Template to improve glycemic control without reducing adiposity or dietary fat

Drugs that improve chronic hyperglycemia independently of insulin signaling or reduction of adiposity or dietary fat intake may be highly desirable. Ad36, a human adenovirus, promotes glucose uptake in vitro independently of adiposity or proximal insulin signaling. We tested the ability of Ad36 to improve glycemic control in vivo and determined if the natural Ad36 infection in humans is associated with better glycemic control. C57BL/6J mice fed a chow diet or made diabetic with a high-fat (HF) diet were mock infected or infected with Ad36 or adenovirus Ad2 as a control for infection. Postinfection (pi), systemic glycemic control, hepatic lipid content, and cell signaling in tissues pertinent to glucose metabolism were determined. Next, sera of 1,507 adults and children were screened for Ad36 antibodies as an indicator of past natural infection. In chow-fed mice, Ad36 significantly improved glycemic control for 12 wk pi. In HF-fed mice, Ad36 improved glycemic control and hepatic steatosis up to 20 wk pi. In adipose tissue (AT), skeletal muscle (SM), and liver, Ad36 upregulated distal insulin signaling without recruiting the proximal insulin signaling. Cell signaling suggested that Ad36 increases AT and SM glucose uptake and reduces hepatic glucose release. In humans, Ad36 infection predicted better glycemic control and lower hepatic lipid content independently of age, sex, or adiposity. We conclude that Ad36 offers a novel tool to understand the pathways to improve hyperglycemia and hepatic steatosis independently of proximal insulin signaling, and despite a HF diet. This metabolic engineering by Ad36 appears relevant to humans for developing more practical and effective antidiabetic approaches.

Apoptosis in nonalcoholic fatty liver disease: diagnostic and therapeutic implications

Pathological increases in cell death in the liver as well as in peripheral tissues has emerged as an important mechanism involved in the development and progression of nonalcoholic fatty liver disease (NAFLD). An increase in hepatocyte cell death by apoptosis is typically present in patients with NAFLD and in experimental models of steatohepatitis, while an increase in adipocyte cell death in visceral adipose tissue may be an important mechanism triggering insulin resistance and hepatic steatosis. The two fundamental pathways of apoptosis, the extrinsic (death receptor-mediated) and intrinsic (organelle-initiated) pathways, are both involved. This article summarizes the current knowledge related to the distinct molecular and biochemical pathways of cell death involved in NAFLD pathogenesis. In particular, it will highlight the efforts for the development of both novel diagnostic and therapeutic strategies based on this knowledge.

Autophagy in nonalcoholic steatohepatitis

Autophagy is a critical pathway for the degradation of intracellular components by lysosomes. Established functions for both macroautophagy and chaperone-mediated autophagy in hepatic lipid metabolism, insulin sensitivity and cellular injury suggest a number of potential mechanistic roles for autophagy in nonalcoholic steatohepatitis (NASH). Decreased autophagic function in particular may promote the initial development of hepatic steatosis and progression of steatosis to liver injury. Additional functions of autophagy in immune responses and carcinogenesis may also contribute to the development of NASH and its complications. The impairment in autophagy that occurs with cellular lipid accumulation, obesity and aging may therefore have an important impact on this disease, and agents to augment hepatic autophagy have therapeutic potential in NASH.

Smoking and severity of hepatic fibrosis in nonalcoholic fatty liver disease

BACKGROUND & AIMS

Although many predictors of disease severity of nonalcoholic fatty liver disease (NAFLD) have been proposed, studies of the potential effects of specific environmental exposures on human NAFLD are lacking. Smoking increases insulin resistance. Given the pathophysiological role of insulin resistance in NAFLD, characterization of the influence of smoking in NAFLD is warranted. The aim of this paper was to study the potential association between cigarette smoking and advanced fibrosis in NAFLD.

METHODS

All adults enrolled in the NASH CRN studies, between October 2004 and February 2008, who had liver biopsies, were included (n=1091). Advanced fibrosis was defined as stages 3-4. Analyses were performed.

RESULTS

Significant bivariate associations were demonstrated between advanced fibrosis and age, gender, ethnicity, diabetes, and smoking history. History of smoking ≥ 10 pack-years was more common (p <0.0001) among patients with advanced fibrosis. Multivariate analysis demonstrated an association between smoking history of ≥ 10 pack-years and advanced fibrosis (OR=1.63). Among non-diabetics, history of ≥ 10 pack-years was associated with an OR of 2.48 for advanced fibrosis. High frequencies of advanced fibrosis were observed among diabetics (with or without ≥ 10 pack-years history) and non-diabetics with ≥ 10 pack-years history as compared to non-diabetics without significant smoking history.

CONCLUSIONS

Smoking history was associated with advanced liver fibrosis in this large multicenter cohort of NAFLD patients. The results indicate that smoking may enhance the progression of NAFLD partly through its effect on insulin resistance. Our results are consistent with recent animal studies suggesting that cigarette smoke may aggravate fatty liver. To our knowledge, this is the first study to show that cigarette smoking is associated with increased fibrosis severity in human NALFD, suggesting it may accelerate disease progression. These results may support a formal recommendation of smoking cessation in patients with NAFLD.

T(1) independent, T(2) (*) corrected chemical shift based fat-water separation with multi-peak fat spectral modeling is an accurate and precise measure of hepatic steatosis

PURPOSE

To determine the precision and accuracy of hepatic fat-fraction measured with a chemical shift-based MRI fat-water separation method, using single-voxel MR spectroscopy (MRS) as a reference standard.

MATERIALS AND METHODS

In 42 patients, two repeated measurements were made using a T(1) -independent, T 2*-corrected chemical shift-based fat-water separation method with multi-peak spectral modeling of fat, and T(2) -corrected single voxel MR spectroscopy. Precision was assessed through calculation of Bland-Altman plots and concordance correlation intervals. Accuracy was assessed through linear regression between MRI and MRS. Sensitivity and specificity of MRI fat-fractions for diagnosis of steatosis using MRS as a reference standard were also calculated.

RESULTS

Statistical analysis demonstrated excellent precision of MRI and MRS fat-fractions, indicated by 95% confidence intervals (units of absolute percent) of [-2.66%,2.64%] for single MRI ROI measurements, [-0.81%,0.80%] for averaged MRI ROI, and [-2.70%,2.87%] for single-voxel MRS. Linear regression between MRI and MRS indicated that the MRI method is highly accurate. Sensitivity and specificity for detection of steatosis using averaged MRI ROI were 100% and 94%, respectively. The relationship between hepatic fat-fraction and body mass index was examined.

CONCLUSION

Fat-fraction measured with T(1) -independent T 2*-corrected MRI and multi-peak spectral modeling of fat is a highly precise and accurate method of quantifying hepatic steatosis.

Acetaminophen pharmacokinetics in children with nonalcoholic fatty liver disease

OBJECTIVES

: The aim of the study was to evaluate UDP-glucuronyltransferase activity and the pharmacokinetics of a single oral dose of acetaminophen (APAP) in children with nonalcoholic fatty liver disease (NAFLD).

PATIENTS AND METHODS

: Twelve boys 10 to 17 years old with biopsy-proven NAFLD and 12 age- and sex-matched controls without NAFLD were recruited. Following administration of a single oral dose of APAP (5 mg/kg, maximum 325 mg), APAP and its glucuronide metabolite (APAP-G) were measured in plasma, urine, and sputum at various intervals up to 24 hours. The activity of UDP-glucuronyltransferase was estimated by the plasma ratio of APAP-G to APAP at 4 hours.

RESULTS

: Following administration of APAP, children with NAFLD had significantly higher concentrations of APAP-G in serum (P = 0.0071) and urine (P = 0.0210) compared with controls. No significant differences in APAP pharmacokinetics parameters were observed between the 2 groups.

CONCLUSIONS

: APAP glucuronidation is altered in children with fatty liver disease. Despite the altered disposition of this metabolite, the pharmacokinetics of a single 5 mg/kg dose of APAP is the same in children with NAFLD as in children with normal liver function.

Metabolic pathways promoting intrahepatic fatty acid accumulation in methionine and choline deficiency: implications for the pathogenesis of steatohepatitis

The pathological mechanisms that distinguish simple steatosis from steatohepatitis (or NASH, with consequent risk of cirrhosis and hepatocellular cancer) remain incompletely defined. Whereas both a methionine- and choline-deficient diet (MCDD) and a choline-deficient diet (CDD) lead to hepatic triglyceride accumulation, MCDD alone is associated with hepatic insulin resistance and inflammation (steatohepatitis). We used metabolic tracer techniques, including stable isotope ([¹³C₄]palmitate) dilution and mass isotopomer distribution analysis (MIDA) of [¹³C₂]acetate, to define differences in intrahepatic fatty acid metabolism that could explain the contrasting effect of MCDD and CDD on NASH in C57Bl6 mice. Compared with control-supplemented (CS) diet, liver triglyceride pool sizes were similarly elevated in CDD and MCDD groups (24.37 ± 2.4, 45.94 ± 3.9, and 43.30 ± 3.5 μmol/liver for CS, CDD, and MCDD, respectively), but intrahepatic neutrophil infiltration and plasma alanine aminotransferase (31 ± 3, 48 ± 4, 231 ± 79 U/l, P < 0.05) were elevated only in MCDD mice. However, despite loss of peripheral fat in MCDD mice, neither the rate of appearance of palmitate (27.2 ± 3.5, 26.3 ± 2.3, and 28.3 ± 3.5 μmol·kg⁻¹·min⁻¹) nor the contribution of circulating fatty acids to the liver triglyceride pool differed between groups. Unlike CDD, MCDD had a defect in hepatic triglyceride export that was confirmed using intravenous tyloxapol (142 ± 21, 122 ± 15, and 80 ± 7 mg·kg⁻¹·h⁻¹, P < 0.05). Moreover, hepatic de novo lipogenesis was significantly elevated in the MCDD group only (1.4 ± 0.3, 2.3 ± 0.4, and 3.4 ± 0.4 μmol/day, P < 0.01). These findings suggest that important alterations in hepatic fatty acid metabolism may promote the development of steatohepatitis. Similar mechanisms may predispose to hepatocyte damage in human NASH.

Overexpression of CD36 and acyl-CoA synthetases FATP2, FATP4 and ACSL1 increases fatty acid uptake in human hepatoma cells

BACKGROUND

Understanding the mechanisms of long chain fatty acid (LCFA) uptake in hepatic cells is of high medical importance to treat and to prevent fatty liver disease (FLD). ACSs (Acyl-CoA synthetases) are a family of enzymes that catalyze the esterification of fatty acids (FA) with CoA. Recent studies suggest that ACS enzymes drive the uptake of LCFA indirectly by their enzymatic activity and could promote special metabolic pathways dependent on their localization.The only protein located at the plasma membrane which has consistently been shown to enhance FA uptake is CD36.

AIMS

The current study investigated whether ACSs and CD36 could regulate hepatic LCFA uptake.

METHODS AND RESULTS

FATP2 and FATP4 were both localized to the ER of HuH7 and HepG2 cells as shown by double immunofluorescence in comparison to marker proteins. ACSL1 was located at mitochondria in both cell lines. Overexpression of FATP2, FATP4 and ACSL1 highly increased ACS activity as well as the uptake of [3H]-oleic acid and fluorescent Bodipy-C12 (B12) fatty acid. Quantitative FACS analysis showed a correlation between ACS expression levels and B12 uptake. FATP2 had the highest effect on B12 uptake of all proteins tested. CD36 was mainly localized at the plasma membrane. Whereas [3H]-oleic acid uptake was increased after overexpression, CD36 had no effect on B12 uptake.

CONCLUSION

Uptake of LCFA into hepatoma cells can be regulated by the expression levels of intracellular enzymes. We propose that ACS enzymes drive FA uptake indirectly by esterification. Therefore these molecules are potential targets for treatment of nonalcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH).

Polychlorinated biphenyls, lead, and mercury are associated with liver disease in American adults: NHANES 2003-2004

BACKGROUND

High-level occupational exposures to some industrial chemicals have been associated with liver diseases, including nonalcoholic fatty liver disease (NAFLD). However, the potential role of low-level environmental pollution on liver disease in the general population has not been evaluated.

OBJECTIVE

We determined whether environmental pollutants are associated with an elevation in serum alanine aminotransferase (ALT) activity and suspected NAFLD in U.S. adults.

METHODS

This cross-sectional cohort study evaluated adult participants without viral hepatitis, hemochromatosis, or alcoholic liver disease from the National Health and Nutrition Examination Survey (NHANES) for 2003-2004. ALT elevation was defined in men as ≥ 37 IU/L (age 18-20 years) and ≥ 48 IU/L (age ≥ 21 years) and in women as ≥ 30 IU/L (age 18-20 years) and ≥ 31 IU/L (age ≥ 21 years). Adjusted odds ratios (ORs) for ALT elevation were determined across exposure quartiles for 17 pollutant subclasses comprising 111 individual pollutants present with at least a 60% detection rate. Adjustments were made for age, race/ethnicity, sex, body mass index, poverty income ratio, and insulin resistance. Individual pollutants from subclasses associated with ALT elevation were subsequently analyzed.

RESULTS

The overall prevalence of ALT elevation was 10.6%. Heavy metals and polychlorinated biphenyls (PCBs) were associated with dose-dependent increased adjusted ORs for ALT elevation. Within these subclasses, increasing whole-blood levels of lead and mercury and increasing lipid-adjusted serum levels of 20 PCBs were individually associated with ALT elevation.

CONCLUSIONS

PCB, lead, and mercury exposures were associated with unexplained ALT elevation, a proxy marker of NAFLD, in NHANES 2003-2004 adult participants.

A high-fat, ketogenic diet causes hepatic insulin resistance in mice, despite increasing energy expenditure and preventing weight gain

Low-carbohydrate, high-fat ketogenic diets (KD) have been suggested to be more effective in promoting weight loss than conventional caloric restriction, whereas their effect on hepatic glucose and lipid metabolism and the mechanisms by which they may promote weight loss remain controversial. The aim of this study was to explore the role of KD on liver and muscle insulin sensitivity, hepatic lipid metabolism, energy expenditure, and food intake. Using hyperinsulinemic-euglycemic clamps, we studied insulin action in mice fed a KD or regular chow (RC). Body composition was assessed by ¹H magnetic resonance spectroscopy. Despite being 15% lighter (P < 0.001) than RC-fed mice because of a 17% increase in energy expenditure (P < 0.001), KD-fed mice manifested severe hepatic insulin resistance, as reflected by decreased suppression (0% vs. 100% in RC-fed mice, P < 0.01) of endogenous glucose production during the clamp. Hepatic insulin resistance could be attributed to a 350% increase in hepatic diacylglycerol content (P < 0.001), resulting in increased activation of PKCε (P < 0.05) and decreased insulin receptor substrate-2 tyrosine phosphorylation (P < 0.01). Food intake was 56% (P < 0.001) lower in KD-fed mice, despite similar caloric intake, and could partly be attributed to a more than threefold increase (P < 0.05) in plasma N-acylphosphatidylethanolamine concentrations. In conclusion, despite preventing weight gain in mice, KD induces hepatic insulin resistance secondary to increased hepatic diacylglycerol content. Given the key role of nonalcoholic fatty liver disease in the development of type 2 diabetes and the widespread use of KD for the treatment of obesity, these results may have potentially important clinical implications.

Clinical, laboratory and histological associations in adults with nonalcoholic fatty liver disease

The Nonalcoholic Steatohepatitis Clinical Research Network (NASH CRN) was formed to conduct multicenter studies on the etiology, contributing factors, natural history, and treatment of nonalcoholic steatohepatitis (NASH). The aim of this study was to determine the associations of readily available demographic, clinical, and laboratory variables with the diagnosis of NASH and its key histological features, and determine the ability of these variables to predict the severity of nonalcoholic fatty liver disease (NAFLD). A total of 1266 adults were enrolled in NASH CRN studies between October 2004 and February 2008, of whom 1101 had available liver histology. The median age was 50 years; 82% were white and 12% Hispanic. The median body mass index was 33 kg/m(2); 49% had hypertension and 31% had type 2 diabetes. On liver biopsy, 57% were judged to have definite NASH and 31% bridging fibrosis or cirrhosis. Using data from the 698 patients with liver biopsies within 6 months of clinical data, patients with definite NASH were more likely to be female and have diabetes, higher levels of aspartate and alanine aminotransferases, alkaline phosphatase, gamma glutamyl transpeptidase, and homeostasis model assessment of insulin resistance (HOMA-IR). Progressive models for predicting histological diagnoses performed modestly for predicting steatohepatitis or ballooning (area under receiver operating characteristic curves [AUROC] ranged from 0.70-0.79), and better for advanced fibrosis (AUROC 0.73-0.85).

CONCLUSION

Readily available clinical and laboratory variables can predict advanced fibrosis in adults with NAFLD, but additional information is needed to reliably predict the presence and severity of NASH. Prospective studies of this well-characterized population and associated tissue bank samples offer a unique opportunity to better understand the cause and natural history of NAFLD and develop more precise means for noninvasive diagnosis.

FATP2 is a hepatic fatty acid transporter and peroxisomal very long-chain acyl-CoA synthetase

Fatty acid transport protein (FATP)2, a member of the FATP family of fatty acid uptake mediators, has independently been identified as a hepatic peroxisomal very long-chain acyl-CoA synthetase (VLACS). Here we address whether FATP2 is 1) a peroxisomal enzyme, 2) a plasma membrane-associated long-chain fatty acid (LCFA) transporter, or 3) a multifunctional protein. We found that, in mouse livers, only a minor fraction of FATP2 localizes to peroxisomes, where it contributes to approximately half of the peroxisomal VLACS activity. However, total hepatic (V)LACS activity was not significantly affected by loss of FATP2, while LCFA uptake was reduced by 40%, indicating a more prominent role in hepatic LCFA uptake. This suggests FATP2 as a potential target for a therapeutic intervention of hepatosteatosis. Adeno-associated virus 8-based short hairpin RNA expression vectors were used to achieve liver-specific FATP2 knockdown, which significantly reduced hepatosteatosis in the face of continued high-fat feeding, concomitant with improvements in liver physiology, fasting glucose, and insulin levels. Based on our findings, we propose a model in which FATP2 is a multifunctional protein that shows subcellular localization-dependent activity and is a major contributor to peroxisomal (V)LACS activity and hepatic fatty acid uptake, suggesting FATP2 as a potential novel target for the treatment of nonalcoholic fatty liver disease.

Predictors of hepatic steatosis in HBeAg-negative chronic hepatitis B patients and their diagnostic values in hepatic fibrosis

OBJECTIVE

To investigate predictors of hepatic steatosis in HBeAg-negative chronic hepatitis B (CHB) patients and their diagnostic values in hepatic inflammation and fibrosis.

METHODS

A total of 106 HBeAg-negative CHB patients with clinically and pathologically proven steatosis and 98 patients without steatosis were recruited into this study. The levels of fasting blood glucose (FBG), fasting insulin (FINS), triglyceride (TG), cholesterol (CHOL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (Alb), globulin (Glb), HBV DNA, body mass index (BMI), homeostatic model assessment of insulin resistance (HOMA-IR) and pathological changes of the liver in inflammation, fibrosis and fatty deposition were examined in all patients.

RESULTS

The levels of BMI, HOMA-IR, FBG, insulin, TG, and CHOL were significantly higher in patients with steatosis than those without steatosis (all P<0.05). But ALT, AST and HBV DNA levels were significantly lower in patients with steatosis (all P<0.05). Logistic regression analysis showed that only FINS was a significant predictor for hepatic steatosis (P<0.05); FINS and Glb were significant predictors for hepatic inflammation (all P<0.05); BMI and TC were significant predictors for hepatic fibrosis (all P<0.05).

CONCLUSIONS

Hepatic steatosis, a common disease in HBeAg-negative CHB patients, was positively associated with BMI, FBG, FINS, TG, TC, GGT, ALP and HOMA-IR. In these patients, the prevalence of hepatic inflammation and fibrosis was also increased.

Grape seed extract to improve liver function in patients with nonalcoholic fatty liver change

BACKGROUND/AIM

Therapeutic interventions in nonalcoholic fatty liver disease are limited, while anti-oxidative materials have shown benefits in animal models. This study aimed to evaluate grape seed extract as an anti-oxidative material in this process. Therapeutic effects of grape seed extract were evaluated in comparison to vitamin C in a double-blind setting.

MATERIALS AND METHODS

Fifteen patients were enrolled in each group. Liver function tests were done; also, grade of steatosis and pattern of echogenicity of the liver were determined. Patients were followed up by the same evaluation repeated in first, second and third months.

RESULTS

Mean age +/- standard deviation was 43.2 +/- 10.3 years. Grape seed extract (GSE) significantly improved the grade of fatty liver change; and resulted in significant decrease in alanine aminotransferase in patients receiving the concentrate compared to those receiving vitamin C independently, from the initial grade of steatosis.

CONCLUSIONS

This study describes the beneficial effect of using grape seed extract for three months in patients with nonalcoholic fatty liver disease. These results may improve with a longer period of follow-up.

Advances in the treatment of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the Western world, and its prevalence is predicted to rise in the future in parallel with rising levels of obesity and type 2 diabetes mellitus. It is commonly associated with insulin resistance. Many patients have coexisting obesity, hypertension, dyslipidaemia or hyperglycaemia, and are at increased risk of developing cardiovascular disease. Although patients with simple steatosis have a good prognosis, a significant percentage will develop nonalcoholic steatohepatitis which may progress to cirrhosis, end-stage liver failure and hepatocellular carcinoma. Despite promising results from several pilot studies and small to medium randomized controlled trials, there is currently no pharmacological agent that is licensed for the treatment of NAFLD. At present the mainstay of treatment for all patients is lifestyle modification using a combination of diet, exercise and behavioural therapy. With recent advances in the understanding of the pathogenesis of NAFLD, the goal of treatment has shifted from simply trying to clear fat from the liver and prevent progressive liver damage to addressing and treating the metabolic risk factors for the condition. To reduce liver-related and cardiovascular morbidity and mortality, all patients with NAFLD should be invited to enrol in adequately powered, randomized controlled studies testing novel therapies, many of which are targeted at reducing insulin resistance or preventing progressive liver disease. Coexisting obesity, hypertension, dyslipidaemia or hyperglycaemia should be treated aggressively. Orlistat, bariatric surgery, angiotensin receptor blockers, statins, fibrates, metformin and thiazolidinediones should all be considered, but treatments should be carefully tailored to meet the specific requirements of each patient. The efficacy and safety of any new treatment, as well as its cost-effectiveness, will need to be carefully evaluated before it can be advocated for widespread clinical use.

Linking endoplasmic reticulum stress to cell death in hepatocytes: roles of C/EBP homologous protein and chemical chaperones in palmitate-mediated cell death

Prolonged endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) have been linked to apoptosis via several mechanisms, including increased expression of C/EBP homologous protein (Chop). Increased long-chain fatty acids, in particular saturated fatty acids, induce ER stress, Chop expression, and apoptosis in liver cells. The first aim of the present study was to determine the role of Chop in lipid-induced hepatocyte cell death and liver injury induced by a methionine-choline-deficient diet. Albumin-bound palmitate increased Chop gene and protein expression in a dose-dependent fashion in H4IIE liver cells. siRNA-mediated silencing of Chop in H4IIE liver cells reduced thapsigargin-mediated cell death by approximately 40% and delayed palmitate-mediated cell death, but only at high concentrations of palmitate (400-500 microM). Similar results were observed in primary hepatocytes isolated from Chop-knockout mice. Indices of liver injury were also not reduced in Chop-knockout mice provided a methionine-choline-deficient diet. To ascertain whether ER stress was linked to palmitate-induced cell death, primary hepatocytes were incubated in the absence or presence of the chemical chaperones taurine-conjugated ursodeoxycholic acid or 4-phenylbutyric acid. The presence of either of these chemical chaperones protected liver cells from palmitate-mediated ER stress and cell death, in part, via inhibition of JNK activation. These data suggest that ER stress is linked to palmitate-mediated cell death via mechanisms that include JNK activation.

Bach1 gene ablation reduces steatohepatitis in mouse MCD diet model

Bach1 is a transcriptional repressor of heme oxygenase-1 (HO-1, a.k.a. HSP-32), which is an inducible enzyme and has anti-oxidation/anti-inflammatory properties shown in various models of organ injuries. Since oxidative stress plays a pivotal role in the pathogenesis of nonalcoholic steatohepatitis (NASH), HO-1 induction would be expected to prevent the development of NASH. In this study, we investigated the influence of Bach1 ablation in mice on the progression of NASH in methionine-choline deficient (MCD) diet model. Bach1 ablation resulted in significant induction of HO-1 mRNA and its activity in the liver. When fed MCD diet, Bach1(-/-) mice exhibited negligible hepatic steatosis compared to pronounced steatohepatitis in wild type mice with 6-fold increase in hepatic triglyceride content. Whereas feeding of MCD diet decreased mRNA expressions of peroxisome proliferator-activated receptor (PPAR) α and microsomal triglyceride transfer protein (MTP) in wild type mice, there were no change in Bach1(-/-) mice. In addition, hepatic concentration of malondialdehyde (MDA), a biomarker for oxidative stress as well as plasma alanine aminotransferase (ALT) was significantly lower in Bach1(-/-) mice. These findings suggest that Bach1 ablation exerts hepatoprotective effect against steatohepatitis presumably via HO-1 induction and may be a potential therapeutic target.

SAFETY study: alanine aminotransferase cutoff values are set too high for reliable detection of pediatric chronic liver disease

BACKGROUND & AIMS

The appropriate alanine aminotransferase (ALT) threshold value to use for diagnosis of chronic liver disease in children is unknown. We sought to develop gender-specific, biology-based, pediatric ALT thresholds.

METHODS

The Screening ALT for Elevation in Today's Youth (SAFETY) study collected observational data from acute care children's hospitals, the National Health and Nutrition Examination Survey (NHANES, 1999-2006), overweight children with and without non-alcoholic fatty liver disease (NAFLD), and children with chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infections. The study compared the sensitivity and specificity of ALT thresholds currently used by children's hospitals vs study-derived, gender-specific, biology-based, ALT thresholds for detecting children with NAFLD, HCV, or HBV.

RESULTS

The median upper limit of ALT at children's hospitals was 53 U/L (range, 30-90 U/L). The 95th percentile levels for ALT in healthy weight, metabolically normal, liver disease-free, NHANES pediatric participants were 25.8 U/L (boys) and 22.1 U/L (girls). The concordance statistics of these NHANES-derived thresholds for liver disease detection were 0.85 (95% confidence interval [CI]: 0.74-0.96) in boys and 0.91 (95% CI: 0.83-0.99) in girls for NAFLD, 0.80 (95% CI: 0.70-0.91) in boys and 0.79 (95% CI: 0.69-0.89) in girls for HBV, and 0.86 (95% CI: 0.77-0.95) in boys and 0.84 (95% CI: 0.75-0.93) in girls for HCV. Using current children's hospitals ALT thresholds, the median sensitivity for detection of NAFLD, HBV, and HCV ranged from 32% to 48%; median specificity was 92% (boys) and 96% (girls). Using NHANES-derived thresholds, the sensitivities were 72% (boys) and 82% (girls); specificities were 79% (boys) and 85% (girls).

CONCLUSIONS

The upper limit of ALT used in children's hospitals varies widely and is set too high to reliably detect chronic liver disease. Biology-based thresholds provide higher sensitivity and only slightly less specificity. Clinical guidelines for use of screening ALT and exclusion criteria for clinical trials should be modified.

Hepatitis C and metabolic syndrome

Hepatitis C virus (HCV) and the hepatic manifestation of metabolic syndrome, nonalcoholic fatty liver disease, are the two major causes of chronic liver disease worldwide. Liver histology of both diseases can be associated with steatosis, oxidative stress and fibrogenesis. Although better defined for HCV, approximately 20% of patients with these diseases can also develop cirrhosis or hepatocellular carcinoma. In recent years, it has become clear that the presence of metabolic syndrome and nonalcoholic fatty liver disease negatively impacts HCV-related outcomes, while simultaneously, the progression of HCV may have metabolic consequences in that it encourages or exacerbates insulin resistance. A growing body of evidence suggests that successful treatment of HCV may rely on understanding and addressing the complex and often mutually confounding relationship between HCV and the individual elements that comprise metabolic syndrome.

Toxicant-associated steatohepatitis in vinyl chloride workers

Although nonalcoholic steatohepatitis (NASH) is typically associated with obesity, it has also been reported to occur in lean individuals exposed to industrial chemicals. Occupational exposure to vinyl chloride (VC) is a well-documented risk factor for hemangiosarcoma, but has not previously been associated with steatohepatitis. Here we evaluate liver biopsies from 25 nonobese, highly exposed VC workers for steatohepatitis. Next, we evaluate associated metabolic and cytokine abnormalities in affected workers controlled by 26 chemical workers with no to minimal VC exposures, and 11 unexposed, healthy volunteers. Among highly exposed VC workers the prevalence of steatohepatitis was 80%. Of these, 55% had fibrosis and four had hemangiosarcoma. We have coined the term toxicant-associated steatohepatitis (TASH) to describe this condition, which was not explained by obesity or alcohol. Although mean serum transaminases were normal in TASH, total cytokeratin 18, but not the caspase-cleaved fragment, was elevated. Despite the absence of obesity, workers with TASH had insulin resistance with reduced adiponectin levels. TASH was also associated with markedly elevated serum tumor necrosis factor alpha and interleukins 1beta, 6, and 8. Serum antioxidant activity was reduced in TASH.

CONCLUSION

TASH occurred frequently in these nonobese VC workers with high cumulative exposures and normal liver enzymes. Elevated total cytokeratin 18 suggested the presence of necrotic cell death in TASH and may be a useful serologic biomarker. TASH was further characterized by insulin resistance, elevated proinflammatory cytokines, and impaired antioxidant defenses. The threshold VC exposure and the role of other chemical agents in TASH are as yet unknown.

Symptoms and quality of life in obese children and adolescents with non-alcoholic fatty liver disease

BACKGROUND

Data on the quality of life (QOL) of children with non-alcoholic fatty liver disease (NAFLD) are needed to estimate the true burden of illness in children with NAFLD.

AIM

To characterize QOL and symptoms of children with NAFLD and to compare QOL in children with NAFLD with that in a sample of healthy children.

METHODS

Quality of life and symptoms were assessed in children with biopsy-proven NAFLD enrolled in the NASH Clinical Research Network. PedsQL scores were compared with scores from healthy children. For children with NAFLD, between-group comparisons were made to test associations of demography, histological severity, symptoms and QOL.

RESULTS

A total of 239 children (mean age 12.6 years) were studied. Children with NAFLD had worse total (72.8 vs. 83.8, P < 0.01), physical (77.2 vs. 87.5, P < 0.01) and psychosocial health (70.4 vs. 81.9, P < 0.01) scores compared with healthy children. QOL scores did not significantly differ by histological severity of NAFLD. Fatigue, trouble sleeping and sadness accounted for almost half of the variance in QOL scores. Impaired QOL was present in 39% of children with NAFLD.

CONCLUSIONS

Children with NAFLD have a decrement in QOL. Symptoms were a major determinant of this impairment. Interventions are needed to restore and optimize QOL in children with NAFLD.

Synergistic association between alcohol intake and body mass index with serum alanine and aspartate aminotransferase levels in older adults: the Rancho Bernardo Study

BACKGROUND

The association between body-mass-index (BMI), alcohol consumption and their joint effect in increasing the risk of elevated serum alanine (ALT) and aspartate (AST) is unclear in older community-dwelling adults.

AIM

To determine the association between alcohol, BMI, and their combined effect with serum ALT and AST in older community-dwelling adults in the United States.

METHODS

A cross-sectional, population-based study in participants (n = 2364) from the Rancho Bernardo Study (54% women; mean age: 70 years, BMI: 25 kg/m(2), alcohol users: 63%) who attended a research visit in 1984-87. BMI was recorded by a trained nurse and alcohol use ascertained by a validated questionnaire. Odds-ratio (OR) and 95% confidence intervals (CI) of elevated serum ALT and AST (defined as > or =30 U/L in men and > or =19 U/L in women) were calculated for alcohol and BMI separately and their joint exposure using logistic regression models.

RESULTS

In multivariate logistic regression models adjusted for age, alcohol use, total cholesterol, serum triglycerides, fasting plasma glucose, systolic blood pressure, and diabetes mellitus, obesity independently increased the odds of elevated ALT in this cohort of older men and women by 3.0 (95% CI, 1.7-5.3) and 1.8 (95% CI, 1.1-2.7) respectively. Joint effects of consuming >3 alcoholic drinks/day and obesity raised the odds of elevated ALT by 8.9 (95% CI, 2.4-33.1) and AST by 21-fold (95% CI, 2.6-170.1), demonstrating synergism. Obese participants had higher odds of elevated ALT even at 0 < or = 1 drink/day.

CONCLUSIONS

In older men and women, the combination of obesity with alcohol is synergistic in increasing the risk of liver injury.

Chronic oxidative stress sensitizes hepatocytes to death from 4-hydroxynonenal by JNK/c-Jun overactivation

Sustained activation of the c-Jun NH(2)-terminal kinase (JNK) signaling pathway mediates the development and progression of experimental diet-induced nonalcoholic fatty liver disease (NAFLD). Delineating the mechanism of JNK overactivation in the setting of a fatty liver is therefore essential to understanding the pathophysiology of NAFLD. Both human and experimental NAFLD are associated with oxidative stress and resultant lipid peroxidation, which have been proposed to mediate the progression of this disease from simple steatosis to steatohepatitis. The ability of oxidants and the lipid peroxidation product 4-hydroxynonenal (HNE) to activate JNK signaling suggested that these two factors may act synergistically to trigger JNK overactivation. The effect of HNE on hepatocyte injury and JNK activation was therefore examined in cells under chronic oxidant stress from overexpression of the prooxidant enzyme cytochrome P450 2E1 (CYP2E1), which occurs in NAFLD. CYP2E1-generated oxidant stress sensitized a rat hepatocyte cell line to death from normally nontoxic concentrations of HNE. CYP2E1-overexpressing cells underwent a more profound depletion of glutathione (GSH) in response to HNE secondary to decreased gamma-glutamylcysteine synthetase activity. GSH depletion led to overactivation of JNK/c-Jun signaling at the level of mitogen-activated protein kinase kinase 4 that induced cell death. Oxidant stress and the lipid peroxidation product HNE cause synergistic overactivation of the JNK/c-Jun signaling pathway in hepatocytes, demonstrating that HNE may not be just a passive biomarker of hepatic oxidant stress but rather an active mediator of hepatocellular injury through effects on JNK signaling.

Glycine and urea kinetics in nonalcoholic steatohepatitis in human: effect of intralipid infusion

The rates of oxidation of glycine and ureagenesis were quantified in the basal state and in response to an intravenous infusion of intralipid with heparin (IL) in healthy subjects (n = 8) and in subjects with nonalcoholic steatohepatitis (NASH) (n = 6). During fasting, no significant difference in weight-specific rate of appearance (R(a)) of glycine, glycine oxidation, and urea synthesis was observed. Intralipid infusion resulted in a significant increase in plasma beta-hydroxybutyrate in both groups. The correlation between free fatty acids and beta-hydroxybutyrate concentration in plasma was 0.94 in NASH compared with 0.4 in controls, indicating greater hepatic fatty acid oxidation in NASH. Intralipid infusion resulted in a significant decrease in urea synthesis and glycine R(a) in both groups and did not impact glycine oxidation. The fractional contribution of glycine carbon to serine was lower in subjects with NASH before and after IL infusion. In contrast, the fractional contribution of serine carbon to cystathionine was higher in NASH before and following IL infusion. These results suggest that hepatic fatty acid oxidation is higher in NASH compared with controls and that glycine oxidation and urea synthesis are not altered. An increase in oxidative stress, induced by a higher rate of fatty acid oxidation in NASH, may have caused an increase in the contribution of serine to cystathionine to meet the higher demands for glutathione.

Diagnosis and treatment of pediatric nonalcoholic steatohepatitis and the implications for bariatric surgery

This review focuses on the diagnosis, risk factors, prevalence, pathogenesis and treatment of pediatric nonalcoholic steatohepatitis (NASH). NASH is a progressive form of nonalcoholic fatty liver disease (NAFLD), the most common cause of chronic liver disease in children. The factors that account for differences between children with NASH and children with milder forms of NAFLD are unclear. The diagnosis of NASH requires interpretation of liver histology because no noninvasive markers predict the presence or severity of NASH. There is no proven treatment for NASH. Several clinical trials for NAFLD are in progress; however, clinical trials focusing on NASH are needed. Heightened physician awareness of NAFLD, NASH, and associated risk factors is important to identify and treat affected children.

Lipotoxicity in nonalcoholic fatty liver disease: not all lipids are created equal

Nonalcoholic fatty liver disease (NAFLD) is currently the most common form of chronic liver disease affecting both adults and children in the USA and many other parts of the world. NAFLD encompasses a wide spectrum of conditions associated with the overaccumulation of lipids in the liver, ranging from steatosis to nonalcoholic steatohepatitis, to cirrhosis and its feared complications of portal hypertension, liver failure and hepatocellular carcinoma. In this article, we will focus on the growing evidence linking changes in hepatic lipid metabolism and accumulation of specific lipid types in the liver with hepatocellular damage, inflammation and apoptosis, resulting in disease progression to the more serious forms of this condition.

Fatty liver in children

AIMS

The aim of this study is to investigate the clinical and laboratory characteristics of nonalcoholic fatty liver disease (NAFLD) in a referral center of pediatrics in the northwest of Iran.

METHODS

In this cross-sectional study all subjects aged between six months to 15 years that were referred to the sonography unit, were investigated for fatty liver from March 2005 to August 2006. Patients with fatty liver change underwent detailed clinical and laboratory evaluation.

RESULTS

From 1500 children who were investigated, 34 subjects with sonographic evidence of fatty liver were enrolled in this study (2.3%). The mean age was 6.53 +/- 3.07 years. Elevated aspartate aminotransferase and alanine aminotransferase was detected in 38.2% and 47.1% of patients, respectively. The mean level of cholesterol was 461 +/- 182.23 mg/dl and 94.1% of patients had hypercholesterolemia. Total cholesterol level and serum aminotransferase levels had a significant positive correlation with severity of fatty liver (p < 0.05). Mean body mass index was significantly higher in patients with severe fatty liver (p < 0.05).

CONCLUSION

The epidemiology of pediatric NAFLD should inform future attempts to develop evaluated screening protocols. Moreover, these data should guide efforts to delineate the pathophysiology of fatty liver in children.

"Second hit" models of alcoholic liver disease

Alcoholic liver disease (ALD) is a lifestyle disease with its pathogenesis and individual predisposition governed by gene-environment interactions. Based on the "second hit" or "multiple hits" hypothesis, patients are predisposed to progressive ALD when a magic combination of gene and environmental interactions exists. Reproduction of second or multiple hits in animal models serves to test a combination and to gain mechanistic insights into synergism achieved by such combination. Numerous environmental factors have been incorporated into animal models, largely classified into nutritional, xenobiotic/pharmacologic, hemodynamic, and viral groups. A loss or gain of function genetic model has become a popular experimental approach to test the role of a gene as a second hit. Future research will need to test more subtle or natural hits combined with excessive alcohol intake to test multiple hits in the genesis of ALD. Additionally, animal models of comorbidities are urgently needed particularly for synergistic liver disease and oncogenesis caused by alcohol, obesity, and hepatitis virus.

A comparative study of nonalcoholic fatty liver disease and hepatitis C virus-related steatosis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) and chronic hepatitis C feature steatosis and insulin resistance (IR), conditions associated with the metabolic syndrome (MS).

OBJECTIVES

To assess the prevalence of MS and determinants of IR in patients with NAFLD and chronic hepatitis C.

METHODS

Ninety-three consecutive patients with NAFLD, 97 with chronic hepatitis C virus (HCV) genotypes 1 and 2, and 182 'healthy' controls without steatosis were enrolled in the present study. The prevalence of MS was assessed by modified Adult Treatment Panel III criteria and IR by the homeostasis model assessment of insulin resistance (HOMA-IR). IR was defined as the 75th percentile of the HOMA-IR of control subjects.

RESULTS

While the prevalence of IR was similar in NAFLD and HCV-infected subjects (70.0% and 78.7%, respectively), the prevalence of MS was significantly higher in NAFLD patients than in HCV-infected patients (27.9% versus 4.1%) and in controls (5.6%). With multivariate analysis, IR was predicted by body mass index (OR 1.263; 95% CI 1.078 to 1.480) and triglyceridemia (OR 1.011; 95% CI 1.002 to 1.020) in NAFLD and by sex (OR for female sex 0.297; 95% CI 0.094 to 0.940) and fibrosis stage (OR 2.751; 95% CI 1.417 to 5.340) in chronic hepatitis C.

CONCLUSIONS

IR is independently associated with body mass index and triglyceridemia in NAFLD, sex and fibrosis in chronic HCV infection, and has a higher prevalence in NAFLD and chronic hepatitis C than in controls. However, the frequency of MS in HCVinfected patients, similar to that of controls, is significantly lower than that seen in NAFLD patients. The current diagnostic criteria of MS are more likely to 'capture' patients with NAFLD than with chronic hepatitis C, although both groups are insulin resistant.

Abnormal glucose tolerance in young male patients with nonalcoholic fatty liver disease

OBJECTIVE

The association of nonalcoholic fatty liver disease (NAFLD) with insulin resistance and metabolic syndrome has been documented for obese men and middle-aged men. This study was designed to determine the relationship between NAFLD and the oral glucose tolerance test (OGTT) to predict preclinical diabetes in nondiabetic young male patients (<30 years old).

METHODS

A total of 75 male patients who had elevated liver enzymes and who were diagnosed with NAFLD were enrolled in this study. A standard 75 g OGTT was carried out on all patients. Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) were defined as a fasting plasma glucose (FPG) level > or =100 mg/dl but <126 mg/dl, and a 2-h post-load glucose on the OGTT of > or =140 mg/dl, but <200 mg/dl respectively.

RESULTS

According to the OGTT results, 24 (32%) patients were diagnosed as having IGT and 12 (16%) patients were diagnosed as having diabetes. Among the 48 patients with normal fasting glucose, 18 (37.6%) patients showed abnormal glucose tolerance (15 had IGT and three had diabetes). The NAFLD patients with abnormal glucose tolerance showed significant differences in age, weight, body mass index, waist-hip ratio, alanine aminotransferase, total bilirubin, total cholesterol, low-density lipoprotein cholesterol, triglyceride, insulin, FPG and homeostasis model for insulin resistance (HOMA-IR). Multiple regression analysis showed that age, FPG and HOMA-IR were independent predictors of abnormal glucose tolerance.

CONCLUSIONS

Although the patients were young men, an OGTT should be recommended for NAFLD patients with elevated liver enzymes and IFG to predict the risk of type 2 diabetes.

Differential effects of JNK1 and JNK2 inhibition on murine steatohepatitis and insulin resistance

Activation of c-Jun N-terminal kinase (JNK) has been implicated as a mechanism in the development of steatohepatitis. This finding, together with the reported role of JNK signaling in the development of obesity and insulin resistance, two components of the metabolic syndrome and predisposing factors for fatty liver disease, suggests that JNK may be a central mediator of the metabolic syndrome and an important therapeutic target in steatohepatitis. To define the isoform-specific functions of JNK in steatohepatitis associated with obesity and insulin resistance, the effects of JNK1 or JNK2 ablation were determined in developing and established steatohepatitis induced by a high-fat diet (HFD). HFD-fed jnk1 null mice failed to develop excessive weight gain, insulin resistance, or steatohepatitis. In contrast, jnk2(-/-) mice fed a HFD were obese and insulin-resistant, similar to wild-type mice, and had increased liver injury. In mice with established steatohepatitis, an antisense oligonucleotide knockdown of jnk1 decreased the amount of steatohepatitis in concert with a normalization of insulin sensitivity. Knockdown of jnk2 improved insulin sensitivity but had no effect on hepatic steatosis and markedly increased liver injury. A jnk2 knockdown increased hepatic expression of the proapoptotic Bcl-2 family members Bim and Bax and the increase in liver injury resulted in part from a Bim-dependent activation of the mitochondrial death pathway.

CONCLUSION

JNK1 and JNK2 both mediate insulin resistance in HFD-fed mice, but the JNK isoforms have distinct effects on steatohepatitis, with JNK1 promoting steatosis and hepatitis and JNK2 inhibiting hepatocyte cell death by blocking the mitochondrial death pathway.

Current status of therapy in nonalcoholic Fatty liver disease

The obesity epidemic has now spread worldwide. With increase in weight, there is an increase in dysregulated energy metabolism ultimately leading to dysfunction of multiple organ systems recognized as the metabolic syndrome. Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease worldwide, and is thought to be the hepatic manifestation of metabolic syndrome. It is a nondiscriminating disease affecting both children and adults and no socioeconomic class is spared. There is a well-defined increase in both liver-related and all-cause mortality. Current projections foresee a continued worsening in prevalence, especially with the increased rate of childhood obesity. Prevention would be the ultimate goal, but with continued trends in obesity, therapeutic options are needed to manage this chronic liver disease and prevent its complications of cirrhosis and even hepatocellular carcinoma. Therapies will need to be affordable, tolerable, and safe to be useful on such a large scale. This article will discuss some of the basic understanding of NAFLD, as well as review the currently tested therapies, some novel therapies, and potential future therapeutic options.

Cytokeratin 18 fragment levels as a noninvasive biomarker for nonalcoholic steatohepatitis in bariatric surgery patients

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is extremely common among morbidly obese patients. We assessed the usefulness of plasma caspase-generated cytokeratin 18 (CK-18) fragments as a novel marker for NAFLD in a bariatric cohort.

METHODS

The cohort consisted of 99 consecutive patients who underwent liver biopsy at the time of bariatric surgery. CK-18 levels were measured by using an enzyme-linked immunosorbent assay before and 6 months after surgery. Patients were subdivided into 4 histologic groups: not NAFLD (normal liver biopsy), nonalcoholic fatty liver (NAFL), borderline diagnosis, and definitive nonalcoholic steatohepatitis (NASH).

RESULTS

CK-18 levels were significantly higher in subjects with NASH compared with those with not NAFLD, NAFL, or borderline diagnosis (median [25th quartile, 75th quartile], 389 U/L [275, 839] vs 196 U/L [158, 245], vs 217 U/L [154, 228], or vs 200 U/L [176, 274], respectively; P < .0001). CK-18 levels were significantly higher in subjects with moderate to severe fibrosis versus those with no or mild fibrosis (334.5 U/L [240.5, 896] vs 207 U/L [175, 275], respectively; P = .007). A significant decrease in CK-18 levels was observed in most patients 6 months postoperatively. The area under the receiver operating characteristic curve for NASH diagnosis was estimated to be 0.88 (95% confidence interval, 0.77-0.99). The values with the best combination of sensitivity and specificity were 252 U/L (sensitivity, 82%; specificity, 77%) and 275 U/L (sensitivity, 77%; specificity, 100%).

CONCLUSIONS

These results support the potential utility of this test for diagnosis and staging of NAFLD before bariatric surgery.

Treatment options for nonalcoholic Fatty liver disease

Nonalcoholic fatty liver disease comprises a range of disorders from steatosis and steatohepatitis through to cirrhosis. Nonalcoholic steatohepatitis can progress to cirrhosis and liver-related death. Therefore, managing this common disorder is becoming an important public health issue. Lifestyle measures are commonly suggested but robust data are lacking. Trials with antioxidants (vitamin E, betaine) as well as cytoprotectants (ursodeoxycholic acid) have been disappointing. While data for insulin sensitizers such as metformin are less conclusive, thiazolidinediones appear promising. However, not all patients respond to thiazolidinediones. Moreover, issues related to weight gain, cardiovascular risk need to be addressed. The use of endocannabinoid antagonists and insulin secretagogues are novel strategies to combat this disorder.

Impact of visceral fat on the metabolic syndrome and nonalcoholic fatty liver disease

Visceral fat has been reported to be associated with nonalcoholic fatty liver disease (NAFLD) and the metabolic syndrome (MetS). We assessed the prevalence of both NAFLD and the MetS, measured visceral fat thickness VFT), and estimated the physical activity indexes of 224 relatively healthy hospital workers. We also investigated the associations between both VFT and physical activity index and each of NAFLD and the MetS. The MetS was diagnosed according to the guidelines outlined by the Adult Treatment Panel III, and NAFLD was diagnosed by ultrasonography. Subjects with hepatitis B and C infections and those reporting moderate alcohol consumption were excluded from the study. The prevalence of the MetS was 11.6% and that of NAFLD was 41.5%. Many subjects with the MetS had NAFLD (73.1%), and some subjects with NAFLD (20.4%) also had several components of the MetS (p=0.001). VFT was significantly increased by both the addition of components of the MetS and the severity of NAFLD (p<0.001). In addition, VFT was independently associated with NAFLD (odds ratio [OR], 1.10; 95% confidence interval [CI], 1.02-1.19) in subjects with more than 2 components of the MetS. In contrast, habitual physical activity was reversely associated with NAFLD (OR, 0.29; 95% CI, 0.10-0.87). In conclusion, an increased visceral fat content and reduced physical activity could be not only biological markers but also therapeutic targets in the treatment of NAFLD and the MetS.

The endoplasmic reticulum as a potential therapeutic target in nonalcoholic fatty liver disease

The endoplasmic reticulum (ER) has emerged as a key to understanding the development and consequences of hepatic fat accumulation in nonalcoholic fatty liver disease (NAFLD). An essential function of this organelle is the proper assembly of proteins that are destined for intracellular organelles and the cell surface. Recent evidence suggests that chemical chaperones that enhance the functional capacity of the ER improve liver function in obesity and NAFLD. These chaperones may therefore provide a novel potential therapeutic strategy in NAFLD.

Parental obesity and offspring serum alanine and aspartate aminotransferase levels: the Framingham heart study

BACKGROUND & AIMS

Obesity is an important correlate of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. We sought to examine the relations between parental obesity and the serum ALT and AST levels among offspring in a community-based sample.

METHODS

Participants (n = 1732) of the Framingham Offspring Study (50% women; mean age, 42 years) who had serum ALT and AST measurements and both parents in the original Framingham cohort were studied. Study participants were grouped into early-onset parental obesity (n = 193) (at least one parent obese), later-onset parental obesity (n = 460), and no parental obesity (n = 1079) subgroups. The association between elevated ALT or AST levels and parental obesity was tested using generalized estimating equations to account for familial correlations.

RESULTS

In multivariable analysis including adjustment for offspring obesity, significantly higher ALT levels were observed among individuals with paternal early-onset obesity as compared with those without paternal obesity (P = .02). Offspring with early-onset paternal obesity were more likely to have elevated ALT levels compared with those without paternal obesity (odds ratio, 1.75; 95% confidence interval, 1.06-2.89; P = .03). There was no association with elevated ALT levels among offspring with maternal early-onset obesity (odds ratio, 1.10; 95% confidence interval, 0.76-1.59; P = .61). There was no association between parental obesity and serum AST levels.

CONCLUSIONS

Early-onset paternal obesity, but not maternal obesity, increases the odds of elevated serum ALT levels in offspring, suggesting a predisposition to developing elevated serum ALT levels that may be mediated through familial early-onset obesity.

Mitochondrial dysfunction due to long-chain Acyl-CoA dehydrogenase deficiency causes hepatic steatosis and hepatic insulin resistance

Alterations in mitochondrial function have been implicated in the pathogenesis of insulin resistance and type 2 diabetes. However, it is unclear whether the reduced mitochondrial function is a primary or acquired defect in this process. To determine whether primary defects in mitochondrial beta-oxidation can cause insulin resistance, we studied mice with a deficiency of long-chain acyl-CoA dehydrogenase (LCAD), a key enzyme in mitochondrial fatty acid oxidation. Here, we show that LCAD knockout mice develop hepatic steatosis, which is associated with hepatic insulin resistance, as reflected by reduced insulin suppression of hepatic glucose production during a hyperinsulinemic-euglycemic clamp. The defects in insulin action were associated with an approximately 40% reduction in insulin-stimulated insulin receptor substrate-2-associated phosphatidylinositol 3-kinase activity and an approximately 50% decrease in Akt2 activation. These changes were associated with increased PKCepsilon activity and an aberrant 4-fold increase in diacylglycerol content after insulin stimulation. The increase in diacylglycerol concentration was found to be caused by de novo synthesis of diacylglycerol from medium-chain acyl-CoA after insulin stimulation. These data demonstrate that primary defects in mitochondrial fatty acid oxidation capacity can lead to diacylglycerol accumulation, PKCepsilon activation, and hepatic insulin resistance.

The role of skeletal muscle insulin resistance in the pathogenesis of the metabolic syndrome

We examined the hypothesis that insulin resistance in skeletal muscle promotes the development of atherogenic dyslipidemia, associated with the metabolic syndrome, by altering the distribution pattern of postprandial energy storage. Following ingestion of two high carbohydrate mixed meals, net muscle glycogen synthesis was reduced by approximately 60% in young, lean, insulin-resistant subjects compared with a similar cohort of age-weight-body mass index-activity-matched, insulin-sensitive, control subjects. In contrast, hepatic de novo lipogenesis and hepatic triglyceride synthesis were both increased by >2-fold in the insulin-resistant subjects. These changes were associated with a 60% increase in plasma triglyceride concentrations and an approximately 20% reduction in plasma high-density lipoprotein concentrations but no differences in plasma concentrations of TNF-alpha, IL-6, adiponectin, resistin, retinol binding protein-4, or intraabdominal fat volume. These data demonstrate that insulin resistance in skeletal muscle, due to decreased muscle glycogen synthesis, can promote atherogenic dyslipidemia by changing the pattern of ingested carbohydrate away from skeletal muscle glycogen synthesis into hepatic de novo lipogenesis, resulting in an increase in plasma triglyceride concentrations and a reduction in plasma high-density lipoprotein concentrations. Furthermore, insulin resistance in these subjects was independent of changes in the plasma concentrations of TNF-alpha, IL-6, high-molecular-weight adiponectin, resistin, retinol binding protein-4, or intraabdominal obesity, suggesting that these factors do not play a primary role in causing insulin resistance in the early stages of the metabolic syndrome.

Bax inhibition protects against free fatty acid-induced lysosomal permeabilization

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

Hypoadiponectinemia and insulin resistance are associated with nonalcoholic fatty liver disease

We investigated the association between nonalcoholic fatty liver disease (NAFLD) and plasma adiponectin levels and insulin resistance. We recruited study subjects among one hundred and eighty one persons who were examined abdominal ultrasound at routine screening tests. A standard interview (consumption of alcohol and medical history), physical examination (height, weight, waist circumference, and blood pressure), and biochemical study (lipid parameters, aminotransferases, fasting plasma glucose, fasting insulin, and plasma adiponectin) were performed. Subjects who consumed alcohol more than moderate, evidence of viral hepatitis, toxic hepatitis, and serious cardiac, renal, or hepatic disease were excluded. Thirty-eight NAFLD patients and 53 control subjects diagnosed by ultrasound were finally analyzed. The plasma adiponectin level was significantly correlated with HDL-cholesterol (r=0. 38, p<0.001), triglycerides (r=-0.22, p=0.04), fasting insulin (r=-0.37, p<0.01), and insulin resistance by homeostasis model of assessment-insulin resistance (HOMAIR) (r=-0.39, p<0.01), after adjusting for age, sex, and adiposity. Multiple logistic regression analysis indicated that HOMA-IR was a significant predictor of having NAFLD (odds ratio [OR]=2.38; 95% confidence interval [CI]: 1.52-5.74), while adiponectin had a protective effect against NAFLD (OR=0.22; 95% CI: 0.09-0.55). We demonstrated that hypoadiponectinemia and insulin resistance are associated with NAFLD independent of obesity.

Synaptic analysis of amacrine cells with neuropeptide Y-like immunoreactivity in turtle retina

Background

Nonalcoholic fatty liver disease (NAFLD) has a high prevalence in the general population and is the most common liver disease in Western countries. It is a feature of metabolic syndrome and is characterized by excessive accumulation of fat in the liver cells.

Methods

We examined 84 consecutive middle-aged (under 45 years) patients with NAFLD and 65 control subjects matched for age, gender, and body mass index to determine carotid intima-media thickness (CIMT) and flow-mediated dilatation (FMD) in the brachial artery.

Results

There was a statistically significant difference between CIMT and percentage increase in FMD in the patient group (P = 0.002; r = 0.33) when compared with the control group (P = 0.97; r = 0.005). The mean ± standard deviation CMIT was 0.65 ± 0.09 mm in patients and 0.55 ± 0.07 mm in controls. This difference was statistically significant (P = 0.001). Mean FMD in patients was 6.4% and 15.7% in controls. This difference was statistically significant (P = 0.001).

Conclusion

This study shows that pure NAFLD without metabolic syndrome in middle-aged subjects is strongly associated with morphological (CIMT) and physiological (FMD) changes. These findings may have an important role in increasing cardiovascular risk in these patients.