Mitochondrial function after associating liver partition and portal vein ligation for staged hepatectomy in an experimental model.

BACKGROUND: Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) is a two-stage strategy to induce rapid regeneration of the remnant liver. The technique has been associated with high mortality and morbidity rates. This study aimed to evaluate mitochondrial function, biogenesis and morphology during ALPPS-induced liver regeneration. METHODS: Male Wistar rats (n = 100) underwent portal vein ligation (PVL) or ALPPS. The animals were killed at 0 h (without operation), and 24, 48, 72 or 168 h after intervention. Regeneration rate and proliferation index were assessed. Mitochondrial oxygen consumption and adenosine 5'-triphosphate (ATP) production were measured. Mitochondrial biogenesis was evaluated by protein level measurements of peroxisome proliferator-activated receptor γ co-activator (PGC) 1-α, nuclear respiratory factor (NRF) 1 and 2, and mitochondrial transcription factor α. Mitochondrial morphology was evaluated by electron microscopy. RESULTS: Regeneration rate and Ki-67 index were significantly raised in the ALPPS group compared with the PVL group (regeneration rate at 168 h: mean(s.d.) 291·2(21·4) versus 245·1(13·8) per cent, P < 0·001; Ki-67 index at 24 h: 86·9(4·6) versus 66·2(4·9) per cent, P < 0·001). In the ALPPS group, mitochondrial function was impaired 48 h after the intervention compared with that in the PVL group (induced ATP production); (complex I: 361·9(72·3) versus 629·7(165·8) nmol per min per mg, P = 0·038; complex II: 517·5(48·8) versus 794·8(170·4) nmol per min per mg, P = 0·044). Markers of mitochondrial biogenesis were significantly lower 48 and 72 h after ALPPS compared with PVL (PGC1-α at 48 h: 0·61-fold decrease, P = 0·045; NRF1 at 48 h: 0·48-fold decrease, P = 0·028). Mitochondrial size decreased significantly after ALPPS (0·26(0·05) versus 0·40(0·07) µm2 ; P = 0·034). CONCLUSION: Impaired mitochondrial function and biogenesis, along with the rapid energy-demanding cell proliferation, may cause hepatocyte dysfunction after ALPPS. Surgical relevance Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) is a well known surgical strategy that combines liver partition and portal vein ligation. This method induces immense regeneration in the future liver remnant. The rapid volume increase is of benefit for resectability, but the mortality and morbidity rates of ALPPS are strikingly high. Moreover, lagging functional recovery of the remnant liver has been reported recently. In this translational study, ALPPS caused an overwhelming inflammatory response that interfered with the peroxisome proliferator-activated receptor γ co-activator 1-α-coordinated, stress-induced, mitochondrial biogenesis pathway. This resulted in the accumulation of immature and malfunctioning mitochondria in hepatocytes during the early phase of liver regeneration (bioenergetic destabilization). These findings might explain some of the high morbidity if confirmed in patients.

Correlations of psycho-physiological parameters influencing the physical fitness of aged women.

Regular assessment of psycho-physiological parameters in aged subjects helps to clarify physical and mental conditions which are important in the prevention of health-endangering events to assure a healthy aging. Thirty older care female residents consented voluntarily to participate in the study. The somatic and psycho-physiological parameters recorded were handgrip force, disjunctive reaction time, balance control and whole body movement coordination, the electrocardiogram and heart rate variability. Significant correlations were found between (a) reaction time and balance control efficiency (r = -0.567, p < 0.009), (b) reaction time and movement coordination accuracy (r = -0.453, p < 0.045), (c) cardiac state and movement coordination accuracy (r = 0.545, p < 0.016), (d) cardiac stress and cardiac state (r = -0.495, p < 0.031), and (e) cardiac stress and force (r = -0.822, p < 0.045). In conclusion, for the aim of establishing basic battery tests for assessing psycho-physiological condition of physical fitness our results emphasize the importance of systematic physical activity, endurance and strength training supporting muscle force, balance control and whole-body movement coordination, in addition to improving the cardiac stress index level. The strong interrelation among these parameters allows the drawing of a more complete view regarding the health condition of aged individuals.

The redox-associated adaptive response of brain to physical exercise.

Reactive oxygen species (ROS) are continuously generated during metabolism. ROS are involved in redox signaling, but in significant concentrations they can greatly elevate oxidative damage leading to neurodegeneration. Because of the enhanced sensitivity of brain to ROS, it is especially important to maintain a normal redox state in brain and spinal cord cell types. The complex effects of exercise benefit brain function, including functional enhancement as well as its preventive and therapeutic roles. Exercise can induce neurogenesis via neurotrophic factors, increase capillarization, decrease oxidative damage, and enhance repair of oxidative damage. Exercise is also effective in attenuating age-associated loss in brain function, which suggests that physical activity-related complex metabolic and redox changes are important for a healthy neural system.

Aerobic endurance capacity affects spatial memory and SIRT1 is a potent modulator of 8-oxoguanine repair.

Regular exercise promotes brain function via a wide range of adaptive responses, including the increased expression of antioxidant and oxidative DNA damage-repairing systems. Accumulation of oxidized DNA base lesions and strand breaks is etiologically linked to for example aging processes and age-associated diseases. Here we tested whether exercise training has an impact on brain function, extent of neurogenesis, and expression of 8-oxoguanine DNA glycosylase-1 (Ogg1) and SIRT1 (silent mating-type information regulation 2 homolog). To do so, we utilized strains of rats with low- and high-running capacity (LCR and HCR) and examined learning and memory, DNA synthesis, expression, and post-translational modification of Ogg1 hippocampal cells. Our results showed that rats with higher aerobic/running capacity had better spatial memory, and expressed less Ogg1, when compared to LCR rats. Furthermore, exercise increased SIRT1 expression and decreased acetylated Ogg1 (AcOgg1) levels, a post-translational modification important for efficient repair of 8-oxo-7,8-dihydroguanine (8-oxoG). Our data on cell cultures revealed that nicotinamide, a SIRT1-specific inhibitor, caused the greatest increase in the acetylation of Ogg1, a finding further supported by our other observations that silencing SIRT1 also markedly increased the levels of AcOgg1. These findings imply that high-running capacity is associated with increased hippocampal function, and SIRT1 level/activity and inversely correlates with AcOgg1 levels and thereby the repair of genomic 8-oxoG.

Does exercise reduce brain oxidative stress? A systematic review.

The aim of the present systematic review was to investigate the influence of different exercise programs on brain oxidative stress. A search of the literature was conducted up to 1 December 2012 across five databases: PUBMED, SCOPUS, SPORTS DISCUS, Web of Science, and The Cochrane Library. The search strategy used in the electronic databases mentioned was established as: (swim* OR exercise OR training) AND ("oxidative stress" AND brain) for each database. A methodological quality assessment valuation/estimation was additionally carried out in the final sample of studies. Of 1553 potentially eligible papers, 19 were included after inclusion and exclusion criteria. The methodological quality assessment showed a total score in the Quality Index between 40% and 80%, with a mean quality of 56.8%. Overall, regular moderate aerobic exercise appears to promote antioxidant capacity on brain. In contrast, anaerobic or high-intensity exercise, aerobic-exhausted exercise, or the combination of both types of training could deteriorate the antioxidant response. Future investigations should be focused on establishing a standardized exercise protocol, depending on the exercise metabolism wanted to test, which could enhance the objective knowledge in this topic.

Long-term exercise treatment reduces oxidative stress in the hippocampus of aging rats.

Exercise can exert beneficial effects on cognitive functions of older subjects and it can also play an important role in the prevention of neurodegenerative diseases. At the same time it is perceivable that limited information is available on the nature of molecular pathways supporting the antioxidant effects of exercise in the brain. In this study 12-month old, middle-aged female Wistar rats were subjected to daily moderate intensity exercise on a rodent treadmill for a period of 15weeks which covered the early aging period unmasking already some aging-related molecular disturbances. The levels of reactive oxygen species (ROS), the amount of protein carbonyls, the levels of antioxidant intracellular enzymes superoxide dismutases (SOD-1, SOD-2) and glutathione peroxidase (GPx) were determined in the hippocampus. In addition, to identify the molecular pathways that may be involved in ROS metabolism and mitochondrial biogenesis, the activation of 5'-AMP-activated protein kinase (AMPK), the protein level of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (mtTFA) were measured. Our results revealed a lower level of ROS associated with a reduced amount of protein carbonyls in the hippocampus of physically trained rats compared to sedentary controls. Furthermore, exercise induced an up-regulation of SOD-1 and GPx enzymes, p-AMPK and PGC-1α, that can be related to an improved redox balance in the hippocampus. These results suggest that long-term physical exercise can comprises antioxidant properties and by this way protect neurons against oxidative stress at the early stage of aging.

Brain-derived neurotrophic factor treatment increases the skeletal muscle glucose transporter 4 protein expression in mice.

The purpose of the present study was to investigate whether peripheral brain-derived neurotrophic factor (BDNF) treatment induced metabolic adaptations in mouse skeletal muscle. BDNF (20 mg/kg/day) was injected subcutaneously for successive 14 days. BDNF treatment significantly reduced the total food intake and inhibited the weight gain in comparison to the control group. The glucose transporter 4 (GLUT4) protein expression in the gastrocnemius muscle was significantly increased by BDNF treatment in comparison to the control and pair-fed groups. Neither the oxidative nor the glycolytic enzyme activities in the gastrocnemius muscle changed after the BDNF treatment. These results suggest that the peripheral BDNF treatment promotes the skeletal muscle GLUT4 protein expression as well as hypophagia.

The effect of exercise and oxidant-antioxidant intervention on the levels of neurotrophins and free radicals in spinal cord of rats.

STUDY DESIGN: This study was designed to investigate the effects of oxidant and antioxidant treatment, as well as regular exercise, on neurotrophin levels in the spinal cord of rats. OBJECTIVES: Reactive oxygen species (ROS) play a role in neurodegenerative diseases, but ROS at moderate levels could stimulate biochemical processes through redox-sensitive transcription. METHODS: Exercised or sedentary animals were injected subcutaneously with hydrogen peroxide (H(2)O(2)), N-tert butyl-alpha-phenyl nitrone (PBN) or saline for the last 2 weeks of a 10-week experimental period to challenge redox balance. Free radical (FR) concentration was evaluated in the spinal cord by electron spin resonance, protein carbonyls, brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) levels and the mRNA expression of BDNF receptor and tyrosine kinase receptor B (TrKB). SETTING: Research Institute of Sport Science, Semmelweis University, Budapest, Hungary. RESULTS: Exercise or PBN decreased the concentration of FR, whereas the carbonyl content did not change. BDNF was significantly decreased in exercised sham and sedentary PBN-treated groups, and its content correlated with the level of FR. GDNF was significantly increased in sedentary H(2)O(2)-treated groups. No differences were observed in TrkB mRNA expression among groups. CONCLUSIONS: Results suggest that regular exercise alone and PBN in sedentary animals can successfully decrease FR levels in the spinal cord. Redox alteration seems to affect the levels of GDNF and BDNF, which might have clinical consequences, as neurotrophins play an important role in cellular resistance and regeneration.

Effect of diazepam treatment on metabolic indices in trained and untrained rats.

Exercise training, like diazepam, is commonly employed as a means of reducing anxiety. Both diazepam and exercise training have been shown to modify carbohydrate and lipid metabolism as well as influence calcium metabolism in skeletal muscle. As receptor binding and thereby efficacy of diazepam has been demonstrated to be modulated by the lipid environment of the receptor, and changes in calcium levels can affect a number of intracellular signalling pathways, we sought to determine if the interaction of both chronic diazepam and exercise training would modify selected metabolic indices in an animal model. For this purpose, muscle and liver glycogen, blood glucose and plasma free fatty acids (FFA) were measured in sedentary, exercise trained and exercise trained, acutely exhausted animals. Alterations in lipid and carbohydrate metabolism were observed in all experimental groups. Diazepam treatment alone exerts metabolic consequences, such as elevated muscle glycogen and plasma FFA and depressed blood glucose levels, which are similar to those observed with exercise training. When animals are acutely exercised to exhaustion, however, differences appear, including a reduced rise in plasma FFA, which suggests that long-term diazepam treatment does influence exercise metabolism, possibly as a result of effects on the sympatho-adrenal system.

Super-marathon race increases serum and urinary nitrotyrosine and carbonyl levels.

BACKGROUND: In normal conditions, proteins are not present in the urine, however, exercise of long duration could result in proteinurea. Increased levels of reactive oxygen and nitrogen species (RONS) are formed during exhaustive physical exercise and causes alterations to cellular proteins. MATERIALS: In the present study serum and urinary nitrotyrosine and protein carbonyl levels were measured before and after each run of a 4-day super-marathon race. RESULT: Serum nitrotyrosine and protein carbonyl levels increased after the first (93 km) day running and reached a plateau on the second (120 km), third (56 km) and forth (59 km) days of the competition. A significant correlation was found between urinary and serum protein carbonyl and nitrotyrosine levels (r=0.78, r=0.71, respectively). A large percentage of urinary proteins were carbonylated and nitrated. Therefore, it appears that clearance of oxidized proteins in certain conditions occurs not only by the proteolytic pathways but also by filtration and urination. CONCLUSION: Data reveals that exhaustive aerobic exercise causes oxidative stress and increases the nitration and carbonylation of serum proteins. The presence of carbonyl and nitrotyrosine in proteins of the urine might reflect oxidative stress and could serve as a noninvasive diagnostic tool for exercise physiology.

Optimized biogas-fermentation by neural network control.

In this work several feed-forward back-propagation neural networks (FFBP) were trained in order to model, and subsequently control, methane production in anaerobic digesters. To produce data for the training of the neural nets, four anaerobic continuous stirred tank reactors (CSTR) were operated in steady-state conditions at organic loading rates (Br) of about 2 kg x m(-3) x d(-1) chemical oxygen demand (COD), and disturbed by pulse-like increase of the organic loading rate. For the pulses additional carbon sources were added to the basic feed (surplus- and primary sludge) to simulate cofermentation and to increase the COD. Measured parameters were: gas composition, methane production rate, volatile fatty acid concentration, pH, redox potential, volatile suspended solids and COD of feed and effluent. A hierarchical system of neural nets was developed and embedded in a Decision Support System (DSS). A 3-3-1 FFBP simulated the pH with a regression coefficient of 0.82. A 9-3-3 FFBP simulated the volatile fatty acid concentration in the sludge with a regression coefficient of 0.86. And a 9-3-2 FFBP simulated the gas production and gas composition with a regression coefficient of 0.90 and 0.80 respectively. A lab-scale anaerobic CSTR controlled by this tool was able to maintain a methane concentration of about 60% at a rather high gas production rate of between 5 to 5.6 m3 x m(-3) x d(-1).

Adaptation to exercise-induced oxidative stress: from muscle to brain.

Exercise increases the generation of reactive oxygen and nitrogen species (RONS) and by causing adaptation, could decrease the incidence of RONS-associated diseases. A single bout of exercise, depending upon intensity and duration, can cause an increase in antioxidant enzyme activity, decrease levels of thiols and antioxidant vitamins, and result in oxidative damage as a sign of incomplete adaptation. Increased levels of RONS and oxidative damage are initiators of a specific adaptive response, such as the stimulation of the activation of antioxidant enzymes, thiols, and enhanced oxidative damage repair. Regular exercise has the capability to develop compensation to oxidative stress, resulting in overcompensation against the increased level of RONS production and oxidative damage. Regular exercise causes adaptation of the antioxidant and repair systems, which could result in a decreased base level of oxidative damage and increased resistance to oxidative stress.

Telomerase activity is not altered by regular strenuous exercise in skeletal muscle or by sarcoma in liver of rats.

Telomerase is a specialized ribonucleoprotein enzyme complex which prevents the loss of the telomere. The activity of telomerase can be up- and down-regulated by various oxidative stresses but the effect of physical exercise is not known, whereas the modifying effect of cancer on telomerase activity is well documented. In the first study, we investigated the effect of mild and strenuous exercise training on telomerase activity, assessed by a PCR ELISA kit. No alteration in telomerase activity was detected. In the second investigation, solid sarcoma cells were transplanted to control, exercise trained or exercise trained and still exercising mice. On the 16th day after the transplantation, the size of tumors in the exercise trained group was 72% and in the exercising group 57% (P < 0.05) of that in the controls. Telomerase activity and 8-hydroxy-2'-deoxyguanosine levels in the liver were not significantly altered by exercise and/or sarcoma. We conclude that mild and strenuous exercise training does not significantly affect the activity of telomerase in the systems studied. Exercise training during sarcoma significantly retards the development of tumors and could possibly serve as a positive adjunct to treatment.

Single bout of exercise eliminates the immobilization-induced oxidative stress in rat brain.

We were interested in the effects of immobilization (IM), a single bout of exercise (E) and immobilization followed by exercise (EIM) on memory and oxidative damage of macromolecules in hippocampus of rat brain. Eight hours of IM resulted in impairment of passive avoidance test (memory retrieval deficit) and increased latency to start locomotion in an open-field test. Two hours of swimming did not significantly alter the memory retrieval deficit and latency, while the EIM group had longer latency and similar memory than control and E groups. The oxidative damage of lipids, proteins and nuclear DNA increased significantly in IM group and no increase was observed in E and EIM animals. The activity of proteasome was not altered in any groups. The activity of glutamine synthetase (GS) was decreased in IM group (P < 0.05), this down regulation was not observed in E and EIM groups. These data suggest that oxidative damage of macromolecules is associated with impaired cognitive function. Single bout of exercise after immobilization eliminates the oxidative damage of macromolecules and normalizes memory function, probably by its ability to restore the activity level of GS and eliminate the consequences of immobilization-induced prolonged efflux of glutamate.

Implications of protein degradation in aging.

Aging is characterized by accumulation of potentially harmful altered proteins that could lead to gradual deterioration of cellular functions and eventually result in increased probability of death. Metabolic turnover of proteins thus plays an essential role in maintaining the life of an organism. In this article we summarize our current knowledge on age-related changes in protein turnover with special reference to degradation. Increase in half-life of proteins with advancing age is well documented. Qualitative rather than quantitative changes of proteasomes appear to be responsible for this change. Dietary restriction and moderate long-term exercise seem to restore higher proteasome activity and turnover rate of proteins in aged animals.

Regular exercise improves cognitive function and decreases oxidative damage in rat brain.

The biochemical mechanisms by which regular exercise significantly benefits health and well being, including improved cognitive function, are not well understood. Four-week-old (young) and 14-month-old (middle aged) Wistar rats were randomly assigned to young control and young exercised, middle-aged control and middle-aged exercised groups. Exercise groups were exposed to a swimming regime of 1 h a day, 5 days a week for 9 weeks. The passive avoidance test showed that middle-aged exercised rats had significantly (P<0.05) better short- (24 h) and long-term (72 h) memory than aged-matched control rats. Conditioned pole-jumping avoidance learning was improved markedly in both age groups by exercise. Brain thiobarbituric acid-reactive substances and 8-hydroxy-2'deoxyguanosine content in the DNA did not change significantly, while the protein carbonyl levels decreased significantly (P<0.05) in both exercised groups. This decrease was accompanied by an increase in the chymotrypsin-like activity of proteasome complex in the exercised groups, whereas trypsin-like activity did not differ significantly between all groups. The DT-diaphorase activity increased significantly (P<0.05) in the brain of young exercised animals. These data show that swimming training improves some cognitive functions in rats, with parallel attenuation of the accumulation of oxidatively damaged proteins.

Regular training modulates the accumulation of reactive carbonyl derivatives in mitochondrial and cytosolic fractions of rat skeletal muscle.

The oxygen flux into the mitochondria of skeletal muscle increases with exercise. However, the extent of oxidative damage to mitochondrial proteins of skeletal muscle has only been estimated. We studied the alteration of reactive carbonyl derivatives (RCD) in mitochondrial and cytosolic fractions of skeletal muscle following 9 weeks of swimming training in rats. The RCD content of mitochondria was significantly elevated compared with the cytosolic fraction of both control and exercised animals. Accumulation of RCD in muscle mitochondria of the exercised group was also significantly elevated (P < 0.05). On the other hand, alteration of the accumulation of RCD was not apparent in the cytosolic fraction of skeletal muscle. The activity of proteasome complex, however, was increased in the cytosolic fraction of exercised muscle (P < 0.05). The data suggest that mitochondria of skeletal muscle accumulate significantly larger amounts of RCD than the cytosolic fraction and the tendency of the accumulation varies in cell fractions. Exercise training increases the accumulation of protein damage in mitochondria of skeletal muscle but cytosolic proteins are protected by increased activity of proteasome complex and possibly by other antioxidant enzymes.

Changes in urine 8-hydroxydeoxyguanosine levels of super-marathon runners during a four-day race period.

We have determined the urinary 8-hydroxydeoxyguanosine (8-OHdG) levels of five well trained supra-marathon runners during a four-day race. The daily running distances of the four-day race were the following; 93 km, 120 km, 56 km and 59 km, respectively. Pre-race and post-race urine samples were collected on each day and analyzed by a monoclonal antibody technique. The urinary 8-OHdG content increased significantly on the first day and tended to decrease from the third day. By the fourth day 8-OHdG content was significantly less than measured on the first three days. The serum creatine kinase activity changed in a similar fashion, showing a large increase (P<0.001) up to the third day when it decreased significantly from the peak value (P<0.05). We conclude that extreme physical exercise causes oxidative DNA damage to well trained athletes. However, repeated extreme exercise-induced oxidative stress does not propagate on increase of urinary 8-OHdG, but rather causes an adaptation leading to normalization of oxidative DNA damage.

Exercise preconditioning against hydrogen peroxide-induced oxidative damage in proteins of rat myocardium.

Both regular physical exercise and low levels of H(2)O(2) administration result in increased resistance to oxidative stress. We measured the accumulation of reactive carbonyl derivatives and the activities of proteasome complex and DT-diaphorase in cardiac muscle of trained and untrained rats after chronic i.p. administration of 1 ml t-butyl H(2)O(2) (1 mmol/kg for 3 weeks every second day). Twenty-four rats were randomly assigned to a control group administered with saline, control administered with H(2)O(2), and exercised administered either saline or H(2)O(2). The activity of DT-diaphorase significantly increased in H(2)O(2) administered and exercised groups, indicating that an increase in H(2)O(2) levels stimulate the activity of this enzyme. The cardiac muscle of H(2)O(2) administered nonexercised animals accumulated significantly more carbonyl than control group (P < 0.05). The exercise and H(2)O(2) administration resulted in less oxidatively modified protein than found in nonexercised groups (P < 0.05). The peptide-like activity of proteasome complex was induced by the treatment of H(2)O(2) and exercise and exercise potentiate the effect of H(2)O(2). On the other hand, the chymotrypsin-like and trypsin-like activities were stimulated only by physical training and H(2)O(2) administration. The data suggest that chronic administration of H(2)O(2) after exercise training decreases the accumulation of carbonyl groups below the steady-state level and induces the activity of proteasome and DT-diaphorase. Hence, the stimulating effect of physical exercise on free radical generation is an important phenomenon of the exercise-induced adaptation process since it increases resistance to oxidative stress. Regular exercise training is a valuable physiological means of preconditioning the myocardium to prolonged oxidative stress.

The effect of exercise training on oxidative damage of lipids, proteins, and DNA in rat skeletal muscle: evidence for beneficial outcomes.

Moderate daily exercise is known to be beneficial to health, reducing risks of a number of age-related disorders. Molecular mechanisms that bring about these effects are not clear. In contrast, it has been claimed that some types of prolonged physical exertion are detrimental to health because active oxygen species are generated excessively by enhanced oxygen consumption. Using two age groups of rats, young (4 week) and middle aged (14 months), we investigated the effects of long-term swimming training on the oxidative status of phospholipids, proteins, and DNA. The concentration of thiobarbituric acid reactive substances and 4-hydroxynonenal protein adducts did not differ in the gastrocnemius muscle between exercised and nonexercised animals in the two age groups. The extent of carbonylation in a protein of molecular weight around 29 KDa and the amount of 8-hydroxydeoxyguanosine in nuclear DNA were smaller (p<.05) in the exercised rats than in the sedentary animals. Activities of DT-diaphorase (C1: 29.3+/-1.9; C2: 36.1+/-2.6; E1: 27.2+/-1.3; C2: 33.4+/-2.9 nmol/mg protein) and proteasome, a major proteolytic enzyme for oxidatively modified proteins were significantly higher in the exercised animals of both age groups (p<.05). The adaptive response against oxidative stress induced by moderate endurance exercise constitutes a beneficial effect of exercise.