Polymorphic Variation of the Guanosine Triphosphate Cyclohydrolase 1 Gene Predicts Outcome in Patients Undergoing Surgical Treatment for Lumbar Degenerative Disc Disease

Study Design. Prospective observational study. Objective. To determine whether polymorphic variations of the guanosine triphosphate (GTP) cyclohydrolase 1 gene (GCH1) are associated with different outcomes in patients undergoing surgical treatment for lumbar degenerative disc disease (DDD). Summary of Background Data. GCH1, the gene encoding the rate-limiting enzyme in tetrahydrobiopterin synthesis, has been strongly implicated as a determinant of pain experience in previous animal and human studies. Methods. A total of 69 patients undergoing surgical treatment for lumbar DDD were prospectively enrolled. Genomic DNA was extracted from a venous blood sample, and DNA sequence analysis was performed of GCH1. Surgery included 65 instrumented fusions and 4 disc arthroplasty procedures. Patients were observed prospectively for 1 year following surgery. Allelic and genotype frequencies were calculated for each of 14 single nucleotide polymorphisms (SNPs). One-year postoperative Oswestry Disability Index (ODI) scores were compared to preoperative scores and the absolute change in ODI score was used to perform genetic association analyses on the basis of both individual SNP markers as well as commonly observed haplotypes for the entire gene sequence. Results. Single marker analysis revealed 1 SNP (rs998259; minor allele T) that was significantly associated with improvement in both absolute ODI score (P = 0.030) and Numerical Rating Scale back pain scores (P = 0.033) following surgery. Haplotype analysis identified a common GCH1 haplotype (CACTTGTTTGAC) with a sample frequency of 12.3%, which was highly associated with improvement in absolute ODI score (P = 0.04). This haplotype frequency reflects the existence of both heterozygous and homozygous individuals in the study population. The presence of 1 unit of this haplotype was associated with an improvement in postoperative ODI score of 15.34 relative to the absence of this haplotype (P = 0.04). Conclusion. Preliminary results from this pilot genetic study of patients undergoing surgery for DDD suggests that the T allele at rs998259 of GCH1 may be associated with improved outcomes 1 year following surgery.