Objective To study the apolipoprotein (apo) B gene XbaI and EcoRI polymorphism of the Li nationality in Hainan Island and to evaluate their effects on serum apolipoproteins and lipids.

Methods The study was carried out in a natural population of 351 (151 samples from the Li nationality and 200 samples from the Han nationality) individuals aged between 20 and 84 from Li nationality in Hainan area. The XbaI and EcoRI polymorphisms of apolipoprotein (apo) B gene were analysed using PCR and Restriction Fragment Length Polymorphism (RFLP) methods. The levels of serum apoA, apoB, total cholesterol (TC), triglyceride (TG), HDL cholesterol (HDL-C) were also measured, and LDL cholesterol (LDL-C) was calculated.

Results The frequency of the Li nationality's X⁺/X⁻ genotype subgroups was 0.119. The frequency of the Li nationality's X⁺ allele was 0.059, which was higher than the Han nationality control group (p<0.05). The frequency of the Li nationality's E⁻/E⁻ genotype subgroups was 0.086. The frequency of the Li nationality's E⁻ allele was 0.043, which was no difference compared to the Han nationality (p<0.05). The levels of TC, LDL-C in the Han nationality were higher than those in the Li nationality, but the levels of HDL-C in the Li nationality were higher than those in the Han nationality. There was no difference about the levels of apoB, apoA and TG between the two groups. The levels of LDL-C in the Li nationality's X⁺/X⁻ genotype subgroups were higher than the same group of X⁻/X⁻ genotype subgroups (p<0.05), but levels of HDL-C were lower than the X⁻/X⁻ genotype subgroups (p<0.05). Also there were no difference in the levels of TG, TC, LDL-C, HDL-C, apoB and apoA in the Li nationality between the E⁻/E⁻ genotype subgroups and the E⁺/E⁻genotype subgroups (p<0.05).

Conclusions The XbaI genotypes and alleles' frequency distribution between Li nationality and Han nationality have significant differences but the EcoRI genotypes and alleles' frequency distribution between Li nationality and Han nationality have no statistical significance (p>0.05). Different genotypes of EcoRI and XbaI have different effects on serum apolipoproteins and lipids. The levels of LDL-C of the genotype subgroups which contains X⁺ allele was higher than the genotype subgroups which does not contain the X⁺ allele. The X⁺ allele can affect lipid levels, but the E⁻ allele can not affect lipid levels.