维生素E对血液透析病人氧化应激的干预效果

目的　研究抗氧化剂维生素E对血液透析病人氧化应激状态的干预效果。方法　处于稳定状态的血液透析病人 5 6例 (不服用任何抗氧化药)采用自身对照的方法 ,观察 1个月后 ,随机均分为两个实验组 ,A组口服维生素E 2 0 0mg/d ,B组口服维生素E 4 0 0mg/d,服药 1个月 ;两组分别在观察期和服用维生素E干预期前后检测循环晚期氧化蛋白产物(AOPP)、丙二醛 (MDA)和谷胱甘肽过氧化物酶(GSHPx)水平以及血清维生素E浓度。另选 5 6例健康者作为正常对照组。结果　实验组血清AOPP、MDA水平明显高于同龄正常对照组(n =5 6 ,P <0 0 1) ,GSHPx、维生素E浓度明显低于正常人(P <0 0 1) ;透析病人在未服抗氧化药的 1个月观察期前后AOPP、MDA、GSHPx及维生素E浓度无明显变化 (P均 >0 0 5 ) ;A组治疗后 ,血清维生素E水平较治疗前明显增高 (P <0 0 1) ,但AOPP、MDA和GSHPx水平与治疗前相比无明显差异 ;B组治疗后血清维生素E、GSHPx水平较治疗前增高 (P <0 0 1,P <0 0 5 ) ,AOPP较治疗前明显降低 (P <0 0 1) ,但MDA水平无明显变化。结论　口服大剂量维生素E(4 0 0mg/d)可以改善血透病人的氧化应激状态 ;血透病人短期服用大剂量维生素E未见明显副作用。     

Neuroendocrine responses to running in women after zinc and vitamin E supplementation

PURPOSE: The study was undertaken to determine whether acute supplementation with zinc or vitamin E would modify neuroendocrine responses to physiologic stress. METHODS: Specifically, the effects of exhaustive running on blood glucose, lactate, ACTH, cortisol, growth hormone, prolactin, catecholamine, and interleukin 6 (IL-6) concentrations were determined in 10 eumenorrheic runners after supplementation with zinc (25 mg), vitamin E (400 IU), or placebo. Subjects ran at 65-70% of their VO2max, to exhaustion, on a treadmill during the follicular phase of their menstrual cycles over three cycles. RESULTS: There were no significant differences associated with supplementation for any of the hormonal and metabolic measures. Exercise, however, significantly (P<0.05) increased plasma lactate, ACTH, prolactin, and catecholamine concentrations, all of which peaked immediately after exercise (POST). Plasma cortisol concentrations were significantly (P<0.05) elevated at POST, and a further increase was noted 1 h after exercise. IL-6 concentrations rose linearly throughout exercise and reached peak values at POST. Exercise-induced changes were transient in that all measures returned to baseline within 24 h. CONCLUSIONS: Acute supplementation with zinc or vitamin E did not influence the effects of exhaustive running on metabolic and endocrine responses in women. The effects of chronic supplementation on neuroendocrine responses to exercise remain to be determined.     

Effect of vitamin E supplementation on hypoxia-induced oxidative damage in male albino rats

BACKGROUND: There is growing evidence that free radicals mediated oxidative injury due to inadequate oxygen availability is an important factor in various pathologies at high altitude. Since vitamin E is known to protect the cells from oxidative damage due to its potent antioxidant properties, the present study was carried out to explore the effect of vitamin E supplementation on various hematological and biochemical parameters in hypoxia-induced oxidative stress in albino rats. METHODS: The experiments were conducted on male albino rats by intermittently exposing them to a simulated altitude of 7,576 m (25,000 ft), daily for 6 h for 15 d at 32 +/- 2 degrees C. The control group was fed vehicle only (1% Tween 80) and the experimental group was given vitamin E (40 mg per rat x d(-1)) orally, 5 d prior to and during the period of hypoxic exposure. The variables studied include: hemoglobin, hematocrit, RBC deformability index, alpha-tocopherol level, malondialdehyde (MDA), reduced glutathione (GSH), oxidized glutathione (GSSG), lactate dehydrogenase (LDH) and protein level in blood/plasma and various tissues. RESULTS: Significant increase in hematocrit and hemoglobin and decrease in RBC deformability index was observed on exposure to hypoxia while vitamin E supplementation maintained them at the normal level. Hypoxia led to the decrease in plasma vitamin E and blood glutathione (GSH) level and two-fold increase in the plasma malondialdehyde (MDA) level. Vitamin E supplementation, on the other hand, resulted in less of an increase in MDA and increased the GSH concentration significantly. LDH activity, which was elevated on exposure to hypoxia, was arrested on vitamin E supplementation. CONCLUSION: The results indicate that vitamin E supplementation results in preventing oxidative damage due to high altitude stress.     

Growth hormone isoform responses to GABA ingestion at rest and after exercise

Oral administration of the amino acid/inhibitory neurotransmitter gamma aminobutyric acid (GABA) reportedly elevates resting serum growth hormone (GH) concentrations. PURPOSE: To test the hypothesis that GABA ingestion stimulates immunoreactive GH (irGH) and immunofunctional GH (ifGH) release at rest and that GABA augments the resistance exercise-induced irGH/ifGH responses. METHODS: Eleven resistance-trained men (18-30 yr) participated in this randomized, double-blind, placebo-controlled, crossover study. During each experimental bout, participants ingested either 3 g of GABA or sucrose placebo (P), followed either by resting or resistance exercise sessions. Fasting venous blood samples were acquired immediately before and at 15, 30, 45, 60, 75, and 90 min after GABA or P ingestion and were assayed for irGH and ifGH. RESULTS: At rest, GABA ingestion elevated both irGH and ifGH compared with placebo. Specifically, peak concentrations of both hormones were elevated by about 400%, and the area under the curve (AUC) was elevated by about 375% (P < 0.05). Resistance exercise (EX-P) elevated time-point (15-60 min) irGH and ifGH concentrations compared with rest (P < 0.05). The combination of GABA and resistance exercise (EX-GABA) also elevated the peak, AUC, and the 15- to 60-min time-point irGH and ifGH responses compared with resting conditions (P < 0.05). Additionally, 200% greater irGH (P < 0.01) and 175% greater ifGH (P < 0.05) concentrations were observed in the EX-GABA than in the EX-P condition, 30 min after ingestion. GABA ingestion did not alter the irGH to ifGH ratio, and, under all conditions, ifGH represented approximately 50% of irGH. CONCLUSIONS: Our data indicate that ingested GABA elevates resting and postexercise irGH and ifGH concentrations. The extent to which irGH/ifGH secretion contributes to skeletal muscle hypertrophy is unknown, although augmenting the postexercise irGH/ifGH response may improve resistance training-induced muscular adaptations.     

Effects of acute modafinil ingestion on exercise time to exhaustion

PURPOSE: The purpose of this study was to investigate the effect of acute ingestion of modafinil (M) on time to exhaustion during high-intensity exercise. Modafinil (M) is a psychostimulant developed to treat narcolepsy, with "arousal" properties attributed to an increased release of dopamine in the CNS. Because other stimulants with similar properties have ergogenic effects, it was hypothesized that acute treatment with M would enhance physical performance. METHODS: Fifteen healthy male subjects, with a maximal aerobic power (VO2max) of 47 +/- SD 8 mL x kg x min, exercised on a cycle ergometer for 5 min at 50% VO2max and then at approximately 85% VO2max to exhaustion. They did this weekly for 3 wk: a control trial (C) the first week, and then 3 h after ingesting either placebo (P) or M (4 mg x kg) during the remaining 2 wk. The P and M trials were conducted with a balanced order, double-blind design. RESULTS:: Mean +/- SD times to exhaustion at 85% VO2max (TE) were 14.3 +/- 2.8, 15.6 +/- 3.8 and 18.3 +/- 3.5 min for the C, P, and M trials, respectively. TE for M was significantly longer than for the C and P trials. Oxygen uptake at exhaustion was slightly but significantly greater for M compared with P and C. HR increased with time and was further elevated by M. Subjective ratings of perceived exertion (RPE) were significantly lower for M compared with C and P but only after 10 min of exercise at 85% VO2max. CONCLUSION: Acute ingestion of modafinil prolonged exercise time to exhaustion at 85% VO2max and reduced RPE. The RPE results suggest that the dampening of the sensation of fatigue was likely a factor responsible for the enhanced performance.     

膳食补铁对心理应激大鼠肝脏氧化应激状态的影响

目的研究喂饲不同铁含量的饲料对心理应激大鼠肝脏氧化应激状态的影响,为心理应激情况下是否应膳食补铁提供实验依据。方法将48只大鼠随机分为空白对照组与心理应激组,再将两组各随机分成3个亚组：低铁组、中铁组及高铁组。心理应激组以电击为应激源建立心理应激模型。实验开始的同时3个亚组分别用不同铁含量的人工合成饲料喂养。实验结束后测定肝脏铁含量、丙二醛（MDA）含量以及抗氧化酶活性。结果随着膳食铁含量的增加,大鼠肝脏铁含量、MDA含量升高,还原型谷胱甘肽（GSH）含量以及超氧化物歧化酶（SOD）活性降低,这种变化在心理应激组更加显著。结论膳食补充铁可加重肝脏的铁蓄积和氧化应激,为了维护经常处于心理应激人群的健康,应对该人群的适宜铁摄入量进行深入研究。     

Effects of chromium supplementation on glycogen synthesis after high-intensity exercise

PURPOSE: Chromium enhances insulin signaling and insulin-mediated glucose uptake in cultured cells. We investigated the effect of chromium on glycogen synthesis and insulin signaling in humans. METHODS: Sixteen overweight men (BMI = 31.1 +/- 3.0 kg.m) were randomly assigned to supplement with 600 microg.d chromium as picolinate (Cr; N = 8) or a placebo (Pl; N = 8). After 4 wk of supplementation, subjects performed a supramaximal bout of cycling exercise to deplete muscle glycogen, which was followed by high-glycemic carbohydrate feedings for the next 24 h. Muscle biopsies were obtained at rest, immediately after exercise, and 2 and 24 h after exercise. RESULTS: Elevations in glucose and insulin during recovery were not different, but the lactate response was significantly higher in Cr. There was a significant depletion in glycogen immediately after exercise, an increase at 2 h, and a further increase above rest at 24 h (P < 0.05). The rate of glycogen synthesis during the 2 h after exercise was not different between groups (Cr: 25.8 +/- 8.0 and Pl: 17.1 +/- 4.7 mmol.kg.h). Glycogen synthase activity was significantly increased immediately after exercise in both groups. Muscle phosphatidylinositol 3-kinase (PI 3-kinase) activity decreased immediately after exercise and increased at 2 h (P < 0.05), with a trend for a lower PI 3-kinase response in Cr (P = 0.08). CONCLUSIONS: Chromium supplementation did not augment glycogen synthesis during recovery from high-intensity exercise and high-carbohydrate feeding, although there was a trend for lower PI 3-kinase activity.     

Effects of 30-h sleep loss on cardiorespiratory functions at rest and in exercise

The effects of 30-h sleep deprivation on cardiorespiratory function either at rest or in exercise were studied in 15 young healthy male volunteers. All subjects performed 1-min incremental exercise tests on a bicycle ergometer until exhaustion and endurance exercise tests at 3/4 of their maximal work rates. Arterialized venous blood samples were withdrawn at rest and during exercise tests to investigate the influence of sleep loss on blood gases. In addition, resting plasma catecholamine levels were also measured in ten subjects. The results showed that 1) resting heart rate, plasma catecholamine levels, and blood pH were decreased while minute ventilation (VI) and CO2 production (VCO2) were increased after 30 h of sleep loss (P less than 0.05), and 2) the maximal exercise performance was reduced by sleeplessness, as indicated by the decreases in the maximal heart rate, peak VI, peak VCO2, peak O2 consumption, and time to exhaustion (P less than 0.05). However, no significant changes in exercise endurance, arterialized venous pH, and PCO2 were found in exercise after sleep deprivation either. We therefore conclude that 30-h sleep loss alters cardiorespiratory function at rest and the ability to perform maximal exercise but not exercise endurance.     

The effects of vitamin E and vitamin C supplementation on bioenergetics index

In order to study the effects of vitamin E and vitamin C supplementation on the bioenergetic index, 36 male physical education students were selected nonrandomly and assigned to a different supplementation protocol. The average age, weight, height, and fat percentage were 22.48 +/- 1.84 years, 64.93 +/- 7.84 kg, 175.4 +/- 5.66 cm, and 10.94 +/- 5.29%, respectively. The period of supplementation lasted 3 weeks. The subjects from group 1 consumed a daily dose of 400 mg of vitamin E, subjects from group 2 ingested 1000 mg of vitamin C, subjects from group 3 ingested 400 mg of vitamin E along with 1000 mg of vitamin C, and subjects from group 4 (control group) consumed a placebo. The tests applied were the running anaerobic sprint test (RAST) and the Cooper 12-min run test. The results indicate that there were no significant differences between groups during the study in anaerobic power assessed by RAST. We found a significant difference between group's, however, in aerobic power (p < 0.05). We concluded that daily consumption of vitamin E, vitamin C, and a combination of vitamin E and vitamin C for a period of 3 week significantly improved aerobic power.     

Combined antioxidant treatment effects on blood oxidative stress after eccentric exercise

PURPOSE: This study was designed to ascertain the effects of a combination antioxidant therapy on plasma protein carbonyls (PC), malondialdehyde (MDA), and whole blood total (TGSH), oxidized (GSSG), and reduced (GSH) glutathione in non-resistance trained females after eccentric resistance exercise. METHODS: Eighteen women (aged 19-31 yr) were randomized in a double-blind manner to either an antioxidant supplement (N = 9; 400 IU vitamin E, 1 g vitamin C, and 90 mug selenium per day) or a lactose placebo (N = 9) for 14 d before and for 2 d after eccentric elbow flexor exercise. Blood samples taken before and immediately, 2, 6, 24, and 48 h postexercise were analyzed for PC, MDA, TGSH, and GSSG. RESULTS: No treatment by time interaction was noted for any variable, with all blood markers experiencing a change after the exercise in both conditions. Time main effects were observed for PC, MDA, and GSSG, with values elevated above preexercise after the eccentric exercise, whereas GSH concentration decreased after the eccentric exercise. Antioxidant supplementation resulted in a condition main effect for PC and MDA, with lower values compared with placebo. The antioxidant treatment attenuated the rise in both PC (75%) and MDA (100%). CONCLUSION: These data suggest that eccentric resistance exercise can increase blood biomarkers of oxidative stress in non-resistance trained females, and this vitamin E, C, and selenium supplementation can attenuate the rise in PC and MDA.     

Association between vitamin E and enhanced athletic performance in sled dogs

PURPOSE: To determine the association between prerace plasma vitamin E concentration and performance in sled dogs competing in the 1998 Iditarod Race. METHODS: Prerace blood samples were collected from 670 dogs. Samples were analyzed for plasma vitamin E concentration while controlling for selected hematological and biochemical variables and signalment. Starting in teams of 16, exercise consisted of running up to 1159 miles pulling a laden sled and musher via checkpoints. The records of dogs that were withdrawn from the race for health reasons, fatigue, or strategic or technical reasons, and those of dogs that finished the race were analyzed. Multiple logistic regression and Cox proportional hazards analysis were used to determine factors associated with endurance. Multiple linear regression analysis was used to determine factors associated with team speed. RESULTS: A total of 323 dogs (48%) were withdrawn from racing at various distances from the start. Median time to finish for 39 teams was 11.5 d and the winning time was 9.2 d. Dogs with prerace plasma vitamin E concentrations > 40.7 microg.mL-1 were 1.9 times more likely to finish (P = 0.0006) and had 1.8 times less of a risk of being withdrawn for every mile ran (P = 0.03) than were dogs with plasma vitamin E concentrations between 16.3 and 40.7 microg.mL-1. Neither a team's mean prerace vitamin E concentration, nor the proportion of dogs within a team with high (> 40.7 microg.mL-1) vitamin E concentration was associated with team speed. CONCLUSIONS: Dogs with higher plasma vitamin E concentrations have enhanced endurance compared with dogs with lower plasma vitamin E concentrations, but the plasma vitamin E status of a team is not associated with team speed.     

Physical stress and qualitative gonadotropin secretion: LH biological activity at rest and after exercise in trained and untrained men

Sports influence the hypothalamus-pituitary-gonadal axis (HPG). The purpose of this study was to analyze the effects of physical stress on qualitative male LH secretion. We evaluated the HPG axis at rest and the LH response to a treadmill exercise (90 % of Vdot;O 2 max) in eight trained (running 50 to 70 km/week) and eight untrained subjects. FSH, total testosterone (T) and free testosterone (FT) were evaluated at rest by radioimmunoassay, whereas serum LH was evaluated both by radioimmunoassay (I-LH) and by a biological assay (RICT, B-LH), before (-30, -15, 0 pre) and after exercise (0 post, + 15, + 30, + 60 min). Semen analysis was performed. The results showed that the B/I LH ratio was significantly lower at rest in athletes than in controls (1.3 +/- 0.5 and 2.1 +/- 0.7 respectively, p < 0.05) and the B-LH and B/I LH ratio were reduced after exercise in controls (from 21.1 +/- 5.7 to 13.9 +/- 3.4 mIU/mL and from 2.3 +/- 0.8 to 1.6 +/- 0.4, at + 60 respectively, p < 0.05). T and FT were significantly lower in athletes compared with controls (4.18 +/- 1.1 vs 5.96 +/- 1.6 ng/ml and 24.3 +/- 4.8 vs 29.7 +/- 5.2 pg/ml respectively, p < 0.05). Semen parameters showed no difference. The B/I LH ratio could be a "marker" of altered LHRH secretion due to an exercise-linked adaptive condition.     

Co-administration of vitamin C or estradiol with aerobic exercise on liver oxidative stress and enzymes in ovariectomized rat

Background

Estrogen insufficiency during postmenopausal life may be the reason of serious metabolic disturbances including oxidative stress that can effect on liver status. It is important to properly assess the benefits of antioxidant therapy and exercise on liver status in menopausal females. The main objective of this study was to investigate the effects of co-administration of vitamin C or estradiol with aerobic exercise on liver oxidative stress of ovariectomized rat.

Materials and methods

Thirty-two ovariectomized female rats were divided into four groups, consisting of sham (Sh), exercise (Ex), exercise + vitamin C (Ex + VitC), exercise + estradiol (Ex + Es). The dose of vitamin C was 250 mg/kg/day that injected three times a week for 6 weeks. The dose of estradiol was 0.25 mg/kg/week that injected for two first weeks. Exercise group performed aerobic exercise on a treadmill at low-moderate intensity (55% VO_2max) 5 days/week for 6 weeks. Liver oxidative damage was determined by the serum and liver tissue levels of nitrite and malondialdehyde (MDA), and the serum levels of alanine amino transferase (ALT) and aspartate amino transferase (AST).

Results

Ovariectomy led to increase in body weight and uterus atrophy. The liver level of nitrite and MDA in Ex group was significantly higher than Sh, Ex + Es and Ex + VitC groups (P < 0.05). The serum level of ALT in the Ex + Es group was significantly lower than the Ex + VitC group (P < 0.05), while the serum level of AST in the Ex + Es group was significantly lower than other groups (P < 0.05).

Conclusion

Aerobic exercise could not attenuate oxidative stress in liver of OV rats; however, administration of vitamin C or estradiol improved partly oxidative stress in liver of OV rats.

     

Effect of prior exercise above and below critical power on exercise to exhaustion

PURPOSE: The aim of the present study was to ascertain whether the intensity of prior exercise altered the time to exhaustion at critical power (CP). METHODS: Eleven participants volunteered to take part in the study (mean +/- SD: VO2max 4.1 +/- 0.5 L x min(-1); age 30.1 +/- 7.2 yr; body mass 74.6 +/- 9.1 kg) and completed three trials to exhaustion at their CP under differing prior exercise conditions: 1) a control trial (CON); 2) a trial preceded by three 60-s efforts at 110% CP (severe); and 3) a trial preceded by three 73-s efforts at 90% CP (heavy). All trials followed a 5-min baseline at 50 W. RESULTS: Time to exhaustion was significantly lengthened after prior heavy exercise (1071 +/- 18 s) when compared with CON (973 +/- 16 s, F = 9.53, P = 0.006). However, there was no effect on TTE after prior severe exercise (967 +/- 16 s). Oxygen deficit was significantly reduced from that in CON (3.8 +/- 0.2 L) after prior heavy (3.2 +/- 0.3 L) and prior severe exercise (3.1 +/- 0.3 L, F = 10.95, P = 0.001). Concurrently, there was a significant reduction in the magnitude of the VO2 slow component (SC) in the trials with prior exercise (197 +/- 34 and 126 +/- 19 mL x min(-1) after heavy and severe exercise, respectively) when compared with CON (223 +/- 31 mL x min(-1), F = 9.62, P = 0.006). CONCLUSION: Prior heavy exercise does appear to improve the time to exhaustion at CP by approximately 10% and is associated with a reduction in the VO2 SC. However, the reduction in the SC, with no change in performance after prior severe exercise, suggests that a reduced SC may not necessarily lead to improved TTE.     

酪氨酸和依那普利对高原运动后自由基代谢的影响

目的：探讨酪氨酸和依那普利对高原人体运动时自由基代谢的影响。方法：对进驻海拔3700m高原半年的30名健康青年随机分为酪氨酸组，依那普利组及安慰剂组，每组10人。在安静时、服药前、服药第10天、第15天及停药第10天、第20天分别采用功率自行车进行渐增负荷运动至力竭，测定其血清中超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH－Px)和丙二醛（MDA）含量。结果：（1）高原力竭运动使GSH－Px、MDA增加（P＜0．05），SOD无统计学差异（P＞0．05）。（2）给予酪氨酸、依那普利10d即可使SOD、GSH－Px活性增强，MDA降低；依那普利停药10d药效消失，酪氨酸停药20d药效消失。结论：酪氨酸、依那普利对高原低氧所致的自由基代谢失衡均有调节作用，可提高高原作业效率，延缓运动性疲劳发生，且酪氨酸效果更适合。