Voluntary Wheel Running Activity Research Articles

The effect of mitochondrial genome heterogeneity on voluntary wheel running activity in aged rats

Introduction: Variation in the response to exercise training is a widely accepted concept. A large portion of exercise response variability is attributable to genetic heritability, potentially due to inherited maternal mitochondrial characteristics. Importantly, humans exhibit a heterogenous mitochondrial genome. Unfortunately, many preclinical models used to investigate molecular transducers of exercise training are inbred rodent models that lack mitochondrial diversity, which has poor translatability to humans. Recently, a rat model has been generated to reflect human mitochondrial genome heterogeneity. Hence, we propose using this rat model to investigate the impact of mitochondrial genome heterogeneity on voluntary wheel running (VWR) activity. Objective: To investigate the effect of mitochondrial genome heterogeneity on VWR activity in aged rats. Hypothesis: VWR activity will differ between two rat strains with divergent mitochondrial genomes. Methodology: Male and female OKC-HETB and OKC-HETW rats were obtained from the Oklahoma City VA Medical Center. Briefly, the OKC-HETB and OKC-HETW rat strains were generated by a four-way cross strategy using four inbred strains (Brown Norway [BN], Fischer 344, Lewis, and Wistar Kyto [WKY]). Subsequent reciprocal crosses between males and females from the two F1 hybrids were made to generate genetically heterogeneous rats with mitochondrial genomes from either the BN (OKC-HETB) or WKY (OKC-HETW) parental strains. As a result, OKC-HETB and OKC-HETW rats have equal numbers of alleles yet divergent mitochondrial genomes. Endurance capacity and neuromuscular function in 18-to 20-month-old rats were assessed by treadmill running and rotarod protocols before and after 8 weeks of VWR. After post-testing, animals are euthanized at 21-24 months old, and tissues are collected. The mitochondrial function of obtained tissues will be analyzed via high-resolution respirometry, and protein levels will be quantified using immunohistochemistry and Western blotting. Results: Current baseline data shows female rats weighed less than males, which was not affected by strain. Although no strain effect on treadmill performance was observed, females ran longer than males during the treadmill test. However, this sex effect was lost within strain comparisons. There was no strain effect on rotarod performance as latency to fall times were similar between strains. However, OKCHetW rats showed some improved latency to falls over time. Female OKC-HETB rats had a longer latency to falls at baseline than their male counterparts, which became similar between the sexes over time. Conversely, female OKC-HETW rats developed longer latency to falls compared to their male counterparts over time. Currently, 2 weeks of VWR activity was highly variable among rats in the W stain but similar among rats in the B strain. Conclusions: Our preliminary findings suggest that mitochondrial genome heterogeneity does not impact baseline physical function outcomes such as endurance capacity and neuromuscular function in exercise naïve 18-20 months old rats. However, biological sex appears to have a greater influence. Currently, strain and sex did not affect 2-weeks of VWR activity. However, this study is currently ongoing using an 8-week VWR intervention. Importantly, this study will evaluate the impact of mitochondrial genome heterogeneity on VWR adaptations in young and aged rats. Wake Forest University School of Medicine Start-up Funds to Ahn. R21 AG072137 to Richardson, Stout, and Austad. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A pilot exploring the impact of paternal puberty blocking on offspring voluntary wheel running

Previous work from our lab has shown puberty blocking treatment in young female rats followed by discontinued use (or detransition) leads to decreased voluntary wheel running activity in their offspring. The purpose of the present study was to determine if puberty blocking and detransition in young male rats affects offspring voluntary wheel running activity. We hypothesized that offspring of previously puberty blocked male rats will have lower wheel running activity than offspring of control rats. Four week old, male Sprague-Dawley rats received either 100 μg of the gonadotropin releasing hormone agonist triptorelin daily as a puberty blocker or 0.9% saline daily as a control. At the end of the 4 week treatment period, injections ceased, and each male rat was paired with an age-matched female rat for breeding. The breeding period lasted approximately 8 weeks and resulted in pregnancy of each paired female. At 6 weeks of age, a portion of the offspring were randomly assigned to the following voluntary wheel running groups: male offspring of previously puberty blocked males (M-PBO, n=2), female offspring of previously puberty blocked males (F-PBO, n=2), male offspring of control males (M-CON, n=5), and female offspring of control males (F-CON, n=5). Offspring were housed in cages outfitted with voluntary running wheels, received food and water ad libitum, and were maintained on a12:12 hour light:dark cycle. Voluntary wheel running activity was monitored for 8 weeks, and between-group comparisons were made via Welch’s t-test. Voluntary wheel running activity is presented as number of wheel running rotations, and data are shown as mean ± standard error. For total wheel running activity over 8 weeks, M-PBO had significantly lower voluntary wheel running activity than M-CON (107,453 ± 50,683 rotations vs. 456,011 ± 62,970 rotations, respectively, p=0.0122). There were no differences observed, however, between F-PBO and F-CON for total 8-week wheel running activity (376,582 ± 1,847 rotations vs. 472,271 ± 116,017 rotations, p=0.4559). Additionally, M-PBO ran significantly less than M-CON in weeks 1, 2, 3, 6, 7, and 8 (Week 1: 5,606 ± 225 rotations vs. 17,824 ± 2,544 rotations, p=0.0084; Week 2: 11,537 ± 3,129 rotations vs. 51,882 ± 6,494 rotations, p=0.0025; Week 3: 10,157 ± 2,639 rotations vs. 79,257 ± 5,842 rotations, p=0.0001; Week 6: 15,816 ± 7,865 rotations vs. 64,425 ± 11,755 rotations, p=0.0207; Week 7: 14,068 ± 6,999 rotations vs. 58,112 ± 9,781 rotations, p=0.0178; Week 8: 13,234 ± 6351 rotations vs. 67,349 ± 16,142 rotations, p=0.0272, respectively). No differences were observed in weekly wheel running activity between F-PBO and F-CON. Based on the observed voluntary wheel running activity, puberty blocking male rats prior to breeding negatively impacted physical activity of male offspring but not female offspring. This is contrary to our previous work showing that puberty blocking treatment followed by detransition in female rats prior to breeding negatively impacted physical activity of both male and female offspring. Our hypothesis was therefore partially supported as M-PBO had significantly less wheel running activity than M-CON, but F-PBO and F-CON had similar wheel running activity. Supported by a University of Northern Colorado Provost's Seed Grant awarded to DSH. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endurance exercise preserves physical function in adult and older male C57BL/6 mice: high intensity interval training (HIIT) versus voluntary wheel running (VWR).

Exercise has been shown to improve physical function, mitigate aspects of chronic disease and to potentially alter the trajectory of age-related onset of frailty and sarcopenia. Reliable and valid preclinical models are necessary to elucidate the underlying mechanisms at the intersection of age, exercise, and functional decline. The purpose of this study was to compare, head to head, the effects of two common pre-clinical models of endurance exercise: high intensity interval training (HIIT) and voluntary wheel running (VWR). The hypothesis was that a prescribed and regimented exercise program, HIIT, would prove to be a superior training method to unregulated voluntary exercise, VWR. To investigate this hypothesis, we evaluated adult (n = 24, designated 10m, aged 6 months at the beginning of the study, 10 months at its completion) and older adult (n = 18, designated 26m, aging from 22 months to 26 months over the course of the study) C57BL/6 male mice. These mice were randomly assigned (with selection criteria) to a 13-week program of voluntary wheel running (VWR), high intensity interval training (HIIT), or sedentary control (SED). The functional aptitude of each mouse was determined pre- and post-training using our composite CFAB (comprehensive functional assessment battery) scoring system consisting of voluntary wheel running (volitional exercise and activity rate), treadmill (endurance), rotarod (overall motor function), grip meter (forelimb strength), and inverted cling (whole body strength/endurance). To measure sarcopenia, we tracked body mass, body composition (with EchoMRI), plantar flexor torque (in 10m), and measured muscle wet mass post-training. Overall, adult CFAB scores decreased while body mass and percent body fat increased as they matured; however, exercise significantly mitigated the changes (p < 0.05) compared to SED. Older adults demonstrated preservation of function (CFAB) and reduced body fat (p < 0.05) compared to SED. To conclude, both types of exercise maintained physical function equally in older mice.

Effects of Puberty Blocker Treatment on Voluntary Wheel Running Activity in Young Rats

Background: Barriers to physical activity in transgender youth often center on social and psychological factors, but the effects of puberty blocking treatment that some youth receive on physical activity have yet to be explored. This study investigated the effects of puberty blocking treatment on physical activity in young female and male rats. Methods: Four week old female (F, n=19) and male rats (M, n=19) received the gonadotropin releasing hormone agonist (GnRHa) triptorelin as a puberty blocker (F-PB, n=10; M-PB, n=10) or saline as a control (F-CON, n=9; M-CON, n=9) for 4 weeks. Animals were then housed in voluntary wheel running (VWR) cages and activity was recorded during treatment period. Results: Main drug (p&lt;0.0001) and sex (p=0.045) effects with a significant drug x sex interaction (p=0.0095) was observed with total 4 week running distance with F-PB having a lower VWR activity than F-CON (240 ± 23 km vs 67 ± 9 km, respectively, p&lt;0.0001) and M-PB having lower VWR activity than M-CON (165 ± 15 km vs. 77 ± 14 km, respectively, p&lt;0.001). Significant differences in daily wheel running distance were first detected on day 5 for F-PB when compared to F-CON (p=0.036) and on day 11 for M-PB when compared to M-CON (p=0.034). Conclusions: Treatment with a GnRHa reduced voluntary running wheel activity in young female and male rats. Social and psychological factors are important variables impacting physical activity in transgender youth, but puberty blocker treatment may be an additional factor to consider when addressing physical activity.

Gut microbiota depletion minimally affects the daily voluntary wheel running activity and food anticipatory activity in female and male C57BL/6J mice.

Emerging evidence has highlighted that the gut microbiota plays a critical role in the regulation of various aspects of mammalian physiology and behavior, including circadian rhythms. Circadian rhythms are fundamental behavioral and physiological processes that are governed by circadian pacemakers in the brain. Since mice are nocturnal, voluntary wheel running activity mostly occurs at night. This nocturnal wheel-running activity is driven by the primary circadian pacemaker located in the suprachiasmatic nucleus (SCN). Food anticipatory activity (FAA) is the increased bout of locomotor activity that precedes the scheduled short duration of a daily meal. FAA is controlled by the food-entrainable oscillator (FEO) located outside of the SCN. Several studies have shown that germ-free mice and mice with gut microbiota depletion altered those circadian behavioral rhythms. Therefore, this study was designed to test if the gut microbiota is involved in voluntary wheel running activity and FAA expression. To deplete gut microbiota, C57BL/6J wildtype mice were administered an antibiotic cocktail via their drinking water throughout the experiment. The effect of antibiotic cocktail treatment on wheel running activity rhythm in both female and male mice was not detectable with the sample size in our current study. Then mice were exposed to timed restricted feeding during the day. Both female and male mice treated with antibiotics exhibited normal FAA which was comparable with the FAA observed in the control group. Those results suggest that gut microbiota depletion has minimum effect on both circadian behavioral rhythms controlled by the SCN and FEO respectively. Our result contradicts recently published studies that reported significantly higher FAA levels in germ-free mice compared to their control counterparts and gut microbiota depletion significantly reduced voluntary activity by 50%.

Physiological and Morphometric Differences in Resident Moderate-Altitude vs. Sea-Level Mice.

INTRODUCTION: High-altitude [>2400 m (7874 ft)] acclimatization has been well studied with physiological adaptations like reductions in body weight and exercise capacity. However, despite the significance of moderate altitude [MA, 1524-2438 m (5000-8000 ft)], acclimatization at this elevation is not well described. We aimed to investigate differences in mice reared at MA compared to sea level (SL). We hypothesized that MA mice would be smaller and leaner and voluntarily run less than SL mice.METHODS: C57BL/6 mice reared for at least three generations in Laramie, WY [2194 m (7198 ft), MA], were compared to C57BL/6J mice from Bar Harbor, ME [20 m (66 ft), SL]. We quantified body composition and exercise outputs as well as cardiopulmonary morphometrics. Subsets of MA and SL mice were analyzed to determine differences in neuronal activation after exercise.RESULTS: When body weight was normalized to tibia length, SL animals weighed 1.30 g ⋅ mm-1 while MA mice weighed 1.13 g · mm-1. Total fat % and trunk fat % were higher in MA mice with values of 41% and 39%, respectively, compared to SL mice with values of 28% and 26%, respectively. However, no differences were noted in leg fat %. MA animals had higher heart mass (119 mg) and lower lung mass (160 mg) compared to SL mice heart mass (100 mg) and lung mass (177 mg). MA mice engaged in about 40% less voluntary wheel-running activity than SL animals.DISCUSSION: Physiological differences are apparent between MA and SL mice, prompting a need to further understand larger scale implications of residence at moderate altitude.O'Connor AE, Hatzenbiler DM, Flom LT, Bobadilla A-C, Bruns DR, Schmitt EE. Physiological and morphometric differences in resident moderate-altitude vs. sea-level mice. Aerosp Med Hum Perform. 2023; 94(12):887-893.

A convolutional neural network to characterize mouse hindlimb foot strikes during voluntary wheel running.

Voluntary wheel running (VWR) is widely used to study how exercise impacts a variety of physiologies and pathologies in rodents. The primary activity readout of VWR is aggregated wheel turns over a given time interval (most often, days). Given the typical running frequency of mice (∼4Hz) and the intermittency of voluntary running, aggregate wheel turn counts, therefore, provide minimal insight into the heterogeneity of voluntary activity. To overcome this limitation, we developed a six-layer convolutional neural network (CNN) to determine the hindlimb foot strike frequency of mice exposed to VWR. Aged female C57BL/6 mice (22months, n = 6) were first exposed to wireless angled running wheels for 2h/d, 5days/wk for 3weeks with all VWR activities recorded at 30 frames/s. To validate the CNN, we manually classified foot strikes within 4800 1-s videos (800 randomly chosen for each mouse) and converted those values to frequency. Upon iterative optimization of model architecture and training on a subset of classified videos (4400), the CNN model achieved an overall training set accuracy of 94%. Once trained, the CNN was validated on the remaining 400 videos (accuracy: 81%). We then applied transfer learning to the CNN to predict the foot strike frequency of young adult female C57BL6 mice (4months, n = 6) whose activity and gait differed from old mice during VWR (accuracy: 68%). In summary, we have developed a novel quantitative tool that non-invasively characterizes VWR activity at a much greater resolution than was previously accessible. This enhanced resolution holds potential to overcome a primary barrier to relating intermittent and heterogeneous VWR activity to induced physiological responses.

Cisplatin decreases voluntary wheel-running activity but does not impair food-motivated behavior in mice

Cisplatin is a chemotherapeutic agent that is still commonly used to treat solid tumors. However, it has several toxic side effects due in large part to the mitochondrial damage that it induces. As this mitochondrial damage is likely to result in a decrease in the amount of metabolic energy that is available for behavioral activities, it is not surprising that fatigue develops in cancer patients treated with cisplatin. The present preclinical study was initiated to determine whether the detrimental effects of cisplatin were more pronounced on physical effort requiring a lot of energy versus effort that not only requires less energy but also procures energy in the form of food. For this purpose, mice were either trained to run in a wheel or to work for food in various schedules of food reinforcement before being treated with cisplatin. The experiments were carried out only in male mice as we had already reported that sex differences in cisplatin-induced neurotoxicities are minimal. Cisplatin was administered daily for one cycle of five days, or two cycles separated by a five-day rest. As observed in previous experiments, cisplatin drastically reduced voluntary wheel running. In contrast, when cisplatin was administered to food-restricted mice trained to work for a food reward in a progressive ratio schedule or in a fixed-interval schedule, it tended to increase the number of responses emitted to obtain the food rewards. This increase was not associated with any change in the temporal distribution of responses during the interval between two reinforcements in mice submitted to the fixed interval schedule of food reinforcement. When cisplatin was administered to food-restricted mice trained in an effort-based decision-making task in which they had to choose between working for a grain pellet with little effort and working for a preferred chocolate pellet with more effort, it decreased the total number of responses emitted to obtain food rewards. However, this effect was much less marked than the decrease in wheel running induced by cisplatin. The decrease in the effort invested in the procurement of food rewards was not associated with any change in the relative distribution of effort between low reward and high reward during the time course of the test session. These findings show that cisplatin decreases energy-consuming activities but not energy-procuring activities unless they require a choice between options differing in their cost-benefit ratio. Furthermore, they indicate that the physical dimension of fatigue is more likely to develop in cisplatin-treated individuals than the motivational dimension of fatigue.

Exercise modifies fatty acid perception and metabolism.

Obesity is a major public health issue, which is associated with several chronic diseases. In rodents, voluntary wheel running (VWR) is a type of exercise that influences ingestive behavior. This study aims to investigate the possible function of VWR activity in the perception of fat taste and if it mitigates the immediate effects of fatty acid (FA) ingestion METHODS: Male C57BL/6 mice were arbitrarily assigned to either a sedentary (SED) lifestyle or free access to a running wheel after 5 weeks of dietary regimen. Later these mice groups were used in the investigations on fat preference, metabolic tolerance, and electrophysiology. Diet-induced alterations in CD36 and GPR120 expression that are related to fat perception and the capacitative calcium signaling caused by FA in taste bud cells (TBCs) were also examined. In obese groups, VWR temporarily reduced body weight, demonstrated improvement in preference scores for FA, and recovered from a deterioration in glucose homeostasis. In CD36-positive TBCs, electrophysiological investigations showed alterations in [Ca2+ ]i caused by FA. Further, in the TBCs of circumvallate papillae (CVP), there are differences in the expression of the genes CD36 and GPR120 between the active and SED controls. Obese mice also show lower incentive salience for long-chain fatty acids (LCFA) and adapted to the reward system of VWR which may lead to improved incentive salience accredited to wheel running CONCLUSION: In conclusion, this study provides the first evidence that VWR causes orosensory adaptations to fat and appears to alter taste preference for LCFAs.

Sex differences in body composition, voluntary wheel running activity, balance performance, and auditory function in CBA/CaJ mice across the lifespan

Hearing loss is the third most prevalent chronic health condition affecting older adults and age-related hearing loss (ARHL) is the most common form of hearing impairment. Significant sex differences in hearing have been documented in humans and rodents. In general, the results of these studies show that men lose their hearing more rapidly than women. However, the cellular mechanism underlying sex differences in hearing or hearing loss remains largely unknown, and to our knowledge, there is no well-established animal model for studying sex differences in hearing. In the current study, we examined sex differences in body composition, voluntary wheel running activity, balance performance, auditory function, and cochlear histology in young, middle-age, and old CBA/CaJ mice, a model of age-related hearing loss. As expected, body weight of young females was lower than that of males. Similarly, lean mass and total water mass of young, middle-age, and old females were lower than those of males. Young females showed higher voluntary wheel running activity during the dark cycle, an indicator of mobility, physical activity, and balance status, compared to males. Young females also displayed higher auditory brainstem response (ABR) wave I amplitudes at 8 kHz, wave II, III, V amplitudes at 8 and 48 kHz, and wave IV/I and V/I amplitude ratios at 48 kHz compared to males. Collectively, our findings suggest that the CBA/CaJ mouse strain is a useful model to study the cellular mechanisms underlying sex differences in physical activity and hearing.

Effect of Metabolic Adaptation by Voluntary Running Wheel Activity and Aldosterone Inhibition on Renal Function in Female Spontaneously Hypertensive Rats.

Metabolic effects of physical activity may be reno-protective in the context of hypertension, although exercise stresses kidneys. Aldosterone participates in renal disease in hypertension, but exercise affects the plasma concentration of aldosterone. This study was designed to evaluate whether physical activity and pharmacological treatment by aldosterone have additive effects on renal protection in hypertensive rats. Female spontaneously hypertensive rats (SHR) or normotensive Wistar rats performed voluntary running wheel activity alone or in combination with aldosterone blockade (spironolactone). The following groups were studied: young and pre-hypertensive SHR (n = 5 sedentary; n = 10 running wheels, mean body weight 129 g), 10-month-old Wistar rats (n = 6 sedentary; n = 6 running wheels, mean body weight 263 g), 10-month-old SHRs (n = 18 sedentary, mean body weight 224 g; n = 6 running wheels, mean body weight 272 g; n = 6 aldosterone, mean body weight 219 g; n = 6 aldosterone and running wheels, mean body weight 265 g). Another group of SHRs had free access to running wheels for 6 months and kept sedentary for the last 3 months (n = 6, mean body weight 240 g). Aldosterone was given for the last 4 months. SHRs from the running groups had free access to running wheels beginning at the age of 6 weeks. Renal function was analyzed by microalbuminuria (Alb/Cre), urinary secretion of kidney injury molecule-1 (uKim-1), and plasma blood urea nitrogen (BUN) concentration. Molecular adaptation of the kidney to hypertension and its modification by spironolactone and/or exercise were analyzed by real-time PCR, immunoblots, and histology. After six months of hypertension, rats had increased Alb/Cre and BUN but normal uKim-1. Voluntary free running activity normalized BUN but not Alb/Cre, whereas spironolactone reduced Alb/Cre but not BUN. Exercise constitutively increased renal expression of proprotein convertase subtilisin/kexin type 9 (PCSK9; mRNA and protein) and arginase-2 (mRNA). Spironolactone reduced these effects. uKim-1 increased in rats performing voluntary running wheel activity exercise irrespectively of blood pressure and aldosterone blockade. We observed independent but no additive effects of aldosterone blockade and physical activity on renal function and on molecules potentially affecting renal lipid metabolism.

The GDF15-GFRAL axis mediates chemotherapy-induced fatigue in mice

Cancer-related fatigue is defined as a distressing persistent subjective sense of physical, emotional, and/or cognitive tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and that interferes with usual functioning. This form of fatigue is highly prevalent during cancer treatment and in some patients, it can persist for years after treatment has ended. An understanding of the mechanisms that drive cancer-related fatigue is still lacking, which hampers the identification of effective treatment options. Various chemotherapeutic agents including cisplatin are known to induce mitochondrial dysfunction and this effect is known to mediate chemotherapy-induced peripheral neuropathy and cognitive dysfunction. Mitochondrial dysfunction results in the release of mitokines that act locally and at distance to promote metabolic and behavioral adjustments to this form of cellular stress. One of these mitokines, growth differentiation factor 15 (GDF15) and its receptor, glial cell line-derived neurotrophic factor family receptor α–like (GFRAL), have received special attention in oncology as activation of GFRAL mediates the anorexic response that is responsible for cancer anorexia. The present study was initiated to determine whether GDF15 and GFRAL are involved in cisplatin-induced fatigue. We first tested the ability of cisplatin to increase circulating GDF15 in mice before assessing whether GDF15 can induce behavioral fatigue measured by decreased wheel running in healthy mice and increase behavioral fatigue induced by cisplatin. Mice administered a long acting form of GDF15, mGDF15-fc, decreased their voluntary wheel running activity. When the same treatment was administered to mice receiving cisplatin, it increased the amplitude and duration of cisplatin-induced decrease in wheel running. To determine whether endogenous GDF15 mediates the behavioral fatigue induced by cisplatin, we then administered a neutralizing monoclonal antibody to GFRAL to mice injected with cisplatin. The GFRAL neutralizing antibody mostly prevented cisplatin-induced decrease in wheel running and accelerated recovery. Taken together these findings demonstrate for the first time the role of the GDF15/GFRAL axis in cisplatin-induced behaviors and indicate that this axis could be a promising therapeutic target for the treatment of cancer-related fatigue.

Sex- and Neuropsychiatric-Dependent Circadian Alterations in Daily Voluntary Physical Activity Engagement and Patterns in Aged 3xTg-AD Mice.

Alzheimer's disease (AD) patients suffer from circadian rhythm alterations affecting their daily physical activity patterns with less willingness to perform a voluntary exercise. In preclinical studies, there is no clarity on whether animal models of AD can replicate these impairments. Here, we provide a proof of concept of the performance and behavioral effects of four weeks of voluntary wheel running (VWR) in a group of 14-month-old male and female 3xTg-AD mice at advanced stages of AD and the daily variance (behavioral circadian rhythmicity) of VWR associated with sex and their neuropsychiatric-like phenotype. Higher levels of horizontal exploration in the open field (OF) test were found in mice submitted to exercise. A linear mixed effect model showed significant sex-dependent differences in the VWR activity performed on the first night of follow-up, with high-NIBI males running less than high-NIBI females. Thus, an influence of NPS-like symptoms on the circadian patterns of VWR may account for such differences. In addition, males remained more active than females during diurnal periods. We hypothesize that this increment in energy expenditure during resting periods may be related to hyperactive behavior, similar to that observed in humans' exacerbated agitation or sundowning behavior. These findings support the usage of the 3xTg-AD mouse as a reliable model for studying circadian rhythm alterations in AD and, at the translational level, the importance of tailored and individualized physical activity programs in clinical settings.

An open-source, low-cost voluntary running activity tracking tool for in vivo rodent studies

In vivo rodent behavioral and physiological studies often benefit from measurement of general activity. However, many existing instruments necessary to track such activity are high in cost and invasive within home cages, some even requiring extensive separate cage systems, limiting their widespread use to collect data. We present here a low-cost open-source alternative that measures voluntary wheel running activity and allows for modulation and customization, along with a reproducible and easy to set-up code pipeline for setup and analysis in Arduino IDE and R. Our robust, non-invasive scalable voluntary running activity tracker utilizes readily accessible magnets, Hall effect sensors, and an Arduino microcontroller. Importantly, it can interface with existing rodent home cages and wheel equipment, thus eliminating the need to transfer the mice to an unfamiliar environment. The system was validated both for accuracy by a rotating motor used to simulate mouse behavior, and in vivo. Our recorded data is consistent with results found in the literature showing that the mice run between 3 to 16 kilometers per night, and accurately captures speed and distance traveled continuously on the wheel. Such data are critical for analysis of highly variable behavior in mouse models and allow for characterization of behavioral metrics such as general activity. This system provides a flexible, low-cost methodology, and minimizes the cost, infrastructure, and personnel required for tracking voluntary wheel activity.

Relationship Between Body Weight And Physical Activity In Aging Female F2 Mice.

Endurance activity and body weight (BW) are typically suggested to be inversely related throughout the lifespan, yet research has provided conflicting results. PURPOSE:We investigated the relationship between body weight and daily voluntary running wheel activity across the lifespan in female F2 mice. METHODS:One hundred twenty-nine female F2 mice derived from high physically active (SWR/J) and low physically active (DBA/2 J) F0 progenitors were individually housed in cages with running wheels and magnetic sensors. Daily duration (min/d), daily distance (km/d) and weekly BW measurements (g) were recorded from nine weeks of age until the end of life. Average daily speed (m/min) was calculated. RESULTS:Body weight increased with age (p < 0.0001). Daily duration increased from age 20 to 44 weeks and decreased thereafter to 88 weeks of age (p < 0.0001), while average daily running speed declined with age (p < 0.0001). Across the lifespan, we found a significant correlation between BW and duration (p < 0.0001, r = -0.117, r2 = 0.014) and between BW and speed (p = 0.005, r = -0.060, r2 = 0.004), with week-specific correlations for these variables both early and late in the lifespan. CONCLUSIONS:The significant correlations of speed and duration to BW early and late in the lifespan suggests differing influence of activity on BW depending upon the age of the mouse.

Remote solid cancers rewire hepatic nitrogen metabolism via host nicotinamide-N-methyltransferase

Cancers disrupt host homeostasis in various manners but the identity of host factors underlying such disruption remains largely unknown. Here we show that nicotinamide-N-methyltransferase (NNMT) is a host factor that mediates metabolic dysfunction in the livers of cancer-bearing mice. Multiple solid cancers distantly increase expression of Nnmt and its product 1-methylnicotinamide (MNAM) in the liver. Multi-omics analyses reveal suppression of the urea cycle accompanied by accumulation of amino acids, and enhancement of uracil biogenesis in the livers of cancer-bearing mice. Importantly, genetic deletion of Nnmt leads to alleviation of these metabolic abnormalities, and buffers cancer-dependent weight loss and reduction of the voluntary wheel-running activity. Our data also demonstrate that MNAM is capable of affecting urea cycle metabolites in the liver. These results suggest that cancers up-regulate the hepatic NNMT pathway to rewire liver metabolism towards uracil biogenesis rather than nitrogen disposal via the urea cycle, thereby disrupting host homeostasis.

Development of a Mouse Model for Chronic Fatigue Syndrome

The purpose of this study was to develop a clinically relevant mouse model of CFS to allow for the testing of underlying mechanisms and development of novel treatment interventions. Mice were injected with either lipopolysaccharide (LPS) or Poly I:C systemically (0.1- 1.0 mg/kg LPS, i.p. or 0.6-6mg/kg Poly I:C) and compared to a vehicle control injection. To test for fatigue-like behaviors, we examined voluntary wheel running (VWR) and open field activity. To test for pain-like behaviors, muscle withdrawal thresholds (MWT) and mechanical sensitivity of the paw. Measurements were assessed before and up to 1 week after injection of LPS or Poly I:C. Differences in voluntary running wheel data were assessed using mixed model analysis for differences between dose, time and an interaction between dose and time. Differences in open field parameters, MWT, and paw sensitivity between groups were assessed using repeated measures ANOVAs. Running wheel activity was reduced after injection of either LPS or Poly I:C (χ2=15.4; p=0.003). LPS reduced running wheel activity on days 1-3 for the 1.0 mg/kg dose of LPS and on Day 1 for Poly I:C when compared to vehicle (p<0.001). Lower doses of LPS showed faster recovery to baseline. For the open field testing, LPS reduced in distance travelled (F=9.1; p<0.001), increase in time standing still (F=6.5, p=0.001) but not time in center (F= 1.1, p=0.36) 24h after infection. Post-hoc testing (Tukey's test) showed a significant difference between the vehicle and the 1.0 mg/kg group of LPS (p=0.001). Similar reductions were observed for the 6 mg/kg group of Poly I:C (p<0.001). For pain behaviors, there was no difference between groups in the MWT or paw sensitivity (p>0.05) for either LPS or Poly I:C. These results show that a single injection of an infectious agent reduces physical activity and exploratory behavior, but does not produce pain behaviors.

BDNF Val66Met Polymorphism Reduces the Fatigue-Like Effects of 5-Fluorouracil on Voluntary Wheel-Running Activity in Mice.

Fatigue is a persistent and debilitating symptom following cancer treatments such as chemotherapy. Recent clinical studies have suggested a common single-nucleotide polymorphism of brain-derived neurotrophic factor (BDNF), Val66Met (rs6265), may be related to the severity of fatigue following cancer treatment. In this study, we tested transgenic mice homozygous for the human Val66Met BDNF gene and wild-type controls. We injected three doses of 5-fluorouracil (5FU) as a model of chemotherapy treatment, and we used changes in voluntary wheel running activity (VWRA) as a measure of fatigue-like behavior. Prior to 5FU injection, we found that during the baseline wheel-running period, the Val66Met mice lost more weight than WT controls. We next administered 5FU and saw a robust fatigue-like phenotype that lasted about 2 weeks. During the first week, the fatigue-like phenotype was less severe in the Val66Met mice and unrelated to the age of the mice. In contrast, during the second week after 5FU treatment, the fatigue-like phenotype was unrelated to the BDNF genotype but was more severe in middle aged mice compared to young mice. We conclude that the BDNF polymorphism may play a direct, protective role against chemotherapy-induced fatigue.

Voluntary wheel running behaviour as a tool to assess the severity in a mouse pancreatic cancer model.

Laboratory animals frequently undergo routine experimental procedures such as handling, restraining and injections. However, as a known source of stress, these procedures potentially impact study outcome and data quality. In the present study, we, therefore, performed an evidence-based severity assessment of experimental procedures used in a pancreatic cancer model including surgical tumour induction and subsequent chemotherapeutic treatment via repeated intraperitoneal injections. Cancer cell injection into the pancreas was performed during a laparotomy under general anaesthesia. After a four-day recovery phase, mice received either drug treatment (galloflavin and metformin) or the respective vehicle substances via daily intraperitoneal injections. In addition to clinical scoring, an automated home-cage monitoring system was used to assess voluntary wheel running (VWR) behaviour as an indicator of impaired well-being. After surgery, slightly elevated clinical scores and minimal body weight reductions, but significantly decreased VWR behaviour were observed. During therapy, body weight declined in response to chemotherapy, but not after vehicle substance injection, while VWR activity was decreased in both cases. VWR behaviour differed between treatment groups and revealed altered nightly activity patterns. In summary, by monitoring VWR a high impact of repeated injections on the well-being of mice was revealed and substance effects on well-being were distinguishable. However, no differences in tumour growth between treatment groups were observed. This might be due to the severity of the procedures uncovered in this study, as exaggerated stress responses are potentially confounding factors in preclinical studies. Finally, VWR was a more sensitive indicator of impairment than clinical scoring in this model.

Effects of voluntary exercise on the expression of browning markers in visceral and subcutaneous fat tissue of normotensive and spontaneously hypertensive rats

High physical activity is important to optimize the function of adipose tissue. Dysfunctional adipose tissue contributes to the development of metabolic stress, chronic inflammation, and hypertension. To improve our current understanding of the interaction between physical exercise and adipose tissue, we analyzed the effect of 10 months voluntary running wheel activity of rats on uncoupling protein (UCP) 1 negative white adipose tissue (visceral and subcutaneous adipose tissue, VWAT and SWAT). Analysis was performed via RT-PCR and immunoblot from adipose tissues depicted from adult normotensive and spontaneously hypertensive female rats. UCP1 negative VWAT differed from UCP1 positive WAT and brown adipose tissue (BAT) from interscapular fat depots, by lacking the expression of UCP1 and low expression of Cidea, a transcriptional co-activator of UCP1. High physical activity affected the expression of five genes in SWAT (Visfatin (up), RBP5, adiponectin, Cidea, and Nrg4 (all down)) but only one gene (Visfatin, up) in VWAT. Furthermore, the expression of these genes is differentially regulated in VWAT and SWAT of normotensive and spontaneously hypertensive rats (SHR) under sedentary conditions (UCP2) and exercise (Visfatin, Cidea, Nrg4). Keeping the animals after 6 months of voluntary exercise under observation for an additional period of 4 months without running wheels, Visfatin, Cidea, and Nrg4 were stronger expressed in VWAT of SHRs than in sedentary control rats. In summary, our study shows that SWAT is more responsible to exercise than VWAT.