Comparison of ultracentrifugation and nuclear magnetic resonance spectroscopy in the quantification of triglyceride-rich lipoproteins after an oral fat load.

Abstract

The measurement of triglyceride (TG)-rich particles after an oral fat challenge has been used to provide a measure of risk for coronary artery disease independent of the fasting plasma triglyceride concentration. The analytical "gold standard" for measuring TG-rich lipoproteins uses density gradient ultracentrifugation; however, this technique is labor-intensive. Because of our need to perform numerous postprandial analyses of TG-rich lipoproteins for a large interventional study (Genetics of Lipid Lowering Drugs and Diet Network), we evaluated the use of nuclear magnetic resonance (NMR) spectroscopy for measuring TG-rich particles. EDTA-blood samples were obtained 0, 3.5, 6, and 8 h after ingestion of an oral fat meal (89% of calories from fat) in 20 apparently healthy individuals. The plasma TG concentrations of chylomicron and chylomicron remnant/VLDL fractions were analyzed by ultracentrifugation and NMR spectroscopy. Comparison of all values (n = 78) by ultracentrifugation (x) and NMR (y) produced a linear regression equation of y = 0.979x - 0.035 mmol/L (R(2) = 0.90) for chylomicrons and y = 1.398x + 0.067 mmol/L (R(2) = 0.96) for the fraction containing chylomicron remnants and VLDL. Postprandial response of chylomicrons and chylomicron remnant/VLDL was similar, with maximum response occurring between 3.5 to 6 h regardless of method of measurement. Chylomicron and chylomicron remnant/VLDL fraction measurements obtained by NMR have a high degree of correlation with results produced by ultracentrifugation. NMR may therefore be suitable as an alternative method for the measurement of postprandial TG-rich lipoproteins in individuals consuming a high-fat meal.