Biomedical subjects

Patrick Y Muller

Publications and source records attributed to Patrick Y Muller.

8 recordsLinked to original sources

PubMed2005

Comparative quantification of pharmacodynamic parameters of chiral compounds (RRR- vs. all-rac-alpha tocopherol) by global gene expression profiling.

Pharmacologically active compounds (e.g. from the groups of pharmaceutical drugs, cofactors or vitamins) often consist of two or more stereoisomers (enantiomers or diastereoisomers) which may differ in their pharmacodynamic/kinetic, toxicological and biological properties. A well-known example is vitamin E which is predominantly administered as two different forms, one derived from natural sources (mainly soybeans), and one from production by chemical total-synthesis. While vitamin E from natural sources occurs as a single stereoisomer (RRR-alpha-tocopherol), synthetic vitamin E (all-rac-alpha-tocopherol) is an equimolar mixture of eight stereoisomers. Based on a number of animal studies it has been suggested that the biological potency of natural-source vitamin E is 1.36 greater compared to its counterpart produced by chemical synthesis. In this study, we have used the Affymetrix GeneChip technology to evaluate the feasibility of a new bio-assay where the gene regulatory activities of RRR-alpha-tocopherol and all-rac-alpha-tocopherol were quantified and compared on the genome-wide level. For this purpose, HepG2 cells were supplemented with increasing amounts of RRR- or all-rac-alpha-tocopherol for 7 days. Genes showing a dose-related induction/repression were identified by global gene expression profiling. Our findings show that RRR- and all-rac-alpha-tocopherol share an identical transcriptional activity, i.e. induce/repress the expression of the same set of genes. Based on the transcriptional dose-response data, EC50 and IC50 values were determined for each of these genes. The feasibility of calculating a "transcriptional potency factor" of RRR- vs. all-rac-e-tocopherol was evaluated by dividing the EC50/IC50 of RRR-alpha-tocopherol by the corresponding EC50/IC50 of all-rac-alpha-tocopherol for every of the vitamin E responsive genes. Using this approach we have calculated 215 single biopotency ratios. Subsequently, the mean of all potency ratios was found to be 1.05. In the present work we propose a new assay for the analysis and comparison of the biological activity and potency of chiral compounds in vivo.

Cell Line, Tumor↗

PubMed2004

Identification of hepatic molecular mechanisms of action of alpha-tocopherol using global gene expression profile analysis in rats.

The recent discovery that vitamin E (VE) regulates gene activity at the transcriptional level indicates that VE may exert part of its biological effects by mechanisms which may be independent of its well-recognised antioxidant function. The objective of this study was the identification of hepatic vitamin E-sensitive genes and examination of the effects of VE on their corresponding biological endpoints. Two groups of male rats were randomly assigned to either a VE-sufficient diet or to a control diet deficient in VE for 290 days. High-density oligonucleotide microarrays comprising over 7000 genes were used to assess the transcriptional response of the liver. Differential gene expression was monitored over a period of 9 months, at four different time-points, and rats were individually profiled. This experimental strategy identified several VE-sensitive genes, which were chronically altered by dietary VE. VE supplementation down-regulated scavenger receptor CD36, coagulation factor IX and 5-alpha-steroid reductase type 1 mRNA levels while hepatic gamma glutamyl-cysteinyl synthetase was significantly up-regulated. Measurement of the corresponding biological endpoints such as activated partial thromboplastin time, plasma dihydrotestosterone and hepatic glutathione substantiated the gene chip data which indicated that dietary VE plays an important role in a range of metabolic processes within the liver.

Animal Feed↗

PubMed2004

Large heterogeneity of mutations in the gene encoding the low-density lipoprotein receptor in subjects with familial hypercholesterolaemia.

Molecular genetic testing for presymptomatic identification of subjects affected by familial hypercholesterolaemia (FH) is difficult due to the heterogeneity of the mutations in the gene encoding the low-density lipoprotein receptor (LDLR) in most populations. This investigation presents a detailed analysis of comparable, country-specific prevalence data of LDLR mutations in subjects with clinically defined FH and assesses the heterogeneous mutation diversity observed in most geographic regions.

Genetic Heterogeneity↗

PubMed2002

Indinavir inhibits sterol-regulatory element-binding protein-1c-dependent lipoprotein lipase and fatty acid synthase gene activations.

BACKGROUND: A syndrome characterized by hypertriglyceridaemia, hypercholesterolaemia, hyperinsulinaemia, and lipodystrophy has been found to be associated with highly active antiretroviral treatment (HAART) including protease inhibitors. A marker predicting this syndrome has been previously identified in the gene encoding the sterol-regulatory element-binding protein (SREBP)-1c, a regulator of triglycerides, cholesterol, insulin, and adipocytes. OBJECTIVE: A possible inhibition of SREBP-1c-dependent genes by the protease inhibitor indinavir and its possible reversal by the lipid-lowering drug simvastatin were studied. METHODS: The effects of indinavir and simvastatin on the inhibition/activation of SREBP-1c-dependent genes were compared with the effects of indinavir and simvastatin on the inhibition/activation of SREBP-1c-independent genes. RESULTS: Indinavir inhibited the SREBP-1c-dependent genes encoding the lipoprotein lipase (103 nmol/l resulted in an inhibition of 12.4%; P = 0.0051) and the fatty acid synthase (103 nmol/l resulted in an inhibition of 30.3%; P = 0.036) in a dose-dependent fashion but not the SREBP-1c-independent gene encoding the low-density lipoprotein receptor. Simvastatin antagonized the indinavir-induced SREBP-1c-inhibition. CONCLUSIONS: Indinavir inhibits important effector genes of the SREBP-1c pathway, explaining major HAART-related adverse effects.

Base Sequence↗

PubMed2002

Sterol-regulatory element-binding protein (SREBP)-2 contributes to polygenic hypercholesterolaemia.

Sterol-regulatory element-binding protein (SREBP)-2 is a key regulator of cholesterol. When cells are deprived of cholesterol, proteolytic cleavage releases the NH(2)-terminal domain of SREBP-2 that binds and activates the promoters of SREBP-2-regulated genes including the genes encoding the low-density lipoprotein (LDL) receptor, 3-hydroxymethyl-3-glutaryl-(HMG-)CoA-synthase, and HMG-CoA-reductase. Thus, SREPB-2 gene activation leads to enhanced cholesterol uptake and biosynthesis. A novel protein polymorphism (SREBP-2-595A/G) discovered in the regulatory domain of human SREBP-2 was investigated regarding its impact on cholesterol homeostasis. In human embryonic kidney (HEK)-293-cells, the cleavage-rate of the SREBP-2-595A-isoform was slightly decreased compared to that of the SREBP-2-595G-isoform. Since cleavage of SREBP-2 activates the LDL receptor-mediated uptake of plasma cholesterol, we hypothesized the LDL receptor-mediated uptake to be decreased in homozygous SREBP-2-595A-carriers and thus, plasma total cholesterol (TC) to be higher than in SREBP-2-595G-carriers. Multiple linear regression analysis of population samples from Switzerland (N=1334) and Israel (N=923) demonstrated a significant positive, gene dose-dependent association of the SREBP-2-595A-isoform with higher plasma TC (P=0.001). This cholesterol-modulating effect was present in hypercholesterolaemic (DeltaTC=1.05 mmol/l, 14.4%; P=0.002; N=477), but absent in normocholesterolaemic subjects (DeltaTC=0.06 mmol/l, 1.4%; P=0.334; N=1780). In summary, a slightly but constantly decreased cleavage-rate of the SREBP-2-595A-isoform compared to that of the SREBP-2-595G-isoform may lead to a reduced transcriptional activation of the LDL receptor-gene weakening the SREBP-mediated compensation mechanisms, and may, therefore, be a critical factor in the development of polygenic hypercholesterolaemia.

Adolescent↗

PubMed2002

Processing of gene expression data generated by quantitative real-time RT-PCR.

Quantitative real-time PCR represents a highly sensitive and powerful technique for the quantitation of nucleic acids. It has a tremendous potential for the high-throughput analysis of gene expression in research and routine diagnostics. However, the major hurdle is not the practical performance of the experiments themselves but rather the efficient evaluation and the mathematical and statistical analysis of the enormous amount of data gained by this technology, as these functions are not included in the software provided by the manufacturers of the detection systems. In this work, we focus on the mathematical evaluation and analysis of the data generated by quantitative real-time PCR, the calculation of the final results, the propagation of experimental variation of the measured values to the final results, and the statistical analysis. We developed a Microsoft Excel-based software application coded in Visual Basic for Applications, called Q-Gene, which addresses these points. Q-Gene manages and expedites the planning, performance, and evaluation of quantitative real-time PCR experiments, as well as the mathematical and statistical analysis, storage, and graphical presentation of the data. The Q-Gene software application is a tool to cope with complex quantitative real-time PCR experiments at a high-throughput scale and considerably expedites and rationalizes the experimental setup, data analysis, and data management while ensuring highest reproducibility.

Computational Biology↗

PubMedDate not supplied

Expression of COX-2 and Wnt pathway genes in adenomas of familial adenomatous polyposis patients treated with meloxicam.

BACKGROUND: Familial adenomatous polyposis (FAP) is an autosomal, dominantly inherited predisposition to colorectal cancer caused by germline mutations within the adenomatous polyposis coli (APC) gene, a key member of the Wnt signalling pathway. A new class of non-steroidal anti-inflammatory drugs (NSAIDs), the specific cyclooxygenase 2 (COX-2) inhibitors, have recently been applied for the treatment of FAP patients. PATIENTS AND METHODS: The expressions of the Wnt members and targets APC, c-myc, cyclin D1 and COX-2, as measured by real-time quantitative RT-PCR, have been evaluated in fresh samples of normal colorectal mucosa and matched adenoma tissue of six unrelated FAP patients before and after treatment with meloxicam. RESULTS: A significant up-regulation of COX-2 in adenomas after treatment with meloxicam was found. Furthermore, in adenomas, a down-regulation of APC after treatment and a tight correlation of the expressions of the two Wnt targets, c-myc and cyclin D1, in both stages of treatment were observed. CONCLUSION: A feedback loop mediated by the peroxisome proliferator-activated receptor (PPAR) gamma is discussed as being responsible for the up-regulation of COX-2

Adenomatous Polyposis Coli↗

PubMedDate not supplied

Overexpression of Wnt target genes in adenomas of familial adenomatous polyposis patients.

Germline mutations within the adenomatous polyposis coli (APC) gene, a key member of the Wnt signalling pathway, have been shown to cause adenoma development in familial adenomatous polyposis (FAP), a dominantly inherited predisposition to colorectal cancer. Although it has been suggested for several years that alterations within the Wnt pathway are the underlying events for the development of colorectal adenomas in FAP patients, no detailed analysis of the gene expressions of Wnt pathway members has been available in fresh colorectal tissue of FAP patients, so far. Thus, we investigated potential differences in the expressions of APC and its Wnt partners conductin, beta-catenin, cyclin D1, and c-myc in normal colorectal mucosa and matched adenoma tissue of 14 FAP patients using real-time quantitative PCR. The expressions of both Wnt target genes, cyclin D1 and c-myc, were significantly increased in adenoma compared to matched normal mucosa. Furthermore, the overexpressions of these two genes showed a highly significant positive correlation. Our data suggest that the concomitant overexpression of the Wnt targets and cell cycle regulators cyclin D1 and c-myc plays an important role in the neoplastic proliferation of adenomas in FAP patients.

Adenomatous Polyposis Coli↗