Nutrition and Genomics Laboratory, JM-USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA, USA. chao.lai@tufts.edu
Singapore comprises three ethnic groups: Chinese (76.7%), Malays (14%), and Asian-Indians (7.9%). Overall, Singaporeans experience coronary heart disease rates similar to those found in the United States. However, there is a dramatic interethnic gradient, with Asian-Indians having significantly higher risk than Chinese and Malays. These differences are associated with HDL cholesterol levels and cannot be solely explained by environmental exposure, and may be driven by genetic factors. The gene encoding apolipoprotein A-V (APOA5) has been located on chromosome 11, and it is emerging as an important candidate gene for lipoprotein metabolism. We investigated associations between APOA5 polymorphisms and plasma lipids in 3,971 Singaporeans to establish whether they accounted for some of the ethnic differences in plasma lipids. We found significant associations between the minor alleles at each of four common polymorphisms and higher plasma triglycerides (TGs) across ethnic groups. Haplotype analyses showed significant associations with TGs, explaining 6.9%, 5.2%, and 2.7% of the TG variance in Malays, Asian-Indians, and Chinese, respectively. Conversely, we observed significant inverse associations between the minor alleles and HDL cholesterol concentrations for Chinese and Malays. These data suggest that APOA5 plays a role in the ethnic differences observed for plasma TG and HDL cholesterol concentrations.