Surfactant-Based Homogeneous Assay for the Measurement of Triglyceride Concentrations in VLDL and Intermediate-Density Lipoprotein

Background: Existing studies have demonstrated the clinical significance of triglyceride content in VLDL (VLDL-TG) and intermediate-density lipoprotein (IDL-TG). We developed a homogeneous assay protocol to directly measure VLDL-TG. Methods: Possible reagents and conditions for measuring VLDL-TG were comprehensively tested, and the “best” combination was determined. Healthy persons were instructed to consume a fatty meal after 15-h overnight fasting. Serum VLDL-TG + IDL-TG concentrations were measured using the proposed method. Patients with serum LDL-cholesterol concentrations ≥3.62 mmol/L (140 mg/dL) were administered simvastatin at a daily dose of 5 mg, and serum VLDL-TG concentrations were then measured. Results: The combination of 2 nonionic surfactants played an important role in differentiating VLDL and IDL from other lipoproteins, probably via specific interactions with phospholipids and apolipoproteins. The regression line of the proposed method ( y ) and the ultracentrifugal assay ( x ) was: y = 0.98 x + 0.31 mmol/L ( r = 0.98; n = 73; P <0.05). The difference between postprandial total TG and VLDL-TG concentrations was statistically significant ( P <0.05). After 8 weeks of therapy with simvastatin, total TG and LDL-cholesterol concentrations were 13.6% and 26.3% lower, respectively ( P <0.05), whereas VLDL-TG did not show any significant decrease. Conclusion: Our homogeneous method can measure TG content in VLDL and IDL.