title: Polyunsaturated fatty acids down-regulate in vitro expression of the key intestinal cholesterol absorption protein NPC1L1: no effect of monounsaturated nor saturated fatty acids.
abstract: Several transporter proteins regulate intestinal cholesterol absorption. Of these proteins, NPC1L1 is a major contributor to this process. Fatty acids (FAs) modulate cholesterol absorption by a mechanism that remains unknown. We evaluate the effect of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) on the expression of NPC1L1 and others proteins associated with cholesterol absorption (SR-BI, ABCG5, ABCG8, ABCA1, CAV-1, ANX-2) in human enterocytes in vitro. The role of SREBPs, PPARs, LXR and RXR in this process was also investigated. Caco-2/TC-7 enterocytes were incubated for 24 h with a wide range of concentrations of FA-bovine serum albumin (50-300 microM). Gene expression was analyzed by quantitative real-time PCR. The NPC1L1 protein present in enterocyte membranes was analyzed using Western blot. NPC1L1 mRNA levels were reduced 35-58% by the n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (P<.05). Linoleic acid (n-6), palmitic acid and oleic acid did not affect NPC1L1 mRNA expression. ABCA1 mRNA levels were reduced 44-70% by n-6 arachidonic acid and 43-55% by n-3 EPA (P<.05). LXR and LXR+RXR agonists decreased NPC1L1 mRNA expression by 28% and 57%, respectively (P<.05). A concentration of 200 microM of EPA and DHA decreased NPC1L1 protein expression in enterocyte membranes by 58% and 59%, respectively. We have demonstrated that the PUFAs n-3 EPA and DHA down-regulate NPC1L1 mRNA expression. In addition, PUFAs also down-regulate NPC1L1 protein expression in enterocyte membranes. LXR and RXR activation induced a similar repression effect. The lipid-lowering effect of n-3 PUFAs could be mediated in part by their action at the NPC1L1 gene level.
authors.affiliation: Research Unit on Lipids and Atherosclerosis, Sant Joan University Hospital, University Rovira and Virgili, Reus, CIBER de Diabetes y Enfermedades Metabólicas Asociadas, IISPV, Spain.
authors.forename: Adriana
authors.initials: A
authors.lastname: Alvaro
authors.forename: Roser
authors.initials: R
authors.lastname: Rosales
authors.forename: Lluís
authors.initials: L
authors.lastname: Masana
authors.forename: Joan-Carles
authors.initials: JC
authors.lastname: Vallvé
mesh_terms: D000042:Absorption; D018938:Caco-2 Cells; D002784:Cholesterol / Q000378:metabolism*; D004281:Docosahexaenoic Acids / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D020895:Enterocytes / Q000378:metabolism; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D019787:Linoleic Acid / Q000737:chemistry; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008954:Models, Biological; D019301:Oleic Acid / Q000737:chemistry; D019308:Palmitic Acid / Q000378:metabolism
chemical_list: D005229:Fatty Acids, Monounsaturated; D005231:Fatty Acids, Unsaturated; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D004281:Docosahexaenoic Acids; D019301:Oleic Acid; D019308:Palmitic Acid; D002784:Cholesterol; D019787:Linoleic Acid; D015118:Eicosapentaenoic Acid