Non-alcoholic fatty liver disease : treatment options based on pathogenic considerations

The term “non-alcoholic fatty liver disease” (NAFLD) is used to describe a wide spectrum of fatty liver changes ranging from steatosis on one side and non-alcoholic steatohepatitis (NASH) on the other. Liver steatosis is a benign, non-progressive condition, in contrast to NASH, which can progress to liver fibrosis and cirrhosis. These two entities are clinically and radiologically indistinguishable and, at present, there is no sensitive non-invasive test to differentiate between them. A liver biopsy is therefore necessary to reach the exact diagnosis and to obtain hereby prognostic information [1–3]. NASH was described twenty two years ago by a pathologist, J. Ludwig [4]. He found lesions of alcoholic steatohepatitis (ASH) in patients who had no history of regular alcohol consumption and did not suffer from other liver diseases. NASH is becoming a frequent liver disease and probably carries a similar risk of progression to cirrhosis as chronic hepatitis C. No treatment has yet proven its efficacy. Pathogenic mechanisms are the mainstay for therapeutic considerations. This review has two purposes, firstly to draw attention to this still under-recognized disease and secondly to focus on therapeutic options based on present knowledge of pathogenesis. NASH is a frequent liver disease that develops in close association with IR and may progress to cirrhosis. Exclusion of excessive alcohol consumption as well as of other liver diseases and liver histology are required for diagnosis. Progress in the understanding of the pathophysiology of NASH allows interesting therapeutic considerations. It is logical to treat the associated metabolic conditions to influence the disease activity and progression. In view of promising preliminary data, several drugs are currently used in clinical trials.


Historical perspectives and prevalence
In the 1970s, "fatty liver hepatitis" (Ludwig et al. coined the name of non-alcoholic steatohepatitis (NASH) in 1980 [4]), was thought to affect mostly morbidly obese patients who had had a jejunoileal bypass [5][6][7].One third of these patients developed fibrosis [8] and several needed liver transplantation after correction of the digestive anatomy [9][10][11].Concerning the pathomechanism of liver fibrosis in these patients, it can be hypothesised that their fatty livers were simultaneously exposed to two important pathogenic factors; to free fatty acids (from the adipose tissue) on the one hand, and to lipopolysaccharides (from the excluded bowel) on the other.Later, histopathological features of NASH were described in patients taking drugs like 4,4'-diethylaminoethoxyhexestrol (DEAEH) [12], perhexiline-maleate [13], steroids [14], amiodarone [15] and isoniazid [16].Another drug associated with NASH is tamoxifen [17].About one third of 105 breast cancer patients developed radiological signs suggestive of hepatic steatosis within the first two years of treatment.In 7 out of 21 patients with increased transaminase levels liver biopsies were performed.6 biopsies revealed NASH.In the 1990s, the entity was expanded by the recognition of the differential diagnostic importance of NASH in patients with abnormal liver enzymes [18].Since then, NASH has emerged as one of the most frequent liver diseases in the Western world [19].Although its exact prevalence in the general population has not yet been defined, it is estimated to be about 3% to 4% [20].Autopsy data indicate that NASH is at least six times more prevalent in obese compared with lean individuals [21].Most cases occur in persons with ponderal excess, hyperlipidaemia and hyperglycaemia [4,[22][23][24][25][26], insulin resistance (IR) probably being a central pathogenic factor [27][28][29][30][31][32].
Non-alcoholic fatty liver disease 494

Clinical description, natural history, and diagnostic approach
Most patients with NASH are asymptomatic and abnormal liver tests are often discovered fortuitously.The disturbance of liver tests is chronic with serum aminotransferase activities usually less than fourfold above the upper limit of normal.Higher aspartate aminotransferase (AST) than alanine aminotransferase (ALT) concentrationsin the absence of alcohol consumption -may indicate the presence of liver cirrhosis.Frequently, IRrelated diseases (obesity, type 2 diabetes mellitus and hyperlipidaemia) coexist, but must not be present [18,33].
NASH is, in a way, a diagnosis of exclusion.There is no biological test to reach the diagnosis positively.The chlorzoxazone test, used in alcoholics to measure the cytochrome P4502E1 (CYP2E1) induction [34], has failed as a non-invasive test to identify patients with NASH [35].
The diagnostic approach is summarised in table 1. Chronic alcohol consumption must be excluded.An AST/ALT ratio less than 1 [36] and the determination of the carbohydrate deficient trans-ferrin [37] may be helpful.Chronic ethanol intake of 20 g/day is considered the hepatotoxic threshold for women and 40 g/day for men [38].In some studies, a daily alcohol intake of 20 g/day has been accepted as non-hepatotoxic [18,33,39,40].Associated metabolic conditions like obesity, diabetes, hyperlipidaemia and hypertension should be searched for and other liver disease excluded.A liver ultrasound shows the typical hyperechogenic parenchyma in most cases.Finally, a liver biopsy is necessary to reach the diagnosis.This should be evaluated by a pathologist familiar with the staging and grading of NASH [39,41].Liver histology has prognostic implications since liver steatosis without inflammation is a benign, non progressive condition [42] and the presence of ballooning degeneration, Mallory hyaline or fibrosis is associated with a liver-related mortality that is 10 times higher than in patients with a pure steatosis [39].Sonography provides no insight into the presence of inflammation [43].About 12% of patients with NASH may progress to cirrhosis within 7 years  Diagnostic approach to a patient suspected to be suffering from NASH.[44], which is a progression comparable with that of hepatitis C.
A substantial fraction of those patients with a cryptogenic cirrhosis probably suffered from NASH, as both diabetes mellitus and obesity were significantly more common in patients with cryptogenic cirrhosis and NASH compared to those with cirrhosis caused by hepatitis C or primary biliary cirrhosis [45,46].Other evidence for the notion that some cases of cryptogenic cirrhosis may represent burned-out NASH comes from a study showing a relatively high incidence of fatty liver disease and NASH in patients after orthotopic liver transplantation for cryptogenic cirrhosis [47].Cirrhosis secondary to NASH may also be complicated by the development of hepatocellular carcinoma [48,49].One study by Ratziu et al. even suggests a comparable carcinogenic potential of obesity-related cryptogenic cirrhosis (probably due to NASH) as in cirrhosis due to chronic hepatitis C [50].Lastly, the histological assessment of hepatic iron stores is of importance, since hepatic iron overload may be pathogenic in hepatic steatosis and fibrosis [18,33,[51][52][53].
Two studies define the indication for liver biopsy.Of 144 patients with NASH, none of those younger than 45 years old showed fibrosis on liver biopsy if their body mass index (BMI) was less than 31 kg/m 2 and diabetes mellitus was absent [54].In the second study by Ratziu et al. an age above 50 years, a BMI >28 kg/m 2 , triglycerides >1.7 mmol/ L, and ALT levels higher than twice the normal upper limit were independently associated with septal fibrosis [55].Table 2 summarises the evidence justifying a liver biopsy in patients suspected to be suffering from NASH.Evidence justifying a liver biopsy in patients with suspected NASH.

Histology and differential diagnosis
Histological findings in NAFLD are very similar to those found in alcoholic liver disease: steatosis, hepatocyte ballooning, mild lobular inflammation and perisinusoidal collagen deposition.Histological features may range from simple steatosis with or without mild inflammation to advanced liver disease with fibrosis and cirrhosis [41].At the cirrhotic stage the steatosis is often absent [23].Histopathological grading and staging of NASH has been proposed by Brunt [41,56].It evaluates the degree of steatosis, the presence of hepatocellular ballooning and the lobular and portal inflammation in order to determine the grade and stages of the disease according to the extent of the fibrosis.
A few entities may pose diagnostic difficulties, for example when NASH affects obese teenagers [57].In these patients, copper studies and genetic testing should be performed to exclude Wilson's disease.Frequently, an iron overload is observed in NASH patients [18,33,48,58] and an increased prevalence of mutations in the HFE gene has been reported [40].Hereditary haemochromatosis has to be excluded by genetic testing when transferrin saturation is increased.The association of increased serum and liver iron concentrations as well as raised serum ferritin levels with a normal transferrin saturation in the absence of genetic haemochromatosis has been proposed as a new syndrome of primary liver iron overload (see below) [59].Finally, variant phenotypes of α 1antitrypsin can occur in patients with NASH [60].Actually, NASH being so prevalent, the coincidental presence of a second liver disease should not be surprising.Indeed, coexistence of steatosis or steatohepatitis has been described in the livers of patients with chronic hepatitis C and steatosis was associated with a higher degree of fibrosis [61][62][63][64][65]. Furthermore, there is evidence that the degree of steatosis may negatively influence treatment response to interferon in chronic hepatitis C [66].

Insulin resistance (IR)
IR leads to an increased hepatic production of free fatty acids (FFAs) from glucose due to hyperinsulinism, and to increased circulating levels of FFAs due to an enhanced peripheral lipolysis [67,68].The increased uptake of FFAs by the liver exceeds its capacity to metabolise them by mitochondrial oxidation and to remove them by secretion into the blood as very low-density lipoproteins (VLDL) [69].As a consequence, hepatic steatosis develops, generally considered as a "benign" prerequisite of NASH.In most cases, IR is seen in the context of obesity and non-insulin dependent diabetes mellitus [26,29].Marchesini et al. have shown that IR is associated with the presence of NASH, irrespective of BMI, fat distribution or glucose tolerance [70] and IR in NASH can occur in the absence of ponderal excess and diabetes [30,31].

The molecular basis of insulin resistance and the role of adipose tissue
Adipose tissue is an important source of tumour necrosis factor alpha (TNFa) [71,72], which regulates insulin sensitivity [71,73,74].TNFa suppresses the expression of proteins regulating fatty acid uptake and lipogenesis leading to elevated FFA levels [75,76].TNFa down regulates proteins mediating the effects of insulin, such as the adipocyte fatty acid binding protein aP2, adipsin and insulin-responsive-glucose-transporter-4 (GLUT4) [76][77][78][79][80][81].TNFa also promotes IR by down regulating peroxisome-proliferatoractivated-receptor gamma (PPARg) [76], a nuclear receptor important in maintaining normal insulin sensitivity [82].Serum TNFa concentrations correlate with the degree of obesity and hyperinsulinaemia [83][84][85].Abdominal obesity is associated with higher circulating TNFa levels than peripheral obesity [86] and abdominal fat distribution reflected in a higher "waist to hip ratio" is a predictor of hepatic steatosis [87].Crespo et al. demonstrated an overexpression of TNFa mRNA in NASH patients in adipose tissue as well as in the liver [88].A polymorphism in the TNFa promoter (TNFA allele) associated with IR [89][90][91] is more prevalent in patients with NASH than in controls [92].
The role of other adipose tissue-derived cytokines such as interleukin-6 (IL-6) as mediators of IR is less clear [93].Like TNFa, IL-6 is known to inhibit lipoprotein lipase (LPL) but, unlike TNFa, it does not stimulate lipolysis [94,95].Nevertheless, a significant relationship between plasma IL-6 and IR has been found in obese subjects [96].
Resistin has been linked to obesity and diabetes [97], but several studies have questioned the role of this adipocyte-derived hormone in the aetiology of IR [98][99][100].In contrast to resistin, leptin is clearly known to inhibit insulin action by attenuating tyrosine phosphorylation of the insulin-receptor substrate-1 (IRS-1) [101].Both IR as well as lipid metabolism are worsened when leptin serum levels are increased [1,2,102].Furthermore, recent data underline a pivotal role of leptin in the development of liver fibrosis [103].Finally, a third adipocyte-derived hormone named adiponectin has been shown to protect against IR [104].Additional data in humans are needed to further define its role.

Pathogenesis of non-alcoholic steatohepatitis (inflammation and necrosis)
A second mechanism has been postulated to explain the progression of fatty liver into NASH [105].An overview of mechanisms leading to NASH, liver fibrosis and cirrhosis is given in figure 1.

Oxidative stress
Free oxygen radicals exert their toxicity by lipid peroxidation, which finds a favourable environment for its perpetuation in a steatotic liver.As a consequence, the signalling molecules, malondialdehyde (MDA) and 4-hydroxynonenal (4-HN), are produced [106].Hepatic stellate cells (HSCs) are activated by CYP2E1-derived reactive oxygen species and lipid peroxides [107].4-HN, for example, acts as a stimulator of HSCs [108,109] leading to the production of collagen I [110].Oxidative stress in hepatocytes has been linked to the expression of cytokines like interleukin-8 (IL-8) [111], providing another damaging pathway for the already exquisitely sensitive fatty liver.Antioxidant defence system: Several endogenous antioxidant defence systems have been elaborated like superoxide dismutase, catalase and glutathione peroxidase.Exogenous antioxidants are b-carotene (vitamin A), lycopene, ascorbic acid (vitamin C) and a-tocopherol (vitamin E).The latter is believed to be the "last antioxidant defence" in lipid membranes [112].A relative deficiency in antioxidants can be important in situations promoting oxidative stress and lipid peroxidation.Obesity or IR could be such situations; decreased a-tocopherol and b-carotene serum levels have been documented in obese children [113].Serum antioxidant levels do not necessarily represent tissue levels [114]; hepatic antioxidant levels could be even lower in these situations.
Oxidants: The liver of patients with NASH provides many ingredients to trigger and promote oxidative stress.Hepatocellular steatosis can per se promote and aggravate lipid peroxidation.The mere presence of oxidizable fat in the liver triggers lipid peroxidation [115].Hyperglycaemia can induce lipid peroxidation through the tricarboxylic Pathogenesis of non-alcoholic fatty liver disease acid cycle pathway [116].The cytochrome P450 2E1 (CYP2E1) plays a pivotal role in the pathogenesis of alcoholic liver disease since it generates superoxide anion, hydroxyl and hydroxyethyl radicals [117,118] and is responsible for the microsomal ω -1 and ω -2 oxidation of FFAs leading to the formation of cytotoxic dicarboxylic acids [1].The regulation of CYP2E1 expression is complex and partially under the negative control of insulin [119][120][121].CYP2E1 is overexpressed in patients with NASH [122].One can speculate that CYP2E1 induction in NASH results from a decreased sensitivity of hepatocytes to insulin due to insulin resistance.Other sources of oxidants are hepatic iron and activation of Kupffer cells (KCs).

Iron overload
Mild hepatic iron overload is found in up to 40% of patients with NASH [18,33].Mutations of the HFE gene may be one reason.C282Y heterozygosity and C282Y/H63D compound heterozygosity in NASH patients were associated with higher transaminase levels as well as more severe hepatic histopathological alterations [40].In 1997, Moirand described a new syndrome with hepatic iron overload, elevated liver tests, hyperferritinaemia, and normal transferrin saturation [59].It is closely associated with insulin resistance and histologically to steatohepatitis [51].It is still a matter of speculation as to how to explain the association of iron overload, liver injury or both with the IR syndrome [123].Based on data from isolated fat cells [124], it has been hypothesized that insulin may lead to a redistribution of transferrin receptors to the cell surface where they mediate uptake of extracellular iron [125].
Two studies revealed that NASH patients with increased hepatic iron stores are at risk of developing hepatic fibrosis [18,40].Iron overload induces oxidative stress and lipid peroxidation by catalysing the production of free radicals such as hydroxyl radicals [126][127][128] and activating KC [129].Elevated intracellular iron levels may promote NF-kB activation and TNFa expression in hepatic macrophages [130].

Endotoxins, endogenous alcohol formation, Kupffer cell activation and cytokine release
Since NASH can be reversed by antibiotics under experimental conditions [131][132][133], intestinal bacterial overgrowth may play a role in the pathogenesis of NASH.Further evidence for this pathogenic mechanism was obtained by Wigg et al., who demonstrated a higher prevalence of small intestinal bacterial overgrowth in NASH patients [134].Diabetes predisposes to bacterial overgrowth by inducing an intestinal dysmotility and stasis.However, no significant differences were found between NASH patients with and without small intestinal bacterial overgrowth concerning intestinal permeability, blood endotoxin levels and TNFa serum concentrations [135].Alcohol production by the intestinal microflora could contribute to this effect.In an animal model for NASH (ob/ob mice) an increased endogenous gastrointestinal production of ethanol was found, which was reversed after antibiotic treatment [135].Once KCs are activated they produce mediators such as prostaglandins, reactive oxygen species, cytokines, nitric oxide and different proteases initiating a cascade of events similar to those in alcoholic liver disease [136].

Pathogenesis of liver fibrosis (Hepatic stellate cell activation)
HSCs are situated in the space of Dissé between endothelial cells and hepatocytes with which they communicate by producing cytokines and growth factors and by expressing cytokine re-ceptors.They are key cells in the process of liver fibrosis by producing extracellular matrix proteins and collagens when activated [137][138][139].Several factors can activate HSCs such as, for example, oxidative stress, transforming growth factor beta-1 (TGFb1) and connective tissue growth factor (CTGF).
HSC activation occurs in NASH, and the degree of HSC activation correlates with the degree of fibrosis [140].HSCs are preferentially activated in zone 3 of the liver lobule [141], the perivenular region where CYP2E1 [120,142] and other cytochromes such as CYP2A and CYP3A [141] are predominantly expressed.These observations and the report of an association between steatosis and lipid peroxidation in zone 3 [143] support the view that cytochrome P450 enzymes are involved in the pathophysiology of NASH.Nieto et al. were able to demonstrate in vitro a complete prevention of HSC activation by the application of CYP2E1 inhibitors [107].
TGFb1 mediates the transformation of quiescent HSCs into myofibroblast-like cells with an increased production of extracellular matrix proteins including type I collagen [144][145][146].TGFb1 is secreted by activated KCs and by HSCs.Its plasma concentration is elevated in NASH patients compared to patients with steatosis and healthy subjects [147], suggesting that this cytokine is involved in the fibrogenesis in NASH.
CTGF is overexpressed in liver cirrhosis and produced in HSCs [148][149][150].The expression of the CTGF gene is induced by TGFb1 [149] and CTGF may mediate many activities of TGFb1 including collagen production [151].Overexpression of CTGF was also observed in the liver of patients with NASH and correlated with fibrosis [152].Incubation of HSCs with glucose or insulin up-regulated CTGF mRNA and protein levels indicating that insulin may directly influence the development of fibrosis.Another in vitro study suggests that TNFa also induces CTGF expression in HSCs [153].
Finally, Ikejima et al. found in an animal model that leptin, produced in transactivated HSCs, promotes hepatic fibrogenesis [103].It may contribute, at least in part, to the progression from benign hepatic steatosis to NASH and cirrhosis [154].

Treatment options
There is no treatment with an efficacy proven in randomised controlled trials.Promising treatment options and their rational are summarised in table 3.

Weight loss
IR is improved by weight loss [155,156].Weight loss is associated with reduced lipid oxidation and increases glucose utilisation [157,158].
Moderate long-term changes in weight of obese subjects may be associated with better insulin sensitivity and glucose tolerance [159][160][161], which translates in normalisation of liver tests [162,163].Gastric bariatric surgery reduces IR [164][165][166] and may improve NASH [167,168].Weight loss should not be as abrupt as after jejunoileal bypass, since this could lead to "acute" NASH and liver failure [169,170].In addition to weight loss, physical activity may further improve IR [171,172].

Enhancing insulin sensitivity (metformin, thiazolidinediones)
Metformin has been shown to be an effective treatment of fasting hyperglycaemia in patients with non insulin-dependent diabetes mellitus (NIDDM).It works by decreasing hepatic glucose output mostly due to an inhibition of the gluconeogenesis [173].Improvement of liver tests and histology in three patients with NASH was first described by Coyle [174].Further evidence for beneficial effects of metformin was provided by Marchesini et al. who treated 20 non-diabetic patients with non-biopsy proven hepatic steatosis and elevated liver transaminases over a period of 4 months [175].A significant decrease in transaminase levels and liver volume was found as well as a significant improvement in insulin sensitivity.However, as discussed in correspondence to their article, metformin should be used with caution in patients with advanced liver disease because of the risk of lactic acidosis [176][177][178][179]. Idiosyncratic hepatotoxicity of metformin itself has been described [180,181].Metformin cannot yet be recommended for the treatment of NASH until the results of randomised controlled studies become available.
Thiazolidinediones (TZDs) -troglitazone, rosiglitazone and pioglitazone -improve insulin sensitivity enhancing glucose disposal and influencing lipid metabolism [182,183].TZDs activate PPARg, a nuclear receptor expressed in adipose tissue to maintain normal insulin sensitivity.PPARg activation reduces release of FFAs and TNFa by adipocytes [184][185][186].Troglitazone is no longer available because of cases of severe hepatotoxicity [187][188][189][190][191][192].In contrast to rosiglitazone and pioglitazone, troglitazone has been found to induce cytochrome P4503A4 (CYP3A4) predisposing it to drug interactions [193].Nevertheless, there are also some reports of possible rosiglitazone-related hepatotoxicity [194,195] and pioglitazone-related hepatotoxicity [196,197].In one pilot study, 10 female patients with histologically proven NASH have been treated with troglitazone for up to 6 months at a dose of 400 mg qd [198].Normalisation of ALT levels was observed in 7 of these patients, but this biochemical response was not paralleled by a significant histological improvement.Although rosiglitazone and pioglitazone do not share the hepatotoxic profile of troglitazone [193,199], their use in NASH patients can be only recommended within protocols.

Treatment of hypertriglyceridaemia (gemfibrozil, clofibrate, bezafibrate)
Since lowering plasma lipids by bilio-pancreatic bypass surgery significantly improves insulin sensitivity before the surgery has effects on body weight [200] and intracellular lipids may be cytotoxic [201], lipid-lowering agents may be beneficial in NASH.Only limited clinical data from pilot studies are available.In a prospective, randomised and placebo-controlled study with 46 patients using oral gemfibrozil for 4 weeks [202], a significant improvement in liver tests and triglyceride levels was observed independent of weight loss.There is further positive report with bezafibrate in three patients with tamoxifen and in one patient with toremifene-induced NASH [203].This PPARg receptor activator may compensate for drug-induced insufficient mitochondrial b-oxidation via the activation of peroxisomal b-oxidation.On the other hand, clofibrate was shown to be ineffective [24].All these lipid lowering substances seem to be safe, although rare cases of fibratesinduced hepatitis have been reported [204][205][206][207].In view of the little clinical information on fibrates in the treatment of NASH no definite conclusions can be made.

Iron depletion
One study tried to elucidate the effect of iron depletion on the development of NASH [53].Repetitive phlebotomie was performed to decrease iron stores to a level of near iron deficiency.No supranormal levels of body iron could be detected in these patients.Iron depletion improved both fasting and glucose-stimulated plasma insulin concentrations suggesting a positive effect on insulin resistance and led to a normalisation of the serum aminotransferase activities.Unfortunately, no Therapeutic options.
liver biopsies were performed to assure the diagnosis of NASH and to quantify the hepatic iron.It has been shown that phlebotomies can be performed safely in these patients [52].These observations as well as the growing evidence from studies investigating iron as co-morbid factor in other chronic liver diseases [208,209] suggest, that iron stores should be depleted in NASH patients with abnormal iron parameters.
Treatment of oxidative stress α -Tocopherol or vitamin E is a powerful scavenger of free radicals in biological membranes [112] and has an excellent safety profile [210] with possible cardiovascular protective properties [211].In an open-labelled pilot study, 11 children with a mean body mass index of 32 kg/m 2 were treated with vitamin E, 400 IU to 1200 IU per day for 4 to 10 months.The diagnosis of NASH was based on chronically elevated serum aminotransferase levels, a diffusely hyperechogenic liver on ultrasonography and on the exclusion of other common causes of liver disease [212].A significant decrease in liver enzyme tests was noted.Unfortunately this study was performed without liver histology.In another trial [213], 8 patients with NASH and 8 patients with fatty liver, as diagnosed by histology, were first subjected to a diet, leading to an improvement of serum alanine aminotransferase levels only in the patients with fatty liver.Then, they were all treated with α -tocopherol.This improved alanine aminotransferase levels in NASH patients and was paralleled by a decrease of TGFβ 1 serum concentration, which was elevated at baseline in patients with NASH.This observation supports a link between free oxygen radical production and the activation of fibrogenic cytokines.In Switzerland, there is an ongoing doubleblind, randomised and placebo-controlled study comparing ursodeoxycholic acid (UDCA) and vitamin E with UDCA monotherapy and placebo.
Betaines are trimethyl amino acids derived either from choline or from the diet.They function as methyl donors and, therefore, reduce lipid accumulation in the liver [214].Betaines are important to form phosphatidyl choline (PC), a component of VLDL, which is the key molecule to export lipids from hepatocytes [215].Supplementation with betaine improves the export of lipids from hepatocytes.In a trial with 10 NASH patients, seven patients took 20 g (!) betaine per day for one year [216].A significant improvement in serum transaminase levels was noted, and in six patients, where a second liver biopsy could be obtained, a marked improvement in the degree of steatosis, necroinflammation and fibrosis occurred.Thus, betaine is a promising compound and may play a role in the future treatment of NASH.
Silymarin acts as a scavenger of free oxygen radicals decreasing lipid peroxidation [217].Although promising results have been obtained with silymarin in patients with alcoholic liver disease [218][219][220][221], the results of a randomised, controlled, double-blind multicentre study on 200 alcoholics with cirrhosis were disappointing, showing neither an effect on the course of the disease nor a survival benefit in patients receiving silymarin compared to the placebo group [222].There are no studies with silymarin in patients with NASH, but according to the data of Velussi et al., who found that silymarin treatment in patients affected by alcoholic cirrhosis and diabetes was associated with a reduction of IR and a significant decrease in fasting insulin levels suggesting an improvement of the activity of endogenous and exogenous insulin, this substance could be interesting for the treatment of NASH [220,221].
S-adenosylmethionine (SAMe), which is the activated form of methionine, has potential in alcoholic as well as in non-alcoholic liver disease [223].N-acetylcysteine, which is a glutathione prodrug and known to decrease oxidative stress in the liver, may theoretically also be helpful in NASH, but clinical data are lacking.

Treatment with ursodeoxycholic acid (UDCA)
UDCA (13-15 mg/kg/d) for one year improved biological abnormalities including steatosis [241].This has been confirmed by other studies, where an improvement of transaminases was observed [224,225] but not by all [226].The mode of action of UDCA is a matter of speculation, but it has cytoprotective, chemoprotective, antioxidant and immunomodulatory properties [227].The long-term treatment of NASH patients with UDCA in monotherapy or in combination with vitamin E is currently under investigation.

Liver transplantation
In a large transplantation programme in the United States about 3% of liver transplantations were performed for NASH-induced end-stage liver disease [228].This study also indicates that post-transplantation steatosis occurred in two thirds of recipients compared to only 5 to 15% in those transplanted for other liver diseases.In one third NASH recurred and significant fibrosis developed within one year post transplantation.Progression to cirrhosis was found in about 12.5% of patients with former NASH.These findings were corroborated in two other studies [229,230].Early treatment of recurrent NASH with antioxidants or UDCA has been advocated [231].

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W I S S M E D W K LY 2 0 0 2 ; 1 3 2 : 4 9 3 -5 0 5 • w w w. s m w. c h 495 Why biopsy?To reach the diagnosis of NASH a liver histology is required To obtain prognostic information (benign steatosis or potentially progressive NASH) To obtain information about the stage of the disease (degree of fibrosis) To estimate iron deposition Whom to biopsy?Patients older than 45 years of age with elevated liver tests of unknown origin Patients of all ages with elevated liver tests of unknown origin and at least two manifestations of the metabolic syndrome Table 2 Figure 1 Pathogenic mechanisms leading to nonalcoholic steatohepatitis (NASH) and liver fibrosis.Increased production of TNFa from adipose tissue leads to insulin resistance.Enhanced concentrations of FFAs and ketones are the main stimulus for CYP2E1-induction in HC.Oxidative stress occurs as a central mechanism in NASH with the consequence of hepatocyte necrosis and activation of HSC, which are responsible for liver fibrosis.KC activation as a result of gut-derived endotoxins produces liver inflammation [HC = hepatocytes, HSC = hepatic stellate cells, KC = Kupffer cells].
: J-F.Dufour, MD Department of Clinical Pharmacology University of Bern 35 Murtenstrasse CH-3010 Bern E-Mail: jf.dufour@ikp.unibe.chSwiss Medical Weekly: Call for papers Swiss Medical Weekly The many reasons why you should choose SMW to publish your research Official journal of the Swiss Society of Infectious disease the Swiss Society of Internal Medicine the Swiss Respiratory Society Med Wochenschr (1871-2000) Swiss Med Wkly (continues Schweiz Med Wochenschr from 2001) Editores Medicorum Helveticorum