Th17 Cell Related Cytokine Profiles in Narcolepsy and Other Types of Excessive Daytime Sleepiness

Narcolepsy is a chronic neurological disorder caused by loss of hypocretin (Hcrt) neurons. Both genetic and environmental factors play an important role for the development of narcolepsy. The mechanism of Hcrt loss in narcolepsy is elusive; however, an autoimmune mediated destruction of Hcrt neurons is suspected. The purpose of this study was to assess Th17 related cytokines: interleukin-6 (IL-6), IL-17, IL-23, and transforming growth factor beta (TGF-β) in the pathophysiology of narcolepsy and other types of excessive daytime sleepiness (EDS).
A total of 15 narcoleptic patients, 35 other patients with EDS and 48 age and sex matched healthy subjects were enrolled in this case-control study. Serum IL-6, IL-17, IL-23, and TGF-β levels were measured using sandwich enzyme-linked immunosorbent assay.
There was no significant difference in IL-6 (P = 0.0618) and IL-23 (P = 0.7717) level among participants with narcolepsy, other patients with EDS and controls, whereas TGF-β was significantly decreased in the ones with narcolepsy and other EDS compared to healthy controls (P = 0.0039).
Decreased level of TGF-β in narcolepsy and other patients with EDS indicates a clue for the presence of dysregulation of inflammatory cascades in these patients. This study sheds a new insight on the pathophysiology of narcolepsy.