Access To Running Wheel Research Articles

Synergy between time-restricted feeding and time-restricted running is necessary to shift the muscle clock in male wistar rats

Circadian disruption is an important factor driving the current-day high prevalence of obesity and type-2 diabetes. While the impact of incorrect timing of caloric intake on circadian disruption is widely acknowlegded, the contribution of incorrect timing of physical activity remains relatively understudied. Here, we modeled the incorrect timing of physical activity in nightshift workers in male Wistar rats, by restricting running wheel access to the innate inactive (light) phase (LR). Controls included no wheel access (NR); access only during the innate active (dark) period (DR); or unrestricted (ad libitum) access (ALR). LR did not shift the phase of the muscle or liver clock, but dampened the muscle clock amplitude. As our previous study demonstrated that light-phase restricted feeding did shift the liver clock, but made the muscle clock arrhythmic, we next combined the time restriction of wheel and food access to either the light phase (LRLF) or dark phase (DRDF). LRLF produced a ∼12 h shift in the majority of clock gene rhythms in both skeletal muscle and liver. On the other hand, DRDF was most effective in reducing body weight and the accumulation of fat mass. Therefore, in order to shift the muscle clock in male Wistar rats, synergy between the timing of feeding and physical activity is necessary. These findings may contribute to further improve the design of lifestyle strategies that try to limit metabolic misalignment caused by circadian disruption.

Effects of chronic alcohol intoxication on aerobic exercise-induced adaptations in female mice.

Chronic alcohol intoxication decreases muscle strength/function and causes mitochondrial dysfunction. Aerobic exercise training improves mitochondrial oxidative capacity and increases muscle mass and strength. Presently, the impact of chronic alcohol on aerobic exercise-induced adaptations was investigated. Female C57BL/6Hsd mice were randomly assigned to one of four groups: control sedentary (CON SED; n = 26), alcohol sedentary (ETOH SED; n = 27), control exercise (CON EX; n = 28), and alcohol exercise (ETOH EX; n = 25). Exercise mice had running wheel access for 2 h a day, 7 days a week. All mice were fed either control or an alcohol-containing liquid diet. Grip strength testing and EchoMRI were performed before and after the interventions. After 6 wk, hindlimb muscles were collected for molecular analyses. A subset of mice performed a treadmill run to fatigue (RTF), then abstained from alcohol for 2 wk and repeated the RTF. Alcohol decreased lean mass and forelimb grip strength compared with control-fed mice. Alcohol blunted the exercise-induced increase in muscle mass (plantaris and soleus), type IIa fiber percentage in the plantaris, and run time to fatigue. Mitochondrial markers (Citrate synthase activity and Complex I-IV, COXIV and Cytochrome C protein expression) were increased with exercise regardless of ETOH in the gastrocnemius but not tibialis anterior muscle. Two weeks of alcohol abstinence improved RTF time in ETOH EX but not in ETOH SED. These data suggest that alcohol impairs some exercise-induced adaptations in skeletal muscle, but not all were negatively affected, indicating that exercise may be a beneficial behavior even while consuming alcohol.NEW & NOTEWORTHY Alcohol consumption during an aerobic exercise training period prevented training-induced increases in run to fatigue time and grip strength. Cessation of alcohol allowed for recovery of endurance performance within 2 wk. The worsened exercise performance after alcohol was unrelated to impairments in markers of mitochondrial health. Therefore, some adaptations to exercise training are impaired with alcohol use (endurance performance, muscle growth, and strength), while others remain mostly unaffected (mitochondrial health).

Establishment of a Murine Chronic Anorexia Nervosa Model.

Anorexia nervosa (AN) is associated with hyperactivity, amenorrhea, and brain atrophy. The underlying pathophysiology is mostly unknown, and new targets for therapeutic interventions are needed. This study aimed to systematically establish a murine AN model with the parameter extent of starvation, animal age, and length of starvation for functional studies. The activity-based anorexia (ABA) model combines food restriction with running wheel access. Early adolescent and adolescent mice received 40% of their baseline food intake until a 20% or 25% weight reduction was reached (acute starvation). To mimic chronic starvation, body weight loss was maintained for another two weeks. Running activity was examined using wheel sensors, while amenorrhea was investigated by analysis of vaginal smears. Brain sections were used to analyze cerebral cortex volumes. Acute starvation did not lead to either AN-related symptoms, whereas chronic starvation led to hyperactivity and amenorrhea except in the adolescent cohort with 20% weight reduction. Only ABA mice with 25% weight reduction revealed a cortex volume reduction. The optimal parameters to mirror AN-related symptoms included a 25% weight reduction, early adolescent or adolescent mice, and chronic starvation. The ABA model enables functional analysis of the impact of chronic AN on the underlying hormonal, behavioral, and brain pathophysiology.

Age and diet modulate the insulin-sensitizing effects of exercise: a tracer-based oral glucose tolerance test

Diet modulates the development of insulin resistance during aging. This includes tissue-specific alterations in insulin signaling and mitochondrial function, which ultimately affect glucose homeostasis. Exercise stimulates glucose clearance, mitochondrial lipid oxidation and enhances insulin sensitivity. It is not well known how exercise interacts with age and diet in the development of insulin resistance. To investigate this, oral glucose tolerance tests (OGTT) with a tracer were conducted in mice ranging from 4 to 21 months of age, fed a low- (LFD) or high-fat diet (HFD), with or without life-long voluntary access to a running wheel (RW). We developed a computational model to derive glucose fluxes, which were commensurate with independent values from steady-state tracer infusions. Both insulin sensitivity indices derived for peripheral tissues and liver (IS-P and IS-L, respectively) were steeply decreased by aging and a HFD. This preceded the age-dependent decline in the mitochondrial capacity to oxidize lipids. In LFD young animals, RW access enhanced the IS-P concomitantly with the muscle β- oxidation capacity. Surprisingly, RW access completely prevented the age-dependent IS-L decrease, but only in LFD animals. This study indicates, therefore, that endurance exercise can improve the age-dependent decline in organ-specific IS mostly in the context of a healthy diet.

Modified activity-based anorexia paradigm dampens chronic food restriction-induced hyperadiponectinemia in adolescent female mice.

Anorexia nervosa (AN) is a chronic, life-threatening disease with mental and physical components that include excessive weight loss, persistent food restriction, and altered body image. It is sometimes accompanied by hyperactivity, day-night reversal, and amenorrhea. No medications have been approved specific to the treatment of AN, partially due to its unclear etiopathogenesis. Because adiponectin is an appetite-regulating cytokine released by adipose tissue, we hypothesized that it could be useful as a specific biomarker that reflects the disease state of AN, so we developed a modified AN mouse model to test this hypothesis. Twenty-eight 3-week-old female C57BL/6J mice were randomly assigned to the following groups: 1) no intervention; 2) running wheel access; 3) food restriction (FR); and 4) activity-based anorexia (ABA) that included running wheel access plus FR. After a 10-day cage adaptation period, the mice of the FR and ABA groups were given 40% of their baseline food intake until 30% weight reduction (acute FR), then the body weight was maintained for 2.5 weeks (chronic FR). Running wheel activity and the incidence of the estrous cycle were assessed. Spontaneous food restriction and the plasma adiponectin level were evaluated at the end of the acute and chronic FR phases. An increase in running wheel activity was found in the light phase, and amenorrhea was found solely in the ABA group, which indicates that this is a good model of AN. This group showed a slight decrease in spontaneous food intake accompanied with an attenuated level of normally induced plasma adiponectin at the end of the chronic FR phase. These results indicate that the plasma adiponectin level may be a useful candidate biomarker for the status or stage of AN.

Reducing short- and long-term cocaine craving with voluntary exercise in male rats.

In a previous study in female rats, voluntary wheel running attenuated incubation of cocaine craving after 30 but not 3days (Zlebnik and Carroll Zlebnik and Carroll, Psychopharmacology 232:3507-3413, 2015). The present study in male rats, using the same procedure, showed that wheel running reduced incubated craving after both 30 and 3days of abstinence. Male rats self-administered i.v. cocaine (0.4mg/kg) during 6-h sessions for 10days. They were then moved from the operant chamber to a home cage with an attached running wheel or stationary wheel, for 6h daily for a 3- or 30-day period when cocaine craving was hypothesized to incubate. Rats were then returned to the operant chamber for a 30-min test of cocaine seeking, or "craving," indicated by responses on the former "drug" lever was formerly associated with drug stimulus lights and responses (vs. no drug stimuli), and lever responding was compared to responses on the "inactive" that was illuminated and counted lever pressing. Mean wheel revolutions were similar across the 3- and 30-day incubation groups, when both groups of rats were given access to wheel running vs. access to a stationary wheel in controls. Subsequently, when rats were tested in the operant chamber for "relapse" responding (drug-lever responding) on the lever formerly associated with drug access, cocaine craving was reduced by recent running wheel access (vs. stationary wheel access) in both the 3- and 30-day wheel exposure groups. Voluntary, self-initiated, and self-sustained physical exercise reduced cocaine craving after short- (3days) and long-term (30days) abstinence periods in male rats that previously self-administered cocaine. This was contrasted with reduction of cocaine seeking in females after 30-day, but not 3-day, incubation periods under the wheel running vs. stationary wheel conditions in a previous study (Zlebnik and Carroll Zlebnik and Carroll, Psychopharmacology 232:3507-3413, 2015). These initial findings suggest males may be more sensitive to incubated craving for cocaine than females.

The effects of voluntary binge-patterned ethanol ingestion and daily wheel running on signaling of muscle protein synthesis and degradation in female mice.

Excessive ethanol ingestion can reduce skeletal muscle protein synthesis (MPS) through the disruption of signaling along the Akt-mTOR pathway and increase muscle protein degradation (MPD) through the Ubiquitin Proteasome Pathway (UPP) and autophagy. Identification of interventions that curb the disrupting effects of alcohol misuse on MPS and MPD are of central importance for the prevention of chronic health complications that arise from muscle loss. Physical activity is one potential strategy to combat the deleterious effects of alcohol on skeletal muscle. Therefore, the purpose of this study was to investigate the interaction between daily wheel running and binge-patterned ethanol consumption, through episodes of voluntary binge-patterned ethanol drinking, on signaling factors along the Akt-mTOR, Ubiquitin-Proteasome, and autophagy pathways. Adult female C57BL/6J mice received daily access to cages with or without running wheels for 2.5h/day for five weeks. During the final five days of the study, mice received 2-4h of daily access to sipper tubes containing water (n=14 sedentary; n=15 running) or 20% ethanol (n=14 sedentary; n=16 running) 30min after running wheel access, using the "Drinking in the Dark" (DID) model of binge-patterned ethanol consumption. Immediately after the final episode of DID, gastrocnemius muscle was extracted. Western blotting was performed to measure proteins along Akt-mTOR, Ubiquitin-Proteasome, and autophagy pathways, and PCR was used to assess mRNA expression of atrogenes. Ethanol access increased expression of MAFbx by 82% (p=0.048), but did not robustly influence Akt-mTOR or UPP signaling. Daily wheel access did not prevent alcohol-induced MAFbx expression; however, ethanol access decreased the phosphorylation of p70S6K by 45% in running mice (p=0.020). These results suggest that physical activity may be insufficient to prevent alcohol-induced changes to signaling factors along pathways involved in muscle loss. Instead, binge-patterned ethanol ingestion may impair the benefits of physical activity on factors involved in MPS.

A red nucleus-VTA glutamate pathway underlies exercise reward and the therapeutic effect of exercise on cocaine use.

Physical exercise is rewarding and protective against drug abuse and addiction. However, the neural mechanisms underlying these actions remain unclear. Here, we report that long-term wheel-running produced a more robust increase in c-fos expression in the red nucleus (RN) than in other brain regions. Anatomic and functional assays demonstrated that most RN magnocellular portion (RNm) neurons are glutamatergic. Wheel-running activates a subset of RNm glutamate neurons that project to ventral tegmental area (VTA) dopamine neurons. Optogenetic stimulation of this pathway was rewarding, as assessed by intracranial self-stimulation and conditioned place preference, whereas optical inhibition blocked wheel-running behavior. Running wheel access decreased cocaine self-administration and cocaine seeking during extinction. Last, optogenetic stimulation of the RNm-to-VTA glutamate pathway inhibited responding to cocaine. Together, these findings indicate that physical exercise activates a specific RNm-to-VTA glutamatergic pathway, producing exercise reward and reducing cocaine intake.

Multiscale Time-resolved Analysis Reveals Remaining Behavioral Rhythms in Mice Without Canonical Circadian Clocks

Circadian rhythms are internal processes repeating approximately every 24 hours in living organisms. The dominant circadian pacemaker is synchronized to the environmental light-dark cycle. Other circadian pacemakers, which can have noncanonical circadian mechanisms, are revealed by arousing stimuli, such as scheduled feeding, palatable meals and running wheel access, or methamphetamine administration. Organisms also have ultradian rhythms, which have periods shorter than circadian rhythms. However, the biological mechanism, origin, and functional significance of ultradian rhythms are not well-elucidated. The dominant circadian rhythm often masks ultradian rhythms; therefore, we disabled the canonical circadian clock of mice by knocking out Per1/2/3 genes, where Per1 and Per2 are essential components of the mammalian light-sensitive circadian mechanism. Furthermore, we recorded wheel-running activity every minute under constant darkness for 272 days. We then investigated rhythmic components in the absence of external influences, applying unique multiscale time-resolved methods to analyze the oscillatory dynamics with time-varying frequencies. We found four rhythmic components with periods of ∼17 h, ∼8 h, ∼4 h, and ∼20 min. When the ∼17-h rhythm was prominent, the ∼8-h rhythm was of low amplitude. This phenomenon occurred periodically approximately every 2-3 weeks. We found that the ∼4-h and ∼20-min rhythms were harmonics of the ∼8-h rhythm. Coupling analysis of the ridge-extracted instantaneous frequencies revealed strong and stable phase coupling from the slower oscillations (∼17, ∼8, and ∼4 h) to the faster oscillations (∼20 min), and weak and less stable phase coupling in the reverse direction and between the slower oscillations. Together, this study elucidated the relationship between the oscillators in the absence of the canonical circadian clock, which is critical for understanding their functional significance. These studies are essential as disruption of circadian rhythms contributes to diseases, such as cancer and obesity, as well as mood disorders.

Microbiome: A Discrete Influencer of Running Behavior?

IntroLiterature establishes conserved changes in the gut microbiome (GMB) correlated with behavior.1 Using voluntary running, we tested if GMB variability explains differences in voluntary exercise using a rat model.MethodsCohabitating male rats were randomized into running (n=8) and sedentary (n=3) groups and placed in individual cages. Running wheel access was withheld for a week. The running group received free access to the wheels for 27 days. Daily and cumulative distances were recorded with weekly fecal collection for 16s amplification and sequencing. Terminal seven‐day distances stratified rats into high (8341‐10209 m/wk) and low (1763‐5201 m/wk) groups. Analysis was done in QIIME2 and R.ResultsAt randomization, alpha‐diversity (AD) was similar between sedentary, low, and high runners (ANOVA, F = 2.812, Pr(>F) = .065). Shannon diversity showed significant correlation with daily distance and an interaction running subgroup (high v. low, MLM, int = ‐6,778, Shannon est. = 2498±118, low running interaction = ‐2135±217). Across all samples, there was a significant correlation between AD and distance (Pearson correlation, p <0.001, corr = 0.41).Fixed slope random intercept modelling showed a significant relationship between distance and phyla abundance. Verrucomicrobia (MLM, int = 3610, est. 294925±142844, p = 0.048), and Saccharibacteria (MLM, int = 3342, est. 3830783±1245092, p = 0.005) showed significant increases in beta‐diversity. Actinobacteria (MLM, int 5634, est. =45608±13682) was negatively associated with distance.DiscussionOur findings that voluntary distances run was associated with increases in microbiome richness supports the importance of ecosystem diversity to support host function. This is consistent with previous research which establishes the role of increasing AD with broad improvements in performance.Decreased Verrucomicrobia is associated with the development of metabolic diseases, which are associated with decreased running behaviors.2 Verrucomicrobia and Actinobacteria impact gut homeostasis by modulating permeability, immune and inflammatory responses at the mucosal level.3 Analysis is ongoing and may influence these findings. Further research is needed on the impact of these changes to determine their effect on the overall health of the organism.

Exercise Duration Differentially Effects Age-related Neuroinflammation and Hippocampal Neurogenesis

The physiological effects of exercise vary as a function of frequency and length. However, research on the duration-dependent effects of exercise has focused primarily on young adults and less is known about the influence of exercise duration in the aged. The current study compared the effects of short-term and long-term running wheel access on hippocampal neurogenesis and neuroimmune markers in aged (19–23 months) male C57BL/6J mice. Aged mice were given 24-hour access to a running wheel for 14 days (short-term) or 51 days (long-term). Groups of non-running aged and young (5 months) mice served as comparison groups to detect age-related differences and effects of exercise. Long-term, but not short-term, exercise increased hippocampal neurogenesis as assessed by number of doublecortin (DCX) positive cells in the granular cell layer. Assessment of cytokines, receptors, and glial-activation markers showed the expected age-related increase compared to young controls. In the aged, exercise as a function of duration regulated select aspects of the neuroimmune profile. For instance, hippocampal expression of interleukin (IL)-10 was increased only following long-term exercise. While in contrast brain levels of IL-6 were reduced by both short- and long-term exercise. Additional findings showed that exercise does not modulate all aspects of age-related neuroinflammation and/or may have differential effects in hippocampal compared to brain samples. Overall, the data indicate that increasing exercise duration produces more robust effects on immune modulation and hippocampal neurogenesis.

The impact of intermittent exercise on mouse ethanol drinking and abstinence-associated affective behavior and physiology.

Negative emotional states are associated with the initiation and maintenance of alcohol use and drive relapse to drinking during withdrawal and protracted abstinence. Physical exercise is correlated with decreased negative affective symptoms, although a direct relationship between drinking patterns and exercise level has not been fully elucidated. We incorporated intermittent running wheel access into a chronic continuous access, two-bottle choice alcohol drinking model in female C57BL/6J mice. Wheel access was granted intermittently once mice established a preference for alcohol over water. After 6weeks, alcohol was removed (forced abstinence) and mice were given continuous access to unlocked or locked wheels. Negative affect-like behavior, home cage behavior, and metabolic activity were measured during protracted abstinence. Wheel access shifted drinking patterns in the mice, increasing drinking when the wheel was locked, and decreasing drinking when unlocked. Moreover, alcohol preference and consumption were strongly negatively correlated with the amount of running. An assessment of negative affect-like behavior in abstinence via the novelty suppressed feeding and saccharin preference tests (SPT) showed that unlimited wheel access mitigated abstinence-induced latency increases. Mice in abstinence also spent more time sleeping during the active dark cycle than control mice, providing additional evidence for abstinence-induced anhedonia- and depression-like behavior. Furthermore, running wheel access in abstinence decreased dark cycle sleep to comparable alcohol- and wheel-naïve mice. Given the positive impact of exercise and the negative impact of alcohol on metabolic health, we compared metabolic phenotypes of alcohol-abstinent mice with and without wheel access. Wheel access increased energy expenditure, carbon dioxide production, and oxygen consumption, providing a potential metabolic mechanism through which wheel access improves affective state. This study suggests that including exercise in AUD treatment regimens has the potential to reduce drinking, improve affective state during abstinence and could serve as a non-pharmacological approach to prevent the development of an AUD in high-risk individuals.

The Role of Dopamine in Contributing to Vulnerable and Resilient Phenotypes in a Mouse Model of Anorexia Nervosa

In the current issue of Biological Psychiatry, Beeler et al. (1) provide a compelling study of potential risk and resilience to activity-based anorexia (ABA), a rodent model of anorexia nervosa (AN). Traditionally, ABA combines restricted intake with unlimited running wheel access, which ultimately leads rodents to increase their activity, self-starve, and expire unless removed from the test paradigm. Working to extend the applicability of this model to risk for AN, Beeler et al. (1) aimed to determine whether genetically modifying dopamine would have an impact on resilience to the expected course of ABA.

Role of ERβ in adipocyte metabolic response to wheel running following ovariectomy.

Estrogen receptor β (ERb), one of the two major estrogen receptors, acts via genomic and non-genomic signaling pathways to affect many metabolic functions, including mitochondrial biogenesis and respiration. This study assessed the effect of ERb classical genomic activity on adipocyte-specific and -systemic metabolic responses to wheel running exercise in a rodent model of menopause. Female mice lacking the ERb DNA-binding domain (ERbDBDKO, n = 20) and WT (n = 21) littermate controls were fed a high-fat diet (HFD), ovariectomized (OVX), and randomized to control (no running wheel) and exercise (running wheel access) groups and were followed for 8 weeks. Wheel running did not confer protection against metabolic dysfunction associated with HFD+OVX in either ERbDBDKO or WT mice, despite increased energy expenditure. Unexpectedly, in the ERbDBDKO group, wheel running increased fasting insulin and surrogate measures of insulin resistance, and modestly increased adipose tissue inflammatory gene expression (P ≤ 0.05). These changes were not accompanied by significant changes in adipocyte mitochondrial respiration. It was demonstrated for the first time that female WT OVX mice do experience exercise-induced browning of white adipose tissue, indicated by a robust increase in uncoupling protein 1 (UCP1) (P ≤ 0.05). However, KO mice were completely resistant to this effect, indicating that full ERb genomic activity is required for exercise-induced browning. The inability to upregulate UCP1 with exercise following OVX may have resulted in the increased insulin resistance observed in KO mice, a hypothesis requiring further investigation.

The Influence of Moderate Physical Activity on Brain Monoaminergic Responses to Binge-Patterned Alcohol Ingestion in Female Mice.

Monoamine neurotransmitter activity in brain reward, limbic, and motor areas play key roles in the motivation to misuse alcohol and can become modified by exercise in a manner that may affect alcohol craving. This study investigated the influence of daily moderate physical activity on monoamine-related neurochemical concentrations across the mouse brain in response to high volume ethanol ingestion. Adult female C57BL/6J mice were housed with or without 2.5 h of daily access to running wheels for 30 days. On the last 5 days, mice participated in the voluntary binge-like ethanol drinking procedure, “Drinking in the dark” (DID). Mice were sampled immediately following the final episode of DID. Monoamine-related neurochemical concentrations were measured across brain regions comprising reward, limbic, and motor circuits using ultra High-Performance Liquid Chromatography (UHPLC). The results suggest that physical activity status did not influence ethanol ingestion during DID. Moreover, daily running wheel access only mildly influenced alcohol-related norepinephrine concentrations in the hypothalamus and prefrontal cortex, as well as serotonin turnover in the hippocampus. However, access to alcohol during DID eliminated wheel running-related decreases of norepinephrine, serotonin, and 5-HIAA content in the hypothalamus, but also to a lesser extent for norepinephrine in the hippocampus and caudal cortical areas. Finally, alcohol access increased serotonin and dopamine-related neurochemical turnover in the striatum and brainstem areas, regardless of physical activity status. Together, these data provide a relatively thorough assessment of monoamine-related neurochemical levels across the brain in response to voluntary binge-patterned ethanol drinking, but also adds to a growing body of research questioning the utility of moderate physical activity as an intervention to curb alcohol abuse.

Gut microbiota and brain alterations in a translational anorexia nervosa rat model

Anorexia nervosa (AN) is an eating disorder that leads to brain volume reduction and is difficult to treat since the underlying pathophysiology is poorly understood. The human gut microbiota is known to be involved in host metabolism, appetite- and bodyweight regulation, gut permeability, inflammation and gut-brain interactions. In this study, we used a translational activity-based anorexia (ABA) rat model including groups with food restriction, running-wheel access and a combination to disentangle the influences on the gut microbiota and associated changes in brain volume parameters. Our data demonstrated that chronic food restriction but not running-wheel activity had a major influence on the gut microbiota diversity and composition and reduced brain volume. Negative correlations were found between global brain weight and α-diversity, and astrocyte markers and relative abundances of the genera Odoribacter and Bifidobacterium. In contrast, the presence of lactobacilli was positively associated with white and grey brain matter volume. ABA and food-restricted rats are an interesting pre-clinical model to assess the causal influence of starvation on the gut microbiome and gut-brain interactions and can help to dissect the underlying pathophysiologic mechanisms relevant to AN.

Does physical activity associated with chronic food restriction alleviate anxiety like behaviour, in female mice?

Anorexia nervosa (AN) is an eating disorder characterized by excessive weight loss, persistent food restriction and inappropriate physical activity relative to declining energy balance. The comorbidity with depression and/or anxiety disorders might contribute to the “chronicization” of the disease. We aimed here to question first the link between physical activity and anxiety from a clinical investigation of AN patients (n = 206). Then, using a rodent model mimicking numerous physiological and metabolic alterations commonly seen in AN patients, we examined whether 1) chronic food restriction increased anxiety-like behaviour and 2) physical activity plays a role in regulating anxiety levels. To this end, we exposed young female mice to a chronic food restriction (FR, n = 8) paradigm combined or not with access to a running wheel (FRW, n = 8) for two weeks. The mice were compared to a group of mice fed ad libitum without (AL, n = 6) or with running wheel access (ALW, n = 8). We explored anxiety-like behaviour of all mice in the following tests: hyponeophagia, marble burying, elevated plus maze, open field, and the light and dark box. On the last day, we used a restraint test of 30 min duration and measured their stress reactivity by assaying plasma corticosterone. In the open field and the elevated plus-maze, we found that FRW mice behaved similarly to AL and ALW mice whereas FR mice did not express anxiety-like behaviour. The FRW mice displayed the lowest latency to reach the food in the hyponeophagia test. Regarding stress reactivity, FRW mice exhibited corticosterone reactivity after acute stress that was similar to the control mice, while FR mice did not fully return to basal corticosterone at one hour after the restraint stress. Taken together, these data demonstrate a differential reactivity to acute stress in FR conditions and a beneficial effect of running wheel activity in ALW and FRW conditions. Moreover, we report the absence of a typical anxiety-like behaviour associated with the food restriction (FR and FRW groups). We conclude that this model (FR and FRW mice) did not express typical anxiety-like behaviour, but that physical activity linked to food restriction improved coping strategies in an anxiogenic context.

Vascular Protection by Exercise in Obesity: Inflammasome-associated Mechanisms.

The nodlike receptor family pyrin domain containing 3 (NLRP3) inflammasome is a critical player in vascular pathology as it regulates caspase-1-mediated interleukin (IL)-1β processing. Physical activity ameliorates obesity-induced inflammation and vascular dysfunction, but the mechanisms responsible for these positive changes are incompletely understood. Here, the protective effect of physical activity on the inflammasome-associated vascular dysfunction in obesity and its putative mechanisms were investigated. Mice were fed a control low-fat diet (LFD) or a high-fat diet (HFD; 45% of calories from fat) and provided with running wheel access (LF-RUN or HF-RUN) or denied wheel access for our sedentary condition (LF-SED or HF-SED). The NLRP3 inflammasome-associated pathway, including NLRP3, caspase-1, and IL-1β, in mice aorta was examined by RT-qPCR and FLICA and DAB staining. The protein expression of zonula occluden-1 (ZO-1), ZO-2, adiponectin (APN), and adiponectin receptor 1 (AdipoR1) in aortic endothelial cells was determined by immunofluorescence double staining. Intracellular reactive oxidative stress and nitric oxide (NO) production were monitored with fluorescence probes, dihydroethidium, and diaminofluorecein. HFD increased caspase-1 and IL-1β at mRNA and protein levels in endothelial cells of the aorta, and this was attenuated by voluntary running. HFD decreased ZO-1 and ZO-2 expression and reduced APN and AdipoR1 signaling; these were restored by running. The elevated intracellular superoxide (O2) production observed in HF-SED was ameliorated in HF-RUN. Finally, HF-RUN improved NO production in the aorta compared with HF-SED. Our findings suggest that voluntary running ameliorates mechanisms associated with vascular dysfunction by suppressing NLRP3 inflammasome, improving NO production, and reducing oxidative stress. Such benefits of physical activity may be, at least in part, associated with APN-AdipoR1 signaling and tight junction protein expression.

Exercise‐mediated Wall Shear Stress Attenuates NLRP3 Inflammasome‐induced Endothelial Dysfunction in Obesity

PURPOSENLRP3 inflammasome plays a pivotal role in obesity‐induced vascular pathology through caspase‐1‐mediated IL‐1β processing, while precise mechanism by which exercise ameliorates the inflammasome remains unknown. Thus, we investigated the effect of exercise on endothelial dysfunction in obesity via NLRP3 inflammasome‐dependent mechanisms.METHODSC57BL/6J male mice were provided a control low‐fat diet (LFD; 4.5% calories from fat) or a high‐fat diet (HFD; 45% calories from fat) with a running wheel access (LF‐RUN or HF‐RUN) or a sedentary no‐wheel condition (LF‐SED or HF‐SED) for 12 to 14 weeks. Endothelium‐dependent vasodilation in response to increasing acetylcholine (ACh, 1 nmol/L to 10 μmol/L) was assessed using intact mesentery arteries isolated from mice. Mouse microvascular endothelial cell (MVEC) line EOMA was treated with palmitate (PA, 20 μmol/L) and laminar shear stress (LSS, 20 dynes/cm2): Static control (STT), PA, LSS, and LSS+PA. The NLRP3 inflammasome axis, including NLRP3, ASC, caspase‐1, p20, and IL‐1β in mice aorta and MVECs was examined by RT‐qPCR, FLICA and DAB staining and western blot.RESULTSHFD significantly increased obesity‐associated parameters while these were attenuated by running exercise. Obesity greatly decreased ACh‐induced endothelium‐dependent vasodilation compared to LF‐SED. Exercise improved reduced vasodilator response to ACh in obese mice. Incubation of caspase‐1 inhibitor (10 μmol/L) to the isolated vessel restored obesity‐induced impairment of vasodilator response similar to one of LF‐SED, LF‐RUN, and HF‐RUN. Exercise‐induced decrease of caspase‐1 and IL‐1β in endothelial cells of obese mice aorta was determined by immunohistochemistry using FLICA and DAB, respectively. Likewise, in in vitro experiment, LSS diminished inflammasome components in PA‐treated MVECs.CONCLUSIONThese findings suggest that exercise attenuates against obesity‐induced endothelial dysfunction through a shear stress‐dependent mechanism. Our finding suggests that exercise may be a therapeutic strategy for inflammation‐related vascular dysfunction in obesity.Exercise attenuates IL‐1β in endothelium of obese mice aorta.Immunohistochemical analysis of IL‐1β expression (dark brown precipitate) in the endothelial layer of the aorta. Summarized data showing area percentage of the endothelium positive for IL‐1β in aorta (n=4–6). Values are means ± SEM. * P<.05 vs. LFSED; # P<.05 vs. HF‐SED.Figure 1Inhibition of caspase‐1 abolishes endothelial dysfunction in mesentery arteries of obese mice.Incubation of the caspase‐1 inhibitor, Ac‐YVAD‐cmk, in isolated mesentery arteries from obese mice showing improved ACh‐induced endothelium‐dependent vasodilation in HF‐SED + Ac‐YVAD‐cmk (n = 3) similar to the levels of LF‐SED (n=8), HF‐RUN (n = 9) and HF‐RUN + Ac‐YVAD‐cmk (n = 7). Values are means ± SEM. ## P<.01 vs. HF‐SED.Figure 2

Low-dose UV radiation before running wheel access activates brown adipose tissue

In previous preclinical studies, low (non-burning) doses of UV radiation (UVR) limited weight gain and metabolic dysfunction in mice fed with a high-fat diet. Here, we explored the effects of low-dose UVR on physical activity and food intake and mechanistic pathways in interscapular brown adipose tissue (iBAT). Young adult C57Bl/6J male mice, housed as individuals, were fed a high-fat diet and exposed to low-dose UVR (sub-oedemal, 1 kJ/m2 UVB, twice-a-week) or 'mock' treatment, with or without running wheel access (2 h, for 'moderate' physical activity) immediately after phototherapy. There was no difference in distance run in mice exposed to UVR or mock-treated over 12 weeks of exposure to running wheels (P = 0.14). UVR (alone) did not significantly affect food intake, adiposity, or signs of glucose dysfunction. Access to running wheels increased food intake (after 10 weeks, P ≤ 0.02) and reduced gonadal white adipose tissue and iBAT mass (P ≤ 0.03). Body weight and hepatic steatosis were lowest in mice exposed to UVR with running wheel access. In the iBAT of mice exposed to UVR and running wheels, elevated Atgl, Cd36, Fasn, Igf1, Pparγ, and Ucp1 mRNAs and reduced CD11c on F4-80 + MHC class II+ macrophages were observed, while renal Sglt2 mRNA levels were increased, compared to high-fat diet alone (P ≤ 0.03). Blood levels of 25-hydroxyvitamin D were not increased by exposure to UVR and/or access to running wheels. In conclusion, when combined with physical activity, low-dose UVR may more effectively limit adiposity (specifically, body weight and hepatic steatosis) and modulate metabolic and immune pathways in iBAT.