Primary Dysbetalipoproteinemia: Predominance of a Specific Apoprotein Species in Triglyceride-Rich Lipoproteins

Lipoproteins of very low density that are unusually rich in cholesteryl esters accumulate in blood plasma in a characteristic primary form of human hyperlipoproteinemia. These lipoproteins, which are thought to be products of the initial catabolic step in the metabolism of normal triglyceride-rich lipoproteins, have beta rather than pre-beta mobility on electrophoresis, presumably because they have lost certain protein components from their surface. In this study, we have used polyacrylamide gel electrophoresis of apoprotein components that are soluble in tetramethylurea to show that the very low-density lipoprotein fraction of blood serum from seven patients with hyperlipoproteinemia contains unusually large amounts of an arginine-rich protein. Pre-beta migrating, very low-density lipoproteins separated from serum of post-absorptive patients and chylomicrons obtained after a fat-rich meal contain normal amounts of this arginine-rich protein, but beta-migrating, very low-density lipoproteins and chylomicron-like particles separated from serum of post-absorptive patients contain more than twice as much. These apparently partially degraded lipoproteins also contain more tetramethylurea-insoluble protein and smaller amounts of the other soluble protein components than their normal counterparts.