Jude A. Oben

Angiotensin II type 1 receptor blocker inhibits fibrosis in rat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is now the most frequent cause of chronic liver impairment in developed countries and is a suggested causative factor in the development of cryptogenic cirrhosis and hepatocellular carcinoma. At present there is no effective and accepted therapy for NASH. The renin‐angiotensin system is involved in hepatic fibrosis through activation of hepatic stellate cells, major fibrogenic cells in the liver. Hepatic stellate cells are activated by liver injury to express excessive matrix proteins and profibrogenic cytokines such as transforming growth factor–beta 1. Medicines that inhibit this pathway may be of therapeutic potential in NASH. Using a methionine‐choline–deficient rat model of NASH, we studied the potential utility of an angiotensin II type 1 receptor blocker (ARB), olmesartan, on biochemical, histologic, and antioxidant measures of disease activity. ARB significantly attenuated increases in aspartate aminotransferase, activation of hepatic stellate cells, oxidative stress, expression of transforming growth factor–beta 1, expression of collagen genes, and liver fibrosis. Conclusion: Our observations strongly suggest a potential preventive role for ARB in the progression of nonalcoholic steatohepatitis. (HEPATOLOGY 2007.)

Maternal obesity during pregnancy and lactation programs the development of offspring non-alcoholic fatty liver disease in mice.

BACKGROUND & AIMS Obesity induced, non-alcoholic fatty liver disease (NAFLD), is now the major cause in affluent countries, of the spectrum of steatosis-to-cirrhosis. Obesity and NAFLD rates in reproductive age women, and adolescents, are rising worldwide. Our hypothesis was that maternal obesity and lactation transmit to the offspring a pre-disposition to dysmetabolism, obesity and NAFLD. METHODS Female mice were fed standard or obesogenic chow, before, throughout pregnancy, and during lactation. The critical developmental period was studied by cross-fostering offspring of lean and obese dams. Offspring were then weaned onto standard chow and studied at 3months. Read-outs included markers of metabolic dysfunction, biochemical and histological indicators of NAFLD, induction of liver fibrogenesis, and activation of pro-fibrotic pathways. Mechanisms involved in programming a dysmetabolic and NAFLD phenotype were investigated by assaying breast milk components. RESULTS Offspring of obese dams had a dysmetabolic, insulin resistant and NAFLD phenotype compared to offspring of lean dams. Offspring of lean dams that were suckled by obese dams showed an exaggerated dysmetabolic and NAFLD phenotype, with increased body weight, as well as increased levels of insulin, leptin, aspartate transaminase, interleukin-6, tumour necrosis factor-alpha, liver triglycerides, steatosis, hepatic fibrogenesis, renal norepinephrine, and liver alpha1-D plus beta1-adrenoceptors, indicative of sympathetic nervous system activation. Obese dams also had raised breast milk leptin levels compared to lean dams. CONCLUSIONS Maternal obesity programs development of a dysmetabolic and NAFLD phenotype, which is critically dependent on the early postnatal period and possibly involving alteration of hypothalamic appetite nuclei signalling by maternal breast milk and neonatal adipose tissue derived, leptin.

Hepatic fibrogenesis requires sympathetic neurotransmitters

Background and aims: Hepatic stellate cells (HSC) are activated by liver injury to become proliferative fibrogenic myofibroblasts. This process may be regulated by the sympathetic nervous system (SNS) but the mechanisms involved are unclear. Methods: We studied cultured HSC and intact mice with liver injury to test the hypothesis that HSC respond to and produce SNS neurotransmitters to promote fibrogenesis. Results: HSC expressed adrenoceptors, catecholamine biosynthetic enzymes, released norepinephrine (NE), and were growth inhibited by α- and β-adrenoceptor antagonists. HSC from dopamine β-hydroxylase deficient (Dbh−/−) mice, which cannot make NE, grew poorly in culture and were rescued by NE. Inhibitor studies demonstrated that this effect was mediated via G protein coupled adrenoceptors, mitogen activated kinases, and phosphatidylinositol 3-kinase. Injury related fibrogenic responses were inhibited in Dbh−/− mice, as evidenced by reduced hepatic accumulation of α-smooth muscle actin+ve HSC and decreased induction of transforming growth factor β1 (TGF-β1) and collagen. Treatment with isoprenaline rescued HSC activation. HSC were also reduced in leptin deficient ob/ob mice which have reduced NE levels and are resistant to hepatic fibrosis. Treating ob/ob mice with NE induced HSC proliferation, upregulated hepatic TGF-β1 and collagen, and increased liver fibrosis. Conclusions: HSC are hepatic neuroglia that produce and respond to SNS neurotransmitters to promote hepatic fibrosis.

Norepinephrine regulates hepatic innate immune system in leptin‐deficient mice with nonalcoholic steatohepatitis

It is not known why natural killer T (NKT) cells, which modulate liver injury by regulating local cytokine production, are reduced in leptin‐deficient ob/ob mice. NKT cells express adrenoceptors. Thus, we hypothesize that the low norepinephrine (NE) activity of ob/ob mice promotes depletion of liver NKT cells, thereby sensitizing ob/ob livers to lipopolysaccharide (LPS) toxicity. To evaluate this hypothesis, hepatic NKT cells were quantified in wild‐type mice before and after treatment with NE inhibitors, and in dopamine β‐hydroxylase knockout mice (which cannot synthesize NE) and ob/ob mice before and after 4 weeks of NE supplementation. Decreasing NE activity consistently reduces liver NKT cells, while increasing NE has the opposite effect. Analysis of hepatic and thymic NKT cells in mice of different ages demonstrate an age‐related accumulation of hepatic NKT cells in normal mice, while liver NKT cells become depleted after birth in ob/ob mice, which have increased apoptosis of hepatic NKT cells. NE treatment inhibits apoptosis and restores hepatic NKT cells. In ob/ob mice with reduced hepatic NKT cells, hepatic T and NKT cells produce excessive T helper (Th)‐1 proinflammatory cytokines and the liver is sensitized to LPS toxicity. NE treatment decreases Th‐1 cytokines, increases production of Th‐2 cytokines, and reduces hepatotoxicity. Studies of CD1d‐deficient mice, which lack the receptor required for NKT cell development, demonstrate that they are also unusually sensitive to LPS hepatotoxicity. In conclusion, low NE activity increases hepatic NKT cell apoptosis and depletes liver NKT cells, promoting proinflammatory polarization of hepatic cytokine production that sensitizes the liver to LPS toxicity. (HEPATOLOGY 2004;40:434–441.)

Maternal obesity programs offspring nonalcoholic fatty liver disease by innate immune dysfunction in mice

The global prevalence of obesity‐induced liver disease (nonalcoholic fatty liver disease; NAFLD) is rising. Suggested causes include a role for in utero influences of maternal obesity compounded by the availability of energy‐dense foods throughout postnatal life. Using a physiologically relevant model, we investigated the role of the innate immune system in liver injury induced by maternal obesity followed by a postnatal obesogenic diet. Female C57BL/6J mice were fed a standard or obesogenic diet before and throughout pregnancy and during lactation. Female offspring were weaned onto a standard or obesogenic diet at 3 weeks postpartum. Biochemical and histological indicators of dysmetabolism, NAFLD and fibrosis, analysis of profibrotic pathways, liver innate immune cells, and reactive oxygen species (ROS) were investigated at 3, 6, and 12 months. Female offspring exposed to a postweaning obesogenic diet (OffCon‐OD) demonstrated evidence of liver injury, which was exacerbated by previous exposure to maternal obesity (OffOb‐OD), as demonstrated by raised alanine aminotransferase, hepatic triglycerides, and hepatic expression of interleukin (IL)‐6, tumor necrosis factor alpha, transforming growth factor beta, alpha smooth muscle actin, and collagen (P < 0.01). Histological evidence of hepatosteatosis and a more‐robust NAFLD phenotype with hepatic fibrosis was observed at 12 months in OffOb‐OD. A role for the innate immune system was indicated by increased Kupffer cell numbers with impaired phagocytic function and raised ROS synthesis (P < 0.01), together with reduced natural killer T cells and raised interleukin (IL)‐12 and IL‐18. Conclusion: Maternal obesity in the context of a postnatal hypercalorific obesogenic diet aggressively programs offspring NAFLD associated with innate immune dysfunction, resulting in a comprehensive phenotype that accurately reflects the human disease. (HEPATOLOGY 2013)

Norepinephrine and neuropeptide Y promote proliferation and collagen gene expression of hepatic myofibroblastic stellate cells.

The mechanisms initiating and perpetuating the fibrogenic response in the injured liver are not well understood. Hepatic stellate cells are activated by liver injury to become proliferative and fibrogenic myofibroblasts. Emerging evidence suggests that the sympathetic nervous system may play a role in the development of cirrhosis. It is not known, however, whether this requires a direct interaction between sympathetic neurotransmitters and stellate cell receptors, or results indirectly, from sympathetic effects on the vasculature. Using cultured hepatic stellate cells, we show that the sympathetic neurotransmitters, norepinephrine and neuropeptide Y, markedly stimulate the proliferation of activated, myofibroblastic, hepatic stellate cells. Norepinephrine, but not neuropeptide Y, also induces collagen gene expression. In conclusion, physiologically relevant concentrations of sympathetic neurotransmitters directly modulate the phenotype of hepatic stellate cells. This suggests that targeted interruption of sympathetic nervous system signaling in hepatic stellate cells may be useful in constraining the fibrogenic response to liver injury.

Norepinephrine induces hepatic fibrogenesis in leptin deficient ob/ob mice

Leptins actions on certain cells require a leptin-inducible neurotransmitter, norepinephrine (NE). NE modulates hepatic fibrosis. Therefore, decreased NE may explain why leptin deficiency inhibits hepatic fibrosis. We manipulated adrenergic activity in leptin-deficient ob/ob mice, leptin-sufficient, dopamine beta-hydroxylase deficient (Dbh(-/-)) mice, and HSC cultures to determine if leptin requires NE to activate HSC and induce hepatic fibrosis. ob/ob mice have chronic liver injury, but reduced numbers of HSC. Supplemental leptin increases HSC, suggesting that leptin-dependent, injury-related factors permit expansion of HSC populations. NE also increases HSC numbers and activation, normalizing fibrogenesis. When fed hepatotoxic diets, NE-deficient Dbh(-/-) mice fail to accumulate activated HSC and have impaired fibrogenesis unless treated with adrenergic agonists. NE acts directly on HSC to modulate leptins actions because leptin increases HSC proliferation and prazosin, an alpha-adrenoceptor antagonist, inhibits this. Thus, leptin permits injury-related increases in adrenergic activity and requires NE to activate HSC and induce hepatic fibrogenesis.

Guidelines for liver transplantation for patients with non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is an increasing cause of liver disease necessitating liver transplantation. In patients with advanced NASH, there are often coexistent clinical issues that impact on the outcome of liver transplantation. There are no guidelines for the assessment and management of patients with NASH undergoing liver transplantation. A group was therefore invited by the Council of the British Transplant Society (BTS) to prepare guidelines for the management of NASH before and after liver transplantation. The guideline is approved by the British Society of Gastroenterology, the British Association for the Study of Liver and NHS Blood and Transplant. The first draft was written by Dr P N Newsome (senior lecturer and consultant hepatologist, Liver Unit, University Hospital Birmingham NHS Foundation Trust) in Autumn 2010 with contributions from the following guideline group: Dr Peter Henriksen (consultant cardiologist and honorary senior lecturer, Edinburgh Heart Centre, NHS Lothian, University Hospitals Division), Professor C P Day (Professor of Liver Medicine, Institute of Cellular Medicine, Newcastle University), Dr D Thorburn (consultant hepatologist, Liver Unit, Royal Free Hospital, London), Mr D F Mirza (consultant hepatobiliary and transplant surgeon, Liver Unit, University Hospital Birmingham NHS Foundation Trust), Dr J W Ferguson (consultant hepatologist and honorary senior lecturer, Liver Unit, University Hospital Birmingham NHS Foundation Trust), Dr G Auzinger (consultant intensive care medicine, Liver Intensive Therapy Unit, Kings College Hospital London NHS Foundation Trust), Dr M Allison (consultant hepatologist, Liver Unit, Department of Medicine, Cambridge University Hospital NHS Foundation Trust), Dr J W Tomlinson (reader in endocrinology, Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham), H Manley (British Liver Trust), Dr K J Simpson (senior lecturer in hepatology, University of Edinburgh and honorary consultant physician, Scottish Liver Transplantation Unit, Royal Infirmary Edinburgh), Professor S G Hubscher (Leith Professor and Professor of Hepatic Pathology, University of Birmingham, and …

Acetylcholine promotes the proliferation and collagen gene expression of myofibroblastic hepatic stellate cells

The mechanisms that initiate and perpetuate the fibrogenic response, during liver injury, are unclear. Animal studies, however, strongly support a role for the autonomic nervous system (ANS) in wound healing. Therefore, the ANS may also mediate the development of cirrhosis. Hepatic stellate cells (HSC), the livers major matrix-producing cells, are activated by injury to become proliferative, fibrogenic myofibroblasts. HSC respond to sympathetic neurotransmitters by changing phenotype, suggesting that HSC may be the cellular effectors of ANS signals that modulate hepatic fibrogenesis during recovery from liver damage. We show here that the parasympathetic neurotransmitter acetylcholine markedly stimulates the proliferation of myofibroblastic HSC and induces HSC collagen gene expression in these cells. By extending evidence that HSC are direct targets of the ANS, these results support the proposed neuroglial role of HSC in the liver and suggest that interrupting ANS signalling may be useful in constraining the fibrogenic response to liver injury.

Maternal obesity programmes offspring development of non-alcoholic fatty pancreas disease

Background and aims The prevalence of pancreatic adenocarcinoma (PAC) parallels rising rates of obesity and dysmetabolism, a possible link being non-alcoholic fatty pancreas disease (NAFPD). We have recently shown that maternal obesity programmes the development of a dysmetabolic and fatty liver (non-alcoholic fatty liver disease, NAFLD) phenotype in adult offspring. Since the pancreas and liver originate from the same embryonic bud, it is plausible that maternal obesity may similarly programme the development of NAFPD. Our objective was to determine the effect of maternal obesity on development of NAFPD in offspring and ascertain contributions of the intra/extra-uterine periods. Methods Female C57BL/6J mice were fed either a standard chow (3% fat, 7% sugar) or a hypercalorific diet (16% fat, 33% sugar) for six weeks prior to mating and throughout pregnancy and lactation. Female offspring were cross-fostered for suckling to dams on the same or opposite diet to yield four groups: offspring of lean suckled by lean dams (n = 6), offspring of obese suckled by obese dams (n = 6), offspring of lean suckled by obese dams (n = 5) and offspring of obese suckled by lean dams (n = 6). All offspring were weaned onto a standard chow diet at 21 days and sacrificed at 3 months post-partum for tissue collection. Results Offspring subjected to an adverse suckling environment showed significant increases in body weight, pancreatic triglyceride content, TGF-β, collagen gene expression and SBP at rest along with an enhanced restraint stress response, indicating a dysmetabolic and NAFPD phenotype. Conclusions Developmental programming is involved in the pathogenesis of NAFPD and appears to be largely dependent on an adverse extra-uterine environment.