Adiponectin, a key adipokine in obesity related liver diseases

Non-alcoholic fatty liver disease (NAFLD) comprising hepatic steatosis,non-alcoholic steatohepatitis (NASH),and progressive liver fibrosis is considered the most common liver disease in western countries.Fatty liver is more prevalent in overweight than normal-weight people and liver fat positively correlates with hepatic insulin resistance.Hepatic steatosis is regarded as a benign stage of NAFLD but may progress to NASH in a subgroup of patients.Besides liver biopsy no diagnostic tools to identify patients ...     

Clinicopathological significance of oxidative cellular damage in non-alcoholic fatty liver diseases.

Oxidative stress may play an important role in the progression of simple steatosis to non-alcoholic steatohepatitis (NASH). Oxidative stress is generated through multiple sources, including oxidation of free fatty acids, cytochrome P4502E1, iron overload, and necro-inflammatory cytokines including tumor necrosis factor-alpha. Oxidative stress may trigger damage to cellular membranes and nuclear DNA, which results in lipid peroxidation and oxidative DNA damage, respectively. Here, we present our data on intrahepatic localization and clinico-pathological significance of oxidative stress-induced cellular damage in the patients with non-alcoholic fatty liver diseases (NAFLD). Our subjects were 23 patients with non-alcoholic simple fatty liver, 17 with NASH, and 7 with normal liver (control). Hepatic expression of 4-hydroxy-2'-nonenal (HNE) and 8-hydroxydeoxyguanosine (8-OHdG), as reliable markers of lipid peroxidation and oxidative DNA damage, was in situ detected by using commercially available monoclonal antibodies. While no HNE adducts were observed in control livers, they were frequently detected in NAFLD. In NASH, the localization of the HNE adducts was in the cytoplasm of sinusoidal cells and hepatocytes with a predominance in zone 3. The grade of necro-inflammation as well as the stage of fibrosis significantly correlated with the HNE labeling index. With respect to 8-OHdG, although no 8-OHdG expression was observed in normal liver and only a few in non-alcoholic simple fatty liver, 11 of 17 patients with NASH (65%) exhibited nuclear expression of 8-OHdG in hepatocytes and sinusoidal cells in areas of active inflammation. The 8-OHdG index significantly correlated with the grade of necro-inflammation, but not with the stage of fibrosis. Our observations suggest that oxidative cellular damage occurs frequently in livers with NAFLD and may be associated with some clinico-pathological features of NAFLD including liver fibrosis and possibly, hepatocarcinogenesis.     

Mechanisms of ductular reaction in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is a disease spectrum caused in part by insulin resistance and genetic predisposition. This disease is primarily characterized by excessive lipid accumulation in hepatocytes in the absence of alcohol abuse and other causes of liver damage. Histologically, NAFLD is divided into several periods: simple steatosis, non-alcoholic steatohepatitis (NASH), hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. With the increasing prevalence of obesity and hyperlipidemia, NAFLD has become the main cause of chronic liver disease worldwide. As a result, the pathogenesis of this disease is drawing increasing attention. Ductular reaction (DR) is a reactive bile duct hyperplasia caused by liver injury that involves hepatocytes, cholangiocytes, and hepatic progenitor cells. Recently, DR is shown to play a pivotal role in simple steatosis progression to NASH or liver fibrosis, providing new research and treatment options. This study reviews several DR signaling pathways, including Notch, Hippo/YAP-TAZ, Wnt/β-catenin, Hedgehog, HGF/c-Met, and TWEAK/Fn14, and their role in the occurrence and development of NASH.     

Liver fat as risk factor of hepatic and cardiometabolic diseases

Non-alcoholic fatty liver disease (NAFLD) is a disorder characterized by excessive accumulation of fat in the liver that can progress to liver inflammation (non-alcoholic steatohepatitis [NASH]), liver fibrosis, and cirrhosis. Although most efforts for drug development are focusing on the treatment of the latest stages of NAFLD, where significant fibrosis and NASH are present, findings from studies suggest that the amount of liver fat may be an important independent risk factor and/or predictor of development and progression of NAFLD and metabolic diseases. In this review, we first describe the current tools available for quantification of liver fat in humans and then present the clinical and pathophysiological evidence that link liver fat with NAFLD progression as well as with cardiometabolic diseases. Finally, we discuss current pharmacological and non-pharmacological approaches to reduce liver fat and present open questions that have to be addressed in future studies.     

Klinische Bedeutung – Sinn und Unsinn – der Leberbiopsie bei NAFLD

Non-alcoholic fatty liver disease (NAFLD) comprises a spectrum ranging from bland non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH), liver cirrhosis, and hepatocellular cancer. Whereas “pure” NAFL rarely results in progressive liver disease, NASH can progress to liver cirrhosis in up to 25% of NASH patients. NAFL and NASH are both associated with an increased cardiovascular mortality, which represents the most important prognosis-limiting factor in both conditions. Diagnosis of NAFLD is based on clinical, biochemical, and sonographic findings. Liver biopsy is required for histologic distinction between NAFL and NASH. Because the therapeutic options for NASH are currently limited, liver biopsy has a rather limited value in the daily clinical management of NAFLD. Non-invasive laboratory and imaging methods (such as ultrasound elastography) may become increasingly important in the future.     

Abnormal glucose tolerance is a predictor of steatohepatitis and fibrosis in patients with non-alcoholic fatty liver disease

OBJECTIVE: The majority of patients with non-alcoholic fatty liver disease (NAFLD) have simple steatosis. A minority, however, present with non-alcoholic steatohepatitis (NASH), a condition that can lead to advanced fibrosis and cirrhosis. The frequencies of NASH and fibrosis among patients with NAFLD and sustained elevation of liver function tests (LFT) are uncertain. Our aim was to estimate these frequencies. We characterize a population with NAFLD, with special emphasis on insulin resistance and the metabolic syndrome, and study possible predictors for different stages of the disease. MATERIAL AND METHODS: All referred patients with sustained elevation of LFT, radiological evidence or clinical suspicion of fatty liver, and absence of other liver disease, were invited to participate in our study in the period June 2002 to December 2004. RESULTS: Of 129 patients who met the inclusion criteria, 88 underwent liver biopsy. NAFLD was verified in 83 of them. Among these patients, 59 (71%) had the metabolic syndrome, 41 (49%) had NASH and 36 (43%) had fibrosis. Abnormal glucose tolerance (T2DM or impaired glucose tolerance) was the only independent risk factor for NASH (OR: 3.14; 95% CI: 1.20-8.23). Independent predictors for fibrosis were abnormal glucose tolerance (OR: 3.83; 95% CI: 1.29-11.40) and body mass index (OR: 1.20; 95% CI: 1.06-1.36) per kg/m2. CONCLUSIONS: Both NASH and fibrosis are frequently present among patients with NAFLD and sustained elevation of LFT. The probability of these potentially progressive stages of NAFLD increases with the presence of abnormal glucose tolerance.     

Clinicopathological features of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease worldwide and its incidence is increasing concomitantly with the increase in the prevalence of metabolic syndrome. Fatty liver encompasses a broad pathological spectrum of disease, from relatively benign accumulation of fat (simple steatosis) to progressive non-alcoholic steatohepatitis (NASH), which is associated with necroinflammation and fibrosis. Approximately 20-30% of the Japanese population is estimated to have NAFLD, 10% of which is suggested to have NASH. The most worrisome feature of NASH is the potential progression to cirrhosis, hepatocellular carcinoma (HCC), and finally, mortality. Several factors, such as insulin resistance, adipokines, endotoxins and oxidative stress, are involved in the pathogenesis of NASH. However, the precise etiological mechanism of NAFLD/NASH has yet to be elucidated. This article reviews the clinical background, pathogenesis, new diagnostic approaches and future directions regarding NAFLD/NASH.     

Insulin resistance and metabolic syndrome in chronic liver diseases: old entities with new implications

Insulin resistance (IR) and metabolic syndrome have recently been implicated in the pathogenesis and progression of chronic liver diseases, especially chronic hepatitis C (CHC) and non-alcoholic fatty liver disease (NAFLD). In this review, we provide current information on their deleterious effect on the liver, with particular interest in those two entities. In NAFLD, IR causes both the accumulation of fat in hepatocytes and the progression to non-alcoholic steatohepatitis (NASH). Moreover, the presence of metabolic syndrome seems to be associated with severe fibrosis in NASH patients. In CHC, IR develops early in the course of the disease and precedes steatosis. It is also independently associated with histological severity and negatively affects treatment response, irrespective of genotype. Consequently, therapies targeting IR and metabolic syndrome could indirectly ameliorate the prognosis of both NAFLD and CHC. As specific therapies do not exist, patients with metabolic syndrome and CHC and NAFLD should be counseled to lose weight and ameliorate their glycemic control and lipid profile.     

Clinical, biochemical and histological correlations in a group of non-drinker subjects with non-alcoholic fatty liver disease

The correlation between biochemistry, imaging-studies and histology is a matter of controversy in non-alcoholic fatty liver disease (NAFLD) and the major pathophysiology of non-alcoholic steatohepatitis (NASH) is still unknown. We aimed to perform a comparative analysis between clinical, biochemical and histological variables of NAFLD. One-hundred and five NAFLD patients (F/M: 51/54), were studied, all with no-alcohol intake. The groups were followed-up for six months. Necroinflammation and fibrosis were more severe in patients with diabetes (p = 0.002, and p = 0.0001, respectively). In comparing NAFL to NASH, plasma nitric-oxide and malondialdehyde levels were significantly higher (p = 0.05, for-both), and vitamin-E and-C levels were significantly lower in NASH (p = 0.002, and 0.001, respectively). The serum ferritin levels were higher in NASH patients (p = 0.016). While the ultrasonographic grade was significantly higher, the liver-spleen density gradient was significantly lower in NASH group (p = 0.017, and 0.005, respectively). Within a six month period, serum ALT levels dropped into the normal range in 23/76 (30.3%) patients and serum ALT in the 6th month correlated significantly with the severity of steatosis, inflammation and fibrosis in initial biopsy (p = 0.023, 0.035, 0.011, respectively). In conclusion, the probability of severe liver disease is higher in patients with elevated-ALT in NAFLD. Serum ferritin levels have some prognostic significance in liver damage and fibrosis. Overt diabetes is predictive of advanced fibrosis and inflammation. However impaired glucose-tolerance is not. The advice on diet and exercise for six months after diagnosis may be a good strategy in NAFLD. The patients with normal-ALT without hepatomegaly, morbid-obesity and diabetes seem to have a good prognosis, however some of these patients may still require liver biopsy.     

改善胰岛素抵抗治疗NAFLD/NASH的循证证据

非酒精性脂肪性肝病/非酒精性脂肪性肝炎(NAFLD/NASH)是指除外酒精和其他明确的肝损伤因素所致的以肝细胞脂肪沉积为特征的临床病理综合征。胰岛素抵抗(IR)与NAFLD/NASH的发病密切相关,因此改善IR或许可以减轻肝损伤。多项随机对照临床试验显示胰岛素增敏剂和逐渐减轻体质量(饮食疗法或体育锻炼等)对NAFLD的治疗有一定作用,但长期疗效尚不明确。本文对近年关于改善IR治疗NAFLD/NASH的临床试验作一综述。     

Cardiovascular risk across the histological spectrum and the clinical manifestations of non-alcoholic fatty liver disease:an update

Non-alcoholic fatty liver disease(NAFLD) is considered to be an independent cardiovascular disease(CVD)risk factor. However, simple steatosis has a benign clinical course without excess mortality. In contrast, the advanced form of NAFLD, non-alcoholic steatohepatitis(NASH) with liver fibrosis increases mortality by approximately 70%, due to an increase in CVD mortality by approximately 300%. Chronic kidney disease(CKD) may be caused by NAFLD/NASH and it substantially increases CVD risk, especially in the presence of type 2 diabetes mellitus. Moreover, CKD may trigger NAFLD/NASH deterioration in a vicious cycle. NAFLD/NASH is also related to increased arterial stiffness(AS), an independent CVD risk factor that further raises CVD risk. Diagnosis of advanced liver fibrosis(mainly by simple non-invasive tests), CKD,and increased AS should be made early in the course of NAFLD and treated appropriately. Lifestyle measures and statin treatment may help resolve NAFLD/NASH and beneficially affect the CVD risk factors mentioned above.     

Evaluation of ballooned hepatocytes as a risk factor for future progression of fibrosis in patients with non-alcoholic fatty liver disease

Journal of Gastroenterology - The prevalence of non-alcoholic fatty liver disease (NAFLD) has increased. Non-alcoholic steatohepatitis (NASH) shows progression of liver fibrosis in NAFLD. It...     

In situ detection of lipid peroxidation and oxidative DNA damage in non-alcoholic fatty liver diseases

BACKGROUND/AIMS: Although oxidative stress is an important candidate in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), the localization and pathological significance of oxidative stress-induced cellular damage in NAFLD remains unclear. METHODS: Hepatic expression of 4-hydroxy-2'-nonenal (HNE) and 8-hydroxydeoxyguanosine (8-OHdG), as reliable markers of lipid peroxidation and oxidative DNA damage, respectively, was immunohistochemically investigated in NAFLD and the results were compared with histological findings. RESULTS: While no HNE adducts were observed in control livers, they were frequently detected in NAFLD. In NASH, the localization of the adducts was in the cytoplasm of sinusoidal cells and hepatocytes with a predominance in zone 3. The grade of necro-inflammation as well as the stage of fibrosis significantly correlated with the HNE index. Regarding 8-OHdG, although no 8-OHdG expression was observed in normal liver and only a few in fatty liver, 11 of 17 cases (64.7%) with NASH exhibited nuclear expression of 8-OHdG in hepatocytes and sinusoidal cells in areas of active inflammation. The 8-OHdG index significantly correlated with the grade of necro-inflammation. CONCLUSIONS: Oxidative cellular damage occurs frequently in livers with NAFLD and may be associated with some clinico-pathological features of NAFLD including liver fibrosis and possibly, hepatocarcinogenesis.     

The use of current knowledge and non-invasive testing modalities for predicting at-risk non-alcoholic steatohepatitis and assessing fibrosis

There is ongoing recognition of the burden of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), with fibrosis being the most important histological feature that is associated with progression to cirrhosis and the occurrence of major adverse liver outcomes. Liver biopsy is the gold standard applied to detect NASH and determine the stage of fibrosis, but its use is limited. There is a need for non-invasive testing (NIT) techniques to identify patients considered at-risk NASH (NASH with NAFLD activity score > 4 and ≥ F2 fibrosis). For NAFLD-associated fibrosis, several wet (serological) and dry (imaging) NITs are available and demonstrate a high negative predictive value (NPV) for excluding those with advanced hepatic fibrosis. However, identifying at-risk NASH is more challenging; there is little guidance on how to use available NITs for these purposes, and these NITs are not specifically designed to identify at-risk NASH patients. This review discusses the need for NITs in NAFLD and NASH and provides data to support the use of NITs, focusing on newer methods to non-invasively identify at-risk NASH patients. This review concludes with an algorithm that serves as an example of how NITs can be integrated into care pathways of patients with suspected NAFLD and potential NASH. This algorithm can be used for staging, risk stratification and the effective transition of patients who may benefit from specialty care.     

Role of hepatic iron in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) includes a spectrum of clinical entities ranging from simple steatosis to non-alcoholic steatohepatitis (NASH) with possible evolution to cirrhosis and hepatocellular carcinoma. Iron is considered a putative element that interacts with oxygen radicals in inducing liver damage and fibrosis. The role of hepatic iron in the progression of NASH remains controversial, but in some patients, iron may have a role in the pathogenesis of NASH. Though genetic factors, insulin resistance, dysregulation of iron-regulatory molecules, erythrophagocytosis by Kupffer cells may be responsible for hepatic iron accumulation in NASH, exact mechanisms involved in iron overload remain to be clarified. Iron reduction therapy such as phlebotomy or dietary iron restriction may be promising in patients with NASH/NAFLD to reduce insulin resistance as well as serum transaminase activities.     

Is there a role of lipid-lowering therapies in the management of fatty liver disease?

Atherogenic dyslipidemia is characterized by increased triglyceride-rich lipoproteins and low high-density lipoprotein cholesterol concentrations. It is highly prevalent in non-alcoholic fatty liver disease (NAFLD) and contributes to the increased cardiovascular risk associated with this condition. Alongside insulin resistance it plays an important pathogenetic role in NAFLD/non-alcoholic steatohepatitis (NASH) development and progression. It has been shown that cholesterol-lowering reduces cardiovascular risk more in NAFLD vs non-NAFLD high-risk individuals. This evidence highlights the importance of effective lipid modulation in NAFLD. In this narrative review the effects of the most commonly used lipid-lowering therapies on liver outcomes alongside their therapeutic implications in NAFLD/NASH are critically discussed. Preclinical and clinical evidence suggests that statins reduce hepatic steatosis, inflammation and fibrosis in patients with NAFLD/NASH. Most data are derived from observational and small prospective clinical studies using changes in liver enzyme activities, steatosis/fibrosis scores, and imaging evidence of steatosis as surrogates. Also, relevant histologic benefits were noted in small biopsy studies. Atorvastatin and rosuvastatin showed greater benefits, whereas data for other statins are scarce and sometimes conflicting. Similar studies to those of statins showed efficacy of ezetimibe against hepatic steatosis. However, no significant anti-inflammatory and anti-fibrotic actions of ezetimibe have been shown. Preclinical studies showed that fibrates through peroxisome proliferator-activated receptor (PPAR)α activation may have a role in NAFLD prevention and management. Nevertheless, no relevant benefits have been noted in human studies. Species-related differences in PPARα expression and its activation responsiveness may help explain this discrepancy. Omega-3 fatty acids reduced hepatic steatosis in numerous heterogeneous studies, but their benefits on hepatic inflammation and fibrosis have not been established. Promising preliminary data for the highly purified eicosapentaenoic acid require further confirmation. Observational studies suggest that proprotein convertase subtilisin/kexin9 inhibitors may also have a role in the management of NAFLD, though this needs to be established by future prospective studies.     

Non-alcoholic fatty liver disease later diagnosed as myotonic dystrophy

BACKGROUND Myotonic dystrophy(MD) is sometimes accompanied by metabolic/endocrine disorders, including dyslipidemia, central obesity, and hypogonadism. Due to considerable individual differences in the severity and progression of myopathy, MD patients with minimal-to-mild muscle symptoms might be followed as having other diseases, such as non-alcoholic fatty liver disease(NAFLD).CASE SUMMARY A 40-year-old non-obese man without a history of regular ethanol consumption was referred to our hospital due to persistent liver dysfunction and hyperlipidemia. His body mass index was 23.4 kg/m~2. Liver histology demonstrated macrovesicular steatosis, ballooned hepatocytes with eosinophilic inclusion bodies, and perisinusoidal fibrosis, leading to the diagnosis of nonalcoholic steatohepatitis(NASH). Although he had no discernable muscle pain or weakness, persistently high serum creatine kinase(CK) and myoglobin levels as well as the presence of frontal baldness, a hatched face, history of cataract surgery, and grip myotonia indicated the possibility of MD. Southern blotting of the patient's DNA revealed the presence of CTG repeats, confirming the diagnosis.CONCLUSION When gastroenterologists encounter NAFLD/NASH patients, serum CK should be verified. If hyperCKemia, frontal baldness, a hatched face, history of cataract surgery, and grip myotonia are noted, the possibility of MD may be considered.     

The metabolic triad of non-alcoholic fatty liver disease,visceral adiposity and type 2 diabetes: Implications for treatment

Non-alcoholic fatty liver disease (NAFLD) is associated with visceral obesity, insulin resistance, type 2 diabetes (T2D) and has been often considered as the hepatic expression of the metabolic syndrome (MetS). Epidemiological studies highlight a bidirectional relationship of NAFLD with T2D in which NAFLD increases the risk of incident T2D and T2D increases the risk of severe non-alcoholic steatohepatitis (NASH) and liver fibrosis. Regarding the molecular determinants of NAFLD, we specifically focused in this review on adipocyte dysfunction as a key molecular link between visceral adipose tissue, MetS and NAFLD. Notably, the subcutaneous white adipose tissue expandability appears a critical adaptive buffering mechanism to prevent lipotoxicity and its related metabolic complications, such as NAFLD and T2D. There is a clinical challenge to consider therapeutic strategies targeting the metabolic dysfunction common to NASH and T2D pathogenesis. Strategies that promote significant and sustained weight loss (~10% of total body weight) such as metabolic and bariatric surgery or incretin-based therapies (GLP-1 receptor agonists or dual GLP-1/GIP or GLP-1/glucagon receptor co-agonists) are among the most efficient ones. In addition, insulin sensitizers such as PPARγ (pioglitazone) and pan-PPARs agonists (lanifibranor) have shown some beneficial effects on both NASH and liver fibrosis. Since NASH is a complex and multifactorial disease, it is conceivable that targeting different pathways, not only insulin resistance but also inflammation and fibrotic processes, is required to achieve NASH resolution.     

Hepatic histology in obese patients undergoing bariatric surgery

BACKGROUND/AIMS: Obesity is one of the most important clinical associations with non-alcoholic steatohepatitis (NASH). Our aim was to assess the prevalence of non-alcoholic fatty liver disease (NAFLD)/NASH in morbidly obese patients and the risk factors to more aggressive liver disease in this population. METHODS: Review of available studies on prevalence of NAFLD/NASH in severely obese patients submitted to bariatric surgery. RESULTS: Twelve observational and transversal studies were included, with consecutive recruitment, and prospective evaluation of data, summing 1620 patients with severe obesity. Prevalence of steatosis and NASH was 91% (range: 85-98%) and 37% (24-98%), respectively, with unexpected cirrhosis in 1.7% (1-7%). NASH was not related with age or body mass index, but there was an association between male sex and NASH/hepatic fibrosis. Diabetes mellitus and insulin resistance were the conditions most frequently associated with NASH, and hypertension with advanced hepatic fibrosis. CONCLUSIONS: There is a very high prevalence of NAFLD in asymptomatic morbidly obese patients, more than one-third presenting histological criteria for NASH. This review underscores the large variations in prevalence of NASH between studies, calling for the need for a better agreement in the use of the histological criteria.     

Abnormal glucose tolerance is a predictor of steatohepatitis and fibrosis in patients with non-alcoholic fatty liver disease

Objective. The majority of patients with non-alcoholic fatty liver disease (NAFLD) have simple steatosis. A minority, however, present with non-alcoholic steatohepatitis (NASH), a condition that can lead to advanced fibrosis and cirrhosis. The frequencies of NASH and fibrosis among patients with NAFLD and sustained elevation of liver function tests (LFT) are uncertain. Our aim was to estimate these frequencies. We characterize a population with NAFLD, with special emphasis on insulin resistance and the metabolic syndrome, and study possible predictors for different stages of the disease. Material and methods. All referred patients with sustained elevation of LFT, radiological evidence or clinical suspicion of fatty liver, and absence of other liver disease, were invited to participate in our study in the period June 2002 to December 2004. Results. Of 129 patients who met the inclusion criteria, 88 underwent liver biopsy. NAFLD was verified in 83 of them. Among these patients, 59 (71%) had the metabolic syndrome, 41 (49%) had NASH and 36 (43%) had fibrosis. Abnormal glucose tolerance (T2DM or impaired glucose tolerance) was the only independent risk factor for NASH (OR: 3.14; 95% CI: 1.20–8.23). Independent predictors for fibrosis were abnormal glucose tolerance (OR: 3.83; 95% CI: 1.29–11.40) and body mass index (OR: 1.20; 95% CI: 1.06–1.36) per kg/m². Conclusions. Both NASH and fibrosis are frequently present among patients with NAFLD and sustained elevation of LFT. The probability of these potentially progressive stages of NAFLD increases with the presence of abnormal glucose tolerance.