title: Decreased plasma levels of orexin-A in sleep apnea.
abstract: BACKGROUND
  Orexin-A, also known as hypocretin, is a neuropeptide implicated in appetite and sleep regulation. Because the obstructive sleep apnea syndrome (OSAS) is characterized by obesity and excessive daytime sleepiness, we hypothesized that orexin-A levels may be abnormal in patients with OSAS. Further, since treatment with continuous positive airway pressure (CPAP) in patients with OSAS is very effective in normalizing daytime sleepiness, we also hypothesized that the chronic use of CPAP may influence plasma levels of orexin-A in these patients.
  
  
  OBJECTIVE
  To evaluate plasma levels of orexin-A in patients with OSAS and the effect of CPAP treatment.
  
  
  METHODS
  We compared the plasma levels of orexin-A in 13 healthy controls, 27 untreated patients with OSAS and 14 patients treated with CPAP during at least 1 year (4.5 +/- 0.5 h/night; mean +/- SEM). All patients had severe OSAS (apnea-hypopnea index, 57 +/- 4 h(-1)).
  
  
  RESULTS
  Orexin-A plasma levels were significantly lower in untreated (9.4 +/- 1.9 pg.ml(-1), p < 0.01) and treated patients with OSAS (4.2 +/- 1.5 pg.ml(-1), p < 0.001) than in healthy subjects (20.6 +/- 4.5 pg.ml(-1)). In untreated patients, orexin-A levels were not significantly related to daytime somnolence assessed by Epworth scale (r = -0.18, p = 0.37) or the body mass index (r = -0.13, p = 0.52).
  
  
  CONCLUSIONS
  Orexin-A plasma levels are abnormally low in patients with OSAS, independently of the level of somnolence and/or presence of obesity. These results suggest that these low orexin-A levels may be related to the pathogenesis of OSAS.
authors.affiliation: Unidad de Investigación, Hospital Universitari Son Dureta, Palma de Mallorca, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Busquets
authors.forename: Ferran
authors.initials: F
authors.lastname: Barbé
authors.forename: Antonia
authors.initials: A
authors.lastname: Barceló
authors.forename: Mónica
authors.initials: M
authors.lastname: de la Peña
authors.forename: Nathalie
authors.initials: N
authors.lastname: Sigritz
authors.forename: Lola R
authors.initials: LR
authors.lastname: Mayoralas
authors.forename: Antoni
authors.initials: A
authors.lastname: Ladaria
authors.forename: Alvar
authors.initials: A
authors.lastname: Agustí
mesh_terms: D000328:Adult; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009479:Neuropeptides / Q000097:blood*; D000068797:Orexins; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000628:therapy; D016896:Treatment Outcome
chemical_list: C000596229:HCRT protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins