The role of adiponectin in the pathogenesis and treatment of non-alcoholic fatty liver disease.
Non-alcoholic fatty liver disease (NAFLD) is recognized as the most common type of chronic liver disease in Western countries and the leading cause of cryptogenic cirrhosis. Insulin resistance (IR) is a key factor in the pathogenesis of NAFLD, the latter being considered as the hepatic component of IR or metabolic syndrome (MetS). Although the pathogenesis of NAFLD is not fully elucidated, a complex interaction between adipokines and cytokines produced by adipocytes and/or inflammatory cells infiltrating adipose tissue appears to play a crucial role in MetS and NAFLD. Adiponectin is the most abundant and adipose-specific adipokine. In the liver, adiponectin acts through the activation of 5-AMP-activated protein kinase and peroxisome proliferator-activated receptor-alpha pathways and inhibition of toll-like receptor-4 mediated signalling. There is an evidence that adiponectin decreases hepatic and systematic IR and attenuates liver inflammation and fibrosis. Adiponectin generally predicts steatosis grade and severity of NAFLD, but it remains to be addressed to what extent this is a direct effect or related to the presence of more severe IR. Although there is no proven pharmacotherapy for the treatment of NAFLD, recent therapeutic strategies have focused on the indirect upregulation of adiponectin through the administration of various therapeutic agents and/or lifestyle modifications. Weight loss, through diet, lifestyle changes and/or medications including orlistat, sibutramine, rimonabant or bariatric surgery, increase adiponectin and may improve liver histology. Insulin sensitizers, including pioglitazone and rosiglitazone, and lipid-lowering agents, including statins and fibrates, also upregulate adiponectin and ameliorate liver histology. The wider use of new treatment approaches appears to signal the dawn of a new era in the management of NAFLD. In this adiponectin-focused review, the pathogenetic role and the potential therapeutic benefits of adiponectin in NAFLD are systematically analysed.
Diabetes Obes Metab. 2010 May;12(5):365-83
The challenge of developing novel pharmacological therapies for non-alcoholic steatohepatitis.
Non-alcoholic fatty liver disease (NAFLD) is an umbrella term for a series of hepatic pathologies that begin with relatively benign steatosis and can, with appropriate triggers, lead to the serious entity of non-alcoholic steatohepatitis (NASH). This sets the stage for liver fibrosis and finally the development of cirrhosis in up to 20% of patients with NASH. NAFLD, already among the most common diseases in industrialized countries, is increasing in prevalence and roughly affects 30% of US adults and 10% of US children alone. NAFLD is strongly associated with insulin resistance (IR) and represents the hepatic manifestation of the metabolic syndrome. Indeed, treatments aimed at reducing IR are the current mainstay of therapeutic approaches to NAFLD. While lifestyle interventions may produce limited degrees of success, there remains an urgent need for improved pharmacological therapies. Emerging diagnostic and therapeutic opportunities as well as future developments in NAFLD, NASH and liver fibrosis were discussed by a panel of experts and are presented herein. Promising novel therapeutic targets include inhibitors of dipeptidyl peptidase 4 and the renin-angiotensin system. However, improved non-invasive technologies to diagnose and stage NAFLD are needed. Combined with a better understanding of the pathophysiological processes that underlie the mechanisms of hepatic fibrogenesis in NASH, rapid clinical validation of novel therapies is expected.
Liver Int. 2010 Jul;30(6):795-808
Review article: current management of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis.
BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome. AIM: To assess the epidemiological impact and the current management of patients with NAFLD. METHODS: Published peer-reviewed literature and abstracts concerning NAFLD and non-alcoholic steatohepatitis (NASH) were reviewed. Articles specifically related to epidemiology, diagnosis and current treatment strategies for NAFLD and NASH are summarized. RESULTS: NAFLD is strongly associated with the epidemic of obesity and type-2 diabetes mellitus, and is estimated to affect about 20-30% of the population in the US. From the spectrum of NAFLD, only patients with biopsy-proven NASH (estimated prevalence in the US population is about 3-5%) have been convincingly shown to progress to cirrhosis, liver failure and hepatocellular carcinoma. The clinical manifestation of NAFLD is usually absent or subtle, with abnormal aminotransferases or incidental radiographic findings of fatty liver. The pathogenesis of NAFLD is attributed to a multi-hit process involving insulin resistance, oxidative stress, apoptotic pathways, and adipocytokines. In 2008, there is no established treatment for NAFLD. Weight loss and treatment for each component of metabolic syndrome. Nevertheless, a large number of agents are being considered in clinical trials of patients with NASH. CONCLUSIONS: Awareness of the tremendous impact of NAFLD as an important cause of chronic liver disease is increasing along with a great deal of information about its pathogenesis. Future, well-designed clinical trials that target specific pathways involved in the pathogenesis of NASH are urgently needed.
Aliment Pharmacol Ther. 2008 Jul;28(1):2-12
Pharmacological and non-pharmacological treatment of non-alcoholic fatty liver disease.
Non-alcoholic fatty liver disease (NAFLD) comprises a disease spectrum ranging from simple steatosis and steatohepatitis to cirrhosis. Based on its strongest risk factors namely visceral obesity and insulin resistance, NAFLD is thought to be the hepatic manifestation of the metabolic syndrome and is considered to be the most common liver disorder in Western countries. Pathophysiological mechanisms include an enlarged pool of fatty acids, subclinical inflammation, oxidative stress and imbalances of various adipocytokines such as adiponectin. Accordingly, targets for therapeutic interventions are miscellaneous: amelioration of obesity by pharmacological, surgical or lifestyle intervention has been evaluated with success in numerous, but not all studies. Some efficacy was reported for metformin and short-term glitazone treatment. In a large recently reported trial, vitamin E supplementation improved biochemical and histological markers in subjects with non-alcoholic steatohepatitis. Blockade of the endocannabinoid system has been proposed to be a promising target in NAFLD; however, very recently the cannabinoid receptor blocker rimonabant has been withdrawn because of central nervous system toxicity. Cytoprotective therapies and statins have been mainly ineffective in NAFLD. New but so far insufficiently studied therapeutic approaches include inhibitors of the renin-angiotensin system as well as incretin mimetics respectively.
Int J Clin Pract. 2010 Jun;64(7):968-83
Non-alcoholic fatty liver disease and hepatitis C infection.
Non-alcoholic fatty liver disease (NAFLD) is now recognized as one of the most important causes of chronic liver disease in Western Countries, and is the hepatic manifestation of metabolic syndrome. The prevalence of NAFLD has increased with the global epidemic of obesity and type 2 diabetes mellitus. The pathophysiological hallmark of NAFLD is insulin resistance, associated with mediators of oxidative stress and inflammatory cytokines. Although simple steatosis by itself is generally benign, patients with histologically proven non-alcoholic steatohepatitis (NASH) can progress to cirrhosis. Hepatitis C (HCV) is another common cause of liver disease with some potential for progression to cirrhosis. Steatosis is present in almost 50% of patients infected by HCV. Hepatic steatosis in the setting of another liver disease (such as HCV) is associated liver disease progression. In particular, significant fibrosis is observed in patients with HCV whose liver biopsies show significant steatosis or superimposed NASH. This article reviews the host and viral factors potentially involved in the interaction between NAFLD and HCV. These factors include mediators of metabolic syndrome such as adipokines, inflammatory cytokines, factors associated with oxidative stress, lipid peroxidation products, as well as apoptosis and hepatic stellate cell activation with the resultant deposition of extracellular matrix. In addition to the mediators of metabolic syndrome (host factors), hepatic steatosis can be influenced by viral factors. The most important viral factor is HCV genotype 3, which has been independently associated with hepatic steatosis. Finally, superimposed NAFLD and visceral fat are associated with lower response rates to antiviral therapy in non-genotype 3 patients. Furthermore, viral clearance is associated with the resolution of hepatic steatosis in HCV genotype 3 but not other HCV genotypes. In these genotypes, hepatic steatosis and its impact on response to therapy are related to metabolic syndrome. Thus, the management of obesity and metabolic syndrome in patients with chronic hepatitis C may be important for reducing the risk of progression as well as improving the efficacy of antiviral therapy.
Minerva Gastroenterol Dietol. 2006 Jun;52(2):135-43
The plasma lipidomic signature of nonalcoholic steatohepatitis.
Specific alterations in hepatic lipid composition characterize the spectrum of nonalcoholic fatty liver disease (NAFLD), which extends from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH). However, the plasma lipidome of NAFLD and whether NASH has a distinct plasma lipidomic signature are unknown. A comprehensive analysis of plasma lipids and eicosanoid metabolites quantified by mass spectrometry was performed in NAFL (n = 25) and NASH (n = 50) subjects and compared with lean normal controls (n = 50). The key findings include significantly increased total plasma monounsaturated fatty acids driven by palmitoleic (16:1 n7) and oleic (18:1 n9) acids content (P < 0.01 for both acids in both NAFL and NASH). The levels of palmitoleic acid, oleic acid, and palmitoleic acid to palmitic acid (16:0) ratio were significantly increased in NAFLD across multiple lipid classes. Linoleic acid (8:2n6) was decreased (P < 0.05), with a concomitant increase in gamma-linolenic (18:3n6) and dihomo gamma-linolenic (20:3n6) acids in both NAFL and NASH (P < 0.001 for most lipid classes). The docosahexanoic acid (22:6 n3) to docosapentenoic acid (22:5n3) ratio was significantly decreased within phosphatidylcholine (PC), and phosphatidylethanolamine (PE) pools, which was most marked in NASH subjects (P < 0.01 for PC and P < 0.001 for PE). The total plasmalogen levels were significantly decreased in NASH compared with controls (P < 0.05). A stepwise increase in lipoxygenase (LOX) metabolites 5(S)-hydroxyeicosatetraenoic acid (5-HETE), 8-HETE, and 15-HETE characterized progression from normal to NAFL to NASH. The level of 11-HETE, a nonenzymatic oxidation product of arachidonic (20:4) acid, was significantly increased in NASH only. Conclusions: Although increased lipogenesis, desaturases, and LOX activities characterize NAFL and NASH, impaired peroxisomal polyunsaturated fatty acid (PUFA) metabolism and nonenzymatic oxidation is associated with progression to NASH.
Hepatology. 2009 Dec;50(6):1827-38
Antioxidant supplements for non-alcoholic fatty liver disease and/or steatohepatitis.
BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is characterised by fatty deposition in the hepatocytes of patients with minimal or no alcohol intake and without other known cause. NAFLD includes a wide spectrum of histologic abnormalities ranging from hepatic steatosis to non-alcoholic steatohepatitis (NASH), or even cirrhosis. Antioxidant supplements, therefore, could potentially protect cellular structures against oxidative stress and the resulting lipid peroxidation. OBJECTIVES: To systematically evaluate the beneficial and harmful effects of antioxidant supplements versus no intervention, placebo, or other interventions for patients with NAFLD or NASH. SEARCH STRATEGY: We searched The Cochrane Hepato-Biliary Group Controlled Trials Register (June 2006), the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Issue 2, 2006), MEDLINE (1966 to June 2006), EMBASE (1980 to June 2006), and the Chinese Biomedical Database (1978 to June 2006). No language restrictions were applied. SELECTION CRITERIA: Randomised clinical trials evaluating any antioxidant supplements versus no intervention, placebo, or other interventions in patients with NAFLD or NASH. Our inclusion criteria for NAFLD or NASH were based on history of minimal or no alcohol intake, imaging techniques showing hepatic steatosis, and/or histological evidence of hepatic damage (including simple steatosis, fatty infiltration plus nonspecific inflammation, steatohepatitis, fibrosis, and cirrhosis), and by exclusion of other causes of hepatic steatosis. DATA COLLECTION AND ANALYSIS: We extracted data from the identified trials and contacted authors. We used a random-effects model and fixed-effect model with the significant level set at P = 0.05. We evaluated the methodological quality of the randomised trials by looking at how the generation of allocation sequence, allocation concealment, blinding, and follow-up were performed. We made our analyses following the intention-to-treat method by imputing missing data. MAIN RESULTS: We identified six trials: two were regarded of high methodological quality and four of low methodological quality. None of the trials reported any deaths. Treatment with antioxidant supplements showed a significant, though not clinically relevant, amelioration of aspartate aminotransferase levels, but not of alanine aminotransferase levels, as compared to placebo or other interventions. Gamma-glutamyl-transpeptidase was decreased, albeit not significantly, in the treatment arm. Radiological and histological data were too limited to draw any definite conclusions on the effectiveness of these agents. Adverse events were non-specific and of no major clinical relevance. AUTHORS’ CONCLUSIONS: There is insufficient data to either support or refute the use of antioxidant supplements for patients with NAFLD. It may be advisable to carry out large prospective randomised clinical trials on this topic.
Cochrane Database Syst Rev. 2007 Jan 24;(1):CD004996
Non-alcoholic fatty liver disease—new view.
Non-alcoholic fatty liver disease (NAFLD) covers a wide spectrum of liver pathology--from steatosis alone, through the necroinflammatory disorder of non-alcoholic steatohepatitis (NASH) to cirrhosis and liver cancer. NAFLD/NASH is mostly related with visceral adiposity, obesity, type 2 diabetes melitus (DM t.2) and metabolic syndrome. Pathogenetic concepts of NAFLD include overnutrition and underactivity, insulin resistance (IR) and genetic factor. The prevalence of NAFLD has been estimated to be 17-33% in some countries, NASH may be present in about 1/3 of such cases, while 20-25% of NASH cases could progress to cirrhosis. NAFLD is now recognized as one of the most frequent reason of liver tests elevation without clinical symptoms. Insulin resistance is considering as having a central role in NAFLD pathogenesis. In hepatocytes, IR is related to hyperglycaemia and hyperinsulinaemia, formation of advanced glycation end-products, increased free fatty acids and their metabolites, oxidative stress and altered profiles of adipocytokines. Early stages of fatty liver are clinically silent and include elevation of ALT and GGTP, hyperechogenic liver in USG and/or hepatomegaly. Among clinical symptoms, abdominal discomfort is relatively common as well as chronic fatigue. NAFLD/NASH is not a benign disease, progressive liver biopsy have shown histological progression of fibrosis in 32%, the estimated rate of cirrhosis development is 20% and a liver--related death is 12% over 10 years. No treatment has scientifically proved to ameliorate NAFLD or to avoid its progression. The various therapeutic alternatives are aimed at interfering with the risk factors involved in the pathogenesis of the disorder in order to prevent the progression to end-stage liver disease. The most important therapeutic measure is increasing insulin sensitivity by an attempt to change a lifestyle mostly by dieting and physical activity in order to loose weight. The most used agent is metformin, the others are under controlled trials or their effectiveness is low. NASH is not a common indication for liver transplantation because of the older age distribution of patients and high prevalence of comorbidity, related to metabolic syndrome. Recurence of NASH in the grafted liver is also a relatively frequent complication.
Pol Merkur Lekarski. 2008 Jun;24(144):568-71
Non-alcoholic fatty liver disease from pathogenesis to management: an update.
Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease in the Western world, is tightly associated with obesity and metabolic syndrome. NAFLD entails an increased cardiometabolic and liver-related risk, the latter regarding almost exclusively non-alcoholic steatohepatitis (NASH), the progressive form of NAFLD. Pathogenetic models encompass altered hepatic lipid partitioning and adipokine action, increased oxidative stress, free fatty acid lipotoxicity. On this basis, lifestyle-, drug- or surgically induced weight loss, insulin sensitizers, antioxidants, lipid-lowering drugs have been evaluated in NAFLD/NASH. Most trials are small, of short duration, nonrandomized, without histological end points, thus limiting assessment of long-term safety and efficacy of proposed treatments. All NAFLD patients should be evaluated for their metabolic, cardiovascular and liver-related risk. Liver biopsy remains the gold standard for staging NAFLD, but non-invasive methods are under intense development. Weight loss through lifestyle intervention is the initial approach, because of established efficacy on NAFLD-associated cardiometabolic abnormalities, and to emerging benefits on necroinflammation and overall disease activity in NASH. Bariatric surgery warrants further evaluation before it can be routinely considered in morbidly obese NASH. Larger- and longer-duration randomized trials assessing safety and benefits of drugs on patient-oriented outcomes are needed before pharmacological treatment can be routinely recommended for NASH.
Obes Rev. 2010 Jun;11(6):430-45
Current and future therapeutic strategies in NAFLD.
Non alcoholic fatty liver disease (NAFLD) is increasingly diagnosed worldwide and considered to be the commonest liver disorder in Western countries. It comprises a disease spectrum ranging from simple steatosis (fatty liver), through non-alcoholic steatohepatitis (NASH) to fat with fibrosis and ultimately cirrhosis. Simple steatosis is largely benign and non-progressive, whereas NASH, characterized by hepatocyte injury, inflammation and fibrosis can lead to cirrhosis, liver failure and hepatocellular carcinoma (HCC). NAFLD is strongly associated with obesity, insulin resistance, hypertension and dyslipidaemia and is now regarded as the liver manifestation of the metabolic syndrome. Rapid spread of the obesity ‘pandemic’ in adults and children, coupled with the realisation that the outcomes of obesity-related liver disease are not entirely benign, has led to rapid growth in clinical and basic studies in NAFLD over the past decade. These studies are now beginning to inform management strategies for patients with NAFLD.
Curr Pharm Des. 2010 Jun;16(17):1958-62