GHRH and sleep

The enigma of sleep: Implications of sleep neuroscience for the dental clinician and patient

BACKGROUND

Sleep disturbances have been shown to result in considerable morbidity and mortality. It is important for dental clinicians to understand the neuroscience behind sleep disorders.

TYPES OF STUDIES REVIEWED

The authors conducted a search of the literature published from January 1990 through March 2024 of sleep medicine-related articles, with a focus on neuroscience. The authors prioritized articles about the science of sleep as related to dental medicine.

RESULTS

The authors found a proliferation of articles related to sleep neuroscience along with its implications in dental medicine. The authors also found that the intricate neuroscientific principles of sleep medicine are being investigated robustly. The salient features of, and the differences between, central and obstructive sleep apneas have been elucidated. Sleep genes, such as CRY, PER1, PER2, and CLOCK, and their relationship to cancer and neurodegeneration are also additions to this rapidly developing science.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The dental clinician has the potential to be the first to screen patients for possible sleep disorders and make prompt referrals to the appropriate medical professionals. This can be lifesaving as well as minimize potential future morbidity for the patient.

Tripping on the edge of consciousness

Herein the major accomplishments, trials and tribulations, and epiphanies experienced by James M. Krueger over the course of his career in sleep research are presented. They include the characterization of a) the supranormal EEG delta waves occurring during NREMS post sleep loss, b) Factor S as a muramyl peptide, c) the physiological roles of cytokines in sleep regulation, d) multiple other sleep regulatory substances, e) the dramatic changes in sleep over the course of infectious diseases, and f) sleep initiation within small neuronal/glial networks. The theory that the preservation of brain plasticity is the primordial sleep function is briefly discussed. These accomplishments resulted from collaborations with many outstanding scientists including James M. Krueger's mentors (John Pappenheimer and Manfred Karnovsky) and collaborators later in life, including Charles Dinarello, Louis Chedid, Mark Opp, Ferenc Obal jr., Dave Rector, Ping Taishi, Linda Toth, Jeannine Majde, Levente Kapas, Eva Szentirmai, Jidong Fang, Chris Davis, Sandip Roy, Tetsuya Kushikata, Fabio Garcia-Garcia, Ilia Karatsoreos, Mark Zielinski, and Alok De, plus many students, e.g. Jeremy Alt, Kathryn Jewett, Erika English, and Victor Leyva-Grado.

Sleep and dreaming in the light of reactive and predictive homeostasis

Dreams are often viewed as fascinating but irrelevant mental epihenomena of the sleeping mind with questionable functional relevance. Despite long hours of oneiric activity, and high individual differences in dream recall, dreams are lost into oblivion. Here, we conceptualize dreaming and dream amnesia as inherent aspects of the reactive and predictive homeostatic functions of sleep. Mental activity during sleep conforms to the interplay of restorative processes and future anticipation, and particularly during the second half of the night, it unfolds as a special form of non-constrained, self-referent, and future-oriented cognitive process. Awakening facilitates constrained, goal-directed prospection that competes for shared neural resources with dream production and dream recall, and contributes to dream amnesia. We present the neurophysiological aspects of reactive and predictive homeostasis during sleep, highlighting the putative role of cortisol in predictive homeostasis and forgetting dreams. The theoretical and methodological aspects of our proposal are discussed in relation to the study of dreaming, dream recall, and sleep-related cognitive processes.

Photoperiod-driven concurrent changes in hypothalamic and brainstem transcription of sleep and immune genes in migratory redheaded bunting

The molecular regulation of sleep in avian migrants is still obscure. We thus investigated this in migratory redheaded buntings, where four life-history states (LHS; i.e. non-migratory, pre-migratory, migratory and refractory states) were induced. There was increased night-time activity (i.e. Zugunruhe) during the migratory state with reduced daytime activity. The recordings of the sleep-wake cycle in buntings showed increased night-time active wakefulness coupled with drastically reduced front and back sleep during migratory phase. Interestingly, we found the buntings to feed and drink even after lights-off during migration. Gene expression studies revealed increased hypothalamic expression of glucocorticoid receptor (nr3c1), and pro-inflammatory cytokines (il1b and il6) in pre-migratory and migratory states, respectively, whereas in brainstem Ca2+/calmodulin-dependent protein kinase 2 (camk2) was upregulated during the migratory state. This suggested a heightened pro-inflammatory state during migration which is a feature of chronic sleep loss, and a possible role of Ca2+ signalling in promoting wakefulness. In both the hypothalamus and brainstem, the expression of melatonin receptors (mel1a and mel1b) was increased in the pre-migratory state, and growth hormone-releasing hormone (ghrh, known to induce sleep) was reduced during the migratory state. The current results demonstrate key molecules involved in the regulation of sleep-wake cycle across LHS in migratory songbirds.

Differential plasticity and fate of brain-resident and recruited macrophages during the onset and resolution of neuroinflammation

Microglia and border-associated macrophages (BAMs) are brain-resident self-renewing cells. Here, we examined the fate of microglia, BAMs, and recruited macrophages upon neuroinflammation and through resolution. Upon infection, Trypanosoma brucei parasites invaded the brain via its border regions, triggering brain barrier disruption and monocyte infiltration. Fate mapping combined with single-cell sequencing revealed microglia accumulation around the ventricles and expansion of epiplexus cells. Depletion experiments using genetic targeting revealed that resident macrophages promoted initial parasite defense and subsequently facilitated monocyte infiltration across brain barriers. These recruited monocyte-derived macrophages outnumbered resident macrophages and exhibited more transcriptional plasticity, adopting antimicrobial gene expression profiles. Recruited macrophages were rapidly removed upon disease resolution, leaving no engrafted monocyte-derived cells in the parenchyma, while resident macrophages progressively reverted toward a homeostatic state. Long-term transcriptional alterations were limited for microglia but more pronounced in BAMs. Thus, brain-resident and recruited macrophages exhibit diverging responses and dynamics during infection and resolution.

Carbohydrate and sleep: An evaluation of putative mechanisms

Sleep problems are extremely common in industrialized countries and the possibility that diet might be used to improve sleep has been considered. The topic has been reviewed many times, resulting in the frequent suggestion that carbohydrate increases the uptake of tryptophan by the brain, where it is metabolized into serotonin and melatonin, with the suggestion that this improves sleep. An alternative mechanism was proposed based on animal literature that has been largely ignored by those considering diet and sleep. The hypothesis was that, as in the hypothalamus there are glucose-sensing neurons associated with the sleep-wake cycle, we should consider the impact of carbohydrate-induced changes in the level of blood glucose. A meta-analysis found that after consuming a lower amount of carbohydrate, more time was spent in slow-wave sleep (SWS) and less in rapid-eye-movement sleep. As the credibility of alternative mechanisms has tended not to have been critically evaluated, they were considered by examining their biochemical, nutritional, and pharmacological plausibility. Although high carbohydrate consumption can increase the uptake of tryptophan by the brain, it only occurs with such low levels of protein that the mechanism is not relevant to a normal diet. After entering the brain tryptophan is converted to serotonin, a neurotransmitter known to influence so many different aspects of sleep and wakefulness, that it is not reasonable to expect a uniform improvement in sleep. Some serotonin is converted to melatonin, although the exogenous dose of melatonin needed to influence sleep cannot be credibly provided by the diet. This review was registered in the International Prospective Register of Systematic Reviews (CRD42020223560).

A practical nutritional guideline to manage neuroendocrine neoplasms through chronotype and sleep

Chronotype is the attitude of subjects to carry out their daily activities mainly in the morning ("lark") or in the evening ("owl"). The intermediate chronotype is located between these two categories. It has been demonstrated that chronotype can influence the incidence, course and response to treatments of tumors. In particular patients diagnosed with gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) and evening chronotype are characterized by unhealthy lifestyle, obesity, metabolic syndrome, a worsen cardiometabolic profile, a poor prognosis with a progressive disease and the development of metastasis. In addition, evening chronotype has been associated with sleep disturbances, which in turn have been related to tumor development and progression of tumors. There is a strict connection between sleep disturbances and NENs because of the hyperactivation of proangiogenic factors that caused aberrant neoangiogenesis. A nutritional tailored approach could represent a tool to align subjects with evening chronotype to physiological biological rhythms based on the properties of some macro and micronutrients of being substrate for melatonin synthesis. Thus, we aimed to provide an overview on the association of chronotype categories and sleep disturbances with NENs and to provide nutritional advices to manage subjects with NENs and these disturbances of circadian rhythm.

Different Intensities of Evening Exercise on Sleep in Healthy Adults: A Systematic Review and Network Meta-Analysis

The effects of different intensities of evening exercise on subsequent sleep remain contradictory. Thus, this systematic review and network meta-analysis aimed to compare and rank the effects of different intensities of acute evening exercise on sleep in healthy adults with good sleep. Articles were systematically searched journals indexed in the PubMed, Web of Science, Cochrane Library, Embase, and Scopus databases from inception to the 5th of May, 2022. The basic search terms included exercise, sleep and timing, which were combined with AND. Of the 12,203 retrieved, twenty-eight studies with 325 participants met the inclusion criteria. Results revealed that there were no significant differences in terms of impacts on sleep caused by different intensities of acute evening exercise, except that when compared to no exercise, acute evening high-intensity exercise decreased rapid eye movement sleep (mean difference [MD] = -1.95%, 95% credible interval [CI] = -3.58 to -0.35). Compared to no exercise, acute evening moderate-intensity exercise was ranked as the most potential method to improve sleep, displaying a trend to improve wake time after sleep onset (MD = -2.50 min, 95% CI = -8.17 to 1.62), sleep efficiency (MD = +0.41%, 95% CI = -0.71 to 1.66), the proportion of stage N1 (MD = -0.72%, 95% CI = -2.08 to 0.71) and N3 sleep (slow-wave sleep) (MD = +0.84%, 95% CI = -1.17 to 2.78). Acute evening low-intensity exercise displayed the greatest tendency to shorten sleep onset latency (MD = -1.02 min, 95% CI = -4.39 to 2.50) compared to no exercise. Overall, regardless of intensity, acute evening exercise completed before bedtime does not disrupt subsequent sleep in healthy young and middle-aged adults.

Eat, sleep, repeat - endocrine regulation of behavioural circadian rhythms

The adaptation of organisms to a rhythmic environment is mediated by an internal timing system termed the circadian clock. In mammals, molecular clocks are found in all tissues and organs. This circadian clock network regulates the release of many hormones, which in turn influence some of the most vital behavioural functions. Sleep-wake cycles are under strict circadian control with strong influence of rhythmic hormones such as melatonin, cortisol and others. Food intake, in contrast, receives circadian modulation through hormones such as leptin, ghrelin, insulin and orexin. A third behavioural output covered in this review is mating and bonding behaviours, regulated through circadian rhythms in steroid hormones and oxytocin. Together, these data emphasize the pervasive influence of the circadian clock system on behavioural outputs and its mediation through endocrine networks.

Sleep deprivation changes thimet oligopeptidase (THOP1) expression and activity in rat brain

The consequences of sleep deprivation on memory, cognition, nociception, stress, and endocrine function are related to the balance of neuropeptides, with peptidases being particularly essential. Thimet oligopeptidase (THOP1) is a metallopeptidase implicated in the metabolism of many sleep-related peptides, including angiotensin I, gonadotropin releasing hormone (GnRH), neurotensin, and opioid peptides. In the present study, we evaluated the effect of sleep deprivation and sleep recovery in male rats on THOP1 expression and specific activity in the central nervous system. In the striatum and hypothalamus, THOP1 activity decreased following sleep deprivation and a recovery period. Meanwhile, THOP1 activity and immunoexpression increased in the hippocampal dentate gyrus during the sleep recovery period. Changes in THOP1 expression after sleep deprivation and during sleep recovery can potentially alter the processing of neuropeptides. In particular, processing of opioid peptides may be related to the known increase in pain sensitivity in this model. These results suggest that THOP1 may be an important player in the effects of sleep deprivation.

The effect of night-time exercise on sleep architecture among well-trained male endurance runners

The aim of the present study was to investigate the effects of night-time (21:00 hours) high-intensity, intermittent exercise on sleep architecture among well-trained athletes in a laboratory setting. In a randomized, counterbalanced order, 11 well-trained male runners completed a simulated trail-running exercise (TRAIL) on a motorized treadmill and a resting condition (REST; no exercise during the day). After each condition, nocturnal autonomic nervous system activity and core body temperature (CBT) were measured and sleep was analysed using polysomnography and actigraphy. Markers of muscle damage (maximal voluntary contraction [MVC], plasma creatine kinase concentration [CK] and perceived muscle soreness) were recorded before and immediately (POST), 24 hr (H24) and 48 hr (H48) after exercise. TRAIL induced a high level of fatigue and mild exercise-induced muscle damage, as determined by a reduction in MVC (-9.4%, p < .01, d = -1.36) and increases in [CK] (+176.0%, p < .01, d = 1.49) and perceived muscle soreness (+4.5 UA, p < .01, d = 2.17) compared with REST at H24. A trend for increased non-rapid eye movement (+4.2%; p = .10; d = 0.86) and reduced rapid eye movement (-4.4%; p = .07; d = -0.87) during sleep was observed for TRAIL compared with the REST condition. Moreover, compared with REST, TRAIL significantly increased CBT and nocturnal HR during the first part of the night. In conclusion, sleep architecture was modified after night-time, high-intensity exercise among well-trained runners.

Nicotinic acid promotes sleep through prostaglandin synthesis in mice

Nicotinic acid has been used for decades for its antiatherogenic properties in humans. Its actions on lipid metabolism intersect with multiple sleep regulatory mechanisms, but its effects on sleep have never been documented. For the first time, we investigated the effects of acute systemic administration of nicotinic acid on sleep in mice. Intraperitoneal and oral gavage administration of nicotinic acid elicited robust increases in non-rapid-eye movement sleep (NREMS) and decreases in body temperature, energy expenditure and food intake. Preventing hypothermia did not affect its sleep-inducing actions suggesting that altered sleep is not secondary to decreased body temperature. Systemic administration of nicotinamide, a conversion product of nicotinic acid, did not affect sleep amounts and body temperature, indicating that it is not nicotinamide that underlies these actions. Systemic administration of monomethyl fumarate, another agonist of the nicotinic acid receptor GPR109A, fully recapitulated the somnogenic and thermoregulatory effects of nicotinic acid suggesting that they are mediated by the GPR109A receptor. The cyclooxygenase inhibitor indomethacin completely abolished the effects of nicotinic acid indicating that prostaglandins play a key role in mediating the sleep and thermoregulatory responses of nicotinic acid.

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.

Obsessive-compulsive disorder and growth factors: A comparative review

The goal of this article is to clarify the role of various growth factors in the establishment and progression of obsessive-compulsive disorder (OCD). OCD is a chronic mental disorder with recurrent intrusive thoughts and/or repetitive compulsive behaviors that increase during stressful periods. Growth and neurotrophic factors may be contributing factors in the pathophysiology of OCD. Many of them are synthesized and released within the central nervous system and act as trophic agents in neurons; some of them are involved in brain growth, development, neurogenesis, myelination and plasticity, while others take part in the protection of the nervous system following brain injuries. This paper attempts to identify all articles investigating the relationship between OCD and neurotrophic and growth factors, in both animal and human studies, with a focus on adult brain studies. Based on the PubMed and Scopus and Science Direct search tools, the available articles and studies are reviewed. Out of 230 records in total, the ones related to our review topic were taken into account to further understand the pathophysiological mechanism(s) of OCD, providing methods to improve its symptoms via the modification of neurotrophins and growth factor imbalances.

Growth and mouth breathers

OBJECTIVE

To assess the relationship between mouth breathing and growth disorders among children and teenagers.

DATA SOURCE

Search on MEDLINE database, over the last 10 years, by using the following terms: "mouth breathing", "adenotonsilar hypertrophy", "allergic rhinitis", "sleep disturbance" AND "growth impairment", "growth hormone", "failure to thrive", "short stature", or "failure to thrive".

DATA SUMMARY

A total of 247 articles were identified and, after reading the headings, this number was reduced to 45 articles, whose abstracts were read and, of these, 20 were deemed important and were included in the review. In addition of these articles, references mentioned in them and specific books on mouth breathing deemed important were included. Hypertrophy of palatine and/or pharyngeal tonsils, whether associated with allergic rhinitis, as well as poorly controlled allergic rhinitis, are the main causes of mouth breathing in children. Respiratory sleep disorders are frequent among these patients. Several studies associate mouth breathing with reduced growth, as well as with reduced growth hormone release, which are reestablished after effective treatment of mouth breathing (clinical and/or surgical).

CONCLUSIONS

Mouth breathing should be considered as a potential cause of growth retardation in children; pediatricians should assess these patients in a broad manner.

Sleep-endocrine effects of growth hormone-releasing hormone (GHRH) in patients with schizophrenia

Changes in sleep-EEG after endocrine stimulation tests in patients with schizophrenia include reduced sleep efficiency, prolonged sleep latency and increased awaking after sleep onset Findings on sleep associated growth hormone (GH) secretion were ambiguous. The aim of this study was to elucidate the sleep-endocrine activity especially in the GH system of patients with schizophrenia after repeated administration of GHRH. The effect of repetitive injections of 4 × 50 μg GHRH between 22.00 and 01.00 h on sleep endocrine parameters was investigated in 9 patients diagnosed for schizophrenia. Patients did not receive any medication for one week. Concentrations of ACTH, cortisol, prolactin and GH were determined. Patients spent three consecutive nights in the sleep laboratory. Blood was taken every 20min. Results were compared with matched healthy controls. A non-significant prolonged sleep onset latency and increased time awake was found in patients compared to controls. Sleep stage 2 was significantly reduced in patients. No significant difference in ACTH and cortisol was detected, whereas the GH secretion in patients following GHRH stimulation was significantly elevated compared to controls. Our results in drug free patients confirm already known changes in sleep-EEG in these patients. The GH response to GHRH-stimulation indicates a different regulatory sensitivity of the system between daytime and night-time.

Abnormal Growth and Feeding Behavior in Upper Airway Obstruction in Rats

Pediatric obstructive sleep apnea (OSA) is a syndrome manifesting with snoring and increased respiratory effort due to increased upper airway resistance. In addition to cause the abnormal sleep, this syndrome has been shown to elicit either growth retardation or metabolic syndrome and obesity. Treating OSA by adenotonsillectomy is usually associated with increased risk for obesity, despite near complete restoration of breathing and sleep. However, the underlying mechanism linking upper airways obstruction (AO) to persistent change in food intake, metabolism, and growth remains unclear. Rodent models have examined the impact of intermittent hypoxia on metabolism. However, an additional defining feature of OSA that is not related to intermittent hypoxia is enhanced respiratory loading leading to increased respiratory effort and abnormal sleep. The focus of this mini review is on recent evidence indicating the persistent abnormalities in endocrine regulation of feeding and growth that are not fully restored by the chronic upper AO removal in rats. Here, we highlight important aspects related to abnormal regulation of metabolism that are not related to intermittent hypoxia per se, in an animal model that mimics many of the clinical features of pediatric OSA. Our evidence from the AO model indicates that obstruction removal may not be sufficient to prevent the post-removal tendency for abnormal growth.

Changes of Cerebral and/or Peripheral Adenosine A₁ Receptor and IGF-I Concentrations under Extended Sleep Duration in Rats

Extended sleep improves sustained attention and reduces sleep pressure in humans. Downregulation of adenosine A₁ receptor (A₁R) and modulation of the neurotrophic factor insulin growth factor-1 (IGF-I) in brain structures controlling attentional capacities could be involved. In the frontal cortex and hippocampus of rats, we measured adenosine A₁R and IGF-I protein concentrations after photoperiod-induced sleep extension. Two groups of twelve rats were adapted over 14 days to a habitual (CON) 12:12 light-dark (LD) schedule and an extended (EXT) 16:8 LD schedule. IGF-I content was also measured in plasma, liver, and skeletal muscle. In EXT, compared to CON rats, A₁R content in the frontal cortex was significantly lower (p < 0.05), while IGF-I content was higher (p < 0.001), and no significant change was observed in the hippocampus. IGF-I content in plasma and muscle was higher (p < 0.001 and p < 0.01), while it was lower in liver (p < 0.001). The absolute weight and weight gain were higher in EXT rats (p < 0.01). These data suggest that 14 days under a 16:8 LD photoperiod respectively down- and upregulated cortical A₁R and IGF-I levels. This photoperiod induced an anabolic profile with increased weight gain and circulating and muscular IGF-I levels. An extension of sleep duration might favor cerebral and peripheral anabolism, which may help attentional and physical capacities.

Altered sleep patterns in patients with non-functional GHRH receptor

OBJECTIVES

GH-releasing hormone (GHRH) exerts hypnotic actions increasing the non-rapid eye movement (NREM) sleep. Conversely, GH stimulates the REM sleep. GH deficiency (GHD) often leads to sleep problems, daytime fatigue and reduced quality of life (QoL). GHD may be due to lack of hypothalamic GHRH or destruction of somatotroph cells. We have described a cohort with isolated GHD (IGHD) due to GHRH resistance caused by a homozygous null mutation (c.57 + 1G > A) in the GHRH receptor gene. They have normal QoL and no obvious complaints of chronic tiredness. The aim of this study was to determine the sleep quality in these subjects.

METHODS

A cross-sectional study was carried out in 21 adult IGHD subjects, and 21 age- and gender-matched controls. Objective sleep assessment included polygraphic records of the awake, stages NREM [N1 (drowsiness), N2 and N3 (already sleeping)] and REM (R). Subjective evaluation included the Pittsburgh Sleep Quality Index, the Insomnia Severity Index and the Epworth Sleepiness Scale.

RESULTS

IGHD subjects showed a reduction in sleep efficiency (P = 0.007), total sleep time (P = 0.028), duration of N2 and R in minutes (P = 0.026 and P = 0.046 respectively), but had increased duration and percentage of N1 stage (P = 0.029 and P = 0.022 respectively), wake (P = 0.007) and wake-time after sleep onset (P = 0.017). There was no difference in N3 or in sleep quality questionnaire scores.

CONCLUSION

Patients with IGHD due to GHRH resistance exhibit objective reduction in the sleep quality, with changes in NREM and REM sleep, with no detectable subjective consequences. GHRH resistance seems to have a preponderant role over GHD in the sleep quality of these subjects.

Corticotropin-releasing hormone induces depression-like changes of sleep electroencephalogram in healthy women

We reported previously that repetitive intravenous injections of corticotropin-releasing hormone (CRH) around sleep onset prompt depression-like changes in certain sleep and endocrine activity parameters (e.g. decrease of slow-wave sleep during the second half of the night, blunted growth hormone peak, elevated cortisol concentration during the first half of the night). Furthermore a sexual dimorphism of the sleep-endocrine effects of the hormones growth hormone-releasing hormone and ghrelin was observed. In the present placebo-controlled study we investigated the effect of pulsatile administration of 4×50μg CRH on sleep electroencephalogram (EEG) and nocturnal cortisol and GH concentration in young healthy women. After CRH compared to placebo, intermittent wakefulness increased during the total night and the sleep efficiency index decreased. During the first third of the night, REM sleep and stage 2 sleep increased and sleep stage 3 decreased. Cortisol concentration was elevated throughout the night and during the first and second third of the night. GH secretion remained unchanged. Our data suggest that after CRH some sleep and endocrine activity parameters show also depression-like changes in healthy women. These changes are more distinct in women than in men.

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.

Effects of growth hormone-releasing hormone on sleep and brain interstitial fluid amyloid-β in an APP transgenic mouse model

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by impairment of cognitive function, extracellular amyloid plaques, intracellular neurofibrillary tangles, and synaptic and neuronal loss. There is substantial evidence that the aggregation of amyloid β (Aβ) in the brain plays a key role in the pathogenesis of AD and that Aβ aggregation is a concentration dependent process. Recently, it was found that Aβ levels in the brain interstitial fluid (ISF) are regulated by the sleep-wake cycle in both humans and mice; ISF Aβ is higher during wakefulness and lower during sleep. Intracerebroventricular infusion of orexin increased wakefulness and ISF Aβ levels, and chronic sleep deprivation significantly increased Aβ plaque formation in amyloid precursor protein transgenic (APP) mice. Growth hormone-releasing hormone (GHRH) is a well-documented sleep regulatory substance which promotes non-rapid eye movement sleep. GHRHR(lit/lit) mice that lack functional GHRH receptor have shorter sleep duration and longer wakefulness during light periods. The current study was undertaken to determine whether manipulating sleep by interfering with GHRH signaling affects brain ISF Aβ levels in APPswe/PS1ΔE9 (PS1APP) transgenic mice that overexpress mutant forms of APP and PSEN1 that cause autosomal dominant AD. We found that intraperitoneal injection of GHRH at dark onset increased sleep and decreased ISF Aβ and that delivery of a GHRH antagonist via reverse-microdialysis suppressed sleep and increased ISF Aβ. The diurnal fluctuation of ISF Aβ in PS1APP/GHRHR(lit/lit) mice was significantly smaller than that in PS1APP/GHRHR(lit/+) mice. However despite decreased sleep in GHRHR deficient mice, this was not associated with an increase in Aβ accumulation later in life. One of several possibilities for the finding is the fact that GHRHR deficient mice have GHRH-dependent but sleep-independent factors which protect against Aβ deposition.

Sleep in the intensive care unit

Sleep is an important physiologic process, and lack of sleep is associated with a host of adverse outcomes. Basic and clinical research has documented the important role circadian rhythm plays in biologic function. Critical illness is a time of extreme vulnerability for patients, and the important role sleep may play in recovery for intensive care unit (ICU) patients is just beginning to be explored. This concise clinical review focuses on the current state of research examining sleep in critical illness. We discuss sleep and circadian rhythm abnormalities that occur in ICU patients and the challenges to measuring alterations in circadian rhythm in critical illness and review methods to measure sleep in the ICU, including polysomnography, actigraphy, and questionnaires. We discuss data on the impact of potentially modifiable disruptors to patient sleep, such as noise, light, and patient care activities, and report on potential methods to improve sleep in the setting of critical illness. Finally, we review the latest literature on sleep disturbances that persist or develop after critical illness.

Sleep/Wake Dynamics Changes during Maturation in Rats

Objectives

Conventional scoring of sleep provides little information about the process of transitioning between vigilance states. We applied the state space technique (SST) using frequency band ratios to follow normal maturation of different sleep/wake states, velocities of movements, and transitions between states of juvenile (postnatal day 34, P34) and young adult rats (P71).

Design

24-h sleep recordings of eight P34 and nine P71 were analyzed using conventional scoring criteria and SST one week following implantation of telemetric transmitter. SST is a non-categorical approach that allows novel quantitative and unbiased examination of vigilance-states dynamics and state transitions. In this approach, behavioral changes are described in a 2-dimensional state space that is derived from spectral characteristics of the electroencephalography.

Measurements and Results

With maturation sleep intensity declines, the duration of deep slow wave sleep (DSWS) and light slow wave sleep (LSWS) decreases and increases, respectively. Vigilance state determination, as a function of frequency, is not constant; there is a substantial shift to higher ratio 1 in all vigilance states except DSWS. Deep slow wave sleep decreases in adult relative to juvenile animals at all frequencies. P71 animals have 400% more trajectories from Wake to LSWS (p = 0.005) and vice versa (p = 0.005), and 100% more micro-arousals (p = 0.021), while trajectories from LSWS to DSWS (p = 0.047) and vice versa (p = 0.033) were reduced by 60%. In both juvenile and adult animals, no significant changes were found in sleep velocity at all regions of the 2-dimensional state space plot; suggesting that maturation has a partial effect on sleep stability.

Conclusions

Here, we present novel and original evidence that SST enables visualization of vigilance-state intensity, transitions, and velocities that were not evident by traditional scoring methods. These observations provide new perspectives in sleep state dynamics and highlight the usefulness of this technique in exploring the development of sleep-wake activity.

Synthesis and biological evaluation of novel structure-related hGHRH agonistic analogs

Activity and half-life play key roles in the application of GHRH analogues. The GHRH monomers produced in a solid synthesizer were incubated, respectively, in NH4OH solution and lyophilized to obtain their dimers. The activities, specificities, and receptor affinities of the GHRH dimers were evaluated in rGH release/inhibition, rACTH/LH/PRL release, pituitary homogenate binding, and fluorescent staining. Compared to hGHRH(1-44)NH2 (S), PP-hGHRH(1-44)-GGC-CGG-hGHRH(44-1)-PP (2D), P-hGHRH(1-44)-GGC-CGG-hGHRH(44-1)-P (2E), (1)P-hGHRH(2-44)-GGC-CGG-hGHRH(44-2)-(1)P (2F), or hGHRH(1-44)-GGC-CGG-hGHRH(44-1) (2Y) had potency of 104 ± 16.7%, 94 ± 32.6%, 114 ± 16.6%, or 122 ± 14.5% and similar specificities. The inhibition effect of GHIH on rGH stimulated by GHRH dimer was in dose-/time-dependent manner. The staining of FITC-labeled dimer showed cytomembrane distribution and the binding ranking was 2F>2D>2Y>2E>S. 2F presents the strongest activity and the highest affinity to pituitary cells. The dimer with (1)Pro-GHRH stimulates stronger rGH release than that with (1)Tyr-GHRH and the N-terminal single cyclic amino acid is required for the stimulation.

Genetic dissection of sleep homeostasis

Sleep is a complex behavior both in its manifestation and regulation, that is common to almost all animal species studied thus far. Sleep is not a unitary behavior and has many different aspects, each of which is tightly regulated and influenced by both genetic and environmental factors. Despite its essential role for performance, health, and well-being, genetic mechanisms underlying this complex behavior remain poorly understood. One important aspect of sleep concerns its homeostatic regulation, which ensures that levels of sleep need are kept within a range still allowing optimal functioning during wakefulness. Uncovering the genetic pathways underlying the homeostatic aspect of sleep is of particular importance because it could lead to insights concerning sleep's still elusive function and is therefore a main focus of current sleep research. In this chapter, we first give a definition of sleep homeostasis and describe the molecular genetics techniques that are used to examine it. We then provide a conceptual discussion on the problem of assessing a sleep homeostatic phenotype in various animal models. We finally highlight some of the studies with a focus on clock genes and adenosine signaling molecules.

Rhythmic control of activity and sleep by class B1 GPCRs

Members of the class B1 family of G-protein coupled receptors (GPCRs) whose ligands are neuropeptides have been implicated in regulation of circadian rhythms and sleep in diverse metazoan clades. This review discusses the cellular and molecular mechanisms by which class B1 GPCRs, especially the mammalian VPAC2 receptor and its functional homologue PDFR in Drosophila and C. elegans, regulate arousal and daily rhythms of sleep and wake. There are remarkable parallels in the cellular and molecular roles played by class B1 intercellular signaling pathways in coordinating arousal and circadian timekeeping across multiple cells and tissues in these very different genetic model organisms.

Chronic upper airway obstruction induces abnormal sleep/wake dynamics in juvenile rats

OBJECTIVES

Conventional scoring of sleep provides little information about the process of transitioning between vigilance-states. We used the state space technique to explore whether rats with chronic upper airway obstruction (UAO) have abnormal sleep/wake states, faster movements between states, or abnormal transitions between states.

DESIGN

The tracheae of 22-day-old Sprague-Dawley rats were surgically narrowed to increase upper airway resistance with no evidence for frank obstructed apneas or hypopneas; 24-h electroencephalography of sleep/wake recordings of UAO and sham-control animals was analyzed using state space technique. This non-categorical approach allows quantitative and unbiased examination of vigilance-states and state transitions. Measurements were performed 2 weeks post-surgery at baseline and following administration of ritanserin (5-HT2 receptor antagonist) the next day to stimulate sleep.

MEASUREMENTS AND RESULTS

UAO rats spent less time in deep (delta-rich) slow wave sleep (SWS) and near transition zones between states. State transitions from light SWS to wake and vice versa and microarousals were more frequent and rapid in UAO rats, indicating that obstructed animals have more regions where vigilance-states are unstable. Ritanserin consolidated sleep in both groups by decreasing the number of microarousals and trajectories between wake and light SWS, and increasing deep SWS in UAO.

CONCLUSIONS

State space technique enables visualization of vigilance-state transitions and velocities that were not evident by traditional scoring methods. This analysis provides new quantitative assessment of abnormal vigilance-state dynamics in UAO in the absence of frank obstructed apneas or hypopneas.

Neuronal activity in the preoptic hypothalamus during sleep deprivation and recovery sleep

The preoptic hypothalamus is implicated in sleep regulation. Neurons in the median preoptic nucleus (MnPO) and the ventrolateral preoptic area (VLPO) have been identified as potential sleep regulatory elements. However, the extent to which MnPO and VLPO neurons are activated in response to changing homeostatic sleep regulatory demands is unresolved. To address this question, we continuously recorded the extracellular activity of neurons in the rat MnPO, VLPO and dorsal lateral preoptic area (LPO) during baseline sleep and waking, during 2 h of sleep deprivation (SD) and during 2 h of recovery sleep (RS). Sleep-active neurons in the MnPO (n = 11) and VLPO (n = 13) were activated in response to SD, such that waking discharge rates increased by 95.8 ± 29.5% and 59.4 ± 17.3%, respectively, above waking baseline values. During RS, non-rapid eye movement (REM) sleep discharge rates of MnPO neurons initially increased to 65.6 ± 15.2% above baseline values, then declined to baseline levels in association with decreases in EEG delta power. Increase in non-REM sleep discharge rates in VLPO neurons during RS averaged 40.5 ± 7.6% above baseline. REM-active neurons (n = 16) in the LPO also exhibited increased waking discharge during SD and an increase in non-REM discharge during RS. Infusion of A2A adenosine receptor antagonist into the VLPO attenuated SD-induced increases in neuronal discharge. Populations of LPO wake/REM-active and state-indifferent neurons and dorsal LPO sleep-active neurons were unresponsive to SD. These findings support the hypothesis that sleep-active neurons in the MnPO and VLPO, and REM-active neurons in the LPO, are components of neuronal circuits that mediate homeostatic responses to sustained wakefulness.

Growth hormone releasing hormone (GHRH) signaling modulates intermittent hypoxia-induced oxidative stress and cognitive deficits in mouse

Intermittent hypoxia (IH) during sleep, such as occurs in obstructive sleep apnea (OSA), leads to degenerative changes in the hippocampus, and is associated with spatial learning deficits in adult mice. In both patients and murine models of OSA, the disease is associated with suppression of growth hormone (GH) secretion, which is actively involved in the growth, development, and function of the central nervous system (CNS). Recent work showed that exogenous GH therapy attenuated neurocognitive deficits elicited by IH during sleep in rats. Here, we show that administration of the Growth Hormone Releasing Hormone (GHRH) agonist JI-34 attenuates IH-induced neurocognitive deficits, anxiety, and depression in mice along with reduction in oxidative stress markers such as MDA and 8-hydroxydeoxyguanosine, and increases in hypoxia inducible factor-1α DNA binding and up-regulation of insulin growth factor-1 and erythropoietin expression. In contrast, treatment with a GHRH antagonist (MIA-602) during intermittent hypoxia did not affect any of the IH-induced deleterious effects in mice. Thus, exogenous GHRH administered as the formulation of a GHRH agonist may provide a viable therapeutic intervention to protect IH-vulnerable brain regions from OSA-associated neurocognitive dysfunction. Sleep apnea, characterized by chronic intermittent hypoxia (IH), is associated with substantial cognitive and behavioral deficits. Here, we show that administration of a GHRH agonist (JI-34) reduces oxidative stress, increases both HIF-1α nuclear binding and downstream expression of IGF1 and erythropoietin (EPO) in hippocampus and cortex, and markedly attenuates water maze performance deficits in mice exposed to intermittent hypoxia during sleep.

Ghrelin and its interactions with growth hormone, leptin and orexins: implications for the sleep-wake cycle and metabolism

Several studies have shown that ghrelin administration promotes wakefulness in rodents, while in human males it induces sleep but has no effect in women. Ghrelin also plays an important role in metabolism and appetite regulation, and as described in this review may participate in the energy balance during sleep. In this review, we summarize some of the effects induced by ghrelin administration on the sleep-wake cycle in relation to the effects of other hormones, such as growth hormone, leptin, and orexin. Finally we discuss the relationship between sleep deprivation, obesity and ghrelin secretion pattern.

Impact of GH replacement therapy on sleep in adult patients with GH deficiency of pituitary origin

OBJECTIVES

We previously reported that adult patients with GH deficiency (GHD) due to a confirmed or likely pituitary defect, compared with healthy controls individually matched for age, gender, and BMI, have more slow-wave sleep (SWS) and higher delta activity (a marker of SWS intensity). Here, we examined the impact of recombinant human GH (rhGH) therapy, compared with placebo, on objective sleep quality in a subset of patients from the same cohort.

DESIGN

Single-blind, randomized, crossover design study.

METHODS

Fourteen patients with untreated GHD of confirmed or likely pituitary origin, aged 22-74 years, participated in the study. Patients with associated hormonal deficiencies were on appropriate replacement therapy. Polygraphic sleep recordings, with bedtimes individually tailored to habitual sleep times, were performed after 4 months on rhGH or placebo.

RESULTS

Valid data were obtained in 13 patients. At the end of the rhGH treatment period, patients had a shorter sleep period time than at the end of the placebo period (479±11 vs 431±19 min respectively; P=0.005), primarily due to an earlier wake-up time, and a decrease in the intensity of SWS (delta activity) (559±125 vs 794±219 μV(2) respectively; P=0.048).

CONCLUSIONS

Four months of rhGH replacement therapy partly reversed sleep disturbances previously observed in untreated patients. The decrease in delta activity associated with rhGH treatment adds further evidence to the hypothesis that the excess of high-intensity SWS observed in untreated pituitary GHD patients is likely to result from overactivity of the hypothalamic GHRH system due to the lack of negative feedback inhibition by GH.

A pathophysiologic approach to growth problems in children with attention-deficit/hyperactivity disorder

In recent years there has been an increasing trend in the diagnosis and treatment of children with attention-deficit/hyperactivity disorder (ADHD) worldwide. One of the most frequently discussed side effects of these treatments is related to problems of growth. In order to better understand what ADHD is and the mechanisms by which it could affect growth, this article reviews relevant data from a clinical and neurophysiologic perspective to improve understanding of this controversial issue.

Ablation of leptin signaling to somatotropes: changes in metabolic factors that cause obesity

Mice with somatotrope-specific deletion of the Janus kinase binding site in leptin receptors are GH deficient as young adults and become obese by 6 months of age. This study focused on the metabolic status of young (3-4.5 month old) preobese mutant mice. These mutants had normal body weights, lean body mass, serum leptin, glucose, and triglycerides. Mutant males and females showed significantly higher respiratory quotients (RQ) and lower energy output, resulting from a higher volume of CO(2) output and lower volume of O(2) consumption. Deletion mutant females were significantly less active than controls; they had higher levels of total serum ghrelin and ate more food. Mutant females also had lower serum insulin and higher glucagon. In contrast, deletion mutant males were not hyperphagic, but they were more active and spent less time sleeping. Adiponectin and resistin, both products of adipocytes, were increased in male and female mutant mice. In addition, mutant males showed an increase in circulating levels of the potent lipogenic hormone, glucose-dependent insulinotropic peptide. Taken together, these results indicate that mutant mice may become obese due to a reduction in lipid oxidation and energy expenditure. This may stem from GH deficiency. Reduced fat oxidation and enhanced insulin sensitivity (in females) are directly related to GH deficiency in mutant mice because GH has been shown by others to increase insulin sensitivity and fat oxidation and reduce carbohydrate oxidation. Gender-dependent alterations in metabolic signals may further exacerbate the future obese phenotype and affect the timing of its onset. Females show a delay in onset of obesity, perhaps because of their low serum insulin, which is lipogenic, whereas young males already have higher levels of the lipogenic hormone, glucose-dependent insulinotropic peptide. These findings signify that leptin signals to somatotropes are vital for the normal metabolic activity needed to optimize body composition.

Somatostatin varicosities contain the vesicular GABA transporter and contact orexin neurons in the hypothalamus

Somatostatin (SST) is a neuropeptide with known inhibitory actions in the hypothalamus, where it inhibits release of growth hormone-releasing hormone (GHRH), while also influencing the sleep-wake cycle. Here we investigated in the rat whether SST neurons might additionally release GABA (gamma-aminobutyric acid) or glutamate in different regions and whether they might contact orexin neurons that play an important role in the maintenance of wakefulness. In dual-immunostained sections viewed by epifluorescence microscopy, we examined if SST varicosities were immunopositive for the vesicular transporter for GABA (VGAT) or glutamate (VGLUT2) in the posterolateral hypothalamus and neighboring arcuate nucleus and median eminence. Of the SST varicosities in the posterolateral hypothalamus, 18% were immunopositive for VGAT, whereas ≤ 1% were immunopositive for VGLUT2. In the arcuate and median eminence, 26 and 64% were VGAT+ and < 3% VGLUT2 + , respectively. In triple-immunostained sections viewed by epifluorescence and confocal microscopy, SST varicosities were seen in contact with orexin somata, and of these varicosities, a significant proportion (23%) contained VGAT along with synaptophysin, the presynaptic marker for small synaptic vesicles, and a similar proportion (25%) abutted puncta that were immunostained for gephyrin, the postsynaptic marker for GABAergic synapses. Our results indicate that a significant proportion of SST varicosities in the hypothalamus have the capacity to release GABA, to form inhibitory synapses upon orexin neurons, and accordingly through their peptide and/or amino acid, to inhibit orexin neurons, as well as GHRH neurons. Thus while regulating GHRH release, SST neurons could serve to attenuate arousal and permit progression through the sleep cycle.

A dietary supplement containing chlorophytum borivilianum and velvet bean improves sleep quality in men and women

BACKGROUND

Impaired sleep quality is commonplace within industrialized societies, as evidenced by the increasing number of prescription sleep aids available. Certain herbal preparations have been suggested to provide a natural benefit to sleep; however, limited controlled data are available documenting this benefit. In the present study we tested the effect of an experimental dietary supplement, containing the active ingredients Chlorophytum borivilianum and Velvet bean, on sleep quality using the Pittsburgh Sleep Quality Index (PSQI).

METHODS

Eighteen healthy and active men and women, with evidence of impaired sleep quality, consumed the supplement daily for 28 days. The PSQI was administered before and after the intervention period. As indicators of safety, resting heart rate and blood pressure were measured, and a complete blood count, comprehensive metabolic panel, and lipid panel were determined.

RESULTS

Sleep quality was influenced by the supplement, as evidenced by an improvement in every category of the PSQI questionnaire (P < 0.05), with most category scores improving approximately 50% from pre to post intervention. No adverse outcomes were noted with use of the supplement, as indicated by no change in resting heart rate, blood pressure, or any bloodborne parameter.

CONCLUSIONS

An investigational dietary supplement containing the active ingredients Chlorophytum borivilianum and Velvet bean improves sleep quality in men and women. Additional placebo controlled trials are needed to corroborate these findings in individuals with self-reported sleeping difficulty.

Effects of replacement therapy on sleep architecture in children with growth hormone deficiency

OBJECTIVE

Children with GH deficiency (GHD) show a general decrease in electroencephalographic (EEG) arousability represented by a significant global decrease in Cyclic Alternating Pattern (CAP). The aim of the present study was to evaluate if sleep structure is influenced by GH substitutive therapy by analyzing the classical sleep architecture parameters and sleep microstructure by means of CAP.

SUBJECTS AND METHODS

Laboratory polysomnographic sleep recordings were obtained from five children affected by GHD (two girls and three boys; mean age: 4.6 ± 3.1 years), at baseline and after GH therapy, and from 10 normal healthy children (four girls and six boys, mean age: 5.6 ± 2.2 years).

RESULTS

Compared to controls, GHD subjects showed a reduced total sleep time with increased wakefulness and a consequent decrease in sleep efficiency; GH therapy was associated with an increase of the awakenings/hour and a large effect size was evident for sleep latency, sleep efficiency, and stage N3, which were decreased, and for stage W, which was increased. CAP appeared to be globally reduced and all phase A subtypes and CAP cycle showed a longer duration in GHD children vs. controls. GH substitutive treatment was followed by an increase in CAP rate (total, in N2, and in N3); additionally, A1 index was also significantly increased, especially during stage N3, with a very large effect size. On the other hand, A2 and A3 index and CAP cycle mean duration were reduced.

CONCLUSION

Sleep stage architecture seems to be influenced by the GH status, but the analysis of sleep microstructure by means of CAP reveals an enhancement of EEG slow oscillations in GHD patients (demonstrated by an increase in CAP rate and A1 index during N3) after the start of GH replacement therapy. These findings deserve to be verified in a larger trial.

Compression of the optic chiasm is associated with permanent shorter sleep duration in patients with pituitary insufficiency

OBJECTIVE

Patients with pituitary insufficiency often experience some degree of impaired sleep. Sleep-wake rhythm is regulated to a large extent by the suprachiasmatic nucleus (SCN). Because the SCN is located just superior to the optic chiasm, we hypothesized that a history of compression of the optic chiasm (CC) due to a tumour with suprasellar extension is associated with altered sleep patterns in patients with pituitary insufficiency.

DESIGN

Case-control study.

PATIENTS

We studied 38 patients (mean age 55·7 ± 13·1 years; 71·1% men) with CC and 18 patients (mean age 53·3 ± 16·6 years, 38·9% men) without CC.

MEASUREMENTS

Objective measures of sleep patterns were assessed by wrist actigraphy. Validated sleep questionnaires were used to evaluate subjective sleep parameters.

RESULTS

Objective total sleep duration was 36 min shorter in patients with CC than in patients without CC [454 (295-553) vs 490 (432-740) min, P = 0·034]. Moreover, patients with CC had a later habitual bedtime [23:15 (22:30-03:00) vs 22:55 (20:00-02:00) h, P = 0·044] and a later actigraphic sleep onset [23:57 (22:31-01:33) vs 23·16 (19:47-03:04) h, P = 0·020]. Linear regression analysis confirmed the difference in total sleep duration after adjustment for age, sex, body mass index, cranial radiotherapy and pituitary/hypothalamic surgery. Subjective sleep parameters were similar in both groups.

CONCLUSIONS

Compression of the optic chiasm due to a tumour with suprasellar extension is associated with permanent changes in total sleep duration in patients with pituitary insufficiency.

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.

Ghrelin in mental health, sleep, memory

Ghrelin acts as a neuropeptide. It participates in sleep-wake regulation. After systemic ghrelin treatment nonREM sleep is promoted in male humans and mice. This effect is influenced by gender, time of administration and depression. Ghrelin does not modulate sleep in healthy women and during the early morning in male subjects. In depressed women REM sleep is diminished after ghrelin. In elderly men and depressed men sleep promotion by ghrelin was preserved. In rats after central ghrelin feeding and wakefulness increased. The nocturnal secretion pattern of cortisol, GH, LH, FSH and hypothalamo-pituitary-thyroid hormones are influenced by ghrelin. Furthermore ghrelin appears to be related to memory and to be involved in the pathophysiology of CNS disorders, particularly depression.

Effect of sodium oxybate on growth hormone secretion in narcolepsy patients and healthy controls

Hypocretin deficiency causes narcolepsy and may affect neuroendocrine systems and body composition. Additionally, growth hormone (GH) alterations my influence weight in narcolepsy. Symptoms can be treated effectively with sodium oxybate (SXB; γ-hydroxybutyrate) in many patients. This study compared growth hormone secretion in patients and matched controls and established the effect of SXB administration on GH and sleep in both groups. Eight male hypocretin-deficient patients with narcolepsy and cataplexy and eight controls matched for sex, age, BMI, waist-to-hip ratio, and fat percentage were enrolled. Blood was sampled before and on the 5th day of SXB administration. SXB was taken two times 3 g/night for 5 consecutive nights. Both groups underwent 24-h blood sampling at 10-min intervals for measurement of GH concentrations. The GH concentration time series were analyzed with AutoDecon and approximate entropy (ApEn). Basal and pulsatile GH secretion, pulse regularity, and frequency, as well as ApEn values, were similar in patients and controls. Administration of SXB caused a significant increase in total 24-h GH secretion rate in narcolepsy patients, but not in controls. After SXB, slow-wave sleep (SWS) and, importantly, the cross-correlation between GH levels and SWS more than doubled in both groups. In conclusion, SXB leads to a consistent increase in nocturnal GH secretion and strengthens the temporal relation between GH secretion and SWS. These data suggest that SXB may alter somatotropic tone in addition to its consolidating effect on nighttime sleep in narcolepsy. This could explain the suggested nonsleep effects of SXB, including body weight reduction.

Angiotensin I-converting enzyme (ACE) activity and expression in rat central nervous system after sleep deprivation

Proteases are essential either for the release of neuropeptides from active or inactive proteins or for their inactivation. Neuropeptides have a fundamental role in sleep-wake cycle regulation and their actions are also likely to be regulated by proteolytic processing. Using fluorescence resonance energy transfer substrates, specific protease inhibitors and real-time PCR we demonstrate changes in angiotensin I-converting enzyme (ACE) expression and proteolytic activity in the central nervous system in an animal model of paradoxical sleep deprivation during 96 h (PSD). Male rats were distributed into five groups (PSD, 24 h, 48 h and 96 h of sleep recovery after PSD and control). ACE activity and mRNA levels were measured in hypothalamus, hippocampus, brainstem, cerebral cortex and striatum tissue extracts. In the hypothalamus, the significant decrease in activity and mRNA levels, after PSD, was only totally reversed after 96 h of sleep recovery. In the brainstem and hippocampus, although significant, changes in mRNA do not parallel changes in ACE specific activity. Changes in ACE activity could affect angiotensin II generation, angiotensin 1–7, bradykinin and opioid peptides metabolism. ACE expression and activity modifications are likely related to some of the physiological changes (cardiovascular, stress, cognition, metabolism function, water and energy balance) observed during and after sleep deprivation.

Circadian modulation of hepatic transcriptome in transgenic rats expressing human growth hormone

The secretory profile of growth hormone (GH) is sexually dimorphic in rats. In male transgenic (TG) rats expressing human GH (hGH) that we generated, the circulating levels of both hGH and endogenous GH are flattened with no male-type pulsatility. To elucidate the regulatory role of episodic GH profile on the liver, the hepatic transcriptome of male TG rats at the middle of the light and dark phases was characterized by genome-wide analyses as compared with that of male wild-type (WT) rats. Transcripts commonly up- or down-regulated regardless of the lighting conditions in TG rats were mainly enriched in the metabolism of xenobiotics. In TG rats, the gene expression profile was functionally feminized, verifying that the sexually dimorphic profile of GH rather than genetic sexuality is a stronger sex-determining factor on the hepatic transcriptome. The common transcripts which fluctuated during the day in both TG and WT rats were enriched in circadian rhythm signaling, and physiological rhythmicity was considered to be finely interconnected with liver metabolism via sexually dimorphic GH secretion. In contrast, some genes were differentially regulated in TG rats at only one of two time points measured, and others were fluctuated daily in only one genotype. In particular, some genes involved in the GH signaling pathway were included, suggesting the signal transduction is circadian-modulated depending upon the GH profile. Our transcriptome analyses clarified the regulatory role of episodic GH profile on the liver and strengthen the functional link between sexually dimorphic GH secretion, liver metabolism, and its circadian regulation.