AGING
Hypocretin-1 (Orexin-A) Levels in Human Lumbar CSF in Different Age Groups:
Infants to Elderly Persons
Takashi Kanbayashi MD,1 Tamami Yano MD,2 Hideaki Ishiguro MD,3 Kentoh Kawanishi MD,4 Shigeru Chiba MD,5 Rika Aizawa,1 Yukio Sawaishi MD,2
Kouichi Hirota MD,3 Seiji Nishino MD,6 and Tetsuo Shimizu MD1
1Department
of Neuropsychiatry, Akita University School of Medicine, Akita 0108543, Japan; 2Department of Pediatrics, Akita University School of
Medicine, Akita 0108543, Japan; 3Department of Neurology, Akita Red Cross Hospital. Akita 0101406, Japan; 4Department of Neurology, KansaiDenryoku Hospital, Osaka, Japan; 5Department of Neuropsychiatry, Asahikawa Medical College, Asahikawa, Japan; 6Center for Narcolepsy,
Stanford University School of Medicine, CA94305, USA.
Study Objectives: Recent CSF and postmortem brain hypocretin measurements in human narcolepsy suggest that hypocretin deficiency is
involved in the pathophysiology of the disease. In this study, we measured
CSF hypocretin-1 levels in various age ranges from infants to elder people to investigate the age-dependent change of hypocretin concentrations.
Design: CSF hypocretin levels were compared by age groups and gender. ANOVA was used to examine the influences of these two parameters
on CSF hypocretin levels.
Setting: University-based sleep and biology laboratory.
Patients or Participants: Two hundred seventy two patients were included in this study, with 157 males and 115 females (0-79 years old) .
Interventions: CSF samples were obtained by lumber punctures with
informed consents.
Measurements and Results: Hypocretin-1 levels are not different in
respect to gender or age, although our samples constitute a heterogeneous group with various disease conditions,. CSF hypocretin-1 levels in
infants under 4 months are similar to those in adults.
Conclusions: Early maturation of hypocretin transmission is suggested.
No age- or gender-dependent changes in CSF hypocretin is observed.
Key words: Hypocretin; orexin; CSF; development; narcolepsy; Guillain
Barre Syndrome
to three years, -80C freezer). Two hundred seventy-two patients
were included in this study, with 157 males and 115 females. The
ethnicity of all subjects was Japanese. The patients were diagnosed by clinical inspection, radiological and laboratory examinations. The diagnoses were malformations (n=19), metabolic
diseases (n=10), hematological diseases (n=16), infections of the
central nervous system (n=36), other neurological disorders
(n=130), narcolepsy (n=5), Guillain Barre Syndrome (GBS,
n=11), and others (n=46). Either patients or families gave
informed consent for the lumbar puncture and for the biochemical analysis of the CSF. Hypocretin-1 was measured in CSF samples at Akita University using 125-I radioimmunoassay kits
(Phoenix Pharmaceuticals, Belmont, CA) as previously reported
by Nishino et al.1,3 The detection limit was 40 pg/ml.
Comparisons of age groups and genders were made by using
two-way ANOVA. Since CSF hypocretin-1 levels from patients
with narcolepsy1,3 and GBS4 were reported to be significantly
low, samples from these patients were excluded from the statistical analysis.
INTRODUCTION
RECENT CSF AND POSTMORTEM BRAIN HYPOCRETIN
MEASUREMENTS IN HUMAN NARCOLEPSY SUGGEST
THAT HYPOCRETIN DEFICIENCY IS INVOLVED IN THE
PATHOPHYSIOLOGY OF THE DISEASE.1,2 Extended studies
in idiopathic and symptomatic narcolepsy, as well as in various
neurological conditions, suggest that CSF hypocretin-1 measures
could be used as a diagnostic tool for narcolepsy.3,4 Although the
levels in selected healthy adult populations tested fall in a relatively narrow range (age: 22-62 years old, range: 230-376 pg/ml,
mean+/-SD: 280+/-33 pg/ml),3 whether CSF hypocretin-1 levels
fluctuate with age or by gender has not been fully studied. This
information is essential for understanding the pathogenesis of
hypocretin deficiency in narcoleptic subjects. In order to investigate the developmental change of hypocretin concentrations, we
measured CSF hypocretin-1 levels across an age range from
infants to elderly people.
METHODS
RESULTS
Since it is shown that CSF hypocretin-1 can be reliably measured in frozen CSF stored for several years,3 we used CSF samples collected for diagnostic purposes (storage period: one week
The CSF hypocretin-1 levels of age groups are shown in
Figure 1. In our sample population, there was no significant difference in CSF hypocretin-1 levels between females and males
(females: 291+/-65 pg/ml, males: 290+/-67 pg/ml, mean+/-SD),
nor between any age groups. In the current study, samples from
15 infants (age<1) were included and seven of them were under
four months. The mean hypocretin-1 levels of these seven infants
were 264pg/ml, which is almost the same range of adult groups.
On the other hand, the samples from all Japanese narcoleptic
patients tested (n=5, age: 6, 7, 24, 27, 68 years old) were under
the detection limit, suggesting that the hypocretin deficiency
Disclosure Statement
Nothing to disclose.
Submitted for publication August 2001
Accepted for publication January 2002
Address correspondence to:Takashi Kanbayashi MD, Department of
Neuropsychiatry, Akita University School of Medicine, 1-1-1 Hondo, Akita 010,
JAPAN, Tel: +81-18-884-6122; Fax: +81-18-844-6445;
E-mail: [email protected]
SLEEP, Vol. 25, No. 3, 2002
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Hypocretin-1 (Orexin-A) Levels in Human Lumbar CSF—Kanbayashi et al
600
female
male
mean level of each group
Hypocretin-1 Concentration (pg/ml)
500
mitochondoria encephalomyopathy
400
300
200
GBS
100
hypoxic encephalopathy
GBS
infantile spasm
narcolepsy
narcolepsy
<1-<1
15—19
narcolepsy
narcolepsy
40
0
5—9
1—4
10—14
30—39
20—29
40—49
50—59
70—79 (age)
60—69
Figure 1—The CSF hypocretin-1 levels of age groups are shown in Fig1. Age groups consisted of 11 groups, age<1, 1-4, 5-9, 10-14, 15-19,20-29, 30-39, 40-49,
50-59, 60-69 and 70-79 years old. The bars indicate the mean levels of each group. In our sample population, there is no significant difference overall between females
and males, nor between any age groups. Some circles and triangles are specified by arrows with diagnosis. The samples from 5 narcoleptic patients were all under
the detection limit (40pg/ml) and triangles were plotted at 40pg/ml. Two cases of GBS and other cases with low or high hypocretin-1 levels were also specified.
occurs in narcolepsy regardless of ethnicity and age. Two cases
of GBS showed low concentrations of 65pg/ml and 125pg/ml,
below the mean minus 2 SD. However, no other disorders had a
clear trend for low or high hypocretin-1 levels.
different in respect to gender or age groups. Thus, the undetectable CSF hypocretin-1 levels seen in narcolepsy are highly
abnormal regardless of age. This examination must be valuable
for the decisive and early diagnosis of narcolepsy in all age
groups. Further studies are needed to determine when a decrease
in the CSF hypocretin-1 level occurs in relation to occurrence of
clinical symptoms and whether the hypocretin deficiency is a
congenital/developmental or an acquired problem as this is critical for understanding the pathogenesis of the disease.
DISCUSSION
It was reported that expression of prepro-hypocretin mRNA in
the rat hypothalamus was weakly detected at the perinatal period
and increased gradually during neonatal and infantile periods.5 In
the weaning period, mRNA expression markedly increased and
then reached a plateau through the pubertal period to the adult
period.5 On the other hand, immunohistochemistry in the rat
brain demonstrated that hypocretin neurons already exist at the
end of the embryonic period, although the cell size is smaller and
is gradually enlarged after birth.6 In this current study, we measured seven CSF samples from the pre-weaning period (under
four months old). CSF hypocretin-1 levels are consistently
detected in these infants and the range is similar to that in adults,
suggesting CSF hypocretin neuro-transmission was already
established at birth. In addition, two narcoleptic patients were
diagnosed at six- and seven years-old,7 indicated that the
hypocretin deficiency can occur in pre-pubertal children.
Although our samples constitute a heterogeneous group with
various kinds of disease conditions, hypocretin-1 levels are not
SLEEP, Vol. 25, No. 3, 2002
ACKNOWLEDGMENTS
We are grateful to Drs. H.Kubota, J. Arii, S. Takasaki, Y.
Tamura, K. Fujii, T. Shiomi, H. Tsukamaoto and Y. Inoue for collecting the samples. The present study was performed through
Special Coordination Funds of the Ministry of Education,
Culture, Sports and Technology, and a Grant-in-Aid for
Cooperative Research from the Ministry of Health, Labour and
Welfare of Japan. A part of the results of this study was presented in Associated Professional Sleep Societies 2001 meeting.
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