Effect of hypertriglyceridaemia on lipoprotein (a) serum concentrations

Area of Science:

• Biochemistry
• Clinical Chemistry
• Cardiovascular Research

Background:

• Lipoprotein (a) [Lp(a)] is a genetically determined, independent risk factor for atherosclerotic vascular disease, with levels >0.3 g/L indicating increased risk.
• Hypertriglyceridaemia (HTG) is common in lipid clinic patients and its effect on Lp(a) quantification is not fully understood.

Purpose of the Study:

• To investigate the relationship between serum triglyceride (TG) concentrations and Lp(a) levels in patients.
• To determine if hypertriglyceridaemia affects the accurate measurement of Lp(a).

Main Methods:

• Multivariate regression analysis of serum samples from 1009 lipid clinic patients and 1237 controls.
• Analysis of Lp(a) frequency distribution across different degrees of hypertriglyceridaemia.
• Dilution experiments with hypertriglyceridaemic and normotriglyceridaemic sera.
• Re-evaluation of samples using enzyme immunoassay and immunoblotting.

Main Results:

• An inverse correlation was found between serum TG and Lp(a) levels in patients (r = -0.31; P < 0.001), but not in controls.
• A decreasing dosage effect of HTG on Lp(a) levels was observed, with 60% of patients with TG > 9.12 mmol/L showing undetectable Lp(a).
• Analytical interference from TG-rich lipoproteins partially explained the decreased Lp(a) readings in HTG samples.
• Enzyme immunoassay and immunoblotting detected Lp(a) in some samples previously considered Lp(a)-free by electroimmunodiffusion.

Conclusions:

• TG-rich lipoproteins interfere with Lp(a) quantification, particularly by electroimmunodiffusion.
• HTG may lead to underestimation of Lp(a) levels in clinical practice.
• HTG might also decrease in vivo Lp(a) concentrations, potentially via increased clearance of TG-rich Lp(a).