ABSTRACT
INTRODUCTION Genetic variation affecting the risk of ischemic heart disease (IHD) is mainly due to mutations in genes encoding apolipoproteins, lipid metabolizing enzymes, and lipoprotein receptors influencing lipid and lipoprotein metabolism. The most common of these mutations affect the regulation of low density lipoprotein (LDL) cholesterol in plasma, leading to severe monogenic hyper - cholesterolemia. Elevated plasma LDL cholesterol levels are causally related to IHD1,2, and a reduction in these levels reduces the incidence of IHD3-5 and the associated mortality rate3,4. Elevated LDL cholesterol levels may be caused by decreased removal of LDL from plasma, as a result of either mutations in the LDL receptor (LDLR) gene (LDLR), as in classic familial hypercholesterolemia (FH)6, or mutations in the ligand domain of the apolipoprotein B gene (APOB), affecting binding of LDL to the LDLR. Apolipoprotein B (apoB) is the chief protein component of LDL and serves as the ligand for the removal of LDL from the circulation by the LDLR. Familial ligand-defective apolipoprotein B (FLDB) results from mutations affecting the structure and function of the ligand binding domain of apoB7-10, while FH results from numerous different mutations affecting the structure and function of the LDLR itself 6.
