Metabolic flexibility associated with flight time among combat pilots of the Brazilian air force.

INTRODUCTION: Fighter pilots must support the effects of many stressors, including physical and psychological exertion, circadian disturbance, jet lag, and environmental stress. Despite the rigorous selection of military pilots, those factors predispose to failures in physiological compensatory mechanisms and metabolic flexibility. OBJECTIVES: We compared through NMR-based metabolomics the metabolic profile of Brazilian F5 fighter pilots with different flight experiences vs. the control group of non-pilots. We hypothesized that combat pilots have metabolic flexibility associated with combat flight time. METHODS: We evaluated for the first time 34 Brazilian fighter pilots from Santa Cruz Air Base (Rio de Janeiro, RJ) allocated into three groups: pilots with lower total accumulated flight experience < 1,100 h (PC1, n = 7); pilots with higher total accumulated flight experience ≥ 1,100 h (PC2, n = 6); military non-pilots (CONT, n = 21). Data collection included anthropometric measurements, total blood count, lipidogram, markers of oxidative stress, and serum NMR-based metabolomics. RESULTS: In comparison with controls (p < 0.05), pilots exhibited decreased levels of white blood cells (-13%), neutrophils (-15%), lymphocytes (-20%), alfa-glucose (-13%), lactate (-26%), glutamine (-11%), histidine (-20%), and tyrosine (-11%), but higher isobutyrate (+ 10%) concentrations. Significant correlations were found between lactate vs. amino acids in CONT (r = 0.55-0.68, p < 0.001), and vs. glutamine in PC2 (r = 0.94, p = 0.01). CONCLUSION: Fighter pilots with lower experience showed a dysregulation in immune-metabolic function in comparison with controls, which seemed to be counteracted by the accumulation of flight hours. Those findings might have implications for the health preservation and operational training of fighter pilots.

Increased vascular function and superoxide dismutase activity in physically active vs inactive adults living with HIV.

This study compared macro- and microvascular endothelial function and redox status in active vs inactive HIV-infected patients (HIVP) under antiretroviral therapy. Using a cross-sectional design, macro- and microvascular reactivity, systemic microvascular density, and oxidative stress were compared between 19 HIVP (53.1 ± 6.1 year) enrolled in a multimodal training program (aerobic, strength and flexibility exercises) for at least 12 months (60-minutes sessions performed 3 times/wk with moderate intensity) vs 25 sedentary HIVP (51.2 ± 6.3 year). Forearm blood flow during reactive hyperemia (521.7 ± 241.9 vs 361.4% ± 125.0%; P = 0.04) and systemic microvascular density (120.8 ± 21.1 vs 105.6 ± 25.0 capillaries/mm2 ; P = 0.03) was greater in active than inactive patients. No significant difference between groups was detected for endothelium-dependent and independent skin microvascular vasodilation (P > 0.05). As for redox status, carbonyl groups (P = 0.22), lipid peroxidation (P = 0.86), catalase activity (P = 0.99), and nitric oxide levels (P = 0.72) were similar across groups. However, superoxide dismutase activity was greater in active vs inactive HIVP (0.118 ± 0.013 vs 0.111 ± 0.007 U/mL; P = 0.05). Immune function reflected by total T CD4 and T CD8 counts (cell/mm3 ) did not differ between active and inactive groups (P > 0.82). In conclusion, physically active HIVP exhibited similar immune function, but greater macrovascular reactivity, systemic microvascular density, and superoxide dismutase activity than inactive patients of similar age.

Platelet hyperaggregability in obesity: is there a role for nitric oxide impairment and oxidative stress?

Epidemiological evidence has shown that platelet activation markers are consistently elevated in obesity, contributing to its prothrombotic state. In order to improve the understanding of the regulation of platelet function in obesity, the aim of this study was to investigate the l-arginine-nitric oxide (NO) pathway in obese adults without other cardiovascular risk factor. Seventeen obese (body mass index [BMI] 35.9±1.0 kg/m(2) ) and eighteen age-matched normal weight subjects (BMI 22.0±0.6 kg/m(2) ) were included in this study. l-arginine influx was measured with incubation of l-[(3) H]-arginine. NO synthase (NOS) and arginase activities were determined by the citrulline assay and the conversion of l-[(14) C]-arginine to [(14) C]-urea, respectively. Cyclic guanosine monophosphate (cGMP) content was evaluated by enzyme-linked immunosorbent assay. In addition, the study analyzed: platelet aggregation; intraplatelet antioxidant enzymes, via superoxide dismutase (SOD) and catalase activities; and systemic levels of l-arginine, fibrinogen, and C-reactive protein (CRP). Obese patients presented a significant decrease of platelet l-arginine influx, NOS activity, and cGMP levels, along with platelet hyperaggregability. On the presence of NO donor, platelet aggregation was similar between the groups. The fibrinogen and CRP systemic levels were significantly higher and SOD activity was reduced in obesity. No significant differences were observed in plasma levels of l-arginine and intraplatelet arginase and catalase activities between groups. The diminished NO bioavailability associated with inflammatory status and impaired enzymatic antioxidant defence may contribute to future cardiovascular complications in obesity.

Diminished nitric oxide generation from neutrophils suppresses platelet activation in chronic renal failure.

Chronic renal failure (CRF) is a complex clinical condition associated with accelerated atherosclerosis and thrombosis leading to cardiovascular events. The aim of this study was to investigate in detail the NO pathway in neutrophils obtained from hemodialysis patients and its association with platelet function and oxidative status. Fifteen CRF patients on hemodialysis and fifteen controls were included in this study. Laboratory and experimental evaluations were performed after hemodialysis in CRF patients. We evaluated L-[³H] arginine transport, NO synthase (NOS) activity, amino acid concentration in neutrophils, and expressions of NOS isoforms and p47(phox) by western blotting. Platelet aggregation was analyzed in the presence or absence of neutrophils. Oxidative status was measured through glutathione peroxidase, catalase activities, protein oxidation, lipid peroxidation, and DNA/RNA oxidation in serum. Basal NOS activity (pmol/106 cells/min) was impaired in CRF patients on hemodialysis (0.33 ± 0.17) compared to controls (0.65 ± 0.12), whereas the expression of NOS isoforms remained unaltered. L-Arginine transport into neutrophils was similar in CRF patients on hemodialysis and controls. In addition, intracellular concentration of L-arginine was increased fourfold in the patient group. Systemic oxidative stress markers were not affected by CRF. On the other hand, NADPH oxidase subunit p47(phox) in neutrophils was overexpressed in CRF. In the presence of neutrophils, there was a reduction time-dependent in platelet aggregation in both groups with no difference between them. This data suggest that reduced basal generation of NO by neutrophils in CRF patients on hemodialysis occurs independently of L-arginine bioavailability and is able to suppress platelet activation.

Effects of Beetroot-Based Supplements on Muscular Endurance and Strength in Healthy Male Individuals: A Systematic Review and Meta-Analysis.

The aim of this study was to systematically review the current literature and analyze the effects of beetroot-based supplements (BRS) on muscular performance. Randomized controlled trials that assessed the acute or short-term effects of BRS administration on muscular endurance and/or strength in healthy male individuals were retrieved from PubMed, EMBASE, CENTRAL, and Web of Science databases from inception to February 20th, 2023. In addition, we also searched preprint papers in medRxiv.org, bibRxiv.org; thesis and dissertations included in oatd.org; and clinical trials published in ClinicalTrials.gov. Data extraction, risk of bias, and study quality were assessed by 2 authors. Meta-analyses and subgroup analyses of standardized mean differences (SMD) were performed using a random-effects model. A total of 1486 records were identified in the databases and 2 were obtained by manual search in the reference list. Of those, 27 studies attended eligibility criteria and composed this systematic review. BRS administration resulted in a positive effect on muscular endurance (SMD: 0.31; 95% confidence interval (CI): 0.10 to 0.51; p < 0.01; n = 16 studies). There was an overall significative effect for muscular strength (SMD: 0.26; 95% CI: 0.03 to 0.48; p < 0.05; n = 18 studies), but a subgroup analysis showed that significant effects were found when strength was measured in a fatigued (SMD: 0.64; 95% CI: 0.25 to 1.03; p < 0.01), but not resting state. BRS administration have a small ergogenic effect on muscular endurance and attenuate the decline in muscular strength in a fatigued state in healthy male individuals.

Beetroot-based supplements can improve muscular endurance and attenuates the decline in muscular strength. These effects are attributed to the inorganic nitrate contained in these products, which ranged from 316­985 mg/day, ingested 2­3 hours before exercise.Beetroot-based supplements administration can generate a modest increase in the number of repetitions performed to failure or in exercise time to exhaustion, which may contribute to the performance and optimization of the results of people involved in isotonic exercises (e.g., resistance training).Beetroot-based supplements ingestion can improve muscular strength, particularly it aids in the recovery of muscular strength after a fatiguing task.

Effects of hypoxia on cerebral and muscle haemodynamics during knee extensions in healthy subjects.

A hypoxic model was used to investigate changes in localized cerebral and muscle haemodynamics during knee extension (KE) in healthy individuals. Thirty-one young healthy volunteers performed one set of KE until failure under hypoxia (14 % O(2)) or normoxia (21 % O(2)) at 50, 75 or 100 % of 1 repetition maximum, in random order, on three occasions. Prefrontal cerebral and vastus lateralis muscle oxygenation and blood volume (Cox, Mox, Cbv and Mbv, respectively) were recorded simultaneously by near-infrared spectroscopy. Hypoxia induced significant declines in Cox [-0.017 ± 0.016 optical density (OD) units] and Mox (-0.014 ± 0.026 OD units) and increases in Cbv (0.017 ± 0.027 OD units) and Mbv (0.016 ± 0.023 OD units) at rest. Hypoxia significantly reduced total work (TW) performed during KE at each exercise intensity. Cox, Cbv, Mox, and Mbv changes during KE did not differ between normoxia and hypoxia. Correlations between TW done and Cox changes under normoxia (r = 0.04, p = 0.182) and hypoxia (r = 0.05, p = 0.122) were not significant. However, TW was significantly correlated with Mox under both normoxia (R (2) = 0.24, p = 0.000) and hypoxia (R (2) = 0.15, p = 0.004). Since changes in Cox and Mox reflect alterations in the balance between oxygen delivery and extraction in these tissues, which, in the brain, is an index of neuronal activation, we conclude that: (1) limitation of KE performance was mediated peripherally under both normoxia and hypoxia, with no additional effect of hypoxia, and (2) because of the low common variance with Mox additional intramuscular factors likely play a role in limiting KE performance.

Defective nitric oxide-cyclic guanosine monophosphate signaling in patients with bipolar disorder: a potential role for platelet dysfunction.

OBJECTIVE: Bipolar disorder (BD) is associated with elevated cardiovascular mortality rates. We investigated the modulation of l-arginine-nitric oxide (NO) signaling in platelets from patients with BD at different phases. METHODS: Platelets obtained from 28 patients with BD and 10 healthy volunteers were analyzed for l-arginine transport, NO synthase (NOS) activity, cyclic guanosine monophosphate content, and biomarkers of oxidative stress. Expressions of NOS isoforms, soluble guanylyl cyclase, and arginase were also measured in platelets. Amino acid and C-reactive protein levels in plasma were assessed. RESULTS: Plasma concentrations of l-arginine (mean [M] ± standard error of the mean [SEM] = 97 ± 10 versus 121 ± 10 µM) and its transport into platelets (median [interquartile range] = 26.0 [28.6] versus 26.5 [43.9] pmol/10(9) cells per minute) did not differ between patients with BD and controls (p > .05). Patients with BD showed reduced NOS activity (M ± SEM = 0.037 ± 0.003 versus 0.135 ± 0.022 pmol/10(8) cells, p < .001), but not endothelial NOS, inducible NOS, and arginase expression, compared with controls (p > .05). Cyclic guanosine monophosphate content was reduced (M ± SEM = 0.022 ± 0.003 versus 0.086 ± 0.020 pmol/10(8) cells, p < .05) despite the absence of changes in soluble guanylyl cyclase expression (median [interquartile range] = 21.6 [15.5] versus 9.5 [9.4] arbitrary units, p > .05) in patients with BD. Superoxide dismutase activity, but not catalase activity, was increased in patients with BD in the manic phase (M ± SEM = 2094 ± 335 versus 172 ± 17 U/mg protein, p < .001). C-reactive protein was elevated only in manic episodes (M ± SEM = 0.8 ± 0.2 versus 0.1 ± 0.02 mg/L, p < .001). CONCLUSIONS: Impaired NO generation from platelets, inflammation, and oxidative stress may play pivotal roles in the multifaceted process of cardiovascular events in BD.

Upregulation of platelet (L)-arginine: nitric oxide pathway after exercise training in hypertension.

We investigated whether physical exercise can affect platelet L-arginine - nitric oxide pathway in spontaneously hypertensive rats (SHR). Sixteen male SHR and 16 Wistar Kyoto rats (WKY) were divided among exercise (EX) and sedentary (SED) groups. After 20 weeks of treadmill training, systolic blood pressure (mm Hg) was significantly lower in exercised spontaneously hypertensive rats (SHR/EX; 138 ± 8) than in sedentary spontaneously hypertensive rats (SHR/SED; 214 ± 9). Exercise significantly increased platelet L-arginine transport (pmol L-arginine·(10(9) cells)(-1)·min(-1)), assessed by incubation with L-[(3)H]-arginine, in both WKY (SED, 0.196 ± 0.054 compared with EX, 0.531 ± 0.052) and SHR (SED, 0.346 ± 0.076 compared with EX, 0.600 ± 0.049). Nitric oxide synthase (NOS) activity (pmol L-citrulline·(10(8) cells)(-1)), measured by the conversion of L-[(3)H]-arginine to L-[(3)H]-citrulline, was significantly increased in SHR/EX (0.072 ± 0.007) compared with SHR/SED (0.038 ± 0.007), but no changes were observed in WKY. The iNOS and eNOS protein levels assessed by Western blot were not affected by exercise. This upregulation of the platelet L-arginine-NO pathway may attenuate the risk of thromboembolic events, supporting the role of exercise in hypertension management.

Physiologic responses of competitive Canadian cross-country skiers with disabilities.

OBJECTIVE: To examine the acute cardiorespiratory and metabolic responses in competitive cross-country skiers with disabilities. DESIGN: Cross-sectional comparisons using a select group of Canadian athletes training for the Vancouver 2010 Paralympic Winter Games. SETTING: Canmore Nordic Centre Provincial Park, Canmore, Alberta. PARTICIPANTS: Nine competitive cross-country skiers (4 with visual impairment, 1 with traumatic brain injury, 3 with spinal cord injury, and 1 with cerebral palsy). INTERVENTIONS: Three-minute and 12-minute exercise tests in the standing or sitting skiing position to voluntary fatigue. MAIN OUTCOME MEASURES: Cardiorespiratory responses using a telemetric system to compare the physiologic responses among the athletes with different disabilities. Heart rate (HR) and capillary lactate were measured at 2, 5, and 10 minutes of recovery. RESULTS: The t test results indicated that the peak values of the absolute and relative oxygen uptake (VO2peak), HR, and ventilation rate were significantly higher during the 12-minute compared with the 3-minute protocol during standing skiing. However, the oxygen pulse and ventilatory equivalent for oxygen ratio were not significantly (P > 0.05) different between the 2 protocols. Analysis of variance revealed no significant (P > 0.05) differences among the 3 trials for these peak physiologic responses during sitting skiing. Cross-sectional comparisons of the peak physiologic responses between the standing and sitting skiers indicated significantly (P < 0.05) higher values in the standing compared with the sitting position. Cardiorespiratory respiratory efficiency was significantly (P < 0.05) lower in the sitting compared with the standing position. HR during 10 minutes of recovery was significantly correlated with VO2peak. Pearson correlations were not significant between VO2peak and lactate removal during recovery. CONCLUSION: These descriptive findings during the standing and sitting skiing protocols provide preliminary data that would be useful in testing, training, and classification of competitive skiers with disabilities.

The obesity and nonalcoholic fatty liver disease mouse model revisited: Liver oxidative stress, hepatocyte apoptosis, and proliferation.

The study revisited the diet-induced obesity (DIO) mice and the nonalcoholic fatty liver disease (NAFLD) pathogenesis to serve as a translational model. Hepatic beta-oxidation pathways, lipogenesis, oxidative stress, hepatocyte apoptosis, and proliferation were investigated in obese mice. Three-month-old male mice were divided according to their diet for fifteen weeks, the control diet (C group, containing 10% energy from fat) and the high-fat diet (HF group, containing 50% energy from fat). Body weight (BW), liver mass, and steatosis were higher in the HF group than in the C group. Also, gene expression related to beta-oxidation and lipogenesis showed an adverse profile, and insulin and glucose signaling pathways were impaired in the HF group compared to the C group. As a result, steatosis was prevalent in the HF group but not in the C group. Furthermore, the pathways that generate NAFLD were negatively modulated by oxidative stress in the HF animals than in the C ones. The caspase 3 immunolabeled HF hepatocytes with increased gene and protein expressions related to apoptosis while proliferating cell nuclear antigen labeled C hepatocytes. In conclusion, the findings in the DIO mouse model reproduce the NAFLD profile relative to the human NAFLD's apoptosis, insulin signaling, lipogenesis, beta-oxidation, and oxidative stress. Therefore, the model is adequate for a translational perspective's morphological, biochemical, and molecular research on NAFLD.

Platelet activation, oxidative stress and overexpression of inducible nitric oxide synthase in moderate heart failure.

1. Chronic heart failure (CHF) is a common disabling disorder associated with thromboembolic events, the genesis of which is not yet fully understood. Nitric oxide (NO), derived from the vascular endothelium and platelets, has an important role in the physiological regulation of blood flow. It is generated from the amino acid L-arginine via NO synthase (NOS). 2. The main objective of the present study was to investigate NO production and its relationship with platelet aggregation, oxidative stress, inflammation and related amino acids in patients with moderate CHF. The expression and activity of NOS isoforms were analysed by western blotting and conversion of L-[(3)H]-arginine to L-[(3)H]-citrulline, respectively, in CHF patients (n = 12) and healthy controls (n = 15). Collagen- and ADP-induced platelet aggregation, oxidative stress (thiobarbituric acid-reactive substances (TBARS) formation and superoxide dismutase (SOD) activity) and plasma levels of amino acids and inflammatory markers (fibrinogen and C-reactive protein (CRP)) were also determined. 3. Both collagen- and ADP-induced platelet aggregation were increased in CHF patients compared with controls. Platelets from CHF patients did not show any changes in NOS activity in the presence of overexpression of inducible NOS. Systemic and intraplatelet TBARS production was elevated, whereas SOD activity was decreased in CHF patients. l-arginine plasma concentrations were lower in CHF patients than in controls. Systemic levels of CRP and fibrinogen were increased in CHF patients. 4. The results show that, in patients with moderate CHF, there is platelet activation and reduced intraplatelet NO bioavailability due to oxidative stress, which suggests a role for platelets in the prothrombotic state.

Aerobic exercise training attenuates doxorubicin-induced ultrastructural changes in rat ventricular myocytes.

AIMS: To investigate the effects of aerobic exercise training on cardiomyocyte ultrastructure, oxidative stress, and activation of protein synthesis pathways in a model of cardiomyopathy induced by doxorubicin (Dox). MAIN METHODS: Male Sprague Dawley rats were randomly assigned to Control (saline, sedentary), Dox/sedentary (DoxSed), or Dox/exercise (DoxEx) groups. Saline or Dox were injected i.p. for 10 days (1 mg/kg/d). Aerobic exercise training was performed for 9 wks (starting with drug administration) on a treadmill, 5 d/wk, 30 min/d at 60% of maximum velocity. After euthanasia, the left ventricle (LV) was dissected, and processed for microscopy or frozen for Western blot and kinetic measurement of antioxidant enzymes activity. KEY FINDINGS: Dox resulted in a mortality of 31.2% of sedentary animals, whilst all animals from both Control and DoxEx groups survived. DoxSed animals presented increased LV connective tissue deposition alongside with massive sarcomeric disorganization with dissolution of myofibrils and wavy Z-lines. There was an increase in oxidative damage and a reduction in the activation of both Akt and ERK pathways in LV from DoxSed compared to Control group. Aerobic training caused notable changes in myocardial structure with reduced fibrosis and preservation of myofibrils integrity and sarcomere organization. This was associated with reduced LV oxidative damage and increased activity of antioxidant enzymes, and an increase in the activation of PI3K-Akt pathway. SIGNIFICANCE: Aerobic exercise training was effective in preventing mortality caused by Dox and in preserving LV ultrastructure, partially via activation of the physiological protein synthesis pathway, PI3K-Akt, and reducing oxidative stress.

Effects of moderate and high intensity isocaloric aerobic training upon microvascular reactivity and myocardial oxidative stress in rats.

Systemic and central cardiovascular adaptations may vary in response to chronic exercise performed with different intensities and volumes. This study compared the effects of aerobic training with different intensities but equivalent volume upon microvascular reactivity in cremaster muscle and myocardial biomarkers of oxidative stress in Wistar rats. After peak oxygen uptake (VO2peak) assessment, rats (n = 24) were assigned into three groups: moderate-intensity exercise training (MI); high-intensity exercise training (HI); sedentary control (SC). Treadmill training occurred during 4 weeks, with exercise bouts matched by the energy expenditure (3.0-3.5 Kcal). Microvascular reactivity was assessed in vivo by intravital microscopy in cremaster muscle arterioles, while biomarkers of oxidative stress and eNOS expression were quantified at left ventricle and at aorta, respectively. Similar increasing vs. sedentary control group (SC) occurred in moderate intensity training group (MI) and high-intensity training group (HI) for endothelium-dependent vasodilation (10-4M: MI: 168.7%, HI: 164.6% vs. SC: 146.6%, P = 0.0004). Superoxide dismutase (SOD) (HI: 0.13 U/mg vs. MI: 0.09 U/mg and SC: 0.06 U/mg; P = 0.02), glutathione peroxidase (GPX) (HI: 0.00038 U/mg vs. MI: 0.00034 U/mg and SC: 0.00024 U/mg; P = 0.04), and carbonyl protein content (HI: 0.04 U/mg vs. MI: 0.03 U/mg and SC: 0.01 U/mg; P = 0.003) increased only in HI. No difference across groups was detected for catalase (CAT) (P = 0.12), Thiobarbituric acid reactive substances (TBARS) (P = 0.38) or eNOS expression in aorta (P = 0.44). In conclusion, higher exercise intensity induced greater improvements in myocardium antioxidant defenses, while gains in microvascular reactivity appeared to rely more on exercise volume than intensity.

Modulation of cardiac renin-angiotensin system, redox status and inflammatory profile by different volumes of aerobic exercise training in obese rats.

Overactivation of the classical arm of the renin-angiotensin (Ang) system (RAS) occurs during inflammation, oxidative stress and obesity-induced cardiomyopathy. The activation of the protective arm of RAS may act to counterbalance the deleterious effects of the classical RAS. Although aerobic exercise training (AET) shifts the balance of the RAS towards the protective arm, little is known about the molecular adaptations to different volumes of AET. The aim of this study was to evaluate the impact of AET volume on the modulation of RAS, as well as on cardiac biomarkers of oxidative stress and inflammation, in a diet-induced obesity model. Male Wistar rats were fed either control (CON) or high fat (HF) diet for 32 weeks. At week 20, HF group was subdivided into sedentary, low (LEV, 150 min/week) or high (HEV, 300 min/week) exercise volume. After 12 weeks of exercise, body mass gain, systolic blood pressure and heart rate were evaluated, as well as RAS, oxidative stress and inflammation in the heart. Body mass gain, systolic blood pressure and heart rate were higher in HF group when compared with SC group. Both trained groups restored systolic blood pressure and heart rate, but only HEV reduced body mass gain. Regarding the cardiac RAS, the HF group exhibited favoring of the classical arm and both trained groups shifted the balance towards the counterregulatory protective arm. The HF group had higher B1R expression and lower B2R expression than the control group, and B2R expression was reverted in both trained groups. The HF group also presented oxidative stress. The LEV and HEV groups improved the cardiac redox status by reducing Nox 2 and nitrotyrosine expression, but only the LEV group was able to increase the antioxidant defense by increasing Nrf2 signaling. While the HF group presented higher TNF-α, IL-6 and NFκB expression, and lower IL-10 expression, than the SC group, both training protocols improved the inflammatory profile. Although both trained groups improved the deleterious changes related to obesity cardiomyopathy, it is clear that the molecular mechanisms differ between them. Our results suggest that different exercise volumes might reach different molecular targets, and this could be a relevant factor when using exercise to manage obesity.

Acute Effects of L-Arginine Supplementation on Oxygen Consumption Kinetics and Muscle Oxyhemoglobin and Deoxyhemoglobin during Treadmill Running in Male Adults.

L-arginine is used as a nitric oxide related supplement intended to improve sports performance, and to enhance muscular recovery during exercise. However, the literature is inconclusive. The aim of this study was to determine the effects of acute oral L-arginine supplementation on O2 consumption kinetics and local muscle blood volume and oxygenation during treadmill running at two different intensities. Using a double-blind, crossover and placebo-controlled design, 11 young healthy male adults were randomly assigned to 6 g of L-arginine (ARG) or placebo (PLA) supplementation that was ingested 60 min before the exercise test. Tests consisted of treadmill run at two different intensities (5 min each; moderate, 90% of ventilatory threshold, VT; and heavy, 50% of the difference between VT and VO2peak) interspersed by 1-min walking. Respiratory gas exchange variables were measured continuously with an automated metabolic cart. Near infrared spectroscopy (NIRS) was used to continuously monitor muscle oxyhemoglobin and deoxyhemoglobin and total hemoglobin. Blood samples were collected before supplementation and 6 min after exercise. Two-way repeated measures ANOVA did not show differences in plasma nitrite concentrations between ARG or PLA conditions during the running tests. No significant differences were observed between ARG and PLA conditions for O2 kinetics as well as for NIRS variables. ARG supplementation does not improve physiological responses associated with oxygen cost and NIRS variables during running treadmill tests. Hence, our results do not support the use of L-arginine as an ergogenic aid for running performance in young healthy males.

Time course of cardiomyopathy induced by doxorubicin in rats.

BACKGROUND: Doxorubicin (DOX)-related cardiotoxicity may expose cancer survivors to increased risk of cardiovascular morbidity and mortality. Here, we characterized the time course of DOX-induced cardiomyopathy in rats. METHODS: Sprague-Dawley male rats (12 wk old) received doxorubicin hydrochloride (1 mg/kg/d, ip) during 10 consecutive days and they were euthanized one (DOX1), two (DOX2) or four (DOX4) weeks after the last drug injection. Control group received NaCl 0.9% (ip). Hearts were mounted on a Langendorff perfusion system, left ventricle fragments were processed for microscopy and oxidative stress-related assays, and blood was collected for cardiac troponin I assay. RESULTS: All DOX-treated groups showed swollen and vacuolated cardiomyocytes with myofilaments disarray and mitochondrial damage. These changes were already evident after one week and became more pronounced after four weeks. Cardiac troponin I plasma levels were significantly increased in DOX1 and further increased in DOX4 compared to control group. Increased oxidative damage to lipids was observed in DOX1, and to proteins in DOX4. Glutathione peroxidase activity increased in DOX4. The morphological changes resulted in cardiac remodeling, including interstitial fibrosis, apoptosis and significant impairment of both contractile and relaxation function in DOX 4 compared to control group. Hearts from all animals displayed an early reduction in the responsiveness to norepinephrine. CONCLUSIONS: These findings support the view that DOX cardiotoxicity occurs in a "continuum", and as the hypothesis of an irreversible cardiac injury is being challenged, understanding the progression of morphological and functional changes caused by DOX may allow proper timing of initiation of prophylactic treatment.

Acute supplementation of L-arginine affects neither strength performance nor nitric oxide production.

BACKGROUND: L-arginine is a semi-essential amino acid involved in nitric oxide production. As nitric oxide is an important vasodilator, L-arginine supplementation would increase blood perfusion and, subsequently, muscle performance during exercises. The aim of this study was to determine the acute effect of L-arginine supplementation on strength performance and nitric oxide levels in healthy trained individuals. METHODS: In a double-blind, placebo-controlled, cross-over study, 12 men were randomly assigned to L-arginine or placebo supplementation. Subjects received 6 g of L-arginine or placebo 60 minutes before strength test (maximum number of repetitions, 3 sets at 70% of one repetition maximum on bench press and at 80% of one repetition maximum on knee extensions, 2 minutes of rest between sets and exercises). Blood samples were collected before supplementation and 6 min after exercise. RESULTS: Plasma nitrite levels did not significantly change after L-arginine or placebo supplementation and strength-training exercise (placebo, from 13.01±1.18 to 11.83±2.81 mM; L-arginine, from 10.95±4.09 to 11.99±2.5 mM). There was a significant reduction in the number of repetitions performed from set 1 to set 3 in each set of both bench press and knee extension, but no significant interactions were observed between placebo and L-arginine. CONCLUSIONS: These results do not support the use of L-arginine as an ergogenic aid for strength performance, at least in context of acute use immediately before resistance exercise performance.

Weight loss enhances hepatic antioxidant status in a NAFLD model induced by high-fat diet.

Nonalcoholic fatty liver disease (NAFLD) is a benign condition that can progress to more severe liver damage in a process mediated, in part, by disturbances in redox balance. Additionally, some argue that it is set to become the main cause of end-stage liver disease in the near future. Here, we investigated whether diet-induced weight loss is able to reverse hepatic lipid accumulation and reduce oxidative stress in liver from C57BL/6 mice fed a high-fat (HF) diet. Male C57BL/6 mice were divided into 4 groups: standard chow (SC; 10% energy from fat, 16 weeks); HF (50% energy from fat, 16 weeks); SC-HF (SC for 8 weeks followed by HF for 8 weeks); and HF-SC (HF for 8 weeks followed by SC for 8 weeks). The HF diet during 8 (SC-HF) and 16 weeks (HF) downregulated messenger RNA levels and protein expression of Nrf2 and endogenous antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) in the liver; caused liver steatosis; affected liver function markers; increased intra-abdominal and subcutaneous adipose tissue; and induced glucose intolerance and hypercholesterolemia compared with controls (SC). Diet-induced weight loss significantly reduced the intrahepatic lipid accumulation, improved glucose tolerance, and restored both gene and protein expression of the antioxidant enzymes. Our findings suggest that a dietary intervention aimed to induce weight loss may exert protective effects in NAFLD as it can reduce hepatic oxidative stress and intrahepatic lipid accumulation, which can hinder the progression of this condition to more severe states.

The impact of exercise frequency upon microvascular endothelium function and oxidative stress among patients with coronary artery disease.

PURPOSE: This study compared the effects of low and high weekly exercise frequencies on microvascular endothelium function and oxidative stress among patients with coronary artery disease. METHODS: Thirty-four male patients completed a 6-month cardiac rehabilitation programme, from which 23 performed exercise with a high frequency (HF) and 11 with a low frequency (LF). Systemic microvascular blood flow, maximal aerobic capacity, blood lipids, oxidative stress and anthropometric data were assessed prior to and after the cardiac rehabilitation programme. Microvascular blood flow was assessed in the skin of the forearm using laser speckle contrast imaging coupled with iontophoresis of acetylcholine. RESULTS: Maximal aerobic capacity, biochemical analysis and anthropometric data were similar between groups prior to and after the cardiac rehabilitation programme (P>0·05). However, after 6 months of cardiac rehabilitation performed with HF, there was an increase in the peak response to acetylcholine compared with LF (83·5 ± 58·5 versus 21·8 ± 22·4%; P<0·05). Changes in lipid peroxidation (HF: -5·5 ± 9·4 versus LF: 2·2 ± 12·0 pmol MDA mg-1 ; P = 0·19), catalase activity (HF: 0·07 ± 0·17 versus LF: 0·04 ± 0·08 U mg-1 ; P = 0·74) and nitric oxide levels (HF: 1·8 ± 15·3 versus LF: -3·2 ± 12·3 µM; P = 0·36) were similar between groups after cardiac rehabilitation. CONCLUSION: Six months of aerobic exercise training performed with high frequency is preferable to low frequency aiming endothelium microvascular function increases in patients with coronary artery disease. The mechanisms involved in this response are unclear and warrant additional research.

Liver and Metformin: Lessons of a fructose diet in mice.

Studies show that the continuous consumption of fructose can lead to nonalcoholic fatty liver disease (NAFLD) and steatohepatitis. We aimed to investigate the role of Metformin in an animal model of liver injury caused by fructose intake, focusing on the molecular markers of lipogenesis, beta-oxidation, and antioxidant defenses. Male three months old C57BL/6 mice were divided into control group (C) and fructose group (F, 47% fructose), maintained for ten weeks. After, the groups received Metformin or vehicle for a further eight weeks: control (C), control + Metformin (CM), fructose (F), and fructose + Metformin (FM). Fructose resulted in hepatic steatosis, insulin resistance and lower insulin sensitivity in association with higher mRNA levels of proteins linked with de novo lipogenesis and increased lipid peroxidation. Fructose diminished mRNA expression of antioxidant enzymes, and of proteins responsible for mitochondrial biogenesis. Metformin reduced de novo lipogenesis and increased the expression of proteins related to mitochondrial biogenesis, thereby increasing beta-oxidation and decreasing lipid peroxidation. Also, Metformin upregulated the expression and activity of antioxidant enzymes, providing a defense against increased reactive oxygen species generation. Therefore, a significant reduction in triglyceride accumulation in the liver, steatosis and lipid peroxidation was observed in the FM group. In conclusion, fructose increases de novo lipogenesis, reduces the antioxidant defenses, and diminishes mitochondrial biogenesis. After an extended period of fructose intake, Metformin treatment, even in continuing the fructose intake, can reverse, at least partially, the liver injury and prevents NAFLD progression to more severe states.