Non-alcoholic steatohepatitis: definitions and pathogenesis

Antioxidants vitamin E and 1-aminobenzotriazole prevent experimental non-alcoholic steatohepatitis in mice

OBJECTIVE

Hepatic oxidative stress plays a key role in the development of non-alcoholic steatohepatitis (NASH). However, the protective effects of antioxidants on NASH are largely unknown. The aim of this study was to elucidate the effect and mechanism of antioxidants on NASH in mice.

MATERIAL AND METHODS

C57BL6/J mice were fed a methionine-choline-deficient (MCD) diet for 10 days or 3 weeks to induce steatohepatitis. Antioxidants (vitamin E, ABT, or vitamin E plus ABT) were supplemented in mice fed a MCD diet, respectively. The effect of antioxidants on oxidative stress and apoptosis was assessed, and activation of adiponectin and expressions of inflammatory factors, apoptosis-related genes, and fibrosis-related genes were assayed.

RESULTS

MCD feeding in mice showed increasing serum alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) levels, and progressive hepatic injury including hepatic steatosis and inflammatory infiltration. Administration of antioxidants vitamin E and/or ABT significantly lowered serum ALAT and ASAT levels (p<0.001) and ameliorated hepatic steatosis and necroinflammation. These effects were associated with repressed hepatic lipid peroxides through reducing hepatic MDA content and enhancing hepatic superoxide dismutase (SOD) activity; down-regulated inflammatory factor COX-2, lowered activity of NF-kappaB, up-regulated anti-apoptotic gene Bcl-2, and down-regulated pro-apoptotic gene Bax suppressed expression of the fibrotic genes TGF-beta1 and MMP2. Moreover, expression of the anti-inflammatory factor adiponectin was also induced by vitamin E or ABT. A combination of vitamin E and ABT showed an additive effect on preventing liver injury.

CONCLUSIONS

The present study provides morphological and molecular biological evidence for the protective role of the antioxidant vitamins E and ABT in ameliorating oxidative stress, hepatic apoptosis, and necroinflammation in experimental nutritional steatohepatitis.

Rats fed fructose-enriched diets have characteristics of nonalcoholic hepatic steatosis

Nonalcoholic steatohepatitis (NASH) and nonalcoholic fatty liver disease are increasing in adults and are likely to be increasing in children. Both conditions are hepatic manifestations of metabolic syndrome. Experimental animals fed fructose-enriched diets are widely recognized as good models for metabolic syndrome. However, few reports have described the hepatic pathology of these experimental animals. In this study, 5-wk-old Wistar specific pathogen-free rats, which are a normal strain, were fed experimental diets for 5 wk. We then evaluated the degree of steatohepatitis. The 5 diet groups were as follows: cornstarch (70% wt:wt) [control (C)], high-fructose (70%) (HFr), high-sucrose (70%) (HS), high-fat (15%) (HF), and high-fat (15%) high-fructose (50%) (HFHFr) diets. The macrovesicular steatosis grade, liver:body weight ratio, and hepatic triglyceride concentration were significantly higher in the HFr group than in the other 4 groups. However, the HFr group had a significantly lower ratio of epididymal white fat:body weight than the other 4 groups and had a lower final body weight than the HF and HFHFr groups. The HF group had a greater final body weight than the C, HFr, and HS groups, but no macrovesicular steatosis was observed. The HFr group had a significantly higher grade of lobular inflammation than the other 4 groups. The distribution of lobular inflammation was predominant over portal inflammation, which is consistent with human NASH. In conclusion, rats fed fructose-enriched diets are a better model for NASH than rats fed fat-enriched diets.

Visceral obesity and hypoadiponectinemia are significant determinants of hepatic dysfunction: An epidemiologic study of 3827 Japanese subjects

BACKGROUND AND AIM

Adiponectin is an anti-inflammatory and insulin-sensitizing adipocytokine, and its serum concentrations are reduced in obesity with visceral fat accumulation. Visceral fat accumulation is an independent determinant of elevated serum liver enzymes. Hypoadiponectinemia plays important roles in the clinical progression of nonalcoholic steatohepatitis. The aim of this study was to evaluate the relation between visceral fat area (VFA), serum adiponectin concentration, and biochemical liver tests, such as aspartate aminotransferase, alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT) in normal subjects.

METHODS

The study group comprised 3827 Japanese subjects [mean age+/-SD; 47.6+/-10.7 y: 2854 males (48.4+/-10.7 y), 973 females (45.3+/-10.1 y)], who underwent annual health checkup in 2004. In addition to parameters measured in the annual health checkup, VFA and serum adiponectin concentration were measured by the bioelectrical impedance analysis method and a latex particle-enhanced turbidimetric assay system, respectively.

RESULTS

Pearson's correlation analysis showed a significant correlation between VFA and the levels of the above 3 liver enzymes in both sexes, and a significant negative correlation between adiponectin and all biochemical liver tests in men and with ALT and GGT in women. Stepwise multiple regression analysis showed that VFA was a significant determinant of serum liver tests in both sexes. Moreover, serum adiponectin concentration significantly and negatively influenced male ALT and GGT and female GGT.

CONCLUSIONS

Both visceral obesity and hypoadiponectinemia are significant determinants of subtle and asymptomatic hepatic dysfunction in normal Japanese subjects.

Teucrium polium in prevention of steatohepatitis in rats

BACKGROUND

In this study, we tried to evaluate whether the ethyl acetate (EtOAc) extract of Teucrium polium, with a high antioxidant activity, is able to prevent the incidence of nonalcoholic steatohepatitis.

METHODS

Nonalcoholic steatohepatitis was induced in male N-Mary rats using a methionine/choline-deficient (MCD) diet. Rats were given normal diet (A), normal diet+EtOAc extract (B), MCD diet (C) and MCD diet+EtOAc (D).

RESULTS

The MCD diet led to grade 1 liver steatosis, inflammation and ballooning degeneration. In group D, these factors abated to grade 0 in 80% of the rats. In groups receiving the EtOAc extract, lipoprotein profiles had significantly improved relative to those not receiving the extract. Also, a dramatic reduction was observed in the sera alkaline phosphatase, aspartate aminotransferase and alanine aminoteransferase activities. The activities of the liver superoxide dismutase, glutathione peroxidase and glutathione reductase enzymes were also enhanced.

CONCLUSION

The EtOAc extract could reverse the adverse effects of the MCD diet.

Pharmacological interventions for nonalcoholic fatty liver disease in adults and in children: a systematic review

BACKGROUND

Uncertainty exists regarding the treatment of patients with nonalcoholic fatty liver disease (NAFLD) who are unable to lose weight and/or change lifestyle. The present study assesses the effectiveness and safety of pharmacological and dietary supplement interventions for NAFLD.

METHODS

MEDLINE, EMBASE, and the Cochrane Library were searched for randomized controlled trials (RCTs) both in adults and in children.

RESULTS

Fifteen (2 pediatric patients and 13 adults) RCTs met the inclusion criteria. A significant effect on normalization of alanine transaminase was found in patients treated with metformin compared with vitamin E, and in those treated with high-dose (3 g) carnitine vs diet. In contrast, there was no difference in patients treated with pioglitazone combined with vitamin E versus vitamin E alone, ursodeoxycholic acid (UDCA) combined with vitamin E or alone versus placebo, or UDCA versus combination of vitamin E and vitamin C, and in patients treated with vitamin E, probucol, N-acetylcysteine, low doses of carnitine, or Yo Jyo Shi Ko compared with placebo. Aspartate aminotransferase normalization was significantly higher in those treated with UDCA combined with vitamin E versus UDCA alone or placebo, and in those treated with metformin. Small number of subjects, high drop-out rates, and numerous interventions in 1 study limit the value of many studies. Only 7 RCTs analyzed biopsy specimens, but most of them have significant methodological limitations. Pioglitazone had reduced liver necrosis and inflammation in 1 large study.

CONCLUSIONS

Limited data do not allow one to draw firm conclusions on the efficacy of various treatments for NAFLD.

Non-alcoholic steatohepatitis: an overview

Non-alcoholic fatty liver disease (NAFLD) includes a broad spectrum of fat-induced liver injury, ranging from mild steatosis to cirrhosis and liver failure. The presence of obesity and insulin resistance is strongly associated with non-alcoholic fatty liver and a greater risk of advanced disease. We present here a review of the mechanisms involved in the pathogenesis of NAFLD, advances in the diagnosis, and options for treatment.

Liver damage underlying unexplained transaminase elevation in human immunodeficiency virus-1 mono-infected patients on antiretroviral therapy

Liver damage associated with chronic unexplained high serum transaminases in human immunodeficiency virus (HIV)-infected patients under combined antiretroviral therapy is unknown. Liver histology was prospectively investigated in patients presenting serum transaminase elevation for more than 6 months, after exclusion of alcohol abuse, hepatitis C virus (HCV) or hepatitis B virus (HBV) infection, autoimmune, and genetic liver diseases. In a subgroup of patients, liver mitochondrial activities were measured by spectrophotometry and mitochondrial DNA (mtDNA) by real-time polymerase chain reaction (PCR). Thirty patients were included with median values of alanine aminotransferase (ALT) levels: 80 U/L, age: 46 years, body mass index: 23 kg/m(2), HIV RNA: 200 copies/mL, CD4 count: 365/mm(3), duration of HIV infection: 13 years, and duration of treatment exposure: 118, 41, and 53 months for nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, and protease inhibitors, respectively. Histological anomalies were found in 22 of 30 patients. Steatosis was present in 18 patients, severe in nine patients, and associated with inflammation in 16 patients with a diagnosis of non-alcoholic steatohepatitis (NASH). Fibrosis was found in 18 patients, severe in six patients and associated with steatosis in 13 patients. Significant liver respiratory complex I defect, contrasting with high complex IV activity and normal mitochondrial DNA content, was observed in the group of patients compared with controls. The presence of NASH was correlated with high fasting glycemia and insulin levels, not with liver mitochondrial function or mitochondrial DNA content.

CONCLUSIONS

HIV-infected patients on combined antiretroviral therapy with chronic transaminase elevation of unknown origin have a high rate of liver lesions, mostly consistent with NASH related to insulin resistance.

Association of liver enzymes with incident type 2 diabetes: A nested case control study in an Iranian population

BACKGROUND

To investigate the association of Aspartate aminotransferase (AST), Alanin aminotranferase (ALT) and Gamma glutamyl transferase (GGT) with incident type 2 diabetes.

METHODS

In a nested case-control study, AST, ALT, GGT as well as classic diabetes risk factors, insulin and C-reactive protein (CRP) were measured in 133 non-diabetic subjects at baseline of which 68 were cases and 65 were controls. Incident diabetes was defined by the WHO 1999 criteria. Conditional logistic regression was used to calculate the odds ratio (OR) of incident diabetes associated with different hepatic markers. We used factor analysis for clustering of classic diabetes risk factors.

RESULTS

In Univariate analysis both ALT and GGT were associated with diabetes with ORs of 3.07(1.21-7.79) and 2.91(1.29-6.53) respectively. After adjustment for CRP and insulin, ALT and GGT were still predictive of incident diabetes. When the model was further adjusted for anthropometric, blood pressure and metabolic factors, only ALT was independently associated with diabetes [OR = 3.18 (1.02-9.86)]. No difference was found between the area under the receiver operating characteristic curves of the models with and without ALT (0.820 and 0.802 respectively, P = 0.4)

CONCLUSION

ALT is associated with incident type 2 diabetes independent of classic risk factors. However, its addition to the classic risk factors does not improve the prediction of diabetes.

Hypoadiponectinemia plays a crucial role in the development of nonalcoholic fatty liver disease in patients with type 2 diabetes mellitus independent of visceral adipose tissue

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver injury. The spectrum of NAFLD is broad, extending from simple steatosis through nonalcoholic steatohepatitis (NASH). Insulin resistance has been found to increase the risk of NASH, and obesity, and decreased levels of adiponectin are important factors in determining the severity of insulin resistance. Recent evidence has indicated that hypoadiponectinemia is involved in hepatic steatosis and NASH.

METHODS

To investigate whether hypoadiponectinemia causes hepatic steatosis in type 2 diabetes mellitus (DM) patients independently of visceral adipose tissue, we measured the plasma adiponectin concentration, hepatic fat content based on the liver-to-spleen ratio (L/S ratio) according to computed tomography (CT) attenuation values, and the amount of visceral adipose tissue and subcutaneous adipose tissue by CT in 248 type 2 DM patients. We also investigated the relationship between the serum level of adiponectin and hepatic fibrosis.

RESULTS

Significant correlations were observed between the L/S ratios and aspartate aminotransferase, alanine aminotransferase, visceral adipose tissue, subcutaneous adipose tissue, and serum adiponectin values (r=0.300, p=0.0007), and there was a highly significant inverse correlation between the visceral adipose tissue values and the serum adiponectin levels (r=-0.327, p<0.0002). The subcutaneous adipose tissue values, however, were not correlated with the serum adiponectin levels. Multiple regression analysis was used to quantify the impact of measured variables on the L/S ratio. After adjustment for age, gender, and visceral adipose tissue, the serum adiponectin levels were still significantly correlated with the L/S ratios (p=0.0064). And there was a stepwise decrease in the serum adiponectin in parallel to the severity of hepatic fibrosis.

CONCLUSIONS

Hypoadiponectinemia is concluded to be involved in the etiology of hepatic steatosis independently of visceral adipose tissue content, and is considered to be an important factor in the progression of fibrosis; further studies will be necessary to elucidate the exact physiological role of adiponectin and its contribution to the progression of NASH.

Serum aminotransferase levels are associated with markers of hypoxia in patients with obstructive sleep apnea

STUDY OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is a disorder that often presents with elevated serum aminotransferase levels. Although it has classically been linked with the metabolic syndrome, recent studies suggest NAFLD may also be associated with obstructive sleep apnea (OSA). This study evaluates the association between serum aminotransferase levels and factors connected with: either the metabolic syndrome (elevated body mass index [BMI], lipid profile, blood pressure, fasting glucose), or with OSA severity (apnea hypopnea index, lowest oxygen saturation level, oxygen desaturation index, percent of time below 90% saturation [%T<90]).

DESIGN

Retrospective case series.

PATIENTS AND SETTING

109 adult patients with OSA at a university hospital general clinical research center.

MEASUREMENTS AND RESULTS

Markers of hypoxia (lowest oxygen saturation level and %T<90), correlated significantly with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels (Pearson's r = -0.31 to -0.38, P <0.003), while apnea hypopnea index, body mass index, blood pressure, fasting glucose, triglyceride, and cholesterol levels did not. Hierarchical linear regression was then done to determine the best predictors of aminotransferase levels. Markers of metabolic syndrome were entered as one block and markers of sleep apnea as another. Regression analyses explained 16.3% of the variance in AST and 18.9% of the variance in ALT, with %T<90 playing the largest role.

CONCLUSIONS

In patients with obstructive sleep apnea, serum aminotransferase levels are better predicted by markers of oxygen desaturation than by factors traditionally associated with the metabolic syndrome.

Nonalcoholic fatty liver disease is a risk factor for type 2 diabetes in middle-aged Japanese men

OBJECTIVE

To determine the association between nonalcoholic fatty liver disease and the risk for development of diabetes.

RESEARCH DESIGN AND METHODS

We conducted an observational cohort study in male workers > or = 40 years old in a Japanese company from 1997 to 2005. We excluded workers with alcohol intake > or = 20 g/day and those with impaired glucose tolerance by a 75-g oral glucose tolerance test. The remaining 3,189 workers were classified into fatty liver (FL) and non-FL group based on the findings of abdominal ultrasonography. Both groups were followed for the development of diabetes. Hazard ratio (HR) was determined in Cox proportional hazard analysis. A nested case-control study was conducted to determine the odds ratio (OR).

RESULTS

The average age of participants was 48.0 years at the entry, and the average follow-up period was 4.0 years. The incidence of diabetes in the FL group was 2,073 per 100,000 person-years (65 cases), whereas 452 per 100,000 person-years (44 cases) in the non-FL group. The age- and BMI-adjusted HR of diabetes associated with FL was 5.5 (95% CI 3.6-8.5, P < 0.001). In the nested case-control analysis, the OR adjusted for age and BMI was 4.6 (3.0-6.9, P < 0.001).

CONCLUSIONS

Nonalcoholic fatty liver disease significantly increases the risk of diabetes in middle-aged Japanese men.

Incidence and characterization of serum transaminases elevations in pegylated interferon and ribavirin treated patients with chronic hepatitis C

BACKGROUND

A virological response to pegylated-interferon and ribavirin is typically associated with a prompt fall in serum transaminases. For some patients, transaminases rise during treatment.

AIM

To assess the frequency and define factors associated with elevations of serum transaminases.

METHODS

A total of 169 treated patients were studied. Transaminase elevations were graded by WHO criteria - grade 0: no value > baseline, grade 1: 1-2x baseline, grade 2: 2.1-5x baseline, grade 3: >5x, grade 4: any rise with evidence of liver failure. Results 60/169 (35%) patients experienced transaminase elevations: 52 grade 1, 6 grade 2, 1 grade 3, 1 grade 4. Overall, end of treatment response and sustained virological response rates were 72% and 55%. Lower rates were observed in the grade 1 elevation group (63% and 40%) compared with patients with grade 0 (79% and 65%) and grade > or =2 elevations (85% and 71%). Grade 1 elevations tended to occur earlier during treatment than grade > or =2 elevations. Transaminase elevations were associated with greater pre-treatment body weight (P = 0.006), steatosis (P = 0.008) and poorer sustained virological response rates (P = 0.007).

CONCLUSIONS

Transaminase elevations during treatment of chronic Hepatitis C virus with pegylated interferon and ribavirin are common but rarely severe. Mild rises may reflect ongoing viral activity in treatment non-responders. More significant rises are frequently observed despite a virological response, and may be because of an immuno-modulating effect of interferon in susceptible patients.

Effect of losartan on early liver fibrosis development in a rat model of nonalcoholic steatohepatitis

BACKGROUND AND AIM

Nonalcoholic steatohepatitis (NASH) is a metabolic disorder of the liver that may evolve into fibrosis or cirrhosis. Recent studies have shown reduction of experimental liver fibrosis with the use of angiotensin-converting-enzyme inhibitors or angiotensin-receptor antagonists. The aim of this study was to determine whether losartan can influence the early phase of fibrogenesis in an animal model of NASH.

METHODS

To induce NASH, a choline-deficient diet (CDD) was given to Sprague-Dawley rats for 12 weeks. These animals were then compared with a control group receiving choline-supplemented diet (CSD) and a group fed a CDD plus losartan (10 mg/kg/day). Biochemical (serum levels of alanine aminotransferase and aspartate aminotransferase) and histological evaluation of fatty liver was performed by conventional techniques. Hydroxyproline content in liver tissue was assayed by spectrophotometry. In addition, mRNA levels of procollagen I and transforming growth factor (TGF)-beta were assessed by semiquantitative RT-PCR and stellate cell activation by alpha-actin immunofluorescence stain.

RESULTS

After 12 weeks CDD induced a marked elevation of serum aminotranferases, a severe fatty liver infiltration with mild histological inflammation and fibrosis. These findings correlated with a significant increase in mRNA levels of both procollagen I and TGF-beta and significant increased liver hydroxyproline content. No differences were seen between rats receiving CDD alone and rats receiving CDD plus losartan with regard to the biochemical, morphological or molecular alterations induced by the CDD.

CONCLUSION

Losartan does not seem to influence liver injury and fibrogenic events in the CDD model of NASH.

Pathogenesis of NASH: animal models

The incidence of non-alcoholic steatohepatitis, a disorder linked to visceral adiposity, insulin resistance, dyslipidemia, and type 2 diabetes mellitus, is increasing with the rise in the prevalence of the metabolic syndrome. This review focuses on animal models of steatohepatitis currently used to study (1) the mechanisms regulating hepatic lipid, glucose, and cholesterol homeostasis and (2) inflammatory recruitment and fibrogenesis in the steatotic liver. The ultimate aim of this research is to gain insights into the role of hepatic lipid, inflammation, and fibrosis in human non-alcoholic fatty liver disease.

Characterization of a lipopolysaccharide mediated neutrophilic hepatitis model in Sprague Dawley rats

Several studies have investigated the role of neutrophils during endotoxin-mediated liver injury, yet the precise mechanism for endotoxin-mediated hepatic neutrophil transmigration is unknown. The primary objective of this study was to establish a reliable lipopolysaccharide (LPS)-mediated necro-hepatitis model to investigate the mechanisms of hepatic neutrophil infiltration following LPS administration. Male Sprague Dawley rats were administered a single (5 or 10 mg kg(-1), i.v.) or repeated injection of LPS (10 mg kg(-1), i.v., 24 h apart) with appropriate controls (i.v. saline) and were killed at various time points following LPS injection. Significant hematologic changes included neutrophilia, elevation of the neutrophil to lymphocyte ratio and toxic changes in neutrophils. Biochemical changes were observed in several liver (aspartate aminotransferase AST, gamma glutamyl transferase GGT) and kidney (blood urea nitrogen BUN) associated parameters generally at the earliest time points. Histopathology revealed a time-dependent neutrophil and mononuclear infiltration around the periportal areas in the single dose study and multifocal midzonal coagulative necrosis in the repeated dose study. The neutrophil adhesion molecule, CD 11b was up-regulated in single and repeat dose studies. Based on these studies, a reliable LPS-mediated hepatitis model with necrosis was developed by intravenous administration of LPS in a repeat dose fashion. Midzonal hepatic necrosis, peripheral neutrophilia, hepatic neutrophil infiltration and up-regulation of CD11b were the most significant and consistent markers of LPS mediated effects in this model.

Review: The role of insulin resistance in nonalcoholic fatty liver disease

CONTEXT

Insulin resistance is an almost universal finding in nonalcoholic fatty liver disease (NAFLD). This review outlines the evidence linking insulin resistance and NAFLD, explores whether liver fat is a cause or consequence of insulin resistance, and reviews the current evidence for treatment of NAFLD.

EVIDENCE ACQUISITION

Evidence from epidemiological, experimental, and clinical research studies investigating NAFLD and insulin resistance was reviewed.

EVIDENCE SYNTHESIS

Insulin resistance in NAFLD is characterized by reductions in whole-body, hepatic, and adipose tissue insulin sensitivity. The mechanisms underlying the accumulation of fat in the liver may include excess dietary fat, increased delivery of free fatty acids to the liver, inadequate fatty acid oxidation, and increased de novo lipogenesis. Insulin resistance may enhance hepatic fat accumulation by increasing free fatty acid delivery and by the effect of hyperinsulinemia to stimulate anabolic processes. The impact of weight loss, metformin, and thiazolidinediones, all treatments aimed at improving insulin sensitivity, as well as other agents such as vitamin E, have been evaluated in patients with NAFLD and have shown some benefit. However, most intervention studies have been small and uncontrolled.

CONCLUSION

Insulin resistance is a major feature of NAFLD that, in some patients, can progress to steatohepatitis. Treatments aimed at reducing insulin resistance have had some success, but larger placebo-controlled studies are needed to fully establish the efficacy of these interventions and possibly others in reducing the deleterious effects of fat accumulation in the liver.

Rosiglitazone treatment alleviates inflammation and improves liver function in overweight women with polycystic ovary syndrome: a randomized placebo-controlled study

In a randomized, placebo-controlled study, we studied the effects of 4 months' treatment with rosiglitazone on low-grade inflammation, liver function, lipid levels, and blood pressure in 30 overweight women with polycystic ovary syndrome. Rosiglitazone significantly decreased serum C-reactive protein levels, white blood cell count, and alanine aminotransferase enzyme activity but did not affect lipid or blood pressure levels. Placebo had no effect on any parameters.

Bax inhibition protects against free fatty acid-induced lysosomal permeabilization

Lysosomal permeabilization is a key feature of hepatocyte lipotoxicity, yet the mechanisms mediating this critical cellular event are unclear. This study examined the mechanisms involved in free fatty acid (FFA)-induced lysosomal permeabilization and the role of Bax, a Bcl-2 family member, in this event. Exposure of liver cells to palmitate induced Bax activation and translocation to lysosomes. Studies to suppress Bax activation either by pharmacological approaches or small interfering-RNA-mediated inhibition of Bax expression showed that lysosomal permeabilization is Bax dependent. In addition, palmitate treatment resulted in a significant decrease in Bcl-X(L), a Bax antagonist. Moreover, forced Bcl-X(L) expression blocked lysosomal permeabilization. Lysosomal permeabilization by FFA was ceramide and caspase independent. Finally, paradigms that inhibit lysosomal permeabilization also reduced apoptosis. In conclusion, these data strongly support a regulatory role for Bax in FFA-mediated lysosomal permeabilization and subsequent cell death.

The medical complications of alcohol use: understanding mechanisms to improve management

The use of alcohol in a dependent or even a regular heavy pattern predisposes the drinker to a range of adverse consequences. These include a risk of direct harm from alcohol, including organ damage, mental health disorders and a range of social and legal problems associated with behaviours due to alcohol's effects. The range of organ damage associated with regular heavy alcohol consumption is well described. Much new information on the mechanisms by which damage occurs is available and is reviewed in this paper. New knowledge can assist in the development of more appropriate management strategies for those affected by the medical complications of alcohol use. Genetic susceptibility to tissue injury is explored and the reasons why many heavy drinkers do not appear to experience organ damage are considered. Approaches to the management of certain alcohol-related disorders are outlined.

Hepatic enzymes, the metabolic syndrome, and the risk of type 2 diabetes in older men

OBJECTIVE

We have examined the relationship between hepatic enzymes, the metabolic syndrome, insulin resistance, and type 2 diabetes and assessed the potential of hepatic enzyme measurements in determining diabetes risk.

RESEARCH DESIGN AND METHODS

We conducted a prospective study of 3,500 nondiabetic men aged 60-79 years who were followed-up for a mean period of 5 years and in whom there were 100 incident type 2 diabetes cases.

RESULTS

In cross-sectional analyses, alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT) were strongly associated with obesity, insulin resistance, and the metabolic syndrome. Prospectively, the risk of type 2 diabetes significantly increased with increasing levels of ALT and GGT even after adjustment for confounders including BMI (top versus bottom quarter ALT: relative risk 2.72 [95% CI 1.47-5.02]; GGT: 3.68 [1.68-8.04]). Additional adjustment for insulin resistance attenuated the effects, but the relationships with ALT and GGT remained significant (1.91 [1.01-3.60] and 2.69 [1.21-5.97], respectively). Further adjustment for inflammatory markers (C-reactive protein) made minor differences. Among high-risk subjects (obese men or those with the metabolic syndrome), elevated GGT and ALT enhanced the prediction of diabetes risk.

CONCLUSIONS

Elevated levels of ALT and GGT within the normal range are independent predictors of type 2 diabetes in older men and are useful additional measures in identifying those at high risk of diabetes.

Nonalcoholic fatty liver disease in the pediatric population: a review

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease is a common condition that may progress to end stage liver disease. It is closely associated with obesity and insulin resistance, two conditions whose prevalence is increasing dramatically in children. This could potentially make nonalcoholic fatty liver disease the most common liver disease in the pediatric population. This review will focus on the current knowledge regarding the epidemiology, clinical presentation, diagnosis, pathogenesis, and management of nonalcoholic fatty liver disease in children.

RECENT FINDINGS

Recent studies suggest that nonalcoholic fatty liver disease is an increasingly recognized condition during childhood, especially in overweight and obese children. Although limited information is currently available on the natural history of the disease in the pediatric population, few cross-sectional studies and a single longitudinal cohort study with follow up data up to 16 years, showed that as in adults, nonalcoholic fatty liver disease in children may have a progressive clinical course with the development of cirrhosis. Emerging data from small pilot studies suggest weight loss through lifestyle modifications as well as insulin sensitizing and antioxidant medications may be of benefit. Moreover, recent advances in the understanding of nonalcoholic fatty liver disease pathogenesis may result in novel therapeutic targets to treat this disease.

SUMMARY

Nonalcoholic fatty liver disease is probably the most common form of chronic liver disease in children and may continue to rise with the increasing prevalence of childhood obesity and metabolic syndrome. Recent studies have provided new insights regarding this condition in children. There is still much progress to be made in terms of the description of pediatric nonalcoholic fatty liver disease, its demographics, pathogenesis, and treatment as well as natural history and long-term prognosis.

Design and validation of a histological scoring system for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis in the absence of a history of significant alcohol use or other known liver disease. Nonalcoholic steatohepatitis (NASH) is the progressive form of NAFLD. The Pathology Committee of the NASH Clinical Research Network designed and validated a histological feature scoring system that addresses the full spectrum of lesions of NAFLD and proposed a NAFLD activity score (NAS) for use in clinical trials. The scoring system comprised 14 histological features, 4 of which were evaluated semi-quantitatively: steatosis (0-3), lobular inflammation (0-2), hepatocellular ballooning (0-2), and fibrosis (0-4). Another nine features were recorded as present or absent. An anonymized study set of 50 cases (32 from adult hepatology services, 18 from pediatric hepatology services) was assembled, coded, and circulated. For the validation study, agreement on scoring and a diagnostic categorization ("NASH," "borderline," or "not NASH") were evaluated by using weighted kappa statistics. Inter-rater agreement on adult cases was: 0.84 for fibrosis, 0.79 for steatosis, 0.56 for injury, and 0.45 for lobular inflammation. Agreement on diagnostic category was 0.61. Using multiple logistic regression, five features were independently associated with the diagnosis of NASH in adult biopsies: steatosis (P = .009), hepatocellular ballooning (P = .0001), lobular inflammation (P = .0001), fibrosis (P = .0001), and the absence of lipogranulomas (P = .001). The proposed NAS is the unweighted sum of steatosis, lobular inflammation, and hepatocellular ballooning scores. In conclusion, we present a strong scoring system and NAS for NAFLD and NASH with reasonable inter-rater reproducibility that should be useful for studies of both adults and children with any degree of NAFLD. NAS of > or =5 correlated with a diagnosis of NASH, and biopsies with scores of less than 3 were diagnosed as "not NASH."

Liver-specific inactivation of the Nrf1 gene in adult mouse leads to nonalcoholic steatohepatitis and hepatic neoplasia

Knockout studies have shown that the transcription factor Nrf1 is essential for embryonic development. Nrf1 has been implicated to play a role in mediating activation of oxidative stress response genes through the antioxidant response element (ARE). Because of embryonic lethality in knockout mice, analysis of this function in the adult knockout mouse was not possible. We report here that mice with somatic inactivation of nrf1 in the liver developed hepatic cancer. Before cancer development, mutant livers exhibited steatosis, apoptosis, necrosis, inflammation, and fibrosis. In addition, hepatocytes lacking Nrf1 showed oxidative stress, and gene expression analysis showed decreased expression of various ARE-containing genes, and up-regulation of CYP4A genes. These results suggest that reactive oxygen species generated from CYP4A-mediated fatty acid oxidation work synergistically with diminished expression of ARE-responsive genes to cause oxidative stress in mutant hepatocytes. Thus, Nrf1 has a protective function against oxidative stress and, potentially, a function in lipid homeostasis in the liver. Because the phenotype is similar to nonalcoholic steatohepatitis, these animals may prove useful as a model for investigating molecular mechanisms of nonalcoholic steatohepatitis and liver cancer.

Small-molecule insulin mimetic reduces hyperglycemia and obesity in a nongenetic mouse model of type 2 diabetes

Adiposity positively correlates with insulin resistance and is a major risk factor of type 2 diabetes. Administration of exogenous insulin, which acts as an anabolic factor, facilitates adipogenesis. Recently nonpeptidal insulin receptor (IR) activators have been discovered. Here we evaluate the effects of the orally bioavailable small-molecule IR activator (Compound-2) on metabolic abnormalities associated with type 2 diabetes using a nongenetic mouse model in comparison with the effects of a novel non-thiazolidinedione (nTZD) peroxisome proliferator-activated receptor-gamma agonist. Both Compound-2 and nTZD alleviated fasting and postprandial hyperglycemia; accelerated glucose clearance rate; and normalized plasma levels of nonesterified fatty acids, triglycerides, and leptin. Unlike nTZD, which increased body weight gain, and total fat mass, which is a common feature for PPARgamma agonists, Compound-2 prevented body weight gain and hypertrophy of brown, and white adipose tissue depots and the development of hepatic steatosis in the mouse model of type 2 diabetes. The effect of the two compounds on proximal steps in insulin signal transduction pathway was analyzed in tissues. Compound-2 enhanced insulin-stimulated phosphorylation of IR tyrosine and/or Akt in the liver, skeletal muscle, and white adipose tissue, whereas nTZD potentiated the phosphorylation of IR and Akt in the adipose tissue only. In conclusion, small-molecule IR activators have unique features as insulin sensitizers and hold potential utility in the treatment of type 2 diabetes and obesity.

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.

The wide spectrum of steatohepatitis: a report of four cases and a review of the literature

We report on four cases displaying the wide range of aetiological risk factors (presence or absence of family history of dyslipidaemia and cryptogenic cirrhosis, from subnormal body mass index through morbid obesity, from absent through hepatotoxic alcohol consumption), laboratory test results (from subnormal through elevated uric acid and ferritin values), ultrasonographic changes (from normal findings through 'bright liver' with or without attenuation of ultrasound beam and absence/presence of focal lesions), and histological severity of steatohepatitis (fibrosis appearing to be inversely related to the amount of liver fat but zone 3 accentuation of lesions and ballooning being observed in all cases). Cases illustrate the concepts of overlapping aetiologies of steatohepatitis (hepatitis C, diabetes and lipodystrophy); the relationships between cryptogenic cirrhosis, familial cirrhosis, non-alcoholic fatty liver disease and hepatocellular carcinoma; familial hypobetalipoproteinaemia as an aetiology of steatohepatitis; and alcoholic liver disease in the obese. These issues, which are worthy of future investigation, are reviewed.

Polymorphisms of microsomal triglyceride transfer protein gene and manganese superoxide dismutase gene in non-alcoholic steatohepatitis

BACKGROUND/AIMS

The pathogenesis of non-alcoholic steatohepatitis (NASH) is poorly understood. The aim of this study was to examine genetic influences on NASH pathogenesis.

METHODS

Blood samples from 63 patients with biopsy-proven NASH and 150 healthy controls were analyzed by the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Two functional polymorphisms were studied: the -493 G/T polymorphism in the promoter of microsomal triglyceride transfer protein (MTP) and the 1183 T/C polymorphism in the mitochondrial targeting sequence of manganese superoxide dismutase (MnSOD).

RESULTS

NASH patients had a much higher incidence of the MTP gene G allele (P=0.001) and of the G/G genotype (P=0.002) compared to the controls. Fat occupied more area in liver lobules and the stage of NASH was advanced in patients with the G/G-genotype than in patients with G/T-genotype (P=0.04). NASH patients also had a higher incidence of the MnSOD T/T genotype (P=0.016).

CONCLUSIONS

The G allele in the MTP promoter leads to decreased MTP transcription, less export of triglyceride from hepatocytes, and greater intracellular triglyceride accumulation. The T allele in MnSOD mitochondrial targeting sequence leads to less transport of MnSOD to the mitochondria. Therefore, functional polymorphisms in MTP and MnSOD may be involved in determining susceptibility of NASH.

Hepatic steatosis: a mediator of the metabolic syndrome. Lessons from animal models

Epidemiological studies in humans, as well as experimental studies in animal models, have shown an association between visceral obesity and dyslipidemia, insulin resistance, and type 2 diabetes mellitus. Recently, attention has been focused on the excessive accumulation of triglycerides (TG) in the liver as part of this syndrome. In this review, important principles of the pathophysiological involvement of the liver in the metabolic syndrome obtained in rodent models are summarized. We focus on non-alcoholic causes of steatosis, because the animal experiments we refer to did not include alcohol as an experimental condition. In general, there is continuous cycling and redistribution of non-oxidized fatty acids between different organs. The amount of TG in an intrinsically normal liver is not fixed but can readily be increased by nutritional, metabolic, and endocrine interactions involving TG/free fatty acid (FFA) partitioning and TG/FFA metabolism. Several lines of evidence indicate that hepatic TG accumulation is also a causative factor involved in hepatic insulin resistance. Complex interactions between endocrine, metabolic, and transcriptional pathways are involved in TG-induced hepatic insulin resistance. Therefore, the liver participates passively and actively in the metabolic derangements of the metabolic syndrome. We speculate that similar mechanisms may also be involved in human pathophysiology.

Fatty liver in type 2 diabetes mellitus: relation to regional adiposity, fatty acids, and insulin resistance

The current study was undertaken to examine metabolic and body composition correlates of fatty liver in type 2 diabetes mellitus (DM). Eighty-three men and women with type 2 DM [mean body mass index (BMI): 34 +/- 0.5 kg/m2] and without clinical or laboratory evidence of liver dysfunction had body composition assessments of fat mass (FM), visceral adipose tissue (VAT), liver and spleen computed tomography (CT) attenuation (ratio of liver to spleen), muscle CT attenuation, and thigh adiposity; these assessments were also performed in 12 lean and 15 obese nondiabetic volunteers. Insulin sensitivity was measured with a euglycemic insulin infusion (40 mU. m-2. min-1) combined with systemic indirect calorimetry to assess glucose and lipid oxidation, and with infusions of [2H2]glucose for assessment of endogenous glucose production. A majority of those with type 2 DM (63%) met CT criteria for fatty liver, compared with 20% of obese and none of the lean nondiabetic volunteers. Fatty liver was most strongly correlated with VAT (r = -0.57, P < 0.0001) and less strongly but significantly associated with BMI (r = -0.42, P < 0.001) and FM (r = -0.37, P < 0.001), but only weakly associated with subcutaneous adiposity (r = -0.29; P < 0.01). Fatty liver was also correlated with subfascial adiposity of skeletal muscle (r = -0.44; P < 0.01). Volunteers with type 2 DM and fatty liver were substantially more insulin resistant those with type 2 DM but without fatty liver (P < 0.001) and had higher levels of plasma free fatty acids (P < 0.01) and more severe dyslipidemia (P < 0.01), a pattern observed in both genders. Plasma levels of cytokines were increased in relation to fatty liver (r = -0.34; P < 0.01). In summary, fatty liver is relatively common in overweight and obese volunteers with type 2 DM and is an aspect of body composition related to severity of insulin resistance, dyslipidemia, and inflammatory markers.