Improved nonalcoholic steatohepatitis after 48 weeks of treatment with the PPAR-gamma ligand rosiglitazone

Nonalcoholic steatohepatitis: recent advances from experimental models to clinical management

A condition defined as nonalcoholic fatty liver disease (NAFLD) is frequently found in humans. Deemed as a benign condition until recently, more emphasis is now put on the potential harmful evolution of the inflammatory form, that is, nonalcoholic steatohepatitis (NASH), toward end-stage liver disease. This review highlights the major morphologic and pathophysiological features of NASH. The link between experimental biochemical findings in animal models and clinical and therapeutic approaches in humans is discussed. Once all the other causes of persistent elevation of serum transaminase levels have been excluded, the diagnosis of NASH can be only confirmed by liver histology. Other noninvasive diagnostic tools, however, are being investigated to assess specific subcellular functions and to allow the follow-up of patients at higher risk for major liver dysfunction. A better understanding of various pathogenic aspects of NASH will help in identifying potential therapeutic approaches in these patients.

Antifibrotic therapy in chronic liver disease

The response to injury is one of wound healing and, subsequently, fibrosis. This response is generalized, occurring in diverse organ systems. Injury and wounding in the liver ultimately lead to cirrhosis in many patients (although not all patients), and are the result of many different diseases. The fact that various diseases result in cirrhosis suggests a common pathogenesis. Study over the past 2 decades has shed considerable light on the pathogenesis of fibrosis and cirrhosis. A growing body of literature indicates that the hepatic stellate cell is a central component in the fibrogenic process. Stellate cells undergo a transformation during injury that has been termed activation. Activation is complex and multifaceted, but one of its most prominent features is the synthesis of large amounts of extracellular matrix, resulting in deposition of scar or fibrous tissue. The fibrogenic process is dynamic; it is noteworthy that even advanced fibrosis (or cirrhosis) is reversible. The best antifibrotic therapy is treatment of the underlying disease. For example, eradication of hepatitis B or C virus can lead to the reversal of fibrosis. In situations in which treating the underlying process is not possible, specific antifibrotic therapy is desirable. A number of specific antifibrotic therapies have been tried, but have been met with poor or mediocre success. However, elucidation of the mechanisms responsible for fibrogenesis, with particular emphasis on stellate cell biology, has highlighted many putative novel therapies. This article emphasizes mechanisms underlying fibrogenesis, and reviews current antifibrotic therapies as well as potential future approaches.

Local and systemic insulin resistance resulting from hepatic activation of IKK-beta and NF-kappaB

We show that NF-kappaB and transcriptional targets are activated in liver by obesity and high-fat diet (HFD). We have matched this state of chronic, subacute 'inflammation' by low-level activation of NF-kappaB in the liver of transgenic mice, designated LIKK, by selectively expressing constitutively active IKK-b in hepatocytes. These mice exhibit a type 2 diabetes phenotype, characterized by hyperglycemia, profound hepatic insulin resistance, and moderate systemic insulin resistance, including effects in muscle. The hepatic production of proinflammatory cytokines, including IL-6, IL-1beta and TNF-alpha, was increased in LIKK mice to a similar extent as induced by HFD in in wild-type mice. Parallel increases were observed in cytokine signaling in liver and mucscle of LIKK mice. Insulin resistance was improved by systemic neutralization of IL-6 or salicylate inhibition of IKK-beta. Hepatic expression of the IkappaBalpha superrepressor (LISR) reversed the phenotype of both LIKK mice and wild-type mice fed an HFD. These findings indicate that lipid accumulation in the liver leads to subacute hepatic 'inflammation' through NF-kappaB activation and downstream cytokine production. This causes insulin resistance both locally in liver and systemically.

[Study of patients referred for elevated ferritin levels and/or transferrin saturation: significance of non-alcoholic fatty liver disease]

OBJECTIVE

To determine the etiology of increased ferritin concentrations and/or transferrin saturation in patients in whom classical causes were ruled out.

PATIENTS AND METHOD

We studied 43 patients (35 males and 8 females) who were referred for ferritinemia greater than 300 ng/ml and or a transferrin saturation index (TSI) greater than 40%. In all patients, glycemia, cholesterol, triglycerides, uric acid, total and fractionated bilirubin, transaminase, gammaglutamyltranspeptidase, sideremia, TSI, ferritin, HFE gene mutations, ceruloplasmin and total 24-hour urine porphyrin were evaluated and abdominal ultrasonography was performed. In 14 patients liver biopsy was performed.

RESULTS

Fifty-three percent was overweight and 19% was obese. Alterations in carbohydrate metabolism were detected in 33%, hypercholesterolemia was found in 14%, hypertriglyceridemia in 35%, and hyperlipemia type IIb in 16%. Thirty-two percent showed isolated elevated ferritin, 12% had elevated TSI and 56% showed elevation of both. Transaminase levels were normal in 61%. No mutation in the HFE gene was found in 10 patients, the H63D/wt mutation was found in 18, C262Y/wt in 1, C282Y/H63D in 5, C282Y/C282Y in 4, H63D/H63D in 3 and Ser65cys/wt in 1. Ultrasonography revealed steatosis in 19 patients (44%). Definitive diagnoses were HFE-linked hemochromatosis (4 patients), juvenile hemochromatosis (1 patient), hepaticocutaneous porphyria (1 patient), and non-alcoholic fatty liver disease (22 patients; 51%). Most of the remaining patients could be included under insulin resistance syndrome. Phlebotomy was performed in 25 patients, with improvement in clinical and laboratory parameters.

CONCLUSIONS

Non-alcoholic fatty acid disease is frequently detected in patients with iron metabolism disorders. These patients should undergo investigations for metabolic alterations and liver ultrasonography and, if necessary, biopsy. Phlebotomy can be useful in the treatment of these patients.

Effect of pioglitazone on body composition and energy expenditure: a randomized controlled trial

BACKGROUND

Several clinical studies have demonstrated that body weight increases after treatment with thiazolidinediones (TZDs). Prior studies have demonstrated an increase in insulin-stimulated lipid storage in adipose tissue. Some, but not all, studies demonstrate reductions in visceral adipose tissue. Changes in body weight are the result of changes in energy intake, energy expenditure, or both.

OBJECTIVES

Based on these findings, the primary aim of this study was to evaluate the effect of TZDs on visceral, subcutaneous, and total body fat. Secondary aims were to determine the effects of pioglitazone on (a) energy expenditure, (b) hunger and satiety, (c) blood lipids, and (d) the role of insulinemia/sulfonylurea usage on weight gain in patients with type 2 diabetes.

SUBJECTS AND METHODS

We performed a randomized, double-blind, placebo-controlled trial in 48 men and women with type 2 diabetes who had not previously received treatment with TZDs. Patients were treated for 24 weeks with 45 mg/d of pioglitazone or a matching placebo. Body composition was measured by dual-energy x-ray absorptiometry. Visceral and subcutaneous fat were measured by computed tomography. Resting metabolic rate and thermogenic response to a test meal were measured by indirect calorimetry before and after a standardized meal. Hunger and satiety were measured with visual analog scales before and after the same test meal. Blood was collected for the measurement of fasting glucose and insulin levels, hemoglobin A 1c levels, and lipid content.

RESULTS

Pioglitazone treatment resulted in a decrease in hemoglobin A(1c) level by 0.96 +/- 1.1% vs 0.11 +/- 0.8% in the placebo group (P < .005). Body weight and fat increased steadily in the patients treated with pioglitazone during the 6 months of the study (+3.9 +/- 3.1 kg at 6 months in pioglitazone-treated patients vs -0.8 +/- 3.4 kg in the placebo-treated patients). Subcutaneous fat in the trunk, arms, and legs were all increased in the pioglitazone-treated group. Visceral fat did not change significantly in either group. Neither resting metabolic rate nor the thermogenic responses to a meal were altered by pioglitazone. Subjective measures of hunger (visual analog scale) did not change with pioglitazone treatment. Triglycerides fell in the pioglitazone-treated group (-58.5 +/- 124 mg/dL, P < .003). Neither the prior use of sulfonylureas nor the level of insulinemia before treatment was a predictor of weight or fat change.

CONCLUSION

Pioglitazone increased subcutaneous body fat, but not visceral fat. There was no measurable effect on energy expenditure or hunger/satiety. In contrast to the placebo-treated patient with diabetes, weight gain occurs in the face of falling hemoglobin A(1c) and triglyceride levels.

A pilot study of vitamin E versus vitamin E and pioglitazone for the treatment of nonalcoholic steatohepatitis

BACKGROUND & AIMS

Insulin resistance and oxidative stress contribute to the pathogenesis of nonalcoholic steatohepatitis (NASH). We conducted a pilot study for the following reasons: (1) to test the hypothesis that a combination of an antioxidant (vitamin E) and an insulin sensitizer (pioglitazone) would be superior to vitamin E alone for the treatment of NASH, and (2) to define the effects of these interventions on insulin-sensitive metabolic functions and correlate the effects with changes in liver histology.

METHODS

A randomized prospective trial was performed to compare the efficacy and safety of vitamin E alone (400 IU/day) vs. vitamin E (400 IU/day) and pioglitazone (30 mg/day) in nondiabetic, noncirrhotic subjects with NASH. Metabolic functions were assessed by a 2-step, hyperinsulinemic (10 and 40 mU/m2/min) euglycemic clamp.

RESULTS

A total of 10 patients were randomized to each arm. Two patients on combination therapy discontinued treatment; one because of pregnancy and the other because of hepatotoxicity. Treatment with vitamin E only produced a significant decrease in steatosis (mean grade, 2.2 vs. 1.4; P < .02). Compared with baseline, combination therapy produced a significant decrease in steatosis (mean, 2.3 vs. 1; P < .002), cytologic ballooning (1.3 vs. 0.2; P < .01), Mallory's hyaline (0.7 vs. 0.2; P < .04), and pericellular fibrosis (1.2 vs. 0.6; P < .03). Although vitamin E had no significant effects, combination therapy produced a significant increase in metabolic clearance of glucose and a decrease in fasting free fatty acid (FFA) and insulin. The decrease in fasting FFA and insulin independently predicted improvement in hepatic steatosis and cytologic ballooning.

CONCLUSIONS

A combination of vitamin E and pioglitazone produces a greater improvement in NASH histology. The improvement in steatosis and cytologic ballooning are related to treatment-associated decreases in fasting FFA and insulin levels.

Nonalcoholic fatty liver disease: a review of current understanding and future impact

Nonalcoholic fatty liver disease (NAFLD), already the most common form of liver disease in the United States, can be expected to increase in prevalence and severity in parallel with national epidemics of obesity and type 2 diabetes. NAFLD is frequently associated with insulin resistance. While insulin resistance, and thereby hyperinsulinemia, are, in large part, metabolic consequences of obesity, the basis of diversity in severity and progression of inflammation and fibrosis is not known. Increased susceptibility to oxidative stress is likely to play a role. Several patient characteristics have been associated with more severe histological findings in patients with NAFLD, including type 2 diabetes, hypertension, age over 40 years, and higher transaminases. Liver biopsy is, however, required to accurately grade and stage NAFLD histologically. Although the natural history of NAFLD is relatively poorly defined, NAFLD is increasingly recognized as an important cause of decompensated liver disease. Weight reduction and improved insulin sensitivity are associated with improved biochemical and histological parameters of NAFLD. There are, however, no proven safe and efficacious pharmacological treatments for NAFLD.

Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is an important medical condition and there is great public health concern related to its increasing incidence and potential implications for the development of end-stage liver disease. NASH represents a progression beyond simple lipid deposition in the liver parenchyma, requiring histologic evidence for hepatocyte injury such as ballooning degeneration, Mallory bodies, and/or pericellular fibrosis that can potentially lead to progressive liver injury and eventually cirrhosis. It is believed that several insults contribute to the evolution of hepatic injury such as insulin dysregulation, lipid deposition, oxidative free radicals, and lipid perioxidation. Initial treatment protocols for NASH focus on various aspects of injury in an attempt to control insulin imbalances, improve lipid regulation, reduce free radicals, and ameliorate the inflammatory process. No therapy is conclusively beneficial in all individuals, but preliminary data suggest several approaches that hold promise.

[Oral diabetes treatment. Which substance is indicated at which time?]

The prevalence of type 2 diabetes continues to show a clear upward trend in Germany. In earlier days it was considered the "harmless diabetes of old age," but has become increasingly recognized as a disease carrying a high risk of vascular sequelae as well as shortening the diabetic's remaining life expectancy if adequate therapy is not initiated. In addition to correcting hyperglycemia, treatment consists in effective management of concomitant risk factors such as hypertension, dyslipidemia, and adiposity resulting from faulty nutrition and lack of exercise. In the large majority of overweight type 2 diabetics, metformin is the oral antidiabetic agent of first choice provided the patient does not exhibit renal insufficiency, which represents the most important contraindication. This recommendation for monotherapy of overweight type 2 diabetics is supported by an endpoint study. In contrast, no equivalent evidence is available on any of the possible options for oral combination therapy.

Hepatitis C and steatosis

Steatosis is a common finding in patients with chronic hepatitis C (CHC) due to a combination of the direct steatogenic effect of hepatitis C virus (HCV) and the prevalence of metabolic risk factors in the HCV population. Steatosis is now established as a risk factor for disease progression in CHC and significantly impacts therapeutic response. Research efforts should continue to focus on defining the complex viral and host interactions involved in the pathogenesis of HCV-related steatosis so that future therapeutic strategies may be accurately and appropriately targeted.

Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a well-recognized form of chronic liver disease affecting both children and adults that has gained increased recognition. Recently NAFLD has been associated with insulin resistance and its incidence and prevalence is likely increasing, paralleling the rise in obesity and diabetes mellitus in the United States. The article includes current thoughts on the natural history and pathogenesis of NAFLD and describes current trends in the diagnosis and treatment of this condition.

Nonalcoholic steatohepatitis: histologic features and clinical correlations with 30 blinded biopsy specimens

Thirty overweight patients with clinically characterized and biopsy proven nonalcoholic steatohepatitis (NASH) were enrolled in a 48-week treatment trial with rosiglitazone, a peroxisome proliferator-activator receptor (PPAR)-gamma agonist that enhances insulin sensitivity. Improvement in laboratory liver tests, insulin resistance and liver fat content were documented; blinded biopsy review demonstrated decreases in necroinflammatory activity or grade and in individual components of grade, and changes in the relationship of lobular and portal inflammation as well as in the nature of perisinusoidal fibrosis. The current study identified correlations of histological features of the protocol entry biopsy specimens with contemporaneous laboratory and imaging tests. Significant correlations with histologically assessed steatosis were liver fat, evaluated by computed tomography (P = 0.001); mean HbA1C, a measure of glycemic control (P = 0.004); and QUICKI, a measure of insulin sensitivity (P = 0.05). Histologically determined grades of steatohepatitis (SH) correlated with HbA1C (P = 0.01), and a trend toward elevated fasting glucose levels was seen. No subject in the study was cirrhotic at entry; fibrosis scores of the 30 subjects did not significantly correlate with age, gender, body mass index, or clinical tests. All subjects underwent 3 biopsies (prior, entry, and posttreatment), and all had undergone a prior biopsy with diagnostic SH. By blinded analysis, 7 study entry biopsy specimens did not fulfill published strict criteria for SH. Laboratory results from these subjects included normal fasting glucose level and, compared with the 23 subjects with criteria for SH, lower mean alanine aminotransferase and aspartate aminotransferase levels (P = 0.02 for both), less insulin resistance (P = 0.03), and lower mean HbA1C (P = 0.001). We conclude that biopsy findings determined by blinded analysis correlated with image-detected steatosis, laboratory markers of hepatic inflammation, insulin resistance, and long-term glycemia; the findings confirm the usefulness of strict histological criteria in the evaluation of NASH.

Avandamet: combined metformin-rosiglitazone treatment for insulin resistance in type 2 diabetes

Insulin resistance is a major endocrinopathy underlying the development of hyperglycaemia and cardiovascular disease in type 2 diabetes. Metformin (a biguanide) and rosiglitazone (a thiazolidinedione) counter insulin resistance, acting by different cellular mechanisms. The two agents can be used in combination to achieve additive glucose-lowering efficacy in the treatment of type 2 diabetes, without stimulating insulin secretion and without causing hypoglycaemia. Both agents also reduce a range of atherothrombotic factors and markers, indicating a lower cardiovascular risk. Early intervention with metformin is already known to reduce myocardial infarction and increase survival in overweight type 2 patients. Recently, a single-tablet combination of metformin and rosiglitazone, Avandamet, has become available. Avandamet is suitable for type 2 diabetic patients who are inadequately controlled by monotherapy with metformin or rosiglitazone. Patients already receiving separate tablets of metformin and rosiglitazone may switch to the single-tablet combination for convenience. Also, early introduction of the combination before maximal titration of one agent can reduce side effects. Use of Avandamet requires attention to the precautions for both metformin and rosiglitazone, especially renal, cardiac and hepatic competence. In summary, Avandamet is a single-tablet metformin-rosiglitazone combination that doubly targets insulin resistance as therapy for hyperglycaemia and vascular risk in type 2 diabetes.

Glitazones and the management of insulin resistance: what they do and how might they be used

Thiazolidinediones (glitazones) are the only compounds currently available that specifically target tissue insulin resistance. The two currently available drugs in this class, pioglitazone and rosiglitazone,are approved by the Food and Drug Administration for the treatment of type 2 diabetes mellitus only. The therapeutic potential of the glitazones for other consequences of insulin resistance has stirred considerable interest, especially with regard to their potential beneficial impact on atherosclerotic cardiovascular disease and diabetes prevention. They also have been considered in the management of polycystic ovarian syndrome, nonalcoholic fatty liver disease, and other consequences of insulin resistance. The nonglycemic potential of glitazones is a clinical area in rapid evolution, wherein most data are on the impact of the glitazones onsurrogate markers that are associated with diseases, not on disease outcomes. This article provides insight and guidance to clinicians on the diverse nonglycemic potential of glitazones until conclusive outcome data become available.

Molecular mediators of hepatic steatosis and liver injury

Obesity and its associated comorbidities are among the most prevalent and challenging conditions confronting the medical profession in the 21st century. A major metabolic consequence of obesity is insulin resistance, which is strongly associated with the deposition of triglycerides in the liver. Hepatic steatosis can either be a benign, noninflammatory condition that appears to have no adverse sequelae or can be associated with steatohepatitis: a condition that can result in end-stage liver disease, accounting for up to 14% of liver transplants in the US. Here we highlight recent advances in our understanding of the molecular events contributing to hepatic steatosis and nonalcoholic steatohepatitis.

Molecular mediators of hepatic steatosis and liver injury

Obesity and its associated comorbidities are among the most prevalent and challenging conditions confronting the medical profession in the 21st century. A major metabolic consequence of obesity is insulin resistance, which is strongly associated with the deposition of triglycerides in the liver. Hepatic steatosis can either be a benign, noninflammatory condition that appears to have no adverse sequelae or can be associated with steatohepatitis: a condition that can result in end-stage liver disease, accounting for up to 14% of liver transplants in the US. Here we highlight recent advances in our understanding of the molecular events contributing to hepatic steatosis and nonalcoholic steatohepatitis.

Mechanisms of non-alcoholic steatohepatitis

In 1980, the term non-alcoholic steatohepatitis was coined to describe a new syndrome occurring in patients who usually were obese (often diabetic) females who had a liver biopsy picture consistent with alcoholic hepatitis, but who denied alcohol use. The causes of this syndrome were unknown, and there was no defined therapy. More than two decades later, this clinical syndrome is only somewhat better understood, and still there is no Food and Drug Administration-approved or even generally accepted drug therapy. Patients with primary non-alcoholic steatohepatitis typically have the insulin resistance syndrome (synonymous with the metabolic syndrome, syndrome X, and so forth), which is characterized by obesity, diabetes, hyperlipidemia, hypertension, and, in some instances, other metabolic abnormalities such as polycystic ovary disease. Secondary non-alcoholic steatohepatitis may be caused by drugs such as tamoxifen, certain industrial toxins, rapid weight loss, and so forth. The cause of non-alcoholic steatohepatitis remains elusive, but most investigators agree that a baseline of steatosis requires a second hit capable of inducing inflammation, fibrosis, or necrosis for non-alcoholic steatohepatitis to develop. Our research group has focused its efforts on the interactions of nutritional abnormalities, cytokines, oxidative stress with lipid peroxidation, and mitochondrial dysfunction in the induction of steatohepatitis, both alcoholic and non-alcoholic in origin. Research findings from other laboratories also support the role of increased cytokine activity, oxidative stress, and mitochondrial dysfunction in the pathogenesis of non-alcoholic steatohepatitis. The objectives of this article are to review the (1) definition and clinical features of non-alcoholic steatohepatitis, (2) potential mechanisms of non-alcoholic steatohepatitis, and (3) potential therapeutic interventions in non-alcoholic steatohepatitis.

Pharmacologic management of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is an emerging epidemic in Western societies, and therapeutic modalities to treat this condition are needed desperately. Most early treatment studies tended to focus on improvement in the serum aminotransferases. Presently, treatment of NAFLD is aimed at improving the underlying steatosis, necroinflammatory activity, and fibrosis because elevations of the aminotransferases may not accurately reflect these important histologic endpoints. Unfortunately, well-defined treatment options are few,which is largely due to limited experience reported in small, prospective pilot trials. This article focuses on the various therapeutic agents that have been evaluated in the treatment of NAFLD and their efficacy as well as their limitations.

The ins and outs of mitochondrial dysfunction in NASH

Rich diet and lack of exercise are causing a surge in obesity, insulin resistance and steatosis, which can evolve into steatohepatitis. Steatosis and nonalcoholic steatohepatitis (NASH) can also be induced by drugs such as amiodarone, tamoxifen and some antiretroviral drugs. There is growing evidence that mitochondrial dysfunction, and more specifically respiratory chain deficiency, plays a role in the pathophysiology of NASH whatever its initial cause. In contrast, the B-oxidation of fatty acids can be either increased (as in insulin resistance-associated NASH) or decreased (as in drug-induced NASH). However, in both circumstances, the generation of reactive oxygen species (ROS) by the damaged respiratory chain is augmented, as components of this chain are over-reduced by electrons, which then abnormally react with oxygen to form increased amounts of ROS. Concomitantly, ROS oxidize fat deposits to release lipid peroxidation products that have detrimental effects on hepatocytes and other hepatic cells. In hepatocytes, ROS and lipid peroxidation products further impair the respiratory chain, either directly or indirectly through oxidative damage to the mitochondrial genome. This, in turn, leads to the generation of more ROS and a vicious cycle ensues. Mitochondrial dysfunction can also lead to apoptosis or necrosis depending on the energy status of the cell. ROS and lipid peroxidation products also activate stellate cells, thus resulting in fibrosis. Finally, ROS and lipid peroxidation increase the generation of several cytokines (TNF-alpha, TGF-B, Fas ligand) that play sundry roles in the pathogenesis of NASH. Recent investigations have shown that some genetic polymorphisms can significantly increase the risk of steatohepatitis and that several drugs can prevent or even reverse NASH. For the next decade, reducing the incidence of NASH will be a major challenge for hepatologists.

Non-alcoholic fatty liver disease, non-alcoholic steatohepatitis and orthotopic liver transplantation

Obesity, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are becoming increasingly common medical problems in the developed world, often in the setting of the metabolic or insulin resistance syndrome (IRS). It is predicted that by the year 2025 > 25 million Americans may have NASH-related liver disease. NASH and NAFLD also affect the donor population. The use of steatotic donor livers for liver transplantation (LT) is associated with an increased risk of primary nonfunction (PNF) in the allograft. There is particular reluctance to use steatotic livers for living donor LT. There is indirect evidence to suggest that patients undergoing LT for cirrhosis resulting from NASH may have poorer outcome, despite careful selection of LT candidates. Indeed it is likely that many potential LT candidates with NASH are excluded from LT due to co-morbid conditions related to IRS. The post-LT patient is at risk of several components of IRS, such as diabetes mellitus, hypertension, hyperlipidaemia and obesity and there is increasing recognition of de novo and recurrent NAFLD and NASH after LT. Thus NAFLD and NASH affect all aspects of LT including donors, patients in evaluation and the LT recipient.

Non-alcoholic fatty liver and insulin resistance: a cause-effect relationship?

The role of insulin resistance in non-alcoholic fatty liver disease is suggested by laboratory data (hyperinsulinemia and decreased sensitivity to endogenous and exogenous insulin). The clinical association with features of the metabolic syndrome, particularly in the most aggressive stages of the disease, further confirms a causative role. Fat accumulation in the liver may stem either from genetic defects, primarily responsible for insulin resistance, or excessive calorie intake and visceral obesity, and is mediated by adipocytokines (leptin, adiponectin, tumour necrosis factor-alpha). Progression of fatty liver to steatohepatitis may be the result of an imbalance between pro-inflammatory and anti-inflammatory cytokines, triggering the formation of reactive oxygen species and intrahepatic lipid peroxidation. This process may also be promoted or accelerated by pro-oxidant xenobiotics or environmental factors. Insulin resistance provides a target for specific treatment of non-alcoholic fatty liver, and insulin-sensitising agents (metformin or thiazolidinediones) as well as lifestyle changes to reduce visceral adiposity are the most promising therapeutic options. Future trials need to be performed in order to test the long-term effectiveness of these treatments on the basis of clinically relevant histological outcomes.

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.