Estrogen signaling and the Metabolic Syndrome: Targeting the hepatic ERalpha action
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE36514 | GEO | 2012/12/01
SECONDARY ACCESSION(S): PRJNA153469
REPOSITORIES: GEO
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Project description:We have previously shown that total estrogen receptor alpha (ERalpha knockout (KO) mice exhibit hepatic insulin resistance. To investigate the contribution of hepatic ERalpha action for the observed phenotype, we established a liver-selective ERalphaKO mouse model, LERKO. We demonstrate that LERKO mice have efficient reduction of ERalpha selectively within the liver. However, LERKO and wild type control mice do not differ in body weight, and have a comparable hormone profile as well as insulin and glucose response, even when challenged with a high fat diet. Furthermore, LERKO mice display very minor changes in their hepatic transcript profile. Collectively, our findings indicate that hepatic ERalpha action may not be the initiating factor for the previously identified hepatic insulin resistance in ERalphaKO mice. We have previously shown that total estrogen receptor alpha (ERalpha knockout (KO) mice exhibit hepatic insulin resistance. To investigate the contribution of hepatic ERalpha action for the observed phenotype, we established a liver-selective ERalphaKO mouse model, LERKO. Using microarray analysis, we compared the hepatic transcriptional profile of LERKO vs control mice.
2012-12-01 | E-GEOD-36514 | biostudies-arrayexpress
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Project description:ChIP followed by deep sequencing was performed with antibodies to ERalpha in U2OS-ERalpha cells treated with 17beta-estradiol.
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Project description:PGC1beta is a transcriptional coactivator that potently stimulates mitochondrial biogenesis and respiration of cells. Here, we have generated mice lacking exons 3 to 4 of the Pgc1beta gene (PGC1beta E3,4-/E3,4- mice). These mice express a mutant protein that has reduced coactivation activity on a subset of transcription factors, including ERRalpha, a major target of PGC1beta in the induction of mitochondrial gene expression. The mutant mice have reduced expression of OXPHOS genes and mitochondrial dysfunction in liver and skeletal muscle as well as elevated liver triglycerides. Euglycemic-hyperinsulinemic clamp and insulin signaling studies show that PGC1beta mutant mice have normal skeletal muscle response to insulin, but have hepatic insulin resistance. These results demonstrate that PGC1beta is required for normal expression of OXPHOS genes and mitochondrial function in liver and skeletal muscle. Importantly, these abnormalities do not cause insulin resistance in skeletal muscle but cause substantially reduced insulin action in the liver. Keywords: Liver and quadricpes muscle gene expression, WT vs. PGC1beta mutant
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Project description:Impaired estrogen production and action are associated with obesity and insulin resistance in male males however the tissues critical for estrogen action in the maintenance of metabolic homeostasis remain inadequately understood. Moreover, the cell specific target genes and molecular actions of estrogen in males remain unknown. We generated male mice with a muscle-specific ERa knockout (MERKO) to determine the role of this hormone nuclear receptor in controlling metabolic function and insulin action in skeletal muscle. Male MERKO mice became insulin resistant with age and accumulated more adipose tissue than floxed control mice. Skeletal muscle was distinguished by enlarged hyper-fused mitochondria that produced increased amounts of superoxide, and this was associated with enhanced proinflammatory signaling. The striking mitochondrial phenotype was accompanied by reduced protein abundance of electron transport chain proteins and the mitochondrial biogenesis marker Pgc1a. Muscle from MERKO mice showed imbalanced protein abundance of mitochondrial fission-fusion proteins most notably marked reductions in total DRP1, MFN1, and OPA1 were observed compared with f/f control. To recapitulate the reduction in DRP1 protein leading to impairment in mitochondrial fission, we generated mice with a muscle-specific heterozygous deletion in Drp1 (mDrp1+/-). mDrp1+/- mice phenocopied the aberrant muscle mitochondrial morphology and dysfunction of the MERKO mice and developed insulin resistance with age. Skeletal muscle ERa is critical for the maintenance of mitochondrial function and metabolic homeostasis in male mice.
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Project description:In addition to the estrogen responsive element (ERE)-dependent gene expression, E2-ERalpha regulates transcription through functional interactions with transfactors bound to their cognate regulatory elements on DNA, hence the ERE-independent signaling pathway. However, the relative importance of the ERE-independent pathway in E2-ERalpha signaling is unclear. Our studies in infected ER-negative cell models with an ERalpha demonstrated that genomic responses assessed by microarrays from the alter cellular growth, death or motility. Keywords: MDA-MB-231 cells
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Project description:Liver-specific Knockdown of JNK1 Up-regulates Proliferator-activated Receptor Coactivator 1 and Increases Plasma Triglyceride despite Reduced Glucose and Insulin Levels in Diet-induced Obese Mice. The c-Jun N-terminal kinases (JNKs) have been implicated in the development of insulin resistance, diabetes, and obesity. Genetic disruption of JNK1, but not JNK2, improves insulin sensitivity in diet-induced obese (DIO) mice. We applied RNA interference to investigate the specific role of hepatic JNK1 in contributing to insulin resistance in DIO mice. Adenovirus-mediated delivery of JNK1 short-hairpin RNA (Ad-shJNK1) resulted in almost complete knockdown of hepatic JNK1 protein without affecting JNK1 protein in other tissues. Liver-specific knockdown of JNK1 resulted in significant reductions in circulating insulin and glucose levels, by 57 and 16%, respectively. At the molecular level, JNK1 knockdown mice had sustained and significant increase of hepatic Akt phosphorylation. Furthermore, knockdown of JNK1 enhanced insulin signaling in vitro. Unexpectedly, plasma triglyceride levels were robustly elevated upon hepatic JNK1 knockdown. Concomitantly, expression of proliferator-activated receptor coactivator 1, glucokinase, and microsomal triacylglycerol transfer protein was increased. Further gene expression analysis demonstrated that knockdown of JNK1 up-regulates the hepatic expression of clusters of genes in glycolysis and several genes in triglyceride synthesis pathways. Our results demonstrate that liver-specific knockdown of JNK1 lowers circulating glucose and insulin levels but increases triglyceride levels in DIO mice. Experiment Overall Design: Liver sample from vehicle, GFP Adv-shRNA, or Jnk1 Adv-shRNA treated DIO mice with 5, 4, and 5 replicates, respectively
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