Association of Nephrolithiasis and Gene for Glucose Transporter Type 9 (SLC2A9): Study of 145 Patients

Aim

To investigate the association of nephrolithiasis and solute carrier family 2, facilitated glucose transporter, member 9 (SLC2A9), also known as glucose transporter type 9, Glut9.

Methods

A total of 145 participants were recruited in the period April-October 2008 from the Department of Mineral Research of the Medical School Osijek, Osijek, Croatia; 58 (40%) had confirmed nephrolithiasis and 87 (60%) were asymptomatic. Four single nucleotide polymorphisms (SNP) from the SLC2A9 gene were genotyped in both groups (rs733175, rs6449213, rs1014290, and rs737267).

Results

There was a weak but significant association of all 4 SNPs and nephrolithiasis (P = 0.029 for rs733175; P = 0.006 for rs6449213; P = 0.020 for rs1014290, and P = 0.011 for rs737267). Logistic regression in an age- and sex-adjusted model suggested that genotype C/T for rs6449213 had odds ratio for nephrolithiasis of 2.89 (95% confidence interval 1.13-7.40). This SNP explained a total of 4.4% of nephrolithiasis variance.

Conclusion

Development of nephrolithiasis may be associated with SLC2A9 gene. Further studies are needed to clarify the role of SLC2A9 gene as a link between uric acid and nephrolithiasis.Renal stone formation (nephrolithiasis) is a disease characterized by the existence of solid deposits in the upper parts of the urinary tract (1). It is estimated to affect between 3%-9% of the population, with large differences between various populations (2,3). There is a number of causes that may lead to the renal stones formation, including diet and obesity status, some drugs, other diseases, climate changes, metabolic disorders, and genetic factors (2,4,5). The complexity of this disease caused researchers to consider nephrolithiasis as one feature of a broader systemic disease, rather than a local disease restricted to a single organic system (6). This is especially interesting in relation to gout and metabolic syndrome, which are both systemic disorders in close relation to nephrolithiasis (6-8). Even the cohort studies have confirmed the association of gout and kidney stones, suggesting that the history of gout increases the risk for kidney stones (9). Another study showed that, in the age-adjusted model, gout had an odds ratio of 1.97 for previous kidney stones (95% confidence interval [CI], 1.37-2.83) and that even after adjustment for sex, race, body mass index, and presence of hypertension the odds ratio remained significant (10).Genetic contribution to renal stones formation has been identified long time ago (2). In line with these suggestions, heritability of some of the traits associated with nephrolithiasis has been shown to be as high as 95% (11). Heritability of the urinary stones was reported to be lower (56%) (12), but still sufficiently high to be considered a substantial genetic proportion of variance and suggesting that it may be under genetic control. So far, a number of studies have established a link between predominantly oxalate kidney stones and several genes, including vitamin-D receptor gene (VDR) and calcitonin receptor (CTR) gene (13), heparan sulfate (HSPG2) gene (14), or fibronectin gene (FN1) (14).The quantitative trait associated with nephrolithiasis is the serum uric acid concentration, which is under strong genetic control by the gene for glucose transporter type 9 (SLC2A9 or Glut 9) (15). The gene was initially described in an isolated island community (16,17), where genetic properties of the population are expected to act in favor of facilitated gene mapping efforts (18). Subsequent meta-analysis of 14 populations confirmed the association of this gene with serum uric acid concentrations (19). This led to a number of clinical studies that have confirmed its involvement in the uric acid metabolism, including urate handling in the kidney and uptake in the liver (20,21). Based on the previous suggestions that gout and nephrolithiasis may share a common pathway (15), it might be interesting to see if SLC2A9 could explain the commonalities in patients with any of the following conditions. Therefore, the aim of this study was to investigate the association of nephrolithiasis and genetic variants of the SLC2A9.