Increased plasma level of tumor necrosis factor a in patients with narcolepsy in Taiwan

Background: Narcolepsy is a neuropsychiatric disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and abnormal rapid eye movement (REM) sleep. Tumor necrosis factor alpha (TNF alpha) and its cognate receptors have been reported to be involved in the pathophysiology of narcolepsy in addition to the HLA antigen system. Our study aimed to determine if the TNF-alpha system was associated with narcolepsy in our patients. Methods: We first measured the plasma level of TNF alpha in 56 narcoleptic patients and 53 control subjects using a highly sensitive enzyme-linked immunosorbent assay. We next determined the genotype of three single nucleotide polymorphisms (SNPs) (T-1031C, C-863A, and C-857T) at the promoter region of the TNF-alpha gene and one missense SNP (T587G, M196R) at the exon 6 of the tumor necrosis factor receptor 2 gene, TNFR2, in a sample of 75 narcoleptic patients and 201 control subjects by direct sequencing analysis. Results: We found a significant elevation of plasma level of TNF alpha in patients with narcolepsy compared with the control subjects (4.64 pg/mL vs 1.06 pg/mL; P=.0013). However, we did not find significant differences between these two groups in the allelic and genotypic distributions of the investigated polymorphisms. Conclusions: Our study suggests that an increased TNF-alpha level was associated with narcolepsy in our patients, and that chronic inflammation due to various factors might have led to the increased TNF-alpha levels found in our patients. (C) 2013 Elsevier B. V. All rights reserved.