Visceral fat: a key mediator of steatohepatitis in metabolic liver disease

Management and diagnosis of fatty liver disease

Nonalcoholic fatty liver disease is a common cause of chronic liver disease and has been an increasingly studied topic of research as the obesity epidemic has been growing. There is a significant morbidity and mortality with uncontrolled steatohepatitis, which can progress to fibrosis, cirrhosis and hepatocellular carcinoma. The prevalence of this disease has been estimated to be roughly one-third of the western population, thought to be largely due to diet and sedentary lifestyle. Several treatments have been studied including vitamin E, insulin-sensitizing agents and ursodeoxycholic acid; however, the only treatment shown to improve the histologic changes of nonalcoholic fatty liver disease is weight loss. Given the proven benefit of weight loss, there may be reason to screen at-risk populations; however, limited availability of other disease-modifying treatments may limit the cost-benefit ratios. A better understanding of the diagnosis and management of this condition is required to alter the course of this modifiable disease.

Circulating phospholipid profiling identifies portal contribution to NASH signature in obesity

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is characterized by steatosis, lobular inflammation, hepatocyte ballooning with fibrosis in severe cases, and high prevalence in obesity. We aimed at defining NASH signature in morbid obesity by mass spectrometry-based lipidomic analysis.

METHODS

We analyzed systemic blood before and 12 months after bariatric surgery, along with portal blood and adipose tissue lipid efflux collected from obese women at the time of surgery (9 structural classes, 150 species).

RESULTS

Increased concentrations of several glycerophosphocholines (PC), glycerophosphoethanolamines (PE), glycerophosphoinositols (PI), glycerophosphoglycerols (PG), lyso-glycerophosphocholines (LPC), and ceramides (Cer) were detected in systemic circulation of NASH subjects. Post-surgery weight loss (12 months) improved the levels of liver enzymes, as well as several lipids, but most PG and Cer species remained elevated. Analysis of lipids from hepatic portal system at the time of surgery revealed limited lipid alterations compared to systemic circulation, but PG and PE classes were found significantly increased in NASH subjects. We evaluated the contribution of visceral adipose tissue to lipid alterations in portal circulation by measuring adipose tissue lipid efflux ex vivo, and observed only minor alterations in NASH subjects. Interestingly, integration of clinical and lipidomic data (portal and systemic) led us to define a NASH signature in which lipids and clinical parameters are equal contributors.

CONCLUSIONS

Circulatory (portal and systemic) phospholipid profiling and clinical data defines NASH signature in morbid obesity. We report weak contribution of visceral adipose tissue to NASH-related portal lipid alterations, suggesting possible contribution from other organs draining into hepatic portal system.

Epicardial fat, cardiac geometry and cardiac function in patients with non-alcoholic fatty liver disease: association with the severity of liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) has been associated with increased cardiovascular risk, including coronary artery disease and cardiac dysfunction. In addition, recent evidence highlighted the possible role of epicardial fat as a new cardiometabolic risk factor. We tested the correlation between epicardial fat, alterations in cardiac geometry and function, and severity of liver damage, in patients with biopsy-proven NAFLD.

METHODS

The anthropometric, biochemical and metabolic features were recorded in 147 consecutive biopsy-proven NAFLD cases (Kleiner score). Epicardial fat thickness was measured by echocardiography.

RESULTS

Epicardial fat was higher in patients with severe vs. milder fibrosis (8.5 ± 3.0 vs. 7.2 ± 2.3 mm; p=0.006); this association was maintained at multivariate logistic regression analysis (OR 1.22, 95%C.I. 1.01-1.47; p=0.04) after correction for gender, age >50 years, visceral obesity, IFG/diabetes, non-alcoholic steatohepatitis and severe steatosis. Of note, 37.1% of patients with epicardial fat >7 mm (median value) had severe liver fibrosis, compared to 18.3% of the cases with lower epicardial fat (p=0.01). As for echocardiographic indices, after adjusting for cardiometabolic confounders, diastolic posterior-wall thickness (p=0.01), left ventricular mass (p=0.03), relative wall thickness (p=0.02), and left atrial volume (0.04), as well as ejection fraction (p=0.004), lower lateral TDI e' (p=0.009), E/A ratio (0.04) (cardiac geometry alterations and diastolic dysfunction) were linked to severe liver fibrosis.

CONCLUSIONS

In patients with NAFLD, a higher epicardial fat thickness is associated with the severity of liver fibrosis, in keeping with a possible pathogenic role of ectopic fat depots in whole body organ damage. In addition, morphological and functional cardiac alterations are more pronounced according to the severity of fibrosis. Further studies are needed to validate our results.

The role of visceral and subcutaneous adipose tissue fatty acid composition in liver pathophysiology associated with NAFLD

Visceral adiposity is associated with type-2-diabetes, inflammation, dyslipidemia and non-alcoholic fatty liver disease (NAFLD), whereas subcutaneous adiposity is not. We hypothesized that the link between visceral adiposity and liver pathophysiology involves inherent or diet-derived differences between visceral and subcutaneous adipose tissue to store and mobilize saturated fatty acids. The goal of the present study was to characterize the fatty acid composition of adipose tissue triglyceride and portal vein fatty acids in relation to indices of liver dysregulation. For 8 weeks rats had free access to control (CON; 12.9% corn/safflower oil; 3.6 Kcal/g), high saturated fat (SAT; 45.2% cocoa butter; 4.5 Kcal/g) or high polyunsaturated fat (PUFA; 45.2% safflower oil; 4.5 Kcal/g) diets. Outcome measures included glucose tolerance, visceral and subcutaneous adipose tissue triglyceride, liver phospholipids and plasma (portal and systemic) free fatty acid composition, indices of inflammation and endoplasmic reticulum stress in the liver and adipose tissue depots and circulating adipo/cytokines. Hepatic triglycerides were significantly increased in both high fat diet groups compared to control and were significantly higher in PUFA compared to SAT. Although glucose tolerance was not different among diet groups, SAT increased markers of inflammation and ER stress in the liver and both adipose tissue depots. Fatty acid composition did not differ among adipose depots or portal blood in any dietary group. Overall, these data suggest that diets enriched in saturated fatty acids are associated with liver inflammation, ER stress and injury, but that any link between visceral adipose tissue and these liver indices does not involve selective changes to fatty acid composition in this depot or the portal vein.

Role of physical activity in nonalcoholic fatty liver disease in terms of visceral obesity and insulin resistance

BACKGROUND & AIMS

Limited evidence supports a role for physical activity (PA) in nonalcoholic fatty liver disease (NAFLD) independent of visceral obesity or/and insulin resistance. We investigated the association between PA and NAFLD while considering visceral adipose tissue (VAT) and insulin resistance in a large general population.

METHODS

Nonalcoholic fatty liver disease was diagnosed based on typical ultrasonographic findings. A detailed PA questionnaire included type, frequency, duration and length of time that the subject engaged in PA. PA was determined by a metabolic equivalent. VAT was evaluated by computed tomography taken at the umbilicus level.

RESULTS

A total of 3718 subjects were enrolled in the analysis. After adjusting for age, gender, body mass index, smoking, hypertension, diabetes, soft drink and coffee consumption, the total PA was inversely associated with NAFLD [4th quartile (highest activities), odds ratio (OR) 0.68, 95% confidence interval (CI) 0.54-0.85; 3rd quartile, OR 0.74, 95% CI 0.59-0.93 vs. 1st quartile (lowest activities), P for trend <0.001]. After further adjusting for VAT or insulin resistance or both (P for trend = 0.027, 0.001 and 0.040 respectively), this relationship was slightly attenuated but remained statistically significant. The leisure-time PA and weighted PA also had inverse associations with NAFLD independent of the VAT or insulin resistance or both.

CONCLUSIONS

This study showed an inverse association between various types of PA and the prevalence of NAFLD in a dose-dependent manner that was independent of visceral obesity and insulin resistance. This finding suggests a beneficial association between PA and NAFLD.

Visceral adipose tissue area as an independent risk factor for elevated liver enzyme in nonalcoholic fatty liver disease

Chronic elevations in alanine aminotransferase (ALT) levels are associated with body composition. The aim of this study was to evaluate the relationship between elevated liver enzyme levels and the visceral tissue area in subjects with and without nonalcoholic fatty liver disease (NAFLD).An observational cohort study was conducted with subjects undergoing general health examinations. To evaluate the visceral and subcutaneous abdominal adipose tissue area, a computed tomography scan was performed. NAFLD was diagnosed if a person demonstrated fatty liver on ultrasonography without a history of significant alcohol consumption or chronic liver disease. Abnormal liver enzyme levels were based on ALT elevations according to the updated Asian definition.Of the 5100 subjects, 3712 (72.8%) met the inclusion criteria, and NAFLD was found in 1185 subjects. Elevated ALT values were positively correlated with body mass index, waist circumference, and subcutaneous and visceral adipose tissue area. These relationships were attenuated, although they remained significant in a dose-dependent manner, after adjusting for multiple liver injury risk factors. In addition, when body mass index and subcutaneous and visceral tissue areas were finally considered in combination, only visceral adipose tissue remained independently associated with elevated ALT levels in the ultrasonographically diagnosed NAFLD group (P for trend <0.001 for men and women).Elevated ALT levels were independently and dose-dependently associated with visceral fat accumulation in the healthy general population, especially in ultrasonographically diagnosed NAFLD patients. These results reemphasize the importance of visceral fat in the pathogenesis of NAFLD.

Usefulness of ultrasonographic estimation of preperitoneal and subcutaneous fat thickness in the diagnosis of nonalcoholic fatty liver disease in diabetic patients

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) have been regarded as the hepatic manifestation of metabolic syndrome. Abdominal wall fat index (AFI), defined as the ratio of preperitoneal and subcutaneous fat thickness in the abdomen estimated by ultrasonography (US), has been shown to be useful in screening for disorders related to metabolic syndrome. We investigated the relation between AFI and NAFLD/NASH in diabetic patients.

METHODS

The degree of fat accumulation in the liver and the thickness of preperitoneal and subcutaneous fat were determined by US in 340 diabetic patients. An NAFLD fibrosis score (NAFLD-FS) was used to assess the advancement of hepatic fibrosis in NAFLD patients.

RESULTS

Of all 340 subjects, 209 (61 %) were diagnosed with NAFLD by US. AFI of NAFLD subjects was significantly higher than that of non-NAFLD subjects. Of the 209 subjects with NAFLD, 31 (15 %) were shown to have advanced NASH fibrosis according to NAFLD-FS. Multivariate analysis identified AFI as a significant predictor of advanced fibrosis.

CONCLUSION

AFI easily obtained by US was significantly related to the presence of NAFLD and/or advanced hepatic fibrosis in diabetic patients.

Exercise training reverses endothelial dysfunction in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is an independent risk factor for cardiovascular disease (CVD). Endothelial dysfunction is an early manifestation of atherosclerosis and an important prognostic marker for future cardiovascular events. The aim of this study was twofold: to examine 1) the association between liver fat, visceral adipose tissue (VAT), and endothelial dysfunction in obese NAFLD patients and 2) the impact of supervised exercise training on this vascular defect. Brachial artery endothelial function was assessed by flow-mediated dilatation (FMD) in 34 obese NAFLD patients and 20 obese controls of similar age and cardiorespiratory fitness [peak oxygen uptake (V̇o2 peak)] (48 ± 2 vs. 47 ± 2 yr; 27 ± 1 vs. 26 ± 2 ml·kg−1·min−1−1). Magnetic resonance imaging and spectroscopy quantified abdominal and liver fat, respectively. Twenty-one NAFLD patients completed either 16 wk of supervised moderate-intensity exercise training (n = 13) or conventional care (n = 8). Differences between NAFLD and controls were compared using independent t-tests and effects of interventions by analysis of covariance. NAFLD patients had higher liver fat [11.6% (95% CI = 7.4, 18.1), P < 0.0005] and VAT [1.6 liters (95% CI = 1.2, 2.0), P < 0.0001] than controls and exhibited impaired FMD compared with controls [−3.6% (95% CI = −4.9, −2.2), P < 0.0001]. FMD was inversely correlated with VAT (r = −0.54, P = 0.001) in NAFLD, although the impairment in FMD remained following covariate adjustment for VAT [3.1% (95% CI = 1.8, 4.5), P < 0.001]. Exercise training, but not conventional care, significantly improved V̇o2 peak [9.1 ml·kg−1·min−1 (95% CI = 4.1, 14.1); P = 0.001] and FMD [3.6% (95% CI = 1.6, 5.7), P = 0.002]. Endothelial dysfunction in NAFLD cannot be fully explained by excess VAT but can be reversed with exercise training; this has potential implications for the primary prevention of CVD in NAFLD.

Significance of oral glucose tolerance tests in non-alcoholic fatty liver disease patients with a fasting plasma glucose level of <126 mg/dL and HbA1c level of ≤ 6.4% in Japan

OBJECTIVE

The aim of this study was to clarify the indications for oral glucose tolerance tests (OGTT) in non-alcoholic fatty liver disease (NAFLD) subjects with a HbA1c level of ≤6.4%, fasting plasma glucose (FPG) level of <126 mg/dL and no history of diabetes.

PATIENTS

A total of 569 NAFLD subjects underwent 75-g OGTT. The plasma glucose and insulin levels were analyzed periodically for three hours during the OGTT examinations. Impaired fasting glucose (IFG) was defined as a plasma glucose level of ≥100 mg/dL to <126 mg/dL. Diabetes was defined as a two-hour post-load plasma glucose level of ≥200 mg/dL. Elevated insulin resistance was defined as a homeostasis model assessment-insulin resistance (HOMA-IR) of ≥2.5. Insulin secretory insufficiency was defined as an insulinogenic index of <0.4.

RESULTS

The prevalence of diabetes on the OGTT was 7.7% (44/569) among the NAFLD patients with an HbA1c level of ≤6.4%, FPG level of <126 mg/dL and no history of diabetes. A multivariate analysis showed that diabetes occurred more frequently when the subjects had IFG [odds ratio (OR) 5.13; 95% confidential interval (CI) 3.01-8.76; p<0.001] and an HbA1c level of 5.7-6.4% (OR 5.45; 95% CI 3.33-8.93; p<0.001). Of the NAFLD subjects with both IFG and an HbA1c level of 5.7-6.4%, 22.8% (28/123) exhibited a pattern of diabetes on OGTT. Regarding insulin dynamics, among the NAFLD subjects with both IFG and an HbA1c level of 5.7-6.4%, 25.2% (31/123) had elevated IR alone, 25.2% (31/123) had insulin secretory deficiency alone and 27.6% (34/123) had both elevated insulin resistance and insulin secretory deficiency.

CONCLUSION

NAFLD subjects with IFG and an HbA1c level of 5.7-6.4% should undergo OGTT in order to determine whether they have diabetes and/or abnormal insulin dynamics.

Prevalence of and risk factors for non-alcoholic fatty liver disease in a non-obese Japanese population, 2011-2012

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) in non-obese subjects is not rare in Japan, but it has not been clearly described. To clarify its prevalence and risk factors, we investigated the clinical characteristics of NAFLD in non-obese subjects in comparison with NAFLD in obese subjects in the Japanese general population.

METHODS

A cross-sectional study was performed with 5433 subjects who received health checkups from 2011 to 2012. Subjects consuming more than 20 g of alcohol per day and those with autoimmune liver disease, viral hepatitis, uncontrolled biliary disease and insufficient data were excluded. Subjects with a body mass index (BMI) ≥25 kg/m(2) were considered obese, and subjects with a BMI <25 kg/m(2) were considered non-obese.

RESULTS

A total of 3271 subjects were enrolled. The overall prevalence of NAFLD was 24.6%: 68.5% in obese subjects and 15.2% in non-obese subjects. The multivariate logistic regression analysis revealed that ≥10 kg of weight gain since the age of 20 was significantly associated with NAFLD in non-obese subjects of both genders, and eating an evening meal within 2 h before going to bed 3 days or more per week and drinking <20 g of alcohol per day were negatively associated in non-obese females. Metabolic factors such as waist circumference and triglycerides were predictors of NAFLD in non-obese subjects, and body fat percentage was a predictor in non-obese males.

CONCLUSIONS

Lifestyle as well as metabolic factors may play crucial roles in the pathogenesis of NAFLD, even in the non-obese Japanese population.

HLA DQB1 alleles are related with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease. NAFLD is a complex disease and inflammation is a crucial component in the disease pathogenesis. Recent genome wide association studies in hepatology area highlighted significant relations with human leukocyte antigen (HLA) DQ region and certain liver diseases. The previous animal models also emphasized the involvement of adaptive immune system in the liver damage pathways. To investigate possible polymorphisms in the HLA region that can contribute to the immune response affecting the NAFLD, we enrolled 93 consecutive biopsy proven NAFLD patients and a control group consisted of 101 healthy people and genotyped HLA DQB1 alleles at high resolution by sequence specific primers-polymerase chain reaction. The mean NAFLD activity score (NAS) was 5.2 ± 1.2, fibrosis score was 0.9 ± 0.9, ALT was 77 ± 47.4 U/L, AST was 49.4 ± 26.3 U/L. Among 13 HLA DQB1 alleles analyzed in this study, DQB1*06:04 was observed significantly at a more frequent rate among the NAFLD patients compared to that of healthy controls (12.9 vs. 2 % χ(2) = 8.6, P = 0.003, P c = 0.039, OR: 7.3 95 % CI 1.6-33.7). In addition, the frequency of DQB1*03:02 was significantly higher in the healthy control group than the NAFLD patients (24.8 vs. 7.5 %, χ(2) = 10.4, P = 0.001, P c = 0.013, OR: 0.2, 95 % CI 0.1-0.6). NAFLD patients were grouped according to their fibrosis score and NAS. The distribution of DQB1 alleles over stratified NAFLD patients did not reveal any statistically significant relation. Taken together, immune repertoire of individuals may have an effect on NAFLD pathogenesis and therefore, in NAFLD, adaptive immunity pathways should be investigated.

Performance and limitations of steatosis biomarkers in patients with nonalcoholic fatty liver disease

BACKGROUND

Several steatosis biomarkers are available with limited independent validation.

AIM

To determine diagnostic value and limitations of several steatosis biomarkers using liver biopsy as reference standard in a large cohort of patients with suspected NAFLD.

METHODS

Three hundred and twenty-four consecutive liver biopsies were included. Histological steatosis was categorised as none (<5%), mild (5-33%), moderate (33-66%) and severe (>66%). Five steatosis biomarkers were measured: fatty liver index (FLI), NAFLD liver fat score (NAFLD-LFS), hepatic steatosis index (HSI), visceral adiposity index (VAI) and triglyceride × glucose (TyG) index.

RESULTS

Steatosis grades prevalence was: none 5%, mild 39%, moderate 30% and severe 27%. Except for VAI, the steatosis biomarkers showed a linear trend across the steatosis grades. However, their correlation with the histological amount of steatosis was only weak-moderate. All steatosis biomarkers had an adequate diagnostic accuracy for the presence of steatosis: AUROCs for FLI, LFS, HSI, VAI and TyG were 0.83, 0.80, 0.81, 0.92 and 0.90. However, their ability to quantify steatosis was poor: none of them distinguished between moderate and severe steatosis and the AUROCs for predicting steatosis >33% were 0.65, 0.72, 0.65, 0.59 and 0.59 for FLI, LFS, HSI, VAI and TyG. Both fibrosis and inflammation significantly confounded the association between steatosis biomarkers and steatosis. The steatosis biomarkers were all correlated with HOMA-IR, independent from histological steatosis.

CONCLUSIONS

All five steatosis biomarkers can diagnose steatosis and are correlated with insulin resistance. They are confounded by fibrosis and inflammation, and do not accurately quantify steatosis; this may limit their clinical utility. More research is needed to identify truly independent and quantitative markers of steatosis.

Non-invasive hepatic biomarkers (ELF and CK18) in people with type 2 diabetes: the Edinburgh type 2 diabetes study

BACKGROUND & AIMS

Type 2 diabetes is an established risk factor for the presence and progression of fatty liver. Little is known about the distributions and correlates of hepatic non-invasive biomarkers in community-based populations with diabetes, unselected for liver disease. We aimed to identify the distribution of, and metabolic risk factors associated with serum cytokeratin-18 (CK18) and the Enhanced Liver Fibrosis score (ELF), in a large, representative cohort of people with type 2 diabetes (the Edinburgh Type 2 Diabetes Study, ET2DS).

METHODS

Nine hundred and thirty-nine ET2DS participants, aged 60-74 years underwent physical examination including ultrasound for assessment of liver fat. Representative subgroups were assessed for markers of chronic liver disease (CK18 and ELF).

RESULTS

CK18 values ranged from 29-993 U/L (median 102, IQR 76-137 U/L) and ELF scores ranged from 6.9-11.6 (mean 8.9, SD 0.8). Statistically significant associations were found between both biomarkers and a number of metabolic risk factors. Neither CK18 nor ELF was consistently or strongly associated with established hepatic risk factors (alcohol excess, hepatotoxic medication use and positive immunology titres).

CONCLUSIONS

We identified the distribution of CK18 and ELF in a large cohort of older people with type 2 diabetes and showed that these markers are associated with an adverse metabolic risk factor profile, although much of the variation in biomarkers remained unexplained. Prospective studies are required to determine the extent to which CK18 and/or ELF predict the development of symptomatic liver disease and to identify additional risk factors which may influence the development of advanced liver disease in people with type 2 diabetes.

Hypovitaminosis D is associated with increased whole body fat mass and greater severity of non-alcoholic fatty liver disease

BACKGROUND & AIMS

Hypovitaminosis D is common in obesity and insulin-resistant states. Increased fat mass in patients with non-alcoholic fatty liver disease (NAFLD) may contribute to hypovitaminosis D. To determine the relation among plasma vitamin D concentration, severity of disease and body composition in NAFLD.

METHODS

Plasma vitamin D concentration was quantified in 148 consecutive biopsy-proven patients with NAFLD (non-alcoholic steatohepatitis - NASH: n = 81; and hepatic steatosis: n = 67) and healthy controls (n = 39). NAFLD was scored using the NASH CRN criteria. Body composition was quantified by bioelectrical impedance analysis and abdominal CT image analysis.

RESULTS

Plasma vitamin D concentration was significantly lower in NAFLD (21.2 ± 10.4 ng/ml) compared with healthy controls (35.7 ± 6.0 ng/ml). Higher NAFLD activity scores were associated with lower plasma concentration of vitamin D (r(2)  = 0.29; P < 0.001). Subgroup analysis among patients with NAFLD showed that patients with NASH had significantly lower (P < 0.01) vitamin D levels than those with steatosis alone (18.1 ± 8.4 vs. 25.0 ± 11.3 ng/ml). Low concentrations of vitamin D were associated with greater severity of steatosis, hepatocyte ballooning and fibrosis (P < 0.05).On multivariate regression analysis, only severity of hepatocyte ballooning was independently associated (P = 0.02) with low vitamin D concentrations. Plasma vitamin D (P = 0.004) and insulin concentrations (P = 0.03) were independent predictors of the NAFLD activity score on biopsy. Patients with NAFLD had higher fat mass that correlated with low vitamin D (r(2)  = 0.26; P = 0.008).

CONCLUSIONS

Low plasma vitamin D concentration is an independent predictor of the severity of NAFLD. Further prospective studies demonstrating the impact of vitamin D replacement in NAFLD patients are required.

Fibrogenesis and Carcinogenesis in Nonalcoholic Steatohepatitis (NASH): Involvement of Matrix Metalloproteinases (MMPs) and Tissue Inhibitors of Metalloproteinase (TIMPs)

Nonalcoholic steatohepatitis (NASH) is emerging worldwide because life-styles have changed to include much over-eating and less physical activity. The clinical and pathophysiological features of NASH are very different from those of HBV- and HCV-chronic liver diseases. The prognosis of NASH is worse among those with nonalcoholic fatty liver diseases (NAFLD), and some NASH patients show HCC with or without cirrhosis. In the present review we discuss fibrogenesis and the relationship between fibrosis and HCC occurrence in NASH to clarify the role of MMPs and TIMPs in both mechanisms. Previously we proposed MMP and TIMP expression in the multi-step occurrence of HCC from the literature based on viral-derived HCC. We introduce again these expressions during hepatocarcinogenesis and compare them to those in NASH-derived HCC, although the relationship with hepatic stem/progenitor cells (HPCs) invasion remains unknown. Signal transduction of MMPs and TIMPs is also discussed because it is valuable for the prevention and treatment of NASH and NASH-derived HCC.

Chronic stress induces steatohepatitis while decreases visceral fat mass in mice

Background

Prolonged stress leads over time to allostatic load on the body and is likely to exacerbate a disease process. Long-term of stress exposure is one of a risk factor for metabolism-related diseases such as obesity and type 2 diabetes. However, the relationship between chronic stress and non-alcoholic fatty liver disease (NAFLD) remain unknown.

Methods

To address the hypothesis that chronic stress associate to NAFLD development, we subjected C57bl/6 mice to electric foot shock and restraint stress for 12 weeks to set up chronic stress model. Then the serum and hepatic triglyceride (TG), total cholesterol (TC) were measured. Hepatic HE and Oil red O staining were used to specify the state of the NAFLD. To investigate whether inflammation takes part in the stress-induced NAFLD process, related visceral fat, serum and hepatic inflammatory factors were measured.

Results

We observed that chronic stress led to an overall increase of hepatic triglyceride and cholesterol while decreasing body weight and visceral fat mass. Microvesicular steatosis, lobular inflammation and ballooning degeneration were seen in stress liver section. This effect was correlated with elevated hepatic and serum inflammatory factors. Although the amount of visceral fat was decreased in stress group, various adipocytokines were elevated.

Conclusions

We showed that chronic stress is associated to NAFLD and chronic inflammation in visceral fat, though food intake and visceral fat mass were decreased. These results may contribute to better understanding of the mechanism from steatosis to steatohepatitis, and propose a novel insight into the prevention and treatment of NAFLD.

Steatosis and steatohepatitis: complex disorders

Non-alcoholic fatty liver disease (NAFLD) which includes steatosis and steatohepatitis, in particular non-alcoholic steatohepatitis (NASH), is a rising health problem world-wide and should be separated from alcoholic steatohepatitis (ASH). NAFLD is regarded as hepatic manifestation of the metabolic syndrome (MetSy), being tightly linked to obesity and type 2 diabetes mellitus (T2DM). Development of steatosis, liver fibrosis and cirrhosis often progresses towards hepatocellular carcinogenesis and frequently results in the indication for liver transplantation, underlining the clinical significance of this disease complex. Work on different murine models and several human patients studies led to the identification of different molecular key players as well as epigenetic factors like miRNAs and SNPs, which have a promoting or protecting function in AFLD/ASH or NAFLD/NASH. To which extent they might be translated into human biology and pathogenesis is still questionable and needs further investigation regarding diagnostic parameters, drug development and a better understanding of the genetic impact. In this review we give an overview about the currently available knowledge and recent findings regarding the development and progression of this disease.

Clinical and metabolic factors associated with development and regression of nonalcoholic fatty liver disease in nonobese subjects

BACKGROUND & AIMS

The course of NAFLD (nonalcoholic fatty liver disease) and associated factors in nonobese subjects are not well established. We investigated contributing factors for the development and regression of NAFLD in nonobese Koreans, and whether they would differ from those of obese subjects.

METHODS

Two thousand three hundred and seven adults aged over 18 years participated in this longitudinal observational study. The mean duration of follow-up was 28.7 (±13.2) months. The participants were divided into two groups according to the baseline BMI (nonobese group: BMI <25 kg/m(2), obese group: BMI ≥25 kg/m(2)). The presence or absence of NAFLD was assessed by abdominal ultrasonography.

RESULTS

Body weight change was independently associated with both the development and regression of NAFLD in nonobese subjects as well as obese subjects. Among the subjects who developed NAFLD, the amount of weight change was higher in nonobese subjects compared to obese subjects (1.6 ± 3.9% vs 0.6 ± 4.2%, P = 0.022); and among those who showed regression of NAFLD, the amount of weight change was lower in nonobese subjects (-1.9 ± 4.0% vs -5.0 ± 4.6%, P < 0.001). Among all the components of metabolic syndrome, only high triglyceride levels (>150 mg/dl) at the baseline were significantly associated with both the development and regression of NAFLD in nonobese subjects (ORs, 1.54 (1.10-2.14), and 0.60 (0.38-0.96) respectively).

CONCLUSION

Body weight change and baseline triglyceride levels were strong indicators for the development and regression of NAFLD in a nonobese population.

Role of adipose tissue in methionine-choline-deficient model of non-alcoholic steatohepatitis (NASH)

Methionine–choline-deficient (MCD) diet is a widely used dietary model of non-alcoholic steatohepatitis (NASH) in rodents. However, the contribution of adipose tissue to MCD-induced steatosis, and inflammation as features of NASH are not fully understood. The goal of this study was to elucidate the role of adipose tissue fatty acid (FA) metabolism, adipogenesis, lipolysis, inflammation and subsequent changes in FA profiles in serum and liver in the pathogenesis of steatohepatitis. We therefore fed ob/ob mice with control or MCD diet for 5 weeks. MCD-feeding increased adipose triglyceride lipase and hormone sensitive lipase activities in all adipose depots which may be attributed to increased systemic FGF21 levels. The highest lipase enzyme activity was exhibited by visceral WAT. Non-esterified fatty acid (NEFA)-18:2n6 was the predominantly elevated FA species in serum and liver of MCD-fed ob/ob mice, while overall serum total fatty acid (TFA) composition was reduced. In contrast, an overall increase of all FA species from TFA pool was found in liver, reflecting the combined effects of increased FA flux to liver, decreased FA oxidation and decrease in lipase activity in liver. NAFLD activity score was increased in liver, while WAT showed no changes and BAT showed even reduced inflammation. Conclusion: This study demonstrates a key role for adipose tissue lipases in the pathogenesis of NASH and provides a comprehensive lipidomic profiling of NEFA and TFA homeostasis in serum and liver. Our findings provide novel mechanistic insights for the role of WAT in progression of MCD-induced liver injury.

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MCD model of NASH increases lipase activity in WAT as a critical determinant of hepatic FA flux and lipotoxicity.

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The maximal increase of ATGL and HSL activity is in visceral WAT.

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Increased lipase activity may be due to enhanced FGF21 signaling.

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NEFA-18:2n6 is preferentially increased in serum and liver due to lipolysis in WAT.

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MCD diet enhances the activity of BAT and diminishes its inflammatory markers.

Clinical approaches to non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) ranges from simple steatosis to nonalcoholic steatohepatitis (NASH), leading to fibrosis and potentially cirrhosis, and it is one of the most common causes of liver disease worldwide. NAFLD is associated with other medical conditions such as metabolic syndrome, obesity, cardiovascular disease and diabetes. NASH can only be diagnosed through liver biopsy, but noninvasive techniques have been developed to identify patients who are most likely to have NASH or fibrosis, reducing the need for liver biopsy and risk to patients. Disease progression varies between individuals and is linked to a number of risk factors. Mechanisms involved in the pathogenesis are associated with diet and lifestyle, influx of free fatty acids to the liver from adipose tissue due to insulin resistance, hepatic oxidative stress, cytokines production, reduced very low-density lipoprotein secretion and intestinal microbiome. Weight loss through improved diet and increased physical activity has been the cornerstone therapy of NAFLD. Recent therapies such as pioglitazone and vitamin E have been shown to be beneficial. Omega 3 polyunsaturated fatty acids and statins may offer additional benefits. Bariatric surgery should be considered in morbidly obese patients. More research is needed to assess the impact of these treatments on a long-term basis. The objective of this article is to briefly review the diagnosis, management and treatment of this disease in order to aid clinicians in managing these patients.

Clinical approaches to non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) ranges from simple steatosis to nonalcoholic steatohepatitis (NASH), leading to fibrosis and potentially cirrhosis, and it is one of the most common causes of liver disease worldwide. NAFLD is associated with other medical conditions such as metabolic syndrome, obesity, cardiovascular disease and diabetes. NASH can only be diagnosed through liver biopsy, but noninvasive techniques have been developed to identify patients who are most likely to have NASH or fibrosis, reducing the need for liver biopsy and risk to patients. Disease progression varies between individuals and is linked to a number of risk factors. Mechanisms involved in the pathogenesis are associated with diet and lifestyle, influx of free fatty acids to the liver from adipose tissue due to insulin resistance, hepatic oxidative stress, cytokines production, reduced very low-density lipoprotein secretion and intestinal microbiome. Weight loss through improved diet and increased physical activity has been the cornerstone therapy of NAFLD. Recent therapies such as pioglitazone and vitamin E have been shown to be beneficial. Omega 3 polyunsaturated fatty acids and statins may offer additional benefits. Bariatric surgery should be considered in morbidly obese patients. More research is needed to assess the impact of these treatments on a long-term basis. The objective of this article is to briefly review the diagnosis, management and treatment of this disease in order to aid clinicians in managing these patients.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

Glucokinase regulatory protein gene polymorphism affects liver fibrosis in non-alcoholic fatty liver disease

BACKGROUND AND AIMS

Variant in glucokinase regulatory protein (GCKR), associated with lipid and glucose traits, has been suggested to affect fatty liver infiltration. We aimed to assess whether GCKR rs780094 C→T SNP influences the expression of steatosis, lobular inflammation and fibrosis in NAFLD patients, after correction for PNPLA3 genotype.

METHODS

In 366 consecutive NAFLD patients (197 from Sicily, and 169 from center/northern Italy), we assessed anthropometric, biochemical and metabolic features; liver biopsy was scored according to Kleiner. PNPLA3 rs738409 C>G and GCKR rs780094 C>T single nucleotide polymorphisms were also assessed.

RESULTS

At multivariate logistic regression analysis in the entire NAFLD cohort, the presence of significant liver fibrosis (>F1) was independently linked to high HOMA (OR 1.12, 95% CI 1.01-1.23, p = 0.02), NAFLD activity score ≥ 5 (OR 4.09, 95% CI 2.45-6.81, p<0.001), and GCKR C>T SNP (OR 2.06, 95% CI 1.43-2.98, p<0.001). Similar results were observed considering separately the two different NAFLD cohorts. GCKR C>T SNP was also associated with higher serum triglycerides (ANOVA, p = 0.02) in the entire cohort.

CONCLUSIONS

In patients with NAFLD, GCKR rs780094 C>T is associated with the severity of liver fibrosis and with higher serum triglyceride levels.

Testosterone replacement ameliorates nonalcoholic fatty liver disease in castrated male rats

Nonalcoholic fatty liver disease is common in developed countries and is associated with obesity, metabolic syndrome, and type 2 diabetes. T deficiency is a risk factor for developing these metabolic deficiencies, but its role in hepatic steatosis has not been well studied. We investigated the effects of T on the pathogenesis of hepatic steatosis in rats fed a high-fat diet (HFD). Adult male rats were randomly placed into four groups and treated for 15 weeks: intact rats on regular chow diet (RCD), intact rats on liquid HFD (I+HFD), castrated rats on HFD (C+HFD), and castrated rats with T replacement on HFD (C+HFD+T). Fat contributed 71% energy to the HFD but only 16% of energy to the RCD. Serum T level was undetectable in castrated rats, and T replacement led to 2-fold higher mean serum T levels than in intact rats. C+HFD rats gained less weight but had higher percentage body fat than C+HFD+T. Severe micro- and macrovesicular fat accumulated in hepatocytes with multiple inflammatory foci in the livers of C+HFD. I+HFD and C+HFD+T hepatocytes demonstrated only mild to moderate microvesicular steatosis. T replacement attenuated HFD-induced hepatocyte apoptosis in castrated rats. Serum glucose and insulin levels were not increased with HFD in any group. Immunoblots showed that insulin-regulated proteins were not changed in any group. This study demonstrates that T deficiency may contribute to the severity of hepatic steatosis and T may play a protective role in hepatic steatosis and nonalcoholic fatty liver disease development without insulin resistance.

Simple steatosis is a more relevant source of serum inflammatory markers than omental adipose tissue

BACKGROUND AND AIMS

Serum inflammatory biomarkers are closely associated with the risk of cardiovascular disease. However, the major source of these biomarkers is not yet determined. Therefore, we aimed to assess whether simple steatosis or visceral adiposity was a more relevant predictor for serum inflammatory biomarkers.

METHODS

A double approach was used: i) clinical: 50 patients with biopsy-proven simple steatosis, 50 non-simple steatosis overweight patients, and 50 controls were explored for their serum biomarkers (high-sensitivity C-reactive protein, plasminogen activator inhibitor-1 activity, tumor necrosis factor α, and fibrinogen levels) and for visceral adiposity (measured by computed tomography); ii) experimental: using a rat simple steatosis model the effect of omentectomy on inflammatory biomarkers was investigated.

RESULTS

Serum inflammatory biomarkers were significantly higher in the simple steatosis group than in the overweight group. Using multivariate analysis, simple steatosis, visceral adiposity index and visceral adiposity were independently associated with inflammatory biomarkers. In particular, serum inflammatory biomarkers increased with the severity of liver histology (p<0.05), but no with visceral adipose tissue increase. In rats with simple steatosis, the omentectomy treatment was not associated with a decrease of serum inflammatory biomarkers in rats with simple steatosis.

CONCLUSIONS

Clinical and experimental data both indicate that simple steatosis may be more associated with inflammatory biomarkers than omental adipose tissue.

The interactions of nonalcoholic fatty liver disease and cardiovascular diseases

A complex interaction among metabolic factors, adipose tissue lipolysis, oxidative stress, and insulin resistance results in a deleterious process that may link nonalcoholic fatty liver disease (NAFLD) with severe cardiovascular (CV) outcomes. Patients with NAFLD are at higher risk of atherosclerosis, new onset of CV events, and overall mortality. The strong association between NAFLD and CV disease should affect clinical practice, with screening and surveillance of patients with NAFLD. This review discusses the data linking these major diseases.

Serum lipocalin-2, cathepsin S and chemerin levels and nonalcoholic fatty liver disease

Several novel circulating adipokines are associated with insulin resistance and inflammation. Little information exists in NAFLD about three recently recognized adipokines lipocalin-2, cathepsin S and chemerin. To assess the relationship between serum lipocalin-2, cathepsin S and chemerin levels and the development of non-alcoholic fatty liver in Chinese subjects, we measured serum lipocalin-2, cathepsin S and chemerin levels in 903 Chinese subjects by ELISA. Among the study population, 436 patients are with B-mode ultrasound-proven NAFLD and 467 controls. Levels of lipocalin-2, but not cathepsin S and chemerin, were significantly elevated in NAFLD versus control [lipocalin-2, 89.67 ± 4.47 vs. 68.70 ± 3.65 ng/mL (p < 0.001)]. After stepwise linear regression analysis adjusting for potential cofounders, further revealed that serum lipocalcin-2 was an independent predictor of NAFLD in whole cohort (standardized β = 0.114, t = 2.347, p = 0.02). Lipocalin-2 levels correlated with insulin resistance (homeostasis model assessment of insulin resistance) and inflammation (CRP) in whole cohorts and NAFLD, whereas cathepsin S and chemerin only correlated positively with insulin resistance and inflammation in whole cohorts. Our results indicated that circulating lipocalin-2, produced by adipocytes, are elevated and may contribute to the development of NAFLD. Serum lipocalin-2, which correlates with inflammation and insulin resistance, may have a direct pathogenic link to disease progression.

Circulating progranulin level is associated with visceral fat and elevated liver enzymes: significance of serum progranulin as a useful marker for liver dysfunction

Progranulin (PRGN) was recently identified as one of the adipokines involved in the development of insulin resistance. Thus, the aim of this study was to explore the importance of PRGN as a novel marker for metabolic diseases in Japanese. A total of 138 subjects were recruited by the Aijinkai Total Health Care Center. Physical examination, blood sample examination and total body CT scan were performed for all participants. Serum PRGN levels were examined in subjects with or without metabolic syndrome and with or without liver enzyme elevation. Association study of serum PRGN levels and regression analysis of the relationship of elevated liver enzymes to representative metabolic parameters were performed. The metabolic syndrome group exhibited older age, and higher BMI, blood pressure, fasting glucose, HbA1c, IRI, HOMA-R, TG, FFA, CRP, AST, ALT, LDH, and ALP, and larger visceral fat area, subcutaneous fat area and visceral fat area/subcutaneous fat area. Serum PRGN concentrations were significantly higher in the metabolic syndrome group than in the non-metabolic syndrome group. Bivariate correlation analysis revealed that serum PRGN concentrations correlated positively and significantly with AST, ALT, LDH, γGTP, ALP, waist circumference and visceral fat area. The group with elevated liver enzymes exhibited higher BMI, blood pressure, IRI, HOMA-R, and PRGN level and larger waist circumference and visceral fat area than the group without them. In logistic regression analysis, visceral fat area and PRGN were significantly predictive of elevated liver enzymes. These results suggest that serum PRGN level as well as visceral fat are associated closely with liver dysfunction.

Effect modification of body mass index and body fat percentage on fatty liver disease in a Japanese population

BACKGROUND AND AIM

No previous study has performed multivariate analysis of the risk factors of fatty liver disease (FL), focusing on the effect of weight gain of ≥ 10 kg since the age of 20, and no analysis model exists that simultaneously evaluates body mass index (BMI) and body fat percentage (BFP) as adjustment variables.

METHODS

To investigate these, we collected anthropometric data from health checkups, and conducted a cross-sectional study (targeting 1851 males and 1259 females aged 30 years or over).

RESULTS

Regardless of sex, weight gain of ≥10 kg since the age of 20 was positively associated with FL. Our stratified analysis of BFP into two categories, to evaluate the interaction between BMI and BFP in FL, indicated an approximately fivefold increase in the odds ratio in the male group with high BMI and BFP values compared to those with low BMI and BFP values, with a synergy index of 1.77 > 1. On the other hand, females demonstrated no significant additive interaction, with a synergy index of 0.49 < 1.

CONCLUSIONS

We revealed that weight gain ≥ 10 kg since the age of 20 is significantly associated with FL regardless of sex. In addition, by performing a synergy index (S), we showed that the additive interaction between BMI and BFP in FL differs according to gender.

Prognostic factors for regression from impaired glucose tolerance to normal glucose regulation in Japanese patients with nonalcoholic fatty liver disease

OBJECTIVE

The aim of this retrospective cohort study was to assess the predictive factors for the regression from impaired glucose tolerance (IGT) to normal glucose regulation (NGR) in patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

A total of 164 NAFLD patients who had IGT in the first 75-g oral glucose tolerance test (OGTT) and underwent a repeated OGTT five years later were enrolled. A multivariate logistic regression analysis was carried out to identify factors predicting the regression from IGT to NGR.

RESULTS

Out of the 164 patients, 29 regressed from IGT to NGR within five years after the first OGTT. The multivariate analysis by logistic regression showed that regression from IGT to NGR occurred when the patient was young (risk ratio for ten years: 0.38; 95% confidence interval [CI] 0.20-0.72; p=0.003), had a fasting plasma glucose (FPG) level of <100 mg/dL (risk ratio: 6.53; 95%CI 1.88-21.73; p=0.003), had a 2-hr post-load plasma glucose (PG) level of <160 mg/dL (risk ratio: 4.86; 95%CI 1.08-22.72; p=0.040), a body mass index (BMI) decrease of ≥1.5 (risk ratio: 5.20; 95% CI 1.41-19.24; p=0.014), physical activity of ≥2 Metabolic Equivalent of Task (MET) h/day (risk ratio: 5.57; 95%CI 1.68-18.44; p=0.005), and showed disappearance of the fatty liver by ultrasonography at five years (risk ratio: 9.92; 95%CI 2.87-34.34; p<0.001).

CONCLUSION

Our results suggest that six factors: young age, FPG <100 mg/dL, 2-hr post-load PG of <160 mg/dL, BMI decrease of ≥1.5, physical activity of ≥2 MET h/day, and the disappearance of fatty liver predict the regression from IGT to NGR in NAFLD patients.

Association between inflammatory markers and liver fat: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a common liver disease. Data is emerging that an independent association between markers of subclinical atherosclerosis and NAFLD exists and it may be considered as an independent predictor of cardiovascular (CV) outcomes. We aim to better characterize the relationship between NAFLD and inflammatory markers in a multi-ethnic cohort by assessing fatty liver on computed tomography (CT) scans.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) is a longitudinal, population-based study from four ethnic groups free of CV disease at baseline. The inflammatory markers studied include: C-reactive protein (CRP) and interleukin 6 (IL-6). On CT scans liver-to-spleen ratio (LSR: Hounsfield Units (HU) of the liver divided by HU of spleen) of <1 and liver attenuation of <40 HU were used as criteria for fatty liver. Unadjusted and adjusted multivariate linear and logistic regression analysis was performed.

RESULTS

4038 participants amongst 6814 MESA population with visible spleen on the CT scan, available CRP and IL-6 levels and no reported liver cirrhosis were included. The average age was 61 +/- 10 years, 37% Caucasians and 45% were males. Mean CRP and IL-6 were 2.36 mg/dl and 1.37 pg/ml respectively. 696 participants (17%) had LSR of <1 and 253 (6%) had liver attenuation of <40 HU. When using LSR <1 as a continuous variable, the correlation (adjusted odds ratio (OR)) with CRP >2.0 was 0.037 (95% CI: 0.02-0.054) and with IL-6 was 0.014 (95% CI: 0.004-0.023). On the other hand when presence and absence of LSR <1 was considered, higher ORs for association with CRP >2: 1.41 (95% CI: 1.16 to 1.73) and IL6:1.18 (95% CI: 1.05 to 1.31) were found. Similarly, the adjusted association of per unit decrease in liver attenuation with CRP>2 was 1.92 (95% CI: 1.20 to 2.63) while for IL-6 was 1.08 (95% CI: 0.69 to 1.47). When considering presence and absence of liver attenuation <40 HU the OR for CRP >2 was 2.27 (95% CI: 1.62 to 3.16) and for IL-6 was 1.33 (95% CI: 1.13 to 1.58).

CONCLUSION

CRP and IL-6 levels were found to be significantly associated with liver fat assessed on CT scan after adjusting for other risk factors for atherosclerosis.

Chemoprevention of nonalcoholic fatty liver disease by dietary natural compounds

Nonalcoholic fatty liver disease (NAFLD) refers to a wide spectrum of liver disease that is not from excess alcohol consumption, but is often associated with obesity, type 2 diabetes, and metabolic syndrome. NAFLD pathogenesis is complicated and involves oxidative stress, lipotoxicity, mitochondrial damage, insulin resistance, inflammation, and excessive dietary fat intake, which increase hepatic lipid influx and de novo lipogenesis and impair insulin signaling, thus promoting hepatic triglyceride accumulation and ultimately NAFLD. Overproduction of proinflammatory adipokines from adipose tissue also affects hepatic metabolic function. Current NAFLD therapies are limited; thus, much attention has been focused on identification of potential dietary substances from fruits, vegetables, and edible plants to provide a new strategy for NAFLD treatment. Dietary natural compounds, such as carotenoids, omega-3-PUFAs, flavonoids, isothiocyanates, terpenoids, curcumin, and resveratrol, act through a variety of mechanisms to prevent and improve NAFLD. Here, we summarize and briefly discuss the currently known targets and signaling pathways as well as the role of dietary natural compounds that interfere with NAFLD pathogenesis.

Hepatocellular Carcinoma in Non-alcoholic Fatty Liver Disease: Epidemiology, Pathogenesis, and Prevention

Hepatocellular cancer (HCC) is the fifth most prevalent cancer worldwide and the third leading cause of cancer-related deaths. Non-alcoholic fatty liver disease (NAFLD), a spectrum of hepatic disorders associated with obesity and the metabolic syndrome, is a recognized risk factor for HCC. NAFLD that is advanced to cirrhosis carries the highest risk for HCC, but there is increasing concern that NAFLD-associated HCC may also occur in non-cirrhotic liver. As NAFLD is rapidly becoming the most common liver condition, it has been implicated in the worrisome trend of rising HCC incidence in a number of countries, which may offset successful measures in reducing the effect of virus-related liver cancer. Independently or in synergy with cirrhosis, NAFLD may provide a special oncogenic microenvironment through its pathogenic association with chronic nutrient excess and adipose tissue remodeling, characterized by pro-inflammatory adipokine profiles, lipotoxicity, altered hepatocellular bioenergetics, and insulin resistance. Better understanding of this complex process, and development of reliable biomarkers for HCC will be critical for early recognition and risk prediction. Moreover, correcting deranged lipid metabolism and restoring insulin sensitivity by lifestyle measures and targeted pharmacotherapy holds major promise for effective prevention of NAFLD-associated HCC.

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

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

Efficacy and safety in sitagliptin therapy for diabetes complicated by non-alcoholic fatty liver disease

AIM

The aim of this case-control study was to assess the efficacy and safety of dipeptidyl peptidase-4 inhibitor (sitagliptin) for type 2 diabetes mellitus (T2DM) with non-alcoholic fatty liver disease (NAFLD).

METHODS

Twenty NAFLD patients with T2DM treated by sitagliptin were retrospectively enrolled as the sitagliptin group. These patients were given sitagliptin between January 2010 and July 2011. Another 20 NAFLD patients with T2DM treated only with diet and exercise for 48 weeks were selected as the control group. Serum levels of fasting plasma glucose (FPG), hemoglobin A1C (HbA1c), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured before and 12, 24, 36 and 48 weeks after the initiation of treatment.

RESULTS

In the sitagliptin group, average HbA1c levels decreased approximately 0.7% at 48 weeks after the initiation of sitagliptin. Next, average FPG levels decreased approximately 15 mg/dL at 48 weeks after the initiation of sitagliptin. The serum levels of HbA1c and FPG in the sitagliptin group decreased with statistical significance compared to those in the control group (P < 0.05). All the patients could take sitagliptin of 50 mg/day without reduction necessitated by sitagliptin-related side-effects. There were no significant changes of average AST and ALT levels during follow up of 48 weeks in both sitagliptin and control groups.

CONCLUSION

Our results indicate sitagliptin is effective and safe for the treatment of T2DM complicated with NAFLD.

Association between UCP3 gene polymorphisms and nonalcoholic fatty liver disease in Chinese children

AIM: To confirm the hypothesis that polymorphisms of the uncoupling protein 3 (UCP3) gene are associated with the occurrence of nonalcoholic fatty liver disease (NAFLD).

METHODS: A total of 250 NAFLD patients (147 males and 103 females) and 200 healthy individuals who served as controls (control, 109 males and 91 females), aged between 6 and 16 years were enrolled in this study. The four non-synonymous single nucleotide polymorphisms (SNPs) in the UCP3 gene polymorphisms of rs1726745, rs3781907, rs11235972 and rs1800849, were genotyped using MassArray. Body mass index (BMI), waist and hip circumference, blood pressure (BP), fasting blood glucose (FBG), insulin and lipid profiles were measured and B-ultrasound examination was performed in all subjects.

RESULTS: NAFLD patients showed risk factors for metabolic syndrome: elevated BMI, waist-to-hip ratio, BP, FBG, homeostasis model assessment-estimated insulin resistance, total triglyceride, total cholesterol and low-density lipoprotein-cholesterol, while decreased high-density lipoprotein-cholesterol level compared with the control group. The GG genotype distributions of rs11235972 in the NAFLD group differed significantly from that in the control group. We found that waist circumference between CC (58.76 ± 6.45 cm) and CT+TT (57.00 ± 5.59 cm), and hip circumference between CC (71.28 ± 7.84 cm) and CT+TT genotypes (69.06 ± 7.75 cm) were significantly different with and without rs1800849 variation (P < 0.05).

CONCLUSION: A higher prevalence of rs11235972 GG genotype was observed in the NAFLD group compared with the control group. No differences were observed for the other SNPs. However, there was a significant difference in body height in addition to waist and hip circumference between the CC (mutant type group) and CT+TT group with and without rs1800849 variation.

Adiposity and insulin resistance in humans: the role of the different tissue and cellular lipid depots

Human adiposity has long been associated with insulin resistance and increased cardiovascular risk, and abdominal adiposity is considered particularly adverse. Intra-abdominal fat is associated with insulin resistance, possibly mediated by greater lipolytic activity, lower adiponectin levels, resistance to leptin, and increased inflammatory cytokines, although the latter contribution is less clear. Liver lipid is also closely associated with, and likely to be an important contributor to, insulin resistance, but it may also be in part the consequence of the lipogenic pathway of insulin action being up-regulated by hyperinsulinemia and unimpaired signaling. Again, intramyocellular triglyceride is associated with muscle insulin resistance, but anomalies include higher intramyocellular triglyceride in insulin-sensitive athletes and women (vs men). Such issues could be explained if the "culprits" were active lipid moieties such as diacylglycerol and ceramide species, dependent more on lipid metabolism and partitioning than triglyceride amount. Subcutaneous fat, especially gluteofemoral, appears metabolically protective, illustrated by insulin resistance and dyslipidemia in patients with lipodystrophy. However, some studies suggest that deep sc abdominal fat may have adverse properties. Pericardial and perivascular fat relate to atheromatous disease, but not clearly to insulin resistance. There has been recent interest in recognizable brown adipose tissue in adult humans and its possible augmentation by a hormone, irisin, from exercising muscle. Brown adipose tissue is metabolically active, oxidizes fatty acids, and generates heat but, because of its small and variable quantities, its metabolic importance in humans under usual living conditions is still unclear. Further understanding of specific roles of different lipid depots may help new approaches to control obesity and its metabolic sequelae.

The role of skeletal muscle in development of nonalcoholic Fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is closely correlated with abnormal accumulation of visceral fat, but the role of skeletal muscle remains unclear. The aim of this study was to elucidate the role of skeletal muscle in development of NAFLD.

METHODS

Among 11,116 subjects (6,242 males), we examined the effects of skeletal muscle mass and visceral fat area (VFA, by bioelectric impedance analysis) on NAFLD using by the fatty liver index (FLI).

RESULTS

Of the total subjects (9,565 total, 5,293 males) included, 1,848 were classified as having NALFD (FLI ≥60). Body mass index, lipid profile, fasting plasma glucose, hemoglobin A1c, prevalence of type 2 diabetes (DM), hypertension (HTN), and metabolic syndrome were higher in males than females, but FLI showed no significant difference. The low FLI group showed the lowest VFA and highest skeletal muscle mass of all the groups. Skeletal muscle to visceral fat ratio (SVR) and skeletal muscle index had inverse correlations with FLI, when adjusted for age and gender. In multivariate regression analysis, SVR was negatively associated with FLI. Among SVR quartiles, the highest quartile showed very low risk of NAFLD when adjusted for age, gender, lipid profile, DM, HTN, and high sensitivity C-reactive protein from the lowest quartiles (odds ratio, 0.037; 95% confidence interval, 0.029 to 0.049).

CONCLUSION

Skeletal muscle mass was inversely associated with visceral fat area, and higher skeletal muscle mass may have a beneficial effect in preventing NAFLD. These results suggest that further studies are needed to ameliorate or slow the progression of sarcopenia.

Non-alcoholic fatty liver disease-related hepatocellular carcinoma: a sleeping tiger in the Asia Pacific

The epidemiology of hepatocellular carcinoma (HCC) in the Asia Pacific will undergo significant change over the next few decades as the prevalence of viral hepatitis declines and the burden of metabolic diseases increases. As the Asia Pacific embraces continued affluence, obesity and diabetes rates are burgeoning, becoming increasingly important to the incidence of HCC. Obesity and diabetes are established risk factors for HCC, either as substrates for non-alcoholic fatty liver disease (NAFLD) or as independent carcinogens themselves. This review summarises the epidemiological data on changing HCC trends in the Asia Pacific, particularly as it pertains to the emerging problem of NAFLD-related HCC.

Metabolic factors and chronic hepatitis C: a complex interplay

In the last years, several lines of evidence showed how metabolic factors may influence the natural history of patients with chronic hepatitis C. Chronic HCV infection is able to perturb the metabolic homeostasis of the host, in a context of complex interactions where pre-existent metabolic status and genetic background play an important role, allowing us to state that HCV infection is a systemic disease. In this review, we discuss the most recent lines of evidence on the main metabolic factors that are known to be associated with CHC, namely, insulin resistance/type 2 diabetes, steatosis, visceral obesity, atherosclerosis, vitamin D, menopause, fructose and coffee intake, lipoproteins, methylenetetrahydrofolate reductase status, and hyperuricaemia. In particular, we focus on the pathophysiological mechanisms underlying the correlation between HCV infection and metabolic disorders, the impact of metabolic factors on the progression of liver and non-liver-related diseases, and, on the contrary, the possible influence of chronic HCV infection on metabolic features. In this setting, the importance of a multifaceted evaluation of CHC patients and a prompt correction of modifiable metabolic risk factors should be emphasized.

The influence of waist circumference on insulin resistance and nonalcoholic fatty liver disease in apparently healthy Korean adults

Background/Aims

Waist circumference (WC) is a risk factor for metabolic syndrome and is related to insulin resistance (IR) and nonalcoholic fatty liver disease (NAFLD). The purpose of this study was to determine the association between WC and IR and NAFLD in apparently healthy Korean adults.

Methods

The volunteers included in this cross-sectional study comprised 9,159 adults (5,052 men, 4,107 women) who participated in a comprehensive health checkup program. IR was evaluated by the homeostasis model assessment of IR (HOMA-IR) and was considered to be present when the HOMA-IR score was >2. NAFLD was evaluated by ultrasound examination. Elevated alanine aminotransferase (ALT) was defined as >40 IU/L in men and >35 IU/L in women. Logistic regression was performed to determine the odds ratios (ORs) and 95% confidence intervals (95% CIs) for NAFLD, IR, and ALT according to categorized levels of WC.

Results

NAFLD was found in 2,553 (27.9%) of the participants (82.6% men, 17.4% women), while IR and elevated ALT were found in 17.2% (68.1% men, 31.9% women) and 10% (83% men, 17% women), respectively. After adjusting for confounding factors, the prevalence of NAFLD, IR, and elevated ALT was significantly associated with increases in WC quartile: highest quartile for NAFLD in men, OR=15.539, 95% CI=12.687-19.033; highest quartile for NAFLD in women, OR=48.732, 95% CI=23.918-99.288 (P<0.001); and highest quartile for IR in men, OR=17.576, 95% CI=13.283-23.255; highest quartile for IR in women, OR=11.078, 95% CI=7.813-15.708 (P<0.001); highest quartile for elevated ALT in men, OR=7.952, 95% CI=6.046-10.459; and highest quartile for elevated ALT in women, OR=8.487, 95% CI=4.679-15.395 (P<0.001).

Conclusions

WC contributes to IR and NAFLD in apparently healthy Korean adults, and thus may be an important factor in the development of IR and NAFLD.

Increased thickness of abdominal subcutaneous adipose tissue occurs more frequently in steatohepatitis than in simple steatosis

CONTEXT

The incidence of obesity is increasing and contributes to the rising incidence of fatty liver. Body mass index (BMI) is used to assess the degree of obesity but does not take into account the pattern of body fat distribution.

OBJECTIVES

To confirm the increasing incidence of fatty liver in an autopsy study. We hypothesized that a standardized measurement of abdominal subcutaneous adipose tissue (ASAT) might be a good noninvasive method for differentiating steatohepatitis from steatosis.

DESIGN

Consecutive complete adult postmortem cases were studied and liver sections were assessed with a steatohepatitis scoring system. Spleen weight, ASAT, and clinical information were obtained. Spleen histology was assessed in a subset of patients having splenomegaly in the absence of cirrhosis.

RESULTS

Patients with human immunodeficiency virus, hepatitis C virus, and appreciable alcohol use were excluded. Of 306 cases, the frequency of fatty liver was 51.6% with 33.3% having simple steatosis and 18.3%, having steatohepatitis. Mean ASAT was 3.7 cm in the steatohepatitis group versus 2.6 cm in the steatosis group (P < .001); this difference was greater in patients with a BMI less than 25 kg/m(2) (P = .05). Fibrocongestive splenomegaly was noted in 9 of 38 patients with nonalcoholic steatohepatitis (24%) in the absence of cirrhosis.

CONCLUSIONS

In this series of autopsy cases, a dramatic increase in the prevalence of fatty liver disease is demonstrated. Thicker ASAT is associated more with steatohepatitis than with simple steatosis, especially in patients with BMI below 25 kg/m(2). Fibrocongestive splenomegaly may occur in the absence of cirrhosis in the presence of steatohepatitis.

Non alcoholic fatty liver disease in southern Iran: a population based study

BACKGROUND

Population based studies on prevalence and risk factors of NAFLD in Iranian population are few. The prevalence of NAFLD and non alcoholic steatohepatitis (NASH) in Iranians varies from 2.9% to 7.1% in general population and 55.8% in patients with type 2 diabetes mellitus.

OBJECTIVES

To determine the prevalence and determinants of non alcoholic fatty liver disease (NAFLD) in a sample of adult Iranian general population.

PATIENTS AND METHODS

This was a cross-sectional study being performed in Shiraz, southern Iran during a 10-month period from November 2010 to September 2011 through cluster random sampling of Iranian general population in Shiraz region. All individuals undergone anthropometric, blood pressure measurements, thorough medical history and physical examinations. Laboratory measurements included fasting blood glucose (FBS), lipid profile, complete blood count (CBC) and liver function tests. NAFLD was diagnosed by transabdominal ultrasonography.

RESULTS

819 subjects were included in this study among which were 340 males (41.5%) and 479 females (58.5%) with the mean age of 43.1 ± 14.1 years. NAFLD was diagnosed in 176 (21.5%) subjects. Patients with NAFLD were significantly older (P < 0.001), had higher proportion of male gender (P = 0.004) and had higher BMI (P < 0.001). They also had higher prevalence of hypertension (P < 0.001), high FBS (P < 0.001), high cholesterol (P = 0.026), high triglyceride (P < 0.001) and high waist circumference (P < 0.001). Taking all these together, patients with NAFLD had significantly higher prevalence of metabolic syndrome when compared to healthy subjects (P < 0.001).

CONCLUSION

The prevalence of NAFLD in this group of Iranian adult general population is 21.5%. NAFLD in Iranian population is associated with male gender, old age, obesity, and features of metabolic syndrome.

Combined ethanol extract of grape pomace and omija fruit ameliorates adipogenesis, hepatic steatosis, and inflammation in diet-induced obese mice

The aim of this study was to evaluate the long-term effects of grape pomace ethanol extract (GPE) with or without omija fruit ethanol extract (OFE) on adiposity, hepatic steatosis, and inflammation in diet-induced obese mice. Male C57BL/6J mice were fed a high-fat diet (HFD) as the control diet and HFD plus GPE (0.5%, w/w) with or without OFE (0.05%, w/w) as the experimental diet for 12 weeks. GPE alone did not significantly affect adipogenesis and hepatic steatosis. However, the supplementation of GPE + OFE significantly lowered body weight gain, white adipose tissue weight, adipocyte size, and plasma free fatty acid and adipokines (leptin, PAI-1, IL-6, and MCP-1) levels in HFD-fed mice compared to those of the control group. These beneficial effects of GPE + OFE were partly related to the decreased expression of lipogenic and inflammatory genes in white adipose tissue. GPE + OFE supplementation also significantly lowered liver weight and ameliorated fatty liver by inhibiting expression of hepatic genes involved in fatty acid and cholesterol syntheses as well as inflammation and by activating hepatic fatty acid oxidation. These findings suggest that the combined ethanol extract of grape pomace and omija fruit has the potential to improve adiposity and fatty liver in diet-induced obese mice.

MRI measurement of liver fat content predicts the metabolic syndrome

BACKGROUND AND AIMS

The prevalence of non-alcoholic fatty liver disease among cardiometabolic patients is not completely known because liver biopsy cannot be routinely performed. However, as magnetic resonance imaging (MRI) allows accurate and safe measurement of the hepatic fat fraction (HFF), the aim of this study was to quantify liver fat content in a dysmetabolic adult population.

METHODS

A total of 156 adults were included in this cross-sectional study. Liver and visceral fat were assessed by MRI in these subjects, who presented with zero to five metabolic components of the metabolic syndrome (MetS). Arterial stiffness was recorded by ultrasonography, and the maximum Youden index was used to set the optimal HFF cutoff value predictive of the presence of the MetS.

RESULTS

Overall, 72% of participants displayed three or more MetS components. HFF ranged from 0.3% to 52% (mean 13.4%). Age- and gender-adjusted HFF was positively correlated with BMI (r=0.44), blood pressure (r=0.19), triglyceridaemia (r=0.22) and glycaemia (r=0.31). MRI-measured visceral adipose tissue did not influence the relationship of steatosis with glycaemia, HOMA-IR and carotid stiffness, but there was a dose-response relationship between the number of MetS components and mean HFF. The optimal HFF for predicting the MetS was found to be 5.2% according to the maximum Youden index point.

CONCLUSION

This study highlighted the impact of liver steatosis on cardiometabolic abnormalities with an optimal cutoff value of 5.2% for defining increased metabolic risk.

Three-dimensional culture model for analyzing crosstalk between adipose tissue and hepatocytes

Systemic adipose tissue is involved in the pathophysiology of obesity-associated liver diseases. However, a method has not been established for analyzing the direct interaction between adipose tissue and hepatocytes. We describe a useful three-dimensional model comprising a collagen gel coculture system in which HepG2 hepatocytes are cultured on a gel layer with visceral adipose tissue fragments (VAT) or subcutaneous tissue samples (SAT). Male adipose tissues were obtained from 5-week-old Wistar rats and human autopsy cases. Cellular behavior was analyzed by electron microscopy, immunohistochemistry, Western blot, real-time reverse transcription plus the polymerase chain reaction and enzyme-linked immunosorbent assay. VAT significantly promoted lipid accumulation and apoptosis in HepG2 cells and suppressed their growth and differentiation compared with SAT. VAT produced higher concentrations of fatty acids (palmitate, oleate, linoleate) than SAT. HepG2 cells significantly decreased the production of these fatty acids in VAT. Only HepG2 cells treated with 250 μM palmitate replicated VAT-induced apoptosis. Neither VAT nor SAT affected lipotoxicity-associated signals of nuclear factor kappa B, c-Jun N-terminal kinase and inositol requiring enzyme-1α in HepG2 cells. HepG2 cells never affected adiponectin, leptin, or resistin production in VAT and SAT. The data indicate that our model actively creates adipose tissue and HepG2 hepatocyte interactions, suggesting that (1) VAT plays more critical roles in hepatocyte lipotoxicity than SAT; (2) palmitate but not adipokines, is partly involved in the mechanisms of VAT-induced lipotoxicity; (3) HepG2 cells might inhibit fatty acid production in VAT to protect themselves against lipotoxicity. Our model should serve in studies of interactions between adipose tissue and hepatocytes and of the mechanisms in obesity-related lipotoxicity and liver diseases.

What is the role of adiponectin in obesity related non-alcoholic fatty liver disease?

Non-alcoholic fatty liver disease (NAFLD) is recognized as the most common type of chronic liver disease in Western countries. Insulin resistance is a key factor in the pathogenesis of NAFLD, the latter being considered as the hepatic component of insulin resistance or obesity. Adiponectin is the most abundant adipose-specific adipokine. There is evidence that adiponectin decreases hepatic and systematic insulin resistance, and attenuates liver inflammation and fibrosis. Adiponectin generally predicts steatosis grade and the severity of NAFLD; however, to what extent this is a direct effect or related to the presence of more severe insulin resistance or obesity remains to be addressed. Although there is no proven pharmacotherapy for the treatment of NAFLD, recent therapeutic strategies have focused on the indirect upregulation of adiponectin through the administration of various therapeutic agents and/or lifestyle modifications. In this adiponectin-focused review, the pathogenetic role and the potential therapeutic benefits of adiponectin in NAFLD are analyzed systematically.

Allostasis in nonalcoholic fatty liver disease: implications for risk assessment

Allostasis, a concept of anticipatory physiological regulation in response to external and internal challenges, was originally developed in the context of neuroendocrinology and behavioral medicine. Allostasis preserves function under changing conditions by abandoning physiological set points and developing new ones. Allostatic load refers to the aggregate effect of adaptation throughout life, and corresponds to the wear and tear associated with this process. In response to chronic stress, allostatic load may accumulate faster than expected if sustained activation of regulatory systems exceeds optimum operating ranges; this results in increased risk of disease. Used in a broader sense, the allostatic model of adaptive responses, trade-offs, feed-forward cycles, and collateral damage provides a framework for assessing the involvement of environmental-genetic interactions and co-morbidities in the course of chronic disease and developing a comprehensive score for personalized risk prediction. The utility of this approach is illustrated for nonalcoholic fatty liver disease, a prevalent condition with common and less common outcomes.