Decreased very low density lipoprotein fluidity in familial hypercholesterolemia

The fluidity of lipoproteins from normolipidemic subjects and from familial hypercholesterolemic patients was investigated by fluorescence polarization. The fluorescent probe DPH (1,6-diphenyl-1,3,5-hexatriene) was incorporated into the lipoprotein fractions, and assessment of the fluidity pattern of each particle was determined by fluorescence anisotropy measurements over a temperature range of 10 to 40 degrees C. The very low density lipoprotein (VLDL) of the hypercholesterolemic patients was found to be considerably more rigid than the respective VLDL of normolipidemic subjects. Analysis of the constituents of the various lipoproteins suggested that the large difference in the fluidity between hypercholesterolemic and normal VLDL patients might be due to increased VLDL cholesterol/triglyceride, cholesterol/protein and cholesterol/phospholipid ratios, which were 10, 2 and 1.4 fold higher, respectively, in the hypercholesterolemic VLDL patients. Decreased VLDL fluidity in familial hypercholesterolemic patients may be of importance in the pathogenesis of their accelerated atherosclerosis.