Systemic inflammation in nonalcoholic fatty liver disease is characterized by elevated levels of CCL2

A casein diet added isoflavone-enriched soy protein favorably affects biomarkers of steatohepatitis in obese Zucker rats

OBJECTIVE

Dietary supplementation of a soy protein enriched with isoflavones (HDI) has been shown to improve fatty liver in obese rats. The main objective of this study was to investigate whether HDI would influence the inflammatory status in livers of obese rats with fatty liver.

METHODS

Male obese Zucker fa/fa rats were fed casein (controls) or casein supplemented with HDI (containing 4.00 g of genistein and 4.50 g of daidzein per kilogram of diet) for 6 wk.

RESULTS

The HDI-fed rats had a markedly lower hepatic concentration of triacylglycerol when compared with controls. The decreased aspartate transaminase/alanine transaminase ratio in plasma, together with lower circulating levels of alkaline phosphatase and bile acids after HDI feeding, implied an improved hepatitis. This was supported by decreased plasma and hepatic mRNA levels of tumor necrosis factor-alpha, lower plasma levels of interleukin-1beta and monocyte chemoattractant protein-1, and an increased anti-inflammatory fatty acid index in plasma. HDI also seemed to protect the rats from oxidative damage, because the level of lipid peroxides in triacylglycerol-rich lipoproteins after in vitro copper oxidation was lower for HDI-fed rats when compared with controls.

CONCLUSION

These results show that isoflavone-enriched soy protein favorably affects biomarkers of hepatic inflammation in obese Zucker fa/fa rats with fatty liver. Thus, dietary soy proteins enriched in isoflavones may be a promising agent to improve steatohepatitis in patients.

[Nonalcoholic fatty liver disease as a risk factor of cardiovascular disease: relation of non-alcoholic fatty liver disease to carotid atherosclerosis]

BACKGROUND/AIMS

Non-alcoholic fatty liver disease (NAFLD) is closely associated with abdominal obesity, dyslipidemia, hypertension, and Type 2 diabetes, which are all features of the metabolic syndrome. The aim of the present study was to elucidate whether NAFLD is associated with carotid atherosclerosis.

METHODS

The study population comprised 659 subjects without hepatitis B and C infections and who did not consume alcohol. Fatty infiltrations of liver were detected by abdominal ultrasonography, and intima-media thickness (IMT) and plaque prevalence were estimated by carotid ultrasonography.

RESULTS

The mean values of systolic and diastolic pressures, body mass index (BMI), aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transpeptidase, uric acid, total cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol, fasting glucose, fasting insulin, homeostasis model of assessment (HOMA) index, hemoglobin A1c, and plasminogen activator inhibitor-1 differed significantly between patients with NAFLD (n=314) and normal controls (n=345). The carotid IMT was 0.817+/-0.212 (mean+/-SD) mm in patients with NAFLD and 0.757+/-0.198 mm in normal controls (p<0.001). The prevalence of carotid plaques was higher in patients with NAFLD (26.4%) than in normal controls (15.9%) (p<0.001). This association persisted significantly after adjusting for age, sex, BMI, HOMA index and individual factors of metabolic syndrome by multiple logistic regression analysis.

CONCLUSIONS

Patients with NAFLD are at a high risk of carotid atherosclerosis regardless of metabolic syndrome and classical cardiovascular risk factors. Therefore, the detection of NAFLD should alert to the existence of an increased cardiovascular risk. Moreover, NAFLD might be an independent risk factor for cardiovascular disease.

Insulin resistance, inflammation, and non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), the major cause of abnormal liver function in the western world, is often associated with obesity and diabetes. In obese individuals, fat accumulation in the abdominal region affects both lipid and glucose metabolism, and a liver loaded with fat is insulin resistant. Insulin resistance (IR) is often associated with chronic low-grade inflammation, and numerous mediators released from immune cells and adipocytes contribute to development of IR. Recent results showing an important role for these mediators in NAFLD are providing us with a better understanding of this highly prevalent disease with implications for novel therapy development. This review highlights new aspects in development of liver steatosis and the relevance of various cytokines and adipocytokines in NAFLD.

Association between non-alcoholic fatty liver disease and cardiovascular disease: a first message should pass

An association between non-alcoholic fatty liver disease (NAFLD) and cardiovascular disease (CVD) has been recently suggested. Indeed, different studies have demonstrated that NAFLD patients present increased subclinical atherosclerosis compared to non-steatosic individuals, and are supported by the few follow-up studies revealing that CVD is the second most common cause of death in NAFLD patients. However, the nature of the relationship NAFLD/CVD is still under debate: is NAFLD a consequence of, or a contributor to, the dysmetabolic cascade leading to atherosclerosis? In this issue of the journal, McKimmie and coauthors analyzed a subset of 623 participants from the Diabetes Heart Study for hepatic steatosis, classic CVD risk factors, subcutaneous and visceral fat, coronary, aortic and carotid artery calcium, and carotid intima-media thickness. After adjusting for all the CVD risk factors plus visceral fat, they did not find independent associations between steatosis and the cardiovascular markers of interest, and conclude that NAFLD may be best described as an epiphenomenon in this context. The strength of this study resides in the numerosity of the sample, the broad cardiovascular examination, and the direct assessment by computed tomography of visceral fat, an undisputed major contributor to NAFLD, the metabolic syndrome and atherosclerosis. However, waiting for prospective and interventional studies in order to definitely determine the nature of the relationship NAFLD/CVD, sufficient evidence exists to derive a first message and transfer it into the clinical practice: an overall assessment of the CVD risk, and the aggressive management of the atherosclerotic risk factors, seem mandatory in all NAFLD patients.

Arsenic and cardiovascular disease

Chronic arsenic exposure is a worldwide health problem. Although arsenic-induced cancer has been widely studied, comparatively little attention has been paid to arsenic-induced vascular disease. Epidemiological studies have shown that chronic arsenic exposure is associated with increased morbidity and mortality from cardiovascular disease. In addition, studies suggest that susceptibility to arsenic-induced vascular disease may be modified by nutritional factors in addition to genetic factors. Recently, animal models for arsenic-induced atherosclerosis and liver sinusoidal endothelial cell dysfunction have been developed. Initial studies in these models show that arsenic exposure accelerates and exacerbates atherosclerosis in apolipoprotein E-knockout mice. Microarray studies of liver mRNA and micro-RNA abundance in mice exposed in utero suggest that a permanent state of stress is induced by the arsenic exposure. Furthermore, the livers of the arsenic-exposed mice have activated pathways involved in immune responses suggesting a pro-hyperinflammatory state. Arsenic exposure of mice after weaning shows a clear dose-response in the extent of disease exacerbation. In addition, increased inflammation in arterial wall is evident. In response to arsenic-stimulated oxidative signaling, liver sinusoidal endothelium differentiates into a continuous endothelium that limits nutrient exchange and waste elimination. Data suggest that nicotinamide adenine dinucleotide phosphate oxidase-derived superoxide or its derivatives are essential second messengers in the signaling pathway for arsenic-stimulated vessel remodeling. The recent findings provide future directions for research into the cardiovascular effects of arsenic exposure.

Clinical and pathologic risk factors for atherosclerosis in cirrhosis: a comparison between NASH-related cirrhosis and cirrhosis due to other aetiologies

BACKGROUND/AIMS

The precise prevalence of risk factors for atherosclerosis in NASH-related cirrhosis is unknown. The aims of this study were: (1) to compare the prevalence of major risk factors for atherosclerosis between subjects who underwent liver transplantation for NASH-related cirrhosis and those with cirrhosis of other aetiologies and (2) to compare pathologic changes of atherosclerosis within the explants hepatic hilar arteries between the groups.

METHODS

Sixty subjects with NASH-related cirrhosis and 60 subjects with cirrhosis of other aetiologies were reviewed retrospectively. Demographic and clinical characteristics related to atherosclerosis were analyzed and compared. The hepatic hilar arteries of the explanted livers were examined for pathologic changes.

RESULTS

The prevalence of all coronary artery disease (CAD) risk factors and the metabolic syndrome was significantly higher in NASH-related cirrhosis group compared to cirrhosis of other aetiologies. The proportion of patients with a diagnosis of CAD was also significantly higher in the NASH-related cirrhosis group (21.6% vs. 5%, p=0.005). Pathological examination of hilar arteries showed possible atherosclerotic changes in only 4 cases (3 NASH-related cirrhosis; 1 HCV).

CONCLUSIONS

Major risk factors for atherosclerosis are significantly more prevalent in subjects with NASH-related cirrhosis than in subjects with cirrhosis of other aetiologies and are predictive of an increased prevalence of CAD. This study suggests that NASH-related cirrhosis is not protective against atherosclerosis.

Dietary single cell protein reduces fatty liver in obese Zucker rats

There is growing evidence that dietary proteins may interfere with lipid metabolism. We therefore examined the effects of feeding obese Zucker rats a single cell protein (SCP) with low ratios of methionine:glycine and lysine:arginine for 6 weeks. SCP feeding reduced the hepatic steatosis and lowered the plasma transaminase levels when compared with casein-fed rats (controls). The fatty acid oxidation was increased in liver mitochondria and peroxisomes, whereas the activities of enzymes involved in lipogenesis and TAG biosynthesis were unaffected. SCP feeding affected the fatty acid composition of liver lipids and plasma, and reduced the mRNA levels of the fatty acid desaturases. The decreased gene expression of stearoyl-CoA desaturase suggested that the fatty acids were directed towards oxidation rather than esterification as TAG. The decreased mRNA levels of VLDL-receptor and lipoprotein lipase in the liver after SCP feeding suggested that the uptake of TAG-rich lipoprotein to the liver was decreased. To conclude, the reduced fatty liver by SCP feeding may be caused by the increased capacity for fatty acid β-oxidation in the liver, combined with changed fatty acid composition and possibly a reduced hepatic clearance of circulating VLDL. An increased awareness of the effect of dietary proteins on lipid metabolism could be of relevance in future dietary treatment of non-alcoholic fatty liver disease.

Advanced glycation end products enhance the proliferation and activation of hepatic stellate cells

BACKGROUND

Advanced glycation end products (AGEs), final reaction products of protein with sugars, are known to contribute to diabetes-related complications. We have recently demonstrated high levels of serum AGEs in patients with nonalcoholic steatohepatitis (NASH). However, direct evidence for the participation of AGEs in hepatic inflammation and fibrosis has not been shown. To explore the pathogenesis of NASH, we examined the biological infl uence of AGEs on hepatic stellate cells (HSCs) in vitro.

METHODS

An established human HSC line, LI90, was exposed to a glyceraldehyde-derived-AGE (glycer-AGE), and the phenotypical changes of the LI90 cells were investigated. Intracellular formation of reactive oxygen species (ROS) was measured using a fl uorescent probe. Cell proliferation was examined by MTS assay. Fibrogenic marker gene expression was analyzed by quantitative real-time polymerase chain reaction. The production of monocyte chemoattractant protein 1 (MCP-1) was assessed by enzyme-linked immunosorbent assay.

RESULTS

The expression of AGE receptor was confirmed in LI90 cells at the mRNA and protein levels. In addition to increasing intracellular ROS generation, glycer-AGE upregulated fibrogenic genes such as those encoding for alpha-smooth muscle actin, transforming growth factor-beta1, and collagen type Ialpha2. The expression of MCP-1 mRNA in LI90 cells as well as its secretion into the culture medium was significantly increased in response to AGEs. These changes were attenuated by treatment with the antioxidant N-acetylcysteine.

CONCLUSIONS

These data indicate that AGEs induce ROS generation and intensify the proliferation and activation of HSCs, supporting the possibility that antioxidants may represent a promising treatment for prevention of the development of hepatic fibrosis in NASH.

Blood F2-isoprostanes are significantly associated with abnormalities of lipid status in rats with steatosis

AIM: To investigate oxidative stress and lipid peroxidation in hepatic steatosis and the underlying implications in pathological mechanisms of non-alcoholic fatty liver disease (NAFLD).

METHODS: F₂-isoprostanes (iPF_2α-III) in blood and liver samples from steatotic (n = 9) and control (n = 7) rats were measured as in vivo marker of lipid peroxidation by a mass spectrometric approach. The lipid profile and endogenous antioxidant status (SOD and CAT) in the rats were also analyzed.

RESULTS: Significantly higher levels of iPF_2α-III (mean 3.47 vs 2.40 pmol/mg tissue, P = 0.004) and lower activities of SOD (mean 1.26 U vs 1.40 U, P < 0.001) and CAT (mean 1026.36 U/mg vs 1149.68 U/mg protein, without significance) were observed in the livers of steatotic rats. Plasma total iPF_2α-III was significantly correlated with the abnormalities of blood lipids as well as alanine aminotransferase (ALT) levels in the rats with simple steatosis, whereas no similar tendencies were observed in the control rats.

CONCLUSION: Enhancement of hepatic oxidative imbalance occurring at the steatotic stage of NAFLD suggests a possibility that manifestation of the local oxidative damage precedes that of systemic oxidative imbalance. Predominant metabolic features of the increased lipid peroxidation further suggest a close association of the oxidative imbalance and the dyslipidemia with functional deterioration of the steatotic liver. The findings need to be further evaluated, especially in human studies.

Beyond insulin resistance: Innate immunity in nonalcoholic steatohepatitis

Obesity is an inflammatory disorder characterized by heightened activity of the innate immune system. Innate immune activation is central to the development of obesity-related insulin resistance; it also plays an important role in obesity-related tissue damage, such as that seen in atherosclerosis. Recent research has implicated the innate immune system in the pathophysiology of obesity-related liver disease. This review summarizes how innate immune processes, occurring both within and outside the liver, cause not only insulin resistance but also end-organ damage in the form of nonalcoholic fatty liver disease.

Clinical trial: insulin-sensitizing agents may reduce consequences of insulin resistance in individuals with non-alcoholic steatohepatitis

BACKGROUND

Currently, although only a few therapies normalize the liver test abnormalities with/without improving the liver histology, no pharmacologic therapy has proved to be effective for the treatment of non-alcoholic steatohepatitis.

AIM

To investigate the role of insulin sensitizers in the treatment of individuals with non-alcoholic steatohepatitis (NASH).

METHODS

A total of 74 individuals with NASH (male/female, 44/30; mean age, 47.2 +/- 9.0 years) were enrolled. Participants were divided into two distinct groups: group 1 (n = 25) participants were administered a conventional diet and exercise programme while those in group 2 (n = 49) were administered the diet and exercise programme plus insulin sensitizers.

RESULTS

With respect to baseline metabolic, biochemical and histological parameters, no significant differences were observed between the two groups (P > 0.05). Insulin sensitizers significantly improved metabolic parameters (homeostasis model assessment-insulin resistance score, P < 0.05), serum aminotransferase levels [aspartate aminotransferase (AST): 45.9 +/- 24.2 to 33.3 +/- 17.7 IU/L, P < 0.01; alanine aminotransferase (ALT): 78.2 +/- 46.3 to 47.3 +/- 34.5 IU/L, P < 0.001] and histological features (median non-alcoholic fatty liver disease activity score: 5.0-3.0, P = 0.01), while diet and exercise improved serum aminotransferase levels (AST: 39.3 +/- 11.1 to 30.0 +/- 8.6 IU/L, P < 0.01; ALT: 66.9 +/- 28.9 to 42.0 +/- 16.2 IU/L, P < 0.001) at the end of the 48 weeks when compared to baseline. Insulin sensitizers improved the high-sensitivity C-reactive protein levels (P < 0.01). No serious adverse effects of insulin sensitizers were observed.

CONCLUSION

Insulin sensitizers can lead to improvement in metabolic, biochemical and histological abnormalities of NASH as a result of improved insulin sensitivity.

Adipose tissue inflammation and liver fat in patients with highly active antiretroviral therapy-associated lipodystrophy

In this cross-sectional study, we sought to determine whether gene expression of macrophage markers and inflammatory chemokines in lipoatrophic subcutaneous abdominal adipose tissue and liver fat content are increased and interrelated in human immunodeficiency virus (HIV)-1-positive, highly active antiretroviral therapy (HAART)-treated patients with lipodystrophy (HAART+LD+; n = 27) compared with those without (HAART+LD-; n = 13). The study groups were comparable with respect to age, gender, and body mass index. The HAART+LD+ group had twofold more intra-abdominal (P = 0.01) and 1.5-fold less subcutaneous (P = 0.091) fat than the HAART+LD- group. As we have reported previously, liver fat was 10-fold higher in the HAART+LD+ compared with the HAART+LD- group (P = 0.00003). Inflammatory gene expression was increased in HAART-lipodystrophy: CD68 4.5-fold (P = 0.000013), tumor necrosis factor (TNF)-alpha 2-fold (P = 0.0094), chemokine (C-C motif) ligand (CCL) 2 2.5-fold (P = 0.0024), CCL3 7-fold (P = 0.0000017), integrin alphaM (ITGAM) 3-fold (P = 0.00067), epidermal growth factor-like module containing, mucin-like, hormone receptor-like (EMR)1 2.5-fold (P = 0.0038), and a disintegrin and metalloproteinase domain (ADAM)8 3.5-fold (P = 0.00057) higher in the HAART+LD+ compared with the HAART+LD- group. mRNA concentration of CD68 (r = 0.37, P = 0.019), ITGAM (r = 0.35, P = 0.025), CCL2 (r = 0.39, P = 0.012), and CCL3 (r = 0.54, P = 0.0003) correlated with liver fat content. In conclusion, gene expression of markers of macrophage infiltration and adipose tissue inflammation is increased in lipoatrophic subcutaneous abdominal adipose tissue of patients with HAART-associated lipodystrophy compared with those without. CD68, ITGAM, CCL2, and CCL3 expression is significantly associated with accumulation of liver fat.

NASH predicts plasma inflammatory biomarkers independently of visceral fat in men

We assessed the differential contribution of nonalcoholic steatohepatitis (NASH) and visceral adiposity to nontraditional cardiovascular risk biomarkers in adult men. We enrolled 45 consecutive, overweight, male patients with biopsy-proven NASH, 45 overweight male patients without ultrasound-diagnosed hepatic steatosis, and 45 healthy male volunteers. All participants were matched for age; NASH and overweight patients were also matched for BMI and visceral adiposity (as estimated by abdominal ultrasonography). Nontraditional cardiovascular risk biomarkers were measured in all participants. Plasma concentrations of high-sensitivity C-reactive protein (hs-CRP), fibrinogen, plasminogen activator inhibitor-1 (PAI-1) activity, and adiponectin were markedly different among the groups; the lowest values (the highest for adiponectin) were in nonobese healthy subjects, intermediate in overweight nonsteatotic patients, and the highest (the lowest for adiponectin) in those with biopsy-proven NASH. The marked differences in these cardiovascular risk biomarkers that were observed between overweight and NASH patients were only slightly weakened after adjustment for age, BMI, smoking, plasma triglycerides, and insulin resistance (IR) as assessed by homeostasis model assessment (HOMA). In multivariate regression analysis, NASH and visceral adiposity predicted cardiovascular risk biomarkers independently of potential confounders. In conclusion, our results suggest that NASH can predict a more atherogenic risk profile in a manner that is partly independent from the contribution of visceral adiposity in adult men.

A randomized controlled pilot study of Pentoxifylline in patients with non-alcoholic steatohepatitis (NASH)

PURPOSE

Tumor necrosis factor-alpha (TNF-alpha) is implicated in non-alcoholic steatohepatitis (NASH). Pentoxifylline inhibits TNF-alpha. We wanted to evaluate the efficacy of Pentoxifylline on NASH patients.

METHODS

Patients with biopsy proven NASH and persistently elevated alanine aminotransferase (ALT) greater than 1.5 times the upper limit of normal were randomized to 3 months of treatment with a step 1 American Heart Association diet and daily exercise with Pentoxifylline or placebo. Liver function tests, serum lipids and TNF-alpha, Interleukin 6 (IL-6), and plasma hyaluronic acid were measured at baseline, at weeks 6 and 12. Categorical data were analyzed by Fisher's exact test while independent sample t-test and Mann-Whitney test were used for continuous data.

RESULTS

Eleven patients were randomized into the Pentoxifylline and nine to the placebo group. After 3 months of treatment body mass index (BMI), ALT and aspartate aminotransferase (AST) decreased significantly in both groups. There was no difference between the two groups in reduction of BMI (P = 0.897). There was significantly greater reduction in AST in the Pentoxifylline group (P = 0.038). There was a trend toward lower ALT level (P = 0.065) in the Pentoxifylline group. TNF-alpha and IL-6 decreased significantly in both groups after treatment, but there was no significant difference between the two groups.

CONCLUSION

Three months of Pentoxifylline treatment in combination with diet and exercise results in significantly greater reduction in AST levels in patients with NASH as compared with controls.

Increased hepatic and circulating interleukin-6 levels in human nonalcoholic steatohepatitis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D) are growing public health problems, and are strongly associated. The link between the two conditions remains poorly understood. Hepatic interleukin-6 (IL-6), a major proinflammatory cytokine, expression is increased in animal models of NAFLD, while in mice, selective sustained upregulation of IL-6 in the liver results in systemic insulin resistance. The extent and clinical significance of hepatic IL-6 expression in human NAFLD, as well as potential mechanisms by which steatosis may increase IL-6 production in the liver, have not been examined.

AIMS

To ascertain the occurrence and significance of IL-6 expression in the liver in human NAFLD.

PATIENTS AND METHODS

Plasma was obtained at time of liver biopsy from 50 consecutive patients with suspected NAFLD. Histology was assessed blindly. Hepatic IL-6 expression was assessed by immunohistochemistry, while plasma IL-6 levels were determined by an enzyme-linked immunosorbent assay.

RESULTS

IL-6 expression was markedly increased in the livers of patients with nonalcoholic steatohepatitis (NASH) as compared to patients with simple steatosis (P < 0.005) or normal biopsies (P < 0.010), confirming the presence of hepatic IL-6 expression in human NASH. A positive correlation was observed between hepatocyte IL-6 expression and degree of inflammation and stage of fibrosis. Furthermore, liver IL-6 expression positively correlated with plasma IL-6 levels and degree of systemic insulin resistance. Culture of liver cells with saturated, but not mono- or polyunsaturated, FFA resulted in a significant increase in IL-6 messenger RNA (mRNA) and protein expression.

CONCLUSION

Collectively, these data suggest that increased hepatic IL-6 production may play an important role in NASH development, as well as in systemic insulin resistance and diabetes.

Gene expression in human NAFLD

Despite the high prevalence of nonalcoholic fatty liver disease (NAFLD), little is known of its pathogenesis based on study of human liver samples. By the use of Affymetrix GeneChips (17,601 genes), we investigated gene expression in the human liver of subjects with extreme steatosis due to NAFLD without histological signs of inflammation (liver fat 66.0 +/- 6.8%) and in subjects with low liver fat content (6.4 +/- 2.7%). The data were analyzed by using sequence-based reannotation of Affymetrix probes and a robust model-based normalization method. We identified genes involved in hepatic glucose and lipid metabolism, insulin signaling, inflammation, coagulation, and cell adhesion to be significantly associated with liver fat content. In addition, genes involved in ceramide signaling (MAP2K4) and metabolism (UGCG) were found to be positively associated with liver fat content. Genes involved in lipid metabolism (PLIN, ACADM), fatty acid transport (FABP4, CD36), amino acid catabolism (BCAT1), and inflammation (CCL2) were validated by real-time PCR and were found to be upregulated in subjects with high liver fat content. The data show that multiple changes in gene expression characterize simple steatosis.

Cytokines in the pathogenesis of fatty liver and disease progression to steatohepatitis: implications for treatment

Nonalcoholic fatty liver disease (NAFLD) has emerged as a growing public health problem worldwide. NAFLD represents a wide spectrum of conditions ranging from fatty liver, that in general follows a benign nonprogressive clinical course, to nonalcoholic steatohepatitis (NASH), a serious form of NAFLD, that may progress to cirrhosis and end-stage liver disease. The mechanisms responsible for NAFLD development and disease progression remain incompletely understood, but are of great clinical interest as current therapies are limited. Future therapies will be predicted based upon the understanding of its pathogenesis. This review focuses on the growing evidence from both experimental and human studies suggesting a central role of cytokines in the pathogenesis of NAFLD. We review the role of cytokines as key regulators of insulin sensitivity and hepatic lipid overloading, liver injury and inflammation, and fibrosis and cirrhosis, with an emphasis on potential therapeutic implications.

The blind men ‘see’ the elephant-the many faces of fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a group of diseases with excess fat in liver in the absence of a poorly defined limit of alcohol consumption. Most common variety, a universal public health problem, is associated with insulin resistance caused by a host of genetic and epigenetic defects modulated by life style and environmental factors. In fact the term NAFLD is loose to incorporate so many etiologies except alcoholism and few other etiologies, presenting as fat in liver. However as a sign fatty liver is very important in predicting the risk of diabetes, cardiovascular disease, stroke, cirrhosis and cancer. Abnormal fat accumulation can result from several defects in nuclear receptors associated with lipid sensing, synthesis and oxidation like LXR, FXR, SREBP, ChREBP and PPAR; defects in the lipid influx-efflux channels, insulin signaling, proteins involved in fatty acid catabolism, defects in adipose tissue development and function, inappropriate nutrition and finally defects in neural regulatory mechanisms. The progress of the disease is determined by the basic defects which results in fat accumulation, an individual’s immunological response to the accumulated fat and its derivatives and the oxidant stress response. Congregation of unrelated genetic defects under same diagnosis ‘NAFLD’ can result in inefficient patient management. Further studies are required to understand the molecular basis of fatty liver to enable a personalized management of diseases presenting as fatty liver in the absence of alcohol abuse.

Chronic prehepatic portal hypertension in the rat: is it a type of metabolic inflammatory syndrome?

BACKGROUND

A progressive development of hepatic steatosis with an increase in the lipid hepatocyte content and the formation of megamitochondria have been demonstrated in rats with prehepatic portal hypertension. The aim of this study is to verify the existence of liver and serum lipid metabolism impairments in rats with long-term (2 years) portal hypertension.

METHODS

Male Wistar rats: Control (n = 10) and with prehepatic portal hypertension by triple partial portal vein ligation (n = 9) were used. Liver content of Triglycerides (TG), phospholipids (PL) and cholesterol and serum cholesterol, lipoproteins (HDL and LDL), TG, glucose and Lipid Binding Protein (LBP) were assayed with specific colorimetric commercial kits. Serum levels of insulin and somatostatin were assayed by RIA.

RESULTS

The liver content of TG (6.30 +/- 1.95 vs. 4.17 +/- 0.59 microg/ml; p < 0.01) and cholesterol (1.48 +/- 0.15 vs. 1.10 +/- 0.13 microg/ml; p < 0.001) increased in rats with portal hypertension. The serum levels of cholesterol (97.00+26.02 vs. 114.78 +/- 37.72 mg/dl), TG (153.41 +/- 80.39 vs. 324.39 +/- 134.9 mg/dl; p < 0.01), HDL (20.45 +/- 5.14 vs. 55.15 +/- 17.47 mg/dl; p < 0.001) and somatostatin (1.32 +/- 0.31 vs. 1.59 +0.37 mg/dl) decreased, whereas LDL (37.83 +/- 15.39 vs. 16.77 +/- 6.81 mg/dl; p < 0.001) and LBP (308.47 +/- 194.53 vs. 60.27 +/- 42.96 ng/ml; p < 0.001) increased.

CONCLUSION

Portal hypertension in the rat presents changes in the lipid and carbohydrate metabolisms similar to those produced in chronic inflammatory conditions and sepsis in humans. These underlying alterations could be involved in the development of hepatic steatosis and, therefore, in those described in the metabolic syndrome in humans.

Antioxidant supplemention in the treatment of skeletal muscle insulin resistance: potential mechanisms and clinical relevance

The incidence of type 2 diabetes has increased dramatically over the past several decades and this trend is projected to continue into the foreseeable future. Skeletal muscle insulin resistance is thought to be a key development in the pathogenesis of type 2 diabetes. Given this fact, interventions that prevent or reverse impairments in skeletal muscle action can have profound effects on whole-body glucose homeostasis. Traditional approaches used in this regard include exercise, weight loss, and insulin-sensitizing drugs such as thiazolidinediones (TZDs). Although these interventions have proven effective in improving glucose homeostasis, there are adherence issues seen with lifestyle interventions and undesirable side effects have been reported with TZDs. With these points in mind, the development of alternative strategies to maintain or improve skeletal muscle insulin sensitivity is warranted. In this context, the purpose of the present review is to highlight the role of antioxidant compounds in the prevention and treatment of skeletal muscle insulin resistance. Specifically, we will briefly describe the mechanisms of insulin-stimulated skeletal muscle glucose uptake and the potential mediators of oxidative stress induced insulin resistance, highlight data suggesting that antioxidant compounds can have beneficial effects on skeletal muscle insulin action, and discuss potential mechanisms mediating this effect.

Molecular basis and mechanisms of progression of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH), a cause of cirrhosis and hepatocellular carcinoma, is characterized by fatty infiltration of the liver, inflammation, hepatocellular damage and fibrosis. Progress has been made in understanding the molecular and cellular mechanisms implicated in the pathogenesis of this condition, therefore, we here review recent developments regarding the basic mechanisms of NASH development. Accumulation of triglycerides in the hepatocytes is the result of increased inflow of free fatty acids and de novo lipogenesis. Steatosis leads to lipotoxicity, which causes apoptosis, necrosis, generation of oxidative stress and inflammation. The resulting chronic injury activates a fibrogenic response that leads eventually to end-stage liver disease. A better understanding of these mechanisms is crucial for the design of novel diagnostic and therapeutic strategies.

Fatty Liver

Although the epidemic of obesity has been accompanied by an increase in the prevalence of the metabolic syndrome, not all obese develop the syndrome and even lean individuals can be insulin resistant. Both lean and obese insulin resistant individuals have an excess of fat in the liver which is not attributable to alcohol or other known causes of liver disease, a condition defined as nonalcoholic fatty liver disease (NAFLD) by gastroenterologists. The fatty liver is insulin resistant. Liver fat is highly significantly and linearly correlated with all components of the metabolic syndrome independent of obesity. Overproduction of glucose, VLDL, CRP, and coagulation factors by the fatty liver could contribute to the excess risk of cardiovascular disease associated with the metabolic syndrome and NAFLD. Both of the latter conditions also increase the risk of type 2 diabetes and advanced liver disease. The reason why some deposit fat in the liver whereas others do not is poorly understood. Individuals with a fatty liver are more likely to have excess intraabdominal fat and inflammatory changes in adipose tissue. Intervention studies have shown that liver fat can be decreased by weight loss, PPARγ agonists, and insulin therapy.

Homocysteine induces monocyte chemoattractant protein-1 expression in hepatocytes mediated via activator protein-1 activation

Hyperhomocysteinemia is characterized by abnormally high concentrations of homocysteine (Hcy) in the plasma. It is a metabolic disorder associated with dysfunction of several organs such as atherosclerosis, altered lipid metabolism, and liver injury. In this study we investigated the effect of Hcy on transcriptional regulation of monocyte chemoattractant protein-1 (MCP-1), a potent chemokine, expression in hepatocytes. Hyperhomocysteinemia was induced in rats by a high-methionine diet for 4 weeks. MCP-1 mRNA and protein levels were significantly elevated in the liver tissue homogenate and in hepatocytes of hyperhomocysteinemic rats. The role of transcription factors in MCP-1 expression was examined by electrophoretic mobility shift assay. Activation of activator protein (AP)-1 but not nuclear factor kappaB was detected in the liver tissue of those rats. Incubation of rat hepatocytes with Hcy (50-200 microm) caused a significant increase in AP-1 activation followed by an increase in intracellular MCP-1 mRNA expression and an elevation of MCP-1 protein secreted into the culture medium. Hcy markedly increased the DNA binding activity of human recombinant AP-1 (c-Fos and c-Jun proteins). The presence of a sulfhydryl group in Hcy was essential for Hcy-induced AP-1 activation. When hepatocytes were transfected with decoy AP-1 oligodeoxynucleotide to inhibit AP-1 activation, Hcy-induced MCP-1 mRNA expression was abolished. Further analysis revealed that increased hepatic MCP-1 expression was positively correlated with the serum MCP-1 level. These results suggest that Hcy-induced MCP-1 expression in the liver is mediated via AP-1 activation, which may contribute to chronic inflammation associated with hyperhomocysteinemia.

Inflammation: a way to understanding the evolution of portal hypertension

BACKGROUND

Portal hypertension is a clinical syndrome that manifests as ascites, portosystemic encephalopathy and variceal hemorrhage, and these alterations often lead to death.

HYPOTHESIS

Splanchnic and/or systemic responses to portal hypertension could have pathophysiological mechanisms similar to those involved in the post-traumatic inflammatory response.The splanchnic and systemic impairments produced throughout the evolution of experimental prehepatic portal hypertension could be considered to have an inflammatory origin. In portal vein ligated rats, portal hypertensive enteropathy, hepatic steatosis and portal hypertensive encephalopathy show phenotypes during their development that can be considered inflammatory, such as: ischemia-reperfusion (vasodilatory response), infiltration by inflammatory cells (mast cells) and bacteria (intestinal translocation of endotoxins and bacteria) and lastly, angiogenesis. Similar inflammatory phenotypes, worsened by chronic liver disease (with anti-oxidant and anti-enzymatic ability reduction) characterize the evolution of portal hypertension and its complications (hepatorenal syndrome, ascites and esophageal variceal hemorrhage) in humans.

CONCLUSION

Low-grade inflammation, related to prehepatic portal hypertension, switches to high-grade inflammation with the development of severe and life-threatening complications when associated with chronic liver disease.

Genes involved in fatty acid partitioning and binding, lipolysis, monocyte/macrophage recruitment, and inflammation are overexpressed in the human fatty liver of insulin-resistant subjects

OBJECTIVE

The objective of this study is to quantitate expression of genes possibly contributing to insulin resistance and fat deposition in the human liver.

RESEARCH DESIGN AND METHODS

A total of 24 subjects who had varying amounts of histologically determined fat in the liver ranging from normal (n = 8) to steatosis due to a nonalcoholic fatty liver (NAFL) (n = 16) were studied. The mRNA concentrations of 21 candidate genes associated with fatty acid metabolism, inflammation, and insulin sensitivity were quantitated in liver biopsies using real-time PCR. In addition, the subjects were characterized with respect to body composition and circulating markers of insulin sensitivity.

RESULTS

The following genes were significantly upregulated in NAFL: peroxisome proliferator-activated receptor (PPAR) gamma 2 (2.8-fold), the monocyte-attracting chemokine CCL2 (monocyte chemoattractant protein [MCP]-1, 1.8-fold), and four genes associated with fatty acid metabolism (acyl-CoA synthetase long-chain family member 4 [ACSL4] [2.8-fold], fatty acid binding protein [FABP]4 [3.9-fold], FABP5 [2.5-fold], and lipoprotein lipase [LPL] [3.6-fold]). PPARgamma coactivator 1 (PGC1) was significantly lower in subjects with NAFL than in those without. Genes significantly associated with obesity included nine genes: plasminogen activator inhibitor 1, PPARgamma, PPARdelta, MCP-1, CCL3 (macrophage inflammatory protein [MIP]-1 alpha), PPAR gamma 2, carnitine palmitoyltransferase (CPT1A), FABP4, and FABP5. The following parameters were associated with liver fat independent of obesity: serum adiponectin, insulin, C-peptide, and HDL cholesterol concentrations and the mRNA concentrations of MCP-1, MIP-1 alpha, ACSL4, FABP4, FABP5, and LPL.

CONCLUSIONS

Genes involved in fatty acid partitioning and binding, lipolysis, and monocyte/macrophage recruitment and inflammation are overexpressed in the human fatty liver.

Noninvasive diagnosis and monitoring of nonalcoholic steatohepatitis: present and future

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the United States, and its prevalence is increasing worldwide. It currently affects approximately 30% of adults and 10% of children in the United States. NAFLD represents a wide spectrum of conditions ranging from simple fatty liver which in general follows a benign nonprogressive clinical course, to nonalcoholic steatohepatitis (NASH), which is a more serious form of NAFLD that may progress to cirrhosis and end-stage liver disease. At present, a liver biopsy remains the only reliable way to diagnose NASH and establish the presence of fibrosis. Current noninvasive clinically available tests lack accuracy and reliability. In light of the dramatic increase in the prevalence of NAFLD in conjunction with the significant research effort in developing novel therapies for patients with NASH, noninvasive, simple, reproducible, and reliable biomarkers are greatly needed. They will not only help in the diagnosis of NASH, but also be useful for assessment of treatment response and prognosis and remain a research priority in the NAFLD field.

Comparative review of diets for the metabolic syndrome: implications for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a significant health problem and affects 70 million adults in the United States (30% of the adult population), and an estimated 20% of these individuals have the most severe form of NAFLD-nonalcoholic steatohepatitis (NASH). The mechanisms underlying disease development and progression are awaiting clarification. Insulin resistance and obesity-related inflammation, among other possible genetic, dietary, and lifestyle factors, are thought to play a key role. A program targeting gradual weight reduction and physical exercise continues to be the gold standard of treatment for all forms of NAFLD. Even though weight loss and dietary and lifestyle changes are recommended as primary treatment for fatty liver, little to no scientific evidence is available on diet and NAFLD. This article reviews the implications of current dietary approaches, including national guidelines and popular weight-loss diets, with a focus on determining the optimal diet to prescribe for NAFLD and NASH patients. The effects of macronutrient content (carbohydrate, fat, and protein ratios) and specific food components, such as soluble fiber, n-3 fatty acids, and fructose, are discussed. The premises, effects, barriers, and issues related to current dietary guidelines and specific diets are discussed, and the question, "Will it work for the pathogenesis of NAFLD and NASH? ", is addressed.

High-sensitivity C-reactive protein is an independent clinical feature of nonalcoholic steatohepatitis (NASH) and also of the severity of fibrosis in NASH

BACKGROUND

The changes in nonalcoholic fatty liver disease (NAFLD) range over a wide spectrum, extending from steatosis to steatohepatitis (NASH). However, it has remained difficult to differentiate between NASH and nonprogressive NAFLD by clinical examination. We investigated the interrelationships between serum high-sensitivity C-reactive protein (hs-CRP) and the pathogenesis and progression of NASH.

METHODS

Hs-CRP was measured in 100 patients with histologically verified NAFLD (29 with steatosis and 71 with NASH), and a real-time reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed to measure the intrahepatic mRNA expressions of CRP and interleukin (IL)-6.

RESULTS

The results of a multiple regression analysis revealed that in comparison with cases of steatosis, hs-CRP was significantly elevated (P = 0.0048) in cases of NASH. Furthermore, among patients with NASH, hs-CRP was significantly elevated in those with advanced fibrosis compared with that in those with mild fibrosis (P = 0.0384), even after adjustment for age, sex, presence of diabetes, body mass index, visceral fat area, subcutaneous fat area, homeostasis model assessment for insulin resistance, high-density lipoprotein cholesterol, triglyceride, and low-density lipoprotein cholesterol. The results of the RT-PCR analysis showed that intrahepatic mRNA expression of CRP, but not IL-6, was increased in patients with NASH compared with those with steatosis (P = 0.0228).

CONCLUSIONS

This is the first report to demonstrate consistent and profound elevation of hs-CRP in cases of NASH compared with in cases of simple nonprogressive steatosis. Our results suggest that hs-CRP may be a clinical feature that not only distinguishes NASH from simple nonprogressive steatosis but also indicates the severity of hepatic fibrosis in cases of NASH.

Prostacyclin in liver disease: a potential therapeutic option

Complex molecular and cellular mechanisms are involved in the initiation and progression of hepatic fibrosis. Recent studies have shown that hepatic stellate cells, endothelin, cytokines and prostacyclin play crucial roles in this pathology. Prostacyclin exerts vasorelaxant, antioxidant and antifibrotic properties that prevent the development of fibrosis and cirrhosis in liver diseases. In this editorial, the authors discuss some of the molecular and cellular mechanisms involved in the initiation and progression of liver fibrosis and the role played by prostacyclin in counteracting it. At the moment, however, only limited information is available from clinical studies demonstrating the effectiveness of prostacyclin in liver diseases and this makes it difficult to draw any conclusions; further efforts are necessary to verify whether prostacyclin, alone or in combination with other drugs, may be a valid therapeutic option in liver diseases.

Nonalcoholic fatty liver disease and cardiovascular disease risk

Nonalcoholic fatty liver disease (NAFLD) is prevalent in people with the metabolic syndrome and type 2 diabetes. Evidence is now accumulating that NAFLD is associated with obesity and diabetes and may serve as a predictor of cardiovascular disease. Although at present, treatment of the individual risk factors pertinent to NAFLD is advocated, novel therapies are emerging that may target steatosis and/or inflammation, thus ameliorating the overall cardiovascular disease risk. Long-term outcome studies need to establish whether treatment of NAFLD (and in particular which therapy) will affect the long-term outcome.

Correlation of serum TNF-alpha levels and histologic liver injury scores in pediatric nonalcoholic fatty liver disease

We tested the power of tumor necrosis factor (TNF)-alpha and/or leptin in predicting the degree of liver involvement in children with nonalcoholic fatty liver disease (NAFLD). We measured serum levels of TNF-alpha and leptin and computed NAFLD activity score (NAS) (NAS >or= 5, diagnostic of nonalcoholic steatohepatitis [NASH]) in 72 consecutive biopsy-proven NAFLD cases (training and validation sets, 36 cases each). Univariate analysis evaluated variables significantly associated with a diagnostic NAS. Receiver operating characteristic (ROC) curve analysis assessed the diagnostic value of selected variables in predicting a NAS of 5 or more.TNF-alpha (P < .0001), leptin (P = .001); triglycerides (P = .013), and alkaline phosphatase (P = .046) levels were significantly associated with a NAS of 5 or more. TNF-alpha and leptin levels predicted the risk of NAS of 5 or more. ROC analyses defined cutoff values for TNF-alpha, leptin, and risk score. They identified 90%, 83%, and 83% of the cases, respectively, with a NAS of 5 or more (true-positive cases) from the validation set.TNF-alpha alone or combined with leptin in a simple risk score can accurately predict a NAS of 5 or more. TNF-alpha seems to be a specific laboratory marker of NASH.

Hepatocyte growth factor induces glucose uptake in 3T3-L1 adipocytes through A Gab1/phosphatidylinositol 3-kinase/Glut4 pathway

Adipose tissue is a source of hepatocyte growth factor (HGF), and circulating HGF levels have been associated with elevated body mass index in human. However, the effects of HGF on adipocyte functions have not yet been investigated. We show here that in 3T3-L1 adipocytes HGF stimulates the phosphatidylinositol (PI) 3-kinase-dependent protein kinase B (PKB) activity, AS160 phosphorylation, Glut4 translocation, and consequently, glucose uptake. The initial steps involved in HGF- and insulin-induced glucose uptake are different. HGF enhanced the tyrosine phosphorylation of Gab1, leading to the recruitment of the p85-regulated subunit of PI 3-kinase, whereas p85 was exclusively recruited by IRS1 in response to insulin. In adipocytes rendered insulin-resistant by a long-lasting tumor necrosis factor alpha treatment, the protein level of Gab1 was strongly decreased, and HGF-stimulated PKB activation and glucose uptake were also altered. Moreover, treatment of 3T3-L1 adipocytes with thiazolidinedione, an anti-diabetic drug, enhanced the expression of both HGF and its receptor. These data provide the first evidence that in vitro HGF promotes glucose uptake through a Gab1/PI 3-kinase/PKB/AS160 pathway which was altered in tumor necrosis factor alpha-treated adipocytes.

Longitudinal analysis of murine steatohepatitis model induced by chronic exposure to high-fat diet

Several lines of epidemiological evidence have suggested that non-alcoholic steatohepatitis (NASH) is closely associated with obesity in humans. However, the precise mechanisms of the progression of NASH and its key metabolic abnormalities remain to be elucidated. We found that long-term high-fat diet (HFD) exposure induces NASH, with excess body weight, hyperinsulinemia and hypercholesteremia in mice. Longitudinal analysis of the model showed that steatohepatitis was induced after onset of metabolic abnormalities. In addition, we found that expression of MCP-1 mRNA was induced in the liver before induction of TNFalpha and type I collagen alpha1 mRNAs, and prior to onset of steatohepatitis. We confirmed that hepatic MCP-1 contents were increased in mice fed HFD for 50 weeks, although the precise role of MCP-1 in the development of NASH remains to be addressed. The mouse model was also characterized by moderate reductions in catalase activity and glutathione content, as well as by overexpression of fatty acid synthase, acetyl-CoA carboxylase 1 and FAT/CD36 mRNAs in the liver. The murine NASH model apparently mimics clinical aspects of the condition and provides insight into NASH.

Non-alcoholic fatty liver disease and increased risk of cardiovascular disease

Non-alcoholic fatty liver disease (NAFLD) is present in up to one-third of the general population and in the majority of patients with cardio-metabolic risk factors such as abdominal obesity, type 2 diabetes and other components of the metabolic syndrome (MetS). Currently, the importance of NAFLD and its relationship to the MetS is increasingly recognized, and this has stimulated an interest in the possible role of NAFLD in the development of cardiovascular disease (CVD). Indeed, the impact of NAFLD on CVD risk deserves particular attention in view of the implications for screening/surveillance strategies in this growing number of patients. Recent evidence suggests that the severity of liver histology in NAFLD patients is closely associated with markers of early atherosclerosis such as greater carotid artery wall thickness and lower endothelial flow-mediated vasodilation independently of classical risk factors and components of the MetS. Moreover, NAFLD is associated with greater overall mortality and independently predicts the risk of future CVD events. Overall, the current body of evidence strongly suggests that NAFLD is likely to be associated with increased CVD risk, and raises the possibility that NAFLD may be not only a marker but also an early mediator of atherosclerosis.

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