Association of Guanosine Triphosphate Cyclohydrolase 1 Gene Polymorphisms with Fibromyalgia Syndrome in a Korean Population

Objective. Guanosine triphosphate cyclohydrolase 1 (GCH1) is the rate-limiting enzyme in the synthesis of tetrahydrobiopterin, which is an essential cofactor in nitric oxide (NO) production. Polymorphisms in the GCHI gene have been implicated in protection against pain sensitivity. The aim of our study was to determine whether single-nucleotide polymorphisms (SNP) in the GCH1 gene affect susceptibility and/or pain sensitivity in fibromyalgia syndrome (FM). Methods. A total of 409 patients with FM and 422 controls were enrolled. The alleles and genotypes at 4 positions [rs3783641(T>A), rs841(C>T), rs752688(C>T), and rs4411417(T>C)] in the GCHI gene were analyzed. The associations of the GCHI SNP with susceptibility and clinical measures in patients with FM were assessed. Results. The frequencies of alleles and genotypes of the 4 SNP did not differ between patients with FM and healthy controls. Among 13 constructed haplotypes, we further examined 4 (CCTT, TTCT, TTCA, and CCTA) with > 1% frequency in both FM and controls. No associations of GCH1 polymorphisms with FM-related activity or severity indexes were found, although the number and total score of tender points in patients with FM differed among the 4 haplotypes (p = 0.03 and p = 0.01, respectively). The CCTA haplotype of GCHI was associated with significantly lower pain sensitivity and occurred less frequently than the CCTT haplotype in patients with FM (p = 0.04, OR 0.45, 95% CI 0.21-0.96). Conclusion. Our study provides evidence that certain GCHI haplotypes may be protective against susceptibility and pain sensitivity in FM. Our data suggest that NO is responsible for pain sensitivity in the pathogenesis of FM. (First Release Jan 15 2013; J Rheumatol 2013;40:316-22; doi:10.3899/jrheum.120929)