Wheel-running Activity Research Articles

Acute Exposure to a High-Fat High-Sugar Diet Alters Wheel Running Activity

BACKGROUND: Literature shows that chronic exposure to a high-fat high-sugar (HFHS) Western diet decreases voluntary physical activity, mainly through decreased duration of activity. PURPOSE: To determine if acute exposures to standard chow and a HFHS diet affect voluntary activity levels in male mice. METHODS: Eight-week- old male C57BL/6J male mice (n=20) were singly housed and provided with running wheels. Wheel running activity was measured daily via mounted odometers. Distance (km) and duration (min) were used to calculate average speed (m/min). Mice were randomly assigned to two experimental groups that alternated between the HFHS diet (20% protein, 35% carbohydrate, 45% fat, with 20% fructose water) and a standard chow diet (24.3% protein, 40.2% CHO, 4.7% fat) in three 5-day cycles followed by two 8-day cycles. At study initiation, Group 1 began with the HFHS diet and Group 2 began with standard chow. At the end of each cycle period, both groups switched to the opposing diet. Data were analyzed using a repeated measures model with distance, duration, and speed for each cycle as dependent variables and diet, group, and diet*group interaction as fixed effects. Alpha value was set a priori at 0.05 and post-hoc tests used Tukey’s HSD. RESULTS: Acute exposure to the HFHS diet decreased speed (p=.0075), while distance (p=.7527) and duration (p=.1077) were not altered. No overall group effects on distance (p=.3670), duration (p=.3747), or speed (p=.5266) were observed; however, animals exposed to the chow diet first (Group 2) showed an increase in activity duration (p=.0040) when exposed to a HFHS diet in all cycles. CONCLUSION: Acute exposure to a HFHS diet only decreased speed, which is surprising given the literature on chronic HFHS exposure that has shown decreases in distance. The observed increase in activity duration in mice that had chow at the initiation of wheel-running exposure (Group 2) suggests that acute and chronic effects of a HFHS diet on physical activity level differ in mice.

Ceramide Accumulation and Insulin Resistance During Hindlimb Suspension In Wheel-Running Mice Is TLR4 Dependent

Short term skeletal muscle inactivity (i.e. hospitalization, bed rest) impairs muscle size, function, and insulin sensitivity. We have suggested that muscle inflammation (TLR4 signaling) and accumulation of the bioactive sphingolipid, ceramide, are potent determinants of muscle health following inactivity periods. PURPOSE: To study specific inflammatory mediated effects on skeletal muscle of physically active mice, following 7-days of inactivity. METHODS: In efforts to build on our recent findings and to study rapid inactivity induced changes, we provided 8-week old C57BL/6 mice access to running wheels for 5-weeks. Mice were then hindlimb suspended for 7-days (HS, n=10) or continued running wheel activity (Con, n=10) during this 7-day period. An additional group of HS mice were given daily injections of TAK242, a TLR4 specific inhibitor (HS+TAK242, n=10), in an attempt to protect muscle health during 7-days of inactivity. Primary outcomes were soleus-specific ceramide content, muscle Akt signaling, insulin sensitivity, and muscle size. RESULTS: Muscle total ceramide abundance was greater (45%, p<0.01) in HS vs. Con, while TLR4 inhibition prevented ceramide accumulation during HS (HS+TAK242 vs. Con, p=0.87). Muscle ceramide increases during inactivity were largely driven by ceramide carbon chain lengths C16:0 & C18:0. Soleus mass declined (27%, p<0.01) in both HS and HS+TAK242. HOMA-IR, an estimate of peripheral insulin sensitivity, was significantly impaired (53%, p<0.01) in HS vs. Con, while TLR4 inhibition provided partial protection (HS+TAK242 vs. Con, p=0.19; HS+TAK242 vs. HS, p=0.24). Muscle Akt S473 and AS160 S588 phosphorylation was not different across the groups. CONCLUSIONS: These data extend the body of evidence implicating the connection between TLR signaling, muscle ceramide accumulation, and impaired metabolic health. Follow-up analyses in other tissues (i.e. liver) are warranted, in order to understand the peripheral insulin sensitivity discrepancies compared to muscle. Funding was provided by the NIH: R01AG050781.

Glucocorticoid receptor isoform-specific regulation of development, circadian rhythm, and inflammation in mice.

Glucocorticoids are primary stress hormones, and their synthetic derivatives are widely used clinically. The therapeutic efficacy of these steroids is limited by side effects and glucocorticoid resistance. Multiple glucocorticoid receptor (GR) isoforms are produced from a single gene by alternative translation initiation; however, the role individual isoforms play in tissue-specific responses to glucocorticoids is unknown. We have generated knockin mice that exclusively express the most active receptor isoform, GR-C3. GR-C3 knockin mice die at birth due to respiratory distress. Microarray analysis of fibroblasts from wild-type and GR-C3 mice indicated that most genes regulated by GR-C3 were unique to this isoform. Antenatal glucocorticoid administration rescued GR-C3 knockin mice from neonatal death. Dual-energy X-ray absorptiometry revealed no major alterations in body composition for rescued knockin mice. Rescued female, but not male, GR-C3 mice exhibited increased wheel running activity in the light portion of the day. LPS administration induced premature mortality in rescued GR-C3 knockin mice, and gene expression studies revealed a deficiency in the ability of GR-C3 to repress a large cohort of immune and inflammatory response genes. These findings demonstrate that specific GR translational isoforms can influence development, circadian rhythm, and inflammation through the regulation of distinct gene networks.-Oakley, R. H., Ramamoorthy, S., Foley, J. F., Busada, J. T., Lu, N. Z., Cidlowski, J. A. Glucocorticoid receptor isoform-specific regulation of development, circadian rhythm, and inflammation in mice.

The effects of scheduled running wheel access on binge-like eating behavior and its consequences

Binge eating disorder (BED) is an eating disorder involving repeated, intermittent over consumption of food in brief periods of time, usually with no compensatory behaviors. There are few successful treatments and the underlying neural mechanisms remain unclear. In the current study, we hypothesized that voluntary running wheel (RW) activity could reduce binge-like eating behavior in a rat model. Rats were given intermittent (3 times/wk) limited (1hr) access to a high-fat food (Crisco), in addition to continuously available chow. Crisco was available every Mon, Wed, and Fri for 1hr before dark onset. Rats were divided into 2 groups: those with RW access during the first half of the experiment and sedentary during the second half (RW-SED) and those that were sedentary during the first half of the experiment and had RW access during the second half (SED-RW). Crisco intake was significantly less in both groups during the period of time with a RW present. Within the bingeing RW-SED rats, the gene expression of the orexigenic neuropeptides AgRP and NPY were similar to a non-bingeing sedentary control (CON) group, while the expression of the anorexigenic neuropeptide POMC was significantly increased relative to the SED-RW and CON groups. Despite elevated POMC, the rats continued to binge. Additionally, within both groups, the gene expression of the D2R and Oprm1 in the NAc and the VTA were altered suggesting that the reward system was stimulated by both the bingeing behavior and the running wheel activity. Overall, access to a RW and the resulting activity significantly reduced binge-like behavior as well as modulated the effects of binging on brain appetite and reward systems.

Brain mRNA Expression Changes Following Orchidectomy Are Not Associated with Physical Activity Levels in Male Mice

Physical activity is a complex phenotypical behavior that is largely associated with improved resistance to disease and health disparities. Despite the well‐established link between physical activity and health, few Americans—5% of males and 3% of females—routinely accumulate minimum recommended amounts of moderate and vigorous physical activity. Delineating the mechanisms that biologically regulate physical activity, therefore, is an important health‐related concern. The purpose of this study was to assess brain mRNA levels in male mice surgically induced—via orchidectomy—to exhibit low sex steroid concentrations and reduced physical activity levels. Male C57BL6/j mice (n=28) were acquired at 8 weeks of age and were housed individually with access to computer‐monitored running wheels. Following a brief wheel running acclimation period, mice underwent sham (control, n=12; 2 mice were removed from study for health‐related reasons) or real (treatment, n=14) bilateral orchidectomy procedures. Following a ten‐day surgical recovery period, all mice were allowed to run freely on in‐cage running wheels which continually monitored wheel running distance (km), duration (min), and speed (m·min−1). Data were collected for ten consecutive days to generate average values for each physical activity index. At the end of the study, all mice were killed and brain tissues were harvested. Reverse transcription followed by polymerase chain reaction assays were conducted to estimate the levels of mRNA transcripts hypothesized to be involved in regulating physical activity patterns. Genes of interested included drd2, drd4, hctr2, htr2c, and slc18a2. Computational analyses were completed to compare relative normalized expression (RNE) difference between control and treatment animals. For genes that were different between the control and the treatment groups, a correlation analysis was conducted to assess the association between wheel running distance and mRNA levels. Mice with low levels of sex steroids induced by orchidectomy (distance: 3.32±2.26 km) ran significantly less than physiologically intact mice [(distance: 7.94±1.84 km), (t(22)=5.4, p=0.00002)]. Both drd2 (RNE=0.509, p=0.008) and slc18a2 (RNE=2.348, p=0.017) exhibited altered mRNA expression in treatment animals following orchidectomy, however, neither gene exhibited a strong linear association with wheel running distance (drd2: r=0.26 and slc18a2: r=0.08). In conclusion, removal of the tissues that act as major producers of the sex steroids in mice resulted in reductions in wheel running activity and in changes to drd2 and slc18a2 gene expression. Although both changes appear to result from alterations to the sex steroid levels, these changes do not appear to be concomitant, indicating that the regulatory pathway for physical activity behavior associated with low levels of the sex steroids stems from other biochemical and biological changes.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cessation of Nightly Voluntary Wheel Running Activity Following Exposure to a Mouse Model of Posttraumatic Stress

Regular physical activity (PA) is well known to positively impact physical and mental health outcomes. In our work to examine cardiovascular benefits of PA in a mouse model of post‐traumatic stress, we stumbled upon the reciprocal relationship between PA and stress exposure, wherein stress significantly reduced healthy levels of routine PA. The aim of the present studies was to define the parameters of our paradigm as first steps for its future use in examining mechanisms that underlie stress‐induced declines in PA. Five week old, C67BL/6J male mice were divided into four groups (n=8/group); sedentary/control, voluntary running/control, sedentary/stress and voluntary running/stress. Voluntary running groups were given 24 hr unlimited access to a running wheel in the home cage for 9 weeks. Mice ran a nightly average of 4.75 ± 1 km. During the 9th week, stress groups were exposed to a 5 day resident‐intruder social stress that models human post traumatic stress outcomes. Running behavior essentially ceased following stress. Running distance dropped to 0.31 km following the 1st stress day. Some habituation to stress occurred, as running distance increased to 1.12 km by the 5th day of stress but remained significantly lower then pre‐stress running distances and distances recorded in non‐stressed mice. A separate study examined a single exposure to resident‐intruder social stress and found plasma corticosterone significantly increased (16.66 ± 4 ng/ml basal to 496 ± 155 ng/ml immediately post stress) while nightly running dropped significantly from 5.58 ± 1.7 km to 1.22 ± 1.1 km, and returned to near normal levels (4.35 ±1.7 km) by the 3rd night post stress. Food intake was moderately increased in the first 2 nights post stress, but also returned to normal by the 3rd night. These studies show the sensitivity of habitual running behavior to stress exposure and suggest the utility of this mouse model in exploring the means by which stress negatively impacts routine PA.Support or Funding InformationLinfield College Student‐Faculty Collaborative Research GrantThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Chronic social defeat stress suppresses locomotor activity but does not affect the free-running circadian period of the activity rhythm in mice

In mammals, daily rhythms in behavior and physiology are under control of an endogenous clock or pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN assures an optimal temporal organization of internal physiological process and also synchronizes rhythms in physiology and behavior to the cyclic environment. The SCN receives direct light input from the retina, which is capable of resetting the master clock and thereby synchronizes internally driven rhythms to the external light-dark cycle. In keeping with its function as a clock and pacemaker, the SCN appears to be well buffered against influences by other stimuli and conditions that contain no relevant timing information, such as acute stressors. On the other hand, it has been suggested that chronic forms of stress may have gradually accumulating effects that can disturb normal clock function and thereby contribute to stress-related disorders. Therefore, in the present study we investigated whether chronic intermittent social stress affects the endogenous period and phase of the free-running activity rhythm in mice. Adult male mice were maintained in constant dim red light conditions and exposed to a daily 20 min social defeat stress session for 10 consecutive days, either during the first half of their activity phase or the first half of their resting phase. The overall amount of running wheel activity was strongly suppressed during the 10 days of social defeat, to about 50% of the activity in non-defeated control mice. Activity levels gradually normalized during post-defeat recovery days. Despite the strong suppression of activity in defeated animals, the endogenous free-running circadian period of the activity rhythm and the phase of activity onset were not affected. These findings are thus in agreement with earlier studies suggesting that the circadian pacemaker in the SCN that is driving the rhythmicity in activity is well-protected against stress. Even severe social defeat stress for 10 consecutive days, which has a major effect on the levels of activity, does not affect the pace of the endogenous clock.

Development of a Low-cost, Comprehensive Recording System for Circadian Rhythm Behavior

Circadian rhythm is defined as a 24-hour biological oscillation, which persists even without any external cues but also can be re-entrained by various environmental cues. One of the widely accepted circadian rhythm behavioral experiment is measuring the wheel-running activity (WRA) of rodents. However, the price for commercially available WRA recording system is not easily affordable for researchers due to high-cost implementation of sensors for wheel rotation. Here, we developed a cost-effective and comprehensive system for circadian rhythm recording by measuring the house-keeping activities (HKA). We have monitored animal's HKA as electrical signal by simply connecting animal housing cage with a standard analog/digital converter: input to the metal lid and ground to the metal grid floor. We show that acquired electrical signals are combined activities of eating, drinking and natural locomotor behaviors which are well-known indicators of circadian rhythm. Post-processing of measured electrical signals enabled us to draw actogram, which verifies HKA to be reliable circadian rhythm indicator. To provide easy access of HKA recording system for researchers, we have developed user-friendly MATLAB-based software, Circa Analysis. This software provides functions for easy extraction of scalable “touch activity” from raw data files by automating seven steps of post-processing and drawing actograms with highly intuitive user-interface and various options. With our cost-effective HKA circadian rhythm recording system, we have estimated the cost of our system to be less than $150 per channel. We anticipate our system will benefit many researchers who would like to study circadian rhythm.

Bmal1 knockdown suppresses wake and increases immobility without altering orexin A, corticotrophin-releasing hormone, or glutamate decarboxylase.

To determine the effect of Bmal1 knockdown (KD) on sleep, activity, immobility, hypothalamic levels of orexin, corticotrophin-releasing hormone (CRH), and GABAergic glutamate decarboxylase (GAD). We used Bmal1 siRNA, or control siRNA intracerebroventricular (ICV) injection to knock down Bmal1 in C57BL/6 mice. Sleep polysomnography, wheel-running activity, and tail suspension test were performed. Polysomnographic (PSG) recordings in both groups were preceded by ICV injection made during both the light phase and the dark phase. We also measured brain orexin A and CRH using an ELISA and measured GAD using immunoblotting. Compared with control group, Bmal1 KD group had reduced wheel activity and increased immobility. Compared with control, the Bmal1 KD group had reduced wheel activity and increased immobility. During the first 24hours after treatment, we observed that control siRNA induced a much greater increase in sleep during the dark phase, which was associated with lower orexin levels. However, beginning 24hours after treatment, we observed an increase in sleep and a decrease in time spent awake during the dark phase in the Bmal1 KD group. These changes were not associated with changes in brain levels of orexin A, CRH, or GAD. Bmal1 KD led to reduced activity, increased immobility, and dramatic reduction in time spent awake as well as an increase in sleep during the dark phase. Early after injection, there was a slight change in sleep but brain levels of orexin, CRH, and GAD remain unchanged. Control siRNA also affected sleep associated with changes in orexin levels.

Tumor-Associated Fatigue in Cancer Patients Develops Independently of IL1 Signaling.

Fatigue is the most common symptom of cancer at diagnosis, yet causes and effective treatments remain elusive. As tumors can be highly inflammatory, it is generally accepted that inflammation mediates cancer-related fatigue. However, evidence to support this assertion is mostly correlational. In this study, we directly tested the hypothesis that fatigue results from propagation of tumor-induced inflammation to the brain and activation of the central proinflammatory cytokine, IL1. The heterotopic syngeneic murine head and neck cancer model (mEER) caused systemic inflammation and increased expression of Il1b in the brain while inducing fatigue-like behaviors characterized by decreased voluntary wheel running and exploratory activity. Expression of Il1b in the brain was not associated with any alterations in motivation, measured by responding in a progressive ratio schedule of food reinforcement, depression-like behaviors, or energy balance. Decreased wheel running occurred prior to Il1b detection in the brain, when systemic inflammation was minimal. Furthermore, mice null for two components of IL1β signaling, the type 1 IL1 receptor or the receptor adapter protein MyD88, were not protected from tumor-induced decreases in wheel running, despite attenuated cytokine action and expression. Behavioral and inflammatory analysis of four additional syngeneic tumor models revealed that tumors can induce fatigue regardless of their systemic or central nervous system inflammatory potential. Together, our results show that brain IL1 signaling is not necessary for tumor-related fatigue, dissociating this type of cancer sequela from systemic cytokine expression.Significance: These findings challenge the current understanding of fatigue in cancer patients, the most common and debilitating sequela associated with malignancy. Cancer Res; 78(3); 695-705. ©2017 AACR.

Regulation of Locomotor activity in fed, fasted, and food-restricted mice lacking tissue-type plasminogen activator

BackgroundCircadian rhythms of physiology and behavior are driven by a circadian clock located in the suprachiasmatic nucleus of the hypothalamus. This clock is synchronized to environmental day/night cycles by photic input, which is dependent on the presence of mature brain-derived neurotrophic factor (BDNF) in the SCN. Mature BDNF is produced by the enzyme plasmin, which is converted from plasminogen by the enzyme tissue-type plasminogen activator (tPA). In this study, we evaluate circadian function in mice lacking functional tPA.ResultstPA−/− mice have normal circadian periods, but show decreased nocturnal wheel-running activity. This difference is eliminated or reversed on the second day of a 48-h fast. Similarly, when placed on daily cycles of restricted food availability the genotypic difference in total wheel-running activity disappears, and tPA−/− mice show equivalent amounts of food anticipatory activity to wild type mice.ConclusionsThese data suggest that tPA regulates nocturnal wheel-running activity, and that tPA differentially affects SCN-driven nocturnal activity rhythms and activity driven by fasting or temporal food restriction.

Chronic sleep disorder induced by psychophysiological stress induces glucose intolerance without adipose inflammation in mice

Sleep disturbances are associated with various metabolic diseases such as hypertension and diabetes. We had previously established a mouse model of a psychophysiological stress-induced chronic sleep disorder (CSD) characterized by disrupted circadian rhythms of wheel-running activity, core body temperature, and sleep-wake cycles. To evaluate the underlying mechanisms of metabolic disorders induced by CSD, we created mice with CSD for six weeks and fed them with a high-fat diet. Glucose intolerance with hyperglycemia resulted, although plasma insulin levels and body weight increases were identical between control and CSD mice. Gluconeogenesis and glycolysis were enhanced and suppressed, respectively, in the livers of CSD mice, because the mRNA expression of Pck1 was significantly increased, whereas that of Gck and Pklr were significantly decreased in the CSD mice. Adipose inflammation induced by the high-fat diet seemed suppressed by the CSD, because the mRNA expression levels of Adgre1, Ccl2, and Tnf were significantly downregulated in the adipose tissues of CSD mice. These findings suggest that CSD impair glucose tolerance by inducing gluconeogenesis and suppressing glycolysis. Hyperphasia with hypoleptinemia, hypercorticosteronemia, and increased plasma free fatty acids might be involved in the impaired glucose metabolism under a CSD. Further studies are needed to elucidate the endocrine and molecular mechanisms underlying the associations between sleep disorders and impaired glucose homeostasis that consequently causes diabetes.

Running wheel exercise reduces α-synuclein aggregation and improves motor and cognitive function in a transgenic mouse model of Parkinson's disease.

Exercise has been recommended to improve motor function in Parkinson patients, but its value in altering progression of disease is unknown. In this study, we examined the neuroprotective effects of running wheel exercise in mice. In adult wild-type mice, one week of running wheel activity led to significantly increased DJ-1 protein concentrations in muscle and plasma. In DJ-1 knockout mice, running wheel performance was much slower and Rotarod performance was reduced, suggesting that DJ-1 protein is required for normal motor activity. To see if exercise can prevent abnormal protein deposition and behavioral decline in transgenic animals expressing a mutant human form of α-synuclein in all neurons, we set up running wheels in the cages of pre-symptomatic animals at 12 months old. Activity was monitored for a 3-month period. After 3 months, motor and cognitive performance on the Rotarod and Morris Water Maze were significantly better in running animals compared to control transgenic animals with locked running wheels. Biochemical analysis revealed that running mice had significantly higher DJ-1, Hsp70 and BDNF concentrations and had significantly less α-synuclein aggregation in brain compared to control mice. By contrast, plasma concentrations of α-synuclein were significantly higher in exercising mice compared to control mice. Our results suggest that exercise may slow the progression of Parkinson’s disease by preventing abnormal protein aggregation in brain.

Dexamethasone exacerbates cytotoxic chemotherapy induced lethargy and weight loss in female tumor free mice

ABSTRACTCytotoxic chemotherapy can induce a systemic inflammatory response which has been proposed to be an underlying mechanism of cancer treatment related fatigue. Dexamethasone, a synthetic glucocorticoid that has potent anti-inflammatory effects, is incorporated into chemotherapy regimens to prevent chemotherapy-induced nausea and vomiting (CINV). The purpose of this study was to determine whether by suppressing cytotoxic chemotherapy-induced inflammation, dexamethasone could ameliorate chemotherapy induced fatigue/lethargy in tumor free mice. The effect of dexamethasone (DEX) on Cytoxan-Adriamycin (CA)-induced inflammation was assessed by measuring circulating levels of IL-1β, TNF-α, IL-6, GCSF, KC, and MCP-1 twenty-four-hours post CA injection. Decline in voluntary wheel running activity (VWRA) from baseline (used as a proxy for fatigue/lethargy), body weight and composition, and food intake were monitored in mice administered four cycles of CA every two weeks with or without DEX. CA increased circulating levels of IL-6, GCSF, KC, and MCP-1 and caused a rapid decline in VWRA and body weight immediately following CA-injection. Although the acute CA-induced decline in VWRA and body weight was not evident in mice administered CA + DEX, DEX alone had a suppressive effect on VWRA, and body weight continued to decline in mice administered both CA and DEX while it returned to baseline in CA-treated mice. CA or DEX alone had no long term impact on VWRA but DEX exacerbated lethargy and weight loss in CA-treated mice. Despite dampening the systemic inflammatory response to chemotherapy, dexamethasone failed to ameliorate acute or long term chemotherapy related fatigue/lethargy. Our pre-clinical findings suggest that supportive therapies like dexamethasone used to acutely control nausea and vomiting in cancer patients may actually contribute to overall symptom burden in cancer patients.

L-Serine Enhances Light-Induced Circadian Phase Resetting in Mice and Humans

Background: The circadian clock is modulated by the timing of ingestion or food composition, but the effects of specific nutrients are poorly understood.Objective: We aimed to identify the amino acids that modulate the circadian clock and reset the light-induced circadian phase in mice and humans.Methods: Male CBA/N mice were orally administered 1 of 20 l-amino acids, and the circadian and light-induced phase shifts of wheel-running activity were analyzed. Antagonists of several neurotransmitter pathways were injected before l-serine administration, and light-induced phase shifts were analyzed. In addition, the effect of l-serine on the light-induced phase advance was investigated in healthy male students (mean ± SD age 22.2 ± 1.8 y) by using dim-light melatonin onset (DLMO) determined by saliva samples as an index of the circadian phase.Results: l-Serine administration enhanced light-induced phase shifts in mice (1.86-fold; P < 0.05). Both l-serine and its metabolite d-serine, a coagonist of N-methyl-d-aspartic acid (NMDA) receptors, exerted this effect, but d-serine concentrations in the hypothalamus did not increase after l-serine administration. The effect of l-serine was blocked by picrotoxin, an antagonist of γ-aminobutyric acid A receptors, but not by MK801, an antagonist of NMDA receptors. l-Serine administration altered the long-term expression patterns of clock genes in the suprachiasmatic nuclei. After advancing the light-dark cycle by 6 h, l-serine administration slightly accelerated re-entrainment to the shifted cycle. In humans, l-serine ingestion before bedtime induced significantly larger phase advances of DLMO after bright-light exposure during the morning (means ± SEMs-l-serine: 25.9 ± 6.6 min; placebo: 12.1 ± 7.0 min; P < 0.05).Conclusion: These results suggest that l-serine enhances light-induced phase resetting in mice and humans, and it may be useful for treating circadian disturbances.

MPeriod2Brdm1 and other single Period mutant mice have normal food anticipatory activity

Animals anticipate the timing of food availability via the food-entrainable oscillator (FEO). The anatomical location and timekeeping mechanism of the FEO are unknown. Several studies showed the circadian gene, Period 2, is critical for FEO timekeeping. However, other studies concluded that canonical circadian genes are not essential for FEO timekeeping. In this study, we re-examined the effects of the Per2Brdm1 mutation on food entrainment using methods that have revealed robust food anticipatory activity in other mutant lines. We examined food anticipatory activity, which is the output of the FEO, in single Period mutant mice. Single Per1, Per2, and Per3 mutant mice had robust food anticipatory activity during restricted feeding. In addition, we found that two different lines of Per2 mutant mice (ldc and Brdm1) anticipated restricted food availability. To determine if FEO timekeeping persisted in the absence of the food cue, we assessed activity during fasting. Food anticipatory (wheel-running) activity in all Period mutant mice was also robust during food deprivation. Together, our studies demonstrate that the Period genes are not necessary for the expression of food anticipatory activity.

Mice Lacking EGR1 Have Impaired Clock Gene (BMAL1) Oscillation, Locomotor Activity, and Body Temperature.

Early growth response transcription factor 1 (EGR1) is expressed in the suprachiasmatic nucleus (SCN) after light stimulation. We used EGR1-deficient mice to address the role of EGR1 in the clock function and light-induced resetting of the clock. The diurnal rhythms of expression of the clock genes BMAL1 and PER1 in the SCN were evaluated by semi-quantitative in situ hybridization. We found no difference in the expression of PER1 mRNA between wildtype and EGR1-deficient mice; however, the daily rhythm of BMAL1 mRNA was completely abolished in the EGR1-deficient mice. In addition, we evaluated the circadian running wheel activity, telemetric locomotor activity, and core body temperature of the mice. Loss of EGR1 neither altered light-induced phase shifts at subjective night nor affected negative masking. Overall, circadian light entrainment was found in EGR1-deficient mice but they displayed a reduced locomotor activity and an altered temperature regulation compared to wild type mice. When placed in running wheels, a subpopulation of EGR1-deficient mice displayed a more disrupted activity rhythm with no measurable endogenous period length (tau). In conclusion, the present study provides the first evidence that the circadian clock in the SCN is disturbed in mice deficient of EGR1.

Tumor-associated fatigue develops independently of inflammation

Purpose Fatigue is a frequent side effect of cancer and cancer treatment, common to multiple tumor sites and therapeutic strategies. The propagation of peripheral inflammation into the brain is thought to mediate this response. The purpose of this study was to evaluate the role of inflammatory signaling in mediating fatigue induced by multiple syngeneic tumors. Materials/Methods WT, IL-1RIKO, and MyD88 were injected in the flank with HPV+ (mEER), HPV- head and neck cancer, Lewis lung carcinoma (LLC), and two ovarian tumors. Fatigue was measured using wheel running and locomotor activity. Cytokine expression was assessed in the brain, liver, serum, and tumor using qRT-PCR or immunoassay. ANOVA with post hoc Dunnett’s test were used for statistical comparisons with significance set at p Results Wheel running decreased in mEER animals beginning after 10 days and continuing until termination. Inflammatory cytokine expression was seen in the brains, livers, and serum of mEER animals 4 weeks after tumor implantation, but not sooner. IL-1RIKO and MyD88 mice exhibited decreased inflammatory cytokine expression and serum corticosterone, but wheel running and locomotor activity deficits were preserved. Additional tumors induced similar decreases in wheel running, despite varying systemic or brain inflammation. Conclusions Inflammation is sufficient, but not necessary for fatigue-like behavior in tumor bearing mice. Together, these data definitively dissociate fatigue from inflammation and suggest an alternative non-inflammatory mechanism likely underlies most cancer-related fatigue.

Temporal relationships between food acquisition and voluntary exercise in mice

Patterns of operant food acquisition in a closed economy and bouts of either voluntary wheel running (WR) or spontaneous locomotor activity in a standard condition (SC) with no wheel were examined in young adult male and female C57BL/6 mice across a range of nose poke prices (FUP) per food pellet. Both sexes showed vigorous WR or locomotor activity. At each FUP, WR groups had higher food intake than SC groups. Despite substantially higher mean body weight of males compared with females, intakes and activity did not differ by sex in the SC groups and males lost weight more rapidly as FUP increased. In contrast, WR males ran ∼33% further per day than females, increased their food intake (above that of SC counterparts) more than females, and lost less body weight than SC males. By parsing the night in four 3h epochs it was found that food intake declined progressively through the night in both WR and SC mice and that the hyperphagia of WR relative to SC groups was most evident early in the night, coincident with highest activity. No large or systematic sex differences were revealed in these temporal analyses. Analysis of data at 60s resolution showed that pellet acquisition occurred in many small or short bouts, the timing of which was either intercalated or concurrent with either locomotor activity or WR. The results show that increased eating due to WR occurs concurrently with maximum running, and with no evidence of delayed compensation.

Prolactin receptors in Rip-cre cells, but not in AgRP neurones, are involved in energy homeostasis.

Among its many functions, prolactin has been implicated in energy homeostasis, particularly during pregnancy and lactation. The arcuate nucleus is a key site in the regulation of energy balance. The present study aimed to examine whether arcuate nucleus neuronal populations involved in energy homeostasis are prolactin responsive and whether they can mediate the effects of prolactin on energy homeostasis. To determine whether Agrp neurones or Rip-Cre neurones are prolactin responsive, transgenic mice expressing the reporter td-tomato in Agrp neurones (td-tomato/Agrp-Cre) or Rip-Cre neurones (td-tomato/Rip-Cre) were treated with prolactin and perfused 45minutes later. Brains were processed for double-labelled immunohistochemistry for pSTAT5, a marker of prolactin-induced intracellular signalling, and td-tomato. In addition, Agrp-Cre mice and Rip-Cre mice were crossed with mice in which the prolactin receptor gene (Prlr) was flanked with LoxP sites (Prlrlox/lox mice). The Prlrlox/lox construct was designed such that Cre-mediated recombination resulted in deletion of the Prlr and expression of green fluorescent protein (GFP) in its place. In td-tomato/Rip-Cre mice, prolactin-induced pSTAT5 was co-localised with td-tomato, indicating that there is a subpopulation of Rip-Cre neurones in the arcuate nucleus that respond to prolactin. Furthermore, mice with a specific deletion of Prlr in Rip-Cre neurones had lower body weights, increased oxygen consumption, increased running wheel activity and numerous cells in the arcuate nucleus had positive GFP staining indicating deletion of Prlr from Rip-Cre neurones. By contrast, no co-localisation of td-tomato and pSTAT5 was observed in td-tomato/Agrp-Cre mice after prolactin treatment. Moreover, Prlrlox/lox /Agrp-Cre mice had no positive GFP staining in the arcuate nucleus and did not differ in body weight compared to littermate controls. Overall, these results indicate that Rip-Cre neurones in the arcuate nucleus are responsive to prolactin and may play a role in the orexigenic effects of prolactin, whereas prolactin does not directly affect Agrp neurones.