Eating disorder and metabolism in narcoleptic patients

Orexin receptor antagonist increases fat oxidation and suppresses protein catabolism during sleep in humans

Suvorexant is an orexin receptor antagonist that targets the wake-promoting system. Orexin is also known to regulate energy metabolism in rodents, but its role in humans remains largely unknown. Here, we assessed the effect of suvorexant (20 mg) on energy metabolism during sleep and shortly after awakening in a randomized, double-blind, placebo-controlled, crossover study in 14 healthy men. Suvorexant increased rapid eye movement (REM) but decreased nonrapid eye movement (NREM) stage 1. Energy expenditure during wake after sleep onset (WASO) was higher than that during NREM and REM sleep in the placebo but not in the suvorexant trial, suggesting that the increase in energy expenditure during WASO was due to an activation of the orexin system. Fat oxidation during sleep increased, and its effect remained after waking the next morning. Suvorexant decreased protein catabolism but did not affect overall energy expenditure. The orexin system may affect fat oxidation independent of its roles in sleep regulation in humans.

Effect of sodium oxybate on body mass index in pediatric patients with narcolepsy

STUDY OBJECTIVES

We examined body mass index (BMI) changes associated with sodium oxybate treatment (SXB) in pediatric patients with narcolepsy with cataplexy who participated in a double-blind, placebo-controlled, randomized withdrawal study and an open-label continuation period.

METHODS

Participants were aged 7-16 years at screening. SXB-naive participants titrated to twice-nightly dosing of SXB then entered a 2-week stable-dose period; participants taking SXB at study entry entered a 3-week stable-dose period. After a 2-week randomized withdrawal period, all participants entered an open-label safety period (OLP; main study duration: ≤ 52 weeks). Participants who completed the OLP were allowed to enter the open-label continuation period (an additional 1-2 years). BMI percentile categories were defined as underweight (< 5th), normal (5th to < 85th), overweight (≥ 85th to < 95th), and obese (≥ 95th).

RESULTS

Median BMI percentile decreased from baseline to OLP week 52 in SXB-naive participants who were normal weight at baseline (decreased from 77.0 to 35.0) or overweight/obese at baseline (98.0 to 86.7). Median BMI percentile decreased to a lesser extent in participants taking twice-nightly SXB at study entry who were normal weight at baseline (54.6 to 53.0) or overweight/obese at baseline (96.5 to 88.9). Shifts in BMI category from baseline to week 52 were sometimes noted. In SXB-naive participants, 9/10 (90.0%) who were overweight became normal weight, 7/25 (28.0%) who were obese became normal weight, 3/25 (12.0%) who were obese became overweight, and 1/16 (6.3%) who was normal weight became obese. In participants taking SXB at baseline, 5/8 (62.5%) who were overweight became normal weight, 3/6 (50.0%) who were obese became overweight, 1/14 (7.1%) who was normal weight became overweight, and 2/14 (14.3%) who were normal weight became underweight. Median BMI percentiles at months 6 and 12 of the open-label continuation period were similar to those at OLP end (OLP week 52). In SXB-naive participants, the evident BMI z-score decrease over time was relative to the screening values.

CONCLUSIONS

Decreases in BMI percentile and z-score, and downward shifts in BMI category, were observed within 1 year of SXB treatment in pediatric participants with narcolepsy with cataplexy. BMI decreases plateaued after approximately 1 year.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: A Multicenter Study of the Efficacy and Safety of Xyrem With an Open-Label Pharmacokinetic Evaluation and Safety Extension in Pediatric Subjects With Narcolepsy With Cataplexy; URL: https://clinicaltrials.gov/study/NCT02221869; Identifier: NCT02221869.

CITATION

Dauvilliers Y, Lammers GJ, Lecendreux M, et al. Effect of sodium oxybate on body mass index in pediatric patients with narcolepsy. J Clin Sleep Med. 2024;20(3):445-454.

Analysis of thyroid function and related factors in narcolepsy patients

The loss of hypocretin is thought to be the main pathophysiological mechanism of narcolepsy. There is strong evidence that hypocretin is related to the regulation of endocrine functions and depression. To explore thyroid hormone levels in narcolepsy patients was our aim. In addition, further is to analyze the relationship between thyroid hormone levels and sleep quality, anxiety, and depression in narcolepsy patients. There are 40 patients with narcolepsy and 40 healthy controls (HCs) were conducted. Blood samples were explored for thyroid function. Correlation analysis between thyroid hormones and clinical characteristics of narcolepsy was performed using Pearson or Spearman. Narcolepsy patients had significantly lower free thyroxine (FT4) levels in comparison to controls (p < 0.001). No subject was diagnosed with primary hypothyroidism. There were 4 (10%) subjects with subclinical hypothyroidism. The serum FT4 levels were positively correlated with HAMA14 score (r = - 0.343, p = 0.030) by Pearson correlation analysis. The serum TSH levels and HAMD24 score (r = - 0.807 p ˂0.001), and ESS score (r = - 0.317, p = 0.046) both showed a negative correction. Hypocretin deficiency may be associated with the regulation of thyroid hormones in narcolepsy patients. The serum thyroid hormones may affect the severity and neuropsychological functions of narcolepsy patients.

Cardiovascular Burden of Narcolepsy Disease (CV-BOND): a real-world evidence study

STUDY OBJECTIVES

Narcolepsy is associated with cardiovascular risk factors; however, the risk of new-onset cardiovascular events in this population is unknown. This real-world study evaluated the excess risk of new-onset cardiovascular events in U.S. adults with narcolepsy.

METHODS

A retrospective cohort study using IBM MarketScan administrative claims data (2014-2019) was conducted. A narcolepsy cohort, comprising adults (≥18 years) with at least two outpatient claims containing a narcolepsy diagnosis, of which at least one was non-diagnostic, was matched to a non-narcolepsy control cohort (1:3) based on cohort entry date, age, sex, geographic region, and insurance type. The relative risk of new-onset cardiovascular events was estimated using a multivariable Cox proportional hazards model to compute adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

The narcolepsy and matched non-narcolepsy control cohorts included 12 816 and 38 441 individuals, respectively. At baseline, cohort demographics were generally similar; however, patients with narcolepsy had more comorbidities. In adjusted analyses, the risk of new-onset cardiovascular events was higher in the narcolepsy cohort compared with the control cohort: any stroke (HR [95% CI], 1.71 [1.24, 2.34]); heart failure (1.35 [1.03, 1.76]); ischemic stroke (1.67 [1.19, 2.34]); major adverse cardiac event (1.45 [1.20, 1.74]); grouped instances of stroke, atrial fibrillation, or edema (1.48 [1.25, 1.74]); and cardiovascular disease (1.30 [1.08, 1.56]).

CONCLUSION

Individuals with narcolepsy are at increased risk of new-onset cardiovascular events compared with individuals without narcolepsy. Physicians should consider cardiovascular risk in patients with narcolepsy when weighing treatment options.

Treating Narcolepsy With Traditional Chinese Medicine

Narcolepsy is an uncommon brain condition characterized by falling asleep suddenly without any proper reason or time. In this chapter, the authors include a brief history of narcolepsy, clinical symptoms, pathophysiology, and current treatments for the disease. The review explains narcolepsy according to the theory of TCM. The authors review the curative effect, pharmacological properties, and clinical results of herbs and prescriptions against narcolepsy. The study searched keywords such as ‘narcolepsy,' ‘Traditional Chinese medicine,' ‘sleep disorder,' ‘excessive sleepiness,' and ‘medicinal treatment' using databases such as CNKI, PubMed, and Google Scholar. Based on the analysis of data obtained from 110 articles, the authors have classified the herbs and prescriptions by their curative effects, following the theory of traditional Chinese medicine. Some herbs can be used alone, while others can use in conjunction with other prescriptions.

Peripheral vs. core body temperature as hypocretin/orexin neurons degenerate: Exercise mitigates increased heat loss

Hypocretins/Orexins (Hcrt/Ox) are hypothalamic neuropeptides implicated in diverse functions, including body temperature regulation through modulation of sympathetic vasoconstrictor tone. In the current study, we measured subcutaneous (Tsc) and core (Tb) body temperature as well as activity in a conditional transgenic mouse strain that allows the inducible ablation of Hcrt/Ox-containing neurons by removal of doxycycline (DOX) from their diet (orexin-DTA mice). Measurements were made during a baseline, when mice were being maintained on food containing DOX, and over 42 days while the mice were fed normal chow which resulted in Hcrt/Ox neuron degeneration. The home cages of the orexin-DTA mice were equipped with running wheels that were either locked or unlocked. In the presence of a locked running wheel, Tsc progressively decreased on days 28 and 42 in the DOX(-) condition, primarily during the dark phase (the major active period for rodents). This nocturnal reduction in Tsc was mitigated when mice had access to unlocked running wheels. In contrast to Tsc, Tb was largely maintained until day 42 in the DOX(-) condition even when the running wheel was locked. Acute changes in both Tsc and Tb were observed preceding, during, and following cataplexy. Our results suggest that ablation of Hcrt/Ox-containing neurons results in elevated heat loss, likely through reduced sympathetic vasoconstrictor tone, and that exercise may have some therapeutic benefit to patients with narcolepsy, a disorder caused by Hcrt/Ox deficiency. Acute changes in body temperature may facilitate prediction of cataplexy onset and lead to interventions to mitigate its occurrence.

A systematic review with meta-analyses of the relationship between recurrent binge eating and sleep parameters

BACKGROUND

Sleep problems are known to compound the negative effects of other health issues, such as eating disorders and the associated behavior of binge eating. Previous studies suggested associations between binge eating and sleep problems, but the strength of the relationship is unknown.

METHODS

We conducted a systematic review with meta-analyses examining the relationship between binge eating and sleep parameters. We searched for studies in Scopus, PubMed, and PsycInfo. The quality of evidence, including risk of bias, was assessed with adaptations of the Newcastle-Ottawa Scale and the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies, depending on study design. Data was synthesized as the difference in sleep between people who did or did not have binge eating.

RESULTS

Thirty-one reports of studies met our eligibility criteria. Results are presented in 12 meta-analyses. In the 7 reports of studies (with 4448 participants) that assessed poor overall sleep quality, we found poorer overall sleep quality in people with binge eating compared to people without binge eating, with a standardized mean difference of 0.77 (95% confidence interval [CI] 0.61-0.92; P < 0.001), which is a large effect size. In addition, we found evidence that people with binge eating had significantly greater hypersomnia/daytime sleepiness (7 reports of studies with 4370 participants), insomnia (5 reports of studies with 12,733 participants), and difficulty falling asleep (3 reports of studies with 4089 participants) compared to people without binge eating, with moderate effect sizes (standardized mean differences of 0.57-0.66).

CONCLUSIONS

People with binge eating exhibit poorer overall sleep quality compared to people without binge eating, and may also exhibit greater hypersomnia/daytime sleepiness, insomnia, and difficulty falling asleep. It is recommended that healthcare professionals routinely screen for poor overall sleep quality when treating people with binge eating-and address sleep difficulties when present.

Alexithymia, impulsiveness, emotion, and eating dyscontrol: similarities and differences between narcolepsy type 1 and type 2

Non-sleep symptoms, as depression, anxiety and overweight, are often encountered in narcoleptic patients. The purposes of this study are to evaluate mood, impulsiveness, emotion, alexithymia, and eating behavior in patients with narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2) compared to healthy controls and to investigate possible correlations between clinical-demographic data, polysomnographic parameters, and subjective questionnaires. Consecutive patients affected by NT1 and NT2 underwent to Patient Health Questionnaire-9, Generalized Anxiety Disorder-7 Scale, Barratt Impulsivity Scale-11, Difficulties in Emotion Regulation Scale, Toronto Alexithymia Scale, and Eating Disorder Evaluation Questionnaire. Daytime sleepiness was assessed using Epworth sleepiness score. Data were compared with controls. Fourteen NT1, 10 NT2, and 24 healthy subjects were enrolled. Toronto Alexithymia Scale total score was significantly higher in NT1 than NT2. Compared to controls, NT1 patients exhibited significantly higher scores at Patient Health Questionnaire-9 and Difficulties in Emotion Regulation Scale. A positive correlation between hypnagogic hallucinations and Difficulties in emotion regulation was found. NT1 and NT2 share several psycho-emotional aspects, but whereas NT1 patients exhibit more depressive mood and emotion dysregulation compared to controls, alexithymic symptoms are more prominent in NT1 than NT2. Hypnagogic hallucinations, emotion dysregulation, and alexithymia appear to be correlated, supporting the hypothesis of mutual interaction of the above areas in narcolepsy.

Body Weight and Metabolic Rate Changes in Narcolepsy: Current Knowledge and Future Directions

Narcolepsy is a known auto-immune disease that presents mainly in the teenage years with irresistible sleep attacks. Patients with narcolepsy, especially NT1, have been found to have a high prevalence of obesity and other metabolic derangements. This narrative review aimed to address the relationship between narcolepsy and changes in weight and metabolic rate, and discuss potential mechanisms for weight gain and metabolic changes and future research agendas on this topic. This article will provide a balanced, up-to-date critical review of the current literature, and delineate areas for future research, in order to understand the pathophysiological metabolic changes in narcolepsy. Articles using predefined keywords were searched for in PubMed and Google Scholar databases, with predefined inclusion and exclusion criteria. Compared to controls, patients with narcolepsy are more likely to be obese and have higher BMIs and waist circumferences. According to recent research, weight gain in narcolepsy patients may be higher during the disease's outset. The precise mechanisms causing this weight gain remains unknown. The available information, albeit limited, does not support differences in basal or resting metabolic rates between patients with narcolepsy and controls, other than during the time of disease onset. The evidence supporting the role of orexin in weight gain in humans with narcolepsy is still controversial, in the literature. Furthermore, the available data did not show any appreciable alterations in the levels of CSF melanin-concentrating hormone, plasma and CSF leptin, or serum growth hormone, in relation to weight gain. Other mechanisms have been proposed, including a reduction in sympathetic tone, hormonal changes, changes in eating behavior and physical activity, and genetic predisposition. The association between increased body mass index and narcolepsy is well-recognized; however, the relationship between narcolepsy and other metabolic measures, such as body fat/muscle distribution and metabolic rate independent of BMI, is not well documented, and the available evidence is inconsistent. Future longitudinal studies with larger sample sizes are needed to assess BMR in patients with narcolepsy under a standard protocol at the outset of narcolepsy, with regular follow-up.

Characterization of rapid weight gain phenotype in children with narcolepsy

Objectives

To characterize the rapid weight gain (RWG) phenotype associated with the onset of childhood narcolepsy and to determine whether it could constitute a marker of severity of the disease.

Methods

RWG was defined using the BMI z‐score slope reported to one year (>0.67 SD) from symptom onset to disease diagnosis. We compared the clinical, metabolic, and sleep characteristics between patients with or without RWG at diagnosis. Pharmacological management, anthropometric, and clinical progression were also evaluated during the follow‐up.

Results

A total of 84 de novo narcoleptic pediatric patients were included; their median age at diagnosis was 12.0 years; 59.5% boys, 90.5% cataplexy, and 98.7% HLA‐DQB1*06:02, 57% had RWG profile. RWG patients were younger at diagnosis than non‐RWG patients, despite a shorter diagnostic delay. They had a higher BMI z‐score and a higher prevalence of obesity at diagnosis, but not at symptom onset, and higher adapted Epworth Sleepiness Scale and Insomnia Severity Index scores than non‐RWG patients. No differences on nocturnal polysomnography and multiple sleep latency tests were found between groups at disease diagnosis. After a median follow‐up of 5 years, RWG patients still had a higher BMI z‐score and a higher prevalence of obesity despite benefiting from the same therapeutic management and displaying improvement in sleepiness and school difficulties.

Conclusions

Narcoleptic RWG patients were younger, sleepier, and the prevalence of obesity was higher at diagnosis despite a shorter diagnostic delay than that of non‐RWG patients. These patients had also a higher risk of developing a long‐term obesity, despite a positive progression of their narcoleptic symptoms. RGW could then represent a maker of a more severe phenotype of childhood narcolepsy, which should inspire a prompt and more offensive management to prevent obesity and its complications.

BMI changes in pediatric type 1 narcolepsy under sodium oxybate treatment

Pediatric type 1 narcolepsy (NT1) is often associated with overweight and obesity. Sodium oxybate (SO), approved for the treatment of narcolepsy with cataplexy from the age of 7 years old in the United States, has been associated with weight loss, although longitudinal pediatric studies are lacking. We report a retrospective cohort of 129 consecutive patients with a 4-year follow-up, to analyze the impact of different pharmacological treatments on body mass index (BMI) z-score. At baseline, the prevalence of obesity and overweight was 26.4% (34/129) and 29.5% (38/129), respectively. Patients were divided into three groups: children treated with SO alone (group 1), with SO-combined therapy (group 2), and without SO (group 3). At the end of the first year of follow-up, group 1 and group 2 showed a significant BMI z-score reduction compared to baseline: from 1.2 ± 1.1 to 0.4 ± 1.4 for group 1 (p < 0.001), and from 1.4 ± 1.1 to 1 ± 1.3 for group 2 (p = 0.002), independently from baseline clinical features. In the second year, only group 2 experienced a further and significant BMI z-score decrease (from 1.0 ± 1.2 to 0.6 ± 1.2, p = 0.037). No further significant BMI z-score changes were observed in SO-treated patients in the following years. Instead, children treated without SO developed a significant weight increase between the second and third year of therapy (BMI z-score from 0.3 ± 0.9 to 0.5 ± 0.9). In conclusion, SO treatment in pediatric NT1 is associated with a favorable weight reduction in the first year of treatment.

Endocrine and metabolic aspects of narcolepsy type 1 in children

STUDY OBJECTIVES

To study whether the onset of narcolepsy type 1 (NT1) in children and adolescents affects BMI, specific metabolic risk factors, the onset of puberty, longitudinal growth or other endocrine functions.

METHODS

A population-based study, comprising 34 patients, was performed with a clinical evaluation, an assessment of puberty and growth, actigraphy and blood samples at fasting, from patients and controls, to evaluate pituitary function, growth factors, thyroid gland, gonads, insulin sensitivity, appetite regulation and blood lipids.

RESULTS

In the post-H1N1 vaccination (PHV) narcolepsy group, the median BMI SDS was higher 6-12 months after the onset of narcolepsy (p < 0.01), but it was no different 10 years after the onset of narcolepsy (p = 0.91), compared with 12-24 months before the onset of narcolepsy. There was a correlation between an increase in BMI and a decrease in total energy expenditure (R = -0.74). In the nPHV group, weight and BMI changes were smaller and no significant changes were recorded. Early puberty was more common in patients with puberty onset after narcolepsy onset (n = 16/19) compared with patients with puberty onset before narcolepsy onset (n = 3/11, p = 0.02). There was no significant change in height SDS during the studied period. Although they were within normal ranges, both median HDL and median TSH levels were significantly lower in NT1 patients, compared with controls.

CONCLUSIONS

We found a high prevalence of large BMI gain in the period immediately after the onset of narcolepsy, which had almost normalized at the long-term follow-up. The onset of narcolepsy led to early puberty in both sexes. Linear growth was not affected. We did not find any strong indicators of metabolic disturbances.

Metabolic profile in patients with narcolepsy: a systematic review and meta-analysis

Narcolepsy, a sleep disorder characterized by loss of hypocretin neurons, has been associated with metabolic disturbances. Although the metabolic alterations in narcolepsy patients are widely investigated in the literature, the results are controversial. We performed a systematic search of literature to identify metabolic profiling studies in narcolepsy patients. A total of 48 studies were included in the meta-analysis. Narcolepsy patients exhibited higher prevalence of obesity (log OR = 0.93 [0.73-1.13], P < 0.001), diabetes mellitus (log OR = 0.64 [0.34, 0.94], P < 0.001), hypertension (log OR = 0.33 [0.11, 0.55], P < 0.001), and dyslipidemia (log OR = 1.19 [0.60, 1.77], P < 0.001) compared with non-narcoleptic controls. Narcolepsy was associated with higher BMI (SMD = 0.50 [0.32-0.68], P < 0.001), waist circumference (MD = 8.61 [2.03-15.19], P = 0.01), and plasma insulin (SMD = 0.61 [0.14-1.09], P = 0.01). Levels of fasting blood glucose (SMD = -0.25 [-0.61,0.10], P = 0.15), BMR-RMR (SMD = -0.17 [-0.52-0.18], P = 0.34), systolic blood pressure (SMD = 0.29 [-0.39-0.97], P = 0.40), diastolic blood pressure (SMD = 0.39 [-0.62, 1.40], P = 0.45), CSF melanin-concentrating hormone (MD = 5.56 [-30.79-41.91], P = 0.76), serum growth hormone (SMD = 7.84 [-7.90-23.57], P = 0.33), as well as plasma and CSF leptin (SMD = 0.10 [-1.32-1.51], P = 0.89 and MD = 0.01 [-0.02-0.04], P = 0.56, respectively) did not significantly differ between narcolepsy patients and controls. These findings necessitate early screening of metabolic alterations and cardiovascular risk factors in narcolepsy patients to reduce the morbidity and mortality rates.

Gut Microbiota in Patients with Type 1 Narcolepsy

PURPOSE

To explore the characteristics of gut microbiota and its relationship between clinical manifestations in patients with type 1 narcolepsy (NT1).

PATIENTS AND METHODS

Scale and polysomnography were performed in 20 NT1 patients and 16 healthy controls (HC group) to evaluate the clinical characteristics of NT1. Illumina sequencing was performed on bacterial 16S ribosomal RNA gene using V3-V4 regions to compare the fecal microbiota in all subjects. Associations between clinical characteristics and gut microbiota were analyzed using partial correlation analysis.

RESULTS

Compared with the HC group, the NT1 group had a significantly higher ESS score, longer total sleep time, increased wakefulness, decreased sleep efficiency, disturbance of sleep structure, shorter mean sleep latency, and increased sleep-onset REM periods (all P < 0.05). No differences in alpha and beta diversity were observed between the two groups. In contrast, there were significant differences at the level of class, order, family, and genus (all P < 0.05). LEfSe analysis showed that the relative abundance of Klebsiella in the NT1 group was higher than that in the HC group (P < 0.05), while the relative abundance of Blautia, Barnesiellaceae, Barnesiella, Phocea, Lactococcus, Coriobacteriia, Coriobacteriales, Ruminiclostridium_5, and Bilophila were lower (all P < 0.05). Partial correlation analysis revealed that partial differential bacteria in the NT1 group were correlated with total sleep time, sleep efficiency, stage 1 sleep, arousal index, and sleep latency (all P < 0.05).

CONCLUSION

Our data revealed differences in intestinal flora structure between NT1 patients and the normal population, thus providing a theoretical basis for future microecological therapy for narcolepsy. However, future larger sample size studies and different study designs are needed to further clarify the possible pathogenesis and potential causality of intestinal flora in NT1 patients and explore the new treatment strategies.

Measured resting metabolic rate, respiratory quotient, and body composition in patients with narcolepsy: a preliminary report of a case-control study

This case–control study compared the body composition, resting metabolic rate (RMR), and respiratory quotient (RQ) of narcolepsy patients with those of body mass index (BMI)- gender and age-matched controls. This study included 14 male patients with narcolepsy and 14 matched controls. The narcolepsy patients were subdivided into two subgroups (n = 7/each): those with cataplexy (NT1) and those without cataplexy (NT2). Anthropometric measurements, bioelectric impedance analysis, and indirect calorimetry were used in addition to the calculation of common body-composition indices (conicity index, abdominal volume index, and body adiposity index). Our results showed no significant difference in fat percentage, fat mass, fat-free mass, and TBW among NT1, NT2, and controls (p > 0.05). Compared to matched controls, there was a reduction of muscle mass in both NT1 and NT2 subgroups. The RMR was similar in all groups, while patients in the NT1/NT2 subgroups had a lower RQ, used more fat and fewer carbohydrates during the fasting period. These findings give an insight into the distinctive state of altered metabolism in patients with narcolepsy, especially the resting metabolic rate, which was not altered in NT1 vs. NT2 compared to the controls when matched for BMI, age, and gender.

Role of Brown Adipose Tissue in Adiposity Associated With Narcolepsy Type 1

Narcolepsy type 1 is a neurological sleep-wake disorder caused by the destruction of orexin (hypocretin)-producing neurons. These neurons are particularly located in the lateral hypothalamus and have widespread projections throughout the brain, where they are involved, e.g., in the regulation of the sleep-wake cycle and appetite. Interestingly, a higher prevalence of obesity has been reported in patients with narcolepsy type 1 compared to healthy controls, despite a normal to decreased food intake and comparable physical activity. This suggests the involvement of tissues implicated in total energy expenditure, including skeletal muscle, liver, white adipose tissue (WAT), and brown adipose tissue (BAT). Recent evidence from pre-clinical studies with orexin knock-out mice demonstrates a crucial role for the orexin system in the functionality of brown adipose tissue (BAT), probably through multiple pathways. Since BAT is a highly metabolically active organ that combusts fatty acids and glucose toward heat, thereby contributing to energy metabolism, this raises the question of whether BAT plays a role in the development of obesity and related metabolic diseases in narcolepsy type 1. BAT is densely innervated by the sympathetic nervous system that activates BAT, for instance, following cold exposure. The sympathetic outflow toward BAT is mainly mediated by the dorsomedial, ventromedial, arcuate, and paraventricular nuclei in the hypothalamus. This review focuses on the current knowledge on the role of the orexin system in the control of energy balance, with specific focus on BAT metabolism and adiposity in both preclinical and clinical studies.

Lisdexamfetamine to improve excessive daytime sleepiness and weight management in narcolepsy: a case series

Objective:

To report the successful use of lisdexamfetamine in the management of narcolepsy.

Methods:

Five narcoleptic patients received lisdexamfetamine, at different dosages and for different periods, for management of excessive daytime sleepiness and weight control.

Results:

All patients experienced improvement of excessive daytime sleepiness and lost weight without side effects.

Conclusion:

Lisdexamfetamine appears promising for the treatment of two of the most common symptoms of narcolepsy: excessive daytime sleepiness and weight gain.

Obesity and other medical comorbidities among NT1 patients after the Norwegian H1N1 influenza epidemic and vaccination campaign

Study Objectives

Narcolepsy type 1 (NT1) may be complicated by comorbidities. We aimed to study the extent of obesity and other medical comorbidities in a Norwegian population of NT1 patients with debut of symptoms after the 2009 H1N1 influenza epidemic and vaccination campaign. We also aimed to explore factors associated with obesity.

Methods

Ninety-one patients (48 children and 43 adults) were included in this cross-sectional study, 80 of whom were H1N1-vaccinated. All participants were hospitalized and underwent sleep investigation and physical examination, and completed a semi-structured clinical interview.

Results

In children, 16 females (70%) and 10 males (40%) were classified as overweight or obese. Twenty children (42%) had a co-existing medical disorder. Medical comorbidity was significantly positively associated with BMI in children (p = .032). In adults, 19 females (58%) and 7 males (70%) were classified as overweight or obese. Twenty-six adults (61%) had a co-existing medical disorder. We found no factors significantly associated with BMI in adults. On a fatigue scale from 0 to 100, lower scores indicating more fatigue, we found a mean (SD) total fatigue score of 50 (17) in children and 39 (16) in adults.

Conclusion

In a cohort of predominantly H1N1-vaccinated NT1 patients, we found a high prevalence of overweight or obesity. Half of the cohort presented with one or more additional medical comorbidities, and patients reported a clinically relevant degree of fatigue. Our findings highlight the importance of carefully monitoring patients with NT1 with regard to the development of obesity, which is a significant risk factor for cardiovascular disorders.

The neurobiological basis of narcolepsy

Narcolepsy is the most common neurological cause of chronic sleepiness. The discovery about 20 years ago that narcolepsy is caused by selective loss of the neurons producing orexins (also known as hypocretins) sparked great advances in the field. Here, we review the current understanding of how orexin neurons regulate sleep-wake behaviour and the consequences of the loss of orexin neurons. We also summarize the developing evidence that narcolepsy is an autoimmune disorder that may be caused by a T cell-mediated attack on the orexin neurons and explain how these new perspectives can inform better therapeutic approaches.

Orexin/hypocretin and dysregulated eating: Promotion of foraging behavior

At its discovery, orexin/hypocretin (OX) was hypothesized to promote food intake. Subsequently, with the identification of the participation of OX in numerous other phenomena, including arousal and drug seeking, this neuropeptide was proposed to be involved in highly motivated behaviors. The present review develops the hypothesis that the primary evolutionary function of OX is to promote foraging behavior, seeking for food under conditions of limited availability. Thus, it will first describe published literature on OX and homeostatic food intake, which shows that OX neurons are activated by conditions of food deprivation and in turn stimulate food intake. Next, it will present literature on excessive and binge-like food intake, which demonstrates that OX stimulates both intake and willingness to work for palatable food. Importantly, studies show that binge-like eating can be inhibited by OX antagonists at doses far lower than those required to suppress homeostatic intake (3 mg/kg vs. 30 mg/kg), suggesting that an OX-based pharmacotherapy, at the right dose, could specifically control dysregulated eating. Finally, the review will discuss the role of OX in foraging behavior, citing literature which shows that OX neurons, which are activated during the anticipation of food reward, can promote a number of phenomena involved in successful foraging, including food-anticipatory locomotor behavior, olfactory sensitivity, visual attention, spatial memory, and mastication. Thus, OX may promote homeostatic eating, as well as binge eating of palatable food, due to its ability to stimulate and coordinate the activities involved in foraging behavior.

Narcolepsy and Psychiatric Disorders: Comorbidities or Shared Pathophysiology?

Narcolepsy and psychiatric disorders have a significant but unrecognized relationship, which is an area of evolving interest, but unfortunately, the association is poorly understood. It is not uncommon for the two to occur co-morbidly. However, narcolepsy is frequently misdiagnosed initially as a psychiatric condition, contributing to the protracted time to accurate diagnosis and treatment. Narcolepsy is a disabling neurodegenerative condition that carries a high risk for development of social and occupational dysfunction. Deterioration in function may lead to the secondary development of psychiatric symptoms. Inversely, the development of psychiatric symptoms can lead to the deterioration in function and quality of life. The overlap in pharmaceutical intervention may further enhance the difficulty to distinguish between diagnoses. Comprehensive care for patients with narcolepsy should include surveillance for psychiatric illness and appropriate treatment when necessary. Further research is necessary to better understand the underlying pathophysiology between psychiatric disease and narcolepsy.

Unexpected Fat Distribution in Adolescents With Narcolepsy

Narcolepsy type 1 is a chronic sleep disorder with significantly higher BMI reported in more than 50% of adolescent patients, putting them at a higher risk for metabolic syndrome in adulthood. Although well-documented, the body fat distribution and mechanisms behind weight gain in narcolepsy are still not fully understood but may be related to the loss of orexin associated with the disease. Orexin has been linked to the regulation of brown adipose tissue (BAT), a metabolically active fat involved in energy homeostasis. Previous studies have used BMI and waist circumference to characterize adipose tissue increases in narcolepsy but none have investigated its specific distribution. Here, we examine adipose tissue distribution in 19 adolescent patients with narcolepsy type 1 and compare them to 17 of their healthy peers using full body magnetic resonance imaging (MRI). In line with previous findings we saw that the narcolepsy patients had more overall fat than the healthy controls, but contrary to our expectations there were no group differences in supraclavicular BAT, suggesting that orexin may have no effect at all on BAT, at least under thermoneutral conditions. Also, in line with previous reports, we observed that patients had more total abdominal adipose tissue (TAAT), however, we found that they had a lower ratio between visceral adipose tissue (VAT) and TAAT indicating a relative increase of subcutaneous abdominal adipose tissue (ASAT). This relationship between VAT and ASAT has been associated with a lower risk for metabolic disease. We conclude that while weight gain in adolescents with narcolepsy matches that of central obesity, the lower VAT ratio may suggest a lower risk of developing metabolic disease.

Hypocretin/Orexin Peptides Excite Rat Neuroendocrine Dopamine Neurons through Orexin 2 Receptor-Mediated Activation of a Mixed Cation Current

Hypocretin/Orexin (H/O) neurons of the lateral hypothalamus are compelling modulator candidates for the chronobiology of neuroendocrine output and, as a consequence, hormone release from the anterior pituitary. Here we investigate the effects of H/O peptides upon tuberoinfundibular dopamine (TIDA) neurons – cells which control, via inhibition, the pituitary secretion of prolactin. In whole cell recordings performed in male rat hypothalamic slices, application of H/O-A, as well as H/O-B, excited oscillating TIDA neurons, inducing a reversible depolarising switch from phasic to tonic discharge. The H/O-induced inward current underpinning this effect was post-synaptic (as it endured in the presence of tetrodotoxin), appeared to be carried by a Na⁺-dependent transient receptor potential-like channel (as it was blocked by 2-APB and was diminished by removal of extracellular Na⁺), and was a consequence of OX2R receptor activation (as it was blocked by the OX2R receptor antagonist TCS OX2 29, but not the OX1R receptor antagonist SB 334867). Application of the hormone, melatonin, failed to alter TIDA membrane potential or oscillatory activity. This first description of the electrophysiological effects of H/Os upon the TIDA network identifies cellular mechanisms that may contribute to the circadian rhythmicity of prolactin secretion.

The Humanistic and Economic Burden of Narcolepsy

STUDY OBJECTIVES

To evaluate the burden of narcolepsy--with respect to psychiatric comorbidities, Health-Related Quality of Life (HRQoL), direct costs for healthcare resource utilization, and indirect costs for reported work loss-through comparison of patients to matched controls.

METHODS

This analysis was conducted on data from the 2011, 2012, and 2013 US National Health and Wellness Survey (NHWS; 2011 NHWS n = 75,000, 2012 NHWS n = 71,157, and 2013 NHWS n = 75,000). Patients who reported a narcolepsy diagnosis (n = 437) were matched 1:2 with controls (n = 874) on age, sex, race/ethnicity, marital status, education, household income, body mass index, smoking status, alcohol use, exercise, and physical comorbidity. Chi-square tests and one-way analyses of variance were used to assess whether the narcolepsy and control groups differed on psychiatric comorbidities, HRQoL, labor force participation, work productivity, and healthcare resource utilization.

RESULTS

Patients with narcolepsy, in comparison to matched controls, reported substantially (two to four times) greater psychiatric comorbidity, HRQoL impairment, prevalence of long-term disability, absenteeism, and presenteeism, and greater resource use in the past 6 mo as indicated by higher mean number of hospitalizations, emergency department visits, traditional healthcare professional visits, neurologist visits, and psychiatrist visits (each p < 0.05).

CONCLUSIONS

These population-based data suggest that a narcolepsy diagnosis is associated with substantial adverse impact on mental health, HRQoL, and key economic burdens that include work impairment, resource use, and both direct and indirect costs. Although this study is cross-sectional, the results highlight the magnitude of the potential opportunity to improve mental health, lower costs, and augment work-related productivity through effective assessment and treatment of narcolepsy.

Growing Up with Type 1 Narcolepsy: Its Anthropometric and Endocrine Features

STUDY OBJECTIVES

To evaluate the effect of type 1 narcolepsy (NT1) on anthropometric and endocrine features in childhood/adolescence, focusing on patterns and correlates of weight, pubertal development, and growth in treated and untreated patients.

METHODS

We collected anthropometric (height, weight, body mass index (BMI) z-scores), pubertal, metabolic, and endocrine data from 72 NT1 patients at diagnosis and all available premorbid anthropometric parameters of patients from their pediatric files (n = 30). New measurements at 1-y reassessment in patients undergoing different treatments were compared with baseline data.

RESULTS

We detected a high prevalence of overweight (29.2%), obesity (25%), metabolic syndrome (18.8%), and precocious puberty (16.1%), but no signs of linear growth alterations at diagnosis. According to anthropometric records, weight gain started soon after NT1 onset. At 1-y follow-up reassessment, sodium oxybate treatment was associated with a significant BMI z-score reduction (-1.29 ± 0.30, p < 0.0005) after adjusting for baseline age, sex, sleepiness, and BMI.

CONCLUSIONS

NT1 onset in children/adolescents is associated with rapid weight gain up to overweight/obesity and precocious puberty without affecting growth. In our study, sodium oxybate treatment resulted in a significant weight reduction in NT1 overweight/obese patients at 1-y follow-up.

Aberrant Food Choices after Satiation in Human Orexin-Deficient Narcolepsy Type 1

STUDY OBJECTIVES

Besides influencing vigilance, orexin neurotransmission serves a variety of functions, including reward, motivation, and appetite regulation. As obesity is an important symptom in orexin-deficient narcolepsy, we explored the effects of satiety on food-related choices and spontaneous snack intake in patients with narcolepsy type 1 (n = 24) compared with healthy matched controls (n = 19). In additional analyses, we also included patients with idiopathic hypersomnia (n = 14) to assess sleepiness-related influences.

METHODS

Participants were first trained on a choice task to earn salty and sweet snacks. Next, one of the snack outcomes was devalued by having participants consume it until satiation (i.e., sensory-specific satiety). We then measured the selective reduction in choices for the devalued snack outcome. Finally, we assessed the number of calories that participants consumed spontaneously from ad libitum available snacks afterwards.

RESULTS

After satiety, all participants reported reduced hunger and less wanting for the devalued snack. However, while controls and idiopathic hypersomnia patients chose the devalued snack less often in the choice task, patients with narcolepsy still chose the devalued snack as often as before satiety. Subsequently, narcolepsy patients spontaneously consumed almost 4 times more calories during ad libitum snack intake.

CONCLUSIONS

We show that the manipulation of food-specific satiety has reduced effects on food choices and caloric intake in narcolepsy type 1 patients. These mechanisms may contribute to their obesity, and suggest an important functional role for orexin in human eating behavior.

CLINICAL TRIALS REGISTRATION

Study registered at Netherlands Trial Register. URL: www.trialregister.nl. Trial ID: NTR4508.

Role of the Orexin System on the Hypothalamus-Pituitary-Thyroid Axis

Hypocretin/orexin (ORX) are two hypothalamic neuropeptides discovered in 1998. Since their discovery, they have been one of the most studied neuropeptide systems because of their projecting fields innervating various brain areas. The orexinergic system is tied to sleep-wakefulness cycle, and narcolepsy is a consequence of their system hypofunction. Orexinergic system is also involved in many other autonomic functions such as feeding, thermoregulation, cardiovascular and neuroendocrine regulation. The main aim of this mini review article is to investigate the relationship between ORX and thyroid system regulation. Although knowledge about the ORX system is evolving, its putative effects on hypothalamic-pituitary-thyroid (HPT) axis still appear unclear. We analyzed some studies about ORX control of HPT axis to know better the relationship between them. The studies that were analyzed suggest Hypocretin/ORX to modulate the thyroid regulation, but the nature (excitatory or inhibitory) of this possible interaction remains actually unclear and needs to be confirmed.

Challenges in the development of therapeutics for narcolepsy

Narcolepsy is a neurological disorder that afflicts 1 in 2000 individuals and is characterized by excessive daytime sleepiness and cataplexy-a sudden loss of muscle tone triggered by positive emotions. Features of narcolepsy include dysregulation of arousal state boundaries as well as autonomic and metabolic disturbances. Disruption of neurotransmission through the hypocretin/orexin (Hcrt) system, usually by degeneration of the HCRT-producing neurons in the posterior hypothalamus, results in narcolepsy. The cause of Hcrt neurodegeneration is unknown but thought to be related to autoimmune processes. Current treatments for narcolepsy are symptomatic, including wake-promoting therapeutics that increase presynaptic dopamine release and anticataplectic agents that activate monoaminergic neurotransmission. Sodium oxybate is the only medication approved by the US Food and Drug Administration that alleviates both sleep/wake disturbances and cataplexy. Development of therapeutics for narcolepsy has been challenged by historical misunderstanding of the disease, its many disparate symptoms and, until recently, its unknown etiology. Animal models have been essential to elucidating the neuropathology underlying narcolepsy. These models have also aided understanding the neurobiology of the Hcrt system, mechanisms of cataplexy, and the pharmacology of narcolepsy medications. Transgenic rodent models will be critical in the development of novel therapeutics for the treatment of narcolepsy, particularly efforts directed to overcome challenges in the development of hypocretin replacement therapy.

Narcolepsy in African Americans

STUDY OBJECTIVES

Although narcolepsy affects 0.02-0.05% of individuals in various ethnic groups, clinical presentation in different ethnicities has never been fully characterized. Our goal was to study phenotypic expression across ethnicities in the United States.

DESIGN/SETTING

Cases of narcolepsy from 1992 to 2013 were identified from searches of the Stanford Center for Narcolepsy Research database. International Classification of Sleep Disorders, Third Edition diagnosis criteria for type 1 and type 2 narcolepsy were used for inclusion, but subjects were separated as with and without cataplexy for the purpose of data presentation. Information extracted included demographics, ethnicity and clinical data, HLA-DQB1*06:02, polysomnography (PSG), multiple sleep latency test (MSLT) data, and cerebrospinal fluid (CSF) hypocretin-1 level.

PATIENTS

182 African-Americans, 839 Caucasians, 35 Asians, and 41 Latinos with narcolepsy.

RESULTS

Sex ratio, PSG, and MSLT findings did not differ across ethnicities. Epworth Sleepiness Scale (ESS) score was higher and age of onset of sleepiness earlier in African Americans compared with other ethnicities. HLA-DQB1*06:02 positivity was higher in African Americans (91.0%) versus others (76.6% in Caucasians, 80.0% in Asians, and 65.0% in Latinos). CSF hypocretin-1 level, obtained in 222 patients, was more frequently low (≤ 110 pg/ml) in African Americans (93.9%) versus Caucasians (61.5%), Asians (85.7%) and Latinos (75.0%). In subjects with low CSF hypocretin-1, African Americans (28.3%) were 4.5 fold more likely to be without cataplexy when compared with Caucasians (8.1%).

CONCLUSIONS

Narcolepsy in African Americans is characterized by earlier symptom onset, higher Epworth Sleepiness Scale score, higher HLA-DQB1*06:02 positivity, and low cerebrospinal fluid hypocretin-1 level in the absence of cataplexy. In African Americans, more subjects without cataplexy have type 1 narcolepsy.

Histamine Transmission Modulates the Phenotype of Murine Narcolepsy Caused by Orexin Neuron Deficiency

Narcolepsy type 1 is associated with loss of orexin neurons, sleep-wake derangements, cataplexy, and a wide spectrum of alterations in other physiological functions, including energy balance, cardiovascular, and respiratory control. It is unclear which narcolepsy signs are directly related to the lack of orexin neurons or are instead modulated by dysfunction of other neurotransmitter systems physiologically controlled by orexin neurons, such as the histamine system. To address this question, we tested whether some of narcolepsy signs would be detected in mice lacking histamine signaling (HDC-KO). Moreover, we studied double-mutant mice lacking both histamine signaling and orexin neurons (DM) to evaluate whether the absence of histamine signaling would modulate narcolepsy symptoms produced by orexin deficiency. Mice were instrumented with electrodes for recording the electroencephalogram and electromyogram and a telemetric arterial pressure transducer. Sleep attacks fragmenting wakefulness, cataplexy, excess rapid-eye-movement sleep (R) during the activity period, and enhanced increase of arterial pressure during R, which are hallmarks of narcolepsy in mice, did not occur in HDC-KO, whereas they were observed in DM mice. Thus, these narcolepsy signs are neither caused nor abrogated by the absence of histamine. Conversely, the lack of histamine produced obesity in HDC-KO and to a greater extent also in DM. Moreover, the regularity of breath duration during R was significantly increased in either HDC-KO or DM relative to that in congenic wild-type mice. Defects of histamine transmission may thus modulate the metabolic and respiratory phenotype of murine narcolepsy.

Case of early childhood-onset narcolepsy with cataplexy: comparison with a monozygotic co-twin

We describe here a rare case of early childhood-onset (5 years of age) narcolepsy. This case was interesting because of the ability to compare the patient's symptoms to the condition of her healthy monozygotic co-twin sister. The only environmental difference between the co-twins was head injury, which may be associated with the presence of narcolepsy. The co-twin was extroverted, sociable, reliable, and dexterous. In contrast, the patient could be described as introverted, gentle, honest and persevering, but was weak at conversation, assessment of a situation, memory, planning, activity (she was inactive), a sense of time, understanding of an analog clock, operating efficiency, and physical education (due to obesity). The sisters showed the same degree of appetite and dexterity with their fingers. Narcolepsy is often under-recognized or underdiagnosed, especially when the onset occurs in childhood. When we observe preschoolers with excessive daytime sleepiness, we should consider the possibility of narcolepsy with cataplexy.

The hypocretins/orexins: integrators of multiple physiological functions

The hypocretins (Hcrts), also known as orexins, are two peptides derived from a single precursor produced in the posterior lateral hypothalamus. Over the past decade, the orexin system has been associated with numerous physiological functions, including sleep/arousal, energy homeostasis, endocrine, visceral functions and pathological states, such as narcolepsy and drug abuse. Here, we review the discovery of Hcrt/orexins and their receptors and propose a hypothesis as to how the orexin system orchestrates these multifaceted physiological functions.

Gender differences between hypocretin/orexin knockout and wild type mice: age, body weight, body composition, metabolic markers, leptin and insulin resistance

Female hypocretin knockout (Hcrt KO) mice have increased body weight despite decreased food intake compared to wild type (WT) mice. In order to understand the nature of the increased body weight, we carried out a detailed study of Hcrt KO and WT, male, and female mice. Female KO mice showed consistently higher body weight than WT mice, from 4 to 20 months (20-60%). Fat, muscle, and free fluid levels were all significantly higher in adult (7-9 months) as well as old (18-20 months) female KO mice compared to age-matched WT mice. Old male KO mice showed significantly higher fat content (150%) compared to age-matched WT mice, but no significant change in body weight. Respiratory quotient (-19%) and metabolic rates (-14%) were significantly lower in KO mice compared to WT mice, regardless of gender or age. Female KO mice had significantly higher serum leptin levels (191%) than WT mice at 18-20 months, but no difference between male mice were observed. Conversely, insulin resistance was significantly higher in both male (73%) and female (93%) KO mice compared to age- and sex-matched WT mice. We conclude that absence of the Hcrt peptide has gender-specific effects. In contrast, Hcrt-ataxin mice and human narcoleptics, with loss of the whole Hcrt cell, show weight gain in both sexes.

Food for thought: understanding the multifaceted nature of orexins

Orexins are a pair of hypothalamic neuropeptides that were discovered in the late 1990s and named initially for their ability to promote feeding. Subsequent studies have revealed the importance of orexins to a variety of physiological functions, including brown fat thermogenesis, sleep/wake cycles, physical activity, and cognition. We aim to elucidate the various roles of orexins and discuss how these multiple functions are interlinked. We explain that although the unique dual roles of orexins in increasing feeding while concomitantly elevating energy expenditure appear counterproductive, they are necessary for physiological scenarios during which simultaneous stimulation of energy expenditure and feeding occur, namely diet-induced thermogenesis and arousal from hibernation. The position of orexins at the interface between sleep/wake cycles, energy homeostasis, and environmental factors has important implications in the treatment of obesity.

Plasma total ghrelin and leptin levels in human narcolepsy and matched healthy controls: basal concentrations and response to sodium oxybate

STUDY OBJECTIVES

Narcolepsy is caused by a selective loss of hypocretin neurons and is associated with obesity. Ghrelin and leptin interact with hypocretin neurons to influence energy homeostasis. Here, we evaluated whether human hypocretin deficiency, or the narcolepsy therapeutic agent sodium oxybate, alter the levels of these hormones.

METHODS

Eight male, medication free, hypocretin deficient, narcolepsy with cataplexy patients, and 8 healthy controls matched for age, sex, body mass index (BMI), waisttohip ratio, and body fat percentage were assessed. Blood samples of total ghrelin and leptin were collected over 24 hours at 60 and 20-min intervals, respectively, during 2 study occasions: baseline, and during the last night of 5 consecutive nights of sodium oxybate administration (2 × 3.0 g/night).

RESULTS

At baseline, mean 24-h total ghrelin (936 ± 142 vs. 949 ± 175 pg/mL, p = 0.873) and leptin (115 ± 5.0 vs. 79.0 ± 32 mg/L, p = 0.18) levels were not different between hypocretin deficient narcolepsy patients and controls. Furthermore, sodium oxybate did not significantly affect the plasma concentration of either one of these hormones.

CONCLUSIONS

The increased BMI of narcolepsy patients is unlikely to be mediated by hypocretin deficiency-mediated alterations in total ghrelin or leptin levels. Thus, the effects of these hormones on hypocretin neurons may be mainly unidirectional. Although sodium oxybate may influence body weight, the underlying mechanism is unlikely to involve changes in total ghrelin or leptin secretion.

Reward-based behaviors and emotional processing in human with narcolepsy-cataplexy

Major advances in the past decade have led a better understanding of the pathophysiology of narcolepsy with cataplexy (NC) caused by the early loss of hypothalamic hypocretin neurons. Although a role for hypocretin in the regulation of sleep/wakefulness state is widely recognized, other functions, not necessarily related to arousal, have been identified. Hence, the hypocretin system enhances signaling in the mesolimbic pathways regulating reward processing, emotion and mood regulation, and addiction. Although studies on hypocretin-deficient mice have shown that hypocretin plays an essential role in reward-seeking, depression-like behavior and addiction, results in human narcolepsy remained subject to debate. Most of studies revealed that hypocretin-deficient narcolepsy patients either drug-free or medicated with psychostimulant had preferences toward risky choices in a decision-making task under ambiguity together with higher frequency of depressive symptoms and binge eating disorder compared to controls. However, human studies mostly reported the lack of association with pathological impulsivity and gambling, and substance and alcohol abuse in the context of narcolepsy-cataplexy. Prospective larger studies are required to confirm these findings in drug-free and medicated patients with narcolepsy. Inclusion of patients with other central hypersomnias without hypocretin deficiency will provide answer to the major question of the role of the hypocretin system in reward-based behaviors and emotional processing in humans.

Impact of obesity in children with narcolepsy

AIMS

To evaluate the impact of obesity on clinical and sleep characteristics in a population of narcoleptic children.

METHODS

Data from the children diagnosed with idiopathic narcolepsy in the National Reference Centers for Narcolepsy were collected between 2008 and 2011. Clinical and electrophysiological characteristics were compared between obese (body mass index [BMI] greater than P97) and nonobese children.

RESULTS

The 117 children (65 boys, 59 de novo patients) had a mean age of 11.6 ± 3.1 years on diagnosis. Cataplexy was present in 81%, DQB1*0602 in 91%. Mean BMI was 23.2 ± 5.2 kg/m(2) and BMI z-score was 2.9 ± 2.6. Obesity was found in 60% with a similar prevalence in treated versus de novo patients and in patients with and without cataplexy. Sleepiness and cataplexy started earlier in obese children. Obese narcoleptic children had lower sleep efficiency, higher apnea hypopnea index and respiratory arousals index (RAI) than nonobese children. BMI z-score was positively correlated with RAI. Obese children were more tired and missed more often school than nonobese children.

CONCLUSION

Obesity affects more than 50% of narcoleptic children, mostly younger at disease onset, and has a deleterious impact on sleep quality as well as on school attendance.

Cerebrospinal fluid hypocretin 1 deficiency, overweight, and metabolic dysregulation in patients with narcolepsy

STUDY OBJECTIVES

The possible relationship between cerebrospinal fluid (CSF) hypocretin and leptin levels, overweight, and association to risk factors for diabetes 2 in narcolepsy with cataplexy were compared to patients with idiopathic hypersomnia and controls.

PATIENTS

26 patients with narcolepsy, cataplexy, and hypocretin deficiency; 23 patients with narcolepsy, cataplexy, and normal hypocretin values; 11 patients with idiopathic hypersomnia; and 43 controls.

MEASUREMENTS AND RESULTS

Body mass index (BMI), serum leptin, and HbA1C were measured in patients and controls; and CSF hypocretin 1 and leptin measured in all patients. Female and male patients with narcolepsy and hypocretin deficiency had the highest mean BMI (27.8 and 26.2, respectively), not statistically different from patients with narcolepsy and normal hypocretin or controls, but statistically higher than the patients with idiopathic hypersomnia (p < 0.001 and 0.011, respectively). The number of obese patients (BMI > 30) was increased in both narcolepsy groups. Serum and CSF leptin levels correlated positively to BMI in patients and controls, but not to CSF hypocretin concentrations. HbA1C was within normal levels and similar in all groups.

CONCLUSIONS

The study confirms a moderate tendency to obesity (BMI > 30) and overweight in patients with narcolepsy and cataplexy. Obesity was not correlated to hypocretin deficiency or reduced serum or CSF leptin concentrations. We suggest that overweight and possible metabolic changes previously reported in narcolepsy, may be caused by other mechanisms.