The Interaction of Duchenne Muscular Dystrophy and Insulin Resistance.

Duchenne muscular dystrophy (DMD), caused by deficiency of functional dystrophin protein, is a fatal, progressive muscle disease that frequently includes metabolic dysregulation. Herein, we explore the physiologic consequences of dystrophin deficiency within the context of obesity and insulin resistance. We hypothesized that dystrophin deficiency increases the frequency of insulin resistance, and insulin resistance potentiates muscle pathology caused by dystrophin deficiency.

Cardiovascular and Blood Oxidative Stress Responses to Exercise and Acute Woodsmoke Exposure in Recreationally Active Individuals.

INTRODUCTION: Those who work and recreate outdoors experience woodsmoke exposure during fire season. Exercise during woodsmoke exposure harms the cardiovascular system, but the acute physiologic and biochemical responses are understudied. The purpose of this pilot laboratory-based study was to examine the effect of exercise during woodsmoke exposure on acute indicators of cardiovascular function, including heart rate variability (HRV), pulse wave velocity (PWV), blood pressure (BP), augmentation index (AIx), and blood oxidative stress. METHODS: Ten participants performed 2 moderate-intensity exercise (70% V˙O2 max) trials (clean air 0 µg·m-3, woodsmoke 250 µg·m-3) in a crossover design. HRV, PWV, BP, AIx, and blood oxidative stress were measured before, after, and 90 min after exercise for each trial. Blood oxidative stress was quantified through lipid damage (LOOH, 8-ISO), protein damage (3-NT, PC), and antioxidant capacity (TEAC). RESULTS: A 45-min woodsmoke exposure combined with moderate-intensity exercise did not result in a statistically significant difference in HRV, PWV, BP, AIx, or oxidative stress (P>0.05). CONCLUSIONS: Despite the known deleterious effects of smoke inhalation, moderate-intensity aerobic exercise while exposed to woodsmoke particulate matter (250 µg·m-3) did not result in a statistically significant difference in HRV, PWV, or blood oxidative stress in this methodologic context. Although findings do not negate the negative impact of woodsmoke inhalation, additional research approaches are needed to better understand the acute effects of smoke exposure on the cardiovascular system.

Blood oxidative stress and post-exercise recovery are unaffected byhypobaric and hypoxic environments.

Hypobaria and hypoxia exert independent effects on oxidative stress during exercise, while combined effectson the post-exercise recovery period remain unclear.Accordingly, this study examined the recovery period during lab-simulated hypoxic and hypobaric conditions following exercise-induced oxidative stress. Participants (n=13) performed 60-minutes of cycling (70% watts max) in a normobaric normoxic environment followed by a four-hour recovery under three conditions; 1000m normobaric normoxia (NN, 675mmHg), 4400m normobaric hypoxia (NH, 675mmHg), or 4400m hypobaric hypoxia (HH, 440mmHg). Blood samples collected at Pre, Post, 2-Hours (2-HR), and 4-Hours (4-HR) post-exercise were analyzed fora potential increase in biochemical modifications of proteins(protein carbonyls, PC; 3-nitrotyrosines, 3NT) lipids (lipid hydroperoxides, LOOH; 8-isoprostanes, 8-ISO), and antioxidant capacity (FRAP, TEAC). Gene transcripts (EPAS, HMOX1, SOD2, NFE2L2) were quantified by qRT-PCR from muscle biopsies taken Pre and Post exercise. Hypoxia and hypobaria had no effect throughout recovery. Post-exercise TEAC (p=0.041), FRAP (p=0.013), and 8-ISO (p=0.044) increased, while PC (p=0.002) and 3-NT (p=0.032) were decreased. LOOH was lower in Post (p=0.018) NH trial samples. Exercise-dependent increases occurred in NFE2L2 (p=0.003), HMXO1 (p<0.001), SOD2 (p=0.046), and EPAS (p=0.038). Exercise recovery under conditions of NH and HH did not impact blood oxidative stress or redox-sensitive gene transcripts.

Cardioprotective Exercise and Pharmacologic Interventions as Complementary Antidotes to Cardiovascular Disease.

Exercise and pharmacologic therapies to prevent and treat cardiovascular disease have advanced largely through independent efforts. Understanding of first-line drug therapies, findings from preclinical animal studies, and the need for research initiatives related to complementary cardioprotective exercise-pharma interventions are reviewed from the premise that contemporary cardioprotective therapies must include adjunctive exercise and lifestyle interventions in addition to pharmacologic agents.

Lifelong quercetin enrichment and cardioprotection in Mdx/Utrn+/- mice.

Duchenne Muscular Dystrophy (DMD) is associated with progressive cardiac pathology; however, the SIRT1/PGC1-α activator quercetin may cardioprotect dystrophic hearts. We tested the extent to which long-term 0.2% dietary quercetin enrichment attenuates dystrophic cardiopathology in Mdx/Utrn+/- mice. At 2 mo, Mdx/Utrn+/- mice were fed quercetin-enriched (Mdx/Utrn+/--Q) or control diet (Mdx/Utrn+/-) for 8 mo. Control C57BL/10 (C57) animals were fed a control diet for 10 mo. Cardiac function was quantified by MRI at 2 and 10 mo. Spontaneous physical activity was quantified during the last week of treatment. At 10 mo hearts were excised for histological and biochemical analysis. Quercetin feeding improved various physiological indexes of cardiac function in diseased animals. Mdx/Utrn+/--Q also engaged in more high-intensity physical activity than controls. Histological analyses of heart tissues revealed higher expression and colocalization of utrophin and α-sarcoglycan. Lower abundance of fibronectin, cardiac damage (Hematoxylin Eosin-Y), and MMP9 were observed in quercetin-fed vs. control Mdx/Utrn+/- mice. Quercetin evoked higher protein abundance of PGC-1α, cytochrome c, ETC complexes I-V, citrate synthase, SOD2, and GPX compared with control-fed Mdx/Utrn+/- Quercetin decreased abundance of inflammatory markers including NFκB, TGF-ß1, and F4/80 compared with Mdx/Utrn+/-; however, P-NFκB, P-IKBα, IKBα, CD64, and COX2 were similar between groups. Dietary quercetin enrichment improves cardiac function in aged Mdx/Utrn+/- mice and increases mitochondrial protein content and dystrophin glycoprotein complex formation. Histological analyses indicate a marked attenuation in pathological cardiac remodeling and indicate that long-term quercetin consumption benefits the dystrophic heart. NEW & NOTEWORTHY: The current investigation provides first-time evidence that quercetin provides physiological cardioprotection against dystrophic pathology and is associated with improved spontaneous physical activity. Secondary findings suggest that quercetin-dependent outcomes are in part due to PGC-1α pathway activation.

Long-term dietary quercetin enrichment as a cardioprotective countermeasure in mdx mice.

NEW FINDINGS: What is the central question of this study? The central question of this study is to understand whether dietary quercetin enrichment attenuates physiologic, histological, and biochemical indices of cardiac pathology. What is the main finding and its importance? Novel findings from this investigation, in comparison to prior published studies, suggest that mouse strain-dependent cardiac outcomes in performance and remodelling exist. Unlike Mdx/Utrn-/+ mice, mdx mice receiving lifelong quercetin treatment did not exhibit improvements cardiac function. Similar to prior work in Mdx/Utrn-/+ mice, histological evidence of remodelling suggests that quercetin consumption may have benefited hearts of mdx mice. Positive outcomes may be related to indirect markers that suggest improved mitochondrial wellbeing and to selected indices of inflammation that were lower in hearts from quercetin-fed mice. Duchenne muscular dystrophy causes a decline in cardiac health, resulting in premature mortality. As a potential countermeasure, quercetin is a polyphenol possessing inherent anti-inflammatory and antioxidant effects that activate proliferator-activated γ coactivator 1α (PGC-1α), increasing the abundance of mitochondrial biogenesis proteins. We investigated the extent to which lifelong 0.2% dietary quercetin enrichment attenuates dystrophic cardiopathology in mdx mice. Dystrophic animals were fed a quercetin-enriched or control diet for 12 months, while control C57 mice were fed a control diet. Cardiac function was assessed via 7 T magnetic resonance imaging at 2, 10 and 14 months. At 14 months, hearts were harvested for histology and Western blotting. The results indicated an mdx strain-dependent decline in cardiac performance at 14 months and that dietary quercetin enrichment did not attenuate functional losses. In contrast, histological analyses provided evidence that quercetin feeding was associated with decreased fibronectin and indirect damage indices (Haematoxylin and Eosin) compared with untreated mdx mice. Dietary quercetin enrichment increased cardiac protein abundance of PGC-1α, cytochrome c, electron transport chain complexes I-V, citrate synthase, superoxide dismutase 2 and glutathione peroxidase (GPX) versus untreated mdx mice. The protein abundance of the inflammatory markers nuclear factor-κB, phosphorylated nuclear factor kappa beta (P-NFκB) and phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (P-IKBα) was decreased by quercetin compared with untreated mdx mice, while preserving nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha( IKBα) compared with mdx mice. Furthermore, quercetin decreased transforming growth factor-ß1, cyclooxygenase-2 (COX2) and macrophage-restricted F4/80 protein (F4/80) versus untreated mdx mice. The data suggest that long-term quercetin enrichment does not impact physiological parameters of cardiac function but improves indices of mitochondrial biogenesis and antioxidant enzymes, facilitates dystrophin-associated glycoprotein complex (DGC) assembly and decreases inflammation in dystrophic hearts.

Consensus Statement Immunonutrition and Exercise.

In this consensus statement on immunonutrition and exercise, a panel of knowledgeable contributors from across the globe provides a consensus of updated science, including the background, the aspects for which a consensus actually exists, the controversies and, when possible, suggested directions for future research.

Impact of extreme exercise at high altitude on oxidative stress in humans.

Exercise and oxidative stress research continues to grow as a physiological subdiscipline. The influence of high altitude on exercise and oxidative stress is among the recent topics of intense study in this area. Early findings indicate that exercise at high altitude has an independent influence on free radical generation and the resultant oxidative stress. This review provides a detailed summary of oxidative stress biochemistry as gleaned mainly from studies of humans exercising at high altitude. Understanding of the human response to exercise at altitude is largely derived from field-based research at altitudes above 3000 m in addition to laboratory studies which employ normobaric hypoxia. The implications of oxidative stress incurred during high altitude exercise appear to be a transient increase in oxidative damage followed by redox-sensitive adaptations in multiple tissues. These outcomes are consistent for lowland natives, high altitude acclimated sojourners and highland natives, although the latter group exhibits a more robust adaptive response. To date there is no evidence that altitude-induced oxidative stress is deleterious to normal training or recovery scenarios. Limited evidence suggests that deleterious outcomes related to oxidative stress are limited to instances where individuals are exposed to extreme elevations for extended durations. However, confirmation of this tentative conclusion requires further investigation. More applicably, altitude-induced hypoxia may have an independent influence on redox-sensitive adaptive responses to exercise and exercise recovery. If correct, these findings may hold important implications for athletes, mountaineers, and soldiers working at high altitude. These points are raised within the confines of published research on the topic of oxidative stress during exercise at altitude.

Oral quercetin administration transiently protects respiratory function in dystrophin-deficient mice.

KEY POINT: PGC-1α pathway activation has been shown to decrease disease severity and can be driven by quercetin. Oral quercetin supplementation protected respiratory function for 4-6 months during a 12 month dosing regimen. This transient protection was probably due to a failure to sustain elevated SIRT1 activity and downstream PGC-1α signalling. Quercetin supplementation may be a beneficial treatment as part of a cocktail provided continued SIRT1 activity elevation is achieved. ABSTRACT: Duchenne muscular dystrophy (DMD) impacts 1 : 3500 boys and leads to muscle dysfunction culminating in death due to respiratory or cardiac failure. There is an urgent need for effective therapies with the potential for immediate application for this patient population. Quercetin, a flavonoid with an outstanding safety profile, may provide therapeutic relief to DMD patients as the wait for additional therapies continues. This study evaluated the capacity of orally administered quercetin (0.2%) in 2 month old mdx mice to improve respiratory function and end-point functional and histological outcomes in the diaphragm following 12 months of treatment. Respiratory function was protected for the first 4-6 months of treatment but appeared to become insensitive to quercetin thereafter. Consistent with this, end-point functional measures were decreased and histopathological measures were more severe in dystrophic muscle compared to C57 and similar between control-fed and quercetin-fed mdx mice. To better understand the transient nature of improved respiratory function, we measured PGC-1α pathway activity, which is suggested to be up-regulated by quercetin supplementation. This pathway was largely suppressed in dystrophic muscle compared to healthy muscle, and at the 14 month time point dietary quercetin enrichment did not increase expression of downstream effectors. These data support the efficacy of quercetin as an intervention for DMD in skeletal muscle, and also indicate the development of age-dependent quercetin insensitivity when continued supplementation fails to drive the PGC-1α pathway. Continued study is needed to determine if this is related to disease severity, age or other factors.

Graded hypoxia and blood oxidative stress during exercise recovery.

Altitude exposure and exercise elicit oxidative stress in blood; however, exercise recovery at 5000 m attenuates oxidative stress. The purpose was to determine the altitude threshold at which blood oxidative stress is blunted during exercise recovery. Twelve males 18-28 years performed four-cycle ergometry bouts (60 min, 70% VO2max, at 975 m). In a randomised counterbalanced crossover design, participants recovered 6 h at 0, 1667, 3333 and 5000 m in a normobaric hypoxia chamber (recovery altitudes were simulated by using a computerised system in an environmental chamber by lowering the partial pressure of oxygen to match that of the respective altitude). Oxygen saturation was monitored throughout exercise recovery. Blood samples obtained pre-, post-, 1 h post- and 5 h post-exercise were assayed for ferric-reducing antioxidant plasma, Trolox equivalent antioxidant capacity, uric acid, lipid hydroperoxides and protein carbonyls. Muscle biopsies obtained pre and 6 h were analysed by real-time polymerase chain reaction to quantify expression of hemeoxgenase 1, superoxide dismutase 2 and nuclear factor (euthyroid-derived 2)-like factor. Pulse oximetry data were similar during exercise, but decreased for the three highest recovery elevations (0 m = 0%, 1667 m = -3%; 3333 m = -7%; 5000 m = -17%). A time-dependent oxidative stress occurred following exercise for all variables, but the two highest recovery altitudes partially attenuated the lipid hydroperoxide response (0 m = +135%, 1667 m = +251%, 3333 m = +99%; 5000 m = +108%). Data may indicate an altitude threshold between 1667 and 3333 m, above which the oxidative stress response is blunted during exercise recovery.

Autonomic Responses to an Acute Bout of High-Intensity Body Weight Resistance Exercise vs. Treadmill Running.

The aim of this study was to compare postexercise autonomic nervous system (ANS) recovery between a high-intensity training protocol (HITP) and high-intensity treadmill running (TM) in 10 physically fit males. For each trial, ANS activity was measured through the heart rate variability markers of log-transformed square root of the successive R-R differences (lnRMSSD) and high frequency power (lnHF). These markers were analyzed in 5-minute segments at 5-10 minutes of the pre-exercise period (PRE) and during the postexercise period at 15-20 minutes (POST15-20min), 20-25 minutes (POST20-25min), 25-30 minutes (POST25-30min), and 1 hour (POST60min). Plasma epinephrine (E) and norepinephrine (NE) were also examined at PRE, immediately post exercise (IPE), 1-hour post (1HP), and 2-hour post (2HP). The results of this study demonstrate a significant overall time-dependent decreases in lnRMSSD and lnHF (p = 0.003 and 0.001, respectively) in both trials. Trial-dependent differences were also observed in postexercise lnRMSSD and lnHF measures, HITP being significantly lower than TM (p = 0.002 and 0.000, respectively). lnRMSSD at POST60min-HITP remained significantly lower compared to PRE (p ≤ 0.05). lnHF returned to baseline in HIPT and TM (p = 0.081 and 0.065, respectively). A time-dependent increase in E and NE was observed in both trials at time point IPE when compared to PRE (p ≤ 0.05). E at 1HP and 2HP returned to near resting levels (p = 0.62, p = 0.26), whereas NE remained slightly elevated in both groups (p = 0.003, p = 0.021). A trial-dependent increase was observed with the HITP eliciting a greater E response (p = 0.025) and NE response (p = 0.03). The HITP causes a greater disruption of the ANS than intensity-matched TM exercise.

Mechanisms of exercise-induced cardioprotection.

Myocardial ischemia-reperfusion (IR) injury can cause ventricular cell death and is a major pathological event leading to morbidity and mortality in those with coronary artery disease. Interestingly, as few as five bouts of exercise on consecutive days can rapidly produce a cardiac phenotype that resists IR-induced myocardial injury. This review summarizes the development of exercise-induced cardioprotection and the mechanisms responsible for this important adaptive response.

Interleukin-6 mediates exercise preconditioning against myocardial ischemia reperfusion injury.

Interleukin-6 (IL-6) is a pleiotropic cytokine that protects against cardiac ischemia-reperfusion (I/R) injury following pharmacological and ischemic preconditioning (IPC), but the affiliated role in exercise preconditioning is unknown. Our study purpose was to characterize exercise-induced IL-6 cardiac signaling (aim 1) and evaluate myocardial preconditioning (aim 2). In aim 1, C57 and IL-6(-/-) mice underwent 3 days of treadmill exercise for 60 min/day at 18 m/min. Serum, gastrocnemius, and heart were collected preexercise, immediately postxercise, and 30 and 60 min following the final exercise session and analyzed for indexes of IL-6 signaling. For aim 2, a separate cohort of exercise-preconditioned (C57 EX and IL-6(-/-) EX) and sedentary (C57 SED and IL-6(-/-) SED) mice received surgical I/R injury (30 min I, 120 min R) or a time-matched sham operation. Ischemic and perfused tissues were examined for necrosis, apoptosis, and autophagy. In aim 1, serum IL-6 and IL-6 receptor (IL-6R), gastrocnemius, and myocardial IL-6R were increased following exercise in C57 mice only. Phosphorylated (p) signal transducer and activator of transcription 3 was increased in gastrocnemius and heart in C57 and IL-6(-/-) mice postexercise, whereas myocardial iNOS and cyclooxygenase-2 were unchanged in the exercised myocardium. Exercise protected C57 EX mice against I/R-induced arrhythmias and necrosis, whereas arrhythmia score and infarct outcomes were higher in C57 SED, IL-6(-/-) SED, and IL-6(-/-) EX mice compared with SH. C57 EX mice expressed increased p-p44/42 MAPK (Thr(202)/Tyr(204)) and p-p38 MAPK (Thr(180)/Tyr(182)) compared with IL-6(-/-) EX mice, suggesting pathway involvement in exercise preconditioning. Findings indicate exercise exerts cardioprotection via IL-6 and strongly implicates protective signaling originating from the exercised skeletal muscle.

Cardioprotective HIF-1α-frataxin signaling against ischemia-reperfusion injury.

Previous studies have demonstrated the protective signaling of hypoxia-inducible factor (HIF)-1 α against ischemia-reperfusion (I/R) injury in the heart. In the present study, we provide further evidence for a cardioprotective mechanism by HIF-1α against I/R injury exerted via the mitochondrial protein frataxin, which regulates mitochondrial Fe-S cluster formation. Disruption of frataxin has been found to induce mitochondrial iron overload and subsequent ROS production. We observed that frataxin expression was elevated in mice hearts subjected to I/R injury, and this response was blunted in cardiomyocyte-specific HIF-1α knockout (KO) mice. Furthermore, these HIF-1α KO mice sustained extensive cardiac damage from I/R injury compared with control mice. Similarly, reduction of HIF-1α by RNA inhibition resulted in an attenuation of frataxin expression in response to hypoxia in H9C2 cardiomyocytes. Therefore, we postulated that HIF-1α transcriptionally regulates frataxin expression in response to hypoxia and offers a cardioprotective mechanism against ischemic injury. Our promoter activity and chromatin immunoprecipitation assays confirmed the presence of a functional hypoxia response element in the frataxin promoter. Our data also suggest that increased frataxin mitigated mitochondrial iron overload and subsequent ROS production, thus preserving mitochondrial membrane integrity and viability of cardiomyocytes. We postulate that frataxin may exert its beneficial effects by acting as an iron storage protein under hypoxia and subsequently facilitates the maintenance of mitochondrial membrane potential and promotes cell survival. The findings from our study revealed that HIF-1α-frataxin signaling promotes a protective mechanism against hypoxic/ischemic stress.

The role of frataxin in doxorubicin-mediated cardiac hypertrophy.

Doxorubicin (DOX) is a highly effective anti-neoplastic agent; however, its cumulative dosing schedules are clinically limited by the development of cardiotoxicity. Previous studies have attributed the cause of DOX-mediated cardiotoxicity to mitochondrial iron accumulation and the ensuing reactive oxygen species (ROS) formation. The present study investigates the role of frataxin (FXN), a mitochondrial iron-sulfur biogenesis protein, and its role in development of DOX-mediated mitochondrial dysfunction. Athymic mice treated with DOX (5 mg/kg, 1 dose/wk with treatments, followed by 2-wk recovery) displayed left ventricular hypertrophy, as observed by impaired cardiac hemodynamic performance parameters. Furthermore, we also observed significant reduction in FXN expression in DOX-treated animals and H9C2 cardiomyoblast cell lines, resulting in increased mitochondrial iron accumulation and the ensuing ROS formation. This observation was paralleled in DOX-treated H9C2 cells by a significant reduction in the mitochondrial bioenergetics, as observed by the reduction of myocardial energy regulation. Surprisingly, similar results were observed in our FXN knockdown stable cell lines constructed by lentiviral technology using short hairpin RNA. To better understand the cardioprotective role of FXN against DOX, we constructed FXN overexpressing cardiomyoblasts, which displayed cardioprotection against mitochondrial iron accumulation, ROS formation, and reduction of mitochondrial bioenergetics. Lastly, our FXN overexpressing cardiomyoblasts were protected from DOX-mediated cardiac hypertrophy. Together, our findings reveal novel insights into the development of DOX-mediated cardiomyopathy.

Histological and biochemical outcomes of cardiac pathology in mdx mice with dietary quercetin enrichment.

NEW FINDINGS: What is the central question of this study? Does dietary quercetin enrichment improve biochemical and histological outcomes in hearts from mdx mice? What is the main finding and what is its importance? Biochemical and histological findings suggest that chronic quercetin feeding of mdx mice may improve mitochondrial function and attenuate tissue pathology. Patients with Duchenne muscular dystrophy suffer from cardiac pathology, which causes up to 40% of all deaths because of fibrosis and cardiac complications. Quercetin is a flavonol with anti-inflammatory and antioxidant effects and is also an activator of peroxisome proliferator-activated receptor γ coactivator 1α capable of antioxidant upregulation, mitochondrial biogenesis and prevention of cardiac complications. We sought to determine the extent to which dietary quercetin enrichment prevents (experiment 1) and rescues cardiac pathology (experiment 2) in mdx mice. In experiment 1, 3-week-old mdx mice were fed control chow (C3w6m, n = 10) or chow containing 0.2% quercetin for 6 months (Q3w6m, n = 10). In experiment 2, 3-month-old mdx mice were fed control chow (C3m6m, n = 10) or 0.2% chow containing 0.2% quercetin for 6 months (Q3m6m, n = 10). Hearts were excised for histological and biochemical analyses. In experiment 1, Western blot targets for mitochondrial biogenesis (cytochrome c, P = 0.007) and antioxidant expression (superoxide dismutase 2, P = 0.014) increased in Q3w6m mice compared with C3w6m. Histology revealed increased utrophin (P = 0.025) and decreased matrix metalloproteinase 9 abundance (P = 0.040) in Q3w6m mice compared with C3w6m. In experiment 2, relative (P = 0.023) and absolute heart weights (P = 0.020) decreased in Q3m6m mice compared with C3m6m. Indications of damage (Haematoxylin- and Eosin-stained sections, P = 0.007) and Western blot analysis of transforming growth factor ß1 (P = 0.009) were decreased in Q3m6m mice. Six months of quercetin feeding increased a mitochondrial biomarker, antioxidant protein and utrophin and decreased matrix metalloproteinase 9 in young mice. Given that these adaptations are associated with attenuated cardiac pathology and damage, the present findings may indicate that dietary quercetin enrichment attenuates dystrophic cardiac pathology, but physiological confirmation is needed.

Involvement of the δ-opioid receptor in exercise-induced cardioprotection.

NEW FINDINGS: What is the central question of this study? Does the δ-opioid receptor trigger exercise-induced cardioprotection against ischaemia-reperfusion injury? What is the main finding and its importance? In exercised hearts, the δ-opioid receptor appears to trigger cardioprotection against ischaemia-reperfusion-induced tissue necrosis but not apoptosis. ABSTRACT: Endogenous opioids mediate exercise-induced cardioprotection against ischaemia-reperfusion (IR) injury, although the opioid receptor subtype mediating this effect is unknown. We investigated whether the δ-opioid receptor mediates exercise-induced cardioprotection against IR injury. Endogenous opioids are produced in various tissues, including the heart and skeletal muscle; therefore, we also sought to identify the effect of exercise on circulating endogenous opioid as well as transcript, protein and receptor expression in heart and skeletal muscle. Male Sprague-Dawley rats (n = 73) were assigned randomly to treadmill exercise or sedentary treatments. Cardiac tissue and serum were harvested 0, 20 and 120 min following exercise and from sedentary animals (n = 32) to quantify effects on proenkephalin and δ-opioid receptor mRNA and protein levels, as well as serum enkephalin. Skeletal muscle (soleus) was harvested at identical time points for determination of proenkephalin protein and mRNA. A separate group of rats (n = 41) were randomly assigned to sham operation (Sham; surgical control), sedentary (Sed), exercise (Ex) or exercise + Î´-opioid receptor antagonist (ExD; naltrindole, 5 mg kg(-1) i.p.) and received IR by left anterior descending coronary artery ligation in vivo. After IR, tissues were harvested to quantify treatment effects on necrosis and apoptosis. Cardiac proenkephalin mRNA expression increased following exercise (0 min, P = 0.03; 120 min, P = 0.021), while soleus expression was unaffected. Exercise-induced changes in serum enkephalin were undetectable. After IR, tissue necrosis was elevated in Sed and ExD hearts (P < 0.001 and P = 0.003, respectively) compared with the Sham group, while the Ex group was partly protected. After IR, apoptosis was evident in Sed hearts (P = 0.016), while Ex and ExD hearts were protected. Data suggest that cardioprotective opioids are produced by the heart, but not by the soleus. After IR, the δ-opioid receptor may mediate, in part, cardioprotection against necrosis but not apoptosis.

Exercise-induced oxidative stress and hypoxic exercise recovery.

Hypoxia due to altitude diminishes performance and alters exercise oxidative stress responses. While oxidative stress and exercise are well studied, the independent impact of hypoxia on exercise recovery remains unknown. Accordingly, we investigated hypoxic recovery effects on post-exercise oxidative stress. Physically active males (n = 12) performed normoxic cycle ergometer exercise consisting of ten high:low intensity intervals, 20 min at moderate intensity, and 6 h recovery at 975 m (normoxic) or simulated 5,000 m (hypoxic chamber) in a randomized counter-balanced cross-over design. Oxygen saturation was monitored via finger pulse oximetry. Blood plasma obtained pre- (Pre), post- (Post), 2 h post- (2Hr), 4 h post- (4Hr), and 6 h (6Hr) post-exercise was assayed for Ferric Reducing Ability of Plasma (FRAP), Trolox Equivalent Antioxidant Capacity (TEAC), Lipid Hydroperoxides (LOOH), and Protein Carbonyls (PC). Biopsies from the vastus lateralis obtained Pre and 6Hr were analyzed by real-time PCR quantify expression of Heme oxygenase 1 (HMOX1), Superoxide Dismutase 2 (SOD2), and Nuclear factor (euthyroid-derived2)-like factor (NFE2L2). PCs were not altered between trials, but a time effect (13 % Post-2Hr increase, p = 0.044) indicated exercise-induced blood oxidative stress. Plasma LOOH revealed only a time effect (p = 0.041), including a 120 % Post-4Hr increase. TEAC values were elevated in normoxic recovery versus hypoxic recovery. FRAP values were higher 6Hr (p = 0.045) in normoxic versus hypoxic recovery. Exercise elevated gene expression of NFE2L2 (20 % increase, p = 0.001) and SOD2 (42 % increase, p = 0.003), but hypoxic recovery abolished this response. Data indicate that recovery in a hypoxic environment, independent of exercise, may alter exercise adaptations to oxidative stress and metabolism.

Acute hypoxia and exercise-induced blood oxidative stress.

Hypoxic exercise is characterized by workloads decrements. Because exercise and high altitude independently elicit redox perturbations, the study purpose was to examine hypoxic and normoxic steady-state exercise on blood oxidative stress. Active males (n = 11) completed graded cycle ergometry in normoxic (975 m) and hypoxic (3,000 m) simulated environments before programing subsequent matched intensity or workload steady-state trials. In a randomized counterbalanced crossover design, participants completed three 60-min exercise bouts to investigate the effects of hypoxia and exercise intensity on blood oxidative stress. Exercise conditions were paired as such; 60% normoxic VO(2)peak performed in a normoxic environment (normoxic intensity-normoxic environment, NI-NE), 60% hypoxic VO(2)peak performed in a normoxic environment (HI-NE), and 60% hypoxic VO(2)peak performed in a hypoxic environment (HI-HE). Blood plasma samples drawn pre (Pre), 0 (Post), 2 (2HR) and 4 (4HR) hr post exercise were analyzed for oxidative stress biomarkers including ferric reducing ability of plasma (FRAP), trolox equivalent antioxidant capacity (TEAC), lipid hydroperoxides (LOOH) and protein carbonyls (PCs). Repeated-measures ANOVA were performed, a priori significance of p ≤ .05. Oxygen saturation during the HI-HE trial was lower than NI-NE and HI-NE (p < .05). A Time × Trial interaction was present for LOOH (p = .013). In the HI-HE trial, LOOH were elevated for all time points post while PC (time; p = .001) decreased post exercise. As evidenced by the decrease in absolute workload during hypoxic VO(2)peak and LOOH increased during HI-HE versus normoxic exercise of equal absolute (HI-NE) and relative (NI-NE) intensities. Results suggest acute hypoxia elicits work decrements associated with post exercise oxidative stress.

Assessment of clinical depression metrics in cardiac patients using the patient health Questionnaire-9 before and after phase-II cardiac rehabilitation.

Cardiovascular disease remains a leading cause of morbidity and mortality, a fact that is commonly associated with co-morbidities such as clinical depression. While phase II cardiac rehabilitation is an established intervention for those with cardiovascular disease, its effect on patients who also suffer from depression are under studied. Aim: To quantify Pre- and Post-cardiac rehabilitation questionnaire scores collected from a large patient data registry. For this investigation, 27 â€‹670 patients completed Patient Health Questionnaire-9 questionnaires both Pre- and Post-rehabilitation (averaging [28.0 â€‹± â€‹8.7] phase II sessions). Findings reveal that questionnaire scores decreased by 40%-48% across all groups, a finding that was independent of assigned sex, race, and ethnicity. Moreover, when data were stratified for questionnaire scores that may indicate major and minor depressive disorder, phase II cardiac rehabilitation outcomes were lower by 61% and 49% respectively. While all groups exhibited lower questionnaire scores following cardiac rehabilitation participation, numerical differences at Pre- and Post-rehabilitation time points indicate that males and White patients have more favorable scores. This latter observation, while not confirmed currently, appears to be linked to referral rates to phase II cardiac rehabilitation, which remain poor for females, racial and ethnic minorities.