ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2008) 16 S20.5

V206M polymorphism of the SLC26A6 gene encoding a Cl--oxalate transporter in patients with primary hyperparathyroidism and kidney stones

Sabrina Corbetta1, Cristina Eller-Vainicher2, Marcello Frigerio3, Rea Valaperta3, Elena Costa3, Leonardo Vicentini4, Paolo Beck-Peccoz2 & Anna Spada2

1Endocrinology and Diabetology Unit, Department Medical-Surgical Sciences, University of Milan, Policlinico S Donato IRCCS, S Donato, Italy; 2Endocrine Unit, Department Medical Sciences, University of Milan, Fondazione Ospedale Maggiore, Mangiagalli e Regina Elena IRCCS, Milan, Italy; 3Laboratory of Molecular Biology, Policlinico S Donato IRCCS, S Donato, Italy; 4Endocrine Surgery, Fondazione Ospedale Maggiore, Mangiagalli e Regina Elena IRCCS, Milan, Italy.

Primary hyperparathyroidism (PHPT) is associated with increased risk of kidney stones. Hypercalciuria and urine oxalate excretion are considered risk factors for urolithiasis in PHPT stone-formers. Recently, the anion-exchanger SLC26A6 has been involved in the oxalate metabolism. Slc26a6-null mice showed hyperoxalemia, hyperoxaluria resulting in dramatic calcium oxalate urolithiasis. We tested the hypothesis that urine oxalate excretion in PHPT patients might be modulated by polymorphic variants of the human SLC26A6 gene. A well-characterized PHPT cohort (n=145) and 129 age- and sex-matched healthy subjects were genotyped by TaqMan allelic discrimination system. The homozygous 206V genotype was the most frequent both in PHPT patients and healthy controls (79.3% and 74.4%, respectively), while heterozygosity for the 206M allele was detected in 20.0% and 23.3%, respectively. Due to the rarity of the 206M allele, homozygous and heterozygous patients were grouped in V/M+M/M set. The prevalence of kidney stone disease did not differ between the V/V and V/M+M/M group as well as the severity of hyperparathyroidism. Nonetheless, the 206M alleles were more frequently associated with higher urine oxalate excretion than the median level (77.7% vs 41.5%, P=0.008). Considering the subset of PHPT stone formers (n=68), though the V/V group did not differ from the V/M+M/M group for age, sex and severity of hyperparathyroidism, urine calcium excretion levels were lower in V/M+M/M PHPT stone formers with respect to V/V stone formers (4.40±1.88 vs 5.92±2.62 mg/kg per 24 h; P=0.034). Finally, the 206M alleles were related to the presence of hypertension (73.3 vs 47.8%, P=0.022), showing an OR for hypertension of 4.2 (95% IC 1.5–12.1, P=0.008). In conclusion, these findings suggested a potential role of SLC26A6 206M polymorphism in kidney stones development in PHPT patients, since it was associated with urolithiasis in the presence of relatively low urinary calcium excretion. Moreover, it was associated with high prevalence of hypertension.

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