7 research outputs found
Analysis of Sterol-Regulatory Element-Binding Protein 1c Target Genes in Mouse Liver during Aging and High-Fat Diet
International audienceBackground: The sterol regulatory element-binding protein (SREBP) 1c contributes to the transcriptional coordination of cholesterol, fatty acid, and carbohydrate metabolisms. Alterations in these processes accelerate the progression of hepatic steatosis and insulin resistance during aging and obesity. Methods: Using an ex vivo chromatin immunoprecipitation coupled to microarray (ChIP-on-chip) technique combined with genome-wide gene expression analysis, we analyzed the transcriptomic adaptations mediated by Srebp-1c binding to gene promoters in the liver of mice fed with a low-fat diet or a high-fat diet (HFD) for either 1 or 12 months. Results: Aging had a higher transcriptional impact than HFD and modified the expression of genes involved in fatty acid oxidation and oxidative stress. HFD was associated with a marked induction of genes involved in lipid and cholesterol metabolism. The prolonged high-fat feeding together with the aging effects stimulates inflammatory pathways. ChIP-on-chip applied to aging and HFD analyses revealed that the binding of SREBP-1c to a series of promoters accompanied a paralleled modification of gene expression. Therefore, SREBP-1c could play a role in aging and high-fat feeding through the regulation of genes involved in lipid metabolism and inflammatory response. Conclusions: This study represents an original ex vivo experiment to elucidate the molecular events involved in metabolic disorders. Copyright (C) 2013 S. Karger AG, Base
Supplementary Material for: Analysis of Sterol-Regulatory Element-Binding Protein 1c Target Genes in Mouse Liver during Aging and High-Fat Diet
<b><i>Background:</i></b> The sterol regulatory element-binding protein (SREBP) 1c contributes to the transcriptional coordination of cholesterol, fatty acid, and carbohydrate metabolisms. Alterations in these processes accelerate the progression of hepatic steatosis and insulin resistance during aging and obesity. <b><i>Methods:</i></b> Using an ex vivo chromatin immunoprecipitation coupled to microarray (ChIP-on-chip) technique combined with genome-wide gene expression analysis, we analyzed the transcriptomic adaptations mediated by <i>Srebp-1c</i> binding to gene promoters in the liver of mice fed with a low-fat diet or a high-fat diet (HFD) for either 1 or 12 months. <b><i>Results:</i></b> Aging had a higher transcriptional impact than HFD and modified the expression of genes involved in fatty acid oxidation and oxidative stress. HFD was associated with a marked induction of genes involved in lipid and cholesterol metabolism. The prolonged high-fat feeding together with the aging effects stimulates inflammatory pathways. ChIP-on-chip applied to aging and HFD analyses revealed that the binding of SREBP-1c to a series of promoters accompanied a paralleled modification of gene expression. Therefore, SREBP-1c could play a role in aging and high-fat feeding through the regulation of genes involved in lipid metabolism and inflammatory response. <b><i>Conclusions:</i></b> This study represents an original ex vivo experiment to elucidate the molecular events involved in metabolic disorders
Pharmacometabonomic Investigation of Dynamic Metabolic Phenotypes Associated with Variability in Response to Galactosamine Hepatotoxicity
Galactosamine (galN) is widely used as an <i>in
vivo</i> model of acute liver injury. We have applied an integrative
approach,
combining histopathology, clinical chemistry, cytokine analysis, and
nuclear magnetic resonance (NMR) spectroscopic metabolic profiling
of biofluids and tissues, to study variability in response to galactosamine
following successive dosing. On re-challenge with galN, primary non-responders
displayed galN-induced hepatotoxicity (induced response), whereas
primary responders exhibited a less marked response (adaptive response).
A systems-level metabonomic approach enabled simultaneous characterization
of the xenobiotic and endogenous metabolic perturbations associated
with the different response phenotypes. Elevated serum cytokines were
identified and correlated with hepatic metabolic profiles to further
investigate the inflammatory response to galN. The presence of urinary <i>N</i>-acetylglucosamine (glcNAc) correlated with toxicological
outcome and reflected the dynamic shift from a resistant to a sensitive
phenotype (induced response). In addition, the urinary level of glcNAc
and hepatic level of UDP-<i>N</i>-acetylhexosamines reflected
an adaptive response to galN. The unique observation of galN-pyrazines
and altered gut microbial metabolites in fecal profiles of non-responders
suggested that gut microfloral metabolism was associated with toxic
outcome. Pharmacometabonomic modeling of predose urinary and fecal
NMR spectroscopic profiles revealed a diverse panel of metabolites
that classified the dynamic shift between a resistant and sensitive
phenotype. This integrative pharmacometabonomic approach has been
demonstrated for a model toxin; however, it is equally applicable
to xenobiotic interventions that are associated with wide variation
in efficacy or toxicity and, in particular, for prediction of susceptibility
to toxicity
The differentiation of prehypertrophic into hypertrophic chondrocytes drives an OA-remodeling program and IL-34 expression
International audienceObjectives. We hypothesize that chondrocytes from the deepest articular cartilage layer are pivotal in maintaining cartilage integrity and that the modification of their prehypertrophic phenotype to a hypertrophic phenotype will drive cartilage degradation in osteoarthritis. Design. Murine immature articular chondrocytes (iMACs) were successively cultured into three different culture media to induce a progressive hypertrophic differentiation. Chondrocyte were phenotypically characterized by whole-genome microarray analysis. The expression of IL-34 and its receptors PTPRZ1 and CSF1R in chondrocytes and in human osteoarthritis tissues was assessed by RT-qPCR, ELISA and immunohistochemistry. The expression of bone remodeling and angiogenesis factors and the cell response to IL-1β and IL-34 were investigated by RT-qPCR and ELISA. Results. Whole-genome microarray analysis showed that iMACs, prehypertrophic and hypertrophic chondrocytes each displayed a specific phenotype. IL-1β induced a stronger catabolic effect in prehypertrophic chondrocytes than in iMACs. Hypertrophic differentiation of prehypertrophic chondrocytes increased Bmp-2 (95%CI [0.78;1.98]), Bmp-4 (95%CI [0.89;1.59]), Cxcl12 (95%CI [2.19;5.41]), CCL2 (95%CI [3.59;11.86]), Mmp3 (95%CI [10.29;32.14]) and Vegf mRNA expression (95%CI [0.20;1.74]). Microarray analysis identified IL-34, PTPRZ1 and CSFR1 as being strongly overexpressed in hypertrophic chondrocytes. IL-34 was released by human osteoarthritis cartilage; its receptors were expressed in human osteoarthritis tissues. IL-34 stimulated CCL2 and MMP13 in osteoblasts and hypertrophic chondrocytes but not in iMACs or prehypertrophic chondrocytes. Conclusion. Our results identify prehypertrophic chondrocytes as being potentially pivotal in the control of cartilage and subchondral bone integrity. Their differentiation int