Transport of diacylalkylglycerols in chylomicrons and very low density lipoproteins of rat intestinal lymph following intragastric administration of 1,3-dioctadecenoyl-2-hexadecylglycerol

The triacylglycerol (TG) analog 1,3-dioctadecenoyl-2-hexadecyl glycerol was used in the study of the transport of dietary lipids by lipoprotein fractions of rat intestinal lymph. 1,3-Diacyl-2-alkyl glycerols (DAG) are hydrolyzed by pancreatic lipase to form 2-alkyl glycerols and free fatty acids. These hydrolysis products are then absorbed, and DAG are resynthesized within the intestinal mucosa. Intestinal lymph of rats was collected following intragastric administration of 1,3-dioctadecenoyl-2-hexadecyl glycerol. The DAG to TG ratios in very low density lipoprotein (VLDL) and chylomicron fractions were determined as a measure of the incorporation of lipid of dietary origin. The ratio of DAG to TG in the VLDL-2 (S_f 12–100) fraction ranged from0.06 to 0.56 indicating a significant amount of DAG transported relative to TG. The glyceryl ether to TG ratio increased with mean lipoprotein volume from the VLDL-2 fraction to the chylomicron (S_f>400) fraction. The correlation between glyceryl ether to TG ratio and average volume and between the amount of DAG per ml of original lymph and average volume within the chylomicron fraction was 0.99. Thus, the amount of dietary fat transported was correlated with the size of the chylomicrons produced. The glyceryl ether to TG ratio was positively correlated with the average volume of the lipoprotein fractions isolated (chylomicrons, chylomicron rich (S_f>100), VLDL-1 (S_f 100–400) and VLDL-2) (r=0.87). These results suggest that the size of the lipoproteins produced by the intestine is determined by the amount of fat available for transport and that particles of larger diameter are formed by the addition of lipid of dietary origin to existing VLDL. Scientific contribution no. 702, Agricultural Experiment Station, University of Connecticut, Storrs, Connecticut 06268