Sitosterol reduces messenger RNA and protein expression levels of Niemann-Pick C1-like 1 in FHs 74 Int cells.
Intake of plant sterols has long been shown to reduce cholesterol absorption and subsequently plasma cholesterol concentrations. Despite competition between plant sterols and cholesterol for incorporation into mixed micelles as a suggested major mechanism for the inhibition of cholesterol absorption by plant sterols, studies exist to support an alternative mechanism. For example, another mechanism may be the action of plant sterols to reduce cholesterol absorption at the cellular level. This study was undertaken to test the hypothesis that plant sterols can modulate the expression of transporters such as Niemann-Pick C1-like 1 (NPC1L1) and scavenger receptor class B, type I (SR-BI) to lower intestinal cholesterol absorption. FHs 74 Int cells, a human small intestine epithelial cell line, were used as a model of enterocytes. The cells were treated with 25alpha-hydroxycholesterol (25 micromol/L) or 250 micromol/L of sitosterol, stigmasterol, and cholesterol for 24 hours to measure genes involved in cholesterol absorption and metabolism by quantitative real-time polymerase chain reaction. 25Alpha-hydroxycholesterol, cholesterol, and sitosterol significantly reduced the messenger RNA (mRNA) expression of NPC1L1 and hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, whereas SR-BI mRNA was not altered by the sterols. Western blot analysis confirmed the reduction in NPC1L1 by sterols. Depletion of cellular cholesterol by mevinolin, a cholesterol synthesis inhibitor, increased NPC1L1 and HMG-CoA reductase mRNA; and repletion of cholesterol abolished the increase. Sitosterol, but not stigmasterol, reduced the mRNA levels of NPC1L1 and HMG-CoA reductase to a similar extent of cholesterol. In conclusion, sitosterol can inhibit the expression of NPC1L1 in the enterocytes, which could be an alternate mechanism for plant sterols to reduce intestinal cholesterol uptake.
Jesch
Elliot D
ED
Department of Nutrition and Health Sciences, University of Nebraska, Lincoln, NE 68583, USA.
Seo
Jeong Min
JM
Carr
Timothy P
TP
Lee
Ji-Young
JY
D000924:Anticholesteremic Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D020895:Enterocytes / Q000378:metabolism; D006801:Humans; D006888:Hydroxycholesterols / Q000378:metabolism; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics / Q000378:metabolism; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000378:metabolism; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D010840:Phytosterols / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051122:Scavenger Receptors, Class B / Q000235:genetics / Q000378:metabolism; D012855:Sitosterols / Q000494:pharmacology*; D051782:Sterol Regulatory Element Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D013265:Stigmasterol / Q000494:pharmacology
D000924:Anticholesteremic Agents; D006888:Hydroxycholesterols; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D010840:Phytosterols; D012333:RNA, Messenger; C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B; D012855:Sitosterols; D051782:Sterol Regulatory Element Binding Protein 2; C007997:25-hydroxycholesterol; D002784:Cholesterol; D013265:Stigmasterol; D006903:Hydroxymethylglutaryl CoA Reductases