Concentrations of apolipoproteins B, C-I, C-II, C-III, E and lipids in serum and serum lipoproteins of normal subjects during alimentary lipaemia

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Abstract
The effect of alimentary lipaemia, induced by ingestion of 100 g of fat (cream), on lipids and apolipoprotein B, C-I, C-II, C-III and E levels was evaluated in 16 normotriglyceridaemic subjects. Apolipoprotein concentrations were determined by enzyme immunoassay in whole serum and, in a subsample of seven subjects, in serum lipoprotein fractions of d < 1.006 kg/l (supernatant) containing very low density lipoproteins (VLDL) and chylomicrons and of d > 1.006 kg/l (infranatant) containing low density lipoproteins (LDL) and high density lipoproteins (HDL). Triglyceride concentrations in the supernatant were increased by 164% 3 h after the fat ingestion. The level of alimentary lipaemia was positively related to the fastig serum concentrations of triglycerides and apolipoproteins C-II and C-III and inversely related to the fasting concentration of apolipoprotein E in the infrantant lipoprotein fraction with d > 1.006 kg/l. No significant changes in the serum levels of apolipoproteins B, C-I and E were found during the postprandial lipaemia. By contrast, serum concentrations of apolipoproteins C-II and C-III were decreased (compared to the fasting levels) 6 h after the fatty meal. In the 3-h samples all apolipoproteins were increased in the supernatant (VLDL+ chylomicrons) and a corresponding decrease was observed in the infranatant (LDL + HDL). In conclusion, this study shows that in normotriglyceridaemic subjects a high serum level of apo C-II is not associated with a more rapid clearance of alimentary lipaemia than a low level. Another role could be played by the concentration of apo E in the LDL- and HDL-containing fraction with a density higher than 1.006 kg/l. A peripheral uptake or a utilization of apo C-II and apo C-III during lipolysis results in partial disappearance of these apolipoproteins from serum. Apolipoprotein C-I seems to be mainly involved in the cholesterol metabolism of the serum.