Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of action of a widely used drug gemfibrozil to reduce triglycerides (TG) and apolipoprotein B (apo B) is incompletely understood. Using human hepatoblastoma (HepG2) cells, we examined the effect of gemfibrozil on apo B secretion and TG synthesis catalyzed by diacylglycerol acyltransferase (DGAT), primary processes associated with the secretion of LDL. Gemfibrozil significantly decreased apo B secretion by HepG2 cells. It decreased oleate-induced stimulation of apo B secretion, suggesting that gemfibrozil-mediated inhibition of apo B secretion may be dependent on the synthesis of TG catalyzed by DGAT. Pre-incubation of HepG2 cells with gemfibrozil (200-400 micromol/l for 48 h) significantly inhibited microsomal DGAT activity. When added directly to the DGAT assay system containing control microsomes, gemfibrozil significantly inhibited the activity of DGAT by 14-25%. Gemfibrozil (200-400 micromol/l) inhibited TG synthesis by 47-50% as measured by the incorporation of 3H-oleic acid into TG. The data indicate that gemfibrozil inhibits DGAT activity resulting in decreased synthesis of TG and its availability for apo B lipidation rendering it susceptible to intracellular apo B degradation leading to the decreased secretion. These in-vitro data suggest a novel additional mechanism by which gemfibrozil lowers plasma TG and atherogenic apo B lipoproteins in dyslipidemic patients.
Atherosclerosis 2002 Oct
PMID:Effect of gemfibrozil on apolipoprotein B secretion and diacylglycerol acyltransferase activity in human hepatoblastoma (HepG2) cells. 1220 91

Although postprandial hypertriglyceridemia is a major contributing factor in the development of atherosclerosis, little information is available on the effect of insulin resistance and diabetes on intestinal fat transport. The aim of the present study was to examine intracellular events that govern lipid transport and apolipoprotein (apo) B-48-containing lipoprotein assembly in the small intestine of Psammomys obesus, a model of nutritionally induced insulin resistance and type 2 diabetes. Animals with normoglycemia/hyperinsulinemia and hyperglycemia/hyperinsulinemia exhibited high levels of triglycerides (TGs) in the plasma and intestine and postprandial plasma chylomicrons and apo B-48 compared with normoglycemic/normoinsulinemic animals. In vitro studies, using cultured jejunal explants incubated with either [14C]oleic acid or [35S]methionine, revealed their higher efficiency in de novo TG synthesis, apo B-48 biogenesis, and TG-rich lipoprotein assembly. Accordingly, enhanced monoacylglycerol and diacylglycerol acyltransferase activity was also discernible and concomitant with an increased content of L-fatty acid binding protein and in vivo chylomicron production rates. However, both the I-fatty acid binding protein amount and the apo B-48 proteasomal degradative pathway were decreased. Overall, our findings show that the development of an insulin-resistant/diabetic state in Psammomys obesus triggers the whole intra-enterocyte machinery, leading to lipoprotein assembly and favoring the intestinal oversecretion of apo B-48-lipoproteins, which may contribute to characteristic hypertriglyceridemia.
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PMID:Cellular aspects of intestinal lipoprotein assembly in Psammomys obesus: a model of insulin resistance and type 2 diabetes. 1451 38

The purpose of the present study was to examine the role of taxifolin, a plant flavonoid, on several aspects involving apolipoprotein B (apoB) secretion and triglyceride (TG) availability in HepG2 cells. Taxifolin was shown by ELISA to markedly reduce apoB secretion under basal and lipid-rich conditions up to 63% at 200 micromol/L. As to the mechanism underlying this effect, we examined whether taxifolin exerted its effect by limiting TG availability in the microsomal lumen essential for lipoprotein assembly. Taxifolin was shown to inhibit microsomal TG synthesis by 37% and its subsequent transfer into the lumen (-26%). The reduction in synthesis was due to a decrease in diacylglycerol acyltransferase (DGAT) activity (-35%). The effect on DGAT activity was found to be non-competitive and non-transcriptional in nature. Both DGAT-1 and DGAT-2 mRNA expression remained essentially unchanged suggesting the point of regulation may be at the post-transcriptional level. Evidence is accumulating that microsomal triglyceride transfer protein (MTP) is also involved in determining the amount of lumenal TG available for lipoprotein assembly and secretion. Taxifolin was shown to inhibit this enzyme by 41%. Whether the reduction in TG accumulation in the microsomal lumen is predominantly due to DGAT and/or MTP activity remains to be addressed. In summary, taxifolin reduced apoB secretion by limiting TG availability via DGAT and MTP activity.
Atherosclerosis 2004 Oct
PMID:Inhibitory activity of diacylglycerol acyltransferase (DGAT) and microsomal triglyceride transfer protein (MTP) by the flavonoid, taxifolin, in HepG2 cells: potential role in the regulation of apolipoprotein B secretion. 1538 Apr 46

The esterification of alcohols such as sterols, diacylglycerols, and monoacylglycerols with fatty acids represents the formation of both storage and cytoprotective molecules. Conversely, the overproduction of these molecules is associated with several disease pathologies, including atherosclerosis and obesity. The human acyl-CoA:diacylglycerol acyltransferase (DGAT) 2 gene superfamily comprises seven members, four of which have been previously implicated in the synthesis of di- or triacylglycerol. The remaining 3 members comprise an X-linked locus and have not been characterized. We describe here the expression of DGAT2 and the three X-linked genes in Saccharomyces cerevisiae strains virtually devoid of neutral lipids. All four gene products mediate the synthesis of triacylglycerol; however, two of the X-linked genes act as acyl-CoA wax alcohol acyltransferases (AWAT 1 and 2) that predominantly esterify long chain (wax) alcohols with acyl-CoA-derived fatty acids to produce wax esters. AWAT1 and AWAT2 have very distinct substrate preferences in terms of alcohol chain length and fatty acyl saturation. The enzymes are expressed in many human tissues but predominate in skin. In situ hybridizations demonstrate a differentiation-specific expression pattern within the human sebaceous gland for the two AWAT genes, consistent with a significant role in the composition of sebum.
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PMID:Identification of two novel human acyl-CoA wax alcohol acyltransferases: members of the diacylglycerol acyltransferase 2 (DGAT2) gene superfamily. 1567 Oct 38

Atherosclerosis remains the leading cause of death in developed countries and thus demands the development of safe therapeutic treatments. Novel risk factors, in addition to the traditional targets, are being assessed. The significance of inflammation in atherosclerotic plaque development has become indisputable. A large number of published studies support the fact that investigations of the inflammatory aspects of atherosclerosis will be the target for future development. The C-reactive protein in particular has drawn specific attention due to its role as an inflammatory marker of atherosclerosis. Novel targets for atherosclerotic intervention include inhibitors of cholesterol synthesis and absorption such as acyl-coenzyme A:cholesterol acyltransferase, acyl-coenzyme A:diacylglycerol acyltransferase and cholesteryl ester transfer protein inhibitors, potential novel antioxidants other than anti-inflammatory peroxisome proliferator activated receptor agonists, and apolipoprotein A-I mimetic peptides.
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PMID:Novel targets for the treatment of atherosclerosis. 1700 60

Nicotinic acid (niacin) has long been used for the treatment of lipid disorders and cardiovascular disease. Niacin favorably affects apolipoprotein (apo) B-containing lipoproteins (eg, very-low-density lipoprotein [VLDL], low-density lipoprotein [LDL], lipoprotein[a]) and increases apo A-I-containing lipoproteins (high-density lipoprotein [HDL]). Recently, new discoveries have enlarged our understanding of the mechanism of action of niacin and challenged older concepts. There are new data on (1) how niacin affects triglycerides (TGs) and apo B-containing lipoprotein metabolism in the liver, (2) how it affects apo A-I and HDL metabolism, (3) how it affects vascular anti-inflammatory events, (4) a specific niacin receptor in adipocytes and immune cells, (5) how niacin causes flushing, and (6) the characterization of a niacin transport system in liver and intestinal cells. New findings indicate that niacin directly and noncompetitively inhibits hepatocyte diacylglycerol acyltransferase-2, a key enzyme for TG synthesis. The inhibition of TG synthesis by niacin results in accelerated intracellular hepatic apo B degradation and the decreased secretion of VLDL and LDL particles. Previous kinetic studies in humans and recent in vitro cell culture findings indicate that niacin retards mainly the hepatic catabolism of apo A-I (vs apo A-II) but not scavenger receptor BI-mediated cholesterol esters. Decreased HDL-apo A-I catabolism by niacin explains the increases in HDL half-life and concentrations of lipoprotein A-I HDL subfractions, which augment reverse cholesterol transport. Initial data suggest that niacin, by inhibiting the hepatocyte surface expression of beta-chain adenosine triphosphate synthase (a recently reported HDL-apo A-I holoparticle receptor), inhibits the removal of HDL-apo A-I. Recent studies indicate that niacin increases vascular endothelial cell redox state, resulting in the inhibition of oxidative stress and vascular inflammatory genes, key cytokines involved in atherosclerosis. The niacin flush results from the stimulation of prostaglandins D(2) and E(2) by subcutaneous Langerhans cells via the G protein-coupled receptor 109A niacin receptor. Although decreased free fatty acid mobilization from adipose tissue via the G protein-coupled receptor 109A niacin receptor has been a widely suggested mechanism of niacin to decrease TGs, physiologically and clinically, this pathway may be only a minor factor in explaining the lipid effects of niacin.
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PMID:Mechanism of action of niacin. 1837 37

Coenzyme A (CoA):diacylglycerol acyltransferase 1 (DGAT1) is 1 of the 2 known DGAT enzymes that catalyze the final and only committed step in triacylglycerol synthesis; this enzyme is considered to be a potential therapeutic target in metabolic disorders such as obesity and its related lipid abnormalities. Compound-Z, a novel specific small-molecule DGAT1 inhibitor, significantly reduced adipose tissue weight and tended to hepatic lipid accumulation in genetically obese KKAy mice. These actions were shown to almost the same extent in both a high-fat feeding condition in which triacylglycerols are synthesized mainly via exogenous fatty acid and a low-fat, high-carbohydrate feeding condition in which triacylglycerols are synthesized mainly via de novo fatty acid synthesis. This inhibitor also significantly reduced plasma and/or hepatic cholesterol levels in KKAy mice in a high-fat feeding condition. This cholesterol-lowering effect was suggested to be due to mainly decreases in cholesterol absorption from the small intestine. These results suggest that Compound-Z is a promising and attractive agent not only for the treatment of obesity but also hepatic steatosis and circulating lipid abnormalities that are the leading causes of atherosclerosis.
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PMID:Coenzyme A: diacylglycerol acyltransferase 1 inhibitor ameliorates obesity, liver steatosis, and lipid metabolism abnormality in KKAy mice fed high-fat or high-carbohydrate diets. 2047 3

Triacylglycerols (TG) are the major storage molecules of metabolic energy and fatty acids in several tissues. The final step in TG biosynthesis is catalyzed by acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes. Lack of whole body DGAT1 is associated with reduced lipid-induced inflammation. Since one major component of atherosclerosis is chronic inflammation we hypothesized that DGAT1 deficiency might ameliorate atherosclerotic lesion development. We therefore crossbred Apolipoprotein E-deficient (ApoE(-/-)) mice with Dgat1(-/-) mice. ApoE(-/-) and ApoE(-/-)Dgat1(-/-) mice were fed Western-type diet (WTD) for 9weeks and thereafter examined for plaque formation. The mean atherosclerotic lesion area was substantially reduced in ApoE(-/-)Dgat1(-/-) compared with ApoE(-/-) mice in en face and aortic valve section analyses. The reduced lesion size was associated with decreased cholesterol uptake and absorption by the intestine, reduced plasma TG and cholesterol concentrations and increased cholesterol efflux from macrophages. The expression of adhesion molecules was reduced in aortas of ApoE(-/-)Dgat1(-/-) mice, which might be the reason for less migration capacities of monocytes and macrophages and the observed decreased amount of macrophages within the plaques. From our results we conclude that the lack of DGAT1 is atheroprotective, implicating an additional application of DGAT1 inhibitors with regard to maintaining cholesterol homeostasis and attenuating atherosclerosis.
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PMID:Lack of acyl-CoA:diacylglycerol acyltransferase 1 reduces intestinal cholesterol absorption and attenuates atherosclerosis in apolipoprotein E knockout mice. 2192 78

Lipoprotein metabolism is an important contributing factor in the development and progression of atherosclerosis. Plasma lipoproteins and their receptors are heavily glycosylated and sialylated, and levels of sialic acids modulate their biological functions. Sialylation is controlled by the activities of sialyltranferases and sialidases. To address the impact of sialidase (neu1) activity on lipoprotein metabolism, we have generated a mouse model with a hypomorphic neu1 allele (B6.SM) that displays reduced sialidase expression and sialidase activity. The objectives of this study are to determine the impact of sialidase on the rate of hepatic lipoprotein secretion and lipoprotein uptake. Our results indicate that hepatic levels of cholesterol and triglycerides are significantly higher in B6.SM mice compared with C57Bl/6 mice; however, VLDL-triglyceride production rate is lower. In addition, B6.SM mice show significantly lower levels of hepatic microsomal triglyceride transfer protein (MTP) and active sterol-regulatory element binding protein (SREBP)-2 but higher levels of diglyceride acyltransferase (DGAT)2; these are all indicative of increased hepatic lipid storage. Rescue of sialidase activity in hypomorphic sialidase mice using helper-dependent adenovirus resulted in increased VLDL production and an increase in MTP levels. Furthermore, hypomorphic sialidase expression results in stabilization of hepatic LDL receptor (LDLR) protein expression, which enhances LDL uptake. These findings provide novel evidence for a central role of sialidase in the cross talk between the uptake and production of lipoproteins.
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PMID:Hypomorphic sialidase expression decreases serum cholesterol by downregulation of VLDL production in mice. 2298 45

Target substrate-specific hammerhead ribozyme cleaves the specific mRNA efficiently and results in the inhibition of gene expression. In humans, overproduction of apolipoprotein B (apoB) is positively associated with premature coronary artery diseases. The goal of this study is to demonstrate that long-term reduction of apoB gene expression using hammerhead ribozyme would result in inhibition of atherosclerosis development. We designed two hammerhead ribozymes targeted at the nucleotides of apoB mRNA GUC(2326) (designated RB1) and GUA(6679) (designated RB15), and we used self-complementary adeno-associated virus 8.2 (scAAV8.2) vector to deliver these active ribozymes of RB1, RB15, combination of RB1/RB15, and an inactive hammerhead ribozyme RB15 mutant to atherosclerosis-prone LDb mice (Ldlr(-/-)Apobec1(-/-)). LDb mice lack both low density lipoproteins (LDL) receptor (Ldlr(-/-)) and apoB mRNA editing enzyme (Apobec1(-/-)) genes and develop atherosclerosis spontaneously. After the RB1, RB15, or combination of RB1/RB15 ribozymes treatment, the LDb mice had significantly decreased plasma triglyceride and apoB levels, resulting in markedly decreased of atherosclerotic lesions, Furthermore, the active ribozymes treatment decreased the levels of diacylglycerol acyltransferase 1 (Dgat1) mRNA and the levels of multiple diacylglycerol (DAG) molecular species. These results provide the first evidence that decreased apoB levels results to reduction of Dgat1 expression and triglyceride levels (TAG), which had a significant impact on the development of atherosclerosis.Molecular Therapy-Nucleic Acids (2013) 2, e125; doi:10.1038/mtna.2013.53; published online 1 October 2013.
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PMID:Long-term Expression of Apolipoprotein B mRNA-specific Hammerhead Ribozyme via scAAV8.2 Vector Inhibits Atherosclerosis in Mice. 2408 45


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