GENETIC HETEROGENEITY OF APOLIPOPROTEIN E: ITS ROLE IN HEALTH AND DISEASE

Apollipoprotein E a major glycoprotein constituent of High Density Lipoprotein and Very LOW Density Lipoprotein is expressed in a number of tissues in human body including liver, brain, spleen, kidneys and macrophages. As such it plays an important role in exogenous and endogenous lipid transport as well as reverse cholesterol transport. Its gene has been localised to 19 cent-q 13.2 region and has been sequenced. All the populations studied to date exhibit genetic heterogeneity at the locus. Three common alleles designated apoE2, apoE3 and apoe4 have been identified. The phenotypes have been found to influence the various parameters associated with lipid levels in the indivitials. The allele apoE2 has been associated with lower cholesterol levels whereas apoE4 has the opposite effect. This has led to investigations into the associations if any between various disorders involving changes in lipid levels and apoE alleles. Literature reveals apoE4 allele as a dose dependent major risk marker gene in Alzheimer's disease. The situation with respect to Coronary Heart Disease as well as atherosclerosis is not very clear. Further investigations to delineate the role of apoE genetic variability with respect to diseases of other tissues in which it is expressed, also need to be carried Out