The key lipid metabolism transcription factor sterol regulatory element-binding protein (SREBP)-1a integrates gene regulatory effects of hormones, cytokines, nutrition and metabolites as lipids, glucose or cholesterol via stimuli specific phosphorylation by different MAPK cascades. We have formerly reported the systemic impact of phosphorylation in transgenic mouse models with liver-specific overexpression of the N-terminal transcriptional active domain of SREBP-1a (alb-SREBP-1a) or a MAPK kinase phosphorylation sites deficient variant (alb-SREBP-1aP; (S63A, S117A, T426V)), respectively. Here we investigated the molecular basis of the systemic observation in holistic hepatic gene expression analyses and lipid degrading organelles involved in the pathogenesis of metabolic syndrome, i.e. peroxisomes, by 2D-DIGE and mass spectrometry analyses. Although alb-SREBP-1a mice develop a severe phenotype with visceral adipositas and hepatic lipid accumulation featuring a fatty liver, the hepatic differential gene expression and alterations in peroxisomal protein patterns compared to control mice were surprisingly relative low. In contrast, phosphorylation site deficient alb-SREBP-1aP mice, protected from hepatic lipid accumulation phenotype, showed gross alteration in hepatic gene expression and peroxisomal proteome. Further knowledge based analyzes revealed that overexpression of SREBP-1a favored mainly acceleration in lipid metabolism and indicated a regular insulin signaling, whereas disruption of SREBP-1a phosphorylation resulted in massive alteration of cellular processes including signs for loss of lipid metabolic targets. These results could be the link to a disturbed lipid metabolism that overall resembles a state of insulin resistance.
Inactivation of SREBP-1a Phosphorylation Prevents Fatty Liver Disease in Mice: Identification of Related Signaling Pathways by Gene Expression Profiles in Liver and Proteomes of Peroxisomes.
Sex, Age, Specimen part
View SamplesMajor causes of lipid accumulation in liver are increased import, synthesis or decreased catabolism of fatty acids. The latter is caused by dysfunction of cellular organelle controlling energy homeostasis, i.e. mitochondria. However, peroxisomes appear to be an important organelle in lipid metabolism of hepatocytes, but little is known about their role in the development of non-alcoholic fatty liver disease (NAFLD). To investigate the role of peroxisomes next to mitochondria in excessive hepatic lipid accumulation we used the leptin resistant db/db mice on C57BLKS background, a mouse model that develops hyperphagia induced diabetes with obesity and NAFLD.
Peroxisomes compensate hepatic lipid overflow in mice with fatty liver.
Sex, Age, Specimen part
View SamplesPurpose: MetS consist of five risk factors: elevated blood pressure and fasting glucose, visceral obesity, dyslipidemia and hypercholesterinemia. The physiological impact of lipid metabolism indicated as visceral obesity and hepatic lipid accumulation is still under debate. One major cause of disturbed lipid metabolism might be dysfunction of cellular organelles controlling energy homeostasis, i.e. mitochondria and peroxisomes.
Alteration of Liver Peroxisomal and Mitochondrial Functionality in the NZO Mouse Model of Metabolic Syndrome.
Sex, Age, Specimen part
View SamplesThe regeneration of diseased hyaline cartilage remains a great challenge, mainly because degeneration activities after major injury or due to age-related processes overwhelm the self-renewal capacity of the tissue. We show that repair tissue from human articular cartilage of late stages of osteoarthritis harbor a unique progenitor cell population, termed chondrogenic progenitor cells exhibiting stem cell characteristics, such as multipotency, lack of immune system activation and, in particular, migratory activity. The isolated CPC exhibit a high chondrogenic potential and were able to populate diseased tissue in vivo. Moreover, down-regulation of the osteogenic transcription factor runx-2 enhanced the expression of the chondrogenic transcription factor sox-9 and consequently the matrix synthesis potential of chondrogenic progenitor cells. Our results, while offering new insight into the biology of progenitor cells from diseased cartilage tissue, might assist future strategies to treat late stages of osteoarthritis.
Migratory chondrogenic progenitor cells from repair tissue during the later stages of human osteoarthritis.
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Epigenetic antagonism between polycomb and SWI/SNF complexes during oncogenic transformation.
Specimen part
View SamplesEpigenetic alterations have been increasingly implicated in oncogenesis. Analysis of Drosophila mutants suggests that Polycomb and SWI/SNF complexes can serve antagonistic developmental roles. However, the relevance of this relationship to human disease is unclear. Here we have investigated functional relationships between these epigenetic regulators in oncogenic transformation. Mechanistically, we show that loss of the SNF5 tumor suppressor leads to elevated expression of the Polycomb gene EZH2 and that Polycomb targets are broadly H3K27-trimethylated and repressed in SNF5-deficient fibroblasts and cancers. Further, we show antagonism between SNF5 and EZH2 in the regulation of stem cell-associated programs and that Snf5 loss activates those programs. Finally, using conditional mouse models, we show that inactivation of Ezh2 blocks tumor formation driven by Snf5 loss.
Epigenetic antagonism between polycomb and SWI/SNF complexes during oncogenic transformation.
Specimen part
View SamplesPrecise nucleosome-positioning patterns at promoters are thought to be crucial for faithful transcriptional regulation. However, the mechanisms by which these patterns are established and dynamically maintained and subsequently contribute to transcriptional control are poorly understood. The Swi/Snf (Baf) chromatin remodeling complex is a master developmental regulator and tumor suppressor that is capable of mobilizing nucleosomes in biochemical assays. Yet, its role in establishing the nucleosome landscape in vivo is unclear. Here we have inactivated Snf5 and Brg1, core subunits of the mammalian Swi/Snf complex, to evaluate their effects on chromatin structure and transcription levels genome-wide. We find that inactivation of either subunit leads to disruptions of specific nucleosome patterning combined with a loss of overall nucleosome occupancy at a large number of promoters, regardless of their association with CpG islands. These rearrangements are accompanied by gene expression changes that promote cell proliferation. Collectively, these findings define a direct relationship between chromatin-remodeling complexes, chromatin structure, and transcriptional regulation.
Swi/Snf chromatin remodeling/tumor suppressor complex establishes nucleosome occupancy at target promoters.
Specimen part
View SamplesRenal hypoxia is widespread in acute kidney injury (AKI) of various aetiologies. Hypoxia adaptation, conferred through the hypoxia-inducible factor (HIF), appears to be insufficient. Here we show that HIF activation in renal tubules through Pax8-rtTA-based inducible knockout of von Hippel-Lindau protein (VHL-KO) protects from rhabdomyolysis-induced AKI. In this model, histological observations indicate that injury mainly affects proximal convoluted tubules, with 5% necrosis at d1 and 40% necrosis at d2. HIF-1alpha up-regulation in distal tubules reflects renal hypoxia. However, lack of HIF in proximal tubules suggests insufficient adaptation by HIF.
Tubular von Hippel-Lindau knockout protects against rhabdomyolysis-induced AKI.
Specimen part, Disease, Disease stage, Treatment
View SamplesThe circadian clock controls a wide variety of metabolic and homeostatic processes in a number of tissues, including the kidney. However, the role of the renal circadian clocks remains largely unknown. To address this question we performed transcriptomic analysis in mice with inducible and conditional ablation of the circadian clock system in the renal tubular cells (Bmal1lox/lox/Pax8-rtTA/LC1 mice). Deep sequencing of the renal transcriptome revealed significant changes in the expression of genes related to metabolic pathways and organic anion transport. In parallel, kidneys from Bmal1lox/lox/Pax8-rtTA/LC1 mice exhibited a significant decrease in the NAD+/NADH ratio suggesting an increased anaerobic glycolysis and/or decreased mitochondrial function. In-depth analysis of two selected pathways revealed (i) a significant increase in plasma urea levels correlating with increased renal arginase 2 (Arg2) activity, hyperargininemia and increase of the kidney arginine content; (ii) a significantly increased plasma creatinine concentration and reduced capacity of the kidney to secrete anionic drugs (furosemide), paralleled by a ~80% decrease in the expression levels of organic anion transporter OAT3 (SLC22a8). Collectively, these results indicate that the renal circadian clocks control a variety of metabolic/homeostatic processes at both the intra-renal and systemic levels and are involved in drug disposition. Overall design: Mice with a specific ablation of the Arntl gene encoding BMAL1 in the renal tubular cells were compared to wild-type littermate at ZT4 and ZT16 (ZT – Zeitgeber time units; ZT0 is the time of light on and ZT12 is the time of light off).
Nephron-Specific Deletion of Circadian Clock Gene Bmal1 Alters the Plasma and Renal Metabolome and Impairs Drug Disposition.
Specimen part, Subject, Time
View SamplesPericytes derived from skin dermis can substantially enhance the short-term tissue-regenerative capacity of human epidermal cells already committed to differentiation; they also display both phenotypic and functional properties of mesenchymal stem cells. In this microarray analysis, we compared the gene expression profile of dermal pericytes to that of the remaining dermal cells of neonatal human foreskin.
A role for pericytes as microenvironmental regulators of human skin tissue regeneration.
Specimen part
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