HPLC analysis of CSF hypocretin-1 in type 1 and 2 narcolepsy

• Published in: Scientific reports Vol. 9; no. 1; p. 477
• Main Authors: Sakai, Noriaki, Matsumura, Mari, Lin, Ling, Mignot, Emmanuel, Nishino, Seiji
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.01.2019; Nature Publishing Group
• Subjects: 692/53/2421; 692/699/375/1816; 82/1; 82/16; Cerebrospinal fluid; High-performance liquid chromatography; Humanities and Social Sciences; Hypothalamus; Immunoreactivity; Liquid chromatography; Metabolites; multidisciplinary; Narcolepsy; Orexins; Peptides; Radioimmunoassay; Science; Science (multidisciplinary); Sleep; Sleep disorders
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-36942-8

Narcolepsy is a chronic sleep disorder caused by a loss of hypocretin (hcrt) neurons in the hypothalamus. Cerebrospinal fluid (CSF) hcrt-1 measurement has been well established as a gold standard of narcolepsy diagnosis, although some portions of narcoleptic patients show normal hcrt-1 levels. We aimed to examine peptide degradation of hcrt-1 and its abnormality in the CSF of patients by using high performance liquid chromatography (HPLC) followed by radioimmunoassay (RIA). CSF was collected from healthy controls, narcoleptic patients of type 1 with hcrt-1 deficiency, type 1 with normal hcrt-1 level, and type 2 with normal hcrt-1 level. We found that the majority of hcrt-1 immunoreactivity in extracted CSF was derived from unauthentic hcrt-1 peaks, which are predicted to be inactive metabolites, and the intact hcrt-1 peptide was less than 10% of the gross amount, suggesting that the regular RIA for CSF hcrt-1 measures largely reflect the unauthentic hcrt-1-related metabolites rather than the intact one. As expected, all hcrt-1-related peaks were abolished in type 1 with hcrt-1 deficiency. Importantly, we also found that the sum of the authentic hcrt-1 peptide (peaks 3 and 4) significantly decreased in non-deficient type 1 and tended to decrease in type 2 narcoleptic patients although the levels with the regular RIA in non-extracted CSF was equivalent to healthy controls. Immunoreactivity with unauthentic hcrt-1 metabolites may masks the possible decline in authentic hcrt-1 level caused by the partial loss of hcrt neurons. Our findings may provide new insights into the degradation of the hcrt-1 peptide and the pathophysiology of narcolepsy.