title: Orlistat limits cholesterol intestinal absorption by Niemann-pick C1-like 1 (NPC1L1) inhibition.
abstract: The known mechanism by which orlistat decreases the absorption of dietary cholesterol is by inhibition of intestinal lipases. The aim of this study was to investigate the ability of orlistat to limit cholesterol absorption by inhibition of the cholesterol transport protein Niemann-Pick C1-like 1 (NPC1L1) as another mechanism of action. In situ rat intestinal perfusion studies were conducted to study the effect of orlistat on jejunal cholesterol absorption. Inhibition kinetic parameters were calculated from in vitro inhibition studies using Caco2 and NPC1L1 transfected cell lines. The in situ studies demonstrated that intestinal perfusion of orlistat (100µM) was able to reduce cholesterol absorption by three-fold when compared to control (i.e. in the absence of orlistat, P<0.01). In vitro studies using Caco2 cells demonstrated orlistat to reduce the cellular uptake of cholesterol by 30%. Additionally, orlistat reduced the cellular uptake of cholesterol in dose dependent manner in NPC1L1 transfected cell line with an IC50=1.2µM. Lineweaver-Burk plot indicated a noncompetitive inhibition of NPC1L1 by orlistat. Beside the already established mechanism by which orlistat reduces the absorption of cholesterol, we demonstrated for the first time that orlistat limits cholesterol absorption by the inhibition of NPC1L1 transport protein.
authors.affiliation: Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, Monroe, LA 71201, USA.
authors.forename: Saeed
authors.initials: S
authors.lastname: Alqahtani
authors.affiliation: Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, Monroe, LA 71201, USA.
authors.forename: Hisham
authors.initials: H
authors.lastname: Qosa
authors.affiliation: Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, Monroe, LA 71201, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Primeaux
authors.affiliation: Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, Monroe, LA 71201, USA. Electronic address: kaddoumi@ulm.edu.
authors.forename: Amal
authors.initials: A
authors.lastname: Kaddoumi
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D002784:Cholesterol / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D007783:Lactones / Q000494:pharmacology*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D026901:Membrane Transport Proteins; D000077403:Orlistat; D010477:Perfusion; D051381:Rats; D013997:Time Factors
chemical_list: D007783:Lactones; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D000077403:Orlistat; D002784:Cholesterol
keywords: Cholesterol; NPC1L1; Orlistat