Partial sleep deprivation by environmental noise increases food intake and body weight in obesity-resistant rats

Behavioral phenotyping based on physical inactivity can predict sleep in female rats before, during, and after sleep disruption

BACKGROUND

A noninvasive method that can accurately quantify sleep before, during, and after sleep disruption (SD) has not been validated in female rats across their estrous cycle. In female rats, we hypothesized that the duration of physical inactivity (PIA) required to predict sleep would 1) change with the differences in baseline sleep between the circadian and estrous cycle phases and 2) predict sleep and the change in sleep (Δsleep) before, during, and after SD independent of circadian and estrous cycle phase.

NEW METHODS

EEG, EMG, physical activity and estrous cycle phase were measured in female Sprague-Dawley rats before, during, and after SD. Sleep was determined by two methods [EEG/EMG and a duration of continuous PIA (i.e., PIA criterion)]. Reliability between the methods was tested with a previously validated criterion (40 s). Sensitivity analyses and criterion-related validity analyses for sleep during SD and recovery were conducted across multiple PIA criteria (10 s-120 s). Predictability between the two methods and Δsleep was calculated.

RESULTS/COMPARISON WITH EXISTING METHODS

Three criteria (10 s, 20 s, 30 s) predicted baseline sleep independent of circadian and estrous cycle phase. Sleep during SD and recovery were predicted by two criteria (30 s and 10 s). Δsleep between study periods was not reliably predicted by a single PIA criterion.

CONCLUSION

PIA predicted sleep independent of estrous cycle phase in female rats. However, the specific criterion was dependent upon the study period (before, during, and after SD) and circadian phase. Thus, prior work validating a PIA criterion in male rodents is not applicable to the female rat.

The stress of losing sleep: Sex-specific neurobiological outcomes

Sleep is a vital and evolutionarily conserved process, critical to daily functioning and homeostatic balance. Losing sleep is inherently stressful and leads to numerous detrimental physiological outcomes. Despite sleep disturbances affecting everyone, women and female rodents are often excluded or underrepresented in clinical and pre-clinical studies. Advancing our understanding of the role of biological sex in the responses to sleep loss stands to greatly improve our ability to understand and treat health consequences of insufficient sleep. As such, this review discusses sex differences in response to sleep deprivation, with a focus on the sympathetic nervous system stress response and activation of the hypothalamic-pituitary-adrenal (HPA) axis. We review sex differences in several stress-related consequences of sleep loss, including inflammation, learning and memory deficits, and mood related changes. Focusing on women's health, we discuss the effects of sleep deprivation during the peripartum period. In closing, we present neurobiological mechanisms, including the contribution of sex hormones, orexins, circadian timing systems, and astrocytic neuromodulation, that may underlie potential sex differences in sleep deprivation responses.

Exogenous growth hormone administration during total sleep deprivation changed the microRNA-9 and dopamine D2 receptor expressions followed by improvement in the hippocampal synaptic potential, spatial cognition, and inflammation in rats

RATIONALE

Disorders caused by total sleep deprivation can be modulated by the administration of growth hormone, which could affect the expression of microRNA-9 and dopamine D2 receptor expressions followed by improvement in the hippocampal synaptic potential, spatial cognition, and inflammation in rats.

OBJECTIVES

The present study aimed to elucidate the putative effects of exogenous growth hormone (GH) against total sleep deprivation (TSD)-induced learning and memory dysfunctions and possible involved mechanisms.

METHODS

To induce TSD, rats were housed in homemade special cages equipped with stainless steel wire conductors to induce general and inconsistent TSD. They received a mild repetitive electric shock to their paws every 10 min for 21 days. GH (1 mg/kg, sc) was administered to adult young male rats once daily for 21-day-duration induction of TSD. Spatial learning and memory performance, inflammatory status, microRNA-9 (miR-9) expression, dopamine D2 receptor (DRD2) protein level, and hippocampal histological changes were assayed at scheduled times after TSD.

RESULTS

The results indicated that TSD impaired spatial cognition, increased TNF-α, decreased level of miR-9, and increased DRD2 levels. Treatment with exogenous GH improved spatial cognition, decreased TNF-α, increased level of miR-9, and decreased DRD2 levels after TSD.

CONCLUSIONS

Our findings suggest that GH may play a key role in the modulation of learning and memory disorders as well as the ameliorating abnormal DRD2-related functional disorders associated with miR-9 in TSD.

Sleep loss in male rats contributes more to weight gain during sleep disruption than stress assessed by corticosterone

Sleep disruption (SD) promotes stress which may mediate the effect of SD induced by noise on bodyweight gain and food intake. We determined if the change in bodyweight during SD caused by noise was driven by stress (assessed by corticosterone) and whether the effects of noise on SD, stress and bodyweight were specific to the method of SD or a consequence of SD per se. We isolated stress from SD due to noise by exposing rats to noise during the darkphase to test whether darkphase noise stimulated weight gain, stress and food intake. Male Sprague-Dawley rats slept undisturbed, were exposed to noise during both circadian phases (lightphase vs darkphase) and lightphase gentle handling. Bodyweight, food intake, physical activity, vigilance states, and plasma corticosterone were determined. Darkphase noise did not affect vigilance states. Unlike lightphase noise, darkphase noise and lightphase gentle handling did not stimulate weight gain or food intake. Only gentle handling significantly increased corticosterone levels. Noise during the lightphase increasesed weight gain and food intake by causing SD and these effects were not driven by stress as assessed by corticosterone. These results may have significant implications for developing translational models of insomnia-induced obesity in humans.

Manganese-enhanced magnetic resonance imaging detects activation of limbic structures in response to auditory stimuli of different frequencies

PURPOSE

As we are exposed to stress on a daily basis, it is important to detect and treat stress during the subclinical period. However, methods to quantify and confirm stress are currently unavailable, and the detection of subclinical stressors is difficult. This study aimed to determine whether manganese-enhanced magnetic resonance imaging (MEMRI) could be used to assess stress in rat brains.

METHODS

We exposed male Wistar/ST rats bred in a specific pathogen-free environment to ultrasound stimuli (22 kHz and 55 kHz) for 10 days and then assessed brain activities using MEMRI, the light/dark box test, and ΔFosB immunohistochemical staining.

RESULTS

In the MEMRI assessments, exposure at 22 kHz activated the periaqueductal gray, while exposure at 55 kHz specifically enhanced activity in the nucleus accumbens core and the orbitofrontal cortex. The exploratory behavior of the 55-kHz group increased sharply, while that of the 22-kHz group showed a lower exploratory value. ΔFosB expression increased in the orbitofrontal cortex, nucleus accumbens, periaqueductal gray, and amygdaloid nucleus in the 22-kHz group.

CONCLUSION

Ultrasound stimuli at 22 kHz suppressed weight gain in rats and excessive ΔFosB induction in the nucleus accumbens caused excessive sensitization of the neural circuit, thereby contributing to pathological behavior. We thus demonstrated that MEMRI can be useful to objectively assess the pathophysiology of stress-related disorders.

Traffic noise and adiposity: a systematic review and meta-analysis of epidemiological studies

Traffic noise has attracted much attention as a significant and intractable public health threat. This study was designed as a systematical review to explore the association of traffic noise with different indicators of obesity, thus providing updated quantitative estimates for the pooled effect estimates of the existing literature. We conducted an extensive search for epidemiological studies that investigated the association of traffic noise with obesity in three electronic databases till February 23, 2021. We used random-effects meta-analysis to calculate the summary effect estimates for each 10-dB(A) increase in noise and compared the highest with the lowest category of noise in relation to seven obesity indicators. Meanwhile, we assessed the risk of bias and the overall quality of the evidence of each study as well as the level of evidence for each exposure-outcome pair. The initial search identified 30 studies, 13 of which were ultimately included. The meta-analysis for the highest versus the lowest category of noise exposure was generally associated with higher waist circumfluence (WC) ranging from 0.326 cm (95% confidence interval (CI) = 0.078, 0.574) to 0.705 cm (95% CI = 0.071, 1.340) and higher odds of central obesity ranging from 1.055 (95% CI = 1.000, 1.109) to 1.167 (95% CI = 1.037, 1.298). When the continuous exposure (each 10 dB(A) increase in noise) was introduced, similar results were found. This study indicated positive associations of traffic noise with WC and central obesity. However, in consideration of some limitations, there is an urgent need for future studies to increase the sample size, discriminate the etiological differences in different noise and obesity indicators, and thoroughly consider socioeconomic status.

Cerebral consequences of environmental noise exposure

The importance of noise exposure as a major environmental determinant of public health is being increasingly recognized. While in recent years a large body evidence has emerged linking environmental noise exposure mainly to cardiovascular disease, much less is known concerning the adverse health effects of noise on the brain and associated neuropsychiatric outcomes. Despite being a relatively new area of investigation, indeed, mounting research and conclusive evidence demonstrate that exposure to noise, primarily from traffic sources, may affect the central nervous system and brain, thereby contributing to an increased risk of neuropsychiatric disorders such as stroke, dementia and cognitive decline, neurodevelopmental disorders, depression, and anxiety disorder. On a mechanistic level, a significant number of studies suggest the involvement of reactive oxygen species/oxidative stress and inflammatory pathways, among others, to fundamentally drive the adverse brain health effects of noise exposure. This in-depth review on the cerebral consequences of environmental noise exposure aims to contribute to the associated research needs by evaluating current findings from human and animal studies. From a public health perspective, these findings may also help to reinforce efforts promoting adequate mitigation strategies and preventive measures to lower the societal consequences of unhealthy environments.

Long-lasting effects of postweaning sleep deprivation on cognitive function and social behaviors in adult mice

Sleep deprivation (SD) has adverse effects on physical and mental health. Recently increasing attention has been given to SD in the early-life stage. However, the effects and mechanisms of postweaning SD on cognitive function and social behaviors are still unclear. In this study, SD was conducted in mice from postnatal Day 21 (PND21) to PND42, 6 h a day. Meanwhile, changes in body weight, food and water intake were continuously monitored. Behavioral tests were carried out in adulthood of mice. The levels of serum corticosterone, the proinflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and the anti-inflammatory cytokines interleukin-10 (IL-10), vasopressin (VP) and oxytocin (OT) were measured by ELISA. Golgi staining was used to calculate neural dendritic spine density in the dorsal hippocampus (dHPC) CA1 region and medial prefrontal cortex (mPFC). We found that postweaning SD increased the food intake and the weight of female mice. Behavioral results showed that postweaning SD caused cognitive impairment and lowered social dominance in adult male mice but not in female mice. ELISA results showed that SD increased the levels of serum corticosterone, VP and OT in male mice and serum OT in female mice. Golgi staining analysis showed that SD decreased neural dendritic spine density in the dHPC in male mice. These results suggest that postweaning SD has a long-term effect on social dominance and cognitive function in male mice, which may provide a new insight into the role of SD in regulating cognitive function and social behaviors.

Orexin enhances neuronal synchronization in adult rat hypothalamic culture: a model to study hypothalamic function

The regulation of sleep/wake behavior and energy homeostasis is maintained in part by the hypothalamic neuropeptide orexin A (OXA, hypocretin). Reduction in orexin signaling is associated with sleep disorders and obesity, whereas higher lateral hypothalamic (LH) orexin signaling and sensitivity promotes obesity resistance. Similarly, dysregulation of hypothalamic neural networks is associated with onset of age-related diseases, including obesity and several neurological diseases. Despite the association of obesity and aging, and that adult populations are the target for the majority of pharmaceutical and obesity studies, conventional models for neuronal networks utilize embryonic neural cultures rather than adult neurons. Synchronous activity describes correlated changes in neuronal activity between neurons and is a feature of normal brain function, and is a measure of functional connectivity and final output from a given neural structure. Earlier studies show alterations in hypothalamic synchronicity following behavioral perturbations in embryonic neurons obtained from obesity-resistant rats and following application of orexin onto embryonic hypothalamic cultures. Synchronous network dynamics in adult hypothalamic neurons remain largely undescribed. To address this, we established an adult rat hypothalamic culture in multi-electrode-array (MEA) dishes and recorded the field potentials. Then we studied the effect of exogenous orexin on network synchronization of these adult hypothalamic cultures. In addition, we studied the wake promoting effects of orexin in vivo when directly injected into the lateral hypothalamus (LH). Our results showed that the adult hypothalamic cultures are viable for nearly 3 mo in vitro, good quality MEA recordings can be obtained from these cultures in vitro, and finally, that cultured adult hypothalamus is responsive to orexin. These results support that adult rat hypothalamic cultures could be used as a model to study the neural mechanisms underlying obesity. In addition, LH administration of OXA enhanced wakefulness in rats, indicating that OXA enhances wakefulness partly by promoting neural synchrony in the hypothalamus.NEW & NOTEWORTHY This study, for the first time, demonstrates that adult hypothalamic cultures are viable in vitro for a prolonged duration and are electrophysiologically active. In addition, the study shows that orexin enhances neural synchronization in adult hypothalamic cultures.

Glutamine restores testicular glutathione-dependent antioxidant defense and upregulates NO/cGMP signaling in sleep deprivation-induced reproductive dysfunction in rats

Oxidative stress has been linked with sleep deprivation (SD)-induced pathological conditions and reproductive dysfunction. On the other hand, glutamine has been established to have antioxidant property. However, the impact of SD, with or without glutamine, on male reproductive function is yet to be elucidated. Thus, this study was designed to investigate the role of SD, with or without glutamine, on male reproductive function and possible associated mechanisms. Ten-week old male Wistar rats weighing 175.6 g± 0.42 were randomly assigned into vehicle that received per os (p.o.) distilled water, glutamine (1 g/kg; po), SD, and SD + glutamine that received treatments as glutamine and SD. Treatment/exposure lasted for 72 h. The results showed that SD led to reduced body weight, seminiferous luminal and epididymal sperm density, low sperm quality, increased testicular and epididymal malondialdehyde, uric acid, DNA fragmentation, and testicular injury markers. In addition, SD caused a reduction in reduced glutathione level and activities of superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase, glutathione peroxidase, and glutathione-S-transferase. Also, SD increased tumor necrotic factor-α, interleukin-1β, and nuclear factor-kappa B levels. Furthermore SD led to impaired libido and erectile dysfunction, and suppression of circulatory nitric oxide, gonadotropins and testosterone, and penile cGMP. However, glutamine attenuated the effects induced by SD. Taken together, the findings of this study demonstrate that SD induces reproductive dysfunction via glutathione-dependent defense depletion and down-regulation of NO/cGMP signaling, which was abolished by glutamine supplementation.

Analysis of Thermogenesis Experiments with CalR

Modern indirect calorimetry systems allow for high-frequency time series measurements of the factors affected by thermogenesis: energy intake and energy expenditure. These indirect calorimetry systems generate a flood of raw data recording oxygen consumption, carbon dioxide production, physical activity, and food intake among other factors. Analysis of these data requires time-consuming manual manipulation for formatting, data cleaning, quality control, and visualization. Beyond data handling, analyses of indirect calorimetry experiments require specialized statistical treatment to account for differential contributions of fat mass and lean mass to metabolic rates.Here we describe how to use the software package CalR version 1.2, to analyze indirect calorimetry data from three examples of thermogenesis, cold exposure, adrenergic agonism, and hyperthyroidism in mice, by providing standardized methods for reproducible research. CalR is a free online tool with an easy-to-use graphical user interface to import data files from the Columbus Instruments' CLAMS, Sable Systems' Promethion, and TSE Systems' PhenoMaster. Once loaded, CalR can quickly visualize experimental results and perform basic statistical analyses. We present a framework that standardizes the data structures and analyses of indirect calorimetry experiments to provide reusable and reproducible methods for the physiological data affecting body weight.

Right stellate ganglion block improves learning and memory dysfunction and hippocampal injury in rats with sleep deprivation

Background

Sleep deprivation (SD) often leads to complex detrimental consequences, though the mechanisms underlying these dysfunctional effects remain largely unknown. We investigated whether the right stellate ganglion block in rats can improve the spatial learning and memory dysfunction induced by sleep deprivation by alleviating the damage of hippocampus in rats.

Methods

Sixty four male Sprague Dawley rats were randomly divided into four groups: Control, SD (sleep deprivation), SGB (stellate ganglion block) and SGB + SD (stellate ganglion block+ sleep deprivation) (n = 16). The SGB and SD + SGB groups were subjected to right stellate ganglion block through posterior approach method once per day. SD and SD + SGB groups were treated with modified multi-platform water environment method for 96 h sleep deprivation in rats and their body weights were analyzed. Histopathological changes of hippocampal neurons in rats and the expression of Caspase-3 in hippocampus of rats was detected by western blotting. ELISA was used to detect the content of IL-6, IL-1 in hippocampus and serum melatonin levels.

Results

Compared with the group SD, the spatial learning and memory function of the group SD + SGB was improved, the weight loss was alleviated, the pathological damage of the hippocampus was reduced and the expression of IL-6, IL-1β and Caspase-3 in the hippocampus was decreased. The content of rat serum melatonin was also increased.

Conclusions

The right stellate ganglion block can improve the spatial learning and memory dysfunction of rats with sleep deprivation, and the underlying mechanism may be related to alleviating the apoptosis and inflammation of hippocampus of rats with sleep deprivation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01486-4.

REM Sleep Deprivation Impairs Learning and Memory by Decreasing Brain O-GlcNAc Cycling in Mouse

Rapid eye movement (REM) sleep is implicated learning and memory (L/M) functions and hippocampal long-term potentiation (LTP). Here, we demonstrate that REM sleep deprivation (REMSD)-induced impairment of contextual fear memory in mouse is linked to a reduction in hexosamine biosynthetic pathway (HBP)/O-GlcNAc flux in mouse brain. In mice exposed to REMSD, O-GlcNAcylation, and O-GlcNAc transferase (OGT) were downregulated while O-GlcNAcase was upregulated compared to control mouse brain. Foot shock fear conditioning (FC) induced activation of protein kinase A (PKA) and cAMP response element binding protein (CREB), which were significantly inhibited in brains of the REMSD group. Intriguingly, REMSD-induced defects in L/M functions and FC-induced PKA/CREB activation were restored upon increasing O-GlcNAc cycling with glucosamine (GlcN) or Thiamet G. Furthermore, Thiamet G restored the REMSD-induced decrease in dendritic spine density. Suppression of O-GlcNAcylation by the glutamine fructose-6-phosphate amidotransferase (GFAT) inhibitor, 6-diazo-5-oxo-L-norleucine (DON), or OGT inhibitor, OSMI-1, impaired memory function, and inhibited FC-induced PKA/CREB activation. DON additionally reduced the amplitude of baseline field excitatory postsynaptic potential (fEPSP) and magnitude of long-term potentiation (LTP) in normal mouse hippocampal slices. To our knowledge, this is the first study to provide comprehensive evidence of dynamic O-GlcNAcylation changes during the L/M process in mice and defects in this pathway in the brain of REM sleep-deprived mice. Our collective results highlight HBP/O-GlcNAc cycling as a novel molecular link between sleep and cognitive function.

Addiction-like response in brain and behavior in a rat experimental model of night-eating syndrome

STUDY OBJECTIVES

Individuals ailing from night eating syndrome (NES) consume more than 25% of their daily food intake during the normal sleep time, delaying their sleep or waking up in the middle of the night to eat. This study explored two experimental conditions resembling NES in Wistar rats by offering palatable food during the sleep phase, alone or combined with sleep delay. Also we explored their impact on addiction-like changes in the brain and behavior.

METHODS

Experiment 1 explored the brain response after a first NES-like event; experiment 2 and 3 explored addiction-like behaviors c-Fos and FosB/ΔFosB in corticolimbic regions after 4 weeks exposition to NES-like conditions and after one week of withdrawal, respectively. For all 3 experiments 6 experimental groups were used: 1. Control; 2. Restricted access (1 h) to high-sugar diet (HSD) or to 3. high-fat diet (HFD); 4., Sleep delay for 4 h (SD) (from ZT0-ZT4, rats using slow rotating wheels); 5. SD + HSD; 6. SD + HFD.

RESULTS

A first event of eating a palatable diet with or without SD was sufficient to stimulate c-Fos and ΔFosB. Along 4 weeks of exposure to the palatable diets rats exhibited escalation and binge eating, which was highest for the HFD. At this stage, SD did not influence behavioral changes nor the neuronal response. After one-week in withdrawal, rats exhibited craving and effort to obtain their palatable diet. The brains of rats previously exposed to sleep delay maintained high levels of FosB/ΔFosB in the accumbens shell and high c-Fos activation in the insular cortex.

CONCLUSIONS

In our experimental models of NES-like a HFD in the sleep phase and SD are risk factors to develop binge eating and addiction-like behaviors.

Synchronous neuronal interactions in rat hypothalamic culture: a novel model for the study of network dynamics in metabolic disorders

Synchronous neural activity is a feature of normal brain function, and altered synchronization is observed in several neurological diseases. Dysfunction in hypothalamic pathways leads to obesity, suggesting that hypothalamic neural synchrony is critical for energy homeostasis. The lateral hypothalamic orexin neurons are extensively interconnected with other brain structures and are important for energy balance. Earlier studies show that rats with higher orexin sensitivity are obesity resistant. Similarly, topiramate, an anti-epileptic drug, has been shown to reduce weight in humans. Since orexin enhances neuronal excitation, we hypothesized that obesity-resistant rats with higher orexin sensitivity may exhibit enhanced hypothalamic synchronization. We further hypothesized that anti-obesity agents such as orexin and topiramate will enhance hypothalamic synchronization. To test this, we examined neural synchronicity in primary embryonic hypothalamic cell cultures, obtained from embryonic day 18 (E18) obesity-susceptible Sprague-Dawley (SD) and obesity-resistant rats. Hypothalamic tissue was cultured in multielectrode array (MEA), and recordings were performed twice weekly, from 4th to 32nd day in vitro (DIV). Next, we tested the effects of orexin and topiramate application on neural synchronicity of hypothalamic cultures obtained from SD rat embryos. Signals were analyzed for synchronization using cross correlation. Our results showed that (1) obesity-resistant hypothalamus exhibits significantly higher synchronization compared to obesity-sensitive hypothalamus; and (2) orexin and topiramate enhance hypothalamic synchronization. These results support that enhanced orexin sensitivity is associated with greater neural synchronization, and that anti-obesity treatments enhance network synchronization, thus constrain variability in hypothalamic output signals, to extrahypothalamic structures involved in energy homeostasis.

Sleep Loss Can Cause Death through Accumulation of Reactive Oxygen Species in the Gut

The view that sleep is essential for survival is supported by the ubiquity of this behavior, the apparent existence of sleep-like states in the earliest animals, and the fact that severe sleep loss can be lethal. The cause of this lethality is unknown. Here we show, using flies and mice, that sleep deprivation leads to accumulation of reactive oxygen species (ROS) and consequent oxidative stress, specifically in the gut. ROS are not just correlates of sleep deprivation but drivers of death: their neutralization prevents oxidative stress and allows flies to have a normal lifespan with little to no sleep. The rescue can be achieved with oral antioxidant compounds or with gut-targeted transgenic expression of antioxidant enzymes. We conclude that death upon severe sleep restriction can be caused by oxidative stress, that the gut is central in this process, and that survival without sleep is possible when ROS accumulation is prevented. VIDEO ABSTRACT.

Jiao-tai-wan inhibits inflammation of the gut-brain-axis and attenuates cognitive impairment in insomnic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Jiao-tai-wan is a well-known traditional Chinese herbal medicine formula that is used to treat insomnia and systemic inflammation. Studies indicate chronic insomnia might contribute to the prevalence of cognitive impairment. The role of systemic inflammation and intestinal permeability in the progression of neurodegenerative diseases attracts much attention.

AIM OF THE STUDY

This study aimed to investigate if Jiao-tai-wan plays a role in promoting the repair of the intestinal epithelial barrier to suppress systemic inflammation and cognitive impairment in sleep-deprived (SD) rats.

MATERIALS AND METHODS

Male obesity-resistant SD rats were partially sleep-deprived for 16 weeks. During the last 8 weeks, they were treated with Jiao-tai-wan. A Morris water maze was used to analyze their cognitive ability. Aβ42 and proinflammation cytokines in the cerebrospinal fluid, tissue, or serum were determined using enzyme-linked immunosorbent assay or polymerase chain reaction. Intestinal permeability was detected using the fluorescein isothiocyanate-dextran perfusion assay method. Plasma lipopolysaccharide (LPS) levels were detected with Tachypleus Amebocyte Lysate. Western bolt was used in the signaling pathway analysis.

RESULTS

Sleep deprivation deteriorated the performance of rats in the Morris water maze and increased the Aβ42, caspase3, IL-6, and TNF-α levels in their brains. The intestinal TLR4/NF-κB pathway was activated with an increase in the expression of IL-6 and TNF-α. The expression of tight junction proteins was also decreased in the intestinal tissue. This increased the intestinal permeability and circulation of LPS, LPS binding protein, IL-6, and TNF-α. Treatment with Jiao-tai-wan could partly reverse these changes.

CONCLUSION

Jiao-tai-wan has the potential to attenuate systemic inflammation and cognitive impairment in partially sleep-deprived rats. The possible underlying mechanism is by preventing an inflammation trigger being transferred through the gut-brain-axis.

Effects of co-exposure to 900 MHz radiofrequency electromagnetic fields and high-level noise on sleep, weight, and food intake parameters in juvenile rats

OBJECTIVE

Electrohypersensitive people attribute various symptoms to exposure of radiofrequency electromagnetic fields (RF-EMF); sleep disturbance is the most frequently cited. However, laboratory experiments have yielded conflicting results regarding sleep alterations. Our hypothesis was that exposure to RF-EMF alone would lead to slight or non-significant effects but that co-exposure to RF-EMFs and other environmental constraints (such as noise) would lead to significant effects.

METHODS

3-week-old male Wistar rats (4 groups, n = 12 per group) were exposed for 5 weeks to continuous RF-EMF (900 MHz, 1.8 V/m, SAR = 30 mW/kg) in the presence or absence of high-level noise (87.5 dB, 50-20000 Hz) during the rest period. After 5 weeks of exposure, sleep (24 h recording), food and water intakes, and body weight were recorded with or without RF-EMF and/or noise. At the end of this recording period, sleep was scored during the 1 h resttime in the absence of noise and of RF-EMF exposure.

RESULTS

Exposure to RF-EMF and/or noise was associated with body weight gain, with hyperphagia in the noise-only and RF-EMF + noise groups and hypophagia in the RF-EMF-only group. Sleep parameters recording over 24 h highlighted a higher frequency of active wakefulness in the RF-EMF-only group and a lower non-rapid eye movement/rapid eye movement sleep ratio during the active period in the noise-only group. There were no differences in sleep duration in either group. During the 1-h, constraint-free sleep recording, sleep rebound was observed in the noise-only group but not in the RF-EMF-only and RF-EMF + noise groups.

CONCLUSION

Our study showed effects of RF-EMF, regardless of whether or not the animals were also exposed to noise. However, the RF-EMF + noise group presented no exacerbation of those effects. Our results did not support the hypothesis whereby the effects of RF-EMF on physiological functions studied are only visible in animals exposed to both noise and RF-EMF.

Impacts of Subchronic, High-Level Noise Exposure on Sleep and Metabolic Parameters: A Juvenile Rodent Model

BACKGROUND

Noise is an environmental factor that has been associated with metabolic and sleep disorders. Sleep is a vital function, since it underpins physiologic processes and cognitive recovery and development. However, the effects of chronic noise exposure on the developing organism are still subject to debate.

OBJECTIVE

The objective of the present study was to assess the effects of subchronic, high-level noise exposure on sleep, apnea, and homeostasis in juvenile rats.

METHODS

Twenty-four 3-wk-old male Wistar rats were exposed to noise [[Formula: see text], [Formula: see text]] for 5 wk and 2 d during the 12-h rest period. Data on sleep stages, food and water intake, apnea, and body and organ weight were recorded.

RESULTS

Five weeks of high-level noise exposure were associated with hyperphagia ([Formula: see text]), body weight gain ([Formula: see text]), a heavier thymus ([Formula: see text]), and heavier adrenal glands ([Formula: see text]). A sleep analysis highlighted microstructural differences in the active period: in particular, the mean daily amount of rapid eye movement (REM) sleep as a proportion of total sleep time (TST) was higher. The mean daily amount of non-REM (NREM) sleep was lower in the exposed group, meaning that the intergroup difference in the TST was not significant. During a 1-h, noise-free plethysmographic recording during the rest period, the mean total amount of active wakefulness (AW) was lower in the exposed group (by 9.1 min), whereas the mean duration of an episode of REM sleep was higher (by 1.8 min), and the TST was higher (by 10.7 min).

DISCUSSION

Subchronic exposure of juvenile rats to high-intensity noise during the rest period was associated with some small but significant sleep disturbances, greater food and water intakes, greater body weight gain, and greater thymus and adrenal gland weights. The main effects of noise exposure on sleep were also observed in the 1-h plethysmography session after 5 wk of exposure. https://doi.org/10.1289/EHP4045.

Noise-induced sleep disruption increases weight gain and decreases energy metabolism in female rats

Background/objectives:

Inadequate sleep increases obesity and environmental noise contributes to poor sleep. However, women may be more vulnerable to noise and hence more susceptible to sleep disruption-induced weight gain than men. In male rats, exposure to environmental (i.e. ambient) noise disrupts sleep and increases feeding and weight gain. However, the effects of environmental noise on sleep and weight gain in female rats are unknown. Thus, this study was designed to determine whether noise exposure would disturb sleep, increase feeding and weight gain and alter the length of the estrous cycle in female rats.

Subjects/methods:

Female rats (12-weeks old) were exposed to noise for 17d (8h/d during the light period) to determine the effects of noise on weight gain and food intake. In a separate set of females, estrous cycle phase and length, EEG, EMG, spontaneous physical activity and energy expenditure were recorded continuously for 27d during baseline (control, 9d), noise exposure (8h/d, 9d) and recovery (9d) from sleep disruption.

Results:

Noise exposure significantly increased weight gain and food intake compared to females that slept undisturbed. Noise also significantly increased wakefulness, reduced sleep and resulted in rebound sleep during the recovery period. Total energy expenditure was significantly lower during both noise exposure and recovery due to lower energy expenditure during spontaneous physical activity and sleep. Notably, noise did not alter the estrous cycle length.

Conclusions:

As previously observed in male rats, noise exposure disrupted sleep and increased weight gain in females but did not alter the length of the estrous cycle. This is the first demonstration of weight gain in female rats during sleep disruption. We conclude that the sleep disruption caused by exposure to environmental noise is a significant tool for determining how sleep loss contributes to obesity in females.

Long-term exposure to transportation noise and its association with adiposity markers and development of obesity

The contribution of different transportation noise sources to metabolic disorders such as obesity remains understudied. We evaluated the associations of long-term exposure to road, railway and aircraft noise with measures of obesity and its subphenotypes using cross-sectional and longitudinal designs. We assessed 3796 participants from the population-based Swiss Cohort Study on Air Pollution and Lung and Heart Diseases (SAPALDIA), who attended the visits in 2001 (SAP2) and 2010/2011 (SAP3) and who were aged 29-72 at SAP2. At SAP2 we measured body mass index (BMI, kg/m²). At SAP3 we measured BMI, waist circumference (centimetres) and Kyle body Fat Index (%) and derived overweight, central and general obesity. Longitudinally for BMI, we derived change in BMI, incidence of overweight and obesity and a 3-category outcome combining the latter two. We assigned source-specific 5-year mean noise levels before visits and during follow-up at the most exposed dwelling façade (Lden, dB), using Swiss noise models for 2001 and 2011 and participants' residential history. Models were adjusted for relevant confounders, including traffic-related air pollution. Exposure to road traffic noise was significantly associated with all adiposity subphenotypes, cross-sectionally (at SAP3) [e.g. beta (95% CI) per 10 dB, BMI: 0.39 (0.18; 0.59); waist circumference: 0.93 (0.37; 1.50)], and with increased risk of obesity, longitudinally (e.g. RR = 1.25, 95% CI: 1.04; 1.51, per 10 dB in 5-year mean). Railway noise was significantly related to increased risk of overweight. In cross-sectional analyses, we further identified a stronger association between road traffic noise and BMI among participants with cardiovascular disease and an association between railway noise and BMI among participants reporting bad sleep. Associations were independent of the other noise sources, air pollution and robust to all adjustment sets. No associations were observed for aircraft noise. Long-term exposure to transportation noise, particularly road traffic noise, may increase the risk of obesity and could constitute a pathway towards cardiometabolic and other diseases.

Chronic Noise Exposure and Adiposity: A Systematic Review and Meta-analysis

CONTEXT

Noise is a key environmental stressor affecting millions of people worldwide on a daily basis. Chronic exposure to noise may elevate the risk of adiposity through sleep deprivation and heightened stress level.

EVIDENCE ACQUISITION

A literature search was conducted in the PubMed, Web of Science, and Cochrane Library for articles published until February 20, 2018, that assessed the relationship between noise and adiposity. A standardized data extraction form was used to collect methodologic and outcome variables from each included study.

EVIDENCE SYNTHESIS

Eleven studies were identified, among which seven reported a positive association between chronic exposure to noise and adiposity. Compared with their counterparts exposed to a lower noise level, adults chronically exposed to a noise level above 55-60 dBA were associated with a higher waist circumference by 7.5 mm per year (95% CI=3.6, 11.4, I2=0.0%). An increase in chronic exposure to noise by 10 dBA was found to be associated with a higher waist circumference by 7.0 mm per year (95% CI=2.5, 11.6, I2=93.9%) in the random effect model but not the inverse variance heterogeneity model. Chronic noise exposure was not found to be associated with BMI.

CONCLUSIONS

Noise tends to be positively associated with waist circumference but not BMI in adults, but current evidence remains limited. Future studies should assess the impact of noise on adiposity in alternative settings and across population subgroups and geographic areas, examine different sources of noise, and elucidate the biomedical and psychosocial pathways linking noise to adiposity.

Jiao-tai-wan Up-regulates Hypothalamic and Peripheral Circadian Clock Gene Cryptochrome and Activates PI3K/AKT Signaling in Partially Sleep-deprived Rats

This study aims to explore the effect and mechanism of Jiao-tai-wan (JTW) on systemic and tissue-specific inflammation and insulin resistance in obesity-resistant (OR) rats with chronic partial sleep deprivation (PSD). OR rats with PSD were orally given JTW and Estazolam for 4 weeks. The amount of food intake and metabolic parameters such as body weight increase rate, fasting plasma glucose (FPG), fasting insulin (FINS), homeostasis model assessment-insulin resistance (HOMA-IR) and plasma inflammatory markers were measured. The expression levels of circadian proteins cryptochrome 1 (Cryl) and cryptochrome 2 (Cry2) in hypothalamus, adipose and liver tissues were also determined. Meanwhile, the mRNA expression of inflammatory markers, activity of nuclear factor kappa B (NF-κB) p65 protein, as well as the expression levels of insulin signaling pathway proteins in hypothalamus, adipose and liver tissues were measured. Additionally, cyclic adenosine 3', 5'-monophosphate (cAMP) and activity of vasodilator-stimulated phosphoprotein (VASP) in hypothalamus tissue were measured. JTW significantly decreased the body weight increase rate and food intake, ameliorated systemic inflammation and insulin resistance. JTW effectively ameliorated inflammation and increased PI3K/AKT signaling activation in hypothalamus, adipose and liver. Interestingly, all these changes were associated with the up-regulation of circadian gene Cryl and Cry2 protein expression. We also found that in hypothalamus tissue of PSD rats, down-regulation of Cryl and Cry2 activated cAMP/PKA signaling and then led to inflammation, while JTW inhibited this signaling. These results suggested that JTW has the beneficial effect on ameliorating inflammation and insulin resistance in partially sleep-deprived rats by up-regulating Cry expression.

Caffeine and Modafinil Ameliorate the Neuroinflammation and Anxious Behavior in Rats during Sleep Deprivation by Inhibiting the Microglia Activation

Background: Sleep deprivation (SD) plagues modern society due to the professional demands. It prevails in patients with mood and neuroinflammatory disorders. Although growing evidence suggests the improvement in the cognitive performance by psychostimulants during sleep-deprived conditions, the impending involved mechanism is rarely studied. Thus, we hypothesized that mood and inflammatory changes might be due to the glial cells activation induced modulation of the inflammatory cytokines during SD, which could be improved by administering psychostimulants. The present study evaluated the role of caffeine/modafinil on SD-induced behavioral and inflammatory consequences.

Methods: Adult male Sprague-Dawley rats were sleep deprived for 48 h using automated SD apparatus. Caffeine (60 mg/kg/day) or modafinil (100 mg/kg/day) were administered orally to rats once every day during SD. Rats were subjected to anxious and depressive behavioral evaluation after SD. Subsequently, blood and brain were collected for biochemical, immunohistochemical and molecular studies.

Results: Sleep deprived rats presented an increased number of entries and time spent in closed arms in elevated plus maze test and decreased total distance traveled in the open field (OF) test. Caffeine/modafinil treatment significantly improved these anxious consequences. However, we did not observe substantial changes in immobility and anhedonia in sleep-deprived rats. Caffeine/modafinil significantly down-regulated the pro- and up-regulated the anti-inflammatory cytokine mRNA and protein expression in the hippocampus during SD. Similar outcomes were observed in blood plasma cytokine levels. Caffeine/modafinil treatment significantly decreased the microglial immunoreactivity in DG, CA1 and CA3 regions of the hippocampus during SD, however, no significant increase in immunoreactivity of astrocytes was observed. Sholl analysis signified the improvement in the morphological alterations of astrocytes and microglia after caffeine/modafinil administration during SD. Stereological analysis demonstrated a significant improvement in the number of ionized calcium binding adapter molecule I (Iba-1) positive cells (different states) in different regions of the hippocampus after caffeine or modafinil treatment during SD without showing any significant change in total microglial cell number. Eventually, the correlation analysis displayed a positive relationship between anxiety, pro-inflammatory cytokines and activated microglial cell count during SD.

Conclusion: The present study suggests the role of caffeine or modafinil in the amelioration of SD-induced inflammatory response and anxious behavior in rats.

Highlights

- SD induced mood alterations in rats.

- Glial cells activated in association with the changes in the inflammatory cytokines.

- Caffeine or modafinil improved the mood and restored inflammatory changes during SD.

- SD-induced anxious behavior correlated with the inflammatory consequences.

Shift-work: is time of eating determining metabolic health? Evidence from animal models

The circadian disruption in shift-workers is suggested to be a risk factor to develop overweight and metabolic dysfunction. The conflicting time signals given by shifted activity, shifted food intake and exposure to light at night occurring in the shift-worker are proposed to be the cause for the loss of internal synchrony and the consequent adverse effects on body weight and metabolism. Because food elicited signals have proven to be potent entraining signals for peripheral oscillations, here we review the findings from experimental models of shift-work and verify whether they provide evidence about the causal association between shifted feeding schedules, circadian disruption and altered metabolism. We found mainly four experimental models that mimic the conditions of shift-work: protocols of forced sleep deprivation, of forced activity during the normal rest phase, exposure to light at night and shifted food timing. A big variability in the intensity and duration of the protocols was observed, which led to a diversity of effects. A common result was the disruption of temporal patterns of activity; however, not all studies explored the temporal patterns of food intake. According to studies that evaluate time of food intake as an experimental model of shift-work and studies that evaluate shifted food consumption, time of food intake may be a determining factor for the loss of balance at the circadian and metabolic level.

Prenatal Exposure to Traffic Pollution and Childhood Body Mass Index Trajectory

Background: Limited evidence suggests an association between prenatal exposure to traffic pollution and greater adiposity in childhood, but the time window during which growth may be most affected is not known. Methods: We studied 1,649 children in Project Viva, a Boston-area pre-birth cohort. We used spatiotemporal models to estimate prenatal residential air pollution exposures and geographic information systems to estimate neighborhood traffic density and roadway proximity. We used weight and stature measurements at clinical and research visits to estimate a BMI trajectory for each child with mixed-effects natural cubic spline models. In primary analyses, we examined associations of residential PM_2.5 and black carbon (BC) exposures during the third trimester and neighborhood traffic density and home roadway proximity at birth address with (1) estimated BMI at 6 month intervals through 10 years of age, (2) magnitude and timing of BMI peak and rebound, and (3) overall BMI trajectory. In secondary analyses, we examined associations of residential PM_2.5 and BC exposures during the first and second trimesters with BMI outcomes. Results: Median (interquartile range; IQR) concentration of residential air pollution during the third trimester was 11.4 (1.7) μg/m³ for PM_2.5 and 0.7 (0.3) μg/m³ for BC. Participants had a median (IQR) of 13 (7) clinical or research BMI measures from 0 to 10 years of age. None of the traffic pollution exposures were significantly associated with any of the BMI outcomes in covariate-adjusted models, although effect estimates were in the hypothesized direction for neighborhood traffic density and home roadway proximity. For example, greater neighborhood traffic density [median (IQR) 857 (1,452) vehicles/day x km of road within 100 m of residential address at delivery] was associated with a higher BMI throughout childhood, with the strongest associations in early childhood [e.g., per IQR increment natural log-transformed neighborhood traffic density, BMI at 12 months of age was 0.05 (-0.03, 0.13) kg/m² higher and infancy peak BMI was 0.05 (-0.03, 0.14) kg/m² higher]. Conclusions: We found no evidence for a persistent effect of prenatal exposure to traffic pollution on BMI trajectory from birth through mid-childhood in a population exposed to modest levels of air pollution.

Role of Sex and the Environment in Moderating Weight Gain Due to Inadequate Sleep

PURPOSE OF REVIEW

The growing prevalence of obesity, inadequate sleep and sleep disorders together with the negative impact of lack of sleep on overall health highlights the need for therapies targeted towards weight gain due to sleep loss.

RECENT FINDINGS

Sex disparities in obesity and sleep disorders are present; yet, the role of sex is inadequately addressed and thus it is unclear whether sensitivity to sleep disruption differs between men and women. Like sex, environmental factors contribute to the development of obesity and poor sleep. The obesogenic environment is characterized by easy access to palatable foods and a low demand for energy expenditure in daily activities. These and other environmental factors are discussed, as they drive altered sleep or their interaction with food choice and intake can promote obesity. We discuss data that suggest differences in sleep patterns and responses to sleep disruption influence sex disparities in weight gain, and that enviromental disturbances alter sleep and interact with features of the obesogenic environment that together promote obesity.

Partial Sleep Deprivation Reduces the Efficacy of Orexin-A to Stimulate Physical Activity and Energy Expenditure

OBJECTIVE

Sufficient sleep is required for weight maintenance. Sleep deprivation due to noise exposure stimulates weight gain by increasing hyperphagia and reducing energy expenditure (EE). Yet the mechanistic basis underlying the weight gain response is unclear. Orexin-A promotes arousal and negative energy balance, and orexin terminals project to the ventrolateral preoptic area (VLPO), which is involved in sleep-to-wake transitions. To determine whether sleep deprivation reduces orexin function in VLPO and to test the hypothesis that sleep deprivation would attenuate the orexin-A-stimulated increase in arousal, physical activity (PA), and EE.

METHODS

Electroencephalogram, electromyogram, distance traveled, and EE were determined in male Sprague-Dawley rats following orexin-A injections into VLPO both before and after acute (12-h) and chronic (8 h/d, 9 d) sleep deprivation by noise exposure.

RESULTS

Orexin-A in the VLPO significantly increased arousal, PA, total EE, and PA-related EE and reduced sleep and respiratory quotient before sleep deprivation. In contrast to after acute sleep deprivation in which orexin-A failed to stimulate EE during PA only, orexin-A failed to significantly increase arousal, PA, fat oxidation, total EE, and PA-related EE after chronic sleep deprivation.

CONCLUSIONS

Sleep deprivation may reduce sensitivity to endogenous stimuli that enhance EE due to PA and thus stimulate weight gain.

The effects of Jiao-Tai-Wan on sleep, inflammation and insulin resistance in obesity-resistant rats with chronic partial sleep deprivation

Background

Jiao-Tai-Wan (JTW), composed of Rhizome Coptidis and Cortex Cinnamomi, is a classical traditional Chinese prescription for treating insomnia. Several in vivo studies have concluded that JTW could exert its therapeutical effect in insomnia rats. However, the specific mechanism is still unclear. The present study aimed to explore the effect of JTW on sleep in obesity-resistant (OR) rats with chronic partial sleep deprivation (PSD) and to clarify its possible mechanism.

Methods

JTW was prepared and the main components contained in the granules were identified by 3D-High Performance Liquid Chromatography (3D-HPLC) assay. The Male Sprague-Dawley (SD) rats underwent 4 h PSD by environmental noise and the treatment with low and high doses of JTW orally for 4 weeks, respectively. Then sleep structure was analyzed by electroencephalographic (EEG). Inflammation markers including high-sensitivity C reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels were examined in the rat plasma. Meanwhile, metabolic parameters as body weight increase rate, fasting plasma glucose (FPG), fasting insulin (FINS) levels and insulin resistance index (HOMA-IR) were measured. The expressions of clock gene cryptochromes (Cry1 and Cry2) and inflammation gene nuclear factor-κB (NF-κB) in peripheral blood monocyte cells (PBMC) were also determined.

Results

The result showed that the administration of JTW significantly increased total sleep time and total slow wave sleep (SWS) time in OR rats with PSD. Furthermore, the treatment with JTW reversed the increase in the markers of systemic inflammation and insulin resistance caused by sleep loss. These changes were also associated with the up-regulation of Cry1 mRNA and Cry 2 mRNA and the down-regulation of NF-κB mRNA expression in PBMC.

Conclusions

This study suggests that JTW has the beneficial effects of improving sleep, inflammation and insulin sensitivity. The mechanism appears to be related to the modulation of circadian clock and inflammation genes expressions in PBMC.

Prenatal and early life exposure to traffic pollution and cardiometabolic health in childhood

BACKGROUND

Prenatal exposure to traffic pollution has been associated with faster infant weight gain, but implications for cardiometabolic health in later childhood are unknown.

METHODS

Among 1418 children in Project Viva, a Boston-area pre-birth cohort, we assessed anthropometric and biochemical parameters of cardiometabolic health in early (median age 3.3 years) and mid- (median age 7.7 years) childhood. We used spatiotemporal models to estimate prenatal and early life residential PM_2.5 and black carbon exposure as well as traffic density and roadway proximity. We performed linear regression analyses adjusted for sociodemographics.

RESULTS

Children whose mothers lived close to a major roadway at the time of delivery had higher markers of adverse cardiometabolic risk in early and mid-childhood. For example, total fat mass was 2.1 kg (95%CI: 0.8, 3.5) higher in mid-childhood for children of mothers who lived <50 m vs. ≥200 m from a major roadway. Black carbon exposure and traffic density were generally not associated with cardiometabolic parameters, and PM_2.5 exposure during the year prior was paradoxically associated with improved cardiometabolic profile.

CONCLUSIONS

Infants whose mothers lived close to a major roadway at the time of delivery may be at later risk for adverse cardiometabolic health.

Acute partial sleep deprivation due to environmental noise increases weight gain by reducing energy expenditure in rodents

OBJECTIVE

Chronic partial sleep deprivation (SD) by environmental noise exposure increases weight gain and feeding in rodents, which contrasts weight loss after acute SD by physical methods. This study tested whether acute environmental noise exposure reduced sleep and its effect on weight gain, food intake, physical activity, and energy expenditure (EE). It was hypothesized that acute exposure would (1) increase weight gain and feeding and (2) reduce sleep, physical activity, and EE (total and individual components); and (3) behavioral changes would persist throughout recovery from SD.

METHODS

Three-month old male Sprague-Dawley rats slept ad libitum, were noise exposed (12-h light cycle), and allowed to recover (36 h). Weight gain, food intake, sleep/wake, physical activity, and EE were measured.

RESULTS

Acute environmental noise exposure had no effect on feeding, increased weight gain (P < 0.01), and reduced sleep (P < 0.02), physical activity (P < 0.03), total EE (P < 0.05), and several components (P < 0.05). Reductions in EE and physical activity persisted during recovery.

CONCLUSIONS

Reductions in EE during sleep, rest, and physical activity reduce total EE and contribute to weight gain during acute SD and recovery from SD. These data emphasize the importance of increasing physical activity after SD to prevent obesity.

Analysis of Sampling Methodologies for Noise Pollution Assessment and the Impact on the Population

Today, noise pollution is an increasing environmental stressor. Noise maps are recognised as the main tool for assessing and managing environmental noise, but their accuracy largely depends on the sampling method used. The sampling methods most commonly used by different researchers (grid, legislative road types and categorisation methods) were analysed and compared using the city of Talca (Chile) as a test case. The results show that the stratification of sound values in road categories has a significantly lower prediction error and a higher capacity for discrimination and prediction than in the legislative road types used by the Ministry of Transport and Telecommunications in Chile. Also, the use of one or another method implies significant differences in the assessment of population exposure to noise pollution. Thus, the selection of a suitable method for performing noise maps through measurements is essential to achieve an accurate assessment of the impact of noise pollution on the population.

Effects of different periods of paradoxical sleep deprivation and sleep recovery on lipid and glucose metabolism and appetite hormones in rats

Sleep has a fundamental role in the regulation of energy balance, and it is an essential and natural process whose precise impacts on health and disease have not yet been fully elucidated. The aim of this study was to assess the consequences of different periods of paradoxical sleep deprivation (PSD) and recovery from PSD on lipid profile, oral glucose tolerance test (OGTT) results, and changes in insulin, corticosterone, ghrelin, and leptin concentrations. Three-month-old male Wistar rats weighing 250–350 g were submitted to 24, 96, or 192 h of PSD or 192 h of PSD with 480 h of recovery. The PSD was induced by the multiple platforms method. Subsequently, the animals were submitted to an OGTT. One day later, the animals were killed and the levels of triglycerides, total cholesterol, lipoproteins (low-density lipoprotein, very-low-density lipoprotein, and high-density lipoprotein), insulin, ghrelin, leptin, and corticosterone in plasma were quantified. There was a progressive decrease in body weight with increasing duration of PSD. The PSD induced basal hypoglycemia over all time periods evaluated. Evaluation of areas under the curve revealed progressive hypoglycemia only after 96 and 192 h of PSD. There was an increase in corticosterone levels after 192 h of PSD. We conclude that PSD induces alterations in metabolism that are reversed after a recovery period of 20 days.

Road traffic noise and markers of obesity - a population-based study

BACKGROUND

Noise has been found to be associated with endocrine changes and cardiovascular disease. Increased cortisol levels and chronic sleep problems due to noise may increase the risk of obesity.

OBJECTIVES

We investigated the relationship between road traffic noise and obesity markers. Furthermore, we explored the modifying role of noise sensitivity, noise annoyance, and sleep disturbances.

METHODS

We used data from a population-based study, HUBRO (N=15,085), and its follow-up study HELMILO (N=8410) conducted in Oslo, Norway. Measurements were used to define body mass index (BMI), waist circumference (WC), waist-hip ratio (WHR), and these binary outcomes: BMI≥30kg/m(2), WC≥102cm (men)/88cm (women), and WHR≥0.90 (men)/0.85 (women). Modelled levels of road traffic noise (Lden) were assigned to each participant's home address. Linear and logistic regression models were used to examine the associations.

RESULTS

The results indicated no significant associations between road traffic noise and obesity markers in the total populations. However, in highly noise sensitive women (n=1106) a 10dB increase in noise level was associated with a slope (=beta) of 1.02 (95% confidence interval (CI): 1.01, 1.03) for BMI, 1.01 (CI: 1.00, 1.02) for WC, and an odds ratio (OR) of 1.24 (CI: 1.01, 1.53) for WHR ≥0.85. The associations appeared weaker in highly noise sensitive men. We found no effect modification of noise annoyance or sleep disturbances. In a sub-population with bedroom facing a road, the associations increased in men (e.g. an OR of 1.25 (CI: 0.88, 1.78) for BMI ≥30kg/m(2)), but not in women. Among long-term residents the associations increased for BMI ≥30kg/m(2) (OR of 1.07 (CI: 0.93, 1.24) in men and 1.10 (CI: 0.97, 1.26) in women), but not for the other outcomes.

CONCLUSION

In an adult urban Scandinavian population, road traffic noise was positively associated with obesity markers among highly noise sensitive women. The associations appeared stronger among men with bedroom facing a street, representing a population with more accurately assigned exposure.

The aetiology of obesity beyond eating more and exercising less

Although recent increases in availability of energy dense, processed foods and reductions in institutionally driven physical activity have created an environment that is permissible for obesity to occur, several other factors may contribute to the development of obesity in this context. We review evidence for eleven such factors: endocrine disruptors, intrauterine effects, epigenetics, maternal age, differential fecundity and assortative mating by body mass index, microorganisms, reduction in variability of ambient temperatures, smoking cessation, sleep debt, and pharmaceutical iatrogenesis. Evidence for the role of endocrine disruptors, microorganisms, ambient temperatures, sleep and reproductive factors is accumulating, but additional research is needed to confirm the causative role of these factors in human obesity. However, the role of certain pharmaceuticals and smoking cessation in development of human obesity is clear. Practice points for consideration and future research needed are highlighted for each factor.

Methodological considerations for measuring spontaneous physical activity in rodents

When exploring biological determinants of spontaneous physical activity (SPA), it is critical to consider whether methodological factors differentially affect rodents and the measured SPA. We determined whether acclimation time, sensory stimulation, vendor, or chamber size affected measures in rodents with varying propensity for SPA. We used principal component analysis to determine which SPA components (ambulatory and vertical counts, time in SPA, and distance traveled) best described the variability in SPA measurements. We compared radiotelemetry and infrared photobeams used to measure SPA and exploratory activity. Acclimation time, sensory stimulation, vendor, and chamber size independently influenced SPA, and the effect was moderated by the propensity for SPA. A 24-h acclimation period prior to SPA measurement was sufficient for habituation. Principal component analysis showed that ambulatory and vertical measurements of SPA describe different dimensions of the rodent's SPA behavior. Smaller testing chambers and a sensory attenuation cubicle around the chamber reduced SPA. SPA varies between rodents purchased from different vendors. Radiotelemetry and infrared photobeams differ in their sensitivity to detect phenotypic differences in SPA and exploratory activity. These data highlight methodological considerations in rodent SPA measurement and a need to standardize SPA methodology.