AGA technical review on nonalcoholic fatty liver disease

Pathologic features associated with fibrosis in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of clinicopatholologic conditions ranging from steatosis alone to nonalcoholic steatohepatitis (NASH), with varying risks for progression to cirrhosis. Although steatosis alone seems to be nonprogressive, some patients with NASH can progress. This study focuses on the clinical and pathological characteristics of patients with NAFLD associated with the development of histological fibrosis. Patients with an established diagnosis of nonalcoholic fatty liver were identified through our NAFLD database containing extensive clinical, demographic, and laboratory data. Liver biopsy specimens were read blindly by one hepatopathologist using a 19-item pathological protocol and by another hepatopathologist using a second pathological protocol. Clinical and pathological data were matched to the presence of different types of histological fibrosis. Univariate and multivariate analyses helped determine all of the variables independently associated with histological fibrosis. Of 132 NAFLD patients, 21.2% had advanced fibrosis (septal/bridging fibrosis or well-established cirrhosis). Sinusoidal fibrosis was present in 20.3% of patients, whereas perivenular fibrosis was seen in 17.2%. Ballooning degeneration and Mallory bodies were independently associated with both sinusoidal fibrosis and perivenular fibrosis. Aspartate aminotransferase/alanine aminotransferase ratio and ballooning degeneration were also independently associated with periportal-portal fibrosis. We conclude that the presence of hepatocyte injury in NAFLD is associated with fibrosis. These pathological features can be used to establish the pathological criteria for diagnosis of the progressive form of NAFLD or NASH.

Hepatic steatosis in obese patients: clinical aspects and prognostic significance

Non-alcoholic fatty liver disease is a new clinicopathological condition of emerging importance, now recognized as the most common cause of abnormal liver tests. It is characterized by a wide spectrum of liver damage: simple steatosis may progress to advanced fibrosis and to cryptogenic cirrhosis through steatohepatitis, and ultimately to hepatocellular carcinoma. Obesity is the most significant single risk factor for the development of fatty liver, both in children and in adults; obesity is also predictive of the presence of fibrosis, potentially progressing to advanced liver disease. From a pathogenic point of view, insulin resistance plays a central role in the accumulation of triglycerides within the hepatocytes and in the initiation of the inflammatory cascade. Chronic hepatocellular injury, necroinflammation, stellate cell activation, progressive fibrosis and ultimately, cirrhosis may be initiated by peroxidation of hepatic lipids and injury-related cytokine release. In the last few years, several pilot studies have shown that treatment with insulin-sensitizing agents, anti-oxidants or cytoprotective drugs may be useful, but there is no evidence-based support from randomized clinical trials. Modifications in lifestyle (e.g. diet and exercise) to reduce obesity remain the mainstay of prevention and treatment of a disease, which puts a large number of individuals at risk of advanced liver disease in the near future.

Steatosis and hepatitis C virus: mechanisms and significance for hepatic and extrahepatic disease

Nonalcoholic fatty liver disease (NAFLD) and hepatitis C virus (HCV)-related liver disease are common in the general population, but their concurrence is 2- to 3-fold higher than would be expected by chance alone. In patients with chronic HCV infection, steatosis is attributable to a variable combination of the mechanisms considered to play a role in the pathogenesis of NAFLD--insulin resistance in the obese and in the lean subject--along with a direct effect of HCV on hepatic lipid metabolism that leads to triglyceride accumulation through inhibition of export proteins that are required for very low density lipoprotein (VLDL) assembly and secretion. Accumulating evidence suggests that steatosis contributes to the progression of fibrosis in HCV-related disease in a pattern similar to that observed in NAFLD. Potential mechanisms of this effect include the increased sensitivity of steatotic livers to oxidative stress and cytokine-mediated injury. Steatosis-related hepatic insulin resistance may also play a role through the profibrogenic effects of the compensatory hyperinsulinemia and provides a potential explanation for the association between HCV and type 2 diabetes mellitus. Indeed, an appreciation of the importance of fat in HCV has recently led to trials of adjuvant therapy for HCV directed at steatosis-associated disease mechanisms, with encouraging results reported for various modalities, including weight loss and antioxidants. Future therapy should be aimed at exploiting the interactions of HCV with host insulin and lipid metabolism, particularly in nonresponders to standard antiviral schedules.

Non-alcoholic fatty liver disease: an emerging pathological spectrum

The spectrum of pathological lesions observed in non-alcoholic fatty liver disease (NAFLD) is wide and strongly resembles that of alcohol-induced liver disease. It ranges from fatty liver to steatohepatitis, progressive fibrosis and cirrhosis. Hepatocellular carcinoma is a possible complication of NAFLD, but whether it is related to frequently associated metabolic disorders (e.g., overweight, diabetes) or to underlying cirrhosis is unclear. This disease is the result of a multi-factorial process in which insulin resistance seems to play a major role in the initial accumulation of fat in the liver, whereas multiple causes of mitochondrial dysfunction and oxidative stress can induce the secondary occurrence of necroinflammatory lesions and fibrosis. Genetic factors might explain why only some patients with simple steatosis will develop steatohepatitis and fibrosis. Due to the increasing prevalence of obesity in Western countries, NAFLD will possibly be a public health problem and the liver disease of the future.

Assessment of the obese patient

Obesity may be the most significant medical problem that health care providers will face over the coming decades. Physicians must aggressively address this chronic disease, providing both preventive and therapeutic care. Because this topic traditionally has not been taught in medical schools, physicians need to acquire the knowledge, skills, and attitudes necessary to be effective obesity care providers. Performing a detailed initial assessment, including an obesity-focused history, physical examination, and selected laboratory and diagnostic tests, is fundamental to the process of care.

Is weight reduction an effective therapy for nonalcoholic fatty liver? A systematic review

PURPOSE

To assess the evidence supporting the efficacy of weight reduction for patients with nonalcoholic fatty liver.

METHODS

Potentially relevant studies were identified by a computerized search of databases and a manual search of abstracts from scientific meetings. Studies were included if they reported histology, serum aminotransferase levels, or radiological imaging of the liver in obese adult patients who had undergone weight reduction. Weight reduction regimens included diet, exercise, antiobesity medications, gastric bypass, gastroplasty, or any combination of these interventions. Studies involving jejunoileal or small bowel bypass surgery were excluded.

RESULTS

We identified 517 potentially relevant studies, of which 15 met the inclusion criteria: one randomized controlled trial (in abstract form), two nonrandomized controlled trials, nine case series, one retrospective review, and two case reports. Three studies included more than 50 patients, whereas nine studies had 25 or fewer patients. Twelve studies used behavioral, dietary, or pharmacologic therapy for weight reduction, and three studies used surgical interventions. Although all 15 studies demonstrated overall improvement in the measurements of liver outcome after weight reduction, more than half did not report histologic results.

CONCLUSION

Despite general acceptance that weight reduction is an effective therapy for nonalcoholic fatty liver, this systematic review found little data to support or refute this recommendation.

Effects of low-calorie diet on steatohepatitis in rats with obesity and hyperlipidemia

AIM: To evaluate the effects of low calorie diet (LCD) on nonalcoholic steatohepatitis (NASH) in rats with obesity and hyperlipidemia.

METHODS: 29 Sprague-Dawley (SD) rats were randomly divided into three groups. The animals in control (n = 9) and NASH group (n = 10) were fed on standard rat diet and high fat diet respectively for 12 weeks, ten rats in LCD group were fed on high fat diet for 10 weeks and then low calorie diet for 2 weeks. At the end of the experiment, body weight, abdominal adipose content, liver function, and hepatopathological changes were examined to evaluate the effect of different feeding protocols on the experimental animals.

RESULTS: There was no death of animal in the experimental period. All rats in the NASH group developed steatohepatitis according to liver histological findings. Compared with the control group, body weight (423.5 ± 65.2 vs 351.1 ± 43.0 g, P < 0.05), abdominal adipose content (14.25 ± 1.86 vs 9.54 ± 1.43, P < 0.05), liver index (3.784 ± 0.533 vs 2.957 ± 0.301%, P < 0.01), total serum cholesterol (1.60 ± 0.41 vs 1.27 ± 0.17 mmol/L, P < 0.05) and free fatty acids (728.2 ± 178.5 vs 429.2 ± 96.7 mmol/L, P < 0.01), serum alanine aminotransferase (1257.51 ± 671.34 vs 671.34 ± 118.57 nkat/L, P < 0.05) and aspartic aminotransferse (2760.51 ± 998.66 vs 1648.29 ± 414.16 nkat/L, P < 0.01) were significantly increased in the NASH group. Whereas, when rats were fed on LCD protocol, their body weight (329.5 ± 38.4 g, P < 0.01), abdominal adipose content (310.21 ± 1.52 g, P < 0.05), liver index (3.199 ± 0.552%, P < 0.05), and serum alanine aminotransferase (683.03 ± 245.49 nkat/L, P < 0.05) were significantly decreased, and the degree of hepatic steatosis (P < 0.05) was markedly improved compared with those in the NASH group. However, no significant difference was found in serum lipid variables and hepatic inflammatory changes between the two groups.

CONCLUSION: LCD might play a role in the prevention and treatment of obesity and hepatic steatosis in SD rats, but it exerts no significant effects on both serum lipid disorders and hepatic inflammatory changes.

Using the PDCA cycle

Nonalcoholic fatty liver disease (NAFLD) is very common in the United States, and in some patients it may lead to cirrhosis, liver failure, and liver cancer. NAFLD encompasses a spectrum of liver injury, ranging from steatosis to steatohepatitis, advanced fibrosis, and cirrhosis. Nonalcoholic steatohepatitis (NASH), an advanced form of NAFLD, histologically comprises steatosis, balloon degeneration, inflammation, and fibrosis in varying degrees. It is generally believed that simple steatosis is benign with minimal risk of progression, whereas NASH is progressive and can lead to cirrhosis. The commonly associated risk factors for NAFLD include obesity, hyperlipidemia, and diabetes mellitus. The pathogenesis of NAFLD and NASH is not fully known; however, current evidence suggests that insulin resistance and lipid peroxidation play a role in the pathogenesis of this condition. Currently, there are no proven effective therapies available for the treatment of NASH. Although there are numerous studies that have explored various treatments for NASH, these generally consist of small numbers of patients with suboptimal endpoints. Treatment strategies for NAFLD and NASH can be broadly divided into 1) treatment or control of underlying risk factors such as hyperlipidemia, diabetes mellitus, and obesity; and 2) specific pharmacologic therapy such as insulin sensitizers, antioxidants, or cytoprotective agents. Newer thiazolidinediones, such as rosiglitazone and pioglitazone, have shown promise in the treatment of NASH in pilot studies. However, these agents should not be used in clinical practice until their efficacy and safety are firmly established in larger studies. Despite encouraging initial studies, the recently completed multicenter, randomized, controlled trial failed to show any efficacy for ursodeoxycholic acid in the treatment of NASH. Other agents, such as vitamin E, betaine, probucol, and atorvastatin, have been explored as therapeutic agents for NASH. However, none of these studies have shown convincingly their utility in the treatment of NASH. Attempts to identify optimal therapy for patients with NASH are being vigorously pursued by the research community and important advances are expected within next several years. Until then, subjects should be advised to avoid alcohol, lose weight, and exercise regularly, and meticulous attention should be paid to the control of their risk factors such as diabetes and hyperlipidemia.