The lipid hypothesis stipulates that the risk of developing CAD is related to the cholesterol levels of various lipoprotein fractions, the risk increasing with either a higher LDL cholesterol level or a lower HDL cholesterol level. The data reviewed here indicate that the measurement of the plasma level of the major apoproteins of LDL and HDL, apoB and apoA-I, respectively, provide additional information in the assessment of a patient at risk for CAD. In the case of LDL B, two "normocholesterolemic" groups with CAD are detected, those with normotriglyceridemic HyperapoB and those with hypertriglyceridemic HyperapoB. In all of these syndromes associated with premature CAD, HyperapoB, FCH, and FH, the common denominator is an increased number of LDL particles. A low level of apoA-I may indicate that one of the subfractions of HDL (HDL2) is decreased. HDL2 is generally decreased in disorders where LDL B is elevated, a combination that may be particularly atherogenic. Conversely, elevated apoA-I and HDL cholesterol levels, or decreased LDL cholesterol and LDL B protein levels, are associated with a low prevalence of CAD and longevity. Thus, LDL and HDL levels may be metabolically linked, a relation which is more evident if apoproteins are measured and which may be obscured if apoproteins are not determined. The assessment of dyslipoproteinemia in a patient at risk for CAD might optimally include measurement of LDL B and apoA-I levels, in addition to LDL cholesterol and HDL cholesterol levels.
ASJC Scopus subject areas
- Public Health, Environmental and Occupational Health