Calculated Non-HDL Cholesterol Includes Cholesterol in Larger Triglyceride-Rich Lipoproteins in Hypertriglyceridemia.

CONTEXT

Calculated non-high-density lipoprotein (HDL) cholesterol (non-HDLC) should selectively include cholesterol from atherogenic lipoproteins to be a reliable risk marker of cardiovascular disease. In hypertriglyceridemia (HTG), there is increased abundance of larger and less atherogenic triglyceride-rich lipoproteins (TRL), namely, larger very-low-density lipoproteins (VLDL), and chylomicrons.

OBJECTIVE

We aim to demonstrate that serum triglyceride (TG) level has a substantial impact on non-HDLC's ability to represent cholesterol from atherogenic lipoproteins, even though TG is not part of the calculation for non-HDLC.

DESIGN

Analysis of lipid profile data.

SETTINGS

Lipid Clinic patient cohort, and Biochemistry Laboratory patient cohort.

PATIENTS OR OTHER PARTICIPANTS

7,492 patients in the Lipid Clinic cohort with baseline lipid profiles documented prior to starting lipid-lowering medications and 156,311 lipid profiles from The Ottawa Hospital Biochemistry Laboratory cohort.

INTERVENTION

None.

MAIN OUTCOME MEASURE

Our modeling process includes derivation of TG-interval-specific lipoprotein composition factor (LCF) for TRL, which represents the mass ratio of cholesterol to TG in TRL. A high LCF indicates that the TRLs are mainly the cholesterol-rich atherogenic remnant lipoproteins. A low LCF indicates that the TRLs are mainly the TG-rich larger VLDL and chylomicrons.

RESULTS

As serum TG increases, there is progressive decline in the LCF for TRL, which indicates that the calculated non-HDLC level reflects progressive inclusion of cholesterol from larger TRL. This is shown in both cohorts.

CONCLUSIONS

Calculated non-HDLC is influenced by TG level. As TG increases, non-HDLC gradually includes more cholesterol from larger TRL, which are less atherogenic than LDL and remnant lipoproteins.