ALTERATIONS OF VLDL COMPOSITION DURING ALIMENTARY LIPEMIA

Apoliprotein (apo) B-100-containing very low density lipoprotein (VLDL ) particles secreted from the liver accumulate in plasma during alimen tary lipemia. To determine whether changes of VLDL composition occur i n the postprandial state that may render these lipoproteins more ather ogenic, apoE, C-I, C-II, and C-III, and lipids (triglycerides, phospho lipids, and cholesterol) were measured in Svedberg flotation (S-f) 60- 400 (large) and S-f 20-60 (small) VLDL before and after an oral fat lo ad. Ten normotriglyceridemic (NTG) and three hypertriglyceridemic (HTG ) healthy men were given a fat-rich mixed meal (1000 kCal with 60.2 E% from fat). Triglyceride-rich lipoproteins were isolated by density gr adient ultracentrifugation from plasma samples obtained before (fastin g) and at 2-h intervals after the meal. VLDL was then separated from c hylomicrons and their remnants by immunoaffinity chromatography using monoclonal antibodies 4G3 and 5E11, recognizing apoB-100, but not apoB -48 epitopes. Large and small VLDL isolated from the NTG group were en riched with apoE and CI, and cholesterol, but depleted of apoC-II in t he postprandial state, whereas the apoC-III, triglyceride, and phospho lipid contents were essentially unchanged. The compositional changes o f VLDL in HTG subjects were similar but more pronounced compared with NTG subjects. We conclude that postprandial lipemia in healthy men ind uces transient compositional alterations of VLDL that link these lipop rotein species to the formation of atherosclerosis.