No influence of SLC22A4 C6607T and RUNX1 G24658C genotypic variants on the circulating carnitine ester profile in patients with rheumatoid arthritis.

OBJECTIVE: In a Japanese study, the C6607T SNP mapping to intron 1 of the SLC22A4 gene encoding the OCTN1 protein was found to be associated with rheumatoid arthritis. Similarly, a G24658C transversion in intron 6 of the gene encoding the RUNX1 transcription factor that regulates OCTN1 and also likely OCTN2 expression was also found to confer susceptibility to the disease. METHODS: We investigated the prevalence of these two SNPs by RFLP analysis in a cohort of 209 Hungarian rheumatoid arthritis patients, and 217 healthy controls. Since both the OCTN1 and OCTN2 play a central role in the transmembrane transport of carnitine, we also determined the quantitative serum carnitine ester profile by ESI tandem mass spectrometry. RESULTS: No statistically significant differences were found comparing the genotype prevalence rates between the patients and the controls for either the SLC22A4 genotypes or for the RUNX1 SNPs. There was no significant difference in the serum carnitine ester profile when the rheumatoid arthritis patients were compared with the controls; furthermore, no significant difference in the carnitine esters could be detected when genotype specific subgroups of the patients and the controls were studied. CONCLUSION: Data of the current study do not confirm the universal and population independent susceptibility role of the SLC22A4 C6607T and RUNX1 G24658C variants for rheumatoid arthritis; furthermore, the data presented here show, that there are no significant carnitine-metabolism associated functional consequences of the different genotypes evidenced by the lack of detectable differences in the carnitine ester profiles.

Prevalence of functional haplotypes of the peptidylarginine deiminase citrullinating enzyme gene in patients with rheumatoid arthritis: no influence of the presence of anti-citrullinated peptide antibodies.

OBJECTIVE: Citrullinated peptides produced by enzymatic deimination of arginine residues in proteins by peptidylarginine deiminases are of particular interest in the pathogenesis of rheumatoid arthritis (RA). One type of citrullinated protein - the cyclic citrullinated peptide - is the target of the anti-cyclic citrullinated peptide antibody, the most sensitive and specific autoantibody in RA. The peptidylarginine deiminase type 4 (PADI4) gene, which codes one of the PADI enzyme isotypes, has genetic variants that confer susceptibility to RA in Asian, but not in European populations. METHODS: Genetic associations were examined in 214 Hungarian RA patients characterized for the presence of anti-CCP and rheumatoid factor. The patients were characterized for the existing haplotypes of the PADI4 gene (defined by the combinations of 4 exonic padi4_89: 163G/A, padi4_90: 245T/C, padi4_92: 335C/G, padi4_104: 349T/C and 2 intronic padi4_94: 17535226C/T and padi4_102: 17546809C/T variants) by the PCR-RFLP method. RESULTS: None of the PADI4 haplotypes was accumulated in RA patients. One new finding was that we also did not detect the accumulation of any haplotypes either in the anti-CCP or in the RF-positive subgroups of patients. CONCLUSION: The data presented here show that none of the naturally occurring haplotypes of the PADI4 gene conferred susceptibility to RA in an average group of Hungarian patients; this is in agreement with findings for other European populations. In addition, none of the functional PADI4 haplotypes were associated with the pathologic immune response, which was evidenced by the absence of accumulation of anti-CCP-positive subjects in the specific PADI4 haplotypes.