Publications by authors named "Janet K Sawyer"

27 Publications

  • Page 1 of 1

Targeted Deletion of Hepatocyte Abca1 Increases Plasma HDL (High-Density Lipoprotein) Reverse Cholesterol Transport via the LDL (Low-Density Lipoprotein) Receptor.

Arterioscler Thromb Vasc Biol 2019 09 6;39(9):1747-1761. Epub 2019 Jun 6.

From the Department of Internal Medicine, Section of Molecular Medicine (A.C.B., M.L., C-C.C.K., E.B., X.W., J.K.S., J.S.P.), Wake Forest School of Medicine, Winston-Salem, NC.

Objective: The role of hepatocyte Abca1 (ATP binding cassette transporter A1) in trafficking hepatic free cholesterol (FC) into plasma versus bile for reverse cholesterol transport (RCT) is poorly understood. We hypothesized that hepatocyte Abca1 recycles plasma HDL-C (high-density lipoprotein cholesterol) taken up by the liver back into plasma, maintaining the plasma HDL-C pool, and decreasing HDL-mediated RCT into feces. Approach and Results: Chow-fed hepatocyte-specific Abca1 knockout (HSKO) and control mice were injected with human HDL radiolabeled with I-tyramine cellobiose (I-TC; protein) and H-cholesteryl oleate (H-CO). I-TC and H-CO plasma decay, plasma HDL H-CO selective clearance (ie, H-I fractional catabolic rate), liver radiolabel uptake, and fecal H-sterol were significantly greater in HSKO versus control mice, supporting increased plasma HDL RCT. Twenty-four hours after H-CO-HDL injection, HSKO mice had reduced total hepatic H-FC (ie, H-CO hydrolyzed to H-FC in liver) resecretion into plasma, demonstrating Abca1 recycled HDL-derived hepatic H-FC back into plasma. Despite similar liver LDLr (low-density lipoprotein receptor) expression between genotypes, HSKO mice treated with LDLr-targeting versus control antisense oligonucleotide had slower plasma H-CO-HDL decay, reduced selective H-CO clearance, and decreased fecal H-sterol excretion that was indistinguishable from control mice. Increased RCT in HSKO mice was selective for H-CO-HDL, since macrophage RCT was similar between genotypes.

Conclusions: Hepatocyte Abca1 deletion unmasks a novel and selective FC trafficking pathway that requires LDLr expression, accelerating plasma HDL-selective CE uptake by the liver and promoting HDL RCT into feces, consequently reducing HDL-derived hepatic FC recycling into plasma.
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http://dx.doi.org/10.1161/ATVBAHA.119.312382DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6703909PMC
September 2019

Feeding of tobacco blend or nicotine induced weight loss associated with decreased adipocyte size and increased physical activity in male mice.

Food Chem Toxicol 2018 Mar 5;113:287-295. Epub 2018 Feb 5.

Departments of Internal Medicine, Section on Molecular Medicine, Winston-Salem, NC 27157, USA; Biochemistry, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA. Electronic address:

Although epidemiological data and results from rodent studies support an inverse relationship between nicotine consumption and body weight, the molecular mechanisms are poorly understood. CD-1 mice were fed a basal diet or a basal diet containing low or high dose smokeless tobacco blend or high dose nicotine tartrate for 14 weeks. High dose tobacco blend and nicotine tartrate diets vs. basal diet reduced mouse body weight (16.3% and 19.7%, respectively), epididymal (67.6% and 72.5%, respectively) and brown adipose weight (42% and 38%, respectively), epididymal adipocyte size (46.4% and 41.4%, respectively), and brown adipose tissue lipid droplet abundance, with no elevation of adipose tissue inflammation. High dose tobacco blend and nicotine diets also increased mouse physical activity and decreased respiratory exchange ratio, suggesting that high dose nicotine intake induces adipose tissue triglyceride lipolysis to provide fatty acids as an energy source. Both low and high dose tobacco blend and nicotine diet feeding vs. basal diet increased plasma insulin levels (2.9, 3.6 and 4.3-fold, respectively) and improved blood glucose disposal without affecting insulin sensitivity. Feeding of the high dose tobacco blend or nicotine feeding in mice induces body weight loss likely by increasing physical activity and stimulating adipose tissue triglyceride lipolysis.
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http://dx.doi.org/10.1016/j.fct.2018.01.058DOI Listing
March 2018

Targeted Deletion of Adipocyte Abca1 (ATP-Binding Cassette Transporter A1) Impairs Diet-Induced Obesity.

Arterioscler Thromb Vasc Biol 2018 04 18;38(4):733-743. Epub 2018 Jan 18.

From the Section on Molecular Medicine, Department of Internal Medicine (H.C., M.L., C.-C.C.K., E.B., J.K.S., A.W., A.B., J.S.P.) and Department of Biochemistry (J.S.P.), Wake Forest School of Medicine, Winston-Salem, NC; Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York (S.K.F.); and Department of Nutrition and Health Sciences, University of Nebraska, Lincoln, NE (S.C.).

Objective: Adipose tissue cholesterol increases with adipocyte triglyceride content and size during development of obesity. However, how adipocyte cholesterol affects adipocyte function is poorly understood. The aim of this study was to evaluate the role of the cellular cholesterol exporter, Abca1 (ATP-binding cassette transporter A1), on adipose tissue function during diet-induced obesity.

Approach And Results: Adiponectin recombinase transgenic mice were crossed with mice to generate ASKO (adipocyte-specific knockout) mice. Control and ASKO mice were then fed a high-fat, high-cholesterol (45% calories as fat and 0.2% cholesterol) diet for 16 weeks. Compared with control mice, ASKO mice had a 2-fold increase in adipocyte plasma membrane cholesterol content and significantly lower body weight, epididymal fat pad weight, and adipocyte size. ASKO versus control adipose tissue had decreased PPARγ (peroxisome proliferator-activated receptor γ) and CCAAT/enhancer-binding protein expression, nuclear SREBP1 (sterol regulatory element-binding protein 1) protein, lipogenesis, and triglyceride accretion but similar Akt activation after acute insulin stimulation. Acute siRNA-mediated silencing during 3T3L1 adipocyte differentiation reduced adipocyte Abca1 and PPARγ protein expression and triglyceride content. Systemic stimulated triglyceride lipolysis and glucose homeostasis were similar between control and ASKO mice.

Conclusions: Adipocyte Abca1 is a key regulator of adipocyte lipogenesis and lipid accretion, likely because of increased adipose tissue membrane cholesterol, resulting in decreased activation of lipogenic transcription factors PPARγ and SREBP1.
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http://dx.doi.org/10.1161/ATVBAHA.117.309880DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864538PMC
April 2018

In vivo activation of leukocyte GPR120/FFAR4 by PUFAs has minimal impact on atherosclerosis in LDL receptor knockout mice.

J Lipid Res 2017 01 3;58(1):236-246. Epub 2016 Nov 3.

Departments of Internal Medicine/Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157

G protein-coupled receptor (GPR)120/FFA receptor (FFAR)4 (GPR120/FFAR4) activation by n-3 PUFAs attenuates inflammation, but its impact on atherosclerosis is unknown. We determined whether in vivo activation of leukocyte GPR120/FFAR4 by n-3 versus n-6 PUFAs is atheroprotective. Leukocyte GPR120/FFAR4 WT or KO mice in the LDL receptor KO background were generated by bone marrow transplantation. Mice were fed one of the four atherogenic diets containing 0.2% cholesterol and 10% calories as palm oil (PO) + 10% calories as: 1) PO, 2) fish oil (FO; 20:5 n-3 and 22:6 n-3 enriched), 3) echium oil (EO; 18:4 n-3 enriched), or 4) borage oil (BO; 18:3 n-6 enriched) for 16 weeks. Compared with PO, mice fed BO, EO, and FO had significantly reduced plasma cholesterol, TG, VLDL cholesterol, hepatic neutral lipid, and atherosclerosis that were equivalent for WT and KO mice. In BO-, EO-, and FO-fed mice, but not PO-fed mice, lack of leukocyte GPR120/FFAR4 resulted in neutrophilia, pro-inflammatory Ly6C monocytosis, increased aortic root monocyte recruitment, and increased hepatic inflammatory gene expression. In conclusion, leukocyte GPR120 expression has minimal effects on dietary PUFA-induced plasma lipid/lipoprotein reduction and atheroprotection, and there is no distinction between n-3 versus n-6 PUFAs in activating anti-inflammatory effects of leukocyte GPR120/FFAR4 in vivo.
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http://dx.doi.org/10.1194/jlr.M072769DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5234726PMC
January 2017

Targeted Knockdown of Hepatic SOAT2 With Antisense Oligonucleotides Stabilizes Atherosclerotic Plaque in ApoB100-only LDLr-/- Mice.

Arterioscler Thromb Vasc Biol 2015 Sep 30;35(9):1920-7. Epub 2015 Jul 30.

From the Department of Pathology, Section on Lipid Sciences (J.T.M., K.L.K., M.D.W., J.K.S., L.L.R.), and Department of Radiology, Center for Biomolecular Imaging (J.D.O., K.M.L.), Wake Forest University Health Sciences, Winston-Salem, NC.

Objective: To test the hypothesis that the attenuation of cholesterol oleate packaging into apoB-containing lipoproteins will arrest progression of pre-existing atherosclerotic lesions.

Approach And Results: Atherosclerosis was induced in apoB-100 only, LDLr(-/-) mice by feeding a diet enriched in cis-monounsaturated fatty acids for 24 weeks. A subset of mice was then euthanized to quantify the extent of atherosclerosis. The remaining mice were continued on the same diet (controls) or assigned to the following treatments for 16 weeks: (1) a diet enriched in n-3 polyunsaturated fatty acids, (2) the cis-monounsaturated fatty acid diet plus biweekly injections of an antisense oligonucleotide specific to hepatic sterol-O-acyltransferase 2 (SOAT2); or (3) the cis-monounsaturated fatty acid diet and biweekly injections of a nontargeting hepatic antisense oligonucleotide. Extent of atherosclerotic lesions in the aorta was monitored morphometrically in vivo with magnetic resonance imaging and ex vivo histologically and immunochemically. Hepatic knockdown of SOAT2 via antisense oligonucleotide treatment arrested lesion growth and stabilized lesions.

Conclusions: Hepatic knockdown of SOAT2 in apoB100-only, LDLr(-/-) mice resulted in remodeling of aortic atherosclerotic lesions into a stable phenotype, suggesting SOAT2 is a viable target for the treatment of atherosclerosis.
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http://dx.doi.org/10.1161/ATVBAHA.115.305747DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4552612PMC
September 2015

Cholesterol esters (CE) derived from hepatic sterol O-acyltransferase 2 (SOAT2) are associated with more atherosclerosis than CE from intestinal SOAT2.

Circ Res 2014 Oct 19;115(10):826-33. Epub 2014 Sep 19.

From the Section on Molecular Medicine, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC (J.Z., J.K.S., S.M.M., K.L.K., M.A.D., M.D.W., L.L.R.); and Department of Cellular and Molecular Medicine, Cleveland Clinic Lerner Research Institute, OH (S.M.M., J.M.B.).

Rationale: Cholesterol esters (CE), especially cholesterol oleate, generated by hepatic and intestinal sterol O-acyltransferase 2 (SOAT2) play a critical role in cholesterol homeostasis. However, it is unknown whether the contribution of intestine-derived CE from SOAT2 would have similar effects in promoting atherosclerosis progression as for liver-derived CE.

Objective: To test whether, in low-density lipoprotein receptor null (LDLr(-/-)) mice, the conditional knockout of intestinal SOAT2 (SOAT2(SI-/SI-)) or hepatic SOAT2 (SOAT2(L-/L-)) would equally limit atherosclerosis development compared with the global deletion of SOAT2 (SOAT2(-/-)).

Methods And Results: SOAT2 conditional knockout mice were bred with LDLr(-/-) mice creating LDLr(-/-) mice with each of the specific SOAT2 gene deletions. All mice then were fed an atherogenic diet for 16 weeks. SOAT2(SI-/SI-)LDLr(-/-) and SOAT2(-/-)LDLr(-/-) mice had significantly lower levels of intestinal cholesterol absorption, more fecal sterol excretion, and lower biliary cholesterol levels. Analysis of plasma LDL showed that all mice with SOAT2 gene deletions had LDL CE with reduced percentages of cholesterol palmitate and cholesterol oleate. Each of the LDLr(-/-) mice with SOAT2 gene deletions had lower accumulations of total cholesterol and CE in the liver compared with control mice. Finally, aortic atherosclerosis development was significantly lower in all mice with global or tissue-restricted SOAT2 gene deletions. Nevertheless, SOAT2(-/-)LDLr(-/-) and SOAT2(L-/L-)LDLr(-/-) mice had less aortic CE accumulation and smaller aortic lesions than SOAT2(SI-/SI-)LDLr(-/-) mice.

Conclusions: SOAT2-derived CE from both the intestine and liver significantly contribute to the development of atherosclerosis, although the CE from the hepatic enzyme appeared to promote more atherosclerosis development.
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http://dx.doi.org/10.1161/CIRCRESAHA.115.304378DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4209196PMC
October 2014

LDL particle core enrichment in cholesteryl oleate increases proteoglycan binding and promotes atherosclerosis.

J Lipid Res 2013 Sep 26;54(9):2495-503. Epub 2013 Jun 26.

Department of Pathology, Section of Lipid Sciences, Wake Forest University School of Medicine, Winston Salem, NC, USA.

Several studies in humans and animals suggest that LDL particle core enrichment in cholesteryl oleate (CO) is associated with increased atherosclerosis. Diet enrichment with MUFAs enhances LDL CO content. Steroyl O-acyltransferase 2 (SOAT2) is the enzyme that catalyzes the synthesis of much of the CO found in LDL, and gene deletion of SOAT2 minimizes CO in LDL and protects against atherosclerosis. The purpose of this study was to test the hypothesis that the increased atherosclerosis associated with LDL core enrichment in CO results from an increased affinity of the LDL particle for arterial proteoglycans. ApoB-100-only Ldlr(-/-) mice with and without Soat2 gene deletions were fed diets enriched in either cis-MUFA or n-3 PUFA, and LDL particles were isolated. LDL:proteogylcan binding was measured using surface plasmon resonance. Particles with higher CO content consistently bound with higher affinity to human biglycan and the amount of binding was shown to be proportional to the extent of atherosclerosis of the LDL donor mice. The data strongly support the thesis that atherosclerosis was induced through enhanced proteoglycan binding of LDL resulting from LDL core CO enrichment.
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http://dx.doi.org/10.1194/jlr.M039644DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3735946PMC
September 2013

Intestinal SR-BI does not impact cholesterol absorption or transintestinal cholesterol efflux in mice.

J Lipid Res 2013 Jun 5;54(6):1567-77. Epub 2013 Apr 5.

Department of Pathology, Section on Lipid Sciences, Wake Forest School of Medicine, Winston-Salem, NC, USA.

Reverse cholesterol transport (RCT) can proceed through the classic hepatobiliary route or through the nonbiliary transintestinal cholesterol efflux (TICE) pathway. Scavenger receptor class B type I (SR-BI) plays a critical role in the classic hepatobiliary route of RCT. However, the role of SR-BI in TICE has not been studied. To examine the role of intestinal SR-BI in TICE, sterol balance was measured in control mice and mice transgenically overexpressing SR-BI in the proximal small intestine (SR-BI(hApoCIII-ApoAIV-Tg)). SR-BI(hApoCIII-ApoAIV-Tg) mice had significantly lower plasma cholesterol levels compared with wild-type controls, yet SR-BI(hApoCIII-ApoAIV-Tg) mice had normal fractional cholesterol absorption and fecal neutral sterol excretion. Both in the absence or presence of ezetimibe, intestinal SR-BI overexpression had no impact on the amount of cholesterol excreted in the feces. To specifically study effects of intestinal SR-BI on TICE we crossed SR-BI(hApoCIII-ApoAIV-Tg) mice into a mouse model that preferentially utilized the TICE pathway for RCT (Niemann-Pick C1-like 1 liver transgenic), and likewise found no alterations in cholesterol absorption or fecal sterol excretion. Finally, mice lacking SR-BI in all tissues also exhibited normal cholesterol absorption and fecal cholesterol disposal. Collectively, these results suggest that SR-BI is not rate limiting for intestinal cholesterol absorption or for fecal neutral sterol loss through the TICE pathway.
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http://dx.doi.org/10.1194/jlr.M034454DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3646458PMC
June 2013

Phytosterol feeding causes toxicity in ABCG5/G8 knockout mice.

Am J Pathol 2013 Apr 1;182(4):1131-8. Epub 2013 Feb 1.

Section on Lipid Sciences, Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.

Plant sterols, or phytosterols, are very similar in structure to cholesterol and are abundant in typical diets. The reason for poor absorption of plant sterols by the body is still unknown. Mutations in the ABC transporters G5 and G8 are known to cause an accumulation of plant sterols in blood and tissues (sitosterolemia). To determine the significance of phytosterol exclusion from the body, we fed wild-type and ABCG5/G8 knockout mice a diet enriched with plant sterols. The high-phytosterol diet was extremely toxic to the ABCG5/G8 knockout mice but had no adverse effects on wild-type mice. ABCG5/G8 knockout mice died prematurely and developed a phenotype that included high levels of plant sterols in many tissues, liver abnormalities, and severe cardiac lesions. This study is the first to report such toxic effects of phytosterol accumulation in ABCG5/G8 knockout mice. We believe these new data support the conclusion that plant sterols are excluded from the body because they are toxic when present at high levels.
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http://dx.doi.org/10.1016/j.ajpath.2012.12.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3620394PMC
April 2013

Scavenger receptor class B type I is a plasma membrane cholesterol sensor.

Circ Res 2013 Jan 28;112(1):140-51. Epub 2012 Sep 28.

Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA.

Rationale: Signal initiation by the high-density lipoprotein (HDL) receptor scavenger receptor class B, type I (SR-BI), which is important to actions of HDL on endothelium and other processes, requires cholesterol efflux and the C-terminal transmembrane domain. The C-terminal transmembrane domain uniquely interacts with plasma membrane (PM) cholesterol.

Objective: The molecular basis and functional significance of SR-BI interaction with PM cholesterol are unknown. We tested the hypotheses that the interaction is required for SR-BI signaling, and that it enables SR-BI to serve as a PM cholesterol sensor.

Methods And Results: In studies performed in COS-M6 cells, mutation of a highly conserved C-terminal transmembrane domain glutamine to alanine (SR-BI-Q445A) decreased PM cholesterol interaction with the receptor by 71% without altering HDL binding or cholesterol uptake or efflux, and it yielded a receptor incapable of HDL-induced signaling. Signaling prompted by cholesterol efflux to methyl-β-cyclodextrin also was prevented, indicating that PM cholesterol interaction with the receptor enables it to serve as a PM cholesterol sensor. Using SR-BI-Q445A, we further demonstrated that PM cholesterol sensing by SR-BI does not influence SR-BI-mediated reverse cholesterol transport to the liver in mice. However, the PM cholesterol sensing does underlie apolipoprotein B intracellular trafficking in response to postprandial micelles or methyl-β-cyclodextrin in cultured enterocytes, and it is required for HDL activation of endothelial NO synthase and migration in cultured endothelial cells and HDL-induced angiogenesis in vivo.

Conclusions: Through interaction with PM cholesterol, SR-BI serves as a PM cholesterol sensor, and the resulting intracellular signaling governs processes in both enterocytes and endothelial cells.
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http://dx.doi.org/10.1161/CIRCRESAHA.112.280081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3564583PMC
January 2013

ACAT2 and ABCG5/G8 are both required for efficient cholesterol absorption in mice: evidence from thoracic lymph duct cannulation.

J Lipid Res 2012 Aug 5;53(8):1598-609. Epub 2012 Jun 5.

Department of Pathology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.

The metabolic fate of newly absorbed cholesterol and phytosterol is orchestrated through adenosine triphosphate-binding cassette transporter G5 and G8 heterodimer (G5G8), and acyl CoA:cholesterol acyltransferase 2 (ACAT2). We hypothesized that intestinal G5G8 limits sterol absorption by reducing substrate availability for ACAT2 esterification and have attempted to define the roles of these two factors using gene deletion studies in mice. Male ACAT2(-/-), G5G8(-/-), ACAT2(-/-)G5G8(-/-) (DKO), and wild-type (WT) control mice were fed a diet with 20% of energy as palm oil and 0.2% (w/w) cholesterol. Sterol absorption efficiency was directly measured by monitoring the appearance of [(3)H]sitosterol and [(14)C]cholesterol tracers in lymph after thoracic lymph duct cannulation. The average percentage (± SEM) absorption of [(14)C]cholesterol after 8 h of lymph collection was 40.55 ± 0.76%, 19.41 ± 1.52%, 32.13 ± 1.60%, and 21.27 ± 1.35% for WT, ACAT2(-/-), G5G8(-/-), and DKO mice, respectively. [(3)H]sitosterol absorption was <2% in WT and ACAT2(-/-) mice, whereas it was up to 6.8% in G5G8(-/-) and DKO mice. G5G8(-/-) mice also produced chylomicrons with ∼70% less cholesterol ester mass than WT mice. In contrast to expectations, the data demonstrated that the absence of G5G8 led to decreased intestinal cholesterol esterification and reduced cholesterol transport efficiency. Intestinal G5G8 appeared to limit the absorption of phytosterols; ACAT2 more efficiently esterified cholesterol than phytosterols. The data indicate that handling of sterols by the intestine involves both G5G8 and ACAT2 but that an additional factor (possibly Niemann-Pick C1-like 1) may be key in determining absorption efficiency.
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http://dx.doi.org/10.1194/jlr.M026823DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3540850PMC
August 2012

Tissue-specific knockouts of ACAT2 reveal that intestinal depletion is sufficient to prevent diet-induced cholesterol accumulation in the liver and blood.

J Lipid Res 2012 Jun 29;53(6):1144-52. Epub 2012 Mar 29.

Section on Lipid Sciences, Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.

Acyl-CoA:cholesterol acyltransferase 2 (ACAT2) generates cholesterol esters (CE) for packaging into newly synthesized lipoproteins and thus is a major determinant of blood cholesterol levels. ACAT2 is expressed exclusively in the small intestine and liver, but the relative contributions of ACAT2 expression in these tissues to systemic cholesterol metabolism is unknown. We investigated whether CE derived from the intestine or liver would differentially affect hepatic and plasma cholesterol homeostasis. We generated liver-specific (ACAT2(L-/L-)) and intestine-specific (ACAT2(SI-/SI-)) ACAT2 knockout mice and studied dietary cholesterol-induced hepatic lipid accumulation and hypercholesterolemia. ACAT2(SI-/SI-) mice, in contrast to ACAT2(L-/L-) mice, had blunted cholesterol absorption. However, specific deletion of ACAT2 in the intestine generated essentially a phenocopy of the conditional knockout of ACAT2 in the liver, with reduced levels of plasma very low-density lipoprotein and hepatic CE, yet hepatic-free cholesterol does not build up after high cholesterol intake. ACAT2(L-/L-) and ACAT2(SI-/SI-) mice were equally protected from diet-induced hepatic CE accumulation and hypercholesterolemia. These results suggest that inhibition of intestinal or hepatic ACAT2 improves atherogenic hyperlipidemia and limits hepatic CE accumulation in mice and that depletion of intestinal ACAT2 is sufficient for most of the beneficial effects on cholesterol metabolism. Inhibitors of ACAT2 targeting either tissue likely would be beneficial for atheroprotection.
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http://dx.doi.org/10.1194/jlr.M024356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3351821PMC
June 2012

Cholesterol esterification by ACAT2 is essential for efficient intestinal cholesterol absorption: evidence from thoracic lymph duct cannulation.

J Lipid Res 2012 Jan 1;53(1):95-104. Epub 2011 Nov 1.

Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC, USA.

The hypothesis tested in this study was that cholesterol esterification by ACAT2 would increase cholesterol absorption efficiency by providing cholesteryl ester (CE) for incorporation into chylomicrons. The assumption was that absorption would be proportional to Acat2 gene dosage. Male ACAT2⁺/⁺, ACAT2⁺/⁻, and ACAT2⁻/⁻ mice were fed a diet containing 20% of energy as palm oil with 0.2% (w/w) cholesterol. Cholesterol absorption efficiency was measured by fecal dual-isotope and thoracic lymph duct cannulation (TLDC) methods using [³H]sitosterol and [¹⁴C]cholesterol tracers. Excellent agreement among individual mice was found for cholesterol absorption measured by both techniques. Cholesterol absorption efficiency in ACAT2⁻/⁻ mice was 16% compared with 46-47% in ACAT2⁺/⁺ and ACAT2⁺/⁻ mice. Chylomicrons from ACAT2⁺/⁺ and ACAT2⁺/⁻ mice carried ∼80% of total sterol mass as CE, whereas ACAT2⁻/⁻ chylomicrons carried >90% of sterol mass in the unesterified form. The total percentage of chylomicron mass as CE was reduced from 12% in the presence of ACAT2 to ∼1% in ACAT2⁻/⁻ mice. Altogether, the data demonstrate that ACAT2 increases cholesterol absorption efficiency by providing CE for chylomicron transport, but one copy of the Acat2 gene, providing ∼50% of ACAT2 mRNA and enzyme activity, was as effective as two copies in promoting cholesterol absorption.
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http://dx.doi.org/10.1194/jlr.M018820DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3243485PMC
January 2012

Adipose tissue ATP binding cassette transporter A1 contributes to high-density lipoprotein biogenesis in vivo.

Circulation 2011 Oct 19;124(15):1663-72. Epub 2011 Sep 19.

Department of Pathology/Section on Lipid Sciences, Wake Forest School of Medicine, Winston-Salem, NC, USA.

Background: Adipose tissue (AT) is the body's largest free cholesterol reservoir and abundantly expresses ATP binding cassette transporter A1 (ABCA1), a key cholesterol transporter for high-density lipoprotein (HDL) biogenesis. However, the extent to which AT ABCA1 expression contributes to HDL biogenesis in vivo is unknown.

Methods And Results: Adipocyte-specific ABCA1 knockout mice (ABCA1(-A/-A)) were generated by crossing ABCA1(floxed) mice with aP2Cre transgenic mice. AT from ABCA1(-A/-A) mice had <10% of wild-type ABCA1 protein expression but normal hepatic and intestinal expression. Deletion of adipocyte ABCA1 resulted in a significant decrease in plasma HDL cholesterol (approximately 15%) and apolipoprotein A-I (approximately 13%) concentrations. AT from ABCA1(-A/-A) mice had a 2-fold increase in free cholesterol content compared with wild-type mice and failed to efflux cholesterol to apolipoprotein A-I. However, cholesterol efflux from AT to plasma HDL was similar for both genotypes of mice. Incubation of wild-type AT explants with apolipoprotein A-I resulted in the formation of multiple discrete-sized nascent HDL particles ranging in diameter from 7.1 to 12 nm; similar incubations with ABCA1(-A/-A) AT explants resulted in nascent HDL <8 nm. Plasma decay and tissue uptake of wild-type (125)I-HDL tracer were similar in both genotypes of recipient mice, suggesting that adipocyte ABCA1 deficiency reduces plasma HDL concentrations solely by reducing nascent HDL particle formation.

Conclusions: We provide in vivo evidence that AT ABCA1-dependent cholesterol efflux and nascent HDL particle formation contribute to systemic HDL biogenesis and that AT ABCA1 expression plays an important role in adipocyte cholesterol homeostasis.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.111.025445DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3202242PMC
October 2011

Biliary sterol secretion is not required for macrophage reverse cholesterol transport.

Cell Metab 2010 Jul;12(1):96-102

Section on Lipid Sciences, Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.

Recent evidence suggests that the intestine may play a direct facilitative role in reverse cholesterol transport (RCT), independent of hepatobiliary secretion. In order to understand the nonbiliary pathway for RCT, we created both genetic and surgical models of biliary cholesterol insufficiency. To genetically inhibit biliary cholesterol secretion, we generated mice in which Niemann-Pick C1-Like 1 (NPC1L1) was overexpressed in the liver. Compared to controls, NPC1L1(Liver-Tg) mice exhibit a >90% decrease in biliary cholesterol secretion, yet mass fecal sterol loss and macrophage RCT are normal. To surgically inhibit biliary emptying into the intestine, we have established an acute biliary diversion model. Strikingly, macrophage RCT persists in mice surgically lacking the ability to secrete bile into the intestine. Collectively, these studies demonstrate that mass fecal sterol loss and macrophage RCT can proceed in the absence of biliary sterol secretion, challenging the obligate role of bile in RCT.
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http://dx.doi.org/10.1016/j.cmet.2010.05.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2913877PMC
July 2010

Inhibition of acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) prevents dietary cholesterol-associated steatosis by enhancing hepatic triglyceride mobilization.

J Biol Chem 2010 May 15;285(19):14267-74. Epub 2010 Mar 15.

Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1040, USA.

Acyl-CoA:cholesterol O-acyl transferase 2 (ACAT2) promotes cholesterol absorption by the intestine and the secretion of cholesteryl ester-enriched very low density lipoproteins by the liver. Paradoxically, mice lacking ACAT2 also exhibit mild hypertriglyceridemia. The present study addresses the unexpected role of ACAT2 in regulation of hepatic triglyceride (TG) metabolism. Mouse models of either complete genetic deficiency or pharmacological inhibition of ACAT2 were fed low fat diets containing various amounts of cholesterol to induce hepatic steatosis. Mice genetically lacking ACAT2 in both the intestine and the liver were dramatically protected against hepatic neutral lipid (TG and cholesteryl ester) accumulation, with the greatest differences occurring in situations where dietary cholesterol was elevated. Further studies demonstrated that liver-specific depletion of ACAT2 with antisense oligonucleotides prevents dietary cholesterol-associated hepatic steatosis both in an inbred mouse model of non-alcoholic fatty liver disease (SJL/J) and in a humanized hyperlipidemic mouse model (LDLr(-/-), apoB(100/100)). All mouse models of diminished ACAT2 function showed lowered hepatic triglyceride concentrations and higher plasma triglycerides secondary to increased hepatic secretion of TG into nascent very low density lipoproteins. This work demonstrates that inhibition of hepatic ACAT2 can prevent dietary cholesterol-driven hepatic steatosis in mice. These data provide the first evidence to suggest that ACAT2-specific inhibitors may hold unexpected therapeutic potential to treat both atherosclerosis and non-alcoholic fatty liver disease.
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http://dx.doi.org/10.1074/jbc.M110.118422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2863169PMC
May 2010

Targeted deletion of hepatocyte ABCA1 leads to very low density lipoprotein triglyceride overproduction and low density lipoprotein hypercatabolism.

J Biol Chem 2010 Apr 23;285(16):12197-209. Epub 2010 Feb 23.

Department of Pathology/Section on Lipid Sciences, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157, USA.

Loss of ABCA1 activity in Tangier disease (TD) is associated with abnormal apoB lipoprotein (Lp) metabolism in addition to the complete absence of high density lipoprotein (HDL). We used hepatocyte-specific ABCA1 knock-out (HSKO) mice to test the hypothesis that hepatic ABCA1 plays dual roles in regulating Lp metabolism and nascent HDL formation. HSKO mice recapitulated the TD lipid phenotype with postprandial hypertriglyceridemia, markedly decreased LDL, and near absence of HDL. Triglyceride (TG) secretion was 2-fold higher in HSKO compared with wild type mice, primarily due to secretion of larger TG-enriched VLDL secondary to reduced hepatic phosphatidylinositol 3-kinase signaling. HSKO mice also displayed delayed clearance of postprandial TG and reduced post-heparin plasma lipolytic activity. In addition, hepatic LDLr expression and plasma LDL catabolism were increased 2-fold in HSKO compared with wild type mice. Last, adenoviral repletion of hepatic ABCA1 in HSKO mice normalized plasma VLDL TG and hepatic phosphatidylinositol 3-kinase signaling, with a partial recovery of HDL cholesterol levels, providing evidence that hepatic ABCA1 is involved in the reciprocal regulation of apoB Lp production and HDL formation. These findings suggest that altered apoB Lp metabolism in TD subjects may result from hepatic VLDL TG overproduction and increased hepatic LDLr expression and highlight hepatic ABCA1 as an important regulatory factor for apoB-containing Lp metabolism.
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http://dx.doi.org/10.1074/jbc.M109.096933DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2852959PMC
April 2010

Combined therapy of dietary fish oil and stearoyl-CoA desaturase 1 inhibition prevents the metabolic syndrome and atherosclerosis.

Arterioscler Thromb Vasc Biol 2010 Jan 15;30(1):24-30. Epub 2009 Oct 15.

Wake Forest University School of Medicine, Department of Pathology, Section on Lipid Sciences, Medical Center Blvd, Winston-Salem, NC 27157-1040, USA.

Background: Stearoyl-CoA desaturase 1 (SCD1) is a critical regulator of energy metabolism and inflammation. We have previously reported that inhibition of SCD1 in hyperlipidemic mice fed a saturated fatty acid (SFA)-enriched diet prevented development of the metabolic syndrome, yet surprisingly promoted severe atherosclerosis. In this study we tested whether dietary fish oil supplementation could prevent the accelerated atherosclerosis caused by SCD1 inhibition.

Methods And Results: LDLr(-/-), ApoB(100/100) mice were fed diets enriched in saturated fat or fish oil in conjunction with antisense oligonucleotide (ASO) treatment to inhibit SCD1. As previously reported, in SFA-fed mice, SCD1 inhibition dramatically protected against development of the metabolic syndrome, yet promoted atherosclerosis. In contrast, in mice fed fish oil, SCD1 inhibition did not result in augmented macrophage inflammatory response or severe atherosclerosis. In fact, the combined therapy of dietary fish oil and SCD1 ASO treatment effectively prevented both the metabolic syndrome and atherosclerosis.

Conclusions: SCD1 ASO treatment in conjunction with dietary fish oil supplementation is an effective combination therapy to comprehensively combat the metabolic syndrome and atherosclerosis in mice.
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http://dx.doi.org/10.1161/ATVBAHA.109.198036DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2796293PMC
January 2010

Inhibition of stearoyl-coenzyme A desaturase 1 dissociates insulin resistance and obesity from atherosclerosis.

Circulation 2008 Sep 15;118(14):1467-75. Epub 2008 Sep 15.

Department of Pathology, Wake Forest University School of Medicine, Section on Lipid Sciences, Winston-Salem, NC 27157-1040, USA.

Background: Stearoyl-coenzyme A desaturase 1 (SCD1) is a well-known enhancer of the metabolic syndrome. The purpose of the present study was to investigate the role of SCD1 in lipoprotein metabolism and atherosclerosis progression.

Methods And Results: Antisense oligonucleotides were used to inhibit SCD1 in a mouse model of hyperlipidemia and atherosclerosis (LDLr(-/-)Apob(100/100)). In agreement with previous reports, inhibition of SCD1 protected against diet-induced obesity, insulin resistance, and hepatic steatosis. Unexpectedly, however, SCD1 inhibition strongly promoted aortic atherosclerosis, which could not be reversed by dietary oleate. Further analyses revealed that SCD1 inhibition promoted accumulation of saturated fatty acids in plasma and tissues and reduced plasma triglyceride, yet had little impact on low-density lipoprotein cholesterol. Because dietary saturated fatty acids have been shown to promote inflammation through toll-like receptor 4, we examined macrophage toll-like receptor 4 function. Interestingly, SCD1 inhibition resulted in alterations in macrophage membrane lipid composition and marked hypersensitivity to toll-like receptor 4 agonists.

Conclusions: This study demonstrates that atherosclerosis can occur independently of obesity and insulin resistance and argues against SCD1 inhibition as a safe therapeutic target for the metabolic syndrome.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.108.793182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2716169PMC
September 2008

Targeted depletion of hepatic ACAT2-driven cholesterol esterification reveals a non-biliary route for fecal neutral sterol loss.

J Biol Chem 2008 Apr 14;283(16):10522-34. Epub 2008 Feb 14.

Department of Pathology, Biochemistry, and Orthopedic Surgery, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1040, USA.

Deletion of acyl-CoA:cholesterol O-acyltransferase 2 (ACAT2) in mice results in resistance to diet-induced hypercholesterolemia and protection against atherosclerosis. Recently, our group has shown that liver-specific inhibition of ACAT2 via antisense oligonucleotide (ASO)-mediated targeting likewise limits atherosclerosis. However, whether this atheroprotective effect was mediated by: 1) prevention of packaging of cholesterol into apoB-containing lipoproteins, 2) augmentation of nascent HDL cholesterol secretion, or 3) increased hepatobiliary sterol secretion was not examined. Therefore, the purpose of these studies was to determine whether hepatic ACAT2 is rate-limiting in all three of these important routes of cholesterol homeostasis. Liver-specific depletion of ACAT2 resulted in reduced packaging of cholesterol into apoB-containing lipoproteins (very low density lipoprotein, intermediate density lipoprotein, and low density lipoprotein), whereas high density lipoprotein cholesterol levels remained unchanged. In the liver of ACAT2 ASO-treated mice, cholesterol ester accumulation was dramatically reduced, yet there was no reciprocal accumulation of unesterified cholesterol. Paradoxically, ASO-mediated depletion of hepatic ACAT2 promoted fecal neutral sterol excretion without altering biliary sterol secretion. Interestingly, during isolated liver perfusion, ACAT2 ASO-treated livers had augmented secretion rates of unesterified cholesterol and phospholipid. Furthermore, we demonstrate that liver-derived cholesterol from ACAT2 ASO-treated mice is preferentially delivered to the proximal small intestine as a precursor to fecal excretion. Collectively, these studies provide the first insight into the hepatic itinerary of cholesterol when cholesterol esterification is inhibited only in the liver, and provide evidence for a novel non-biliary route of fecal sterol loss.
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http://dx.doi.org/10.1074/jbc.M707659200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2447638PMC
April 2008

Dietary fat-induced alterations in atherosclerosis are abolished by ACAT2-deficiency in ApoB100 only, LDLr-/- mice.

Arterioscler Thromb Vasc Biol 2007 Jun 12;27(6):1396-402. Epub 2007 Apr 12.

Wake Forest University School of Medicine, Department of Pathology/Lipid Sciences, Medical Center Blvd, Winston-Salem, NC 27157, USA.

Objectives: The enzyme acyl-coenzymeA (CoA):cholesterol O-acyltransferase 2 (ACAT2) in the liver synthesizes cholesteryl esters (CE) from cholesterol and fatty acyl-CoA, which get incorporated into apoB-containing lipoproteins that are secreted into the bloodstream. Dietary fatty acid composition influences the amount and fatty acid composition of CE within apoB-containing lipoproteins. We hypothesized that when ACAT2 activity is removed by gene deletion, hepatic CE synthesis and secretion would be minimal and, as a result, dietary fat-related differences in atherosclerosis would be eliminated.

Methods And Results: Groups of female apoB100 only, LDLr-/- mice with and without ACAT2 were fed diets enriched in either omega-3 or omega-6 polyunsaturated fat, saturated fat, and cis or trans monounsaturated fat. After 20 weeks on diet, mice fed diets enriched in monounsaturated or saturated fat exhibited significantly higher amounts of plasma cholesterol, larger LDL particles enriched in monounsaturated CE, and more atherosclerosis than mice fed polyunsaturated fat. The dietary fat-induced shifts in plasma cholesterol, LDL size, LDL CE composition, and atherosclerosis were not observed in ACAT2-/- mice. Regardless of the diet fed, the ACAT2-/- mice were protected from atherosclerosis.

Conclusions: The results indicate that in apoB100 only, LDLr-/- mice, ACAT2 plays an essential role in facilitating dietary fat type-specific atherosclerosis through its various effects on plasma lipoprotein concentration and composition.
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http://dx.doi.org/10.1161/ATVBAHA.107.142802DOI Listing
June 2007

Monounsaturated fatty acyl-coenzyme A is predictive of atherosclerosis in human apoB-100 transgenic, LDLr-/- mice.

J Lipid Res 2007 May 4;48(5):1122-31. Epub 2007 Feb 4.

Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.

ACAT2, the enzyme responsible for the formation of cholesteryl esters incorporated into apolipoprotein B-containing lipoproteins by the small intestine and liver, forms predominantly cholesteryl oleate from acyl-CoA and free cholesterol. The accumulation of cholesteryl oleate in plasma lipoproteins has been found to be predictive of atherosclerosis. Accordingly, a method was developed in which fatty acyl-CoA subspecies could be extracted from mouse liver and quantified. Analyses were performed on liver tissue from mice fed one of four diets enriched with one particular type of dietary fatty acid: saturated, monounsaturated, n-3 polyunsaturated, or n-6 polyunsaturated. We found that the hepatic fatty acyl-CoA pools reflected the fatty acid composition of the diet fed. The highest percentage of fatty acyl-CoAs across all diet groups was in monoacyl-CoAs, and values were 36% and 46% for the n-3 and n-6 polyunsaturated diet groups and 55% and 62% in the saturated and monounsaturated diet groups, respectively. The percentage of hepatic acyl-CoA as oleoyl-CoA was also highly correlated to liver cholesteryl ester, plasma cholesterol, LDL molecular weight, and atherosclerosis extent. These data suggest that replacing monounsaturated with polyunsaturated fat can benefit coronary heart disease by reducing the availability of oleoyl-CoA in the substrate pool of hepatic ACAT2, thereby reducing cholesteryl oleate secretion and accumulation in plasma lipoproteins.
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http://dx.doi.org/10.1194/jlr.M600526-JLR200DOI Listing
May 2007

Intestinal cholesterol absorption is substantially reduced in mice deficient in both ABCA1 and ACAT2.

J Lipid Res 2005 Nov 8;46(11):2423-31. Epub 2005 Sep 8.

Department of Pathology, Section on Lipid Sciences, Wake Forest University Health Sciences, Winston-Salem, NC, USA.

The process of cholesterol absorption has yet to be completely defined at the molecular level. Because of its ability to esterify cholesterol for packaging into nascent chylomicrons, ACAT2 plays an important role in cholesterol absorption. However, it has been found that cholesterol absorption is not completely inhibited in ACAT2-deficient (ACAT2 KO) mice. Because ABCA1 mRNA expression was increased 3-fold in the small intestine of ACAT2 KO mice, we hypothesized that ABCA1-dependent cholesterol efflux sustains cholesterol absorption in the absence of ACAT2. To test this hypothesis, cholesterol absorption was measured in mice deficient in both ABCA1 and ACAT2 (DKO). Compared with wild-type, ABCA1 KO, or ACAT2 KO mice, DKO mice displayed the lowest level of cholesterol absorption. The concentrations of hepatic free and esterified cholesterol and gallbladder bile cholesterol were significantly reduced in DKO compared with wild-type and ABCA1 KO mice, although these measures of hepatic cholesterol metabolism were very similar in DKO and ACAT2 KO mice. We conclude that ABCA1, especially in the absence of ACAT2, can have a significant effect on cholesterol absorption, although ACAT2 has a more substantial role in this process than ABCA1.
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http://dx.doi.org/10.1194/jlr.M500232-JLR200DOI Listing
November 2005

ACAT2 contributes cholesteryl esters to newly secreted VLDL, whereas LCAT adds cholesteryl ester to LDL in mice.

J Lipid Res 2005 Jun 1;46(6):1205-12. Epub 2005 Apr 1.

Arteriosclerosis Research Program, Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC, USA.

The relative contributions of ACAT2 and LCAT to the cholesteryl ester (CE) content of VLDL and LDL were measured. ACAT2 deficiency led to a significant decrease in the percentage of CE (37.2 +/- 2.1% vs. 3.9 +/- 0.8%) in plasma VLDL, with a concomitant increase in the percentage of triglyceride (33.0 +/- 3.2% vs. 66.7 +/- 2.5%). Interestingly, the absence of ACAT2 had no apparent effect on the percentage CE in LDL, whereas LCAT deficiency significantly decreased the CE percentage (38.6 +/- 4.0% vs. 54.6 +/- 1.9%) and significantly increased the phospholipid percentage (11.2 +/- 0.9% vs. 19.3 +/- 0.1%) of LDL. When both LCAT and ACAT2 were deficient, VLDL composition was similar to VLDL of the ACAT2-deficient mouse, whereas LDL was depleted in core lipids and enriched in surface lipids, appearing discoidal when observed by electron microscopy. We conclude that ACAT2 is important in the synthesis of VLDL CE, whereas LCAT is important in remodeling VLDL to LDL. Liver perfusions were performed, and perfusate apolipoprotein B accumulation rates in ACAT2-deficient mice were not significantly different from those of controls; perfusate VLDL CE decreased from 8.0 +/- 0.8% in controls to 0 +/- 0.7% in ACAT2-deficient mice. In conclusion, our data establish that ACAT2 provides core CE of newly secreted VLDL, whereas LCAT adds CE during LDL particle formation.
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http://dx.doi.org/10.1194/jlr.M500018-JLR200DOI Listing
June 2005

Effects of peroxisome proliferator-activated receptor alpha/delta agonists on HDL-cholesterol in vervet monkeys.

J Lipid Res 2005 May 16;46(5):1009-16. Epub 2005 Feb 16.

Department of Pathology/Comparative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.

The objective of this study was to demonstrate the efficacy of a novel peroxisome proliferator-activated receptor (PPAR) agonist and known PPARalpha and PPARdelta agonists to increase HDL-cholesterol (HDL-C) in the St. Kitts vervet, a nonhuman primate model of atherosclerosis. Four groups (n = 6) were studied and each group was assigned one of the following "treatments": a) vehicle only (vehicle); b) the PPARdelta selective agonist GW501516 (GW); c) the PPARalpha/delta agonist T913659 (T659); and d) the PPARalpha agonist TriCor (fenofibrate). No statistically significant changes were seen in body weight, total plasma cholesterol, plasma triglycerides, VLDL-C, LDL-C, or apolipoprotein B (apoB) concentrations. Each of the PPARalpha and PPARdelta agonists investigated in this study increased plasma HDL-C, apoA-I, and apoA-II concentrations and increased HDL particle size in St. Kitts vervets. The maximum percentage increase in HDL-C from baseline for each group was as follows: vehicle, 5%; GW, 43%; T659, 43%; and fenofibrate, 20%. Treatment with GW and T659 resulted in an increase in medium-sized HDL particles, whereas fenofibrate showed increases in large HDL particles. These data provide additional evidence that PPARalpha and PPARdelta agonists (both mixed and selective) have beneficial effects on HDL-C in these experimental primates.
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http://dx.doi.org/10.1194/jlr.M500002-JLR200DOI Listing
May 2005

Plasma cholesteryl esters provided by lecithin:cholesterol acyltransferase and acyl-coenzyme a:cholesterol acyltransferase 2 have opposite atherosclerotic potential.

Circ Res 2004 Nov 14;95(10):998-1004. Epub 2004 Oct 14.

Arteriosclerosis Research Program, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.

Evidence suggests that ACAT2 is a proatherogenic enzyme that contributes cholesteryl esters (CEs) to apoB-containing lipoproteins, whereas LCAT is an antiatherogenic enzyme that facilitates reverse cholesterol transport by esterifying free cholesterol on HDL particles. We hypothesized that deletion of LCAT and ACAT2 would lead to absence of plasma CEs and reduced atherosclerosis. To test this hypothesis, ACAT2-/- LCAT-/- LDLr-/-, ACAT2-/- LDLr-/-, and LCAT-/- LDLr-/- mice were fed a 0.15% cholesterol diet for 20 weeks. In comparison to LDLr-/- mice, the total plasma cholesterol (TPC) of ACAT2-/- LCAT-/- LDLr-/- mice was 67% lower because of the complete absence of plasma CEs, leading to 94% less CE accumulation in the aorta. In the LCAT-/- LDLr-/- mice, TPC and atherosclerosis were significantly higher because of increased accumulations of ACAT2-derived CE. In ACAT2-/- LDLr-/- mice, again compared with LDLr-/- mice, TPC was 19% lower, whereas atherosclerosis was 88% lower. Therefore, the absence of ACAT2 led to a significant reduction in TPC although benefits in reduction of atherosclerosis were much more pronounced. Overall, the data suggest that ACAT2-derived CE is the predominant atherogenic lipid in blood, and that an important goal for prevention of atherosclerosis is to limit ACAT2-derived CE accumulation in lipoproteins.
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http://dx.doi.org/10.1161/01.RES.0000147558.15554.67DOI Listing
November 2004

Lecithin:cholesterol acyltransferase deficiency increases atherosclerosis in the low density lipoprotein receptor and apolipoprotein E knockout mice.

J Biol Chem 2002 Feb 21;277(5):3511-9. Epub 2001 Nov 21.

Department of Pathology, Section on Comparative Medicine, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, North Carolina 27157-1040, USA.

The purpose of the present study was to test the hypothesis that lecithin:cholesterol acyltransferase (LCAT) deficiency would accelerate atherosclerosis development in low density lipoprotein (LDL) receptor (LDLr-/-) and apoE (apoE-/-) knockout mice. After 16 weeks of atherogenic diet (0.1% cholesterol, 10% calories from palm oil) consumption, LDLr-/- LCAT-/- double knockout mice, compared with LDLr-/- mice, had similar plasma concentrations of free (FC), esterified (EC), and apoB lipoprotein cholesterol, increased plasma concentrations of phospholipid and triglyceride, decreased HDL cholesterol, and 2-fold more aortic FC (142 +/- 28 versus 61 +/- 20 mg/g protein) and EC (102 +/- 27 versus 61+/- 27 mg/g). ApoE-/- LCAT-/- mice fed the atherogenic diet, compared with apoE-/- mice, had higher concentrations of plasma FC, EC, apoB lipoprotein cholesterol, and phospholipid, and significantly more aortic FC (149 +/- 62 versus 109 +/- 33 mg/g) and EC (101 +/- 23 versus 69 +/- 20 mg/g) than did the apoE-/- mice. LCAT deficiency resulted in a 12-fold increase in the ratio of saturated + monounsaturated to polyunsaturated cholesteryl esters in apoB lipoproteins in LDLr-/- mice and a 3-fold increase in the apoE-/- mice compared with their counterparts with active LCAT. We conclude that LCAT deficiency in LDLr-/- and apoE-/- mice fed an atherogenic diet resulted in increased aortic cholesterol deposition, likely due to a reduction in plasma HDL, an increased saturation of cholesteryl esters in apoB lipoproteins and, in the apoE-/- background, an increased plasma concentration of apoB lipoproteins.
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http://dx.doi.org/10.1074/jbc.M109883200DOI Listing
February 2002