Article

Inactivation of NPC1L1 Causes Multiple Lipid Transport Defects and Protects against Diet-induced Hypercholesterolemia

Department of Human Genetics, Mount Sinai School of Medicine, New York, New York 10029, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 05/2005; 280(13):12710-20. DOI: 10.1074/jbc.M409110200
Source: PubMed

ABSTRACT

NPC1L1, a recently identified relative of Niemann-Pick C1, was characterized to determine its subcellular location and potential
function(s). NPC1L1 was highly expressed in HepG2 cells and localized in a subcellular vesicular compartment rich in the small
GTPase Rab5. mRNA expression profiling revealed significant differences between mouse and man with highest expression found
in human liver and significant expression in the small intestine. In contrast, liver expression in mouse was extremely low
with mouse small intestine exhibiting the highest NPC1L1 expression. A mouse knock-out model of NPC1L1 was generated and revealed
that mice lacking a functional NPC1L1 have multiple lipid transport defects. Surprisingly, lack of NPC1L1 exerts a protective
effect against diet-induced hyperlipidemia. Further characterization of cell lines generated from wild-type and knock-out
mice revealed that in contrast to wild-type cells, NPC1L1 cells exhibit aberrant plasma membrane uptake and subsequent transport
of various lipids, including cholesterol and sphingolipids. Furthermore, lack of NPC1L1 activity causes a deregulation of
caveolin transport and localization, suggesting that the observed lipid transport defects may be the indirect result of an
inability of NPC1L1 null cells to properly target and/or regulate caveolin expression.

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Available from: Yiannis A Ioannou, Nov 13, 2015
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    • "However, such[19], or when the three data were combined[20]. Unlike rodents, where NPC1L1 is mainly expressed in the intestine, NPC1L1 is highly expressed in human liver[1,3,21]. Hepatic NPC1L1 has been demonstrated to play a direct role in regulating biliary cholesterol content[4,22]. "
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    ABSTRACT: Niemann Pick Type C1 Like 1 (NPC1L1) protein plays a key role in intestinal and hepatic cholesterol metabolism in humans. Genetic variation in NPC1L1 has been widely studied in recent years. We analyzed NPC1L1 single nucleotide polymorphisms in Chinese gallstone disease patients to investigate their association with gallstone disease. NPC1L1 mRNA expression was also measured in liver biopsies from patients with cholesterol gallstone disease and compared between genotypes. The G allele of the g1679C>G (rs2072183) polymorphism was significantly more prevalent in patients with gallstones compared with gallstone-free subjects. Moreover, patients carrying the G allele had lower hepatic NPC1L1 mRNA expression and higher biliary cholesterol (molar percentages) and cholesterol saturation index. Our study suggests that the G allele of the NPC1L1 polymorphism g1679C>G may be a positive marker of gallstone formation risk.
    Full-text · Article · Jan 2016 · PLoS ONE
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    • "In addition to its cholesterol-lowering action, ezetimibe may exert a direct cholesterol-independent effect on cells78798082]. A feasible explanation is that NPC1L1 is widely expressed in many other tissues including liver, kidney, muscle, and heart[83]. Cell culture studies support the possible direct effect of ezetimibe on cellular oxidative/nitrative stress, for example, knockdown of NPC1L1 in hepatocytes attenuated ROS production[84]. Based on these findings it is plausible to speculate that ezetimibe has a direct impact on the heart and may decrease cholesterol-induced oxidative stress. "
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    ABSTRACT: Hypercholesterolemia is a frequent metabolic disorder associated with increased risk for cardiovascular morbidity and mortality. In addition to its well-known proatherogenic effect, hypercholesterolemia may exert direct effects on the myocardium resulting in contractile dysfunction, aggravated ischemia/reperfusion injury, and diminished stress adaptation. Both preclinical and clinical studies suggested that elevated oxidative and/or nitrative stress plays a key role in cardiac complications induced by hypercholesterolemia. Therefore, modulation of hypercholesterolemia-induced myocardial oxidative/nitrative stress is a feasible approach to prevent or treat deleterious cardiac consequences. In this review, we discuss the effects of various pharmaceuticals, nutraceuticals, some novel potential pharmacological approaches, and physical exercise on hypercholesterolemia-induced oxidative/nitrative stress and subsequent cardiac dysfunction as well as impaired ischemic stress adaptation of the heart in hypercholesterolemia.
    Full-text · Article · Jan 2016
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    • "Ezetimibe administration in OLETF rats (n = 5) significantly decreased liver weight and serum and liver lipid parameters including TG, FFA, and TC levels, compared to OLETF control animals (n = 6). In addition to the improvement of hepatic fat accumulation, we also found that ezetimibe significantly decreased serum concentrations of glucose and insulin and HOMA-IR, an index of insulin resistance in OLETF rats, consistent with our previous study[41]and numerous other studies78913,17,20]. Moreover, in vitro hepatocytes, ezetimibe treatment significantly reduced PA-induced TG accumulation (P < 0.05). "
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    ABSTRACT: To investigate whether ezetimibe ameliorates hepatic steatosis and induces autophagy in a rat model of obesity and type 2 diabetes. Male age-matched lean control LETO and obese and diabetic OLETF rats were administered either PBS or ezetimibe (10 mg/kg per day) via stomach gavage for 20 wk. Changes in weight gain and energy intake were regularly monitored. Blood and liver tissue were harvested after overnight fasting at the end of study. Histological assessment was performed in liver tissue. The concentrations of glucose, insulin, triglycerides (TG), free fatty acids (FFA), and total cholesterol (TC) in blood and TG, FFA, and TG in liver tissue were measured. mRNA and protein abundance involved in autophagy was analyzed in the liver. To investigate the effect of ezetimibe on autophagy and reduction in hepatic fat accumulation, human Huh7 hepatocytes were incubated with ezetimibe (10 μmol/L) together with or without palmitic acid (PA, 0.5 mmol/L, 24 h). Transmission electron microscopy (TEM) was employed to demonstrate effect of ezetimibe on autophagy formation. Autophagic flux was measured with bafilomycin A1, an inhibitor of autophagy and following immunoblotting for autophagy-related protein expression. In the OLETF rats that received ezetimibe (10 mg/kg per day), liver weight were significantly decreased by 20% compared to OLETF control rats without changes in food intake and body weight (P < 0.05). Lipid parameters including TG, FFA, and TC in liver tissue of ezetimibe-administrated OLETF rats were dramatically decreased at least by 30% compared to OLETF controls (P < 0.01). The serum glucose, insulin, HOMA-IR, and lipid profiles were also improved by ezetimibe (P < 0.05). In addition, autophagy-related mRNA expression including ATG5, ATG6, and ATG7 and the protein level of microtubule-associated protein light chain 3 (LC3) were significantly increased in the liver in rats that received ezetimibe (P < 0.05). Likewise, for hepatocytes cultured in vitro, ezetimibe treatment significantly decreased PA-induced fat accumulation and increased PA-reduced mRNA and protein expression involved in autophagy (P < 0.05). Ezetimibe-increased autophagosomes was observed in TEM analysis. Immunoblotting analysis of autophagy formation with an inhibitor of autophagy demonstrated that ezetimibe-increased autophagy resulted from increased autophagic flux. The present study demonstrates that ezetimibe-mediated improvement in hepatic steatosis might involve the induction of autophagy.
    Full-text · Article · Jul 2015
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