title: Lack of the intestinal Muc1 mucin impairs cholesterol uptake and absorption but not fatty acid uptake in Muc1-/- mice.
abstract: Before cholesterol and fatty acid molecules in the small intestinal lumen can interact with their possible transporters for uptake and absorption, they must pass through a diffusion barrier, which may modify the kinetics of nutrient assimilation. This barrier includes an unstirred water layer and a surface mucous coat, which is located at the intestinal lumen-membrane interface. In the present study, we investigated whether disruption of the mucin gene (Muc)1 may influence intestinal uptake and absorption of cholesterol and fatty acid in male Muc1(-/-) mice. The wild-type mice displayed relatively high levels of Muc1, Muc2, Muc3, and Muc4 mRNAs and relatively low levels of Muc5ac and Muc5b mRNAs in the small intestine. The absence of Muc1 mRNA and protein in the small intestines of Muc1(-/-) mice confirmed complete knockout of the Muc1 gene, but the mRNA expression for other mucin genes remained unchanged. Intestinal uptake and absorption of cholesterol but not palmitic acid were significantly reduced in Muc1(-/-) mice compared with the wild-type mice. However, knockout of the Muc1 gene did not impair either expression levels of the genes that encode intestinal sterol efflux transporters Abcg5 and Abcg8 and fatty acid transporter Fatp4 or small intestinal transit rates. We conclude that physiological levels of the epithelial mucin produced by the Muc1 gene are necessary for normal intestinal uptake and absorption of cholesterol in mice. Our study implies that because cholesterol absorption efficiency is reduced by approximately 50% in Muc1-deficient mice, there may be one or more additional pathways for cholesterol absorption.
authors.affiliation: Department of Medicine, Liver Center and Gastroenterology Division, Beth Israel Deaconess Medical Center, Harvard Medical School and Harvard Digestive Diseases Center, Boston, Massachusetts 02215, USA.
authors.forename: Helen H
authors.initials: HH
authors.lastname: Wang
authors.forename: Nezam H
authors.initials: NH
authors.lastname: Afdhal
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Gendler
authors.forename: David Q-H
authors.initials: DQ
authors.lastname: Wang
mesh_terms: D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D020895:Enterocytes / Q000378:metabolism; D050612:Fatty Acid Transport Proteins; D005227:Fatty Acids / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005769:Gastrointestinal Motility / Q000235:genetics / Q000502:physiology; D005772:Gastrointestinal Transit / Q000235:genetics / Q000502:physiology; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology; D007408:Intestinal Absorption; D008074:Lipoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D018345:Mice, Knockout; D018396:Mucin-1 / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013261:Sterols / Q000378:metabolism
chemical_list: C462600:ABCG5 protein, mouse; C462601:ABCG8 protein, mouse; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D050612:Fatty Acid Transport Proteins; D005227:Fatty Acids; D008074:Lipoproteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D018396:Mucin-1; D012333:RNA, Messenger; C493572:Slc27a4 protein, mouse; D013261:Sterols; D002784:Cholesterol