Ascorbic acid prevents stress-induced hypercoagulability in overweight and obese individuals.

Ascorbic acid (AA) may contribute to restoring hemostatic balance after mental stress (MS) in overweight/obese adults. We aimed to determine the effects of AA administration on hemostatic responses to MS in overweight/obese men. Fourteen overweight/obesity men (27 ± 7 years; BMI: 29.7 ± 2.6 kg m-2) performed the Stroop color-word stress task for 5 min after non-simultaneous infusion of placebo (PL, 0.9% NaCl) and AA (3 g). Blood was collected at baseline, during MS, and 60 min after MS to measure: activated partial thromboplastin time, prothrombin time, and fibrinogen concentration, by coagulometer; platelet-derived microvesicles (PMV, mv/µL), by flow cytometry; nitrite (µM), by chemiluminescence. In PL session, MS led to decreases in PTs (stress, p = 0.03; 60 min, p < 0.001), PT-INR (stress, p < 0.001; 60 min, p < 0.01), aPTTs (60 min, p = 0.03), aPTT ratio (60 min, p = 0.04) and fibrinogen (60 min, p = 0.04), while increased PT activity (60 min, p = 0.01) when compared to baseline. Furthermore, AA increased PTs (60 min, p < 0.001), PT-INR (60 min, p = 0.03) and decreased PT activity (60 min, p < 0.001) and fibrinogen (stress, p = 0.04) when compared to PL. Nitrite was increased in response to stress during AA session (p < 0.001 vs PL). There was no difference in PMV. Ascorbic acid prevented the impaired hemostatic profile and improved nitrite response to stress in the overweight and obese adults.

AT1R blocker prevents mental stress induced retrograde blood flow in overweight/obese men.

The main goal was to determine the impact of mental stress (MS) on blood flow regulation in overweight/obese men. Fourteen overweight/obese men (27 ± 7 years; 29.8 ± 2.6 kg/m2 ) participated in two randomized experimental sessions with oral administration of the AT1R blocker Olmesartan (40 mg; AT1RB) or placebo (PL). After 2 h, a 5-min acute MS session (Stroop Color Word Test) was administered. Blood flow was assessed at baseline and during the first 3 min of MS by vascular ultrasound in the brachial artery. Blood was collected before (baseline) and during mental stress (MS) for measurement of nitrite (chemiluminescence) and endothelin-1 (ELISA kit). The AT1R blocker was able to reverse the MS responses observed in the placebo session for retrograde flow (p < 0.01), retrograde SR (p < 0.01) and oscillatory shear index (p = 0.01). Regarding vasoactive substances, no differences were observed in ET-1 (p > 0.05) responses to MS between experimental sessions. However, for nitrite responses, the administration of the AT1R blocker was able to increase circulating levels of NO (p = 0.03) Blockade of AT1R appears to prevent the decrease in endothelial function by reducing low shear stress and maintaining the vasoactive substances balance after MS in overweight/obese men.

Oxidative stress in the pathophysiology of metabolic syndrome: which mechanisms are involved? / Estresse oxidativo na fisiopatologia da síndrome metabólica: quais mecanismos estão envolvidos?

ABSTRACTMetabolic syndrome (MS) is a combination of cardiometabolic risk factors, including obesity, hyperglycemia, hypertriglyceridemia, dyslipidemia and hypertension. Several studies report that oxidative condition caused by overproduction of reactive oxygen species (ROS) plays an important role in the development of MS. Our body has natural antioxidant system to reduce oxidative stress, which consists of numerous endogenous and exogenous components and antioxidants enzymes that are able to inactivate ROS. The main antioxidant defense enzymes that contribute to reduce oxidative stress are superoxide dismutase (SOD), catalase (CAT) and gluthatione peroxidase (GPx). The high-density lipoprotein cholesterol (HDL-c) is also associated with oxidative stress because it presents antioxidant and anti-inflammatory properties. HDL-c antioxidant activity may be attributed at least in part, to serum paraoxonase 1 (PON1) activity. Furthermore, derivatives of reactive oxygen metabolites (d-ROMs) also stand out as acting in cardiovascular disease and diabetes, by the imbalance in ROS production, and close relationship with inflammation. Recent reports have indicated the gamma-glutamyl transferase (GGT) as a promising biomarker for diagnosis of MS, because it is related to oxidative stress, since it plays an important role in the metabolism of extracellular glutathione. Based on this, several studies have searched for better markers for oxidative stress involved in development of MS.

RESUMOA síndrome metabólica (SM) representa uma conjunção de fatores de risco cardiometabólicos, incluindo obesidade, hiperglicemia, hipertrigliceridemia, dislipidemia e hipertensão. Vários estudos reportam que a condição oxidativa causada pela superprodução de espécies reativas de oxigênio (EROs) desempenha importante papel no desenvolvimento da SM. Nosso organismo apresenta sistema antioxidante natural para diminuir o estresse oxidativo, o qual consiste em numerosos componentes endógenos e exógenos e enzimas antioxidantes que são capazes de inativar as EROs. As principais enzimas de defesa antioxidante que contribuem para o processo de redução do estresse oxidativo são a superóxido dismutase (SOD), a catalase (CAT) e a glutationa peroxidase (GPx). O colesterol associado à lipoproteína de alta densidade (HDL-c) também está relacionado com o estresse oxidativo por apresentar propriedades antioxidantes e anti-inflamatórias. A atividade antioxidante do HDL-c pode ser atribuída, pelo menos em parte, à atividade da paraoxonase 1 (PON1) sérica. Além disso, os metabólitos derivados de oxigênio reativo (d-ROMs) também se destacam como atuantes nas doenças cardiovasculares e no diabetes, pelo desequilíbrio na produção de EROs, tendo relação importante com a inflamação. Relatos recentes vêm apontando a gama-glutamiltransferase (GGT) como biomarcador promissor para diagnóstico da SM, pois esta se associa ao estresse oxidativo, uma vez que desempenha papel relevante no metabolismo extracelular de glutationa. Com base nisso, vários estudos vêm buscando melhores marcadores do estresse oxidativo e sua relação com o desenvolvimento da SM.