Evidence for the association of the SLC22A4 and SLC22A5 genes with Type I Diabetes: A case control study

Abstract

Background: Types 1 diabetes (TID) is a chronic, autoimmune and multifactorial disease characterized by abnormal metabolism of carbohydrate and fat. Diminished carnitine plasma levels have been previously reported in TID patients and carnitine increases the sensitivity of the cells to insulin. Polymorphisms in the carnitine transporters, encoded by the SLC22A4 and SLC22A5 genes, have been involved in susceptibility to two other autoimmune diseases, rheumatoid arthritis and Crohn's disease. For these reasons, we investigated for the first time the association with TID of six single nucleotide polymorphisms (SNPs) mapping to these candidate genes: slc2F2, slc2F11, T3061, L503F, OCTN2-promoter and OCTN2-intron. Methods: A case-control study was performed in the Spanish population with 295 TID patients and 508 healthy control subjects. Maximum-likelihood haplotype frequencies were estimated by applying the Expectation-Maximization (EM) algorithm implemented by the Arlequin software. Results: When independently analyzed, one of the tested polymorphisms in the SLC22A4 gene at 1672 showed significant association with TID in our Spanish cohort. The overall comparison of the inferred haplotypes was significantly different between patients and controls (X2 = 10.43; p = 0.034) with one of the haplotypes showing a protective effect for TID (rs3792876/rs1050152/rs2631367/rs274559, CCGA: OR = 0.62 (0.41-0.93); p = 0.02). Conclusion: The haplotype distribution in the carnitine transporter locus seems to be significantly different between TID patients and controls; however, additional studies in independent populations would allow to confirm the role of these genes in TID risk. © 2006 Santiago et al; licensee Biomed Central Ltd.