822 Physiology & Biochemistry
Oxidative Stress and Inflammation Response Following Aerobic Exercise: Role of Ethnicity
Affiliations
Key words ▶ glutathione ● ▶ lipid hydroperoxides ● ▶ malondialdehyde ● ▶ protein carbonyl ● ▶ xanthine oxidase ● ▶ interleukin 6 ●
M. J. McKenzie1, A. Goldfarb2, R. S. Garten3, L. Vervaecke2 1
Winston Salem State University, Human Performance and Sport Sciences, Winston-Salem, United States UNC Greensboro, Kinesiology, Greensboro, United States 3 George E. Whalen Veterans Affairs Medical Center, Aging, Salt Lake City, United States 2
Abstract
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African-Americans are at a significantly greater risk for developing several diseases and conditions. These conditions often have underlying oxidative stress mechanisms. Therefore the purpose of this investigation was to ascertain the post-exercise oxidative response to a single bout of aerobic exercise in African-American and Caucasian college-age females. A total of 10 African-American and 10 Caucasian females completed the study. Each subject had her VO2 max measured while exercising on a treadmill. A week later, each subject returned to the laboratory and performed a 30-min run at 70 % of her VO2max. Blood samples were taken immediately prior to and following exercise for analysis. Lipid
Introduction
▼ accepted after revision November 27, 2013 Bibliography DOI http://dx.doi.org/ 10.1055/s-0033-1363982 Published online: April 15, 2014 Int J Sports Med 2014; 35: 822–827 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Michael Jon McKenzie Human Performance and Sport Sciences Winston Salem State University 601 S. MLK Jr Dr. 27107 Winston-Salem United States Tel.: + 1/336/750 3136 Fax: + 1/336/750 2591 [email protected]
According to the Centers for Disease Control and Prevention (CDC), the risks for obtaining many diseases and conditions are substantially higher among African-Americans minorities. AfricanAmericans were estimated to have a 77 % greater risk for diagnosed diabetes compared to Caucasians, and cancer rates were 13 % greater per 100 000 individuals reported by the American Cancer Society [27]. In addition, African-Americans appear to be more susceptible to asthmarelated complications as well as having mortality rates 2 to 3 times higher than Caucasians subjects from these complications [31]. African-Americans develop hypertension earlier with more manifestations than Caucasians [42]. AfricanAmericans in the US have a greater mortality rate from cardiovascular disease (CVD) and have higher hypertension rates compared to Caucasians or Mexican-Americans [28–30]. Additionally, African-American patients have a significantly higher mortality rate than Caucasian patients following a myocardial infarction
McKenzie MJ et al. Oxidative Stress and Inflammation … Int J Sports Med 2014; 35: 822–827
hydroperoxides, protein carbonyls, malondialdehyde, xanthine oxidase, glutathione in the reduced (GSH) and oxidized (GSSG) forms, TNFα and interleukin 6 were measured from blood taken before and after exercise. Significance was set at p ≤ 0.05 a priori. Xanthine oxidase was the only measure that did not significantly increase following exercise. All other markers showed a significant elevation in response to the exercise bout with no difference between groups except that the Caucasian group had significantly higher malondialdehyde post-exercise compared to the African-American group. This cohort of collegeage African-American and Caucasian females showed little difference in their response to a single 30-min run at 70 % of their max in the markers of oxidative stress within the blood.
(MI) [10]. Therefore, African-American ethnicity has been designated as an independent risk factor for both hypertension and cardiovascular disease risk [23]. While some of these disparities are likely explained by various lifestyle risk factors, such as activity level, socioeconomic status and nutrition, there is now some evidence that ethnic groups may respond to stressors differently in vivo. However, this should be examined in more detail. Research has attempted to establish whether racial differences exist that might explain a difference in both the development and progression of these diseases within an ethnic group. A common link in many of these diseases relates to mechanisms that manifest or are associated with these diseases. It would appear that what many of these diseases have in common are conditions that promote oxidative stress and inflammation. Oxidative stress and inflammation have been implicated in a variety of conditions from heart disease [8, 27] to diabetes [43]. It has recently been reported that ethnicity influences a persons’
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Authors
oxidative stress status at rest and in cultured cells placed under stress [7, 12]. Brown et al. and Feairheller et al. both recently noted that basal levels of IL-6 were significantly higher in African-Americans than Caucasians. They also indicated that cultured human umbilical vein endothelial cells placed under stress in vitro demonstrated greater oxidative stress and inflammation in the African-American isolated cells [7, 12]. These 2 in vitro studies suggest that oxidative stress and inflammation in vivo may be a contributory factor to why African-Americans may be more prone to certain diseases. While the types and levels of oxidative stress involved in the disease process is likely very different from the oxidative stress that occurs during exercise, examining ethnicity-related influences in this process would seem to be warranted. Exercise of appropriate intensity and duration has been shown to be an appropriate stressor to induce both oxidative stress [6, 17, 19, 37] and inflammation [6, 32]. Since muscle mass activation and adiposity appear to be contributory factors in both the inflammatory process [11, 34] and the oxidative stress response to exercise [2, 3], relative exercise intensity is imperative to control and match across subjects for similar muscle activation. One should also try to control the amount of body fat ( % body fat or obesity), as this has an influence on oxidative stress and inflammation. A good method to control for muscle stress is to adjust to one’s relative workload or relative intensity of exercise [25]. In addition, training status can influence both the antioxidant defense mechanism and the inflammatory processes [20, 26, 37, 39]. Therefore, as a first attempt to determine if ethnicity influences the exercise-induced responses to oxidative stress and inflammation in vivo we chose to examine untrained young yet apparently healthy women and controlled the relative intensity of exercise. We exposed them to an acute exercise bout previously shown to result in elevations of both oxidative stress and inflammatory markers in young healthy individuals.
Materials & Methods
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All methods were approved by both Institutional Review Boards prior to recruitment and data collection. The current investigation meets all ethical standards required by the journal and as published by Harriss and Atkinson [21].
Subjects 20 females (10 Caucasians (C), and 10 African-Americans (AA)) were recruited for the current study. All subjects were classified as untrained; meaning none of the subjects had participated in any regular type of exercise for a minimum of 6 months prior to data collection. All subjects were non-tobacco users and did not take antioxidant supplements for at least 6 months prior to the study. None of the subjects reported having any colds, diseases or infections that would have influenced oxidative stress or inflammatory processes. Any subject who did not subjectively identify herself as either AA or C was excluded from the study. All subjects reported to the laboratory 2 times. During the first visit, each subject signed the informed consent, completed a health history questionnaire and had her body fat assessed using the 7-site skin fold analysis with Harpenden calipers. Subjects then completed a maximal oxygen consumption (VO2 max) exercise test on a treadmill using a graded exercise protocol. Expired gases were analyzed by a True 1 analyzing system calibrated to known gases. Heart rates (Polar monitors) and blood
pressure (automated system) were obtained periodically during the test. Each subject performed a 3–5 min warm-up at a selfselected speed. Subjects then breathed through a one way valve which enabled expired gases to be processed by the True 1 analyzing system. Subjects started the test at a self-selected running speed at 0 % grade. The grade was increased 2 % every 2 min until VO2 leveled off or the subject stopped the test (8–10 min). All subjects attained their age-predicted maximal heart rate (HR) ± 10 bpm, reported an RPE > 19 on the Borg scale during the last stage of the test and had RER > 1.10. The VO2 max data was utilized to predict the workload and intensity for the submaximal run. For visit 2, each subject arrived in the morning following an overnight fast (7 p.m. to 9 a.m.) to minimize dietary effects on the oxidative stress markers. Subjects rested at least 30 min after arriving at the laboratory (Temp = 22 ± 1 °C, Humidity 40 ± 5 %) to aid in facilitating a true resting sample. Blood was then obtained using sterile techniques via vacutainer from an antecubital vein and immediately processed, centrifuged, placed in storage vials and then placed in a − 80 °C freezer until analyzed. A Polar monitor was then worn around the chest to enable continuous HR determination. Subjects completed the 30-min run at 70 % VO2 max. Oxygen consumption was monitored every 5 min to ensure VO2 was at the appropriate intensity. If necessary, speed and incline were adjusted to maintain the 70 % VO2 max intensity. We have previously used this intensity in several studies and have found it sufficiently produced elevations in oxidative stress markers [5, 19]. A blood sample was taken immediately ( < 1 min) after the exercise from an antecubital vein and processed as previously noted.
Blood markers Lipid hydroperoxides (LH) were determined using Cayman Chemical Company’s LOOH kit following the manufacturer’s instructions. Plasma (500ul) was extracted in chloroform (gassed with N2), prepared with methanol (gassed with N2), and reacted with 4.5 mM ferrous sulfate in 0.2M HCL and then a 3 % methanol solution of ammonium thiocyanate. The absorbance was monitored at 500 nm on a Shimadzu 1 801 spectrophotometer and compared to standards. All samples were measured in duplicate. Protein carbonyls were analyzed using the Biocell ELISA kit per manufacturer’s instructions, and the absorbance of the samples analyzed at 450 nm on a Biotex plate reader. The data were processed by a KC Junior software package. All samples were measured in duplicate and compared to standards. Malondialdehyde (MDA) concentration was analyzed using a colorimetric kit from Oxis (LPO-586) per manufacturer’s instructions. This procedure used N-methyl-2-pheylindole (NMP) to yield a stable chromophore which has maximal absorbance at 586 nm wavelength. Probucol (10 ul) was used to stabilize the plasma (200 ul) and then the NMP was added. Concentrated HCL (150 ul) was added and incubated at 45 °C for 60 min, and then the tubes were centrifuged. The absorbance was read at 586 nm wavelength on a microplate reader (Biotek instruments) and processed by a KC Junior software package. All samples were determined in duplicate and compared to standards. Interleukin-6 (IL-6) concentrations were determined using an immunoassay from R&D systems (IL-6 HS600B) per the manufacturer’s instructions. This is a high-sensitivity sandwich enzyme immunoassay using monoclonal antibodies specific to IL-6 coated on the microplate. The absorbance was read at
McKenzie MJ et al. Oxidative Stress and Inflammation … Int J Sports Med 2014; 35: 822–827
823
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Physiology & Biochemistry
824 Physiology & Biochemistry
Treatment of blood for glutathione analysis Whole blood (1 ml for both GSH and GSSG) was immediately pipetted into chilled tubes containing 1 ml of 10 % of 5-sulfosalicylic acid with 1 mM bathophenantrolinedisulfonic acid. These tubes were mixed to ensure red blood cells were lysed and destroyed all enzymatic activity. The tubes were then centrifuged at 3 000 rpm at 4- °C for 15 min (Beckman 6KR4, Fullerton, CA). The supernatant was then pipetted into 1.5 ml microcentrifuge tubes and centrifuged at 11 000 rpm for 10 min to remove any remaining cellular debris and then stored at − 80 °C until analyzed for glutathione status using an HPLC method.
Glutathione measurement Samples were thawed, passed through a 0.1 micron polypropylene filters (Whatman), and the effluent was then collected in microtubes. Twenty microliters of this effluent were injected into the HPLC (Shimadzu Prominence System).The HPLC was a Shimadzu Prominence ECD Eicom 700 series system. The electrochemical detector used an Eicom boron-doped diamond electrode to enable a burn-off after each run at 5 mV. The column was an Eicopak SC-30DS (4.6 mm × 100 mm), and the mobile phase was at a flow rate of 0.40 ml/min using 0.1M Na2HPO4 pH 2.5 as the mobile phase at a temperature of 21 ± 0.3 °C. The samples were run at least in duplicate and compared to GSH and GSSG standards (Sigma Aldrich Chemical Co.) We utilized the LC solutions computer software to identify the proper peaks and area of the curve for both GSH and GSSG to obtain concentrations. These peaks were compared to standard curves of both GSH and GSSG which had to be run through this same system.
Statistics All data were analyzed using a repeated measure 2 × 2 ANOVA (ethnicity by time) by SPSS, and statistical significance was set a priori at p ≤ 0.05. If there was an interaction effect, a Scheffe’s post-hoc test was utilized to identify differences.
Results
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Subject characteristics between the groups showed no significant differences in any aspects measured except body weight, as AA ▶ Table 1). were significantly heavier than their C counterparts (●
Table 1 Subject characteristics. Variable
African-Americans
subject Number age (years) height (cm) weight (kg) SBP (mmHg) DBP (mmHg) VO2max (ml.kg − 1min − 1) % body fat resting HR (bpm) % exercise VO2 exercise HR (bpm) exercise RPE
Caucasians
10 23.1 ± 1.1 168.3 ± 1.78 73.6 ± 3.40* 118.8 ± 1.87 72.0 ± 1.49 35.82 ± 1.71 29.2 ± 1.7 79.0 ± 3.0 73.4 ± 1.03 170.5 ± 3.59 14.7 ± 0.70
10 24.8 ± 2.0 161.0 ± 1.63 64.1 ± 3.16 109.2 ± 3.03 72.3 ± 2.56 39.98 ± 2.52 28.0 ± 2.5 78.7 ± 2.7 72.17 ± 0.96 171.7 ± 5.07 14.1 ± 0.70
Table 2 Blood markers of oxidative stress. Marker
LOOH nmol/
PC nM/mg
group
ml
protein
C pre AA pre C post AA post
0.80 ± 0.20 0.87 ± 0.32 1.01 ± 0.31* 1.47 ± 0.74*
0.097 ± 0.01 0.104 ± 0.01 0.123 ± 0.02* 0.136 ± 0.03*
XO mU/ml 21.13 ± 3.29 19.58 ± 2.96 24.8 ± .2.89 21.94 ± 3.33
MDA uM 3.52 ± 0.20 2.42 ± 0.29 5.46 ± 0.35^ 3.33 ± 0.41^
*denotes main effect for time (pre vs. post), ^ denotes main effect for time (pre vs. post) and group (AA vs. C)
Therefore, our subjects were matched for age, activity level, height, and % body fat. Additionally, all performance measures during the 30-min run were not significantly different between the groups. Since we controlled for relative intensity of aerobic capacity, % VO2max was similar. The average HR response and mean perceived exertion (RPE) were all similarly elevated during the acute bout of exercise. We feel that the stress on both the cardiovascular and muscular systems were similar for the aerobic exercise session for the 2 groups. Lipid hydroperoxides were significantly higher following exercise in both groups, as there was a time main effect. However, there was no difference based on a subject’s ethnicity. LOOH increased 46.8 % after the exercise compared to resting inde▶ Table 2). pendent of ethnicity (● The same outcome was evident in terms of PC measures, as PC was higher immediately after exercise in both ethnicities, but not different between C and AA. PC increased a modest 26.7 % as ▶ Table 2). a result of the exercise (● XO did not differ between ethnic groups and was in turn not significantly altered as a result of the exercise in either group ▶ Table 2). (● While MDA results showed a time main effect as well as a significant main effect for ethnicity, a significant interaction was not noted. MDA increased significantly in both groups, being more pronounced in the C women (54.9 %) compared to the AA ▶ Table 2). (35.8 %) (● Reduced glutathione (GSH) and oxidized glutathione (GSSG) were assessed along with the ratio of oxidized glutathione to total glutathione. No main effects for GSH were found. A time main effect (pre vs. post) was noted for both GSSG and the glutathione ratio. GSSG increased in response to the exercise 1.75 ▶ Table 3). fold, as did the glutathione ratio (increased 1.82 fold) (● IL-6 was similar prior to exercise for the 2 groups. After exercise IL-6 significantly increased in both groups 56 %, with no differ▶ Table 4). ences between groups based on ethnic status (●
McKenzie MJ et al. Oxidative Stress and Inflammation … Int J Sports Med 2014; 35: 822–827
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490 nm after correction at 650 nm wavelength on a microplate reader (Biotek instruments) and processed by a KC Junior software package. TNFα was ascertained using an ELISA kit from R & D systems catalog # DTAOOC. We followed the procedures and ran all samples on one plate in duplicate. Each plate was loaded with standards, controls and unknown samples, and read at 450-nm and corrected at 570 nm wavelength to subtract imperfections on the microplate reader (BioTek Instruments, Winesski, VT). The data were processed by a KC Junior software package. All samples were measured in duplicate and compared with standards. Xanthine oxidase (XO) levels were ascertained using an enzymatic assay from Cayman Chemical Company and monitored fluorometrically per manufacturer’s instructions. The plasma (50 ul) was added to wells and incubated with assay cocktail for 45 min at 37 °C. The plate was read at an excitation wavelength of 525 nm and an emission wavelength of 585 nm on a Cary Eclipse fluorescence spectrophotometer (Agilent Tech). Samples were performed in duplicate and compared to standards.
Table 3 Blood glutathione status. Marker/group
GSH mM
GSSG mM
GSSG/total GSH ratio
C Pre AA Pre C Post AA Post
1.125 ± 0.06 1.132 ± 0.06 0.996 ± 0.05 1 ± 0.04
0.085 ± 0.02 0.106 ± 0.02 0.233 ± 0.04* 0.231 ± 0.03*
0.067 ± 0.02 0.089 ± 0.01 0.189 ± 0.03* 0.192 ± 0.02*
Significant main effect for time (pre vs. post) denoted by *
Table 4 Blood markers of inflammation. Marker group
IL-6 pg/ml
TNF α pg/ml
C Pre AA Pre C Post AA Post
0.96 ± 0.10 1.12 ± 0.20 1.57 ± 0.20* 1.67 ± 0.20*
1.722 ± 0.18 1.57 ± 0.31 2.93 ± 0.22* 2.76 ± 0.74*
*denotes main effect for time (pre vs. post)
TNF α showed a main effect for time, as it increased after exercise by 70.2 %. However, there were no differences based on eth▶ Table 4). nicity (●
Discussion
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The results of the current study are the first to demonstrate that exercise-induced blood oxidative stress markers increase to a similar extent in a cohort of young untrained African-American women compared to a cohort of young untrained Caucasian women working at a similar relative exercise intensity. This study also shows that the inflammatory markers TNF α and IL-6 also increased in a similar manner in these 2 cohort groups. The increase in oxidative stress noted in this study is comparable to several other published studies on the oxidative stress response to exercise at this exercise intensity [5, 6, 17]. Elevations in markers of oxidative stress (lipid hydroperoxides, protein carbonyls, xanthine oxidase, malondialdehyde) and markers of inflammation as denoted by cytokines (interleukin-6) and TNF α have been reported to increase immediately post-exercise in studies if the exercise intensity was sufficient and the duration adequate [15]. Furthermore, the resting values for these markers of oxidative stress and inflammation were not different between the groups. This suggests that resting values of these stress-related markers can be similar in these 2 groups if matched for a young age, gender, % fat and fitness level. It has been reported that with increased age oxidative stress levels within the blood are higher in an older African-Americans [40]. It is possible that older individuals start to lose their ability to control the handling of oxidative stress factors and inflammation. The current investigation reports elevated PC levels following exercise regardless of these 2 cohort groups. These findings are similar to results previously published by our group and several others following aerobic exercise. Alessio reported increased PC immediately after exercise and 1 h post-exercise [3]. Our group has replicated this, with several studies following both aerobic and resistance exercise with and without anti-oxidant supplementation in both trained and untrained individuals [4, 5, 16– 18]. It is hypothesized that the increase in markers of oxidative stress such as PC, MDA and LOOH as well as an increase in the ratio of GSSG/TGSH in response to exercise is related to many factors such as prostanoids, xanthine oxidase, activation of NADPH oxidase, neutrophil activation and possible disruption of
iron-containing molecules. [36]. Muscle activation can also activate numerous processes that increase the production and release of the superoxide radical and the formation of peroxynitrite to the extracellular space outside muscle [33]. Xanthine oxidase activity was unchanged by exercise, and there was no difference between our groups. Xanthine oxidase is a known radical-producing enzyme and is often elevated in periods of chronic activation of the oxidative stress system as with heart disease [22], lung disease [41] and exercise [1]. However, extreme endurance exercise or very high-intensity exercise [1, 24] appears to be needed to elevate xanthine oxidase. It is likely that our 30 min of running at 70 % VO2 max intensity may not have been sufficient stress to invoke an activation of this response. It should be noted that while all subjects did complete the task, several had a difficult time completing this task, making a higher intensity of their aerobic capacity inappropriate among this group of untrained subjects. Results from the current study demonstrate significantly higher levels of MDA after the exercise in both groups compared to their resting levels. However, the Caucasian group demonstrated a greater level of MDA than the African-American group (p = 0.04). Several investigations have noted that MDA will increase after exercise [2, 4, 5, 19]. Most of these studies report that MDA goes up quickly. It has been speculated that the increased MDA levels are likely due to increased periods of ischemia and reperfusion within the muscles during aerobic activity [5]. It is unclear why the Caucasian women had a greater MDA response than the AA group, which this should be investigated further. IL-6 is an interleukin that is released during the immune response and is released from muscle during exercise. It has been reported to be elevated following muscle contractions [13]. It has also been suggested that IL-6 is a signaling cytokine released from muscle that may increase health-related benefits and protect against chronic diseases in response to exercise bout [35]. As seen with most exercise studies that measure IL-6, the post-exercise IL-6 level was elevated, but the response was similar between our ethnic groups. Our results are similar to the cellular data reported by Brown et al. [7] at basal level and Feairheller in a follow-up study with plasma levels at rest [12]. However, both studies reported differences post-agitation in cells [7, 12]. However, it should be noted that these studies used agitation as a model for stress, but that agitation may not be physiological. Additionally, there was a sample size of 3 subjects in each group in the aforementioned Brown and Feairheller studies. Tumor necrosis factor alpha is a widely measured cytokine used to denote whether inflammation has occurred. Several investigations (for example [9, 38]) have noted significant increases in plasma TNFα levels when exercise is of sufficient duration and intensity. Our results are similar to a recently published study by Fisher et al. [14]. Like the Fisher group, we found no differences due to ethnicity in TNFα in untrained individuals. Fisher et al. did not note differences due to ethnicity until all subjects completed a weight loss intervention. At that point, C did reported lower levels than that of AA. Our results are also similar to the TNFα response noted by Brown et al. [7] in HUVAC cells. Our laboratory has measured glutathione from denatured whole blood and repeatedly reported elevated GSSG/TGSH ratios after exercise similar to what is being reported in the current investigation [5, 17, 18]. The intensity of exercise in the present study was sufficient to increase the oxidized glutathione concentration (GSSG) compared to pre-exercise values. However, there was no difference in the extent of the change between the 2
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Physiology & Biochemistry
groups in response to this level of exercise for 30 min. The extent of the increase in GSSG/TGSH is comparable to what we have reported with similar relative intensity of exercise with both men and women of similar age [6, 19]. In conclusion, our pilot study showed no differences between AA and C in basal levels of blood oxidative stress markers and blood inflammatory markers in apparently healthy young untrained women. This study also found that imposing an exercise stress at the same relative intensity and duration increases markers of blood oxidative stress and inflammation to a comparable extent within the blood. In contrast, Brown et al. reported that African-Americans had enhanced oxidative stress using and in vitro model. They noted that the umbilical cells would produce more oxidative stress. It is possible their in vitro study stimulated the production of oxidative stress, thus yielding enhanced production of oxidative stress markers. In contrast, exercise not only enhances production but can also enhance removal of radicals by activating the antioxidant system, which could have occurred in our study. In addition, we examined what is occuring within the blood and did not investigate what was happening within the muscles or tissues, which is clearly warranted in the future. It is possible that the isolated cells from older individuals would be more susceptible to producing enhanced reactive oxygen species [40], and since there was no clearance they would have accumulated more. It is proposed that an older population of woman be studied in the future to determine whether the aging factor contributes to these health-related differences appearing in AfricanAmericans. In addition, the present study sampled a small group of individuals. We recommend that a larger cohort of individuals be studied in the future as some subjects are probably more prone to these health-related differences, and we could have missed ethnicity differences. In conclusion, our pilot study shows that an acute bout of exercise with similar relative intensity and duration induces similar oxidative stress and inflammatory responses within the blood in untrained healthy young African-American compared to Caucasian women with similar characteristics.
Acknowledgements
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This study was supported by a grant from the HBCU Research Foundation (McKenzie) and the Winston-Salem State University Research Initiative Program (McKenzie). The authors wish to acknowledge the expertise provided by Dr. Jeffery Labban from the Office of Research from the School of Health and Human Sciences at the University of North Carolina at Greensboro.
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29 Lloyd-Jones D, Adams RJ, Brown TM, Carnethon M, Dai S, De Simone G, Ferguson TB, Ford E, Furie K, Gillespie C, Go A, Greenlund K, Haase N, Hailpern S, Ho PM, Howard V, Kissela B, Kittner S, Lacklan D, Lisabeth L, Marelli A, McDermott MM, Meigs J, Mozaffarian D, Mussolino M, Nichol G, Roger VL, Rosamond W, Sacco R, Sorlie P, Stafford R, Thom T, Wasserthiel-Smoller S, Wong ND, Wylie-Rosett J. Heart disease and stroke statistics – 2010 update: a report from the American Heart Association. Circulation 2010; 121: e46–e215 30 Lloyd-Jones DM. Cardiovascular risk prediction: basic concepts, current status, and future directions. Circulation 2010; 121: 1768–1777 31 Moorman JE, Rudd RA, Johnson CA, King M, Minor P, Bailey C, Scalia MR, Akinbami LJ. National surveillance for asthma – United States, 1980-2004. Morbidity and mortality weekly report Surveillance summaries 2007; 56: 1–54 32 Nieman DC, Davis JM, Henson DA, Walberg-Rankin J, Shute M, Dumke CL, Utter AC, Vinci DM, Carson JA, Brown A, Lee WJ, McAnulty SR, McAnulty LS. Carbohydrate ingestion influences skeletal muscle cytokine mRNA and plasma cytokine levels after a 3-h run. J Appl Physiol 2003; 94: 1917–1925 33 Pattwell DM, McArdle A, Morgan JE, Morgan JE, Patridge TA, Jackson MJ. Release of reactive oxygen and nitrogen species from contracting skeletal muscle cells. Free Radic Biol Med 2004; 37: 1064–1072 34 Pedersen BK. The diseasome of physical inactivity – and the role of myokines in muscle – fat cross talk. J Physiol 2009; 587: 5559–5568 35 Petersen AM, Pedersen BK. The anti-inflammatory effect of exercise. J Appl Physiol 2005; 98: 1154–1162
36 Powers SK, Jackson MJ. Exercise-induced oxidative stress: cellular mechanisms and impact on muscle force production. Physiol Rev 2008; 88: 1243–1276 37 Powers SK, Ji LL, Leeuwenburgh C. Exercise training-induced alterations in skeletal muscle antioxidant capacity: a brief review. Med Sci Sports Exerc 1999; 31: 987–997 38 Scott JP, Sale C, Greeves JP, Casey A, Dutton J, Fraser WD. Cytokine response to acute running in recreationally-active and endurancetrained men. Eur J Appl Physiol 2013; 113: 1871–1882 39 Sen CK, Packer L, Hanninen O. Handbook of oxidants and antioxidants in exercise. Amsterdam; Oxford: Elsevier, 2000 40 Sturgeon KM, Feairheller DL, Diaz KM, Williamson ST, Veerabhadrappa P, Brown MD. Clinical risk factors demonstrate an age-dependent relationship with oxidative stress biomarkers in African-Americans. Ethn Dis 2010; 20: 403–408 41 Teke T, Maden E, Kiyici A, Korkmaz C, Gok M, Ozer F, Imecik O, Uzun K. Cigarette smoke and bleomycin-induced pulmonary oxidative stress in rats. Exp Ther Med 2012; 4: 121–124 42 Textor SC. Renovascular hypertension in 2007: where are we now? Curr Cardiol Rep 2007; 9: 453–461 43 Whaley-Connell A, McCullough PA, Sowers JR. The role of oxidative stress in the metabolic syndrome. Rev Cardiovasc Med 2011; 12: 21–29
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Oxidative Stress and Inflammation Response Following Aerobic Exercise: Role of Ethnicity
Affiliations
Key words ▶ glutathione ● ▶ lipid hydroperoxides ● ▶ malondialdehyde ● ▶ protein carbonyl ● ▶ xanthine oxidase ● ▶ interleukin 6 ●
M. J. McKenzie1, A. Goldfarb2, R. S. Garten3, L. Vervaecke2 1
Winston Salem State University, Human Performance and Sport Sciences, Winston-Salem, United States UNC Greensboro, Kinesiology, Greensboro, United States 3 George E. Whalen Veterans Affairs Medical Center, Aging, Salt Lake City, United States 2
Abstract
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African-Americans are at a significantly greater risk for developing several diseases and conditions. These conditions often have underlying oxidative stress mechanisms. Therefore the purpose of this investigation was to ascertain the post-exercise oxidative response to a single bout of aerobic exercise in African-American and Caucasian college-age females. A total of 10 African-American and 10 Caucasian females completed the study. Each subject had her VO2 max measured while exercising on a treadmill. A week later, each subject returned to the laboratory and performed a 30-min run at 70 % of her VO2max. Blood samples were taken immediately prior to and following exercise for analysis. Lipid
Introduction
▼ accepted after revision November 27, 2013 Bibliography DOI http://dx.doi.org/ 10.1055/s-0033-1363982 Published online: April 15, 2014 Int J Sports Med 2014; 35: 822–827 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Michael Jon McKenzie Human Performance and Sport Sciences Winston Salem State University 601 S. MLK Jr Dr. 27107 Winston-Salem United States Tel.: + 1/336/750 3136 Fax: + 1/336/750 2591 [email protected]
According to the Centers for Disease Control and Prevention (CDC), the risks for obtaining many diseases and conditions are substantially higher among African-Americans minorities. AfricanAmericans were estimated to have a 77 % greater risk for diagnosed diabetes compared to Caucasians, and cancer rates were 13 % greater per 100 000 individuals reported by the American Cancer Society [27]. In addition, African-Americans appear to be more susceptible to asthmarelated complications as well as having mortality rates 2 to 3 times higher than Caucasians subjects from these complications [31]. African-Americans develop hypertension earlier with more manifestations than Caucasians [42]. AfricanAmericans in the US have a greater mortality rate from cardiovascular disease (CVD) and have higher hypertension rates compared to Caucasians or Mexican-Americans [28–30]. Additionally, African-American patients have a significantly higher mortality rate than Caucasian patients following a myocardial infarction
McKenzie MJ et al. Oxidative Stress and Inflammation … Int J Sports Med 2014; 35: 822–827
hydroperoxides, protein carbonyls, malondialdehyde, xanthine oxidase, glutathione in the reduced (GSH) and oxidized (GSSG) forms, TNFα and interleukin 6 were measured from blood taken before and after exercise. Significance was set at p ≤ 0.05 a priori. Xanthine oxidase was the only measure that did not significantly increase following exercise. All other markers showed a significant elevation in response to the exercise bout with no difference between groups except that the Caucasian group had significantly higher malondialdehyde post-exercise compared to the African-American group. This cohort of collegeage African-American and Caucasian females showed little difference in their response to a single 30-min run at 70 % of their max in the markers of oxidative stress within the blood.
(MI) [10]. Therefore, African-American ethnicity has been designated as an independent risk factor for both hypertension and cardiovascular disease risk [23]. While some of these disparities are likely explained by various lifestyle risk factors, such as activity level, socioeconomic status and nutrition, there is now some evidence that ethnic groups may respond to stressors differently in vivo. However, this should be examined in more detail. Research has attempted to establish whether racial differences exist that might explain a difference in both the development and progression of these diseases within an ethnic group. A common link in many of these diseases relates to mechanisms that manifest or are associated with these diseases. It would appear that what many of these diseases have in common are conditions that promote oxidative stress and inflammation. Oxidative stress and inflammation have been implicated in a variety of conditions from heart disease [8, 27] to diabetes [43]. It has recently been reported that ethnicity influences a persons’
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Authors
oxidative stress status at rest and in cultured cells placed under stress [7, 12]. Brown et al. and Feairheller et al. both recently noted that basal levels of IL-6 were significantly higher in African-Americans than Caucasians. They also indicated that cultured human umbilical vein endothelial cells placed under stress in vitro demonstrated greater oxidative stress and inflammation in the African-American isolated cells [7, 12]. These 2 in vitro studies suggest that oxidative stress and inflammation in vivo may be a contributory factor to why African-Americans may be more prone to certain diseases. While the types and levels of oxidative stress involved in the disease process is likely very different from the oxidative stress that occurs during exercise, examining ethnicity-related influences in this process would seem to be warranted. Exercise of appropriate intensity and duration has been shown to be an appropriate stressor to induce both oxidative stress [6, 17, 19, 37] and inflammation [6, 32]. Since muscle mass activation and adiposity appear to be contributory factors in both the inflammatory process [11, 34] and the oxidative stress response to exercise [2, 3], relative exercise intensity is imperative to control and match across subjects for similar muscle activation. One should also try to control the amount of body fat ( % body fat or obesity), as this has an influence on oxidative stress and inflammation. A good method to control for muscle stress is to adjust to one’s relative workload or relative intensity of exercise [25]. In addition, training status can influence both the antioxidant defense mechanism and the inflammatory processes [20, 26, 37, 39]. Therefore, as a first attempt to determine if ethnicity influences the exercise-induced responses to oxidative stress and inflammation in vivo we chose to examine untrained young yet apparently healthy women and controlled the relative intensity of exercise. We exposed them to an acute exercise bout previously shown to result in elevations of both oxidative stress and inflammatory markers in young healthy individuals.
Materials & Methods
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All methods were approved by both Institutional Review Boards prior to recruitment and data collection. The current investigation meets all ethical standards required by the journal and as published by Harriss and Atkinson [21].
Subjects 20 females (10 Caucasians (C), and 10 African-Americans (AA)) were recruited for the current study. All subjects were classified as untrained; meaning none of the subjects had participated in any regular type of exercise for a minimum of 6 months prior to data collection. All subjects were non-tobacco users and did not take antioxidant supplements for at least 6 months prior to the study. None of the subjects reported having any colds, diseases or infections that would have influenced oxidative stress or inflammatory processes. Any subject who did not subjectively identify herself as either AA or C was excluded from the study. All subjects reported to the laboratory 2 times. During the first visit, each subject signed the informed consent, completed a health history questionnaire and had her body fat assessed using the 7-site skin fold analysis with Harpenden calipers. Subjects then completed a maximal oxygen consumption (VO2 max) exercise test on a treadmill using a graded exercise protocol. Expired gases were analyzed by a True 1 analyzing system calibrated to known gases. Heart rates (Polar monitors) and blood
pressure (automated system) were obtained periodically during the test. Each subject performed a 3–5 min warm-up at a selfselected speed. Subjects then breathed through a one way valve which enabled expired gases to be processed by the True 1 analyzing system. Subjects started the test at a self-selected running speed at 0 % grade. The grade was increased 2 % every 2 min until VO2 leveled off or the subject stopped the test (8–10 min). All subjects attained their age-predicted maximal heart rate (HR) ± 10 bpm, reported an RPE > 19 on the Borg scale during the last stage of the test and had RER > 1.10. The VO2 max data was utilized to predict the workload and intensity for the submaximal run. For visit 2, each subject arrived in the morning following an overnight fast (7 p.m. to 9 a.m.) to minimize dietary effects on the oxidative stress markers. Subjects rested at least 30 min after arriving at the laboratory (Temp = 22 ± 1 °C, Humidity 40 ± 5 %) to aid in facilitating a true resting sample. Blood was then obtained using sterile techniques via vacutainer from an antecubital vein and immediately processed, centrifuged, placed in storage vials and then placed in a − 80 °C freezer until analyzed. A Polar monitor was then worn around the chest to enable continuous HR determination. Subjects completed the 30-min run at 70 % VO2 max. Oxygen consumption was monitored every 5 min to ensure VO2 was at the appropriate intensity. If necessary, speed and incline were adjusted to maintain the 70 % VO2 max intensity. We have previously used this intensity in several studies and have found it sufficiently produced elevations in oxidative stress markers [5, 19]. A blood sample was taken immediately ( < 1 min) after the exercise from an antecubital vein and processed as previously noted.
Blood markers Lipid hydroperoxides (LH) were determined using Cayman Chemical Company’s LOOH kit following the manufacturer’s instructions. Plasma (500ul) was extracted in chloroform (gassed with N2), prepared with methanol (gassed with N2), and reacted with 4.5 mM ferrous sulfate in 0.2M HCL and then a 3 % methanol solution of ammonium thiocyanate. The absorbance was monitored at 500 nm on a Shimadzu 1 801 spectrophotometer and compared to standards. All samples were measured in duplicate. Protein carbonyls were analyzed using the Biocell ELISA kit per manufacturer’s instructions, and the absorbance of the samples analyzed at 450 nm on a Biotex plate reader. The data were processed by a KC Junior software package. All samples were measured in duplicate and compared to standards. Malondialdehyde (MDA) concentration was analyzed using a colorimetric kit from Oxis (LPO-586) per manufacturer’s instructions. This procedure used N-methyl-2-pheylindole (NMP) to yield a stable chromophore which has maximal absorbance at 586 nm wavelength. Probucol (10 ul) was used to stabilize the plasma (200 ul) and then the NMP was added. Concentrated HCL (150 ul) was added and incubated at 45 °C for 60 min, and then the tubes were centrifuged. The absorbance was read at 586 nm wavelength on a microplate reader (Biotek instruments) and processed by a KC Junior software package. All samples were determined in duplicate and compared to standards. Interleukin-6 (IL-6) concentrations were determined using an immunoassay from R&D systems (IL-6 HS600B) per the manufacturer’s instructions. This is a high-sensitivity sandwich enzyme immunoassay using monoclonal antibodies specific to IL-6 coated on the microplate. The absorbance was read at
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Treatment of blood for glutathione analysis Whole blood (1 ml for both GSH and GSSG) was immediately pipetted into chilled tubes containing 1 ml of 10 % of 5-sulfosalicylic acid with 1 mM bathophenantrolinedisulfonic acid. These tubes were mixed to ensure red blood cells were lysed and destroyed all enzymatic activity. The tubes were then centrifuged at 3 000 rpm at 4- °C for 15 min (Beckman 6KR4, Fullerton, CA). The supernatant was then pipetted into 1.5 ml microcentrifuge tubes and centrifuged at 11 000 rpm for 10 min to remove any remaining cellular debris and then stored at − 80 °C until analyzed for glutathione status using an HPLC method.
Glutathione measurement Samples were thawed, passed through a 0.1 micron polypropylene filters (Whatman), and the effluent was then collected in microtubes. Twenty microliters of this effluent were injected into the HPLC (Shimadzu Prominence System).The HPLC was a Shimadzu Prominence ECD Eicom 700 series system. The electrochemical detector used an Eicom boron-doped diamond electrode to enable a burn-off after each run at 5 mV. The column was an Eicopak SC-30DS (4.6 mm × 100 mm), and the mobile phase was at a flow rate of 0.40 ml/min using 0.1M Na2HPO4 pH 2.5 as the mobile phase at a temperature of 21 ± 0.3 °C. The samples were run at least in duplicate and compared to GSH and GSSG standards (Sigma Aldrich Chemical Co.) We utilized the LC solutions computer software to identify the proper peaks and area of the curve for both GSH and GSSG to obtain concentrations. These peaks were compared to standard curves of both GSH and GSSG which had to be run through this same system.
Statistics All data were analyzed using a repeated measure 2 × 2 ANOVA (ethnicity by time) by SPSS, and statistical significance was set a priori at p ≤ 0.05. If there was an interaction effect, a Scheffe’s post-hoc test was utilized to identify differences.
Results
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Subject characteristics between the groups showed no significant differences in any aspects measured except body weight, as AA ▶ Table 1). were significantly heavier than their C counterparts (●
Table 1 Subject characteristics. Variable
African-Americans
subject Number age (years) height (cm) weight (kg) SBP (mmHg) DBP (mmHg) VO2max (ml.kg − 1min − 1) % body fat resting HR (bpm) % exercise VO2 exercise HR (bpm) exercise RPE
Caucasians
10 23.1 ± 1.1 168.3 ± 1.78 73.6 ± 3.40* 118.8 ± 1.87 72.0 ± 1.49 35.82 ± 1.71 29.2 ± 1.7 79.0 ± 3.0 73.4 ± 1.03 170.5 ± 3.59 14.7 ± 0.70
10 24.8 ± 2.0 161.0 ± 1.63 64.1 ± 3.16 109.2 ± 3.03 72.3 ± 2.56 39.98 ± 2.52 28.0 ± 2.5 78.7 ± 2.7 72.17 ± 0.96 171.7 ± 5.07 14.1 ± 0.70
Table 2 Blood markers of oxidative stress. Marker
LOOH nmol/
PC nM/mg
group
ml
protein
C pre AA pre C post AA post
0.80 ± 0.20 0.87 ± 0.32 1.01 ± 0.31* 1.47 ± 0.74*
0.097 ± 0.01 0.104 ± 0.01 0.123 ± 0.02* 0.136 ± 0.03*
XO mU/ml 21.13 ± 3.29 19.58 ± 2.96 24.8 ± .2.89 21.94 ± 3.33
MDA uM 3.52 ± 0.20 2.42 ± 0.29 5.46 ± 0.35^ 3.33 ± 0.41^
*denotes main effect for time (pre vs. post), ^ denotes main effect for time (pre vs. post) and group (AA vs. C)
Therefore, our subjects were matched for age, activity level, height, and % body fat. Additionally, all performance measures during the 30-min run were not significantly different between the groups. Since we controlled for relative intensity of aerobic capacity, % VO2max was similar. The average HR response and mean perceived exertion (RPE) were all similarly elevated during the acute bout of exercise. We feel that the stress on both the cardiovascular and muscular systems were similar for the aerobic exercise session for the 2 groups. Lipid hydroperoxides were significantly higher following exercise in both groups, as there was a time main effect. However, there was no difference based on a subject’s ethnicity. LOOH increased 46.8 % after the exercise compared to resting inde▶ Table 2). pendent of ethnicity (● The same outcome was evident in terms of PC measures, as PC was higher immediately after exercise in both ethnicities, but not different between C and AA. PC increased a modest 26.7 % as ▶ Table 2). a result of the exercise (● XO did not differ between ethnic groups and was in turn not significantly altered as a result of the exercise in either group ▶ Table 2). (● While MDA results showed a time main effect as well as a significant main effect for ethnicity, a significant interaction was not noted. MDA increased significantly in both groups, being more pronounced in the C women (54.9 %) compared to the AA ▶ Table 2). (35.8 %) (● Reduced glutathione (GSH) and oxidized glutathione (GSSG) were assessed along with the ratio of oxidized glutathione to total glutathione. No main effects for GSH were found. A time main effect (pre vs. post) was noted for both GSSG and the glutathione ratio. GSSG increased in response to the exercise 1.75 ▶ Table 3). fold, as did the glutathione ratio (increased 1.82 fold) (● IL-6 was similar prior to exercise for the 2 groups. After exercise IL-6 significantly increased in both groups 56 %, with no differ▶ Table 4). ences between groups based on ethnic status (●
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490 nm after correction at 650 nm wavelength on a microplate reader (Biotek instruments) and processed by a KC Junior software package. TNFα was ascertained using an ELISA kit from R & D systems catalog # DTAOOC. We followed the procedures and ran all samples on one plate in duplicate. Each plate was loaded with standards, controls and unknown samples, and read at 450-nm and corrected at 570 nm wavelength to subtract imperfections on the microplate reader (BioTek Instruments, Winesski, VT). The data were processed by a KC Junior software package. All samples were measured in duplicate and compared with standards. Xanthine oxidase (XO) levels were ascertained using an enzymatic assay from Cayman Chemical Company and monitored fluorometrically per manufacturer’s instructions. The plasma (50 ul) was added to wells and incubated with assay cocktail for 45 min at 37 °C. The plate was read at an excitation wavelength of 525 nm and an emission wavelength of 585 nm on a Cary Eclipse fluorescence spectrophotometer (Agilent Tech). Samples were performed in duplicate and compared to standards.
Table 3 Blood glutathione status. Marker/group
GSH mM
GSSG mM
GSSG/total GSH ratio
C Pre AA Pre C Post AA Post
1.125 ± 0.06 1.132 ± 0.06 0.996 ± 0.05 1 ± 0.04
0.085 ± 0.02 0.106 ± 0.02 0.233 ± 0.04* 0.231 ± 0.03*
0.067 ± 0.02 0.089 ± 0.01 0.189 ± 0.03* 0.192 ± 0.02*
Significant main effect for time (pre vs. post) denoted by *
Table 4 Blood markers of inflammation. Marker group
IL-6 pg/ml
TNF α pg/ml
C Pre AA Pre C Post AA Post
0.96 ± 0.10 1.12 ± 0.20 1.57 ± 0.20* 1.67 ± 0.20*
1.722 ± 0.18 1.57 ± 0.31 2.93 ± 0.22* 2.76 ± 0.74*
*denotes main effect for time (pre vs. post)
TNF α showed a main effect for time, as it increased after exercise by 70.2 %. However, there were no differences based on eth▶ Table 4). nicity (●
Discussion
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The results of the current study are the first to demonstrate that exercise-induced blood oxidative stress markers increase to a similar extent in a cohort of young untrained African-American women compared to a cohort of young untrained Caucasian women working at a similar relative exercise intensity. This study also shows that the inflammatory markers TNF α and IL-6 also increased in a similar manner in these 2 cohort groups. The increase in oxidative stress noted in this study is comparable to several other published studies on the oxidative stress response to exercise at this exercise intensity [5, 6, 17]. Elevations in markers of oxidative stress (lipid hydroperoxides, protein carbonyls, xanthine oxidase, malondialdehyde) and markers of inflammation as denoted by cytokines (interleukin-6) and TNF α have been reported to increase immediately post-exercise in studies if the exercise intensity was sufficient and the duration adequate [15]. Furthermore, the resting values for these markers of oxidative stress and inflammation were not different between the groups. This suggests that resting values of these stress-related markers can be similar in these 2 groups if matched for a young age, gender, % fat and fitness level. It has been reported that with increased age oxidative stress levels within the blood are higher in an older African-Americans [40]. It is possible that older individuals start to lose their ability to control the handling of oxidative stress factors and inflammation. The current investigation reports elevated PC levels following exercise regardless of these 2 cohort groups. These findings are similar to results previously published by our group and several others following aerobic exercise. Alessio reported increased PC immediately after exercise and 1 h post-exercise [3]. Our group has replicated this, with several studies following both aerobic and resistance exercise with and without anti-oxidant supplementation in both trained and untrained individuals [4, 5, 16– 18]. It is hypothesized that the increase in markers of oxidative stress such as PC, MDA and LOOH as well as an increase in the ratio of GSSG/TGSH in response to exercise is related to many factors such as prostanoids, xanthine oxidase, activation of NADPH oxidase, neutrophil activation and possible disruption of
iron-containing molecules. [36]. Muscle activation can also activate numerous processes that increase the production and release of the superoxide radical and the formation of peroxynitrite to the extracellular space outside muscle [33]. Xanthine oxidase activity was unchanged by exercise, and there was no difference between our groups. Xanthine oxidase is a known radical-producing enzyme and is often elevated in periods of chronic activation of the oxidative stress system as with heart disease [22], lung disease [41] and exercise [1]. However, extreme endurance exercise or very high-intensity exercise [1, 24] appears to be needed to elevate xanthine oxidase. It is likely that our 30 min of running at 70 % VO2 max intensity may not have been sufficient stress to invoke an activation of this response. It should be noted that while all subjects did complete the task, several had a difficult time completing this task, making a higher intensity of their aerobic capacity inappropriate among this group of untrained subjects. Results from the current study demonstrate significantly higher levels of MDA after the exercise in both groups compared to their resting levels. However, the Caucasian group demonstrated a greater level of MDA than the African-American group (p = 0.04). Several investigations have noted that MDA will increase after exercise [2, 4, 5, 19]. Most of these studies report that MDA goes up quickly. It has been speculated that the increased MDA levels are likely due to increased periods of ischemia and reperfusion within the muscles during aerobic activity [5]. It is unclear why the Caucasian women had a greater MDA response than the AA group, which this should be investigated further. IL-6 is an interleukin that is released during the immune response and is released from muscle during exercise. It has been reported to be elevated following muscle contractions [13]. It has also been suggested that IL-6 is a signaling cytokine released from muscle that may increase health-related benefits and protect against chronic diseases in response to exercise bout [35]. As seen with most exercise studies that measure IL-6, the post-exercise IL-6 level was elevated, but the response was similar between our ethnic groups. Our results are similar to the cellular data reported by Brown et al. [7] at basal level and Feairheller in a follow-up study with plasma levels at rest [12]. However, both studies reported differences post-agitation in cells [7, 12]. However, it should be noted that these studies used agitation as a model for stress, but that agitation may not be physiological. Additionally, there was a sample size of 3 subjects in each group in the aforementioned Brown and Feairheller studies. Tumor necrosis factor alpha is a widely measured cytokine used to denote whether inflammation has occurred. Several investigations (for example [9, 38]) have noted significant increases in plasma TNFα levels when exercise is of sufficient duration and intensity. Our results are similar to a recently published study by Fisher et al. [14]. Like the Fisher group, we found no differences due to ethnicity in TNFα in untrained individuals. Fisher et al. did not note differences due to ethnicity until all subjects completed a weight loss intervention. At that point, C did reported lower levels than that of AA. Our results are also similar to the TNFα response noted by Brown et al. [7] in HUVAC cells. Our laboratory has measured glutathione from denatured whole blood and repeatedly reported elevated GSSG/TGSH ratios after exercise similar to what is being reported in the current investigation [5, 17, 18]. The intensity of exercise in the present study was sufficient to increase the oxidized glutathione concentration (GSSG) compared to pre-exercise values. However, there was no difference in the extent of the change between the 2
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groups in response to this level of exercise for 30 min. The extent of the increase in GSSG/TGSH is comparable to what we have reported with similar relative intensity of exercise with both men and women of similar age [6, 19]. In conclusion, our pilot study showed no differences between AA and C in basal levels of blood oxidative stress markers and blood inflammatory markers in apparently healthy young untrained women. This study also found that imposing an exercise stress at the same relative intensity and duration increases markers of blood oxidative stress and inflammation to a comparable extent within the blood. In contrast, Brown et al. reported that African-Americans had enhanced oxidative stress using and in vitro model. They noted that the umbilical cells would produce more oxidative stress. It is possible their in vitro study stimulated the production of oxidative stress, thus yielding enhanced production of oxidative stress markers. In contrast, exercise not only enhances production but can also enhance removal of radicals by activating the antioxidant system, which could have occurred in our study. In addition, we examined what is occuring within the blood and did not investigate what was happening within the muscles or tissues, which is clearly warranted in the future. It is possible that the isolated cells from older individuals would be more susceptible to producing enhanced reactive oxygen species [40], and since there was no clearance they would have accumulated more. It is proposed that an older population of woman be studied in the future to determine whether the aging factor contributes to these health-related differences appearing in AfricanAmericans. In addition, the present study sampled a small group of individuals. We recommend that a larger cohort of individuals be studied in the future as some subjects are probably more prone to these health-related differences, and we could have missed ethnicity differences. In conclusion, our pilot study shows that an acute bout of exercise with similar relative intensity and duration induces similar oxidative stress and inflammatory responses within the blood in untrained healthy young African-American compared to Caucasian women with similar characteristics.
Acknowledgements
▼
This study was supported by a grant from the HBCU Research Foundation (McKenzie) and the Winston-Salem State University Research Initiative Program (McKenzie). The authors wish to acknowledge the expertise provided by Dr. Jeffery Labban from the Office of Research from the School of Health and Human Sciences at the University of North Carolina at Greensboro.
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