Presence of apolipoprotein B-100 in human intestine epithelial cells

Postprandial Hyperlipidemia and Atherosclerosis

The development of the remnant like particle (RLP) method for conveniently measuring serum remnant lipoprotein levels in 1993 promoted much research on atherogenic significance and metabolism of remnant lipoproteins. This research brought about many results as the following. A novel apolipoprotein B48 receptor incorporating remnant lipoproteins into macrophages in arterial wall was discovered and the structure of the gene of the receptor was clarified. The expression of apolipoprotein B100 was recognized in the human small intestine, suggesting that dietary very low density lipoproteins (VLDL) might be synthesized in the human small intestine and converted into VLDL remnants and low density lipoproteins (LDL). It is recognized that the atherosclerotic risk of postprandial hyperlipidemia is derived from an increase of remnant lipoproteins and that measurement of serum RLP levels in postprandial state is more sensitive and necessary for evaluating an atherosclerotic risk because serum RLP levels remain high all day in patients with diabetes mellitus or coronary heart disease. The relation between postprandial hyperlipidemia and insulin resistance was clarified.

Sources and properties of triglyceride-rich lipoproteins containing apoB-48 and apoB-100 in postprandial blood plasma of patients with primary combined hyperlipidemia

Although editing of apolipoprotein (apo)B in the small intestine, yielding apoB-48, is thought to be nearly complete in adult humans, small amounts of intestinal apoB-100 may also be produced. We have evaluated the fraction of unedited apoB secreted from the intestine postprandially in subjects with primary combined hyperlipidemia, a disorder in which secretion of apoB-100 into the blood is increased. Three hours after these subjects and healthy controls were fed a fat-rich meal containing retinol, the distribution of retinyl esters (RE) between plasma triglyceride-rich lipoprotein (TRL) fractions containing apoB-100 and apoB-48 was measured under conditions minimizing transfer of RE between lipoprotein particles. The estimated maximal percentage of unedited intestinal apoB-100 (approximately 3%) was not increased in subjects with primary combined hyperlipidemia, suggesting that reduced editing of intestinal mRNA does not contribute to the pathogenesis of this disorder. Postprandially, the triglyceride content of TRL containing apoB-48 more than doubled, leading to a 20% increase in mean diameter, yet the surface concentration of phospholipids and soluble apolipoproteins (apoE and total apoC) was unchanged. Furthermore, the surface concentrations of these components did not differ among TRL containing apoB-48 and two smaller fractions of apoB-100 TRL with distinct immunoreactivities. These findings suggest that available surface area is a major determinant of the particle content of each of these surface components of TRL species of differing size and origin.