Melanin concentrating hormone in central hypersomnia.

Area of Science:

• Neuroscience
• Sleep Medicine
• Endocrinology

Background:

• Narcolepsy with cataplexy (NC) is a disabling sleep disorder linked to hypocretin/orexin deficiency.
• Melanin Concentrating Hormone (MCH) neurons regulate REM sleep and are intact in NC.
• An increased MCH release was hypothesized to contribute to NC's abnormal REM sleep.

Purpose of the Study:

• To measure Melanin Concentrating Hormone (MCH) levels in cerebrospinal fluid (CSF) of patients with central hypersomnia, including narcolepsy with cataplexy (NC).
• To investigate the potential role of MCH in the pathophysiology of NC and other central hypersomnias.
• To assess the utility of MCH measurement in differentiating causes of central hypersomnia.

Main Methods:

• Radioimmunoassays were used to measure hypocretin-1 and MCH levels in CSF.
• Twenty-two untreated patients with central hypersomnia (14 NC, 6 idiopathic hypersomnia, 2 post-traumatic hypersomnia) were studied.
• Fourteen healthy neurological patients served as controls.

Main Results:

• MCH levels were not significantly different between patients with hypersomnia and controls.
• No association was found between MCH levels and hypocretin levels, sleepiness severity, SOREMPs, cataplexy, or other NC symptoms.
• Excluding post-traumatic hypersomnia cases did not alter the non-significant MCH difference.

Conclusions:

• This study provides the first CSF MCH measurements using radioimmunoassay.
• MCH levels in CSF do not appear to be a useful biomarker for differentiating central hypersomnia etiologies.
• MCH is unlikely to be a primary factor in the REM sleep dysregulation observed in narcolepsy with cataplexy.