Glycine N-Methyltransferase Deficiency Affects Niemann-Pick Type C2 Protein Stability and Regulates Hepatic Cholesterol Homeostasis

Niemann-Pick type C2 (NP-C2) disease is a rare hereditary disease caused by mutations in the NPC2 gene. NPC2 is a small, soluble protein consisting of 151 amino acids, primarily expressed in late endosomes and lysosomes (LE/LY). Together with NPC1, a transmembrane protein found in these organelles, NPC2 accomplishes the exclusion of cholesterol; thus, both proteins are essential to maintain cellular cholesterol homeostasis. Consequently, mutations in the NPC2 or NPC1 gene result in pathophysiological accumulation of cholesterol and sphingolipids in LE/LY. The vast majority of Niemann-Pick type C disease patients, 95%, suffer from a mutation of NPC1, and only 5% display a mutation of NPC2. The biochemical phenotype of NP-C1 and NP-C2 appears to be indistinguishable, and both diseases share several commonalities in the clinical manifestation. Studies of the pathological mechanisms underlying NP-C2 are mostly based on NP-C2 animal models and NP-C2 patient-derived fibroblasts. Recently, we established induced pluripotent stem cells (iPSCs), derived from a donor carrying the NPC2 mutations c.58G>T/c.140G>T. Here, we present a profile of pathophysiological in vitro features, shared by NP-C1 and NP-C2, of neural differentiated cells obtained from the patient specific iPSCs. Profiling comprised a determination of the NPC2 protein level, detection of cholesterol accumulation by filipin staining, analysis of oxidative stress, and determination of autophagy. As expected, the NPC2-deficient cells displayed a significantly reduced amount of NPC2 protein, and, accordingly, we observed a significantly increased amount of cholesterol. Most notably, NPC2-deficient cells displayed only a slight increase of reactive oxygen species (ROS), suggesting that they do not suffer from oxidative stress and express catalase at a high level. As a site note, comparable NPC1-deficient cells suffer from a lack of catalase and display an increased level of ROS. In summary, this cell line provides a valuable tool to gain deeper understanding, not only of the pathogenic mechanism of NP-C2, but also of NP-C1.

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Niemann-Pick C1 Like 1 (NPC1L1) Is the Intestinal Phytosterol and Cholesterol Transporter and a Key Modulator of Whole-body Cholesterol Homeostasis

Journal of Biological Chemistry ◽

10.1074/jbc.m405817200 ◽

2004 ◽

Vol 279 (32) ◽

pp. 33586-33592 ◽

Cited By ~ 488

Author(s):

Harry R. Davis ◽

Li-ji Zhu ◽

Lizbeth M. Hoos ◽

Glen Tetzloff ◽

Maureen Maguire ◽

...

Keyword(s):

Cholesterol Homeostasis ◽

Whole Body ◽

Niemann Pick

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Mechanisms of cholesterol-lowering effects of dietary insoluble fibres: relationships with intestinal and hepatic cholesterol parameters

British Journal Of Nutrition ◽

10.1079/bjn20051498 ◽

2005 ◽

Vol 94 (3) ◽

pp. 331-337 ◽

Cited By ~ 80

Author(s):

Ariëtte M. van Bennekum ◽

David V. Nguyen ◽

Georg Schulthess ◽

Helmut Hauser ◽

Michael C. Phillips

Keyword(s):

Bile Acid ◽

Food Intake ◽

Serum Cholesterol ◽

Cholesterol Absorption ◽

Cholesterol Homeostasis ◽

Hepatic Cholesterol ◽

Intestinal Cholesterol Absorption ◽

Cholesterol Lowering ◽

Dietary Fibres ◽

Bile Acid Binding

Fibres with a range of abilities to perturb cholesterol homeostasis were used to investigate how the serum cholesterol-lowering effects of insoluble dietary fibres are related to parameters of intestinal cholesterol absorption and hepatic cholesterol homeostasis in mice. Cholestyramine, chitosan and cellulose were used as examples of fibres with high, intermediate and low bile acid-binding capacities, respectively. The serum cholesterol levels in a control group of mice fed a high fat/high cholesterol (HFHC) diet for 3 weeks increased about 2-fold to 4·3 mm and inclusion of any of these fibres at 7·5 % of the diet prevented this increase from occurring. In addition, the amount of cholesterol accumulated in hepatic stores due to the HFHC diet was reduced by treatment with these fibres. The three kinds of fibres showed similar hypocholesterolaemic activity; however, cholesterol depletion of liver tissue was greatest with cholestyramine. The mechanisms underlying the cholesterol-lowering effect of cholestyramine were (1) decreased cholesterol (food) intake, (2) decreased cholesterol absorption efficiency, and (3) increased faecal bile acid and cholesterol excretion. The latter effects can be attributed to the high bile acid-binding capacity of cholestyramine. In contrast, incorporation of chitosan or cellulose in the diet reduced cholesterol (food) intake, but did not affect either intestinal cholesterol absorption or faecal sterol output. The present study provides strong evidence that above all satiation and satiety effects underlie the cholesterol-lowering properties of insoluble dietary fibres with moderate or low bile acid-binding capabilities.

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Wnt5a Promotes Lysosomal Cholesterol Egress and Protects Against Atherosclerosis

Circulation Research ◽

10.1161/circresaha.121.318881 ◽

2021 ◽

Author(s):

Sara Awan ◽

Magalie Lambert ◽

Ali Imtiaz ◽

Fabien Alpy ◽

Catherine Tomasetto ◽

...

Keyword(s):

Dietary Cholesterol ◽

Cell Types ◽

Cholesterol Content ◽

Cholesterol Homeostasis ◽

Cholesterol Trafficking ◽

Atherosclerotic Lesions ◽

Crucial Component ◽

Multiple Cell ◽

Niemann Pick

Background: Impairment of cellular cholesterol trafficking is at the heart of atherosclerotic lesions formation. This involves egress of cholesterol from the lysosomes and two lysosomal proteins, the Niemann-Pick C1 (NPC1) and NPC2 that promotes cholesterol trafficking. However, movement of cholesterol out the lysosome and how disrupted cholesterol trafficking leads to atherosclerosis is unclear. As the Wnt ligand, Wnt5a inhibits the intracellular accumulation of cholesterol in multiple cell types, we tested whether Wnt5a interacts with the lysosomal cholesterol export machinery and studied its role in atherosclerotic lesions formation. Methods: We generated mice deleted for the Wnt5a gene in vascular smooth muscle cells (VSMCs). To establish whether Wnt5a also protects against cholesterol accumulation in human VSMCs, we used a CRISPR/Cas9 guided nuclease approach to generate human VSMCs knockout for Wnt5a. Results: We show that Wnt5a is a crucial component of the lysosomal cholesterol export machinery. By increasing lysosomal acid lipase expression, decreasing metabolic signaling by the mTORC1 kinase, and through binding to NPC1 and NPC2, Wnt5a senses changes in dietary cholesterol supply and promotes lysosomal cholesterol egress to the endoplasmic reticulum (ER). Consequently, loss of Wnt5a decoupled mTORC1 from variations in lysosomal sterol levels, disrupted lysosomal function, decreased cholesterol content in the ER, and promoted atherosclerosis. Conclusions: These results reveal an unexpected function of the Wnt5a pathway as essential for maintaining cholesterol homeostasis in vivo.

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A therapy with miglustat, 2-hydroxypropyl-ß-cyclodextrin and allopregnanolone restores splenic cholesterol homeostasis in Niemann-pick disease type C1

Lipids in Health and Disease ◽

10.1186/s12944-019-1088-2 ◽

2019 ◽

Vol 18 (1) ◽

Cited By ~ 6

Author(s):

Anna-Maria Neßlauer ◽

Anne Gläser ◽

Markus Gräler ◽

Robby Engelmann ◽

Brigitte Müller-Hilke ◽

...

Keyword(s):

Disease Type ◽

Cholesterol Homeostasis ◽

Niemann Pick Disease ◽

Niemann Pick ◽

Pick Disease

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Multiple mechanisms limit the accumulation of unesterified cholesterol in the small intestine of mice deficient in both ACAT2 and ABCA1

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00190.2010 ◽

2010 ◽

Vol 299 (5) ◽

pp. G1012-G1022 ◽

Cited By ~ 25

Author(s):

Stephen D. Turley ◽

Mark A. Valasek ◽

Joyce J. Repa ◽

John M. Dietschy

Keyword(s):

Small Intestine ◽

Mrna Level ◽

Cholesterol Absorption ◽

Cholesterol Homeostasis ◽

High Cholesterol Diet ◽

Unesterified Cholesterol ◽

Compensatory Mechanisms ◽

Niemann Pick ◽

Sterol Excretion ◽

Deficient Mice

Cholesterol homeostasis in the enterocyte is regulated by the interplay of multiple genes that ultimately determines the net amount of cholesterol reaching the circulation from the small intestine. The effect of deleting these genes, particularly acyl CoA:cholesterol acyl transferase 2 (ACAT2), on cholesterol absorption and fecal sterol excretion is well documented. We also know that the intestinal mRNA level for adenosine triphosphate-binding cassette transporter A1 (ABCA1) increases in Acat2−/− mice. However, none of these studies has specifically addressed how ACAT2 deficiency impacts the relative proportions of esterified and unesterified cholesterol (UC) in the enterocyte and whether the concurrent loss of ABCA1 might result in a marked buildup of UC. Therefore, the present studies measured the expression of numerous genes and related metabolic parameters in the intestine and liver of ACAT2-deficient mice fed diets containing either added cholesterol or ezetimibe, a selective sterol absorption inhibitor. Cholesterol feeding raised the concentration of UC in the small intestine, and this was accompanied by a significant reduction in the relative mRNA level for Niemann-Pick C1-like 1 (NPC1L1) and an increase in the mRNA level for both ABCA1 and ABCG5/8. All these changes were reversed by ezetimibe. When mice deficient in both ACAT2 and ABCA1 were fed a high-cholesterol diet, the increase in intestinal UC levels was no greater than it was in mice lacking only ACAT2. This resulted from a combination of compensatory mechanisms including diminished NPC1L1-mediated cholesterol uptake, increased cholesterol efflux via ABCG5/8, and possibly rapid cell turnover.

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