Figure 1.

Apolipoprotein B 100 metabolic heterogeneity in hypertriglyceridemia. Elevation in plasma triglyceride is associated with an increased concentration of large VLDL-VLDL₁ (A). VLDL₁ once secreted from the liver enters a delipidation cascade leading to the formation of smaller VLDL₂, IDL, and LDL (main diagram). Kinetic investigations reveal metabolic heterogeneity within the delipidation pathway. As shown in (B) [taken from Björnson et al. (29)], a tracer of deuterated leucine administered at time 0 h appears rapidly in VLDL₁ and VLDL₂. Decay curves in both fractions have an initial rapid phase reflecting lipolysis and a second, slower phase due to remnant removal. This metabolic heterogeneity (as depicted by the two circles in each lipoprotein class in the main diagram) is more evident as plasma triglyceride rises (B). For further detail see Packard and Shepherd (13), Björnson et al. (29), Shepherd and Packard (30), and Packard et al. (31).