Sleep duration and fragmentation in relation to leukocyte DNA methylation in adolescents.

STUDY OBJECTIVES: Sleep deprivation and low sleep quality are widespread among adolescents, and associate with obesity risk. Plausible mediators include diet and physical activity. Another potential interrelated pathway, as yet unexplored in adolescents, could involve epigenetic modification of metabolism genes. METHODS: In a cohort of 351 Mexico City adolescents (47% male; mean [SD] age = 14 [2] years), 7-day actigraphy was used to assess average sleep duration, sleep fragmentation, and movement index. DNA isolated from blood leukocytes was bisulfite-converted, amplified, and pyrosequenced at four candidate regions. Linear mixed models evaluated sex-stratified associations between sleep characteristics (split into quartiles [Q]) and DNA methylation of each region, adjusted for potential confounders. RESULTS: Mean sleep duration was 8.5 [0.8] hours for boys and 8.7 [1] hours for girls. There were sex-specific associations between sleep duration and LINE-1 (long interspersed nuclear element) methylation. Boys with longer sleep duration (Q4) had lower LINE-1 methylation than boys in the 3rd quartile reference category, while girls with both longer and shorter sleep duration had higher LINE-1 methylation compared to Q3. Longer sleep duration was associated with higher H19 methylation among girls (comparing highest to third quartile, -0.9% [-2.2, 0.5]; p, trend = 0.047). Sleep fragmentation was inversely associated with peroxisome proliferator-activated receptor alpha (PPARA) methylation among girls (comparing highest to lowest fragmentation quartile, 0.9% [0.1 to 1.8]). Girls also showed an inverse association between sleep fragmentation and hydroxysteroid (11-beta) dehydrogenase 2 (HSD11B2; Q4 to Q1, 0.6% [-1.2%, 0%]). CONCLUSIONS: Sleep duration and fragmentation in adolescents show sex-specific associations with leukocyte DNA methylation patterns of metabolism genes.

Sleep deprivation induces pathological changes in rat masticatory muscles: Role of Toll like signaling pathway and atrophy.

The aim of this study was to evaluate the Toll like signaling pathway and atrophy after sleep deprivation (SD) in rat masticatory muscles: masseter and temporal. A total of 24 animals was distributed into three groups: Control group (CTL, n = 8), subjected to SD for 96 h (SD96, n = 8) and subjected to SD for 96 h more 96 h of sleep recovery (SD96 + R, n = 8). Histopathological analysis revealed the presence of acute inflammatory cells, congested vessels, fibrosis, and high cellularity in the skeletal muscle fibers from masseter and temporal submitted to SD. These morphological alterations were not observed in the control group since neither inflammatory cells nor congested vessels were observed to this group. In the group SD96 + R, the absence of inflammation was noticed to the masseter only. In this group, COX-2 and TNF-alpha downregulation were detected when comparing to control group. MyD88 and pIKK decreased in SD96 and SD96 + R groups being pNFKBp50 downregulatated in SD96 + R. MyD88 expression increased in rats submitted to SD96 and SD96 + R in temporal when compared to control group. On the other hand, pIKK decreased the protein expression in groups SD96 and SD96 + R while pNFKBp50 showed a decreased protein expression in group SD96 only. The activation of atrophy by means of MAFbx upregulation was detected in temporal muscle in SD96 and SD96 + R when compared to control. In summary, our results show that SD is able to induce morphological alterations in rat masticatory muscles. Toll like signaling pathway and atrophy play important roles in ethiopathogenesis induced by SD, being dependent of skeletal muscle type.

Sleep deprivation predisposes allergic mice to neutrophilic lung inflammation.

BACKGROUND: Although different studies associated sleep deprivation (SD) with systemic inflammatory changes, the effect of sleep duration on the pathology of allergic chronic diseases is poorly understood. OBJECTIVE: We sought to evaluate the influence of SD on allergen-induced pulmonary inflammation. METHODS: Ovalbumin (OVA)-sensitized C57BL/6 mice were exposed to a first set of intranasal OVA challenge under SD or healthy sleep (HS) conditions, followed by a second OVA challenge, 1 week apart. Some groups were subjected to corticosteroid treatment with dexamethasone. RESULTS: OVA-sensitized mice with SD had more severe airway inflammation than the allergic group with HS. Analysis of lung parenchyma revealed that the inflammation in allergic mice with SD was marked by an influx of neutrophils (mainly) and eosinophils and secretion of IL-6, TNF-α, and IL-17 in contrast to the eosinophilic inflammation and IL-4 production observed in allergic mice with HS. The same cytokine profile was observed in ex vivo culture of cervical lymph node cells and splenocytes, indicating that in allergic mice SD favors immune responses toward a proinflammatory TH17 profile. This idea is supported by the fact that disruption of IL-17 signaling (IL-17 receptor A-/-) prevented airway neutrophilia in allergic mice with SD. Furthermore, allergic mice with SD became refractory to corticosteroid treatment in contrast to the allergic group with HS. CONCLUSION: Collectively, our data show that sleep quality participates in the progression of allergen-induced eosinophilic lung inflammation to corticosteroid-refractory neutrophilic manifestation.

Genetic Dissociation of Daily Sleep and Sleep Following Thermogenetic Sleep Deprivation in Drosophila.

STUDY OBJECTIVES: Sleep rebound-the increase in sleep that follows sleep deprivation-is a hallmark of homeostatic sleep regulation that is conserved across the animal kingdom. However, both the mechanisms that underlie sleep rebound and its relationship to habitual daily sleep remain unclear. To address this, we developed an efficient thermogenetic method of inducing sleep deprivation in Drosophila that produces a substantial rebound, and applied the newly developed method to assess sleep rebound in a screen of 1,741 mutated lines. We used data generated by this screen to identify lines with reduced sleep rebound following thermogenetic sleep deprivation, and to probe the relationship between habitual sleep amount and sleep following thermogenetic sleep deprivation in Drosophila. METHODS: To develop a thermogenetic method of sleep deprivation suitable for screening, we thermogenetically stimulated different populations of wake-promoting neurons labeled by Gal4 drivers. Sleep rebound following thermogenetically-induced wakefulness varies across the different sets of wake-promoting neurons that were stimulated, from very little to quite substantial. Thermogenetic activation of neurons marked by the c584-Gal4 driver produces both strong sleep loss and a substantial rebound that is more consistent within genotypes than rebound following mechanical or caffeine-induced sleep deprivation. We therefore used this driver to induce sleep deprivation in a screen of 1,741 mutagenized lines generated by the Drosophila Gene Disruption Project. Flies were subjected to 9 h of sleep deprivation during the dark period and released from sleep deprivation 3 h before lights-on. Recovery was measured over the 15 h following sleep deprivation. Following identification of lines with reduced sleep rebound, we characterized baseline sleep and sleep depth before and after sleep deprivation for these hits. RESULTS: We identified two lines that consistently exhibit a blunted increase in the duration and depth of sleep after thermogenetic sleep deprivation. Neither of the two genotypes has reduced total baseline sleep. Statistical analysis across all screened lines shows that genotype is a strong predictor of recovery sleep, independent from effects of genotype on baseline sleep. CONCLUSIONS: Our data show that rebound sleep following thermogenetic sleep deprivation can be genetically separated from sleep at baseline. This suggests that genetically controlled mechanisms of sleep regulation not manifest under undisturbed conditions contribute to sleep rebound following thermogenetic sleep deprivation.

Leucine supplementation is anti-atrophic during paradoxical sleep deprivation in rats.

The purpose of this study was to identify sleep deprivation-induced atrophy and the muscle-specific fiber types affected and to determine the effects of leucine supplementation on atrophy and pertinent portions of the pathways of muscle protein synthesis and degradation in rats. A total of 46 Wistar rats were distributed in four groups: control (CTL), leucine supplementation (LEU), sleep deprivation (SD), and leucine supplementation + sleep deprivation (LEU + SD). Leucine supplementation was by gavage (1.35 g/kg/daily), and the animals were subjected to SD for 96 h. Testosterone and corticosterone concentrations, along with proteins involved in protein synthesis and degradation and proteasome activity levels, were measured in the gastrocnemius (GA) muscle. Myosin ATPase staining was used to evaluate the different muscle fibers. After sleep deprivation, GA muscle and body masses decreased in the SD group compared to the CTL, LEU, and LEU + SD groups. There was no difference between groups in type I fiber cross-sectional area (CSA). The CSAs for type IIa fibers were lower in the SD and LEU + SD groups vs. the CTL and LEU groups, while the IIb fiber CSA was lower in the SD group vs. the CSAs in all other groups. The phospho (p)-Akt levels were lower in the SD and LEU + SD groups vs. the CTL and LEU groups. The p-mTORC1 levels were higher in the LEU, SD, and LEU + SD groups vs. the CTL group. The p-p70S6k levels were higher in the LEU and LEU + SD groups; the 4E-BP1 levels were higher in the SD and LEU + SD groups compared to those in the CTL and LEU groups, and the p-4E-BP1 levels were higher in the LEU and SD groups compared to those in the CTL group and even higher in the LEU + SD group compared to those in the LEU and SD groups. Ubiquitinated proteins, LC3, and p62/SQSTM, and proteasome activity levels were higher in the SD and LEU + SD groups vs. the LEU and CTL groups. Sleep deprivation led to the atrophy of IIa and IIb muscle fibers; however, leucine supplementation prevented muscle loss and type IIb fiber atrophy.

Differences in planning performance, a neurocognitive endophenotype, are associated with a functional variant in PER3 gene.

Performance alterations in executive function have been studied as potential endophenotypes for several neuropsychiatric diseases. Planning is an important component of executive function and has been shown to be affected in diseases such as attention deficit hyperactivity disorder, schizophrenia, obsessive-compulsive disorder and Parkinson's disease. Several genes related to dopaminergic systems, such as COMT, have been explored as candidates for influencing planning performance. The circadian clock gene PERIOD3 (PER3) has been shown to be associated with several complex behaviors in humans and could be involved in different signaling mechanisms. In this study, we evaluated the possible association between a functional polymorphism in the PER3 gene (PER3-VNTR, rs57875989) and performance in a commonly used test of planning (Tower of London, TOL) in 229 healthy subjects from Bogotá, Colombia. PER3-VNTR genotyping was carried out with conventional PCR and all participants completed the TOL test using the computerized Psychology Experiment Building Language (PEBL) battery. A linear regression model was used for the analysis of association with the SNPStats program. We found that 4/4 genotype carriers showed a better performance and made fewer moves, in comparison to 4/5 and 5/5 genotype carriers (p = 0.003). These results appear to be independent from effects of this polymorphism on self-reported average hours of sleep during work days in our sample. This is the first evidence of an association between PER3-VNTR and planning performance in a sample of healthy subjects and our results are consistent from previous findings for alterations in other cognitive domains. Future studies examining additional genes could lead to the identification of novel molecular underpinnings of planning in healthy subjects and in patients with neuropsychiatric disorders.

Impairment of male reproductive function after sleep deprivation.

OBJECTIVE: To evaluate the influence of sleep loss on sexual behavior, hormone levels, sperm parameters, and testis-specific gene expression in male rats. DESIGN: Experimental research. SETTING: Animal laboratory. ANIMAL(S): Male adult Wistar-Hannover rats. INTERVENTION(S): Sexually experienced rats were subjected to paradoxic sleep deprivation (PSD) for 96 hours or sleep restriction (SR) for 21 days or kept in their home cage as control (CTRL). MAIN OUTCOME MEASURE(S): Sexual behavior, hormone levels, sperm parameters and expression of stress and nitric oxide-related genes were evaluated. RESULT(S): PSD significantly decreased sexual behavior compared with the CTRL group, whereas SR had no effect. The PSD group had significantly lower testosterone levels than the CTRL group. Both PSD and SR groups had lower sperm viabilities than the CTRL group. The decrease in the number of live sperm compared with the CTRL group was larger in the PSD group than in the SR group. Regarding testicular gene expression, both PSD and SR led to an increase of iNOS and hydroxysteroid 11ß-dehydrogenase 1 expressions compared with the CTRL group. These changes were more pronounced in the PSD group. A significant increase in endothelial nitric oxide synthase expression was observed in the PSD groups compared with the CTRL group. No changes were observed in dimethylarginine dimethylaminohydrolase 1 and casein kinase 2ß-polypeptide expressions. CONCLUSION(S): Sleep loss can promote marked changes in the male reproductive system of rats, particularly affecting spermatic function in part by interfering in the testicular nitric oxide pathway.

Distinct genetic architecture underlies the emergence of sleep loss and prey-seeking behavior in the Mexican cavefish.

BACKGROUND: Sleep is characterized by extended periods of quiescence and reduced responsiveness to sensory stimuli. Animals ranging from insects to mammals adapt to environments with limited food by suppressing sleep and enhancing their response to food cues, yet little is known about the genetic and evolutionary relationship between these processes. The blind Mexican cavefish, Astyanax mexicanus is a powerful model for elucidating the genetic mechanisms underlying behavioral evolution. A. mexicanus comprises an extant ancestral-type surface dwelling morph and at least five independently evolved cave populations. Evolutionary convergence on sleep loss and vibration attraction behavior, which is involved in prey seeking, have been documented in cavefish raising the possibility that enhanced sensory responsiveness underlies changes in sleep. RESULTS: We established a system to study sleep and vibration attraction behavior in adult A. mexicanus and used high coverage quantitative trait loci (QTL) mapping to investigate the functional and evolutionary relationship between these traits. Analysis of surface-cave F2 hybrid fish and an outbred cave population indicates that independent genetic factors underlie changes in sleep/locomotor activity and vibration attraction behavior. High-coverage QTL mapping with genotyping-by-sequencing technology identify two novel QTL intervals that associate with locomotor activity and include the narcolepsy-associated tp53 regulating kinase. These QTLs represent the first genomic localization of locomotor activity in cavefish and are distinct from two QTLs previously identified as associating with vibration attraction behavior. CONCLUSIONS: Taken together, these results localize genomic regions underlying sleep/locomotor and sensory changes in cavefish populations and provide evidence that sleep loss evolved independently from enhanced sensory responsiveness.

Sleep deprivation and gene expression.

Sleep occurs in a wide range of animal species as a vital process for the maintenance of homeostasis, metabolic restoration, physiological regulation, and adaptive cognitive functions in the central nervous system. Long-term perturbations induced by the lack of sleep are mostly mediated by changes at the level of transcription and translation. This chapter reviews studies in humans, rodents, and flies to address the various ways by which sleep deprivation affects gene expression in the nervous system, with a focus on genes related to neuronal plasticity, brain function, and cognition. However, the effects of sleep deprivation on gene expression and the functional consequences of sleep loss are clearly not restricted to the cognitive domain but may include increased inflammation, expression of stress-related genes, general impairment of protein translation, metabolic imbalance, and thermal deregulation.

The influence of sleep deprivation and obesity on DNA damage in female Zucker rats.

OBJECTIVE: The aim of this study was to evaluate overall genetic damage induced by total sleep deprivation in obese, female Zucker rats of differing ages. METHOD: Lean and obese Zucker rats at 3, 6, and 15 months old were randomly distributed into two groups for each age group: home-cage control and sleep-deprived (N = 5/group). The sleep-deprived groups were deprived sleep by gentle handling for 6 hours, whereas the home-cage control group was allowed to remain undisturbed in their home-cage. At the end of the sleep deprivation period, or after an equivalent amount of time for the home-cage control groups, the rats were brought to an adjacent room and decapitated. The blood, brain, and liver tissue were collected and stored individually to evaluate DNA damage. RESULTS: Significant genetic damage was observed only in 15-month-old rats. Genetic damage was present in the liver cells from sleep-deprived obese rats compared with lean rats in the same condition. Sleep deprivation was associated with genetic damage in brain cells regardless of obesity status. DNA damage was observed in the peripheral blood cells regardless of sleep condition or obesity status. CONCLUSION: Taken together, these results suggest that obesity was associated with genetic damage in liver cells, whereas sleep deprivation was associated with DNA damage in brain cells. These results also indicate that there is no synergistic effect of these noxious conditions on the overall level of genetic damage. In addition, the level of DNA damage was significantly higher in 15-month-old rats compared to younger rats.

Oxidative stress, cancer, and sleep deprivation: is there a logical link in this association?

INTRODUCTION: Sleep disorders are associated with various human pathologies and interfere with biological processes essential for health and quality of life. On the other hand, cancer is one of the most common diseases worldwide with an average of 1,500 deaths per day in the USA. Is there a factor common to both sleep disorders and cancer that serves to link these conditions? DISCUSSION: It is a normal process for cellular metabolism to produce reactive oxidant series (ROS). However, when the production of ROS overcomes the antioxidant capacity of the cell to eliminate these products, the resulting state is called oxidative stress. Oxidative DNA damage may participate in ROS-induced carcinogenesis. Moreover, ROS are also produced in the sleep deprivation process. The aim of this article is to review pathways and mechanisms that may point to oxidative stress as a link between sleep deprivation and cancer.

The influence of sleep deprivation and obesity on DNA damage in female Zucker rats

OBJECTIVE: The aim of this study was to evaluate overall genetic damage induced by total sleep deprivation in obese, female Zucker rats of differing ages. METHOD: Lean and obese Zucker rats at 3, 6, and 15 months old were randomly distributed into two groups for each age group: home-cage control and sleep-deprived (N = 5/group). The sleep-deprived groups were deprived sleep by gentle handling for 6 hours, whereas the home-cage control group was allowed to remain undisturbed in their home-cage. At the end of the sleep deprivation period, or after an equivalent amount of time for the home-cage control groups, the rats were brought to an adjacent room and decapitated. The blood, brain, and liver tissue were collected and stored individually to evaluate DNA damage. RESULTS: Significant genetic damage was observed only in 15-month-old rats. Genetic damage was present in the liver cells from sleep-deprived obese rats compared with lean rats in the same condition. Sleep deprivation was associated with genetic damage in brain cells regardless of obesity status. DNA damage was observed in the peripheral blood cells regardless of sleep condition or obesity status. CONCLUSION: Taken together, these results suggest that obesity was associated with genetic damage in liver cells, whereas sleep deprivation was associated with DNA damage in brain cells. These results also indicate that there is no synergistic effect of these noxious conditions on the overall level of genetic damage. In addition, the level of DNA damage was significantly higher in 15-month-old rats compared to younger rats.

Whole blood genome-wide gene expression profile in males after prolonged wakefulness and sleep recovery.

Although the specific functions of sleep have not been completely elucidated, the literature has suggested that sleep is essential for proper homeostasis. Sleep loss is associated with changes in behavioral, neurochemical, cellular, and metabolic function as well as impaired immune response. Using high-resolution microarrays we evaluated the gene expression profiles of healthy male volunteers who underwent 60 h of prolonged wakefulness (PW) followed by 12 h of sleep recovery (SR). Peripheral whole blood was collected at 8 am in the morning before the initiation of PW (Baseline), after the second night of PW, and one night after SR. We identified over 500 genes that were differentially expressed. Notably, these genes were related to DNA damage and repair and stress response, as well as diverse immune system responses, such as natural killer pathways including killer cell lectin-like receptors family, as well as granzymes and T-cell receptors, which play important roles in host defense. These results support the idea that sleep loss can lead to alterations in molecular processes that result in perturbation of cellular immunity, induction of inflammatory responses, and homeostatic imbalance. Moreover, expression of multiple genes was downregulated following PW and upregulated after SR compared with PW, suggesting an attempt of the body to re-establish internal homeostasis. In silico validation of alterations in the expression of CETN3, DNAJC, and CEACAM genes confirmed previous findings related to the molecular effects of sleep deprivation. Thus, the present findings confirm that the effects of sleep loss are not restricted to the brain and can occur intensely in peripheral tissues.

Behavioral and genetic effects promoted by sleep deprivation in rats submitted to pilocarpine-induced status epilepticus.

The interaction between sleep deprivation and epilepsy has been well described in electrophysiological studies, but the mechanisms underlying this association remain unclear. The present study evaluated the effects of sleep deprivation on locomotor activity and genetic damage in the brains of rats treated with saline or pilocarpine-induced status epilepticus (SE). After 50 days of pilocarpine or saline treatment, both groups were assigned randomly to total sleep deprivation (TSD) for 6 h, paradoxical sleep deprivation (PSD) for 24 h, or be kept in their home cages. Locomotor activity was assessed with the open field test followed by resection of brain for quantification of genetic damage by the single cell gel electrophoresis (comet) assay. Status epilepticus induced significant hyperactivity in the open field test and caused genetic damage in the brain. Sleep deprivation procedures (TSD and PSD) did not affect locomotor activity in epileptic or healthy rats, but resulted in significant DNA damage in brain cells. Although PSD had this effect in both vehicle and epileptic groups, TSD caused DNA damage only in epileptic rats. In conclusion, our results revealed that, despite a lack of behavioral effects of sleep deprivation, TSD and PSD induced genetic damage in rats submitted to pilocarpine-induced SE.

Sleep loss and acute drug abuse can induce DNA damage in multiple organs of mice.

The purpose of the present study was to characterize the genetic damage induced by paradoxical sleep deprivation (PSD) in combination with cocaine or ecstasy (3,4-methylenedioxymethamphetamine; MDMA) in multiple organs of male mice using the single cell gel (comet) assay. C57BL/6J mice were submitted to PSD by the platform technique for 72 hours, followed by drug administration and evaluation of DNA damage in peripheral blood, liver and brain tissues. Cocaine was able to induce genetic damage in the blood, brain and liver cells of sleep-deprived mice at the majority of the doses evaluated. Ecstasy also induced increased DNA migration in peripheral blood cells for all concentrations tested. Analysis of damaged cells by the tail moment data suggests that ecstasy is a genotoxic chemical at the highest concentrations tested, inducing damage in liver or brain cells after sleep deprivation in mice. Taken together, our results suggest that cocaine and ecstasy/MDMA act as potent genotoxins in multiple organs of mice when associated with sleep loss.

TNF-α gene polymorphisms and excessive daytime sleepiness in pediatric obstructive sleep apnea.

OBJECTIVE: To assess sleepiness, TNF-α plasma levels, and genomic variance in the TNF-α gene in children with obstructive sleep apnea (OSA). STUDY DESIGN: Children being evaluated for OSA (n = 60) and matched control children (n = 80) were assessed with a modified Epworth Sleepiness Scale questionnaire and underwent a blood draw the morning after nocturnal polysomnography. TNF-α plasma concentrations were assayed using ELISA, and genomic DNA was extracted. Genotyping and allelic frequencies were determined for 4 TNF-α single nucleotide polymorphisms using real-time polymerase chain reaction genotyping assays. RESULTS: Morning TNF-α levels and Epworth Sleepiness Scale scores were increased in the presence of OSA, but substantial variability was present. Although TNF-α plasma concentrations were globally increased in OSA, most of the variance was attributable to the presence or absence of TNF-α -308G gene polymorphism. CONCLUSIONS: TNF-α levels are increased in a subset of children with OSA, particularly among those harboring the TNF-α -308G single nucleotide polymorphism. Among the latter, significant increases in excessive daytime sleepiness symptoms are also present. The relatively high variability of excessive daytime sleepiness in pediatric OSA may be related to underlying TNF-α gene polymorphisms, particularly -308G.

Sleep loss induces differential response related to genotoxicity in multiple organs of three different mice strains.

The purpose of the present study was to determine the genetic damage induced by paradoxical sleep deprivation (PSD) in three different male mice strains in peripheral blood, heart, kidney and liver tissues by the single cell gel (comet) assay. Swiss, C57BL/6j and hairless (HRS/j) mice were submitted to PSD by the multiple platform technique for 72 hr, and DNA damage was evaluated. Statistically significant differences in DNA damage were found in blood cells of the Swiss mice strain when compared to negative controls. By contrast, no statistically significant differences were found in the C57BL/6j or hairless mice strains. With regard to the liver, extensive genotoxic effects were found in the Swiss strain. The hairless and C57BL/6j mice strains did not show any signs of genotoxocity in this organ. The same lack of effect was noted in kidney and heart cells of all strains evaluated. In conclusion, our results reveal that sleep deprivation exerted genetic damage in the form of DNA breakage in blood and liver cells of the Swiss mice strain only. This type of approach should be considered when studying noxious activities on genetic apparatus induced by sleep deprivation in mice since the Swiss strain is more suitable for this purpose.

Orexin activation precedes increased NPY expression, hyperphagia, and metabolic changes in response to sleep deprivation.

Several pieces of evidence support that sleep duration plays a role in body weight control. Nevertheless, it has been assumed that, after the identification of orexins (hypocretins), the molecular basis of the interaction between sleep and energy homeostasis has been provided. However, no study has verified the relationship between neuropeptide Y (NPY) and orexin changes during hyperphagia induced by sleep deprivation. In the current study we aimed to establish the time course of changes in metabolite, endocrine, and hypothalamic neuropeptide expression of Wistar rats sleep deprived by the platform method for a distinct period (from 24 to 96 h) or sleep restricted for 21 days (SR-21d). Despite changes in the stress hormones, we found no changes in food intake and body weight in the SR-21d group. However, sleep-deprived rats had a 25-35% increase in their food intake from 72 h accompanied by slight weight loss. Such changes were associated with increased hypothalamus mRNA levels of prepro-orexin (PPO) at 24 h followed by NPY at 48 h of sleep deprivation. Conversely, sleep recovery reduced the expression of both PPO and NPY, which rapidly brought the animals to a hypophagic condition. Our data also support that sleep deprivation rapidly increases energy expenditure and therefore leads to a negative energy balance and a reduction in liver glycogen and serum triacylglycerol levels despite the hyperphagia. Interestingly, such changes were associated with increased serum levels of glucagon, corticosterone, and norepinephrine, but no effects on leptin, insulin, or ghrelin were observed. In conclusion, orexin activation accounts for the myriad changes induced by sleep deprivation, especially the hyperphagia induced under stress and a negative energy balance.

Are endogenous sex hormones related to DNA damage in paradoxically sleep-deprived female rats?

The aim of this investigation was to evaluate overall DNA damage induced by experimental paradoxical sleep deprivation (PSD) in estrous-cycling and ovariectomized female rats to examine possible hormonal involvement during DNA damage. Intact rats in different phases of the estrous cycle (proestrus, estrus, and diestrus) or ovariectomized female Wistar rats were subjected to PSD by the single platform technique for 96 h or were maintained for the equivalent period as controls in home-cages. After this period, peripheral blood and tissues (brain, liver, and heart) were collected to evaluate genetic damage using the single cell gel (comet) assay. The results showed that PSD caused extensive genotoxic effects in brain cells, as evident by increased DNA migration rates in rats exposed to PSD for 96 h when compared to negative control. This was observed for all phases of the estrous cycle indistinctly. In ovariectomized rats, PSD also led to DNA damage in brain cells. No significant statistically differences were detected in peripheral blood, the liver or heart for all groups analyzed. In conclusion, our data are consistent with the notion that genetic damage in the form of DNA breakage in brain cells induced by sleep deprivation overrides the effects related to endogenous female sex hormones.