title: Up-regulation of cholesterol absorption is a mechanism for cholecystokinin-induced hypercholesterolemia.
abstract: Excessive absorption of intestinal cholesterol is a risk factor for atherosclerosis. This report examines the effect of cholecystokinin (CCK) on plasma cholesterol level and intestinal cholesterol absorption using the in vivo models of C57BL/6 wild-type and low density lipoprotein receptor knock-out (LDLR(-/-)) mice. These data were supported by in vitro studies involving mouse primary intestinal epithelial cells and human Caco-2 cells; both express CCK receptor 1 and 2 (CCK1R and CCK2R). We found that intravenous injection of [Thr(28),Nle(31)]CCK increased plasma cholesterol levels and intestinal cholesterol absorption in both wild-type and LDLR(-/-) mice. Treatment of mouse primary intestinal epithelial cells with [Thr(28),Nle(31)]CCK increased cholesterol absorption, whereas selective inhibition of CCK1R and CCK2R with antagonists attenuated CCK-induced cholesterol absorption. In Caco-2 cells, CCK enhanced CCK1R/CCK2R heterodimerization. Knockdown of both CCK1R and CCK2 or either one of them diminished CCK-induced cholesterol absorption to the same extent. CCK also increased cell surface-associated NPC1L1 (Niemann-Pick C1-like 1) transporters but did not alter their total protein expression. Inhibition or knockdown of NPC1L1 attenuated CCK-induced cholesterol absorption. CCK enhanced phosphatidylinositide 3-kinase (PI3K) and Akt phosphorylation and augmented the interaction between NPC1L1 and Rab11a (Rab-GTPase-11a), whereas knockdown of CCK receptors or inhibition of G protein βγ dimer (Gβγ) diminished CCK-induced PI3K and Akt phosphorylation. Inhibition of PI3K and Akt or knockdown of PI3K diminished CCK-induced NPC1L1-Rab11a interaction and cholesterol absorption. Knockdown of Rab11a suppressed CCK-induced NPC1L1 translocation and cholesterol absorption. These data imply that CCK enhances cholesterol absorption by activation of a pathway involving CCK1R/CCK2R, Gβγ, PI3K, Akt, Rab11a, and NPC1L.
authors.affiliation: From the Department of Physiology, Meharry Medical College, Nashville, Tennessee 37208.
authors.forename: LiChun
authors.initials: L
authors.lastname: Zhou
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: Emmanuel U
authors.initials: EU
authors.lastname: Okoro
authors.forename: Zhongmao
authors.initials: Z
authors.lastname: Guo
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D002766:Cholecystokinin / Q000235:genetics / Q000378:metabolism*; D002784:Cholesterol / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006937:Hypercholesterolemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D043887:Receptor, Cholecystokinin B / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D015854:Up-Regulation; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D002766:Cholecystokinin; D002784:Cholesterol; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D043887:Receptor, Cholecystokinin B; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C410800:NPC1L1 protein, human; C482445:Npc1l1 protein, mouse
keywords: Cholesterol Metabolism; Hormone Receptors; Intestine; Signal Transduction; Transporters