Voluntary Wheel Running Research Articles

Effects of long-term voluntary wheel running and selective breeding for wheel running on femoral nutrient canals.

The nutrient artery provides ~50%-70% of the total blood volume to long bones in mammals. Studying the functional characteristics of this artery invivo can be difficult and expensive, so most researchers have measured the nutrient foramen, an opening on the outer surface of the bone that served as the entry point for the nutrient artery during development and bone ossification. Others have measured the nutrient canal (i.e., the passage which the nutrient artery once occupied), given that the external dimensions of the foramen do not necessarily remain uniform from the periosteal surface to the medullary cavity. The nutrient canal, as an indicator of blood flow to long bones, has been proposed to provide a link to studying organismal activity (e.g., locomotor behavior) from skeletal morphology. However, although external loading from movement and activity causes skeletal remodeling, it is unclear whether it affects the size or configuration of nutrient canals. To investigate whether nutrient canals can exhibit phenotypic plasticity in response to physical activity, we studied a mouse model in which four replicate high runner (HR) lines have been selectively bred for high voluntary wheel-running behavior. The selection criterion is the average number of wheel revolutions on days 5 and 6 of a 6-day period of wheel access as young adults (~6-8 weeks old). An additional four lines are bred without selection to serve as controls (C). For this study, 100 female mice (half HR, half C) from generation 57 were split into an active group housed with wheels and a sedentary group housed without wheels for 12 weeks starting at ~24 days of age. Femurs were collected, soft tissues were removed, and femora were micro-computed tomography scanned at a resolution of 12 μm. We then imported these scans into AMIRA and created 3D models of femoral nutrient canals. We tested for evolved differences in various nutrient canal traits between HR and C mice, plastic changes resulting from chronic exercise, and the selection history-by-exercise interaction. We found few differences between the nutrient canals of HR versus C mice, or between the active and sedentary groups. We did find an interaction between selection history and voluntary exercise for the total number of nutrient canals per femur, in which wheel access increased the number of canals in C mice but decreased it in HR mice. Our results do not match those from an earlier study, conducted at generation 11, which was prior to the HR lines reaching selection limits for wheel running. The previous study found that mice from the HR lines had significantly larger total canal cross-sectional areas compared to those from C lines. However, this discrepancy is consistent with studies of other skeletal traits, which have found differences between HR and C mice to be somewhat inconsistent across generations, including the loss of some apparent adaptations with continued selective breeding after reaching a selection limit for wheel-running behavior.

Estrogen-mediated individual differences in female rat voluntary running behavior.

Regular exercise has numerous health benefits, but the human population displays significant variability in exercise participation. Rodent models, such as voluntary wheel running (VWR) in rats, can provide insight into the underlying mechanisms of exercise behavior and its regulation. In this study, we focused on the role of estrogen on VWR in female rats. Female rats run more than males, and we aimed to determine to what extent running levels in females were regulated by estrogen signaling. The running behavior of rats (duration, speed, and total distance run) was measured under normal physiological conditions, ovariectomy (OVX), and estrogen replacement in an OVX background. Results show cyclic variations in running linked to the estrous cycle. Ovariectomy markedly reduced running and eliminated the cyclic pattern. Estrogen replacement through estradiol benzoate (EB) injections and osmotic minipumps reinstated running activity to pre-OVX levels and restored the cyclic pattern. Importantly, individual differences and ranking are preserved such that high versus low runners before OVX remain high and low runners after treatment. Further analysis revealed that individual variation in running distance was primarily caused by rats running different speeds, but rats also varied in running duration. However, it is noteworthy that this model also displays features distinct from estrogen-driven running behavior under physiological conditions, notably a delayed onset and a broader duration of running activity. Collectively, this estrogen causality VWR model presents a unique opportunity to investigate sex-specific mechanisms that control voluntary physical activity.NEW & NOTEWORTHY This study investigates estrogen's role in voluntary wheel running (VWR) behavior in female rats. Female rats exhibit greater running than males, with estrogen signaling regulating this activity. The estrous cycle influences running, whereas ovariectomy reduces it, and estrogen replacement restores it, maintaining individual differences under all conditions. Both running speed and duration contribute to VWR variations. These findings emphasize individual estrogen regulation in female exercise and provide an estrogen replacement animal model for investigating neurobiological underpinnings that drive voluntary exercise behavior.

The fatigue-inducing effects of cancer and its therapy are characterized by decreased physical activity in the absence of any motivational deficit

Although cancer and its therapy are well known to be associated with fatigue, the exact nature of cancer-related fatigue remains ill-defined. We previously reported that fatigue-like behavior induced independently by tumor growth and by the chemotherapeutic agent cisplatin is characterized by reduced voluntary wheel running and an intact motivation to expand effort for food rewards. The present set of experiments was initiated to characterize the functional consequences of fatigue induced by chemoradiotherapy in tumor-bearing mice and relate them to changes in the expression of genes coding for inflammation, mitochondria dynamics and metabolism. Two syngeneic murine models of cancer were selected for this purpose, a model of human papilloma virus-related head and neck cancer and a model of lung cancer. In both models, tumor-bearing mice were submitted to chemoradiotherapy to limit tumor progression. Two dimensions of fatigue were assessed, the physical dimension by changes in physical activity in mice trained to run in wheels and the motivational dimension by changes in the performance of mice trained to nose poke to obtain a food reward in a progressive ratio schedule of food reinforcement. Chemoradiotherapy reliably decreased wheel running activity but had no effect on performance in the progressive ratio in both murine models of cancer. These effects were the same for the two murine models of cancer and did not differ according to sex. Livers and brains were collected at the end of the experiments for qRT-PCR analysis of expression of genes coding for inflammation, mitochondria dynamics, and metabolism. The observed changes were mainly apparent in the liver and typical of activation of type I interferon and NF-κB-dependent signaling, with alterations in mitochondrial dynamics and a shift toward glycolysis. Although the importance of these alterations for the pathophysiology of cancer-related fatigue remains to be explored, the present findings indicate that fatigue brought on by cancer therapy in tumor-bearing mice is more physical than motivational.

Simple and Complex Wheel Running Effect on Depression, Memory, Neuroinflammation, and Neurogenesis in Alzheimer's Rat Model.

The aim of this study was to investigate 12 wk of simple and complex voluntary wheel running on Alzheimer's disease (AD), associated biomarkers, and behaviors. Sixty male Wistar rats were randomly divided into six groups: healthy control (Con-Sed), AD only (AD-Sed), simple wheel control (SWC), complex wheel control (CWC), simple wheel AD (SWAD), and complex wheel AD (CWAD). Novelty-suppressed feeding test and the Morris water maze test were used to evaluate depression and memory, respectively. Ki67 was measured in the hippocampus, whereas interleukin (IL)-1β and neural/glial antigen 2 (NG2) were measured in both the hippocampus and the prefrontal cortex. One-way ANOVA with Tukey's post hoc test was performed. AD-Sed group had significantly lower spacial memory ( P < 0.001) compared with Con-Sed. Simple and complex wheel running attenuated these deficits in the SWAD and CWAD groups, respectively ( P < 0.001). Only the CWAD group had significantly improved novelty-suppressed feeding test time compared with AD-Sed ( P < 0.001), equivalent to the healthy wheel running groups. AD-Sed has significantly higher hippocampal concentrations of Ki67 ( P = 0.01) compared with the Con-Sed. Both SWAD and CWAD had significantly reduced Ki67 with similar concentrations compared with the SWC and CWC groups ( P > 0.05). AD-Sed animals also presented with significantly higher hippocampal and prefrontal cortex concentrations of IL-1β compared with Con-Sed ( P < 0.001). SWAD and CWAD had no effect in changing these concentrations. Complex wheel running significantly increased NG2 in the healthy control and AD models, whereas simple wheel running significantly increased NG2 in the AD model. The results of our study suggest that complex wheel running might be more advantageous in promoting memory and neuroplasticity while reducing depression that is associated with AD.

A Single-Cell Transcriptomic Analysis of the Mouse Hippocampus After Voluntary Exercise

Exercise has been recognized as a beneficial factor for cognitive health, particularly in relation to the hippocampus, a vital brain region responsible for learning and memory. Previous research has demonstrated that exercise-mediated improvement of learning and memory in humans and rodents correlates with increased adult neurogenesis and processes related to enhanced synaptic plasticity. Nevertheless, the underlying molecular mechanisms are not fully understood. With the aim to further elucidate these mechanisms, we provide a comprehensive dataset of the mouse hippocampal transcriptome at the single-cell level after 4 weeks of voluntary wheel-running. Our analysis provides a number of interesting observations. For example, the results suggest that exercise affects adult neurogenesis by accelerating the maturation of a subpopulation of Prdm16-expressing neurons. Moreover, we uncover the existence of an intricate crosstalk among multiple vital signaling pathways such as NF-κB, Wnt/β-catenin, Notch, and retinoic acid (RA) pathways altered upon exercise in a specific cluster of excitatory neurons within the Cornu Ammonis (CA) region of the hippocampus. In conclusion, our study provides an important resource dataset and sheds further light on the molecular changes induced by exercise in the hippocampus. These findings have implications for developing targeted interventions aimed at optimizing cognitive health and preventing age-related cognitive decline.

Age-Dependent Effects of Voluntary Wheel Running Exercise on Voiding Behavior and Potential Age-Related Molecular Mechanisms in Mice.

Older men frequently develop lower urinary tract symptoms attributed to benign prostatic hyperplasia (LUTS/BPH). Risk factors for LUTS/BPH include sedentary lifestyle, anxiety/depression, obesity, and frailty, which all increase with age. Although physical exercise may reduce the progression and/or severity of LUTS/BPH, the age-related mechanisms responsible remain unknown. Voiding symptoms, body mass, and frailty were assessed after 4-weeks of voluntary wheel running in 2-month (n = 10) and 24-month (n = 8) old C57Bl/6J male mice. In addition, various social and individual behaviors were examined in these cohorts. Finally, cellular and molecular markers of inflammation and mitochondrial protein expression were assessed in prostate tissue and systemically. Despite running less (aged vs young X¯ = 12.3 vs 30.6 km/week; p = .04), aged mice had reduced voiding symptoms (X¯ = 67.3 vs 23.7; p < .0001) after 1 week of exercise, which was sustained through week 4 (X¯ = 67.3 vs 21.5; p < .0001). Exercise did not affect voiding symptoms in young mice. Exercise also increased mobility and decreased anxiety in both young and aged mice (p < .05). Exercise decreased expression of a key mitochondrial protein (PINK1; p < .05) and inflammation within the prostate (CD68; p < .05 and plasminogen activator inhibitor-1; p < .05) and in the serum (p < .05). However, a frailty index (X¯ = 0.17 vs 0.15; p = .46) and grip strength (X¯ = 1.10 vs 1.19; p = .24) were unchanged after 4 weeks of exercise in aged mice. Voluntary aerobic exercise improves voiding behavior and mobility, and decreases prostatic mitochondrial protein expression and inflammation in aged mice. This promising model could be used to evaluate molecular mechanisms of aerobic exercise as a novel lifestyle intervention for older men with LUTS/BPH.

Endurance Exercise Training Mitigates Diastolic Dysfunction in Diabetic Mice Independent of Phosphorylation of Ulk1 at S555.

Millions of diabetic patients suffer from cardiovascular complications. One of the earliest signs of diabetic complications in the heart is diastolic dysfunction. Regular exercise is a highly effective preventive/therapeutic intervention against diastolic dysfunction in diabetes, but the underlying mechanism(s) remain poorly understood. Studies have shown that the accumulation of damaged or dysfunctional mitochondria in the myocardium is at the center of this pathology. Here, we employed a mouse model of diabetes to test the hypothesis that endurance exercise training mitigates diastolic dysfunction by promoting cardiac mitophagy (the clearance of mitochondria via autophagy) via S555 phosphorylation of Ulk1. High-fat diet (HFD) feeding and streptozotocin (STZ) injection in mice led to reduced endurance capacity, impaired diastolic function, increased myocardial oxidative stress, and compromised mitochondrial structure and function, which were all ameliorated by 6 weeks of voluntary wheel running. Using CRISPR/Cas9-mediated gene editing, we generated non-phosphorylatable Ulk1 (S555A) mutant mice and showed the requirement of p-Ulk1at S555 for exercise-induced mitophagy in the myocardium. However, diabetic Ulk1 (S555A) mice retained the benefits of exercise intervention. We conclude that endurance exercise training mitigates diabetes-induced diastolic dysfunction independent of Ulk1 phosphorylation at S555.

Exercise leads to sex-specific recovery of behavior and pathological AD markers following adolescent ethanol exposure in the TgF344-AD model.

Human epidemiological studies suggest that heavy alcohol consumption may lead to earlier onset of Alzheimer's Disease (AD), especially in individuals with a genetic predisposition for AD. Alcohol-related brain damage (ARBD) during a critical developmental timepoint, such as adolescence, interacts with AD-related pathologies to accelerate disease progression later in life. The current study investigates if voluntary exercise in mid-adulthood can recover memory deficits caused by the interactions between adolescence ethanol exposure and AD-transgenes. Male and female TgF344-AD and wildtype F344 rats were exposed to an intragastric gavage of water (control) or 5 g/kg of 20% ethanol (adolescent intermittent ethanol; AIE) for a 2 day on/off schedule throughout adolescence (PD27-57). At 6 months old, rats either remained in their home cage (stationary) or were placed in a voluntary wheel running apparatus for 4 weeks and then underwent several behavioral tests. The number of cholinergic neurons in the basal forebrain and measure of neurogenesis in the hippocampus were assessed. Voluntary wheel running recovers spatial working memory deficits selectively in female TgF344-AD rats exposed to AIE and improves pattern separation impairment seen in control TgF344-AD female rats. There were sex-dependent effects on brain pathology: Exercise improves the integration of recently born neurons in AIE-exposed TgF344-AD female rats. Exercise led to a decrease in amyloid burden in the hippocampus and entorhinal cortex, but only in male AIE-exposed TgF344-AD rats. Although the number of basal forebrain cholinergic neurons was not affected by AD-transgenes in either sex, AIE did reduce the number of basal forebrain cholinergic neurons in female rats. These data provide support that even after symptom onset, AIE and AD related cognitive decline and associated neuropathologies can be rescued with exercise in unique sex-specific ways.

Multiple Sex- and Circuit-Specific Mechanisms Underlie Exercise-Induced Stress Resistance.

Prior physical activity reduces the risk of future stress-related mental health disorders including depression, anxiety, and post-traumatic stress disorder. Rodents allowed to engage in voluntary wheel running are similarly protected from behavioral consequences of stress. The present review summarizes current knowledge on mechanisms underlying exercise-induced stress resistance. A conceptual framework involving the development (during exercise) and expression (during stress) of stress resistance from exercise is proposed. During the development of stress resistance, adaptations involving multiple exercise signals and molecular mediators occur within neural circuits orchestrating various components of the stress response, which then respond differently to stress during the expression of stress resistance. Recent data indicate that the development and expression of stress resistance from exercise involve multiple independent mechanisms that depend on sex, stressor severity, and behavioral outcome. Recent insight into the role of the prefrontal cortex in exercise-induced stress resistance illustrates these multiple mechanisms. This knowledge has important implications for the design of future experiments aimed at identifying the mechanisms underlying exercise-induced stress resistance.

Voluntary wheel running access produces opposite effects in male and female rats on both palatable diet consumption and associated ventral striatal opioid- and dopamine-related gene expression.

The relationship between physical activity levels and feeding behaviors has been a focus of preclinical research for decades, yet this interaction has only recently been explored for potential sex differences. The aim of the present study was to isolate sex-dependent effects of voluntary wheel running (RUN) vs. sedentary locked wheel (SED) home cage conditions on palatability-driven feeding behavior using a 2-diet choice task between standard chow and a high-fat diet. The sex-dependent effects of physical activity on feeding behavior were examined following a within-subject novel reversal design of physical activity conditions (i.e., RUN > SED > RUN), to assess temporal sensitivity of the interaction. Following the final 2 weeks of reestablished and sustained RUN vs. SED conditions in separate groups of both males and females, reward-related opioid and dopamine gene expression within the nucleus accumbens (Acb) brain region were analyzed. Results demonstrated that the initial RUN > SED transition led to sex-dependent effects of SED condition, as males increased, and females decreased their high fat consumption, compared to their respective high fat consumption during previous RUN condition phase. Following reintroduction to the RUN condition, males decreased, and females increased their high fat consumption, compared to their separate SED control group. Last, sex-dependent shifts in ventral striatal opioid- and dopamine-related gene expression were observed to parallel the behavioral effects. The major findings of the study reveal that SED and RUN home cage conditions shift palatability-driven feeding in the opposite direction for males and females, these effects are sensitive to reversal, and these sex-dependent feeding behaviors track sex-dependent changes to critical reward-related gene expression patterns in the Acb. Considering the present high rates of sedentary behavior and obesity, furthering our understanding of the interaction between physical activity (or lack thereof) and feeding behavior should be a priority, especially in the context of these divergent sex-dependent outcomes.

Hypothalamic Orexinergic Neurons Projecting to the Mesencephalic Locomotor Region Are Activated by Voluntary Wheel Running Exercise in Rats.

Cardiovascular changes during exercise are regulated by a motor volitional signal, called central command, which originates in the rostral portions of the brain and simultaneously regulates somatomotor and autonomic nervous systems. Whereas we recently elucidated mesencephalic locomotor region (MLR) neurons projecting to the rostral ventrolateral medulla as a crucial component of the central circuit responsible for transmitting central command signals, upstream circuits that regulate the MLR neurons remain unknown. Orexinergic neurons, which primarily originate from the perifornical area (PeFA) of the hypothalamus and reportedly play roles in eliciting locomotion and elevating sympathetic activity, send axonal projection to the MLR. The knowledge led us to investigate whether central command signals are relayed through orexinergic neurons projecting to the MLR. We performed anterograde transsynaptic tagging with AAV1 encoding Cre to confirm the presence of MLR neurons postsynaptic to the PeFA in rats. We also conducted retrograde neural tracing with retrograde AAV, combined with immunohistochemical staining, to examine the excitability of MLR-projecting orexinergic neurons in rats that were allowed to freely run on the wheel for 90 min. A significant number of MLR neurons were labeled with Cre, indicating that PeFA neurons make synaptic contacts with MLR neurons. Moreover, immunoreactivities of Fos, a marker of neuronal excitation, were found in many MLR-projecting orexinergic neurons by voluntary wheel running exercise, compared to non-exercising control rats, especially in the intermediate-posterior, rather than anterior, and medial, rather than lateral, portions within the orexinergic neuron-distributing domain. The findings suggest that specifically located orexinergic neurons transmit central command signals onto the MLR for running exercise. Elucidating the role of these MLR-projecting orexinergic neurons in somatomotor control and autonomic cardiovascular control deserves further study to unveil central circuit mechanisms responsible for central command function.

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.

Voluntary wheel running is a non-invasive test to measure physical performance in aging mice

Voluntary wheel running is a non-invasive test to measure physical performance in aging mice

Voluntary exercise during puberty promotes spatial memory and hippocampal DG/CA3 synaptic transmission in mice.

Physical exercise has been shown to have an impact on memory and hippocampal function across different age groups. Nevertheless, the influence and mechanisms underlying how voluntary exercise during puberty affects memory are still inadequately comprehended. This research aims to examine the impacts of self-initiated physical activity throughout adolescence on spatial memory. Developing mice were exposed to a 4-wk voluntary wheel running exercise protocol, commencing at the age of 30d. After engaging in voluntary wheel running exercise during development, there was an enhancement in spatial memory. Moreover, hippocampal dentate gyrus and CA3 neurons rather than CA1 neurons exhibited an increase in the miniature excitatory postsynaptic currents and miniature inhibitory postsynaptic currents. In addition, there was an increase in the expression of NR2A/NR2B subunits of N-methyl-D-aspartate receptors and α1GABAA subunit of gamma-aminobutyric acid type A receptors, as well as dendritic spine density, specifically within dentate gyrus and CA3 regions rather than CA1 region. The findings suggest that voluntary exercise during development can enhance spatial memory in mice by increasing synapse numbers and improving synaptic transmission in hippocampal dentate gyrus and CA3 regions, but not in CA1 region. This study sheds light on the neural mechanisms underlying how early-life exercise improves cognitive function.

The role of TFE3 in mediating skeletal muscle mitochondrial adaptations to exercise training.

Transcription factor E3 (TFE3) is a transcription factor that activates the expression of lysosomal genes involved in the clearance of dysfunctional mitochondria, termed mitophagy. With exercise, TFE3 is presumed to optimize the mitochondrial pool through the removal of organelles via lysosomes. However, the molecular mechanisms of the involved pathways remain unknown. Wild-type (WT) and TFE3 knockout (KO) mice were subjected to 6 wk of voluntary wheel running as an endurance training regimen. This was followed by a 45-min bout of in situ stimulation of the sciatic nerve innervating hindlimb muscles to evaluate muscle fatigue and contractile properties. A subset of animals was treated with colchicine to measure autophagy and mitophagy flux. Fatigability during stimulation was reduced with training in WT animals, as seen by a 13% increase in the percentage of maximum force at 5 min of stimulation, and a 30% increase at 30 minutes. Permeabilized fiber oxygen consumption was also improved with training. Concurrent with improved muscle and mitochondrial function, cytochrome c oxidase (COX) activity and COX I protein expression were increased in trained WT animals compared to untrained animals, signifying an increase in mitochondrial content. These training adaptations were abolished with the loss of TFE3. Surprisingly, the absence of TFE3 did not affect lysosomal content nor did it blunt the induction of mitophagy flux with contractile activity compared to WT mice. Our results suggest that the loss of TFE3 compromises beneficial training adaptations that lead to improved muscle endurance and mitochondrial function.NEW & NOTEWORTHY Our understanding of the role of transcription factor E3 (TFE3) in skeletal muscle is very limited. This research shows that TFE3 plays a direct role in skeletal muscle mitochondrial enhancement with exercise training, thereby introducing a paradigm shift in our perception of the function of TFE3 in mitochondrial maintenance, beyond mitophagy. This research serves to introduce TFE3 as a protein that holds promise as a future therapeutic target for metabolic diseases and skeletal muscle dysfunction.

PAW, a cost-effective and open-source alternative to commercial rodent running wheels

Voluntary wheel running is a common measure of general activity in many rodent models across neuroscience and physiology. However, current commercial wheel monitoring systems can be cost-prohibitive to many investigators, with many of these systems requiring investments of thousands of dollars. In recent years, several open-source alternatives have been developed, and while these tools are much more cost effective than commercial system, they often lack the flexibility to be applied to a wide variety of projects. Here, we have developed PAW, a 3D Printable Arduino-based Wheel logger. PAW is wireless, fully self-contained, easy to assemble, and all components necessary for its production can be obtained for only $75 CAD. Furthermore, with its compact internal electronics, the 3D printed casing can be easily modified to be used with a wide variety of running wheel designs for a wide variety of rodent species. Data recorded with the PAW system shows circadian patterns of activity which is expected from mice and is consistent with results found in the literature. Altogether, PAW is a flexible, low-cost system that can be beneficial to a broad range of researchers who study rodent models.

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%.

Accelerated Ovarian Failure (AOF) is an Effective Transitional Menopausal Model for the Study of Alzheimer’s Disease

AbstractBackgroundBiological females account for 70% of Alzheimer’s disease (AD) cases. It’s hypothesized that the estrogen depletion females experience during menopause is a factor in the pathogenesis of AD1. The gold standard rodent model of ovariectomy doesn’t allow for the examination of the gradual loss of estrogen that occurs in humans through perimenopause to menopause2. Administration of 4‐vinylcyclohexene diepoxide (VCD) has emerged as a rodent model of transitional menopause. The goal of this study was to determine how AD and neuronal markers were impacted by the gradual depletion of estrogen in a VCD model of transitional menopause.MethodMature CD1 female mice were injected with VCD (160 mg/kg/d IP for 15 days) to cause gradual ovarian failure over 120 days. A control group was also injected with a vehicle. Sample was collected at four timepoints, two representative of early and late perimenopause (60 and 120 days post injection) while the other two represented early and late menopause (137 and 176 days post injection). At each timepoint, novel object recognition testing (NORT) was performed to assess changes in behavior and memory2. At euthanasia, the prefrontal cortex and hippocampus were collected for protein analysis.ResultThe NORT demonstrated that the VCD groups at all timepoints had lowered activate memory recall. The prefrontal cortex western blotting results demonstrated that the VCD mice had lower NeuN content across all timepoints. NeuN is a marker of mature neurons which when lowered can have detrimental consequences on memory. SNAP25, a pre‐synaptic protein involved in neuronal synaptic communication, was also lower in the prefrontal cortex of VCD mice across all timepoints.ConclusionThe VCD model had impacts on active memory recall which was accompanied by reductions in neuronal and synaptic markers. This indicates that the loss of estrogen through transitional menopause results in early changes in neuronal markers and memory.1. Iqbal, J. &amp; Zaidi, M. Understanding Estrogen Action during Menopause. Endocrinology 150, 3443‐3445 (2009).2. Mohammad, A., Finch, M. S., Sweezey‐Munroe, J. &amp; MacPherson, R. E. K. Voluntary wheel running alters markers of amyloid‐beta precursor protein processing in an ovarian hormone depleted model. Front. Endocrinol. 13, 1069404 (2022).

Regulation of insulin entry into the brain

AbstractBackgroundCentral nervous system (CNS) insulin has repeatedly been shown to play a role in cognition. Little, if any, insulin is synthesized in the brain and therefore requires navigation of the blood‐brain barrier (BBB) to act. The BBB is a unique structure in the brain that regulates the entry of serum substrates and can act as both a barrier and signaling structure. We hypothesize the BBB is a critical structure involved in the regulation of CNS insulin signaling and CNS insulin availability. We have investigated the regulation of insulin BBB transport and interactions under various conditions including exercise, brain insulin resistance, and have begun to explore the mechanisms for insulin transport across the BBB.MethodFor exercise, male and female mice were habituated to locked voluntary running wheels. After habituation, wheels were unlocked in some cages (exercise) for 24 hours while remaining locked (sedentary) in the others. For brain insulin resistance, mice were treated with an intracerebroventricular delivery of the insulin receptor antagonist, S961. For mechanisms involved in insulin BBB transport and interactions, endocytosis inhibitors were used to differentiate between clathrin and caveolin endocytosis. Following manipulation, insulin BBB pharmacokinetics were assessed with the quantitative multiple‐time regression analysis using radioactively labeled insulin and albumin, a marker for vascular space. Mice were injected intravenously or perfused in situ with the radiolabeled substrates and at timepoints up to 10 min, blood and brains collected and radioactivity measured. 125I‐insulin entry and binding to the BBB was assessed.ResultExercise enhanced 125I‐insulin interactions at the BBB. Specifically, exercise increased insulin BBB transport by two‐fold in males and increased insulin binding at the BBB in females. Brain insulin resistance impaired 125I‐insulin transport across the BBB, particularly in females. Lastly, caveolin‐mediated endocytosis may be involved in hypothalamic 125I‐insulin BBB transport.ConclusionWe have shown insulin BBB transport is highly regulated and can be impacted by exercise, brain insulin resistance, and may involve various endocytic pathways in a regional‐dependent manner. Continued investigation on the pathways involved in insulin BBB transport is warranted to aid in treating or preventing brain insulin resistance as occurs in Alzheimer’s disease.

Voluntary running wheel exercise induces cognitive improvement post traumatic brain injury in mouse model through redressing aberrant excitation regulated by voltage-gated sodium channels 1.1, 1.3, and 1.6

Traumatic brain injury (TBI) leads to disturbed brain discharge rhythm, elevated excitability, anxiety-like behaviors, and decreased learning and memory capabilities. Cognitive dysfunctions severely affect the quality of life and prognosis of TBI patients, requiring effective rehabilitation treatment. Evidence indicates that moderate exercise after brain injury decreases TBI-induced cognitive decline. However, the underlying mechanism remains unelucidated. Our results demonstrate that TBI causes cognitive impairment behavior abnormalities and overexpression of Nav1.1, Nav1.3 and Nav1.6 proteins inside the hippocampus of mice models. Three weeks of voluntary running wheel (RW) exercise treatments before or/and post-injury effectively redressed the aberrant changes caused by TBI. Additionally, a 10% exercise-conditioned medium helped recover cell viability, neuronal sodium current and expressions of Nav1.1, Nav1.3 and Nav1.6 proteins across cultured neurons after injury. Therefore, the results validate the neuroprotection induced by voluntary RW exercise treatment before or/and post-TBI. The RW exercise-induced improvement in cognitive behaviors and neuronal excitability could be associated with correcting the Nav1.1, Nav1.3, and Nav1.6 expression levels. The current study proves that voluntary exercise is an effective treatment strategy against TBI. The study also highlights novel potential targets for rehabilitating TBI, including the Navs proteins.