The g.-762T>C polymorphism of the NPC1L1 gene is common in Chinese and contributes to a higher promoter activity and higher serum cholesterol levels.
Niemann-Pick type C1-like 1 (NPC1L1) protein is responsible for intestinal cholesterol absorption. The aim of the study was to identify genetic polymorphisms of the NPC1L1 gene as well as their functional significance. The method involved screening of promoter and coding regions of the NPC1L1 gene for genetic polymorphisms by direct DNA sequencing of genomic DNA from 50 individuals. Functional studies on promoter polymorphisms were performed using luciferase assay. Association between the polymorphisms and serum cholesterol levels were investigated in 224 individuals. The results showed that in total, 11 single nucleotide polymorphisms were identified. Among them, a promoter polymorphism, g.-762T>C, and a synonymous polymorphism, g.1679C>G, were common (34 and 36%, respectively). These two polymorphisms were highly linked (D' value=0.7459, P-value <0.00001). For the g.-762T>C promoter polymorphism, luciferase assay in HepG2 cell line demonstrated that the -762C allele had a significantly higher promoter activity than the -762T allele (1.30+/-0.22 vs 0.37+/-0.06, 3.5-fold, P<0.05). We also showed that the NPC1L1 promoter activity was downregulated by cholesterol content in both genotypes. When association studies were performed, we found that -762C allele was associated with significantly higher serum total cholesterol and LDL-cholesterol content levels in a recessive model (LDL-cholesterol value=131.2+/-8.1 vs 116.4+/-2.2 mg dl(-1); total cholesterol value=214.7+/-9.0 mg dl(-1) vs 196.9+/-2.6, P-value <0.05, n=224). In conclusion, the C allele at -762 position of the NPC1L1 gene was common in people of Chinese ethnicity. The -762C allele had a higher promoter activity and was associated with a higher serum total cholesterol and LDL-cholesterol level.
Chen
Chun-Wu
CW
Institute of Pharmacology, School of Medicine, National Taiwan University, Taipei, Taiwan.
Hwang
Juey-Jen
JJ
Tsai
Chia-Ti
CT
Su
Yi-Ning
YN
Hsueh
Chia-Hsiang
CH
Shen
Mark J
MJ
Lai
Ling-Ping
LP
D044466:Asian People / Q000235:genetics*; D001384:Azetidines / Q000494:pharmacology; D002681:China; D002784:Cholesterol / Q000097:blood* / Q000494:pharmacology; D003710:Demography; D000069438:Ezetimibe; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D056945:Hep G2 Cells; D006801:Humans; D006937:Hypercholesterolemia / Q000235:genetics; D008148:Lovastatin / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D026901:Membrane Transport Proteins; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011401:Promoter Regions, Genetic
D001384:Azetidines; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D002784:Cholesterol; D008148:Lovastatin; D000069438:Ezetimibe