Apoprotein A-I Synthesis in Normal Intestinal Mucosa and in Tangier Disease

Abstract

To determine whether human small intestine synthesizes apoA-I, the major apoprotein of plasma high-density lipoproteins, we used immunofluorescence technics and monospecific antiserums to visualize apoA-I within intestinal epithelial cells from four normal subjects and one patient with Tangier disease. Biopsies from all subjects during fasting showed limited fluorescence. After lipid feeding intracellular apoA-I markedly increased in both normal subjects and the patient. During alimentary lipemia, mean plasma apoA-I levels (milligrams per deciliter) increased in four normal subjects from 161±12 (± S.E.M.) to 180±15 (P<0.05) and in the patient from 1.9 to 6.8. Normal plasma chylomicrons contained apoB, apoE and the C peptides but not apoA-I. The patient's chylomicrons contained apoA-I. Normal and Tangier-disease intestinal-mucosa cells increase their content of apoA-I during chylomicron formation and subsequently contribute to plasma apoA-I levels. The low levels of apoA-I in Tangier disease are not due to a failure of intestinal synthesis but might be due to abnormal metabolism of chylomicron apoproteins. (N Engl J Med 299:1424–1427, 1978)