The global NAFLD epidemic

TM6SF2 E167K Variant, a Novel Genetic Susceptibility Variant, Contributing to Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of liver dysfunction worldwide, and its prevalence is highly associated with genetic susceptibility. The transmembrane 6 superfamily member 2 (TM6SF2) E167K variant represents a general genetic determinant of hepatic triglyceride content and lobular inflammation, and its presence appears to be directly involved in the pathogenesis and development of NAFLD. Although this variant appears to be a novel powerful modifier in the development of NAFLD, whether it is associated with an increased risk of NAFLD-related liver fibrosis and hepatocellular carcinoma (HCC) remains to be determined. The aim of this review is to describe the functions of the TM6SF2 E167K variant and its association with NAFLD, with particular emphasis on the underlying mechanisms of its role in the development and progression of NAFLD. Additionally, the links between the TM6SF2 E167K variant and NAFLD-related liver fibrosis and HCC will be discussed.

Nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a disorder characterized by excess accumulation of fat in hepatocytes (nonalcoholic fatty liver (NAFL)); in up to 40% of individuals, there are additional findings of portal and lobular inflammation and hepatocyte injury (which characterize nonalcoholic steatohepatitis (NASH)). A subset of patients will develop progressive fibrosis, which can progress to cirrhosis. Hepatocellular carcinoma and cardiovascular complications are life-threatening co-morbidities of both NAFL and NASH. NAFLD is closely associated with insulin resistance; obesity and metabolic syndrome are common underlying factors. As a consequence, the prevalence of NAFLD is estimated to be 10-40% in adults worldwide, and it is the most common liver disease in children and adolescents in developed countries. Mechanistic insights into fat accumulation, subsequent hepatocyte injury, the role of the immune system and fibrosis as well as the role of the gut microbiota are unfolding. Furthermore, genetic and epigenetic factors might explain the considerable interindividual variation in disease phenotype, severity and progression. To date, no effective medical interventions exist that completely reverse the disease other than lifestyle changes, dietary alterations and, possibly, bariatric surgery. However, several strategies that target pathophysiological processes such as an oversupply of fatty acids to the liver, cell injury and inflammation are currently under investigation. Diagnosis of NAFLD can be established by imaging, but detection of the lesions of NASH still depend on the gold-standard but invasive liver biopsy. Several non-invasive strategies are being evaluated to replace or complement biopsies, especially for follow-up monitoring.

Global publication trends and research hotspots of nonalcoholic fatty liver disease: a bibliometric analysis and systematic review

With the globally increasing prevalence, nonalcoholic fatty liver disease (NAFLD) becomes the predominant cause of chronic liver disease. A global look at the publication trends and the research hotspots of NAFLD are urgently needed to assess the situation of NAFLD research. The global scientific research in the Science Citation Index-Expanded covered articles relevant to NAFLD was retrieved and its bibliometric parameters and research hotspots of NAFLD were systematically evaluated. To sum up, 6356 articles were published in 994 different journals covering 93 SCI subject categories during 1986–2013, in which English was the most predominant language used. Starting from the late 1980s, the publication on NAFLD grew slowly and entered into a highly developing period in the 21st century, especially in the last decade. Besides hepatic steatosis, metabolic syndrome and its combination of symptoms such as obesity, insulin resistance are listed as the top frequent keywords. Bibliometric results suggest that the obviously rapid growth of the articles in recent years appears to be associated with the accelerating incidence of NAFLD and its cofactors such as metabolic syndrome. In addition, epidemiology focusing on comparing different regions and population is attracting ever-growing attention. Meantime, pathology plays an important role in NAFLD research.

Lipidomics comparing DCD and DBD liver allografts uncovers lysophospholipids elevated in recipients undergoing early allograft dysfunction

Finding specific biomarkers of liver damage in clinical evaluations could increase the pool of available organs for transplantation. Lipids are key regulators in cell necrosis and hence this study hypothesised that lipid levels could be altered in organs suffering severe ischemia. Matched pre- and post-transplant biopsies from donation after circulatory death (DCD, n = 36, mean warm ischemia time = 2 min) and donation after brain death (DBD, n = 76, warm ischemia time = none) were collected. Lipidomic discovery and multivariate analysis (MVA) were applied. Afterwards, univariate analysis and clinical associations were conducted for selected lipids differentiating between these two groups. MVA grouped DCD vs. DBD (p = 6.20 × 10(-12)) and 12 phospholipids were selected for intact lipid measurements. Two lysophosphatidylcholines, LysoPC (16:0) and LysoPC (18:0), showed higher levels in DCD at pre-transplantation (q < 0.01). Lysophosphatidylcholines were associated with aspartate aminotransferase (AST) 14-day post-transplantation (q < 0.05) and were more abundant in recipients undergoing early allograft dysfunction (EAD) (p < 0.05). A receiver-operating characteristics (ROC) curve combining both lipid levels predicted EAD with 82% accuracy. These findings suggest that LysoPC (16:0) and LysoPC (18:0) might have a role in signalling liver tissue damage due to warm ischemia before transplantation.

The dual and opposite role of the TM6SF2-rs58542926 variant in protecting against cardiovascular disease and conferring risk for nonalcoholic fatty liver: A meta-analysis

The aim of this work was to estimate the strength of the effect of the TM6SF2 E167K (rs58542926 C/T) variant on blood lipid traits and nonalcoholic fatty liver disease (NAFLD) across different populations. We performed a systematic review by a meta-analysis; literature searches identified 10 studies. The rs58542926 exerts a significant role in modulating lipid traits, including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and NAFLD. However, this influence on lipids and NAFLD is opposite between genotypes in the dominant model of inheritance. Pooled estimates of random effects in 101,326 individuals showed that carriers of the minor T allele (EK+KK individuals), compared with subjects homozygous for the ancestral C allele (EE genotype), are protected from cardiovascular disease (CVD), showing lower levels of TC, LDL-C, and TG; the differences in mean ± standard error (mg/dL) are -8.38 ± 1.56, -3.7 ± 0.9, and -9.4 ± 2.1, respectively. The rs58542926 variant was not associated with high-density lipoprotein cholesterol in a large sample (n = 91,937). In contrast, carriers of the T allele showed a moderate effect on the risk of NAFLD (odds ratio: 2.13; 95% confidence interval: 1.36-3.30; P = 0.0009; n = 3273) and approximately ∼2.2% higher lipid fat content when compared with homozygous EE (n = 3,413).

CONCLUSIONS

The rs58542926 appears to be an important modifier of blood lipid traits in different populations. As a challenge for personalized medicine, the C-allele, which has an overall frequency as high as 93%, is associated with higher blood lipids, whereas the T allele confers risk for NAFLD; in turn, CVD and NAFLD are strongly related outcomes. Although the variant confers protection against CVD at the expense of an increased risk of NAFLD, it does not explain the link between these two complex diseases.

Interactions of Hepatitis B Virus Infection with Nonalcoholic Fatty Liver Disease: Possible Mechanisms and Clinical Impact

Hepatitis B virus (HBV) infection is a major etiology of chronic liver disease worldwide. In the past decade, nonalcoholic fatty liver disease (NAFLD) has emerged as a common liver disorder in general population. Accordingly, the patient number of chronic hepatitis B (CHB) concomitant with NAFLD grows rapidly. The present article reviewed the recent studies aiming to explore the relationship between CHB and NAFLD from different aspects, including the relevant pathogenesis of CHB and NAFLD, the intracellular molecular mechanisms overlaying HBV infection and hepatic steatosis, and the observational studies with animal models and clinical cohorts for analyzing the coincidence of the two diseases. It is concluded that although numerous cross-links have been suggested between the molecular pathways in HBV infection and NAFLD pathogenesis, regarding whether HBV infection can substantially interfere with the occurrence of NAFLD or vice versa in the patients, there is still far from a conclusive agreement.

Heritability of Hepatic Fibrosis and Steatosis Based on a Prospective Twin Study

BACKGROUND & AIMS

Little is known about the heritability of hepatic fibrosis, and the heritability of hepatic steatosis has not been assessed systematically in adults. We investigated the heritability of hepatic fibrosis and steatosis in a community-dwelling twin cohort.

METHODS

We performed a cross-sectional analysis of a cohort of well-characterized twins residing in Southern California including 60 pairs of twins (42 monozygotic and 18 dizygotic; average age, 45.7 ± 22.1 y; average body mass index, 26.4 ± 5.7 kg/m(2)). We collected data on medical history, physical examinations, fasting laboratory test results, and liver health; all participants underwent an advanced magnetic resonance imaging (MRI) examination of the liver from January 2012 through January 2015. Hepatic steatosis was quantified noninvasively by MRI and determined based on the proton-density fat fraction (MRI-PDFF); liver fibrosis was measured based on stiffness measured by magnetic resonance elastography.

RESULTS

Twenty-six of the 120 subjects (21.7%) had nonalcoholic fatty liver disease (defined as MRI-PDFF ≥ 5% after exclusion of other causes of hepatic steatosis). The presence of hepatic steatosis correlated between monozygotic twins (r(2) = 0.70; P < .0001) but not between dizygotic twins (r(2) = 0.36; P = .2). The level of liver fibrosis also correlated between monozygotic twins (r(2) = 0.48; P < .002) but not between dizygotic twins (r(2) = 0.12; P = .7). In multivariable models adjusted for age, sex, and ethnicity, the heritability of hepatic steatosis (based on MRI-PDFF) was 0.52 (95% confidence interval, 0.31-0.73; P < 1.1 × 10(-11)) and the heritability of hepatic fibrosis (based on liver stiffness) was 0.5 (95% confidence interval, 0.28-0.72; P <6.1 × 10(-11)).

CONCLUSIONS

A study of twins provides evidence that hepatic steatosis and hepatic fibrosis are heritable traits.

S100A8 Production in CXCR2-Expressing CD11b+Gr-1high Cells Aggravates Hepatitis in Mice Fed a High-Fat and High-Cholesterol Diet

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease with a spectrum of presentations. S100A8 has been suggested to play a pivotal role as an endogenous immune-activator in inflammatory diseases. In this study, we investigated the involvement of S100A8 in the development of NAFLD. We used a diet model of NAFLD, in which mice were fed either a high-fat and high-cholesterol diet (HFHCD) or a normal diet (ND) as a control. We also assessed liver tissues from patients with NAFLD, including patients with nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). HFHCD-fed mice, but not ND-fed mice, developed steatohepatitis. S100A8 expression was significantly elevated in the livers of HFHCD-fed mice compared with the controls. S100A8 was exclusively expressed in CXCR2-expressing CD11b(+)Gr-1(high) cells, which significantly increased in the livers of HFHCD-fed mice. These cells were F4/80 negative and did not possess a suppressor function. TNF-α expression was enhanced by S100A8 in primary liver leukocytes or a hepatocyte cell line and significantly elevated in the livers of HFHCD-fed mice. TNF-α was primarily produced from CD11b(+)F4/80(+) cells in liver leukocytes in response to S100A8. TNF-α deficiency attenuated hepatitis in HFHCD-fed mice. S100A8 was significantly more expressed in the liver tissues of patients with NASH than in those of patients with NAFL. In conclusion, these results suggest that S100A8 is primarily produced from CXCR2-expressing CD11b(+)Gr-1(high) cells, and it upregulates TNF-α production in CD11b(+)F4/80(+) cells through cellular cross-talk, which is an important mechanism in the development of NAFLD.

Cholesterol induces lipoprotein lipase expression in a tree shrew (Tupaia belangeri chinensis) model of non-alcoholic fatty liver disease

Animal models are indispensible to investigate the pathogenesis and treatments of non-alcoholic fatty liver diseases (NAFLD). Altered cholesterol metabolism has been implicated into the pathogenesis of NAFLD. Here, using high fat, cholesterol and cholate diet (HFHC), we generated a novel tree shrew (Tupaia belangeri chinensis) model of NAFLD, which displayed dyslipidemia with increased levels of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST), total cholesterol (TC), low density lipoprotein-cholesterol (LDL-c) and high density lipoprotein-cholesterol (HDL-c), but decreased level of triglycerides (TG). Liver histopathology and genes expression indicated that HFHC diet successfully induced liver steatosis to inflammation and fibrosis progressively within 10 weeks. Moreover, HFHC induced the transcriptional expression of lipoprotein lipase (lpl) in the liver, but repressed the expression of LDL receptor, and the endogenous synthesis pathway and excretion of cholesterol. Notably, Poloxamer 407 (P-407) inhibition of LPL improved the severity of steatosis and reduced inflammation. These results illustrated that LPL plays an important role in cholesterol metabolism in NAFLD, and the tree shrew may be a valuable animal model for further research into NAFLD.

Comparative effectiveness of pharmacological interventions for nonalcoholic steatohepatitis: A systematic review and network meta-analysis

We performed a Bayesian network meta-analysis combining direct and indirect treatment comparisons to assess the comparative effectiveness of pharmacological agents for the treatment of nonalcoholic steatohepatitis (NASH). Through systematic literature review, we identified nine randomized, controlled trials (RCTs) including 964 patients with biopsy-proven NASH, comparing vitamin E, thiazolidinediones (TZDs), pentoxifylline, or obeticholic acid to one another or placebo. The primary outcome was improvement in fibrosis stage; secondary outcomes were improvement in ballooning degeneration, lobular inflammation, and steatosis. We reported relative risks (RRs) and 95% confidence intervals (CIs) from direct meta-analysis and 95% credible intervals (CrIs) from Bayesian network meta-analysis, and used Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria to appraise quality of evidence. Moderate-quality evidence supports the use of pentoxifylline (RR, 0.26; 95% CrI: 0.05-1.00) and obeticholic acid (RR, 0.81; 95% CI: 0.70-0.95) over placebo in improving fibrosis. High-quality evidence supports the effect of vitamin E, TZDs, and obeticholic acid over placebo in improving ballooning degeneration. All four interventions seemed to have at least moderate-quality evidence over placebo to improve steatosis. Moderate-quality evidence supports that TZDs, pentoxifylline, and obeticholic acid decrease lobular inflammation. All the head-to-head comparisons were supported by very-low-quality evidence except for superiority of TZDs over vitamin E on improving steatosis and lobular inflammation, which had moderate-quality evidence.

CONCLUSIONS

Based on direct and network meta-analysis, pentoxifylline and obeticholic acid improve fibrosis, and vitamin E, TZDs, and obeticholic acid improve ballooning degeneration in patients with NASH. Future comparative trials of combination therapies targeting distinct histological features are warranted.

Nonalcoholic Fatty Liver Disease Review: Diagnosis, Treatment, and Outcomes

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of abnormal serum aminotransferase levels in both developed and developing countries. Patients with nonalcoholic steatohepatitis (NASH), a subset of NAFLD, are at risk for progressive liver disease and in need of effective treatment options. A practical approach may be pursued by identifying patients with NAFLD with the highest likelihood for histologic evidence of NASH. Despite decades of clinical trials, no single treatment can be recommended to all patients with NASH. Importantly, there is no evidence that pioglitazone or vitamin E improves fibrosis. Bariatric surgeries may improve hepatic histology in morbidly obese patients with NASH, although randomized clinical trials are lacking. Currently, NASH is the second leading etiology of liver disease among adults awaiting liver transplantation in the United States. The primary and secondary prevention of NAFLD may require aggressive strategies for managing obesity, diabetes, and metabolic syndrome.

Prevalence of Nonalcoholic Fatty Liver Disease and Economy

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a growing health issue around the world.

AIM

This study is to investigate whether adult prevalence of NAFLD correlates with national economic status.

METHODS

Literature search on PubMed database was conducted to identify eligible records fully published before September 2014. Gross national income (GNI) per capita was chosen to evaluate national economic status. Pearson coefficient, linear regression, and unpaired t test were performed in the statistical analyses.

RESULTS

Twenty-one population-based surveys (seven in East Asia, five in South Asia, three in Middle East, and six in Europe) were included. The pooled prevalence of NAFLD was 24.24%, and the global prevalence was positively correlated with GNI per capita (r = 0.4782, P = 0.0283). Europe witnessed a higher prevalence (28.04%) than Middle East (12.95%, P = 0.0092) and East Asia (19.24%, P = 0.0083). Male presented a higher prevalence than female (P = 0.019), especially in Europe (P = 0.0132) and in Caucasians (P = 0.0383). Furthermore, male prevalence and rural prevalence individually were correlated with economic status (r = 0.5725, P = 0.0257 and r = 0.7389, P = 0.0060). Lastly, the urban (23.93%) witnessed a higher prevalence than the rural or the urban + rural (12.65%, P = 0.0141) in the countries of GNI per capita <$10,000.

CONCLUSIONS

This study suggested that countries with higher economic status tend to present a higher prevalence of NAFLD. It is believed to provide a distinctive epidemiologic perspective to global situation of NAFLD.

Phosphorylation of the nuclear receptor corepressor 1 by protein kinase B switches its corepressor targets in the liver in mice

Nuclear receptor corepressor 1 (NCoR1) is a transcriptional coregulator that has wide-ranging effects on gene expression patterns. In the liver, NCoR1 represses lipid synthesis in the fasting state, whereas it inhibits activation of peroxisome proliferator-activated receptor alpha (PPARα) upon feeding, thereby blunting ketogenesis. Here, we show that insulin by activation of protein kinase B induces phosphorylation of NCoR1 on serine 1460, which selectively favors its interaction with PPARα and estrogen-related receptor alpha (ERRα) over liver X receptor alpha (LXRα). Phosphorylation of NCoR1 on S1460 selectively derepresses LXRα target genes, resulting in increased lipogenesis, whereas, at the same time, it inhibits PPARα and ERRα targets, thereby attenuating oxidative metabolism in the liver. Phosphorylation-gated differential recruitment of NCoR1 to different nuclear receptors explains the apparent paradox that liver-specific deletion of NCoR1 concurrently induces both lipogenesis and oxidative metabolism owing to a global derepression of LXRα, PPARα, and ERRα activity.

CONCLUSION

Phosphorylation-mediated recruitment switch of NCoR1 between nuclear receptor subsets provides a mechanism by which corepressors can selectively modulate liver energy metabolism during the fasting-feeding transition.

Tyrosol Attenuates High Fat Diet-Induced Hepatic Oxidative Stress: Potential Involvement of Cystathionine β-Synthase and Cystathionine γ-Lyase

The Mediterranean diet is known for its cardioprotective effects. Recently, its protective qualities have also been reported in patients with non-alcoholic fatty liver disease (NAFLD). Oxidative stress is one of the important factors responsible for the development and progression of NAFLD. Hydrogen sulfide (H2S), a multifaceted gasotransmitter, has emerged as a potential therapeutic target in NAFLD. Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are major enzymes responsible for endogenous H2S synthesis. Since oxidative stress contributes to NAFLD pathogenesis, the objective of this study was to investigate the effect of tyrosol, a major compound in olive oil and white wine, on high fat diet-induced hepatic oxidative stress and the mechanisms involved. Mice (C57BL/6) were fed for 5 weeks with a control diet (10 % kcal fat), a high fat diet (60 % kcal fat, HFD) or a HFD supplemented with tyrosol. High fat diet feeding induced hepatic oxidative stress, as indicated by the significant increase in lipid peroxidation and NADPH oxidase activity. Tyrosol supplementation significantly increased hepatic CBS and CSE expression and H2S synthesis in high fat diet-fed mice. Such effects were associated with the attenuation of high fat diet-induced hepatic lipid peroxidation and the restoration of the redox equilibrium of the antioxidant glutathione. Tyrosol also inhibited palmitic acid-induced oxidative stress in hepatocytes (HepG2 cells). These results suggest that the antioxidant properties of tyrosol may be mediated through functional changes in CBS and CSE activity, which might contribute to the hepatoprotective effect of the Mediterranean diet.

Surgical removal of inflamed epididymal white adipose tissue attenuates the development of non-alcoholic steatohepatitis in obesity

Background:

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with abdominal obesity. Growing evidence suggests that inflammation in specific depots of white adipose tissue (WAT) has a key role in NAFLD progression, but experimental evidence for a causal role of WAT is lacking.

Methods:

A time-course study in C57BL/6J mice was performed to establish which WAT depot is most susceptible to develop inflammation during high-fat diet (HFD)-induced obesity. Crown-like structures (CLS) were quantified in epididymal (eWAT), mesenteric (mWAT) and inguinal/subcutaneous (iWAT) WAT. The contribution of inflamed WAT to NAFLD progression was investigated by surgical removal of a selected WAT depot and compared with sham surgery. Plasma markers were analyzed by enzyme-linked immunosorbent assay (cytokines/adipokines) and lipidomics (lipids).

Results:

In eWAT, CLS were formed already after 12 weeks of HFD, which coincided with maximal adipocyte size and fat depot mass, and preceded establishment of non-alcoholic steatohepatitis (NASH). By contrast, the number of CLS were low in mWAT and iWAT. Removal of inflamed eWAT after 12 weeks (eWATx group), followed by another 12 weeks of HFD feeding, resulted in significantly reduced NASH in eWATx. Inflammatory cell aggregates (−40% P<0.05) and inflammatory genes (e.g., TNFα, −37% P<0.05) were attenuated in livers of eWATx mice, whereas steatosis was not affected. Concomitantly, plasma concentrations of circulating proinflammatory mediators, viz. leptin and specific saturated and monounsaturated fatty acids, were also reduced in the eWATx group.

Conclusions:

Intervention in NAFLD progression by removal of inflamed eWAT attenuates the development of NASH and reduces plasma levels of specific inflammatory mediators (cytokines and lipids). These data support the hypothesis that eWAT is causally involved in the pathogenesis of NASH.

Genetic background in nonalcoholic fatty liver disease: A comprehensive review

In the Western world, nonalcoholic fatty liver disease (NAFLD) is considered as one of the most significant liver diseases of the twenty-first century. Its development is certainly driven by environmental factors, but it is also regulated by genetic background. The role of heritability has been widely demonstrated by several epidemiological, familial, and twin studies and case series, and likely reflects the wide inter-individual and inter-ethnic genetic variability in systemic metabolism and wound healing response processes. Consistent with this idea, genome-wide association studies have clearly identified Patatin-like phosholipase domain-containing 3 gene variant I148M as a major player in the development and progression of NAFLD. More recently, the transmembrane 6 superfamily member 2 E167K variant emerged as a relevant contributor in both NAFLD pathogenesis and cardiovascular outcomes. Furthermore, numerous case-control studies have been performed to elucidate the potential role of candidate genes in the pathogenesis and progression of fatty liver, although findings are sometimes contradictory. Accordingly, we performed a comprehensive literature search and review on the role of genetics in NAFLD. We emphasize the strengths and weaknesses of the available literature and outline the putative role of each genetic variant in influencing susceptibility and/or progression of the disease.

Perceptions of non-alcoholic fatty liver disease - an Asian community-based study

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is closely related to metabolic syndrome and its risk factors. Worldwide, epidemiological studies have reported NAFLD prevalence rates of 5% to 30% depending on geographical variations. While epidemiological data suggest a progressively increasing prevalence of metabolic risk factors in Singapore, there are limited data about NAFLD per se in the community. We aim to explore the prevalence and perceptions of NAFLD in Singapore.

METHODS

Attendees at a gastroenterology public forum were enrolled in a cross-sectional observational study evaluating demographic, anthropometric and clinical information. The diagnosis of NAFLD was based on sonographic criteria. Metabolic syndrome was defined according to International Diabetes Federation guidelines. Perceptions of NAFLD were explored using a self-administered survey questionnaire.

RESULTS

A total of 227 subjects were recruited, with NAFLD being diagnosed in 40% of the cohort. Relative to those without NAFLD, subjects with NAFLD had higher male preponderance, older age, higher body mass index, waist circumference and more metabolic syndrome (all P < 0.05). Although 71.2% subjects had heard about NAFLD before, only 25.4% of them felt that they were at risk of NAFLD. Comparable responses were observed in subjects with no metabolic risk factors relative to subjects with one or more metabolic risk factors (P > 0.05). Of note, 75.6% of subjects with one or more metabolic risk factors did not think that they were at risk of NAFLD.

CONCLUSION

Our study suggests a significant local prevalence of NAFLD in the community including non-obese individuals. Considering the tendency to underestimate risk of NAFLD, enhanced public education about NAFLD is warranted to improve understanding.

Ultrashort-TE stimulated echo acquisition mode (STEAM) improves the quantification of lipids and fatty acid chain unsaturation in the human liver at 7 T

Ultrahigh-field, whole-body MR systems increase the signal-to-noise ratio (SNR) and improve the spectral resolution. Sequences with a short TE allow fast signal acquisition with low signal loss as a result of spin-spin relaxation. This is of particular importance in the liver for the precise quantification of the hepatocellular content of lipids (HCL). In this study, we introduce a spoiler Gradient-switching Ultrashort STimulated Echo AcqUisition (GUSTEAU) sequence, which is a modified version of a stimulated echo acquisition mode (STEAM) sequence, with a minimum TE of 6 ms. With the high spectral resolution at 7 T, the efficient elimination of water sidebands and the post-processing suppression of the water signal, we estimated the composition of fatty acids (FAs) via the detection of the olefinic lipid resonance and calculated the unsaturation index (UI) of hepatic FAs. The performance of the GUSTEAU sequence for the assessment of UI was validated against oil samples and provided excellent results in agreement with the data reported in the literature. When measuring HCL with GUSTEAU in 10 healthy volunteers, there was a high correlation between the results obtained at 7 and 3 T (R(2) = 0.961). The test-retest measurements yielded low coefficients of variation for HCL (4 ± 3%) and UI (11 ± 8%) when measured with the GUSTEAU sequence at 7 T. A negative correlation was found between UI and HCL (n = 10; p < 0.033). The ultrashort TE MRS sequence (GUSTEAU; TE = 6 ms) provided high repeatability for the assessment of HCL. The improved spectral resolution at 7 T with the elimination of water sidebands and the offline water subtraction also enabled an assessment of the unsaturation of FAs. This all highlights the potential use of this MRS acquisition scheme for studies of hepatic lipid composition in vivo.

Genetic Variants in the SAMM50 Gene Create Susceptibility to Nonalcoholic Fatty Liver Disease in a Chinese Han Population

BACKGROUND

Genome-wide association studies have shown that rs738491, rs2143571, and rs3761472 in the sorting and assembly machinery component 50 homolog (SAMM50) gene are significantly associated with susceptibility to nonalcoholic fatty liver disease (NAFLD).

OBJECTIVES

The present study evaluated the association between the three genetic variants in the SAMM50 gene and susceptibility to NAFLD in a Chinese Han population.

PATIENTS AND METHODS

Genotypes for 3 single nucleotide polymorphisms (SNPs), viz rs738491, rs2143571, and rs3761472, in the SAMM50 gene were determined using an improved multiplex ligation detection reaction technique in 340 B-type ultrasonography-diagnosed NAFLD patients and 452 healthy controls. Meanwhile, serum lipid profiles and liver enzymes were estimated using standard clinical laboratory methods. The SNP-SNP interactions were analyzed by performing multifactor dimensionality reduction (MDR) and generalized multifactor dimensionality reduction (GMDR).

RESULTS

The genotype and allele frequencies of the SAMM50 polymorphisms between the NAFLD group and the control group were significantly different (all Ps < 0.05). In the multivariate analysis adjusted for gender, age, and body mass index, the carriers of the rs738491 T allele, rs2143571 A allele, and rs3761472 G allele had significantly increased susceptibility to NAFLD (OR, 1.507; 95% CI, 1.035 to 2.195; P = 0.032; OR, 1.761; 95% CI, 1.232 to 2.517; P = 0.002; OR, 1.483; 95% CI, 1.039 to 2.115; P = 0.030, respectively). Moreover, the rs738491 T allele carriers had significantly higher levels of alanine aminotransferase (ALT) (P = 0.017) than did the noncarriers. However, differences in the levels of serum triglyceride (TG) and aspartate aminotransferase (AST) were not statistically significant (P = 0.123; P = 0.107). The Rs2143571 A allele and the rs3761472 G allele were both deeply associated with increased levels of serum TG, ALT, and AST (all Ps < 0.05). Furthermore, the MDR and GMDR showed that a synergistic relationship might exist between rs738491, rs2143571, and rs3761472 in the SAMM50 gene and the pathophysiology and genetics of NAFLD.

CONCLUSIONS

We first demonstrated that the rs738491 T allele, rs2143571 A allele, and rs3761472 G allele in the SAMM50 gene created susceptibility to NAFLD in a Chinese Han population. The combination of the three SNPs in the SAMM50 gene may have synergism to predict the predisposition to NAFLD.

The Crosstalk between Hypoxia and Innate Immunity in the Development of Obesity-Related Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) has become a major health issue in western countries in parallel with the dramatic increase in the prevalence of obesity and all obesity related conditions, including respiratory diseases as obstructive sleep apnea-hypopnea syndrome (OSAHS). Interestingly, the severity of the liver damage in obesity-related NAFLD has been associated with the concomitant presence of OSAHS. In the presence of obesity, the proinflammatory state in these patients together with intermittent episodes of hypoxia, characteristic of OSAHS pathogenesis, may lead to an enhanced inflammatory response mediated by a positive feedback loop mechanism that implicates HIF-1 and NFκB. Thus, the severity of liver involvement in obese NAFLD patients with a concomitant diagnosis of OSAHS could be explained. In this review, we focus on the molecular mechanisms underlying the hepatic response to chronic intermittent hypoxia and its interaction with innate immunity in obesity-related NAFLD.

Bioenergetic cues shift FXR splicing towards FXRα2 to modulate hepatic lipolysis and fatty acid metabolism

Objective

Farnesoid X receptor (FXR) plays a prominent role in hepatic lipid metabolism. The FXR gene encodes four proteins with structural differences suggestive of discrete biological functions about which little is known.

Methods

We expressed each FXR variant in primary hepatocytes and evaluated global gene expression, lipid profile, and metabolic fluxes. Gene delivery of FXR variants to Fxr^−/− mouse liver was performed to evaluate their role in vivo. The effects of fasting and physical exercise on hepatic Fxr splicing were determined.

Results

We show that FXR splice isoforms regulate largely different gene sets and have specific effects on hepatic metabolism. FXRα2 (but not α1) activates a broad transcriptional program in hepatocytes conducive to lipolysis, fatty acid oxidation, and ketogenesis. Consequently, FXRα2 decreases cellular lipid accumulation and improves cellular insulin signaling to AKT. FXRα2 expression in Fxr^−/− mouse liver activates a similar gene program and robustly decreases hepatic triglyceride levels. On the other hand, FXRα1 reduces hepatic triglyceride content to a lesser extent and does so through regulation of lipogenic gene expression. Bioenergetic cues, such as fasting and exercise, dynamically regulate Fxr splicing in mouse liver to increase Fxrα2 expression.

Conclusions

Our results show that the main FXR variants in human liver (α1 and α2) reduce hepatic lipid accumulation through distinct mechanisms and to different degrees. Taking this novel mechanism into account could greatly improve the pharmacological targeting and therapeutic efficacy of FXR agonists.

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FXR variants regulate discrete gene programs with distinct biological outcomes.

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FXRα2 (but not α1) enhances fatty acid handling and insulin responsiveness.

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FXRα1 and α2 reduce liver lipid content through different mechanisms.

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Fasting and physical exercise dynamically regulate Fxr splicing in liver.

Effect of Creosote Bush-Derived NDGA on Expression of Genes Involved in Lipid Metabolism in Liver of High-Fructose Fed Rats: Relevance to NDGA Amelioration of Hypertriglyceridemia and Hepatic Steatosis

Nordihydroguaiaretic acid (NDGA), the main metabolite of Creosote bush, has been shown to have profound effects on the core components of the metabolic syndrome (MetS), lowering blood glucose, free fatty acids (FFA) and triglyceride (TG) levels in several models of dyslipidemia, as well as improving body weight (obesity), insulin resistance, diabetes and hypertension, and ameliorating hepatic steatosis. In the present study, a high-fructose diet (HFrD) fed rat model of hypertriglyceridemia was employed to further delineate the underlying mechanism by which NDGA exerts its anti-hypertriglyceridemic action. In the HFrD treatment group, NDGA administration by oral gavage decreased plasma levels of TG, glucose, FFA, and insulin, increased hepatic mitochondrial fatty acid oxidation and attenuated hepatic TG accumulation. qRT-PCR measurements indicated that NDGA treatment increased the mRNA expression of key fatty acid transport (L-FABP, CD36), and fatty acid oxidation (ACOX1, CPT-2, and PPARα transcription factor) genes and decreased the gene expression of enzymes involved in lipogenesis (FASN, ACC1, SCD1, L-PK and ChREBP and SREBP-1c transcription factors). Western blot analysis indicated that NDGA administration upregulated hepatic insulin signaling (P-Akt), AMPK activity (P-AMPK), MLYCD, and PPARα protein levels, but decreased SCD1, ACC1 and ACC2 protein content and also inactivated ACC1 activity (increased P-ACC1). These findings suggest that NDGA ameliorates hypertriglyceridemia and hepatic steatosis primarily by interfering with lipogenesis and promoting increased channeling of fatty acids towards their oxidation.

Genetic control of obesity, glucose homeostasis, dyslipidemia and fatty liver in a mouse model of diet-induced metabolic syndrome

BACKGROUND/OBJECTIVES

Both genetic and dietary factors contribute to the metabolic syndrome (MetS) in humans and animal models. Characterizing their individual roles as well as relationships among these factors is critical for understanding MetS pathogenesis and developing effective therapies. By studying phenotypic responsiveness to high-risk versus control diet in two inbred mouse strains and their derivatives, we estimated the relative contributions of diet and genetic background to MetS, characterized strain-specific combinations of MetS conditions, and tested genetic and phenotypic complexity on a single substituted chromosome.

METHODS

Ten measures of metabolic health were assessed in susceptible C57BL/6 J and resistant A/J male mice fed either a control or a high-fat, high-sucrose (HFHS) diet, permitting estimates of the relative influences of strain, diet and strain-diet interactions for each trait. The same traits were measured in a panel of C57BL/6 J (B6)-Chr(A/J) chromosome substitution strains (CSSs) fed the HFHS diet, followed by characterization of interstrain relationships, covariation among metabolic traits and quantitative trait loci (QTLs) on Chromosome 10.

RESULTS

We identified significant genetic contributions to nine of ten metabolic traits and significant dietary influence on eight. Significant strain-diet interaction effects were detected for four traits. Although a range of HFHS-induced phenotypes were observed among the CSSs, significant associations were detected among all traits but one. Strains were grouped into three clusters based on overall phenotype and specific CSSs were identified with distinct and reproducible trait combinations. Finally, several Chr10 regions were shown to control the severity of MetS conditions.

CONCLUSIONS

Generally strong genetic and dietary effects validate these CSSs as a multifactorial model of MetS. Although traits tended to segregate together, considerable phenotypic heterogeneity suggests that underlying genetic factors influence their co-occurrence and severity. Identification of multiple QTLs within and among strains highlights both the complexity of genetically regulated, diet-induced MetS and the ability of CSSs to prioritize candidate loci for mechanistic studies.

Hyperinsulinemia shifted energy supply from glucose to ketone bodies in early nonalcoholic steatohepatitis from high-fat high-sucrose diet induced Bama minipigs

The minipig can serve as a good pharmacological model for human subjects. However, the long-term pathogenesis of high-calorie diet-induced metabolic syndromes, including NASH, has not been well described in minipigs. We examined the development of metabolic syndromes in Bama minipigs that were fed a high-fat, high-sucrose diet (HFHSD) for 23 months, by using histology and serum biochemistry and by profiling the gene expression patterns in the livers of HFHSD pigs compared to controls. The pathology findings revealed microvesicular steatosis, iron overload, arachidonic acid synthesis, lipid peroxidation, reduced antioxidant capacity, increased cellular damage, and inflammation in the liver. RNA-seq analysis revealed that 164 genes were differentially expressed between the livers of the HFHSD and control groups. The pathogenesis of early-stage NASH was characterized by hyperinsulinemia and by de novo synthesis of fatty acids and nascent triglycerides, which were deposited as lipid droplets in hepatocytes. Hyperinsulinemia shifted the energy supply from glucose to ketone bodies, and the high ketone body concentration induced the overexpression of cytochrome P450 2E1 (CYP2E1). The iron overload, CYP2E1 and alcohol dehydrogenase 4 overexpression promoted reactive oxygen species (ROS) production, which resulted in arachidonic and linoleic acid peroxidation and, in turn, led to malondialdehyde production and a cellular response to ROS-mediated DNA damage.

Clinical value of liver ultrasound for the diagnosis of nonalcoholic fatty liver disease in overweight and obese patients

BACKGROUND & AIMS

Liver ultrasound (US) is usually used in the clinical setting for the diagnosis and follow-up of patients with nonalcoholic fatty liver disease (NAFLD). However, no large study has carefully assessed its performance using a semiquantitative ultrasonographic scoring system in overweight/obese patients, in comparison to magnetic resonance spectroscopy ((1) H-MRS) and histology.

METHODS

We recruited 146 patients and performed: a liver US using a 5-parameter scoring system, a liver (1) H-MRS to quantify liver fat content, and a liver biopsy to assess histology. All measurements were repeated in a subgroup of patients (n = 62) after 18 months of follow-up.

RESULTS

The performance of liver US (parenchymal echo alone) was rather modest, and significantly worse than (1) H-MRS (AUROC: 0.82 [0.69-0.94] vs. 0.96 [0.90-1.00]; P = 0.04). However, the AUROC improved when different echographic parameters were taken into account (AUROC: 0.89 [0.83-0.96], P = 0.15 against (1) H-MRS). Optimum sensitivity for liver US was achieved at a liver fat content ≥12.5%, suggesting that below this threshold, liver US is less sensitive. Liver (1) H-MRS showed a high accuracy for the diagnosis of NAFLD, and correlated strongly with histological steatosis (r = 0.73, P < 0.0001). None of the imaging tests was adequate enough to predict changes over time in histology.

CONCLUSIONS

Despite its widespread use, liver US has several important limitations that healthcare providers should recognize, particularly because of its low sensitivity. Using a combination of echographic parameters, liver US showed a significant improvement in its diagnostic performance, but still was of limited value for monitoring treatment over time.

Fructose and liver function--is this behind nonalcoholic liver disease?

PURPOSE OF REVIEW

The purpose was to summarize recent advances in the understanding of nonalcoholic fatty liver disease (NAFLD) pathophysiology and the role of fructose in NAFLD.

RECENT FINDINGS

Epidemiological studies continue to point to a strong association between high fructose intake and NAFLD and its severity. New studies of NAFLD reveal the importance of upregulated de novo lipogenesis as a key feature in its pathophysiology along with increased visceral adiposity and alteration of gut microbiome. Studies of fructose in NAFLD show how this nutrient may uniquely exacerbate the phenotype of NAFLD. The timing of exposure to fructose may be important with early (in utero) exposure being particularly harmful.

SUMMARY

Fructose is a potentially modifiable environmental exposure that appears to exacerbate NAFLD through multiple mechanisms. Although larger, longer clinical studies are still needed, it appears that limitation of fructose sources in the diet is beneficial in NAFLD.

Epigenetic Modifications in the Biology of Nonalcoholic Fatty Liver Disease: The Role of DNA Hydroxymethylation and TET Proteins

The 5-Hydroxymethylcytosine (5-hmC) is an epigenetic modification whose role in the pathogenesis of metabolic-related complex diseases remains unexplored; 5-hmC appears to be prevalent in the mitochondrial genome. The Ten-Eleven-Translocation (TET) family of proteins is responsible for catalyzing the conversion of 5-methylcytosine to 5-hmC. We hypothesized that epigenetic editing by 5-hmC might be a novel mechanism through which nonalcoholic fatty liver disease (NAFLD)-associated molecular traits could be explained.Hence, we performed an observational study to explore global levels of 5-hmC in fresh liver samples of patients with NAFLD and controls (n = 90) using an enzyme-linked-immunosorbent serologic assay and immunohistochemistry. We also screened for genetic variation in TET 1-3 loci by next generation sequencing to explore its contribution to the disease biology. The study was conducted in 2 stages (discovery and replication) and included 476 participants.We observed that the amount of 5-hmC in the liver of both NAFLD patients and controls was relatively low (up to 0.1%); a significant association was found with liver mitochondrial DNA copy number (R = 0.50, P = 0.000382) and PPARGC1A-mRNA levels (R = -0.57, P = 0.04).We did not observe any significant difference in the 5-hmC nuclear immunostaining score between NAFLD patients and controls; nevertheless, we found that patients with NAFLD (0.4 ± 0.5) had significantly lower nonnuclear-5-hmC staining compared with controls (1.8 ± 0.8), means ± standard deviation, P = 0.028. The missense p.Ile1123Met variant (TET1-rs3998860) was significantly associated with serum levels of caspase-generated CK-18 fragment-cell death biomarker in the discovery and replication stage, and the disease severity (odds ratio: 1.47, 95% confidence interval: 1.10-1.97; P = 0.005). The p.Ile1762Val substitution (TET2-rs2454206) was associated with liver PPARGC1A-methylation and transcriptional levels, and Type 2 diabetes.Our results suggest that 5-hmC might be involved in the pathogenesis of NAFLD by regulating liver mitochondrial biogenesis and PPARGC1A expression. Genetic diversity at TET loci suggests an "epigenetic" regulation of programmed liver-cell death and a TET-mediated fine-tuning of the liver PPARGC1A-transcriptional program.

Recommendations for Diagnosis, Referral for Liver Biopsy, and Treatment of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the primary cause of chronic liver disease in the United States, afflicting an estimated 80 to 100 million Americans. Nonalcoholic fatty liver disease is a spectrum of liver diseases composed of nonalcoholic fatty liver and nonalcoholic steatohepatitis (NASH). Although nonalcoholic fatty liver has a negligible risk of progression, patients with NASH often develop cirrhosis or hepatocellular carcinoma. Although liver biopsy is required to diagnose NASH, only patients with a high risk of NASH or advanced fibrosis require this evaluation. Despite the high prevalence of NAFLD, well-defined screening recommendations are currently lacking. In this review, suggestions for screening, diagnosis, and initial work-up of NAFLD are given on the basis of established guidelines and recent publications. Proposed drug treatments of NASH are also discussed, highlighting the study outcomes, as well as proposed uses and limitations of these drugs. The literature was searched in PubMed using search terms nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, with filters of "English language." A date range of January 1, 2000, to May 1, 2015, was used for the search. The bibliographies of key references were also searched manually, and seminal publications before the year 2000 were included.

Liver Perilipin 5 Expression Worsens Hepatosteatosis But Not Insulin Resistance in High Fat-Fed Mice

Perilipin 5 (PLIN5) is a lipid droplet (LD) protein highly expressed in oxidative tissues, including the fasted liver. However, its expression also increases in nonalcoholic fatty liver. To determine whether PLIN5 regulates metabolic phenotypes of hepatosteatosis under nutritional excess, liver targeted overexpression of PLIN5 was achieved using adenoviral vector (Ad-PLIN5) in male C57BL/6J mice fed high-fat diet. Mice treated with adenovirus expressing green fluorescent protein (GFP) (Ad-GFP) served as control. Ad-PLIN5 livers increased LD in the liver section, and liquid chromatography with tandem mass spectrometry revealed increases in lipid classes associated with LD, including triacylglycerol, cholesterol ester, and phospholipid classes, compared with Ad-GFP liver. Lipids commonly associated with hepatic lipotoxicity, diacylglycerol, and ceramides, were also increased in Ad-PLIN5 liver. The expression of genes in lipid metabolism regulated by peroxisome proliferator-activated receptor-α was reduced suggestive of slower mobilization of stored lipids in Ad-PLIN5 mice. However, the increase of hepatosteatosis by PLIN5 overexpression did not worsen glucose homeostasis. Rather, serum insulin levels were decreased, indicating better insulin sensitivity in Ad-PLIN5 mice. Moreover, genes associated with liver injury were unaltered in Ad-PLIN5 steatotic liver compared with Ad-GFP control. Phosphorylation of protein kinase B was increased in Ad-PLIN5-transduced AML12 hepatocyte despite of the promotion of fatty acid incorporation to triacylglycerol as well. Collectively, our data indicates that the increase in liver PLIN5 during hepatosteatosis drives further lipid accumulation but does not adversely affect hepatic health or insulin sensitivity.

Mechanistic link between nonalcoholic fatty liver disease and cardiometabolic disorders

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition characterized by fat accumulation combined with low-grade inflammation in the liver. A large body of clinical and experimental data shows that increased flux of free fatty acids from increased visceral adipose tissue can lead to NAFLD related with insulin resistance. Thus, individuals with obesity, insulin resistance, and dyslipidemia are at the greatest risk of developing NAFLD. Conversely, NAFLD is one of the phenotypes of insulin resistance or metabolic syndrome. Many researchers have discovered a close association between NAFLD and insulin resistance, and focused on the role of NAFLD in the development of type 2 diabetes. Further, substantial evidence has suggested the association between NAFLD and cardiovascular disease (CVD). In the current review, we provide a plausible mechanistic link between NAFLD and CVD and the potential of the former as a therapeutic target based on pathophysiology. We also discuss in detail about the role of insulin resistance, oxidative stress, low-grade inflammation, abnormal lipid metabolism, gut microbiota, changes of biomarkers, and genetic predisposition in the pathological linking between NAFLD and cardiometabolic disorders.

Clinical Model for NASH and Advanced Fibrosis in Adult Patients With Diabetes and NAFLD: Guidelines for Referral in NAFLD

OBJECTIVE

Approximately 18 million people in the U.S. have coexisting type 2 diabetes and nonalcoholic fatty liver disease (NAFLD). It is not known who among these patients has nonalcoholic steatohepatitis (NASH) with advanced fibrosis. Therefore, we aimed to determine factors that are associated with both NASH and advanced fibrosis in patients with diabetes and NAFLD in order to identify who should be prioritized for referral to a hepatologist for further diagnostic evaluation and treatment.

RESEARCH DESIGN AND METHODS

This study was derived from the NASH Clinical Research Network studies and included 1,249 patients with biopsy-proven NAFLD (including a model development cohort of 346 patients and an independent validation cohort of 100 patients with type 2 diabetes as defined by the American Diabetes Association criteria). Outcome measures were presence of NASH or advanced fibrosis (stage 3 or 4) using cross-validated, by jackknife method, multivariable-adjusted area under the receiver operating characteristic curve (AUROC) and 95% CI.

RESULTS

The mean ± SD age and BMI of patients with diabetes and NAFLD was 52.5 ± 10.3 years and 35.8 ± 6.8 kg/m(2), respectively. The prevalence of NASH and advanced fibrosis was 69.2% and 41.0%, respectively. The model for NASH included white race, BMI, waist, alanine aminotransferase (ALT), Aspartate aminotransferase (AST), albumin, HbA1c, HOMA of insulin resistance, and ferritin with an AUROC of 0.80 (95% CI 0.75-0.84, P = 0.007). The specificity, sensitivity, negative predictive values (NPVs), and positive predictive values (PPVs) were 90.0%, 56.8%, 47.7%, and 93.2%, respectively, and the model correctly classified 67% of patients as having NASH. The model for predicting advanced fibrosis included age, Hispanic ethnicity, BMI, waist-to-hip ratio, hypertension, ALT-to-AST ratio, alkaline phosphatase, isolated abnormal alkaline phosphatase, bilirubin (total and direct), globulin, albumin, serum insulin, hematocrit, international normalized ratio, and platelet count with an AUROC of 0.80 (95% CI 0.76-0.85, P < 0.001). The specificity, sensitivity, NPV, and PPV were 90.0%, 57%, 75.1%, and 80.2%, respectively, and the model correctly classified 76.6% of patients as having advanced fibrosis. Results remained consistent for both models in the validation cohort. The proposed model performed better than the NAFLD fibrosis score in detecting advanced fibrosis.

CONCLUSIONS

Routinely available clinical variables can be used to quantify the likelihood of NASH or advanced fibrosis in adult diabetic patients with NAFLD. The clinical models presented can be used to guide clinical decision making about referrals of patients with diabetes and NAFLD to hepatologists.

Osteopontin neutralisation abrogates the liver progenitor cell response and fibrogenesis in mice

BACKGROUND

Chronic liver injury triggers a progenitor cell repair response, and liver fibrosis occurs when repair becomes deregulated. Previously, we reported that reactivation of the hedgehog pathway promotes fibrogenic liver repair. Osteopontin (OPN) is a hedgehog-target, and a cytokine that is highly upregulated in fibrotic tissues, and regulates stem-cell fate. Thus, we hypothesised that OPN may modulate liver progenitor cell response, and thereby, modulate fibrotic outcomes. We further evaluated the impact of OPN-neutralisation on murine liver fibrosis.

METHODS

Liver progenitors (603B and bipotential mouse oval liver) were treated with OPN-neutralising aptamers in the presence or absence of transforming growth factor (TGF)-β, to determine if (and how) OPN modulates liver progenitor function. Effects of OPN-neutralisation (using OPN-aptamers or OPN-neutralising antibodies) on liver progenitor cell response and fibrogenesis were assessed in three models of liver fibrosis (carbon tetrachloride, methionine-choline deficient diet, 3,5,-diethoxycarbonyl-1,4-dihydrocollidine diet) by quantitative real time (qRT) PCR, Sirius-Red staining, hydroxyproline assay, and semiquantitative double-immunohistochemistry. Finally, OPN expression and liver progenitor response were corroborated in liver tissues obtained from patients with chronic liver disease.

RESULTS

OPN is overexpressed by liver progenitors in humans and mice. In cultured progenitors, OPN enhances viability and wound healing by modulating TGF-β signalling. In vivo, OPN-neutralisation attenuates the liver progenitor cell response, reverses epithelial-mesenchymal-transition in Sox9+ cells, and abrogates liver fibrogenesis.

CONCLUSIONS

OPN upregulation during liver injury is a conserved repair response, and influences liver progenitor cell function. OPN-neutralisation abrogates the liver progenitor cell response and fibrogenesis in mouse models of liver fibrosis.

Application of hepatocellular carcinoma surveillance in a European setting. What can we learn from clinical practice?

BACKGROUND & AIMS

Surveillance for hepatocellular carcinoma (HCC) in patients with cirrhosis is recommended in clinical guidelines. In real-life management, surveillance rates below 20% have been reported from the United States. We aimed to determine the use of HCC-surveillance in patients diagnosed with HCC in a European setting, and to identify the reasons for surveillance failures.

METHODS

Age, gender, tumour characteristics, BCLC classification, Child-Pugh stage, pre-existing liver disease, treatment, survival, frequency of HCC surveillance and reasons for surveillance failures were retrospectively determined in 616 patients diagnosed with HCC at Karolinska University Hospital 2005-2012.

RESULTS

Hepatitis C, alcoholic liver disease and non-alcoholic fatty liver disease (NAFLD) were the most common diagnoses. The proportion of HCC patients diagnosed through surveillance was 22%. In 35% of cases, surveillance was missed due to doctor's failure to order surveillance or to diagnose the underlying liver disease. Diagnosis of NAFLD or alcoholic liver disease increased the risk of not receiving surveillance more than two-fold. Undiagnosed liver disease was most common in NAFLD patients. Patients who underwent surveillance had smaller tumours, more frequently received curative treatment, and had better survival compared to those in whom surveillance was indicated but missed.

CONCLUSION

In a European setting, only 22% of HCCs were diagnosed by surveillance, and in more than one-third of cases, surveillance was indicated but missed. NAFLD and alcoholic liver disease were associated with deficient surveillance. Survival was significantly better in patients who underwent surveillance compared with those in whom surveillance was missed although indicated.

Strategies, models and biomarkers in experimental non-alcoholic fatty liver disease research

Non-alcoholic fatty liver disease encompasses a spectrum of liver diseases, including simple steatosis, steatohepatitis, liver fibrosis and cirrhosis and hepatocellular carcinoma. Non-alcoholic fatty liver disease is currently the most dominant chronic liver disease in Western countries due to the fact that hepatic steatosis is associated with insulin resistance, type 2 diabetes mellitus, obesity, metabolic syndrome and drug-induced injury. A variety of chemicals, mainly drugs, and diets is known to cause hepatic steatosis in humans and rodents. Experimental non-alcoholic fatty liver disease models rely on the application of a diet or the administration of drugs to laboratory animals or the exposure of hepatic cell lines to these drugs. More recently, genetically modified rodents or zebrafish have been introduced as non-alcoholic fatty liver disease models. Considerable interest now lies in the discovery and development of novel non-invasive biomarkers of non-alcoholic fatty liver disease, with specific focus on hepatic steatosis. Experimental diagnostic biomarkers of non-alcoholic fatty liver disease, such as (epi)genetic parameters and '-omics'-based read-outs are still in their infancy, but show great promise. In this paper, the array of tools and models for the study of liver steatosis is discussed. Furthermore, the current state-of-art regarding experimental biomarkers such as epigenetic, genetic, transcriptomic, proteomic and metabonomic biomarkers will be reviewed.

High Prevalence of Nonalcoholic Fatty Liver Disease in Patients With Type 2 Diabetes Mellitus and Normal Plasma Aminotransferase Levels

CONTEXT AND OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) and its more severe form with steatohepatitis (NASH) are common in patients with type 2 diabetes mellitus (T2DM). However, they are usually believed to largely affect those with elevated aminotransferases. The aim of this study was to determine the prevalence of NAFLD by the gold standard, liver magnetic resonance spectroscopy ((1)H-MRS) in patients with T2DM and normal aminotransferases, and to characterize their metabolic profile.

PARTICIPANTS AND METHODS

We recruited 103 patients with T2DM and normal plasma aminotransferases (age, 60 ± 8 y; body mass index [BMI], 33 ± 5 kg/m(2); glycated hemoglobin [A1c], 7.6 ± 1.3%). We measured the following: 1) liver triglyceride content by (1)H-MRS; 2) systemic insulin sensitivity (homeostasis model assessment-insulin resistance); and 3) adipose tissue insulin resistance, both fasting (as the adipose tissue insulin resistance index: fasting plasma free fatty acids [FFA] × insulin) and during an oral glucose tolerance test (as the suppression of FFA).

RESULTS

The prevalence of NAFLD and NASH were much higher than expected (50% and 56% of NAFLD patients, respectively). The prevalence of NAFLD was higher in obese compared with nonobese patients as well as with increasing BMI (P = .001 for trend). Higher plasma A1c was associated with a greater prevalence of NAFLD and worse liver triglyceride accumulation (P = .01). Compared with nonobese patients without NAFLD, patients with NAFLD had severe systemic (liver/muscle) and, particularly, adipose tissue (fasting/postprandial) insulin resistance (all P < .01).

CONCLUSIONS

The prevalence of NAFLD is much higher than previously believed in overweight/obese patients with T2DM and normal aminotransferases. Moreover, many are at increased risk of NASH. Physicians should have a lower threshold for screening patients with T2DM for NAFLD/NASH.

Comparative diagnostic accuracy of magnetic resonance elastography vs. eight clinical prediction rules for non-invasive diagnosis of advanced fibrosis in biopsy-proven non-alcoholic fatty liver disease: a prospective study

BACKGROUND

Two-dimensional magnetic resonance elastography (2D-MRE) is an advanced magnetic resonance method with high diagnostic accuracy for predicting advanced fibrosis in non-alcoholic fatty liver disease (NAFLD) patients. However, no prospective, head-to-head comparisons between 2D-MRE and clinical prediction rules (CPRs) have been performed in patients with biopsy-proven NAFLD.

AIM

To compare the diagnostic utility of 2D-MRE against that of eight CPRs (AST:ALT ratio, APRI, BARD, FIB-4, NAFLD Fibrosis Score, Bonacini cirrhosis discriminant score, Lok Index and NASH CRN model) for predicting advanced fibrosis in a prospective cohort with paired liver biopsy as the gold standard.

METHODS

This is a cross-sectional analysis of a prospective study of 102 patients (58.8% women) with biopsy-proven NAFLD, 2D-MRE and clinical research assessment within 90 days of biopsy. Receiver operating characteristic (ROC) analysis was performed to assess the performance of 2D-MRE and CPRs for predicting advanced fibrosis.

RESULTS

The mean (±s.d.) age and BMI were 51.3 (±14.0) years and 31.7 (±5.5) kg/m(2) respectively. 48, 26, 9, 13 and 6 patients had stage 0, 1, 2, 3 and 4 fibrosis respectively. The area under ROC curve (AUROC) was 0.957 for 2D-MRE and between 0.796 and 0.861 for the CPRs. FIB-4 was the best-performing CPR at predicting advanced fibrosis with AUROC of 0.861. In head-to-head comparisons using the DeLong test, 2D-MRE had significantly better AUROC (P < 0.05) than each CPR for predicting advanced fibrosis.

CONCLUSION

Compared to clinical prediction rules, 2D-MRE provides significantly higher accuracy for the diagnosis of advanced fibrosis in NAFLD patients.

Use of farnesoid X receptor agonists to treat nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is a common cause of liver related morbidity and mortality. It is closely linked to underlying insulin resistance. It has recently been shown that bile acids modulate insulin signaling and can improve insulin resistance in cell based and animal studies. These effects are mediated in part by activation of farnesoid x receptors by bile acids. In human studies, FXR agonists improve insulin resistance and have recently been shown to improve NAFLD. The basis for the use of FXR agonists for the treatment of NAFLD and early human experience with such agents is reviewed in this paper.

Mouse models of diet-induced nonalcoholic steatohepatitis reproduce the heterogeneity of the human disease

BACKGROUND AND AIMS

Non-alcoholic steatohepatitis (NASH), the potentially progressive form of nonalcoholic fatty liver disease (NAFLD), is the pandemic liver disease of our time. Although there are several animal models of NASH, consensus regarding the optimal model is lacking. We aimed to compare features of NASH in the two most widely-used mouse models: methionine-choline deficient (MCD) diet and Western diet.

METHODS

Mice were fed standard chow, MCD diet for 8 weeks, or Western diet (45% energy from fat, predominantly saturated fat, with 0.2% cholesterol, plus drinking water supplemented with fructose and glucose) for 16 weeks. Liver pathology and metabolic profile were compared.

RESULTS

The metabolic profile associated with human NASH was better mimicked by Western diet. Although hepatic steatosis (i.e., triglyceride accumulation) was also more severe, liver non-esterified fatty acid content was lower than in the MCD diet group. NASH was also less severe and less reproducible in the Western diet model, as evidenced by less liver cell death/apoptosis, inflammation, ductular reaction, and fibrosis. Various mechanisms implicated in human NASH pathogenesis/progression were also less robust in the Western diet model, including oxidative stress, ER stress, autophagy deregulation, and hedgehog pathway activation.

CONCLUSION

Feeding mice a Western diet models metabolic perturbations that are common in humans with mild NASH, whereas administration of a MCD diet better models the pathobiological mechanisms that cause human NAFLD to progress to advanced NASH.

Relevance of liver fat to the impact of dietary extrinsic sugars on lipid metabolism

In contrast to the decline in mortality from many non-infectious, chronic diseases in the UK, death from liver disease has increased exponentially in men and women over the past 40 years. This is primarily because of the over consumption of alcohol, but also the increased prevalence of obesity, which is linked to early pathology through the accumulation of liver fat. Supra-physiological intakes of fructose-containing sugar can produce acute, adverse effects on lipid metabolism, and deliver excess energy that increases bodyweight and the deposition of fat in sites other than adipose tissue, including the liver. This review addresses the variable metabolic origins of liver fat, and the key importance of postprandial lipid metabolism in this respect. The effects of supra-physiological intakes of sugar are also considered in context of the real world and established threshold for the adverse effects of sugar on cardio-metabolic risk factors. The review concludes that while the average intake of sugar in the UK falls well below this critical threshold, intakes in subgroups of adults, and especially adolescents, may be cause for concern. There is also evidence to suggest that raised liver fat, acquired, in part, through an impaired removal of postprandial lipaemia, can increase sensitivity to the adverse effects of sugar at all ages.

Low-normal thyroid function and the pathogenesis of common cardio-metabolic disorders

BACKGROUND

Subclinical hypothyroidism may adversely affect the development of cardiovascular disease (CVD). Less is known about the role of low-normal thyroid function, that is higher thyroid-stimulating hormone and/or lower free thyroxine levels within the euthyroid reference range, in the development of cardio-metabolic disorders. This review is focused on the relationship of low-normal thyroid function with CVD, plasma lipids and lipoprotein function, as well as with metabolic syndrome (MetS), chronic kidney disease (CKD) and nonalcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

This narrative review, which includes results from previously published systematic reviews and meta-analyses, is based on clinical and basic research papers, obtained via MEDLINE and PubMed up to November 2014.

RESULTS

Low-normal thyroid function could adversely affect the development of (subclinical) atherosclerotic manifestations. It is likely that low-normal thyroid function relates to modest increases in plasma total cholesterol, LDL cholesterol and triglycerides, and may convey pro-atherogenic changes in lipoprotein metabolism and in HDL function. Most available data support the concept that low-normal thyroid function is associated with MetS, insulin resistance and CKD, but not with high blood pressure. Inconsistent effects of low-normal thyroid function on NAFLD have been reported so far.

CONCLUSIONS

Observational studies suggest that low-normal thyroid function may be implicated in the pathogenesis of CVD. Low-normal thyroid function could also play a role in the development of MetS, insulin resistance and CKD, but the relationship with NAFLD is uncertain. The extent to which low-normal thyroid function prospectively predicts cardio-metabolic disorders has been insufficiently established so far.

The complex myeloid network of the liver with diverse functional capacity at steady state and in inflammation

In recent years, it has been an explosion of information regarding the role of various myeloid cells in liver pathology. Macrophages and dendritic cell (DC) play crucial roles in multiple chronic liver diseases such as fibrosis and non-alcoholic fatty liver disease (NAFLD). The complexity of myeloid cell populations and the missing exclusive marker combination make the interpretation of the data often extremely difficult. The current review aims to summarize the multiple roles of macrophages and DCs in chronic liver diseases, especially pointing out how these cells influence liver immune and parenchymal cells thereby altering liver function and pathology. Moreover, the review outlines the currently known marker combinations for the identification of these cell populations for the study of their role in liver immunology.

Fibrosis progression in nonalcoholic fatty liver vs nonalcoholic steatohepatitis: a systematic review and meta-analysis of paired-biopsy studies

BACKGROUND & AIMS

Little is known about differences in rates of fibrosis progression between patients with nonalcoholic fatty liver (NAFL) vs nonalcoholic steatohepatitis (NASH). We conducted a systematic review and meta-analysis of all studies that assessed paired liver biopsy specimens to estimate the rates of fibrosis progression in patients with nonalcoholic fatty liver disease (NAFLD) including NAFL and NASH.

METHODS

Through a systematic search of multiple databases and author contact, up to June 2013, we identified studies of adults with NAFLD that collected paired liver biopsy specimens at least 1 year apart. From these, we calculated a pooled-weighted annual fibrosis progression rate (number of stages changed between the 2 biopsy samples) with 95% confidence intervals (CIs), and identified clinical risk factors associated with progression.

RESULTS

We identified 11 cohort studies including 411 patients with biopsy-proven NAFLD (150 with NAFL and 261 with NASH). At baseline, the distribution of fibrosis for stages 0, 1, 2, 3, and 4 was 35.8%, 32.5%, 16.7%, 9.3%, and 5.7%, respectively. Over 2145.5 person-years of follow-up evaluation, 33.6% had fibrosis progression, 43.1% had stable fibrosis, and 22.3% had an improvement in fibrosis stage. The annual fibrosis progression rate in patients with NAFL who had stage 0 fibrosis at baseline was 0.07 stages (95% CI, 0.02-0.11 stages), compared with 0.14 stages in patients with NASH (95% CI, 0.07-0.21 stages). These findings correspond to 1 stage of progression over 14.3 years for patients with NAFL (95% CI, 9.1-50.0 y) and 7.1 years for patients with NASH (95% CI, 4.8-14.3 y).

CONCLUSIONS

Based on a meta-analysis of studies of paired liver biopsy studies, liver fibrosis progresses in patients with NAFL and NASH.