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Hubler Z, Friedrich RM, Sax JL, Allimuthu D, Gao F, Rivera-León AM, Pleshinger MJ, Bederman I, Adams DJ. Modulation of lanosterol synthase drives 24,25-epoxysterol synthesis and oligodendrocyte formation. Cell Chem Biol 2021; 28:866-875.e5. [PMID: 33636107 PMCID: PMC8217109 DOI: 10.1016/j.chembiol.2021.01.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 12/23/2020] [Accepted: 01/28/2021] [Indexed: 02/07/2023]
Abstract
Small molecules that promote the formation of new myelinating oligodendrocytes from oligodendrocyte progenitor cells (OPCs) are potential therapeutics for demyelinating diseases. We recently established inhibition of specific cholesterol biosynthesis enzymes and resulting accumulation of 8,9-unsaturated sterols as a unifying mechanism through which many such molecules act. To identify more potent sterol enhancers of oligodendrocyte formation, we synthesized a collection of 8,9-unsaturated sterol derivatives and found that 24,25-epoxylanosterol potently promoted oligodendrocyte formation. In OPCs, 24,25-epoxylanosterol was metabolized to 24,25-epoxycholesterol via the epoxycholesterol shunt pathway. Increasing flux through the epoxycholesterol shunt using genetic manipulation or small-molecule inhibition of lanosterol synthase (LSS) increased endogenous 24,25-epoxycholesterol levels and OPC differentiation. Notably, exogenously supplied 24,25-epoxycholesterol promoted oligodendrocyte formation despite lacking an 8,9-unsaturation. This work highlights epoxycholesterol shunt usage, controlled by inhibitors of LSS, as a target to promote oligodendrocyte formation. Additionally, sterols beyond the 8,9-unsaturated sterols, including 24,25-epoxycholesterol, drive oligodendrocyte formation.
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Affiliation(s)
- Zita Hubler
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Ryan M Friedrich
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Joel L Sax
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Dharmaraja Allimuthu
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Farrah Gao
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Adrianna M Rivera-León
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Matthew J Pleshinger
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Ilya Bederman
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Drew J Adams
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
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A gas chromatography–mass spectrometry-based whole-cell screening assay for target identification in distal cholesterol biosynthesis. Nat Protoc 2019; 14:2546-2570. [DOI: 10.1038/s41596-019-0193-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 05/16/2019] [Indexed: 12/14/2022]
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Phospholipid Remodeling and Cholesterol Availability Regulate Intestinal Stemness and Tumorigenesis. Cell Stem Cell 2018; 22:206-220.e4. [PMID: 29395055 PMCID: PMC5807072 DOI: 10.1016/j.stem.2017.12.017] [Citation(s) in RCA: 183] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 10/31/2017] [Accepted: 12/20/2017] [Indexed: 02/02/2023]
Abstract
Adequate availability of cellular building blocks, including lipids, is a prerequisite for cellular proliferation, but excess dietary lipids are linked to increased cancer risk. Despite these connections, specific regulatory relationships between membrane composition, intestinal stem cell (ISC) proliferation, and tumorigenesis are unclear. We reveal an unexpected link between membrane phospholipid remodeling and cholesterol biosynthesis and demonstrate that cholesterol itself acts as a mitogen for ISCs. Inhibition of the phospholipid-remodeling enzyme Lpcat3 increases membrane saturation and stimulates cholesterol biosynthesis, thereby driving ISC proliferation. Pharmacologic inhibition of cholesterol synthesis normalizes crypt hyperproliferation in Lpcat3-deficient organoids and mice. Conversely, increasing cellular cholesterol content stimulates crypt organoid growth, and providing excess dietary cholesterol or driving endogenous cholesterol synthesis through SREBP-2 expression promotes ISC proliferation in vivo. Finally, disruption of Lpcat3-dependent phospholipid and cholesterol homeostasis dramatically enhances tumor formation in Apcmin mice. These findings identify a critical dietary-responsive phospholipid-cholesterol axis regulating ISC proliferation and tumorigenesis.
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Engelking LJ, Cantoria MJ, Xu Y, Liang G. Developmental and extrahepatic physiological functions of SREBP pathway genes in mice. Semin Cell Dev Biol 2017; 81:98-109. [PMID: 28736205 DOI: 10.1016/j.semcdb.2017.07.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/07/2017] [Indexed: 12/17/2022]
Abstract
Sterol regulatory element-binding proteins (SREBPs), master transcriptional regulators of cholesterol and fatty acid synthesis, have been found to contribute to a diverse array of cellular processes. In this review, we focus on genetically engineered mice in which the activities of six components of the SREBP gene pathway, namely SREBP-1, SREBP-2, Scap, Insig-1, Insig-2, or Site-1 protease have been altered through gene knockout or transgenic approaches. In addition to the expected impacts on lipid metabolism, manipulation of these genes in mice is found to affect a wide array of developmental and physiologic processes ranging from interferon signaling in macrophages to synaptic transmission in the brain. The findings reviewed herein provide a blueprint to guide future studies defining the complex interactions between lipid biology and the physiologic processes of many distinct organ systems.
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Affiliation(s)
- Luke J Engelking
- Departments of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Mary Jo Cantoria
- Departments of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yanchao Xu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Guosheng Liang
- Departments of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Chuang JC, Lopez AM, Turley SD. Quantitation of the rates of hepatic and intestinal cholesterol synthesis in lysosomal acid lipase-deficient mice before and during treatment with ezetimibe. Biochem Pharmacol 2017; 135:116-125. [PMID: 28322747 PMCID: PMC5489310 DOI: 10.1016/j.bcp.2017.03.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 03/14/2017] [Indexed: 01/28/2023]
Abstract
Esterified cholesterol (EC) and triglycerides, contained within lipoproteins taken up by cells, are hydrolysed by lysosomal acid lipase (LAL) in the late endosomal/lysosomal (E/L) compartment. The resulting unesterified cholesterol (UC) is transported via Niemann-Pick type C2 and C1 into the cytosolic compartment where it enters a putative pool of metabolically active cholesterol that is utilized in accordance with cellular needs. Loss-of-function mutations in LIPA, the gene encoding LAL, result in dramatic increases in tissue concentrations of EC, a hallmark feature of Wolman disease and cholesteryl ester storage disease (CESD). The lysosomal sequestration of EC causes cells to respond to a perceived deficit of sterol by increasing their rate of cholesterol synthesis, particularly in the liver. A similar compensatory response occurs with treatments that disrupt the enterohepatic movement of cholesterol or bile acids. Here we measured rates of cholesterol synthesis in vivo in the liver and small intestine of a mouse model for CESD given the cholesterol absorption inhibitor ezetimibe from weaning until early adulthood. Consistent with previous findings, this treatment significantly reduced the amount of EC sequestered in the liver (from 132.43±7.35 to 70.07±6.04mg/organ) and small intestine (from 2.78±0.21 to 1.34±0.09mg/organ) in the LAL-deficient mice even though their rates of hepatic and intestinal cholesterol synthesis were either comparable to, or exceeded those in matching untreated Lal-/- mice. These data reveal the role of intestinal cholesterol absorption in driving the expansion of tissue EC content and disease progression in LAL deficiency.
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Affiliation(s)
- Jen-Chieh Chuang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Adam M Lopez
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Stephen D Turley
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
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Lopez AM, Chuang JC, Turley SD. Measurement of Rates of Cholesterol and Fatty Acid Synthesis In Vivo Using Tritiated Water. Methods Mol Biol 2017; 1583:241-256. [PMID: 28205179 DOI: 10.1007/978-1-4939-6875-6_18] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Every organ in the body is capable of synthesizing cholesterol de novo but at rates that vary with a constellation of factors. A significant proportion of the hydrogen atoms present in cholesterol that is synthesized in the body are derived from water. Thus, although water ordinarily makes up the bulk of body mass, the acute enrichment of the body water pool with a sufficiently large amount of tritiated water over a short interval of time (usually 1 h) yields measurable rates of incorporation of the labeled water into newly generated cholesterol and also fatty acids. Such data can provide a quantitative measure of how specific genetic, dietary, and pharmacological manipulations impact not just the rate of cholesterol synthesis in particular organs but also rates of whole-body cholesterol production and turnover.
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Affiliation(s)
- Adam M Lopez
- Division of Digestive and Liver Diseases, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9151, USA
| | - Jen-Chieh Chuang
- Division of Digestive and Liver Diseases, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9151, USA
| | - Stephen D Turley
- Division of Digestive and Liver Diseases, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-9151, USA.
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Schonewille M, de Boer JF, Mele L, Wolters H, Bloks VW, Wolters JC, Kuivenhoven JA, Tietge UJF, Brufau G, Groen AK. Statins increase hepatic cholesterol synthesis and stimulate fecal cholesterol elimination in mice. J Lipid Res 2016; 57:1455-64. [PMID: 27313057 DOI: 10.1194/jlr.m067488] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Indexed: 12/19/2022] Open
Abstract
Statins are competitive inhibitors of HMG-CoA reductase, the rate-limiting enzyme of cholesterol synthesis. Statins reduce plasma cholesterol levels, but whether this is actually caused by inhibition of de novo cholesterol synthesis has not been clearly established. Using three different statins, we investigated the effects on cholesterol metabolism in mice in detail. Surprisingly, direct measurement of whole body cholesterol synthesis revealed that cholesterol synthesis was robustly increased in statin-treated mice. Measurement of organ-specific cholesterol synthesis demonstrated that the liver is predominantly responsible for the increase in cholesterol synthesis. Excess synthesized cholesterol did not accumulate in the plasma, as plasma cholesterol decreased. However, statin treatment led to an increase in cholesterol removal via the feces. Interestingly, enhanced cholesterol excretion in response to rosuvastatin and lovastatin treatment was mainly mediated via biliary cholesterol secretion, whereas atorvastatin mainly stimulated cholesterol removal via the transintestinal cholesterol excretion pathway. Moreover, we show that plasma cholesterol precursor levels do not reflect cholesterol synthesis rates during statin treatment in mice. In conclusion, cholesterol synthesis is paradoxically increased upon statin treatment in mice. However, statins potently stimulate the excretion of cholesterol from the body, which sheds new light on possible mechanisms underlying the cholesterol-lowering effects of statins.
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Affiliation(s)
- Marleen Schonewille
- Department of Pediatrics University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jan Freark de Boer
- Department of Pediatrics, Section Molecular Genetics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Laura Mele
- Department of Pediatrics University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Henk Wolters
- Department of Pediatrics University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Vincent W Bloks
- Department of Pediatrics University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Justina C Wolters
- Department of Pediatrics, Section Molecular Genetics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jan A Kuivenhoven
- Department of Pediatrics, Section Molecular Genetics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Uwe J F Tietge
- Department of Pediatrics University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Gemma Brufau
- Department of Pediatrics University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Albert K Groen
- Department of Pediatrics University Medical Center Groningen, University of Groningen, Groningen, The Netherlands Department of Laboratory Medicine, Center for Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands Amsterdam Diabetes Center, Department of Vascular Medicine, Academic Medical Center, The Netherlands
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The cholesterol biosynthesis enzyme oxidosqualene cyclase is a new target to impair tumour angiogenesis and metastasis dissemination. Sci Rep 2015; 5:9054. [PMID: 25761781 PMCID: PMC4357009 DOI: 10.1038/srep09054] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 02/16/2015] [Indexed: 12/13/2022] Open
Abstract
Aberrant cholesterol homeostasis and biosynthesis has been observed in different tumour types. This paper investigates the role of the post-squalenic enzyme of cholesterol biosynthesis, oxidosqualene cyclase (OSC), in regulating tumour angiogenesis and metastasis dissemination in mouse models of cancer. We showed that Ro 48-8071, a selective inhibitor of OSC, reduced vascular density and increased pericyte coverage, with a consequent inhibition of tumour growth in a spontaneous mouse model of pancreatic tumour (RIP-Tag2) and two metastatic mouse models of human colon carcinoma (HCT116) and pancreatic adenocarcinoma (HPAF-II). Remarkably, the inhibition of OSC hampered metastasis formation in HCT116 and HPAF-II models. Ro 48-8071 induced tumour vessel normalization and enhanced the anti-tumoral and anti-metastatic effects of 5-fluorouracil (5-FU) in HCT116 mice. Ro 48-8071 exerted a strong anti-angiogenic activity by impairing endothelial cell adhesion and migration, and by blocking vessel formation in angiogenesis assays. OSC inhibition specifically interfered with the PI3K pathway. According to in vitro results, Ro 48-8071 specifically inhibited Akt phosphorylation in both cancer cells and tumour vasculature in all treated models. Thus, our results unveil a crucial role of OSC in the regulation of cancer progression and tumour angiogenesis, and indicate Ro 48-8071 as a potential novel anti-angiogenic and anti-metastatic drug.
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Jones RD, Lopez AM, Tong EY, Posey KS, Chuang JC, Repa JJ, Turley SD. Impact of physiological levels of chenodeoxycholic acid supplementation on intestinal and hepatic bile acid and cholesterol metabolism in Cyp7a1-deficient mice. Steroids 2015; 93:87-95. [PMID: 25447797 PMCID: PMC4297738 DOI: 10.1016/j.steroids.2014.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 11/07/2014] [Indexed: 01/07/2023]
Abstract
Mice deficient in cholesterol 7α-hydroxylase (Cyp7a1) have a diminished bile acid pool (BAP) and therefore represent a useful model for investigating the metabolic effects of restoring the pool with a specific BA. Previously we carried out such studies in Cyp7a1(-/-) mice fed physiological levels of cholic acid (CA) and achieved BAP restoration, along with an increased CA enrichment, at a dietary level of just 0.03% (w/w). Here we demonstrate that in Cyp7a1(-/-) mice fed chenodeoxycholic acid (CDCA) at a level of 0.06% (w/w), the BAP was restored to normal size and became substantially enriched with muricholic acid (MCA) (>70%), leaving the combined contribution of CA and CDCA to be <15%. This resulted in a partial to complete reversal of the main changes in cholesterol and BA metabolism associated with Cyp7a1 deficiency such as an elevated rate of intestinal sterol synthesis, an enhanced level of mRNA for Cyp8b1 in the liver, and depressed mRNA levels for Ibabp, Shp and Fgf15 in the distal small intestine. When Cyp7a1(-/-) and matching Cyp7a1(+/+) mice were fed a diet with added cholesterol (0.2%) (w/w), either alone, or also containing CDCA (0.06%) (w/w) or CA (0.03%) (w/w) for 18days, the hepatic total cholesterol concentrations (mg/g) in the Cyp7a1(-/-) mice were 26.9±3.7, 16.4±0.9 and 47.6±1.9, respectively, vs. 4.9±0.4, 5.0±0.7 and 6.4±1.9, respectively in the corresponding Cyp7a1(+/+) controls. These data affirm the importance of using moderate levels of dietary BA supplementation to elicit changes in hepatic cholesterol metabolism through shifts in BAP size and composition.
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Affiliation(s)
- Ryan D Jones
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Adam M Lopez
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Ernest Y Tong
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Kenneth S Posey
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Jen-Chieh Chuang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Joyce J Repa
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States; Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Stephen D Turley
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
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Aqul A, Lopez AM, Posey KS, Taylor AM, Repa JJ, Burns DK, Turley SD. Hepatic entrapment of esterified cholesterol drives continual expansion of whole body sterol pool in lysosomal acid lipase-deficient mice. Am J Physiol Gastrointest Liver Physiol 2014; 307:G836-47. [PMID: 25147230 PMCID: PMC4200320 DOI: 10.1152/ajpgi.00243.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cholesteryl ester storage disease (CESD) results from loss-of-function mutations in LIPA, the gene that encodes lysosomal acid lipase (LAL). Hepatomegaly and deposition of esterified cholesterol (EC) in multiple organs ensue. The present studies quantitated rates of synthesis, absorption, and disposition of cholesterol, and whole body cholesterol pool size in a mouse model of CESD. In 50-day-old lal(-/-) and matching lal(+/+) mice fed a low-cholesterol diet, whole animal cholesterol content equalled 210 and 50 mg, respectively, indicating that since birth the lal(-/-) mice sequestered cholesterol at an average rate of 3.2 mg·day(-1)·animal(-1). The proportion of the body sterol pool contained in the liver of the lal(-/-) mice was 64 vs. 6.3% in their lal(+/+) controls. EC concentrations in the liver, spleen, small intestine, and lungs of the lal(-/-) mice were elevated 100-, 35-, 15-, and 6-fold, respectively. In the lal(-/-) mice, whole liver cholesterol synthesis increased 10.2-fold, resulting in a 3.2-fold greater rate of whole animal sterol synthesis compared with their lal(+/+) controls. The rate of cholesterol synthesis in the lal(-/-) mice exceeded that in the lal(+/+) controls by 3.7 mg·day(-1)·animal(-1). Fractional cholesterol absorption and fecal bile acid excretion were unchanged in the lal(-/-) mice, but their rate of neutral sterol excretion was 59% higher than in their lal(+/+) controls. Thus, in this model, the continual expansion of the body sterol pool is driven by the synthesis of excess cholesterol, primarily in the liver. Despite the severity of their disease, the median life span of the lal(-/-) mice was 355 days.
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Affiliation(s)
- Amal Aqul
- 2Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas;
| | - Adam M. Lopez
- 1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas;
| | - Kenneth S. Posey
- 1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas;
| | - Anna M. Taylor
- 3Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Joyce J. Repa
- 1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; ,3Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Dennis K. Burns
- 4Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Stephen D. Turley
- 1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas;
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