The influence of lipoproteins on whole-blood viscosity at multiple shear rates.

Whole-blood viscosity appears to be an independent predictor of stroke, carotid intima-media thickening, and carotid atherosclerosis. The purpose of this study was to examine for relationships between whole-blood viscosity and blood lipids in young healthy subjects over a range of shear rates. Twenty-seven healthy men and women aged 10 to 25 years having a range of low-density lipoprotein (LDL) cholesterol values 88 to 258 mg/dL and body mass index z scores -1.18 to 2.64 SDs were studied. Whole-blood viscosity at shear rates from 1 to 1000 per second was measured using an automated capillary viscometer. Blood lipids were measured using standard techniques. Triglyceride-rich lipoproteins were isolated by ultracentrifugation at density of <1.020 g/mL, and a high ratio of cholesterol to triglyceride was used as an indicator of lipoprotein remnants. Whole-blood viscosity at shear rates of 100 to 1000 per second showed significant negative correlations with apolipoprotein A-1, but not with high-density lipoprotein cholesterol. Whole-blood viscosity at a shear rate of 1000 per second correlated with LDL cholesterol and inversely with LDL size. On stepwise multivariate analysis, apolipoprotein A-1 accounted for 14.7% of the variation in whole-blood viscosity at a shear rate of 150 per second. This study points to the importance of high-density lipoprotein particle number on whole-blood viscosity at physiological shear rates. The physiological significance of the relationships between whole-blood viscosity and LDL cholesterol and LDL particle size at a very high shear rate remains to be determined.