Polymorphisms in sodium taurocholate cotransporting polypeptide are not associated with hepatitis B virus clearance in Chinese Tibetans and Uygurs.

An association between polymorphisms in the sodium taurocholate cotransporting polypeptide (NTCP) and the natural course of hepatitis B virus (HBV) infection in the Chinese Han population has been noted. However, it is not known whether these polymorphisms are associated with the risk of developing chronic HBV infection in other racial or ethnic populations. Accordingly, we conducted a candidate single nucleotide polymorphism (SNP) association study in Tibetan and Uygur HBV-infected patients. A total of 1302 subjects including 871 Tibetans and 431 Uygurs were recruited. According to their serological and clinical characteristics, each ethnic group was divided into two groups comprising spontaneous clearance individuals and persistently infected patients. Three SNPs were genotyped by a high resolution melting curve methodology. Among the SNPs, rs2296651 exhibited a minor allele frequency of <0.01. The frequency of allele A at rs4646287 was much higher in Tibetans (9.4% for Tibetans and 4.6% for Uygurs, p<0.001) than in Uygurs, but the frequency of allele A at rs7154439 was the opposite (15.7% for Tibetans and 20.5% for Uygurs, p=0.002). Irrespective of race, no significant differences in the frequency distributions of the three SNP alleles or genotypes were observed between the case and clearance groups. Moreover, none of the NTCP haplotypes were statistically different between the two groups. Data from the Tibetan patients could be grouped by HBeAg status, viral load and HBV genotype; however, no significant differences were found in the SNP genotype distribution for each characteristic. In conclusion, the NTCP polymorphisms we identified tended to be ethnicity-dependent. For Tibetans and Uygurs, no association of the three SNPs (rs7154439, rs4646287 and rs2296651) and their haplotypes with HBV chronicity was observed. Examination of SNPs in NTCP for their specific associations with the course of HBV infection in other ethnic minority groups is now required.