Genetic demonstration of intestinal NPC1L1 as a major determinant of hepatic cholesterol and blood atherogenic lipoprotein levels

Ping Xie; Hongling Zhu; Lin Jia; Yinyan Ma; Weiqing Tang; Youlin Wang; Bingzhong Xue; Hang Shi; Liqing Yu

doi:10.1016/j.atherosclerosis.2014.09.036

Genetic demonstration of intestinal NPC1L1 as a major determinant of hepatic cholesterol and blood atherogenic lipoprotein levels

Atherosclerosis. 2014 Dec;237(2):609-17. doi: 10.1016/j.atherosclerosis.2014.09.036. Epub 2014 Oct 17.

Authors

Ping Xie¹, Hongling Zhu², Lin Jia³, Yinyan Ma⁴, Weiqing Tang², Youlin Wang², Bingzhong Xue⁵, Hang Shi⁵, Liqing Yu⁶

Affiliations

¹ Department of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA; Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA; Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100193, China.
² Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA.
³ Department of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA; Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
⁴ Department of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA; Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA; Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA.
⁵ Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
⁶ Department of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA; Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA; Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA. Electronic address: lyu123@umd.edu.

PMID: 25463095
PMCID: PMC4262594
DOI: 10.1016/j.atherosclerosis.2014.09.036

Abstract

Objective: The correlation between intestinal cholesterol absorption values and plasma low-density lipoprotein-cholesterol (LDL-C) levels remains controversial. Niemann-Pick-C1-Like 1 (NPC1L1) is essential for intestinal cholesterol absorption, and is the target of ezetimibe, a cholesterol absorption inhibitor. However, studies with NPC1L1 knockout mice or ezetimibe cannot definitively clarify this correlation because NPC1L1 expression is not restricted to intestine in humans and mice. In this study we sought to genetically address this issue.

Methods and results: We developed a mouse model that lacks endogenous (NPC1L1) and LDL receptor (LDLR) (DKO), but transgenically expresses human NPC1L1 in gastrointestinal tract only (DKO/L1(IntOnly) mice). Our novel model eliminated potential effects of non-intestinal NPC1L1 on cholesterol homeostasis. We found that human NPC1L1 was localized at the intestinal brush border membrane of DKO/L1(IntOnly) mice. Cholesterol feeding induced formation of NPC1L1-positive vesicles beneath this membrane in an ezetimibe-sensitive manner. Compared to DKO mice, DKO/L1(IntOnly) mice showed significant increases in cholesterol absorption and blood/hepatic/biliary cholesterol. Increased blood cholesterol was restricted to very low-density lipoprotein (VLDL) and LDL fractions, which was associated with increased secretion and plasma levels of apolipoproteins B100 and B48. Additionally, DKO/L1(IntOnly) mice displayed decreased fecal cholesterol excretion and hepatic/intestinal expression of cholesterologenic genes. Ezetimibe treatment virtually reversed all of the transgene-related phenotypes in DKO/L1(IntOnly) mice.

Conclusion: Our findings from DKO/L1(IntOnly) mice clearly demonstrate that NPC1L1-mediated cholesterol absorption is a major determinant of blood levels of apolipoprotein B-containing atherogenic lipoproteins, at least in mice.

Keywords: Apolipoprotein B; Cholesterol absorption; Chylomicron remnant; Fecal neutral sterol excretion; Low-density lipoprotein receptor; Niemann-Pick-C1-Like 1.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Animals
Apolipoprotein B-100
Apolipoprotein B-48 / metabolism
Apolipoproteins B / metabolism
Azetidines / pharmacology
Cholesterol / blood
Cholesterol / metabolism
Cholesterol, LDL / blood*
Ezetimibe
Gene Expression Regulation*
Homeostasis
Humans
Intestinal Mucosa / metabolism
Liver / metabolism
Male
Membrane Proteins / genetics
Membrane Proteins / metabolism*
Membrane Transport Proteins
Mice
Mice, Inbred C57BL
Mice, Knockout
Microscopy, Fluorescence
Phenotype
Receptors, LDL / genetics
Receptors, LDL / metabolism*
Transgenes

Substances

Apob protein, mouse
Apolipoprotein B-100
Apolipoprotein B-48
Apolipoproteins B
Azetidines
Cholesterol, LDL
Membrane Proteins
Membrane Transport Proteins
NPC1L1 protein, human
Receptors, LDL
Cholesterol
Ezetimibe

Abstract

Publication types

MeSH terms

Substances

Grants and funding