Insulin resistance, adiponectin, cytokines in NASH: Which is the best target to treat?

[Effects of Chinese herbal medicine Jiangzhi Granule on expressions of liver X receptor α and sterol regulatory element-binding protein-1c in a rat model of non-alcoholic fatty liver disease]

OBJECTIVE

To study the effects of Jiangzhi Granule (JZG), a compound traditional Chinese herbal medicine, in regulating liver X receptor α (LXRα) and sterol regulatory element-binding protein-1c (SREBP-1c) expressions in a rat model of non-alcoholic fatty liver disease (NAFLD).

METHODS

Forty specific pathogen-free Wistar male rats were randomly divided into normal group, untreated group, pioglitazone (PIO) group and JZG group. All rats were fed with high-fat diet (88% normal chow plus 10% lard plus 2% cholesterol) for 4 weeks except for the normal group. After the NAFLD model was established, PIO and JZG were fed to rats in the corresponding groups respectively for another 4 weeks. At the end of the 8th week, liver steatosis level was observed under a light microscope with hematoxylin and eosin (HE) staining; serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and triacylglycerol (TAG) and free fatty acid (FFA) contents in liver tissues were measured. LXRα and SREBP-1c expressions in liver tissues were determined by real-time polymerase chain reaction and Western blot methods.

RESULTS

Compared with the normal group, there were physiological changes for hepatic steatosis in liver tissues in the untreated group as observed by HE staining. JZG improved serum ALT and AST levels which were significantly increased in the untreated group. Both JZG and PIO improved FFA and TAG levels in liver tissues which were significantly increased in the untreated group. mRNA and protein levels of LXRα and SREBP-1c in the untreated group were higher than those in the normal group, while the treatment of JZG and PIO lowered their expressions.

CONCLUSION

JZG may regulate fatty acid metabolic disorder by decreasing the levels of LXRα and SREBP-1c.

Diabetes is a progression factor for hepatic fibrosis in a high fat fed mouse obesity model of non-alcoholic steatohepatitis

BACKGROUND & AIMS

While type 2 diabetes is an independent risk factor for worsening of human non-alcoholic steatohepatitis (NASH) in clinical studies, it has not been systematically reported in any model whether diabetes exacerbates NASH. The study aim was to determine if diabetes causes NASH progression in a mouse model of diet induced obesity.

METHODS

C57BL/6 mice were fed a high fat diet (HFD: 45% kcal fat) or standard chow (CHOW: 12% kcal fat) for 20 weeks and some animals (HFD+DM or CHOW+DM) were also rendered diabetic by low dose streptozotocin for the final 5 weeks, to model type 2 diabetes. Serum assays included circulating insulin, triglyceride, ALT and AST, glucose, and ultrasensitive CRP and results of insulin tolerance tests. Intrahepatic lipid, triglyceride, macrophage infiltration, and fibrosis were determined. Fibrosis markers collagen-I, collagen-III, CTGF, TIMP-1, and FAP were assessed by qPCR and CTGF and collagen-I by immunostaining.

RESULTS

HFD mice were obese, insulin resistant and hyperinsulinaemic, with NASH features of elevated intrahepatic lipid and macrophages, but without fibrosis. In contrast, the HFD+DM mice exhibited fibrosis in addition to these NASH features. By ANOVA, Sirius red staining at perisinusoidal, portal tract and central vein sites, collagen-I, collagen-III, FAP, and TIMP-1 transcripts and collagen-I and CTGF protein were each significantly increased in HFD+DM, compared with CHOW alone. In a further experiment, insulin treatment protected against fibrosis and CRP increases in HFD+DM, showing that diabetes, not streptozotocin, causes the fibrosis.

CONCLUSIONS

This novel model indicates that diet-induced NASH fibrosis is exacerbated by diabetes and attenuated by insulin therapy.

Limited therapeutic effect of N-acetylcysteine on hepatic insulin resistance in an experimental model of alcohol-induced steatohepatitis

BACKGROUND

Alcohol-related steatohepatitis is associated with increased oxidative stress, DNA damage, lipotoxicity, and insulin resistance in liver. As inflammation and oxidative stress can promote insulin resistance, effective treatment with antioxidants, for example, N-acetylcysteine (NAC), may restore ethanol-impaired insulin signaling in the liver.

METHODS

Adult male Sprague-Dawley rats were fed for 130 days with liquid diets containing 0 or 37% ethanol by caloric content, and simultaneously treated with vehicle or NAC. Chow-fed controls were studied in parallel. Liver tissues were used for histopathology, cytokine activation, and insulin/IGF-1 signaling assays.

RESULTS

We observed significant positive trends of increasing severity of steatohepatitis (p = 0.016) with accumulation of neutral lipid (p = 0.0002) and triglycerides (p = 0.0004) from chow to control, to the ethanol diet, irrespective of NAC treatment. In ethanol-fed rats, NAC reduced inflammation, converted the steatosis from a predominantly microvesicular to a mainly macrovesicular histological pattern, reduced pro-inflammatory cytokine gene expression, ceramide load, and acid sphingomyelinase activity, and increased expression of IGF-1 receptor and IGF-2 in liver. However, NAC did not abrogate ethanol-mediated impairments in signaling through insulin/IGF-1 receptors, IRS-1, Akt, GSK-3β, or p70S6K, nor did it significantly reduce pro-ceramide or GM3 ganglioside gene expression in liver.

CONCLUSIONS

Antioxidant treatments reduce the severity of chronic alcohol-related steatohepatitis, possibly because of the decreased expression of inflammatory mediators and ceramide accumulation, but they do not restore insulin/IGF-1 signaling in liver, most likely due to persistent elevation of GM3 synthase expression. Effective treatment of alcohol-related steatohepatitis most likely requires dual targeting of oxidative stress and insulin/IGF resistance.

IRS2 and PTP1B: Two opposite modulators of hepatic insulin signalling

Type 2 Diabetes mellitus (T2D) is the most common endocrine disorder associated to metabolic syndrome (MS) and occurs when insulin secretion can no compensate peripheral insulin resistance. Among peripheral tissues, the liver controls glucose homeostasis due to its ability to consume and produce glucose. The molecular mechanism underlying hepatic insulin resistance is not completely understood; however, it involves the impairment of the insulin signalling network. Among the critical nodes of hepatic insulin signalling, insulin receptor substrate 2 (IRS2) and protein tyrosine phosphatase 1B (PTP1B) modulate the phosphatidylinositol (PI) 3-kinase/Akt/Foxo1 pathway that controls the suppression of gluconeogenic genes. In this review, we will focus on recent findings regarding the molecular mechanism by which IRS2 and PTP1B elicit opposite effects on carbohydrate metabolism in the liver in response to insulin. Finally, we will discuss the involvement of the critical nodes of insulin signalling in non-alcoholic fatty liver disease (NAFLD) in humans.

High liver RBP4 protein content is associated with histological features in patients with genotype 1 chronic hepatitis C and with nonalcoholic steatohepatitis

BACKGROUND AND AIM

To investigate the hepatic expression of retinol-binding protein-4 (RBP4) in chronic hepatitis C (CHC) and nonalcoholic steatohepatitis (NASH) patients, and its association with biochemical and histological patterns of liver damage.

MATERIALS AND METHODS

Sixty-six genotype 1 CHC and 32 NASH patients were tested for hepatic RBP4 expression. Liver expression at immunostaining was scored as 0 (slight), 1 (mild), 2 (moderate), and 3 (intense). In addition, the mRNA and the quantitative protein expressions of RBP4 were tested by PCR and by western blot, respectively, in 12 NASH and 28 CHC patients. Twelve subjects undergoing elective cholecystectomy served as controls.

RESULTS

Ten (31%), 16 (50%) and 6 (19%) NASH patients, and 21 (32%), 31 (47%) and 14 (21%) CHC patients had scores of 1, 2 and 3, respectively. All control subjects scored 0. In both CHC and NASH liver RBP4 scores were directly related to western blot (p=0.001 and p=0.03), not to mRNA expression (p=0.77 and p=0.40). Older age (OR, 1.07; 95%CI, 1.01-1.13), RBP4 score (4.26; 1.27-14.21) and HOMA (2.26; 1.15-4.42) were independently associated with steatosis≥10% in CHC patients. In NASH lobular inflammation (OR, 3.77; 95%CI, 1.01-24.22) and RBP4 score (4.87; 1.003-23.65) were the only risk factors for fibrosis ≥2 at logistic regression analysis.

CONCLUSION

Hepatic storage of RBP4, unrelated to its expression, could cause liver damage both in NASH and CHC.

Microsomal triglyceride transfer protein and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is currently one of the most common forms of liver disease, covering cases from simple steatosis without inflammation, to cases of steatohepatitis and fibrosis, and may lead to liver cirrhosis and hepatocellular carcinoma. The pathophysiology of nonalcoholic fatty liver disease is based on multiple events; changes in the secretion of lipoproteins can lead to steatosis. Liver lipid secretion is mediated by apoB100 and microsomal triglyceride transfer protein (MTP). The pharmacological suppression of MTP is suggested as a possible treatment for hyperlipidemia, although the upregulation of this protein can be a treatment for nonalcoholic steatohepatitis.

Transient increase in HDL-cholesterol during weight gain by hyperalimentation in healthy subjects

Determination of lipid levels is fundamental in cardiovascular risk assessment. We studied the short-term effects of fast food-based hyperalimentation on lipid levels in healthy subjects. Twelve healthy men and six healthy women with a mean age of 26 ± 6.6 years and an aged-matched control group were recruited for this prospective interventional study. Subjects in the intervention group aimed for a body weight increase of 5-15% by doubling the baseline caloric intake by eating at least two fast food-based meals a day in combination with adoption of a sedentary lifestyle for 4 weeks. This protocol induced a weight gain from 67.6 ± 9.1 kg to 74.0 ± 11 kg (P < 0.001). A numerical increase in the levels of high-density lipoprotein (HDL)-cholesterol occurred in all subjects during the study and this was apparent already at the first week in 16/18 subjects (mean increase at week 1: +22.0 ± 16%, range from -7 to +50%), whereas the highest level of HDL during the study as compared with baseline values varied from +6% to +58% (mean +31.6 ± 15%). The intake of saturated fat in the early phase of the trial related positively with the HDL-cholesterol-increase in the second week (r = 0.53, P = 0.028). Although the levels of insulin doubled at week 2, the increase in low-density lipoprotein (LDL)-cholesterol was only +12 ± 17%, and there was no statistically significant changes in fasting serum triglycerides. We conclude that hyperalimentation can induce a fast but transient increase in HDL-cholesterol that is of clinical interest when estimating cardiovascular risk based on serum lipid levels.

Enhanced expression of pro-inflammatory mediators and liver X-receptor-regulated lipogenic genes in non-alcoholic fatty liver disease and hepatitis C

NAFLD (non-alcoholic fatty liver disease) is one of the most frequent chronic liver diseases worldwide. The metabolic factors associated with NAFLD are also determinants of liver disease progression in chronic HCV (hepatitis C virus) infection. It has been reported that, besides inducing hepatic fatty acid biosynthesis, LXR (liver X receptor) regulates a set of inflammatory genes. We aimed to evaluate the hepatic expression of LXRα and its lipogenic and inflammatory targets in 43 patients with NAFLD, 44 with chronic HCV infection and in 22 with histologically normal liver. Real-time PCR and Western blot analysis were used to determine hepatic expression levels of LXRα and related lipogenic and inflammatory mediators in the study population. We found that the LXRα gene and its lipogenic targets PPAR-γ (peroxisome-proliferator-activated receptor-γ), SREBP (sterol-regulatory-element-binding protein)-1c, SREBP-2 and FAS (fatty acid synthase) were overexpressed in the liver of NAFLD and HCV patients who had steatosis. Moreover, up-regulation of inflammatory genes, such as TNF (tumour necrosis factor)-α, IL (interleukin)-6, OPN (osteopontin), iNOS (inducible NO synthase), COX (cyclo-oxygenase)-2 and SOCS (suppressors of cytokine signalling)-3, was observed in NAFLD and HCV patients. Interestingly, TNF-α, IL-6 and osteopontin gene expression was lower in patients with steatohepatitis than in those with steatosis. In conclusion, hepatic expression of LXRα and its related lipogenic and inflammatory genes is abnormally increased in NAFLD and HCV patients with steatosis, suggesting a potential role of LXRα in the pathogenesis of hepatic steatosis in these chronic liver diseases.

NCX 1000 Alone or in Combination with Vitamin E Reverses Experimental Nonalcoholic Steatohepatitis in the Rat Similarly to UDCA

We explored the therapeutic effect of NCX 1000, a derivative of ursodeoxycholic acid (UDCA) with nitric oxide (NO) donating properties, alone or in combination with vitamin E, in an experimental model of NASH in the rat. Methods. A control group was fed a standard liquid diet (Control), and the NASH groups were fed a high-fat liquid diet for 12 weeks without (NASH) or with simultaneous daily gavage with either NCX 1000 at 15 or 30 mg/kg (N15 and N30, resp.), or N15 plus vitamin E 100 mg/kg (N15  + VitE) for the last 6 weeks; UDCA 17.2 mg/kg was used as a reference. Results. NASH rats developed all key features of the disease. Treatments with N30 improved liver histology, decreased lipid peroxidation, and completely suppressed increases in LDH release, plasma insulin, and TNF-α. It also decreased O(2) (∙-) release and returned liver weight and glutathione back to normal. All effects were similar to the reference treatment, UDCA. The N15 treatment was less efficient than the N30 group, but became comparable to the latter when combined to vitamin E. Conclusion. Our study demonstrates that NCX 1000 has potent cytoprotective, antioxidant, and hypoinsulinemic properties that can be enhanced by combination with vitamin E.

Hepatic insulin resistance is associated with increased apoptosis and fibrogenesis in nonalcoholic steatohepatitis and chronic hepatitis C

BACKGROUND & AIMS

We aimed to elucidate whether hepatic insulin resistance may contribute to hepatocyte apoptosis and fibrogenesis in nonalcoholic fatty liver disease (NAFLD) and in chronic hepatitis C virus (HCV) infection.

METHODS

Twenty-seven nonalcoholic steatosis (NAST), 24 nonalcoholic steatohepatitis (NASH), 71 HCV, and 29 patients with histological normal liver (NL) were studied. Real-time PCR, the TUNEL assay, and Western blots were used to assess insulin-signaling molecules, hepatocyte apoptosis, antiapoptotic mediators, active caspase 3, and type I collagen in liver biopsies. HCV core-transfected human hepatocytes were used as an in vitro model.

RESULTS

In NAFLD patients, hepatic levels of insulin receptor substrate (IRS) 1, IRS2 2, the p85α subunit of phosphatidylinositol 3-kinase (p85α), phosphorylated protein kinase B (pAkt), phosphorylated forkhead box-containing protein O subfamily-1 (FoxO), and phosphorylated 5' adenosine monophosphate-activated protein kinase (pAMPK) as well as the antiapoptotic mediators B-cell lymphoma 2 protein (Bcl-2) and myeloid cell leukemia protein-1 (Mcl-1) were significantly lower in NASH than in NAST and NL. Furthermore, hepatocyte apoptosis and increased active caspase 3 were only present in NASH. In HCV patients, hepatic insulin signaling was markedly impaired, regardless of viral genotype and the presence of steatosis paralleled with enhanced apoptosis. In cultured human hepatocytes, HCV core protein decreased pAkt and increased phosphorylation of c-Jun N-terminal kinase (JNK). This effect was more pronounced in lipid-loaded hepatocytes.

CONCLUSIONS

Hepatic insulin signaling is impaired in NASH and HCV patients, and downregulation of insulin-sensitive targets is associated with increased apoptosis and fibrogenesis in both conditions. JNK might be a target for HCV-induced insulin resistance.

Suboptimal maternal nutrition, during early fetal liver development, promotes lipid accumulation in the liver of obese offspring

Maternal nutrition during the period of early organ development can modulate the offspring's ability to metabolise excess fat as young adults when exposed to an obesogenic environment. This study examined the hypothesis that exposing offspring to nutrient restriction coincident with early hepatogenesis would result in endocrine and metabolic adaptations that subsequently lead to increased ectopic lipid accumulation within the liver. Pregnant sheep were fed either 50 or 100% of total metabolisable energy requirements from 30 to 80 days gestation and 100% thereafter. At weaning, offspring were made obese, and at ∼1 year of age livers were sampled. Lipid infiltration and molecular indices of gluconeogenesis, lipid metabolism and mitochondrial function were measured. Although hepatic triglyceride accumulation was not affected by obesity per se, it was nearly doubled in obese offspring born to nutrient-restricted mothers. This adaptation was accompanied by elevated gene expression for peroxisome proliferator-activated receptor γ (PPARG) and its co-activator PGC1α, which may be indicative of changes in the rate of hepatic fatty acid oxidation. In contrast, maternal diet had no influence on the stimulatory effect of obesity on gene expression for a range of proteins involved in glucose metabolism and energy balance including glucokinase, glucocorticoid receptors and uncoupling protein 2. Similarly, although gene expressions for the insulin and IGF1 receptors were suppressed by obesity they were not influenced by the prenatal nutritional environment. In conclusion, excess hepatic lipid accumulation with juvenile obesity is promoted by suboptimal nutrition coincident with early development of the fetal liver.

A fresh look at NASH pathogenesis. Part 1: the metabolic movers

The strong relationship between over-nutrition, central obesity, insulin resistance/metabolic syndrome and non-alcoholic fatty liver disease (NAFLD) suggest pathogenic interactions, but key questions remain. NAFLD starts with over-nutrition, imbalance between energy input and output for which the roles of genetic predisposition and environmental factors (diet, physical activity) are being redefined. Regulation of energy balance operates at both central nervous system and peripheral sites, including adipose and liver. For example, the endocannabinoid system could potentially be modulated to provide effective pharmacotherapy of NAFLD. The more profound the metabolic abnormalities complicating over-nutrition (glucose intolerance, hypoadiponectinemia, metabolic syndrome), the more likely is NAFLD to take on its progressive guise of non-alcoholic steatohepatitis (NASH). Interactions between steatosis and insulin resistance, visceral adipose expansion and subcutaneous adipose failure (with insulin resistance, inflammation and hypoadiponectinemia) trigger amplifying mechanisms for liver disease. Thus, transition from simple steatosis to NASH could be explained by unmitigated hepatic lipid partitioning with failure of local adaptive mechanisms leading to lipotoxicity. In part one of this review, we discuss newer concepts of appetite and metabolic regulation, bodily lipid distribution, hepatic lipid turnover, insulin resistance and adipose failure affecting adiponectin secretion. We review evidence that NASH only occurs when over-nutrition is complicated by insulin resistance and a highly disordered metabolic milieu, the same 'metabolic movers' that promote type 2 diabetes and atheromatous cardiovascular disease. The net effect is accumulation of lipid molecules in the liver. Which lipids and how they cause injury, inflammation and fibrosis will be discussed in part two.

The importance of steatosis in chronic hepatitis C infection and its management: A review

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease with approximately 180 million people infected worldwide. Hepatic steatosis is a frequent histological finding in chronic hepatitis C (CHC) infection and is 2- to 3-fold more common than would be expected by chance alone. A high body mass index with excess visceral fat distribution is associated with steatosis in patients infected with HCV genotype 1 but not genotype 3, re-enforcing the concept that in patients with CHC, some have "metabolic steatosis", predominantly HCV genotype 1, and others "viral steatosis", mainly HCV genotype 3. Accumulating evidence suggests that steatosis may contribute to progression of fibrosis in CHC. Hepatic insulin resistance appears to play a role through the pro-fibrogenic effects of compensatory hyperinsulinemia. The aim of this review was to assess the effect host and viral factors play in steatosis development in patients with CHC infection and its possible relationship with hepatocellular carcinoma. The review examines the mechanisms by which CHC infection causes hepatic steatosis, the impact hepatic steatosis has on the natural history of the disease and finally, explores if treatments leading to a reduction in the amount of steatosis might lead to improved treatment outcomes. The basic medical science of steatosis in CHC will be discussed including proposed models of steatogenesis and the influence of viral and metabolic factors at the molecular level and how these might impact on current and future therapies.

Interaction of adipokines and hepatitis B virus on histological liver injury in the Chinese

OBJECTIVES

Chronic hepatitis B patients with diabetes and metabolic syndrome are at increased risk of cirrhosis and hepatocellular carcinoma, but the underlying mechanism is unclear. Our objective was to test whether dysregulation of adipokines contributes to liver injury. We also studied whether viral factors affected adipokines, insulin resistance, and hepatic steatosis.

METHODS

A prospective cohort of 266 chronic hepatitis B patients undergoing liver biopsy was studied. Fasting blood was taken for the analysis of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), adiponectin, leptin, and resistin. Insulin resistance was assessed by the homeostasis model assessment of insulin resistance (HOMA-IR). Factors associated with significant necroinflammation and cirrhosis were identified.

RESULTS

Histological activity index was correlated with serum TNF-alpha (R=0.40, P<0.0001) and IL-6 (R=0.32, P<0.0001) but not with adiponectin, leptin, or resistin. By multivariate analysis, TNF-alpha was associated with significant necroinflammation after adjusting for age and viral factors (odds ratio (OR) 1.041, 95% confidence interval (CI) 1.002-1.082, P=0.04). Serum adiponectin had positive correlation with hepatitis B virus DNA (R=0.17, P=0.007) and was decreased in patients with insulin resistance and hepatic steatosis. On the other hand, viral load, hepatitis B e-antigen status, and genotypes had no association with insulin resistance, hepatic steatosis, and the levels of TNF-alpha and IL-6. A total of 68 (25.6%) patients had cirrhosis. HOMA-IR, but not adipokine dysregulation, was independently associated with cirrhosis (OR 1.09, 95% CI 1.02-1.15, P=0.006).

CONCLUSIONS

TNF-alpha and/or IL-6 contribute to hepatic necroinflammation in chronic hepatitis B patients. Adiponectin protects against insulin resistance and hepatic steatosis but does not affect liver injury. Adipokines and viral factors contribute to liver injury independently.

IL-6 deficiency attenuates murine diet-induced non-alcoholic steatohepatitis

BACKGROUND

The role of inflammation in the pathogenesis of non-alcoholic steatohepatitis (NASH), a common cause of liver disease, is still poorly understood. This study aimed at assessing the involvement of a major inflammatory cytokine, IL-6, in NASH.

MATERIALS AND METHODS

Steatohepatitis was induced by feeding wild-type or IL-6(-/-) mice for 5 weeks with a methionine and choline-deficient (MCD) diet.

RESULTS

Whereas MCD diet-induced weight loss and decreases in serum glucose, cholesterol and triglyceride levels were similar in both genotypes, serum alanine aminotransferase was less elevated in IL-6(-/-) mice than in wild-type animals. Despite having a comparable liver steatosis score, IL-6-deficient mice exhibited less lobular inflammation than their wild-type littermates. Liver gene expression of TGF-beta and MCP-1 was also strongly attenuated in mutant mice; a more modest reduction was observed for PPAR-gamma and F4/80 transcripts as well as proteins. Chromatographic analysis of liver lipids demonstrated that MCD diet induced in normal and mutant mice a similar decrease in the ratio of phosphatidylcholine to phosphatidylethanolamine. However, the diet-induced increase in the levels of sphingomyelin and ceramide was less important in IL-6(-/-) mice.

CONCLUSION

Altogether, these results indicate that IL-6 deficiency does not block the development of NASH; yet, IL-6 plays a critical role in the accompanying liver inflammation.

Crosstalk between angiogenesis, cytokeratin-18, and insulin resistance in the progression of non-alcoholic steatohepatitis

AIM: To elucidate the possible crosstalk between angiogenesis, cytokeratin-18 (CK-18), and insulin resistance (IR) especially in patients with non-alcoholic steatohepatitis (NASH).

METHODS: Twenty-eight patients with NASH and 11 with simple fatty liver disease (FL) were enrolled in this study and underwent clinicopathological examination. The measures of angiogenesis, CK-18, and IR employed were CD34-immunopositive vessels, CK-18-immunopositive cells, and homeostasis model assessment of IR (HOMA-IR), respectively. The correlations of these factors with NASH were elucidated.

RESULTS: Significant development of hepatic neovascularization was observed only in NASH, whereas almost no neovascularization could be observed in FL and healthy liver. The degree of angiogenesis was almost parallel to liver fibrosis development, and both parameters were positively correlated. Similarly, CK-18 expression and HOMA-R were significantly increased in NASH as compared with FL and healthy liver. Furthermore, CK-18 and HOMA-IR were also positively correlated with the degree of neovascularization.

CONCLUSION: These results indicate that the crosstalk between angiogenesis, CK-18, and IR may play an important role in the onset and progression of NASH.

Identifying non-alcoholic fatty liver disease among asymptomatic overweight and obese individuals by clinical and biochemical characteristics

OBJECTIVE

To determine the prevalence of liver steatosis among asymptomatic individuals attending an out-patient clinic for a problem of overweight, and to define the discriminatory value of several characteristics for predicting liver steatosis among them.

DESIGN AND PARTICIPANTS

Consecutive patients Swith a body mass index (BMI) of > or =25 kg/m2 who consented to undergo liver ultrasound and blood tests were recruited for inclusion. Receiver operating characteristic (ROC) curves were generated and statistical indices of diagnostic performance and their corresponding 95% confidence intervals (95% CI) were computed. Logistic regression analyses were performed to determine whether a combination of characteristics could improve diagnostic accuracy.

RESULTS

We enrolled sixty-eight subjects (mean BMI, 37.5 kg/m2), of whom 39 (57.4%) had liver steatosis on ultrasound. Logistic regression analyses indicated that only 3 variables were significantly and independently correlated with liver steatosis: female gender, low adiponectin levels, and high insulin resistance index. A composite index for predicting liver steatosis was calculated by summing the risk factors of female gender, low adiponectin, and insulin resistance index (FAIR score). The accuracy of this score was determined by ROC analysis to be 0.85 (95% CI, 0.74-0.96; P < 0.001). The presence of two or more risk factors (FAIR score > or =2) had a sensitivity, specificity, positive predictive value, and negative predictive value of 77%, 91%, 92%, and 74%, respectively. The likelihood ratio for a positive result was 8.43.

CONCLUSIONS

Among asymptomatic overweight individuals attending an out-patient clinic, the prevalence of liver steatosis on ultrasound is 57%. Female gender, the insulin resistance index, and low adiponectin are significant and independent predictors of liver steatosis. A combination of these three factors allows sensitivity and specificity for non alcoholic fatty liver of 77% and 91%, respectively.

The liver and the waistline: Fifty years of growth

Fifty years of the Gastroenterological Society of Australia have witnessed the changing appearance of Australians. Asian immigration has transformed the dominant urban culture from European to Eurasian, with some unique Australian attributes. Meanwhile, global conditions have altered body shape, and our sports-proud country is now fat! Thus, as in North America, Europe, China, and affluent Asia-Pacific countries, prosperity and lifestyle, cheap processed foods coupled with reduced physical activity have created an epidemic of over-nutrition resulting in overweight/obesity. Additional genetic factors are at the core of the apple shape (central obesity) that typifies over-nourished persons with metabolic syndrome. Indigenous Australians, once the leanest and fittest humans, now have exceedingly high rates of obesity and type 2 diabetes, contributing to shorter life expectancy; Asian Australians are also at higher risk. Like non-steroidal anti-inflammatory drugs (NSAIDs) and cigarette smoking, obesity now contributes much to gastrointestinal morbidity and mortality (gastroesophageal reflux disease, cancers, gallstones, endoscopy complications). This review focuses on Australian research about fatty liver, particularly roles of central obesity/insulin resistance in non-alcoholic fatty liver disease/steatohepatitis (NAFLD/NASH). The outputs include many highly cited original articles and reviews and the first book on NAFLD. Studies have identified community prevalence, clinical outcomes, association with insulin resistance, metabolic syndrome and hypoadiponectinemia, developed and explored animal models for mechanisms of inflammation and fibrosis, conceptualized etiopathogenesis, and demonstrated that NASH can be reversed by lowering body weight and increasing physical activity. The findings have led to development of regional guidelines on NAFLD, the first internationally, and should now inform daily practice of gastroenterologists.

Roles of adipose restriction and metabolic factors in progression of steatosis to steatohepatitis in obese, diabetic mice

BACKGROUND AND AIMS

We previously reported that steatohepatitis develops in obese, hypercholesterolemic, diabetic foz/foz mice fed a high-fat (HF) diet for 12 months. We now report earlier onset of steatohepatitis in relation to metabolic abnormalities, and clarify the roles of dietary fat and bodily lipid partitioning on steatosis severity, liver injury and inflammatory recruitment in this novel non-alcoholic steatohepatitis (NASH) model.

METHODS

Foz/foz (Alms1 mutant) and wild-type (WT) mice were fed a HF diet or chow, and metabolic characteristics and liver histology were studied at 2, 6, 12 and 24 weeks.

RESULTS

After 12 weeks HF-feeding, foz/foz mice were obese and diabetic with approximately 70% reduction in serum adiponectin. Hepatomegaly developed at this time, corresponding to a plateau in adipose expansion and increased adipose inflammation. Liver histology showed mild inflammation and hepatocyte ballooning as well as steatosis. By 24 weeks, HF-fed foz/foz mice developed severe steatohepatitis (marked steatosis, alanine aminotransferase elevation, ballooning, inflammation, fibrosis), whereas dietary and genetic controls showed only simple steatosis. While steatosis was associated with hepatic lipogenesis, indicated by increased fatty acid synthase activity, steatohepatitis was associated with significantly higher levels of CD36, indicating active fatty acid uptake, possibly under the influence of peroxisome proliferator-activated receptor-gamma.

CONCLUSION

In mice genetically predisposed to obesity and diabetes, HF feeding leads to restriction of adipose tissue for accommodation of excess energy, causing lipid partitioning into liver, and transformation of simple steatosis to fibrosing steatohepatitis. The way in which HF feeding 'saturates' adipose stores, decreases serum adiponectin and causes hepatic inflammation in steatohepatitis may provide clues to pathogenesis of NASH in metabolic syndrome.

Low serum adiponectin levels are predictive of advanced hepatic fibrosis in patients with NAFLD

BACKGROUND

Adiponectin, an adipocytokine-mediating insulin action, has recently been found to be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to assess possible associations between serum adiponectin levels and factors of the metabolic syndrome or histologic parameters in biopsy-proven NAFLD.

METHODS

Patients with persistently abnormal liver function tests satisfying inclusion criteria were subjected to liver biopsy. Fibrosis stage and the NAFLD activity score were recorded for each patient. Body mass index, waist-to-hip ratio, factors of the metabolic syndrome (central obesity, hyperglycemia, hypertriglyceridemia, low high-density lipoprotein, and hypertension), and biochemical tests were also recorded. Insulin resistance was calculated by the homeostasis model assessment method. Serum adiponectin concentration was measured by an enzyme-linked immunosorbent assay.

RESULTS

Forty-two NAFLD patients, including 9 with compensated cirrhosis, were included in the study. The presence of each factor of the metabolic syndrome was associated with hypoadiponectinemia. Adiponectin negatively correlated with homeostasis model assessment (r=-0.551, P=0.001). Adiponectin concentration was negatively associated with higher stages of fibrosis (one-wayanalysis of variance, P=0.007), and was not associated with NAFLD activity score. Using multivariate logistic regression, adiponectin concentration, aspartate aminotransferase/alanine aminotransferase ratio, and the presence of waist-to-hip ratio >1 were independent predictors of advanced fibrosis. The receiver operating characteristic curve for detecting advanced fibrosis using a combination of the independent variables had an area under the curve of 0.902+/-0.054, P<0.0001.

CONCLUSIONS

Low serum adiponectin levels in NAFLD patients are suggestive of advanced fibrosis. Therefore, assessment of serum adiponectin levels may be useful in clinical follow-up.

Non-alcoholic fatty liver disease pathogenesis: the present and the future

Non-alcoholic fatty liver disease is the clinical hepatic expression of metabolic syndrome. The prevalence of non-alcoholic fatty liver disease is around 20-30%, and with a rapid increase in the metabolic risk factors in the general population, non-alcoholic fatty liver disease has become the most common cause of liver disease worldwide. A fraction (20-30%) of non-alcoholic fatty liver disease patients develop a potentially progressive hepatic disorder, namely non-alcoholic steatohepatitis, leading to end-stage liver disease. The pathogenesis of non-alcoholic fatty liver disease is not entirely understood, and even if insulin resistance is a major pathogenetic key, many other factors are implicated in both liver fat accumulation and disease progression to non-alcoholic steatohepatitis. In this review we aim to examine the literature, principally concerning human non-alcoholic fatty liver disease pathogenesis, and to identify the newest, most promising clinical and basic research data.

Targeted disruption of carcinoembryonic antigen-related cell adhesion molecule 1 promotes diet-induced hepatic steatosis and insulin resistance

Carcinoembryonic antigen-related cell adhesion molecule 1 (CC1) is a cell adhesion molecule within the Ig superfamily. The Tyr-phosphorylated isoform of CC1 (CC1-L) plays an important metabolic role in the regulation of hepatic insulin clearance. In this report, we show that CC1-deficient (Cc1(-/-)) mice are prone to hepatic steatosis, as revealed by significantly elevated hepatic triglyceride and both total and esterified cholesterol levels compared with age-matched wild-type controls. Cc1(-/-) mice were also predisposed to lipid-induced hepatic steatosis and dysfunction as indicated by their greater susceptibility to store lipids and express elevated levels of enzymatic markers of liver damage after chronic feeding of a high-fat diet. Hepatic steatosis in the Cc1(-/-) mice was linked to a significant increase in the expression of key lipogenic (fatty acid synthase, acetyl CoA carboxylase) and cholesterol synthetic (3-hydroxy-3-methylglutaryl-coenzyme A reductase) enzymes under the control of sterol regulatory element binding proteins-1c and -2 transcription factors. Cc1(-/-) mice also exhibited impaired insulin clearance, glucose intolerance, liver insulin resistance, and elevated hepatic expression of the key gluconeogenic transcriptional activators peroxisome proliferator-activated receptor-gamma coactivator-1 and Forkhead box O1. Lack of CC1 also exacerbated both glucose intolerance and hepatic insulin resistance induced by high-fat feeding, but insulin clearance was not further deteriorated in the high-fat-fed Cc1(-/-) mice. In conclusion, our data indicate that CC1 is a key regulator of hepatic lipogenesis and that Cc1(-/-) mice are predisposed to liver steatosis, leading to hepatic insulin resistance and liver damage, particularly when chronically exposed to dietary fat.

Apoptosis in experimental NASH is associated with p53 activation and TRAIL receptor expression

BACKGROUND AND AIMS

We examined extrinsic and intrinsic (endogenous) mitochondrial apoptosis pathways in experimental non-alcoholic steatohepatitis (NASH).

METHODS

To assess extrinsic pathways, we measured hepatic expression of death-inducing cytokine receptors (tumor necrosis factor-alpha-receptor (TNF-R)1, TNF-R2, Fas, and TNFalpha-related apoptosis-inducing ligand-receptor (TRAIL-R) mRNA, TUNEL, caspase 3 activation, liver injury and liver pathology in mice fed a methionine and choline deficient (MCD) diet. For endogenous stress pathways, we determined serum insulin-like growth factor-1 (IGF-1), hepatic p53, Bcl-XL, tBid and p21 expression.

RESULTS

Methionine and choline deficient feeding increased alanine aminotransferase (ALT) and apoptosis from day 10, without increases in TNF-R1, TNF-R2, and Fas. However, murine TRAIL receptors, particularly decoyTRAIL-R1/TNFRSFH23 and Killer/DR5 mRNA increased. MCD feeding enhanced hepatic p53 expression, corresponding to approximately 50% fall in serum IGF-1, decreased Bcl-XL, enhanced Bid cleavage to tBid, and up-regulation of p21. Nutritional restitution experiments showed that correcting either methionine or choline deficiency suppressed liver inflammation (extrinsic pathway), but failed to correct apoptosis, IGF-1 or p53.

CONCLUSIONS

Methionine and choline deficiency lower IGF-1 to de-repress p53 during induction of steatohepatitis. The p53 induced by nutritional stress is biologically active in mediating mitochondrial cell death pathways, but may also be responsible for TRAIL receptor expression, thereby linking intrinsic and exogenous apoptosis pathways in NASH.

VSL#3 probiotic treatment attenuates fibrosis without changes in steatohepatitis in a diet-induced nonalcoholic steatohepatitis model in mice

Nonalcoholic fatty liver disease (NAFLD) and its advanced stage, nonalcoholic steatohepatitis (NASH), are the most common causes of chronic liver disease in the United States. NASH features the metabolic syndrome, inflammation, and fibrosis. Probiotics exhibit immunoregulatory and anti-inflammatory activity. We tested the hypothesis that probiotic VSL#3 may ameliorate the methionine-choline-deficient (MCD) diet-induced mouse model of NASH. MCD diet resulted in NASH in C57BL/6 mice compared to methionine-choline-supplemented (MCS) diet feeding evidenced by liver steatosis, increased triglycerides, inflammatory cell accumulation, increased tumor necrosis factor alpha levels, and fibrosis. VSL#3 failed to prevent MCD-induced liver steatosis or inflammation. MCD diet, even in the presence of VSL#3, induced up-regulation of serum endotoxin and expression of the Toll-like receptor 4 signaling components, including CD14 and MD2, MyD88 adaptor, and nuclear factor kappaB activation. In contrast, VSL#3 treatment ameliorated MCD diet-induced liver fibrosis resulting in diminished accumulation of collagen and alpha-smooth muscle actin. We identified increased expression of liver peroxisome proliferator-activated receptors and decreased expression of procollagen and matrix metalloproteinases in mice fed MCD+VSL#3 compared to MCD diet alone. MCD diet triggered up-regulation of transforming growth factor beta (TGFbeta), a known profibrotic agent. In the presence of VSL#3, the MCD diet-induced expression of TGFbeta was maintained; however, the expression of Bambi, a TGFbeta pseudoreceptor with negative regulatory function, was increased. In summary, our data indicate that VSL#3 modulates liver fibrosis but does not protect from inflammation and steatosis in NASH. The mechanisms of VSL#3-mediated protection from MCD diet-induced liver fibrosis likely include modulation of collagen expression and impaired TGFbeta signaling.

A rabbit model of pediatric nonalcoholic steatohepatitis: the role of adiponectin

AIM

To create a rabbit model of pediatric nonalcoholic steatohepatitis (NASH) and to evaluate the role of adiponectin in the process.

METHODS

Thirty-two specific pathogen-free male New Zealand rabbits were divided randomly into three groups: (1) the normal control group (n = 10) was fed with standard diet for 12 wk; (2) the model group A (n = 11); and (3) model group B (n = 11) were fed with a high-fat diet (standard diet + 10% lard + 2% cholesterol) for 8 and 12 wk, respectively. Hepatic histological changes were observed and biochemical parameters as well as serum levels of adiponectin, interleukin (IL)-6, IL-10 and tumor necrosis factor (TNF)-alpha were measured.

RESULTS

Typical histological hepatic lesions of NASH were observed in both model groups described as liver steatosis, liver inflammatory infiltration, cytologic ballooning, perisinusoidal fibrosis and overall fibrosis. Compared with the normal control group, there were significant increases in model groups A and B in weight gain (1097.2 +/- 72.3, 1360.5 +/- 107.6 vs 928.0 +/- 58.1, P < 0.05, P < 0.01), liver weight (93.81 +/- 6.64, 104.6 +/- 4.42 vs 54.4 +/- 1.71, P < 0.01), Lg (ALT) (1.9 +/- 0.29, 1.84 +/- 0.28 vs 1.60 +/- 0.17, P < 0.01), and Lg (TG) (1.03 +/- 0.24, 1.16 +/- 0.33 vs 0.00 +/- 0.16, P < 0.01). Weight gain was much more in model group B than in model group A (1360.5 +/- 107.6 vs 1097.2 +/- 72.3, P < 0.05). But, there was no significant difference between the two groups concerning the other indexes. Pro-inflammatory cytokines (IL-6 and TNF-alpha) increased in model group B compared with that of control and model group A (IL-6: 1.86 +/- 0.21 vs 1.41 +/- 0.33, 1.38 +/- 0.42, P < 0.01; TNF-alpha: 1.18 +/- 0.07 vs 0.66 +/- 0.08, 0.86 +/- 0.43, P < 0.01, P < 0.05), whereas serum adiponectin and IL-10 decreased in model groups compared with that in the control (adiponectin: A: 21.87 +/- 4.84 and B: 21.48 +/- 4.60 vs 27.36 +/- 7.29, P < 0.05. IL-10: A: 1.72 +/- 0.38 and B: 1.83 +/- 0.39 vs 2.26 +/- 0.24, P < 0.01). Lg (TC) and the degree of liver fatty infiltration was an independent determinant of serum adiponectin level analyzed by stepwise multiple regressions, resulting in 29.4% of variances.

CONCLUSION

This rabbit model produces the key features of pediatric NASH and may provide a realistic model for future studies. Adiponectin level partially reflects the severity of liver steatosis, but not the degree of liver inflammation.

Chitosan ameliorates the severity of steatohepatitis induced by high fat diet in rats

OBJECTIVE

Currently, no agent has been conclusively demonstrated to prevent the progression of non-alcoholic steatohepatitis (NASH). Chitosan, a natural product derived from chitin, was thought to possess hypocholesterolemic properties. The aim of this study was to evaluate the potential effects of chitosan on nutritional steatohepatitis in rats.

MATERIAL AND METHODS

Rats were fed with a high fat diet for 4 weeks to develop NASH that was confirmed by liver biopsy, and then 4 weeks of chitosan was given. Serum chemistry and liver histology were assessed and the steatoinflammatory mechanisms were studied.

RESULTS

Chitosan significantly protected against high fat diet-induced hepatic steatohepatitis. This effect was associated with repressed serum levels of total protein (TP), globulin (GLO), alanine aminotransferase (ALAT), alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (GGT), total cholesterol (TC) and low-density lipoprotein (LDL). Chitosan elevated the serum levels of high-density lipoprotein (HDL) and the ratio of albumin to globulin. Furthermore, increased TNF-alpha, lipoemia, hyperinsulinemia, hyperleptinemia and hypoadiponectin in NASH were significantly ameliorated by treatment with chitosan.

CONCLUSIONS

Chitosan effectively attenuated the steatohepatitis induced by a high fat diet. The therapeutic effect of chitosan on NASH may be activated through exerting an influence on adipokines.

Comparative therapeutic effects of metformin and vitamin E in a model of non-alcoholic steatohepatitis in the young rat

Only in the last few years has non-alcoholic steatohepatitis been recognized as an important and relatively common liver disease. To date, the therapeutic options are limited, vitamin E and metformin have been proposed for the treatment of this condition, although their mechanisms are not completely clarified as yet. The aim of this study was to investigate the anti-inflammatory and anti-oxidative mechanisms of these drugs in an experimental model of non-alcoholic steatohepatitis in the young rat. Male rats, just after weaning, were divided into four groups: a control group that received a standard diet; a high fat diet group; two high fat diet fed groups treated with vitamin E or metformin, respectively. After 4 weeks, we evaluated in the liver the modification of lipid peroxidation, assessed by malondialdehyde, TNF-alpha levels, S-nitrosylated protein, inducible nitric oxide sinthase (iNOS), and peroxisome proliferators-activated receptors (PPAR) expression and metalloproteinase activity. High fat diet increased malondialdehyde, nitrotyrosilated proteins, and TNF-alpha tissue content. Moreover, a decrease of PPAR-alpha and an increase of PPAR-gamma expression were observed. An increase of metalloproteinase activity was also shown. Among drug treatments, metformin reduced body weight gain and fat mass, metalloproteinase activity, and TNF-alpha tissue content, while it restored PPAR-alpha expression and downregulated PPAR-gamma expression. Vitamin E reduced the oxidative damage, protein nitrotyrosilation, and tissue TNF-alpha levels. Moreover a decrease of PPAR-gamma expression was also shown. These findings confirm the efficacy of both drugs as therapeutic tools in preventing the early onset of liver damage and non-alcoholic fatty liver disease progression.

Effects of n-3 polyunsaturated fatty acids from seal oils on nonalcoholic fatty liver disease associated with hyperlipidemia

AIM: To investigate the efficacy and safety of n-3 polyunsaturated fatty acids (PUFA) from seal oils for patients with nonalcoholic fatty liver disease (NAFLD) associated with hyperlipidemia.

METHODS: One hundred and forty-four patients with NAFLD associated with hyperlipidemia were included in the 24-wk, randomized, controlled trial. The patients were randomized into two groups. Group A (n = 72) received recommended diet and 2 g n-3 PUFA from seal oils, three times a day. Group B (n = 72) received recommended diet and 2 g placebo, three times a day. Primary endpoints were fatty liver assessed by symptom scores, liver alanine aminotransferase (ALT) and serum lipid levels after 8, 12, 16, and 24 wk. Hepatic fat infiltration was detected by ultrasonography at weeks 12 and 24 after treatment.

RESULTS: A total of 134 patients (66 in group A, 68 in group B) were included in the study except for 10 patients who were excluded from the study. After 24 wk of treatment, no change was observed in body weight, fasting blood glucose (FBG), renal function and blood cells of these patients. Total symptom scores, ALT and triglyceride (TG) levels decreased more significantly in group A than in group B (P < 0.05). As expected, there was a tendency toward improvement in aspartate aminotransferase (AST), γ-glutamyltranspeptidase (GGT), and total cholesterol (TCHO) and high-density lipoprotein (HDL) cholesterol levels (P < 0.05) after administration in the two groups. However, no significant differences were found between the two groups. The values of low-density lipoprotein (LDL) were significantly improved in group A (P < 0.05), but no significant change was found in group B at different time points and after a 24-wk treatment. After treatment, complete fatty liver regression was observed in 19.70% (13/66) of the patients, and an overall reduction was found in 53.03% (35/66) of the patients in group A. In contrast, in group B, only five patients (7.35%, 5/68) achieved complete fatty liver regression (P = 0.04), whereas 24 patients (35.29%, 24/68) had a certain improvement in fatty liver (P = 0.04). No serious adverse events occurred in all the patients who completed the treatment.

CONCLUSION: Our results indicate that n-3 PUFA from seal oils is safe and efficacious for patients with NAFLD associated with hyperlipidemia and can improve their total symptom scores, ALT, serum lipid levels and normalization of ultrasonographic evidence. Further study is needed to confirm these results.

Animal models of NASH: getting both pathology and metabolic context right

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of referral to liver clinics, and its progressive form, non-alcoholic steatohepatitis (NASH), can lead to cirrhosis and end-stage liver disease. The main risk factors for NAFLD/NASH are the metabolic abnormalities commonly observed in metabolic syndrome: insulin resistance, visceral obesity, dyslipidemia and altered adipokine profile. At present, the causes of progression from NAFLD to NASH remain poorly defined, and research in this area has been limited by the availability of suitable animal models of this disease. In the past, the main models used to investigate the pathogenesis of steatohepatitis have either failed to reproduce the full spectrum of liver pathology that characterizes human NASH, or the liver pathology has developed in a metabolic context that is not representative of the human condition. In the last few years, a number of models have been described in which the full spectrum of liver pathology develops in an appropriate metabolic context. In general, the underlying cause of metabolic defects in these models is chronic caloric overconsumption, also known as overnutrition. Overnutrition has been achieved in a number of different ways, including forced feeding, administration of high-fat diets, the use of genetically hyperphagic animals, or a combination of these approaches. The purpose of the present review is to critique the liver pathology and metabolic abnormalities present in currently available animal models of NASH, with particular focus on models described in approximately the last 5 years.

Nonalcoholic fatty liver disease: the potential role of nutritional management

PURPOSE OF REVIEW

To review available data pertaining to dietary imbalances and metabolic alterations leading to the development of fatty liver disease and nutritional managements.

RECENT FINDINGS

The importance of treating fatty liver disease is now firmly recognized not only because of the risk of progression toward a more aggressive liver disease but also because the fatty liver is an important provider of cardiovascular risks. The ideal diet for nonalcoholic fatty liver disease/nonalcoholic steatohepatitis patients should reduce fat mass and inflammation in the adipose tissue, restore insulin sensitivity, and provide low amounts of substrates for de-novo lipogenesis, but scientific evidence to recommend specific diets is currently lacking. Moderate weight loss, low-calorie diets, reduction in saturated fatty acids intake, together with an increase in monosaturated and n-3 polyunsaturated fatty acids appear to be beneficial. Excessive consumption of high glycemic index carbohydrates appears deleterious, as it favors hyperglycemia and hyperinsulinemia and stimulates de-novo lipogenesis. Physical exercise is an important component of the approach, as it improves insulin sensitivity. Behavioral therapy promotes long-term compliance to lifestyle modifications.

SUMMARY

One panacea is unlikely to be found, the more useful approach is probably multimodal and includes tailored lifestyle modifications. Randomized controlled trials are needed to establish dietary recommendations. While awaiting such trials, reduced consumption of simple sugar, especially sweetened beverages, and incremental increase in physical activity must be encouraged.

Extrahepatic hepatitis C virus after transplantation: diabetes and renal dysfunction

1. Insulin resistance is associated with hepatitis C virus infection and plays a role in the progression of hepatitis C virus-related liver disease and fibrosis. 2. Treating insulin resistance and achieving glycemic control will be important for improving post-liver transplant morbidity and mortality: control of the hepatitis C virus will help to accomplish this. 3. The main renal complication of hepatitis C virus is membranoproliferative glomerulonephritis, and this occurs most commonly in the setting of mixed cryoglobulinemia.

Retinol-binding protein 4: a new marker of virus-induced steatosis in patients infected with hepatitis c virus genotype 1

Retinol-binding protein 4 (RBP4) is an adipocytokine associated with insulin resistance (IR). We tested serum levels of RBP4 to assess its link with steatosis in patients with genotype 1 chronic hepatitis C (CHC) or nonalcoholic fatty liver disease (NAFLD). Nondiabetic patients with CHC (n = 143) or NAFLD (n = 37) were evaluated by liver biopsy and anthropometric and metabolic measurements, including IR by the homeostasis model assessment. Biopsies were scored by Scheuer classification for CHC, and Kleiner for NAFLD. Steatosis was tested as a continuous variable and graded as absent-mild <30%, or moderate-severe > or =30%. Thirty nondiabetic, nonobese blood donors served as controls. RBP4 levels were measured by a human competitive enzyme-linked immunosorbent assay kit (AdipoGen). Mean values of RBP4 were similar in NAFLD and CHC (35.3 +/- 9.3 microg/L versus 36.8 +/- 17.6; P = 0.47, respectively), and both were significantly higher than in controls (28.9 +/- 12.1; P = 0.02 and P = 0.01, respectively). RBP4 was higher in CHC patients with steatosis than in NAFLD (42.1 +/- 19.7 versus 35.2 +/- 9.3; P = 0.04). By linear regression, RBP4 was independently linked to steatosis only (P = 0.008) in CHC, and to elevated body mass index (P = 0.01) and low grading (P = 0.04) in NAFLD. By linear regression, steatosis was independently linked to homeostasis model assessment score (P = 0.03) and high RBP4 (P = 0.003) in CHC. By logistic regression, RBP4 was the only variable independently associated with moderate-severe steatosis in CHC (odds ratio, 1.045; 95% confidence interval, 1.020 to 1.070; P = 0.0004), whereas waist circumference was associated with moderate-severe steatosis in NAFLD (odds ratio, 1.095; 95% confidence interval, 1.007 to 1.192; P = 0.03).

CONCLUSION

In nondiabetic, nonobese patients with genotype 1 CHC, serum RBP4 levels might be the expression of a virus-linked pathway to steatosis, largely unrelated to IR.

Hepatic microcirculation in fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), the most common cause of steatosis, is associated with visceral obesity and insulin resistance. With more severe risk factors (obesity, type 2 diabetes [T2D], metabolic syndrome), steatosis may be complicated by hepatocellular injury and liver inflammation (steatohepatitis or NASH). NASH can lead to perisinusoidal fibrosis and cirrhosis. Fat-laden hepatocytes are swollen, and in steatohepatitis, further swelling occurs due to hydropic change (ballooning) of hepatocytes to cause sinusoidal distortion, as visualized by in vivo microscopy, reducing intrasinusoidal volume and microvascular blood flow. Involvement of other cell types (sinusoidal endothelial cells, Kupffer cells, stellate cells) and recruitment of inflammatory cells and platelets lead to dysregulation of microvascular blood flow. In animal models, the net effect of such changes is a marked reduction of sinusoidal space (approximately 50% of control), and a decrease in the number of normally perfused sinusoids. Such microvascular damage could accentuate further liver injury and disease progression in NASH. The fatty liver is also exquisitely sensitive to ischemia-reperfusion injury, at least partly due to the propensity of unsaturated fatty acids to undergo lipid peroxidation in the face of reactive oxygen species (ROS). This has important clinical consequences, particularly limiting the use of fatty donor livers for transplantation. In this review, we discuss available data about the effects of steatosis and steatohepatitis on the hepatic microvascular structure and sinusoidal blood flow, highlighting areas for future investigation.

Metabolic profiles in patients with chronic hepatitis C: a case-control study

BACKGROUND

The clinical implications of metabolic profiles in patients with chronic hepatitis C remain controversial. To study the association of metabolic abnormalities with chronic hepatitis C, we conducted a case-control study with special emphasis on serum lipid pattern, fasting blood glucose, and adiponectin.

METHODS

We enrolled 500 patients with chronic hepatitis C and 536 sex and age-matched controls. Unadjusted and adjusted associations of demographic and metabolic variables were estimated.

RESULTS

Chronic hepatitis C patients had higher alanine aminotransferase (ALT) and high-density lipoprotein-cholesterol levels, but lower total cholesterol (TC), triglyceride (TG), and low-density lipoprotein-cholesterol levels than controls. Stratifying ALT level according to its upper limit of normal, HCV infection was associated with younger age, female gender, and higher TC levels in chronic hepatitis C patients with normal ALT levels, but with lower TC and lower TG levels in those with abnormal ALT levels. By using multiple linear regression analyses for subjects with available adiponectin data, presence of HCV infection was independently associated with higher serum adiponectin levels.

CONCLUSIONS

Metabolic profiles of chronic hepatitis C patients are affected by age, gender, serum adiponectin, and ALT levels. Further longitudinal studies are needed to clarify the complex interplay between HCV infection and metabolic profiles.

Fast-food-based hyper-alimentation can induce rapid and profound elevation of serum alanine aminotransferase in healthy subjects

OBJECTIVE

To study the effect of fast-food-based hyper-alimentation on liver enzymes and hepatic triglyceride content (HTGC).

DESIGN

Prospective interventional study with parallel control group.

SETTING

University Hospital of Linköping, Sweden.

PARTICIPANTS

12 healthy men and six healthy women with a mean (SD) age of 26 (6.6) years and a matched control group.

INTERVENTION

Subjects in the intervention group aimed for a body weight increase of 5-15% by eating at least two fast-food-based meals a day with the goal to double the regular caloric intake in combination with adoption of a sedentary lifestyle for 4 weeks.

MAIN OUTCOME MEASURES

Weekly changes of serum aminotransferases and HTGC measured by proton nuclear magnetic resonance spectroscopy at baseline and after the intervention.

RESULTS

Subjects in the intervention group increased from 67.6 (9.1) kg to 74.0 (11) kg in weight (p<0.001). Serum ALT increased from 22.1 (11.4) U/l at study start to an individual mean maximum level of 97 (103) U/l (range 19.4-447 U/l). Eleven of the 18 subjects persistently showed ALT above reference limits (women >19 U/l, men >30 U/l) during the intervention. Sugar (mono- and disaccharides) intake during week 3 correlated with the maximal ALT/baseline ALT ratio (r = 0.62, p = 0.006). HTGC increased from 1.1 (1.9)% to 2.8 (4.8)%, although this was not related to the increase in ALT levels. ALT levels were unchanged in controls.

CONCLUSION

Hyper-alimentation per se can induce profound ALT elevations in less than 4 weeks. Our study clearly shows that in the evaluation of subjects with elevated ALT the medical history should include not only questions about alcohol intake but also explore whether recent excessive food intake has occurred.

Impact of non-alcoholic fatty liver disease on accelerated metabolic complications

Insulin resistance is the basis of both non-alcoholic fatty liver disease (NAFLD) and metabolic syndrome (MetS), the two conditions are often found in the same individual. The mortality of patients with NAFLD is significantly higher than that among the general population and cardiovascular risk may compete with liver-related risk in dictating the final outcome. Recent prospective studies have reported that NAFLD is associated with an increased incidence of MetS and type 2 diabetes mellitus, independent of obesity and other components of MetS. Thus, NAFLD may not only be a liver disease but also an early mediator of type 2 diabetes mellitus and MetS. The biological mechanisms by which NAFLD contributes to a higher risk of developing metabolic disorders are not fully understood. However, the fatty liver could contribute in the same way as visceral adipose tissue to insulin resistance, systemic inflammation and oxidative stress, while the decreased serum adiponectin concentrations might also be part of the mechanism. In contemporary clinical practice, it has become mandatory to evaluate the metabolic risk factors in NAFLD patients and to consider careful surveillance and aggressive treatment, not only of the resultant liver disease, but also of the possible underlying metabolic and vascular complications. Future studies might address the question whether earlier adjustment to a more efficient lifestyle or a pharmacological treatment that mobilizes fat out of the liver could reduce these risks.

Hepatic free fatty acids accumulate in experimental steatohepatitis: role of adaptive pathways

BACKGROUND/AIMS

We determined the effects of dietary lipid composition on steatohepatitis development with particular attention to the nature of lipid molecules that accumulate in the liver and pathways of hepatic triglyceride synthesis.

METHODS

Mice were fed methionine and choline deficient (MCD) diets supplemented with 20% fat as lard (saturated) or olive oil (monounsaturated), for 3 weeks.

RESULTS

Irrespective of dietary lipid composition, MCD-fed mice developed steatosis, ballooning degeneration and lobular inflammation. MCD-feeding increased hepatic free fatty acid (FFA) levels 2-3-fold, as well as total triglyceride levels. Hepatic FFA composition was characterized by increased ratio of monounsaturated: saturated FFA. There were reduced nuclear levels of the lipogenic transcription factor sterol regulatory element binding protein-1 in MCD-fed mice, but no consistent reduction in fatty acid synthesis genes (acetyl-CoA carboxylase and fatty acid synthase). Consistent with pathways of hepatic triglyceride synthesis, expression of diacylglycerol acyltransferase-1 and -2 was increased, as were delta-5- and delta-6- fatty acid desaturase mRNA levels.

CONCLUSIONS

In this nutritional model of steatohepatitis, accumulation of FFA occurs despite substantial suppression of lipogenesis and induction of triglyceride synthesis genes. Accumulation of FFA supports a lipotoxicity mechanism for liver injury in this form of fatty liver disease.

Evidence-Based Efficacy of Kampo Formulas in a Model of Non Alcoholic Fatty Liver

Data on the efficacy of herbal compounds are often burdened by the lack of appropriate controls or a limited statistical power. Treatments to prevent the progression of non alcoholic fatty liver disease (NAFLD) to steatohepatitis (NASH) remain unsatisfactory. A total of 56 rabbits were arrayed into 7 groups fed with standard rabbit chow (SRC), SRC with 1% cholesterol, or each of the five experimental treatments (Kampo formulas 1% keishibukuryogan [KBG], 1% orengedokuto [OGT], and 1% shosaikoto [SST]; vitamin E [VE]; or pioglitazone [PG]) in a 1% cholesterol SRC. We analyzed changes after 12 weeks in plasma and liver lipid profiles, glucose metabolism, adipocytokines, oxidative stress, and liver fibrosis. Data demonstrated that all five treatments were associated with significant amelioration of lipid profiles, oxidative stress, and liver fibrosis compared to no supplementation. KBG was superior to VE and PG in the reduction of liver total cholesterol ( P < 0.01) and lipid peroxidase levels ( P < 0.05), urinary 8-hydroxy-2′-deoxyguanosine ( P < 0.05), hepatic α-smooth muscle actin positive areas ( P < 0.01) and activated stellate cells ( P < 0.01). In conclusion, there was a statistically significant benefit of Kampo formulas (KBG in particular) on a dietary model of NAFLD/NASH. Future studies need to be directed at the mechanisms in the treatment of NASH.

Infliximab restores glucose homeostasis in an animal model of diet-induced obesity and diabetes

TNF-alpha plays an important role in obesity-linked insulin resistance and diabetes mellitus by activating at least two serine kinases capable of promoting negative regulation of key elements of the insulin signaling pathway. Pharmacological inhibition of TNF-alpha is currently in use for the treatment of rheumatoid and psoriatic arthritis, and some case reports have shown clinical improvement of diabetes in patients treated with the TNF-alpha blocking monoclonal antibody infliximab. The objective of this study was to evaluate the effect of infliximab on glucose homeostasis and insulin signal transduction in an animal model of diabetes. Diabetes was induced in Swiss mice by a fat-rich diet. Glucose and insulin homeostasis were evaluated by glucose and insulin tolerance tests and by the hyperinsulinemic-euglycemic clamp. Signal transduction was evaluated by immunoprecipitation and immunoblotting assays. Short-term treatment with infliximab rapidly reduced blood glucose and insulin levels and glucose and insulin areas under the curve during a glucose tolerance test. Furthermore, infliximab increased the glucose decay constant during an insulin tolerance test and promoted a significant increase in glucose infusion rate during a hyperinsulinemic-euglycemic clamp. In addition, the clinical outcomes were accompanied by improved insulin signal transduction in muscle, liver, and hypothalamus, as determined by the evaluation of insulin-induced insulin receptor, insulin receptor substrate-1, and receptor substrate-2 tyrosine phosphorylation and Akt and forkhead box protein O1 serine phosphorylation. Thus, pharmacological inhibition of TNF-alpha may be an attractive approach to treat severely insulin-resistant patients with type 2 diabetes mellitus.

Nonalcoholic steatohepatitis (NASH) in ob/ob mice treated with yo jyo hen shi ko (YHK): effects on peroxisome proliferator-activated receptors (PPARs) and microsomal triglyceride transfer protein (MTP)

YHK has antioxidant properties, has a hypoglycemic effect, and may reduce plasma lipid levels. In this study, we examined the hepatic expression of PPAR-alpha and -gamma and MTP in ob/ob mice receiving or not receiving YHK. Ob/ob mice were assigned to receive oral YHK (20 mg/kg/day) fed solution (methionine/choline-deficient [MCD] diet+YHK group) or vehicle (MCD group) by gavage for 4 weeks. Liver fragments were collected for histologic examination and mRNA isolation. PPAR-alpha and -gamma and MTP gene expression was examined by RT-qPCR. YHK treatment was associated with NASH prevention, weight loss, and reduction of visceral fat and of serum concentrations of aminotransferases in comparison to the MCD group. YHK promoted an increment in PPAR-alpha and MTP and a decrement in PPAR-gamma mRNA contents. These findings suggest that modulation of PPAR-alpha and -gamma and MTP RNA expression may be implicated in the protective effect of YHK in experimental NASH, limiting hepatocyte lipid accumulation.

The impact of visceral fat in nonalcoholic fatty liver disease: cross-sectional and longitudinal studies

BACKGROUND

Nonalcoholic fatty liver disease is increasing worldwide, and attention is being paid to its association with obesity and metabolic syndrome. The aim of this study was to elucidate the role of visceral fat accumulation in hepatic steatosis by cross-sectional and longitudinal studies.

METHODS

We enrolled 125 patients in a cross-sectional study and 28 patients in a longitudinal study and examined visceral and subcutaneous fat thickness, hepatic steatosis score, and biochemical parameters. In the longitudinal study, the influence of weight change on fat distribution and hepatic steatosis was investigated.

RESULTS

In the cross-sectional study, the severity of hepatic steatosis showed a significant positive correlation with body mass index, visceral fat thickness, serum albumin, alanine aminotransferase (ALT), cholinesterase, fasting insulin, and the homeostasis model assessment of insulin resistance. ALT, visceral fat thickness, and serum albumin were independent factors for hepatic steatosis. In the longitudinal study, visceral fat thickness fluctuated closely with changes in body weight, and had the strongest relationship with the change of hepatic steatosis by multivariate analysis.

CONCLUSIONS

Visceral fat was the most important factor for the development of hepatic steatosis. Visceral fat thickness can be measured by sonography easily, noninvasively, and repeatedly for assessment of central obesity and monitoring of the efficacy of treatment of nonalcoholic fatty liver disease.

S-adenosylmethionine attenuates hepatic lipid synthesis in micropigs fed ethanol with a folate-deficient diet

BACKGROUND

To demonstrate a causative role of abnormal methionine metabolism in the pathogenesis of alcoholic steatosis, we measured the effects on hepatic lipid synthesis of supplementing ethanol and folate-deficient diets with S-adenosylmethionine (SAM), a metabolite that regulates methionine metabolism.

METHODS

Yucatan micropigs were fed folate-deficient diets as control, with ethanol at 40% of kcal, and with ethanol supplemented with SAM at 0.4 g/1,000 kcal for 14 weeks. Histopathology, triglyceride levels and transcripts, and protein levels of the regulatory signals of hepatic lipid synthesis were measured in terminal omental adipose and liver samples.

RESULTS

Feeding ethanol at 40% of kcal with folate-deficient diets for 14 weeks increased and supplemental SAM maintained control levels of liver and plasma triglyceride. Serum adiponectin, liver transcripts of adiponectin receptor-1 (AdipoR1), and phosphorylated adenosine monophosphate kinase-beta (p-AMPKbeta) were each reduced by ethanol feeding and were sustained at normal levels by SAM supplementation of the ethanol diets. Ethanol feeding activated and SAM supplementation maintained control levels of ER stress-induced transcription factor sterol regulatory element-binding protein-1c (SREBP-1c) and its targeted transcripts of lipid synthesizing enzymes acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), and glycerol-3-phosphate acyltransferase (GPAT).

CONCLUSIONS

Ethanol feeding with a folate-deficient diet stimulates hepatic lipid synthesis by down-regulating adiponectin-mediated pathways of p-AMPK to increase the expression of nSREBP-1c and its targeted lipogenic enzymes. Preventing abnormal hepatic methionine metabolism by supplementing ethanol diets with SAM reduces liver triglyceride levels by up-regulation of adiponectin-mediated pathways to decrease fatty acid and triglyceride synthesis. This study demonstrates that ethanol-induced hepatic lipid synthesis is mediated in part by abnormal methionine metabolism, and strengthens the concept that altered methionine metabolism plays an integral role in the pathogenesis of steatosis.

Modulation of hepatic microsomal triglyceride transfer protein (MTP) induced by S-nitroso-N-acetylcysteine in ob/ob mice

We evaluated the effects of a potent NO donor, S-nitroso-N-acetylcysteine (SNAC), on microsomal triglyceride transfer protein (MTP) expression in ob/ob mice. NAFLD was induced in male ob/ob mice using a methionine-choline deficient diet (MCD) concomitantly with oral SNAC fed solution (n=5) or vehicle (control; n=5) by gavage daily for 4 weeks. Livers were collected for histology and for assessing MTP by RT-qPCR, Western blot, immunohistochemistry and immunogold electron microscopy analyses. Histological analysis showed diffuse macro and microvesicular steatosis, moderate hepatocellular ballooning and moderate inflammatory infiltrate in ob/ob mice fed the MCD diet. With SNAC, mice showed a marked reduction in liver steatosis (p<0.01), in parenchymal inflammation (p=0.02) and in MTP protein immunoexpression in zone III (p=0.05). Moreover, SNAC caused reduction of MTP protein in Western blot analysis (p<0.05). In contrast, MTP mRNA content was significantly higher (p<0.05) in mice receiving SNAC. Immuno-electron microscopy showed MTP localized in the rough endoplasmic reticulum of hepatocytes in both treated and untreated groups. However with SNAC treatment, MTP was also observed surrounding fat globules. Histological improvement mediated by a nitric oxide donor is associated with significantly altered expression and distribution of MTP in this animal model of fatty liver disease. Further studies are in progress to examine possible mechanisms and to develop SNAC as a possible therapy for human fatty liver disease.