Transient triglyceridemia in healthy normolipidemic men increases cellular processing of large very low density lipoproteins by fibroblasts in vitro.
Björkegren J., Karpe F., Vitols S., Tornvall P., Hamsten A.
Exaggerated and prolonged postprandial triglyceridemia is a characteristic of patients with precocious coronary heart disease. Although large very low density lipoprotein (VLDL) particles accumulate during alimentary lipemia, the biological properties of the postprandial VLDL remain unknown. In the present study, an intravenous infusion of a chylomicron-like emulsion was given to healthy normolipidemic men to examine the effects of transient triglyceridemia in vivo on compositional and cell biological characteristics of VLDL. The postinfusion large(Svedberg flotation rate (Sf) (60-400) VLDL was found to have increased capacity to inhibit low density lipoprotein (LDL) binding to the LDL-receptor and a greater ability to suppress the 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity of cultured fibroblasts compared to VLDL isolated from fasting plasma. These alterations in cellular interactions were accompanied by increases in the number of apolipoprotein (apo) E, C-I, and C-III molecules per large VLDL particle and loss of apoC-II, compositional changes similar to those observed after an oral fat load. The increase in number of apoE molecules per large VLDL particle correlated positively and significantly with the increase in the capacity of large VLDL to inhibit LDL binding to the LDL receptor (r = 0.76, P = 0.01, n = 10). In contrast, the composition of the small (Sf 20-60) VLDL particles did not change significantly, nor was the LDL receptor-mediated processing of these particles altered consistently. These observations indicate that large VLDL particles that accumulate during alimentary lipemia undergo compositional changes that render them more prone to cellular binding and uptake.