Influence of aquaporin-1 gene polymorphism on water retention in liver cirrhosis

Abstract

Water retention is a major clinical problem in patients with liver cirrhosis. The factors that predispose to water retention are poorly understood but may involve genetic factors. Recent research suggests that renal aquaporins may be a pathophysiological factor involved in this condition. Aquaporin-1 (AQP1) is expressed in the proximal tubule and aquaporin-2 (AQP2) in the renal collecting duct cells. The aim of our study was to investigate the distribution of single nucleotide polymorphisms (SNPs) of AQP1: rs1049305 (C/G) and AQP2: rs3741559 (A/G) and rs467323 (C/T) in 100 cirrhotic patients with ascites and to analyze their relationship with dilutional hyponatremia. Methods. Genomic DNA was extracted from peripheral blood. Genotyping for the presence of different polymorphisms was performed using the Custom Taqman SNP Genotyping Assays. The possible influence of rs1049305 (C/G) in AQP1 gene expression was evaluated by luciferase assays in vitro. Results. The allelic frequencies of the AQP1 gene were the following: CC = 15%; CG = 49%; GG = 36%. Patients with CC genotype had significantly lower plasma sodium concentration than those with CG or GG genotype. Luciferase assays showed that the rs1049305 (C/G) in the AQP1 gene functionally affected the expression level in vitro. In addition, we did not find any relationship between AQP2 SNPs observed and plasma sodium concentration. Conclusions. Our results suggest that the rs1049305 (C/G, UTR3) AQP1 polymorphism could be involved in the genetic susceptibility to develop water retention in patients with liver cirrhosis.

Key Words::

• Aquaporins
• hepatic cirrhosis
• luciferase assays
• single nucleotide polymorphisms

Acknowledgements

This work was supported in part by grant FIS PI030330.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.