Implications of sleep restriction and recovery on metabolic outcomes

Insulin Resistance in Type 1 Diabetes: Pathophysiological, Clinical, and Therapeutic Relevance

People with type 1 diabetes (T1D) are usually considered to exclusively exhibit β-cell failure, but they frequently also feature insulin resistance. This review discusses the mechanisms, clinical features, and therapeutic relevance of insulin resistance by focusing mainly on human studies using gold-standard techniques (euglycemic-hyperinsulinemic clamp). In T1D, tissue-specific insulin resistance can develop early and sustain throughout disease progression. The underlying pathophysiology is complex, involving both metabolic- and autoimmune-related factors operating synergistically. Insulin treatment may play an important pathogenic role in predisposing individuals with T1D to insulin resistance. However, the established lifestyle-related risk factors and peripheral insulin administration inducing glucolipotoxicity, hyperinsulinemia, hyperglucagonemia, inflammation, mitochondrial abnormalities, and oxidative stress cannot always fully explain insulin resistance in T1D, suggesting a phenotype distinct from type 2 diabetes. The mutual interaction between insulin resistance and impaired endothelial function further contributes to diabetes-related complications. Insulin resistance should therefore be considered a treatment target in T1D. Aside from lifestyle modifications, continuous subcutaneous insulin infusion can ameliorate insulin resistance and hyperinsulinemia, thereby improving glucose toxicity compared with multiple injection insulin treatment. Among other concepts, metformin, pioglitazone, incretin-based drugs such as GLP-1 receptor agonists, sodium-glucose cotransporter inhibitors, and pramlintide can improve insulin resistance, either directly or indirectly. However, considering the current issues of high cost, side effects, limited efficacy, and their off-label status, these agents in people with T1D are not widely used in routine clinical care at present.

Sleep Deficiency and Cardiometabolic Disease

Epidemiologic studies have demonstrated that short sleep duration is associated with an increased risk of cardio-metabolic health outcomes including cardiovascular disease mortality, coronary heart disease, type 2 diabetes mellitus, hypertension, and metabolic syndrome. Experimental sleep restriction studies have sought to explain these findings. This review describes the main evidence of these associations and possible mechanisms explaining them. Whether sleep extension reverses these now widely acknowledged adverse health effects and the feasibility of implementing such strategies on a public health level is discussed.

Insufficient sleep and weekend recovery sleep: classification by a metabolomics-based machine learning ensemble

Although weekend recovery sleep is common, the physiological responses to weekend recovery sleep are not fully elucidated. Identifying molecular biomarkers that represent adequate versus insufficient sleep could help advance our understanding of weekend recovery sleep. Here, we identified potential molecular biomarkers of insufficient sleep and defined the impact of weekend recovery sleep on these biomarkers using metabolomics in a randomized controlled trial. Healthy adults (n = 34) were randomized into three groups: control (CON: 9-h sleep opportunities); sleep restriction (SR: 5-h sleep opportunities); or weekend recovery (WR: simulated workweek of 5-h sleep opportunities followed by ad libitum weekend recovery sleep and then 2 days with 5-h sleep opportunities). Blood for metabolomics was collected on the simulated Monday immediately following the weekend. Nine machine learning models, including a machine learning ensemble, were built to classify samples from SR versus CON. Notably, SR showed decreased glycerophospholipids and sphingolipids versus CON. The machine learning ensemble showed the highest G-mean performance and classified 50% of the WR samples as insufficient sleep. Our findings show insufficient sleep and recovery sleep influence the plasma metabolome and suggest more than one weekend of recovery sleep may be necessary for the identified biomarkers to return to healthy adequate sleep levels.

Sleep Deficiency and Cardiometabolic Disease

Epidemiologic studies have demonstrated that short sleep duration is associated with an increased risk of cardio-metabolic health outcomes including cardiovascular disease mortality, coronary heart disease, type 2 diabetes mellitus, hypertension, and metabolic syndrome. Experimental sleep restriction studies have sought to explain these findings. This review describes the main evidence of these associations and possible mechanisms explaining them. Whether sleep extension reverses these now widely acknowledged adverse health effects and the feasibility of implementing such strategies on a public health level is discussed.

Sleep Patterns, Eating Behavior and the Risk of Noncommunicable Diseases

Sleep is extremely important for the homeostasis of the organism. In recent years, various studies have been carried out to address factors related to sleep patterns and their influence on food choices, as well as on the onset of chronic noncommunicable diseases. The aim of this article is to provide a scientific literature review on the possible role of sleep patterns on eating behavior and the risk of noncommunicable diseases. A search was performed on Medline (PubMed interface) using several keywords (e.g., "Factors Influencing Sleep" OR "Sleep and Chronic Diseases"). Articles published between 2000 and the present date that relate sleep to cyclic metabolic processes and changes in eating behavior were selected. Changes in sleep patterns are increasingly detected today, and these modifications are mainly caused by work and lifestyle conditions as well as a growing dependence on electronic devices. Sleep deprivation and the resultant short sleep duration lead to an increased appetite via an increase in the hunger hormone (ghrelin) and a decrease in the satiety hormone (leptin). Nowadays, sleep is undervalued, and thus often impaired, with consequences for the performance of various body systems. Sleep deprivation alters physiological homeostasis and influences eating behavior as well as the onset of chronic diseases.

Endogenous Diurnal Patterns of Adrenal and Gonadal Hormones During a 24-Hour Constant Routine After Simulated Shift Work

Context

Night-shift work causes circadian misalignment, predicts the development of metabolic diseases, and complicates the interpretation of hormone measurements.

Objective

To investigate endogenous circadian rhythms, dissociated from behavioral and environmental confounds, in adrenal and gonadal steroids after simulated shift work.

Methods

Fourteen healthy adults (ages 25.8 ± 3.2 years) were randomized to 3 days of night or day (control) shift work followed by a constant routine protocol designed to experimentally unveil rhythms driven endogenously by the central circadian pacemaker. Blood was sampled every 3 hours for 24 hours during the constant routine to concurrently obtain 16 Δ4 steroid profiles by mass spectrometry. Cosinor analyses of these profiles provided mesor (mean abundance), amplitude (oscillation magnitude), and acrophase (peak timing).

Results

Night-shift work marginally increased cortisol by 1 μg/dL (P = 0.039), and inactive/weak derivatives cortisone (P = 0.003) and 18-hydroxycortisol (P < 0.001), but did not alter the mesor of potent androgens testosterone and 11-ketotestosterone. Adrenal-derived steroids, including 11-ketotestosterone (P < 0.01), showed robust circadian rhythmicity after either day- or night-shift work. In contrast, testosterone and progesterone showed no circadian pattern after both shift work conditions. Night-shift work did not alter the amplitude or acrophase of any of the steroid profiles.

Conclusion

Experimental circadian misalignment had minimal effects on steroidogenesis. Adrenal steroids, but not gonadal hormones, showed endogenous circadian regulation robust to prior shift schedule. This dichotomy may predispose night-shift workers to metabolic ill health. Furthermore, adrenal steroids, including cortisol and the main adrenal androgen 11-ketostosterone, should always be evaluated during the biological morning whereas assessment of gonadal steroids, particularly testosterone, is dependent on the shift-work schedule.

Cross talk mechanism of disturbed sleep patterns in neurological and psychological disorders

The incidence and prevalence of sleep disorders continue to increase in the elderly populace, particularly those suffering from neurodegenerative and neuropsychiatric disorders. This not only affects the quality of life but also accelerates the progression of the disease. There are many reasons behind sleep disturbances in such patients, for instance, medication use, nocturia, obesity, environmental factors, nocturnal motor disturbances and depressive symptoms. This review focuses on the mechanism and effects of sleep dysfunction in neurodegenerative and neuropsychiatric disorders. Wherein we discuss disturbed circadian rhythm, signaling cascade and regulation of genes during sleep deprivation. Moreover, we explain the perturbation in brainwaves during disturbed sleep and the ocular perspective of neurodegenerative and neuropsychiatric manifestations in sleep disorders. Further, as the pharmacological approach is often futile and carries side effects, therefore, the non-pharmacological approach opens newer possibilities to treat these disorders and widens the landscape of treatment options for patients.

Human fertility and sleep disturbances: A narrative review

INTRODUCTION

Many factors may be hidden behind the global fertility decline observed in Western countries. Alongside the progressively increased age of infertile couples, environmental and behavioural factors, including non-optimal lifestyle habits, should be considered. Among these, sleep disorders have been suggested to be linked to human fertility.

METHODS

This is a narrative review, describing first sleep physiology, its disturbances, and the tools able to quantify sleep dysfunction. Then, we consider all available studies aimed at investigating the connection between sleep disorders and human fertility, providing a comprehensive view on this topic.

RESULTS

Forty-two studies investigating the relationship between sleep habits and human reproduction were included. All the published evidence was grouped according to the aspect of human fertility considered, i.e. i) female reproductive functions, ii) male reproductive functions, iii) natural conception and iv) assisted reproduction. For each of the sub-groups considered, the connection between sleep dysregulation and human fertility was classified according to specific sleep characteristics, such as sleep duration, quality, and habits. In addition, possible physio-pathological mechanisms proposed to support the link between sleep and fertility were summarized.

CONCLUSION

This review summarizes the most relevant findings about the intricate and still largely unknown network of molecular pathways involved in the regulation of circadian homeostasis, to which sleep contributes, essential for reproductive physiology. Thus, many mechanisms seem correlate sleep disorders to reproductive health, such as adrenal activation, circadian dysregulation, and genetic influences. This review highlights the need to properly designed trials on the topic.

The circadian system, sleep, and the health/disease balance: a conceptual review

The field of "circadian medicine" is a recent addition to chronobiology and sleep research efforts. It represents a logical step arising from the increasing insights into the circadian system and its interactions with life in urbanised societies; applying these insights to the health/disease balance at home and in the medical practice (outpatient) and clinic (inpatient). Despite its fast expansion and proliferating research efforts, circadian medicine lacks a formal framework to categorise the many observations describing interactions among the circadian system, sleep, and the health/disease balance. A good framework allows us to categorise observations and then assign them to one or more components with hypothesised interactions. Such assignments can lead to experiments that document causal (rather than correlational) relationships and move from describing observations to discovering mechanisms. This review details such a proposed formal framework for circadian medicine and will hopefully trigger discussion among our colleagues, so that the framework can be improved and expanded. As the basis of the framework for circadian medicine, we define "circadian health" and how it links to general health. We then define interactions among the circadian system, sleep, and the health/disease balance and put the framework into the context of the literature with examples from six domains of health/disease balance: fertility, cancer, immune system, mental health, cardiovascular, and metabolism.

Sleep Deficiency and Cardiometabolic Disease

Epidemiologic studies have demonstrated that short sleep duration is associated with an increased risk of cardio-metabolic health outcomes including cardiovascular disease mortality, coronary heart disease, type 2 diabetes mellitus, hypertension, and metabolic syndrome. Experimental sleep restriction studies have sought to explain these findings. This review describes the main evidence of these associations and possible mechanisms explaining them. Whether sleep extension reverses these now widely acknowledged adverse health effects and the feasibility of implementing such strategies on a public health level is discussed.

Possible Association of Telomere Length With Sleep Duration. A Preliminary Pilot Study in a Sicilian Cohort with Centenarians

Telomere length (TL) is considered a biomarker of ageing although this topic is still debated. Also, sleep pattern changes are physiological part of the normal ageing process. In fact, it is widely recognized that sleep duration declines with age, leading to dysregulation of circadian rhythms. The aim of our study was to analyse the possible association of sleep duration with TL in a sample of 135 subjects with ages ranging from 20 to 111 years, recruited from Palermo and neighbouring municipalities in Sicily (Italy). Preliminary data suggest that relative TL (RTL) decreases with age in both men and women. However, at older ages, the difference between men and women tends to narrow. Nonagenarian and centenarian women do not show RTL values significantly different from those observed in adult and old women (40-89 years aged). Moreover, to analyse the relationship between TL and sleep, we stratified sleep duration into greater or lesser than 8-h periods. We found that centenarians, who daily sleep 8 hours or more, have longer RTL than centenarians who sleep fewer than 8 hours. Although the relatively small sample size of centenarians, we provide preliminary evidence that sleep duration may affect the RTL of centenarians. To the best of our knowledge, this is the first study to examine the relationship between centenarians, RTL and sleep duration. Further studies with greater sample size of centenarians are required to replicate and extend these data.

Assessment of effects of total sleep deprivation and subsequent recovery sleep: a methodological strategy feasible without sleep laboratory

Background

Sleep is critical for maintaining homeostasis in bodily and neurobehavioral functions. This homeostasis can be disturbed by sleep interruption and restored to normal by subsequent recovery sleep. Most research regarding recovery sleep (RS) effects has been conducted in specialized sleep laboratories, whereas small, less-well equipped research units may lack the possibilities to run studies in this area. Hence, the aims of the present study were to develop and validate an experimental protocol, which allows a thorough assessment of at-home recovery sleep after sleep deprivation.

Methods

The experimental protocol, comprising one night of baseline sleep (BL) at home, one night of monitored total sleep deprivation and a subsequent recovery night at home, was tested in a sample of 30 healthy participants. Subjects’ fatigue and alertness were assessed prior to and after each night. Sleep at home (BL, RS) was objectively assessed using portable polysomnography. To check whether our at-home sleep assessments yielded results that are comparable to those conducted in sleep laboratories, we compared the sleep data assessed in our study with sleep data assessed in laboratory studies.

Results

Sleep parameters assessed during RS exhibited changes as expected (prolonged total sleep time, better sleep efficiency, slow wave sleep rebound). Sleep parameters of BL and RS were in line with parameters assessed in previous studies examining sleep in a laboratory setting. Fatigue normalized after one night of RS; alertness partly recovered.

Conclusions

Our results suggest a successful implementation of our new experimental protocol, emphasizing it as a useful tool for future studies on RS outside of well-equipped sleep laboratories.

Clamping Cortisol and Testosterone Mitigates the Development of Insulin Resistance during Sleep Restriction in Men

CONTEXT

Sleep loss in men increases cortisol and decreases testosterone, and sleep restriction by 3 to 4 hours/night induces insulin resistance.

OBJECTIVE

We clamped cortisol and testosterone and determined the effect on insulin resistance.

METHODS

This was a randomized double-blind, in-laboratory crossover study in which 34 healthy young men underwent 4 nights of sleep restriction of 4 hours/night under 2 treatment conditions in random order: dual hormone clamp (cortisol and testosterone fixed), or matching placebo (cortisol and testosterone not fixed). Fasting blood samples, and an additional 23 samples for a 3-hour oral glucose tolerance test (OGTT), were collected before and after sleep restriction under both treatment conditions. Cytokines and hormones were measured from the fasting samples. Overall insulin sensitivity was determined from the OGTT by combining complementary measures: homeostasis model assessment of insulin resistance of the fasting state; Matsuda index of the absorptive state; and minimal model of both fasting and absorptive states.

RESULTS

Sleep restriction alone induced hyperinsulinemia, hyperglycemia, and overall insulin resistance (P < 0.001 for each). Clamping cortisol and testosterone alleviated the development of overall insulin resistance (P = 0.046) and hyperinsulinemia (P = 0.014) by 50%. Interleukin-6, high-sensitivity C-reactive protein, peptide YY, and ghrelin did not change, whereas tumor necrosis factor-α and leptin changed in directions that would have mitigated insulin resistance with sleep restriction alone.

CONCLUSION

Fixing cortisol-testosterone exposure mitigates the development of insulin resistance and hyperinsulinemia, but not hyperglycemia, from sustained sleep restriction in men. The interplay between cortisol and testosterone may be important as a mechanism by which sleep restriction impairs metabolic health.

The Role of AMPK Signaling in Brown Adipose Tissue Activation

Obesity is becoming a pandemic, and its prevalence is still increasing. Considering that obesity increases the risk of developing cardiometabolic diseases, research efforts are focusing on new ways to combat obesity. Brown adipose tissue (BAT) has emerged as a possible target to achieve this for its functional role in energy expenditure by means of increasing thermogenesis. An important metabolic sensor and regulator of whole-body energy balance is AMP-activated protein kinase (AMPK), and its role in energy metabolism is evident. This review highlights the mechanisms of BAT activation and investigates how AMPK can be used as a target for BAT activation. We review compounds and other factors that are able to activate AMPK and further discuss the therapeutic use of AMPK in BAT activation. Extensive research shows that AMPK can be activated by a number of different kinases, such as LKB1, CaMKK, but also small molecules, hormones, and metabolic stresses. AMPK is able to activate BAT by inducing adipogenesis, maintaining mitochondrial homeostasis and inducing browning in white adipose tissue. We conclude that, despite encouraging results, many uncertainties should be clarified before AMPK can be posed as a target for anti-obesity treatment via BAT activation.

Age and time-of-day differences in the hypothalamo-pituitary-testicular, and adrenal, response to total overnight sleep deprivation

STUDY OBJECTIVES

In young men, sleep restriction decreases testosterone (Te) and increases afternoon cortisol (F), leading to anabolic-catabolic imbalance, insulin resistance, and other andrological health consequences. Age-related differences in the hypothalamo-pituitary-testicular/adrenal response to sleep restriction could expose older individuals to greater or lesser risk. We aimed to evaluate and compare the 24-h and time-of-day effect of sleep restriction on F, luteinizing hormone (LH), and Te in young and older men.

METHODS

Thirty-five healthy men, aged 18-30 (n = 17) and 60-80 (n =18) years, underwent overnight sleep deprivation (complete nighttime wakefulness) or nighttime sleep (10 pm to 6 am) with concurrent 10-min blood sampling in a prospectively randomized crossover study. F, LH, and Te secretion were calculated by deconvolution analysis.

RESULTS

Sleep deprivation had multiple effects on 24-h Te secretion with significant reductions in mean concentrations, basal, total and pulsatile secretion, and pulse frequency (each p < 0.05), in the absence of detectable changes in LH. These effects were most apparent in older men and differed according to age for some parameters: pulsatile Te secretion (p = 0.03) and Te pulse frequency (p = 0.02). Time-of-day analyses revealed that sleep restriction significantly reduced Te in the morning and afternoon, reduced LH in the morning in both age groups, and increased F in the afternoon in older men.

CONCLUSIONS

These data suggest a time-of-day dependent uncoupling of the regulatory control of the testicular axis and of F secretion. Future studies will need to directly verify these regulatory possibilities specifically and separately in young and older men.

CLINICAL TRIAL

Not applicable.

Sleep and the Testis

Disordered sleep impairs neurocognitive performance, and is now recognized to cause metabolic ill-health. This review assesses the nascent relationship between insufficient, misaligned, and disrupted sleep with andrological health. High-quality cohort studies show a reduced sperm count in men with sleep disturbances. Well-designed interventional studies show a reduction in testosterone with sleep restriction. Studies of long-term shift workers show no effect of misaligned sleep on mean testosterone concentrations. Men with obstructive sleep apnea (OSA) and more severe hypoxemia have lower testosterone levels, although it is unknown if this relationship is entirely explained by concomitant obesity, or is reversible. Nevertheless, erectile dysfunction, which is common in men with OSA, is clinically improved when OSA is properly treated. Few studies manipulating sleep have been performed in older men, in whom the accumulation of sleep disturbances over decades of life may contribute to age-related illnesses. Improving sleep could ameliorate the development of these disorders.

Sleep Disturbance Induces Increased Cholesterol Level by NR1D1 Mediated CYP7A1 Inhibition

Disturbed sleep is closely associated with an increased risk of metabolic diseases. However, the underlying mechanisms of circadian clock genes linking sleep and lipid profile abnormalities have not been fully elucidated. This study aimed to explore the important role of the circadian clock in regulating impaired cholesterol metabolism at an early stage of sleep deprivation (SD). Sleep disturbance was conducted using an SD instrument. Our results showed that SD increased the serum cholesterol levels. Concentrations of serum leptin and resistin were much lower after SD, but other metabolic hormone concentrations (adiponectin, glucagon, insulin, thyroxine, norepinephrine, and epinephrine) were unchanged before and after SD. Warning signs of cardiovascular diseases [decreased high density lipoprotein (HDL)-cholesterol and increased corticosterone and 8-hydroxyguanosine levels] and hepatic cholestasis (elevated total bile acids and bilirubin levels) were observed after SD. Cholesterol accumulation was also observed in the liver after SD. The expression levels of HMGCR, the critical enzyme for cholesterol synthesis, remained unchanged in the liver. However, the expression levels of liver CYP7A1, the enzyme responsible for the conversion of cholesterol into bile acids, significantly reduced after SD. Furthermore, expression of NR1D1, a circadian oscillator and transcriptional regulator of CYP7A1, strikingly decreased after SD. Moreover, NR1D1 deficiency decreased liver CYP7A1 levels, and SD could exacerbate the reduction of CYP7A1 expression in NR1D1^-/- mouse livers. Additionally, NR1D1 deficiency could further increase serum cholesterol levels under SD. These results suggest that sleep disturbance can induce increased serum cholesterol levels and liver cholesterol accumulation by NR1D1 mediated CYP7A1 inhibition.

Sleep Deprivation and Neurological Disorders

Sleep plays an important role in maintaining neuronal circuitry, signalling and helps maintain overall health and wellbeing. Sleep deprivation (SD) disturbs the circadian physiology and exerts a negative impact on brain and behavioural functions. SD impairs the cellular clearance of misfolded neurotoxin proteins like α-synuclein, amyloid-β, and tau which are involved in major neurodegenerative diseases like Alzheimer's disease and Parkinson's disease. In addition, SD is also shown to affect the glymphatic system, a glial-dependent metabolic waste clearance pathway, causing accumulation of misfolded faulty proteins in synaptic compartments resulting in cognitive decline. Also, SD affects the immunological and redox system resulting in neuroinflammation and oxidative stress. Hence, it is important to understand the molecular and biochemical alterations that are the causative factors leading to these pathophysiological effects on the neuronal system. This review is an attempt in this direction. It provides up-to-date information on the alterations in the key processes, pathways, and proteins that are negatively affected by SD and become reasons for neurological disorders over a prolonged period of time, if left unattended.

Sleep quantity and quality and cardiometabolic risk factors in Indigenous Australians

Poor sleep is associated with increased risk of cardiovascular disease (CVD). Indigenous Australians have 1.3 times higher risk of CVD compared to non-indigenous Australians. However, there are limited data describing sleep problems and cardiometabolic risk in this population. This study aimed to investigate sleep quantity and quality in indigenous Australians and assess its association with cardiometabolic risk. Two hundred and forty-five indigenous Australians aged > 18 years were recruited via convenience sampling from communities in the Northern Territory and Queensland. Sleep quantity and quality was assessed subjectively with questionnaires including the Epworth Sleepiness Scale. In a sub-population (n = 46), objective sleep assessment was performed over three nights of actigraphy. Cardiometabolic risk measures included glycated haemoglobin, lipids, anthropometric measurements and sitting blood pressure. Sleep duration measured subjectively and objectively averaged 7.5 ± 2.0 hr/night; however, over one-third of participants (self-report 35%; actigraphy 39%) obtained < 7 hr/night. Overall, more than a third of participants experienced poor-quality sleep, with 27% reporting severe daytime sleepiness (ESS score > 10) and a high number of objectively measured awakenings/night (6 ± 4). Short sleep duration (<6 hr/night) measured both subjectively and objectively was an independent predictor of diastolic (β = 5.37, p = .038) and systolic blood pressure (β = 14.30, p = .048). More objectively measured night-time awakenings were associated with increased glycated haemoglobin levels (β = 0.07, p = .020) and greater sleep fragmentation was associated with lower high-density lipoprotein levels (β = -0.01, p = .025). A large proportion of indigenous Australians experienced short sleep durations and had significant sleep disruption. Poor sleep quantity and quality may contribute to heightened cardiometabolic risk in this population.

Differential effects of split and continuous sleep on neurobehavioral function and glucose tolerance in sleep-restricted adolescents

Study Objectives

Many adolescents are exposed to sleep restriction on school nights. We assessed how different apportionment of restricted sleep (continuous vs. split sleep) influences neurobehavioral function and glucose levels.

Methods

Adolescents, aged 15–19 years, were evaluated in a dormitory setting using a parallel-group design. Following two baseline nights of 9-hour time-in-bed (TIB), participants underwent either 5 nights of continuous 6.5-h TIB (n = 29) or 5-hour nocturnal TIB with a 1.5-hour afternoon nap (n = 29). After two recovery nights of 9-hour TIB, participants were sleep restricted for another three nights. Sleep was assessed using polysomnography (PSG). Cognitive performance and mood were evaluated three times per day. Oral glucose tolerance tests (OGTT) were conducted on mornings after baseline sleep, recovery sleep, and the third day of each sleep restriction cycle.

Results

The split sleep group had fewer vigilance lapses, better working memory and executive function, faster processing speed, lower level of subjective sleepiness, and more positive mood, even though PSG-verified total sleep time was less than the continuous sleep group. However, vigilance in both sleep-restricted groups was inferior to adolescents in a prior sample given 9-hour nocturnal TIB. During both cycles of sleep restriction, blood glucose during the OGTT increased by a greater amount in the split sleep schedule compared with persons receiving 6.5-hour continuous sleep.

Conclusions

In adolescents, modest multinight sleep restriction had divergent negative effects on cognitive performance and glucose levels depending on how the restricted sleep was apportioned. They are best advised to obtain the recommended amount of nocturnal sleep.

Trial registration

https://clinicaltrials.gov/ct2/show/NCT03333512

A Clinical Perspective of Sleep and Andrological Health: Assessment, Treatment Considerations, and Future Research

CONTEXT

Sleep that is insufficient, misaligned, or disrupted causes hypersomnolence and neuropsychological deficits, adversely affects cardiometabolic health, and is increasingly recognized to impair other biological processes that lead to conditions important to men, such as hypogonadism, erectile dysfunction, and infertility.

EVIDENCE ACQUISITION

Literature review from 1970 to December 2018.

EVIDENCE SYNTHESIS

High-quality and complementary epidemiological and interventional studies establish that abnormal sleep is associated with increased mortality, hypertension, and other cardiometabolic disorders (insufficient, disrupted, and misaligned sleep), as well as reduced fecundity and total sperm count (insufficient sleep), erectile dysfunction (disrupted sleep), and low testosterone (both). Circadian misalignment shifts the peak of testosterone's diurnal rhythm to occur soon after waking up, irrespective of the biological clock time, but it does not change the mean concentration. Preliminary studies show that extending sleep in individuals who are chronically sleep deprived may become a strategy to reduce insulin resistance and hypertension. Continuous positive airway pressure therapy can improve erectile function, and possibly systemic testosterone exposure, but only when used adherently by men with obstructive sleep apnea. Both high-dose and replacement-dose testosterone therapies modestly worsen sleep-disordered breathing, but they also improve cardiometabolic function and sexual desire. Persistence of either the adverse or beneficial outcomes over the longer term requires further investigation.

CONCLUSIONS

Sleep is increasingly recognized to be essential for healthy living. Establishing the effect of abnormal sleep, and of improving sleep, on andrological issues of prime interest to men will promote prioritization of sleep, and may thereby improve overall long-term health outcomes.

Sleep influences on cardio-metabolic health in Indigenous populations

Indigenous populations continue to be among the world's most marginalized population groups. Studies in Indigenous populations from high income countries (including the United States, Canada, Australia, and New Zealand) indicate increased risk of sleep disorders compared to non-Indigenous populations. Poor sleep, whether it be short sleep duration or fragmented sleep, is a well-established risk factor for cardio-metabolic diseases. Given the implications, targeted improvement of poor sleep may be beneficial for the health and well-being of Indigenous people. In this narrative review, we will: (1) discuss the effects of sleep on the cardio-metabolic processes; (2) examine sleep in Indigenous populations; (3) review the association between sleep and cardio-metabolic risk in Indigenous populations; and (4) review the potential role of sleep in cardiovascular disease risk detection and interventions to improve sleep and cardio-metabolic health in Indigenous people. In particular, this review highlights that the assessment of sleep quality and quantity may be a beneficial step toward identifying Indigenous people at risk of cardio-metabolic diseases and may represent a key intervention target to improve cardio-metabolic outcomes.

A Pilot Study Examining Biofeedback and Structured Napping to Promote Medical Student Wellbeing

This article was migrated. The article was marked as recommended. Objective: To examine medical students' engagement in wellness activities and evaluate the effects of biofeedback and structured napping on measures of stress, burnout and wellbeing. Method: A randomized trial of heart-rate variability (HRV) biofeedback and structured napping used by pre-clinical medical students at the University of Central Florida College of Medicine compared with a control group was conducted. Baseline measurement occurred in August 2016 with the follow-up period in March 2017. To measure biofeedback, participants used Heartmath Biofeedback® with Inner Balance® software to record HRV measurements while they engaged in self-guided breathing three times weekly. The biofeedback device connected to participants' iPhone or iPad with a sensor that clipped to users' earlobes. HRV recordings were stored in a heart-cloud database, and participants had the option to share their recordings with the researchers. Participants used sleep pods (MetroNaps Energy Pods®) to engage in 20-minute structured naps three times weekly. Participants completed six psychosocial self-report questionnaires at baseline (T1) and two follow-up points (T2, T3). The questionnaires included the Interpersonal Reactivity Index; Perceived Stress Scale; Quality of life scale; Oldenburg Burnout Inventory; and the Physician Well-Being Index. Results: Forty-two students enrolled in the study. Throughout the study, participants recorded 276 structured naps lasting approximately 20 minutes in duration and shared 24 personalized biofeedback recordings. Conclusions: Promotion of structured napping offers promise as an institution-initiated wellness intervention to promote medical students' mental health and wellbeing. HRV biofeedback warrants further study given the lack of conclusive findings in this study.

Sleep Duration Is Associated With Testis Size in Healthy Young Men

STUDY OBJECTIVES

Sleep is increasingly recognized to influence a growing array of physiological processes. The relationship between sleep duration and testis size, a marker of male reproductive potential, has not been studied.

METHODS

This was a preliminary cross-sectional analysis of the baseline data from 92 healthy men (mean ± standard deviation, age 33 ± 6 years, body mass index [BMI] 24.7 ± 6.1 kg/m2), of whom 66 underwent at-home actigraphy and 47 underwent in-laboratory polysomnography. Sleep duration and architecture were measured by actigraphy and polysomnography, testicular volume by Prader orchidometer, total testosterone by liquid chromatography tandem mass spectrometry, free testosterone by equilibrium dialysis, and luteinizing hormone and follicle-stimulating hormone (FSH) by immunochemiluminometric assay.

RESULTS

Sleep duration was correlated with testicular volume (r = .31, P = .046) and with FSH (r = -.30, P = .035), and rapid eye movement sleep was correlated with FSH (r = .44, P = .006). The significance of these findings did not change after adjustment for age and BMI, and were confirmed nonparametrically by resampling. A putative inverse U-shaped relationship between testicular volume and sleep duration was observed by polynomial regression (P = .049), but not with resampling (P = .068).

CONCLUSIONS

There is a positive linear and a possible inverse U-shaped relationship between sleep duration and testis volume. Longitudinal or interventional studies manipulating sleep are required to better define causality, and ultimately to establish how much sleep is needed to maximize male reproductive potential.

CLINICAL TRIAL REGISTRATION

Title: Hormonal Mechanisms of Sleep Restriction, Registry: ClinicalTrials.gov, Identifier: NCT02256865, URL: https://clinicaltrials.gov/ct2/show/NCT02256865.

Sleep deprivation and obesity in adults: a brief narrative review

Background/aims

Obesity and sleep deprivation are two epidemics that pervade developed nations. Their rates have been steadily rising worldwide, especially in the USA. This short communication will explore the link between the two conditions and outline the proposed mechanisms behind their relationship.

Methods

Studies on the topic of sleep and obesity were reviewed, and findings were used to develop a theoretical model for the biological link between short sleep duration and obesity.

Results

Individuals who regularly slept less than 7  hours per night were more likely to have higher average body mass indexes and develop obesity than those who slept more. Studies showed that experimental sleep restriction was associated with increased levels of ghrelin, salt retention and inflammatory markers as well as decreased levels of leptin and insulin sensitivity.

Conclusions

There may be a link between obesity and sleep deprivation. We recommend further investigations are to elucidate the potential mechanisms.

Shared Genetic Control of Brain Activity During Sleep and Insulin Secretion: A Laboratory-Based Family Study

Over the past 20 years, a large body of experimental and epidemiologic evidence has linked sleep duration and quality to glucose homeostasis, although the mechanistic pathways remain unclear. The aim of the current study was to determine whether genetic variation influencing both sleep and glucose regulation could underlie their functional relationship. We hypothesized that the genetic regulation of electroencephalographic (EEG) activity during non-rapid eye movement sleep, a highly heritable trait with fingerprint reproducibility, is correlated with the genetic control of metabolic traits including insulin sensitivity and β-cell function. We tested our hypotheses through univariate and bivariate heritability analyses in a three-generation pedigree with in-depth phenotyping of both sleep EEG and metabolic traits in 48 family members. Our analyses accounted for age, sex, adiposity, and the use of psychoactive medications. In univariate analyses, we found significant heritability for measures of fasting insulin sensitivity and β-cell function, for time spent in slow-wave sleep, and for EEG spectral power in the delta, theta, and sigma ranges. Bivariate heritability analyses provided the first evidence for a shared genetic control of brain activity during deep sleep and fasting insulin secretion rate.

The role of sleep duration and sleep disordered breathing in gestational diabetes mellitus

Many women experience sleep problems during pregnancy. This includes difficulty initiating and maintaining sleep due to physiologic changes that occur as pregnancy progresses, as well as increased symptoms of sleep-disordered breathing (SDB). Growing evidence indicates that sleep deficiency alters glucose metabolism and increases risk of diabetes. Poor sleep may exacerbate the progressive increase in insulin resistance that normally occurs during pregnancy, thus contributing to the development of maternal hyperglycemia. Here, we critically review evidence that exposure to short sleep duration or SDB during pregnancy is associated with gestational diabetes mellitus (GDM). Several studies have found that the frequency of GDM is higher in women exposed to short sleep compared with longer sleep durations. Despite mixed evidence regarding whether symptoms of SDB (e.g., frequent snoring) are associated with GDM after adjusting for BMI or obesity, it has been shown that clinically-diagnosed SDB is prospectively associated with GDM. There are multiple mechanisms that may link sleep deprivation and SDB with insulin resistance, including increased levels of oxidative stress, inflammation, sympathetic activity, and cortisol. Despite emerging evidence that sleep deficiency and SDB are associated with increased risk of GDM, it has yet to be demonstrated that improving sleep in pregnant women (e.g., by extending sleep duration or treating SDB) protects against the development of hyperglycemia. If a causal relationship can be established, behavioral therapies for improving sleep can potentially be used to reduce the risk and burden of GDM.

Sleep Duration and Cardiometabolic Risk Among Chinese School-aged Children: Do Adipokines Play a Mediating Role?

Study Objectives

To assess the associations between sleep duration and cardiometabolic risk factors in Chinese school-aged children and to explore the possible mediating role of adipokines.

Methods

Sleep duration was collected in 3166 children from the Beijing Child and Adolescent Metabolic Syndrome study. Glucose homeostasis and other cardiometabolic risk factors were assessed. Serum adipokines including leptin, total and high-molecular-weight (HMW) adiponectin, resistin, fibroblast growth factor 21 (FGF21), and retinol binding protein 4 (RBP4) were determined.

Results

Among the 6- to 12-year-old children, after adjusting for covariates including puberty, short sleep duration was associated with increased body mass index (BMI), waist circumference, fasting glucose, insulin and homeostasis model assessment of insulin resistance (all p < .0001), higher triglyceride and lower high-density lipoprotein cholesterol (p < .05), along with increased leptin (p < .0001), FGF21 (p < .05) and decreased HMW-adiponectin (p ≤ .01); the association with leptin remained significant after further adjustment for BMI. However, these associations, except for glucose (p < .0001), disappeared after further adjusted for leptin. For the 13-18 years old group, short sleep duration was associated with higher BMI, waist circumference, and RBP4 (all p < .05), but the association with RBP4 was attenuated after adjusting for BMI (p = .067).

Conclusions

Short sleep duration is strongly associated with obesity and hyperglycemia (in 6-12 years old), along with adverse adipokine secretion patterns among Chinese children. The associations with cardiometabolic risk factors appear to be more pronounced in younger children, and could be explained, at least partially, by leptin levels.

Impact of clinic follow-up visits on body weight control in people with prediabetes or diabetes mellitus: Japanese nonelderly cohort study

BACKGROUND

Body weight control is considered essential for the management of diabetes mellitus. Clinicians have an important role in educating and guiding patients with diabetes to control their body weight. The aim of the present study was to clarify if clinic visits influenced body weight control of people with prediabetes or diabetes mellitus.

OBJECTIVE

To examine whether individuals with diabetes mellitus who visit clinics show better weight control.

METHOD

We used a large Japanese database (Japan Medical Data Center, Tokyo, Japan) of screening for lifestyle disease linked with administrative claim data to retrospectively identify people with prediabetes or diabetes mellitus based on their fasting plasma glucose and glycated haemoglobin (HbA1c) concentration. We collected data on their baseline characteristics (including age, sex, body mass index and disease history) and their lifestyles. We used propensity-score inverse probability of treatment weighted generalized estimating equations to examine the association between clinic visits and change in body mass index.

RESULTS

Between 2013 and 2014, we identified 11004 individuals with prediabetes or diabetes. The proportions visiting clinics after the first diagnosis made at screening was 27.8%. Clinic visit was significantly associated with lower body mass index after adjustment for baseline patient characteristics a year after first screening (-0.17 kg/m2; 95% confidence interval, -0.22 to -0.12).

CONCLUSION

In Japanese people found to have prediabetes or diabetes during an annual health screen, those who visited clinics after their first diagnosis were likely to have better body weight control.

Overweight in youth and sleep quality: is there a link?

OBJECTIVE

Overweight seems to be related to a higher prevalence of sleep disturbances. Decreased sleep duration and altered sleep quality are risk factors for obesity. Our aim was to compare the sleep pattern of overweight children with that of a matched control group and assess the relationship between sleep quality and obesity.

MATERIALS AND METHODS

Retrospective cohort study comparing 41 overweight children with a normal-weight control group, both submitted to polysomnography. The samples were matched for age, sex, and apnea-hypopnea index. Body mass index (BMI) z-scores were calculated using World Health Organization (WHO) growth charts. Insulin resistance in the study group was determined using the homeostatic model assessment for insulin resistance (HOMA-IR). Sleep patterns were compared. The statistical analysis was performed using SPSS® version 21.

RESULTS

The mean age (± standard deviation) of the population was 10 ± 3.4 years (min. 5 years; max. 17 years). Fifty-six percent of the participants in both groups were girls. N3% was lower in the study group (18.95 ± 6.18%) compared with the control group (21.61 ± 7.39%; t (40) = 2.156, p = 0.037). We found a correlation in the study group between HOMA-IR and N3% (Rs = -0.434, p = 0.008).

CONCLUSION

The present study suggests a link between overweight/obesity and altered sleep quality due to compromised non-rapid eye movement sleep, an indirect marker of sleep quality. There was also a link between slow-wave sleep duration and insulin resistance. We must find a strategy to provide adequate slow-wave sleep duration to reduce the obesity epidemic at young ages. Further research is needed.

Effects of Yoga and Aerobic Exercise on Actigraphic Sleep Parameters in Menopausal Women with Hot Flashes

STUDY OBJECTIVES

To determine effects of yoga and aerobic exercise compared with usual activity on objective assessments of sleep in midlife women.

METHODS

Secondary analyses of a randomized controlled trial in the Menopause Strategies: Finding Lasting Answers for Symptoms and Health (MsFLASH) network conducted among 186 late transition and postmenopausal women aged 40-62 y with hot flashes. Women were randomized to 12 w of yoga, supervised aerobic exercise, or usual activity. The mean and coefficient of variation (CV) of change in actigraph sleep measures from each intervention group were compared to the usual activity group using linear regression models.

RESULTS

Baseline values of the primary sleep measures for the entire sample were mean total sleep time (TST) = 407.5 ± 56.7 min; mean wake after sleep onset (WASO) = 54.6 ± 21.8 min; mean CV for WASO = 37.7 ± 18.7 and mean CV for number of long awakenings > 5 min = 81.5 ± 46.9. Changes in the actigraphic sleep outcomes from baseline to weeks 11-12 were small, and none differed between groups. In an exploratory analysis, women with baseline Pittsburgh Sleep Quality Index higher than 8 had significantly reduced TST-CV following yoga compared with usual activity.

CONCLUSIONS

This study adds to the currently scant literature on objective sleep outcomes from yoga and aerobic exercise interventions for this population. Although small effects on self-reported sleep quality were previously reported, the interventions had no statistically significant effects on actigraph measures, except for potentially improved sleep stability with yoga in women with poor self-reported sleep quality.

Estimating individual optimal sleep duration and potential sleep debt

In this study, we hypothesized that dynamics of sleep time obtained over consecutive days of extended sleep in a laboratory reflect an individual's optimal sleep duration (OSD) and that the difference between OSD and habitual sleep duration (HSD) at home represents potential sleep debt (PSD). We found that OSD varies among individuals and PSD showed stronger correlation with subjective/objective sleepiness than actual sleep time, interacting with individual's vulnerability of sleep loss. Furthermore, only 1 h of PSD takes four days to recover to their optimal level. Recovery from PSD was also associated with the improvement in glycometabolism, thyrotropic activity and hypothalamic-pituitary-adrenocortical axis. Additionally, the increase (rebound) in total sleep time from HSD at the first extended sleep would be a simple indicator of PSD. These findings confirmed self-evaluating the degree of sleep debt at home as a useful clinical marker. To establish appropriate sleep habits, it is necessary to evaluate OSD, vulnerability to sleep loss, and sleep homeostasis characteristics on an individual basis.

One-night sleep deprivation induces changes in the DNA methylation and serum activity indices of stearoyl-CoA desaturase in young healthy men

Background

Sleep deprivation has been associated with obesity among adults, and accumulating data suggests that stearoyl-CoA desaturase 1 (SCD1) expression has a relevant impact on fatty acid (FA) composition of lipid pools and obesity. The aim of this study was to investigate the effect of one-night total sleep deprivation (TSD) on DNA methylation in the 5’-prime region of SCD1, and whether detected changes in DNA methylation are associated with SCD activity indices (product to precursor FA ratios; 16:1n-7/16:0 and 18:1n-9/18:0) derived from serum phospholipids (PL).

Methods

Sixteen young, normal-weight, healthy men completed two study sessions, one with one-night TSD and one with one-night normal sleep (NS). Sleep quality and length was assessed by polysomnography, and consisted of electroencephalography, electrooculography, and electromyography. Fasting whole blood samples were collected on the subsequent morning for analysis of DNA methylation and FAs in serum PL. Linear regression analyses were performed to assess the association between changes in DNA methylation and SCD activity indices.

Results

Three CpG sites close to the transcription start site (TSS) of SCD1 (cg00954566, cg24503796, cg14089512) were significantly differentially methylated in dependency of sleep duration (−log₁₀P-value > 1.3). Both SCD-16 and SCD-18 activity indices were significantly elevated (P < 0.05) following one-night TSD, and significantly associated with DNA methylation changes of the three mentioned probes in the 5’ region of SCD1.

Conclusion

Our results suggest a relevant link between TSD, hepatic SCD1 expression and de-novo fatty acid synthesis via epigenetically driven regulatory mechanisms.

Effects of sleep disruption and high fat intake on glucose metabolism in mice

Poor sleep quality or quantity impairs glycemic control and increases risk of disease under chronic conditions. Recovery sleep may offset adverse metabolic outcomes of accumulated sleep debt, but the extent to which this occurs is unclear. We examined whether recovery sleep improves glucose metabolism in mice subjected to prolonged sleep disruption, and whether high fat intake during sleep disruption exacerbates glycemic control. Adult male C57BL/6J mice were subjected to 18-h sleep fragmentation daily for 9 days, followed by 1 day of recovery. During sleep disruption, one group of mice was fed a high-fat diet (HFD) while another group was fed standard laboratory chow. Insulin sensitivity and glucose tolerance were assessed by insulin and glucose tolerance testing at baseline, after 3 and 7 days of sleep disruption, and at the end of the protocol after 24h of undisturbed sleep opportunity (recovery). To characterize changes in sleep architecture that are associated with sleep debt and recovery, we quantified electroencephalogram (EEG) recordings during sleep fragmentation and recovery periods from an additional group of mice. We now report that 9 days of 18-h daily sleep fragmentation significantly reduces rapid eye movement sleep (REMS) and non-rapid eye movement sleep (NREMS). Mice respond with increases in REMS, but not NREMS, during the daily 6-h undisturbed sleep opportunity. However, both REMS and NREMS increase significantly during the 24-h recovery period. Although sleep disruption alone has no effect in this protocol, high fat feeding in combination with sleep disruption impairs glucose tolerance, effects that are reversed by recovery sleep. Insulin sensitivity modestly improves after 3 days of sleep fragmentation and after 24h of recovery, with significantly greater improvements in mice exposed to HFD during sleep disruption. Improvements in both glucose tolerance and insulin sensitivity are associated with NREMS rebound, raising the possibility that this sleep phase contributes to restorative effects of recovery sleep on glycemic control.

Sleep quality and risk of diabetes and coronary artery disease among young men

AIMS

To assess the time-dependent effect of sleep quality on diabetes and coronary artery disease (CAD) incidence among young adults.

METHODS

Incident rates of diabetes and CAD during a mean follow-up of 6.4 ± 4.1 years were assessed among 26,023 men (mean age 30.9 ± 5.6 years) of the Metabolic Lifestyle and Nutrition Assessment in Young Adults stratified by sleep quality at baseline, as assessed by the Mini-Sleep Questionnaire (MSQ). Incident diabetes and CAD were analyzed using a Cox proportional hazard model.

RESULTS

There were 445 cases of diabetes and 92 cases of CAD during 151,312 person-years. An abnormal MSQ score was associated with a 53 % higher incidence of diabetes (95 % CI 1.22-1.94, p < 0.001) compared to those with a normal score, after adjustment for clinical and biochemical diabetes risk factors. The increased risk associated with abnormal sleep quality remained when MSQ was modeled as a continuous time-dependent variable in a multivariable model (HR = 1.036, 95 % CI 1.024-1.049, p < 0.001). The increased risk was higher among overweight or obese participants (BMI and MSQ interaction p = 0.046). Sustained abnormality in MSQ score resulted in higher HR for diabetes (2.35; 95 % CI 1.564-3.519, p < 0.001). In addition, abnormal sleep quality was associated with a 2.38 higher incidence of CAD (95 % CI 1.38-4.11, p = 0.002), after adjustment for traditional clinical and biochemical risk factors.

CONCLUSIONS

Sleep quality contributes to the development of diabetes and CAD in apparently healthy young adults in a time-dependent manner. The use of a simple questionnaire to assess sleep quality may be a useful tool for risk stratification in this population.

Sleep Restriction Enhances the Daily Rhythm of Circulating Levels of Endocannabinoid 2-Arachidonoylglycerol

STUDY OBJECTIVES

Increasing evidence from laboratory and epidemiologic studies indicates that insufficient sleep may be a risk factor for obesity. Sleep curtailment results in stimulation of hunger and food intake that exceeds the energy cost of extended wakefulness, suggesting the involvement of reward mechanisms. The current study tested the hypothesis that sleep restriction is associated with activation of the endocannabinoid (eCB) system, a key component of hedonic pathways involved in modulating appetite and food intake.

METHODS

In a randomized crossover study comparing 4 nights of normal (8.5 h) versus restricted sleep (4.5 h) in healthy young adults, we examined the 24-h profiles of circulating concentrations of the endocannabinoid 2-arachidonoylglycerol (2-AG) and its structural analog 2-oleoylglycerol (2-OG). We concomitantly assessed hunger, appetite, and food intake under controlled conditions.

RESULTS

A robust daily variation of 2-AG concentrations with a nadir around the middle of the sleep/overnight fast, followed by a continuous increase culminating in the early afternoon, was evident under both sleep conditions but sleep restriction resulted in an amplification of this rhythm with delayed and extended maximum values. Concentrations of 2-OG followed a similar pattern, but with a lesser amplitude. When sleep deprived, participants reported increases in hunger and appetite concomitant with the afternoon elevation of 2-AG concentrations, and were less able to inhibit intake of palatable snacks.

CONCLUSIONS

Our findings suggest that activation of the eCB system may be involved in excessive food intake in a state of sleep debt and contribute to the increased risk of obesity associated with insufficient sleep.

COMMENTARY

A commentary on this article appears in this issue on page 495.

Metabolic and hormonal effects of 'catch-up' sleep in men with chronic, repetitive, lifestyle-driven sleep restriction

OBJECTIVE

Acutely restricting sleep worsens insulin sensitivity in healthy individuals whose usual sleep is normal in duration and pattern. The effect of recovery or weekend 'catch-up' sleep on insulin sensitivity and metabolically active hormones in individuals with chronic sleep restriction who regularly 'catch-up' on sleep at weekends is as yet unstudied.

DESIGN

19 men (mean ± SEM age 28·6 ± 2·0 years, BMI 26·0 ± 0·8 kg/m(2) ) with at least 6 months' history (5·1 ± 0·9 years) of lifestyle-driven, restricted sleep during the working week (373 ± 6·6 min/night) with regular weekend 'catch-up' sleep (weekend sleep extension 37·4 ± 2·3%) completed an in-laboratory, randomized, crossover study comprising two of three conditions, stratified by age. Conditions were 3 weekend nights of 10 hours, 6 hours or 10 hours time-in-bed with slow wave sleep (SWS) suppression using targeted acoustic stimuli.

MEASUREMENTS

Insulin sensitivity was measured in the morning following the 3rd intervention night by minimal modelling of 19 samples collected during a 2-h oral glucose tolerance test. Glucose, insulin, c-peptide, leptin, peptide YY (PYY), ghrelin, cortisol, testosterone and luteinizing hormone (LH) were measured from daily fasting blood samples; HOMA-IR, HOMA-β and QUICKI were calculated.

RESULTS

Insulin sensitivity was higher following three nights of sleep extension compared to sustained sleep restriction. Fasting insulin, c-peptide, HOMA-IR, HOMA-β, leptin and PYY decreased with 'catch-up' sleep, QUICKI and testosterone increased, while morning cortisol and LH did not change. Targeted acoustic stimuli reduced SWS by 23%, but did not alter insulin sensitivity.

CONCLUSIONS

Three nights of 'catch-up' sleep improved insulin sensitivity in men with chronic, repetitive sleep restriction. Methods to improve metabolic health by optimizing sleep are plausible.

Prolonged daily light exposure increases body fat mass through attenuation of brown adipose tissue activity

Disruption of circadian rhythmicity is associated with obesity and related disorders, including type 2 diabetes and cardiovascular disease. Specifically, prolonged artificial light exposure associates with obesity in humans, although the underlying mechanism is unclear. Here, we report that increasing the daily hours of light exposure increases body adiposity through attenuation of brown adipose tissue (BAT) activity, a major contributor of energy expenditure. Mice exposed to a prolonged day length of 16- and 24-h light, compared with regular 12-h light, showed increased adiposity without affecting food intake or locomotor activity. Mechanistically, we demonstrated that prolonged day length decreases sympathetic input into BAT and reduces β3-adrenergic intracellular signaling. Concomitantly, prolonging day length decreased the uptake of fatty acids from triglyceride-rich lipoproteins, as well as of glucose from plasma selectively by BAT. We conclude that impaired BAT activity is an important mediator in the association between disturbed circadian rhythm and adiposity, and anticipate that activation of BAT may overcome the adverse metabolic consequences of disturbed circadian rhythmicity.

Altered sigma-1 receptor expression in two animal models of cognitive impairment

PURPOSE

Sigma-1 receptors are involved in learning and memory processes. We assessed sigma-1 receptor expression and memory function in two animal models of cognitive impairment.

PROCEDURES

Male Wistar-Hannover rats were either lesioned by unilateral injection of N-methyl-D-aspartic acid in the nucleus basalis, or deprived of rapid eye movement sleep for 48 h, using the modified multiple platform method. Sigma-1 receptor expression was examined with the positron emission tomography radiotracer [(11)C]SA4503, immunohistochemistry, and Western blotting.

RESULTS

Cortical tracer uptake after 1 week was not significantly affected by lesioning. Immunohistochemistry revealed moderate increases of sigma-1 receptors at bregma level -2.8, in parietal cortex layer V of the lesioned hemisphere. Sleep deprivation lowered passive avoidance test scores and reduced [(11)C]SA4503 accumulation and sigma-1 receptor expression in pons.

CONCLUSIONS

Cholinergic lesioning causes an increase of sigma-1 receptor expression in a small cortical area which may be neuroprotective. Sleep deprivation decreases receptor expression in midbrain and pons.

Rodent models to study the metabolic effects of shiftwork in humans

Our current 24-h society requires an increasing number of employees to work nightshifts with millions of people worldwide working during the evening or night. Clear associations have been found between shiftwork and the risk to develop metabolic health problems, such as obesity. An increasing number of studies suggest that the underlying mechanism includes disruption of the rhythmically organized body physiology. Normally, daily 24-h rhythms in physiological processes are controlled by the central clock in the brain in close collaboration with peripheral clocks present throughout the body. Working schedules of shiftworkers greatly interfere with these normal daily rhythms by exposing the individual to contrasting inputs, i.e., at the one hand (dim)light exposure at night, nightly activity and eating and at the other hand daytime sleep and reduced light exposure. Several different animal models are being used to mimic shiftwork and study the mechanism responsible for the observed correlation between shiftwork and metabolic diseases. In this review we aim to provide an overview of the available animal studies with a focus on the four most relevant models that are being used to mimic human shiftwork: altered timing of (1) food intake, (2) activity, (3) sleep, or (4) light exposure. For all studies we scored whether and how relevant metabolic parameters, such as bodyweight, adiposity and plasma glucose were affected by the manipulation. In the discussion, we focus on differences between shiftwork models and animal species (i.e., rat and mouse). In addition, we comment on the complexity of shiftwork as an exposure and the subsequent difficulties when using animal models to investigate this condition. In view of the added value of animal models over human cohorts to study the effects and mechanisms of shiftwork, we conclude with recommendations to improve future research protocols to study the causality between shiftwork and metabolic health problems using animal models.

The metabolic burden of sleep loss

In parallel with the increasing prevalence of obesity and type 2 diabetes, sleep loss has become common in modern societies. An increasing number of epidemiological studies show an association between short sleep duration, sleep disturbances, and circadian desynchronisation of sleep with adverse metabolic traits, in particular obesity and type 2 diabetes. Furthermore, experimental studies point to distinct mechanisms by which insufficient sleep adversely affects metabolic health. Changes in the activity of neuroendocrine systems seem to be major mediators of the detrimental metabolic effects of insufficient sleep, through favouring neurobehavioural outcomes such as increased appetite, enhanced sensitivity to food stimuli, and, ultimately, a surplus in energy intake. The effect of curtailed sleep on physical activity and energy expenditure is less clear, but changes are unlikely to outweigh increases in food intake. Although long-term interventional studies proving a cause and effect association are still scarce, sleep loss seems to be an appealing target for the prevention, and probably treatment, of metabolic disease.

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.

Sleep Is Not for Slackers

Sufficient sleep is as important as healthy eating and regular exercise to maintain a healthy lifestyle. However, many individuals do not obtain enough sleep or follow healthy sleep hygiene recommendations. The interaction of both biological and behavioral factors may affect sleep. Recommendations of healthy sleep habits that may assist in improving sleep quality and quantity are discussed in this article.

Sleep duration and cardiometabolic risk factors among individuals with type 2 diabetes

OBJECTIVE

To examine the association between sleep duration and cardiometabolic risk factors among individuals with recently diagnosed type 2 diabetes (n = 391).

METHODS

Sleep duration was derived using a combination of questionnaire and objective heart rate and movement sensing in the UK ADDITION-Plus study (2002-2007). Adjusted means were estimated for individual cardiometabolic risk factors and clustered cardiometabolic risk (CCMR) by five categories of sleep duration.

RESULTS

We observed a J-shaped association between sleep duration and CCMR - individuals sleeping 7 to <8 h had a significantly better CCMR profile than those sleeping ≥9 h. Independent of physical activity and sedentary time, individuals sleeping 7 to <8 h had lower triacylglycerol (0.62 mmol/l (0.29, 1.06)) and higher high-density lipoprotein (HDL)-cholesterol levels (0.23 mmol/l (0.16, 0.30)) compared with those sleeping ≥9 h, and a lower waist circumference (7.87 cm (6.06, 9.68)) and body mass index (BMI) (3.47 kg/m(2) (2.69, 4.25)) than those sleeping <6 h. Although sleeping 7 to <8 h was associated with lower levels of systolic and diastolic blood pressure, HbA1c, total cholesterol, and low-density lipoprotein (LDL)-cholesterol, these associations were not statistically significant.

CONCLUSIONS

Sleep duration has a J-shaped association with CCMR in individuals with diabetes, independent of potential confounding. Health promotion interventions might highlight the importance of adequate sleep in this high-risk population.

Interactions between sleep, circadian function, and glucose metabolism: implications for risk and severity of diabetes

Sleep disturbances, including sleep insufficiency and sleep fragmentation, have been linked to abnormal glucose metabolism and increased diabetes risk. Well-controlled laboratory studies have provided insights regarding the underlying mechanisms. Several large prospective studies suggest that these sleep disturbances are associated with an increased risk of incident diabetes. Obstructive sleep apnea, which combines sleep fragmentation and hypoxemia, is a major risk factor for insulin resistance and possibly diabetes. Whether glycemic control in type 2 diabetes patients can be improved by treating sleep apnea remains controversial. Recently, sleep disturbances during pregnancy and their relationship to gestational diabetes and hyperglycemia have received considerable attention owing to potential adverse effects on maternal and fetal health. Additionally, evidence from animal models has identified disruption of the circadian system as a putative risk factor for adverse metabolic outcomes. The purpose of this review is to provide an update on the current state of knowledge linking sleep disturbances, circadian dysfunction, and glucose metabolism. Experimental, prospective, and interventional studies are discussed.