Exercise by lifelong voluntary wheel running reduces subsarcolemmal and interfibrillar mitochondrial hydrogen peroxide production in the heart

Evidence suggests that mitochondrial dysfunction and oxidant production, in association with an accumulation of oxidative damage, contribute to the aging process. Regular physical activity can delay the onset of morbidity, increase mean lifespan, and reduce the risk of developing several pathological states. No studies have examined age-related changes in oxidant production and oxidative stress in both subsarcolemmal (SSM) and interfibrillar (IFM) mitochondria in combination with lifelong exercise. Therefore, we investigated whether long-term voluntary wheel running in Fischer 344 rats altered hydrogen peroxide (H2O2) production, antioxidant defenses, and oxidative damage in cardiac SSM and IFM. At 10-11 wk of age, rats were randomly assigned to one of two groups: sedentary and 8% food restriction (sedentary; n = 20) or wheel running and 8% food restriction (runners; n = 20); rats were killed at 24 mo of age. After the age of 6 mo, running activity was maintained at an average of 1,145 +/- 248 m/day. Daily energy expenditure determined by doubly labeled water technique showed that runners expended on average approximately 70% more energy per day than the sedentary rats. Long-term voluntary wheel running significantly reduced H2O2 production from both SSM (-10.0%) and IFM (-9.6%) and increased daily energy expenditure (kJ/day) significantly in runners compared with sedentary controls. Additionally, MnSOD activity was significantly lowered in SSM and IFM from wheel runners, which may reflect a reduction in mitochondrial superoxide production. Activities of the other major antioxidant enzymes (glutathione peroxidase and catalase) and glutathione levels were not altered by wheel running. Despite the reduction in mitochondrial oxidant production, no significant differences in oxidative stress levels (4-hydroxy-2-nonenal-modified proteins, protein carbonyls, and malondialdehyde) were detected between the two groups. The health benefits of chronic exercise may be, at least partially, due to a reduction in mitochondrial oxidant production; however, we could not detect a significant reduction in several selected parameters of oxidative stress.     

Conditioned taste avoidance induced by forced and voluntary wheel running in rats

Voluntary exercise by rats running in a freely rotating wheel (free wheel) produces conditioned taste avoidance (CTA) of a flavored solution consumed before running [e.g., Lett, B.T., Grant, V.L., 1996. Wheel running induces conditioned taste aversion in rats trained while hungry and thirsty. Physiol. Behav. 59, 699-702]. Forced exercise, swimming or running, also produces CTA in rats [e.g., Masaki, T., Nakajima, S., 2006. Taste aversion induced by forced swimming, voluntary running, forced running, and lithium chloride injection treatments. Physiol. Behav. 88, 411-416]. Energy expenditure may be the critical factor in producing such CTA. If so, forced running in a motorized running wheel should produce CTA equivalent to that produced by a similar amount of voluntary running. In two experiments, we compared forced running in a motorized wheel with voluntary running in a free wheel. Mean distance run over 30 min was equated as closely as possible in the two apparatuses. Both types of exercise produced CTA relative to sedentary, locked-wheel controls. However, voluntary running produced greater CTA than forced running. We consider differences between running in the free and motorized wheels that may account for the differences in strength of CTA.     

Behaviour of house mice artificially selected for high levels of voluntary wheel running

We have developed a novel model to study the correlated evolution of behavioural and morphophysiological traits in response to selection for increased locomotor activity. We used selective breeding to increase levels of voluntary wheel running in four replicate lines of laboratory house mice, Mus domesticus, with four random-bred lines maintained as controls. The experiment presented here tested for correlated behavioural responses in the wheel-cage complex, with wheels either free to rotate or locked (environmental factor). After 13 generations, mice from selected lines ran 2.2 times as many revolutions/day as controls on days 5 and 6 of initial exposure to wheels (10 826 versus 4890 revolutions/day, corresponding to 12.1 and 5.5 km/day, respectively). This increase was caused primarily by mice from selected lines running faster, not more minutes per day. Focal-animal observations confirmed that the increase in revolutions/day involved more actual running (or climbing in locked wheels), not an increase in coasting (or hanging). Not surprisingly, access to free versus locked wheels had several effects on behaviour, including total time spent in wheels, sniffing and biting. However, few behaviours showed statistically significant differences between the selected and control lines. Selection did not increase the total time spent in wheels (either free or locked), the frequency of nonlocomotor activities performed in the wheels, nor the amount of locomotor activity in cages attached to the wheels; as well, selection did not decrease the amount of time spent sleeping. Thus, wheel running is, at the genetic level, a largely independent axis of behaviour. Moreover, the genetic architecture of overall wheel running and its components seem conducive to increasing total distance moved without unduly increasing energy or time-related costs. The selection experiment also offers a new approach to study the proximate mechanisms of wheel-running behaviour itself. For example, frequencies of sniffing and wire biting were reduced in selected females but not males. This result suggests that motivation or function of wheel running may differ between the sexes. Copyright 1999 The Association for the Study of Animal Behaviour.     

Cloning and establishment of a line of rats for high levels of voluntary wheel running

We generated an original Wistar line of rats that displayed increased levels of wheel running, which we named SPORTS (Spontaneously-Running-Tokushima-Shikoku). Male SPORTS rats ran voluntarily in a running wheel almost six times longer than male control Wistar rats, established without selection for their running activity. The running phenotype of female SPORTS rats was the same as female control Wistar rats. However, male offspring from the cross-mating between a female SPORTS rat and a male control rat also showed a similar level of hyper-running activity as the original SPORTS line. Compared to control rats, male SPORTS rats had lower levels of mean body weight, abdominal fat and plasma insulin after 4 weeks of running. It is likely that all these beneficial changes observed in the SPORTS rats reflected the increases in glucose disposal we observed in oral glucose tolerance tests carried out on the animals. We also found hyper-running caused a significant increase in skeletal muscle oxidative capacity, measured as the ratio of malate dehydrogenase to phosphofructokinase activity, an index of aerobic metabolism. These results indicate that the SPORTS rat may be a good animal model for determining the mechanisms responsible for up-regulation of running motivation, in addition to investigating changes in nutrient metabolism induced by high intensity exercise.     

Cardiac and skeletal muscle adaptations to voluntary wheel running in the mouse.

In this paper, we describe the effects of voluntary cage wheel exercise on mouse cardiac and skeletal muscle. Inbred male C57/Bl6 mice (age 6-8 wk; n = 12) [corrected] ran an average of 4.3 h/24 h, for an average distance of 6.8 km/24 h, and at an average speed of 26.4 m/min. A significant increase in the ratio of heart mass to body mass (mg/g) was evident after 2 wk of voluntary exercise, and cardiac atrial natriuretic factor and brain natriuretic peptide mRNA levels were significantly increased in the ventricles after 4 wk of voluntary exercise. A significant increase in the percentage of fibers expressing myosin heavy chain (MHC) IIa was observed in both the gastrocnemius and the tibialis anterior (TA) by 2 wk, and a significant decrease in the percentage of fibers expressing IIb MHC was evident in both muscles after 4 wk of voluntary exercise. The TA muscle showed a greater increase in the percentage of IIa MHC-expressing fibers than did the gastrocnemius muscle (40 and 20%, respectively, compared with 10% for nonexercised). Finally, the number of oxidative fibers as revealed by NADH-tetrazolium reductase histochemical staining was increased in the TA but not the gastrocnemius after 4 wk of voluntary exercise. All results are relative to age-matched mice housed without access to running wheels. Together these data demonstrate that voluntary exercise in mice results in cardiac and skeletal muscle adaptations consistent with endurance exercise.     

Effects of access to voluntary wheel running on the development of stereotypy

Stereotyped motor behaviors are a common consequence of environmental restriction in a wide variety of species. Although environmental enrichment has been shown to substantially reduce stereotypy levels, the various components of enrichment have not been evaluated independently to determine which is responsible for this effect. Exercise, particularly voluntary wheel running, is a promising candidate based on several lines of behavioral and neurobiological evidence. To test the hypothesis that access to wheel running will reduce stereotyped motor behavior, we reared deer mice from weaning with continuous access to either a functional running wheel or a locked wheel. We assessed running behavior throughout this time period and stereotypy levels in a test context at 30 and 45 days post-weaning. We found that exercise did not significantly affect stereotypy level nor was there an association between wheel running and stereotypy. Thus, exercise alone, unlike environmental enrichment, does not prevent the development of stereotypy. These results have important implications for animal welfare.     

Scheduled voluntary wheel running activity modulates free-running circadian body temperature rhythms in Octodon degus

Entrainment of the circadian pacemaker to nonphotic stimuli, such as scheduled wheel-running activity, is well characterized in nocturnal rodents, but little is known about activity-dependent entrainment in diurnal or crepuscular species. In the present study, effects of scheduled voluntary wheel-running activity on circadian timekeeping were investigated in Octodon degus, a hystricomorph rodent that exhibits robust crepuscular patterns of wakefulness. When housed in constant darkness, O. degus exhibited circadian rhythms in wheel-running activity and body temperature (Tb) with an average period length (tau) of 23.39 +/- 0.11 h. When wheel running was restricted to a fixed 2-h schedule every 24 h, tau increased on average 0.39 +/- 0.09 h but did not result in steady-state entrainment. Instead, relative coordination between the fixed running schedule and circadian timing was observed. Tau was greatest when scheduled wheel running occurred at CT 20.5 (0.4 h greater than DD baseline tau). Scheduled running activity also influenced Tb waveform symmetry, reflecting concomitant changes in the circadian activity-rest ratio (alpha:rho). Aftereffects of the scheduled wheel-running paradigm were also observed. In 2 animals, tau lengthened from 23.20 and 23.80 h to 24.14 and 24.15 h, respectively, and remained relatively stable for approximately 1 month during the wheel schedule. Although behavioral activity appears to be a weak zeitgeber in this species, these data suggest that nonphotic stimuli can phase delay the circadian pacemaker in O. degus at similar times of the day as in nocturnal hamsters and mice, and in humans.     

Relationship between skeletal muscle MCT1 and accumulated exercise during voluntary wheel running.

We examined whether the quantity of exercise performed influences the expression of monocarboxylate transporter (MCT) 1 and MCT4 in mouse skeletal muscles (plantaris, tibialis anterior, soleus) and heart. Wheel running exercise (1, 3, and 6 wk) was used, which results in marked variations in self-selected running activity. Differences in muscle MCT1 and MCT4 among animals, before the initiation of running, were not related to the quantity of exercise performed on the first day of wheel running. No changes in MCT4 were observed over the course of the study (P > 0.05). After 6 wk of running, were there significant increases in heart (50%; P < 0.05) and muscle MCT1 (31-60%; P < 0.05) but not after 1 and 3 wk (P > 0.05). Because skeletal muscle MCT1 and running distances varied considerably, we examined the relationship between these two parameters. Within the first week of training, MCT1 was negatively correlated with the accumulated running distance (r = -0.70, P < 0.05). On further analysis, it appears that, in the first week, excessive running (>20 km/wk) represses MCT1 (-16.1%; P < 0.05), whereas more modest amounts of running (<20 km/wk) increase MCT1 (+37%; P < 0.05). After 3 wk of running, a positive relationship was observed between MCT1 and running distance (r = +0.76), although there is a threshold that must be exceeded before an increase over the control animals occurs. Finally, in week 6, when MCT1 was increased in the tibialis anterior and plantaris muscles, there were no correlations with the accumulated running distances. These studies have shown that mild exercise training fails to increase MCT4 and that changes in MCT1 are complex, depending not only the accumulated exercise but also on the stage of training.     

Loss of desmin leads to impaired voluntary wheel running and treadmill exercise performance.

We examined voluntary wheel running and forced treadmill running exercise performance of wild-type mice and mice null for the desmin gene. When given access to a cage wheel, desmin null mice spent less time running and ran less far than wild-type mice. Wild-type mice showed a significant training effect with prolonged voluntary wheel running, as evidenced by an increase in mean running speed across the 3-wk exercise period, whereas desmin null mice did not. Desmin null mice also performed less well in acute treadmill stress and endurance tests compared with wild-type mice. We also evaluated serum creatine kinase (CK) activity in wild-type and desmin null mice in response to running. Voluntary running did not result in elevated CK activity in either wild-type or desmin null mice, whereas downhill treadmill running caused significant increases in serum CK activity in both wild-type and desmin null mice. However, the increase in serum CK was significantly less in desmin null mice than in wild-type mice. These results suggest that the lack of desmin adversely affects the ability of mice to engage in both chronic and acute bouts of endurance running exercise but that this decrement in performance is not associated with an increase in serum CK activity.     

Effects of a high-fat diet and voluntary wheel running on gluconeogenesis and lipolysis in rats.

The purpose of the present study was to determine the effects of diet composition and exercise on glycerol and glucose appearance rate (Ra) and on nonglycerol gluconeogenesis (Gneo) in vivo. Male Wistar rats were fed a high-starch diet (St, 68% of energy as cornstarch, 12% corn oil) for a 2-wk baseline period and then were randomly assigned to one of four experimental groups: St (n = 7), high-fat (HF; 35% cornstarch, 45% corn oil; n = 8), St with free access to exercise wheels (StEx; n = 7), and HF with free access to exercise wheels (HFEx; n = 7). After 8 wk, glucose Ra when using [3-3H]glucose, glycerol Ra when using [2H5]glycerol (estimate of whole body lipolysis), and [3-13C]alanine incorporation into glucose (estimate of alanine Gneo) were determined. Body weight and fat pad mass were significantly (P < 0.05) decreased in exercise vs. sedentary animals only. The average amount of exercise was not significantly different between StEx (3,212 +/- 659 m/day) and HFEx (3,581 +/- 765 m/day). The ratio of glucose to alanine enrichment and absolute glycerol Ra (micromol/min) were higher (P < 0.05) in HF and HFEx compared with St and StEx rats. In separate experiments, the ratio of 3H in C-2 to C-6 of glucose from 3H2O (estimate of Gneo from pyruvate) was also higher (P < 0.05) in HF (n = 5) and HFEx (n = 5), compared with St (n = 5) and StEx (n = 5) rats. Voluntary wheel running did not significantly increase estimated alanine or pyruvate Gneo or absolute glycerol Ra. Voluntary wheel running increased (P < 0.05) glycerol Ra when normalized to fat pad mass. These data suggest that a high-fat diet can increase in vivo Gneo from precursors that pass through pyruvate. They also suggest that changes in the absolute rate of glycerol Ra may contribute to the high-fat diet-induced increase in Gneo.     

Endurance capacity in maturing mdx mice is markedly enhanced by combined voluntary wheel running and green tea extract.

Duchenne muscular dystrophy is characterized by the absence of dystrophin from muscle cells. Dystrophic muscle cells are susceptible to oxidative stress. We tested the hypothesis that 3 wk of endurance exercise starting at age 21 days in young male mdx mice would blunt oxidative stress and improve dystrophic skeletal muscle function, and these effects would be enhanced by the antioxidant green tea extract (GTE). In mice fed normal diet, average daily running distance increased 300% from week 1 to week 3, and total distance over 3 wk was improved by 128% in mice fed GTE. Running, independent of diet, increased serum antioxidant capacity, extensor digitorum longus tetanic stress, and total contractile protein content, heart citrate synthase, and heart and quadriceps beta-hydroxyacyl-CoA dehydrogenase activities. GTE, independent of running, decreased serum creatine kinase and heart and gastrocnemius lipid peroxidation and increased gastrocnemius citrate synthase activity. These data suggest that both endurance exercise and GTE may be beneficial as therapeutic strategies to improve muscle function in mdx mice.     

Effects of voluntary wheel running on cardiac function and myosin heavy chain in chemically gonadectomized rats

Reducing testosterone and estrogen levels with a luteinizing hormone-releasing hormone agonist such as Zoladex (i.e., chemical gonadectomy) is a common treatment for many prostate and breast cancer patients, respectively. There are reports of surgical gonadectomy inducing cardiac dysfunction, and exercise has been shown to be cardioprotective under these circumstances. Minimal research has been done investigating the effects of chemical gonadectomy and increased physical activity on cardiac function. The purpose of this investigation was to examine the effects of chemical gonadectomy and physical activity on cardiac function. Male (M) and female (F) Sprague-Dawley rats received either Zoladex treatment (Zol) that suppressed gonadal function for 8 wk or control implants (Con) and either were allowed unlimited access to voluntary running wheels (WR) or remained sedentary (Sed) throughout the treatment period. In vivo and ex vivo left ventricle (LV) function were then assessed, and myosin heavy chain (MHC) expression was analyzed to help explain LV functional differences. Hearts from M Sed+Zol exhibited significantly lower aortic blood flow velocity, developed pressure, and maximal rate of pressure development and higher beta-MHC expression than M Sed+Con. Hearts from F Sed+Zol exhibited significantly lower LV wall thicknesses, fractional shortening, and developed pressure and higher beta-MHC expression than F Sed+Con. This cardiac dysfunction was not evident in hearts from M or F WR+Zol, and this was associated with a preservation of the MHC isoform distribution. Thus an 8-wk chemical gonadectomy with Zoladex promoted cardiac dysfunction in male and female rats, and voluntary wheel running protected against this cardiac dysfunction.     

Baseline and stress-induced plasma corticosterone concentrations of mice selectively bred for high voluntary wheel running

The hypothalamic-pituitary-adrenal (HPA) axis is important in regulating energy metabolism and in mediating responses to stressors, including increasing energy availability during physical exercise. In addition, glucocorticoids act directly on the central nervous system and influence behavior, including locomotor activity. To explore potential changes in the HPA axis as animals evolve higher voluntary activity levels, we characterized plasma corticosterone (CORT) concentrations and adrenal mass in four replicate lines of house mice that had been selectively bred for high voluntary wheel running (HR lines) for 34 generations and in four nonselected control (C) lines. We determined CORT concentrations under baseline conditions and immediately after exposure to a novel stressor (40 min of physical restraint) in mice that were housed without access to wheels. Resting daytime CORT concentrations were approximately twice as high in HR as in C mice for both sexes. Physical restraint increased CORT to similar concentrations in HR and C mice; consequently, the proportional response to restraint was smaller in HR than in C animals. Adrenal mass did not significantly differ between HR and C mice. Females had significantly higher baseline and postrestraint CORT concentrations and significantly larger adrenal glands than males in both HR and C lines. Replicate lines showed significant variation in body mass, length, baseline CORT concentrations, and postrestraint CORT concentrations in one or both sexes. Among lines, both body mass and length were significantly negatively correlated with baseline CORT concentrations, suggesting that CORT suppresses growth. Our results suggest that selection for increased locomotor activity has caused correlated changes in the HPA axis, resulting in higher baseline CORT concentrations and, possibly, reduced stress responsiveness and a lower growth rate.     

Skeletal muscle adaptations in response to voluntary wheel running in myosin heavy chain null mice.

10.1152/ japplphysiol.00832.2001.-To examine the effects of gene inactivation on the plasticity of skeletal muscle, mice null for a specific myosin heavy chain (MHC) isoform were subjected to a voluntary wheel-running paradigm. Despite reduced running performance compared with nontransgenic C57BL/6 mice (NTG), both MHC IIb and MHC IId/x null animals exhibited increased muscle fiber size and muscle oxidative capacity with wheel running. In the MHC IIb null animals, there was no significant change in the percentage of muscle fibers expressing a particular MHC isoform with voluntary wheel running at any time point. In MHC IId/x null mice, wheel running produced a significant increase in the percentage of fibers expressing MHC IIa and MHC I and a significant decrease in the percentage of fibers expressing MHC IIb. Muscle pathology was not affected by wheel running for either MHC null strain. In summary, despite their phenotypes, MHC null mice do engage in voluntary wheel running. Although this wheel-running activity is lessened compared with NTG, there is evidence of distinct patterns of muscle adaptation in both null strains.     

Muscle-bone properties after prolonged voluntary wheel running in a mouse model of dominant severe osteogenesis imperfecta

Objective:The objective of the current study is to assess the effect of a seven-week voluntary wheel running intervention on muscles and bones properties in a mouse model mimicking dominant severe osteogenesis imperfecta (OI).Methods:Female wild-type (WT) and OI (Col1a1^Jrt/+) mice either performed voluntarily wheel-running exercise for 7-weeks or remained sedentary. Running distance and speed, forelimb grip strength, isolated muscle force and fatigability as well as bone morphology and mechanical properties were assessed.Results:We demonstrate that female WT and OI mice voluntarily performed exercise, although OI mice exercised less than WT littermates. The exercise regimen increased soleus muscle masses in WT and OI but increased relative grip strength in WT mice only. Specific muscle force and fatigability were similar between WT and OI mice and did not improve with exercise. Furthermore, the exercise regimen did not improve the femoral architectural and biomechanical properties in OI mice.Conclusion:Our study suggests that voluntary wheel running is not appropriate to assess the effects of exercise in a mouse model of OI. Findings from exercising OI mice model studies may not necessarily be transferable to humans.     

Taste aversion induced by confinement in a running wheel

Behavioural lateralisation, which has been postulated to be an individual personality trait, is related to the activity of various physiological systems including the immune system. As lateralisation has been related to anxiety, which is known to influence immune reactivity, it can be hypothesized that the relation between lateralisation and immune reactivity involves individual behavioural patterns as they appear in exploratory-based anxiety models. In order to answer this question, a behavioural investigation focussing on exploratory activity was undertaken in male and female C3H mice previously selected for their paw preference. The observations were performed using two generic paradigms: elevated plus-maze and open field. Exploratory behaviour in the open field, but not in the plus-maze, was influenced by the interactive effect of gender and behavioural lateralisation. A significant difference between male and female mice was found in left-pawed but not in right-pawed nor ambidextrous animals, left-pawed female mice displaying the less exploratory behaviours. These results provide a first evidence of inter-individual variations in exploratory behaviours involving interaction between gender and lateralisation.     

Variations in running activity and enzymatic adaptations in voluntary running rats

The running behavior and biochemical markers of oxidative and glycolytic activities associated with voluntary running activity were studied in male Sprague-Dawley rats after 6 wk of training in exercise wheel cages. Twenty-four-hour recordings of running activity were used to quantify the number of individual running bouts, their duration and running speed, and the distance run per day. We then established three categories of voluntary running activity based on the mean distance run per day during the last 3 wk of training: low-activity runners averaged 2-5 km/day, medium runners 6-9 km/day, and high runners greater than 11 km/day. Each group demonstrated an intermittent, nocturnal running pattern, at relatively high intensities, with a similar mean running speed for all groups (avg approximately 45 m/min). Differences in total distance run per day were the result of variations in both the number and duration of individual running bouts. Specifically, high runners (n = 7) had 206 +/- 30 individual running bouts per 24 h, each lasting 87 +/- 7 s; medium runners (n = 7) 221 +/- 22 running bouts, lasting 47 +/- 5 s; and low runners (n = 7) 113 +/- 7 bouts, each lasting 40 +/- 7 s. Voluntary running depressed the rate of body weight gain compared with sedentary control rats, despite an increased food and water intake for all runners. Furthermore, drinking activity was temporally associated with running periods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antioxidant enzyme activities,lipid peroxidation,and DNA oxidative damage: the effects of short-term voluntary wheel running

We examined the effect of voluntary exercise on antioxidant enzyme activities (catalase, glutathione peroxidase, superoxide dismutase) in skeletal muscle (hind- and forelimb) and heart of a model small mammal species: short-tailed field vole Microtus agrestis. In addition, DNA oxidation was determined in lymphocytes and hepatocytes using the comet assay and lipid peroxidation estimated in hindlimb muscle by measurement of thiobarbituric-acid-reactive substances. Voles (approximately 6 weeks old), exposed to a 16L:8D photoperiod (lights on 0500 h), ran almost continuously during darkness. We studied the effects of voluntary running over 1 or 7 days duration, with or without an 8-h rest period, on various biomarkers of oxidative stress compared to nonrunning controls. No differences were observed in antioxidant enzyme activities, except in heart total superoxide dismutase activity (P=0.037), with the lowest levels in 1- and 7-day runners at 0500 h. DNA oxidative damage, in lymphocytes or hepatocytes, and lipid peroxidation did not differ between groups. There was no evidence of any significant increase in any oxidative stress parameter in running individuals, despite having significantly elevated energy expenditures compared to sedentary controls.