Cerebrospinal fluid hypocretin-1 levels in multiple system atrophy

Hypocretin (orexin) cerebrospinal fluid (CSF) levels have been previously found normal or decreased in Dementia with Lewy bodies and Parkinson disease, two synucleinopathies commonly associated with excessive daytime sleepiness (EDS). We evaluated CSF hypocretin-1 levels in 15 patients with moderately severe multiple system atrophy (MSA), another synucleinopathy where sleep disorders occur frequently and EDS has been reported, performing additional electrophysiological studies in 5 of them to assess the presence of EDS and sleep onset REM (SOREM) periods. Despite relatively low sleep efficiencies in nocturnal sleep, mean sleep latencies in the Multiple Sleep Latency Test were normal with no SOREM periods. All patients had CSF hypocretin-1 levels in the normal range (>200 pg/mL) suggesting that the hypocretin system is not altered in MSA, at least in patients with a moderately severe disease.

CSF orexin levels of Parkinson's disease, dementia with Lewy bodies, progressive supranuclear palsy and corticobasal degeneration

Excessive daytime sleepiness has been widely accepted as a common problem not only in Parkinson's disease (PD) but also in other related disorders. Lowered excretion of orexin A (hypocretin 1) into the cerebrospinal fluid (CSF) is known to play a pathological role in narcolepsy and secondary hypersomnia due to hypothalamic dysfunction. Although the levels of CSF orexin in PD have been previously examined, the results have been controversial, and no systematic investigation of CSF orexin excretion has been conducted on PD related disorders. In this study, orexin was measured in CSF collected by lumbar puncture in 62 patients with PD, 13 patients with dementia with Lewy bodies (DLB), 16 patients with progressive supranuclear palsy (PSP), and 7 patients with corticobasal degeneration (CBD). Levels of CSF orexin (mean+/-SD pg/ml) were 302+/-38 in PD, 297+/-48 in DLB, 258+/-37 in PSP, 246+/-90 in CBD. The occurrence of low orexin levels (<or=110pg/ml) was rare in both PD and DLB, and orexin levels were significantly lower in the PSP and CBD groups compared to PD (PSP: p<0.001, CBD: p<0.05). Orexin levels were inversely correlated with duration of morbidity in PSP but not in the other conditions studied. These findings suggest that loss of orexin neurons or impaired orexin neurotransmission might exist as a part of the neurodegeneration associated with advanced PSP with long duration of morbidity.

Serial neurochemical measurement of cerebrospinal fluid during the human sexual response cycle

Recent studies examining the neuroendocrine response pattern underlying the human sexual response cycle revealed transient activation of the sympathoadrenal system and a substantial, long-lasting increase in plasma prolactin concentrations following orgasm in men and women. Prolactin has been discussed as being part of a feedback mechanism that signals centers in the central nervous system, such as the dopaminergic system controlling sexual arousal. To further elucidate the central role of neuropeptides, biogenic monoamines and neurotransmitters in human sexual behavior, a serial cerebrospinal fluid (CSF)-sampling technique was implemented using a previously established experimental paradigm for sexual activity in a laboratory setting. In parallel with peripheral endocrine measures, lumbar CSF was drawn via an indwelling spinal catheter during the sexual response cycle in 10 healthy males and 10 age-matched controls, and analysed for prolactin, oxytocin, biogenic monoamines and/or their metabolites as well as inhibitory and excitatory neurotransmitter concentrations. Parallel to raised peripheral sympathetic activity, norepinephrine also increased in CSF during audiovisual, masturbation-induced sexual arousal and orgasm, and remained elevated for the remainder of the session (F(4,72) = 8.79, P = 0.000). In contrast, none of the other measures, in particular prolactin and dopamine or its metabolites, reflected significant alteration. In conclusion, the human sexual response cycle is characterized by an increase in sympathetic activity in plasma and CSF, and by pronounced secretion of plasma prolactin after orgasm. However, alterations in dopaminergic or peptidergic activity are not found in lumbar CSF, possibly due to local and restricted release in diencephalic and mesencephalic brain regions.

Kleine–Levin syndrome in a 14-year-old girl: CSF hypocretin-1 measurements

CSF hypocretin-1 measurements were performed during a period of hypersomnia and during an asymptomatic interval in a 14-year-old girl affected with severe Kleine-Levin syndrome. A twofold decrease in hypocretin-1 was evidenced during the period of hypersomnia in comparison with the asymptomatic interval. Together with previous data, this result is in favour of recurrent dysfunction at the hypothalamic level in Kleine-Levin syndrome.

[Narcolepsy--new implications of molecular biology]

Narcolepsy is a common but underdiagnosed sleep disorder characterized by excessive daytime sleepiness and abnormal manifestations of REM sleep: cataplexy, sleep paralysis and hypnagogogic hallucinations. Sleep onset REM periods (SOREMPs) are diagnostic. Within the last five years the pathogenesis has become clearer: narcolepsy is associated with almost total absence of the neuropeptides hypocretin-1 and -2 in the hypothalamus and CSF. A low level of CSF hypocretin is now recognized as a new diagnostic tool. This review provides updated knowledge of narcolepsy.

Narcolepsy and the hypocretins

Narcolepsy is a chronic neurologic disease characterized by excessive daytime sleepiness and one or more of three additional symptoms (cataplexy, or sudden loss of muscle tone; vivid hallucinations; and brief periods of total paralysis) related to the occurrence of rapid eye movement (REM) sleep at inappropriate times. The daytime sleepiness typically presents as a sudden overwhelming urge to sleep, followed by periods of sleep that last for seconds or minutes, or even longer. During daytime sleep episodes, patients may exhibit "automatic behavior," performing conventionalized functions (eg, taking notes), but not remembering having done so once they are awake. About 10% of narcoleptics are members of familial clusters; however, genetic factors alone are apparently insufficient to cause the disease, inasmuch as the most common genetic disorder, a mutation in chromosome 6 controlling the HLA antigen immune complex, although seen in 90% to 100% of patients, also occurs in as many as 50% of people without narcolepsy. A dog model of narcolepsy exhibits a mutation on chromosome 12 that disrupts the processing of the peptide neurotransmitter hypocretin. No such mutation characterizes human narcolepsy; however, cerebrospinal fluid (CSF) hypocretin levels are profoundly depressed in narcoleptic patients, and a specific reduction in hypocretin-containing neurons has been described. One hypothesis concerning the pathophysiology of narcolepsy proposes that the HLA subtype resulting from the mutation on chromosome 6 increases the susceptibility of hypocretin-containing brain neurons to immune attack. Because hypocretin may normally participate in the maintenance of wakefulness, the loss of neurons that release this peptide might allow REM sleep to occur at inappropriate times, ie, while the patient is awake, in contrast to its normal cyclic appearance after a period of slow-wave sleep. The cataplexy, hallucinations, and/or paralysis associated with REM episodes normally are unnoticed-or, at least, not remembered-when the transition to REM follows slow wave sleep, as is normally the case; however, they are remembered when, in people with narcolepsy, the REM episode starts during a period of wakefulness. The association of narcolepsy with a deficiency in a specific neurotransmitter, in this case, hypocretin, is reminiscent of the associations between Parkinson disease and dopamine, or early Alzheimer disease and acetylcholine.

Immunohistochemical staining patterns using epitope-specific antibodies indicate conformation variants of antisecretory factor/S5a in the CNS

Antisecretory factor (AF/S5a/Rpn10) was originally identified through its ability to counteract pathological secretion. AF is also a potent anti-inflammatory agent, a neuromodulator, and an important component of the proteasome. Human AF has a calculated molecular mass of 41 kDa and a pI of 4.7. No family of AF-like proteins has been identified. AF has multiple functions in the cell, and different functional forms could exist as a result of post-translational modifications. Epitope-specific antibodies covering the entire length of AF were used to investigate whether modified forms of AF could be detected in the porcine spinal cord by Western blots, 2D gels, and immunohistochemistry (IHC). Western blot and 2D gels showed that all antisera detected a single protein with very similar molecular mass and pI. However, IHC resulted in an epitope-specific subcellular staining pattern. Antisera recognizing epitopes in the N-terminal part of AF, containing the antisecretory activity, showed a more restricted localisation than antisera directed at the C-terminal part, containing the ubiquitin-binding sites. We suggest that AF can exist in several conformational variants, perhaps due to differences in redox state and/or pH in the various cellular compartments. Such conformational changes could be of functional importance.

CSF orexin A concentrations and expressions of the orexin-1 receptor in rat hippocampus after cardiac arrest

Orexins/hypocretins are neuropeptides that have various physiological effects, including the regulation of feeding behavior, neuroendocrine functions and sleep-wake cycles. Recent studies have suggested that the orexin system may also be involved in brain ischemic reactions. It is also known that changes in sleep patterns, energy homeostasis and neuroendocrine functions are often occur in neurological conditions associated brain ischemia. In the current study, we investigated the time-dependent changes in cerebrospinal fluid (CSF) orexin-A concentration and the expression of the orexin-1 receptor (OX1R) in the rat hippocampus after global ischemia-reperfusion (5 min cardiopulmonary arrest), which is known to induce delayed cell death in the CA1 region of the hippocampus. The CSF orexin-A concentration was elevated transiently at 24 h after ischemia. On days 2 and 4 after ischemia, CSF orexin concentrations were significantly reduced relative to the baseline, and returned to the baseline level by day 7. These changes were correlated with increased expression of OX1R in the CA1 on days 1 and 2 post-ischemia. These results suggest that dynamics of orexin signaling observed may have functional roles for neuronal damage associated with transient ischemia.

Daytime sleepiness with and without cataplexy in Chinese–Taiwanese patients

BACKGROUND AND PURPOSE

Investigation of Chinese-Taiwanese patients with excessive sleepiness, but no association with other sleep disorders, and with the presence or absence of cataplexy.

PATIENTS AND METHODS

Thirty-five patients, successively referred between 2002 and 2004, underwent polysomnography (PSG), repeat multiple sleep latency test (MSLT), and human leukocyte antigen (HLA) typing. Three patients without cataplexy also had cerebrospinal fluid (CSF) hypocretin measurements.

RESULTS

DQB1*0602 was associated with cataplexy in over 90% of Chinese-Taiwanese cases. Absence of cataplexy and <2 sleep-onset REM periods (SOREMPs) was seen in only two subjects, but presence of two SOREMPs did not dissociate DQB1*0602 positive and negative or cataplexy positive and negative subjects. As a group, narcoleptics with cataplexy had a higher number of SOREMPs, and the mean sleep latency was much shorter in narcoleptics with cataplexy than in the non-cataplectic patients, independent of the number of SOREMPs.

CONCLUSIONS

Chinese-Taiwanese patients with cataplexy present with similar HLA findings as Black and Caucasian patients, but the presence of two or more SOREMPs in Chinese-Taiwanese patients is not a sufficient diagnostic tool to identify narcolepsy. When cataplexy is not present, description of PSG nd HLA findings may be a better approach than using a label with little scientific significance, allowing for better collection of patients' phenotype.

Diurnal variation in CSF orexin-A in healthy male subjects

STUDY OBJECTIVE

Orexin-A is hypothesized to promote wakefulness, and we examined whether cerebrospinal fluid (CSF) orexin-A levels are higher during the waking period in man.

DESIGN

Within-subjects, repeated-measures design with balanced ordering of sampling at approximately 5 AM and 5 PM.

PARTICIPANTS

Eight healthy young males. MESUREMENTS: CSF orexin-A levels and standard polysomnography.

RESULTS

Orexin-A levels during the sleep period were 4% higher than during the waking period (314.9 pg/ml versus 302.8 pg/ml, p < 0.03). Sleep period orexin-A levels were negatively correlated with REM sleep as a percentage of total sleep time (p < 0.05). The day and night levels of orexin-A were strongly correlated within subjects (r = 0.97; p < 0.0001) even though the samples were collected 1-2 weeks apart.

CONCLUSIONS

Orexin-A levels in lumbar CSF are slightly higher at 5 AM than at 5 PM. Because orexin release is thought to be highest during the waking period, this observation was unexpected and may reflect a long delay between the release of orexin and its appearance in lumbar CSF. Orexin-A levels vary moderately between subjects, but are quite consistent within the same subject. Thus, for the diagnostic evaluation of narcolepsy, the time of CSF collection should have little impact.

Hypocretin-1 (orexin A) deficiency in acute traumatic brain injury

Hypocretin-1 is involved in the regulation of the sleep-wake cycle. The authors prospectively assessed CSF hypocretin-1 levels in 44 consecutive patients with acute traumatic brain injury (TBI). Compared with controls, hypocretin-1 levels were abnormally lower in 95% of patients with moderate to severe TBI and in 97% of patients with posttraumatic brain CT changes. Hypocretin-1 deficiency after TBI may reflect hypothalamic damage and be linked with the frequent development of posttraumatic sleep-wake disorders.

Identification of potential CSF biomarkers in ALS

BACKGROUND

The clinical diagnosis of ALS is based entirely on clinical features. Identification of biomarkers for ALS would be important for diagnosis and might also provide clues to pathogenesis.

OBJECTIVE

To determine if there is a specific protein profile in the CSF that distinguishes patients with ALS from those with purely motor peripheral neuropathy (PN) and healthy control subjects.

METHODS

CSF obtained from patients with ALS, disease controls (patients with other neurologic disorders), and normal controls were analyzed using the surface-enhanced laser desorption/ionization time-of-flight mass spectrometry proteomics technique. Biomarker sensitivity and specificity was calculated with receiver operating characteristic curve methodology. ALS biomarkers were purified and sequence identified by mass spectrometry-directed peptide sequencing.

RESULTS

In initial proteomic discovery studies, three protein species (4.8-, 6.7-, and 13.4-kDa) that were significantly lower in concentration in the CSF from patients with ALS (n = 36) than in normal controls (n = 21) were identified. A combination of three protein species (the "three-protein" model) correctly identified patients with ALS with 95% accuracy, 91% sensitivity, and 97% specificity from the controls. Independent validation studies using separate cohorts of ALS (n = 13), healthy control (n = 25), and PN (n = 7) subjects confirmed the ability of the three CSF protein species to separate patients with ALS from other diseases. Protein sequence analysis identified the 13.4-kDa protein species as cystatin C and the 4.8-kDa protein species as a peptic fragment of the neurosecretory protein VGF.

CONCLUSION

Additional application of a "three-protein" biomarker model to current diagnostic criteria may provide an objective biomarker pattern to help identify patients with ALS.

Niemann-Pick Disease Type C: Cataplexy and Hypocretin in Cerebrospinal Fluid

Niemann-Pick disease type C (NPC) is an inherited lipid storage disorder, characterized by a defect in intracellular trafficking of exogenous cholesterol that leads to the lysosomal accumulation of unesterified cholesterol. We report a Japanese patient with NPC caused by a homozygous c.2974 G > T mutation of the NPC1 gene, which predicts a glycine (GGG) to tryptophan (TGG) change at codon 992 (designated as p.G992W). This is a well-known NPC1 gene mutation that causes a unique phenotype of NPC, which has been limited to a single Acadian ancestor in Nova Scotia, Canada. Our patient characteristically started presenting with cataplexy at the age of 9 years. Recent studies have shown reduced hypocretin-1 levels in the cerebrospinal fluid (CSF) of narcoleptic patients with cataplexy. In our patient, the level of hypocretin-1 was determined as moderately low, 174 pg/ml (normal, > 200 pg/ml). To date, CSF levels of hypocretin-1 have been determined by using an identical assay method in 7 cases of NPC, including our case. All of the NPC cases with cataplexy demonstrated low levels of CSF hypocretin-1, confirming the association of reduced CSF hypocretin-1 levels with cataplexy in NPC.

Identification of mature nocistatin and nociceptin in human brain and cerebrospinal fluid by mass spectrometry combined with affinity chromatography and HPLC

Nocistatin (NST) and nociceptin/orphanin FQ (NCP) are two important bio-peptides derived from the precursor protein prepronociceptin (ppNCP), involved in several central nervous system (CNS) functions including pain transmission. Since the actual form of human NST in CNS is not fully characterized, we studied the structure of NST from human brain tissue and cerebrospinal fluid (CSF) samples. NST and NCP were isolated from human brain and CSF samples by affinity chromatography combined with HPLC. Mass spectrometry was used for the identification and characterization of the peptides. The total NST immunoreactivity was detected as 11.5+/-2.3 pmol/g tissue for the brain and 0.44 pmol/ml for the pooled CSF sample after the HPLC purification by radioimmunoassay. The presence of two different forms of mature nocistatin (NST-17 and NST-30) and a possible N-terminal methionine cleaved NST-29 were confirmed by both radioimmunoassay and mass spectrometry. Affinity chromatography, HPLC and mass spectrometry methods used in this study were highly sensitive and suitable for identification of actual chemical structures and quantification of very small amounts of peptides in biological samples. The present findings may help further for search for new treatment of neuropathic pain, which is often poorly managed by current therapies.

Narcolepsy: a review of evidence for autoimmune diathesis

Sporadic narcolepsy with cataplexy is a disabling disease that is strongly associated with the major histocompatibility class II allele HLA DQB1*0602 and is characterized by profound reduction in the cerebrospinal fluid (CSF) concentration of hypocretin 1 levels. This article provides a comprehensive review of the evidence that neurologic autoimmunity is the pathogenic basis of narcolepsy with cataplexy. Despite this evidence, specific antibody markers for narcolepsy have been elusive. Clinical trials using intravenous immunoglobulin infusions in recent onset narcolepsy with cataplexy have led to improvement in cataplexy in some patients. Future research must focus on elucidation of immune markers and early ameliorative treatments for narcolepsy.

Conditions of Primary Excessive Daytime Sleepiness

Excessive daytime somnolence is a prevalent problem in medical practice and in society. It exacts a great toll in quality of life, personal and public safety, and productivity. The causes of EDS are myriad, and careful evaluation is needed to determine the cause in each case. Although much progress has been made in discovering the pathophysiology of narcolepsy, much more remains to be understood, and far less is known about other primary conditions of EDS. Several methods have been developed to assess EDS, although each of them has limitations. Treatment is available for the great majority of cases.

CSF hypocretin-1/orexin-A concentrations in patients with subarachnoid hemorrhage (SAH)

The aim of this study was to examine the role of the hypothalamic hypocretin/orexin system in complications of delayed ischemic neuronal deficit (DIND) resulting from symptomatic vasospasm in patients with aneurysmal subarachnoid hemorrhage (SAH). CSF hypocretin-1/orexin-A levels were measured in 15 SAH patients. DIND complications occurred in seven patients with symptomatic vasospasm. Hypocretin-1/orexin-A levels were low in SAH patients during the 10 days following the SAH event. CSF hypocretin-1/orexin-A levels were lower in patients with DIND complications than in those who did not develop DIND. A significant transient decline in CSF hypocretin-1/orexin-A levels was also observed at the onset of DIND in all patients with symptomatic vasospasm. The reduced hypocretin/orexin production observed in SAH patients may reflect reduced brain function due to the decrease in cerebral blood flow. These results, taken together with recent experimental findings in rats that indicate hypocretin receptor 1 (orexin 1 receptor) mRNA and protein are elevated following middle cerebral artery occlusion, suggest that a reduction in hypocretin/orexin production in SAH and DIND patients is associated with alterations in brain hypocretin/orexin signaling in response to ischemia.

Hypersomnolence and increased REM sleep with low cerebrospinal fluid hypocretin level in a patient after removal of craniopharyngioma

Here we report a hypersomnolent girl with extensive hypothalamic damage after removal of a craniopharyngioma. The presence of a short sleep latency, sleep onset REM periods during a multiple sleep latency test (MSLT) and negative HLA DQB1*0602 typing suggested a diagnosis of symptomatic narcolepsy. Low cerebrospinal fluid hypocretin-1 level indicated destruction of hypocretin-producing neurons in the hypothalamus. An increased amount of REM sleep and a lack of REM sleep cyclicity documented by all-night polysomnography were different findings from previous reports of hypocretin-deficient idiopathic symptomatic narcolepsy. A more global hypothalamic lesion demonstrated by brain magnetic resonance imaging (MRI) after surgery seemed to cause marked disinhibition of REM sleep as well as hypersomnolence in this patient.

Normal hypocretin-1 (orexin-A) levels in the cerebrospinal fluid of patients with Huntington's disease

A significant atrophy and loss of hypocretin neurons in the brains of human patients with Huntington's disease (HD) and in R6/2 mice have been reported. We included 10 patients with HD and 12 patients with chorea-like hyperkinetic movement disorders (non-HD). All patients of the HD group and eleven patients of the non-HD group showed normal hypocretin-1 levels. Thus, hypocretin-1 may not serve as an additional diagnostic marker for HD.

Studies of humoral immunity to preprohypocretin in human leukocyte antigen DQB1*0602-positive narcoleptic subjects with cataplexy

BACKGROUND

Canine models for narcolepsy have mutations of the hypocretin receptor 2 gene, and preprohypocretin knockout murine lines exhibit narcoleptic-like behaviors. Human narcolepsy with cataplexy is associated with human leukocyte antigen DQB1*0602 and reduced hypocretin levels in cerebrospinal fluid, suggesting an autoimmune diathesis. We tested the hypothesis that DQB1*0602-positive narcoleptic subjects with cataplexy have immunoglobulin (Ig)G reactive to human preprohypocretin and its cleavage products.

METHODS

Serum samples of 41 DQB1*0602-positive narcoleptic subjects with cataplexy and 55 control subjects were studied, as were 19 narcoleptic and 13 control samples of cerebrospinal fluid. We tested for IgG reactive to preprohypocretin and its major cleavage products (including hypocretin 1 and 2), using immunoprecipitation assays (IP), immunofluorescence microscopy (IF) of Chinese hamster ovarian cells expressing preprohypocretin, and Western blots.

RESULTS

There was no evidence for IgG reactive to preprohypocretin or its cleavage products in CSF of subjects with narcolepsy as measured by IPs, Western blots, and IF. Although the IP with CSF and the C-terminal peptide showed significant differences by two methods of comparison, the control subjects had higher counts per minute than narcoleptic subjects, which was opposite to our hypothesis.

CONCLUSIONS

The hypothesis that DQB1*0602-positive narcoleptic subjects with cataplexy have IgG reactive to preprohypocretin or its cleavage products was not supported.