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Cholesterol Biosynthesis Pathway (cholesterol + biosynthesis_pathway)
Selected AbstractsChronic Alcohol Consumption Disrupted Cholesterol Homeostasis in Rats: Down-Regulation of Low-Density Lipoprotein Receptor and Enhancement of Cholesterol Biosynthesis Pathway in the LiverALCOHOLISM, Issue 3 2010Zhigang Wang Background:, Chronic alcohol consumption causes alcoholic liver disease, which is associated, or initiated, with dysregulated lipid metabolism. Very recent evidence suggested that dysregulated cholesterol metabolism plays an important role in the pathogenesis of alcoholic fatty liver diseases, however, the effects of chronic alcohol exposure on cholesterol homeostasis have not been well studied and underlying mechanisms behind are still elusive. Methods:, Male Sprague,Dawley rats weighing 250 ± 5.5 g (mean ± SEM) divided into 2 groups (8 rats per group) and pair-fed with liquid diets containing (in percent of energy intake) 18% protein, 35% fat, 12% carbohydrate, and 35% either ethanol (ethanol diet) or an isocaloric maltose-dextrin mixture (control diet), according to Lieber and De Carli, for 4 weeks. Results:, Long-term excessive alcohol feeding to rats caused fatty liver and liver injury, which was associated with disrupted cholesterol homeostasis, characterized by increased hepatic cholesterol levels and hypercholesterolemia. Hepatic cholesterol increases were concomitant with constantly activated sterol regulatory element-binding protein-2 (SREBP-2) in the liver and increased expression of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase, a rate-limiting enzyme for cholesterol de novo synthesis, indicating enhanced cholesterol biosynthesis. Alcohol-induced hypercholesterolemia was accompanied by decreased LDL receptor (LDLr) levels in the liver. Further investigations revealed that chronic alcohol exposure increased hepatic proprotein convertase subtilisin/kexin type 9 (PCSK9) contents to down-regulate LDLr via a post-translational mechanism. Moreover, alcohol feeding suppressed extracellular signal-regulated kinase (ERK) activation in the liver. In vitro studies showed that inhibition of ERK activation was associated with decreased LDLr expression in HepG2 cells. Conclusions:, Our study provides the first evidence that both increased PCSK9 expression and suppressed ERK activation in the liver contributes to alcohol-induced hypercholesterolemia in rats. [source] A free radical-generating system induces the cholesterol biosynthesis pathway: a role in Alzheimer's diseaseAGING CELL, Issue 2 2009Marķa Recuero Summary Oxidative stress, which plays a critical role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD), is intimately linked to aging , the best established risk factor for AD. Studies in neuronal cells subjected to oxidative stress, mimicking the situation in AD brains, are therefore of great interest. This paper reports that, in human neuronal cells, oxidative stress induced by the free radical-generating xanthine/xanthine oxidase (X-XOD) system leads to apoptotic cell death. Microarray analyses showed a potent activation of the cholesterol biosynthesis pathway following reductions in the cell cholesterol synthesis caused by the X-XOD treatment; furthermore, the apoptosis was reduced by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) expression with an interfering RNA. The potential importance of this mechanism in AD was investigated by genetic association, and it was found that HMGCR, a key gene in cholesterol metabolism and among those most strongly upregulated, was associated with AD risk. In summary, this work presents a human cell model prepared to mimic the effect of oxidative stress in neurons that might be useful in clarifying the mechanism involved in free radical-induced neurodegeneration. Gene expression analysis followed by genetic association studies indicates a possible link among oxidative stress, cholesterol metabolism and AD. [source] Gene expression changes following androgen receptor elimination in LNCaP prostate cancer cellsMOLECULAR CARCINOGENESIS, Issue 4 2003Iris E. Eder Abstract We have shown recently that inhibition of androgen receptor (AR) expression with an antisense AR oligonucleotide (ODN) inhibits LNCaP prostate tumor cells in vitro as well as in vivo. In this study, we investigated gene expression changes that occur after AR signaling blockade, either through AR elimination by antisense treatment or through complete androgen receptor inhibition by androgen deprivation combined with the antiandrogen bicalutamide, in order to search for genes that are directly or indirectly regulated through the AR. Gene expression changes were investigated with cDNA NIH 10K gene microarrays in response to treatment over 48 h. Expression of selected genes was further analyzed by real-time reverse transcriptase (RT)-polymerase chain reaction (PCR), Western blotting, and radioimmunoassay. A comparison of antisense-treated and androgen-deprived cells revealed several concordances such as significant downregulation of prostate-specific genes, cell-cycle regulatory genes, genes of the cholesterol biosynthesis pathway, and several cytoskeletal genes. However, there were also several genes that were differentially regulated. Among the genes that were exclusively changed by treatment with the antisense AR ODN were the insulin-like growth factor binding protein 2 (IGFBP2) and the phosphatidylinositol-4-phosphate 5-kinase type I alpha (PIP5KIA). On the other hand, complete androgen receptor blockade induced changes in the expression of the prostate overexpressed gene 1 and the S100 calcium binding protein P. In summary, we identified a cohort of interesting genes whose expression was highly affected by elimination of the AR in LNCaP prostate cancer cells. Further investigations are warranted to clarify their role in the AR signaling pathway and their susceptibility as a target for the treatment of prostate cancer. © 2003 Wiley-Liss, Inc. [source] Molecular prenatal diagnosis in a case of an X-linked dominant chondrodysplasia punctataPRENATAL DIAGNOSIS, Issue 9 2003N. V. Whittock Abstract X-linked dominant chondrodysplasia punctata, (CDPX2,MIM302960) also known as Conradi,Hünermann,Happle syndrome, is a rare form of skeletal dysplasia that affects the skeleton, skin, hair, and eyes. The disorder is caused by mutations within the emopamil binding protein (Ebp) that functions as a delta(8), delta(7) sterol isomerase in the cholesterol biosynthesis pathway. To date, over 40 separate mutations have been reported in the Ebp gene, EBP, with no obvious correlation between the molecular defects and the severity of the clinical phenotype. We have studied a 30-year-old woman who presented in adulthood with skin, hair, and mild skeletal defects but no ocular abnormalities and have identified a heterozygous missense mutation within the third transmembrane domain of the protein. In addition, we have performed molecular prenatal testing on her unborn fetus. The results demonstrate inter-familial variability for missense mutations within the emopamil binding protein and add to the molecular data for CDPX2. Copyright © 2003 John Wiley & Sons, Ltd. [source] Squalene synthase: a critical enzyme in the cholesterol biosynthesis pathwayCLINICAL GENETICS, Issue 1 2009R Do High levels of plasma low-density lipoprotein cholesterol (LDL-C) are a significant risk factor for heart disease. Statins (3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors) have been extensively used to treat high-plasma LDL-C levels and are effective in preventing heart disease. However, statins can be associated with adverse side effects in some patients and do not work effectively in others. As an alternative to statins, the development of cholesterol-lowering agents that directly inhibit squalene synthase have shown promise. Clinical studies have shown that squalene synthase inhibitors are effective in lowering plasma levels of total cholesterol and LDL-C. Squalene synthase plays an important role in the cholesterol biosynthesis pathway as it is responsible for the flow of metabolites into either the sterol or the non-sterol branches of the pathway. In addition, variants of the squalene synthase gene appear to modulate plasma cholesterol levels in human populations and therefore may be linked to cardiovascular disease. In this review, we examine squalene synthase and the gene that codes for it (farnesyldiphosphate farnesyltransferase 1). In particular, we investigate their role in the regulation of cellular and plasma cholesterol levels, including data that suggest that squalene synthase may be involved in the etiology of hypercholesterolemia. [source] | |||||||||||||