Narcolepsy and Disorders of Excessive Somnolence

Sleep disorders, obesity, and aging: the role of orexin

The hypothalamic neuropeptides orexin A and B (hypocretin 1 and 2) are important homeostatic mediators of central control of energy metabolism and maintenance of sleep/wake states. Dysregulation or loss of orexin signaling has been linked to narcolepsy, obesity, and age-related disorders. In this review, we present an overview of our current understanding of orexin function, focusing on sleep disorders, energy balance, and aging, in both rodents and humans. We first discuss animal models used in studies of obesity and sleep, including loss of function using transgenic or viral-mediated approaches, gain of function models using exogenous delivery of orexin receptor agonist, and naturally-occurring models in which orexin responsiveness varies by individual. We next explore rodent models of orexin in aging, presenting evidence that orexin loss contributes to age-related changes in sleep and energy balance. In the next section, we focus on clinical importance of orexin in human obesity, sleep, and aging. We include discussion of orexin loss in narcolepsy and potential importance of orexin in insomnia, correlations between animal and human studies of age-related decline, and evidence for orexin involvement in age-related changes in cognitive performance. Finally, we present a summary of recent studies of orexin in neurodegenerative disease. We conclude that orexin acts as an integrative homeostatic signal influencing numerous brain regions, and that this pivotal role results in potential dysregulation of multiple physiological processes when orexin signaling is disrupted or lost.

Modeling human disease with pluripotent stem cells: from genome association to function

Mechanistic insights into human disease may enable the development of treatments that are effective in broad patient populations. The confluence of gene-editing technologies, induced pluripotent stem cells, and genome-wide association as well as DNA sequencing studies is enabling new approaches for illuminating the molecular basis of human disease. We discuss the opportunities and challenges of combining these technologies and provide a workflow for interrogating the contribution of disease-associated candidate genetic variants to disease-relevant phenotypes. Finally, we discuss the potential utility of human pluripotent stem cells for placing disease-associated genetic variants into molecular pathways.

Clinical assessment and management of sleep disorders in multiple sclerosis: a literature review

The major sleep disorders are common in multiple sclerosis (MS) and are associated with significant morbidity. Despite this, the rate of recognition and management of these conditions are low. All types of sleep disorders are seen in patients with MS: insomnia, circadian rhythm sleep disorders, sleep-related movement disorders, sleep-related breathing disorders, hypersomnia (narcolepsy), and parasomnia (REM sleep behavior disorder; RBD). This literature review covers the prevalence, clinical features, and treatment of sleep disorders in MS. Based on clinical experience, the spectrum of symptoms associated with MS, and the current knowledge of MS pathophysiology, we have also enclosed proposed strategies for clinical assessment and investigation of sleep disorders in MS patients.

A review of tolerability and abuse liability of gamma-hydroxybutyric acid for insomnia in patients with schizophrenia

BACKGROUND

Approved therapeutic uses for gamma-hydroxybutyric acid (GHB) (or sodium oxybate), a gamma-aminobutyric acid type B and GHB receptor agonist, include narcolepsy in the United States and Europe and alcohol abuse treatment in Italy. Possible efficacy of GHB in schizophrenia has also been proposed. A tolerability concern regarding use of GHB is its abuse potential. Given the high comorbidity of substance disorders and schizophrenia, a systematic assessment of the published literature is crucial.

OBJECTIVE

The aim of this review was to assess the tolerability and abuse liability of GHB in the context of future clinical studies as a potential treatment for insomnia in patients with schizophrenia.

METHODS

A literature search in English (inception through April 2009, inclusive) was conducted of MEDLINE, EMBASE, and PsycINFO using the search term GHB. All articles whose abstracts mentioned human use of GHB were read in their entirety. The reference sections of identified articles were reviewed for publications that might have been missed by the initial search.

RESULTS

GHB is abused by a small percentage of people (<1%) as a "club drug" and is commonly associated with enhanced sexual experiences (65%), euphoria (41%), somnolence (71%), and confusion (24%), according to a recent study. A review of all available emergency room case series suggests that while GHB can be associated with serious coma necessitating intubation, the number of reported fatal cases associated with GHB appears limited. Clarity on the lethality of GHB is complicated by instability of GHB in postmortem samples and frequent concomitant ingestions. Furthermore, formal abuse liability studies do not support high abuse propensity for GHB, mainly because oversedation and dizziness may lead most individuals to find GHB unpleasant at high doses. As supported by 2 large studies, there is limited evidence to suggest widespread use as an agent in sexual assault. Years of clinical use in narcolepsy do not support the development of tolerance or withdrawal in those subjects without substance dependence.

CONCLUSIONS

Tolerability and abuse liability issues, while a concern with GHB given its abuse potential, do not preclude further study of the potential use for insomnia in nondually diagnosed schizophrenia. Full cognizance must be taken of risk/benefit tradeoffs, and to the development of improved formulations with decreased abuse liability.

Les médicaments du sommeil et de la vigilance et leurs indications

This paper is a review of the use of drugs in sleep and wakefulness disorders. Insomnia is more often a symptom than an autonomic disorder. Good knowledge of the clinical facts is required before prescribing hypnotics. Sedative drugs are potentially hypnotics; yet, melatonin is not sedative and may be considered to resynchronise of sleep phases. Stimulant drugs are prescribed in attention disorders; methylphenidate is the more frequently used. Narcolepsy, which is characterized by daytime sleepiness and irresistible episodes of sleep, is treated by an alpha1 noradrenergic stimulant modafinil which has no amphetaminic properties.