The beneficial role of exercise in mitigating doxorubicin-induced Mitochondrionopathy.

Doxorubicin (DOX) is a widely used antineoplastic agent for a wide range of cancers, including hematological malignancies, soft tissue sarcomas and solid tumors. However, DOX exhibits a dose-related toxicity that results in life-threatening cardiomyopathy. In addition to the heart, there is evidence that DOX toxicity extends to other organs. This general toxicity seems to be related to mitochondrial network structural, molecular and functional impairments. Several countermeasures for these negative effects have been proposed, being physical exercise, not only one of the most effective non-pharmacologic strategy but also widely recommended as booster against cancer-related fatigue. It is widely accepted that mitochondria are critical sensors of tissue functionality, both modulated by DOX and exercise. Therefore, this review focuses on the current understanding of the mitochondrial-mediated mechanisms underlying the protective effect of exercise against DOX-induced toxicity, not only limited to the cardiac tissue, but also in other tissues such as skeletal muscle, liver and brain. We here analyze recent developments regarding the beneficial effects of exercise targeting mitochondrial responsive phenotypes against redox changes, mitochondrial bioenergetics, apoptotic, dynamics and quality control signalling affected by DOX treatment.

Exercise and Doxorubicin Treatment Modulate Cardiac Mitochondrial Quality Control Signaling.

The cross-tolerance effect of exercise against heart mitochondrial-mediated quality control, remodeling and death-related mechanisms associated with sub-chronic Doxorubicin (DOX) treatment is yet unknown. We therefore analyzed the effects of two distinct chronic exercise models (endurance treadmill training-TM and voluntary free wheel activity-FW) performed during the course of the sub-chronic DOX treatment on mitochondrial susceptibility to permeability transition pore (mPTP), apoptotic and autophagic signaling and mitochondrial dynamics. Male Sprague-Dawley rats were divided into six groups (n = 6 per group): saline sedentary (SAL + SED), SAL + TM (12-weeks treadmill), SAL + FW (12-weeks voluntary free-wheel), DOX + SED [7-weeks sub-chronic DOX treatment (2 mg kg-1 week-1)], DOX + TM and DOX + FW. Apoptotic signaling and mPTP regulation were followed by measuring caspase 3, 8 and 9 activities, Bax, Bcl2, CypD, ANT, and cophilin expression. Mitochondrial dynamics (Mfn1, Mfn2, OPA1 and DRP1) and auto(mito)phagy (LC3, Beclin1, Pink1, Parkin and p62)-related proteins were semi-quantified. DOX treatment results in augmented mPTP susceptibility and apoptotic signaling (caspases 3, 8 and 9 and Bax/Bcl2 ratio). Moreover, DOX decreased the expression of fusion-related proteins (Mfn1, Mfn2, OPA1), increased DRP1 and the activation of auto(mito)phagy signaling. TM and FW prevented DOX-increased mPTP susceptibility and apoptotic signaling, alterations in mitochondrial dynamics and inhibits DOX-induced increases in auto(mito)phagy signaling. Collectively, our results suggest that both used chronic exercise models performed before and during the course of sub-chronic DOX treatment limit cardiac mitochondrial-driven apoptotic signaling and regulate alterations in mitochondrial dynamics and auto(mito)phagy in DOX-treated animals.

The influence of hyperbaric environment on the skeletal muscle mitochondrial energetic of rats after induced muscle contusion.

OBJECTIVE: Analyze the influence of the hyperbaric environment on skeletal muscle mitochondrial bioenergetic end-points of rats submitted to muscle contusion. METHODS: Twelve female Wistar rats were randomly assigned to three groups. All rats were submitted to muscle contusion in the right gastrocnemius through a standard protocol. The control group (C) remained under normobaric conditions without any treatment. The hyperbaric air (HB) and the hyperbaric oxygen (HBO2) groups had four sessions of HBO2 therapy 60 minutes, six, 12, 24 and 48 hours after the injury at 253.25 kPa (2.5 atmospheres absolute/ATA) with air or 100% oxygen, respectively. The animals were sacrificed 48 hours after muscle injury, and both muscles (injured and non-injured) were analyzed. Muscle mitochondrial bioenergetics and mitochondrial permeability transition pore (MPTP) susceptibility were evaluated. RESULTS: Significant differences were found in all parameters between the injured and the non-injured gastrocnemius in the C group. In the HB group, significantly better results concerning bioenergetics-related end points with complex I and II substrates where found in the right gastrocnemius, whereas in the HBO2 group the time to Vmax (time that elapsed until the faster swelling kinetics starts) was significantly higher and the swelling amplitude was significantly smaller than in other groups, which suggest a lower susceptibility to MPTP opening. CONCLUSION: The present data suggest that hyperbaric exposure, particularly with oxygen, positively modulates the efficiency of skeletal muscle mitochondria after muscle contusion.

Intermittent hypobaric hypoxia combined with aerobic exercise improves muscle morphofunctional recovery after eccentric exercise to exhaustion in trained rats.

Unaccustomed eccentric exercise leads to muscle morphological and functional alterations, including microvasculature damage, the repair of which is modulated by hypoxia. We present the effects of intermittent hypobaric hypoxia and exercise on recovery from eccentric exercise-induced muscle damage (EEIMD). Soleus muscles from trained rats were excised before (CTRL) and 1, 3, 7, and 14 days after a double session of EEIMD protocol. A recovery treatment consisting of one of the following protocols was applied 1 day after the EEIMD: passive normobaric recovery (PNR), a 4-h daily exposure to passive hypobaric hypoxia at 4,000 m (PHR), or hypobaric hypoxia exposure followed by aerobic exercise (AHR). EEIMD produced an increase in the percentage of abnormal fibers compared with CTRL, and it affected the microvasculature by decreasing capillary density (CD, capillaries per mm2) and the capillary-to-fiber ratio (CF). After 14 days, AHR exhibited CD and CF values similar to those of CTRL animals (789 and 3.30 vs. 746 and 3.06) and significantly higher than PNR (575 and 2.62) and PHR (630 and 2.92). Furthermore, VEGF expression showed a significant 43% increase in AHR when compared with PNR. Moreover, after 14 days, the muscle fibers in AHR had a more oxidative phenotype than the other groups, with significantly smaller cross-sectional areas (AHR, 3,745; PNR, 4,502; and PHR, 4,790 µm2), higher citrate synthase activity (AHR, 14.8; PNR, 13.1; and PHR, 12 µmol·min-1·mg-1) and a significant 27% increment in PGC-1α levels compared with PNR. Our data show that hypoxia combined with exercise attenuates or reverses the morphofunctional alterations induced by EEIMD.NEW & NOTEWORTHY Our study provides new insights into the use of intermittent hypobaric hypoxia combined with exercise as a strategy to recover muscle damage induced by eccentric exercise. We analyzed the effects of hypobaric exposure combined with aerobic exercise on histopathological features of muscle damage, fiber morphofunctionality, capillarization, angiogenesis, and the oxidative capacity of damaged soleus muscle. Most of these parameters were improved after a 2-wk protocol of intermittent hypobaric hypoxia combined with aerobic exercise.

Physical Exercise and Brain Mitochondrial Fitness: The Possible Role Against Alzheimer's Disease.

Exercise is one of the most effective strategies to maintain a healthy body and mind, with particular beneficial effects of exercise on promoting brain plasticity, increasing cognition and reducing the risk of cognitive decline and dementia in later life. Moreover, the beneficial effects resulting from increased physical activity occur at different levels of cellular organization, mitochondria being preferential target organelles. The relevance of this review article relies on the need to integrate the current knowledge of proposed mechanisms, focus mitochondria, to explain the protective effects of exercise that might underlie neuroplasticity and seeks to synthesize these data in the context of exploring exercise as a feasible intervention to delay cognitive impairment associated with neurodegenerative conditions, particularly Alzheimer disease.

Physical exercise mitigates doxorubicin-induced brain cortex and cerebellum mitochondrial alterations and cellular quality control signaling.

Doxorubicin (DOX) is a highly effective anti-neoplastic agent, whose clinical use is limited by a dose-dependent mitochondrial toxicity in non-target tissues, including the brain. Here we analyzed the effects of distinct exercise modalities (12-week endurance treadmill-TM or voluntary free-wheel activity-FW) performed before and during sub-chronic DOX treatment on brain cortex and cerebellum mitochondrial bioenergetics, oxidative stress, permeability transition pore (mPTP), and proteins involved in mitochondrial biogenesis, apoptosis and auto(mito)phagy. Male Sprague-Dawley rats were divided into saline-sedentary (SAL+SED), DOX-sedentary (DOX+SED; 7-week DOX (2 mg · kg(-1)per week)), DOX+TM and DOX+FW. Animal behavior and post-sacrifice mitochondrial function were assessed. Oxidative phosphorylation (OXPHOS) subunits, oxidative stress markers or related proteins (SIRT3, p66shc, UCP2, carbonyls, MDA, -SH, aconitase, Mn-SOD), as well as proteins involved in mitochondrial biogenesis (PGC1α and TFAM) were evaluated. Apoptotic signaling was followed through caspases 3, 8 and 9-like activities, Bax, Bcl2, CypD, ANT and cofilin expression. Mitochondrial dynamics (Mfn1, Mfn2, OPA1 and DRP1) and auto(mito)phagy (LC3II, Beclin1, Pink1, Parkin and p62)-related proteins were measured by semi-quantitative Western blotting. DOX impaired behavioral performance, mitochondrial function, including lower resistance to mPTP and increased apoptotic signaling, decreased the content in OXPHOS complex subunits and increased oxidative stress in brain cortex and cerebellum. Molecular markers of mitochondrial biogenesis, dynamics and autophagy were also altered by DOX treatment in both brain subareas. Generally, TM and FW were able to mitigate DOX-related impairments in brain cortex and cerebellum mitochondrial activity, mPTP and apoptotic signaling. We conclude that the alterations in mitochondrial biogenesis, dynamics and autophagy markers induced by exercise performed before and during treatment may contribute to the observed protective brain cortex and cerebellum mitochondrial phenotype, which is more resistant to oxidative damage and apoptotic signaling in sub-chronically DOX treated animals.

A semiquantitative scoring tool to evaluate eccentric exercise-induced muscle damage in trained rats.

Unaccustomed eccentric exercise is a well-documented cause of exercise-induced muscle damage. However, in trained subjects muscle injury involves only light or moderate tissue damage. Since trained rats are widely used as a model for skeletal muscle injury, here we propose a semiquantitative scoring tool to evaluate muscle damage in trained rats. Twenty male Sprague-Dawley rats were trained fortwo weeks following a two-week preconditioning period, and randomly divided into two groups: control rats (CTL; n=5) and rats with eccentric exercise-induced muscle damage (INJ; n=15). Injured rats were sacrificed at three time points: 1, 3 and 7 days post injury (n=5 each). Transverse sections from the right soleus were cut (10 µm) and stained with haematoxylin-eosin. Samples were evaluated by two groups of observers (four researchers experienced in skeletal muscle histopathology and four inexperienced) using the proposed tool, which consisted of six items organised in three domains: abnormal fibre morphology, necrotic/(re)degenerating fibres (muscle fibre domain), endomysial and perimysial infiltration (inflammatory state domain) and endomysium and perimysium distension (interstitial compartment domain). We observed the expected time course in the six evaluated items. Furthermore, agreement among observers was evaluated by measuring the Intraclass Correlation Coefficient (ICC). Within the experienced group, items from the muscle fibre and interstitial compartment domains showed good agreement and the two items from the infiltration compartment domain showed excellent agreement. in conclusion, the proposed tool allowed quick and correct evaluation of light to moderate muscle damage in trained rats with good agreement between observers.

Exercise modulates liver cellular and mitochondrial proteins related to quality control signaling.

AIMS: The effects of exercise on cardiac and skeletal muscle, including the increase on mitochondrial function, dynamics, biogenesis and autophagy signaling are well described. However, these same effects on liver mitochondria, important in the context of hepatocyte ability to mitigate drug-induced injury and obesity-related disorders, are not fully understood. Therefore, the effects of two distinct chronic exercise models (endurance training--ET and voluntary physical activity--VPA) on liver cellular and mitochondrial quality control were analyzed. MAIN METHODS: Eighteen male-adult Sprague-Dawley rats were divided into sedentary (SED), ET (12-week treadmill) and VPA (12-week voluntary free wheel). Liver mitochondrial alterations were evaluated by semi-quantification of proteins involved in oxidative stress (SIRT3, p66shc, p66(Ser36)), biogenesis (citrate synthase, PGC-1α and mtTFA), dynamics (MFN1, OPA1 and DRP1) and auto(mito)phagy (Beclin-1, Bcl-2, LC3II/LC3I, p62, Parkin and PINK) signaling. Liver ultrastructural alterations were also evaluated. KEY FINDINGS: Both exercise models induced beneficial alterations on liver mitochondrial morphology and increased mitochondrial biogenesis (PGC-1α and mtTFA), autophagy-related proteins (Beclin-1, LC3-II, LC3II/LC3I), and DRP1 and SIRT3 proteins. Increased citrate synthase activity and OPA1, p62 and Parkin content as well as decreased PINK protein levels were only observed after ET. VPA decreased OPA1, Beclin-1/Bcl-2, Parkin and p66(Ser36). Mitochondrial density and circularity increased in both exercised groups. SIGNIFICANCE: Both chronic exercise models increased proteins related with mitochondrial biogenesis and alteration proteins involved in mitochondrial dynamics and autophagy signaling, suggesting that exercise can induce liver mitochondrial adaptive remodeling and hepatocyte renewal.

Physical exercise improves brain cortex and cerebellum mitochondrial bioenergetics and alters apoptotic, dynamic and auto(mito)phagy markers.

We here investigate the effects of two exercise modalities (endurance treadmill training-TM and voluntary free-wheel activity-FW) on the brain cortex and cerebellum mitochondrial bioenergetics, permeability transition pore (mPTP), oxidative stress, as well as on proteins involved in mitochondrial biogenesis, apoptosis, and quality control. Eighteen male rats were assigned to sedentary-SED, TM and FW groups. Behavioral alterations and ex vivo brain mitochondrial function endpoints were assessed. Proteins involved in oxidative phosphorylation (OXPHOS, including the adenine nucleotide translocator), oxidative stress markers and regulatory proteins (SIRT3, p66shc, UCP2, carbonyls, MDA, -SH, aconitase, Mn-SOD), as well as proteins involved in mitochondrial biogenesis (PGC1α, TFAM) were evaluated. Apoptotic signaling was measured through quantifying caspase 3, 8 and 9-like activities, Bax, Bcl2, CypD, and cofilin expression. Mitochondrial dynamics (Mfn1/2, OPA1 and DRP1) and auto(mito)phagy (LC3II, Beclin1, Pink1, Parkin, p62)-related proteins were also measured by Western blotting. Only the TM exercise group showed increased spontaneous alternation and exploratory activity. Both exercise regimens improved mitochondrial respiratory activity, increased OXPHOS complexes I, III and V subunits in both brain subareas and decreased oxidative stress markers. Increased resistance to mPTP and decreased apoptotic signaling were observed in the brain cortex from TM and in the cerebellum from TM and FW groups. Also, exercise increased the expression of proteins involved in mitochondrial biogenesis, autophagy and fusion, simultaneous with decreased expression of mitochondrial fission-related protein DRP1. In conclusion, physical exercise improves brain cortex and cerebellum mitochondrial function, decreasing oxidative stress and apoptotic related markers. It is also possible that favorable alterations in mitochondrial biogenesis, dynamics and autophagy signaling induced by exercise contributed to increased mitochondrial plasticity leading to a more robust phenotype.

Role of physical exercise on hepatic insulin, glucocorticoid and inflammatory signaling pathways in an animal model of non-alcoholic steatohepatitis.

AIMS: Pro-inflammatory mediators, glucocorticoids and transforming growth factor (TGF)-ß are implicated in the pathogenesis of non-alcoholic steatohepatitis (NASH)-related insulin resistance. As physical activity is beneficial against NASH, we analyzed the voluntary physical activity (VPA) and endurance training (ET) (preventive and therapeutic strategies) effects on hepatic insulin, pro-inflammatory and glucocorticoid signaling regulators/mediators in high-fat (Lieber-DeCarli) diet (HFD)-induced NASH. MAIN METHODS: Adult male Sprague-Dawley rats were divided in standard diet (SD) or HFD, with sedentary, VPA and ET animals in both diet regimens. Plasma glucose and insulin concentrations were analyzed; plasma insulin sensitivity index (ISI) was calculated. Hepatic insulin, pro-inflammatory and glucocorticoid signaling regulators/mediators were evaluated by Western blot or reverse transcriptase-PCR. KEY FINDINGS: ET improved ISI in both diet regimens. HFD-feeding increased interleukin-1ß and induced a similar pattern on interleukin-6 and TGF-ß, which were globally reduced by physical exercise. ET decreased HFD leukemia inhibitory factor level, SD+VPA animals presenting higher values than HFD+VPA animals. HFD increased the ratio of IRS-1(Ser307)/total IRS-1, which was completely mitigated by physical exercise. Physical exercise reduced total ERK and JNK (total and activated) expression in HFD. In SD vs. HFD, VPA presented higher activated JNK and ET presented higher total JNK. Generally, in HFD, the ratio (activated/total) of AKT, and each separately, decreased with exercise and also for activated AKT in SD. Overall, in both diets, exercise reduced 11ß-hydroxysteroid dehydrogenase type 1. ET increased glucocorticoid receptor and reduced PTP1B in HFD. SIGNIFICANCE: Physical exercise mitigates the expression of pro-inflammatory mediators and positively modulates insulin and glucocorticoid signaling in NASH.

Modulation of cardiac mitochondrial permeability transition and apoptotic signaling by endurance training and intermittent hypobaric hypoxia.

BACKGROUND: Modulation of the mitochondrial permeability transition pore (MPTP) and inhibition of the apoptotic signaling are critically associated with the cardioprotective phenotypes afforded by both intermittent hypobaric-hypoxia (IHH) and endurance-training (ET). We recently proposed that IHH and ET improve cardiac function and basic mitochondrial capacity, although without showing addictive effects. Here we investigate whether a combination of IHH and ET alters cardiac mitochondrial vulnerability to MPTP and related apoptotic signaling. METHODS: Male Wistar rats were divided into normoxic-sedentary (NS), normoxic-exercised (NE, 1h/day/5 week treadmill-running), hypoxic-sedentary (HS, 6000 m, 5h/day/5 weeks) and hypoxic-exercised (HE) to study susceptibility to calcium-induced cardiac MPTP opening. Mitochondrial cyclophilin D (CypD), adenine nucleotide translocator (ANT), Bax and Bcl-2 protein contents were semi-quantified by Western blotting. Cardiac caspase 3-, 8- and 9-like activities were measured. Mitochondrial aconitase and superoxide dismutase (MnSOD) activity and malondialdehyde (MDA) and sulphydryl group (-SH) content were determined. RESULTS: Susceptibility to MPTP decreased in NE and HS vs. NS and even further in HE. The ANT content increased in HE vs. NS. Bcl-2/Bax ratio increased in NE and HS compared to NS. Decreased activities in tissue caspase 3-like (HE vs. NS) and caspase 9-like (HS and HE vs. NS) were observed. Mitochondrial aconitase increased in NE and HS vs. NS. No alterations between groups were observed for caspase 8-like activity, MnSOD, CypD, MDA and -SH. CONCLUSIONS: Data confirm that IHH and ET modulate cardiac mitochondria to a protective phenotype characterized by decreased MPTP induction and apoptotic signaling, although without visible addictive effects as initially hypothesized.

Synergistic impact of endurance training and intermittent hypobaric hypoxia on cardiac function and mitochondrial energetic and signaling.

BACKGROUND: Intermittent hypobaric-hypoxia (IHH) and endurance-training (ET) are cardioprotective strategies against stress-stimuli. Mitochondrial modulation appears to be an important step of the process. This study aimed to analyze whether a combination of these approaches provides additive or synergistic effects improving heart-mitochondrial and cardiac-function. METHODS: Two-sets of rats were divided into normoxic-sedentary (NS), normoxic-exercised (NE, 1 h/day/5 weeks treadmill-running), hypoxic-sedentary (HS, 6000 m, 5h/day/5 weeks) and hypoxic-exercised (HE) to study overall cardiac and mitochondrial function. In vitro cardiac mitochondrial oxygen consumption and transmembrane potential were evaluated. OXPHOS subunits and ANT protein content were semi-quantified by Western blotting. HIF-1α, VEGF, VEGF-R1 VEGF-R2, BNP, SERCA2a and PLB expressions were measured by qRT-PCR and cardiac function was characterized by echocardiography and hemodynamic parameters. RESULTS: Respiratory control ratio (RCR) increased in NE, HS and HE vs. NS. Susceptibility to anoxia/reoxygenation-induced dysfunction decreased in NE, HS and HE vs. NS. HS decreased mitochondrial complex-I and -II subunits; however HE completely reverted the decreased content in complex-II subunits. ANT increased in HE. HE presented normalized ventricular-arterial coupling (Ea) and BNP myocardial levels and significantly improved myocardial performance as evaluated by increased cardiac output and normalization of the Tei index vs. HS CONCLUSION: Data demonstrates that IHH and ET confer cardiac mitochondria with a more resistant phenotype although without visible addictive effects at least under basal conditions. It is suggested that the combination of both strategies, although not additive, results into improved cardiac function.

Breath tests with novel 13C-substrates for clinical studies of liver mitochondrial function in health and disease.

Mitochondrial dysfunction determines the onset and progression of chronic deleterious conditions including liver diseases. The in vivo assessment of mitochondrial function, by providing more insight into the pathogenesis of liver diseases, would be a helpful tool to study specific functions and to develop diagnostic, prognostic and therapeutic strategies. The application of breath tests in the clinical setting to evaluate mitochondrial fitness may elegantly and noninvasively overcome the difficulties due to previous complex techniques and may provide clinically relevant information, i.e the effects of drugs presenting mitochondrial liabilities. Substrates meeting this requirement include alpha-ketoisocaproic acid and methionine, both decarboxylated by mitochondria. Long and medium chain fatty acids that are metabolized through the Krebs cycle and benzoic acid, which undergoes glycine conjugation, may also reflect the mitochondrial performance. This review focuses on the utility of breath tests to assess mitochondrial function in humans, thus contributing to unravel potential mechanisms associated with the dysfunction of this organelle network in the pathophysiology of liver diseases.

Endurance training and chronic intermittent hypoxia modulate in vitro salicylate-induced hepatic mitochondrial dysfunction.

Mitochondrial function is modulated by multiple approaches including physical activity, which can afford cross-tolerance against a variety of insults. We therefore aimed to analyze the effects of endurance-training (ET) and chronic-intermittent hypobaric-hypoxia (IHH) on liver mitochondrial bioenergetics and whether these effects translate into benefits against in vitro salicylate mitochondrial toxicity. Twenty-eight young-adult male rats were divided into normoxic-sedentary (NS), normoxic-exercised (NE), hypoxic-sedentary (HS) and hypoxic-exercised (HE). ET consisted of 1h/days of treadmill running and IHH of simulated atmospheric pressure of 49.3 kPa 5h/days during 5weeks. Liver mitochondrial oxygen consumption, transmembrane-electric potential (ΔΨ) and permeability transition pore induction (MPTP) were evaluated in the presence and absence of salicylate. Aconitase, MnSOD, caspase-3 and 8 activities, SH, MDA, SIRT3, Cyp D, HSP70, and OXPHOS subunit contents were assessed. ET and IHH decreased basal mitochondrial state-3 and state-4 respiration, although no alterations were observed in ΔΨ endpoints evaluated in control mitochondria. In the presence of salicylate, ET and IHH decreased state-4 and lag-phase of ADP-phosphorylation. Moreover, ADP-lag phase in hypoxic was further lower than in normoxic groups. Neither ET nor IHH altered the susceptibility to calcium-induced MPTP. IHH lowered MnSOD and increased aconitase activities. ET and IHH decreased caspase 8 activity whereas no effect was observed on caspase 3. The levels of SIRT3 increased with ET and IHH and Cyp D decreased with IHH. Data suggest that ET and IHH do not alter general basal liver mitochondrial function, but may attenuate some adverse effects of salicylate.

In vitro salicylate does not further impair aging-induced brain mitochondrial dysfunction.

Aging and drug-induced side effects may contribute to the deterioration of mitochondrial bioenergetics in the brain. One hypothesis is that the combination of both deleterious stimuli accelerates the process of mitochondrial degradation, leading to progressive bioenergetic disruption. The hypothesis was tested by analyzing the isolated and combined effect of aging and salicylate, a vastly used anti-inflammatory drug, on isolated brain fractions in rats. Male Wistar rats were divided according to age in two groups: adult (n=8, 19 weeks of age) and aged (n=8, 106 weeks of age). In vitro endpoints of brain mitochondrial function including oxygen consumption and transmembrane electric potential (ΔΨ) were evaluated in the absence and in the presence of salicylate (0.5mM). Brain mitochondrial susceptibility to calcium-induced permeability transition pore (MPTP) was also assessed. Mitochondrial oxidative stress was determined by measuring aconitase and manganese-superoxide dismutase (SOD) activity, and content in sulfhydryl groups (SH) and malondialdehyde (MDA). Mitochondrial content in apoptotic-related proteins Bax, Bcl-2 and cyclophilin D was determined by Western Blotting. Under basal, untreated, conditions, aging affected brain mitochondrial state 3 respiration, maximal ΔΨ developed, ADP phosphorylation lag phase and calcium-induced MPTP. Interestingly, MDA decreased and Mn-SOD activity increased in the aged group. Brain mitochondrial Bcl-2 content decreased and Bax/Bcl-2 ratio increased in aged group. Salicylate incubation for 20min increased lipid peroxidation in the aged group only and stimulated respiration during state 2, accompanied by decreased ΔΨ, although both effects were independent of the animal age. We confirmed that both aging and salicylate per se impaired brain mitochondrial bioenergetics, although the combination of both does not seem to worsen the mitochondrial end-points studied.

Physiological and neuromuscular impact of beach-volleyball with reference to fatigue and recovery.

AIM: The aim of the present study was to analyze the physiological and neuromuscular impact of a one 3-set beach-volleyball match and to analyze the ability of the players to recover from fatigue. METHODS: Heart rate (HR) and blood lactate concentration (BLC) were measured in sixteen Portuguese male elite volleyball players during beach-volleyball matches. Vertical countermovement jump (CMJ), sprint (7.5 and 15m) ability and maximal isometric voluntary contraction (MIVC) were evaluated at baseline, immediately (0h) and 3 hours after each match. RESULTS: Mean HR during the match was 146 ± 3 bpm (117 ± 2-185 ± 3 bpm) corresponding to about 75% of HRmax (61-90%HRmax). Players spent 34% of match time above 80% HRmax. BLC during the 3-sets increased from rest (0.95 ± 0.23 vs. 2.10 ± 0.66 [1st-set] vs. 2.41 ± 0.15 [2nd-set] vs. 2.39 ± 0.21mM [3rd-set]). No changes in CMJ were observed at 0 and 3h. Knee extensor and flexor muscles MIVC decreased at 0h (~19 and 17%, respectively) and returned to baseline 3h after. Sprint performance was the only variable that was impaired both at 0h and 3h after the match (~3%). CONCLUSION: Beach-volleyball is performed intermittently at moderate-to-high intensity with brief bouts of high intensity exercise interspersed by long low intensity periods. Match induced a temporary reduction in lower limb strength and sprinting time but 3h after the match all variables with the exception of the sprinting time, that was only slightly reduced, were recovered.

Physiological, biochemical and functional changes induced by a simulated 30 min off-road competitive motocross heat.

AIM: Up to now, few studies regarding the impact of motocross heats on functional and physiological variables have been addressed so far. The aim of the present study was to analyze physiological and functional changes induced by a simulated off-road motocross heat. METHODS: Fifteen motocross riders (28.3+/-7.9 yrs; 71.1+/-7.0 kg; 169.0+/-4.0 cm; 53.5+/-3.7 mL.kg(-1).min(-1); 14.9+/-3.3% fat) performed one treadmill running to exhaustion to determine maximal heart rate (HRmax) and maximal oxygen consumption. Thereafter, simulated 30 min competitive off-road motocross heats were performed to measure biochemical (blood lactate and urine catecholamine concentrations) and functional (upper-limb power and fatigue--Wingate and Handgrip) alterations induced by the race. Exercise intensity through HR monitoring, rating of perceived exertion and upper-limb pain were also accomplished. RESULTS: During the 30 min heats, the riders spent 87% of time above 90% of their HRmax. Significant impairments were observed on maximal isometric handgrip as well as on Wingate variables after the race. Blood lactate concentrations significantly increased from rest vs 10 min, 20 min and final time of analysis (P < 0.05). However, a significant decrease was observed between 10 min vs 20 min and final of the race. A significant increase in the 24-h urine catecholamine levels was observed after the race. CONCLUSION: The present data suggest that motocross heats are performed at high exercise intensity. Motocross specific effort induces significant functional alterations that may reflect muscle fatigue with consequent decrement on physical performance.

Slow component of VO(2) during level and uphill treadmill running: relationship to aerobic fitness in endurance runners.

AIM: The aim of this study was to compare the oxygen uptake (VO(2)) slow component (SC) during level and uphill running in endurance runners, and to identify associations between the SC and the following aerobic fitness indicators: peak VO(2), running speed associated with the peak VO(2) (Vpeak), running speed at the lactic threshold and the VO(2) fraction elicited at the lactic threshold. METHODS: Fourteen male endurance-trained runners underwent several 6-min bouts of level (LTR) and 10.5% uphill treadmill running. VO(2) SC was calculated as the difference between mean VO(2) during the 6th and the 3rd minutes. RESULTS: The highest mean values for the SC were 181.9+/-240.2 mL x min(-1) for level running at approximately 94% peak VO(2)2 and 105.4+/-154.6 mL x min(-1) for uphill running at approximately 90% peak VO(2). The SC observed during the last bout of the LTR correlated with peak VO(2) and with Vpeak (-0.71 and -0.76, P<0.05, respectively). CONCLUSION: The results show that for endurance-trained runners the magnitude of the SC is not affected by the treadmill gradient and that within a homogeneous sample of endurance-trained runners the SC does not correlate with indicators of aerobic fitness.

Hemostatic response to acute physical exercise in healthy adolescents.

The chronic and immediate post-exercise responses in the hemostatic and fibrinolytic systems have been shown to be variable and reflect differing adaptations with ageing and responses to exercise protocols. This study investigated the effects of acute and exhaustive exercise on the amplitude and duration of hemostatic and fibrinolytic responses in young adolescent males. The sample comprised 10 sedentary boys (13.2+/-0.5 years, 55.8+/-11.3kg, 165.7+/-7.4cm), who had not exercised or received any medication for at least 2 weeks before the experiments. The subjects performed exhaustive stepping exercise, consisting of 1s up and down cycles to fatigue. When the subjects were unable to maintain the required stepping rhythm, they were given a 30s recovery period. Following each 30s recovery participants recommenced the stepping cadence until fatigue prevented them continuing. Venous blood samples were drawn before and immediately, 1 and 24h after exercise to assess the following coagulation and fibrinolytic parameters: Platelet counts, activated partial thromboplastin time (aPTT), prothrombin time (PT), coagulation factor VIII (FVIII:C), von Willebrand factor (vWF), fibrinogen concentration, thrombin-antithrombin complex (TAT), D-dimer, plasminogen activator inhibitor (PAI-1), and tissue-type plasminogen activator (t-PA). Immediately following exercise, platelet counts, aPTT, FVIII, vWF and t-PA were significantly elevated in contrast to PAI-1, which decreased significantly until 1h after exercise. FVIII and platelet counts were elevated at 1 and 24h after exercise, respectively. Only the parameters FVIII and PAI-1 did not return to baseline values during the first hour after physical exercise. When compared to adults the results revealed different rates and ranges of coagulation and fibrinolysis parameters being activated by exhaustive exercise in this group of adolescents.

Relationship between physical activity and obesity in children and adolescents.

AIM: The purpose of the present study was to analyze the relationship between physical activity (PA) and obesity in Portuguese children and adolescents. METHODS: The sample consisted of 1341 children and adolescents (8-15 years of age), 634 males (age, 10.6+/-2.3 y; body mass, 40.6+/-12.7 kg; height, 1.431+/-1.41 m) and 707 females (age, 10.9+/-2.4 y; body mass, 50+/-12.4 kg; height, 1.428+/-1.32 m). The sample was divided into quartiles of percentage of body fat (%BF) and physical activity index (PAI), within age and gender. Children in the upper %BF quartile were defined as obese (arbitrary definition). Logistic regression for each PAI quartile was used to determine the odds ratio of obese children and adolescents (> or = P75 of %BF) in comparison to their non-obese counterparts (< P75 of %BF). RESULTS: Males in the lowest PAI quartile have an odds ratio of 2.1 of having obesity in relation to males in the highest PAI quartile. For females any significant result was found between PAI quartiles. CONCLUSIONS: The results obtained in this study add some data to the controversy of PA and obesity relationship youth. Logistical regression shows that males who have a lower PAI have an odds ratio of 2.1 of obesity, in comparison with males that have higher PAI. Those findings were not found in girls.