Increased heart rate variability but normal resting metabolic rate in hypocretin/orexin-deficient human narcolepsy.
OBJECTIVE
We investigated autonomic balance and resting metabolic rate to explore their possible involvement in obesity in hypocretin/orexin-deficient narcoleptic subjects.


METHODS
Resting metabolic rate (using indirect calorimetry) and variability in heart rate and blood pressure were determined in the fasted resting state. Subjects included 15 untreated, hypocretin-deficient male narcoleptics and 15 male controls matched for age and body mass index.


RESULTS
Spectral power analysis revealed greater heart rate and blood pressure variability in hypocretin-deficient male narcoleptic patients (heart rate: p = 0.01; systolic blood pressure: p = 0.02; diastolic: p < 0.01). The low to high frequency ratio of heart rate power did not differ between groups (p = 0.48), nor did resting metabolic rate (controls: 1767 +/- 226 kcal/24 h; patients: 1766 +/- 227 kcal/24h; p = 0.99).


CONCLUSIONS
Resting metabolic rate was not reduced in hypocretin-deficient narcoleptic men and therefore does not explain obesity in this group. Whether the increased heart rate and blood pressure variability--suggesting reduced sympathetic tone--is involved in this regard remains to be elucidated.
Fronczek
Rolf
R
Department of Neurology and Clinical Neurophysiology, Leiden University Medical Centre, Leiden, The Netherlands. r.fronczek@lumc.nl
Overeem
Sebastiaan
S
Reijntjes
Robert
R
Lammers
Gert Jan
GJ
van Dijk
J Gert
JG
Pijl
Hanno
H
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency*; D008297:Male; D008875:Middle Aged; D009290:Narcolepsy / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology*; D009479:Neuropeptides / Q000172:deficiency*; D000068797:Orexins; D010101:Oxygen Consumption; D012146:Rest
D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins