Effects of oral and intravenous fat administration on the levels of apoproteins A-I, A-II AND C-III in human subjects

Abstract

Changes of plasma levels of apoproteins A-I, A-II and C-III were determined after oral and intravenous fat administration. The A-I levels increased in three out of four subjects after fat ingestion but no changes or even a slight decrease in the levels of A-I were observed after intravenous fat infusion. The A-II levels also increased after fat ingestion in two subjects but the levels either did not change or decreased slightly after fat infusion. The levels of C-III increased concomitantly with the increase of triglyceride levels after fat ingestion as well as fat infusion. After intravenous fat infusion, part of the C-III in the d > 1.006 fraction shifted to the lighter fraction (d < 1.006). These observations suggest that the increase in the levels of A-I and A-II after fat ingestion are a consequence of an increase in apoprotein synthesis in the intestine during fat absorption. The increase in the levels of C-III after fat ingestion as well as fat infusion seemed to be related to the capture of C-III in the triglyceride rich particles, i.e. C-III accumulated in the circulation with triglyceride-rich particles. However, it appeared also to be possible that the rate of C-III synthesis increases during hyperlipidemia induced by fat infusion.