Increased potassium excretion in children with monosymptomatic nocturnal enuresis: could it be related to Kir 4.1- KCNJ10 gene polymorphism?

Background and objectives: There are controversial results in the literature regarding urinary electrolytes, especially potassium, in enuretic children. KCNJ10 channel protein, a member of the Kir 4.1 family is expressed in renal distal tubules and has an important function in renal ion transport. We investigated whether KCNJ10 gene polymorphisms are associated with clinical and laboratory findings of a group of Turkish children with monosymptomatic primary nocturnal enuresis (MNE).

Method: Ninety-seven MNE children and 100 healthy controls were tested for three single nucleotide polymorphisms (SNPs) in the KCNJ10 gene. The transversions in SNPs were G to A for intron 1(SNP1), G to A for exon 2 (SNP2), and T to C transition for promoter (SNP3). All SNPs were genotyped by PCR-restriction fragment length polymorphism.

Results: SNP3 in promoter of KCNJ10 gene showed strong association with MNE children for distribution of genotype and allele frequency, while SNP1 in intron 1 and SNP2 in exon 2 were noninformative. The distribution of TT, TC, and CC genotypes for SNP3 was 66%, 26.8% and 7.2% respectively in MNE compared with 38%, 59% and 3% respectively in controls (p < 0.0001). In enuretic children, TT genotype was higher and there was an increased potassium excretion in children with TT genotype (P < 0.05).

Conclusion: We conclude that KCNJ10 gene promoter polymorphism may have a role on potassium excretion in Turkish MNE children. This is the first study in literature evaluating KCNJ10 gene polymorphism in this patient population. Future studies investigating the other SNPs, mutations or altered regulation of Kir4.1 in larger samples would help clarify the role (s) of KCNJ10 gene in enuresis.

Keywords: KCNJ10 gene; Kir 4.1 family; monosymptomatic nocturnal enuresis; polymorphism; primary nocturnal enuresis.