A third of nonfasting plasma cholesterol is in remnant lipoproteins: Lipoprotein subclass profiling in 9293 individuals

Background and aims: Increased concentrations of calculated remnant cholesterol in triglyceride-rich lipoproteins are observationally and genetically, causally associated with increased risk of ischemic heart disease; however, when measured directly the fraction of plasma cholesterol present in remnant particles is unclear. We tested the hypothesis that a major fraction of plasma cholesterol is present in remnant lipoproteins in individuals in the general population.

Methods: We examined 9,293 individuals from the Copenhagen General Population Study using nuclear magnetic resonance spectroscopy measurements of total cholesterol, free- and esterified cholesterol, triglycerides, phospholipids, and particle concentration. Fourteen subclasses of decreasing size and their lipid constituents were analysed: six subclasses were very low-density lipoprotein(VLDL), one intermediate-density lipoprotein(IDL), three low-density lipoprotein(LDL), and four subclasses were high-density lipoprotein(HDL). Remnant lipoproteins were VLDL and IDL combined.

Results: Mean nonfasting cholesterol concentration was 1.84mmol/L(72mg/dL) for remnants, 2.01mmol/L(78mg/dL) for LDL, and 1.83mmol/L(71mg/dL) for HDL, equivalent to remnants containing 32% of plasma total cholesterol. Of 14 lipoprotein subclasses, large LDL and IDL were the ones containing most of plasma cholesterol. The plasma concentration of remnant cholesterol was from ~1.4mmol/L(54mg/dL) at age 20 to ~1.9mmol/L(74mg/dL) at age 60. Corresponding values for LDL cholesterol were from ~1.5mmol/L(58mg/dL) to 2.1~mmol/L(81mg/dL).

Conclusion: Using direct measurements, one third of total cholesterol in plasma was present in remnant lipoproteins, that is, in the triglyceride-rich lipoproteins IDL and VLDL.