title: Luteolin and quercetin affect the cholesterol absorption mediated by epithelial cholesterol transporter niemann-pick c1-like 1 in caco-2 cells and rats.
abstract: Niemann-Pick C1-Like 1 (NPC1L1) mediates cholesterol absorption, and ezetimibe is a potent NPC1L1 inhibitor applicable for medication of hypercholesterolemia. Epidemiological studies demonstrated that consumption of polyphenols correlates with a decreased risk for atherosclerosis due to their antioxidant effect. This activity can hardly be attributable to the antioxidant activity only, and we hypothesized that polyphenols inhibit intestinal transport of cholesterol. We elucidated the kinetic parameters of intestinal cholesterol absorption, screened several polyphenols for their ability to specifically inhibit intestinal cholesterol absorption, and determined the inhibitory effects of selected flavonoids in vitro and in vivo. The concentration-dependent uptake of cholesterol by Caco-2 cells obeyed a monophasic saturation process. This indicates the involvement of an active-passive transport, i.e., NPC1L1. Parameters of cholesterol uptake by Caco-2 cells were as follows: Jmax, Kt, and Kd were 6.89±2.96 19.03±11.58 µM, and 0.11±0.02 pmol/min/mg protein, respectively. Luteolin and quercetin inhibited cholesterol absorption by Caco-2 cells and human embryonic kidney 293T cells expressing NPC1L1. When preincubated Caco-2 cells with luteolin and quercetin before the assay, cholesterol uptake significantly decreased. The inhibitory effects of these flavonoids were maintained for up to 120 min. The level of inhibition and irreversible effects were similar to that of ezetimibe. Serum cholesterol levels significantly decreased more in rats fed both cholesterol and luteolin (or quercetin), than in those observed in the cholesterol feeding group. As quercetin induced a significant decrease in the levels of NPC1L1 mRNA in Caco-2 cells, the in vivo inhibitory effect may be due to the expression of NPC1L1. These results suggest that luteolin and quercetin reduce high blood cholesterol levels by specifically inhibiting intestinal cholesterol absorption mediated by NPC1L1.
authors.affiliation: Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Nekohashi
authors.affiliation: Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Mana
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki, Gunma, Japan.
authors.forename: Takuo
authors.initials: T
authors.lastname: Ogihara
authors.affiliation: Corporate Sponsored Research Program "Food for Life," Organization for Interdisciplinary Research Projects, The University of Tokyo, Tokyo, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nakazawa
authors.affiliation: Corporate Sponsored Research Program "Food for Life," Organization for Interdisciplinary Research Projects, The University of Tokyo, Tokyo, Japan.
authors.forename: Hisanori
authors.initials: H
authors.lastname: Kato
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Misaka
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan; Kanagawa Academy of Science and Technology Life Science & Environment Research Center 4F C-4, Kawasaki, Kanagawa, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Abe
authors.affiliation: Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D002784:Cholesterol / Q000378:metabolism*; D004353:Drug Evaluation, Preclinical; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D006937:Hypercholesterolemia / Q000188:drug therapy / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects*; D047311:Luteolin / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D011794:Quercetin / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats
chemical_list: D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; C482444:NPC1L1 protein, rat; D002784:Cholesterol; D011794:Quercetin; D047311:Luteolin