Association of Hypoglycemia with Biomarkers of Oxidative Stress and Antioxidants: An Observational Study.

Hypoglycemia has been associated with complications from the vasculature. The contributing effects of oxidative stress (OS) on these actions have not been sufficiently studied, especially in daily, routine clinical practice. We examined the association of hypoglycemia encountered in daily clinical practice with biomarkers of OS and endogenous antioxidant activity in persons with diabetes [type 1 (T1D) or type 2 (T2D)], as well as individuals without diabetes, with a history of hypoglycemia. Several biomarkers of OS (MDA, ADMA, ox-LDL, 3-NT, protein carbonyls, 4-HNE, TBARS) and antioxidant capacity (TAC, superoxide scavenging capacity, hydroxyl radical scavenging capacity, reducing power, ABTS) were measured. Blood was drawn at the time of hypoglycemia detection and under euglycemic conditions on a different day. A total of 31 participants (mean age [±SD] 52.2 ± 21.1 years, 45.2% males) were included in the study. There were 14 (45.2%) persons with T2D, 12 (38.7%) with T1D, and 5 (16.1%) without diabetes. We found no differences in the examined biomarkers. Only TBARS, a biomarker of lipid peroxidation, showed lower values during hypoglycemia (p = 0.005). This finding needs confirmation in more extensive studies, given that MDA, another biomarker of lipid peroxidation, was not affected. Our study suggests that hypoglycemia encountered in daily clinical practice does not affect OS.

Association of Melatonin Administration in Pregnant Ewes with Growth, Redox Status and Immunity of Their Offspring.

In this study, the effects of melatonin treatment on growth, redox status and immunity in prenatally stressed newborn lambs were evaluated. Thirty-seven newborn lambs were allocated into two groups (melatonin-MEL and control-CON), based on whether their mothers were treated with melatonin implants or not, respectively. All pregnant ewes were exposed to heat stress. The body weight of lambs was recorded at birth (L0), and then on days 15 (L15) and 40 (L40). Redox biomarkers [total antioxidant capacity (TAC), glutathione (GSH), thiobarbituric acid reactive substances (TBARS)] were assayed in blood samples collected from lambs on days L0, L1, L2, L5, L10 and L40. Chemical analysis and antioxidant capacity were evaluated in colostrum and milk samples collected at the same time points with blood samples. Cytokines (IL-1ß, IL-6, IL-10, IFN-γ) and immunoglobulin (IgG) were assayed in blood and colostrum samples collected from ewes on days L0 and L1, and in lambs' blood on days L0, L1 and L2. The results revealed that body weight gain of newborn lambs did not differ between the two groups (p > 0.05). Better redox status was found in MEL lambs until L2, as well as higher antioxidant capacity in the colostrum of MEL ewes compared to CON ones on day L0 (p < 0.05). In MEL ewes' colostrum, higher protein content was measured on day L0 and higher fat content on L1 compared to CON group (p < 0.05). The highest level of IL-6 was found in MEL ewes on L1, with a concomitant increase of IL-10 level in MEL lambs in comparison to CON lambs on L2. Moreover, CON colostrum resulted in a higher level of IL-10 within time, coupled with an increased level of IgG found in lambs' plasma on L2 (p = 0.04). This study indicated that melatonin could be administered as antioxidant and immune-modulatory regime in prenatally stressed offspring in order to cope with the crucial first days of their life. This effect of melatonin was also amplified by crosstalk between IL-6, IL-10 and IgG production, resulting in an improved quality of produced milk.

Effects of a 12-Month Treatment with Glucagon-like Peptide-1 Receptor Agonists, Sodium-Glucose Cotransporter-2 Inhibitors, and Their Combination on Oxidant and Antioxidant Biomarkers in Patients with Type 2 Diabetes.

Imbalance between oxidative stress burden and antioxidant capacity is implicated in the course of atherosclerosis among type 2 diabetic patients. We addressed the effects of insulin, glucagon-like peptide-1 receptor agonists (GLP1-RA), sodium-glucose cotransporter-2 inhibitors (SGLT-2i), and their combination on levels of oxidant and antioxidant biomarkers. We recruited a total of 160 type 2 diabetics, who received insulin (n = 40), liraglutide (n = 40), empagliflozin (n = 40), or their combination (GLP-1RA+SGLT-2i) (n = 40). We measured at baseline, at 4 and at 12 months of treatment: (a) Thiobarbituric Acid Reactive Substances (TBARS), (b) Malondialdehyde (MDA), (c) Reducing Power (RP), (d) 2,2¢-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) radical (ABTS) and (e) Total Antioxidant Capacity TAC). Dual treatment resulted in significant improvement of TBARS, MDA, and ABTS at four months compared with the other groups (p < 0.05 for all comparisons). At twelve months, all participants improved TBARS, MDA, and ABTS (p < 0.05). At 12 months, GLP1-RA and GLP-1RA+SGLT2-i provided a greater reduction of TBARS (-8.76% and -9.83%) compared with insulin or SGLT2i (-0.5% and 3.22%), (p < 0.05). GLP1-RA and GLP-1RA+SGLT-2i showed a greater reduction of MDA (-30.15% and -31.44%) compared with insulin or SGLT2i (4.72% and -3.74%), (p < 0.05). SGLT2i and GLP-1RA+SGLT2-i showed increase of ABTS (12.87% and 14.13%) compared with insulin or GLP1-RA (2.44% and -3.44%), (p < 0.05). Only combined treatment resulted in increase of TAC compared with the other groups after 12 months of treatment (p < 0.05).12-month treatment with GLP1-RA and SGLT2i resulted in reduction of biomarkers responsible for oxidative modifications and increase of antioxidant biomarker, respectively. The combination treatment was superior and additive to each separate agent and also the beneficial effects appeared earlier.

The Effects of Spirulina Supplementation on Redox Status and Performance Following a Muscle Damaging Protocol.

Spirulina plantensis is a popular supplement which has been shown to have antioxidant and performance enhancing properties. The purpose of this study was to evaluate the effects of spirulina supplementation on (a) redox status (b) muscle performance and (c) muscle damage following an eccentric bout of exercise that would induce muscle damage. Twenty-four healthy, recreationally trained males participated in the study and were randomly separated into two groups: a spirulina supplementation (6 g per day) and a placebo group. Both groups performed an eccentric bout of exercise consisting of 5 sets and 15 maximum reps per set. Blood was collected at 24, 48, 72 and 96 h after the bout and total antioxidant capacity (TAC) and protein carbonyls (PC) were assessed in plasma. Delayed onset muscle soreness (DOMS) was also assessed at the same aforementioned time points. Eccentric peak torque (EPT) was evaluated immediately after exercise, as well as at 24, 48, 72 and 96 h post exercise. Redox status indices (TAC and PC) did not change significantly at any time point post exercise. DOMS increased significantly 24 h post exercise and remained elevated until 72 h and 96 h post exercise for the placebo and spirulina group, respectively. EPT decreased significantly and immediately post exercise and remained significantly lower compared to baseline until 72 h post exercise. No significant differences between groups were found for DOMS and EPT. These results indicate that spirulina supplementation following a muscle damaging protocol does not confer beneficial effects on redox status, muscle performance or damage.

Aldehyde levels in e-cigarette aerosol: Findings from a replication study and from use of a new-generation device.

PURPOSE: A recent study identified high aldehyde emissions from e-cigarettes (ECs), that when converted to reasonable daily human EC liquid consumption, 5 g/day, gave formaldehyde exposure equivalent to 604-3257 tobacco cigarettes. We replicated this study and also tested a new-generation atomizer under verified realistic (no dry puff) conditions. DESIGN: CE4v2 atomizers were tested at 3.8 V and 4.8 V, and a Nautilus Mini atomizer was tested at 9.0 W and 13.5 W. All measurements were performed in a laboratory ISO-accredited for EC aerosol collection and aldehyde measurements. RESULTS: CE4v2 generated dry puffs at both voltage settings. Formaldehyde levels were >10-fold lower, acetaldehyde 6-9-fold lower and acrolein 16-26-fold lower than reported in the previous study. Nautilus Mini did not generate dry puffs, and minimal aldehydes were emitted despite >100% higher aerosol production per puff compared to CE4v2 (formaldehyde: 16.7 and 16.5 µg/g; acetaldehyde: 9.6 and 10.3 µg/g; acrolein: 8.6 and 11.7 µg/g at 9.0 W and 13.5 W, respectively). EC liquid consumption of 5 g/day reduces aldehyde exposure by 94.4-99.8% compared to smoking 20 tobacco cigarettes. CONCLUSION: Checking for dry puffs is essential for EC emission testing. Under realistic conditions, new-generation ECs emit minimal aldehydes/g liquid at both low and high power. Validated methods should be used when analyzing EC aerosol.

Resveratrol enhances exercise training responses in rats selectively bred for high running performance.

High Capacity Runner (HCR) rats have been developed by divergent artificial selection for treadmill endurance running capacity to explore an aerobic biology-disease connection. The beneficial effects of resveratrol supplementation have been demonstrated in endurance running and the antioxidant capacity of resveratrol is also demonstrated. In this study we examine whether 12 weeks of treadmill exercise training and/or resveratrol can enhance performance in HCR. Indeed, resveratrol increased aerobic performance and strength of upper limbs of these rats. Moreover, we have found that resveratrol activated the AMP-activated protein kinase, SIRT1, and mitochondrial transcription factor A (p<0.05). The changes in mitochondrial fission/fusion and Lon protease/HSP78 levels suggest that exercise training does not significantly induce damage of proteins. Moreover, neither exercise training nor resveratrol supplementation altered the content of protein carbonyls. Changes in the levels of forkhead transcription factor 1 and SIRT4 could suggest increased fat utilization and improved insulin sensitivity. These data indicate, that resveratrol supplementation enhances aerobic performance due to the activation of the AMPK-SIRT1-PGC-1α pathway.

Adipocytokine levels in children: effects of fatness and training.

To investigate the effects of obesity and exercise training on plasma adipocytokines a sample of 42 children (lean = 24, %BF = 17.8 ± 7.5%; obese = 18; %BF = 29.1 ± 9.3%; mean age = 12.4 ± 1.9 yrs), were divided into 4 age-matched for activity groups: lean inactive (n = 11), obese inactive (n = 9), lean active (n = 13) and obese active (n = 9). Active children participated in swimming training (≥1 year, ≥3 times/week, ≥1 h per session, covering a distance of 10,000-12,000 m per week).Obese individuals demonstrated greater visfatin levels (3.3 ± 1.3 ng/ml) than their lean counterparts (2.6 ± 1.1 ng/ml; p = .06) whereas adiponectin was significantly lower in obese children (3.8 ± 1.9) than their lean counterparts (5.9 ± 2.7; p £ .05). Insulin and HOMA values were significantly greater in obese compared with lean children (p £ .05). Within obese individuals, active individuals had significantly lower visfatin levels (2.8 ± 1.2 ng/ml) compared with their inactive counterparts (3.8 ± 1.2 ng/ml; p £ .05). Resistin levels were comparable between groups (p > .05). Childhood obesity elevates visfatin and lowers adiponectin levels whereas exercise training could reduce visfatin levels in obese children.

Ergogenic and antioxidant effects of spirulina supplementation in humans.

PURPOSE: Spirulina is a popular nutritional supplement that is accompanied by claiMSS for antioxidant and performance-enhancing effects. Therefore, the aim of the present study was to examine the effect of spirulina supplementation on (i) exercise performance, (ii) substrate metabolism, and (iii) blood redox status both at rest and after exercise. METHODS: Nine moderately trained males took part in a double-blind, placebo-controlled, counterbalanced crossover study. Each subject received either spirulina (6 g x d(-1)) or placebo for 4 wk. Each subject ran on a treadmill at an intensity corresponding to 70%-75% of their VO2max for 2 h and then at 95% VO2max to exhaustion. Exercise performance and respiratory quotient during exercise were measured after both placebo and spirulina supplementation. Blood samples were drawn before, immediately after, and at 1, 24, and 48 h after exercise. Reduced glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG, thiobarbituric acid-reactive substances (TBARS), protein carbonyls, catalase activity, and total antioxidant capacity (TAC) were determined. RESULTS: Time to fatigue after the 2-h run was significantly longer after spirulina supplementation (2.05 +/- 0.68 vs 2.70 +/- 0.79 min). Ingestion of spirulina significantly decreased carbohydrate oxidation rate by 10.3% and increased fat oxidation rate by 10.9% during the 2-h run compared with the placebo trial. GSH levels were higher after the spirulina supplementation compared with placebo at rest and 24 h after exercise. TBARS levels increased after exercise after placebo but not after spirulina supplementation. Protein carbonyls, catalase, and TAC levels increased similarly immediately after and 1 h after exercise in both groups. CONCLUSIONS: Spirulina supplementation induced a significant increase in exercise performance, fat oxidation, and GSH concentration and attenuated the exercise-induced increase in lipid peroxidation.

Redox, iron, and nutritional status of children during swimming training.

Effects of exercise training on important determinants of children's long-term health, such as redox and iron status, have not been adequately investigated. The aim of the present study was to examine changes in markers of the redox, iron and nutritional status of boy and girl swimmers during a prolonged period of training. 11 boys and 13 girls, aged 10-11 years, were members of a swimming club. They were assessed at the beginning of the training season, at 13 weeks and at 23 weeks through blood sampling and recording of the diet. Reduced glutathione increased at 13 and 23 weeks, whereas oxidised glutathione decreased at 13 weeks, resulting in an increase of the reduced/oxidised glutathione ratio at 13 and 23 weeks. Total antioxidant capacity, catalase, thiobarbituric acid-reactive substances, hemoglobin, transferrin saturation and ferritin did not change significantly. Carbohydrate intake was below 50% of energy and fat intake was above 40% of energy. Intakes of saturated fatty acids and cholesterol were excessive. Iron intake was adequate but intakes of folate, vitamin E, calcium and magnesium did not meet the recommended daily allowances. No significant differences were found between sexes in any of the parameters measured. In conclusion, child swimmers improved the redox status of glutathione during training, although the intake of antioxidant nutrients did not change. The iron status was not impaired by training. Suboptimal intake of several nutrients suggests the need for nutritional monitoring and education of children athletes.

The effect of muscle-damaging exercise on blood and skeletal muscle oxidative stress: magnitude and time-course considerations.

The aim of this article is to present the effects of acute muscle-damaging exercise on oxidative stress/damage of animal and human tissues using a quantitative approach and focusing on the time-course of exercise effects. The reviewed studies employed eccentric contractions on a dynamometer or downhill running. The statistical power of each study to detect a 20% or 40% post-exercise change compared with pre-exercise value in each oxidative stress/damage biomarker was calculated. Muscle-damaging exercise can increase free radical levels and augment oxidation of lipids, proteins, glutathione and possibly DNA in the blood. In contrast, the effect of muscle-damaging exercise on concentration of antioxidants in the blood, except for glutathione, was little. Muscle-damaging exercise induces oxidative stress/damage in skeletal muscle, even though this is not fully supported by the original statistical analysis of some studies. In contrast, muscle-damaging exercise does not appear to affect--at least to similar extent as the oxidative stress/damage markers--the levels of antioxidants in skeletal muscle. Based on the rather limited data available, the oxidative stress response of skeletal muscle to exercise was generally independent of muscle fibre type. Most of the changes in oxidative stress/damage appeared and were sustained for days after muscle-damaging exercise. The major part of the delayed oxidative stress/damage production that follows muscle-damaging exercise probably comes from phagocytic cells that are activated and recruited to the site of the initial damage. A point that emerged and potentially explains much of the lack of consensus among studies is the low statistical power of many of them. In summary, muscle-damaging exercise can increase oxidative stress/damage in blood and skeletal muscle of rats and humans that may persist for and/or appear several days after exercise.

Uniform and prolonged changes in blood oxidative stress after muscle-damaging exercise.

BACKGROUND: The effect of eccentric exercise on the time-course changes in several indices of muscle damage and blood oxidative stress was examined. MATERIALS AND METHODS: Isometric torque, delayed-onset muscle soreness, creatine kinase, reduced glutathione (GSH), oxidized glutathione (GSSG), thiobarbituric-acid reactive substances (TBARS), protein carbonyls, catalase, uric acid, bilirubin and total antioxidant capacity (TAC) in blood were measured pre-, 24 h, 48 h and 72 h post-eccentric exercise of knee extensors in ten females. RESULTS: The concentration of all oxidative stress indices changed significantly in a way indicating increased oxidative stress in the blood (GSH and GSH/GSSG, decreased, whereas GSSG, TBARS, protein carbonyls, catalase, uric acid, bilirubin and TAC increased) peaking, in all but TBARS, at 48 h and returning toward baseline afterwards. CONCLUSION: We believe that muscle-damaging exercise should be viewed as a different challenge compared to non-muscle-damaging exercise with regard to its effects on blood oxidative stress.

Decreased blood oxidative stress after repeated muscle-damaging exercise.

PURPOSE: To examine the effect of repeated muscle-damaging exercise on the time-course changes in several indices of muscle damage, and to compare them with changes in blood oxidative stress indices. METHODS: Twelve females underwent an isokinetic exercise session consisting of 75 lengthening knee flexions, which was repeated after 3 wk. Isometric torque, range of movement (ROM), delayed-onset muscle soreness (DOMS), creatine kinase (CK), reduced glutathione (GSH), oxidized glutathione (GSSG), thiobarbituric acid-reactive substances (TBARS), protein carbonyls, catalase, uric acid, bilirubin, and total antioxidant capacity (TAC) in blood were measured before, immediately after, and 1, 2, 3, 4, and 7 d after lengthening contractions. RESULTS: All muscle damage indices (torque, ROM, DOMS, and CK) changed significantly after exercise. The concentration of all oxidative stress indices changed significantly in a way indicating increased oxidative stress in the blood (GSH and GSH/GSSG decreased, whereas GSSG, TBARS, protein carbonyls, catalase, uric acid, bilirubin, and TAC increased), peaking in all but bilirubin at 3 d and returning to baseline values by 7 d after exercise. The repeated bout of lengthening contractions induced significantly less changes in indices of muscle damage and blood oxidative stress than the first bout. In general, from the increasing or decreasing area under the curve calculated for each oxidative stress index, the second bout produced 1.8- to 6.1-fold less changes in oxidative stress than after the first bout. CONCLUSION: A repeated bout of lengthening contractions attenuated muscle damage and blood oxidative stress compared with the first bout.

Sampling time is crucial for measurement of aerobic exercise-induced oxidative stress.

PURPOSE: To thoroughly investigate the time-course changes of several commonly used markers of oxidative stress by performing serial measurements during a 24-h period after an acute bout of strenuous cardiovascular exercise. METHODS: Eleven untrained men performed two trials. In the experimental trial, the subjects exercised for 45 min at 70-75% VO2max and then at 90% VO2max to exhaustion on a treadmill; in the control trial, the subjects remained at rest. Blood samples were drawn before and after exercise (immediately after exercise and at 0.5, 1, 2, 3, 4, 5, 6, 8, 10, and 24 h). Reduced glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG, thiobarbituric acid-reactive substances (TBARS), protein carbonyls, catalase activity, and total antioxidant capacity (TAC) were determined. RESULTS: The time to lowest concentration after exercise was 1.7 +/- 0.7 h (mean +/- SD) for GSH/GSSG, and the time to highest concentration after exercise was 1.2 +/- 0.6 h for TBARS, 4.4 +/- 0.5 h for protein carbonyls, 0.5 +/- 0.4h for catalase, and 2.2 +/- 0.9 h for TAC. The greatest change after exercise was -74 +/- 9% for GSH/GSSG, 129 +/- 29% for TBARS, 135 +/- 53% for protein carbonyls, 51 +/- 16% for catalase, and 24 +/- 10% for TAC. CONCLUSION: There is no best time point applying to all markers for collecting blood samples after aerobic exercise. The optimum postexercise time points for blood collection in untrained individuals are immediately after exercise for catalase, 1 h for TBARS, 2 h for TAC, GSH, and GSSG, and 4 h after exercise for protein carbonyls.

Acute exercise markedly increases blood oxidative stress in boys and girls.

This study investigated the effect of an acute swimming protocol on selected blood redox status indices in trained children. Eleven boys and 11 girls (aged 9-11 y) swam 12 bouts of 50 m at a pace corresponding to 70%-75% of the participant's 50 m maximum velocity, with each bout separated by 1 min rest periods. At rest, no differences in any redox status marker between boys and girls were observed. As compared with the pre-exercise values, significant increases in thiobarbituric acid-reactive substances (TBARS), protein carbonyls, catalase activity, total antioxidant capacity (TAC), and oxidized glutathione (GSSG) concentration, as well as significant decreases in reduced glutathione (GSH) concentration and GSH:GSSG, were found post-exercise in both boys and girls. The magnitude of the exercise-induced alterations in the blood redox status based on the calculated effect sizes could be considered large for all parameters in both sexes (median effect size in absolute values was equal to 1.38). The main finding of the present study is that an acute swimming bout at 70%-75% maximum velocity resulted in blood oxidative stress in a similar manner in both trained young boys and girls.

Increased oxidative stress indices in the blood of child swimmers.

The blood redox status of child athletes is compared with that of age-matched untrained individuals. In the present study, 17 swimmers (10.1 +/- 1.6 years) and 12 non-athletes (9.9 +/- 1.1 years) participated. Reduced glutathione (GSH) was lower by 37% in swimmers compared to non-athletes (P < 0.01), oxidized glutathione (GSSG) was not different and their ratio (GSH/GSSG) was lower by 43% in swimmers compared to non-athletes (P < 0.01). Thiobarbituric acid-reactive substances concentration was higher by 25% in swimmers compared to controls. Catalase exhibited a strong trend toward lower levels in swimmers (P = 0.08). Finally, total antioxidant capacity was found lower by 28% in swimmers compared to controls (P < 0.05). In conclusion, we report that children participating in swimming training exhibit increased oxidative stress and less antioxidant capacity compared to untrained counterparts and suggest that children may be more susceptible to oxidative stress induced by chronic exercise.

Exercise-induced oxidative stress in G6PD-deficient individuals.

PURPOSE: This study was designed to investigate whether individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency can exercise without greater perturbations in their redox status compared with non-G6PD-deficient individuals. METHODS: Nine males with established G6PD deficiency and nine males with normal G6PD activity performed two exhaustive treadmill exercise protocols of different duration (the shorter one lasting 12 min and the longer one 50 min). Several hematological parameters, reduced glutathione (GSH), oxidized glutathione (GSSG), thiobarbituric acid reactive substances (TBARS), protein carbonyls, catalase, and total antioxidant capacity (TAC) were measured in the blood before and after each exercise bout. RESULTS: Both GSH and GSSG were significantly higher in the control group compared with the G6PD-deficient group at baseline (0.404 +/- 0.101 vs 0.195 +/- 0.049 mmol.L(-1) for GSH and 0.047 +/- 0.012 vs 0.012 +/- 0.006 mmol.L(-1) for GSSG; P < 0.05); as a result, their ratio was not significantly different between the two groups (P > 0.05). All other oxidative stress indices were not different between groups at rest (P > 0.05). Exercise of both durations affected significantly (P < 0.05) and similarly the levels of all oxidative stress indices either in the G6PD-deficient group or in the control group. Only the long exercise affected GSH status significantly (P < 0.05), whereas both short and long exercise increased the levels of TBARS, protein carbonyls, catalase activity, and TAC to a similar extent (P < 0.05). CONCLUSION: G6PD-deficient individuals are able to exercise until exhaustion without higher oxidative stress compared with non-G6PD-deficient individuals. Exercise duration is an important determinant of the magnitude of exercise-induced changes for GSH, GSSG, and GSH/GSSG, but not for TBARS, protein carbonyls, catalase activity, or TAC.