Juvenile physical activity protects against isoproterenol-induced cardiac dysfunction later in life.

Cardiovascular disease is an enormous public health problem, particularly in older populations. Exercise is the most potent cardioprotective intervention identified to date, with exercise in the juvenile period potentially imparting greater protection, given the plasticity of the developing heart. To test the hypothesis that voluntary wheel running early in life would be cardioprotective later in life when risk for disease is high, we provided male and female juvenile (3 wk old) mice access to a running wheel for 2 wk. Mice then returned to a home cage to age to adulthood (4-6 mo) before exposure to isoproterenol (ISO) to induce cardiac stress. Cardiac function and remodeling were compared with sedentary control mice, sedentary mice exposed to ISO, and mice that exercised in adulthood immediately before ISO. Early in life activity protected against ISO-induced stress as evidenced by attenuated cardiac mass, myocyte size, and fibrosis compared with sedentary mice exposed to ISO. ISO-induced changes in cardiac function were ameliorated in male mice that engaged in wheel running, with ejection fraction and fractional shortening reversed to control values. Adrenergic receptor expression was downregulated in juvenile male runners. This suppression persisted in adulthood following ISO, providing a putative mechanism by which exercise in the young male heart provides resilience to cardiac stress later in life. Together, we show that activity early in life induces persistent cardiac changes that attenuate ISO-induced stress in adulthood. Identification of the mechanisms by which early in life exercise is protective will yield valuable insights into how exercise is medicine across the life course.NEW & NOTEWORTHY Voluntary wheel running activity early in life induces persistent changes in the heart that attenuate isoproterenol-induced hypertrophy and fibrosis in adulthood. Though the mechanisms of this protection remain incompletely understood, activity-induced downregulation of adrenergic receptor expression early in life may contribute to later protection against adrenergic stress. Together these data suggest that efforts to maintain an active lifestyle early in life may have long-lasting cardioprotective benefits.

The Effects of a Western Diet vs. a High-Fiber Unprocessed Diet on Health Outcomes in Mice Offspring.

Diet influences critical periods of growth, including gestation and early development. We hypothesized that a maternal/early life diet reflecting unprocessed dietary components would positively affect offspring metabolic and anthropometric parameters. Using 9 C57BL-6 dams, we simulated exposure to a Western diet, a high-fiber unprocessed diet (HFUD), or a control diet. The dams consumed their respective diets (Western [n = 3], HFUD [n = 3], and control [n = 3]) through 3 weeks of pregnancy and 3 weeks of weaning; their offspring consumed the diet of their mother for 4.5 weeks post weaning. Measurements included dual X-ray absorptiometry (DEXA) scans, feed consumption, body weight, blood glucose, and insulin and glycated hemoglobin (HbA1c) in the offspring. Statistical analyses included one-way ANOVA with Tukey's post hoc analysis. The offspring DEXA measures at 5 and 7.5 weeks post parturition revealed higher lean body mass development in the HFUD and control diet offspring compared to the Western diet offspring. An analysis indicated that blood glucose (p = 0.001) and HbA1c concentrations (p = 0.002) were lower among the HFUD offspring compared to the Western and control offspring. The results demonstrate that diet during gestation and early life consistent with traditional diet patterns may influence hyperglycemia and adiposity in offspring.

Voluntary Wheel Running Exercise Does Not Attenuate Circadian and Cardiac Dysfunction Caused by Conditional Deletion of Bmal1.

Circadian misalignment occurs with age, jet lag, and shift work, leading to maladaptive health outcomes including cardiovascular diseases. Despite the strong link between circadian disruption and heart disease, the cardiac circadian clock is poorly understood, prohibiting identification of therapies to restore the broken clock. Exercise is the most cardioprotective intervention identified to date and has been suggested to reset the circadian clock in other peripheral tissues. Here, we tested the hypothesis that conditional deletion of core circadian gene Bmal1 would disrupt cardiac circadian rhythm and function and that this disruption would be ameliorated by exercise. To test this hypothesis, we generated a transgenic mouse with spatial and temporal deletion of Bmal1 only in adult cardiac myocytes (Bmal1 cardiac knockout [cKO]). Bmal1 cKO mice demonstrated cardiac hypertrophy and fibrosis concomitant with impaired systolic function. This pathological cardiac remodeling was not rescued by wheel running. While the molecular mechanisms responsible for the profound cardiac remodeling are unclear, it does not appear to involve activation of the mammalian target of rapamycin (mTOR) signaling or changes in metabolic gene expression. Interestingly, cardiac deletion of Bmal1 disrupted systemic rhythms as evidenced by changes in the onset and phasing of activity in relationship to the light/dark cycle and by decreased periodogram power as measured by core temperature, suggesting cardiac clocks can regulate systemic circadian output. Together, we suggest a critical role for cardiac Bmal1 in regulating both cardiac and systemic circadian rhythm and function. Ongoing experiments will determine how disruption of the circadian clock causes cardiac remodeling in an effort to identify therapeutics to attenuate the maladaptive outcomes of a broken cardiac circadian clock.

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

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

Exposure to High Altitude Promotes Loss of Muscle Mass That Is Not Rescued by Metformin.

Fullerton, Zackery S., Benjamin D. McNair, Nicholas A. Marcello, Emily E. Schmitt, and Danielle R. Bruns. Exposure to high altitude promotes loss of muscle mass that is not rescued by metformin. High Alt Med Biol. 23:215-222, 2022. Background: Exposure to high altitude (HA) causes muscle atrophy. Few therapeutic interventions attenuate muscle atrophy; however, the diabetic drug, metformin (Met), has been suggested as a potential therapeutic to preserve muscle mass with aging and obesity-related atrophy. The purpose of the present study was to test the hypothesis that HA would induce muscle atrophy that could be attenuated by Met. Methods: C57Bl6 male and female mice were exposed to simulated HA (∼5,200 m) for 4 weeks, while control (Con) mice remained at resident altitude (∼2,180 m). Met was administered in drinking water at 200 mg/(kg·day). We assessed muscle mass, myocyte cell size, muscle and body composition, and expression of molecular mediators of atrophy. Results: Mice exposed to HA were leaner and had a smaller hind limb complex (HLC) mass than Con mice. Loss of HLC mass and myocyte size were not attenuated by Met. Molecular markers for muscle atrophy were activated at HA in a sex-dependent manner. While the atrophic regulator, atrogin, was unchanged at HA or with Met, myostatin expression was upregulated at HA. In female mice, Met further stimulated myostatin expression. Conclusions: Although HA exposure resulted in loss of muscle mass, particularly in male mice, Met did not attenuate muscle atrophy. Identification of other interventions to preserve muscle mass during ascent to HA is warranted.

Mechanisms of Exercise-Induced Cardiac Remodeling Differ Between Young and Aged Hearts.

Aging induces physiological and molecular changes in the heart that increase the risk for heart disease. Several of these changes are targetable by exercise. We hypothesize that the mechanisms by which exercise improves cardiac function in the aged heart differ from those in the young exercised heart.

Uneven but Conservative Pacing Is Associated With Performance During Uphill and Downhill Running.

PURPOSE: To investigate the relationship between pacing strategy and performance during uphill and downhill running-specifically, what distribution of energy corresponds to faster race finish times between and among participants. METHODS: Eighteen years of race data from a 10.2-mile running race with an uphill first half and a downhill second half were analyzed to identify relationships between pacing and performance. A pacing coefficient (PC), equal to a participant's ascent time divided by finishing time (FT), was used to define each participant's pacing strategy. The American College of Sports Medicine metabolic running equation was used to estimate energy expenditure during the ascent, descent, and total race. Statistical analyses compared participants' PC to their FT and finishing place within their age and gender category. Additionally, FT and finishing place were compared between groups of participants who exhibited similar pacing strategies. RESULTS: PCs were positively associated with faster FTs (r2 = .120, P < .001) and better finishing positions (r2 = .104, P < .001). PCs above .600 were associated with the fastest average FTs and best average finishing position within age and gender categories (all P ≤ .047). CONCLUSIONS: Participants performed the best when energy expenditure increased no more than 10.4% during the uphill portion compared to their overall average. It is not possible to state that overly aggressive uphill efforts resulted in premature fatigue and thus slower decent times and worse race performance. However, participants should still avoid overly aggressive uphill pacing, as performance was associated with larger PCs.

Transcriptomic analysis of cardiac gene expression across the life course in male and female mice.

Risk for heart disease increases with advanced age and differs between sexes, with females generally protected from heart disease until menopause. Despite these epidemiological observations, the molecular mechanisms that underlie sex-specific differences in cardiac function have not been fully described. We used high throughput transcriptomics in juvenile (5 weeks), adult (4-6 months), and aged (18 months) male and female mice to understand how cardiac gene expression changes across the life course and by sex. While male gene expression profiles differed between juvenile-adult and juvenile-aged (254 and 518 genes, respectively), we found no significant differences in adult-aged gene expression. Females had distinct gene expression changes across the life course with 1835 genes in juvenile-adult and 1328 in adult-aged. Analysis of differentially expressed genes (DEGs) suggests that juvenile to adulthood genes were clustered in cell cycle and development-related pathways in contrast to adulthood-aged which were characterized by immune-and inflammation-related pathways. Analysis of sex differences within each age suggests that juvenile and aged cardiac transcriptomes are different between males and females, with significantly fewer DEGs identified in adult males and females. Interestingly, the male-female differences in early age were distinct from those in advanced age. These findings are in contrast to expected sex differences historically attributed to estrogen and could not be explained by estrogen-direct mechanisms alone as evidenced by juvenile sexual immaturity and reproductive incompetence in the aged mice. Together, distinct trajectories in cardiac transcriptomic profiles highlight fundamental sex differences across the life course and demonstrate the need for the consideration of age and sex as biological variables in heart disease.

Cardiac response to adrenergic stress differs by sex and across the lifespan.

The aging heart is well-characterized by a diminished responsiveness to adrenergic activation. However, the precise mechanisms by which age and sex impact adrenergic-mediated cardiac function remain poorly described. In the current investigation, we compared the cardiac response to adrenergic stress to gain mechanistic understanding of how the response to an adrenergic challenge differs by sex and age. Juvenile (4 weeks), adult (4-6 months), and aged (18-20 months) male and female mice were treated with the ß-agonist isoproterenol (ISO) for 1 week. ISO-induced morphometric changes were age- and sex-dependent as juvenile and adult mice of both sexes had higher left ventricle weights while aged mice did not increase cardiac mass. Adults increased myocyte cell size and deposited fibrotic matrix in response to ISO, while juvenile and aged animals did not show evidence of hypertrophy or fibrosis. Juvenile females and adults underwent expected changes in systolic function with higher heart rate, ejection fraction, and fractional shortening. However, cardiac function in aged animals was not altered in response to ISO. Transcriptomic analysis identified significant differences in gene expression by age and sex, with few overlapping genes and pathways between groups. Fibrotic and adrenergic signaling pathways were upregulated in adult hearts. Juvenile hearts upregulated genes in the adrenergic pathway with few changes in fibrosis, while aged mice robustly upregulated fibrotic gene expression without changes in adrenergic genes. We suggest that the response to adrenergic stress significantly differs across the lifespan and by sex. Mechanistic definition of these age-related pathways by sex is critical for future research aimed at treating age-related cardiac adrenergic desensitization.

Changes in Muscle Mass and Composition by Exercise and Hypoxia as Assessed by DEXA in Mice.

Background and Objective: Skeletal muscle is critical for overall health and predicts quality of life in several chronic diseases, thus quantification of muscle mass and composition is necessary to understand how interventions promote changes in muscle quality. The purpose of this investigation was to quantify changes in muscle mass and composition in two distinct pre-clinical models of changes in muscle quality using a clinical dual X-ray absorptiometry (DEXA), validated for use in mice. Materials and Methods: Adult C57Bl6 male mice were given running wheels (RUN; muscle hypertrophy) or placed in hypobaric hypoxia (HH; muscle atrophy) for four weeks. Animals received weekly DEXA and terminal collection of muscle hind limb complex (HLC) and quadriceps weights and signaling for molecular regulators of muscle mass and composition. Results: HH decreased total HLC muscle mass with no changes in muscle composition. RUN induced loss of fat mass in both the quadriceps and HLC. Molecular mediators of atrophy were upregulated in HH while stimulators of muscle growth were higher in RUN. These changes in muscle mass and composition were quantified by a clinical DEXA, which we described and validated for use in pre-clinical models. Conclusions: RUN improves muscle composition while HH promotes muscle atrophy, though changes in composition in hypoxia remain unclear. Use of the widely available clinical DEXA for use in mice enhances translational research capacity to understand the mechanisms by which atrophy and hypertrophy promote skeletal muscle and overall health.

Sex Differences in Cardiac AMP-Activated Protein Kinase Following Exhaustive Exercise.

Ischemic heart disease presents with significant differences between sexes. Endurance exercise protects the heart against ischemic disease and also distinctly impacts male and female patients through unidentified mechanisms, though some evidence implicates 5'-AMP-activated protein kinase (AMPK). The purpose of this investigation was to assess the impact of training and sex on cardiac AMPK activation following exhaustive exercise. AMPK activation was measured in trained and sedentary mice of both sexes. Trained mice ran on a treadmill at progressively increasing speeds and duration for 12 weeks. Trained and sedentary mice of both sexes were euthanized immediately following exhaustive exercise and compared to sedentary controls. Endurance training elicited adaptations indicative of aerobic adaptation including higher max running velocities and cardiac hypertrophy with no differences between males and females. AMPK activity was higher in male compared to females, and trained exhibited higher AMPK activity compared to sedentary mice. In response to training, male mice activated AMPK more robustly than female mice. Chronic exercise training increases the ability to activate cardiac AMPK in response to exhaustive exercise in a sex-specific manner. Understanding the interaction between exercise and sex is vital for use of exercise as medicine for heart disease in both men and women.

The Peripheral Circadian Clock and Exercise: Lessons from Young and Old Mice.

Critical biological processes are under control of the circadian clock. Disruption of this clock, e.g. during aging, results in increased risk for development of chronic disease. Exercise is a protective intervention that elicits changes in both age and circadian pathologies, yet its role in regulating circadian gene expression in peripheral tissues is unknown. We hypothesized that voluntary wheel running would restore disrupted circadian rhythm in aged mice. We analyzed wheel running patterns and expression of circadian regulators in male and female C57Bl/6J mice in adult (~4 months) and old (~18 months) ages. As expected, young female mice ran further than male mice, and old mice ran significantly less than young mice. Older mice of both sexes had a delayed start time in activity which likely points to a disrupted diurnal running pattern and circadian disruption. Voluntary wheel running rescued some circadian dysfunction in older females. This effect was not present in older males, and whether this was due to low wheel running distance or circadian output is not clear and warrants a future study. Overall, we show that voluntary wheel running can rescue some circadian dysfunction in older female but not male mice; and these changes are tissue dependent. While voluntary running was not sufficient to fully rescue age-related changes in circadian rhythm, ongoing studies will determine if forced exercise (e.g. treadmill) and/or chrono-timed exercise can improve age-related cardiovascular, skeletal muscle, and circadian dysfunction.

The renal molecular clock: broken by aging and restored by exercise.

The mammalian circadian clock governs physiological, endocrine, and metabolic responses coordinated in a 24-h rhythmic pattern by the suprachiasmatic nucleus (SCN) of the anterior hypothalamus. The SCN also dictates circadian rhythms in peripheral tissues like the kidney. The kidney has several important physiological functions, including removing waste and filtering the blood and regulating fluid volume, blood osmolarity, blood pressure, and Ca2+ metabolism, all of which are under tight control of the molecular/circadian clock. Normal aging has a profound influence on renal function, central and peripheral circadian rhythms, and the sleep-wake cycle. Disrupted circadian rhythms in the kidney as a result of increased age likely contribute to adverse health outcomes such as nocturia, hypertension, and increased risk for stroke, cardiovascular disease, and end organ failure. Regular physical activity improves circadian misalignment in both young and old mammals, although the precise mechanisms for this protection remain poorly described. Recent advances in the heart and skeletal muscle literature suggest that regular endurance exercise entrains peripheral clocks, and we propose that similar beneficial adaptations occur in the kidney through regulation of renal blood flow and fluid balance.

ATM-dependent activation of SIM2s regulates homologous recombination and epithelial-mesenchymal transition.

There is increasing evidence that genomic instability is a prerequisite for cancer progression. Here we show that SIM2s, a member of the bHLH/PAS family of transcription factors, regulates DNA damage repair through enhancement of homologous recombination (HR), and prevents epithelial-mesenchymal transitions (EMT) in an Ataxia-telangiectasia mutated (ATM)-dependent manner. Mechanistically, we found that SIM2s interacts with ATM and is stabilized through ATM-dependent phosphorylation in response to IR. Once stabilized, SIM2s interacts with BRCA1 and supports RAD51 recruitment to the site of DNA damage. Loss of SIM2s through the introduction of shSIM2 or the mutation of SIM2s at one of the predicted ATM phosphorylation sites (S115) reduces HR efficiency through disruption of RAD51 recruitment, resulting in genomic instability and induction of EMT. The EMT induced by the mutation of S115 is characterized by a decrease in E-cadherin and an induction of the basal marker, K14, resulting in increased invasion and metastasis. Together, these results identify a novel player in the DNA damage repair pathway and provides a link in ductal carcinoma in situ progression to invasive ductal carcinoma through loss of SIM2s, increased genomic instability, EMT, and metastasis.

PER2 regulation of mammary gland development.

The molecular clock plays key roles in daily physiological functions, development and cancer. Period 2 (PER2) is a repressive element, which inhibits transcription activated by positive clock elements, resulting in diurnal cycling of genes. However, there are gaps in our understanding of the role of the clock in normal development outside of its time-keeping function. Here, we show that PER2 has a noncircadian function that is crucial to mammalian mammary gland development. Virgin Per2-deficient mice, Per2-/- , have underdeveloped glands, containing fewer bifurcations and terminal ducts than glands of wild-type mice. Using a transplantation model, we show that these changes are intrinsic to the gland and further identify changes in cell fate commitment. Per2-/- mouse mammary glands have a dual luminal/basal phenotypic character in cells of the ductal epithelium. We identified colocalization of E-cadherin and keratin 14 in luminal cells. Similar results were demonstrated using MCF10A and shPER2 MCF10A human cell lines. Collectively this study reveals a crucial noncircadian function of PER2 in mammalian mammary gland development, validates the Per2-/- model, and describes a potential role for PER2 in breast cancer.

Circadian Regulation of Benzo[a]Pyrene Metabolism and DNA Adduct Formation in Breast Cells and the Mouse Mammary Gland.

The circadian clock plays a role in many biologic processes, yet very little is known about its role in metabolism of drugs and carcinogens. The purpose of this study was to define the impact of circadian rhythms on benzo-a-pyrene (BaP) metabolism in the mouse mammary gland and develop a circadian in vitro model for investigating changes in BaP metabolism resulting from cross-talk between the molecular clock and aryl hydrocarbon receptor. Female 129sv mice (12 weeks old) received a single gavage dose of 50 mg/kg BaP at either noon or midnight, and mammary tissues were isolated 4 or 24 hours later. BaP-induced Cyp1a1 and Cyp1b1 mRNA levels were higher 4 hours after dosing at noon than at 4 hours after dosing at midnight, and this corresponded with parallel changes in Per gene expression. In our in vitro model, we dosed MCF10A mammary cells at different times after serum shock to study how time of day shifts drug metabolism in cells. Analysis of CYP1A1 and CYP1B1 gene expression showed the maximum enzyme-induced metabolism response 12 and 20 hours after shock, as determined by ethoxyresorufin-O-deethylase activity, metabolism of BaP, and formation of DNA-BaP adducts. The pattern of PER-, BMAL-, and aryl hydrocarbon receptor-induced P450 gene expression and BaP metabolism was similar to BaP-induced Cyp1A1 and Cyp1B1 and molecular clock gene expression in mouse mammary glands. These studies indicate time-of-day exposure influences BaP metabolism in mouse mammary glands and describe an in vitro model that can be used to investigate the circadian influence on the metabolism of carcinogens.

Weekly Physical Activity Levels of Older Adults Regularly Using a Fitness Facility.

The aim of this paper was to determine if weekly physical activity levels were greater in an independent-living older adult population that was regularly participating in structured fitness activities. Also, lifetime exercise history and sex differences were investigated in an effort to understand how they relate to current weekly step activity. Total weekly step counts, measured with a pedometer, were assessed in two older adult groups; the first consisted of members of a local senior center who regularly used the fitness facility (74.5 ± 6.0 yrs; mean ± SD) while the second group consisted of members who did not use the fitness facility (74.8 ± 6.0 yrs). Participants also completed the Lifetime Physical Activity Questionnaire (LPAQ). No significant difference was found in the total number of weekly steps between groups (p = 0.88) or sexes (p = 0.27). The LPAQ suggested a significant decline in activity with aging (p = 0.01) but no difference between groups (p = 0.54) or sexes (p = 0.80). A relationship was observed between current step activity and MET expenditure over the past year (p = 0.008, r (2) = 0.153) and from ages 35 to 50 years (p = 0.037, r (2) = 0.097). The lack of difference in weekly physical activity level between our groups suggests that independent-living older adults will seek out and perform their desired activity, in either a scheduled exercise program or other leisure-time activities. Also, the best predictor of current physical activity level in independent-living older adults was the activity performed over the past year.

Environmental Endocrine Disruptor Affects Voluntary Physical Activity in Mice.

INTRODUCTION: Voluntary physical activity levels are regulated by sex hormones. The purpose of this study was to determine the effect of the endocrine disruptor benzyl butyl phthalate (BBP) on the regulation of physical activity in mice. METHODS: Mouse dams were treated with 500 mg·kg·d of BBP or vehicle on gestation days 9-16. Pups were weaned and analyzed for voluntary physical activity levels, puberty development, sex hormone levels, and body composition during the 20-wk period. RESULTS: Seventy-three offspring from BBP-treated dams were studied (n = 43 males and n = 30 females). Endocrine disruption was indicated by decreased anogenital distances in BBP-treated male offspring at 10 (P = 0.001) and 20 wk (P = 0.038) and delayed vaginal openings in BBP-treated female offspring (P = 0.001). Further, there was a significant decrease in serum testosterone concentration in male mice between control and BBP at 10 wk (P = 0.039) and at 20 wk (P = 0.022). In female mice, there was a significant increase in serum testosterone concentration in BBP mice at 20 wk (P = 0.002) and a significant increase in estrogen (estradiol) concentrations at 20 wk in the control female mice (P = 0.015). Overall, BBP mice ran significantly less distance (males, P = 0.008; females, P = 0.042) than controls. Other than a significant increase in BBP-treated males in fat mass at 20 wk (P = 0.040), there was no significant decrease in weight, lean mass, or fat mass in either female or male mice, regardless of treatment. CONCLUSION: Maternal endocrine disruption altered hormone response, but not body composition in either sex of offspring, with a corresponding decreased activity throughout early adulthood in all offspring. These results suggest that exposure to common environmental endocrine disruptors in utero can reduce and alter physical activity levels in offspring.

Differential protein expression in the nucleus accumbens of high and low active mice.

Physical inactivity is associated with the development of a variety of chronic illnesses. Literature has shown that physical activity is genetically regulated; however there is limited information on the mechanisms that influence this process with existing studies primarily focused on genomic and/or transcription association studies. There have been no studies to determine differential protein expression in the nucleus accumbens, the brain site thought to be involved in activity regulation, between high and low active animals. We compared the global nucleus accumbens proteome signature from known high- and low-active mice and identified seven differentially expressed proteins. Low active mice generally over expressed proteins associated with neural stress (Stress 70 protein and V type proton ATPase catalytic subunit A), and the high-active mice over expressed proteins associated with metabolism (creatine kinase B, succinyl-CoA ligase). Previously suggested mechanisms associated with activity regulation in the nucleus accumbens have centered on dopamine receptor 1 and endocannabinoid receptor 1. However, these proteins and the associated pathways were not differentially expressed between high and low active mice. In conclusion, protein expression must be determined as part of the effort to identify involved mechanisms in regulating activity and there appears to be separate nucleus accumbens proteome signatures associated with high- and low-active mice.

Differential skeletal muscle proteome of high- and low-active mice.

Physical inactivity contributes to cardiovascular disease, type II diabetes, obesity, and some types of cancer. While the literature is clear that there is genetic regulation of physical activity with existing gene knockout data suggesting that skeletal muscle mechanisms contribute to the regulation of activity, actual differences in end-protein expression between high- and low-active mice have not been investigated. This study used two-dimensional differential gel electrophoresis coupled with mass spectrometry to evaluate the proteomic differences between high-active (C57L/J) and low-active (C3H/HeJ) mice in the soleus and extensor digitorum longus (EDL). Furthermore, vivo-morpholinos were used to transiently knockdown candidate proteins to confirm their involvement in physical activity regulation. Proteins with higher expression patterns generally fell into the calcium-regulating and Krebs (TCA) cycle pathways in the high-active mice (e.g., annexin A6, P = 0.0031; calsequestrin 1; P = 0.000025), while the overexpressed proteins in the low-active mice generally fell into cytoskeletal structure- and electron transport chain-related pathways (e.g., ATPase, P = 0.031; NADH dehydrogenase, P = 0.027). Transient knockdown of annexin A6 and calsequestrin 1 protein of high-active mice with vivo-morpholinos resulted in decreased physical activity levels (P = 0.001). These data suggest that high- and low-active mice have unique protein expression patterns and that each pattern contributes to the peripheral capability to be either high- or low-active, suggesting that different specific mechanisms regulate activity leading to the high- or low-activity status of the animal.