The impact of osteopontin promoter polymorphisms on the risk of calcium urolithiasis

Background: Osteopontin (OPN) is an important modulator of urolithiasis formation. Three functional polymorphisms (-66T/G, -156delG/G, and -443T/G) on the promoter region of the OPN gene have been found to affect the gene expression and transcriptional activity. This study investigated the association of those three functional polymorphisms with the risk of calcium urolithiasis. Methods: A total of 249 cases diagnosed with calcium urolithiasis and 247 age- and sex-matched healthy controls were recruited from Kaohsiung Medical University Hospital between June, 2003 and February, 2007. All subjects completed a detailed questionnaire survey, and provided blood and urine samples for biochemical evaluations. Three single nucleotide polymorphisms were determined by using TaqMan 5' allelic discrimination assay. Results: In-156delG/G polymorphism, subjects who carried delG allele had a significantly higher risk of developing calcium urolithiasis than those with G allele (odds ratio = 1.39; 95% confidence interval = 1.02-1.90; P = 0.037). In stone cases, subjects with delG/G and delG/delG genotypes also had significantly higher urinary ratio of calcium to OPN than those with GIG genotype (11.8 +/- 15.9 vs 7.08 +/- 5.26, P = 0.021). Conclusions: The -156 delG/G polymorphism of OPN gene could serve as a candidate genetic marker used to evaluate the risk of calcium urolithiasis. (C) 2010 Elsevier B.V. All rights reserved.