Gene polymorphism of apolipoprotein AI, the major protein of high density lipoprotein in predicting stroke risk among white and black subjects.

BACKGROUND AND PURPOSE

Restriction fragment length polymorphism of the apolipoprotein AI gene, which encodes the most prominent apoproteins in high density lipoprotein (HDL), were investigated using the restriction enzymes Sac I and Pst I in white and black subjects to determine the potential role of genetic variations as stroke risks as determined by carotid stenosis and an atherogenic serum profile, such as elevated total cholesterol and low density lipoprotein (LDL) levels or reduced HDL levels.

METHODS

Ninety-eight subjects, including normal control subjects with no carotid stenosis and subjects with carotid stenosis, who were believed to be at stroke risk, were the study subjects and included 70 white and 28 black subjects.

RESULTS

Sac I polymorphic S2 allele frequency was higher in stroke-risk groups. Significantly higher levels of serum cholesterol, triglycerides, and LDL (P < .05) and significantly lower levels of HDL (P < .05) were present in the stroke-risk group with carotid stenosis. Our study showed the following: Sac I polymorphism frequency was significantly higher in black than white subjects (chi 2 = 3.92, P < .05). Triglyceride level was significantly higher in white subjects compared with black subjects (P < .05). In white subjects, carotid artery stenosis was associated with significantly elevated total cholesterol and LDL levels (P < .01) but not with Sac I polymorphism. In black subjects, the reverse was seen with the Sac I polymorphic S2 allele associated with carotid bifurcation stenosis but did not reach statistical significance because of the small number of subjects. In addition, Sac I polymorphism did not correlate with any lipid profile. Pst I polymorphism was not associated with an abnormal atherogenic lipid profile or carotid artery stenosis abnormalities.

CONCLUSIONS

Our study shows that carotid artery stenosis in white subjects is associated with increased plasma total cholesterol and LDL levels and an atherogenic profile but not with Sac I polymorphism for apoprotein AI. In black subjects, Sac I polymorphism appears to identify individuals with significant carotid stenosis, a necessary precursor to atherothrombotic brain infarction, but not those with elevated total cholesterol or LDL and/or reduced HDL levels. These results suggest that Sac I polymorphism may identify black subjects at increased risk for atherothrombotic brain infarctions.