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Altemus JB, Patel SB, Sehayek E. Liver-specific induction of Abcg5 and Abcg8 stimulates reverse cholesterol transport in response to ezetimibe treatment. Metabolism 2014; 63:1334-41. [PMID: 25060694 DOI: 10.1016/j.metabol.2014.06.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 06/02/2014] [Accepted: 06/17/2014] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Previous studies have shown ezetimibe treatment results in a 2-6-fold increase in reverse cholesterol transport (RCT). However, recent sterol balance studies question the role of biliary sterol secretion in RCT, and challenge the hypothesis that ezetimibe increases RCT through decreased absorption of biliary cholesterol in the intestine. We set out to determine whether ezetimibe may increase RCT by mechanisms that are independent of its well-established inhibition of intestinal cholesterol absorption. METHODS C57BL/6J, Npc1l1-KO, and/or Abcg8-KO mice were fed a chow diet with or without ezetimibe and fecal [(14)C]-neutral and [(14)C]-acidic sterols were measured to examine macrophage-to-feces RCT. We measured the expression of RCT related genes in the liver and jejunum in these mice. To confirm our significant gene expression findings, we utilized primary human hepatocytes cultured with or without a glucuronated metabolite of ezetimibe. RESULTS Our studies revealed that treatment with ezetimibe was associated with increased expression of hepatic Abcg5 and Abcg8. Ezetimibe did not directly affect expression in the liver, but this expression was due to the inhibition of intestinal cholesterol absorption. This conclusion was supported by the absence of an ABCG5/ABCG8 expression response to treatment with an ezetimibe metabolite in primary human hepatocytes. Finally, we found that the ezetimibe-dependent stimulation of RCT was attenuated in the absence of Abcg8. CONCLUSIONS Our study is the first to demonstrate ezetimibe treatment cooperatively stimulated macrophage-to-feces RCT by indirectly increasing liver Abcg5/Abcg8 expression in addition to its known suppression of intestinal cholesterol absorption.
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Cannon MV, Buchner DA, Hester J, Miller H, Sehayek E, Nadeau JH, Serre D. Maternal nutrition induces pervasive gene expression changes but no detectable DNA methylation differences in the liver of adult offspring. PLoS One 2014; 9:e90335. [PMID: 24594983 PMCID: PMC3940881 DOI: 10.1371/journal.pone.0090335] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 01/31/2014] [Indexed: 12/11/2022] Open
Abstract
AIMS Epidemiological and animal studies have shown that maternal diet can influence metabolism in adult offspring. However, the molecular mechanisms underlying these changes remain poorly understood. Here, we characterize the phenotypes induced by maternal obesity in a mouse model and examine gene expression and epigenetic changes induced by maternal diet in adult offspring. METHODS We analyzed genetically identical male mice born from dams fed a high- or low-fat diet throughout pregnancy and until day 21 postpartum. After weaning, half of the males of each group were fed a high-fat diet, the other half a low-fat diet. We first characterized the genome-wide gene expression patterns of six tissues of adult offspring - liver, pancreas, white adipose, brain, muscle and heart. We then measured DNA methylation patterns in liver at selected loci and throughout the genome. RESULTS Maternal diet had a significant effect on the body weight of the offspring when they were fed an obesogenic diet after weaning. Our analyses showed that maternal diet had a pervasive effect on gene expression, with a pronounced effect in liver where it affected many genes involved in inflammation, cholesterol synthesis and RXR activation. We did not detect any effect of the maternal diet on DNA methylation in the liver. CONCLUSIONS Overall, our findings highlighted the persistent influence of maternal diet on adult tissue regulation and suggested that the transcriptional changes were unlikely to be caused by DNA methylation differences in adult liver.
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Meller N, Morgan ME, Wong WP, Altemus JB, Sehayek E. Targeting of Acyl-CoA synthetase 5 decreases jejunal fatty acid activation with no effect on dietary long-chain fatty acid absorption. Lipids Health Dis 2013; 12:88. [PMID: 23767941 PMCID: PMC3699395 DOI: 10.1186/1476-511x-12-88] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 06/10/2013] [Indexed: 12/12/2022] Open
Abstract
Background The absorption of dietary long chain fatty acids (LCFA) largely occurs in the jejunum. LCFA are activated via conjugation with Coenzyme A (CoA), a reaction catalyzed by Acyl-CoA synthetases (ACS). Acyl-CoA sythesis is critical for dietary LCFA absorption; yet, the jejunal ACS enzymes that catalyze the reaction are largely unknown. Findings High throughput mRNA sequencing of the mouse jejunum revealed that the expression of acyl-CoA synthetase 5 (Acsl5) and fatty-acid transport protein 4 (Fatp4) largely exceeded all other annotated ACS genes that activate LCFA. Interestingly, Acsl5 knockout (KO) mice displayed a decrease of 60% in jejunal total long chain acyl-CoA synthesis rate. Nevertheless, and despite of this decrease, dietary LCFA absorption and body-weight gain in response to high fat diet remained unaffected. Conclusion Acsl5 is a major activator of dietary LCFA, yet in Acsl5 KO mice residual ACS activity is sufficient for maintaining a normal LCFA absorption. Our findings provide further evidence for a robust small intestine LCFA absorption capacity.
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Wong WPS, Altemus JB, Hester JF, Chan ER, Côté JF, Serre D, Sehayek E. Cathepsin B is a novel gender-dependent determinant of cholesterol absorption from the intestine. J Lipid Res 2012; 54:816-822. [PMID: 23248330 DOI: 10.1194/jlr.m034579] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We used a mouse C57BL/6J×CASA/Rk intercross to map a locus on chromosome 14 that displayed a gender-dependent effect on cholesterol absorption from the intestine. Studies in congenic animals revealed a complex locus with multiple operating genetic determinants resulting in alternating gender-dependent phenotypic effects. Fine-mapping narrowed the locus to a critical 6.3 Mb interval. Female subcongenics, but not males, of the critical interval displayed a decrease of 33% in cholesterol absorption. RNA-Seq analysis of female subcongenic jejunum revealed that cysteine protease cathepsin B (Ctsb) is a candidate to explain the interval effect. Consistent with the phenotype in critical interval subcongenics, female Ctsb knockout mice, but not males, displayed a decrease of 31% in cholesterol absorption. Although studies in Ctsb knockouts revealed a gender-dependent effect on cholesterol absorption, further fine-mapping dismissed a role for Ctsb in determining the effect of the critical 6.3 Mb interval on cholesterol absorption.
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Lee BH, Taylor MG, Robinet P, Smith JD, Schweitzer J, Sehayek E, Falzarano SM, Magi-Galluzzi C, Klein EA, Ting AH. Dysregulation of cholesterol homeostasis in human prostate cancer through loss of ABCA1. Cancer Res 2012; 73:1211-8. [PMID: 23233737 DOI: 10.1158/0008-5472.can-12-3128] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Recent epidemiologic data show that low serum cholesterol level as well as statin use is associated with a decreased risk of developing aggressive or advanced prostate cancer, suggesting a role for cholesterol in aggressive prostate cancer development. Intracellular cholesterol promotes prostate cancer progression as a substrate for de novo androgen synthesis and through regulation of AKT signaling. By conducting next-generation sequencing-based DNA methylome analysis, we have discovered marked hypermethylation at the promoter of the major cellular cholesterol efflux transporter, ABCA1, in LNCaP prostate cancer cells. ABCA1 promoter hypermethylation renders the promoter unresponsive to transactivation and leads to elevated cholesterol levels in LNCaP. ABCA1 promoter hypermethylation is enriched in intermediate- to high-grade prostate cancers and not detectable in benign prostate. Remarkably, ABCA1 downregulation is evident in all prostate cancers examined, and expression levels are inversely correlated with Gleason grade. Our results suggest that cancer-specific ABCA1 hypermethylation and loss of protein expression direct high intracellular cholesterol levels and hence contribute to an environment conducive to tumor progression.
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Wong WP, Schweitzer JB, Hester JF, Chan ER, Serre D, Sehayek E. Abstract 173: Cathepsin B Is a Novel Gender-Dependent Modifier of Dietary Cholesterol and Fat Absorption from the Intestine. Arterioscler Thromb Vasc Biol 2012. [DOI: 10.1161/atvb.32.suppl_1.a173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The absorption of dietary cholesterol and fat from the intestine is an important determinant of major risk factors for atherosclerotic cardiovascular diseases including hypercholesterolemia, obesity, metabolic syndrome, and type 2 diabetes. Nevertheless, the molecular mechanisms regulating the absorption process are only partially understood. We used two inbred mouse strains, C57BL/6J and CASA/Rk that differ in dietary cholesterol and fat absorption, to map a locus on chromosome 14 that modifies the absorption process. Studies in congenics of this locus revealed a complex effect of several genetic determinants. Fine mapping of one genetic determinant allowed identification of a critical 6.3Mb CASA/Rk interval (63.3-69.7 Mb) with gender dependent effect. Therefore, congenic females of the critical interval, but not congenic males, displayed a 30% decrease in dietary cholesterol absorption. RNA-seq studies in jejuna of congenic females found 50% suppression of Cathepsin B (Ctsb), a gene that maps within the critical congenic interval and encodes for a ubiquitously expressed lysosomal cysteine protease. Concordant with findings in congenic females, Ctsb knockout females, but not knockout males, displayed significantly (25%) decreased dietary cholesterol absorption rates and a large (80%) decrease in dietary fat absorption. These studies indicate that: (i) Cathepsin B is a novel gender-dependent determinant of cholesterol and fat absorption from the intestine, and (ii) the critical chromosome 14 interval is likely to harbor additional genetic determinants of cholesterol and fat absorption from the intestine.
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Greenberg ME, Smith JD, Sehayek E. Moderately decreased cholesterol absorption rates are associated with a large atheroprotective effect. Arterioscler Thromb Vasc Biol 2009; 29:1745-50. [PMID: 19661480 DOI: 10.1161/atvbaha.109.194605] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Human treatment with ezetimibe results in a moderate 50% to 54% decrease in cholesterol absorption and a 15% to 20% decrease in plasma LDL-cholesterol levels; nevertheless, the efficacy of ezetimibe therapy has been recently challenged by the ENHANCE trial. We examined the efficacy of a moderate decrease in cholesterol absorption in preventing atherosclerosis formation in the mouse. METHODS AND RESULTS Congenic 14DKK animals, consisting of a castaneus (CASA/Rk) chromosome 14 interval introgressed onto the C57BL/6J background, displayed a moderate decrease in cholesterol absorption rates. The effect of moderately decreased absorption on atherosclerosis formation was determined in 14DKK apolipoprotein E knockouts (14DKK-apoEKO). When compared to chow diet-fed control apoEKO mice, congenic 14DKK-apoEKO displayed a moderate 41% decrease in cholesterol absorption rates, 30% to 37% decrease in plasma cholesterol levels, and a 70% decrease in atherosclerosis formation. Studies on cholesterol efflux and reverse cholesterol transport (RCT) from 14DKK bone marrow-derived macrophages rejected a 14DKK interval-dependent atheroprotective effects that operate in macrophages. In contrast, 14DKK-apoEKO congenics were characterized by a 60% increase in RCT from peripheral tissue macrophages. CONCLUSIONS These studies strongly suggest that moderately decreased cholesterol absorption rates result in a large atheroprotective effect attributable to a decrease in plasma cholesterol levels and an increase in RCT from peripheral tissue macrophages.
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Sehayek E, Hazen SL. Cholesterol absorption from the intestine is a major determinant of reverse cholesterol transport from peripheral tissue macrophages. Arterioscler Thromb Vasc Biol 2008; 28:1296-7. [PMID: 18420997 DOI: 10.1161/atvbaha.108.165803] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE We examined the effect of ezetimibe, a cholesterol absorption (CA) inhibitor, and genetic determinants of CA on reverse cholesterol transport (RCT) from subcutaneously injected macrophages using a new dual isotope label technique. METHODS AND RESULTS Treatment of C57BL/6J mice with ezetimibe decreased dietary CA by 86% and increased RCT from peripheral tissue macrophages (PTM) by 6-fold (P<0.0001). Moreover, congenic 14DKK mice with a modest 41% decrease in dietary CA displayed a 67% increase in RCT from PTM (P<0.007). CONCLUSIONS These findings indicate that pharmacological and genetic modifiers of cholesterol absorption are major determinants of reverse cholesterol transport from peripheral tissue macrophages.
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Wittkowski KM, Haider A, Sehayek E, Suárez-Fariñas M, Pellegrino M, Peshansky A, Coffran C, Coker S. Bioinformatics tools enabling u-statistics for microarrays. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2008; 2006:3464-9. [PMID: 17947031 DOI: 10.1109/iembs.2006.260846] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It is rare that a single gene is sufficient to represent all aspects of genomic activity. Similarly, most common diseases cannot be explained by a mutations at a single locus. Since complex systems tend to be neither linear nor hierarchical in nature, but to have correlated components of unknown relative importance, the assumptions of traditional (parametric) multivariate statistical methods can rarely be justified on theoretical grounds. Empirical "validation" is not only problematic, but also time consuming. Here we demonstrates how bioinformatics tools, ranging from spreadsheets to grids, can enable u-statistics as a non-parametric alternative for scoring multivariate ordinal data. Applications are shown to improve assessment of genetic risk factors, quality control of microarrays and signal value estimation, scoring genomic profiles that best correlated with complex risk factors (cardiovascular diseases), and complex responses to an intervention (treatment of psoriasis).
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Sehayek E. Effect of Aerobic Exercise on Paraoxonase Activity in a Cardiac Rehabilitation Setting. J Cardiopulm Rehabil Prev 2007; 27:155-6. [PMID: 17558197 DOI: 10.1097/01.hcr.0000270690.71140.bf] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Vitarius JA, Sehayek E, Breslow JL. Identification of quantitative trait loci affecting body composition in a mouse intercross. Proc Natl Acad Sci U S A 2006; 103:19860-5. [PMID: 17179051 PMCID: PMC1750913 DOI: 10.1073/pnas.0609232103] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Gravimetric analysis and dual energy x-ray absorptiometry densitometry were used to determine lean, fat, and bone tissue traits in a F(2) mouse population from a C57BL/6J and CASA/Rk intercross (B6CASAF2). These traits were used in a linkage analysis to identify quantitative trait loci that affect body composition. Linkage mapping showed that body weight (BW) loci on proximal chromosome 2 occurred in the same region as body length, lean tissue mass, and bone mineral content and on chromosome 13 in the same region as lean tissue mass, bone mineral density, and bone mineral content. Fat-related loci occurring on mid-chromosome 2 near 60 cM, proximal chromosome 6, and mid-chromosome 10 were distinct from BW, lean tissue, and bone tissue loci. In B6CASAF2 females, heterozygotes and CASA/Rk homozygotes at the chromosome 6 locus marker had higher body fat percentages, and this locus was responsible for 11% of the variance for body fat percentage. Female heterozygotes and C57BL/6J homozygotes at the chromosome 15 locus marker had higher bone mineral densities, and this locus could explain 8% of that trait's variance. A survey of the literature did not reveal any previous reports of fat-specific loci in the chromosomal 10 region near 42 cM reported in this study. The results of this study indicate that BW and BMI have limited usefulness as phenotypes in linkage or association studies when used as obesity phenotypes.
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Sehayek E, Hagey LR, Fung YY, Duncan EM, Yu HJ, Eggertsen G, Björkhem I, Hofmann AF, Breslow JL. Two loci on chromosome 9 control bile acid composition: evidence that a strong candidate gene, Cyp8b1, is not the culprit. J Lipid Res 2006; 47:2020-7. [PMID: 16763287 DOI: 10.1194/jlr.m600176-jlr200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An intercross between C57BL/6J and CASA/Rk mice was used to study the genetics of biliary bile acid composition. In parental strains, male C57BL/6J mice had significantly higher cholic acid (CA; 14%) and lower beta-muricholic acid (betaMC; 27%) than CASA/Rk mice, whereas females did not differ. However, quantitative trait locus analysis of F2 mice revealed no significant chromosome 9 loci in males but loci in females on chromosome 9 for percentage CA (%CA) at 72 centimorgan (cM) [logarithm of the odds (LOD) 5.89] and %betaMC at 54 cM (LOD 4.09). Chromosome 9 congenic and subcongenic strains representing CASA/Rk intervals 38-73 cM (9KK) and 68-73 cM (9DKK) on the C57BL/6J background were made. In 9KK and 9DKK males, %CA was increased and %betaMC was unchanged, whereas in 9KK but not 9DKK females, %CA was increased and %betaMC was decreased. Sterol 12alpha-hydroxylase (Cyp8b1) channels bile acid precursors into CA and maps at chromosome 9 (73 cM). However, there was no significant difference in Cyp8b1 mRNA or enzymatic activity between parental mice, parental-congenic-subcongenic mice, or high-low biliary %CA F2 mice. In summary, two chromosome 9 loci control sexually dimorphic effects on biliary bile acid composition: a distal (68-73 cM) major determinant in males, and a more proximal (38-68 cM) major determinant in females. In this intercross, Cyp8b1, a strong candidate, does not appear to be responsible.
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Sehayek E, Fung YY, Yu HJ, Lembcke J, Ceglarek U, Teupser D, Thiery J, Lutjohann D, von Bergmann K, Breslow JL. A complex plasma plant sterol locus on mouse chromosome 14 has at least two genes regulating intestinal sterol absorption. J Lipid Res 2006; 47:2291-6. [PMID: 16840795 DOI: 10.1194/jlr.m600202-jlr200] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously identified two inbred mouse strains, C57BL/6J and CASA/Rk, with different plasma plant sterol levels. An intercross between these strains revealed a broad plasma plant sterol locus on chromosome 14, which peaked at 17 centimorgan (cM) with a maximum logarithm of the odds score of 9.9. Studies in a chromosome 14 congenic strain, 14KK, with a 4-60 cM CASA/Rk interval on the C57BL/6J background revealed that males, but not females, had decreased plasma plant sterol levels and intestinal cholesterol absorption. In two subcongenic strains, 14PKK and 14DKK, with 4-19.5 and 19.5-60 cM CASA/Rk intervals, respectively, both males and females had decreased plasma plant sterol levels and decreased intestinal cholesterol absorption. Compatible with the decreased plasma plant sterol phenotype, 14PKK mice had increased biliary plant sterol excretion, whereas 14DKK mice did not. Therefore, gender-dependent interactions of genes at the 14PKK and 14DKK intervals are likely to underlie the 14KK interval effect on plasma plant sterol levels and sterol absorption from the intestine. These studies confirm the plasma plant sterol locus on mouse chromosome 14 and provide evidence that there are at least two sets of genes operating: one set affecting intestinal sterol absorption and biliary excretion, and the other set mainly affecting intestinal sterol absorption.
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Sehayek E, Yu HJ, von Bergmann K, Lutjohann D, Stoffel M, Duncan EM, Garcia-Naveda L, Salit J, Blundell ML, Friedman JM, Breslow JL. Phytosterolemia on the island of Kosrae. J Lipid Res 2004; 45:1608-13. [PMID: 15210841 DOI: 10.1194/jlr.m400006-jlr200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Screening of 932 adults on the Pacific island of Kosrae for plasma plant sterol levels disclosed three subjects, two of them asymptomatic, with phytosterolemia. Sequencing the ATP binding cassette subfamily G member 8 (ABCG8) gene revealed a novel exon 2 mutation that causes a change in codon 24 from glutamine to histidine and a frame shift followed by a premature stop codon, precluding the formation of a functional ABCG8 protein. Genotyping of 1,090 Kosraens revealed 150 as carriers, a 13.8% carrier rate. DNA sequencing of 67 carriers revealed the same mutation as in the probands. In carriers, plasma campesterol and sitosterol levels were 55% and 30% higher, respectively, than in noncarriers. Moreover, compared with noncarriers, carriers showed 21% lower plasma levels of lathosterol, a surrogate marker for cholesterol biosynthesis. There was no difference between the groups in plasma total cholesterol, triglycerides, apolipoprotein B, or apolipoprotein A-I levels. In summary, on the island of Kosrae, a strong founder effect of a mutant ABCG8 allele results in a large number of carriers with increased plasma plant sterol levels and decreased lathosterol levels. The latter finding suggests that heterozygosity for a mutated ABCG8 allele results in a modest increase in dietary cholesterol absorption and a decrease in cholesterol biosynthesis.
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Goldberg IJ, Isaacs A, Sehayek E, Breslow JL, Huang LS. Effects of streptozotocin-induced diabetes in apolipoprotein AI deficient mice. Atherosclerosis 2004; 172:47-53. [PMID: 14709356 DOI: 10.1016/j.atherosclerosis.2003.09.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During the past decade a number of investigators have attempted to develop mouse models of diabetic macrovascular disease. Hyperglycemia might increase vascular damage because it increases oxidant stress. For this reason we studied animals that were deficient in HDL; HDL is widely believed to protect against oxidant stress. An inbred line of mice doubly deficient in LDL receptor and apoAI was made diabetic with streptozotocin (STZ); control mice had an average glucose of 7.2+/-2mmol/l and STZ-treated mice had an average glucose of 19.4+/-6.5mmol/l. The animals were fed a high cholesterol but low fat diet leading to plasma cholesterol levels of 9.4+/-1.6mmol/l in control animals and 10.1+/-1.8mmol/l in STZ-treated mice. The control and STZ-treated animals had similar plasma lipoprotein profiles. Atherosclerosis assessed at 23 weeks averaged 38154microm(2) in control and 32962microm(2) in STZ-treated mice. Therefore STZ-induced diabetes does not alter plasma lipoproteins or atherosclerosis in HDL deficient mice.
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Tiemann M, Han Z, Soccio R, Bollineni J, Shefer S, Sehayek E, Breslow JL. Cholesterol feeding of mice expressing cholesterol 7alpha-hydroxylase increases bile acid pool size despite decreased enzyme activity. Proc Natl Acad Sci U S A 2004; 101:1846-51. [PMID: 14762172 PMCID: PMC357015 DOI: 10.1073/pnas.0308426100] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dietary cholesterol regulation of cholesterol 7alpha-hydroxylase (Cyp7a1), the rate-limiting enzyme in the classical pathway of bile acid synthesis, has been implicated in plasma cholesterol responsiveness. In the current study, the effects of 0.0% and 0.5% cholesterol diets were examined in Cyp7a1 knockout (KO), heterozygous Cyp7a1 KO (Het), and human Cyp7a1 transgenic mice on the mouse Cyp7a1 KO background (Tg+KO). We confirmed previous findings that dietary cholesterol increased mouse Cyp7a1 activity in Het mice but decreased human Cyp7a1 activity in Tg+KO mice. However, in both Het and Tg+KO mice, dietary cholesterol increased bile acid pool size (36% and 72%, respectively) and fecal bile acid excretion (2.2- and 3.6-fold, respectively). The expression of cholesterol 27-hydroxylase (Cyp27), the major enzyme of the alternative pathway of bile acid synthesis, was not significantly different in cholesterol-fed KO, Het, or Tg+KO mice. Furthermore, dietary cholesterol had comparable effects on total plasma cholesterol and non-high-density lipoprotein cholesterol in KO, Het, and Tg+KO mice. Thus, in Tg+KO mice, dietary cholesterol regulates bile acid pool size, fecal bile acid excretion, and plasma cholesterol independently of Cyp7a1 activity. These results challenge the notion that dietary cholesterol regulation of Cyp7a1 is a major determinant of plasma cholesterol responsiveness.
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Sehayek E. Genetic regulation of cholesterol absorption and plasma plant sterol levels: commonalities and differences. J Lipid Res 2003; 44:2030-8. [PMID: 12897193 DOI: 10.1194/jlr.r300008-jlr200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The molecular basis of the processes that control two closely related traits, the absorption of cholesterol from the intestines and plasma plant sterol levels, are only partially understood. The discovery that mutations in two novel hemitransporters, ATP binding cassette transporter G5 (ABCG5) and ABCG8, underlie a rare inborn error in plant sterol metabolism, beta-sitosterolemia, represents a major breakthrough in this field. More recently, genetic studies in the mouse that mapped loci in linkage with cholesterol absorption and plasma plant sterol levels and studies in humans that examined the relationship of plasma plant sterol levels to sequence variation in the ABCG5/ABCG8 locus suggested the involvement of other genes. Moreover, studies in beta-sitosterolemic patients, in ABCG5/ABCG8-targeted animals, and on a newly developed cholesterol absorption inhibitor, ezetimibe, suggest commonalities and differences in the regulation of the two traits. This review summarizes the evidence for genetic control of cholesterol absorption and plasma plant sterol levels, presents the evidence for commonalities and differences between the two traits, and discusses recent developments and future perspectives in this field.
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Maxwell KN, Soccio RE, Duncan EM, Sehayek E, Breslow JL. Novel putative SREBP and LXR target genes identified by microarray analysis in liver of cholesterol-fed mice. J Lipid Res 2003; 44:2109-19. [PMID: 12897189 DOI: 10.1194/jlr.m300203-jlr200] [Citation(s) in RCA: 291] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
High-cholesterol diets elicit changes in gene expression via such transcription factors as sterol-regulatory element binding proteins (SREBPs) and liver X receptors (LXRs). We used Affymetrix microarrays to identify genes in mouse liver regulated by dietary cholesterol (0.0% vs. 0.5% cholesterol wt/wt). Three independent experiments were performed, and data were analyzed with Affymetrix Microarray Suite and ANOVA statistical software. There were 69 unique Unigene clusters consistently regulated by dietary cholesterol (37 downregulated and 32 upregulated). The array results were confirmed by quantitative RT-PCR (Q-PCR) for seven of nine downregulated genes and five of six upregulated genes. A time course of dietary cholesterol feeding over 1 week revealed different temporal patterns of gene regulation for these confirmed genes. Six downregulated genes were examined in transgenic mice overexpressing truncated nuclear forms of SREBP-1a and SREBP-2, and all were induced in these mice. A second microarray analysis of mice treated with the LXR agonist TO901317 confirmed that 13 of the 32 cholesterol upregulated genes were also LXR-activated. This array result was confirmed by Q-PCR for three of three genes. In summary, these studies identified and confirmed six novel dietary cholesterol-regulated genes, three putative SREBP target genes (calcium/calmodulin-dependent protein kinase 1D, fatty acid binding protein 5, and proprotein convertase subtilisin/kexin 9), and three putative LXR target genes (a disintegrin and metalloprotease domain 11, apoptosis-inhibitory 6, and F-box-only protein 3).
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Sehayek E, Duncan EM, Yu HJ, Petukhova L, Breslow JL. Loci controlling plasma non-HDL and HDL cholesterol levels in a C57BL /6J x CASA /Rk intercross. J Lipid Res 2003; 44:1744-50. [PMID: 12810823 DOI: 10.1194/jlr.m300139-jlr200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasma non-HDL and HDL cholesterol levels are predictors of cardiovascular diseases. We carried out a genetic cross between two laboratory inbred mouse strains, C57BL/6J and CASA/Rk, to detect loci that control the plasma levels of non-HDL and HDL cholesterol. With regard to non-HDL cholesterol, chow-fed CASA/Rk males and females had 87% and 25% higher levels, respectively, than did C57BL/6Js. The levels of non-HDL cholesterol in F1s were similar to C57BL/6J. There was no strain difference in HDL cholesterol levels. An intercross between F1s was performed, and plasma non-HDL and HDL cholesterol was measured in 185 male and 184 female mice. In both male and female F2 mice, plasma non-HDL and HDL cholesterol levels were unimodally distributed; however, in both cases the values for females were significantly lower than for males. Therefore, linkage analysis was performed with sex as a covariate. Significant linkage for non-HDL cholesterol was found on chromosome 6 at 49 cM (LOD 5.17), chromosome 4 at 55 cM (LOD 4.22), and chromosome 8 at 7 cM (LOD 3.68). Significant linkage for HDL cholesterol was found on chromosome 9 at 14 cM (LOD 7.52) and chromosome 8 at 76 cM (LOD 4.69). A significant epistatic interaction involving loci on chromosomes 2 and 5 was also observed for non-HDL cholesterol. In summary, linkage analysis in these cross-identified novel loci confirmed previously identified loci in control of plasma non-HDL and HDL cholesterol and disclosed a novel interaction in controlling non-HDL cholesterol levels in the mouse.
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Sehayek E, Wang R, Ono JG, Zinchuk VS, Duncan EM, Shefer S, Vance DE, Ananthanarayanan M, Chait BT, Breslow JL. Localization of the PE methylation pathway and SR-BI to the canalicular membrane: evidence for apical PC biosynthesis that may promote biliary excretion of phospholipid and cholesterol. J Lipid Res 2003; 44:1605-13. [PMID: 12810817 DOI: 10.1194/jlr.m200488-jlr200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To better understand the regulation of biliary phospholipid and cholesterol excretion, canalicular membranes were isolated from the livers of C57BL/6J mice and abundant proteins separated by SDS-PAGE and identified by matrix-assisted laser desorption/ionization mass spectrometry. A prominent protein revealed by this analysis was betaine homocysteine methyltransferase (BHMT). This enzyme catalyzes the first step in a three-enzyme pathway that promotes the methylation of phosphatidylethanolamine (PE) to phosphatidylcholine (PC). Immunoblotting confirmed the presence of BHMT on the canalicular membrane, failed to reveal the presence of the second enzyme in this pathway, methionine adenosyltransferase, and localized the third enzyme of the pathway, PE N-methyltransferase (PEMT). Furthermore, immunfluorescence microscopy unambiguously confirmed the localization of PEMT to the canalicular membrane. These findings indicate that a local mechanism exists in or around hepatocyte canalicular membranes to promote phosphatidylethnolamine methylation and PC biosynthesis. Finally, immunoblotting revealed the presence and immunofluorescence microscopy unambiguously localized the scavenger receptor class B type I (SR-BI) to the canalicular membrane. Therefore, SR-BI, which is known to play a role in cholesterol uptake at the hepatocyte basolateral membrane, may also be involved in biliary cholesterol excretion. Based on these findings, a model is proposed in which local canalicular membrane PC biosynthesis in concert with the phospholipid transporter mdr2 and SR-BI, promotes the excretion of phospholipid and cholesterol into the bile.
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Chen F, Ma L, Dawson PA, Sinal CJ, Sehayek E, Gonzalez FJ, Breslow J, Ananthanarayanan M, Shneider BL. Liver receptor homologue-1 mediates species- and cell line-specific bile acid-dependent negative feedback regulation of the apical sodium-dependent bile acid transporter. J Biol Chem 2003; 278:19909-16. [PMID: 12456679 DOI: 10.1074/jbc.m207903200] [Citation(s) in RCA: 181] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Intestinal reclamation of bile salts is mediated in large part by the apical sodium-dependent bile acid transporter (ASBT). The bile acid responsiveness of ASBT is controversial. Bile acid feeding in mice results in decreased expression of ASBT protein and mRNA. Mouse but not rat ASBT promoter activity was repressed in Caco-2, but not IEC-6, cells by chenodeoxycholic acid. A potential liver receptor homologue-1 (LRH-1) cis-acting element was identified in the bile acid-responsive region of the mouse but not rat promoter. The mouse, but not rat, promoter was activated by LRH-1, and this correlated with nuclear protein binding to the mouse but not rat LRH-1 element. The short heterodimer partner diminished the activity of the mouse promoter and could partially offset its activation by LRH-1. Interconversion of the potential LRH-1 cis-elements between the mouse and rat ASBT promoters was associated with an interconversion of LRH-1 and bile acid responsiveness. LRH-1 protein was found in Caco-2 cells and mouse ileum, but not IEC-6 cells or rat ileum. Bile acid response was mediated by the farnesoid X receptor, as shown by the fact that overexpression of a dominant-negative farnesoid X-receptor eliminated the bile acid mediated down-regulation of ASBT. In addition, ASBT expression in farnesoid X receptor null mice was unresponsive to bile acid feeding. In summary cell line- and species-specific negative feedback regulation of ASBT by bile acids is mediated by farnesoid X receptor via small heterodimer partner-dependent repression of LRH-1 activation of the ASBT promoter.
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Erickson SK, Lear SR, Deane S, Dubrac S, Huling SL, Nguyen L, Bollineni JS, Shefer S, Hyogo H, Cohen DE, Shneider B, Sehayek E, Ananthanarayanan M, Balasubramaniyan N, Suchy FJ, Batta AK, Salen G. Hypercholesterolemia and changes in lipid and bile acid metabolism in male and female cyp7A1-deficient mice. J Lipid Res 2003; 44:1001-9. [PMID: 12588950 DOI: 10.1194/jlr.m200489-jlr200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cholesterol 7alpha-hydroxylase, a rate-limiting enzyme for bile acid synthesis, has been implicated in genetic susceptibility to atherosclerosis. The gene, CYP7A1, encoding a protein with this activity, is expressed normally only in hepatocytes and is highly regulated. Our cyp7A1 gene knockout mouse colony, as young adults on a chow diet, is hypercholesterolemic. These mice were characterized extensively to understand how cyp7A1 affects lipid and bile acid homeostasis in different tissue compartments and whether gender plays a modifying role. Both male and female cyp7A1-deficient mice had decreased hepatic LDL receptors, unchanged hepatic cholesterol synthesis, increased intestinal cholesterol synthesis and bile acid transporters, and decreased fecal bile acids but increased fecal sterols. In females, cyp7A1 deficiency also caused changes in hepatic fatty acid metabolism, decreased hepatic canalicular bile acid transporter, Bsep, and gallbladder bile composition altered to a lithogenic profile. Taken together, the data suggest that cyp7A1 deficiency results in a proatherogenic phenotype in both genders and leads to a prolithogenic phenotype in females.
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Sehayek E, Duncan EM, Lutjohann D, Von Bergmann K, Ono JG, Batta AK, Salen G, Breslow JL. Loci on chromosomes 14 and 2, distinct from ABCG5/ABCG8, regulate plasma plant sterol levels in a C57BL/6J x CASA/Rk intercross. Proc Natl Acad Sci U S A 2002; 99:16215-9. [PMID: 12446833 PMCID: PMC138591 DOI: 10.1073/pnas.212640599] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2002] [Indexed: 01/24/2023] Open
Abstract
Plasma plant sterol levels differ among humans due to genetic and dietary factors. A disease characterized by high plasma plant sterol levels, beta-sitosterolemia, was recently found to be due to mutations at the ABCG5ABCG8 locus. To detect variants at this and other loci, a genetic cross was carried out between two laboratory mouse strains. Parental C57BL6J had almost twice the campesterol and sitosterol levels compared with parental CASARk mice, and F(1) mice had levels halfway between the parentals. An intercross between F(1)s was performed and plasma plant sterol levels measured in 102 male and 99 female F(2) mice. Plasma plant sterols in F(2)s displayed a unimodal distribution, suggesting the effects of several rather a single major gene. In the F(2) mice, a full genome scan revealed significant linkages on chromosomes 14 and 2. With regard to chromosome 14, analysis showed a single peak for linkage at 17 cM with a logarithm of odds (LOD) score of 9.9, designated plasma plant sterol 14 (Plast14). With regard to chromosome 2, analysis showed two significant peaks for linkage at 18 and 65 cMs with LOD scores of 4.1 and 3.65, respectively, designated Plast2a and Plast2b, respectively. Four interactions between loci, predominantly of an additive nature, were also demonstrated, the most significant between Plast14 and Plast2b (LOD 16.44). No significant linkage or gene interaction was detected for the ABCG5ABCG8 locus on chromosome 17. Therefore, other genes besides ABCG5ABCG8 influence plasma plant sterol levels and now become candidates to explain differences in plasma plant sterol levels between humans.
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Soccio RE, Adams RM, Romanowski MJ, Sehayek E, Burley SK, Breslow JL. The cholesterol-regulated StarD4 gene encodes a StAR-related lipid transfer protein with two closely related homologues, StarD5 and StarD6. Proc Natl Acad Sci U S A 2002; 99:6943-8. [PMID: 12011452 PMCID: PMC124508 DOI: 10.1073/pnas.052143799] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Using cDNA microarrays, we identified StarD4 as a gene whose expression decreased more than 2-fold in the livers of mice fed a high-cholesterol diet. StarD4 expression in cultured 3T3 cells was also sterol-regulated, and known sterol regulatory element binding protein (SREBP)-target genes showed coordinate regulation. The closest homologues to StarD4 were two other StAR-related lipid transfer (START) proteins named StarD5 and StarD6. StarD4, StarD5, and StarD6 are 205- to 233-aa proteins consisting almost entirely of START domains. These three constitute a subfamily among START proteins, sharing approximately 30% amino acid identity with one another, approximately 20% identity with the cholesterol-binding START domains of StAR and MLN64, and less than 15% identity with phosphatidylcholine transfer protein (PCTP) and other START domains. StarD4 and StarD5 were expressed in most tissues, with highest levels in liver and kidney, whereas StarD6 was expressed exclusively in the testis. In contrast to StarD4, expression of StarD5 and MLN64 was not sterol-regulated. StarD4, StarD5, and StarD6 may be involved in the intracellular transport of sterols or other lipids.
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