Transcriptional changes of adult liver biliary epithelial cells in vivo upon high-fat diet
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ABSTRACT: Background and Aims: During severe or chronic hepatic injury, biliary epithelial cells (BECs), also known as cholangiocytes, undergo rapid reprogramming and proliferation, a process known as ductular reaction (DR), and allow liver regeneration by differentiating into both functional cholangiocytes and hepatocytes. While DR is a hallmark of chronic liver diseases, including advanced stages of non-alcoholic fatty liver disease (NAFLD), the early events underlying BEC activation are largely unknown. Since NAFLD initiates with increased lipid accumulation, a stage called steatosis; we hypothesized that BECs isolated directly from steatotic livers might address current knowledge gaps in early BEC activation. Approach and Results: Here, we used methods allowing isolation and extensive transcriptional characterization of BECs from chow diet (CD)- and high-fat diet (HFD)-fed mice livers. We demonstrate that BECs readily accumulate lipids during HFD feeding and that lipid overload induces the conversion of adult cholangiocytes into active BECs through upregulation of the cell cycle and DNA replication signature. This event is accompanied by significant downregulation of extracellular matrix organization in BECs derived from HFD-fed mice livers but not CD-fed mice livers. Mechanistically, we found that lipid overload unleashes the activation of the E2F transcription factors in BECs, which drives cell cycle progression.
Project description:Obesity is tightly associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). However, the molecular mechanisms of obesity-induced fatty liver remain largely unknown.In order to identify genes that are potentially involved in dysfunctional hepatic lipid homeostasis in obesity, we performed a clustering analysis of Affymetrix arrays,which revealed that a number of mRNAs were dys-regulated in the livers of mice fed a high-fat diet (HFD), compared with mice fed a normal chow diet (ND). To identify genes that are potentially involved in dysfunctional hepatic lipid homeostasis in obesity, male C57BL/6 mice aged 8 weeks were fed a normal diet (ND) or high-fat-diet (HFD) containing 60 Kcal% of fat for 12 weeks. Then mice were sacrificed and total RNAs were isoloated from hepatic tissues. Affymetrix array hybridisation and scanning were performed using Mouse Genome 430 2.0 chips.Total RNA samples obtained from six mice per group (ND and HFD) and pooled by each of the two were used for microarray analysis.
Project description:Biliary epithelial cells (BECs) form bile ducts in the liver, and are facultative liver stem cells that establish a ductular reaction (DR) to support liver regeneration following injury. Liver damage induces periportal LGR5+ putative liver stem cells which can form BEC-like organoids, suggesting RSPO-LGR4/5-mediated WNT/β-catenin activity is important for a DR. We addressed the roles for this and other signaling pathways in a DR by performing a focused CRISPR-based loss-of-function screen in BEC-like organoids, followed by in vivo validation and single-cell RNA sequencing. We found BECs lack and do not require LGR4/5-mediated WNT/β-Catenin signaling during DR, while YAP and mTORC1 signaling are required for this process. Upregulation of LGR5/AXIN2 is required in hepatocytes to enable their regenerative capacity in response to injury. Together, these data highlight heterogeneity within the BEC pool and delineate signaling pathways involved.
Project description:Obesity caused by overnutrition is a major risk factor for non-alcoholic fatty liver disease (NAFLD). Several lipid intermediates such as fatty acids, glycerophospholipids and sphingolipids are implicated in NAFLD, but detailed characterization of lipids and their functional links to proteome and phosphoproteome remain to be elucidated. To characterize this complex molecular relationship, we used multi-omics approach by conducting comparative proteomic, phoshopro-teomic and lipidomic analyses of high fat (HFD) and low fat (LFD) diet fed mice livers. We quantified 2447 proteins and 1339 phosphoproteins containing 1650 class I phosphosites (with localization probability > 0.75), of which 669 phosphosites were significantly different between HFD and LFD mice livers. We detected alterations of proteins associated with cellular metabolic processes such as small molecule catabolic process, monocarboxylic acid, long- and medium-chain fatty acid, and ketone body metabolic processes, and peroxisome organization. We observed significant downregulation of protein phosphorylation in HFD fed mice liver in general. Untargeted lipidomics identified upregulation of triacylglycerols, glycerolipids and ether glycerophosphocholines and downregulation of glycerophospholipids such as lysoglycerophospholipids, as well as ceramides and acylcarnitines. Analysis of differentially regulated phosphosites revealed phosphorylation dependent deregulation of insulin signaling as well as lipogenic and lipolytic pathways during HFD induced obesity. Thus, this study reveals a molecular connection between decreased protein phosphorylation and lipolysis, as well as lipid-mediated signaling in diet-induced obesity.
Project description:In searching for common and specific features of transcriptional changes associated with non-obese NAFLD induced by GP73 and obese NAFLD induced by high-fat diet (HFD), we used Agilent SurePrint G3 Mouse Gene Expression Microarray 8x60K to analyze gene expression in the livers isolated from mice 12 months after AAV-V or AAV-GP73 injection and in the livers isolated from AAV-V control mice fed a HFD for 12 months.
Project description:Obesity is tightly associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). However, the molecular mechanisms of obesity-induced fatty liver remain largely unknown.In order to identify genes that are potentially involved in dysfunctional hepatic lipid homeostasis in obesity, we performed a clustering analysis of Affymetrix arrays,which revealed that a number of mRNAs were dys-regulated in the livers of mice fed a high-fat diet (HFD), compared with mice fed a normal chow diet (ND).
Project description:Ductular reaction (DR) is the hallmark of cholestatic diseases manifested in the proliferation of bile ductules lined by biliary epithelial cells (BECs). It is commonly associated with increased risk of fibrosis and liver failure. The Receptor for Advanced Glycation End Products (RAGE) was identified as a critical mediator of DR during chronic injury. Yet, the direct link between RAGE-mediated DR and fibrosis as well as the mode of interaction between BECs and hepatic stellate cells (HSCs) to drive fibrosis remains elusive. In this study, we aimed to delineate the specific function of RAGE on BECs during DR and its potential association with fibrosis in the context of cholestasis. Employing a biliary lineage tracing cholestatic liver injury mouse model, combined with whole transcriptome sequencing and in vitro analyses, we revealed the central role of BEC-specific Rage activity in fostering a pro-fibrotic milieu. RAGE is predominantly expressed in BECs and contributes to DR. Notch ligand Jagged1 is secreted from activated BECs in a Rage-dependent manner and signals HSCs in trans, eventually enhancing fibrosis during cholestasis.
Project description:We perform scRNA-seq in the livers of C57BL/6 mice fed a CD-HFD or control diet for 3 months (NAFLD), 6 months (NASH) or 15 months (HCC)
Project description:Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder with high morbidity and mortality. The current study aims to explore the role of Cullin-associated and neddylation-dissociated protein 1 (CAND1) in the development of NAFLD and the underlying mechanisms. CAND1 is reduced in the liver of NAFLD male patients and high fat diet (HFD)-fed male mice. CAND1 alleviates palmitate (PA) induced lipid accumulation in vitro. Hepatocyte-specific knockout of CAND1 exacerbates HFD-induced liver injury in HFD-fed male mice, while hepatocyte-specific knockin of CAND1 ameliorates these pathological changes. Mechanistically, deficiency of CAND1 enhances the assembly of Cullin1, F-box only protein 42 (FBXO42) and acetyl-CoA acyltransferase 2 (ACAA2) complexes, and thus promotes the ubiquitinated degradation of ACAA2. ACAA2 overexpression abolishes the exacerbated effects of CAND1 deficiency on NAFLD. Additionally, androgen receptor binds to the -187 to -2000 promoter region of CAND1. Collectively, CAND1 mitigates NAFLD by inhibiting Cullin1/FBXO42 mediated ACAA2 degradation
Project description:Purpose: While various functions of peripheral serotonin are known, the direct role of serotonin in regulating hepatic lipid metabolism in vivo is not well understood. We studied whether serotonin directly acts on liver to regulate lipid metabolism. Methods: Methods: 12 weeks aged liver-specific Htr2a KO (Albumin-Cre+/-; Htr2aflox/flox, herein named Htr2a LKO) mice and wildtype (WT) littermates were fed a high-fat diet (HFD, 60% fat calories) for 8 weeks. Results: Hepatic lipid droplet accumulation, NAFLD activity score, and hepatic triglyceride levels were dramatically reduced in HFD-fed Htr2a LKO mice compared to WT littermates. Conclusions: Gut-derived serotonin is a direct regulator of hepatic lipid metabolism via a gut TPH1-liver HTR2A endocrine axis. And shows promise as a novel drug target to ameliorate NAFLD with minimal systemic metabolic effects.
Project description:This study sought to interrogate the effects of lipids and lipid metabolites on the hepatic proteome. Protein expression in high-fat diet (HFD) mouse livers vs. livers of normal chow fed (NC) mice were investigated using multiplexed quantitative LC-MS/MS (TMT labeling). This experiment contains additional replicates for normal chow and mice on high-fat diet for 16 weeks.