The secondary bile acid isoursodeoxycholate correlates with post-prandial lipemia, inflammation, and appetite and changes post-bariatric surgery.

Primary and secondary bile acids (BAs) influence metabolism and inflammation, and the gut microbiome modulates levels of BAs. We systematically explore the host genetic, gut microbial, and habitual dietary contribution to a panel of 19 serum and 15 stool BAs in two population-based cohorts (TwinsUK, n = 2,382; ZOE PREDICT-1, n = 327) and assess changes post-bariatric surgery and after nutritional interventions. We report that BAs have a moderately heritable genetic component, and the gut microbiome accurately predicts their levels in serum and stool. The secondary BA isoursodeoxycholate (isoUDCA) can be explained mostly by gut microbes (area under the receiver operating characteristic curve [AUC] = ∼80%) and associates with post-prandial lipemia and inflammation (GlycA). Furthermore, circulating isoUDCA decreases significantly 1 year after bariatric surgery (ß = -0.72, p = 1 × 10-5) and in response to fiber supplementation (ß = -0.37, p < 0.03) but not omega-3 supplementation. In healthy individuals, isoUDCA fasting levels correlate with pre-meal appetite (p < 1 × 10-4). Our findings indicate an important role for isoUDCA in lipid metabolism, appetite, and, potentially, cardiometabolic risk.

Plasma metabolites to profile pathways in noncommunicable disease multimorbidity.

Multimorbidity, the simultaneous presence of multiple chronic conditions, is an increasing global health problem and research into its determinants is of high priority. We used baseline untargeted plasma metabolomics profiling covering >1,000 metabolites as a comprehensive readout of human physiology to characterize pathways associated with and across 27 incident noncommunicable diseases (NCDs) assessed using electronic health record hospitalization and cancer registry data from over 11,000 participants (219,415 person years). We identified 420 metabolites shared between at least 2 NCDs, representing 65.5% of all 640 significant metabolite-disease associations. We integrated baseline data on over 50 diverse clinical risk factors and characteristics to identify actionable shared pathways represented by those metabolites. Our study highlights liver and kidney function, lipid and glucose metabolism, low-grade inflammation, surrogates of gut microbial diversity and specific health-related behaviors as antecedents of common NCD multimorbidity with potential for early prevention. We integrated results into an open-access webserver ( https://omicscience.org/apps/mwasdisease/ ) to facilitate future research and meta-analyses.

Genome-wide association study in frontal fibrosing alopecia identifies four susceptibility loci including HLA-B*07:02.

Frontal fibrosing alopecia (FFA) is a recently described inflammatory and scarring type of hair loss affecting almost exclusively women. Despite a dramatic recent increase in incidence the aetiopathogenesis of FFA remains unknown. We undertake genome-wide association studies in females from a UK cohort, comprising 844 cases and 3,760 controls, a Spanish cohort of 172 cases and 385 controls, and perform statistical meta-analysis. We observe genome-wide significant association with FFA at four genomic loci: 2p22.2, 6p21.1, 8q24.22 and 15q2.1. Within the 6p21.1 locus, fine-mapping indicates that the association is driven by the HLA-B*07:02 allele. At 2p22.1, we implicate a putative causal missense variant in CYP1B1, encoding the homonymous xenobiotic- and hormone-processing enzyme. Transcriptomic analysis of affected scalp tissue highlights overrepresentation of transcripts encoding components of innate and adaptive immune response pathways. These findings provide insight into disease pathogenesis and characterise FFA as a genetically predisposed immuno-inflammatory disorder driven by HLA-B*07:02.

Hedgehog-YAP Signaling Pathway Regulates Glutaminolysis to Control Activation of Hepatic Stellate Cells.

BACKGROUND & AIMS: Cirrhosis results from accumulation of myofibroblasts derived from quiescent hepatic stellate cells (Q-HSCs); it regresses when myofibroblastic HSCs are depleted. Hedgehog signaling promotes transdifferentiation of HSCs by activating Yes-associated protein 1 (YAP1 or YAP) and inducing aerobic glycolysis. However, increased aerobic glycolysis alone cannot meet the high metabolic demands of myofibroblastic HSCs. Determining the metabolic processes of these cells could lead to strategies to prevent progressive liver fibrosis, so we investigated whether glutaminolysis (conversion of glutamine to alpha-ketoglutarate) sustains energy metabolism and permits anabolism when Q-HSCs become myofibroblastic, and whether this is controlled by hedgehog signaling to YAP. METHODS: Primary HSCs were isolated from C57BL/6 or Smoflox/flox mice; we also performed studies with rat and human myofibroblastic HSCs. We measured changes of glutaminolytic genes during culture-induced primary HSC transdifferentiation. Glutaminolysis was disrupted in cells by glutamine deprivation or pathway inhibitors (bis-2-[5-phenylacetamido-1,2,4-thiadiazol-2-yl] ethyl sulfide, CB-839, epigallocatechin gallate, and aminooxyacetic acid), and effects on mitochondrial respiration, cell growth and migration, and fibrogenesis were measured. Hedgehog signaling to YAP was disrupted in cells by adenovirus expression of Cre-recombinase or by small hairpin RNA knockdown of YAP. Hedgehog and YAP activity were inhibited by incubation of cells with cyclopamine or verteporfin, and effects on glutaminolysis were measured. Acute and chronic liver fibrosis were induced in mice by intraperitoneal injection of CCl4 or methionine choline-deficient diet. Some mice were then given injections of bis-2-[5-phenylacetamido-1,2,4-thiadiazol-2-yl] ethyl sulfide to inhibit glutaminolysis, and myofibroblast accumulation was measured. We also performed messenger RNA and immunohistochemical analyses of percutaneous liver biopsies from healthy human and 4 patients with no fibrosis, 6 patients with mild fibrosis, and 3 patients with severe fibrosis. RESULTS: Expression of genes that regulate glutaminolysis increased during transdifferentiation of primary Q-HSCs into myofibroblastic HSCs, and inhibition of glutaminolysis disrupted transdifferentiation. Blocking glutaminolysis in myofibroblastic HSCs suppressed mitochondrial respiration, cell growth and migration, and fibrogenesis; replenishing glutaminolysis metabolites to these cells restored these activities. Knockout of the hedgehog signaling intermediate smoothened or knockdown of YAP inhibited expression of glutaminase, the rate-limiting enzyme in glutaminolysis. Hedgehog and YAP inhibitors blocked glutaminolysis and suppressed myofibroblastic activities in HSCs. In livers of patients and of mice with acute or chronic fibrosis, glutaminolysis was induced in myofibroblastic HSCs. In mice with liver fibrosis, inhibition of glutaminase blocked accumulation of myofibroblasts and fibrosis progression. CONCLUSIONS: Glutaminolysis controls accumulation of myofibroblast HSCs in mice and might be a therapeutic target for cirrhosis.

Loss of pericyte smoothened activity in mice with genetic deficiency of leptin.

BACKGROUND: Obesity is associated with multiple diseases, but it is unclear how obesity promotes progressive tissue damage. Recovery from injury requires repair, an energy-expensive process that is coupled to energy availability at the cellular level. The satiety factor, leptin, is a key component of the sensor that matches cellular energy utilization to available energy supplies. Leptin deficiency signals energy depletion, whereas activating the Hedgehog pathway drives energy-consuming activities. Tissue repair is impaired in mice that are obese due to genetic leptin deficiency. Tissue repair is also blocked and obesity enhanced by inhibiting Hedgehog activity. We evaluated the hypothesis that loss of leptin silences Hedgehog signaling in pericytes, multipotent leptin-target cells that regulate a variety of responses that are often defective in obesity, including tissue repair and adipocyte differentiation. RESULTS: We found that pericytes from liver and white adipose tissue require leptin to maintain expression of the Hedgehog co-receptor, Smoothened, which controls the activities of Hedgehog-regulated Gli transcription factors that orchestrate gene expression programs that dictate pericyte fate. Smoothened suppression prevents liver pericytes from being reprogrammed into myofibroblasts, but stimulates adipose-derived pericytes to become white adipocytes. Progressive Hedgehog pathway decay promotes senescence in leptin-deficient liver pericytes, which, in turn, generate paracrine signals that cause neighboring hepatocytes to become fatty and less proliferative, enhancing vulnerability to liver damage. CONCLUSIONS: Leptin-responsive pericytes evaluate energy availability to inform tissue construction by modulating Hedgehog pathway activity and thus, are at the root of progressive obesity-related tissue pathology. Leptin deficiency inhibits Hedgehog signaling in pericytes to trigger a pericytopathy that promotes both adiposity and obesity-related tissue damage.

Hedgehog regulates yes-associated protein 1 in regenerating mouse liver.

UNLABELLED: Adult liver regeneration requires induction and suppression of proliferative activity in multiple types of liver cells. The mechanisms that orchestrate the global changes in gene expression that are required for proliferative activity to change within individual liver cells, and that coordinate proliferative activity among different types of liver cells, are not well understood. Morphogenic signaling pathways that are active during fetal development, including Hedgehog and Hippo/Yes-associated protein 1 (Yap1), regulate liver regeneration in adulthood. Cirrhosis and liver cancer result when these pathways become dysregulated, but relatively little is known about the mechanisms that coordinate and control morphogenic signaling during effective liver regeneration. We evaluated the hypothesis that the Hedgehog pathway controls Yap1 activation during liver regeneration by studying intact mice and cultured liver cells. In cultured hepatic stellate cells (HSCs), disrupting Hedgehog signaling blocked activation of Yap1, and knocking down Yap1 inhibited induction of both Yap1- and Hedgehog-regulated genes that enable HSC to become myofibroblasts (MFs). In mice, disrupting Hedgehog signaling in MFs inhibited liver regeneration after partial hepactectomy (PH). Reduced proliferative activity in the liver epithelial compartment resulted from loss of stroma-derived paracrine signals that activate Yap1 and the Hedgehog pathway in hepatocytes. This prevented hepatocytes from up-regulating Yap1- and Hedgehog-regulated transcription factors that normally promote their proliferation. CONCLUSIONS: Morphogenic signaling in HSCs is necessary to reprogram hepatocytes to regenerate the liver epithelial compartment post-PH. This discovery identifies novel molecules that might be targeted to correct defective repair during cirrhosis and liver cancer. (Hepatology 2016;64:232-244).

Inflammation-Dependent IL18 Signaling Restricts Hepatocellular Carcinoma Growth by Enhancing the Accumulation and Activity of Tumor-Infiltrating Lymphocytes.

Chronic inflammation in liver tissue is an underlying cause of hepatocellular carcinoma. High levels of inflammatory cytokine IL18 in the circulation of patients with hepatocellular carcinoma correlates with poor prognosis. However, conflicting results have been reported for IL18 in hepatocellular carcinoma development and progression. In this study, we used tissue specimens from hepatocellular carcinoma patients and clinically relevant mouse models of hepatocellular carcinoma to evaluate IL18 expression and function. In a mouse model of liver fibrosis that recapitulates a tumor-promoting microenvironment, global deletion of the IL18 receptor IL18R1 enhanced tumor growth and burden. Similarly, in a carcinogen-induced model of liver tumorigenesis, IL18R1 deletion increased tumor burden. Mechanistically, we found that IL18 exerted inflammation-dependent tumor-suppressive effects largely by promoting the differentiation, activity, and survival of tumor-infiltrating T cells. Finally, differences in the expression of IL18 in tumor tissue versus nontumor tissue were more predictive of patient outcome than overall tissue expression. Taken together, our findings resolve a long-standing contradiction regarding a tumor-suppressive role for IL18 in established hepatocellular carcinoma and provide a mechanistic explanation for the complex relationship between its expression pattern and hepatocellular carcinoma prognosis. Cancer Res; 76(8); 2394-405. ©2016 AACR.

Temporal Dissection of Rate Limiting Transcriptional Events Using Pol II ChIP and RNA Analysis of Adrenergic Stress Gene Activation.

In mammals, increasing evidence supports mechanisms of co-transcriptional gene regulation and the generality of genetic control subsequent to RNA polymerase II (Pol II) recruitment. In this report, we use Pol II Chromatin Immunoprecipitation to investigate relationships between the mechanistic events controlling immediate early gene (IEG) activation following stimulation of the α1a-Adrenergic Receptor expressed in rat-1 fibroblasts. We validate our Pol II ChIP assay by comparison to major transcriptional events assessable by microarray and PCR analysis of precursor and mature mRNA. Temporal analysis of Pol II density suggests that reduced proximal pausing often enhances gene expression and was essential for Nr4a3 expression. Nevertheless, for Nr4a3 and several other genes, proximal pausing delayed the time required for initiation of productive elongation, consistent with a role in ensuring transcriptional fidelity. Arrival of Pol II at the 3' cleavage site usually correlated with increased polyadenylated mRNA; however, for Nfil3 and probably Gprc5a expression was delayed and accompanied by apparent pre-mRNA degradation. Intragenic pausing not associated with polyadenylation was also found to regulate and delay Gprc5a expression. Temporal analysis of Nr4a3, Dusp5 and Nfil3 shows that transcription of native IEG genes can proceed at velocities of 3.5 to 4 kilobases/min immediately after activation. Of note, all of the genes studied here also used increased Pol II recruitment as an important regulator of expression. Nevertheless, the generality of co-transcriptional regulation during IEG activation suggests temporal and integrated analysis will often be necessary to distinguish causative from potential rate limiting mechanisms.

Inflammatory models drastically alter tumor growth and the immune microenvironment in hepatocellular carcinoma.

Initiation and progression of hepatocellular carcinoma (HCC) is intimately associated with a chronically diseased liver tissue. This diseased liver tissue background is a drastically different microenvironment from the healthy liver, especially with regard to immune cell prevalence and presence of mediators of immune function. To better understand the consequences of liver disease on tumor growth and the interplay with its microenvironment, we utilized two standard methods of fibrosis induction and orthotopic implantation of tumors into the inflamed and fibrotic liver to mimic the liver condition in human HCC patients. Compared to non-diseased controls, tumor growth was significantly enhanced under fibrotic conditions. The immune cells that infiltrated the tumors were also drastically different, with decreased numbers of natural killer cells but greatly increased numbers of immune-suppressive CD11b+ Gr1hi myeloid cells in both models of fibrosis. In addition, there were model-specific differences: Increased numbers of CD11b+ myeloid cells and CD4+ CD25+ T cells were found in tumors in the bile duct ligation model but not in the carbon tetrachloride model. Induction of fibrosis altered the cytokine production of implanted tumor cells, which could have farreaching consequences on the immune infiltrate and its functionality. Taken together, this work demonstrates that the combination of fibrosis induction with orthotopic tumor implantation results in a markedly different tumor microenvironment and tumor growth kinetics, emphasizing the necessity for more accurate modeling of HCC progression in mice, which takes into account the drastic changes in the tissue caused by chronic liver disease.

Micro-RNA 21 inhibition of SMAD7 enhances fibrogenesis via leptin-mediated NADPH oxidase in experimental and human nonalcoholic steatohepatitis.

Hepatic fibrosis in nonalcoholic steatohepatitis (NASH) is the common pathophysiological process resulting from chronic liver inflammation and oxidative stress. Although significant research has been carried out on the role of leptin-induced NADPH oxidase in fibrogenesis, the molecular mechanisms that connect the leptin-NADPH oxidase axis in upregulation of transforming growth factor (TGF)-ß signaling have been unclear. We aimed to investigate the role of leptin-mediated upregulation of NADPH oxidase and its subsequent induction of micro-RNA 21 (miR21) in fibrogenesis. Human NASH livers and a high-fat (60% kcal) diet-fed chronic mouse model, where hepatotoxin bromodichloromethane was used to induce NASH, were used for this study. To prove the role of the leptin-NADPH oxidase-miR21 axis, mice deficient in genes for leptin, p47phox, and miR21 were used. Results showed that wild-type mice and human livers with NASH had increased oxidative stress, increased p47phox expression, augmented NF-κB activation, and increased miR21 levels. These mice and human livers showed increased TGF-ß, SMAD2/3-SMAD4 colocalizations in the nucleus, increased immunoreactivity against Col1α, and α-SMA with a concomitant decrease in protein levels of SMAD7. Mice that were deficient in leptin or p47phox had decreased activated NF-κB and miR21 levels, suggesting the role of leptin and NADPH oxidase in inducing NF-κB-mediated miR21 expression. Further miR21 knockout mice had decreased colocalization events of SMAD2/3-SMAD4 in the nucleus, increased SMAD7 levels, and decreased fibrogenesis. Taken together, the studies show the novel role of leptin-NADPH oxidase induction of miR21 as a key regulator of TGF-ß signaling and fibrogenesis in experimental and human NASH.

Role of Fn14 in acute alcoholic steatohepatitis in mice.

TNF-like weak inducer of apoptosis (TWEAK) is a growth factor for bipotent liver progenitors that express its receptor, fibroblast growth factor-inducible 14 (Fn14), a TNF receptor superfamily member. Accumulation of Fn14(+) progenitors occurs in severe acute alcoholic steatohepatitis (ASH) and correlates with acute mortality. In patients with severe ASH, inhibition of TNF-α increases acute mortality. The aim of this study was to determine whether deletion of Fn14 improves the outcome of liver injury in alcohol-consuming mice. Wild-type (WT) and Fn14 knockout (KO) mice were fed control high-fat Lieber deCarli diet or high-fat Lieber deCarli diet with 2% alcohol (ETOH) and injected intraperitoneally with CCl4 for 2 wk to induce liver injury. Mice were euthanized 3 or 10 days after CCl4 treatment. Survival was assessed. Liver tissues were analyzed for cell death, inflammation, proliferation, progenitor accumulation, and fibrosis by quantitative RT-PCR, immunoblot, hydroxyproline content, and quantitative immunohistochemistry. During liver injury, Fn14 expression, apoptosis, inflammation, hepatocyte replication, progenitor and myofibroblast accumulation, and fibrosis increased in WT mice fed either diet. Mice fed either diet expressed similar TWEAK/Fn14 levels, but ETOH-fed mice had higher TNF-α expression. The ETOH-fed group developed more apoptosis, inflammation, fibrosis, and regenerative responses. Fn14 deletion did not reduce hepatic TNF-α expression but improved all injury parameters in mice fed the control diet. In ETOH-fed mice, Fn14 deletion inhibited TNF-α induction and increased acute mortality, despite improvement in liver injury. Fn14 mediates wound-healing responses that are necessary to survive acute liver injury during alcohol exposure.

M1 polarization bias and subsequent nonalcoholic steatohepatitis progression is attenuated by nitric oxide donor DETA NONOate via inhibition of CYP2E1-induced oxidative stress in obese mice.

Activation of M1 macrophages in nonalcoholic steatohepatitis (NASH) is produced by several external or endogenous factors: inflammatory stimuli, oxidative stress, and cytokines are known. However, any direct role of oxidative stress in causing M1 polarization in NASH has been unclear. We hypothesized that CYP2E1-mediated oxidative stress causes M1 polarization in experimental NASH, and that nitric oxide (NO) donor administration inhibits CYP2E1-mediated inflammation with concomitant attenuation of M1 polarization. Because CYP2E1 takes center stage in these studies, we used a toxin model of NASH that uses a ligand and a substrate of CYP2E1 for inducing NASH. Subsequently, we used a methionine and choline-deficient diet-induced rodent NASH model where the role of CYP2E1 in disease progression has been shown. Our results show that CYP2E1 causes M1 polarization bias, which includes a significant increase in interleukin-1ß (IL-1ß) and IL-12 in both models of NASH, whereas CYP2E1-null mice or diallyl sulfide administration prevented it. Administration of gadolinium chloride (GdCl3), a macrophage toxin, attenuated both the initial M1 response and the subsequent M2 response, showing that the observed increase in cytokine levels is primarily from macrophages. Based on the evidence of an adaptive NO increase, the NO donor administration in vivo that mechanistically inhibited CYP2E1 catalyzed the oxidative stress during the entire study in NASH-abrogated M1 polarization and NASH progression. The results obtained show the association of CYP2E1 in M1 polarization, and that inhibition of CYP2E1 catalyzed oxidative stress by an NO donor (DETA NONOate [(Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate]) can be a promising therapeutic strategy in NASH.

TWEAK/Fn14 signaling is required for liver regeneration after partial hepatectomy in mice.

BACKGROUND & AIMS: Pro-inflammatory cytokines are important for liver regeneration after partial hepatectomy (PH). Expression of Fibroblast growth factor-inducible 14 (Fn14), the receptor for TNF-like weak inducer of apoptosis (TWEAK), is induced rapidly after PH and remains elevated throughout the period of peak hepatocyte replication. The role of Fn14 in post-PH liver regeneration is uncertain because Fn14 is expressed by liver progenitors and TWEAK-Fn14 interactions stimulate progenitor growth, but replication of mature hepatocytes is thought to drive liver regeneration after PH. METHODS: To clarify the role of TWEAK-Fn14 after PH, we compared post-PH regenerative responses in wild type (WT) mice, Fn14 knockout (KO) mice, TWEAK KO mice, and WT mice treated with anti-TWEAK antibodies. RESULTS: In WT mice, rare Fn14(+) cells localized with other progenitor markers in peri-portal areas before PH. PH rapidly increased proliferation of Fn14(+) cells; hepatocytic cells that expressed Fn14 and other progenitor markers, such as Lgr5, progressively accumulated from 12-8 h post-PH and then declined to baseline by 96 h. When TWEAK/Fn14 signaling was disrupted, progenitor accumulation, induction of pro-regenerative cytokines, hepatocyte and cholangiocyte proliferation, and over-all survival were inhibited, while post-PH liver damage and bilirubin levels were increased. TWEAK stimulated proliferation and increased Lgr5 expression in cultured liver progenitors, but had no effect on either parameter in cultured primary hepatocytes. CONCLUSIONS: TWEAK-FN14 signaling is necessary for the healthy adult liver to regenerate normally after acute partial hepatectomy.

Hepatic gene expression profiles differentiate presymptomatic patients with mild versus severe nonalcoholic fatty liver disease.

UNLABELLED: Clinicians rely upon the severity of liver fibrosis to segregate patients with well-compensated nonalcoholic fatty liver disease (NAFLD) into subpopulations at high- versus low-risk for eventual liver-related morbidity and mortality. We compared hepatic gene expression profiles in high- and low-risk NAFLD patients to identify processes that distinguish the two groups and hence might be novel biomarkers or treatment targets. Microarray analysis was used to characterize gene expression in percutaneous liver biopsies from low-risk, "mild" NAFLD patients (fibrosis stage 0-1; n = 40) and high-risk, "severe" NAFLD patients (fibrosis stage 3-4; n = 32). Findings were validated in a second, independent cohort and confirmed by real-time polymerase chain reaction and immunohistochemistry (IHC). As a group, patients at risk for bad NAFLD outcomes had significantly worse liver injury and more advanced fibrosis (severe NAFLD) than clinically indistinguishable NAFLD patients with a good prognosis (mild NAFLD). A 64-gene profile reproducibly differentiated severe NAFLD from mild NAFLD, and a 20-gene subset within this profile correlated with NAFLD severity, independent of other factors known to influence NAFLD progression. Multiple genes involved with tissue repair/regeneration and certain metabolism-related genes were induced in severe NAFLD. Ingenuity Pathway Analysis and IHC confirmed deregulation of metabolic and regenerative pathways in severe NAFLD and revealed overlap among the gene expression patterns of severe NAFLD, cardiovascular disease, and cancer. CONCLUSION: By demonstrating specific metabolic and repair pathways that are differentially activated in livers with severe NAFLD, gene profiling identified novel targets that can be exploited to improve diagnosis and treatment of patients who are at greatest risk for NAFLD-related morbidity and mortality.

NAFLD, NASH and liver cancer.

NAFLD affects a large proportion of the US population and its incidence and prevalence are increasing to epidemic proportions around the world. As with other liver diseases that cause cirrhosis, NAFLD increases the risk of liver cancer, a disease with poor outcomes and limited therapeutic options. The incidences of hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma are also rising, and HCC is now the leading cause of obesity-related cancer deaths in middle-aged men in the USA. In this Review, we summarize the correlations between liver cancer and NAFLD-related cirrhosis, and the role of the metabolic syndrome in the development of liver cancer from diverse aetiologies, including HCV-mediated cirrhosis. Recent advances in understanding the progression of NAFLD to HCC from preclinical models will also be discussed. Targeted genetic manipulation of certain metabolic or stress-response pathways, including one-carbon metabolism, NF-κB, PTEN and microRNAs, has been valuable in elucidating the pathways that regulate carcinogenesis in NAFLD. Although tremendous advances have occurred in the identification of diagnostic and therapeutic opportunities to reduce the progression of NAFLD, considerable gaps in our knowledge remain with regard to the mechanisms by which NAFLD and its risk factors promote liver cancer.

Hedgehog signalling regulates liver sinusoidal endothelial cell capillarisation.

OBJECTIVE: Vascular remodelling during liver damage involves loss of healthy liver sinusoidal endothelial cell (LSEC) phenotype via capillarisation. Hedgehog (Hh) signalling regulates vascular development and increases during liver injury. This study therefore examined its role in capillarisation. DESIGN: Primary LSEC were cultured for 5 days to induce capillarisation. Pharmacological, antibody-mediated and genetic approaches were used to manipulate Hh signalling. Effects on mRNA and protein expression of Hh-regulated genes and capillarisation markers were evaluated by quantitative reverse transcription PCR and immunoblot. Changes in LSEC function were assessed by migration and tube forming assay, and gain/loss of fenestrae was examined by electron microscopy. Mice with acute or chronic liver injury were treated with Hh inhibitors; effects on capillarisation were assessed by immunohistochemistry. RESULTS: Freshly isolated LSEC expressed Hh ligands, Hh receptors and Hh ligand antagonist Hhip. Capillarisation was accompanied by repression of Hhip and increased expression of Hh-regulated genes. Treatment with Hh agonist further induced expression of Hh ligands and Hh-regulated genes, and upregulated capillarisation-associated genes; whereas Hh signalling antagonist or Hh ligand neutralising antibody each repressed expression of Hh target genes and capillarisation markers. LSEC isolated from Smo(loxP/loxP) transgenic mice that had been infected with adenovirus expressing Cre-recombinase to delete Smoothened showed over 75% knockdown of Smoothened. During culture, Smoothened-deficient LSEC had inhibited Hh signalling, less induction of capillarisation-associated genes and retention of fenestrae. In mice with injured livers, inhibiting Hh signalling prevented capillarisation. CONCLUSIONS: LSEC produce and respond to Hh ligands, and use Hh signalling to regulate complex phenotypic changes that occur during capillarisation.

Paracrine Hedgehog signaling drives metabolic changes in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) typically develops in cirrhosis, a condition characterized by Hedgehog (Hh) pathway activation and accumulation of Hh-responsive myofibroblasts. Although Hh signaling generally regulates stromal-epithelial interactions that support epithelial viability, the role of Hh-dependent myofibroblasts in hepatocarcinogenesis is unknown. Here, we used human HCC samples, a mouse HCC model, and hepatoma cell/myofibroblast cocultures to examine the hypothesis that Hh signaling modulates myofibroblasts' metabolism to generate fuels for neighboring malignant hepatocytes. The results identify a novel paracrine mechanism whereby malignant hepatocytes produce Hh ligands to stimulate glycolysis in neighboring myofibroblasts, resulting in release of myofibroblast-derived lactate that the malignant hepatocytes use as an energy source. This discovery reveals new diagnostic and therapeutic targets that might be exploited to improve the outcomes of cirrhotic patients with HCCs.

Hedgehog controls hepatic stellate cell fate by regulating metabolism.

BACKGROUND & AIMS: The pathogenesis of cirrhosis, a disabling outcome of defective liver repair, involves deregulated accumulation of myofibroblasts derived from quiescent hepatic stellate cells (HSCs), but the mechanisms that control transdifferentiation of HSCs are poorly understood. We investigated whether the Hedgehog (Hh) pathway controls the fate of HSCs by regulating metabolism. METHODS: Microarray, quantitative polymerase chain reaction, and immunoblot analyses were used to identify metabolic genes that were differentially expressed in quiescent vs myofibroblast HSCs. Glycolysis and lactate production were disrupted in HSCs to determine if metabolism influenced transdifferentiation. Hh signaling and hypoxia-inducible factor 1α (HIF1α) activity were altered to identify factors that alter glycolytic activity. Changes in expression of genes that regulate glycolysis were quantified and localized in biopsy samples from patients with cirrhosis and liver samples from mice following administration of CCl(4) or bile duct ligation. Mice were given systemic inhibitors of Hh to determine if they affect glycolytic activity of the hepatic stroma; Hh signaling was also conditionally disrupted in myofibroblasts to determine the effects of glycolytic activity. RESULTS: Transdifferentiation of cultured, quiescent HSCs into myofibroblasts induced glycolysis and caused lactate accumulation. Increased expression of genes that regulate glycolysis required Hh signaling and involved induction of HIF1α. Inhibitors of Hh signaling, HIF1α, glycolysis, or lactate accumulation converted myofibroblasts to quiescent HSCs. In diseased livers of animals and patients, numbers of glycolytic stromal cells were associated with the severity of fibrosis. Conditional disruption of Hh signaling in myofibroblasts reduced numbers of glycolytic myofibroblasts and liver fibrosis in mice; similar effects were observed following administration of pharmacologic inhibitors of Hh. CONCLUSIONS: Hedgehog signaling controls the fate of HSCs by regulating metabolism. These findings might be applied to diagnosis and treatment of patients with cirrhosis.

Hedgehog signaling antagonist promotes regression of both liver fibrosis and hepatocellular carcinoma in a murine model of primary liver cancer.

OBJECTIVE: Chronic fibrosing liver injury is a major risk factor for hepatocarcinogenesis in humans. Mice with targeted deletion of Mdr2 (the murine ortholog of MDR3) develop chronic fibrosing liver injury. Hepatocellular carcinoma (HCC) emerges spontaneously in such mice by 50-60 weeks of age, providing a model of fibrosis-associated hepatocarcinogenesis. We used Mdr2(-/-) mice to investigate the hypothesis that activation of the hedgehog (Hh) signaling pathway promotes development of both liver fibrosis and HCC. METHODS: Hepatic injury and fibrosis, Hh pathway activation, and liver progenitor populations were compared in Mdr2(-/-) mice and age-matched wild type controls. A dose finding experiment with the Hh signaling antagonist GDC-0449 was performed to optimize Hh pathway inhibition. Mice were then treated with GDC-0449 or vehicle for 9 days, and effects on liver fibrosis and tumor burden were assessed by immunohistochemistry, qRT-PCR, Western blot, and magnetic resonance imaging. RESULTS: Unlike controls, Mdr2(-/-) mice consistently expressed Hh ligands and progressively accumulated Hh-responsive liver myofibroblasts and progenitors with age. Treatment of aged Mdr2-deficient mice with GDC-0449 significantly inhibited hepatic Hh activity, decreased liver myofibroblasts and progenitors, reduced liver fibrosis, promoted regression of intra-hepatic HCCs, and decreased the number of metastatic HCC without increasing mortality. CONCLUSIONS: Hh pathway activation promotes liver fibrosis and hepatocarcinogenesis, and inhibiting Hh signaling safely reverses both processes even when fibrosis and HCC are advanced.

Leptin promotes the myofibroblastic phenotype in hepatic stellate cells by activating the hedgehog pathway.

Trans-differentiation of quiescent hepatic stellate cells (Q-HSCs), which exhibit epithelial and adipocytic features, into myofibroblastic-HSC (MF-HSCs) is a key event in liver fibrosis. Culture models demonstrated that Hedgehog (Hh) pathway activation is required for transition of epithelioid/adipocytic Q-HSCs into MF-HSCs. Hh signaling inhibits adiposity and promotes epithelial-to-mesenchymal transitions (EMTs). Leptin (anti-adipogenic, pro-EMT factor) promotes HSC trans-differentiation and liver fibrosis, suggesting that the pathways may interact to modulate cell fate. This study aimed to determine whether leptin activates Hh signaling and whether this is required for the fibrogenic effects of leptin. Cultures of primary HSCs from lean and fa/fa rats with an inherited ObRb defect were examined. Inhibitors of PI3K/Akt, JAK/STAT, and Hh signaling were used to delineate how ObRb activation influenced Hh signaling and HSC trans-differentiation. Fibrogenesis was compared in wild type and db/db mice (impaired ObRb function) to assess the profibrotic role of leptin. The results demonstrate that leptin-ObR interactions activate Hh signaling with the latter necessary to promote trans-differentiation. Leptin-related increases in Hh signaling required ObR induction of PI3K/Akt, which was sufficient for leptin to repress the epithelioid/adipocytic program. Leptin-mediated induction of JAK/STAT was required for mesenchymal gene expression. Leptin-ObRb interactions were not necessary for HSC trans-differentiation to occur in vitro or in vivo but are important because liver fibrogenesis was attenuated in db/db mice. These findings reveal that leptin activates Hh signaling to alter gene expression programs that control cell fate and have important implications for liver fibrosis and other leptin-regulated processes involving EMTs, including development, obesity, and cancer metastasis.