Treadmill running produces both positive and negative physiological adaptations in Sprague-Dawley rats

Voluntary Wheel Running Reduces Cardiometabolic Risks in Female Offspring Exposed to Lifelong High-Fat, High-Sucrose Diet

PURPOSE

Maternal and postnatal overnutrition has been linked to an increased risk of cardiometabolic diseases in offspring. This study investigated the impact of adult-onset voluntary wheel running to counteract cardiometabolic risks in female offspring exposed to a life-long high-fat, high-sucrose (HFHS) diet.

METHODS

Dams were fed either an HFHS or a low-fat, low-sucrose (LFLS) diet starting from 8 wk before pregnancy and continuing throughout gestation and lactation. Offspring followed their mothers' diets. At 15 wk of age, they were divided into sedentary (Sed) or voluntary wheel running (Ex) groups, resulting in four groups: LFLS/Sed ( n = 10), LFLS/Ex ( n = 5), HFHS/Sed ( n = 6), HFHS/Ex ( n = 5). Cardiac function was assessed at 25 wk, with tissue collection at 26 wk for mitochondrial respiratory function and protein analysis. Data were analyzed using two-way ANOVA.

RESULTS

Although maternal HFHS diet did not affect the offspring's body weight at weaning, continuous HFHS feeding postweaning resulted in increased body weight and adiposity, irrespective of the exercise regimen. HFHS/Sed offspring showed increased left ventricular wall thickness and elevated expression of enzymes involved in fatty acid transport (CD36, FABP3), lipogenesis (DGAT), glucose transport (GLUT4), oxidative stress (protein carbonyls, nitrotyrosine), and early senescence markers (p16, p21). Their cardiac mitochondria displayed lower oxidative phosphorylation (OXPHOS) efficiency and reduced expression of OXPHOS complexes and fatty acid metabolism enzymes (ACSL5, CPT1B). However, HFHS/Ex offspring mitigated these effects, aligning more with LFLS/Sed offspring.

CONCLUSIONS

Adult-onset voluntary wheel running effectively counteracts the detrimental cardiac effects of a lifelong HFHS diet, improving mitochondrial efficiency, reducing oxidative stress, and preventing early senescence. This underscores the significant role of physical activity in mitigating diet-induced cardiometabolic risks.

Benefits of exercise on cognitive impairment in alcohol use disorder following alcohol withdrawal

Although most cognitive impairments induced by prolonged alcohol consumption tend to improve within the initial months of abstinence, there is evidence suggesting certain cognitive deficits may persist. This study aimed to investigate the impact of aerobic exercise on learning and memory in alcohol use disorder (AUD) mice following a period of abstinence from alcohol. We also sought to assess the levels of monoamine neurotransmitters in the hippocampus. To this end, we established an AUD mouse model through a two-bottle choice (sucrose fading mode and normal mode) and chronic intermittent alcohol vapor (combined with intraperitoneal injection) and randomly allocated mice into exercise groups to undergo treadmill training. Learning and memory abilities were assessed through the Morris water maze test and spontaneous activity was evaluated using the open field test. The levels of dopamine, norepinephrine, serotonin, and brain-derived neurotrophic factor in the hippocampus were quantified using enzyme-linked immunoassay (ELISA) kits. The findings reveal that after cessation of alcohol consumption, learning and memory abilities in AUD mice did not completely return to normal levels. The observed enhancement of cognitive functions in AUD mice through aerobic exercise may be attributed to restoring levels of monoamine neurotransmitters in the hippocampus, boosting brain-derived neurotrophic factor (BDNF) concentrations, and facilitating an increase in hippocampal mass. These results offer empirical evidence to support aerobic exercise as a viable therapeutic strategy to alleviate cognitive deficits associated with AUD.

Treadmill Exercise Improves Behavioral and Neurobiological Alterations in Restraint-Stressed Rats

Stress is a state that is known to impact an organism's physiological and psychological balance as well as the morphology and functionality of certain brain areas. In the present work, chronic restraint stress (CRS) model rats treated with treadmill exercise were used to examine anomalies associated to emotion and mood as well as molecular changes in the brain. Forty male Sprague-Dawley rats were divided into control, stress, exercise, and stress+exercise groups. CRS were exposed to stress group rats and exercise group underwent a chronic treadmill exercise. Depressive-like behavior was evaluated with the forced swim test (FST) and tail suspension test (TST). For assessing anxiety-like behavior, the light-dark test (LDT) and the open field test (OFT) were used. The Morris water maze test (MWMT) was used for testing memory and learning. Brain's monoamine level and the expression of genes related to stress were measured. It was discovered that CRS lengthens latency in the MWMT, increases immobility in the FST and TST, decreases time in the light compartment, and causes hypoactivity in the OFT. CRS reduced the dopamine levels in the nucleus accumbens(NAc). Brain-derived neurotrophic factor (BDNF), dopamine receptors, and serotonin receptor (HTR2A) gene expression in the prefrontal cortex, corpus striatum, and hypothalamus were decreased by CRS. Exercise on a treadmill leads to increase NAc's dopamine and noradrenaline levels and prevented behavioral alterations. Exercise increased the alterations of BDNF expressions in the brain in addition to improving behavior. As a result, CRS-induced behavioral impairments were effectively reversed by chronic treadmill exercise with molecular alterations in the brain.

Animal model for tendinopathy

Background

Tendinopathy is a common motor system disease that leads to pain and reduced function. Despite its prevalence, our mechanistic understanding is incomplete, leading to limited efficacy of treatment options. Animal models contribute significantly to our understanding of tendinopathy and some therapeutic options. However, the inadequacies of animal models are also evident, largely due to differences in anatomical structure and the complexity of human tendinopathy. Different animal models reproduce different aspects of human tendinopathy and are therefore suitable for different scenarios. This review aims to summarize the existing animal models of tendinopathy and to determine the situations in which each model is appropriate for use, including exploring disease mechanisms and evaluating therapeutic effects.

Methods

We reviewed relevant literature in the PubMed database from January 2000 to December 2022 using the specific terms ((tendinopathy) OR (tendinitis)) AND (model) AND ((mice) OR (rat) OR (rabbit) OR (lapin) OR (dog) OR (canine) OR (sheep) OR (goat) OR (horse) OR (equine) OR (pig) OR (swine) OR (primate)). This review summarized different methods for establishing animal models of tendinopathy and classified them according to the pathogenesis they simulate. We then discussed the advantages and disadvantages of each model, and based on this, identified the situations in which each model was suitable for application.

Results

For studies that aim to study the pathophysiology of tendinopathy, naturally occurring models, treadmill models, subacromial impingement models and metabolic models are ideal. They are closest to the natural process of tendinopathy in humans. For studies that aim to evaluate the efficacy of possible treatments, the selection should be made according to the pathogenesis simulated by the modeling method. Existing tendinopathy models can be classified into six types according to the pathogenesis they simulate: extracellular matrix synthesis-decomposition imbalance, inflammation, oxidative stress, metabolic disorder, traumatism and mechanical load.

Conclusions

The critical factor affecting the translational value of research results is whether the selected model is matched with the research purpose. There is no single optimal model for inducing tendinopathy, and researchers must select the model that is most appropriate for the study they are conducting.

The translational potential of this article

The critical factor affecting the translational value of research results is whether the animal model used is compatible with the research purpose. This paper provides a rationale and practical guide for the establishment and selection of animal models of tendinopathy, which is helpful to improve the clinical transformation ability of existing models and develop new models.

The pathophysiology of rhabdomyolysis in ungulates and rats: towards the development of a rodent model of capture myopathy

Capture myopathy (CM), which is associated with the capture and translocation of wildlife, is a life-threatening condition that causes noteworthy morbidity and mortality in captured animals. Such wildlife deaths have a significant impact on nature conservation efforts and the socio-economic wellbeing of communities reliant on ecotourism. Several strategies are used to minimise the adverse consequences associated with wildlife capture, especially in ungulates, but no successful preventative or curative measures have yet been developed. The primary cause of death in wild animals diagnosed with CM stems from kidney or multiple organ failure as secondary complications to capture-induced rhabdomyolysis. Ergo, the development of accurate and robust model frameworks is vital to improve our understanding of CM. Still, since CM-related complications are borne from biological and behavioural factors that may be unique to wildlife, e.g. skeletal muscle architecture or flighty nature, certain differences between the physiology and stress responses of wildlife and rodents need consideration in such endeavours. Therefore, the purpose of this review is to summarise some of the major etiological and pathological mechanisms of the condition as it is observed in wildlife and what is currently known of CM-like syndromes, i.e. rhabdomyolysis, in laboratory rats. Additionally, we will highlight some key aspects for consideration in the development and application of potential future rodent models.

The Preventive Effect of Exercise and Oral Branched-Chain Amino Acid Supplementation on Obesity-Induced Brain Changes in Ldlr−/−.Leiden Mice

Exercise and dietary interventions are promising approaches to tackle obesity and its obesogenic effects on the brain. We investigated the impact of exercise and possible synergistic effects of exercise and branched-chain amino acids (BCAA) supplementation on the brain and behavior in high-fat-diet (HFD)-induced obese Ldlr−/−.Leiden mice. Baseline measurements were performed in chow-fed Ldlr−/−.Leiden mice to assess metabolic risk factors, cognition, and brain structure using magnetic resonance imaging. Thereafter, a subgroup was sacrificed, serving as a healthy reference. The remaining mice were fed an HFD and divided into three groups: (i) no exercise, (ii) exercise, or (iii) exercise and dietary BCAA. Mice were followed for 6 months and aforementioned tests were repeated. We found that exercise alone changed cerebral blood flow, attenuated white matter loss, and reduced neuroinflammation compared to non-exercising HFD-fed mice. Contrarily, no favorable effects of exercise on the brain were found in combination with BCAA, and neuroinflammation was increased. However, cognition was slightly improved in exercising mice on BCAA. Moreover, BCAA and exercise increased the percentage of epididymal white adipose tissue and muscle weight, decreased body weight and fasting insulin levels, improved the circadian rhythm, and transiently improved grip strength. In conclusion, BCAA should be supplemented with caution, although beneficial effects on metabolism, behavior, and cognition were observed.

The effect of single bout and prolonged aerobic exercise on tumor hypoxia in mice

The objectives of this study were to investigate 1) the effect of acute aerobic exercise on tumor hypoxia and blood perfusion, 2) the impact of exercise intensity, 3) the duration of the effect, and 4) the effect of prolonged training on tumor hypoxia and tumor growth. Female CDF1 mice were inoculated with the C3H mammary carcinoma either in the mammary fat pad or subcutaneously in the back. For experiments on the effect of different intensities in a single exercise bout, mice were randomized to 30-min treadmill running at low-, moderate-, or high-intensity speeds or no exercise. To investigate the prolonged effect on hypoxia and tumor growth, tumor-bearing mice were randomized to no exercise (CON) or daily 30-min high-intensity exercise averaging 2 wk (EX). Tumor hypoxic fraction was quantified using the hypoxia marker Pimonidazole. Initially, high-intensity exercise reduced tumor hypoxic fraction by 37% compared with CON [P = 0.046; 95% confidence interval (CI): 0.1; 10.3] in fat pad tumors. Low- and moderate-intensity exercises did not. Following experiments investigating the duration of the effect-as well as experiments in mice with back tumors-failed to show any exercise-induced changes in hypoxia. Interestingly, prolonged daily training significantly reduced hypoxic fraction by 60% (P = 0.002; 95% CI: 2.5; 10.1) compared with CON. Despite diverging findings on the acute effect of exercise on hypoxia, our data indicate that if exercise has a diminishing effect, high-intensity exercise is needed. Prolonged training reduced tumor hypoxic fraction-cautiously suggesting a potential clinical potential.NEW & NOTEWORTHY This study provides novel information on the effects of acute and chronic exercise on tumor hypoxia in mice. In contrast to the few related existing studies, diverging findings on tumor hypoxia after acute exercise were observed, suggesting that tumor model and location should be considered in future studies. Highly significant reductions in tumor hypoxia following chronic high-intensity exercise propose a future clinical potential but this should be investigated in patients.

Treadmill exercise training improves the high-fat diet-induced behavioral changes in the male rats

The purpose of this study was to investigate the effects of treadmill exercise training on obesity-induced behavioral changes in high-fat diet (HFD)-induced male rats. In this study, 40 male Sprague-Dawley rats were divided into 4 groups after they were weaned: Control (C), Exercise (E), Obese (O) and Obese + Exercise (O + E). For the obesity model % 60 high-fat diet were applied. After obesity was induced, rats were either moderate aerobic exercise (treadmill running) trained or left untrained. Different tasks to assess spatial learning and memory (Morris water maze test (MWMT)), depressive-like behavior (forced swimming test(FST), tail suspension test (TST) and anxiety-like behavior (light-dark test (LDT) and open field test (OFT)) were conducted. Exercise caused a significant reduction in duration of immobility in the O group in FST and the decrease in immobility in the O + E rats in TST. The O + E rats demonstrated a significant increase in the time spent in the light box as compared to the O group in the LDT. The O + E rats did not show any behavioral alterations as compared to all the other groups in the OFT. In the O + E group, there was a significant increase in the time spent in the target quadrant compared to the O group in the MWMT. Our results support that treadmill exercise could improve cognitive, depressive-like, anxiety-like behavioral changes in the HFD-induced obese rats.

Treadmill running increases the calcium sensitivity of myofilaments in diabetic rats

The cardiovascular benefits of regular exercise are unequivocal, yet patients with type 2 diabetes respond poorly to exercise due to a reduced cardiac reserve. The contractile response of diabetic cardiomyocytes to beta-adrenergic stimulation is attenuated, which may result in altered myofilament calcium sensitivity and post-translational modifications of cardiac troponin I (cTnI). Treadmill running increases myofilament calcium sensitivity in non‑diabetic rats, and thus we hypothesized that endurance training would increase calcium sensitivity of diabetic cardiomyocytes and alter site-specific phosphorylation of cTnI. Calcium sensitivity, or pCa₅₀, was measured in Zucker Diabetic Fatty (ZDF) non-diabetic (nDM) and diabetic (DM) rat hearts after 8 weeks of either a sedentary (SED) or progressive treadmill running (TR) intervention. Skinned cardiomyocytes were connected to a capacitance-gauge transducer and a torque motor to measure force as a function of pCa (‑log[Ca²⁺]). Specific phospho-sites on cTnI and O‑GlcNAcylation were quantified by immunoblot and total protein phosphorylation by fluorescent gel staining (ProQ Diamond). The novel finding in this study was that training increased pCa₅₀ in both DM and nDM cardiomyocytes (p = 0.009). Phosphorylation of cTnI amino acid residues Ser23/24, a crucial protein kinase A site, and Threonine (Thr)144, was lower in DM hearts, but there was no effect of training on site-specific phosphorylation. Additionally, total phosphorylation and O-GlcNAcylation levels were not different between SED and TR groups. These findings suggest that regular exercise may benefit the diabetic heart by specifically targeting myofilament contractile function.

Voluntary Wheel Running Reduces Vesicle Development in an Endometriosis Animal Model Through Modulation of Immune Parameters

Introduction

Endometriosis is a chronic gynecological disorder characterized by the growth of endometrial glands and stroma outside the endometrial cavity producing inflammation and pain. Previously we demonstrated that modulation of the hypothalamic pituitary adrenal (HPA) axis exacerbates the development and severity of this condition. A physically active lifestyle has been shown to confer health benefits in many chronic conditions by potentially acting as a stress buffer, thus we hypothesized that voluntary physical exercise can “realign/reset” the HPA axis resulting in reduced endometriosis symptoms in an animal model.

Methods

Endometriosis was induced in female Sprague Dawley rats by implanting uterine tissue next to the intestinal mesentery on day 0. Sham controls received sutures only. One group of endometriosis animals had access to a running wheel for 2 weeks prior to endometriosis induction until time of sacrifice at day 60. Sham and endometriosis controls received no exercise. All animals were examined for developed vesicles which were collected and measured. Uterine tissue was analyzed for cellular infiltration. Brain, liver, spleen, adrenal glands, leg muscles, and fat were collected, along with peritoneal fluid and blood.

Results

Endometriosis animals developed vesicles in 86.96% of the implants with significantly increased mesenteric fat compared to sham (p < 0.05). Exposure to exercise significantly decreased the size (p < 0.01) and number (p < 0.05) of vesicles that developed, as well as the mesenteric fat (p < 0.01). Exercised animals had higher levels of lactoferrin in peritoneal fluid, and decreased serum fractalkine and leptin. Exercise significantly increased estrogen alpha receptor expression levels (p < 0.01), while significantly decreasing estrogen receptor beta expression (p < 0.01) and macrophage infiltration (p < 0.05) in vesicles compared to non- exercised animals.

Conclusions

Our results suggest that voluntary physical activity might protect against endometriosis and alleviate the associated inflammation via immune modulation of the HPA axis. This offers the potential for further exploration of exercise as a complementary therapy in endometriosis patients.

Wireless, battery-free, and fully implantable electrical neurostimulation in freely moving rodents

Implantable deep brain stimulation (DBS) systems are utilized for clinical treatment of diseases such as Parkinson's disease and chronic pain. However, long-term efficacy of DBS is limited, and chronic neuroplastic changes and associated therapeutic mechanisms are not well understood. Fundamental and mechanistic investigation, typically accomplished in small animal models, is difficult because of the need for chronic stimulators that currently require either frequent handling of test subjects to charge battery-powered systems or specialized setups to manage tethers that restrict experimental paradigms and compromise insight. To overcome these challenges, we demonstrate a fully implantable, wireless, battery-free platform that allows for chronic DBS in rodents with the capability to control stimulation parameters digitally in real time. The devices are able to provide stimulation over a wide range of frequencies with biphasic pulses and constant voltage control via low-impedance, surface-engineered platinum electrodes. The devices utilize off-the-shelf components and feature the ability to customize electrodes to enable broad utility and rapid dissemination. Efficacy of the system is demonstrated with a readout of stimulation-evoked neural activity in vivo and chronic stimulation of the medial forebrain bundle in freely moving rats to evoke characteristic head motion for over 36 days.

Two weeks of moderate intensity locomotor training increased corticosterone concentrations but did not alter the number of adropin-immunoreactive cells in the hippocampus of diabetic type 2 and control rats

Adropin (ADR) plays a role in metabolism regulation and its alterations in obesity and diabetes have been found. Treatment with ADR was beneficial in metabolic diseases, and physical exercise increased ADR concentrations in obese patients. However, data on the distribution of ADR in the brain are sparse. The role of metabolic status and physical exercise on its expression in the brain is undiscovered. We hypothesized that diabetes type 2 (DM2) and/or exercise will alter number of ADR-immunoractive (-ir) cells in the rat brain. Animals were divided into groups: diabetes type 2 (receiving high-fat diet and injections of streptozotocin) and control (fed laboratory chow diet; C). Rats were further divided into: running group (2 weeks of forced exercise on a treadmill) and non-running group. Body mass, metabolic and hormonal profiles were assessed. Immunohistochemistry was run to study ADR-ir cells in the brain. We found that: 1) in DM2 animals, running decreased insulin and increased glucose concentrations; 2) in C rats, running decreased insulin concentrations and had no effect on glucose concentration in blood; 3) running increased corticosterone (CORT) concentrations in DM2 and C rats; 4) ADR-ir cells were detected in the hippocampus and ADR-ir fibers in the arcuate nucleus of the hypothalamus, which is a novel location; 5) metabolic status and running, however, did not change number of these cells. We concluded that 2 weeks of forced moderate intensity locomotor training induced stress response present as increased concentration of CORT and did not influence number of ADR-ir cells in the brain.

The role of pre-pubertal training history on hippocampal neurotrophic factors and glucocorticoid receptor protein levels in adult male rats

Neurotrophic factors play an integral role in hippocampal plasticity, and interaction with HPA axis components, especially glucocorticoid receptors (GR), can mediate the structural and functional changes. In the present work, we investigated the long-term effects of combined exercise training (CET) and voluntary physical activity in an enriched environment (EE) in the pre-pubertal period on hippocampal neurotrophic factors and GR. For this purpose, a longitudinal study was designed. After three weeks, all rats were kept in the standard cages without any interventions until adulthood. Western blot analysis revealed a significant increase in hippocampal BDNF and VEGF protein levels in both EE and CET groups (P < 0.001), along with an increase in GR protein levels. In addition, EE decreased serum corticosterone levels compared to CET (P < 0.05). Serum insulin-like growth factor-1 (IGF-1) levels did not demonstrate remarkable changes between groups. Training interventions during sensitive developmental periods may produce profound and long-lasting effects on the hippocampus, at least in part by interactive effects of neurotrophic factors cascades and GR.

The downstream effects of forced exercise training and voluntary physical activity in an enriched environment on hippocampal plasticity in preadolescent rats

During critical periods of brain development, exercise-induced physical fitness may greatly impact the brain structure and function. Nevertheless, forced and intensive physical activities may display negative effects, particularly in the pre-pubertal period. Preadolescent rats were exposed to an enriched environment and combined exercise training for three consecutive weeks in the present study. There was a large cage with enriching stimuli and voluntary physical activity opportunities as an enriched environment (EE). The combined exercise training (CET) consisted of aerobic and resistance training programs. The protein levels of corticosterone (CORT), glucocorticoid receptors (GR_s), insulin-like growth factor-1 (IGF-1), brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF) were assessed using Enzyme-linked immunosorbent assay and western blotting. Cresyl violet staining was also used to evaluate the number of cells in the hippocampus. While GR_s levels were significantly increased in both EE and CET groups (P < 0.001), decreased CORT levels were found in enriched rats (P < 0.05). Moreover, elevated BDNF levels were found in the EE (P < 0.01) and CET (P < 0.05) groups. Similarly, VEGF significantly increased in the EE (P < 0.01) and CET (P < 0.05) animals. However, IGF-1 levels were high only in trained rats (P < 0.05). The number of cells also significantly increased in the DG and CA1 region of the hippocampus after each intervention (P < 0.001). These findings clarified that combined exercise training and voluntary physical activity in an enriched environment during the preadolescent period might promote the downstream plasticity effects on the hippocampus.

Comparison of murine behavioural and physiological responses after forced exercise by electrical shock versus manual prodding

NEW FINDINGS

What is the central question of this study? Forced treadmill exercise using electrical shock is the most common technique in rodent exercise studies. Here, we examined how the use of electrical shock during forced treadmill exercise affects behavioural and physiological responses in comparison to a novel non-electrical shock technique. What is the main finding and its importance? In comparison to mice that underwent traditional treadmill running induced by electrical shock, mice that underwent forced running using a novel technique involving gentle prodding to induce running showed: (i) higher locomotor activity; (ii) less anxiety-like behaviour; and (iii) altered exercise-induced muscle pain immediately after exercise.

ABSTRACT

Animal models of exercise have been useful to understand underlying cellular and molecular mechanisms. Many studies have used methods of exercise that are unduly stressful (e.g., electrical shock to force running), potentially skewing results. Here, we compared physiological and behavioural responses of mice after exercise induced using a prodding technique that avoids electrical shock versus a traditional protocol using electrical shock. We found that exercise performance was similar for both techniques; however, the shock group demonstrated significantly lower locomotor activity and higher anxiety-like behaviour. We also observed divergent effects on muscle pain; the prodding group showed hyperalgesia immediately after exercise, whereas the shock group showed hypoalgesia. Corticosterone concentrations were elevated to a similar extent for both groups. In conclusion, mice that were exercised without shock generated similar maximal exercise performance, but postexercise these mice showed an increase in locomotor activity, less anxiety-like behaviour and altered muscle pain in comparison to mice that exercised with shock. Our data suggest that running of mice without the use of electrical shock is potentially less stressful and might be a better technique to study the physiological and behavioural responses to exercise.

Barriers in translating preclinical rodent exercise metabolism findings to human health

Physical inactivity and low aerobic capacity are primary drivers of chronic disease pathophysiology and are independently associated with all-cause mortality. Conversely, increased physical activity and exercise are central to metabolic disease prevention and longevity. Although these relationships are well characterized in the literature, what remains incompletely understood are the mechanisms by which physical activity/exercise prevents disease. Given methodological constraints of clinical research, investigators must often rely on preclinical rodent models to investigate these potential underlying mechanisms. However, there are several key barriers to applying exercise metabolism findings from rodent models to human health. These barriers include housing temperature, nutrient metabolism, exercise modality, exercise testing, and sex differences. Increased awareness and understanding of these barriers will enhance the ability to impact human health through more appropriate experimental design and interpretation of data within the context of these factors.

Difference in the brain serotonin and its metabolite level and anxiety-like behavior between forced and voluntary exercise conditions in rats

Physical exercise is beneficial to both physical and mental health, though it is unclear whether voluntary and forced exercise have the same effects. We investigated the effects of chronic forced and voluntary wheel running on brain levels of serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and anxiety-like behavioral change in rats. Forty-eight rats were randomly assigned to standard cages (sedentary control: SC); voluntary exercise (free running on a wheel, V-EX); voluntary limited exercise (wheel available only 1 h per day, VL-EX); and forced exercise (running on a motorized wheel, F-EX). After 4 weeks, rats either underwent the open field test (OFT) or their 5-HT and 5-HIAA levels were measured in the major serotonergic neural cell bodies and projection areas. 5-HT and 5-HIAA levels in the dorsal and median raphe nuclei were increased in the V-EX, but not in the VL-EX and F-EX groups, compared with the SC group. In the paraventricular hypothalamic nucleus and caudate putamen, only 5-HT levels were increased in the V-EX group. Interestingly, in the amygdala, only 5-HIAA levels were significantly increased in the V-EX group. Conversely, we found that F-EX rats showed no significant 5-HT changes and increased anxiety-like behavior. VL-EX did not have significant beneficial effects on any of the experimental parameters. These data suggest that only unlimited voluntary exercise stimulates the serotonergic system and suppresses anxiety-like behavior.

Physical Activity Shapes the Intestinal Microbiome and Immunity of Healthy Mice but Has No Protective Effects against Colitis in MUC2-/- Mice

Perturbation in the gut microbial ecosystem has been associated with various diseases, including inflammatory bowel disease. Habitual physical activity, through its ability to modulate the gut microbiome, has recently been shown to prophylactically protect against chemically induced models of murine colitis. Here, we (i) confirm previous reports that physical activity has limited but significant effects on the gut microbiome of mice and (ii) show that such changes are associated with anti-inflammatory states in the gut, such as increased production of beneficial short-chain fatty acids and lower levels of proinflammatory immune markers implicated in human colitis; however, we also show that (iii) these physical activity-derived benefits are completely lost in the absence of a healthy intestinal mucus layer, a hallmark phenotype of human colitis.

The interactions among humans, their environment, and the trillions of microbes residing within the human intestinal tract form a tripartite relationship that is fundamental to the overall health of the host. Disruptions in the delicate balance between the intestinal microbiota and host immunity are implicated in various chronic diseases, including inflammatory bowel disease (IBD). There is no known cure for IBD; therefore, novel therapeutics targeting prevention and symptom management are of great interest. Recently, physical activity in healthy mice was shown to be protective against chemically induced colitis; however, the benefits of physical activity during or following disease onset are not known. In this study, we examine whether voluntary wheel running is protective against primary disease symptoms in a mucin 2-deficient (Muc2^−/−) lifelong model of murine colitis. We show that 6 weeks of wheel running in healthy C57BL/6 mice leads to distinct changes in fecal bacteriome, increased butyrate production, and modulation in colonic gene expression of various cytokines, suggesting an overall primed anti-inflammatory state. However, these physical activity-derived benefits are not present in Muc2^−/− mice harboring a dysfunctional mucosal layer from birth, ultimately showing no improvements in clinical signs. We extrapolate from our findings that while physical activity in healthy individuals may be an important preventative measure against IBD, for those with a compromised intestinal mucosa, a commonality in IBD patients, these benefits are lost.

IMPORTANCE Perturbation in the gut microbial ecosystem has been associated with various diseases, including inflammatory bowel disease. Habitual physical activity, through its ability to modulate the gut microbiome, has recently been shown to prophylactically protect against chemically induced models of murine colitis. Here, we (i) confirm previous reports that physical activity has limited but significant effects on the gut microbiome of mice and (ii) show that such changes are associated with anti-inflammatory states in the gut, such as increased production of beneficial short-chain fatty acids and lower levels of proinflammatory immune markers implicated in human colitis; however, we also show that (iii) these physical activity-derived benefits are completely lost in the absence of a healthy intestinal mucus layer, a hallmark phenotype of human colitis.

Neuroprotective Effects of Chronic Resveratrol Treatment and Exercise Training in the 3xTg-AD Mouse Model of Alzheimer's Disease

To date, there is no cure or effective treatment for Alzheimer’s disease (AD), a chronic neurodegenerative condition that affects memory, language, and behavior. AD is characterized by neuroinflammation, accumulation of brain amyloid-beta (Aβ) oligomers and neurofibrillary tangles, increased neuronal apoptosis, and loss of synaptic function. Promoting regular exercise and a diet containing polyphenols are effective non-pharmacological approaches that prevent the progression of neurodegenerative diseases. In this study, we measured various conformational toxic species of Aβ and markers of inflammation, apoptosis, endolysosomal degradation, and neuroprotection after 5 months of exercise training (ET), resveratrol (Resv) treatment, or combination treatment in the 3xTg-AD mouse model of AD. Our main results indicate that Resv decreased neuroinflammation and accumulation of Aβ oligomers, increased levels of neurotrophins, synaptic markers, silent information regulator, and decreased markers of apoptosis, autophagy, endolysosomal degradation and ubiquitination in the brains of 3xTg-AD mice. ET improved some markers related to neuroprotection, but when combined with Resv treatment, the benefits achieved were as effective as Resv treatment alone. Our results show that the neuroprotective effects of Resv, ET or Resv and ET are associated with reduced toxicity of Aβ oligomers, suppression of neuronal autophagy, decreased apoptosis, and upregulation of key growth-related proteins.

Treadmill exercise has minimal impact on obesogenic diet-related gut microbiome changes but alters adipose and hypothalamic gene expression in rats

Background

Exercise has been extensively utilised as an effective therapy for overweight- and obesity-associated changes that are linked to health complications. Several preclinical rodent studies have shown that treadmill exercise alongside an unhealthy diet improves metabolic health and microbiome composition. Furthermore, chronic exercise has been shown to alter hypothalamic and adipose tissue gene expression in diet-induced obesity. However, limited work has investigated whether treadmill exercise commenced following exposure to an obesogenic diet is sufficient to alter microbiome composition and metabolic health.

Methods

To address this gap in the literature, we fed rats a high-fat/high-sugar western-style cafeteria diet and assessed the effects of 4 weeks of treadmill exercise on adiposity, diet-induced gut dysbiosis, as well as hypothalamic and retroperitoneal white adipose tissue gene expression. Forty-eight male Sprague-Dawley rats were allocated to either regular chow or cafeteria diet and after 3 weeks half the rats on each diet were exposed to moderate treadmill exercise for 4 weeks while the remainder were exposed to a stationary treadmill.

Results

Microbial species diversity was uniquely reduced in exercising chow-fed rats, while microbiome composition was only changed by cafeteria diet. Despite limited effects of exercise on overall microbiome composition, exercise increased inferred microbial functions involved in metabolism, reduced fat mass, and altered adipose and hypothalamic gene expression. After controlling for diet and exercise, adipose Il6 expression and liver triglyceride concentrations were significantly associated with global microbiome composition.

Conclusions

Moderate treadmill exercise induced subtle microbiome composition changes in chow-fed rats but did not overcome the microbiome changes induced by prolonged exposure to cafeteria diet. Predicted metabolic function of the gut microbiome was increased by exercise. The effects of exercise on the microbiome may be modulated by obesity severity. Future work should investigate whether exercise in combination with microbiome-modifying interventions can synergistically reduce diet- and obesity-associated comorbidities.

Differential effects of chronic voluntary wheel-running on morphine induced brain stimulation reward, motor activity and striatal dopaminergic activity

Physical exercise could be a protective factor against the development of substance use disorders; however, a number of preclinical studies report reward-enhancing effects of exercise for various drugs of abuse. We examined the effects of chronic wheel-running on brain reward sensitivity, reaction to novelty, reward-facilitating and locomotor-stimulating effects of morphine, using the intracranial self-stimulation (ICSS) and the open field test (OFT). Male Sprague-Dawley rats were randomly assigned to a sedentary or exercised group. For the ICSS procedure, rats were implanted with electrodes and trained to respond for electrical stimulation. Several indices were recorded in the training phase to estimate brain reward sensitivity. Once responding was stable, the animals of both groups received systemic injections of morphine and their ICSS thresholds were measured with the curve-shift paradigm. Employing the OFT, basal and morphine-induced locomotor activity was measured. Finally, basal and morphine-evoked tissue levels of dopamine and its metabolites were determined in the striatum using gas chromatography/mass spectrometry. Chronic wheel-running decreased brain reward sensitivity and subsequently increased the reward-facilitating effect of morphine. Exercised animals demonstrated a decreased reaction to novelty and reduced morphine-induced locomotion. Lastly, dopaminergic activity was decreased in the striatum of exercised animals under basal conditions, whereas morphine administration led to an increase in dopamine turnover. These findings indicate that chronic voluntary exercise exerts divergent effects on reward function, psychomotor activity and the reward-facilitating and locomotor-activating effects of opioids during adulthood. Our results provide insights into the increased non-medical use of opioids among young athletes reported in the literature.

Islets of Langerhans phenotype alterations induced by fatty diet and physical activity levels in Wistar rats

OBJECTIVES

Physical inactivity (PIn) and a fatty diet (FD) are closely linked to development of metabolic syndrome (MetS), overloading the endocrine pancreas seeking energy homeostasis. However, the relative contribution of FD and PIn to the pancreatic overload is unknown. The aim of this study was to verify the isolated and conjugated influence of FD and PIn in the islets of Langer hans (islets) structure and function related to overload in Wistar rats.

METHODS

Male Wistar rats were divided into four groups (n = 10/group): active groups, fed with fat (AFD) or standard (ASD) diet; and physically inactive groups, fed with fat (SFD) or standard (SSD) diet for 21 wk. Glucose tolerance (GT) and insulin sensitivity (IS) were assessed before sacrifice. Retroperitoneal adipose tissue and pancreas were weighted (PW), and pancreas samples processed for histologic analyses.

RESULTS

Only the FD-fed animals presented MS. Compared with standard diet, FD impaired GT and IS, decreased PW, and enlarged islets dimensions, with islets cellular death, inflammatory response, and enhanced collagen content, which were attenuated in AFD. Independent of the diet, PIn groups presented higher amounts of islets connective tissue, but without influence on inflammatory reaction and cellular death. The GT impairment was higher in the FD-fed groups, whereas the decreased IS was more pronounced in the PIn groups.

CONCLUSION

FD induced MS with detrimental effects on pancreas overload, inducing islets morphologic and functional maladaptation, which were attenuated in active animals. Physical activity was not able to prevent FD-induced MS. FD showed a negative influence on GT, whereas PIn mainly affected IS.

JumpDetector: An automated monitoring equipment for the locomotion of jumping insects

Continuous jumping behavior, a kind of endurance locomotion, plays important roles in insect ecological adaption and survival. However, the methods used for the efficient evaluation of insect jumping behavior remain largely lacking. Here, we developed a locomotion detection system named JumpDetector with automatic trajectory tracking and data analysis to evaluate the jumping of insects. This automated system exhibits more accurate, efficient, and adjustable performance than manual methods. By using this automatic system, we characterized a gradually declining pattern of continuous jumping behavior in 4th-instar nymphs of the migratory locust. We found that locusts in their gregarious phase outperformed locusts in their solitary phase in the endurance jumping locomotion. Therefore, the JumpDetector could be widely used in jumping behavior and endurance locomotion measurement.

Environmental Enrichment and Physical Exercise Attenuate the Depressive-Like Effects Induced by Social Isolation Stress in Rats

We assessed the antidepressant-like effects of environmental enrichment (EE) and physical exercise (PE) compared with the selective serotonin reuptake inhibitor fluoxetine against the depression-related neurobehavioral alterations induced by postweaning social isolation (SI) in rats. After 1 month of SI, rats were submitted to PE (treadmill), EE, or fluoxetine (10 mg/kg), which were compared with naïve SI and group-housed rats. After 1 month, behavior was analyzed in the open field (OFT), the sucrose preference (SPT), and the forced swimming (FST) tests. Afterward, the hippocampal serotonin contents, its metabolite, and turnover were measured. SI induced a depression-related phenotype characterized by a marginal bodyweight gain, anxiety, anhedonia, behavioral despair, and alterations of serotonin metabolism. EE produced the widest and largest antidepressive-like effect, followed by PE and fluoxetine, which were almost equivalent. The treatments, however, affected differentially the neurobehavioral domains investigated. EE exerted its largest effect on anhedonia and was the only treatment inducing anxiolytic-like effects. Fluoxetine, in contrast, produced its largest effect on serotonin metabolism, followed by its anti-behavioral despair action. PE was a middle-ground treatment with broader behavioral outcomes than fluoxetine, but ineffective to reverse the serotonergic alterations induced by SI. The most responsive test to the treatments was the FST, followed closely by the SPT. Although OFT locomotion and body weight varied considerably between groups, they were barely responsive to PE and fluoxetine. From a translational standpoint, our data suggest that exercise and recreational activities may have broader health benefits than antidepressants to overcome confinement and the consequences of chronic stress.

Running wheel access fails to resolve impaired sustainable health in mice feeding a high fat sucrose diet

Diet and physical activity are thought to affect sustainable metabolic health and survival. To improve understanding, we studied survival of mice feeding a low-fat (LF) or high-saturated fat/high sugar (HFS) diet, each with or without free running wheel (RW) access. Additionally several endocrine and metabolic health indices were assessed at 6, 12, 18 and 24 months of age. As expected, HFS feeding left-shifted survival curve of mice compared to LF feeding, and this was associated with increased energy intake and increased (visceral/total) adiposity, liver triglycerides, and increased plasma cholesterol, corticosterone, HOMA-IR, and lowered adiponectin levels. Several of these health parameters improved (transiently) by RW access in HFS and LF fed mice (i.e., HOMA-IR, plasma corticosterone), others however deteriorated (transiently) by RW access only in HFS-fed mice (i.e., body adiposity, plasma resistin, and free cholesterol levels). Apart from these multiple and sometimes diverging health effects of RW access, RW access did not affect survival curves. Important to note, voluntary RW activity declined with age, but this effect was most pronounced in the HFS fed mice. These results thus challenge the hypothesis that voluntary wheel running can counteract HFS-induced deterioration of survival and metabolic health.

Hypothalamic Crh/Avp, Plasmatic Glucose and Lactate Remain Unchanged During Habituation to Forced Exercise

It has been demonstrated that physical activity contributes to a healthier life. However, there is a knowledge gap regarding the neural mechanisms producing these effects. One of the keystones to deal with this problem is to use training programs with equal loads of physical activity. However, irregular motor and stress responses have been found in murine exercise models. Habituation to forced exercise facilitates a complete response to a training program in all rodents, reaching the same load of physical activity among animals. Here, it was evaluated if glucose and lactate - which are stress biomarkers - are increased during the habituation to exercise. Sprague-Dawley rats received an 8-days habituation protocol with progressive increments of time and speed of running. Then, experimental and control (non-habituated) rats were subjected to an incremental test. Blood samples were obtained to determine plasmatic glucose and lactate levels before, immediately after and 30 min after each session of training. Crh and Avp mRNA expression was determined by two-step qPCR. Our results revealed that glucose and lactate levels are not increased during the habituation period and tend to decrease toward the end of the protocol. Also, Crh and Avp were not chronically activated by the habituation program. Lactate and glucose, determined after the incremental test, were higher in control rats without previous contact with the wheel, compared with habituated and wheel control rats. These results suggest that the implementation of an adaptive phase prior to forced exercise programs might avoid non-specific stress responses.

Role of damage and management in muscle hypertrophy: Different behaviors of muscle stem cells in regeneration and hypertrophy

Skeletal muscle is a dynamic tissue with two unique abilities; one is its excellent regenerative ability, due to the activity of skeletal muscle-resident stem cells named muscle satellite cells (MuSCs); and the other is the adaptation of myofiber size in response to external stimulation, intrinsic factors, or physical activity, which is known as plasticity. Low physical activity and some disease conditions lead to the reduction of myofiber size, called atrophy, whereas hypertrophy refers to the increase in myofiber size induced by high physical activity or anabolic hormones/drugs. MuSCs are essential for generating new myofibers during regeneration and the increase in new myonuclei during hypertrophy; however, there has been little investigation of the molecular mechanisms underlying MuSC activation, proliferation, and differentiation during hypertrophy compared to those of regeneration. One reason is that 'degenerative damage' to myofibers during muscle injury or upon hypertrophy (especially overloaded muscle) is believed to trigger similar activation/proliferation of MuSCs. However, evidence suggests that degenerative damage of myofibers is not necessary for MuSC activation/proliferation during hypertrophy. When considering MuSC-based therapy for atrophy, including sarcopenia, it will be indispensable to elucidate MuSC behaviors in muscles that exhibit non-degenerative damage, because degenerated myofibers are not present in the atrophied muscles. In this review, we summarize recent findings concerning the relationship between MuSCs and hypertrophy, and discuss what remains to be discovered to inform the development and application of relevant treatments for muscle atrophy.

Voluntary Exercise Suppresses Choroidal Neovascularization in Mice

Purpose

To determine the effect of voluntary exercise on choroidal neovascularization (CNV) in mice.

Methods

Age-matched wild-type C57BL/6J mice were housed in cages equipped with or without running wheels. After four weeks of voluntary running or sedentariness, mice were subjected to laser injury to induce CNV. After surgical recovery, mice were placed back in cages with or without exercise wheels for seven days. CNV lesion volumes were measured by confocal microscopy. The effect of wheel running only in the seven days after injury was also evaluated. Macrophage abundance and cytokine expression were quantified.

Results

In the first study, exercise-trained mice exhibited a 45% reduction in CNV volume compared to sedentary mice. In the replication study, a 32% reduction in CNV volume in exercise-trained mice was observed (P = 0.029). Combining these two studies, voluntary exercise was found to reduce CNV by 41% (P = 0.0005). Exercise-trained male and female mice had similar CNV volumes (P = 0.99). The daily running distance did not correlate with CNV lesion size. Exercise only after the laser injury without a preconditioning period did not reduce CNV size (P = 0.41). CNV lesions of exercise-trained mice also exhibited significantly lower F4/80+ macrophage staining and Vegfa and Ccl2 mRNA expression.

Conclusions

These findings provide the first experimental evidence that voluntary exercise improves CNV outcomes. These studies indicate that exercise before laser treatment is required to improve CNV outcomes.

Impacts of exercise intervention on various diseases in rats

BACKGROUND

Exercise is considered as an important intervention for treatment and prevention of several diseases, such as osteoarthritis, obesity, hypertension, and Alzheimer's disease. This review summarizes decadal exercise intervention studies with various rat models across 6 major systems to provide a better understanding of the mechanisms behind the effects that exercise brought.

METHODS

PubMed was utilized as the data source. To collect research articles, we used the following terms to create the search: (exercise [Title] OR physical activity [Title] OR training [Title]) AND (rats [Title/Abstract] OR rat [Title/Abstract] OR rattus [Title/Abstract]). To best cover targeted studies, publication dates were limited to "within 11 years." The exercise intervention methods used for different diseases were sorted according to the mode, frequency, and intensity of exercise.

RESULTS

The collected articles were categorized into studies related to 6 systems or disease types: motor system (17 articles), metabolic system (110 articles), cardiocerebral vascular system (171 articles), nervous system (71 articles), urinary system (2 articles), and cancer (21 articles). Our review found that, for different diseases, exercise intervention mostly had a positive effect. However, the most powerful effect was achieved by using a specific mode of exercise that addressed the characteristics of the disease.

CONCLUSION

As a model animal, rats not only provide a convenient resource for studying human diseases but also provide the possibility for exploring the molecular mechanisms of exercise intervention on diseases. This review also aims to provide exercise intervention frameworks and optimal exercise dose recommendations for further human exercise intervention research.

Forced treadmill running reduces systemic inflammation yet worsens upper limb discomfort in a rat model of work-related musculoskeletal disorders

BACKGROUND

Musculoskeletal disorders can result from prolonged repetitive and/or forceful movements. Performance of an upper extremity high repetition high force task increases serum pro-inflammatory cytokines and upper extremity sensorimotor declines in a rat model of work-related musculoskeletal disorders. Since one of the most efficacious treatments for musculoskeletal pain is exercise, this study investigated the effectiveness of treadmill running in preventing these responses.

METHODS

Twenty-nine young adult female Sprague-Dawley rats were used. Nineteen were trained for 5 weeks to pull a lever bar at high force (15 min/day). Thirteen went on to perform a high repetition high force reaching and lever-pulling task for 10 weeks (10-wk HRHF; 2 h/day, 3 days/wk). From this group, five were randomly selected to undergo forced treadmill running exercise (TM) during the last 6 weeks of task performance (10-wk HRHF+TM, 1 h/day, 5 days/wk). Results were compared to 10 control rats and 6 rats that underwent 6 weeks of treadmill running following training only (TR-then-TM). Voluntary task and reflexive sensorimotor behavioral outcomes were assessed. Serum was assayed for inflammatory cytokines and corticosterone, reach limb median nerves for CD68+ macrophages and extraneural thickening, and reach limb flexor digitorum muscles and tendons for pathological changes.

RESULTS

10-wk HRHF rats had higher serum levels of IL-1α, IL-1β and TNFα, than control rats. In the 10-wk HRHF+TM group, IL-1β and TNFα were lower, whereas IL-10 and corticosterone were higher, compared to 10-wk HRHF only rats. Unexpectedly, several voluntary task performance outcomes (grasp force, reach success, and participation) worsened in rats that underwent treadmill running, compared to untreated 10-wk HRHF rats. Examination of forelimb tissues revealed lower cellularity within the flexor digitorum epitendon but higher numbers of CD68+ macrophages within and extraneural fibrosis around median nerves in 10-wk HRHF+TM than 10-wk HRHF rats.

CONCLUSIONS

Treadmill running was associated with lower systemic inflammation and moderate tendinosis, yet higher median nerve inflammation/fibrosis and worse task performance and sensorimotor behaviors. Continued loading of the injured tissues in addition to stress-related factors associated with forced running/exercise likely contributed to our findings.

Role of glucocorticoid signaling in exercise-associated changes in high-fat diet preference in rats

The simultaneous introduction of wheel running (WR) and diet choice (high-carbohydrate chow vs. high-fat diet) results in sex-specific diet choice patterns in rats. WR induces a high-fat (HF) diet avoidance, and such avoidance persists in the majority of males, but not females, throughout a 2-wk period. Exercise is a physiological stressor that activates the hypothalamic-pituitary-adrenal (HPA) axis and stimulates glucocorticoid (GC) release, which can alter dietary preferences. Here, we examined the role of the HPA axis and GC signaling in mediating exercise-induced changes in diet preference and the associated neurobiological adaptations that may underlie sex differences in diet choice patterns. Experiment 1 revealed that adrenalectomy did not significantly alter the initiation and persistence of running-induced HF diet avoidance in male rats. Experiment 2 showed that acute WR resulted in greater neural activation than chronic WR in the medial prefrontal (mPFC) and insular cortices (IC) in male rats. Experiment 3 revealed sex differences in the molecular adaptation to exercise and diet preference. First, exercise increased gene expression of fkbp5 in the mPFC, IC, and hippocampus of WR females but had limited influence in males. Second, male and female WR rats that reversed or maintained HF diet avoidance showed distinct sex- and HF diet preference-dependent expression profiles of genes involved in cortical GC signaling (e.g., nr3c1, nr3c2, and src1). Taken together, our results suggest sex differences in region-specific neural adaptations may underlie sex differences in diet preference and the health benefits from exercise.

A Review of the Role of the Gut Microbiome in Personalized Sports Nutrition

The gut microbiome is a key factor in determining inter-individual variability in response to diet. Thus, far, research in this area has focused on metabolic health outcomes such as obesity and type 2 diabetes. However, understanding the role of the gut microbiome in determining response to diet may also lead to improved personalization of sports nutrition for athletic performance. The gut microbiome has been shown to modify the effect of both diet and exercise, making it relevant to the athlete's pursuit of optimal performance. This area of research can benefit from recent developments in the general field of personalized nutrition and has the potential to expand our knowledge of the nexus between the gut microbiome, lifestyle, and individual physiology.

Glucocorticoid Metabolism in Obesity and Following Weight Loss

Glucocorticoids are steroid hormones produced by the adrenal cortex and are essential for the maintenance of various metabolic and homeostatic functions. Their function is regulated at the tissue level by 11β-hydroxysteroid dehydrogenases and they signal through the glucocorticoid receptor, a ligand-dependent transcription factor. Clinical observations have linked excess glucocorticoid levels with profound metabolic disturbances of intermediate metabolism resulting in abdominal obesity, insulin resistance and dyslipidaemia. In this review, we discuss the physiological mechanisms of glucocorticoid secretion, regulation and function, and survey the metabolic consequences of excess glucocorticoid action resulting from elevated release and activation or up-regulated signaling. Finally, we summarize the reported impact of weight loss by diet, exercise, or bariatric surgery on circulating and tissue-specific glucocorticoid levels and examine the therapeutic possibility of reversing glucocorticoid-associated metabolic disorders.

Remarkable cell recovery from cerebral ischemia in rats using an adaptive escalator-based rehabilitation mechanism

Currently, many ischemic stroke patients worldwide suffer from physical and mental impairments, and thus have a low quality of life. However, although rehabilitation is acknowledged as an effective way to recover patients’ health, there does not exist yet an adaptive training platform for animal tests so far. For this sake, this paper aims to develop an adaptive escalator (AE) for rehabilitation of rats with cerebral ischemia. Rats were observed to climb upward spontaneously, and a motor-driven escalator, equipped with a position detection feature and an acceleration/deceleration mechanism, was constructed accordingly as an adaptive training platform. The rehabilitation performance was subsequently rated using an incline test, a rotarod test, the infarction volume, the lesion volume, the number of MAP2 positive cells and the level of cortisol. This paper is presented in 3 parts as follows. Part 1 refers to the escalator mechanism design, part 2 describes the adaptive ladder-climbing rehabilitation mechanism, and part 3 discusses the validation of an ischemic stroke model. As it turned out, a rehabilitated group using this training platform, designated as the AE group, significantly outperformed a control counterpart in terms of a rotarod test. After the sacrifice of the rats, the AE group gave an average infarction volume of (34.36 ± 3.8)%, while the control group gave (66.41 ± 3.1)%, validating the outperformance of the escalator-based rehabilitation platform in a sense. An obvious difference between the presented training platform and conventional counterparts is the platform mechanism, and for the first time in the literature rats can be well and voluntarily rehabilitated at full capacity using an adaptive escalator. Taking into account the physical diversity among rats, the training strength provided was made adaptive as a reliable way to eliminate workout or secondary injury. Accordingly, more convincing arguments can be made using this mental stress-free training platform.

Effect of chronic corticosterone treatment on expression and distribution of serotonin 5-HT7 receptors in rat adrenal glands

Sensitized stress-induced corticosterone (CORT) secretion in chronically stressed rats involves 5-HT7 receptor activation. The effect of 14-day chronic CORT and vehicle (VEH) administration on 5-HT7 receptor expression in adrenal glands, adrenal 5-HT content, and adrenocorticotropic hormone and CORT secretion was analysed. On day 15, VEH- and CORT-treated animals were perfused or decapitated without stress exposure (0 min) or after 10 and 30 min of restraint for collection of trunk blood and tissues. 5-HT7 receptor-like immunoreactivity (5-HT7R-LI), 5-HT7 receptor protein, and mRNA levels were determined by immunohistochemistry, Western blot, and reverse transcription polymerase chain reaction assays, respectively; 5-HT levels and hormones were quantified using HPLC and ELISA kits, respectively. An undisturbed control group was included for most experimental comparisons. Chronic CORT strongly increased 5-HT7R-LI in the outer adrenal cortex, as well as 5-HT7 receptor protein and mRNA in whole adrenal glands; adrenal 5-HT content also increased in these animals. Decreased adrenocorticotropic hormone and CORT secretion at 30 min of restraint occurred in CORT-treated rats. The results support the notion that chronic stress-induced increase of adrenocortical 5-HT7 receptors and adrenal 5-HT content is a glucocorticoid-dependent phenomenon; the development of magnified stress-induced 5-HT7 receptor-mediated CORT responses in chronically stressed animals nevertheless likely involves additional mechanisms.

A three-criteria performance score for rats exercising on a running treadmill

In this study, we propose a novel three-criteria performance score to semiquantitatively classify the running style, the degree of involvement and compliance and the validity of electric shock count for rats exercising on a treadmill. Each score criterion has several style-marks that are based on the observational registry of male Sprague-Dawley rats running for 4-7 weeks. Each mark was given a score value that was averaged throughout a session-registry and resulting in a session score for each criterion, ranging from "0" score for a hypothetical "worst runner", to score "1" for a hypothetical "perfect runner" rat. We found significant differences throughout a training program, thus providing evidence of sufficient sensitivity of this score to reflect the individual evolution of performance improvement in exercise capacity due to training. We hypothesize that this score could be correlated with other physiological or metabolic parameters, thus refining research results and further helping researchers to reduce the number of experimental subjects.

Resistance-exercise training ameliorates LPS-induced cognitive impairment concurrent with molecular signaling changes in the rat dentate gyrus

Effective treatments preventing brain neuroinflammatory diseases are lacking. Resistance-exercise training (RT) ameliorates mild cognitive impairment (MCI), a forerunner to neuroinflammatory diseases. However, few studies have addressed the molecular basis by which RT abates MCI. Thus experiments were performed to identify some molecular changes occurring in response to RT in young, female Wistar rats. To induce MCI, intraventricular lipopolysaccharide (LPS) injections were used to increase dentate gyrus inflammation, reflected by significantly increased TNF-α (~400%) and IL-1β (~1,500%) mRNA (P < 0.0001) after 6 wk. Five days after LPS injections, half of LPS-injected rats performed RT by ladder climbing for 6 wk, 3 days/wk, whereas half remained without ladders. RT for 6 wk increased lean body mass percentage (P < 0.05), individual muscle masses (gastrocnemius and tibialis anterior) (P < 0.05), and maximum lifting capacity (P < 0.001). The RT group, compared with sedentary controls, had 1) ameliorated spatial learning deficits (P < 0.05), 2) increased dentate gyrus phosphorylation of IGF-1R, protein kinase B, and GSK-3β proteins (P < 0.05), components of downstream IGF-1 signaling, and 3) increased dentate gyrus synaptic plasticity marker synapsin protein (P < 0.05). Two follow-up experiments (without LPS) characterized dentate gyrus signaling during short-term RT. Twenty-four hours following the third workout in a 1-wk training duration, phosphorylation of ERK1/2 and GSK-3β proteins, as well as proliferation marker protein, PCNA, were significantly increased (P < 0.05). Similar changes did not occur in a separate group of rats following a single RT workout. Taken together, these data indicate that RT ameliorates LPS-induced MCI after RT, possibly mediated by increased IGF-1 signaling pathway components within the dentate gyrus. NEW & NOTEWORTHY The data suggest that resistance-exercise training restores cognitive deficits induced by lipopolysaccharides and can activate associated IGF-1 signaling in the dentate gyrus. Our data show, for the first time, that as few as three resistance-exercise workouts (spread over 1 wk) can activate IGF-1 downstream signaling and increase proliferation marker PCNA in the dentate gyrus.

Reliability of blood lactate as a measure of exercise intensity in different strains of mice during forced treadmill running

Exercise has long been known to be beneficial to human health. Studies aimed at understanding the effects of exercise specifically focus on predetermined exercise intensities defined by measuring the aerobic capacity of each individual. Many disease models involving animal training often establish aerobic capacity by using the maximal lactate steady state (MLSS), a widely used method in humans that has frequently been used in rodent studies. The MLSS is defined as the highest exercise intensity at which blood lactate concentration remains constant and is roughly equivalent to 70–80% of maximal aerobic capacity. Due to our up-coming experiments investigating the effect of different exercise intensities in specific strains of tumor-bearing mice, the aim of the present study was to determine the MLSS in athymic nude (NCr nu/nu and NMRI), CDF1, and C3H mice by treadmill running at increasing speeds. However, despite thorough exercise acclimation and the use of different exercise protocols and aversive stimuli, less than half of the experiments across strains pointed towards an established MLSS. Moreover, gently prodding the mice during low to moderate intensity running caused a 30–121% (p<0.05) increase in blood lactate concentration compared to running without stimulation, further questioning the use of lactate as a measure of exercise intensity. Overall, MLSS is difficult to determine and large variations of blood lactate levels were observed depending on the exercise protocol, mice handling strategy and strain. This should be considered when planning experiments in mice using forced exercise protocols.

ISSLS Prize in Basic science 2019: Physical activity attenuates fibrotic alterations to the multifidus muscle associated with intervertebral disc degeneration

PURPOSE

Chronic low back pain causes structural remodelling and inflammation in the multifidus muscle. Collagen expression is increased in the multifidus of humans with lumbar disc degeneration. However, the extent and mechanisms underlying the increased fibrotic activity in the multifidus are unknown. Physical activity reduces local inflammation that precedes multifidus fibrosis during intervertebral disc degeneration (IDD), but its effect on amelioration of fibrosis is unknown. This study aimed to assess the development of fibrosis and its underlying genetic network during IDD and the impact of physical activity.

METHODS

Wild-type and SPARC-null mice were either sedentary or housed with a running wheel, to allow voluntary physical activity. At 12 months of age, IDD was assessed with MRI, and multifidus muscle samples were harvested from L2 to L6. In SPARC-null mice, the L1/2 and L3/4 discs had low and high levels of IDD, respectively. Thus, multifidus samples from L2 and L4 were allocated to low- and high-IDD groups compared to assess the effects of IDD and physical activity on connective tissue and fibrotic genes.

RESULTS

High IDD was associated with greater connective tissue thickness and dysregulation of collagen-III, fibronectin, CTGF, substance P, TIMP1 and TIMP2 in the multifidus muscle. Physical activity attenuated the IDD-dependent increased connective tissue thickness and reduced the expression of collagen-I, fibronectin, CTGF, substance P, MMP2 and TIMP2 in SPARC-null animals and wild-type mice. Collagen-III and TIMP1 were only reduced in wild-type animals.

CONCLUSIONS

These data reveal the fibrotic networks that promote fibrosis in the multifidus muscle during chronic IDD. Furthermore, physical activity is shown to reduce fibrosis and regulate the fibrotic gene network. These slides can be retrieved under Electronic Supplementary Material.

Sleeping through anything: The effects of unpredictable disruptions on mouse sleep, healing, and affect

Many aspects of the laboratory environment are not tailored to the needs of rodents, which may cause stress. Unpredictable stressors can cause ulcers, prolonged pituitary-adrenal activation, and anhedonia. Similarly, pain has been demonstrated to slow wound healing, and mice experiencing pain exhibit altered behavior. However it is unknown how husbandry, which occurs when the mice are inactive, and lack of analgesia, specifically in a punch biopsy procedure, effects animal physiology, behavior, and welfare, particularly as it relates to sleep fragmentation. We hypothesized that sleep fragmentation, induced by unpredictable husbandry and lack of pain management will slow wound healing. Two main treatments were tested in a factorial design in C57BL/6 mice of both sexes (64 mice total); 1) analgesia (carprofen and saline) and 2) sleep disruptions (random and predictable). Mice were singly housed in a non-invasive sleep monitoring apparatus on arrival (Day -4). Disruption treatments were applied from Day -3 to 2. All mice received a punch biopsy surgery (Day 0) with topical lidocaine gel and their analgesic treatment prior to recovery, and on Days 1 and 2. Nesting behavior was assessed daily and a sugar cereal consumption test, as a measure of anhedonia, was conducted on Days -1 to 2. On Day 3, mice were euthanized and wound tissue and adrenal glands were collected. We found that the disruption predictability had no effect on mouse sleep, wound healing, or adrenal cortex:medulla ratio. It's possible that the disruption period was not long enough to induce chronic stress. However, male mice who received analgesia slept more than their female counterparts; this may be related to sex differences in pain perception. Overall, it does not appear that the predictability of disturbance effects sleep fragmentation or stress responses, indicating that husbandry activities do not need to occur at set predictable times to improve welfare.

An adaptive fall-free rehabilitation mechanism for ischemic stroke rat patients

Today’s commercial forced exercise platforms had been validated not as a well-designed rehabilitation environment for rats with a stroke, for the reason that rat with a stroke cannot take exercise at a constant intensity for a long period of time. In light of this, this work presented an adaptive, fall-free ischemic stroke rehabilitation mechanism in an animal model, which was implemented in an infrared-sensing adaptive feedback control running wheel (IAFCRW) platform. Consequently, rats with a stroke can be safely rehabilitated all the time, and particularly at full capacity for approximately one third of a training duration, in a completely fall-free environment according to individual physical differences by repeated use of an acceleration/deceleration mechanism. The performance of this platform was assessed using an animal ischemic stroke model. The IAFCRW therapy regimen was validated to outperform a treadmill and a conventional running wheel counterpart with respect to the reduction in the neurobehavioral deficits caused by middle cerebral artery occlusion (MCAo). IAFCRW is the first adaptive forced exercise training platform short of electrical stimulation-assistance in the literature, and ischemic stroke rats benefit more in terms of the behavioral tests run at the end of a 3-week rehabilitation program after a stroke thereby.

Exercise as a therapeutic intervention for motor and non-motor symptoms in Parkinson's disease: Evidence from rodent models

Parkinson's disease (PD) is characterised by degeneration of dopaminergic neurons of the nigrostriatal pathway, which leads to the cardinal motor symptoms of the disease - tremor, rigidity and postural instability. A number of non-motor symptoms are also associated with PD, including cognitive impairment, mood disturbances and dysfunction of gastrointestinal and autonomic systems. Current therapies provide symptomatic relief but do not halt the disease process, so there is an urgent need for preventative strategies. Lifestyle interventions such as aerobic exercise have shown potential to lower the risk of developing PD and to alleviate both motor and non-motor symptoms. However, there is a lack of large-scale randomised clinical trials that have employed exercise in PD patients. This review will focus on the evidence from studies on rodent models of PD, for employing exercise as an intervention for both motor and non-motor symptoms.

Amount of daily exercise is an essential stimulation to alter the epigenome of skeletal muscle in rats

Long-term running training causes epigenetic changes in the skeletal muscles. Here we tested the effects of the total amount or duration of running training on the distribution of histones in the rat plantaris muscle. Post-weaned young rats were assigned to 3 different training groups: Run-1, 30 min/day running exercise for 8 wk using an animal treadmill at 24 m/min; Run-2, 15 min/day for 8 wk; and Run-3, 60 min/day for 4 wk. Citrate synthase activity was not significantly changed by running training, although the slight increase was observed in Run-3. Genes that were previously defined as showing the typical responses to running training were targeted to measure the distribution of histones using chromatin immunoprecipitation. The distribution of acetylated histone 3 was elevated in Run-2 and Run-3, but not in Run-1. Incorporation of H3.3 into the nucleosome was stimulated in Run-1, whereas H3.3 distribution was unchanged in Run-2 or downregulated in Run-3. Significant downregulation of H3.3 expression was also detected in Run-3. We further checked the responses of the target genes during acute running. Target genes were transcriptionally activated and histone acetylation was stimulated at the loci in response to acute running. These results suggested that the exchange of the histone component to H3.3 was stimulated by running training, inhibiting the accumulation of acetylated histones in Run-1. Additionally, it was further suggested that the enhanced daily amount of running caused changes in the H3.3 expression, affecting the rate of the histone exchange in Run-3. NEW & NOTEWORTHY Chromatin remodeling in the skeletal muscle is a potent mechanism preventing disuse atrophy in later life that can be acquired via long-term exercise training. Here we demonstrated in rats that daily exercise amount is a key factor in the development of epigenetic changes in the skeletal muscle. To acquire a health benefit, our research suggests the importance of considering the time endurance for daily exercise bouts.

The Impact of Exercise in Rodent Models of Chronic Pain

PURPOSE OF REVIEW

Physical activity is increasingly recommended for chronic pain. In this review, we briefly survey recent, high-quality meta-analyses on the effects of exercise in human chronic pain populations, followed by a critical discussion of the rodent literature.

RECENT FINDINGS

Most meta-analytical studies on the effects of exercise in human chronic pain populations describe moderate improvements in various types of chronic pain, despite substantial variability in the outcomes reported in the primary literature. The most consistent findings suggest that while greater adherence to exercise programs produces better outcomes, there is minimal support for the superiority of one type of exercise over another. The rodent literature similarly suggests that while regular exercise reduces hypersensitivity in rodent models of chronic pain, exercise benefits do not appear to relate to either the type of injury or any particular facet of the exercise paradigm. Potential factors underlying these results are discussed, including the putative involvement of stress-induced analgesic effects associated with certain types of exercise paradigms. Exercise research using rodent models of chronic pain would benefit from increased attention to the role of stress in exercise-induced analgesia, as well as the incorporation of more clinically relevant exercise paradigms.

Activation of mesolimbic reward system via laterodorsal tegmental nucleus and hypothalamus in exercise-induced hypoalgesia

Ventral tegmental area (VTA) dopamine (DA) neurons are the primary source of dopamine in target structures that constitute the mesolimbic reward system. Previous studies demonstrated that voluntary wheel running (VWR) by neuropathic pain (NPP) model mice produces exercise-induced hypoalgesia (EIH), and that activation of mesolimbic reward system may lead to EIH. However, the neuronal mechanism by which the mesolimbic reward system is activated by VWR is unknown. Here, we found that VWR produces EIH effects and reverses the marked reduction in activated lateral VTA (lVTA)-DA neurons induced by NPP. The proportions of activated laterodorsal tegmental nucleus (LDT)-cholinergic and lateral hypothalamus-orexin neurons were significantly enhanced by VWR. Retrograde tracing and dual immunostaining revealed that VWR activates lVTA-projecting LDT-cholinergic/non-cholinergic and lateral hypothalamic area (LHA)-orexin/non-orexin neurons. Therefore, EIH effects may be produced, at least in part, by activation of the mesolimbic reward system via activation of LDT and LHA neurons.

Interactions between stress and physical activity on Alzheimer's disease pathology

Physical activity and stress are both environmental modifiers of Alzheimer's disease (AD) risk. Animal studies of physical activity in AD models have largely reported positive results, however benefits are not always observed in either cognitive or pathological outcomes and inconsistencies among findings remain. Studies using forced exercise may increase stress and mitigate some of the benefit of physical activity in AD models, while voluntary exercise regimens may not achieve optimal intensity to provide robust benefit. We evaluated the findings of studies of voluntary and forced exercise regimens in AD mouse models to determine the influence of stress, or the intensity of exercise needed to outweigh the negative effects of stress on AD measures. In addition, we show that chronic physical activity in a mouse model of AD can prevent the effects of acute restraint stress on Aβ levels in the hippocampus. Stress and physical activity have many overlapping and divergent effects on the body and some of the possible mechanisms through which physical activity may protect against stress-induced risk factors for AD are discussed. While the physiological effects of acute stress and acute exercise overlap, chronic effects of physical activity appear to directly oppose the effects of chronic stress on risk factors for AD. Further study is needed to identify optimal parameters for intensity, duration and frequency of physical activity to counterbalance effects of stress on the development and progression of AD.