A brain-derived neurotrophic factor polymorphism Val66Met identifies fibromyalgia syndrome subgroup with higher body mass index and C-reactive protein

A common single nucleotide polymorphism (SNP) in the gene of brain-derived neurotrophic factor (BDNF) results from a substitution at position 66 from valine (Val) to methionine (Met) and may predispose to human neuropsychiatric disorders. We proposed to determine whether these BDNF gene SNPs were associated with fibromyalgia syndrome (FMS) and/or any of its typical phenotypes. Patients with FMS (N = 95) and healthy normal controls (HNC, N = 58) were studied. Serum highsensitivity C-reactive protein (hsCRP) levels were measured using an enzyme-linked immunosorbent assay (ELISA). The BDNF SNPs were determined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The BDNF SNP distribution was 65 (68%) Val/Val, 28 (30%) Val/Met, and 2 (2%) Met/Met for FMS and 40 (69%), 17(29%), and 1 (2%) for HNC, respectively. The serum high-sensitivity C-reactive protein (hsCRP)and body mass index (BMI) in FMS were higher than in HNC. The FMS with BDNF Val66Val had significantly higher mean BMI (P = 0.0001) and hsCRP (P = 0.02) than did FMS carrying the Val66Met genotype. This pattern was not found in HNC. Phenotypic measures of subjective pain, pain threshold, depression, or insomnia did not relate to either of the BDNF SNPs in FMS. The relative distribution BDNF SNPs did not differ between FMS and HNC. The BDNF Val66Met polymorphism is not selective for FMS. The BDNF Val66Val SNP identifies a subgroup of FMS with elevated hsCRP and higher BMI. This is the first study to associate a BDNF polymorphism with a FMS subgroup phenotype.