Drugs Used in Circadian Sleep-Wake Rhythm Disturbances

Chronotherapy

The objective of chronotherapy is to optimize medical treatments taking into account the body's circadian rhythms. Chronotherapy is referred to and practiced in two different ways: (1) to alter the sleep-wake rhythms of patients to improve the sequels of several pathologies; (2) to take into account the circadian rhythms of patients to improve therapeutics. Even minor dysfunction of the biological clock can greatly affect sleep/wake physiology causing excessive diurnal somnolence, increase in sleep onset latency, phase delays or advances in sleep onset, frequent night awakenings, reduced sleep efficiency, delayed and shortened rapid eye movement sleep, or increased periodic leg movements. Chronotherapy aims to restore the proper circadian pattern of the sleep-wake cycle, through adequate sleep hygiene, timed light exposure, and the use of chronobiotic medications, such as melatonin, that affect the output phase of circadian rhythms, thus controlling the clock. Concerning the second use of chronotherapy, therapeutic outcomes as diverse as the survival after open-heart surgery or the efficacy and tolerance to chemotherapy vary according to the time of day. However, humans are heterogeneous concerning the timing of their internal clocks. Not only different chronotypes exist but also the endogenous human circadian period (τ) is not a stable trait as it depends on many internal and external factors. If any scheduled therapeutic intervention is going to be optimized, a tool is needed for simple diagnostic and objectively measurement of an individual's internal time at any given time. Methodologic advances like the use of single-sample gene expression and metabolomics are discussed.

Melatonin and healthy aging

Preservation of a robust circadian rhythmicity (particulsarly of the sleep/wake cycle), a proper nutrition and adequate physical exercise are key elements for healthy aging. Aging comes along with circadian alteration, e.g. a disrupted sleep and inflammation, that leads to metabolic disorders. In turn, sleep cycle disturbances cause numerous pathophysiological changes that accelerates the aging process. In the central nervous system, sleep disruption impairs several functions, among them, the clearance of waste molecules. The decrease of plasma melatonin, a molecule of unusual phylogenetic conservation present in all known aerobic organisms, plays a particular role as far as the endocrine sequels of aging. Every day, the late afternoon/nocturnal increase of melatonin synchronizes both the central circadian pacemaker located in the hypothalamic suprachiasmatic nuclei as well as myriads of peripheral cellular circadian clocks. This is called the "chronobiotic effect" of melatonin, the methoxyindole being the prototype of the endogenous family of chronobiotic agents. In addition, melatonin exerts a significant cytoprotective action by buffering free radicals and reversing inflammation via down regulation of proinflammatory cytokines, suppression of low degree inflammation and prevention of insulin resistance. Because of these properties melatonin has been advocated to be a potential therapeutic tool in COVID 19 pandemic. Melatonin administration to aged animals counteracts a significant number of senescence-related changes. In humans, melatonin is effective both as a chronobiotic and a cytoprotective agent to maintain a healthy aging. Circulating melatonin levels are consistently reduced in the metabolic syndrome, ischemic and non-ischemic cardiovascular diseases and neurodegenerative disorders like the Alzheimer's and Parkinson's diseases. The potential therapeutic value of melatonin has been suggested by a limited number of clinical trials generally employing melatonin in the 2-10mg/day range. However, from animal studies the cytoprotective effects of melatonin need higher doses to become apparent (i.e. in the 100mg/day range). Hence, controlled studies employing melatonin doses in this range are urgently needed.

Switching diseased cells from cytosolic aerobic glycolysis to mitochondrial oxidative phosphorylation: A metabolic rhythm regulated by melatonin?

This commentary reviews the concept of the circadian melatonin rhythm playing an essential role in reducing the development of diseases such as solid tumors which adopt cytosolic aerobic glycolysis (Warburg effect) to support their enhanced metabolism. Experimental data show that solid mammary tumors depend on aerobic glycolysis during the day but likely revert to mitochondrial oxidative phosphorylation at night for ATP production. This conversion of diseased cells during the day to a healthier phenotype at night occurs under control of the circulating melatonin rhythm. When the nocturnal melatonin rise is inhibited by light exposure at night, cancer cells function in the diseased state 24/7. The ability of melatonin to switch cancer cells as well as other diseased cells, for example, Alzheimer disease, fibrosis, hyperactivation of macrophages, etc, from aerobic glycolysis to mitochondrial oxidative phosphorylation may be a basic protective mechanism to reduce pathologies.

Sleep in autism: A biomolecular approach to aetiology and treatment

People with autism spectrum disorder (ASD) commonly experience other comorbidities. Studies indicate that between 50% and 83% of individuals with ASD have sleep problems or disorders. The most commonly reported sleep problems are: (a) insomnia symptoms including the inability to get to sleep or stay asleep; and (b) circadian rhythm sleep-wake disorders, defined as a misalignment between the timing of endogenous circadian rhythms and the external environment. The circadian system provides timing information for the sleep-wake cycle that is regulated by the interaction of an endogenous processes (circadian - Process C, and homeostatic - Process S) and synchronizing agents (neurohormones and neurotransmitters), which produce somnogenic activity. A clinical priority in ASD is understanding the cause of these sleep problems in order to improve treatment outcomes. This review approaches sleep in autism from several perspectives: Sleep-wake mechanisms and problems, and brain areas and molecules controlling sleep (e.g., GABA and melatonin) and wake maintenance (e.g., serotonin, acetylcholine and glutamate). Specifically, this review examines how altered sleep structure could be related to neurobiological alterations or genetic mutations and the implications this may have for potential pharmacological treatments in individuals with ASD.

Increased plasma melatonin in presymptomatic Huntington disease sheep (Ovis aries): Compensatory neuroprotection in a neurodegenerative disease?

Melatonin is a pleiotrophic hormone, synthesised primarily by the pineal gland under the control of the suprachiasmatic nuclei (SCN). It not only provides a hormonal signal of darkness but also has neuroprotective properties. Huntington's disease (HD) is a progressive neurodegenerative disorder characterised by abnormal motor, cognitive and psychiatric symptoms. There is growing evidence, particularly from animal models, that circadian rhythms may also be disturbed in HD. We measured two circadian-regulated hormones, melatonin and cortisol, in plasma samples collected around-the-clock from normal and presymptomatic transgenic HD sheep (Ovis aries) at 5 and 7 years of age, to assess SCN-driven rhythms and the effect of genotype, sex and age. Melatonin-related precursors and metabolites (tryptophan, serotonin, kynurenine) were also measured by liquid chromatography (LC)-mass spectrometry (MS). At 5 years of age in both rams and ewes, plasma melatonin levels were significantly elevated in HD sheep. In ewes measured 2 years later, there was still a significant elevation of nocturnal melatonin. Furthermore, the daytime baseline levels of melatonin were significantly higher in HD sheep. Since increased melatonin could have global beneficial effects on brain function, we suggest that the increased melatonin measured in presymptomatic HD sheep is part of an autoprotective response to mutant huntingtin toxicity that may account, at least in part, for the late onset of disease that characterises HD.

Advances in Characterizing Recently-Identified Molecular Actions of Melatonin: Clinical Implications

Melatonin, N-acetyl-5-methoxy-tryptamine, was discovered to be a product of serotonin metabolism in the mammalian pineal gland where its synthesis is under control of the light:dark cycle. Besides its regulatory pathway involving ganglion cells in the retina, the neural connections between the eyes and the pineal gland include the master circadian clock, the suprachiasmatic nuclei, and the central and peripheral nervous systems. Since pineal melatonin is released into the blood and into the cerebrospinal fluid, it has access to every cell in an organism and it mediates system-wide effects. Subsequently, melatonin was found in several extrapineal organs and, more recently, perhaps in every cell of every organ. In contrast to the pinealocytes, non-pineal cells do not discharge melatonin into the blood; rather it is used locally in an intracrine, autocrine, or paracrine manner. Melatonin levels in non-pineal cells do not exhibit a circadian rhythm and do not depend on circulating melatonin concentrations although when animals are treated with exogenous melatonin it is taken up by presumably all cells. Mitochondria are the presumed site of melatonin synthesis in all cells; the enzymatic machinery for melatonin synthesis has been identified in mitochondria. The association of melatonin with mitochondria, because of its ability to inhibit oxidative stress, is very fortuitous since these organelles are a major site of damaging reactive oxygen species generation. In this review, some of the actions of non-pineal-derived melatonin are discussed in terms of cellular and subcellular physiology.

The use and misuse of exogenous melatonin in the treatment of sleep disorders

PURPOSE OF REVIEW

To explore the evidence for using exogenous melatonin in the treatment of sleep disorders, both primary and secondary, in children and adults.

RECENT FINDINGS

A number of recently published meta-analyses have shown that there is evidence for the efficacy of exogenously administered melatonin in a number of sleep disorders. However, melatonin is likely to be prescribed largely for reasons of perceived minimal side-effect profile and very low cost in situations in which high-quality evidence for its usefulness is not forthcoming.

SUMMARY

There is evidence for the efficacy of melatonin in the management of insomnia and some intrinsic disorders of circadian rhythm in adults and children as well as in reducing sleep onset latency in jet-lag and shift work disorder in adults. Melatonin is used routinely in the treatment of rapid-eye movement sleep-behaviour disorder despite limited trial evidence. Increasingly, dual melatonin receptor agonists are being trialled in a variety of sleep disorders. Long-term adverse effects are currently not fully identified.

Mental health in elite athletes: International Olympic Committee consensus statement (2019)

Mental health symptoms and disorders are common among elite athletes, may have sport related manifestations within this population and impair performance. Mental health cannot be separated from physical health, as evidenced by mental health symptoms and disorders increasing the risk of physical injury and delaying subsequent recovery. There are no evidence or consensus based guidelines for diagnosis and management of mental health symptoms and disorders in elite athletes. Diagnosis must differentiate character traits particular to elite athletes from psychosocial maladaptations.

Management strategies should address all contributors to mental health symptoms and consider biopsychosocial factors relevant to athletes to maximise benefit and minimise harm. Management must involve both treatment of affected individual athletes and optimising environments in which all elite athletes train and compete. To advance a more standardised, evidence based approach to mental health symptoms and disorders in elite athletes, an International Olympic Committee Consensus Work Group critically evaluated the current state of science and provided recommendations.

The potential utility of melatonin in the treatment of childhood cancer

Childhood cancer management has improved considerably, with the overall objective of preventing early-life cancers completely. However, cancer remains a major cause of death in children, with the survivors developing anticancer treatment-specific health problems. Therefore, the anticancer treatment needs further improvement. Melatonin is a effective antioxidant and circadian pacemaker. Through multiple mechanisms, melatonin has significant positive effects on multitude adult cancers by increasing survival and treatment response rates, and slowing disease progression. In addition, melatonin appears to be safe for children. As an appealing therapeutic agent, we herein address several key concerns regarding melatonin's potential for treating children with cancer.

Clinical and Experimental Human Sleep-Wake Pharmacogenetics

Sleep and wakefulness are highly complex processes that are elegantly orchestrated by fine-tuned neurochemical changes among neuronal and non-neuronal ensembles, nuclei, and networks of the brain. Important neurotransmitters and neuromodulators regulating the circadian and homeostatic facets of sleep-wake physiology include melatonin, γ-aminobutyric acid, hypocretin, histamine, norepinephrine, serotonin, dopamine, and adenosine. Dysregulation of these neurochemical systems may cause sleep-wake disorders, which are commonly classified into insomnia disorder, parasomnias, circadian rhythm sleep-wake disorders, central disorders of hypersomnolence, sleep-related movement disorders, and sleep-related breathing disorders. Sleep-wake disorders can have far-reaching consequences on physical, mental, and social well-being and health and, thus, need be treated with effective and rational therapies. Apart from behavioral (e.g., cognitive behavioral therapy for insomnia), physiological (e.g., chronotherapy with bright light), and mechanical (e.g., continuous positive airway pressure treatment of obstructive sleep apnea) interventions, pharmacological treatments often are the first-line clinical option to improve disturbed sleep and wake states. Nevertheless, not all patients respond to pharmacotherapy in uniform and beneficial fashion, partly due to genetic differences. The improved understanding of the neurochemical mechanisms regulating sleep and wakefulness and the mode of action of sleep-wake therapeutics has provided a conceptual framework, to search for functional genetic variants modifying individual drug response phenotypes. This article will summarize the currently known genetic polymorphisms that modulate drug sensitivity and exposure, to partly determine individual responses to sleep-wake pharmacotherapy. In addition, a pharmacogenetic strategy will be outlined how based upon classical and opto-/chemogenetic strategies in animals, as well as human genetic associations, circuit mechanisms regulating sleep-wake functions in humans can be identified. As such, experimental human sleep-wake pharmacogenetics forms a bridge spanning basic research and clinical medicine and constitutes an essential step for the search and development of novel sleep-wake targets and therapeutics.

Neuroendocrine aspects of improving sleep in epilepsy

Sleep plays an intricate role in epilepsy and can affect the frequency and occurrence of seizures. With nearly 35% of U.S. adults failing to obtain the recommended 7 h of sleep every night, understanding the complex relationship between sleep and epilepsy is of utmost relevance. Sleep deprivation is a common trigger of seizures in many persons with epilepsy and sleep patterns play a role in the occurrence of seizures. Some patients have their first seizure or repeated seizures after an "all-nighter" at college or after a long period of chronic sleep deprivation. The strength of the relationship between sleep and seizures varies between patients, but improving sleep and optimizing seizure control can have significant positive effects on the quality of life for all these patients. Research has shown that the changes in the brain's electrical and hormonal activity occurring during normal sleep-wake cycles can be linked to both sleep and seizure patterns. Many questions remain to be answered about sleep and epilepsy. How can sleep deprivation trigger an epileptic seizure? How do circadian and hormonal changes influence sleep pattern and seizure occurrence? Can hormones or sleeping pills help with sleep in epilepsy? In this article we discuss these and many other questions on sleep in epilepsy, with an emphasis on sleep architecture, hormone changes, mechanistic factors, and possible prevention strategies.