A novel haplotype in ABCA1 gene effects plasma HDL-C concentration

Background and objectives: ATP-binding cassette transporter 1 (ABCA1) is a trans-membrane protein responsible for the efflux of cholesterol and phospholipids across the cell membrane, an essential step in the reverse cholesterol transport system. This study investigates the effect of five non-synonymous SNPs of ABCA1 gene on plasma HDL-C levels in Pakistani individuals free of ischemic heart disease and stroke. Methods: Five non-synonymous SNPs were selected after sequencing ABCA1 gene in patients of Hypoalphalipoproteinemia. The presence of these SNPs was then checked in 200 individuals by using PCR-RFLP. Plasma glucose and lipid fractions were measured in fasting state. Ethical approval was obtained from the Ethical Review Committee, Aga Khan University and informed consent was obtained from all subjects. Results: LL genotype of V825L polymorphism was associated with decreased levels of HDL-C [- 0.17 (- 0.32 to - 0.19); P = 0.02] and P774 allele showed a significant increase in HDL-C levels as compared to T774 allele [- 0.15 (- 0.18 to - 0.02); P = 0.01]. R219K, A399V and V771M polymorphisms did not show any association with levels of HDL-C, LDL-C, cholesterol and triglycerides. Haplotype analysis between R219K and V825L polymorphisms showed a unique interaction between R219 allele and L825 allele. The RL haplotype was found to be associated with decreased levels of HDL-C [- 0.12 (- 0.22 to - 0.03); P = 0.001]. Conclusions: ABCA1 polymorphisms are associated with varying levels of HDL-C in Pakistani individuals. These results warrant further investigations as ABCA1 polymorphisms may have a major role in the high incidence of cardiovascular disorders in South Asians.