Liver-specific induction of Abcg5 and Abcg8 stimulates reverse cholesterol transport in response to ezetimibe treatment.

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.

Maternal nutrition induces pervasive gene expression changes but no detectable DNA methylation differences in the liver of adult offspring.

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.

Targeting of Acyl-CoA synthetase 5 decreases jejunal fatty acid activation with no effect on dietary long-chain fatty acid absorption.

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.

Cathepsin B is a novel gender-dependent determinant of cholesterol absorption from the intestine.

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.

Dysregulation of cholesterol homeostasis in human prostate cancer through loss of ABCA1.

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.

Systematic haplotype analysis resolves a complex plasma plant sterol locus on the Micronesian Island of Kosrae.

Pinpointing culprit causal variants along signal peaks of genome-wide association studies (GWAS) is challenging. To overcome confounding effects of multiple independent variants at such a locus and narrow the interval for causal allele capture, we developed an approach that maps local shared haplotypes harboring a putative causal variant. We demonstrate our method in an extreme isolate founder population, the pacific Island of Kosrae.

Moderately decreased cholesterol absorption rates are associated with a large atheroprotective effect.

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.

Cholesterol absorption from the intestine is a major determinant of reverse cholesterol transport from peripheral tissue macrophages.

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).

Bioinformatics tools enabling u-statistics for microarrays.

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.

Identification of quantitative trait loci affecting body composition in a mouse intercross.

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.

A complex plasma plant sterol locus on mouse chromosome 14 has at least two genes regulating intestinal sterol absorption.

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.

Two loci on chromosome 9 control bile acid composition: evidence that a strong candidate gene, Cyp8b1, is not the culprit.

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.

Phytosterolemia on the island of Kosrae: founder effect for a novel ABCG8 mutation results in high carrier rate and increased plasma plant sterol levels.

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.

Cholesterol feeding of mice expressing cholesterol 7alpha-hydroxylase increases bile acid pool size despite decreased enzyme activity.

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.

Effects of streptozotocin-induced diabetes in apolipoprotein AI deficient mice.

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.

Genetic regulation of cholesterol absorption and plasma plant sterol levels: commonalities and differences.

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.

Novel putative SREBP and LXR target genes identified by microarray analysis in liver of cholesterol-fed mice.

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.

Loci controlling plasma non-HDL and HDL cholesterol levels in a C57BL /6J x CASA /Rk intercross.

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.

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.

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).

Hypercholesterolemia and changes in lipid and bile acid metabolism in male and female cyp7A1-deficient mice.

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.

Liver receptor homologue-1 mediates species- and cell line-specific bile acid-dependent negative feedback regulation of the apical sodium-dependent bile acid transporter.

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.

Loci on chromosomes 14 and 2, distinct from ABCG5/ABCG8, regulate plasma plant sterol levels in a C57BL/6J x CASA/Rk intercross.

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.

The cholesterol-regulated StarD4 gene encodes a StAR-related lipid transfer protein with two closely related homologues, StarD5 and StarD6.

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.