title: Diurnal fluctuation in histidine decarboxylase expression, the rate limiting enzyme for histamine production, and its disorder in neurodegenerative diseases.
abstract: OBJECTIVE
  Neuronal histamine shows diurnal rhythms in rodents and plays a major role in the maintenance of vigilance. No data are available on its diurnal fluctuation in humans, either in health or in neurodegenerative disorders such as Parkinson disease (PD), Alzheimer disease (AD), or Huntington disease (HD), all of which are characterized by sleep-wake disturbances.
  
  
  METHODS
  Quantitative in situ hybridization was used to study the mRNA expression of histidine decarboxylase (HDC), the key enzyme of histamine production in the tuberomammillary nucleus (TMN) in postmortem human hypothalamic tissue, obtained from 33 controls and 31 patients with a neurodegenerative disease-PD (n = 15), AD (n = 9), and HD (n = 8)-and covering the full 24-h cycle with respect to clock time of death.
  
  
  RESULTS
  HDC-mRNA levels in controls were found to be significantly higher during the daytime than at night (e.g., 08:01-20:00 versus 20:01-08:00, P = 0.004). This day-night fluctuation was markedly different in patients with neurodegenerative diseases.
  
  
  CONCLUSIONS
  The diurnal fluctuation of HDC-mRNA expression in human TMN supports a role for neuronal histamine in regulating day-night rhythms. Future studies should investigate histamine rhythm abnormalities in neurodegenerative disorders.
  
  
  BACKGROUND
  Shan L; Hofman MA; van Wamelen DJ; Van Someren EJW; Bao AM; Swaab DF. Diurnal fluctuation in histidine decarboxylase expression, the rate limiting enzyme for histamine production, and its disorder in neurodegenerative diseases.
authors.affiliation: Department of Neurobiology, Key Laboratory of Medical Neurobiology of Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, Hangzhou, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Shan
authors.forename: Michel A
authors.initials: MA
authors.lastname: Hofman
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: van Wamelen
authors.forename: Eus J W
authors.initials: EJ
authors.lastname: Van Someren
authors.forename: Ai-Min
authors.initials: AM
authors.lastname: Bao
authors.forename: F
authors.initials: F
authors.lastname: Swaab Dick
mesh_terms: D000544:Alzheimer Disease / Q000201:enzymology; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology; D015870:Gene Expression / Q000502:physiology; D006632:Histamine / Q000096:biosynthesis; D006639:Histidine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000502:physiology; D006801:Humans; D006816:Huntington Disease / Q000201:enzymology; D006827:Hydantoins; D007026:Hypothalamic Area, Lateral / Q000201:enzymology; D017403:In Situ Hybridization; D019636:Neurodegenerative Diseases / Q000201:enzymology*; D010300:Parkinson Disease / Q000201:enzymology
chemical_list: D006827:Hydantoins; C021693:histidine hydantoin; D006639:Histidine; D006632:Histamine