Project description:Purpose: to identify the impact of cdk4 inhibition on genes and pathways involved in age-associated liver disorders using next generation sequencing on young and control- or PD0332991-treated aged mice. Methods: RNA was isolated from livers of young (2 month old) and old (20-22 month old) C57Bl6 mice. Old mice were either either control-aged mice or PD-0332991 treated aged mice (450mg/dk for 2 weeks). The three conditions were represented in triplicate. Raw reads passing quality filtration were aligned to the mm10 mouse genome using UCSC annotations by pseudoalignment in Kallisto. All reasonably expressed transcripts were submitted for statistical analysis to identify age-altered transcripts corrected by cdk4 inhibition. Results: We mapped a minimum of 20 million reads per sample, which corresponded to a total of 25,240 transcripts. Of these, 12,551 were considered reasonably expressed and were included in analysis comparing control-aged v young and PD0332991-treated-aged v young. Conclusion: Inhibition of cdk4 in ages wildtype mice by cdk4 inhibitor PD-0332991 reduces CEBPa-p300 and reduced aged-related alterations of hepatic structure and function.
Project description:The pathophysiologic continuum of non-alcoholic fatty liver disease begins with steatosis. Despite great progress in understanding the gene regulatory program directing steatosis, how it is orchestrated epigenetically is unclear. Here we show that the histone H3-lysine-4-methyltransferase, MLL4/KMT2D, plays critical roles in overnutrition-induced murine steatosis via dual mechanisms. First, in response to high fat diet (HFD), MLL4 activates the expression of PPARγ2, an overnutrition-induced steatotic transcription factor. Second, HFD enables the coactivator function of MLL4 for PPARγ2, as overnutrition-activated ABL1 kinase phosphorylates PPARγ2 and enhances its association with MLL4, facilitating recruitment of MLL4 to steatotic target genes of PPARγ2, including the PPARγ2-encoding gene itself, and their transactivation via H3-lysine-4-methylation. Consistently, inhibition of ABL1 improves the fatty liver condition of ob/ob mice by suppressing the pro-steatotic action of MLL4. Our results uncover a critical regulatory axis in overnutrition-directed steatosis, and present this ABL1-PPARγ2-MLL4 axis as a new target for anti-steatosis drug development.
Project description:Pyrimidine catabolism is implicated in hepatic steatosis. Dihydropyrimidine Dehydrogenase (DPYD) is an enzyme responsible for uracil and thymine catabolism, and DPYD human genetic variability affects clinically observed toxicity following 5-Fluorouracil (5-FU) administration. In an in vitro model of diet-inducedfatty acid-induced steatosis, the pharmacologic inhibition of DPYD resulted in protection from lipid accumulation. Additionally, a gain-of-function mutation of DPYD, created through clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR-Cas9) engineering, led to an increased lipid burden, which was associated with altered mitochondrial functionality in a hepatocarcionma cell line. The studies presented herein describe a novel role for DPYD in hepatocyte metabolic regulation as a modulator of hepatic steatosis.
Project description:Hepatic steatosis is the result of an imbalance between nutrient delivery and metabolism in the liver. It is the first hallmark of Non-alcoholic fatty liver disease (NAFLD) and is characterized by the accumulation of excess lipids in the liver that can drive liver failure, inflammation, and cancer. Mitochondria control the fate and function of cells and compelling evidence implicates these multifunctional organelles in the appearance and progression of liver dysfunction, although it remains to be elucidated which specific mitochondrial functions are actually causally linked to NAFLD. In this study, we identified Mitochondrial Fission Process 1 protein (MTFP1) as a key regulator of mitochondrial and metabolic activity in the liver. Deletion of Mtfp1 in hepatocytes is physiologically benign in mice yet leads to the upregulation of oxidative phosphorylation (OXPHOS) complexes and mitochondrial respiration, independently of mitochondrial biogenesis. Consequently, hepatocyte-specific knockout mice are protected against high fat diet-induced hepatic steatosis and metabolic dysregulation. Additionally, we find that deletion of Mtfp1 in liver mitochondria inhibits mitochondrial permeability transition pore opening in hepatocytes, conferring protection against apoptotic liver damage in vivo and ex vivo. Our work uncovers novel functions of MTFP1 in the liver, positioning this gene as an unexpected regulator of OXPHOS and a therapeutic candidate for NAFLD.
Project description:The impairment of the intestinal barrier will lead to the accumulation of fat and harmful substances in the liver, inducing hepatic steatosis or steatohepatitis. Zhang et al. identified NSD2 in the intestine as a novel and essential regulator of hepatic steatosis. NSD2 directly regulates transcriptional activation of ERN1 through the modification of H3 dimethylated on lysine 36 (H3K4me36), thereby activating the ERN1-JNK axis to induce inflammatory response, intestinal barrier impairment, and hepatic steatosis. This functional mechanism of NSD2 provides a potential therapeutic target for this disease.
Project description:The impairment of the intestinal barrier will lead to the accumulation of fat and harmful substances in the liver, inducing hepatic steatosis or steatohepatitis. Zhang et al. identified NSD2 in the intestine as a novel and essential regulator of hepatic steatosis. NSD2 directly regulates transcriptional activation of ERN1 through the modification of H3 dimethylated on lysine 36 (H3K4me36), thereby activating the ERN1-JNK axis to induce inflammatory response, intestinal barrier impairment, and hepatic steatosis. This functional mechanism of NSD2 provides a potential therapeutic target for this disease.
Project description:Expanding beta cell mass is a critical goal in the fight against diabetes. CDK4, an extensively characterized cell cycle activator, is required to establish and maintain beta cell number. Beta cell failure in the IRS2-deletion mouse type 2 diabetes model is in part due to loss of CDK4 regulator Cyclin D2. We set out to determine whether replacement of endogenous CDK4 with the inhibitor-resistant mutant CDK4-R24C rescued the loss of beta cell mass in Irs2-deficient mice. Surprisingly, not only beta cell mass but also beta cell dedifferentiation was effectively rescued, despite no improvement in whole body insulin sensitivity. Ex vivo studies in primary islet cells revealed a novel mechanism in which CDK4 intervened downstream in the insulin signaling pathway to prevent FOXO1-mediated transcriptional repression of critical beta cell transcription factor Pdx1. FOXO1 inhibition was not related to E2F1 activity, to FOXO1 phosphorylation, or even to FOXO1 subcellular localization, but rather was related to deacetylation and reduced FOXO1 abundance. Taken together, these results demonstrate a novel differentiation-promoting activity of the classical cell cycle activator CDK4 and support the concept that beta cell mass can be expanded without compromising function.
Project description:We demonstrated that RORa-deficient staggerer mice (RORasg/sg) fed with a high fat diet (HFD) showed reduced adiposity and hepatic triglyceride levels compared to wild type (WT) littermates and were resistant to the development of hepatic steatosis, adipose-associated inflammation, and insulin resistance. Gene expression profiling showed that many genes involved in triglyceride synthesis and storage, including Cidec, Cidea, and Mogat1, were expressed at much lower levels in liver of RORasg/sg mice. In addition to reduced lipid accumulation, inflammation was greatly diminished in white adipose tissue (WAT) of RORasg/sg mice fed with a HFD. The infiltration of macrophages and the expression of many immune-response and pro-inflammatory genes, including those encoding various chemo/cytokines, toll-like receptors, and TNF signaling proteins, were significantly reduced in RORasg/sg WAT. Moreover, RORasg/sg mice fed with a HFD were protected from the development of insulin resistance. Together, these results indicate that RORa plays a critical role in the regulation of several aspects of metabolic syndrome. Therefore, RORa may provide a novel therapeutic target in the management of obesity and associated metabolic diseases. Liver and white adipose tissue (WAT) total RNAs were purified from 5 WT and 5 RORasg/sg (natural deletion of RORa gene in mice) mice fed with a high fat diet for 6 weeks. Then samples were applied on Agilent mouse genome chip.