Narcolepsy: immunological aspects

Health-related quality of life in narcolepsy: A systematic review and meta-analysis

To date, there has been no systematic analysis of the literature regarding health-related quality of life in narcolepsy. This systematic review aimed to examine the impact of narcolepsy on health-related quality of life, measured through standardised health-related quality of life questionnaires such as the Short Form 36 and Functional Outcome of Sleep Questionnaire. The following databases: Medline, Embase, Cinahl, and Web of Science were searched for studies that investigated health-related quality of life in adults with narcolepsy. Studies were reviewed independently by two reviewers, and a random-effects meta-analysis was performed. A total of 30 studies were eligible for inclusion in the review. Additionally, meta-analyses were conducted for the Short Form 36 and the EQ5D. The Short Form 36 meta-analysis identified that the pooled mean scores for the Physical Component Summary (45.91) were less affected than the Mental Component Summary (42.98). People with narcolepsy experience substantially lower health-related quality of life when compared with the general population norms of the USA, UK, France and Norway, as well as compared with people with chronic diseases such as multiple sclerosis, diabetes, hypertension and epilepsy. Further research is warranted to identify the longitudinal effects of narcolepsy on health-related quality of life, and to develop a narcolepsy-specific health-related quality of life tool.

Polysomnographic nighttime features of narcolepsy: A systematic review and meta-analysis

Polysomnographic studies have been conducted to explore nighttime sleep features in narcolepsy, but their relationship to narcolepsy is still imperfectly understood. We conducted a systematic review of the literature exploring polysomnographic differences between narcolepsy patients and healthy controls (HCs) in EMBASE, MEDLINE, All EBM databases, CINAHL, and PsycINFO. 108 studies were identified for this review, 105 of which were used for meta-analysis. Meta-analyses revealed significant reductions in sleep latency, sleep efficiency, slow wave sleep percentage, rapid eye movement sleep (REM) latency, cyclic alternating pattern rate, and increases in total sleep time, wake time after sleep onset (WASO), awakening numbers (AWN) per hour, stage shift (SS) per hour, N1 percentage, apnea hypopnea index, and periodic limb movement index in narcolepsy patients compared with HCs. Furthermore, narcolepsy type 1 patients showed more disturbed nighttime sleep compared with narcolepsy type 2 patients. Children and adolescent narcolepsy patients show increased WASO, AWN, and SS compared with adult patients. Macro- and micro-structurally, our study suggests that narcolepsy patients have poor nighttime sleep. Sex, age, body mass index, disease duration, disease type, medication status, and adaptation night are demographic, clinical and methodological factors that contribute to heterogeneity between studies.

Decreased concentration of klotho and increased concentration of FGF23 in the cerebrospinal fluid of patients with narcolepsy

OBJECTIVE

to explore the status of concentration of klotho and fibroblast growth factor 23 (FGF23) in cerebrospinal fluid (CSF) of patients with narcolepsy.

PATIENTS/METHODS

59 patients with narcolepsy and 17 control individuals were enrolled. We used radioimmunoassay, human klotho enzyme-linked immunosorbent assay (ELISA), human intact FGF23 ELISA and spectrophotometry to measure hypocretin-1, klotho, FGF-23 and phosphorus, respectively. T-Student Test was used to compare klotho and phosphate concentrations, Mann-Whitney U Test were used to compare FGF-23 levels between groups. ANOVA Test was used to compare klotho and phosphate CSF concentrations among narcolepsy patients with CSF hypocretin-1 <110 pg/ml (HCRT-) and narcolepsy patients with CSF hypocretin-1 >110 pg/ml (HCRT+) versus control subjects.

RESULTS

Klotho and phosphorus CSF levels were lower in narcoleptic patients than in control (908.18 ± 405.51 versus 1265.78 ± 523.26 pg/ml; p = 0.004 and 1.34 ± 0.25 versus 1.58 ± 0.23 mg/dl; p = 0.001, respectively). We found higher FGF-23 levels in narcoleptic patients (5.51 versus 4.00 pg/mL; p = 0.001). Klotho and phosphorus CSF levels were lower in both HCRT- and HCRT+ than controls. Moreover, there were higher FGF-23 levels in both HCRT-/HCRT+ groups versus controls. However, we did not find differences comparing HCRT- and HCRT+ groups, analyzing CSF klotho, FGF-23 or phosphorus levels.

CONCLUSIONS

Patients with narcolepsy have decreased CSF concentration of klotho and increased CSF levels of FGF-23. These findings may play a role in understanding the pathogenesis of narcolepsy.

The impact of the HLA DQB1 gene and amino acids on the development of narcolepsy

INTRODUCTION

Narcolepsy is a chronic neurological and a genetic disorder of autoimmune origin, which is characterized by five main symptoms, including excessive day time sleepiness, sudden loss of muscle tone or cataplexy, sleep paralysis, hypnagogic hallucinations, and disturbed nocturnal sleep. While there are several diagnostic tests for Narcolepsy such as MSLT (mean sleep latency test), polysomnography and low range of hypocretin in cerebrospinal fluid (CSF), sensitivity and specificity in these methodologies are not sufficient enough. Therefore, methods with higher sensitivity for the accurate diagnosis and confirmation of the disease are necessary.

METHODS

According to the infrequent prevalence of narcolepsy disease, we scheduled a case-control association study with 20 narcoleptic patients and 150 healthy individuals in a high-resolution HLA typing procedure employing SSP-PCR.

RESULTS

Our study demonstrates that the DQB1*06:02 allele provides the highest susceptibility with absolute risk of 0.13%, for Narcolepsy (P = 1x10^-14, RR = 60.5, PcPPV = 0.13%), while, HLA-DQB1* 03:05 allele presents protection to Narcolepsy (P = 1x10^-4, PcPPV = 3.19x10^-4%). Furthermore, for the first time, the AA analysis displayed that AA serine¹⁸² and threonine¹⁸⁵ located on epitope of DQβ1 chain receptor (DQB1^{Ser182,Thr185}) present significant susceptibility for Narcolepsy (Pc= 87.03 × 10^-13, PcPPV = 0.024%) while, asparagine¹⁸² located on epitope of DQβ1 protein receptor (DQB1^Asn182) confers the highest protection against development of Narcolepsy (Pc= 2.16 × 10^-5, PcPPV = 0.0012%).

CONCLUSION

Thus, this can be proposed that the polymorphic differences in the epitope of the HLA receptor could contribute to their differential association with the Narcolepsy in Iranian population.

Narcolepsy in children and young people in Ireland: 2006-2017

AIM

To describe the population of young people in Ireland diagnosed with narcolepsy with regards to vaccine exposure, symptomatology, investigation results and experience of medical treatment.

METHOD

Retrospective review of medical records at the single tertiary referral centre for young people with narcolepsy in Ireland.

RESULTS

Sixty-seven patients were diagnosed with narcolepsy between July 2006 and July 2017. Sixty-one (91%) of these developed symptoms after receiving the Pandemrix vaccine. The population was largely homogeneous with low hypocretin (87.5%), HLA DQB1∗0602 positivity (95%) and unremarkable findings on MRI Brain (100%). 77.6% experienced cataplexy; we also measured high levels of obesity, school non-attendance and psychosocial complexity. Symptoms often continued despite treatment, with multiple medications prescribed in 76.1% of patients. Prescription of sodium oxybate was associated with a significant reduction in BMI standard deviation scores at 6 months, with improved IOTF obesity scores seen at 36 month follow-up.

CONCLUSIONS

This paper describes the experience of narcolepsy in children and young people in Ireland from 2006 - 2017 at the national tertiary referral centre. Narcolepsy in children and young people in Ireland carries a significant burden of illness, with impact on participation in education as well as physical and mental health. Symptoms can be refractory to medical treatment. Referral to tertiary centres for prompt treatment and multidisciplinary input is essential.

Study protocol: A profile of physical performance variables in an outpatient adult population with narcolepsy

Background: Narcolepsy is a sleep disorder characterised by excessive daytime sleepiness and significantly impacts quality of life. People with narcolepsy demonstrate many potential barriers to being physically fit and active, such as sleepiness and social isolation. Very little is known about how physical performance variables may be affected in people with narcolepsy. This study aims to profile the physical fitness of adults with narcolepsy and to explore the relationship between physical fitness and quality of life, symptom severity and disease duration in this cohort. Methods and Analysis: In this cross-sectional observational study, participants will undergo a comprehensive physical performance test battery that will investigate cardiopulmonary fitness, objective measures of physical activity, muscle strength and endurance. Furthermore, quality of life, symptom severity and physical activity will be ascertained through self-report questionnaires. The study population will consist of adults with narcolepsy aged 18-65 years attending the National Narcolepsy Centre located in St. James’s Hospital as an outpatient. Ethics and Dissemination: Ethical approval has been obtained from the St. James’s Hospital and Tallaght University Hospital Research Ethics Committee, and this study is presently underway. The results obtained from this study will be used to help tailor exercise and possible rehabilitation strategies for this population. Dissemination will be sought through peer-reviewed journals, national and international conferences, and through engagement with service user groups. Registration: ClinicalTrials.gov Identifier NCT04419792; registered on 5 June 2020.

[Narcolepsy: From the discovery of a wake promoting peptide to autoimmune T cell biology and molecular mimicry with flu epitopes]

Narcolepsy-cataplexy was first described in the late 19th century in Germany and France. Prevalence was established to be 0.05 % and a canine model was discovered in the 1970s. In 1983, a Japanese study found that all patients carried HLA-DR2, suggesting autoimmunity as the cause of the disease. Studies in the canine model established that dopaminergic stimulation underlies anti-narcoleptic action of psychostimulants, while antidepressants were found to suppress cataplexy through adrenergic reuptake inhibition. No HLA association was found in canines. A linkage study initiated in 1988 revealed in hypocretin (orexin) receptor two mutations as the cause of canine narcolepsy in 1999. In 1992, studies on African Americans showed that DQ0602 was a better marker than DR2 across all ethnic groups. In 2000, hypocretin-1/orexin A levels were measured in the cerebrospinal fluid (CSF) and found to be undetectable in most patients, establishing hypocretin deficiency as the cause of narcolepsy. Decreased CSF hypocretin-1 was then found to be secondary to the loss of the 70,000 neurons producing hypocretin in the hypothalamus, suggesting immune destruction of these cells as the cause of the disease. Additional genetic studies, notably genome wide associations (GWAS), found multiple genetic predisposing factors for narcolepsy. These were almost all involved in other autoimmune diseases, although a strong and unique association with T cell receptor (TCR) alpha and beta loci were observed. Nonetheless, all attempts to demonstrate presence of autoantibodies against hypocretin cells in narcolepsy failed, and the presumed autoimmune cause remained unproven. In 2009, association with strep throat infections were found, and narcolepsy onsets were found to occur more frequently in spring and summer, suggesting upper away infections as triggers. Following reports that narcolepsy cases were triggered by vaccinations and infections against influenza A 2009 pH1N1, a new pandemic strain that erupted in 2009, molecular mimicry with influenza A virus was suggested in 2010. This hypothesis was later confirmed by peptide screening showing higher activity of CD4⁺ T cell reactivity to a specific post-translationally amidated segment of hypocretin (HCRT-_NH2) and cross-reactivity of specific TCRs with a pH1N1-specific segment of hemagglutinin that shares homology with HCRT-_NH2. Strikingly, the most frequent TCR recognizing these antigens was found to carry sequences containing TRAJ24 or TRVB4-2, segments modulated by narcolepsy-associated genetic polymorphisms. Cross-reactive CD4⁺ T cells with these cross-reactive TCRs likely subsequently recruit CD8⁺ T cells that are then involved in hypocretin cell destruction. Additional flu mimics are also likely to be discovered since narcolepsy existed prior to 2009. The work that has been conducted over the years on narcolepsy offers a unique perspective on the conduct of research on the etiopathogeny of a specific disease.

Molecular mechanism of tumour necrosis factor alpha regulates hypocretin (orexin) expression, sleep and behaviour

Hypocretin 1 and hypocretin 2 (orexin A and B) regulate sleep, wakefulness and emotion. Tumour necrosis factor alpha (TNF-α) is an important neuroinflammation mediator. Here, we examined the effects of TNF-α treatment on hypocretin expression in vivo and behaviour in mice. TNF-α decreased hypocretin 1 and hypocretin 2 expression in a dose-dependent manner in cultured hypothalamic neurons. TNF-α decreased mRNA stability of prepro-hypocretin, the single precursor of hypocretin 1 and hypocretin 2. Mice challenged with TNF-α demonstrated decreased expression of prepro-hypocretin, hypocretin 1 and hypocretin 2 in hypothalamus. In response to TNF-α, prepro-hypocretin mRNA decay was increased in hypothalamus. TNF-α neutralizing antibody restored the expression of prepro-hypocretin, hypocretin 1 and hypocretin 2 in vivo in TNF-α challenged mice, supporting hypocretin system can be impaired by increased TNF-α through decreasing hypocretin expression. Repeated TNF-α challenge induced muscle activity during rapid eye movement sleep and sleep fragmentation, but decreased learning, cognition and memory in mice. TNF-α neutralizing antibody blocked the effects of TNF-α; in contrast, hypocretin receptor antagonist enhanced the effects of TNF-α. The data support that TNF-α is involved in the regulation of hypocretin expression, sleep and cognition. The findings shed some lights on the role of neuroinflammation in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease.

Narcolepsy and adjuvanted pandemic influenza A (H1N1) 2009 vaccines - Multi-country assessment

BACKGROUND

In 2010, a safety signal was detected for narcolepsy following vaccination with Pandemrix, an AS03-adjuvanted monovalent pandemic H1N1 influenza (pH1N1) vaccine. To further assess a possible association and inform policy on future use of adjuvants, we conducted a multi-country study of narcolepsy and adjuvanted pH1N1 vaccines.

METHODS

We used electronic health databases to conduct a dynamic retrospective cohort study to assess narcolepsy incidence rates (IR) before and during pH1N1 virus circulation, and after pH1N1 vaccination campaigns in Canada, Denmark, Spain, Sweden, Taiwan, the Netherlands, and the United Kingdom. Using a case-control study design, we evaluated the risk of narcolepsy following AS03- and MF59-adjuvanted pH1N1 vaccines in Argentina, Canada, Spain, Switzerland, Taiwan, and the Netherlands. In the Netherlands, we also conducted a case-coverage study in children born between 2004 and 2009.

RESULTS

No changes in narcolepsy IRs were observed in any periods in single study sites except Sweden and Taiwan; in Taiwan incidence increased after wild-type pH1N1 virus circulation and in Sweden (a previously identified signaling country), incidence increased after the start of pH1N1 vaccination. No association was observed for Arepanrix-AS03 or Focetria-MF59 adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the case-control study nor for children born between 2004 and 2009 in the Netherlands case-coverage study for Pandemrix-AS03.

CONCLUSIONS

Other than elevated narcolepsy IRs in the period after vaccination campaigns in Sweden, we did not find an association between AS03- or MF59-adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the sites studied, although power to evaluate the AS03-adjuvanted Pandemrix brand vaccine was limited in our study.

Pandemic influenza vaccine & narcolepsy: simulations on the potential impact of bias

Several studies have identified an association between Pandemrix(TM), an AS03 adjuvanted pandemic influenza A(H1N1) vaccine, and narcolepsy, a rare and under-diagnosed sleep disorder with a median onset-to-diagnosis interval of ten years. This paper reviews potential sources of bias in published studies and aims to provide, through simulation, methodological recommendations for assessment of vaccine safety signals. Our simulation study showed that in the absence of an association between the vaccine and the outcome, presence of detection bias and differential exposure misclassification could account for elevated risk estimates. These may play a major role, particularly in alert situations when observation times are limited and the disease has a long latency period. Estimates from the case-control design were less inflated than those from the cohort design when these biases were present. Overall, these simulations provide useful insights for the design and interpretation of future studies.

A practical approach to the diagnosis and management of sleep disorders in patients with multiple sclerosis

Patients with multiple sclerosis (MS) are at increased risk for comorbid sleep disturbances, which can profoundly contribute to poor functional status and fatigue. Insomnia, sleep-disordered breathing, and restless legs syndrome are among the most common sleep disorders experienced by patients with MS. Despite their impact, these underlying sleep disorders may escape routine clinical evaluations in persons with MS, thereby leading to missed opportunities to optimize functional status and quality of life in patients with MS. A practical, systematic approach to the evaluation and treatment of sleep disorders in MS, in the context of MS-specific variables that may influence risk for these conditions or response to therapy, is recommended to facilitate early diagnosis and successful treatment. This review summarizes the most common sleep disorders experienced by persons with MS, and offers a practical approach to diagnosis and management of these conditions.

Incidence of narcolepsy before and after MF59-adjuvanted influenza A(H1N1)pdm09 vaccination in South Korean soldiers

BACKGROUND

Previous reports mostly from Europe suggested an association between an occurrence of narcolepsy and an influenza A(H1N1)pdm09 vaccine adjuvanted with AS03 (Pandemrix(®)). During the 2009 H1N1 pandemic vaccination campaign, the Korean military performed a vaccination campaign with one type of influenza vaccine containing MF59-adjuvants. This study was conducted to investigate the background incidence rate of narcolepsy in South Korean soldiers and the association of the MF59-adjuvanted vaccine with the occurrence of narcolepsy in a young adult group.

METHODS

To assess the incidence of narcolepsy, we retrospectively reviewed medical records of suspicious cases of narcolepsy in 2007-2013 in the whole 20 military hospitals of the Korean military. The screened cases were classified according to the Brighton Collaboration case definition of narcolepsy. After obtaining the number of confirmed cases of narcolepsy per 3 months in 2007-2013, we compared the crude incidence rate of narcolepsy before and after the vaccination campaign.

RESULTS

We included 218 narcolepsy suspicious cases in the initial review, which were screened by the diagnostic code on the computerized disease registry in 2007-2013. Forty-one cases were finally diagnosed with narcolepsy in 2007-2013 (male sex, 95%; median age, 21 years). The average background incidence rate of narcolepsy in Korean soldiers was 0.91 cases per 100,000 persons per year. During the 9 months before vaccination implementation (April to December 2009), 6 narcolepsy cases occurred, whereas during the next 9 months (January to September 2010) including the 3-month vaccination campaign, 5 cases occurred.

CONCLUSIONS

The incidence of narcolepsy in South Korean soldiers was not increased after the pandemic vaccination campaign using the MF59-adjuvanted vaccine. Our results suggest that the MF59-adjuvanted H1N1 vaccine did not contribute to the occurrence of narcolepsy in this young adult group.

The complementary roles of Phase 3 trials and post-licensure surveillance in the evaluation of new vaccines

Vaccines have led to significant reductions in morbidity and saved countless lives from many infectious diseases and are one of the most important public health successes of the modern era. Both vaccines' effectiveness and safety are keys for the success of immunisation programmes. The role of post-licensure surveillance has become increasingly recognised by regulatory authorities in the overall vaccine development process. Safety, purity, and effectiveness of vaccines are carefully assessed before licensure, but some safety and effectiveness aspects need continuing monitoring after licensure; Post-marketing activities are a necessary complement to pre-licensure activities for monitoring vaccine quality and to inform public health programmes. In the recent past, the availability of large databases together with data-mining and cross-linkage techniques have significantly improved the potentialities of post-licensure surveillance. The scope of this review is to present challenges and opportunities offered by vaccine post-licensure surveillance. While pre-licensure activities form the foundation for the development of effective and safe vaccines, post-licensure monitoring and assessment, are necessary to assure that vaccines are effective and safe when translated in real world settings. Strong partnerships and collaboration at an international level between different stakeholders is necessary for finding and optimally allocating resources and establishing robust post-licensure processes.

Alterations of orexinergic and melanin-concentrating hormone neurons in experimental sleeping sickness

Human African trypanosomiasis or sleeping sickness is a severe, neglected tropical disease caused by the extracellular parasite Trypanosoma brucei. The disease, which leads to chronic neuroinflammation, is characterized by sleep and wake disturbances, documented also in rodent models. In rats and mice infected with Trypanosoma brucei brucei, we here tested the hypothesis that the disease could target neurons of the lateral hypothalamus (LH) containing orexin (OX)-A or melanin-concentrating hormone (MCH), implicated in sleep/wake regulation. In the cerebrospinal fluid of infected rats, the OX-A level was significantly decreased early after parasite neuroinvasion, and returned to the control level at an advanced disease stage. The number of immunohistochemically characterized OX-A and MCH neurons decreased significantly in infected rats during disease progression and in infected mice at an advanced disease stage. A marked reduction of the complexity of dendritic arborizations of OX-A neurons was documented in infected mice. The evaluation of NeuN-immunoreactive neurons did not reveal significant neuronal loss in the LH of infected mice, thus suggesting a potential selective vulnerability of OX-A and MCH neurons. Immunophenotyping and quantitative analysis showed in infected mice marked activation of microglial cells surrounding OX-A neurons. Day/night oscillation of c-Fos baseline expression was used as marker of OX-A neuron activity in mice. In control animals Fos was expressed in a higher proportion of OX-A neurons in the night (activity) phase than in the day (rest) phase. Interestingly, in infected mice the diurnal spontaneous Fos oscillation was reversed, with a proportion of OX-A/Fos neurons significantly higher at daytime than at nighttime. Altogether the findings reveal a progressive decrease of OX-A and MCH neurons and dysregulation of OX-A neuron diurnal activity in rodent models of sleeping sickness. The data point to the involvement of these peptidergic neurons in the pathogenesis of sleep/wake alterations in the disease and to their vulnerability to inflammatory signaling.

History of narcolepsy at Stanford University

Although narcolepsy was first described in the late nineteenth century in Germany and France, much of the research on this disorder has been conducted at Stanford University, starting with Drs. William C. Dement and Christian Guilleminault in the 1970s. The prevalence of narcolepsy was established, and a canine model discovered. Following the finding in Japan that almost all patients with narcolepsy carry a specific HLA subtype, HLA-DR2, Hugh Mac Devitt, F. Carl Grumet, and Larry Steinman initiated immunological studies, but results were generally negative. Using the narcoleptic canines, Dr. Nishino and I established that stimulants increased wakefulness by stimulating dopaminergic transmission while antidepressants suppress cataplexy via adrenergic reuptake inhibition. A linkage study was initiated with Dr. Grumet in 1988, and after 10 years of work, the canine narcolepsy gene was cloned by in 1999 and identified as the hypocretin (orexin) receptor 2. In 1992, studying African Americans, we also found that DQ0602 rather than DR2 was a better marker for narcolepsy across all ethnic groups. In 2000, Dr. Nishino and I, in collaboration with Dr. Lammers in the Netherlands, found that hypocretin 1 levels in the cerebrospinal fluid (CSF) were undetectable in most cases, establishing hypocretin deficiency as the cause of narcolepsy. Pursuing this research, our and Dr. Siegel's group, examining postmortem brains, found that the decreased CSF hypocretin 1 was secondary to the loss the 70,000 neurons producing hypocretin in the hypothalamus. This finding revived the autoimmune hypothesis but attempts at demonstrating immune targeting of hypocretin cells failed until 2013. At this date, Dr. Elisabeth Mellins and I discovered that narcolepsy is characterized by the presence of autoreactive CD4(+) T cells to hypocretin fragments when presented by DQ0602. Following reports that narcolepsy cases were triggered by vaccinations and infections against influenza A 2009 pH1N1, a new pandemic strain that erupted in 2009, our groups also established that a small epitope of pH1N1 resembles hypocretin and is likely involved in molecular mimicry. Although much remains to be done, these achievements, establishing hypocretin deficiency as the cause of narcolepsy, demonstrating its autoimmune basis, and showing molecular mimicry between hypocretin and sequences derived from a pandemic strain of influenza, are likely to remain classics in human immunology.

Investigation of an association between onset of narcolepsy and vaccination with pandemic influenza vaccine, Ireland April 2009-December 2010

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The adjuvant component α-tocopherol triggers via modulation of Nrf2 the expression and turnover of hypocretin in vitro and its implication to the development of narcolepsy

BACKGROUND

After the H1N1 swine flu vaccination campaign an increased number of narcolepsy cases in children and adolescents was observed in Scandinavian and later in further European countries that correlated with the vaccination by an AS03-adjuvanted influenza vaccine (Pandemrix). Narcolepsy is a chronic sleep disorder characterized by the loss of hypocretin in the cerebrospinal fluid due to selective destruction of hypocretin-producing neurons in the perifornical hypothalamus. In >99% of the cases narcolepsy is associated with the HLA-subtype DQB1*602 giving the link to an autoimmune process. In contrast to other squalene-based adjuvants, for which no association with narcolepsy was reported so far, ASO3 contains in addition α-tocopherol. It could be observed recently that α-tocopherol activates the transcription factor Nrf2. Nrf2 triggers the expression of cytoprotective genes, i.e. the catalytic active subunits of the constitutive proteasome, by binding to the antioxidant response element (ARE). It was hypothesized that α-tocopherol via activation of Nrf2 affects expression and turnover of hypocretin, leading to an increased amount of hypocretinα-specific fragments that bind to DQB1*602.

RESULTS

α-Tocopherol activates Nrf2 in neuronal cells in vitro. Promoter analysis revealed an ARE sequence in the hypocretin promoter. Indeed, α-tocopherol increases by activation of Nrf2 the expression of hypocretin. In parallel, α-tocopherol -dependent induction of Nrf2 augments expression of catalytic subunits of the proteasome leading to increased degradation of hypocretin. Moreover, elevated activation of Nrf2 is associated with a decreased activity of NF-κB that results in an increased sensitivity to apoptotic stimuli.

CONCLUSION

In case of a genetic predisposition (DQB1*602) α-tocopherol could confer to development of narcolepsy by activation of Nrf2 that finally leads to an elevated formation of longer hypocretin-derived fragments that can be presented by HLA-subtype DQB1*602. These cells are recognized by the immune system and due to their increased sensitivity to apoptotic stimuli they can be destroyed, finally leading to a lack of hypocretin.

Cerebrospinal fluid and serum cytokine profiles in narcolepsy with cataplexy: a case-control study

Recent advances in the identification of susceptibility genes and environmental exposures provide strong support that narcolepsy-cataplexy is an immune-mediated disease. Only few serum cytokine studies with controversial results were performed in narcolepsy and none in the cerebrospinal fluid. We measured a panel of 12 cytokines by a proteomic approach in the serum of 35 patients with narcolepsy-cataplexy compared to 156 healthy controls, and in the cerebrospinal fluid of 34 patients with narcolepsy-cataplexy compared to 17 non-narcoleptic patients; and analyzed the effect of age, duration and severity of disease on the cytokine levels. After multiple adjustments we reported lower serum IL-2, IL-8, TNF-α, MCP-1 and EGF levels, and a tendency for higher IL-4 level in narcolepsy compared to controls. Significant differences were only found for IL-4 in cerebrospinal fluid, being higher in narcolepsy. Positive correlations were found in serum between IL-4, daytime sleepiness, and cataplexy frequency. The expression of some pro-inflammatory cytokines (MCP-1, VEGF, EGF, IL2, IL-1β, IFN-γ) in either serum or CSF was negatively correlated with disease severity and duration. No correlation was found for any specific cytokine in 18 of the patients with narcolepsy with peripheral and central samples collected the same day. Significant decreased pro/anti-inflammatory cytokine profiles were found at peripheral and central levels in narcolepsy, together with a T helper 2/Th1 serum cytokine secretion imbalance. To conclude, we showed some evidence for alterations in the cytokine profile in patients with narcolepsy-cataplexy compared to controls at peripheral and central levels, with the potential role of IL-4 and significant Th1/2 imbalance in the pathophysiology of narcolepsy.

A/H1N1 antibodies and TRIB2 autoantibodies in narcolepsy patients diagnosed in conjunction with the Pandemrix vaccination campaign in Sweden 2009-2010

Narcolepsy is a lifelong sleep disorder related to hypocretin deficiency resulting from a specific loss of hypocretin-producing neurons in the lateral hypothalamic area. The disease is thought to be autoimmune due to a strong association with HLA-DQB1*06:02. In 2009 the World Health Organization (WHO) declared the H1N1 2009 flu pandemic (A/H1N1PDM09). In response to this, the Swedish vaccination campaign began in October of the same year, using the influenza vaccine Pandemrix(®). A few months later an excess of narcolepsy cases was observed. It is still unclear to what extent the vaccination campaign affected humoral autoimmunity associated with narcolepsy. We studied 47 patients with narcolepsy (6-69 years of age) and 80 healthy controls (3-61 years of age) selected after the Pandemrix vaccination campaign. The first aim was to determine antibodies against A/H1N1 and autoantibodies to Tribbles homolog 2 (TRIB2), a narcolepsy autoantigen candidate as well as to GAD65 and IA-2 as disease specificity controls. The second aim was to test if levels and frequencies of these antibodies and autoantibodies were associated with HLA-DQB1*06:02. In vitro transcribed and translated [(35)S]-methionine and -cysteine-labeled influenza A virus (A/California/04/2009/(H1N1)) segment 4 hemagglutinin was used to detect antibodies in a radiobinding assay. Autoantibodies to TRIB2, GAD65 and IA-2 were similarly detected in standard radiobinding assays. The narcolepsy patients had higher median levels of A/H1N1 antibodies than the controls (p = 0.006). A/H1N1 antibody levels were higher among the <13 years old (n = 12) compared to patients who were older than 30 years (n = 12, p = 0.014). Being HLA-DQB1*06:02 positive was associated with higher A/H1N1 antibody levels in both patients and controls (p = 0.026). Serum autoantibody levels to TRIB2 were low overall and high binders did not differ between patients and controls. We observed an association between levels of A/H1N1 antibodies and TRIB2 autoantibody levels particularly among the youngest narcolepsy patients (r = 0.819, p < 0.001). In conclusion, following the 2009 influenza pandemic vaccination, A/H1N1 antibody levels were associated with young age-at-onset narcolepsy patients positive for HLA-DQB1*06:02. The possibility that TRIB2 is an autoantigen in narcolepsy remains to be clarified. We could verify autoantibody responses against TRIB2 which needs to be determined in larger patient cohorts and control populations.

Increased plasma level of tumor necrosis factor α in patients with narcolepsy in Taiwan

BACKGROUND

Narcolepsy is a neuropsychiatric disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and abnormal rapid eye movement (REM) sleep. Tumor necrosis factor α (TNF α) and its cognate receptors have been reported to be involved in the pathophysiology of narcolepsy in addition to the HLA antigen system. Our study aimed to determine if the TNF-α system was associated with narcolepsy in our patients.

METHODS

We first measured the plasma level of TNF α in 56 narcoleptic patients and 53 control subjects using a highly sensitive enzyme-linked immunosorbent assay. We next determined the genotype of three single nucleotide polymorphisms (SNPs) (T-1031C, C-863A, and C-857T) at the promoter region of the TNF-α gene and one missense SNP (T587G, M196R) at the exon 6 of the tumor necrosis factor receptor 2 gene, TNFR2, in a sample of 75 narcoleptic patients and 201 control subjects by direct sequencing analysis.

RESULTS

We found a significant elevation of plasma level of TNF α in patients with narcolepsy compared with the control subjects (4.64pg/mL vs 1.06pg/mL; P=.0013). However, we did not find significant differences between these two groups in the allelic and genotypic distributions of the investigated polymorphisms.

CONCLUSIONS

Our study suggests that an increased TNF-α level was associated with narcolepsy in our patients, and that chronic inflammation due to various factors might have led to the increased TNF-α levels found in our patients.

Association analysis of the major histocompatibility complex, class II, DQ β1 gene, HLA-DQB1, with narcolepsy in Han Chinese patients from Taiwan

BACKGROUND

Narcolepsy is a rare, chronic, disabling neuropsychiatric disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, sleep paralysis, and abnormal rapid eye movement sleep. It is strongly associated with the HLA-DQB1(∗)06:02 allele in various ethnic groups. Our study aimed to investigate the allelic spectrum of HLA-DQB1 in a sample of Han Chinese patients with narcolepsy and control subjects from Taiwan.

METHODS

We determined the genotype of the major histocompatibility complex, class II, DQ β1 gene, HLA-DQB1, in 72 narcolepsy subjects (44 men, 28 women), including 52 narcolepsy subjects with cataplexy (narcolepsy+cataplexy), 20 narcolepsy subjects without cataplexy (narcolepsy-cataplexy), and 194 control subjects (94 men, 100 women) using a sequence-specific oligonucleotide-probe hybridization technique.

RESULTS

We found a strong HLA-DQB1(∗)06:02 association in narcolepsy+cataplexy subjects (odds ratio [OR], 321.4 [95% confidence interval {CI}, 70.7-1461.4]). The association was less prominent in narcolepsy-cataplexy subjects (OR, 6.9 [95% CI, 2.4-20.1]). In addition to the DQB1(∗)06:02, we found that (∗)03:01 also was a predisposing allele (OR, 2.0 [95% CI, 1.1-3.7]) in narcolepsy+cataplexy subjects, though the (∗)06:01 was a predisposing allele (OR, 2.8 [95% CI, 1.2-6.7]) in narcolepsy-cataplexy subjects. Furthermore, we found a significant overrepresentation of DQB1(∗)06:02 homozygotes in narcolepsy+cataplexy subjects.

CONCLUSIONS

Our data add further support to the strong association of the HLA-DQB1(∗)06:02 allele with narcolepsy, especially in narcolepsy+cataplexy patients. Our study also indicates additional HLA-DQB1 alleles may modify the presentation of narcolepsy+cataplexy patients, such as DQB1(∗)03:01 and DQB1(∗)06:01 in our study. Our results are limited by the small sample size and can only be considered as preliminary findings.

The autoimmune basis of narcolepsy

Narcolepsy is a neurological disorder characterized by excessive daytime sleepiness, cataplexy, hypnagonic hallucinations, sleep paralysis, and disturbed nocturnal sleep patterns. Narcolepsy is caused by the loss of hypocretin (orexin)-producing neurons in the lateral hypothalamus. Evidence, such as a strong association with HLA DQB1*06:02, strongly suggests an autoimmune basis targeting hypocretin neurons. Genome-wide association studies have strengthened the association between narcolepsy and immune system gene polymorphisms, including the identification of polymorphisms in the T cell receptor alpha locus, TNFSF4 (also called OX40L), Cathepsin H (CTSH) the purinergic receptor P2RY11, and the DNA methyltransferase DNMT1. Recently, attention has been raised regarding a spike in cases of childhood narcolepsy in 2010 following the 2009 H1N1 pandemic (pH1N1) in China and vaccination with Pandemrix, an adjuvanted H1N1 vaccine that was used in Europe. How the immune system may be involved in disease initiation and/or progression remains a challenge to researchers. Potential immunological pathways that could lead to the specific elimination of hypocretin producing neurons include molecular mimicry or bystander activation, and are likely a combination of genetic and environmental factors, such as upper airway infections.

The incidence of narcolepsy in Europe: before, during, and after the influenza A(H1N1)pdm09 pandemic and vaccination campaigns

BACKGROUND

In August 2010 reports of a possible association between exposure to AS03 adjuvanted pandemic A(H1N1)pdm09 vaccine and occurrence of narcolepsy in children and adolescents emerged in Sweden and Finland. In response to this signal, the background rates of narcolepsy in Europe were assessed to rapidly provide information for signal verification.

METHODS

We used a dynamic retrospective cohort study to assess the narcolepsy diagnosis rates during the period 2000-2010 using large linked automated health care databases in six countries: Denmark, Finland, Italy, the Netherlands, Sweden and the United Kingdom.

RESULTS

Overall, 2608 narcolepsy cases were identified in almost 280 million person years (PY) of follow up. The pooled incidence rate was 0.93 (95% CI: 0. 90-0.97) per 100,000 PY. There were peaks between 15 and 30 year of age (women>men) and around 60 years of age. In the age group 5-19 years olds rates were increased after the start of pandemic vaccination compared to the period before the start of campaigns, with rate ratios (RR) of 1.9 (95% CI: 1.1-3.1) in Denmark, 6.4 (95% CI: 4.2-9.7) in Finland and 7.5 (95% CI: 5.2-10.7) in Sweden. Cases verification in the Netherlands had a significant effect on the pattern of incidence over time.

CONCLUSIONS

The results of this incidence study provided useful information for signal verification on a population level. The safety signal of increased narcolepsy diagnoses following the start of the pandemic vaccination campaign as observed in Sweden and Finland could be observed with this approach. An increase in narcolepsy diagnoses was not observed in other countries, where vaccination coverage was low in the affected age group, or did not follow influenza A(H1N1)pdm09 vaccination. Patient level analyses in these countries are being conducted to verify the signal in more detail.

Physiology of the orexinergic/hypocretinergic system: a revisit in 2012

The neuropeptides orexins and their G protein-coupled receptors, OX(1) and OX(2), were discovered in 1998, and since then, their role has been investigated in many functions mediated by the central nervous system, including sleep and wakefulness, appetite/metabolism, stress response, reward/addiction, and analgesia. Orexins also have peripheral actions of less clear physiological significance still. Cellular responses to the orexin receptor activity are highly diverse. The receptors couple to at least three families of heterotrimeric G proteins and other proteins that ultimately regulate entities such as phospholipases and kinases, which impact on neuronal excitation, synaptic plasticity, and cell death. This article is a 10-year update of my previous review on the physiology of the orexinergic/hypocretinergic system. I seek to provide a comprehensive update of orexin physiology that spans from the molecular players in orexin receptor signaling to the systemic responses yet emphasizing the cellular physiological aspects of this system.

AS03 adjuvanted AH1N1 vaccine associated with an abrupt increase in the incidence of childhood narcolepsy in Finland

Background

Narcolepsy is a chronic sleep disorder with strong genetic predisposition causing excessive daytime sleepiness and cataplexy. A sudden increase in childhood narcolepsy was observed in Finland soon after pandemic influenza epidemic and vaccination with ASO3-adjuvanted Pandemrix. No increase was observed in other age groups.

Methods

Retrospective cohort study. From January 1, 2009 to December 31, 2010 we retrospectively followed the cohort of all children living in Finland and born from January 1991 through December 2005. Vaccination data of the whole population was obtained from primary health care databases. All new cases with assigned ICD-10 code of narcolepsy were identified and the medical records reviewed by two experts to classify the diagnosis of narcolepsy according to the Brighton collaboration criteria. Onset of narcolepsy was defined as the first documented contact to health care because of excessive daytime sleepiness. The primary follow-up period was restricted to August 15, 2010, the day before media attention on post-vaccination narcolepsy started.

Findings

Vaccination coverage in the cohort was 75%. Of the 67 confirmed cases of narcolepsy, 46 vaccinated and 7 unvaccinated were included in the primary analysis. The incidence of narcolepsy was 9.0 in the vaccinated as compared to 0.7/100,000 person years in the unvaccinated individuals, the rate ratio being 12.7 (95% confidence interval 6.1–30.8). The vaccine-attributable risk of developing narcolepsy was 1∶16,000 vaccinated 4 to 19-year-olds (95% confidence interval 1∶13,000–1∶21,000).

Conclusions

Pandemrix vaccine contributed to the onset of narcolepsy among those 4 to 19 years old during the pandemic influenza in 2009–2010 in Finland. Further studies are needed to determine whether this observation exists in other populations and to elucidate potential underlying immunological mechanism. The role of the adjuvant in particular warrants further research before drawing conclusions about the use of adjuvanted pandemic vaccines in the future.

Increased incidence and clinical picture of childhood narcolepsy following the 2009 H1N1 pandemic vaccination campaign in Finland

Background

Narcolepsy is a rare neurological sleep disorder especially in children who are younger than 10 years. In the beginning of 2010, an exceptionally large number of Finnish children suffered from an abrupt onset of excessive daytime sleepiness (EDS) and cataplexy. Therefore, we carried out a systematic analysis of the incidence of narcolepsy in Finland between the years 2002–2010.

Methods

All Finnish hospitals and sleep clinics were contacted to find out the incidence of narcolepsy in 2010. The national hospital discharge register from 2002 to 2009 was used as a reference.

Findings

Altogether 335 cases (all ages) of narcolepsy were diagnosed in Finland during 2002–2009 giving an annual incidence of 0.79 per 100 000 inhabitants (95% confidence interval 0.62–0.96). The average annual incidence among subjects under 17 years of age was 0.31 (0.12–0.51) per 100 000 inhabitants. In 2010, 54 children under age 17 were diagnosed with narcolepsy (5.3/100 000; 17-fold increase). Among adults ≥20 years of age the incidence rate in 2010 was 0.87/100 000, which equals that in 2002–2009. Thirty-four of the 54 children were HLA-typed, and they were all positive for narcolepsy risk allele DQB1*0602/DRB1*15. 50/54 children had received Pandemrix vaccination 0 to 242 days (median 42) before onset. All 50 had EDS with abnormal multiple sleep latency test (sleep latency <8 min and ≥2 sleep onset REM periods). The symptoms started abruptly. Forty-seven (94%) had cataplexy, which started at the same time or soon after the onset of EDS. Psychiatric symptoms were common. Otherwise the clinical picture was similar to that described in childhood narcolepsy.

Interpretation

A sudden increase in the incidence of abrupt childhood narcolepsy was observed in Finland in 2010. We consider it likely that Pandemrix vaccination contributed, perhaps together with other environmental factors, to this increase in genetically susceptible children.

Excessive daytime sleepiness and narcolepsy--an approach to investigation and management

Excessive daytime sleepiness is a common presentation to physicians both in general practice and hospital settings. In this review, we provide an update on the latest theories on the pathogenesis of the condition, and discuss the approach to investigation of the sleepy patient, with particular reference to narcolepsy. Recommended therapy is reviewed for both narcolepsy and cataplexy, to provide physicians with an important reference on the investigation and management of these troubling conditions.

Rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation: analysis of hypothalamic and autonomic candidate genes

Rapid-onset Obesity with Hypothalamic Dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD) is a rare and complex pediatric disorder. Despite increased identification and advancing knowledge of the disease course, the variable onset and timing of phenotypic features in ROHHAD often result in delayed or missed diagnosis, potentially leading to fatal central hypoventilation, cardiorespiratory arrest, and impaired neurocognitive development. The 5-hydroxytryptamine receptor 1A (HTR1A), orthopedia (OTP), and pituitary adenylate cyclase activating polypeptide (PACAP) genes were targeted in the etiology of ROHHAD based on their roles in the embryologic development of the hypothalamus and autonomic nervous system. We hypothesized that variations of HTR1A, OTP, and/or PACAP would be associated with ROHHAD. All coding regions and intron-exon boundaries of the HTR1A, OTP, and PACAP genes, in addition to the promoter region of the HTR1A gene, were analyzed by standard sequencing in 25 ROHHAD cases and 25 matched controls. Thirteen variations, including six protein-changing mutations, were identified. None of these variations were significantly correlated with ROHHAD. This report provides evidence that variation of the HTR1A, OTP, and PACAP genes are not responsible for ROHHAD. These results represent a further step in the investigation of the genetic determinants of ROHHAD.

Narcolepsy with hypocretin/orexin deficiency, infections and autoimmunity of the brain

The loss of hypothalamic hypocretin/orexin (hcrt) producing neurons causes narcolepsy with cataplexy. An autoimmune basis for the disease has long been suspected and recent results have greatly strengthened this hypothesis. Narcolepsy with hcrt deficiency is now known to be associated with a Human Leukocyte Antigen (HLA) and T-cell receptor (TCR) polymorphisms, suggesting that an autoimmune process targets a single peptide unique to hcrt-cells via specific HLA-peptide-TCR interactions. Recent data have shown a robust seasonality of disease onset in children and associations with Streptococcus Pyogenes, and influenza A H1N1-infection and H1N1-vaccination, pointing towards processes such as molecular mimicry or bystander activation as crucial for disease development. We speculate that upper airway infections may be common precipitants of a whole host of CNS autoimmune complications including narcolepsy.

Genetics of sleep and sleep disorders

Sleep remains one of the least understood phenomena in biology--even its role in synaptic plasticity remains debatable. Since sleep was recognized to be regulated genetically, intense research has launched on two fronts: the development of model organisms for deciphering the molecular mechanisms of sleep and attempts to identify genetic underpinnings of human sleep disorders. In this Review, we describe how unbiased, high-throughput screens in model organisms are uncovering sleep regulatory mechanisms and how pathways, such as the circadian clock network and specific neurotransmitter signals, have conserved effects on sleep from Drosophila to humans. At the same time, genome-wide association studies (GWAS) have uncovered ∼14 loci increasing susceptibility to sleep disorders, such as narcolepsy and restless leg syndrome. To conclude, we discuss how these different strategies will be critical to unambiguously defining the function of sleep.

Orexin/hypocretin plays a role in the response to physiological disequilibrium

In the decade since the discovery that pathology of the orexin/hypocretin system is causative for the sleep disorder narcolepsy, considerable progress has been made in understanding the functional role of the neuropeptide. Two, apparently separate functions of orexin have emerged as a consensus from studies to date. The first is the effect on vigilance state boundaries, as exemplified by narcolepsy. Thus the absence of orexin severely limits the ability to maintain prolonged periods of wakefulness or sleep and also allows the unregulated appearance of cataplexy as sudden muscle weakness during wakefulness. The second function is that orexin acts as a signaling molecule in transferring information about physiological disequilibrium to the central nervous system. Orexin activates the central arousal and motor systems during such disequilibrium and so may facilitate the necessary response and adaptation to restore equilibrium. A feasible relationship between these two functions is therefore that the maintenance of prolonged and active wakefulness is an integral part of this adaptive process. Furthermore, the limit placed on the onset of sleep by orexin suggests that these adaptive processes then continue during sleep to become integrated into the development of a coping strategy for the longer term.

[Narcolepsy associated with systemic lupus erythematosus]

Many neurologic and psychiatric manifestations have been associated with systemic lupus erythematosus. Narcolepsy, currently hypothesized as related to an autoimmune process, has been rarely associated with systemic lupus erythematosus. We report a 36-year-old woman who presented with narcolepsy and who subsequently developed systemic lupus erythematosus. Excessive daytime sleepiness resolved after the administration of four intravenous bolus of cyclophosphamide and methylprednisolone followed by maintenance therapy with hydroxychloroquine, aspirine and prednisone. Narcolepsy should be included in the neuropsychiatric manifestations of systemic lupus erythematosus and it may have a parallel clinical course to the activity of the lupus.

Tumor necrosis factor-alpha regulates the Hypocretin system via mRNA degradation and ubiquitination

Recent studies recognize that Hypocretin system (also known as Orexin) plays a critical role in sleep/wake disorders and feeding behaviors. However, little is known about the regulation of the Hypocretin system. It is also known that tumor necrosis factor alpha (TNF-α) is involved in the regulation of sleep/wake cycle. Here, we test our hypothesis that the Hypocretin system is regulated by TNF-α. Prepro-Hypocretin and Hypocretin receptor 2 (HcrtR2) can be detected at a very low level in rat B35 neuroblastoma cells. In response to TNF-α, Prepro-Hypocretin mRNA and protein levels are down-regulated, and also HcrtR2 protein level is down-regulated in B35 cells. To investigate the mechanism, exogenous rat Prepro-Hypocretin and rat HcrtR2 were overexpressed in B35 cells. In response to TNF-α, protein and mRNA of Prepro-Hypocretin are significantly decreased (by 93% and 94%, respectively), and the half-life of Prepro-Hypocretin mRNA is decreased in a time- and dose-dependent manner. The level of HcrtR2 mRNA level is not affected by TNF-α treatment; however, HcrtR2 protein level is significantly decreased (by 86%) through ubiquitination in B35 cells treated with TNF-α. Downregulation of cellular inhibitor of apoptosis protein-1 and -2 (cIAP-1 and -2) abrogates the HcrtR2 ubiquitination induced by TNF-α. The control green fluorescent protein (GFP) expression is not affected by TNF-α treatment. These studies demonstrate that TNF-α can impair the function of the Hypocretin system by reducing the levels of both Prepro-Hypocretin and HcrtR2.

Increased immune complexes of hypocretin autoantibodies in narcolepsy

Background

Hypocretin peptides participate in the regulation of sleep-wake cycle while deficiency in hypocretin signaling and loss of hypocretin neurons are causative for narcolepsy-cataplexy. However, the mechanism responsible for alteration of the hypocretin system in narcolepsy-cataplexy and its relevance to other central hypersomnias remain unknown. Here we studied whether central hypersomnias can be associated with autoantibodies reacting with hypocretin-1 peptide present as immune complexes.

Methodology

Serum levels of free and dissociated (total) autoantibodies reacting with hypocretin-1 peptide were measured by enzyme-linked immunosorbent assay and analyzed with regard to clinical parameters in 82 subjects with narcolepsy-cataplexy, narcolepsy without cataplexy or idiopathic hypersomnia and were compared to 25 healthy controls.

Principal Findings

Serum levels of total but not free IgG autoantibodies against hypocretin-1 were increased in narcolepsy-cataplexy. Increased levels of complexed IgG autoantibodies against hypocretin-1 were found in all patients groups with a further increase in narcolepsy-cataplexy. Levels of total IgM hypocretin-1 autoantibodies were also elevated in all groups of patients. Increased levels of anti-idiotypic IgM autoantibodies reacting with hypocretin-1 IgG autoantibodies affinity purified from sera of subjects with narcolepsy-cataplexy were found in all three groups of patients. Disease duration correlated negatively with serum levels of hypocretin-1 IgG and IgM autoantibodies and with anti-idiotypic IgM autoantibodies.

Conclusion

Central hypersomnias and particularly narcolepsy-cataplexy are characterized by higher serum levels of autoantibodies directed against hypocretin-1 which are present as immune complexes most likely with anti-idiotypic autoantibodies suggesting their relevance to the mechanism of sleep-wake cycle regulation.

Anti-Tribbles homolog 2 (TRIB2) autoantibodies in narcolepsy are associated with recent onset of cataplexy

STUDY OBJECTIVE

Recent studies have found increased autoantibodies against Tribbles homolog 2 (anti-TRIB2) and anti-streptolysin O (ASO) in narcolepsy. In this study, we replicated this finding with a primary focus on recent onset cases.

PARTICIPANTS AND METHODS

Participants included (1) 90 cases with cataplexy, (2) 57 cases without cataplexy, and (3) 156 age-sex matched controls, including 73 human leukocyte antigen (HLA)-DQB1*0602 allele carriers. A radioligand binding assay was used to detect anti-TRIB2 antibodies.

RESULTS

Anti-TRIB2 antibodies were prevalent in HLA-DQB1*0602 positive cases with cataplexy (25.0% of 76) and rare in cases without cataplexy (3.5% of 57, OR = 9.2, 95% CI = 2.5 - 33.5, P = 6.0 x 10(-4)) or controls (4.5% of 156, OR = 7.1, 95% CI = 3.1 - 16.2, P = 9.3 x 10(-6)). Anti-TRIB2 positivity in controls was not associated with DQB1*0602. In DQB1*0602 narcolepsy-cataplexy cases, the presence of anti-TRIB2 was associated with short disease duration (2.3 years from cataplexy onset), with 41.0% positive in this group (OR = 7.4 versus cases with onset > 2.3 years, 95% CI = 1.9- 28.5, P = 9.0 x 10(-4)). Anti-TRIB2 positivity in 39 DQB1*0602 positive recent onset cases was associated with increased ASO antibody (> 200 IU) (OR = 6.2, 95% CI = 1.6 - 24.6, P = 0.01), but did not correlate with age, gender, or body mass index.

CONCLUSION

Anti-TRIB2 autoantibodies are strongly associated with narcolepsy close to cataplexy onset (< or = 2.3 years). Anti-TRIB2 was rarely found in cases without cataplexy or with distant onset.

[Brazilian guidelines for the diagnosis of narcolepsy]

This manuscript contains the conclusion of the consensus meeting on the diagnosis of narcolepsy based on the review of Medline publications between 1980-2010. Narcolepsy is a chronic disorder with age at onset between the first and second decade of life. Essential narcolepsy symptoms are cataplexy and excessive sleepiness. Cataplexy is defined as sudden, recurrent and reversible attacks of muscle weakness triggered by emotions. Accessory narcolepsy symptoms are hypnagogic hallucinations, sleep paralysis and nocturnal fragmented sleep. The clinical diagnosis according to the International Classification of Sleep Disorders is the presence of excessive sleepiness and cataplexy. A full in-lab polysomnography followed by a multiple sleep latency test is recommended for the confirmation of the diagnosis and co-morbidities. The presence of two sleep-onset REM period naps in the multiple sleep latency test is diagnostic for cataplexy-free narcolepsy. A positive HLA-DQB1*0602 with lower than 110pg/mL level of hypocretin-1 in the cerebrospinal fluid is required for the final diagnosis of cataplexy- and sleep-onset REM period -free narcolepsy.

Does narcolepsy symptom severity vary according to HLA-DQB1*0602 allele status?

STUDY OBJECTIVES

To investigate associations between HLA-DQB1*0602 allele status and measures of narcolepsy symptom severity.

DESIGN

Cross-sectional study of population-based narcolepsy patients.

SETTING

King County, Washington.

PARTICIPANTS

All prevalent cases (n = 279) of physician-diagnosed narcolepsy ascertained from 2001-2005.

INTERVENTIONS

N/A.

MEASUREMENTS

Narcolepsy diagnosis was based on cataplexy status, diagnostic sleep study results, and chart review. The number of HLA-DQB1 alleles was determined from buccal genomic DNA. Symptom severity instruments included the Epworth Sleepiness Scale (ESS), the Ullanlinna Narcolepsy Scale (UNS), age of symptom onset, subjective sleep latency and duration, and various clinical sleep parameters. We used linear regression adjusted for African American race and an extended chi-square test of trend to assess relationships across ordered groups defined by allele number (0, 1, or 2).

RESULTS

Narcolepsy patients were 63% female and 82% Caucasian, with a mean age of 47.6 years (SD = 17.1). One hundred forty-one (51%) patients had no DQB1*0602 alleles; 117 (42%) had one; and 21 (7%) had two. In the complete narcolepsy sample after adjustment for African American race, we observed a linear relationship between HLA-DQB1*0602 frequency and sleepiness as defined by the ESS (P < 0.01), narcolepsy severity as defined by UNS (P < 0.001), age of symptom onset (P < 0.05), and sleep latency (P < 0.001). In univariate analyses, HLA-DQB1*0602 frequency was also associated with napping (P < 0.05) and increased car and work accidents or near accidents (both P < 0.01). Habitual sleep duration was not associated with HLA status. These race-adjusted associations remained for the ESS (P < 0.05), UNS (P < 0.01), and sleep latency (P < 0.001) when restricting to narcolepsy with cataplexy.

CONCLUSIONS

Narcolepsy symptom severity varies in a linear manner according to HLA-DQB1*0602 allele status. These findings support the notion that HLA-DQ is a disease-modifying gene.

Childhood-onset narcolepsy, obesity and puberty in four consecutive children: a close temporal link

Narcolepsy is a rare but disabling condition that causes excessive daytime sleepiness. Interestingly, weight gain is frequent in patients with narcolepsy and it has sometimes been described very early in the course of the disease. Here, we report four consecutive obese children who were referred to our sleep laboratory for excessive daytime sleepiness and suspected sleep apnoea syndrome. They underwent nocturnal polysomnography associated with multiple sleep latency tests. Narcolepsy was diagnosed in all children with a close temporal link between the onset of narcolepsy, obesity and puberty. Scientifically, the relationship between sleep, weight, growth rate and puberty onset is striking and merits further investigation. From the clinical point of view, narcolepsy must be investigated in obese sleepy children along with obstructive sleep apnoea. Indeed, it can be controlled with appropriate treatment but the proper diagnosis relies not only upon nocturnal polysomnography but involves the systematic use of multiple sleep latency tests.

Elevated Tribbles homolog 2-specific antibody levels in narcolepsy patients

Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness and attacks of muscle atonia triggered by strong emotions (cataplexy). Narcolepsy is caused by hypocretin (orexin) deficiency, paralleled by a dramatic loss in hypothalamic hypocretin-producing neurons. It is believed that narcolepsy is an autoimmune disorder, although definitive proof of this, such as the presence of autoantibodies, is still lacking. We engineered a transgenic mouse model to identify peptides enriched within hypocretin-producing neurons that could serve as potential autoimmune targets. Initial analysis indicated that the transcript encoding Tribbles homolog 2 (Trib2), previously identified as an autoantigen in autoimmune uveitis, was enriched in hypocretin neurons in these mice. ELISA analysis showed that sera from narcolepsy patients with cataplexy had higher Trib2-specific antibody titers compared with either normal controls or patients with idiopathic hypersomnia, multiple sclerosis, or other inflammatory neurological disorders. Trib2-specific antibody titers were highest early after narcolepsy onset, sharply decreased within 2-3 years, and then stabilized at levels substantially higher than that of controls for up to 30 years. High Trib2-specific antibody titers correlated with the severity of cataplexy. Serum of a patient showed specific immunoreactivity with over 86% of hypocretin neurons in the mouse hypothalamus. Thus, we have identified reactive autoantibodies in human narcolepsy, providing evidence that narcolepsy is an autoimmune disorder.

Potentiation of a functional autoantibody in narcolepsy by a cholinesterase inhibitor

We have recently reported the presence of an immunoglobulin G (IgG) autoantibody (Ab) in patients with narcolepsy with cataplexy that abolishes spontaneous colonic migrating motor complexes (CMMCs) and increases smooth muscle tension and atropine-sensitive phasic contractions in a physiological assay of an isolated colon. In this study, we used the cholinesterase inhibitor, neostigmine, to explore the mechanism of the narcoleptic IgG-mediated disruption of enteric motor function in four patients with narcolepsy with cataplexy and to identify a pharmacological mimic of the Ab. Neostigmine potentiated the narcoleptic IgG-mediated increase in smooth muscle resting tension and phasic smooth muscle contractions by an atropine-sensitive mechanism but exerted no effect on resting tension in the presence of control IgG. Decreased frequency of CMMCs mediated by IgG with anti-M3R activity was reversed by neostigmine. Therefore, a challenge with a cholinesterase inhibitor improves the specificity of the CMMC assay for narcoleptic IgG. Tetrodotoxin (TTX), a neuronal sodium channel blocker, also abolished CMMCs and increased resting tone, and a similar potentiation was observed with neostigmine; thus, TTX is a mimic of the functional effects of the narcoleptic IgG in this bioassay. These findings provide a link to pharmacological studies of canine narcolepsy and are consistent with a functional blockade of both excitatory and inhibitory motor neurons by the narcoleptic Ab, similar to the TTX mimic, presumably by binding to an autoantigenic target expressed in both populations of neurons.