NASH--hepatic metabolism and not simply the metabolic syndrome

Loss of Hepatic Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 Links Nonalcoholic Steatohepatitis to Atherosclerosis

Patients with nonalcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) commonly develop atherosclerosis through a mechanism that is not well delineated. These diseases are associated with steatosis, inflammation, oxidative stress, and fibrosis. The role of insulin resistance in their pathogenesis remains controversial. Albumin (Alb)Cre⁺Cc1^flox(fl)/fl mice with the liver‐specific null deletion of the carcinoembryonic antigen‐related cell adhesion molecule 1 (Ceacam1; alias Cc1) gene display hyperinsulinemia resulting from impaired insulin clearance followed by hepatic insulin resistance, elevated de novo lipogenesis, and ultimately visceral obesity and systemic insulin resistance. We therefore tested whether this mutation causes NAFLD/NASH and atherosclerosis. To this end, mice were propagated on a low‐density lipoprotein receptor (Ldlr)^−/− background and at 4 months of age were fed a high‐cholesterol diet for 2 months. We then assessed the biochemical and histopathologic changes in liver and aortae. Ldlr^−/−AlbCre⁺Cc1^fl/fl mice developed chronic hyperinsulinemia with proatherogenic hypercholesterolemia, a robust proinflammatory state associated with visceral obesity, elevated oxidative stress (reduced NO production), and an increase in plasma and tissue endothelin‐1 levels. In parallel, they developed NASH (steatohepatitis, apoptosis, and fibrosis) and atherosclerotic plaque lesions. Mechanistically, hyperinsulinemia caused down‐regulation of the insulin receptor followed by inactivation of the insulin receptor substrate 1–protein kinase B–endothelial NO synthase pathway in aortae, lowering the NO level. This also limited CEACAM1 phosphorylation and its sequestration of Shc‐transforming protein (Shc), activating the Shc–mitogen‐activated protein kinase–nuclear factor kappa B pathway and stimulating endothelin‐1 production. Thus, in the presence of proatherogenic dyslipidemia, hyperinsulinemia and hepatic insulin resistance driven by liver‐specific deletion of Ceacam1 caused metabolic and vascular alterations reminiscent of NASH and atherosclerosis. Conclusion: Altered CEACAM1‐dependent hepatic insulin clearance pathways constitute a molecular link between NASH and atherosclerosis.

Pattern of some risk factors of cardiovascular diseases and liver enzymes among Iranian seafarers

Background: Little information is available on the trend in cardiovascular risk factors and hepatic enzymes in Iranian seafarers. The present study aimed at assessing the pattern of obesity, hypertension, diabetes, elevated serum glutamic oxaloacetate transaminase (SGOT), and serum glutamate pyruvate transaminase (SGPT) in Iranian seafarers during 2010 to 2014.

Methods: Data on cardiovascular risk factors and hepatic enzymes were extracted from seafarers’ annual health examination of National Iranian Tanker Company (NITC) of 2010, 2012, and 2014. The repeated measure ANOVA was used to compare continuous variables across 3 years. Categorical data were analyzed using Chi-square test. Over weight was defined as BMI (Body Mass Index) >25 kg/m²; obesity was defined as BMI>=30 kg/m²; hypertension was defined as systolic blood pressure (SBP)> 140 mmHg, and diastolic blood pressure (DBP)> 90 mmHg, or a history of antihypertensive drug use. Diabetes (DM) was defined as fasting blood sugar (FBS) > 110 mg/dl, or having a history of oral hypoglycemic agents; and elevated SGOT and SGPT were defined as SGOT > 40 U/L and SGPT > 40 U/L, respectively.

Results: The BMI mean±SD values of Iranian seafarers were 24.81±3.07 kg/m², 25.51±2.96 kg/m², and 25.96 ± 3.02 kg/m² in 2010, 2012, and 2014, respectively. A significant difference was observed in BMI over the study period. The mean of systolic and diastolic blood pressure did not significantly increase over time. The SGOT and SGPT means were not significantly different from 2010 to 2014. The prevalence of overweight increased significantly from 46.7% to 60.9% over the study period; however, the prevalence of obesity, hypertension, elevated SGOT, and elevated SGPT did not change significantly.

Conclusion: The current survey showed that the obesity problem has increased among Iranian seafarers working on tankers, which is a concerning problem because obesity has negative effects on seafarers’ health.

Peroxisome Proliferator-Activated Receptors Associated with Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming a major cause of chronic liver disease worldwide. Concurrent to an increase in NAFLD prevalence, there is an increase in the obesity epidemic and the correlated insulin-resistant state. It is a challenge to diagnose NAFLD because many patients are asymptomatic until the later stages of disease. The most common symptoms include fatigue, malaise, and discomfort in the right upper quadrant. The major and most accurate tool to clinically diagnose NAFLD is a liver biopsy, followed by histological analysis. However, this procedure is invasive and often carries a high risk of complications. Currently, there are no officially approved medications for the treatment of NAFLD. Although lifestyle modifications with proper diet and exercise have been shown to be beneficial, this has been difficult to achieve and sustain for many patients. Effective pharmacological treatments are still lacking; therefore, additional research to identify novel drugs is clearly warranted. PPARs are promising drug targets for the management of NAFLD and its related conditions of type 2 diabetes mellitus and cardiovascular disease. In this review, we provide an overview of recent studies on the association of PPARs and NAFLD.

Exenatide induces carcinoembryonic antigen-related cell adhesion molecule 1 expression to prevent hepatic steatosis

Exenatide, a glucagon-like peptide-1 receptor agonist, induces insulin secretion. Its role in insulin clearance has not been adequately examined. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes hepatic insulin clearance to maintain insulin sensitivity. Feeding C57BL/6J mice a high-fat diet down-regulates hepatic Ceacam1 transcription to cause hyperinsulinemia, insulin resistance, and hepatic steatosis, as in Ceacam1 null mice (Cc1^-/- ). Thus, we tested whether exenatide regulates Ceacam1 expression in high-fat diet-fed mice and whether this contributes to its insulin sensitizing effect. Exenatide (100 nM) induced the transcriptional activity of wild-type Ceacam1 promoter but not the constructs harboring block mutations of peroxisome proliferator-activated receptor response element and retinoid X receptor alpha, individually or collectively, in HepG2 human hepatoma cells. Chromatin immunoprecipitation analysis demonstrated binding of peroxisome proliferator-activated receptor gamma to Ceacam1 promoter in response to rosiglitazone and exenatide. Consistently, exenatide induced Ceacam1 messenger RNA expression within 12 hours in the absence but not in the presence of the glucagon-like peptide-1 receptor antagonist exendin 9-39. Exenatide (20 ng/g body weight once daily intraperitoneal injection in the last 30 days of feeding) restored hepatic Ceacam1 expression and insulin clearance to curb diet-induced metabolic abnormalities and steatohepatitis in wild-type but not Cc1^-/- mice fed a high-fat diet for 2 months. Conclusion: Exenatide promotes insulin clearance in parallel with insulin secretion to prevent chronic hyperinsulinemia and the resulting hepatic steatosis, and this contributes to its insulin sensitizing effect. Our data further highlight the relevance of physiologic insulin metabolism in maintaining insulin sensitivity and normal lipid metabolism. (Hepatology Communications 2018;2:35-47).

The effect of β-caryophyllene on nonalcoholic steatohepatitis

The pathogenesis of nonalcoholic steatohepatitis (NASH) is not fully understood, but many studies have suggested that oxidative stress plays a key role. The methionine- and choline-deficient diet (MCD) administration model can reproduce histopathological features of human NASH and is widely used for investigating NASH. C57BL/6J mice have been used in many studies, but strain differences in pathogenesis have not been sufficiently investigated. We administred MCD to two mouse strains and then compared difference between strains and investigated the effects of β-caryophyllene (BCP), which possesses an antioxidant effect, on development and progression of NASH. ICR and C57BL/6J mice were administred a control diet, MCD, MCD containing 0.02% BCP, or MCD containing 0.2% BCP. After 4 or 8 weeks, mice were sacrificed. In both strains, MCD administration induced hepatic steatosis and inflammation. These lesions were more severe in C57BL/6J mice than ICR mice, and liver fibrosis was observed at 8 weeks in C57BL/6J mice. These changes were attenuated by BCP coadministration. The mRNA expression of monocyte chemotactic and activating factor (MCP)-1 and fibrosis-related factors increased in C57BL/6J mice, and these increases were reduced by BCP coadministration. The mRNA expression of antioxidant-related factors decreased in both strains, and these decreases were attenuated by BCP coadministration. Based on these results, the C57BL/6J mouse was a more suitable model for MCD-induced NASH than the ICR mouse. In addition, it was suggested that antioxidant effect of BCP might suppressed the damage of hepatocytes caused by oxidative stress and following inflammation and fibrosis.

Pigment Epithelium-Derived Factor (PEDF) Prevents Hepatic Fat Storage, Inflammation, and Fibrosis in Dietary Steatohepatitis of Mice

BACKGROUND AND AIMS

Pigment epithelium-derived factor (PEDF) has been shown to be a potent inhibitor of inflammation through its anti-oxidative property. Since oxidative response is considered to play the pivotal role of the development and progression of nonalcoholic steatohepatitis (NASH), it is conceivable that PEDF may play a protective role against NASH. In this study, we examined whether administration of PEDF slowed the progression of NASH in mice models.

METHODS

Mice were fed methionine- and choline-deficient (MCD) diet with or without intramuscular administration of adenovirus-expressing PEDF (Ad-PEDF). Effects of PEDF administration on NASH were histologically and biochemically evaluated.

RESULTS

Administration of Ad-PEDF significantly decreased hepatic fat storage as well as serum levels of ALT in MCD diet-fed mice. Dihydroethidium staining showed that MCD diet-triggered oxidative stress was reduced in the liver of Ad-PEDF-administered mice compared to that of PBS- or Ad-LacZ-administered mice. Activation of Kupffer cells and hepatic fibrosis was also inhibited by Ad-PEDF administration. Quantitative real-time RT-PCR revealed that MCD diet up-regulated expressions of TNF-α, IL-1β, IL-6, TGF-β, collagen-1, and collagen-3 mRNA, which were also attenuated with Ad-PEDF administration, whereas MCD diet-induced down-regulation of expressions of PPAR-γ mRNA was restored with Ad-PEDF administration. Furthermore, immunoblotting analysis showed that MCD diet-induced up-regulation of NADPH oxidase components was significantly decreased in Ad-PEDF-administered mice.

CONCLUSIONS

The present results demonstrated for the first time that PEDF could slow the development and progression of steatohepatitis through the suppression of steatosis and inflammatory response in MCD diet-fed mice. Our study suggests that PEDF supplementation may be a novel therapeutic strategy for the treatment of NASH.

Pigment epithelium-derived factor improves TNFα-induced hepatic steatosis in grass carp (Ctenopharyngodon idella)

Pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNFα), may contribute to hepatic steatosis in the situation of excess lipid accumulation in farmed fish. Pigment epithelium-derived factor (PEDF) is an endogenous anti-inflammatory factor and promotes lipolysis. Accordingly, we isolated PEDF from grass carp and investigated its role in TNFα-induced hepatic steatosis. Sequence analysis showed that PEDF gene, which possesses 8 exons and 7 introns, encodes a protein with 409 amino acids. PEDF was a critical determinant of the transcriptional response to nutrient availability in grass carp. Endogenous PEDF was an intracellular protein with cytoplasmic distribution and directly interacts with adipose triglyceride lipase (ATGL), which might mediate PEDF-induced lipolysis. TNFα significantly promoted lipid accumulation in vivo and in vitro, accompanied with a decrease in mRNA levels of PEDF and peroxisome proliferator-activated receptor alpha (PPARα). Recombinant PEDF and PPARα agonist diminished the TNFα-induced hepatic steatosis. Meanwhile, PPARα agonist caused an increase in PEDF expression, suggesting that TNFα antagonizes the actions of PEDF possibly in a PPARα-dependent manner. These findings suggest that PEDF is an important protective factor against hepatic steatosis induced by TNFα, which provided a new therapeutic target for inflammation-associated hepatic steatosis.

Epigallocatechin gallate attenuated non-alcoholic steatohepatitis induced by methionine- and choline-deficient diet

Nonalcoholic fatty liver disease (NAFLD) and its progressive form, nonalcoholic steatohepatitis (NASH), are the most common causes of chronic liver disease. In this study, we evaluated the effects of Epigallocatechin gallate (EGCG) on methionine- and choline-deficient (MCD) diet-induced NASH. Our data showed that EGCG significantly prevented MCD diet-induced liver and body weight loss. Histological analysis showed that EGCG inhibited MCD diet-induced steatohepatitis including fat accumulation and inflammatory cells infiltration. Biochemical analysis data showed that EGCG significantly reduced the elevation of plasma ALT and AST levels but increased plasma triglyceride and cholesterol contents. However, EGCG significantly inhibited hepatic triglyceride and cholesterol content in MCD diet fed mice. Consistent with histology results, EGCG treatment significantly inhibited MCD diet-induced IL-1β, IL-6, TNF-α and MCP-1 mRNA expression. As an antioxidant, EGCG treatment significant inhibited hepatic MDA contents and increased hepatic SOD contents. In addition, transforming growth factor (TGF)-β, collagen I-α1, tissue inhibitor of metalloproteinase 1 (TIMP-1) and α-smooth muscle actin (SMA) mRNA expression, which are markers of hepatic fibrosis, were markedly inhibited by EGCG treatment. Western blot data showed that EGCG inhibited Smad2 and Smad3 phosphorylation in the liver and LX-2 cells which were involved in TGF-β-induced pathway. Taken together, EGCG attenuated NASH induced by MCD diet associated with ameliorating fibrosis, oxidative stress, and hepatic inflammation. Our results indicate that EGCG has beneficial roles in the development of MCD diet-induced NASH.

Effects of n-3 fish oil on metabolic and histological parameters in NASH: a double-blind, randomized, placebo-controlled trial

BACKGROUND & AIMS

This study's aim was to assess the histological and metabolic effects of n-3 polyunsaturated fatty acids (PUFAs) vs. placebo while adjusting for the impact of age and weight change in NASH patients. (ClinicalTrials.gov: NCT00681408).

METHODS

Forty-one subjects with non-cirrhotic NASH were enrolled, and 34 completed the study. 17 received n-3 fish oil 3000 mg/day and 17 received placebo daily for 1 year with typical counselling on caloric intake and physical activity for all subjects.

RESULTS

N-3- and placebo-treated groups showed no significant difference for the primary end point of NASH activity score (NAS) reduction ⩾ 2 points without fibrosis progression after adjustment for known covariates (n-3, 4/17 (23.5%); placebo, 3/17, (17.6%), p = 0.99). Among subjects with increased or stable weight, n-3 subjects showed a larger decrease in liver fat content by MRI than placebo-treated subjects (p = 0.014 for 2nd quartile, p = 0.003 for 3rd quartile of weight change). N-3 treatment showed significant fat reduction on the paired analysis of image-assisted fat morphometry regardless of weight loss or gain. Exercise capacity remained markedly reduced in all subjects. No independent effects on markers of hepatocyte injury or insulin sensitivity indices were observed.

CONCLUSION

N-3 PUFAs at 3000 mg/day for one year did not lead to an improvement in the primary outcome of histological activity in NASH patients (⩾ 2 point NAS reduction). N-3 led to reduced liver fat by multiple measures. Other metabolic effects were not seen, although no detrimental effects were apparent. Whether longer duration, higher dose, or different composition of n-3 therapy would lead to additional benefits is uncertain.

The prevalence of nonalcoholic fatty liver disease in the Americas

Nonalcoholic fatty liver disease (NAFLD) is an alarming public health problem. The disease is one of the main causes of chronic liver disease worldwide and is directly linked to the increased prevalence of obesity and type 2 diabetes mellitus (T2DM) in the general population. The worldwide prevalence of NAFLD has been estimated at 20-30%, but the prevalence is unknown in the Americas because of a lack of epidemiological studies. However, given the trends in the prevalence of diabetes and obesity, the prevalence of NAFLD and its consequences are expected to increase in the near future. The aim of the present study is to present the current data on the prevalence of NAFLD in the Americas. We performed an electronic search of the main databases from January 2000 to September 2013 and identified 356 reports that were reviewed. We focused on the epidemiology and prevalence of known NAFLD risk factors including obesity, T2DM, and the metabolic syndrome (MS). The prevalence of the MS was highest in the United States, Mexico, Costa Rica, Puerto Rico, Chile, and Venezuela. In addition, Puerto Rico, Guyana, and Mexico have the highest prevalence of T2DM in the Americas, while USA has the most people with T2DM. In conclusion, the prevalence rates of NAFLD and obesity were highest in the United States, Belize, Barbados, and Mexico.

CEACAM1 loss links inflammation to insulin resistance in obesity and non-alcoholic steatohepatitis (NASH)

Mounting epidemiological evidence points to an association between metabolic syndrome and non-alcoholic steatohepatitis (NASH), an increasingly recognized new epidemic. NASH pathologies include hepatocellular ballooning, lobular inflammation, hepatocellular injury, apoptosis, and hepatic fibrosis. We will review the relationship between insulin resistance and inflammation in visceral obesity and NASH in an attempt to shed more light on the pathogenesis of these major metabolic diseases. Moreover, we will identify loss of the carcinoembryonic antigen-related cell adhesion molecule 1 as a unifying mechanism linking the immunological and metabolic abnormalities in NASH.

What about non-alcoholic fatty liver disease as a new criterion to define metabolic syndrome?

Non-alcoholic fatty liver disease (NAFLD) is currently not a component of the diagnostic criteria for metabolic syndrome (MetS); however, the development of NAFLD has some common mechanisms with the development of MetS, as they share the pathophysiologic basis of insulin resistance. It is also recognized that NAFLD is the hepatic manifestation of MetS. To define MetS, the presence of at least three of the proposed criteria is required, and sometimes it is sufficient to have only one laboratory value, modified by diet or drugs, for the classification of MetS. Ultrasonographically-detected NAFLD (US-NAFLD) is more stable, only changing during the middle- to long-term. Although controversies over MetS continue, and considering that abdominal ultrasonography for diagnosing NAFLD has high specificity and guidelines to modify the natural course of NAFLD by diet composition or lifestyle have not yet been established, why should we not introduce US-NAFLD as a new criterion to define MetS?

Rosiglitazone and bezafibrate modulate gene expression in a rat model of non-alcoholic fatty liver disease--a historical prospective

Background

Genetic factors implicated in the pathogenesis of non-alcoholic fatty liver disease are poorly understood. Our aim was to characterize three genes involved in a rat model of non-alcoholic fatty liver disease and investigate the effect of rosiglitazone and bezafibrate.

Method

Five rats were fed a chow diet (controls) and 18 a fructose-enriched diet (FED) for 5 weeks: 6 were administered rosiglitazone and 6 bezafibrate during the last 2 weeks and 6 were not treated at all. Livers were examined by reverse transcription-PCR for the genes encoding peroxisome proliferator-activated receptors (PPAR), PPAR-α, PPAR-γ, and Mn superoxide dismutase2 (Mn SOD2). Western blot was used for proteins levels.

Result

The FED rats showed a decrease in mRNA of MnSOD2, PPAR-α, and PPAR-γ (3, 3.5 fold, and 27%, respectively) (p<0.05). The 3 genes normalized in response to rosiglitazone and bezafibrate. The proteins of MnSOD2, PPAR-α and PPAR-γ in the FED rats decreased (2.5, 2, and 2.2, respectively) (p<0.05). Following administration of rosiglitazone, proteins of MnSOD2, PPAR-α and PPAR-γ in the FED rats increased (reaching 1.5-fold, a 20% increase and normalization, respectively), (p<0.05). Administration of bezafibrate to the FED rats restored the proteins of 3 genes to baseline.

Conclusion

A consistent reduction in hepatic expression of MnSOD2, PPAR-α and PPAR-γ in the FED rats compared with controls was observed. Administration of either rosiglitazone or bezafibrate to the FED rats restored these genes to a pre-morbid state.

Is nonalcoholic fatty liver disease the hepatic expression of the metabolic syndrome?

Nonalcoholic fatty liver disease (NAFLD) is generally considered as the hepatic manifestation of the metabolic syndrome (MS). Although there is no doubt that NAFLD is tightly linked to the MS, the diagnosis of NAFLD encompasses a broad range of histological entities and as a composite phenotype may be hindering attempts to understand the mechanistic basis of these variants. The awareness that NAFLD is not solely and invariably associated with the MS is a useful means to help direct future studies. We should be aware that mechanisms other than insulin resistance may contribute to the chronic inflammatory processes that underpin the development of liver fat accumulation and the subsequent architectural distortion of the liver. Further studies with special focus on hemoglobin as a risk factor for the development of NAFLD in the absence of MS should be performed.

Nonalcoholic fatty liver disease is associated with atherosclerosis in middle-aged and elderly Chinese

OBJECTIVE

To evaluate the associations between nonalcoholic fatty liver disease (NAFLD) and atherosclerosis.

METHODS AND RESULTS

A total of 8632 participants aged ≥ 40 years from Jiading district, Shanghai, were included in the present study. The presence of NAFLD was evaluated by ultrasonography. Carotid intima-media thickness (CIMT) and brachial-ankle pulse wave velocity (ba-PWV) were measured in each participant. The prevalence of NAFLD was 30.0% in the total population, with 30.3% in men and 29.9% in women, respectively. Subjects with NAFLD had remarkably higher CIMT and ba-PWV compared with those without NAFLD (0.594 ± 0.105 mm versus 0.578±0.109 mm, P<0.0001; 1665 ± 424 cm/s versus 1558 ± 430 cm/s, P<0.0001). Subjects with both NAFLD and metabolic syndrome had significantly higher CIMT and ba-PWV compared with those with neither or either of these 2 diseases after adjustment for age and sex (all P<0.05). Logistic regressions also revealed that NAFLD conferred 35% and 30% increased odds ratios of elevated CIMT and ba-PWV, independent of conventional risk factors and the presence of metabolic syndrome.

CONCLUSIONS

NAFLD was associated with elevated CIMT and ba-PWV, independent of conventional cardiovascular disease risk factors and metabolic syndrome. The effects of NAFLD and metabolic syndrome on atherosclerosis might not fully overlap.

Characterization of nonalcoholic fatty liver disease unrelated to the metabolic syndrome

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome (MS). However, not all patients with the MS will develop NAFLD and not all patients with NAFLD have the MS. We sought to investigate the differences between patients with biopsy-proven NAFLD with and without the MS.

METHODS

A total of 357 consecutive patients with biopsy-proven NAFLD were analysed. Of them, 216 patients had nonalcoholic steatohepatitis (NASH) and 96 a fibrosis score ≥ 2. The MS was defined as ≥ 3 of the ATP III criteria.

RESULTS

A total of 214 patients with NAFLD met the criteria for the MS, while the remaining 143 did not. In NAFLD patients with the MS, homeostasis model of insulin resistance (P = 0·03; OR, 1·06; 95% CI, 1·023-1·25 per unit increase) and diabetes (P = 0·01; OR, 1·2; 95% CI, 1·1-2·4) were independent predictors of NASH. In NAFLD patients without the MS, the only variable independently associated with NASH was haemoglobin (P = 0·007; OR, 1·9; 95% CI, 1·4-3·6 per 50 g/L increase). Alanine aminotransferase (P = 0·03; OR, 1·04; 95% CI, 1·006-1·11 per 10 U/L increase) was an independent predictor of fibrosis ≥ 2 in NAFLD patients with the MS, while haemoglobin (P = 0·02; OR, 1·4; 95% CI, 1·2-1·9 per 50 g/L increase) was the only variable significantly associated with fibrosis ≥ 2 in NAFLD patients without the MS.

CONCLUSIONS

Increased haemoglobin in NAFLD subjects without MS should be considered in the selection of cases for histological assessment.

Obesity-dependent metabolic signatures associated with nonalcoholic fatty liver disease progression

Our understanding of the mechanisms by which nonalcoholic fatty liver disease (NAFLD) progresses from simple steatosis to steatohepatitis (NASH) is still very limited. Despite the growing number of studies linking the disease with altered serum metabolite levels, an obstacle to the development of metabolome-based NAFLD predictors has been the lack of large cohort data from biopsy-proven patients matched for key metabolic features such as obesity. We studied 467 biopsied individuals with normal liver histology (n=90) or diagnosed with NAFLD (steatosis, n=246; NASH, n=131), randomly divided into estimation (80% of all patients) and validation (20% of all patients) groups. Qualitative determinations of 540 serum metabolite variables were performed using ultraperformance liquid chromatography coupled to mass spectrometry (UPLC-MS). The metabolic profile was dependent on patient body-mass index (BMI), suggesting that the NAFLD pathogenesis mechanism may be quite different depending on an individual's level of obesity. A BMI-stratified multivariate model based on the NAFLD serum metabolic profile was used to separate patients with and without NASH. The area under the receiver operating characteristic curve was 0.87 in the estimation and 0.85 in the validation group. The cutoff (0.54) corresponding to maximum average diagnostic accuracy (0.82) predicted NASH with a sensitivity of 0.71 and a specificity of 0.92 (negative/positive predictive values=0.82/0.84). The present data, indicating that a BMI-dependent serum metabolic profile may be able to reliably distinguish NASH from steatosis patients, have significant implications for the development of NASH biomarkers and potential novel targets for therapeutic intervention.

Niemann-pick C1-like 1 (NPC1L1) protein in intestinal and hepatic cholesterol transport

Increased blood cholesterol is an independent risk factor for atherosclerotic cardiovascular disease. Cholesterol homeostasis in the body is controlled mainly by endogenous synthesis, intestinal absorption, and hepatic excretion. Niemann-Pick C1-Like 1 (NPC1L1) is a polytopic transmembrane protein localized at the apical membrane of enterocytes and the canalicular membrane of hepatocytes. It functions as a sterol transporter to mediate intestinal cholesterol absorption and counter-balances hepatobiliary cholesterol excretion. NPC1L1 is the molecular target of ezetimibe, a potent cholesterol absorption inhibitor that is widely used in treating hypercholesterolemia. Recent findings suggest that NPC1L1 deficiency or ezetimibe treatment also prevents diet-induced hepatic steatosis and obesity in addition to reducing blood cholesterol. Future studies should focus on molecular mechanisms underlying NPC1L1-dependent cholesterol transport and elucidation of how a cholesterol transporter modulates the pathogenesis of metabolic diseases.

Correlation of hepatic vein Doppler waveform and hepatic artery resistance index with the severity of nonalcoholic fatty liver disease

PURPOSE

The study was conducted to evaluate the effect of various degrees of fatty infiltration in patients with nonalcoholic fatty liver disease on hepatic artery resistance index and hepatic vein waveform patterns.

METHODS

After identification and grading of fatty infiltration, 60 patients and 20 normal healthy subjects were examined using color and spectral Doppler sonography. The level of fatty liver infiltration was ascertained and graded by biopsy in patients and excluded by MRI in controls. The patients were allocated to four study groups consecutively, until the required number was reached, according to infiltration level as follows: normal (group A), mild (group B), moderate (group C), and severe (group D). The hepatic vein waveforms were classified into the three following groups: triphasic, biphasic, and monophasic waveform. The hepatic artery resistance index was calculated as the mean of three different measurements.

RESULTS

The incidence of monophasic and biphasic hepatic vein waveform was 2 (10%) for group B, 11 (55%) for group C, 16 (80%) for group D, and none for group A. The difference in the distribution of triphasic Doppler waveform pattern between the patients and the control group was significant (p < 0.001). Hepatic artery resistance index was 0.81 (+ or - 0.02), 0.78 (+ or - 0.03), 0.73 (+ or - 0.03), and 0.68 (+ or - 0.05), respectively, in groups A, B, C, and D and was significantly different between groups (p < 0.001).

CONCLUSION

As the severity of nonalcoholic fatty infiltration increases, the incidence of abnormal hepatic vein waveforms increases and hepatic artery resistance index decreases.

A novel role for the dioxin receptor in fatty acid metabolism and hepatic steatosis

BACKGROUND & AIMS

The aryl hydrocarbon receptor (AhR) also known as the dioxin receptor or xenobiotic receptor is a member of the basic helix-loop-helix/period AhR nuclear translocator single minded family. The goal of this study was to determine the endobiotic role of AhR in hepatic steatosis.

METHODS

Wild-type, constitutively activated AhR transgenic, AhR null and CD36/fatty acid translocase null mice were used to investigate the role of AhR in steatosis and the involvement of CD36 in the steatotic effect of AhR. The promoters of the mouse and human CD36 genes were cloned and their regulation by AhR was analyzed.

RESULTS

Activation of AhR induced spontaneous hepatic steatosis characterized by the accumulation of triglycerides. The steatotic effect of AhR likely is owing to the combined up-regulation of CD36 and fatty acid transport proteins, suppression of fatty acid oxidation, inhibition of hepatic export of triglycerides, increase in peripheral fat mobilization, and increased hepatic oxidative stress. Promoter analysis established CD36 as a novel transcriptional target of AhR. Activation of AhR in liver cells induced CD36 gene expression and enhanced fatty acid uptake. The steatotic effect of an AhR agonist was inhibited in CD36-/- mice.

CONCLUSIONS

Our study reveals a novel link between AhR-induced steatosis and the expression of CD36. Industrial or military exposures to dioxin and related compounds have been linked to increased prevalence of fatty liver in human beings. Results from this study may help to establish AhR and its target CD36 as novel therapeutic and preventive targets for fatty liver disease.

Crucial role of impaired Kupffer cell phagocytosis on the decreased Sonazoid-enhanced echogenicity in a liver of a nonalchoholic steatohepatitis rat model

AIMS

To evaluate the dynamics of Kupffer cell (KC) phagocytosis by performing both in vivo and in vitro studies using Sonazoid (GE Healthcare, Oslo) in a rat nonalcoholic steatohepatitis (NASH) model.

METHODS

Contrast enhanced ultrasonography (CEUS) was performed on a rat NASH model induced by a methionine choline deficient diet (MCDD) and control rats, and Sonazoid was used to measure the signal intensity in the liver parenchyma. The uptake of Sonazoid by the KCs was observed by intravital microscopy. Their phagocytic capability was evaluated in vitro using isolated and cultured KCs. The uptake of fluorescein isothiocyanate (FITC)-labeled latex beads was observed and quantitatively analyzed by flow cytometry.

RESULTS

In the MCDD group, liver parenchymal enhancement was reduced 20 min after the Sonazoid injection. Microscopic observation of the isolated and cultured KCs revealed that the number of phagocytosed Sonazoid microbubbles was significantly decreased. Confocal laser scanning microscopic (CLSM) observation showed a decrease in the uptake of the latex beads. A decreased phagocytic capacity in the MCDD group was suggested by the quantitative analysis using flow cytometry, as well as by intravital microscopy.

CONCLUSIONS

CEUS with Sonazoid is a powerful evaluation tool to diagnose NASH from an early stage of the disease.

Hepatic lipotoxicity and the pathogenesis of nonalcoholic steatohepatitis: the central role of nontriglyceride fatty acid metabolites

A significant body of evidence now forces us to rethink the causes of NASH. Once thought to be a disease caused by triglyceride accumulation in hepatocytes with subsequent oxidant stress and lipid peroxidation causing inflammation and fibrosis, new data from animal studies and a limited number of human studies now provide convincing evidence that triglyceride accumulation does not cause insulin resistance or cellular injury in the liver. The lipotoxic liver injury hypothesis for the pathogenesis of NASH suggests that we need to focus our therapeutic efforts on reducing the burden of fatty acids going to the liver or being synthesized in the liver. This can be accomplished by improving insulin sensitivity at the level of adipose tissue to prevent inappropriate peripheral lipolysis and by preventing unnecessary de novo lipogenesis in the liver. Excess carbohydrates are the major substrates for de novo lipogenesis, and thus, reducing carbohydrate consumption through dietary changes and increasing muscle glucose uptake through exercise remain important cornerstones of treatment and prevention of lipotoxic liver injury, a disease hitherto called NASH.

Mice with null mutation of Ceacam I develop nonalcoholic steatohepatitis

Transgenic liver-specific inactivation of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM1) impairs hepatic insulin clearance and causes hyperinsulinemia, insulin resistance, elevation in hepatic and serum triglyceride levels, and visceral obesity. It also predisposes to nonalchoholic steatohepatitis (NASH) in response to a high-fat diet. To discern whether this phenotype reflects a physiological function of CEACAM1 rather than the effect of the dominant-negative transgene, we investigated whether Ceacam1 (gene encoding CEACAM1 protein) null mice with impaired insulin clearance also develop a NASH-like phenotype on a prolonged high-fat diet. Three-month-old male null and wild-type mice were fed a high-fat diet for 3 months and their NASH phenotype was examined. While high-fat feeding elevated hepatic triglyceride content in both strains of mice, it exacerbated macrosteatosis and caused NASH-characteristic fibrogenic changes and inflammatory responses more intensely in the null mouse. This demonstrates that CEACAM1-dependent insulin clearance pathways are linked with NASH pathogenesis.

Thioredoxin-binding protein-2 deficiency enhances methionine-choline deficient diet-induced hepatic steatosis but inhibits steatohepatitis in mice

In nonalcoholic fatty liver disease, oxidative stress is believed to play a crucial role as a second-hit for the progression of simple steatosis to steatohepatitis. Thioredoxin (TRX) is a potent antioxidant molecule that exerts anti-apoptotic and anti-inflammatory functions. TRX-binding protein-2 (TBP-2) is an endogenous negative regulator of TRX. Deficiency of TBP-2 in mice causes hyperlipidemia, hepatic steatosis, hypoglycemia, and bleeding tendency, resembling Reye syndrome in a fasting/glucose-deficient state. The aim of this study was to investigate the role of TBP-2 in the development of nonalcoholic steatohepatitis (NASH). TBP-2-deficient (TBP-2(-/-)) and wild-type (WT) mice were fed either a normal or methionine-choline-deficient (MCD) diet for up to 10 weeks. Compared with WT mice, TBP-2(-/-) mice showed severe simple steatosis rather than steatohepatitis. However, oxidative stress determined by lipid peroxidation and DNA damage, neutrophil infiltration, and hepatic fibrosis were attenuated in TBP-2(-/-) mice. PCR analysis showed the expressions of fibrosis-inducing and inflammatory cytokine-related genes were less in TBP-2(-/-) mice. Moreover, leptin, SREBP1c, PPARgamma, and adipogenesis-lipogenesis-related genes were upregulated in TBP-2(-/-) mice. These results strongly suggested that TBP-2 might be involved in pathogenesis of NASH in WT mice, and inhibitors of TBP-2 could be useful in the prevention or treatment of NASH.

Bile acids and insulin resistance: implications for treating nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is characterized by an accumulation of excess triglycerides in hepatocytes, and insulin resistance is now considered the fundamental operative mechanism throughout the prevalence and progression of the disease. Besides their role in dietary lipid absorption and cholesterol homeostasis, evidence has accumulated that bile acids are also signaling molecules that play two important roles in glucose and lipid metabolism: in the nuclear hormone receptors as farnesoid X receptors (FXR), as well as ligands for G-protein-coupled receptors TGR5. The activated FXR-SHP pathway regulates the enterohepatic recycling and biosynthesis of bile acids and underlies the down-regulation of hepatic fatty acid and triglyceride biosynthesis and very low density lipoprotein production mediated by sterol-regulatory element-binding protein-1c. The bile acid-TGR5-cAMP-D2 signaling pathway in human skeletal muscle in the fasting-feeding cycle increases energy expenditure and prevents obesity. Therefore, a molecular basis has been provided for a link between bile acids, lipid metabolism and glucose homeostasis, which can open novel pharmacological approaches against insulin resistance and nonalcoholic fatty liver disease.

The alpha-glucosidase inhibitor acarbose prevents obesity and simple steatosis in sequestosome 1/A170/p62 deficient mice

AIM

Sequestosome 1 (SQSTM1)/A170/p62 plays an important role in membrane-receptor mediated signal transduction and autophagic protein degradation. Although the mechanism involved is not clear, sqstm1 gene knockout (KO) mice develop mature-onset obesity and insulin resistance, leading to type II diabetes. KO mice show accumulation of fat in white adipose tissue and the liver when fed a standard diet. Acarbose is an alpha-glucosidase inhibitor that improves insulin sensitivity and decreases postprandial hyperglycemia, and it is used to treat type 2 diabetes. We examined whether or not dietary acarbose prevented obesity and simple steatosis in KO mice.

METHODS

Wild-type (WT) and KO mice were fed a standard diet with or without acarbose (0.8% w/w) from 15-25 weeks of age. The body weight and the fat content of adipose tissue and the liver were measured, and changes of lipid metabolism in these tissues were assessed from gene expression.

RESULTS

Acarbose treatment suppressed weight gain and the development of hepatic steatosis in KO mice. Acarbose treatment up-regulated hepatic expression of the pparalpha, ucp-2, and abca1 genes, as well as srebp1c, pparalpha, and ppargamma in adipose tissue. In WT mice, however, acarbose treatment had little influence on weight gain and gene expression.

CONCLUSIONS

The results of this study suggest that long-term administration of acarbose is effective for prevention of obesity and simple steatosis in SQSTM1-KO mice.

[Nonalcoholic steatohepatitis: pathogenesis and treatment]

Nonalcoholic fatty liver disease (NAFLD) is characterized by a wide spectrum of liver damage spanning steatosis, nonalcoholic steatohepatitis (NASH), cryptogenic liver cirrhosis, and even to hepatocellular carcinoma. Investigations in the last few years have focused on NASH, a relatively aggressive form of liver disease, due largely to the explosion of information provided by clinical and basic science studies related to the widespread presence of risk factors, such as obesity, type II diabetes mellitus, and dyslipidemia. This is especially important given that obesity and type II diabetes mellitus have recently reached epidemic proportions in Korea. The pathogenesis of NASH is multifactorial, with insulin resistance and increased fatty acid possibly being important factors in the accumulation of hepatocellular fat, and oxidant stress, lipid peroxidation, mitochondrial dysfunction, and dysregulation of variable cytokines possibly being important causes of hepatocellular injury in steatotic liver. Because not all steatotic livers progress to NASH, some other environmental factors or a combination of genetic factors are thought to be required for progression to NASH and fibrosis. Lifestyle modifications continue to be the cornerstone therapy in NAFLD, but some insulin-sensitizing drugs might be more effective in treating NASH. Many pilot trials for antioxidants and lipid-lowering and hepatic protective agents have yielded promising initial results in improving liver enzymes or features of liver histology. However, the efficacy of these agents remains questionable. Despite recent gains in understanding NASH, several issues related to its natural history, pathogenesis, and treatment remain unresolved.

Development of nonalcoholic steatohepatitis in insulin-resistant liver-specific S503A carcinoembryonic antigen-related cell adhesion molecule 1 mutant mice

BACKGROUND & AIMS

Liver-specific inactivation of carcinoembryonic antigen-related cell adhesion molecule 1 causes hyperinsulinemia and insulin resistance, which result from impaired insulin clearance, in liver-specific S503A carcinoembryonic antigen-related cell adhesion molecule 1 mutant mice (L-SACC1). These mice also develop steatosis. Because hepatic fat accumulation precedes hepatitis, lipid peroxidation, and apoptosis in the pathogenesis of nonalcoholic steatohepatitis (NASH), we investigated whether a high-fat diet, by causing inflammation, is sufficient to induce hepatitis and other features of NASH in L-SACC1 mice.

METHODS

L-SACC1 and wild-type mice were placed on a high-fat diet for 3 months, then several biochemical and histologic analyses were performed to investigate the NASH phenotype.

RESULTS

A high-fat diet caused hepatic macrosteatosis and hepatitis, characterized by increased hepatic tumor necrosis factor alpha levels and activation of the NF-kappaB pathway in L-SACC1 but not in wild-type mice. The high-fat diet also induced necrosis and apoptosis in the livers of the L-SACC1 mice. Insulin resistance in L-SACC1 fed a high-fat diet increased the hepatic procollagen protein level, suggesting a role in the development of fibrosis.

CONCLUSIONS

A high-fat diet induces key features of human NASH in insulin-resistant L-SACC1 mice, validating this model as a tool to study the molecular mechanisms of NASH.

Hepatic triglyceride synthesis and nonalcoholic fatty liver disease

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease is a spectrum of diseases ranging from simple steatosis to cirrhosis. The hallmark of nonalcoholic fatty liver disease is hepatocyte accumulation of triglycerides. We will review the role of triglyceride synthesis in nonalcoholic fatty liver disease progression and summarize recent findings about triglyceride synthesis inhibition and prevention of progressive disease.

RECENT FINDINGS

Attempts to inhibit triglyceride synthesis in animal models have resulted in improvement in hepatic steatosis. Studies in animal models of nonalcoholic fatty liver disease demonstrate that inhibition of acyl-coenzyme A:diacylglycerol acyltransferase, the enzyme that catalyzes the final step in triglyceride synthesis, results in improvement in hepatic steatosis and insulin sensitivity. We recently confirmed that hepatic specific inhibition of acyl-coenzyme A:diacylglycerol acyltransferase with antisense oligonucleotides improves hepatic steatosis in obese, diabetic mice but, unexpectedly, exacerbated injury and fibrosis in that model of progressive nonalcoholic fatty liver disease. When hepatocyte triglyceride synthesis was inhibited, free fatty acids accumulated in the liver, leading to induction of fatty acid oxidizing systems that increased hepatic oxidative stress and liver damage. These findings suggest that the ability to synthesize triglycerides may, in fact, be protective in obesity.

SUMMARY

Nonalcoholic fatty liver disease is strongly associated with obesity and peripheral insulin resistance. Peripheral insulin resistance increases lipolysis in adipose depots, promoting increased free fatty acid delivery to the liver. In states of energy excess, such as obesity, the latter normally triggers hepatic triglyceride synthesis. When hepatic triglyceride synthesis is unable to accommodate increased hepatocyte free fatty acid accumulation, however, lipotoxicity results. Thus, rather than being hepatotoxic, liver triglyceride accumulation is actually hepato-protective in obese, insulin-resistant individuals.

Significant correlations between severe fatty liver and risk factors for metabolic syndrome

BACKGROUND AND AIM

It is known that ultrasonography (US) cannot differentiate between non-alcoholic fatty liver disease (NAFLD) and steatohepatitis. However, US can accurately estimate the severity of the steatosis. The clinical significance of severe hepatic fatty change by US has not been explored. The aim of this study was to investigate the relationship between the severity of the fatty liver, classified by US, and the degree of metabolic disorders with insulin resistance.

METHODS

In 16 486 Taiwanese patients, severity of fatty change on US was classified as follows: group A (n = 6950), absence of fatty change; group B (n = 8694), mild; and group C (n = 842), severe fatty liver change. Biometabolic parameters included body mass index (BMI), blood pressure (BP), fasting plasma glucose, triglycerides, cholesterol, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and serum creatinine. Nominal logistic regression analysis was used to estimate the odds ratio for different degrees of fatty liver.

RESULTS

The frequencies of obesity, hypertension, glucose intolerance and hypertriglyceridemia were all significantly higher in group C than in group A or B (P < 0.0001), and the mean values of BMI, BP, fasting glucose, triglyceride and ALT were also higher in group C (P < 0.0001). High BMI (>or=30 kg/m(2)) appears to be the most important factor for progression from mild to severe fatty liver in both sexes.

CONCLUSIONS

The presence of severe fatty liver by US correlated significantly with the prevalence and degree of hypertension, abnormal glucose and triglyceride metabolism. Patients with severe fatty liver could be at an increased risk of atherosclerotic cardiovascular disease and should be screened regularly for metabolic disorders. The physician may also evaluate ALT and hepatic fat content by US in patients with metabolic syndrome. Evaluating the severity of fatty liver by US may be useful because it correlates with the status of hyperinsulinemia, the risks of developing cardiovascular disease, and the threshold for oxidative stress.

Nonalcoholic fatty liver disease as a complication of insulin resistance

Nonalcoholic fatty liver disease (NAFLD) refers to a spectrum of liver damage ranging from simple steatosis to nonalcoholic steatohepatitis, advanced fibrosis, and rarely, progression to cirrhosis. The pathogenesis of NAFLD is thought to be related to insulin resistance and oxidant stress. Truncal obesity, dyslipidema, hypertension, and hyperglycemia are strongly associated with NAFLD; therefore, management of NAFLD entails identification and treatment of metabolic risk factors, improving insulin sensitivity, and increasing antioxidant defenses in the liver. This article briefly summarizes advances in our understanding of the relationship between NAFLD and the insulin resistance (metabolic) syndrome, its prevalence, natural history, and treatment.

Nutritional Status of Vitamin A in Morbid Obesity before and after Roux-en-Y Gastric Bypass

The objective of the present study was to identify the factors which contribute to the appearance and/or aggravation of Vitamin A Deficiency (VAD) in individuals with morbid obesity in the pre- and postoperative stages of Roux-en-Y gastric bypass (RYGBP). Bibliography searches were done in the data-bases of Medline and Lilacs, published in the last 35 years, priorizing the studies which assessed VAD through serum levels of retinol. The principal factors identified as contributors to VAD were oxidative stress, deficiency of other nutrients, lipid malabsorption in the postoperative stage, insufficient intake of lipids and food sources of Vitamin A, and presence of nonalcoholic fatty liver disease. The investigation of the nutritional status of Vitamin A in those individuals may foment intervention strategies easily incorporated in already established routine procedures, aiming to reduce VAD rates, which will reflect upon those individuals' quality of life.

Angiotensin II type 1 receptor blocker inhibits fibrosis in rat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is now the most frequent cause of chronic liver impairment in developed countries and is a suggested causative factor in the development of cryptogenic cirrhosis and hepatocellular carcinoma. At present there is no effective and accepted therapy for NASH. The renin-angiotensin system is involved in hepatic fibrosis through activation of hepatic stellate cells, major fibrogenic cells in the liver. Hepatic stellate cells are activated by liver injury to express excessive matrix proteins and profibrogenic cytokines such as transforming growth factor-beta 1. Medicines that inhibit this pathway may be of therapeutic potential in NASH. Using a methionine-choline-deficient rat model of NASH, we studied the potential utility of an angiotensin II type 1 receptor blocker (ARB), olmesartan, on biochemical, histologic, and antioxidant measures of disease activity. ARB significantly attenuated increases in aspartate aminotransferase, activation of hepatic stellate cells, oxidative stress, expression of transforming growth factor-beta 1, expression of collagen genes, and liver fibrosis.

CONCLUSION

Our observations strongly suggest a potential preventive role for ARB in the progression of nonalcoholic steatohepatitis.

Current concepts in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is an increasingly recognized cause of chronic liver disease, representing the leading cause of hepatology referral in some centres. However, its pathophysiology is not completely understood. Insulin resistance is one of the major mechanisms involved in disease prevalence and progression. Owing to the lack of an effective pharmacological therapy, recommendations on treatment are scarce and are based mainly on lifestyle changes, including diet and exercise. A review of the current literature on pathogenesis of NAFLD is presented in this article.

Steatosis as a risk factor in liver surgery

OBJECTIVE

To review present knowledge of the influence of hepatic steatosis in liver surgery as derived from experimental and clinical studies.

SUMMARY BACKGROUND DATA

Hepatic steatosis is the most common chronic liver disease in the Western world, and it is associated with obesity, diabetes, and metabolic syndrome. Fatty accumulation affects hepatocyte homeostasis and potentially impairs recovery of steatotic livers after resection. This is reflected clinically in increased mortality and morbidity after liver resection in patients with any grade of steatosis. Because of the epidemic increase of obesity, hepatic steatosis will play an even more significant role in liver surgery.

METHODS

A literature review was performed using MEDLINE and key words related to experimental and clinical studies concerning steatosis.

RESULTS

Experimental studies show the increased vulnerability of steatotic livers to various insults, attributed to underlying metabolic and pathologic derangements induced by fatty accumulation. In clinical studies, the severity of steatosis has an important impact on patient outcome and mortality. Even the mildest form of steatosis increases the risk of postoperative complications.

CONCLUSIONS

Hepatic steatosis is a major factor determining patient outcome after surgery. Further research is needed to clarify the clinical relevance of all forms and severity grades of steatosis for patient outcome. Standardized grading and diagnostic methods need to be used in future clinical trials to be able to compare outcomes of different studies.

Effect of insulin-sensitizing agents in combination with ezetimibe, and valsartan in rats with non-alcoholic fatty liver disease

AIM: To assess whether treatment with insulin-sensitizing agents (ISAs) in combination with ezetimibe and valsartan have greater effect on hepatic fat content and lipid peroxidation compared to monotherapy in the methionine choline-deficient diet (MCDD) rat model of non-alcoholic fatty liver disease (NAFLD).

METHODS: Rats (n = 6 per group) were treated with different drugs, including MCDD only, MCDD diet with either metformin (200 mg/kg), rosiglitazone (3 mg/kg), metformin plus rosiglitazone (M+R), ezetimibe (2 mg/kg), valsartan (2 mg/kg), or combination of all drugs for a total of 15 wk. Liver histology, lipids, parameters of oxidative stress and TNF-alpha were measured.

RESULTS: Fatty liver (FL) rats demonstrated severe hepatic fatty infiltration (> 91% fat), with an increase in hepatic TG (+1263%, P < 0.001), hepatic cholesterol (+245%, P < 0.03), hepatic MDA levels (+225%, P < 0.001), serum TNF-alpha (17.8 ± 10 vs 7.8 ± 0.0, P < 0.001), but a decrease in hepatic alpha tocopherol (-74%, P < 0.001) as compared to the control rats. Combination therapy with all drugs produced a significant decrease in liver steatosis (-54%), hepatic TG (-64%), hepatic cholesterol (-31%) and hepatic MDA (-70%), but increased hepatic alpha tocopherol (+443%) as compared to FL rats. Combination therapy with ISA alone produced a smaller decrease in liver steatosis (-32% vs -54%, P < 0.001) and in hepatic MDA levels (-55% vs -70%, P < 0.01), but a similar decrease in hepatic lipids when compared with the all drugs combination. TNF-alpha levels decreased significantly in all treatment groups except in ISA group.

CONCLUSION: Combination therapies have a greater effect on liver fat content as compared to monotherapy. Rosiglitazone appears to improve hepatic steatosis to a greater extent than metformin.

COX-2 induction in mice with experimental nutritional steatohepatitis: Role as pro-inflammatory mediator

The underlying mechanisms that perpetuate liver inflammation in nonalcoholic steatohepatitis are poorly understood. We explored the hypothesis that cyclooxygenase-2 (COX-2) can exert pro-inflammatory effects in metabolic forms of fatty liver disease. Male wild-type (WT) C57BL6/N or peroxisome proliferator-activated receptor alpha knockout (PPAR-alpha-/-) mice were fed a lipogenic, methionine- and choline-deficient (MCD) diet or the same diet with supplementary methionine and choline (control). COX-2 was not expressed in livers of mice fed the control diet. In mice fed the MCD diet, hepatic expression of COX-2 messenger RNA and protein occurred from day 5, continued to rise, and was 10-fold higher than controls after 5 weeks, thereby paralleling the development of steatohepatitis. Upregulation of COX-2 was even more pronounced in PPAR-alpha-/- mice. Induction of COX-2 was completely prevented by dietary supplementation with the potent PPAR-alpha agonist Wy-14,643 in WT but not PPAR-alpha-/- mice. COX-2 upregulation was preceded by activation of nuclear factor kappaB (NF-kappaB) and coincided with increased levels of tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, and intercellular adhesion molecule 1 (ICAM-1). Selective COX-2 inhibitors (celecoxib and NS-398) protected against the development of steatohepatitis in WT but not PPAR-alpha-/- mice. In conclusion, induction of COX-2 occurs in association with NF-kappaB activation and upregulation of TNF-alpha, IL-6, and ICAM-1 in MCD diet-induced steatohepatitis. PPAR-alpha suppresses both COX-2 and development of steatohepatitis, while pharmacological inhibition of COX-2 activity ameliorates the severity of experimental steatohepatitis. COX-2 may therefore be a pro-inflammatory mediator in metabolic forms of steatohepatitis.

Effects of bezafibrate, PPAR pan-agonist, and GW501516, PPARδ agonist, on development of steatohepatitis in mice fed a methionine- and choline-deficient diet

We evaluated the effects of bezafibrate, a peroxisome proliferator-activated receptor (PPAR) pan-agonist, and GW501516, a PPARdelta agonist, on mice fed a methionine- and choline-deficient (MCD) diet, a model of non-alcholic steatohepatitis (NASH), to investigate (a) the efficacy of bezafibrate against non-alcholic steatohepatitis and (b) the relation between non-alcholic steatohepatitis and the functional role of PPARdelta. Bezafibrate (50 or 100 mg/kg/day) and GW501516 (10 mg/kg/day) were administered by gavage once a day for 5 weeks. Hepatic lipid contents, plasma triglyceride, high density lipoprotein (HDL)-cholesterol and alanine aminotransferase (ALT) concentrations were evaluated, as were histopathological changes in the liver and hepatic mRNA expression levels. Bezafibrate and GW501516 inhibited the MCD-diet-induced elevations of hepatic triglyceride and thiobarbituric acid-reactants contents and the histopathological increases in fatty droplets within hepatocytes, liver inflammation and number of activated hepatic stellate cells. In this model, bezafibrate and GW501516 increased the levels of hepatic mRNAs associated with fatty acid beta-oxidation [acyl-CoA oxidase (ACO), carnitine palmitoyltransferase-1 (CPT-1), liver-fatty acid binding protein (L-FABP) and peroxisomal ketothiolase], and reduced the levels of those associated with inflammatory cytokines or chemokine [transforming growth factor (TGF)-beta1, interleukin (IL)-6, IL-1beta, monocyte chemoattractant protein (MCP)-1, tumor necrosis factor (TNF) alpha and nuclear factor (NF)-kappaB1]. In addition, bezafibrate characteristically reduced the elevation in the level of plasma ALT, but enhanced that in plasma adiponectin and increased the mRNA expression levels of its receptors (adiponectin receptors 1 and 2). These results suggest that (a) bezafibrate (especially) and GW501516 might improve hepatic steatosis via an improvement in fatty acid beta-oxidation and a direct prevention of inflammation, (b) treatment with a PPARdelta agonist might improve non-alcholic steatohepatitis, (c) bezafibrate may improve non-alcholic steatohepatitis via activation not only of PPARalpha but also of PPARdelta, because bezafibrate is a PPAR pan-agonist.

Serum levels of hepatoprotective peptide adiponectin in non-alcoholic fatty liver disease

OBJECTIVE

Adiponectin is an adipose tissue-specific protein that has anti-inflammatory, antidiabetic and antiobesity effects. It has been suggested that adiponectin has a hepatoprotective role. Non-alcoholic fatty liver disease (NAFLD) is becoming more prevalent with increasingly adverse clinical outcomes. In this study, serum adiponectin levels were investigated in patients with NAFLD to determine its possible role on hepatic inflammation and injury.

METHODS

Twenty-nine biopsy-proven NAFLD patients (14 women, 15 men) with elevated liver enzymes, 20 clinically diagnosed NAFLD patients (13 women, seven men) with normal liver enzymes, and 20 healthy adults (10 women, 10 men) were enrolled. From fasting blood samples, serum adiponectin levels were measured by enzyme-linked immunosorbent assay. The body mass index, serum glucose, insulin, cholesterol and triglyceride levels were determined.

RESULTS

Serum adiponectin levels were 4.99+/-2.1, 9.49+/-3.91 and 7.74+/-4.41 micro/ml in the NAFLD with elevated liver enzymes, NAFLD with normal liver enzymes and healthy adult control groups, respectively. The mean serum adiponectin level in the NAFLD with elevated liver enzymes group was significantly lower than those of other groups tested (P<0.001). Insulin, cholesterol and triglyceride levels of NAFLD patients with elevated liver enzymes were significantly higher than control groups (P<0.05) but were not significantly different from the NAFLD group with normal liver enzymes (P>0.05). On histopathologic examination, the mean serum adiponectin levels of non-alcoholic steatohepatitis patients with grade 2 or more inflammatory activity was significantly lower than patients with grade 1 inflammatory activity (P=0.013).

CONCLUSION

Serum adiponectin levels are significantly lower in NAFLD patients with elevated liver enzymes. Non-alcoholic steatohepatitis patients show lower levels of adiponectin with higher grades of inflammation.

Measurement of the total antioxidant response using a novel automated method in subjects with nonalcoholic steatohepatitis

BACKGROUND

Oxidative stress, an increase in oxidants and/or a decrease in antioxidant capacity, is one of the potential biochemical mechanisms involved in the pathogenesis of nonalcoholic steatohepatitis. We aimed to investigate the total antioxidant response using a novel automated method in nonalcoholic steatohepatitis subjects. As a reciprocal measure, we also aimed to determine total peroxide level in the same plasma samples.

METHODS

Twenty-two subjects with biopsy proven nonalcoholic steatohepatitis and 22 healthy controls were enrolled. Total antioxidant response and total peroxide level measurements were done in all participants. The ratio percentage of total peroxide level to total antioxidant response was regarded as oxidative stress index.

RESULTS

Total antioxidant response of subjects with nonalcoholic steatohepatitis was significantly lower than controls (p < 0.05), while mean total peroxide level and mean oxidative stress index were higher (all p < 0.05). In subjects with nonalcoholic steatohepatitis, fibrosis score was significantly correlated with total peroxide level, total antioxidant response and oxidative stress index (p < 0.05, r = 0.607; p < 0.05, r = -0.506; p < 0.05, r = 0.728, respectively). However, no correlation was observed between necroimflamatory grade and those oxidative status parameters (all p > 0.05).

CONCLUSION

Nonalcoholic steatohepatitis is associated with increased oxidant capacity, especially in the presence of liver fibrosis. The novel automated assay is a reliable and easily applicable method for total plasma antioxidant response measurement in nonalcoholic steatohepatitis.

Peroxisome Proliferator-Activated Receptor α L162V Polymorphism in Nonalcoholic Steatohepatitis and Genotype 1 Hepatitis C Virus-Related Liver Steatosis

BACKGROUND

Peroxisome proliferator-activated receptor alpha (PPARalpha) plays important roles in lipid metabolism. A recently discovered L162V polymorphism of the PPARalpha gene is associated with enhanced transcriptional activity. In this study, the frequency of L162V was investigated in nonalcoholic steatohepatitis (NASH) and genotype 1 hepatitis C virus (HCV)-related liver steatosis.

METHODS

Seventy-two NASH and 141 HCV-infected patients (54 with steatosis, 87 without steatosis) and 119 healthy controls were included. L162V polymorphism of the PPARalpha gene was analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).

RESULTS

PCR and RFLP analysis of the related gene segment was successful in 93%, 96%, and 100% of NASH and HCV-infected patients and controls, respectively. The frequency of the L162V polymorphism was similar in the NASH and HCV-infected patients and controls (5.9%, 3.6%, and 2.5%, respectively). No difference in the frequency of this polymorphism was observed in HCV-infected patients with or without significant liver steatosis. L162V was not associated with obesity, type 2 diabetes mellitus, hypercholesterolemia, or hypertriglyceridemia.

CONCLUSIONS

Neither NASH nor genotype 1 HCV-related liver steatosis seems to be associated with the PPARalpha L162V polymorphism. This polymorphism may have no association with the presence of type 2 diabetes mellitus, obesity, or various blood lipid alterations in NASH and HCV-infected patients.

Steatohepatitis develops rapidly in transgenic mice overexpressing Abcb11 and fed a methionine-choline-deficient diet

Nonalcoholic fatty liver disease is the most common reason for abnormal liver chemistries in the United States. The factors that lead from benign steatosis to nonalcoholic steatohepatitis are poorly understood. Transthyretin-Abcb11 (TTR-Abcb11) transgenic mice overexpress the bile salt transporter Abcb11 and hypersecrete biliary lipids. Thus the aim of this study is to employ feeding of the methionine-choline-deficient (MCD) diet to TTR-Abcb11 transgenic mice to further determine the mechanisms responsible for the development of steatohepatitis. FVB/NJ and TTR-Abcb11 mice were fed control or MCD diets for up to 30 days. Serum aminotransferase levels, serum and hepatic triglyceride content, cytokines, markers of oxidative stress, and expression of selective genes were examined. MCD diet-fed TTR-Abcb11, but not wild-type, mice have elevated serum aminotransferase levels when compared after 7 days. They also have significantly lower hepatic triglyceride levels at all time points studied. After 14 days on the MCD diet, TTR-Abcb11 mice have 3-fold increases in TNF-alpha mRNA and 3.9-fold increases in IL-6 mRNA compared with FVB/NJ mice. TTR-Abcb11 mice also had a greater increase in cytochrome P-450 2E1 expression. A greater decrease in sterol regulatory element binding protein-1c and fatty acid synthase mRNA expression was also seen in TTR-Abcb11 compared with wild-type mice fed an MCD diet. They also have enhanced TNF-alpha, IL-6, and cytochrome P-450 2E1 expression. We conclude that TTR-Abcb11 mice develop a more rapid hepatitis with less steatosis.

Fructose-induced fatty liver disease: hepatic effects of blood pressure and plasma triglyceride reduction

The most known risk factor for nonalcoholic fatty liver disease (NAFLD) is the metabolic syndrome. In this study, we characterized changes in liver pathology, hepatic lipid composition, and hepatic iron concentration (HIC) occurring in rats given fructose-enriched diet (FED), with and without therapeutic maneuvers to reduce blood pressure and plasma triglycerides. Rats were given FED or standard rat chow for 5 weeks. Rats on FED were divided into 4 groups: receiving amlodipine (15 mg/kg per day), captopril (90 mg/kg per day), bezafibrate (10 mg/kg per day) in the last 2 weeks, or a control group that received FED only. FED rats had hepatic macrovesicular and microvesicular fat deposits develop, with increase in hepatic triglycerides (+198%) and hepatic cholesterol (+89%), but a decrease in hepatic phospholipids (-36%), hypertriglyceridemia (+223%), and hypertension (+15%), without increase in HIC. Amlodipine reduced blood pressure (-18%), plasma triglycerides (-12%), but there was no change in hepatic triglycerides and phospholipids concentrations. Captopril reduced blood pressure (-24%), plasma triglycerides (-36%), hepatic triglycerides (-51%), and hepatic macrovesicular fat (-51%), but increased HIC (+23%), with a borderline increase in hepatic fibrosis. Bezafibrate reduced plasma triglycerides (-49%), hepatic triglycerides (-78%), hepatic macrovesicular fat (-90%), and blood pressure (-11%). We conclude that FED rats can be a suitable model for human NAFLD. Drugs administered to treat various aspects of the metabolic syndrome could have hepatic effects. An increase in HIC in rats with NAFLD could be associated with increased hepatic fibrosis.

Oxidative DNA damage and DNA repair enzyme expression are inversely related in murine models of fatty liver disease

Mitochondrial generation of reactive oxygen species (ROS) is increased in mice with fatty livers induced by genetic obesity, chronic consumption of ethanol, or methionine/choline-deficient diets. Both nuclear and mitochondrial (mt) DNA are targets for ROS-induced damage and accumulate hydroxylated bases, such as 8-hydroxy-2'-deoxyguanosine (8-oxoG) and base substitution of adenine with 8-oxoG (A*8-oxoG), that introduce mutations that promote cancer as well as cell death. The mammalian homolog of the bacterial DNA mismatch repair enzyme MutY (MYH) removes A*8-oxoG from nuclear and mtDNA, reduces 8-oxoG accumulation, and restores genomic stability after ROS exposure. Cumulative damage to mtDNA occurs as fatty liver disease progresses. Therefore, differences in hepatic MYH activity may influence the severity of fatty liver disease. To evaluate this hypothesis, we compared mtH2O2 production, MYH expression, oxidative DNA damage, and hepatocyte death in healthy mice and different mouse models of fatty liver disease. The results show that diverse causes of steatohepatitis increase mtROS production, limit repair of mtDNA, and oxidatively damage DNA. However, there are important differences in the DNA repair response to oxidant stress among mouse models of fatty liver disease. Independent of the degree of mtROS generation, models with the least MYH exhibit the greatest accumulation of 8-oxoG and the most hepatocyte death. These findings raise the intriguing possibility that inherited or acquired differences in DNA repair enzyme activity may underlie some of the interindividual differences in fatty liver disease outcomes.

Association between elevated liver enzymes and C-reactive protein: possible hepatic contribution to systemic inflammation in the metabolic syndrome

OBJECTIVE

The objective of this study was to test whether the frequent association between liver enzyme elevations and various components of the metabolic syndrome is associated with higher C-reactive protein (CRP) levels.

METHODS AND RESULTS

Alanine aminotransferase (ALT), alkaline phosphatase (Alk-P), and high-sensitivity CRP were measured in 1740 subjects. Adjusted geometric mean CRP was calculated for subjects with normal and elevated ALT and for subjects with normal and elevated Alk-P, adjusting for age, sex, smoking, physical activity, body mass index, fasting glucose, triglycerides, the presence of hypertension and low HDL cholesterol, and use of aspirin or hormone replacement therapy. Adjusted CRP levels were higher in subjects with elevated ALT (2.21 versus 1.94 mg/L, P=0.028) or elevated Alk-P (2.58 versus 1.66 mg/L, P<0.0001). Logistic regression showed that compared with subjects with normal liver function tests, the adjusted odds for high-risk CRP (>3 mg/L) were significantly higher in subjects with elevated ALT (OR, 1.5; 95% CI, 1.2 to 1.9, P=0.002) or elevated Alk-P (OR, 2.1; 95% CI, 1.7 to 2.6, P<0.0001).

CONCLUSIONS

Elevations of liver enzymes are associated with higher CRP concentrations. Hepatic inflammation secondary to liver steatosis is a potential contributor to the low-grade inflammation associated with the metabolic syndrome.

Pentoxifylline attenuates steatohepatitis induced by the methionine choline deficient diet

BACKGROUND/AIMS

Feeding mice a methionine choline deficient (MCD) diet serves as a nutritional model of non-alcoholic steatohepatitis (NASH). NASH and alcohol-induced steatohepatitis are histologically similar, suggesting a similar pathogenesis. Pentoxifylline (PTX) attenuates TNF-alpha production, acts as an antioxidant and decreases mortality in alcoholic steatohepatitis. The aim of our study is to determine if PTX attenuates MCD diet induced steatohepatitis and determine the mechanism of this effect.

METHODS

Mice were placed on an MCD or control diet for 2 weeks and were treated with or without PTX. Serum ALT, liver histology, and inflammatory mechanisms were evaluated.

RESULTS

PTX attenuates MCD diet induced steatohepatitis, decreasing both serum ALT levels and hepatic inflammation. Serum ALT levels were reduced approximately 50% in the MCD+PTX group compared to the MCD group. Hepatic glutathione levels were significantly higher in the MCD+PTX group compared to the MCD group. There was also a reduction in TNF-alpha mRNA in female mice treated with PTX. MCD+PTX mice had increased hepatic triglyceride content compared to the MCD mice, but less histologic evidence of inflammation despite the increased steatosis. Serum lipid and bile salt levels also were similar in PTX and vehicle control treated mice.

CONCLUSIONS

PTX decreases serum ALT levels and hepatic inflammation in the MCD model of steatohepatitis, likely via increasing glutathione levels or reducing TNF-alpha expression.

Obesity and alcoholic liver disease

Obesity potentiates the severity of alcohol-induced liver damage. Ethanol influences adipose tissue production of hormones and cytokines. The mechanisms by which adiposity and ethanol interact to produce hepatic steatosis and steatohepatitis are beginning to be studied. Exacerbation of the proinflammatory state that induces tumor necrosis factor activity and hepatic insulin resistance seems to be involved. However, the precise cellular signals that culminate in hepatocyte dysfunction and death remain controversial. Both hepatocyte apoptosis and necrosis are likely, but further study is needed to develop optimal hepatoprotective strategies. It is currently unclear whether the hepatotoxic consequences of obesity and ethanol ingestion are additive or synergistic. This information has important prognostic implications and might be useful to formulate body mass index-based guidelines for "safe" alcohol consumption. Findings of studies in experimental animals also raise questions about the relation between steatohepatitis and cirrhosis. Despite overwhelming evidence that obesity promotes alcohol-induced steatosis and steatohepatitis, most obese human beings (and mice) who drink alcohol do not become cirrhotic. Moreover, at least in mice, even severe steatohepatitis leads to cirrhosis relatively infrequently. Thus, it is conceivable that, although steatohepatitis is a permissive factor for cirrhosis, it is neither necessary nor sufficient for cirrhosis to occur. The quest to identify the proximal mediators of hepatic fibrosis should probably include an investigation of how various adipokines, neurotransmitters, and cytokines interact to regulate hepatic stellate cells. Armed with such knowledge, further modifying actions of ethanol on these mechanisms can be explored by investigators.