Contribution of common polymorphisms in reduced folate carrier and ??-glutamylhydrolase to methotrexate polyglutamate levels in patients with rheumatoid arthritis

Abstract

We investigated whether polymorphisms in reduced folate carrier (SLC19A1 G80A) and gamma-glutamyl-hydrolase (GGH-401C/T) are predictive of methotrexate polyglutamate (MTXPG) levels in patients with rheumatoid arthritis treated with weekly low-dose methotrexate (MTX). Adult patients treated with MTX were enrolled in a multicentred study. Blood was drawn at the time of the visit, DNA was extracted and red blood cell (RBC) MTXPG levels (up to the penta-order of glutamation) were measured by high-performance liquid chromatography-fluorometry. A G80A polymorphism in SLC19A1 and a -401C/T promoter polymorphism in GGH were measured by polymerase chain reaction-restriction fragment length polymorphism. Multivariate linear and logistic regressions were used to predict long-chain RBC MTXPG3-5. In 226 adult patients receiving MTX (median 15 mg range: 5-25 mg) median RBC long-chain MTXPG3-5 was 56 nmol/l (range < 5-224 nmol/l). A total of 35 patients carried the SLC19A1 80AA genotype whereas 36 patients carried the GGH-401TT genotype. Weekly MTX dose, age, presence of the SLC19A1 80AA and GGH-401TT genotypes predicted independently and significantly MTXPG3-5 levels (global r = 0.38; P < 0.0001). Patients with the GGH-401TT genotype were 4.8-fold [odds ratio (OR) 95% confidence interval (CI) 1.8-13.0; P = 0.002] more likely to have MTXPG3-5 below the group median compared to patient carriers of the GGH-401CC or CT genotype. Conversely, those with the SLC19A1 80AA genotype were 3.4-fold more likely to have MTXPG3-5 levels above the group median compared to those with the SLC19A1 80GG or 80GA genotype (OR CI 95% 1.4-8.4; P = 0.007). These data demonstrate that polymorphisms in SLC19A1 and GGH affect polyglutamation of MTX.

Reduced folate carrier-1 80G>A polymorphism affects methotrexate treatment outcome in rheumatoid arthritis

“…An increased toxicity observed in this group of patients may be related to elevated levels of MTX polyglutamates seen in RFC-1 80AA individuals. 18 These observations are in keeping with previous studies, which demonstrated an association between increased MTX polyglutamate levels and hepatotoxic effects of the drug. 19,20 In a previous study Laverdiere et al 8 suggested an influence of RFC-1 gene (G80A) polymorphism on MTX plasma levels and treatment outcome of childhood acute lymphoblastic leukemia.…”

“…However, the polymorphism could also directly impact disease activity through more subtle alteration in folate homeostasis. 15,18 In our study hepatotoxicity, measured as ALT and AST activities, after MTX treatment was observed in some 4-5% of patients and more frequently affected individuals with RFC-1 80AA (10.5%) genotype than 80GG genotype (2.3%). An increased toxicity observed in this group of patients may be related to elevated levels of MTX polyglutamates seen in RFC-1 80AA individuals.…”

“…Similarly, in a series of studies carried out to determine the association of RFC-1 gene (G80A) polymorphism with MTX treatment outcome, Dervieux et al 18 evaluated the influence of the polymorphism on MTX polyglutamate levels and MTX effects in RA patients. The authors observed increased concentrations of MTX polyglutamates in erythrocytes from patients with AA genotype.…”

Genetic polymorphisms and folate status

“…To date, most studies have shown that the MTHFR C677T genotype is related to biomarkers, such as serum folate, tHcy concentration, and folate intake. Other polymorphisms in the folate pathway have been found to be associated with a variety of complex traits and disorders including MTHFR A1298C, MTRR A66G, MTR A2756G, MTHFD1 G1958A, FOLH1 T484C, SLC19A1 A80G, and transcobalamin II ( TCN2 ) C776G, the transport protein of vitamin B12 (Weisberg et al 1998; Gaughan et al 2001; Laverdiere et al 2002; Kluijtmans et al 2003; Dervieux et al 2004; Martinelli et al 2006; Moskau et al 2007; Silva et al 2011; Pangilinan et al 2012; Xie et al 2012). Table 1 summarizes the distribution of serum tHcy, folate, vitamin B6, and vitamin B12 according to polymorphisms related to folate and tHcy metabolism (Hiraoka et al 2004; Hiraoka et al 2009).…”

Investigation of inter-individual variability of the one-carbon folate pathway: a bioinformatic and genetic review

“…65 Gamma-glutamyl hydrolase (GGH; EC, 3.4.19.9) catalyzes the hydrolysis of folylpoly-gamma-glutamates by removing g-linked glutamate and polyglutamates. Similar to a number of other genes within the one-carbon folate pathway, polymorphisms in the GGH gene have been associated with lower response to administration of the anti-folate, methotrexate, for the treatment of various conditions including rheumatoid arthritis 66 and acute lymphoblastic leukemia. 67 The enzyme 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC; EC, 2.1.2.3) is able to convert 10-formyl THF to THF (Figure 1).…”