Objectives: This study was undertaken to examine the relation of in vivo low density lipoprotein (LDL) oxidation and other lipid risk factors to coronary reactivity in normal subjects.
Background: Experimental studies have shown that oxidized LDL (ox-LDL) particles are injurious to the vascular wall by impairing its normal vasodilator function.
Methods: We used noninvasive positron emission tomographic (PET) imaging with intravenous dipyridamole to measure coronary flow reserve, a marker of coronary endothelial and smooth muscle function, in 30 healthy men (mean [+/-SD] age 34.4 +/- 3.2 years). As a marker of in vivo LDL oxidation, the autoantibody titer against ox-LDL was measured by the enzyme-linked immunosorbent assay method.
Results: Plasma levels of autoantibody titer against ox-LDL were inversely associated with coronary flow reserve (r = -0.42, p = 0.023). High LDL cholesterol levels (above median > 3.0 mmol/liter) were associated with a low coronary flow reserve only in subjects expressing simultaneously high levels of ox-LDL titer (above median). Subjects with simultaneously high levels of LDL cholesterol and ox-LDL titer had lower coronary flow reserve values than subjects in other groups (3.89 vs. > 5.0 in other groups, p = 0.066).
Conclusions: These data provide evidence for the role of ox-LDL in affecting the coronary reactivity in vivo and support the concept that oxidative modification of LDL particles provides a mechanism by which high LDL concentrations exhibit injurious effects on the coronary vascular bed.