Comparative Review of Approved Melatonin Agonists for the Treatment of Circadian Rhythm Sleep-Wake Disorders

Apparent resolution of hypersomnia episodes in two patients with Kleine-Levin syndrome following treatment with the melatonin receptor agonist ramelteon

Kleine-Levin syndrome (KLS) is a rare disorder characterized by episodic bouts of severe hypersomnia associated with cognitive and behavioral abnormalities and normal alertness and functioning in between episodes. The pathophysiology is unclear but may involve neurotransmitter abnormalities, hypothalamic/thalamic dysfunction, viral/autoimmune etiology, or circadian abnormalities. No single treatment has been shown to be reliably efficacious; lithium has demonstrated the most consistent efficacy, although many do not respond and its use is limited by side effects. Due to the evidence of circadian involvement, we hypothesized that strengthening circadian signals may ameliorate symptoms. Ramelteon is a potent melatonin receptor agonist. In this report, two patients with KLS are described with apparent resolution of hypersomnia episodes following ramelteon initiation.

CITATION

Dominguez D, Rudock R, Tomko S, Pathak S, Mignot E, Licis A. Apparent resolution of hypersomnia episodes in two patients with Kleine-Levin syndrome following treatment with the melatonin receptor agonist ramelteon. J Clin Sleep Med. 2024;20(4):657-662.

Improvement in non-24-h sleep-wake rhythm disorder in a sighted individual treated with a melatonin receptor agonist

Non-24-hour sleep-wake rhythm disorder (N24SWD) typically presents in patients with visual impairments that disrupt the ability to entrain to the 24 hour solar cycle. We discuss a 43 year old sighted man who presented with periodic daytime hypersomnia and nighttime insomnia, occasionally leading to <3 hours of sleep per day. Previous polysomnography showed an apnea hypopnea index of 6.2 events per hour. A sleep log of 3 months showed irregular time of sleep onset, and an average of 3 hours of sleep per day. Wrist actigraphy confirmed N24SWD. A trial of tasimelteon 20 mg/day resulting in improved daytime hypersomnia (pre-Epworth Sleepiness Scale (ESS) = 21/24, post-ESS = 5/24; a score of > 10/24 is considered sleepy). Follow-up actigraphy showed marked resolution of phase delay with an average of five hours of sleep. The case demonstrates that tasimelteon is a possible treatment for N24SWD in sighted individuals.

2-Phenylcyclopropylmethylamine (PCPMA) as a privileged scaffold for central nervous system drug design

The use of privileged scaffolds in medicinal chemistry is an effective way to accelerate the drug discovery process, especially at the hit/lead optimization stage. 2-Phenylcyclopropylmethylamine (PCPMA) is a less commonly used chemical scaffold in medicinal chemistry, but many PCPMA-containing compounds exert therapeutic effects for various diseases, in particular central nervous system (CNS) diseases such as depression, schizophrenia, sleep disorder, and Parkinson's disease. The backbone of the PCPMA scaffold enables a unique structure of an amino group linked to a benzene ring through an alkyl linker, making it a useful template for the design of bioactive compounds especially for CNS drug targets including aminergic GPCRs and transporters. This review summarizes the medicinal chemistry studies of PCPMA-containing drugs and drug-like molecules, their mechanisms of action, and biological activities. We conclude that PCPMA is a unique and useful privileged scaffold for CNS drug design.

Ameliorative effects of topical ramelteon on imiquimod-induced psoriasiform inflammation in mice

Psoriasis is a long-lasting, immune-related inflammatory skin disease that affects 2-3% of the global population. It is distinguished by erythematous, silvery, and scaly patches. Ramelteon is a type of melatonin agonist that is used to treat insomnia. It has enhanced non-classical immunomodulatory and anti-inflammatory activities. The aim of the study is to assess the ameliorative effects of topical ramelteon on imiquimod (IMQ)-aggravated psoriasiform-like dermatosis in mice. The 32 albino mouse males were placed into six groups of eight animals, all of them. With the exception of the control group, all groups gained a once-a-day regimen of topical imiquimod 5% cream at a dose of 62.5 mg for eight uninterrupted days, while mice in the control group gained vaseline-based ointment alternately. Immediately after an 8-day induction period in the imiquimod group, mice in the clobetasol and ramelteon treatment groups obtained a twice-daily regimen of topical clobetasol propionate 0.05% ointment and 0.1% ointment, respectively, for a further 8 days. This extends the total duration of the experimental study to 16 continuous days. The findings of our study found that ramelteon significantly mitigated the concentrations of inflammatory cytokines in the skin tissue, including interleukin (IL)-6, IL-17A, IL-23, tumor necrosis factor-α (TNF-α), and vascular endothelial growth factor (VEGF), as well as the scores associated with psoriatic lesions, including erythema, scaling, skin thickening, ear thickness, and overall cumulative PASI scores. Additionally, the anti-inflammatory impact of ramelteon was achieved by markedly increasing IL-10 levels in the skin tissue and correcting cutaneous histopathological alterations. Ramelteon ointment (0.1%) was comparable to that of clobetasol (0.05%) ointment in alleviating a mouse model of imiquimod-induced psoriasiform inflammation; this is probably due to its potential anti-inflammatory and immunomodulatory activities. Therefore, ramelteon could be a good additive option for therapeutic management of immune-triggered inflammatory conditions such as psoriasis.

Photoperiod and metabolic health: evidence, mechanism, and implications

Circadian rhythms are evolutionarily programmed biological rhythms that are primarily entrained by the light cycle. Disruption of circadian rhythms is an important risk factor for several metabolic disorders. Photoperiod is defined as total duration of light exposure in a day. With the extended use of indoor/outdoor light, smartphones, television, computers, and social jetlag people are exposed to excessive artificial light at night increasing their photoperiod. Importantly long photoperiod is not limited to any geographical region, season, age, or socioeconomic group, it is pervasive. Long photoperiod is an established disrupter of the circadian rhythm and can induce a range of chronic health conditions including adiposity, altered hormonal signaling and metabolism, premature ageing, and poor psychological health. This review discusses the impact of exposure to long photoperiod on circadian rhythms, metabolic and mental health, hormonal signaling, and ageing and provides a perspective on possible preventive and therapeutic approaches for this pervasive challenge.

Understanding the role of chronopharmacology for drug optimization: what do we know?

INTRODUCTION

Circadian rhythm influences the pharmacokinetics and pharmacodynamics of a number of drugs and affects their therapeutic efficacy and toxicity depending on the time of day they are administered. Chronopharmacology is a method for incorporating knowledge about circadian rhythm into pharmacotherapy. Chronotherapy, which is the clinical application of chronopharmacology, is particularly relevant when the risk and/or severity of symptoms of a disease change in a predictable manner over time. Chronotherapy has potential benefits in the treatment of many diseases.

AREAS COVERED

Although a considerable amount of knowledge about chronopharmacology and chronotherapy has been accumulated, its therapeutic application in clinical practice remains limited in terms of therapy optimization. Resolution of these issues will improve our ability to deliver adequate drug treatment.

EXPERT OPINION

We propose four approaches for promoting chronotherapy-based drug treatment in clinical practice: targeting drug development and regulatory authorities; education about chronotherapy; drug information for both health professionals and consumers; and a chronotherapy network.

Melatonin use in children and adolescents: A scoping review of caregiver perspectives

Despite melatonin's popularity as a pediatric sleep-aid, little has been investigated around caregivers' understanding and perception of melatonin use for their dependent. This scoping review analyzes the current literature on pediatric melatonin use, to understand how caregivers' perceptions around melatonin are shaped by their illness/medication-related beliefs, treatment experience and preferences. A literature search was conducted across Embase, Medline, PsycINFO, PubMed and Scopus, generating 184 results for screening against the inclusion criteria. Nineteen studies were retrieved, comprising of 1561 children and adolescents, aged 8.7 ± 2.3 years (range: 0-44 years), conducted primarily in the United States of America (n = 6), Canada (n = 3) and the Netherlands (n = 3). Studies were evaluated for their study design and caregiver-centered outcomes, encompassing: 1) illness/treatment-related beliefs, 2) treatment satisfaction/effectiveness, 3) treatment preference/acceptability, and 4) impact of child's sleep disturbance on caregivers' quality-of-life. Sleep disturbances necessitating melatonin use occurred alongside congenital/neurodevelopmental comorbidities in 18 studies (95%). Melatonin was commonly associated with "naturalness" and "safety". Concepts of treatment satisfaction versus effectiveness were minimally differentiated within included studies. Caregivers preferred concurrent use of melatonin and behavioral interventions for management of their dependents' sleep. Improved sleep in the dependent generally led to better quality-of-life for caregivers and their family.

360-Degree Perspectives on Obesity

Alarming statistics show that the number of people affected by excessive weight has surpassed 2 billion, representing approximately 30% of the world's population. The aim of this review is to provide a comprehensive overview of one of the most serious public health problems, considering that obesity requires an integrative approach that takes into account its complex etiology, including genetic, environmental, and lifestyle factors. Only an understanding of the connections between the many contributors to obesity and the synergy between treatment interventions can ensure satisfactory outcomes in reducing obesity. Mechanisms such as oxidative stress, chronic inflammation, and dysbiosis play a crucial role in the pathogenesis of obesity and its associated complications. Compounding factors such as the deleterious effects of stress, the novel challenge posed by the obesogenic digital (food) environment, and the stigma associated with obesity should not be overlooked. Preclinical research in animal models has been instrumental in elucidating these mechanisms, and translation into clinical practice has provided promising therapeutic options, including epigenetic approaches, pharmacotherapy, and bariatric surgery. However, more studies are necessary to discover new compounds that target key metabolic pathways, innovative ways to deliver the drugs, the optimal combinations of lifestyle interventions with allopathic treatments, and, last but not least, emerging biological markers for effective monitoring. With each passing day, the obesity crisis tightens its grip, threatening not only individual lives but also burdening healthcare systems and societies at large. It is high time we took action as we confront the urgent imperative to address this escalating global health challenge head-on.

Delayed sleep-wake phase disorder and its related sleep behaviors in the young generation

Delayed sleep-wake phase disorder (DSWPD) is a sleep disorder in which the habitual sleep-wake timing is delayed, resulting in difficulty in falling asleep and waking up at the desired time. Patients with DSWPD frequently experience fatigue, impaired concentration, sleep deprivation during weekdays, and problems of absenteeism, which may be further complicated by depressive symptoms. DSWPD is typically prevalent during adolescence and young adulthood. Although there are no studies comparing internationally, the prevalence of DSWPD is estimated to be approximately 3% with little racial differences between Caucasians and Asians. The presence of this disorder is associated with various physiological, genetic and psychological as well as behavioral factors. Furthermore, social factors are also involved in the mechanism of DSWPD. Recently, delayed sleep phase and prolonged sleep duration in the young generation have been reported during the period of COVID-19 pandemic-related behavioral restrictions. This phenomenon raises a concern about the risk of a mismatch between their sleep-wake phase and social life that may lead to the development of DSWPD after the removal of these restrictions. Although the typical feature of DSWPD is a delay in circadian rhythms, individuals with DSWPD without having misalignment of objectively measured circadian rhythm markers account for approximately 40% of the cases, wherein the psychological and behavioral characteristics of young people, such as truancy and academic or social troubles, are largely involved in the mechanism of this disorder. Recent studies have shown that DSWPD is frequently comorbid with psychiatric disorders, particularly mood and neurodevelopmental disorders, both of which have a bidirectional association with the pathophysiology of DSWPD. Additionally, patients with DSWPD have a strong tendency toward neuroticism and anxiety, which may result in the aggravation of insomnia symptoms. Therefore, future studies should address the effectiveness of cognitive-behavioral approaches in addition to chronobiological approaches in the treatment of DSWPD.

Evaluation of the Anxiolytic Effect of Ramelteon in Various Rat Models of Anxiety

Background Melatonin was found to have anxiolytic properties in several animal and human studies. The melatonin receptor agonist ramelteon might also have a similar anxiolytic action. Objectives The objective of the study was to evaluate the effect of ramelteon in various rat models of anxiety and to explore the possible mechanism of action. Methods The anxiolytic effect was compared between the control group, diazepam group (1 mg/kg and 0.5 mg/kg), and ramelteon group (0.25 mg/kg, 0.5 mg/kg, and 1 mg/kg) by an elevated plus maze, light-dark box, hole board apparatus, and open field test in Sprague Dawley rats. Antagonists flumazenil, picrotoxin, and Luzindole were used to explore the possible mechanism of action of ramelteon if it showed an anxiolytic property. Results Ramelteon as a standalone drug did not show an anxiolytic effect. However, a combination of ramelteon (1 mg/kg) and diazepam (0.5 mg/kg) showed an anxiolytic effect. Conclusion Further studies can evaluate the use of a fixed-dose combination of ramelteon and already-approved anxiolytic drugs to reduce the dose of the latter.

Neuroprotective effects of melatonin in neurodegenerative and autoimmune central nervous system diseases

The suprachiasmatic nucleus (SCN) in the anterior hypothalamus is the major circadian pacemaker in humans. Melatonin is a key hormone secreted by the pineal gland in response to darkness. Light-induced stimuli are transmitted along the retinohypothalamic tract to the SCN. Activation of the SCN inhibits the production of melatonin by the pineal gland through a complex neural pathway passing through the superior cervical ganglion. Accordingly, when light is unavailable, the pineal gland secretes melatonin. The circadian rhythm modulates sleep-wake cycles as well as many physiological functions of the endocrine system, including core body temperature, pulse rate, oxygen consumption, hormone levels, metabolism, and gastrointestinal function. In neurodegenerative disorders, the sleep-wake cycle is disrupted and circadian regulation is altered, which accelerates disease progression, further disrupting circadian regulation and setting up a vicious cycle. Melatonin plays a critical role in the regulation of circadian rhythms and is a multifunctional pleiotropic agent with broad neuroprotective effects in neurodegenerative disorders, viral or autoimmune diseases, and cancer. In this review, I discuss the neuroprotective functions of melatonin in circadian regulation and its roles in promoting anti-inflammatory activity, enhancing immune system functions, and preventing alterations in glucose metabolism and mitochondrial dysfunction in neurodegenerative disorders and autoimmune central nervous system diseases.

Common Sleep Disorders Affecting Older Adults

Sleep disorders in older adults increase with aging, likely due to increased sleep latency, decreased sleep efficiency, and total sleep time. Common sleep issues include chronic insomnia, circadian rhythm sleep-wake disorders, sleep-related movement disorders, and sleep-disordered breathing. Diagnostic tools, such as a comprehensive sleep history and questionnaires, or a sleep log for more specific complaints, are commonly used. Polysomnography is not recommended as a routine test; however, it can be used for abnormal behaviors during sleep or if treatment fails. Sleep disorder management is based on the etiology and may include nonpharmacological and pharmacological alternative treatments. For example, nonpharmacological management for chronic insomnia and some sleep disorders may consist of cognitive behavioral therapy, sleep hygiene education, relaxation therapy, sleep restriction, light therapy, and stimulus control therapy. Because the quality of evidence for pharmacological treatment is poor, the medication choice should be based on shared decision-making between the practitioner and the patient, with limited prescription.

Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism

Availability of artificial light and light-emitting devices have altered human temporal life, allowing 24-hour healthcare, commerce and production, and expanding social life around the clock. However, physiology and behavior that evolved in the context of 24 h solar days are frequently perturbed by exposure to artificial light at night. This is particularly salient in the context of circadian rhythms, the result of endogenous biological clocks with a rhythm of ~24 h. Circadian rhythms govern the temporal features of physiology and behavior, and are set to precisely 24 h primarily by exposure to light during the solar day, though other factors, such as the timing of meals, can also affect circadian rhythms. Circadian rhythms are significantly affected by night shift work because of exposure to nocturnal light, electronic devices, and shifts in the timing of meals. Night shift workers are at increased risk for metabolic disorder, as well as several types of cancer. Others who are exposed to artificial light at night or late mealtimes also show disrupted circadian rhythms and increased metabolic and cardiac disorders. It is imperative to understand how disrupted circadian rhythms alter metabolic function to develop strategies to mitigate their negative effects. In this review, we provide an introduction to circadian rhythms, physiological regulation of homeostasis by the suprachiasmatic nucleus (SCN), and SCN-mediated hormones that display circadian rhythms, including melatonin and glucocorticoids. Next, we discuss circadian-gated physiological processes including sleep and food intake, followed by types of disrupted circadian rhythms and how modern lighting disrupts molecular clock rhythms. Lastly, we identify how disruptions to hormones and metabolism can increase susceptibility to metabolic syndrome and risk for cardiovascular diseases, and discuss various strategies to mitigate the harmful consequences associated with disrupted circadian rhythms on human health.

Recommended timing of medications that impact sleep and wakefulness: A review of the American Prescribers' Digital Reference

An appreciable number of medicines have a recommended unique single time-of-day or asymmetrical or unequal-interval multiple-daily administration schedule. Many prescription and over-the-counter (OTC) products, according to administration time, can exert positive or negative impact on nighttime sleep and daytime wakefulness. Intuitively, medicines used to manage nighttime sleep and daytime wake disorders should be taken, respectively, at night before bedtime and morning after arising. However, some utilized for other medical conditions, if improperly timed, may compromise nocturnal sleep and diurnal attentiveness. We conducted a comprehensive review of the American Prescribers' Digital Reference, internet version of the Physician's Desk Reference, for the recommended scheduling of medications and OTC remedies that can impact sleep and wakefulness. The search revealed several hundred therapies of various classes -- α₂-receptor agonists, antidepressants, barbiturates, central nervous system stimulants, benzodiazepines, dopamine agonists, dopamine norepinephrine reuptake inhibitors, selective norepinephrine reuptake inhibitors, eugeroics, γ-aminobutyric acid modulators, H₁ and H₃-receptor antagonists, melatonin analogues, OTC melatonin-containing products, non-benzodiazepine benzodiazepine-receptor agonists, dual orexin-receptor antagonists, and serotonin modulators -- that have a recommended unique dosing schedule. The tables and text of this article are intended to guide the proper scheduling of these medicines to optimize desired and/or minimize undesired effects.

Multiplatform-Integrated Identification of Melatonin Targets for a Triad of Psychosocial-Sleep/Circadian-Cardiometabolic Disorders

Several psychosocial, sleep/circadian, and cardiometabolic disorders have intricately interconnected pathologies involving melatonin disruption. Therefore, we hypothesize that melatonin could be a therapeutic target for treating potential comorbid diseases associated with this triad of psychosocial-sleep/circadian-cardiometabolic disorders. We investigated melatonin's target prediction and tractability for this triad of disorders. The melatonin's target prediction for the proposed psychosocial-sleep/circadian-cardiometabolic disorder triad was investigated using databases from Europe PMC, ChEMBL, Open Targets Genetics, Phenodigm, and PheWAS. The association scores for melatonin receptors MT1 and MT2 with this disorder triad were explored for evidence of target-disease predictions. The potential of melatonin as a tractable target in managing the disorder triad was investigated using supervised machine learning to identify melatonin activities in cardiovascular, neuronal, and metabolic assays at the cell, tissue, and organism levels in a curated ChEMBL database. Target-disease visualization was done by graphs created using "igraph" library-based scripts and displayed using the Gephi ForceAtlas algorithm. The combined Europe PMC (data type: text mining), ChEMBL (data type: drugs), Open Targets Genetics Portal (data type: genetic associations), PhenoDigm (data type: animal models), and PheWAS (data type: genetic associations) databases yielded types and varying levels of evidence for melatonin-disease triad correlations. Of the investigated databases, 235 association scores of melatonin receptors with the targeted diseases were greater than 0.2; to classify the evidence per disease class: 37% listed psychosocial disorders, 9% sleep/circadian disorders, and 54% cardiometabolic disorders. Using supervised machine learning, 546 cardiovascular, neuronal, or metabolic experimental assays with predicted or measured melatonin activity scores were identified in the ChEMBL curated database. Of 248 registered trials, 144 phase I to IV trials for melatonin or agonists have been completed, of which 33.3% were for psychosocial disorders, 59.7% were for sleep/circadian disorders, and 6.9% were for cardiometabolic disorders. Melatonin's druggability was evidenced by evaluating target prediction and tractability for the triad of psychosocial-sleep/circadian-cardiometabolic disorders. While melatonin research and development in sleep/circadian and psychosocial disorders is more advanced, as evidenced by melatonin association scores, substantial evidence on melatonin discovery in cardiovascular and metabolic disorders supports continued R&D in cardiometabolic disorders, as evidenced by melatonin activity scores. A multiplatform analysis provided an integrative assessment of the target-disease investigations that may justify further translational research.

Circadian rhythm and disease: Relationship, new insights, and future perspectives

The circadian system is responsible for internal functions and regulation of the organism according to environmental cues (zeitgebers). Circadian rhythm dysregulation or chronodisruption has been associated with several diseases, from mental to autoimmune diseases, and with life quality change. Following this, some therapies have been developed to correct circadian misalignments, such as light therapy and chronobiotics. In this manuscript, we describe the circadian-related diseases so far investigated, and studies reporting relevant data on this topic, evidencing this relationship, are included. Despite the actual limitations in published work, there is clear evidence of the correlation between circadian rhythm dysregulation and disease origin/development, and, in this way, clock-related therapies emerge as great progress in the clinical field. Future improvements in such interventions can lead to the development of successful chronotherapy strategies, deeply contributing to enhanced therapeutic outcomes.

Non-24-Hour Sleep–Wake Disorder and Tasimelteon: A Review for Practitioners Who Work with Blind People

Introduction

This narrative review summarizes the biology of human circadian rhythms; details the epidemiology, clinical manifestation, and diagnosis of non-24-hour sleep–wake disorder (N24SWD); and reviews the efficacy of possible treatments.

Methods

Searches of targeted phrases, such as “non-24-hour sleep–wake disorder” and “tasimelteon,” were conducted on PubMed between December 2016 and March 2020.

Results

As the world’s population ages, health practitioners frequently work with people who are blind. Damage to the retinal ganglion cells that signal environmental irradiance levels to the suprachiasmatic nucleus prevents many of these individuals from synchronizing their internal clocks to the 24-hour day. As a result, they experience a condition called N24SWD, where the body’s circadian rhythms fall in and out of phase with the solar cycle. The ability to fall asleep and remain asleep is a complex process that depends on many variables, including the release of the neurohormone melatonin. Melatonin is produced at night and is a key regulator of regular sleep cycles. Periods of interrupted sleep, increased sleep latency, and reduced total sleep time occur when melatonin production peaks during daytime. Thus, many persons with N24SWD have difficulty maintaining normal schedules due in part to the mistimed release of melatonin. Randomized clinical trials have shown that melatonin receptor agonist tasimelteon is an effective therapy for individuals with N24SWD. Other treatments have varying efficacy profiles.

Conclusions

Although rare, N24SWD is a serious condition that can impair quality of life for blind persons. Tasimelteon appears to be a safe and efficacious treatment option.

Implications for practitioners

Practitioners can use this information to better understand why blind persons often report difficulties sleeping and to realize that therapeutic options are available to these individuals.

Melatonin for premenstrual syndrome: A potential remedy but not ready

Premenstrual syndrome (PMS), a recurrent and moderate disorder that occurs during the luteal phase of the menstrual cycle and quickly resolves after menstruation, is characterized by somatic and emotional discomfort that can be severe enough to impair daily activities. Current therapeutic drugs for PMS such as selective serotonin reuptake inhibitors are not very satisfying. As a critical pineal hormone, melatonin has increasingly been suggested to modulate PMS symptoms. In this review, we update the latest progress on PMS-induced sleep disturbance, mood changes, and cognitive impairment and provide possible pathways by which melatonin attenuates these symptoms. Moreover, we focus on the role of melatonin in PMS molecular mechanisms. Herein, we show that melatonin can regulate ovarian estrogen and progesterone, of which cyclic fluctuations contribute to PMS pathogenesis. Melatonin also modulates gamma-aminobutyric acid and the brain-derived neurotrophic factor system in PMS. Interpreting the role of melatonin in PMS is not only informative to clarify PMS etiology but also instructive to melatonin and its receptor agonist application to promote female health. As a safe interaction, melatonin treatment can be effective in alleviating symptoms of PMS. However, symptoms such as sleep disturbance, depressive mood, cognitive impairment are not specific and can be easily misdiagnosed. Connections between melatonin receptor, ovarian steroid dysfunction, and PMS are not consistent among past studies. Before final conclusions are drawn, more well-organized and rigorous studies are recommended.

Chronopharmacology in Therapeutic Drug Monitoring-Dependencies between the Rhythmics of Pharmacokinetic Processes and Drug Concentration in Blood

The objective of the optimization of pharmacotherapy compliant with the basic rules of clinical pharmacology is its maximum individualization, ensuring paramount effectiveness and security of the patient's therapy. Thus, multiple factors that are decisive in terms of uniqueness of treatment of the given patient must be taken into consideration, including, but not limited to, the patient's age, sex, concomitant diseases, special physiological conditions (e.g., pregnancy, lactation, extreme age groups), polypharmacotherapy and polypragmasia (particularly related to increased risk of drug interactions), and patient's phenotypic response to the administered drug with possible genotyping. Conducting therapy while monitoring the concentration of certain drugs in blood (Therapeutic Drug Monitoring; TDM procedure) is also one of the factors enabling treatment individualization. Furthermore, another material, and yet still a marginalized pharmacotherapeutic factor, is chronopharmacology, which indirectly determines the values of drug concentrations evaluated in the TDM procedure. This paper is a brief overview of chronopharmacology, especially chronopharmacokinetics, and its connection with the clinical interpretation of the meaning of the drug concentrations determined in the TDM procedure.

Regulatory aspects and evidences of melatonin use for sleep disorders and insomnia: an integrative review

BACKGROUND

Insomnia is a sleep disorder characterized by difficulty of falling asleep or maintaining sleep, which affects different age groups. Currently, melatonin is used as a therapeutic treatment in cases of insomnia in children, adults, and elderly people.

OBJECTIVE

To evaluate the effectiveness of melatonin in sleep disorders, its dosage, potential adverse effects, as well as labeling laws and regulations in Brazil.

METHODS

This integrative review was carried out using the Cochrane Library, Medline (Pubmed), and Science Direct databases. Twenty-five articles and three documents available on the Brazilian Society of Endocrinology and Metabology (SBEM) and National Health Surveillance Agency (ANVISA) websites published between 2015 and 2020 were selected to be evaluated in full.

RESULTS

It was found that in most of the selected articles the use of melatonin reduces sleep latency. The effective melatonin doses varied according to each age group, from 0.5 to 3 mg in children, 3 to 5 mg in adolescents, 1 to 5 mg in adults, and 1 to 6 mg in elderly people. Side effects are mild when taking usual doses. In Brazil, no registered drug and current regulation on the use and marketing of melatonin has been identified.

CONCLUSION

The use of melatonin is an alternative therapy that can be used for sleeping disorders. According to the evidences found, it did not demonstrate toxicity or severe side effects, nor dependence even when administered at high doses, suggesting that it is a safe medication to treat patients of different ages suffering from sleeping disorders.

Sleep Disorders and Mood, Anxiety, and Post-Traumatic Stress Disorders: Overview of Clinical Treatments in the Context of Sleep Disturbances

Sleep disruptions are frequently reported by persons with mood, anxiety, and post-traumatic stress disorders, and co-occur with psychiatric disorders. There is evidence that sleep disorders can predict the likelihood of developing a future psychiatric disorder and exacerbate existing symptoms. Understanding the inter-relationships between sleep and psychiatric disorders is important. The primary goals of this article are to describe the interactions between psychiatric and sleep disorders in the context of sleep disturbances, underscore the bidirectional effects of mental health treatments on sleep disorder outcomes, and provide general recommendations to optimize treatment in the context of sleep disturbances.

Sleep, Cognition, and Yoga

Stress is one of the major problems globally, associated with poor sleep quality and cognitive dysfunction. Modern society is plagued by sleep disturbances, either due to professional demands or lifestyle or both the aspects, often leading to reduced alertness and compromised mental function, besides the well documented ill effects of disturbed sleep on physiological functions. This pertinent issue needs to be addressed. Yoga is an ancient Indian science, philosophy and way of life. Recently, yoga practice has become increasingly popular worldwide. Yoga practice is an adjunct effective for stress, sleep and associated disorders. There are limited well controlled published studies conducted in this area. We reviewed the available literature including the effect of modern lifestyle in children, adolescents, adults and geriatric population. The role of yoga and meditation in optimizing sleep architecture and cognitive functions leading to optimal brain functioning in normal and diseased state is discussed. We included articles published in English with no fixed time duration for literature search. Literature was searched mainly by using PubMed and Science Direct search engines and critically examined. Studies have revealed positive effects of yoga on sleep and cognitive skills among healthy adults as well as patients of some neurological diseases. Further, on evaluating the published studies, it is concluded that sleep and cognitive functions are optimized by yoga practice, which brings about changes in autonomic function, structural changes, changes in metabolism, neurochemistry and improved functional brain network connectivity in key regions of the brain.

Advances in the pharmacological management of non-24-h sleep-wake disorder

Introduction: Melatonin, a hormone that regulates circadian rhythms and the sleep-wake cycle, is produced mainly during the dark period in the pineal gland and is suppressed by light exposure. Patients with non-24-h sleep-wake disorder (non-24) fail to entrain the master clock with the 24-h light-dark cycle due to the lack of light perception to the suprachiasmatic nucleus typically in totally blind individuals or other organic disorders in sighted individuals, causing a progressive delay in the sleep-wake cycle and periodic insomnia and daytime sleepiness.Areas covered: Herein, the authors review the pharmacological therapies including exogenous melatonin and melatonin receptor agonists for the management of non-24. They introduce a historical report about the effects of melatonin on the phase shift and entrainment for blind individuals with the free-running circadian rhythm.Expert opinion: Orally administered melatonin entrains the endogenous circadian rhythm and improves nighttime sleep and daytime alertness for non-24. Currently, tasimelteon is the only approved medication for non-24 by the US Food and Drug Administration and the European Medicines Agency. Treatments that focus only on sleep problems are insufficient for the treatment of non-24, and aids to entrain the free-running rhythm with the light-dark cycle are needed.

Circadian rhythm as a therapeutic target

The circadian clock evolved in diverse organisms to integrate external environmental changes and internal physiology. The clock endows the host with temporal precision and robust adaptation to the surrounding environment. When circadian rhythms are perturbed or misaligned, as a result of jet lag, shiftwork or other lifestyle factors, adverse health consequences arise, and the risks of diseases such as cancer, cardiovascular diseases or metabolic disorders increase. Although the negative impact of circadian rhythm disruption is now well established, it remains underappreciated how to take advantage of biological timing, or correct it, for health benefits. In this Review, we provide an updated account of the circadian system and highlight several key disease areas with altered circadian signalling. We discuss environmental and lifestyle modifications of circadian rhythm and clock-based therapeutic strategies, including chronotherapy, in which dosing time is deliberately optimized for maximum therapeutic index, and pharmacological agents that target core clock components and proximal regulators. Promising progress in research, disease models and clinical applications should encourage a concerted effort towards a new era of circadian medicine.

Daily Morning Blue Light Therapy for Post-mTBI Sleep Disruption: Effects on Brain Structure and Function

Background: Mild traumatic brain injuries (mTBIs) are associated with novel or worsened sleep disruption. Several studies indicate that daily morning blue light therapy (BLT) is effective for reducing post-mTBI daytime sleepiness and fatigue. Studies demonstrating changes in brain structure and function following BLT are limited. The present study's purpose is to identify the effect of daily morning BLT on brain structure and functional connectivity and the association between these changes and self-reported change in post-mTBI daytime sleepiness. Methods: A total of 62 individuals recovering from a mTBI were recruited from two US cities to participate in a double-blind placebo-controlled trial. Eligible individuals were randomly assigned to undergo 6 weeks of 30 min daily morning blue or placebo amber light therapy (ALT). Prior to and following treatment all individuals completed a comprehensive battery that included the Epworth Sleepiness Scale as a measure of self-reported daytime sleepiness. All individuals underwent a multimodal neuroimaging battery that included anatomical and resting-state functional magnetic resonance imaging. Atlas-based regional change in gray matter volume (GMV) and region-to-region functional connectivity from baseline to post-treatment were the primary endpoints for this study. Results: After adjusting for pre-treatment GMV, individuals receiving BLT had greater GMV than those receiving amber light in 15 regions of interest, including the right thalamus and bilateral prefrontal and orbitofrontal cortices. Improved daytime sleepiness was associated with greater GMV in 74 ROIs, covering many of the same general regions. Likewise, BLT was associated with increased functional connectivity between the thalamus and both prefrontal and orbitofrontal cortices. Improved daytime sleepiness was associated with increased functional connectivity between attention and cognitive control networks as well as decreased connectivity between visual, motor, and attention networks (all FDR corrected p < 0.05). Conclusions: Following daily morning BLT, moderate to large increases in both gray matter volume and functional connectivity were observed in areas and networks previously associated with both sleep regulation and daytime cognitive function, alertness, and attention. Additionally, these findings were associated with improvements in self-reported daytime sleepiness. Further work is needed to identify the personal characteristics that may selectively identify individuals recovering from a mTBI for whom BLT may be optimally beneficial.

Melatonin: From Pharmacokinetics to Clinical Use in Autism Spectrum Disorder

The role of melatonin has been extensively investigated in pathophysiological conditions, including autism spectrum disorder (ASD). Reduced melatonin secretion has been reported in ASD and led to many clinical trials using immediate-release and prolonged-release oral formulations of melatonin. However, melatonin’s effects in ASD and the choice of formulation type require further study. Therapeutic benefits of melatonin on sleep disorders in ASD were observed, notably on sleep latency and sleep quality. Importantly, melatonin may also have a role in improving autistic behavioral impairments. The objective of this article is to review factors influencing treatment response and possible side effects following melatonin administration. It appears that the effects of exposure to exogenous melatonin are dependent on age, sex, route and time of administration, formulation type, dose, and association with several substances (such as tobacco or contraceptive pills). In addition, no major melatonin-related adverse effect was described in typical development and ASD. In conclusion, melatonin represents currently a well-validated and tolerated treatment for sleep disorders in children and adolescents with ASD. A more thorough consideration of factors influencing melatonin pharmacokinetics could illuminate the best use of melatonin in this population. Future studies are required in ASD to explore further dose-effect relationships of melatonin on sleep problems and autistic behavioral impairments.

Non‐24‐hour sleep‐wake disorder successfully treated with the combination of ramelteon and suvorexant in a case of autism spectrum disorder

Introduction

Non‐24‐hour sleep‐wake disorder (N24SWD) is often observed in the visually impaired and those who isolate indoors. Melatonin receptor agonists may be used for treatment, but there is currently no evidence that they are effective in patients without visual impairment.

Case

We report a case of a 23‐year‐old woman who withdrew from her social life owing to autism spectrum disorder and experienced an unusual sleep rhythm. She presented with N24SWD. The N24SWD cycle averaged 25.6 days but was extended to 42 days using ramelteon. However, this was not enough. We prescribed the addition of suvorexant and the sleep cycle returned to normal.

Conclusion

N24SWD is a disease that seriously impairs social life and productivity. We propose a possible treatment strategy for N24SWD using ramelteon and suvorexant.

We present a case in which the combination therapy of ramelteon and suvorexant was effective for a patient with autism spectrum disorder with non‐24‐hour sleep‐wake disorder (N24SWD) owing to social withdrawal. Here, we discussed the pharmacological mechanism of the combination of ramelteon and suvorexant as a possible therapeutic strategy for patients with N24SWD.

Angelman syndrome and melatonin: What can they teach us about sleep regulation

In 1965, Dr Harry Angelman reported a neurodevelopmental disorder affecting three unrelated children who had similar symptoms: brachycephaly, mental retardation, ataxia, seizures, protruding tongues, and remarkable paroxysms of laughter. Over the past 50 years, the disorder became Angelman's namesake and symptomology was expanded to include hyper-activity, stereotypies, and severe sleep disturbances. The sleep disorders in many Angelman syndrome (AS) patients are broadly characterized by difficulty falling and staying asleep at night. Some of these patients sleep less than 4 hours a night and, in most cases, do not make up this lost sleep during the day-leading to the speculation that AS patients may "need" less sleep. Most AS patients also have severely reduced levels of melatonin, a hormone produced by the pineal gland exclusively at night. This nightly pattern of melatonin production is thought to help synchronize internal circadian rhythms and promote nighttime sleep in humans and other diurnal species. It has been proposed that reduced melatonin levels contribute to the sleep problems in AS patients. Indeed, emerging evidence suggests melatonin replacement therapy can improve sleep in many AS patients. However, AS mice show sleep problems that are arguably similar to those in humans despite being on genetic backgrounds that do not make melatonin. This suggests the hypothesis that the change in nighttime melatonin may be a secondary factor rather than the root cause of the sleeping disorder. The goals of this review article are to revisit the sleep and melatonin findings in both AS patients and animal models of AS and discuss what AS may tell us about the underlying mechanisms of, and interplay between, melatonin and sleep.

Sleep and Glycemia in Youth With Type 1 Diabetes

INTRODUCTION

Short sleep duration and quality are problems for many youth, and are associated with difficulties in executive function. Our purpose was to describe subjective and objective sleep characteristics and their associations with executive function, stress and coping, adjustment, and self-management in youth with type 1 diabetes (T1D).

METHOD

Youth with T1D (N = 40; mean age, 13.4 ± 1.9 years; 60% female; 77.1% non-Hispanic white; diabetes duration, 7.1 ± 4.6 years; and hemoglobin A1c, 8.2 ± 1.2%) wore an actigraph and a continuous glucose monitor for 3-7 days and completed questionnaires. Descriptive and bivariate analyses were conducted.

RESULTS

Sleep variability was associated with stress and depressive symptoms, as well as more glucose variability. Consistent rest-activity rhythm timing was associated with fewer trait anxiety symptoms. Robust rhythms were associated with better diabetes self-management.

DISCUSSION

Providers should routinely assess sleep habits in youth, especially those with T1D. Improving consistency in sleep timing and sleep duration may be a potential therapeutic target to improve diabetes clinical outcomes.

Diabetes and atherothrombosis: The circadian rhythm and role of melatonin in vascular protection

Obesity-related euglycaemic insulin resistance clusters with cardiometabolic risk factors, contributing to the development of both type 2 diabetes and cardiovascular disease. An increased thrombotic tendency in diabetes stems from platelet hyperactivity, enhanced activity of prothrombotic coagulation factors and impaired fibrinolysis. Furthermore, a low-grade inflammatory response and increased oxidative stress accelerate the atherosclerotic process and, together with an enhanced thrombotic environment, result in premature and more severe cardiovascular disease. The disruption of circadian cycles in man secondary to chronic obesity and loss of circadian cues is implicated in the increased risk of developing diabetes and cardiovascular disease. Levels of melatonin, the endogenous synchronizer of circadian rhythm, are reduced in individuals with vascular disease and those with deranged glucose metabolism. The anti-inflammatory, antihypertensive, antioxidative and antithrombotic activities of melatonin make it a potential therapeutic agent to reduce the risk of vascular occlusive disease in diabetes. The mechanisms behind melatonin-associated reduction in procoagulant response are not fully known. Current evidence suggests that melatonin inhibits platelet aggregation and might affect the coagulation cascade, altering fibrin clot structure and/or resistance to fibrinolysis. Large-scale clinical trials are warranted to investigate the effects of modulating the circadian clock on insulin resistance, glycaemia and cardiovascular outcome.

Melatonergic agonist regulates circadian clock genes and peripheral inflammatory and neuroplasticity markers in patients with depression and anxiety

OBJECTIVE

Circadian dysfunction is a core manifestation and a risk factor for psychiatric disorders. Ramelteon (RMT), a melatonin receptor agonist, has been shown to induce sleep phase shifts and has been used to normalize sleep onset time. RMT has been used in sleep disorders, depression and anxiety. In this study, we aimed to investigate the effects of RMT in regulating gene expression profiles of the circadian clock and peripheral markers of inflammation and neuroplasticity.

METHODS

Sixteen patients with a diagnosis of primary insomnia comorbid with depression and anxiety and ten healthy controls were recruited in an 8-week open-label trial. The patients with primary insomnia received RMT 8 mg/day. The morning expression profiles of 15 core clock genes from peripheral blood mononuclear cells (PBMCs), urine and plasma levels of melatonin and its metabolite levels, and plasma inflammatory markers and neurotrophin levels were evaluated at baseline, 4th and 8th week of RMT treatment.

RESULTS

RMT treatment was associated with significant clinical improvement in depression scores at 8th week (Hamilton depression rating scale scores (Mean ± SEM) from 21.5 ± 2.44 to 14.31 ± 2.25, p ≤ 0.05). The overall poor sleep quality (Pittsburgh sleep quality index) of the patient group significantly improved (p ≤ 0.05) following RMT treatment. The mRNA level analysis showed a significant association between RMT treatment and alterations of the nine core circadian genes (CLOCK, PER1, PER2, CRY1, CRY2, NR1D1, NR1D2, DEC1 and TIMELESS) in the patient group when compared with the control group (p ≤ 0.05). Compared with the controls, the patient group had a decrease in neurotrophins (brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor and beta-nerve growth factor; p ≤ 0.05) but an increase in pro-inflammatory cytokine levels (interleukin-6, interleukin-1b, tumour necrosis factor-alpha and interferon gamma; p ≤ 0.05); RMT treatment normalized the levels of neurotrophins and cytokine levels.

CONCLUSION

RMT treatment is able to restore phase-shifted melatonin markers, normalized the altered expression of the circadian genes, the levels of inflammatory cytokines and neurotrophins in patients with insomnia comorbid anxiety and depression.

Ramelteon for Delayed Sleep-wake Phase Disorder: A Case Report

Recently developed melatonin receptor agonists are expected to be effective for delayed sleep-wake phase disorder (DSWPD). To date, however, no study has described the effect of melatonin receptor agonists on DSWPD. We report the case of a 15-year-old girl with DSWPD who was successfully treated with ramelteon 4 mg at 7 pm. DSWPD symptoms were resolved; her sleep-wake and biological rhythms were normalized.

Is Agomelatine Associated with Less Sedative-Hypnotic Usage in Patients with Major Depressive Disorder? A Nationwide, Population-Based Study

BACKGROUND

To examine the association between the usage of agomelatine in patients with major depressive disorder and the usage of sedative-hypnotics.

METHODS

This population-based, cross-sectional study used Taiwan's National Health Insurance Research Database (NHIRD) between 2012 and 2015. The agomelatine-only group and matched control (1:3) with the usage of other antidepressants were enrolled. The association between the usage of the agomelatine and other antidepressants and the usage of sedative-hypnotics in the patients were also assessed.

RESULTS

A total of 7961 subjects were enrolled comprising 1985 with the usage of agomelatine only, and 5976 with other antidepressants. In the present study, a total of 3322 subjects who used the sedative-hypnotics were recorded, with 811 (40.86%) from the agomelatine-only group and 2511 (42.02%) from the non-agomelatine group, which have used sedative-hypnotics. After adjusting for covariates, the odds ratio (OR) of the usage of sedative-hypnotics in the agomelatine only-group was 0.892 (95% CI: 0.306-1.601, p = 0.533), in comparison to the controls, and the relative risk (RR) of the usage of sedative-hypnotics in the agomelatine only-group was 0.910 (95% CI: 0.312-1.633, p = 0.520), in comparison to the controls. No matter as to whether the treatment duration was <30 days or ≧ 30 days of agomelatine treatment was not associated with the increased usage of the sedative-hypnotics. The OR or RR for usage of the sedative-hypnotics was associated with the Charlson Comorbidity Index (CCI) scores as 2, 3, and ≧ 4, and the medical care from the medical center and regional hospital.

CONCLUSION

Patients with the agomelatine-only group were not associated with the usage of sedative-hypnotics in comparison to the group using other antidepressants.

Evaluation of agomelatine for the treatment of sleep problems in adults with autism spectrum disorder and co-morbid intellectual disability

PURPOSE

Intellectual disability (ID) and autism spectrum disorder (ASD) are common, co-occurring developmental disorders and are frequently associated with sleep problems. This study aimed to assess the effectiveness and tolerability of agomelatine as a pharmacotherapy for sleep problems in ASD adults with ID.

METHOD

A randomised, crossover, triple-blind, placebo-controlled clinical trial, with two three-month periods of treatment starting with either agomelatine or placebo and a washout period of two weeks. Ambulatory circadian monitoring (24 hours/7 days) evaluated total sleep time (TST) as the primary outcome variable.

RESULTS

Participants (N=23; 35±12 years old; 83% male) had a median of three (interquartile range (IQR) 1-4) co-morbidities and were taking a median of five (IQR 2-7) prescribed drugs. Before agomelatine or placebo treatment, all subjects presented with insomnia symptoms, including sleep latency (100% abnormal, 55±23 minutes) or TST (55% abnormal, 449±177 minutes), and 66% had circadian rhythm sleep-wake abnormalities with rhythm phase advancements according to the M5 sleep phase marker values. During the three-month agomelatine treatment, night TST significantly increased by a mean of 83 minutes (16% abnormal, 532±121 minutes), together with a phase correction (M5 1:45±2:28 hours vs. 3:15±2:20 hours), improving sleep stability in wrist temperature rhythm (0.43±0.29 vs. 0.52±0.18 AU). Adverse events were mild and transient.

CONCLUSIONS

Agomelatine was effective and well tolerated for treating insomnia and circadian rhythm sleep problems present in adults with ASD and ID.

The Neuroprotective Effects of Melatonin: Possible Role in the Pathophysiology of Neuropsychiatric Disease

Melatonin is a hormone that is secreted by the pineal gland. To date, melatonin is known to regulate the sleep cycle by controlling the circadian rhythm. However, recent advances in neuroscience and molecular biology have led to the discovery of new actions and effects of melatonin. In recent studies, melatonin was shown to have antioxidant activity and, possibly, to affect the development of Alzheimer's disease (AD). In addition, melatonin has neuroprotective effects and affects neuroplasticity, thus indicating potential antidepressant properties. In the present review, the new functions of melatonin are summarized and a therapeutic target for the development of new drugs based on the mechanism of action of melatonin is proposed.

Use of nutritional supplements based on melatonin, tryptophan and vitamin B6 (Melamil Tripto®) in children with primary chronic headache, with or without sleep disorders: a pilot study

BACKGROUND

Headache is one of the main complaints in pediatric neurology. Exogenous melatonin has been shown to be useful and safe in improving sleep-wake cycles and sleep quality in children. Tryptophan as well plays a key role in sleep regulation. So far, no studies tried to analyze the effects of a combination of both melatonin and tryptophan in treating chronic headache in children affected also by night-time awakenings.

METHODS

Thirty-four children with a diagnosis of chronic headache (with or without sleep disorders) have been enrolled. The study was articulated in two steps: 1) each child was observed for one month without any intervention; 2) children have been then randomized into two groups: the "ME-group", which received the nutritional supplement melatonin for two months and the "MET-group", which received the nutritional supplements melatonin, tryptophan, and vitamin B6 for two months.

RESULTS

In terms of changes in number of headache events, responders in the ME-group were 91.7% and those in the MET-group were 66.7% (P=0.113). In terms of changes in number of night awakenings, in the ME group, mean number at baseline, after 30 days, and after 60 days were 3.6±3.2, 3.2±3.5, and 2.7±3.4 (P=0.495). In the MET group, mean number of night awakenings was 7.4±8.1, 4.0±4.4, and 3.3±2.9 (P=0.041).

CONCLUSIONS

Using either nutritional supplement for two months can help in decreasing the monthly number of headache episodes and night awakenings. The addition of tryptophan and vitamin B6 appears to have stronger influence on night awakenings reduction than melatonin only.

Cardioprotective Melatonin: Translating from Proof-of-Concept Studies to Therapeutic Use

In this review we summarized the actual clinical data for a cardioprotective therapeutic role of melatonin, listed melatonin and its agonists in different stages of development, and evaluated the melatonin cardiovascular target tractability and prediction using machine learning on ChEMBL. To date, most clinical trials investigating a cardioprotective therapeutic role of melatonin are in phase 2a. Selective melatonin receptor agonists Tasimelteon, Ramelteon, and combined melatonergic-serotonin Agomelatine, and other agonists with registered structures in CHEMBL were not yet investigated as cardioprotective or cardiovascular drugs. As drug-able for these therapeutic targets, melatonin receptor agonists have the benefit over melatonin of well-characterized pharmacologic profiles and extensive safety data. Recent reports of the X-ray crystal structures of MT1 and MT2 receptors shall lead to the development of highly selective melatonin receptor agonists. Predictive models using machine learning could help to identify cardiovascular targets for melatonin. Selecting ChEMBL scores > 4.5 in cardiovascular assays, and melatonin scores > 4, we obtained 284 records from 162 cardiovascular assays carried out with 80 molecules with predicted or measured melatonin activity. Melatonin activities (agonistic or antagonistic) found in these experimental cardiovascular assays and models include arrhythmias, coronary and large vessel contractility, and hypertension. Preclinical proof-of-concept and early clinical studies (phase 2a) suggest a cardioprotective benefit from melatonin in various heart diseases. However, larger phase 3 randomized interventional studies are necessary to establish melatonin and its agonists’ actions as cardioprotective therapeutic agents.

Sleep modulating agents

Sleep and wake are two fundamental states of human existence. Conditions such as insomnia and hypersomnia can have profound negative effects on human health. Many pharmacological interventions impacting sleep and wake are available or are under development. This brief digest surveys early approaches to sleep modulation and highlights recent developments in sleep modulating agents.

Melatonin MT2 receptor agonist IIK-7 produces antinociception by modulation of ROS and suppression of spinal microglial activation in neuropathic pain rats

Background

In recent years, several melatonin (MLT) receptor agonists have been approved by FDA for the treatment of sleep disorders and depression. Very few studies have shed light on their efficacy against neuropathic pain (NP). IIK-7 is an MT-2 agonist known to promote sleep. Whether IIK-7 suppresses NP has not been reported, and the signaling profile is unknown.

Objective

To investigate the effect of melatonin type 2 receptor agonist IIK-7 on partial sciatic nerve transection-induced NP in rats and elucidate the underlying molecular mechanisms.

Methods

NP was induced by the PSNT in the left leg of adult male Wistar rats. On post-transection day 7, rats were implanted with intrathecal (i.t) catheter connected to an infusion pump and divided in to four groups: sham-operated/vehicle, PSNT/vehicle, PSNT/0.5 μg/hr IIK-7 and PSNT/0.5 μg IIK-7/1 μg 4-p/hr. To test the MT-2 dependence on IIK-7 activity, the animals were implanted with a single i.t catheter and injected MT-2 antagonist 4-Phenyl-2-propionamidotetralin (4-p) 20 mins prior to IIK-7 injection on day 7 after PSNT. The antinociceptive response was measured using a mechanical paw withdrawal threshold. Activation of microglial cells and the expression of NP-associated proteins in the spinal cord dorsal horn was assessed by immunofluorescence assay (IFA) and Western blotting (WB). Reactive oxygen species (ROS) scavenging ability of IIK-7 was evaluated by using bone marrow-derived macrophages (BMDM).

Results

Treatment with the MT-2 agonist IIK-7 significantly alleviated PSNT-induced mechanical allodynia and glial activation along with the inhibition of P44/42 MAPK, HMGB-1, STAT3, iNOS and casp-3 proteins.

Conclusion

IIK-7 attenuates NP through the suppression of glial activation and suppression of proteins involved in inflammation and apoptosis. MT-2 receptor agonists may establish a promising and unique therapeutic approach for the treatment of NP.

Approaches to the Pharmacological Management of Jet Lag

For many years now a treatment mitigating the debilitating effects of jet lag has been sought. Rapid travel across time zones leads, in most people, to temporary symptoms, in particular poor sleep, daytime alertness and poor performance. Mis-timed circadian rhythms are considered to be the main factor underlying jet-lag symptoms, together with the sleep deprivation from long haul flights. Virtually all aspects of physiology are rhythmic, from cells to systems, and circadian rhythms are coordinated by a central pacemaker or clock in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN adapts slowly to changes in time zone, and peripheral clocks or oscillators adapt at different rates, such that the organism is in a state of desynchrony from the external environment and internally. Light exposure is the main factor controlling the circadian system and needs to be considered together with any pharmacological interventions. This review covers the relatively new chronobiotic drugs, which can hasten adaptation of the circadian system, together with drugs directly affecting alertness and sleep propensity. No current treatment can instantly shift circadian phase to a new time zone; however, adaptation can be hastened. The melatoninergic drugs are promising but larger trials in real-life situations are needed. For short stopovers it is recommended to preserve sleep and alertness without necessarily modifying the circadian system. New research suggests that modification of clock function via genetic manipulation may one day have clinical applications.

Perspectives in affective disorders: Clocks and sleep

Mood disorders are often characterised by alterations in circadian rhythms, sleep disturbances and seasonal exacerbation. Conversely, chronobiological treatments utilise zeitgebers for circadian rhythms such as light to improve mood and stabilise sleep, and manipulations of sleep timing and duration as rapid antidepressant modalities. Although sleep deprivation ("wake therapy") can act within hours, and its mood-elevating effects be maintained by regular morning light administration/medication/earlier sleep, it has not entered the regular guidelines for treating affective disorders as a first-line treatment. The hindrances to using chronotherapeutics may lie in their lack of patentability, few sponsors to carry out large multi-centre trials, non-reimbursement by medical insurance and their perceived difficulty or exotic "alternative" nature. Future use can be promoted by new technology (single-sample phase measurements, phone apps, movement and sleep trackers) that provides ambulatory documentation over long periods and feedback to therapist and patient. Light combinations with cognitive behavioural therapy and sleep hygiene practice may speed up and also maintain response. The urgent need for new antidepressants should hopefully lead to reconsideration and implementation of these non-pharmacological methods, as well as further clinical trials. We review the putative neurochemical mechanisms underlying the antidepressant effect of sleep deprivation and light therapy, and current knowledge linking clocks and sleep with affective disorders: neurotransmitter switching, stress and cortico-limbic reactivity, clock genes, cortical neuroplasticity, connectomics and neuroinflammation. Despite the complexity of multi-system mechanisms, more insight will lead to fine tuning and better application of circadian and sleep-related treatments of depression.

Melatonin: Countering Chaotic Time Cues

Last year melatonin was 60 years old, or at least its discovery was 60 years ago. The molecule itself may well be almost as old as life itself. So it is time to take yet another perspective on our understanding of its functions, effects and clinical uses. This is not a formal review-there is already a multitude of systematic reviews, narrative reviews, meta-analyses and even reviews of reviews. In view of the extraordinary variety of effects attributed to melatonin in the last 25 years, it is more of an attempt to sort out some areas where a consensus opinion exists, and where placebo controlled, randomized, clinical trials have confirmed early observations on therapeutic uses. The current upsurge of concern about the multiple health problems associated with disturbed circadian rhythms has generated interest in related therapeutic interventions, of which melatonin is one. The present text will consider the physiological role of endogenous melatonin, and the mostly pharmacological effects of exogenous treatment, on the assumption that normal circulating concentrations represent endogenous pineal production. It will concentrate mainly on the most researched, and accepted area of therapeutic use and potential use of melatonin-its undoubted ability to realign circadian rhythms and sleep-since this is the author's bias. It will touch briefly upon some other systems with prominent rhythmic attributes including certain cancers, the cardiovascular system, the entero-insular axis and metabolism together with the use of melatonin to assess circadian status. Many of the ills of the developed world relate to deranged rhythms-and everything is rhythmic unless proved otherwise.

Assessment of exogenous melatonin action on mouse liver cells after exposure to soman

Melatonin is a hormone with many different biological activities and therefore seems to be an important factor reducing the harmful effects caused by toxic organophosphorus compounds. In this study, we attempted to evaluate the protective effect of melatonin on liver cells of mice challenged with chemical warfare agent-soman. The study was conducted at the level of ultrastructural and biochemical changes (analysis of the activity of model lysosomal enzymes and assessment of the level of lipid peroxidation). Significant biochemical and ultrastructural changes were found in the studied mouse hepatocytes after administration of soman alone, and soman in combination with melatonin, and the scope of the disclosed changes was dependent on the time of action of the examined factors. Melatonin has shown protective action, shielding liver cells from toxic effects of soman, which may result from its antioxidant properties and stimulation of the lysosomal compartment, the system coordinating the isolation and removal of cell-threatening processes.

Melatonin as a Hormone: New Physiological and Clinical Insights

Melatonin is a ubiquitous molecule present in almost every live being from bacteria to humans. In vertebrates, besides being produced in peripheral tissues and acting as an autocrine and paracrine signal, melatonin is centrally synthetized by a neuroendocrine organ, the pineal gland. Independently of the considered species, pineal hormone melatonin is always produced during the night and its production and secretory episode duration are directly dependent on the length of the night. As its production is tightly linked to the light/dark cycle, melatonin main hormonal systemic integrative action is to coordinate behavioral and physiological adaptations to the environmental geophysical day and season. The circadian signal is dependent on its daily production regularity, on the contrast between day and night concentrations, and on specially developed ways of action. During its daily secretory episode, melatonin coordinates the night adaptive physiology through immediate effects and primes the day adaptive responses through prospective effects that will only appear at daytime, when melatonin is absent. Similarly, the annual history of the daily melatonin secretory episode duration primes the central nervous/endocrine system to the seasons to come. Remarkably, maternal melatonin programs the fetuses' behavior and physiology to cope with the environmental light/dark cycle and season after birth. These unique ways of action turn melatonin into a biological time-domain-acting molecule. The present review focuses on the above considerations, proposes a putative classification of clinical melatonin dysfunctions, and discusses general guidelines to the therapeutic use of melatonin.