Macrophage ABCA2 deletion modulates intracellular cholesterol deposition, affects macrophage apoptosis, and decreases early atherosclerosis in LDL receptor knockout mice

Biopharmaceutic

Molecular cloning, tissue expression and regulation of Liver X Receptor (LXR) transcription factors of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss)

Fish are important sources of high quality protein, essential minerals such as iodine and selenium, vitamins including A, D and E, and omega-3 fatty acids in the human diet. With declining fisheries worldwide, farmed fish constitute an ever-increasing proportion of fish in the food basket. Sustainable development of aquaculture dictates that diets will have to contain increasing levels of plant products that are devoid of cholesterol, but contain phytosterols that are known to have physiological effects in mammals. Liver X receptors (LXR) are transcription factors whose activity is modulated by sterols, with activation inducing cholesterol catabolism and de novo fatty acid biosynthesis in liver. Transcriptomic analysis has shown that substitution of fish meal and oil with plant products induces genes of cholesterol and fatty acid metabolism in salmonids. Here we report the cloning of LXR cDNAs from two species of salmonid fish that are important in aquaculture. The full-length cDNA (mRNA) of LXR obtained from salmon was shown to be 3766 bp, which included a 5’-untranslated region (UTR) of 412 bp and a 3’-UTR of 1960 bp and an open reading frame (ORF) of 1394 bp, which specified a protein of 462 amino acids. The trout LXR full-length cDNA was 2056 bp, including 5’- and 3’-UTRs of 219 and 547 bp, respectively, and an ORF of 1290 bp, which specified a protein of 427 amino acids. The protein sequences included characteristic features of mammalian LXRs, including the DNA binding (DBD), containing P-box, ligand binding (LBD) and activation function-2 (AF-2) domains, D-box, D (hinge) region, and eight cysteines that belong to the two zinc fingers. Phylogenetic analysis clustered the salmonid LXRs together, more closely with zebrafish and more distantly from medaka and stickleback. A pair-wise comparison among vertebrate LXR sequences showed the amino acid sequence predicted by the salmon LXR ORF showed greatest identity to that of trout 97%, and 97%, 87% and 81% identity to LXRs of zebrafish, frog and human (LXRα). The trout LXR ORF showed 96%, 92% and 82% identity to LXRs of zebrafish, frog and human (LXRα). Surprisingly, the expression of LXR was lowest in liver of all tissues examined and in salmon the greatest expression was observed in pyloric caeca with liver showing intermediate expression. It is likely that tissue expression was affected by the physiological status of the sampled animals. Certainly, nutritional, environmental and/or developmental regulation was evident in salmon, where the expression of LXR in liver was higher in fish in seawater than in freshwater, and higher in fish fed fish oil compared to fish fed vegetable oil in adult salmon

Metabolite Profiling Identifies Candidate Markers Reflecting the Clinical Adaptations Associated with Roux-en-Y Gastric Bypass Surgery

Background: Roux-en-Y gastric bypass (RYGB) surgery is associated with weight loss, improved insulin sensitivity and glucose homeostasis, and a reduction in co-morbidities such as diabetes and coronary heart disease. To generate further insight into the numerous metabolic adaptations associated with RYGB surgery, we profiled serum metabolites before and after gastric bypass surgery and integrated metabolite changes with clinical data. Methodology and Principal Findings: Serum metabolites were detected by gas and liquid chromatography-coupled mass spectrometry before, and 3 and 6 months after RYGB in morbidly obese female subjects (n = 14; BMI = 46.261.7). Subjects showed decreases in weight-related parameters and improvements in insulin sensitivity post surgery. The abundance of 48 % (83 of 172) of the measured metabolites changed significantly within the first 3 months post RYGB (p,0.05), including sphingosines, unsaturated fatty acids, and branched chain amino acids. Dividing subjects into obese (n = 9) and obese/ diabetic (n = 5) groups identified 8 metabolites that differed consistently at all time points and whose serum levels changed following RYGB: asparagine, lysophosphatidylcholine (C18:2), nervonic (C24:1) acid, p-Cresol sulfate, lactate, lycopene, glucose, and mannose. Changes in the aforementioned metabolites were integrated with clinical data for body mass index (BMI) and estimates for insulin resistance (HOMA-IR). Of these, nervonic acid was significantly and negatively correlated with HOMA-IR (p = 0.001, R = 20.55)

Effects of Deletion of Macrophage ABCA7 on Lipid Metabolism and the Development of Atherosclerosis in the Presence and Absence of ABCA1

ABCA7, a close relative of ABCA1 which facilitates cholesterol efflux to lipid-poor apoproteins, has been implicated in macrophage lipid efflux and clearance of apoptotic cells in in vitro studies. In the current study, we investigated the in vivo effects of macrophage ABCA7 deficiency on lipid metabolism and atherosclerosis. Chimeras with dysfunctional ABCA7 in macrophages and other blood cells were generated by transplantation of bone marrow from ABCA7 knockout (KO) mice into irradiated low-density lipoprotein receptor (LDLr) KO mice. Unexpectedly, macrophage ABCA7 deficiency did not significantly affect atherosclerosis susceptibility of LDLr KO mice after 10 weeks Western-type diet feeding. However, ABCA7 deficiency was associated with 2-fold (p<0.05) higher macrophage ABCA1 mRNA expression levels. Combined disruption of ABCA1 and ABCA7 in bone-marrow-derived cells increased atherosclerotic lesion development (1.5-fold (p>0.05) as compared to wild type transplanted mice. However, single deletion of ABCA1 had a similar effect (1.8-fold, p<0.05). Macrophage foam cell accumulation in the peritoneal cavity was reduced in ABCA1/ABCA7 dKO transplanted animals as compared to single ABCA1 KO transplanted mice, which was associated with increased ABCG1 expression. Interestingly, spleens of ABCA1/ABCA7 double KO transplanted mice were significantly larger as compared to the other 3 groups and showed massive macrophage lipid accumulation, a reduction in CD3+ T-cells, and increased expression of key regulators of erythropoiesis. In conclusion, deletion of ABCA7 in bone marrow-derived cells does not affect atherogenesis in the arterial wall neither in the absence or presence of ABCA1. Interestingly, combined deletion of bone marrow ABCA1 and ABCA7 causes severe splenomegaly associated with cellular lipid accumulation, a reduction in splenic CD3+ T cells, and induced markers of erythropoeisis. Our data indicate that ABCA7 may play a role in T cell proliferation and erythropoeisis in spleen

Impact of bone marrow ATP-binding cassette transporter A1 deficiency on atherogenesis is independent of the presence of the low-density lipoprotein receptor

BACKGROUND AND AIMS\nMETHODS\nRESULTS\nCONCLUSIONS\nThere is extensive evidence from bone marrow transplantation studies that hematopoietic ATP binding cassette A1 (Abca1) is atheroprotective in low-density lipoprotein receptor (Ldlr) deficient mice. In contrast, studies using lysosyme M promoter-driven deletion of Abca1 in Ldlr deficient mice failed to show similar effects. It was hypothesized that the discrepancy between these studies might be due to the presence of Ldlr in bone marrow-derived cells in the transplantation model. In this study, we aim to determine the contribution of Ldlr to the atheroprotective effect of hematopoietic Abca1 in the murine bone marrow transplantation model.\nWild-type, Ldlr-/-, Abca1-/-, and Abca1-/-Ldlr-/- bone marrow was transplanted into hypercholesterolemic Ldlr-/- mice.\nBone marrow Lldr deficiency did not influence the effects of Abca1 on macrophage cholesterol efflux, foam cell formation, monocytosis or plasma cholesterol. Ldlr deficiency did reduce circulating and peritoneal lymphocyte counts, albeit only in animals lacking Abca1 in bone marrow-derived cells. Importantly, the effects of Abca1 deficiency on atherosclerosis susceptibility were unaltered by the presence or absence of Ldlr. Bone marrow Ldlr deficiency did lead to marginally but consistently decreased atherosclerosis, regardless of Abca1 deficiency. Thus, Ldlr expression on bone marrow-derived cells does, to a minimal extent, influence atherosclerotic lesion development, albeit independent of Abca1.\nThis study provides novel insight into the relative impact of Ldlr and Abca1 in bone marrow-derived cells on macrophage foam cell formation and atherosclerosis development in vivo. We have shown that Ldlr and Abca1 differentially and independently influence atherosclerosis development in a murine bone marrow transplantation model of atherosclerosis.Biopharmaceutic

Disodium ascorbyl phytostanol phosphate (FM-VP4), a modified phytostanol, is a highly active hypocholesterolaemic agent that affects the enterohepatic circulation of both cholesterol and bile acids in mice

Disodium ascorbyl phytostanol phosphate (FM-VP4) is a synthetic compound derived from sitostanol and campestanol that has proved to be efficient as a cholesterol-lowering therapy in mice and human subjects. However, the mechanism of action of FM-VP4 remains unknown. The present study tests the ability of FM-VP4 to alter intestinal and liver cholesterol homeostasis in mice. Female C57BL/6J mice were fed either a control chow or a 2 % FM-VP4-enriched diet for 4 weeks. FM-VP4 reduced the in vivo net intestinal cholesterol absorption and plasma and liver cholesterol concentrations by 2.2-, 1.5- and 1.6-fold, respectively, compared with control mice. Furthermore, FM-VP4 also showed an impact on bile acid homeostasis. In FM-VP4 mice, liver and intestinal bile acid content was increased by 1.3- and 2.3-fold, respectively, whereas faecal bile acid output was 3.3-fold lower. FM-VP4 also increased the intestinal absorption of orally administered [H-3]taurocholic acid to small intestine in vivo. Inhibition of intestinal cholesterol absorption by FM-VP4 was not mediated via transcriptional increases in intestine liver X receptor (LXR)-alpha, adenosine triphosphate-binding cassette transporter (ABC)-A1, ABCG5/G8 nor to decreases in intestinal Niemann-Pick Cl-like 1 (NPC1L1) expression. In contrast, FM-VP4 up-regulated liver LXR alpha, ABCA1, ABCG5, scavenger receptor class BI (SR-BI) and hydroxymethylglutaryl coenzyme A reductase (HMGCoA-R) gene expression, whereas it down-regulated several farnesoid X receptor (FXR)-target genes such as cytochrome P450 family 7 subfamily A polypeptide I (CYP7AI) and Na+/taurocholate co-transporter polypeptide (NTCP). In conclusion, FM-VP4 reduced intestinal cholesterol absorption, plasma and liver cholesterol and affected bile acid homeostasis by inducing bile acid intestinal reabsorption and changed the liver expression of genes that play an essential role in cholesterol homeostasis. This is the first phytosterol or stanol that affects bile acid metabolism and lowers plasma cholesterol levels in normocholesterolaemic mice

Disodium ascorbyl phytostanol phosphate (FM-VP4), a modified phytostanol, is a highly active hypocholesterolaemic agent that affects the enterohepatic circulation of both cholesterol and bile acids in mice

Disodium ascorbyl phytostanol phosphate (FM-VP4) is a synthetic compound derived from sitostanol and campestanol that has proved to be efficient as a cholesterol-lowering therapy in mice and human subjects. However, the mechanism of action of FM-VP4 remains unknown. The present study tests the ability of FM-VP4 to alter intestinal and liver cholesterol homeostasis in mice. Female C57BL/6J mice were fed either a control chow or a 2 % FM-VP4-enriched diet for 4 weeks. FM-VP4 reduced the in vivo net intestinal cholesterol absorption and plasma and liver cholesterol concentrations by 2.2-, 1.5- and 1.6-fold, respectively, compared with control mice. Furthermore, FM-VP4 also showed an impact on bile acid homeostasis. In FM-VP4 mice, liver and intestinal bile acid content was increased by 1.3- and 2.3-fold, respectively, whereas faecal bile acid output was 3.3-fold lower. FM-VP4 also increased the intestinal absorption of orally administered [H-3]taurocholic acid to small intestine in vivo. Inhibition of intestinal cholesterol absorption by FM-VP4 was not mediated via transcriptional increases in intestine liver X receptor (LXR)-alpha, adenosine triphosphate-binding cassette transporter (ABC)-A1, ABCG5/G8 nor to decreases in intestinal Niemann-Pick Cl-like 1 (NPC1L1) expression. In contrast, FM-VP4 up-regulated liver LXR alpha, ABCA1, ABCG5, scavenger receptor class BI (SR-BI) and hydroxymethylglutaryl coenzyme A reductase (HMGCoA-R) gene expression, whereas it down-regulated several farnesoid X receptor (FXR)-target genes such as cytochrome P450 family 7 subfamily A polypeptide I (CYP7AI) and Na+/taurocholate co-transporter polypeptide (NTCP). In conclusion, FM-VP4 reduced intestinal cholesterol absorption, plasma and liver cholesterol and affected bile acid homeostasis by inducing bile acid intestinal reabsorption and changed the liver expression of genes that play an essential role in cholesterol homeostasis. This is the first phytosterol or stanol that affects bile acid metabolism and lowers plasma cholesterol levels in normocholesterolaemic mice

Effects of Deletion of Macrophage ABCA7 on Lipid Metabolism and the Development of Atherosclerosis in the Presence and Absence of ABCA1

Diabetes mellitus: pathophysiological changes and therap