Effect of sleep deprivation on overall 24 h growth-hormone secretion

Twenty-four-hour rhythmicities in disorders of consciousness are associated with a favourable outcome

Fluctuations of consciousness and their rhythmicities have been rarely studied in patients with a disorder of consciousness after acute brain injuries. 24-h assessment of brain (EEG), behaviour (eye-opening), and circadian (clock-controlled hormones secretion from urine) functions was performed in acute brain-injured patients. The distribution, long-term predictability, and rhythmicity (circadian/ultradian) of various EEG features were compared with the initial clinical status, the functional outcome, and the circadian rhythmicities of behaviour and clock-controlled hormones. Here we show that more physiological and favourable patterns of fluctuations are associated with a higher 24 h predictability and sharp up-and-down shape of EEG switches, reminiscent of the Flip-Flop model of sleep. Multimodal rhythmic analysis shows that patients with simultaneous circadian rhythmicity for brain, behaviour, and hormones had a favourable outcome. Finally, both re-emerging EEG fluctuations and homogeneous 24-h cycles for EEG, eye-opening, and hormones appeared as surrogates for preserved functionality in brainstem and basal forebrain, which are key prognostic factors for later improvement. While the recovery of consciousness has previously been related to a high short-term complexity, we suggest in this exploratory study the importance of the high predictability of the 24 h long-term generation of brain rhythms and highlight the importance of circadian body-brain rhythms in awakening.

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.

Administration of growth hormone ameliorates adverse effects of total sleep deprivation

Total sleep deprivation (TSD) causes several harmful changes including anxiety, inflammation, and increased expression of extracellular signal-regulated kinase (ERK) and tropomyosin receptor kinase B (TrkB) genes in the hippocampus. The current study was conducted to explain the possible effects of exogenous GH against the above parameters caused by TSD and the possible mechanisms involved. Male Wistar rats were divided into 1) control, 2) TSD and 3) TSD + GH groups. To induce TSD, the rats received a mild repetitive electric shock (2 mA, 3 s) to their paws every 10 min for 21 days. Rats in the third group received GH (1 ml/kg, sc) for 21 days as treatment for TSD. The motor coordination, locomotion, the level of IL-6, and expression of ERK and TrkB genes in hippocampal tissue were measured after TSD. The motor coordination (p < 0.001) and locomotion indices (p < 0.001) were impaired significantly by TSD. The concentrations of serum corticotropin-releasing hormone (CRH) (p < 0.001) and hippocampal interleukin-6 (IL-6) (p < 0.001) increased. However, there was a significant decrease in the interleukin-4 (IL-4) concentration and expression of ERK (p < 0.001) and TrkB (p < 0.001) genes in the hippocampus of rats with TSD. Treatment of TSD rats with GH improved motor balance (p < 0.001) and locomotion (p < 0.001), decreased serum CRH (p < 0.001), IL-6 (p < 0.01) but increased the IL-4 and expression of ERK (p < 0.001) and TrkB (p < 0.001) genes in the hippocampus. Results show that GH plays a key role in modulating the stress hormone, inflammation, and the expression of ERK and TrkB genes in the hippocampus following stress during TSD.

Therapeutic effects of growth hormone in a rat model of total sleep deprivation: Evaluating behavioral, hormonal, biochemical and electrophysiological parameters

OBJECTIVE

Total sleep deprivation (TSD) causes several harmful changes in the brain, including memory impairment, increased stress and depression levels, as well as reduced antioxidant activity. Growth hormone (GH) has been shown to boost antioxidant levels while improving memory and depression. The present study was conducted to explain the possible effects of exogenous GH against behavioral and biochemical disorders caused by TSD and the possible mechanisms involved.

MAIN 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 ml/kg, sc) was administered to rats during induction of TSD for 21 days. Memory retrieval, anxiety, depression-like behaviors, pain behaviors, antioxidant activity, hippocampal level of BDNF, and simultaneously brain electrical activity were measured at scheduled times after TSD.

KEY FINDINGS

The results showed that GH treatment improved memory (p < 0.001) in the PAT test of rats exposed to TSD. These beneficial effects were associated with lowering the level of anxiety and depression-like behavior (p < 0.001), rising the pain threshold (p < 0.01), increasing the activity of antioxidants (p < 0.01), hippocampal BDNF (p < 0.001), and regular brain electrical activity.

SIGNIFICANCE

Our findings show that GH plays a key role in modulating memory, anxiety and depression behaviors, as well as reducing oxidative stress and improve hippocampal single-unit activity in the brain during TSD.

Safety issues regarding melatonin use in child and adolescent patients with sleep problems

Several studies have reported that melatonin may be effective in treating sleep problems in children and adolescents. However, evidence regarding the safety of melatonin use in children and adolescents in their growth and developmental stages is warranted. Therefore, we aimed to summarize the literature on the safety of melatonin use in children and adolescents with insomnia and sleep disturbances. According to existing evidence, there are no serious adverse effects of long-term melatonin use in children and adolescents. The common adverse effects reported in long-term studies are fatigue, somnolence, and mood swings. In addition, there is no evidence that long-term use of melatonin inhibits the natural secretion of melatonin. It is necessary to monitor potential drug interactions with medications such as inhibitors and enhancers of cytochrome P450 1A2 (CYP1A2). Furthermore, low CYP1A2 expression in young children requires proper dose adjustment. Although sufficient experience of melatonin use in children and adolescents has yet to be attained, accumulating evidence suggests that the use of melatonin in children and adolescents with sleep problems might be effective and tolerable. Considering the abuse or overdose risk of hypnotics or benzodiazepines, melatonin supplements may be a good therapeutic alternative. Future studies on the long-term safety of melatonin for physiological and mental function in children and adolescents are required to establish certainty about melatonin use in children and adolescents.

Sleep and Anabolic/Catabolic Hormonal Profile in Sedentary Middle-Aged Adults: The FIT-AGEING Study

Sleep quality plays an important role in the modulation of several aging markers. This influence could be explained by aging-induced hormonal changes. Indeed, poor sleep quality has been associated with the development of several endocrine-related health complications. This study examined the relationship of both subjective and objective sleep quantity and quality, with basal levels of selected plasma anabolic and catabolic hormones in sedentary middle-aged adults. A total of 74 volunteers (52.7% women; aged 53.7 ± 5.1) were recruited for this study. Subjective sleep quality was assessed by the Pittsburgh Sleep Quality Index (PSQI; higher scores indicate worse sleep quality), and objective sleep quality parameters (total sleep time [TST], wake after sleep onset [WASO], and sleep efficiency [SE]) were measured using a wrist-worn accelerometer. Basal levels of plasma dehydroepiandrosterone sulphate (DHEAS), total testosterone, sex hormone binding globulin (SHBG), somatotropin, and cortisol levels, were determined. Free testosterone was calculated from the total testosterone and SHBG levels. No associations of global PSQI score, TST, WASO, and SE with DHEAS, free testosterone, and somatotropin plasma levels were found, neither in men nor in women (all p ≥ 0.05). Global PSQI score was inversely related to cortisol plasma levels in women (p = 0.043). WASO was positively associated with cortisol plasma levels, while SE was negatively associated with cortisol plasma levels in women (all p ≤ 0.027). Sleep quality is not related to levels of plasma anabolic hormones, but to levels of catabolic hormones, in sedentary middle-aged adults. Therefore, these results suggest that potential changes in aging biomarkers associated with sleep disturbances, could be mediated by age-related changes in the catabolic endocrine system.

Adding Insult to Injury: Sleep Deficiency in Hospitalized Patients

Sleep deficiency is a common problem in the hospital setting. Contributing factors include preexisting medical conditions, illness severity, the hospital environment, and treatment-related effects. Hospitalized patients are particularly vulnerable to the negative health effects of sleep deficiency that impact multiple organ systems. Objective sleep measurement is difficult to achieve in the hospital setting, posing a barrier to linking improvements in hospital outcomes with sleep promotion protocols. Key next steps in hospital sleep promotion include improvement in sleep measurement techniques and harmonization of study protocols and outcomes to strengthen existing evidence and facilitate data interpretation across studies.

Disruption of the circadian clock component BMAL1 elicits an endocrine adaption impacting on insulin sensitivity and liver disease

SignificanceWhile increasing evidence associates the disruption of circadian rhythms with pathologic conditions, including obesity, type 2 diabetes, and nonalcoholic fatty liver diseases (NAFLD), the involved mechanisms are still poorly described. Here, we show that, in both humans and mice, the pathogenesis of NAFLD is associated with the disruption of the circadian clock combined with perturbations of the growth hormone and sex hormone pathways. However, while this condition protects mice from the development of fibrosis and insulin resistance, it correlates with increased fibrosis in humans. This suggests that the perturbation of the circadian clock and its associated disruption of the growth hormone and sex hormone pathways are critical for the pathogenesis of metabolic and liver diseases.

Contemporary Variables that Impact Sleep and Development in Female Adolescent Swimmers and Gymnasts

The effects of sleep on elite athletes in late adolescence and early adulthood have been well documented in a myriad of sports. However, there is underrepresentation of pre-pubertal and young female adolescent athlete research between the ages of 11-17, and specifically female gymnast and swimmers. Neglecting to understand how high energy demand at a young age relates to sleep and restoration may lead to developmental ramifications for this group, as they display physiological dysfunctions like delayed puberty, amenorrhea and are at risk for the female athlete triad or components of the triad. This review aims to summarize the contemporary variables of blue light emitting screens, social media, and caffeine on quality and quantity of sleep in young athletes while identifying gaps in the literature on how these factors impact the target group of young female swimmers and gymnasts.  The implications of this work include sleep hygiene recommendations for increasing duration and quality of sleep, as well as future research with respect to electronic device usage, social media participation, caffeine consumption, and sport engagement in female early adolescent athletes.

Importance of circadian timing for aging and longevity

Dietary restriction (DR) decreases body weight, improves health, and extends lifespan. DR can be achieved by controlling how much and/or when food is provided, as well as by adjusting nutritional composition. Because these factors are often combined during DR, it is unclear which are necessary for beneficial effects. Several drugs have been utilized that target nutrient-sensing gene pathways, many of which change expression throughout the day, suggesting that the timing of drug administration is critical. Here, we discuss how dietary and pharmacological interventions promote a healthy lifespan by influencing energy intake and circadian rhythms.

Circadian clocks link physiologic processes to environmental conditions and a mismatch between internal and external rhythms has negative effects on organismal health. In this review, the authors discuss the interactions between circadian clocks and dietary interventions targeted to promote healthy aging.

Sleeping patterns and childhood obesity: an epidemiological study in 1,728 children in Greece

STUDY OBJECTIVES

Sleep is an essential normal function for children's growth and development, but over the years, lifestyle changes have resulted in insufficient sleep, a factor that may be associated with increased childhood obesity. The aim of this study was to evaluate the association between sleep duration and sleep patterns separately on weekdays and weekends regarding children's weight status.

METHODS

This study was conducted among Greek students (55.1% girls) in 2014-2016. Children's weight status was classified according to the International Obesity Task Force tables and guidelines. Sleep duration was determined based on the sleep and wake time that children reported, separately for weekdays and weekends. Classification and regression tree analysis was used to derive sleep patterns and evaluate their relation to children's weight status.

RESULTS

Multiadjusted analysis revealed an inverse association between average duration of sleep on weekdays and weekends with the likelihood of being overweight/obese (odds ratio per 1 hour 0.82; 95% confidence interval, 0.73-0.92). This was more prominent on weekends than on weekdays. Children who had lower duration on weekdays, but catch-up sleep duration on weekends, were 2% (95% confidence interval, 0.97-0.99) less likely to be overweight/obese compared to those children having both less or increased sleep duration on weekdays and weekends.

CONCLUSIONS

Sleep duration and sleep patterns seem to be associated with childhood weight status. Interventions should be developed to educate parents on the importance of an adequate sleep duration and healthy sleep patterns for their children's healthy development.

Proceedings of the Sleep and Epilepsy Workgroup: Section 2 Comorbidities: Sleep Related Comorbidities of Epilepsy

Epilepsy is a chronic disease with multiple, complex comorbidities. Bidirectional relationships exist among seizures, sleep, circadian rhythms, and diseases within and outside of the central nervous system. Seizures fragment sleep and can contribute to development of sleep disorders, which in turn leads to worse overall health and more seizures. Moreover, treatment options are often limited by interactions with anti-seizure medications. Advances in the fields of epilepsy and in sleep medicine have been made separately, and therefore treating patients with these comorbidities necessitates interdisciplinary approach. The focus of this section of the Sleep and Epilepsy Workgroup was to identify methods of collaboration and outline investigational, educational, and treatment priorities to mutually advance what we consider a combined field.

Dexamethasone Rescues an Acute High-Fat Diet-Induced Decrease in Human Growth Hormone Gene Expression in Male Partially Humanized CD-1 Mice

Obesity in puberty, already a time of insulin resistance, increases the risk of developing type 2 diabetes. Human (h) growth hormone (GH) levels also peak during puberty, where it contributes to growth and energy homeostasis through positive effects on maintaining pancreatic β cell mass. Thus, it is important to understand the effects of overeating and obesity on hGH production in puberty. Three days of overeating in young male adults or high-fat diet (HFD) in pubescent male transgenic (171hGH/CS) CD-1 mice containing the hGH gene (hGH-N) results in excess insulin and a decrease in hGH production. This reduction in these mice occurred during the light phase of the daily cycle, and was associated with decreased availability of the clock-related transcription factor Brain and Muscle ARNT-Like 1 (Bmal1). However, the HFD-induced decrease in hGH-N expression was blocked by forced daily swim activity, which is expected to increase glucocorticoid (GC) levels. The aim of the study was to assess whether GCs, specifically daily injections with a pharmacological dose of dexamethasone (DEX) in the light or dark phase of the daily cycle, can limit the negative effect of HFD for 3 days on hGH-N expression in male 171hGH/CS mice. DEX treatment increased or rescued hGH-N RNA levels, and was associated with elevated Bmal1 transcripts when assessed 12 h after final treatment, and at a time when serum corticosterone levels were suppressed >90%. In addition, a diet-dependent effect on hGH-N RNA levels was observed at 36 h after final treatment, but only in the light stage, presumably due to residual effects of DEX treatment and/or recovery of endogenous corticosterone levels. This is the first evidence for a direct effect of GCs on hGH-N expression in vivo and the ability to potentially limit the negative effect of overeating/obesity on hGH production in puberty.

Sleep deprivation and diet affect human GH gene expression in transgenic mice in vivo

Human (h) growth hormone (GH) production studies are largely limited to effects on secretion. How pituitary hGH gene (hGH-N/GH1) expression is regulated is important in our understanding of the role hGH plays in physiology and disease. Here we assess for the first time the effect of sleep deprivation (SD) and high-fat diet (HFD) on hGH-N expression in vivo using partially humanized 171hGH/CS transgenic (TG) mice, and attempted to elucidate a role for DNA methylation. Activation of hGH-N expression requires interactions between promoter and upstream locus control region (LCR) sequences including pituitary-specific hypersensitive site (HS) I/II. Both SD and diet affect hGH secretion, but the effect of SD on hGH-N expression is unknown. Mice fed a HFD or regular chow diet for 3 days underwent SD (or no SD) for 6 h at Zeitgeber time (ZT) 3. Serum and pituitaries were assessed over 24 h at 6-h intervals beginning at ZT 14. SD and HFD caused significant changes in serum corticosterone and insulin, as well as hGH and circadian clock-related gene RNA levels. No clear association between DNA methylation and the negative effects of SD or diet on hGH RNA levels was observed. However, a correlation with increased methylation at a CpG (cytosine paired with a guanine) in a putative E-box within the hGH LCR HS II was suggested in situ. Methylation at this site also increased BMAL1/CLOCK-related nuclear protein binding in vitro. These observations support an effect of SD on hGH synthesis at the level of gene expression.

Acute sleep deprivation leads to growth hormone (GH) resistance in rats

Sleep is an essential physiological process that is required by all higher animals. Sleep has many important physiological functions. Previous studies have focused on the relationship between sleep and growth hormone secretion patterns. However, to date, whether sleep affects the biological activities of GH remains unclear. Here, we investigated this issue by evaluating the growth hormone receptor (GHR)-mediated intracellular signalling pathway in a sleep-deprived rat model. The results showed that GH's signalling ability is decreased in an acute sleep deprivation rat model. JAK2-STAT signalling was decreased significantly compared to that in control rats. We further analysed the possible molecular mechanism of GH signal inhibition in sleep-deprived rats. The results showed that the protein expression levels of SOCS3 (suppressors of cytokine signalling 3, which functions as the negative regulatory molecule of GH's signalling) increased; however, other negative regulatory proteins, such as protein phosphatase (PTP1B), did not change. In addition, acute sleep deprivation results in a significant increase in serum FFA (free fatty acid) level, which is also one of the factors contributing to GH inhibition. These findings suggest that GH signal resistance may be caused by a combination of factors. This study could serve as an important reference for related studies on the effect of sleep deprivation on endocrine systems.

Sleep and the GH/IGF-1 axis: Consequences and countermeasures of sleep loss/disorders

This article presents an up-to-date review of the state-of-the-art knowledge regarding the effect of sleep on the anabolic growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis. This axis is involved in learning and memory and neuroprotection at the central level, and in the crosstalk between sleep and the immune system, with respect to its anti-inflammatory properties. We also aim to provide insight into the consequences of sleep loss on cognitive capacities in healthy individuals and patients with obstructive sleep apnea (OSA), regarding the mechanistic association with the GH/IGF-1 axis. Finally, this review examines the inflammatory/endocrine pathways that are affected by sleep loss, and which may consequently interact with the GH/IGF-1 axis. The deleterious effects of sleep loss include fatigue, and can cause several adverse age-dependent health outcomes. It is therefore important to improve our understanding of the fundamental physiology underlying these effects in order to better apply non-pharmacological countermeasures (e.g., sleep strategies, exercise training, continuous positive airway pressure therapy) as well as pharmacological solutions, so as to limit the deleterious consequences of sleep loss/disorders.

Effects of acute lying and sleep deprivation on the behavior of lactating dairy cows

The objective was to determine the effects of sleep or lying deprivation on the behavior of dairy cows. Data were collected from 8 multi- and 4 primiparous cows (DIM = 199 ± 44 (mean ± SD); days pregnant = 77 ± 30). Using a crossover design, each cow experienced: 1) sleep deprivation implemented by noise or physical contact when their posture suggested sleep, and 2) lying deprivation imposed by a grid placed on the pen floor. One day before treatment (baseline), and treatment day (treatment) were followed by a 12-d washout period (with the first 7 d used to evaluate recovery). Study days were organized from 2100 to 2059. During habituation (d -3 and -2 before treatment), baseline (d -1), and trt (d 0), housing was individual boxstalls (mattress with no bedding). After treatment, cows returned to sand-bedded freestalls for a 7-d recovery period (d 1 to 7) where data on lying behaviors were collected. Following the recovery period, an additional 5-d period was provided to allow the cows a 12-d period between exposures to treatments. Daily lying time, number lying bouts, bout duration, and number of steps were recorded by dataloggers attached to the hind leg of cows throughout the study period. Data were analyzed using a mixed model including fixed effects of treatment (sleep deprivation vs. sleep and lying deprivation), day, and their interaction with significant main effects separated using a PDIFF statement (P ≤ 0.05). Interactions between treatment and day were detected for daily lying time and the number of bouts. Lying time was lower for both treatments during the treatment period compared to baseline. Lying time increased during the recovery period for both lying and sleep deprived cows. However, it took 4 d for the lying deprived cows to fully recover their lying time after treatment, whereas it took the sleep deprived cows 2 d for their lying time to return to baseline levels. Results suggest that both sleep and lying deprivation can have impact cow behavior. Management factors that limit freestall access likely reduce lying time and sleep, causing negative welfare implications for dairy cows.

Mutual influence of sleep and circadian clocks on physiology and cognition

The 24-h sleep-wake cycle is one of the most prominent outputs of the circadian clock system. At the same time, changes in sleep-wake behavior feedback on behavioral and physiological circadian rhythms, thus altering the coordination of the body's clock network. Sleep and circadian rhythm disruption have similar physiological endpoints including metabolic, cognitive, and immunologic impairments. This raises the question to which extent these phenomena are causally linked. In this review, we summarize different physiologic outcomes of sleep deprivation and mistimed sleep and discuss the experimental evidence for a mediating role of the circadian clock machinery in this context.

Endocrine rhythms of growth hormone release: Insights from animal studies

Growth hormone (GH) secretory patterns emerge following birth, and changes in patterning occur throughout life. These secretory patterns are coupled to growth, reproduction and metabolism. Comparing human and animal studies, this review will highlight ultradian patterning of GH release and the mechanisms that contribute to this. Discussions will focus on the emergence in variations in the number and frequency of GH secretory events, and the amounts of GH released (peak and basal). Animal studies have contributed significantly to our understanding of the processes that regulate GH release. However, translation of knowledge from animal models to benefit our understanding of human physiology is sometimes limited. To overcome these limitations, it is critical that we reconcile the cause and consequences of differences in GH release between humans and model organisms. In doing so, we can embrace emerging technologies that will rapidly advance our knowledge of endogenous process that control GH release.

Neuroendocrine Regulation of Growth Hormone Secretion

This article reviews the main findings that emerged in the intervening years since the previous volume on hormonal control of growth in the section on the endocrine system of the Handbook of Physiology concerning the intra- and extrahypothalamic neuronal networks connecting growth hormone releasing hormone (GHRH) and somatostatin hypophysiotropic neurons and the integration between regulators of food intake/metabolism and GH release. Among these findings, the discovery of ghrelin still raises many unanswered questions. One important event was the application of deconvolution analysis to the pulsatile patterns of GH secretion in different mammalian species, including Man, according to gender, hormonal environment and ageing. Concerning this last phenomenon, a great body of evidence now supports the role of an attenuation of the GHRH/GH/Insulin-like growth factor-1 (IGF-1) axis in the control of mammalian aging.

Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise

Although its true function remains unclear, sleep is considered critical to human physiological and cognitive function. Equally, since sleep loss is a common occurrence prior to competition in athletes, this could significantly impact upon their athletic performance. Much of the previous research has reported that exercise performance is negatively affected following sleep loss; however, conflicting findings mean that the extent, influence, and mechanisms of sleep loss affecting exercise performance remain uncertain. For instance, research indicates some maximal physical efforts and gross motor performances can be maintained. In comparison, the few published studies investigating the effect of sleep loss on performance in athletes report a reduction in sport-specific performance. The effects of sleep loss on physiological responses to exercise also remain equivocal; however, it appears a reduction in sleep quality and quantity could result in an autonomic nervous system imbalance, simulating symptoms of the overtraining syndrome. Additionally, increases in pro-inflammatory cytokines following sleep loss could promote immune system dysfunction. Of further concern, numerous studies investigating the effects of sleep loss on cognitive function report slower and less accurate cognitive performance. Based on this context, this review aims to evaluate the importance and prevalence of sleep in athletes and summarises the effects of sleep loss (restriction and deprivation) on exercise performance, and physiological and cognitive responses to exercise. Given the equivocal understanding of sleep and athletic performance outcomes, further research and consideration is required to obtain a greater knowledge of the interaction between sleep and performance.

Novel therapeutics for type 2 diabetes: insulin resistance

Insulin resistance (IR) plays an important role in the pathogenesis of type 2 diabetes (T2D) and cardiovascular disease. Hence improving IR is a major target of treatment in patients with T2D. Obesity and lack of exercise are major causes of IR. However, recent evidence implicates sleep disorders and disorders of the circadian rhythm in the pathogenesis of IR. Weight loss and lifestyle changes are the cornerstone and most effective treatments of IR, but adherence and patient's acceptability are poor. Bariatric surgery results in significant and sustainable long-term weight loss associated with beneficial impact on IR and glucose metabolism, making this an attractive treatment option for patients with T2D. Currently available pharmacological options targeting IR (such as metformin and thiazolidinediones) do not maintain glycaemic measures within targets long term and can be associated with significant side effects. Over the last two decades, many pharmacological agents targeting different aspects of the insulin signalling pathway were developed to improve IR, but only a minority reached clinical trials. Such treatments need to be specific and reversible as many of the components of the insulin signalling pathway are involved in other cellular functions such as apoptosis. Recent evidence highlighted the role of circadian rhythm and sleep-related disorders in the pathogenesis of IR. In this article, we review the latest developments in the pharmacological and non-pharmacological interventions targeting IR including bariatric surgery. We will also review the role of circadian rhythm and sleep-related disorders in the development and treatment of IR.

Exercise-Induced growth hormone during acute sleep deprivation

The effect of acute (24‐h) sleep deprivation on exercise‐induced growth hormone (GH) and insulin‐like growth factor‐1 (IGF‐1) was examined. Ten men (20.6 ± 1.4 years) completed two randomized 24‐h sessions including a brief, high‐intensity exercise bout following either a night of sleep (SLEEP) or (24‐h) sleep deprivation (SLD). Anaerobic performance (mean power [MP], peak power [PP], minimum power [MinP], time to peak power [TTPP], fatigue index, [FI]) and total work per sprint [TWPS]) was determined from four maximal 30‐sec Wingate sprints on a cycle ergometer. Self‐reported sleep 7 days prior to each session was similar between SLEEP and SLD sessions (7.92 ± 0.33 vs. 7.98 ± 0.39 h, P =0.656, respectively) and during the actual SLEEP session in the lab, the total amount of sleep was similar to the 7 days leading up to the lab session (7.72 ± 0.14 h vs. 7.92 ± 0.33 h, respectively) (P =0.166). No differences existed in MP, PP, MinP, TTPP, FI, TWPS, resting GH concentrations, time to reach exercise‐induced peak GH concentration (TTP), or free IGF‐1 between sessions. GH area under the curve (AUC) (825.0 ± 199.8 vs. 2212.9 ± 441.9 μg/L*min, P <0.01), exercise‐induced peak GH concentration (17.8 ± 3.7 vs. 39.6 ± 7.1 μg/L, P <0.01) and ΔGH (peak GH – resting GH) (17.2 ± 3.7 vs. 38.2 ± 7.3 μg/L, P <0.01) were significantly lower during the SLEEP versus SLD session. Our results indicate that the exercise‐induced GH response was significantly augmented in sleep‐deprived individuals.

Human growth hormone release is heavily influenced by sleep and exercise. Our study shows that sleep deprivation dramatically augments the exercise‐induced human growth hormone response.

Somatic growth of lean children: the potential role of sleep

BACKGROUND

Despite the current obesity pandemic, childhood malnutrition remains an urgent, public health concern. Similar to the obesity pandemic, childhood malnutrition is influenced by genetic and a number of social, environmental and biological factors. In this study, we investigated the association between sleep duration and somatic growth in lean children.

METHODS

A stratified, randomly clustered sampling design was used to select fifth grade students from 10 primary schools in Shanghai. Based on a body mass index below the 15th percentile a subsample of 143 lean children aged 10-11 years old was defined. Sleep duration and other potential confounders were surveyed through parental or self-report questionnaires. Body measurements were collected and used to calculate the Z score of weight, height, body mass index as well as body fat percentage.

RESULTS

Compared with children who slept <9 hours, those who slept for ≥10 hours grew taller and gained more weight after adjusting for confounding factors. When children slept 9-10 hours, they had significantly higher Z score of weight and body mass index.

CONCLUSIONS

Prolonged sleep not only benefits weight gain but also improves height in lean children. Our findings might provide important public health advice such that prolonged sleep may be an effective modifier of nutritional problems in childhood.

[Circadian clock and non-visual functions: the role of light in humans]

Hormonal secretion, cognitive performance, motor activity, metabolic processes, the sleep wake cycle and, most recently shown, cell division and ADN repair show a 24 h rhythmicity that is driven by the circadian timing system (the biological clock). Their appropriate activity over the 24 h requires appropriate entrainment of the circadian clock, which is achieved through the synchronizing effects of ocular light exposure. The activation of melanopsin-expressing ganglion cells in the retina depends on timing, quality, intensity, and history of light exposure. Inappropriate lighting leads to inappropriate synchronization of the clock, and activation of non-visual functions (mood, wakefulness, cognition, etc.). In turn, a deficit of circadian entrainment to the 24 h is responsible for alterations of a large number of functions, and leads to altered sleep, wake, mood, neurobehavioral processes and cell division, but also to pathologies. The crucial role of the circadian clock and the nature of the non-visual functions activated by light give rise to the concept that light is a biological need fundamental to health. Without an appropriate light hygiene, the clock receives an odd tempo, and it is cacophony!

Effects of sustained sleep restriction on mitogen-stimulated cytokines, chemokines and T helper 1/ T helper 2 balance in humans

Background

Recent studies suggest that acute sleep deprivation disrupts cellular immune responses by shifting T helper (Th) cell activity towards a Th2 cytokine profile. Since little is known about more long-term effects, we investigated how five days of sleep restriction would affect pro-inflammatory, chemotactic, Th1- and Th2 cytokine secretion.

Methods

Nine healthy males participated in an experimental sleep protocol with two baseline sleep-wake cycles (sleep 23.00 – 07.00 h) followed by 5 days with restricted sleep (03.00 – 07.00 h). On the second baseline day and on the fifth day with restricted sleep, samples were drawn every third hour for determination of cytokines/chemokines (tumor necrosis factor alpha (TNF-α), interleukin (IL) -1β, IL-2, IL-4 and monocyte chemoattractant protein-1 (MCP-1)) after invitro stimulation of whole blood samples with the mitogen phytohemagglutinin (PHA). Also leukocyte numbers, mononuclear cells and cortisol were analysed.

Results

5-days of sleep restriction affected PHA-induced immune responses in several ways. There was a general decrease of IL-2 production (p<.05). A shift in Th1/Th2 cytokine balance was also evident, as determined by a decrease in IL2/IL4 ratio. No other main effects of restricted sleep were shown. Two significant interactions showed that restricted sleep resulted in increased TNF-α and MCP-1 in the late evening and early night hours (p’s<.05). In addition, all variables varied across the 24 h day.

Conclusions

5-days of sleep restriction is characterized by a shift towards Th2 activity (i.e. lower 1L-2/IL-4 ratio) which is similar to the effects of acute sleep deprivation and psychological stress. This may have implications for people suffering from conditions characterized by excessive Th2 activity like in allergic disease, such as asthma, for whom restricted sleep could have negative consequences.

Effects of partial sleep deprivation on proinflammatory cytokines, growth hormone, and steroid hormone concentrations during repeated brief sprint interval exercise

The purpose of this study was to evaluate the effects of partial sleep deprivation (PSD) on circulating concentrations of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in relation to the secretory profiles of growth hormone (GH), cortisol, and testosterone during a repeated brief sprint interval exercise. Thirty healthy football players (mean age: 21.1 [range: 18-24] years; body mass index [BMI]: 22.6 [range: 18.47-24.46] Kg/m(2)) completed two test sessions at 08:00 h, one scheduled after a baseline night (bedtime: from 22:30 to 07:00 h) and the other after a PSD night caused by an early awakening (bedtime: from 22:30 to 03:00 h). During each session, participants performed 4 × 250-m run on a treadmill at a constant intensity of 80% of the personal maximal speed with a 3-min recovery in between. Tests session were performed at 08:00 h. Blood samples were collected before, immediately after the first and the fourth 250-m run, and 60 min after the exercise. The results showed that cortisol concentrations were not affected by the PSD. However, GH and testosterone concentrations were higher (p < .05) 60 min after the exercise during PSD in comparison with baseline. Likewise, plasma concentrations of IL-6 and TNF-α were higher (p < .05) after PSD during the exercise (i.e., the first and the fourth run) and remained elevated during the recovery period (i.e., 60 min after the exercise). In conclusion, these results showed that sleep restriction increases the proinflammatory cytokine, GH, and testosterone concentrations after physical exercise but did not affect the cortisol responses.

Quantification of sleep behavior and of its impact on the cross-talk between the brain and peripheral metabolism

Rates of obesity have been steadily increasing, along with disorders commonly associated with obesity, such as cardiovascular disease and type II diabetes. Simultaneously, average sleep times have progressively decreased. Recently, evidence from both laboratory and epidemiologic studies has suggested that insufficient sleep may stimulate overeating and thus play a role in the current epidemic of obesity and diabetes. In the human sleep laboratory it is now possible to carefully control sleep behavior and study the link between sleep duration and alterations in circulating hormones involved in feeding behavior, glucose metabolism, hunger, and appetite. This article focuses on the methodologies used in experimental protocols that have examined modifications produced by sleep restriction (or extension) compared with normal sleep. The findings provide evidence that sleep restriction does indeed impair glucose metabolism and alters the cross-talk between the periphery and the brain, favoring excessive food intake. A better understanding of the adverse effects of sleep restriction on the CNS control of hunger and appetite may have important implications for public health.

A role for central nervous growth hormone-releasing hormone signaling in the consolidation of declarative memories

Contributions of somatotropic hormonal activity to memory functions in humans, which are suggested by clinical observations, have not been systematically examined. With previous experiments precluding a direct effect of systemic growth hormone (GH) on acute memory formation, we assessed the role of central nervous somatotropic signaling in declarative memory consolidation. We examined the effect of intranasally administered growth hormone releasing-hormone (GHRH; 600 µg) that has direct access to the brain and suppresses endogenous GHRH via an ultra-short negative feedback loop. Twelve healthy young men learned word-pair associates at 2030 h and were administered GHRH and placebo, respectively, at 2100 h. Retrieval was tested after 11 hours of wakefulness. Compared to placebo, intranasal GHRH blunted GH release within 3 hours after substance administration and reduced the number of correctly recalled word-pairs by ∼12% (both P<0.05). The impairment of declarative memory consolidation was directly correlated to diminished GH concentrations (P<0.05). Procedural memory consolidation as examined by the parallel assessment of finger sequence tapping performance was not affected by GHRH administration. Our findings indicate that intranasal GHRH, by counteracting endogenous GHRH release, impairs hippocampal memory processing. They provide first evidence for a critical contribution of central nervous somatotropic activity to hippocampus-dependent memory consolidation.

Growth hormone improves hippocampal adult cell survival and counteracts the inhibitory effect of prolonged sleep deprivation on cell proliferation

Sleep deprivation (SD) produces numerous deleterious changes in brain cells, including apoptosis. It has been demonstrated that growth hormone (GH) stimulates cell growth and counteracts apoptosis, although this anti-apoptotic effect has not been tested against SD. To determine the protective effect of GH administration on cell proliferation and survival in the dentate gyrus (DG) of the hippocampus after sleep deprivation; we injected Wistar adult rats with a low dose of recombinant human GH (rhGH 5 ng/kg) per seven days and then we gently sleep deprived the animals for 48 consecutive hours. 5-Bromodeoxiuridine (BrdU) was administered to assess cell proliferation after the GH treatment and NeuN was used as marker of cell fate. Our results indicate that GH produced a three fold increase in the number of BrdU positive cells within the DG [Control = 1044 ± 106.38 cells, rhGH = 2952 ± 99.84 cells, P<0.01]. In contrast, 48 h of SD significantly reduced cell proliferation but this effect was antagonized by the GH administration [SD = 540 ± 18.3 cells, rhGH + SD = 1116 ± 84.48 cells, P<0.004]. Paradoxically, SD and GH administration increased cell survival separately but no significantly compared with control animals. However, cell survival was increased in animals treated with rhGH+SD compared to rats injected with saline solution [P<0.04]. Within the survival cells, the percentage of neurons was higher in SD animals [95%] compared with saline group, while this percentage (NeuN positive cells) was increased in animals treated with rhGH+SD [120%] compared with rhGH [25%] alone. Our findings indicate that GH strongly promotes cell proliferation in the adult brain and also protects the hippocampal neuronal precursors against the deleterious effect of prolonged sleep loss.

Growth hormone rescues hippocampal synaptic function after sleep deprivation

Sleep is required for, and sleep loss impairs, normal hippocampal synaptic N-methyl-D-aspartate (NMDA) glutamate receptor function and expression, hippocampal NMDA receptor-dependent synaptic plasticity, and hippocampal-dependent memory function. Although sleep is essential, the signals linking sleep to hippocampal function are not known. One potential signal is growth hormone. Growth hormone is released during sleep, and its release is suppressed during sleep deprivation. If growth hormone links sleep to hippocampal function, then restoration of growth hormone during sleep deprivation should prevent adverse consequences of sleep loss. To test this hypothesis, we examined rat hippocampus for spontaneous excitatory synaptic currents in CA1 pyramidal neurons, long-term potentiation in area CA1, and NMDA receptor subunit proteins in synaptic membranes. Three days of sleep deprivation caused a significant reduction in NMDA receptor-mediated synaptic currents compared with control treatments. When rats were injected with growth hormone once per day during sleep deprivation, the loss of NMDA receptor-mediated synaptic currents was prevented. Growth hormone injections also prevented the impairment of long-term potentiation that normally follows sleep deprivation. In addition, sleep deprivation led to a selective loss of NMDA receptor 2B (NR2B) from hippocampal synaptic membranes, but normal NR2B expression was restored by growth hormone injection. Our results identify growth hormone as a critical mediator linking sleep to normal synaptic function of the hippocampus.

Polysomnographic sleep, growth hormone insulin-like growth factor-I axis, leptin, and weight loss

Short sleep appears to be strongly associated with obesity and altered metabolic function, and sleep and growth hormone (GH) secretion seems interlinked. In obesity, both the GH-insulin-like-growth-factor-I (GH-IGF-I) axis and sleep have been reported to be abnormal, however, no studies have investigated sleep in relation to the GH-IGF-I axis and weight loss in obese subjects. In this study polygraphic sleep recordings, 24-h GH release, 24-h leptin levels, free-IGF-I, total-IGF-I, IGF-binding protein-3 (IGFBP-3), acid-labile subunit (ALS), cortisol and insulin sensitivity were determined in six severely obese subjects (BMI: 41+/-1 kg/m(2), 32+/-2 years of age), cross-sectional at baseline, and longitudinal after a dramatically diet-induced weight loss (36+/-7 kg). Ten age- and gender-matched nonobese subjects served as controls. Sleep duration (360+/-17 vs. 448+/-15 min/night; P<0.01), 24-h GH (55+/-9 vs. 344+/-55 mU/l.24 h; P<0.01), free-IGF-I (2.3+/-0.42 vs. 5.7+/-1.2 microg/l; P<0.01), and total-IGF-I (186+/-21 vs. 301+/-18 microg/l; P<0.01) were significantly decreased and 24-h leptin levels were increased (35+/-5 vs. 12+/-3 microg/l; P<0.01) in obese subjects at pre-weight loss compared with nonobese subjects After diet-induced weight loss the differences in GH, free IGF-I, and leptin were no longer present between previously obese and nonobese subjects, whereas a significant difference in sleep duration and total IGF-I levels persisted. Rapid eye movement (REM) sleep, non-REM sleep, IGFBP-3, ALS, and cortisol levels were similar in obese and nonobese subjects. Sleep duration, 24-h GH, and IGF-I levels were decreased and 24-h leptin levels were increased in obese subjects. We conclude that hyposomatotropism and hyperleptinemia in obesity are transient phenomena reversible with weight loss, whereas short sleep seems to persist after weight has been reduced dramatically.

Sleep duration from ages 1 to 10 years: variability and stability in comparison with growth

OBJECTIVE

Our goal was to describe the variability of sleep duration (time in bed per 24 hours) in healthy children from 1 to 10 years of age in comparison with growth measures.

METHODS

A total of 305 children were followed with structured sleep-related interviews and measurements of height and weight 12, 18, and 24 months after birth and then at annual intervals until 10 years of age. SD scores were calculated, and smooth curves were fitted by smoothing splines through the SD scores. The long-term variability channel within children (units SD score) was defined as the difference between the maximum and the minimum of the smooth curves and the short-term variability channel (units SD score) as the difference of the largest and the smallest deviations of the original SD scores from the smooth curve.

RESULTS

Sleep duration remained within a long-term variability channel <0.5 SD score in 21% of the children (34% for height, 21% for weight). Nearly every second child (46%) stayed within a long-term variability channel <1.0 SD score (76% for height, 64% for weight). Sleep duration of approximately 90% of all children ran within a long-term variability channel of <2.0 SD score (corresponding, eg, to the range between the 2nd and the 50th percentile). No single child's sleep duration remained within a short-term variability channel <0.5 SD score, indicating fluctuations from year to year (60% for height, 53% for weight). An association between aspects of sleep duration and somatic growth was not observed at any age.

CONCLUSIONS

Sleep duration during early and middle childhood shows large variability among children, as well as trait-like long-term stability and state-like yearly fluctuations within children. An individual approach to the child's sleep behavior is needed; expectations in terms of appropriate sleep duration of the child should be adjusted to the individual sleep need.

Reductions in circulating anabolic hormones induced by sustained sleep deprivation in rats

The main systemic disorders resulting from prolonged sleep deprivation in laboratory animals are a negative energy balance, low circulating thyroid hormones, and host defense impairments. Low thyroid hormones previously have been found caused by altered regulation at the level of the hypothalamus with possible pituitary involvement. The present studies investigated the effects of sleep deprivation on other major anabolic hormonal systems. Plasma growth hormone (GH) concentrations and major secretory bursts were characterized. Insulin-like growth factor I (IGF-I) was evaluated as an integrative marker of peripheral GH effector activity. Prolactin (PRL) was assessed by basal concentrations and by stimulating the pituitary with exogenous thyrotropin-releasing hormone. Leptin was studied for its linkage to metabolic signs of sleep loss and its correspondence to altered neuroendocrine regulation in other disease states. Last, plasma corticosterone was measured to investigate the degree of hypothalamic-pituitary-adrenal activation. Sleep deprivation was produced by the disk-over-water method, a well-established means of selective deprivation of sleep and noninterference with normal waking behaviors. Hormone concentrations were determined in sham comparisons and at intervals during baseline and experimental periods lasting at least 15 days in partially and totally sleep-deprived rats. The results indicate that high-amplitude pulses of GH were nearly abolished and that concentrations of GH, IGF-I, PRL, and leptin all were suppressed by sleep deprivation. Corticosterone concentration was relatively unaffected. Features of these results, such as low GH and low IGF-I, indicate failed negative feedback and point to hypothalamic mechanisms as containing the foci responsible for peripheral signs.

Growth hormone-insulin-like growth factor-1 axis, leptin and sleep in anorexia nervosa patients

The present study characterizes the relationships between severe malnutrition, sleep, growth hormone-insulin-like growth factor-1 (GH-IGF-1) axis, and leptin levels in anorexia nervosa (AN) patients before and after weight gain. Eleven restricting-type anorectic females (mean age = 19.7 years) with severe starvation state [mean body mass index (BMI) = 13.3] were studied using polysomnography and spectral power analysis. The hormone levels were measured in the morning after sleep recording. Eleven normal-weight, age- and gender-matched healthy volunteers without a history of any eating disorder served as controls. After nutritional treatment for about 2 months (65.7 +/- 6.4 days), sleep examinations and blood tests were repeated. At this stage, the study group consisted of 5 patients (mean BMI = 15.6). Higher IGF-1 and leptin levels were associated with longer and deeper sleep among anorectics. The sleep parameters including the percentages of stage 1 sleep and SWS as well as IGF-1 tended to normalize after only limited weight gain. Sleep disturbances in anorectics may be mediated through changes in the levels of the GH-IGF-1 axis hormones, as well as the levels of leptin.

Neuroendocrine facets of human puberty

The unfolding of pubertal growth and maturation entails multisystem collaboration. Most notably, the outflow of gonadotropins and growth hormone (GH) proceeds both independently and jointly. The current update highlights this unique dependency in the human.