Abstract
Current information suggests that the major forms of the human B apolipoproteins, B-100 and B-48, are under separate genetic control and are synthesized by the liver and intestine, respectively. The apolipoprotein B composition of plasma lipoproteins has been determined in order to gain insight into the metabolic defects in patients with dyslipoproteinemias. Patients with type I and type V hyperlipoproteinemia can be separated into two groups based on apolipoprotein composition and triglyceride concentration. The first group had markedly elevated plasma triglycerides with B-48 in the 1.006 g/ml density fraction and only B-100 within IDL and LDL. The second group had plasma triglycerides less than 1200 mg % and only B-100 in all density fractions. Patients with type III hyperlipoproteinemia had B-48 in only the density less than 1.006 g/ml with B-100 in IDL and LDL; the type III hyperlipoproteinemic patient with apolipoprotein E deficiency, however, had B-48 in density less than 1.006 g/ml fraction, IDL, and LDL. Patients with type IIa, IIb, and IV hyperlipoproteinemia had only B-100 in all density fractions. These combined results are interpreted as indicating that B-48 is associated with triglyceride-rich lipoproteins synthesized by the intestine and that patients with phenotypes I, III, and V have defects in chylomicron remnant metabolism. In addition, in patients with types I and V hyperlipoproteinemia, mild hypertriglyceridemia appears to be associated with lipoprotein particles of liver origin.
Highlights
Current information suggests that the major forms of the human B apolipoproteins, B-100 and B-48, are under separate genetic control and are synthesized by the liver and intestine, respectively
The identification, isolation, and characterbation of the plasma apolipoproteins has permitted a more definitive analysis ofthe mechanismsand pathways involved in lipoprotein biosynthesis, transport, and metabolism
The present studies were designed to determine the site of synthesisof the lipoprotein particles elevated in patients with hyperlipoproteinemias types I to V,and a number of rare genetic diseases
Summary
Current information suggests that the major forms of the human B apolipoproteins, B-100 and B-48, are under separate genetic control and are synthesized by the liver and intestine, respectively. The apolipoprotein B composition of plasma lipoproteins has been determined in order to gain insight into the metabolic defects in patients with dyslipoproteinemias. Patients with type I and type V hyperlipoproteinemia can be separated into two groups based on apolipoprotein composition and triglyceride concentration. The first group had markedly elevated plasma triglycerides with B-48 in the 1.006 g/ml density fraction and only B-100 within IDL and LDL. The second group had plasma triglycerides < 1200 mg % and only B-100 in all density fractions. Patients with type Ha, IIb, and IV hyperlipoproteinemia had only E100 in all density fractions.M These combined results are interpreted as indicating that B-48 is associated with triglyceride-rich lipoproteins synthesized by the intestine and that patients with phenotypes I, 111, and V have defects in chylomicron remnant metabolism.
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