions.

/pdf/measurement-and-clinical-significance-of-biomarkers-of-4b5iqooayx.pdf

Measurement and Clinical Significance of Biomarkers of Oxidative Stress in Humans

The prevalence of diabetes mellitus is rising all over the world. Uncontrolled state of hyperglycemia due to defects in insulin secretion/action leads to a variety of complications including peripheral vascular diseases, nephropathy, neuropathy, retinopathy, morbidity, and/or mortality. Large body of evidence suggests major role of reactive oxygen species/oxidative stress in development and progression of diabetic complications. In the present paper, we have discussed the recent researches on the biomarkers of oxidative stress during type 2 diabetes mellitus.

/pdf/markers-of-oxidative-stress-during-diabetes-mellitus-2m33qf01re.pdf

Markers of Oxidative Stress during Diabetes Mellitus.

Chronic overnutrition creates chronic hyperglycemia that can gradually induce insulin resistance and insulin secretion impairment. These disorders, if not intervened, will eventually be followed by appearance of frank diabetes. The mechanisms of this chronic pathogenic process are complex but have been suggested to involve production of reactive oxygen species (ROS) and oxidative stress. In this review, I highlight evidence that reductive stress imposed by overflux of NADH through the mitochondrial electron transport chain is the source of oxidative stress, which is based on establishments that more NADH recycling by mitochondrial complex I leads to more electron leakage and thus more ROS production. The elevated levels of both NADH and ROS can inhibit and inactivate glyceraldehyde 3-phosphate dehydrogenase (GAPDH), respectively, resulting in blockage of the glycolytic pathway and accumulation of glycerol 3-phospate and its prior metabolites along the pathway. This accumulation then initiates all those alternative glucose metabolic pathways such as the polyol pathway and the advanced glycation pathways that otherwise are minor and insignificant under euglycemic conditions. Importantly, all these alternative pathways lead to ROS production, thus aggravating cellular oxidative stress. Therefore, reductive stress followed by oxidative stress comprises a major mechanism of hyperglycemia-induced metabolic syndrome.

/pdf/pathogenesis-of-chronic-hyperglycemia-from-reductive-stress-2p1agxvv54.pdf

Pathogenesis of Chronic Hyperglycemia: From Reductive Stress to Oxidative Stress

https://doi.org/10.1016/j.exger.2022.111945

Frequency and factors associated with sarcopenia prediction in adult and elderly patients hospitalized for COVID-19

BACKGROUND
An individual's dietary pattern contributes in different ways to the prevention and control of recurrent cardiovascular events. However, the quality of the diet is influenced by several factors. The present study aimed to evaluate the quality of the diet of individuals with cardiovascular diseases and determine whether there is an association between sociodemographic and lifestyle factors.


METHODS
This is a cross-sectional study carried out with individuals with atherosclerosis (coronary artery disease, cerebrovascular disease or peripheral arterial disease) recruited from 35 reference centres for the treatment of cardiovascular disease in Brazil. Diet quality was assessed according to the Modified Alternative Healthy Eating Index (mAHEI) and stratified into tertiles. For comparing two groups, the Mann-Whitney or Pearson's chi-squared tests were used. However, for comparing three or more groups, analysis of variance or Kruskal-Wallis was used. For the confounding analysis, a multinomial regression model was used. p < 0.05 was considered statistically significant.


RESULTS
In total, 2360 individuals were evaluated: 58.5% male and 64.2% elderly. The median (interquartile range [IQR]) of the mAHEI was 24.0 (20.0-30.0), ranging from 0.4 to 56.0 points. When comparing the odds ratios (ORs) for the low (first tertile) and medium (second tertile) diet quality groups with the high-quality group (third tertile), it was observed that there was an association between diet quality with a family income of 1.885 (95% confidence intervals [CI] = 1.302-2.729) and 1.566 (95% CI = 1.097-2.235), as well as physical activity of 1.391 (95% CI = 1.107-1.749) and 1.346 (95% CI = 1.086-1.667), respectively. In addition, associations were observed between diet quality and region of residence.


CONCLUSIONS
A low-quality diet was associated with family income, sedentarism and geographical area. These data are extremely relevant to assist in coping with cardiovascular disease because they enable an assessment of the distribution of these factors in different regions of the country.

Factors associated with diet quality among Brazilian individuals with cardiovascular diseases.

Objetivo: Identificar preditores antropométricos para o surgimento de novos Eventos Cardiovasculares Não Fatais (ECNF) em indivíduos em prevenção cardiovascular secundária. Métodos: Foram realizadas buscas nas bases de dados MedLine, Scopus, Web of Science, EBSCO e LILACS e incluídos os estudos de coorte e seguimentos de ensaios clínicos que analisaram a ocorrência de ECNF em adultos e idosos com histórico pessoal de evento cardiovascular. Resultados: Foram incluídos 20 estudos para a síntese narrativa, sendo estes realizados com indivíduos de ambos os sexos, apresentando doenças das artérias coronárias e cerebrais e o índice de massa corporal foi o indicador mais utilizado na predição de novos ECNF. Ao avaliar a qualidade metodológica, apenas sete estudos foram classificados com “forte” nível de evidência. Considerações finais: A presente revisão, identificou o “paradoxo da obesidade” ou seja, o Índice de Massa Corporal (IMC) elevado como fator de proteção para a ocorrência de novos ECNF, e que, com a abordagem estratificada por estado nutricional e alterações metabólicas esta associação não se mantém, apontando esta abordagem como promissora para a compreensão deste fenômeno.

Sandra Mary Lima Vasconcelos

Papers

Frequency and factors associated with sarcopenia prediction in adult and elderly patients hospitalized for COVID-19

Factors associated with diet quality among Brazilian individuals with cardiovascular diseases.

Indicadores antropométricos de um novo evento cardiovascular não fatal: uma revisão sistemática