Does LDL contribute to Viscosity?

There is a large body of evidence that large plasma proteins such as fibrinogen, IgM and alpha2‐macroglobulin contribute to plasma viscosity. Although familial hypercholesterolemia (FH) is often associated with hyperfibrinogenemia, elevated viscosity in FH patients independent from fibrinogen plasma levels was communicated in the literature. Selective LDL‐apheresis such as Apo‐B‐100 immunoadsorption, dextran sulfate adsorption and heparin‐induced extracorporeal LDL‐precipitation (HELP) are effective tools for investigating the effect of selective elimination of LDL and/or fibrinogen on viscosity. The decrease in viscosity during selective LDL‐apheresis was correlated to the differences in LDL and/or fibrinogen concentrations. Regression analysis of data obtained from 12 FH patients shows a strong correlation between LDL‐cholesterol and viscosity (r = 0.6892; P < 0.001). Fibrinogen is also correlated with viscosity (r = 0.5433; P < 0.001). The slope of LDL/viscosity regression shows a 5‐fold difference (0.00097 vs. 0.00018) for LDL and fibrinogen, respectively, thus demonstrating a strong contribution LDL‐cholesterol on viscosity.