Steatosis and steatohepatitis: complex disorders. Int J Mol Sci. 2014;15:9924-9944. [PMID: 24897026 PMCID: PMC4100130 DOI: 10.3390/ijms15069924]

Emerging role of lipophagy in liver disorders

Lipophagy is a selective degradation of lipids by a lysosomal-mediated pathway, and dysregulation of lipophagy is linked with the pathological hallmark of many liver diseases. Downregulation of lipophagy in liver cells results in abnormal accumulation of LDs (Lipid droplets) in hepatocytes which is a characteristic feature of several liver pathologies such as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Contrarily, upregulation of lipophagy in activated hepatic stellate cells (HSCs) is associated with hepatic fibrosis and cirrhosis. Lipid metabolism reprogramming in violent cancer cells contributes to the progression of liver cancer. In this review, we have summarized the recent studies focusing on various components of the lipophagic machinery that can be modulated for their potential role as therapeutic agents against a wide range of liver diseases.

Effects of the Water Extract of Fermented Rice Bran on Liver Damage and Intestinal Injury in Aged Rats with High-Fat Diet Feeding

The purpose of this study was to investigate the protective effects of the water extract of fermented rice bran (FRB) on liver damage and intestinal injury in old rats fed a high-fat (HF) diet. Rice bran (RB) was fermented with Aspergillus kawachii, and FRB was produced based on a previous study. Male Sprague Dawley rats at 36 weeks of age were allowed free access to a standard rodent diet and water for 8 weeks of acclimation then randomly divided into four groups (six rats/group), including a normal control (NC) group (normal diet), HF group (HF diet; 60% of total calories from fat), HF + 1% FRB group (HF diet + 1% FRB w/w), and HF + 5% FRB group (HF diet + 5% FRB w/w). It was found that the antioxidant ability of FRB was significantly increased when compared to RB. After 8 weeks of feeding, the HF group exhibited liver damage including an increased non-alcoholic fatty liver disease score (hepatic steatosis and inflammation) and higher interleukin (IL)-1β levels, while these were attenuated in the FRB-treated groups. Elevated plasma leptin levels were also found in the HF group, but the level was down-regulated by FRB treatment. An altered gut microbiotic composition was observed in the HF group, while beneficial bacteria including of the Lactobacillaceae and Lachnospiraceae had increased after FRB supplementation. In conclusion, it was found that FRB had higher anti-oxidative ability and showed the potential for preventing liver damage induced by a HF diet, which might be achieved through regulating imbalanced adipokines and maintaining a healthier microbiotic composition.

Di(2-ethylhexyl)phthalate exposure exacerbates metabolic disorders in diet-induced obese mice

Both phthalate exposure and obesity are positively associated with metabolic disorders. The study aimed to investigate whether DEHP exposure caused metabolic disorders in an obesity-dependent manner. Both lean and diet-induced obese mice were subjected to environmentally relevant DEHP exposure. DEHP-treated obese mice exhibited higher glucose intolerance and insulin resistance than obese mice; the metabolic disorders were accompanied by increased blood levels of leptin, LDL cholesterol, and alanine transaminase. In obese mice, DEHP enhanced macrophage infiltration into epididymal white adipose tissue (eWAT) and hepatic tissue, and promoted hepatic steatosis/steatohepatitis. The DEHP effects were not observed in lean mice. Transcriptomic changes in eWAT and hepatic tissue were determined with microarray analysis. Results indicated that obesity and DEHP synergistically regulated carbohydrate uptake, lipolysis, and abnormality of adipose tissue, via the upstream regulators Pparg, Lipe, Cd44, and Irs1. Meanwhile, obesity and DEHP differentially modulated transcriptomic changes in hepatic tissue. Obesity was associated with lipid/cholesterol synthesis, lipid accumulation, and inflammation in hepatic tissue via the upstream regulators Zbtb20 and Nr1i2. In obese mice, DEHP exposure caused hepatic injury, cell migration, and changes in glycogen quantity mainly via Cd44. Microarray analysis suggested the potential mechanism underlying the early onset of metabolic disorders in DEHP-treated obese mice.

Effect of Betaine Supplementation on Liver Tissue and Ultrastructural Changes in Methionine-Choline-Deficient Diet-Induced NAFLD

Nonalcoholic fatty liver disease (NAFLD) represents a hepatic manifestation of metabolic syndrome. The aim of this study was to examine the effect of betaine on ultrastructural changes in the mouse liver with methionine- and choline-deficient (MCD) diet-induced NAFLD. Male C57BL/6 mice were divided into groups: Control-fed with standard chow, BET-standard chow supplemented with betaine (1.5% w/v drinking water), MCD-fed with MCD diet, and MCD + BET-MCD diet with betaine supplementation for 6 weeks. Liver samples were taken for pathohistology and transmission electron microscopy. The MCD diet-induced steatosis, inflammation, and balloon-altered hepatocytes were alleviated by betaine. MCD diet induced an increase in mitochondrial size versus the control group (p < 0.01), which was decreased in the betaine-treated group. In the MCD diet-fed group, the total mitochondrial count decreased versus the control group (p < 0.01), while it increased in the MCD + BET group versus MCD (p < 0.01). Electron microscopy showed an increase in the number of autophagosomes in the MCD and MCD + BET group versus control, and a significant difference in autophagosomes number was detected in the MCD + BET group by comparison with the MCD diet-treated group (p < 0.05). Betaine decreases the number of enlarged mitochondria, alleviates steatosis, and increases the number of autophagosomes in the liver of mice with NAFLD.

Identifying Shared Risk Genes between Nonalcoholic Fatty Liver Disease and Metabolic Traits by Cross-Trait Association Analysis

Nonalcoholic fatty liver disease (NAFLD) generally co-occurs with metabolic disorders, but it is unclear which genes have a pleiotripic effect on NAFLD and metabolic traits. We performed a large-scale cross-trait association analysis to identify the overlapping genes between NAFLD and nine metabolic traits. Among all the metabolic traits, we found that obesity and type II diabetes are associated with NAFLD. Then, a multitrait association analysis among NAFLD, obesity and type II diabetes was conducted to improve the overall statistical power. We identified 792 significant variants by a cross-trait meta-analysis involving 100 pleiotripic genes. Moreover, we detected another two common genes by a genome-wide gene test. The results from the pathway enrichment analysis show that the 102 shared risk genes are enriched in cancer, diabetes, insulin secretion, and other related pathways. This study can help us understand the molecular mechanisms underlying comorbid NAFLD and metabolic disorders.

Non-alcoholic fatty liver disease: molecular and cellular interplays of the lipid metabolism in a steatotic liver

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) affects ~25% of world population and cases have increased in recent decades. These anomalies have several etiologies; however, obesity and metabolic dysfunctions are the most relevant causes. Despite being considered a public health problem, no effective therapeutic approach to treat NAFLD is available. For that, a deep understanding of metabolic routes that support hepatic diseases is needed.

AREAS COVERED

This review covers aspects of the onset of NAFLD. Thereby, biochemistry routes as well as cellular and metabolic effects of the gut microbiota in body's homeostasis and epigenetics are contextualized.

EXPERT OPINION

Recently, the development of biological sciences has generated innovative knowledge, bringing new insights and perspectives to clarify the systems biology of liver diseases. A detailed comprehension of epigenetics mechanisms will offer possibilities to develop new therapeutic and diagnostic strategies for NAFLD. Different epigenetic processes have been reported that are modulated by the environment such as gut microbiota, suggesting strong interplays between cellular behavior and pathology. Thus, a more complete description of such mechanisms in hepatic diseases will help to clarify how to control the establishment of fatty liver, and precisely describe molecular interplays that potentially control NAFLD.

Modeling Non-Alcoholic Fatty Liver Disease (NAFLD) Using "Good-Fit" Genome-Editing Tools

Non-alcoholic fatty liver disease (NAFLD), which affects both adults and children, is the most common liver disorder worldwide. NAFLD is characterized by excess fat accumulation in the liver in the absence of significant alcohol use. NAFLD is strongly associated with obesity, insulin resistance, metabolic syndrome, as well as specific genetic polymorphisms. Severe NAFLD cases can further progress to cirrhosis, hepatocellular carcinoma (HCC), or cardiovascular complications. Here, we describe the pathophysiological features and critical genetic variants associated with NAFLD. Recent advances in genome-engineering technology have provided a new opportunity to generate in vitro and in vivo models that reflect the genetic abnormalities of NAFLD. We review the currently developed NAFLD models generated using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) genome editing. We further discuss unique features of CRISPR/Cas9 and Cas9 variants, including base editors and prime editor, that are useful for replicating genetic features specific to NAFLD. We also compare advantages and limitations of currently available methods for delivering genome-editing tools necessary for optimal genome editing. This review should provide helpful guidance for selecting “good fit” genome-editing tools and appropriate gene-delivery methods for the successful development of NAFLD models and clinical therapeutics.

Curcuma longa and Trigonella foenum graecum-enriched nutrient mixture from germinated Macrotyloma uniflorum and Vigna radiate ameliorate nonalcoholic fatty liver diseases in rats

The prevalence of nonalcoholic fatty liver is increasing due to modern lifestyle. Germinated and dehulled Macrotyloma uniflorum and Vigna radiate were shown to have enhanced nutrients. Curcuma longa and Trigonella foenum graecum were proven hepatoprotective.The supplementation of the nutrient herbal mixture to the MCD diet-induced steatosis shows reduced hepatic fat accumulation and lipid profile, and liver injury markers in serum also reserved in normal. Increased serum albumin in the treatment group indicates that the liver function is enhanced than that of steatosis. The supplementation of the herbal mixture has preserved the hepatic antioxidant. Zymographic analysis of matrix metalloproteinase, western blot determination of α-SMA, and histological evolution (H&E, Sirius red) depicted reduced fibrosis and reveled management of hepatic stellate cells in quiescent form. The present study concludes that the herbal mixture has reduced hepatocyte fat accumulation in steatotic animals, and curtailed the oxidative stress, further it prevents the progression of steatohepatitis. PRACTICAL APPLICATIONS: Fatty liver diseases can be treated by modulating the diet composition such as consuming food rich in the nutrient herbal mixture. In this study, the nutrient mixture was made with dynamic food processing techniques such as germination, dehulling, and milling to augment the nutritional contents. Besides, Macrotyloma uniflorum, Vigna radiate, Curcuma longa, and Trigonella foenum graecum were used to improve the medicinal value and antioxidant. This formulation could target the various stages of NAFLD. This study revealed that the nutrient herbal mixture reduces the steatosis of the liver and curtailed the progression of steatohepatitis from hepatic steatosis. Since the edible foodstuff was used to make the nutrient mixture, it has excellent clinical application.

Omics-based Investigation of Diet-induced Obesity Synergized with HBx, Src, and p53 Mutation Accelerating Hepatocarcinogenesis in Zebrafish Model

The primary type of liver cancer, hepatocellular carcinoma (HCC), has been associated with nonalcoholic steatohepatitis, diabetes, and obesity. Previous studies have identified some genetic risk factors, such as hepatitis B virus X antigens, overexpression of SRC oncogene, and mutation of the p53 tumor suppressor gene; however, the synergism between diet and genetic risk factors is still unclear. To investigate the synergism between diet and genetic risk factors in hepatocarcinogenesis, we used zebrafish with four genetic backgrounds and overfeeding or high-fat-diet-induced obesity with an omics-based expression of genes and histopathological changes. The results show that overfeeding and high-fat diet can induce obesity and nonalcoholic steatohepatitis in wild-type fish. In HBx, Src (p53-) triple transgenic zebrafish, diet-induced obesity accelerated HCC formation at five months of age and increased the cancer incidence threefold. We developed a global omics data analysis method to investigate genes, pathways, and biological systems based on microarray and next-generation sequencing (NGS, RNA-seq) omics data of zebrafish with four diet and genetic risk factors. The results show that two Kyoto Encyclopedia of Genes and Genomes (KEGG) systems, metabolism and genetic information processing, as well as the pathways of fatty acid metabolism, steroid biosynthesis, and ribosome biogenesis, are activated during hepatocarcinogenesis. This study provides a systematic view of the synergism between genetic and diet factors in the dynamic liver cancer formation process, and indicate that overfeeding or a high-fat diet and the risk genes have a synergistic effect in causing liver cancer by affecting fatty acid metabolism and ribosome biogenesis.

Protective Effect of Hepatitis B Against Metabolic Syndrome in Patients with Nonalcoholic Fatty Liver Disease But Not in Normal Individuals

Background: Both hepatitis B (HB) and nonalcoholic fatty liver disease (NAFLD) are related to metabolic syndrome (MetS); however, this relationship remains controversial. In this study, we determined the effects of NAFLD and HB infection on the risk of MetS among elderly individuals. Methods: In total, 24,500 individuals aged >65 years were enrolled; they were classified into four groups: normal individuals (N), patients with only HB infection without abnormal echogenicity (HB-alone), patients with only abnormal echogenicity or fatty liver alone (FL-alone), and patients with both HB infection and abnormal echogenicity (HB-FL). Results: After adjustment for age, compared with group N, men and women with NAFLD (FL-alone and HB-FL) had a significantly higher risk of MetS, whereas no significant difference was observed in the incidence of MetS between groups HB-alone and N. However, group HB-FL had a lower risk of MetS than did group FL-alone. HB infection (HB-alone and HB-FL) was associated with a lower risk of high triglycerides (TGs) and fasting plasma glucose (FPG) than HB infection absence (groups N and FL-alone) in men and women. Lower risk of TG derangement was observed in group HB-alone than in group N. In addition, both men and women in group HB-FL had a lower risk of TG and FPG abnormalities than in group FL-alone, whereas a decrease in incidence of high waist circumference and blood pressure was observed only in men. Conclusion: HB infection protects against MetS development, only in patients with HB infection and NAFLD, but not in normal individuals. Additional studies are warranted to clarify the pathogenesis.

Hepatocyte nuclear receptor SHP suppresses inflammation and fibrosis in a mouse model of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a burgeoning health problem worldwide, ranging from nonalcoholic fatty liver (NAFL, steatosis without hepatocellular injury) to the more aggressive nonalcoholic steatohepatitis (NASH, steatosis with ballooning, inflammation, or fibrosis). Although many studies have greatly contributed to the elucidation of NAFLD pathogenesis, the disease progression from NAFL to NASH remains incompletely understood. Nuclear receptor small heterodimer partner (Nr0b2, SHP) is a transcriptional regulator critical for the regulation of bile acid, glucose, and lipid metabolism. Here, we show that SHP levels are decreased in the livers of patients with NASH and in diet-induced mouse NASH. Exposing primary mouse hepatocytes to palmitic acid and lipopolysaccharide in vitro, we demonstrated that the suppression of Shp expression in hepatocytes is due to c-Jun N-terminal kinase (JNK) activation, which stimulates c-Jun-mediated transcriptional repression of Shp Interestingly, in vivo induction of hepatocyte-specific SHP in steatotic mouse liver ameliorated NASH progression by attenuating liver inflammation and fibrosis, but not steatosis. Moreover, a key mechanism linking the anti-inflammatory role of hepatocyte-specific SHP expression to inflammation involved SHP-induced suppression of NF-κB p65-mediated induction of chemokine (C-C motif) ligand 2 (CCL2), which activates macrophage proinflammatory polarization and migration. In summary, our results indicate that a JNK/SHP/NF-κB/CCL2 regulatory network controls communications between hepatocytes and macrophages and contributes to the disease progression from NAFL to NASH. Our findings may benefit the development of new management or prevention strategies for NASH.

Probiotics may delay the progression of nonalcoholic fatty liver disease by restoring the gut microbiota structure and improving intestinal endotoxemia

Gut-derived bacterial lipopolysaccharide (LPS) and subsequent hepatic toll-like receptor 4 (TLR4) activation have been recognized to be involved in the onset of diet-induced nonalcoholic fatty liver disease (NAFLD), but little is known about the variation of LPS and TLR4 during the progression of NAFLD. Probiotics were able to inhibit proliferation of harmful bacteria and improve gastrointestinal barrier function. However, it's unclear whether LPS/TLR4 is involved in the protection effect of probiotics on NAFLD. In this study, we described characteristic of gut microbiota structure in the progression of NAFLD, and we also analyzed the relationship between gut microbiota and LPS/TLR4 in this process. Furthermore, we applied probiotics intervention to investigate the effect of probiotics on gut flora structure, intestinal integrity, serum LPS, liver TLR4 and liver pathology. Our results showed that serum LPS and liver TLR4 were highly increased during progression of NAFLD, with gut flora diversity and gut mircobiological colonization resistance (B/E) declining. Furthermore, probiotics could improve gut microbiota structure and liver pathology. Probiotics could also downregulate serum LPS and liver TLR4. Our results suggested that both gut flora alteration and endotoxemia may be involved in the progression of NAFLD. Probiotics may delay the progression of NAFLD via LPS/TLR4 signaling.

Decreased lipid metabolism but increased FA biosynthesis are coupled with changes in liver microRNAs in obese subjects with NAFLD

BACKGROUND/OBJECTIVE

Many controversies regarding the association of liver miRNAs with obesity and nonalcoholic fatty liver diseases (NAFLD) call for additional validations. This study sought to investigate variations in genes and hepatic miRNAs in a sample of obese patients with or without NAFLD and human hepatocytes (HH).

SUBJECTS/METHODS

A total of 60 non-consecutive obese women following bariatric surgery were recruited. Subjects were classified as NAFLD (n=17), borderline (n=24) and controls (n=19) with normal enzymatic profile, liver histology and ultrasound assessments. Profiling of 744 miRNAs was performed in 8 obese women with no sign of hepatic disease and 11 NAFLD patients. Additional validation and expression of genes related to de novo fatty acid (FA) biosynthesis, uptake, transport and β-oxidation; glucose metabolism, and inflammation was tested in the extended sample. Induction of NAFLD-related genes and miRNAs was examined in HepG2 cells and primary HH treated with palmitic acid (PA), a combination of palmitate and oleic acid, or high glucose, and insulin (HG) mimicking insulin resistance in NAFLD.

RESULTS

In the discovery sample, 14 miRNAs were associated with NAFLD. Analyses in the extended sample confirmed decreased miR-139-5p, miR-30b-5p, miR-122-5p and miR-422a, and increased miR-146b-5p in obese subjects with NAFLD. Multiple linear regression analyses disclosed that NAFLD contributed independently to explain miR-139-5p (P=0.005), miR-30b-5p (P=0.005), miR-122-5p (P=0.021), miR-422a (P=0.007) and miR-146a (P=0.033) expression variance after controlling for confounders. Decreased miR-122-5p in liver was associated with impaired FA usage. Expression of inflammatory and macrophage-related genes was opposite to decreased miR-30b-5p, miR-139-5p and miR-422a, whereas increased miR-146b-5p was associated with FABP4 and decreased glucose metabolism and FA mobilization. In partial agreement, PA (but not HG) led to decreased miR-139-5p, miR-30b-5p, miR-422a and miR-146a in vitro, in parallel with increased lipogenesis and FA transport, decreased glucose metabolism and diminished FA oxidation.

CONCLUSION

This study confirms decreased liver glucose and lipid metabolism but increased FA biosynthesis coupled with changes in five unique miRNAs in obese patients with NAFLD.

Antibody-Directed Glucocorticoid Targeting to CD163 in M2-type Macrophages Attenuates Fructose-Induced Liver Inflammatory Changes

Increased consumption of high-caloric carbohydrates contributes substantially to endemic non-alcoholic fatty liver disease in humans, covering a histological spectrum from fatty liver to steatohepatitis. Hypercaloric intake and lipogenetic effects of fructose and endotoxin-driven activation of liver macrophages are suggested to be essential to disease progression. In the present study, we show that a low dose of an anti-CD163-IgG-dexamethasone conjugate targeting the hemoglobin scavenger receptor CD163 in Kupffer cells and other M2-type macrophages has a profound effect on liver inflammatory changes in rats on a high-fructose diet. The diet induced severe non-alcoholic steatohepatitis (NASH)-like changes within a few weeks but the antibody-drug conjugate strongly reduced inflammation, hepatocyte ballooning, fibrosis, and glycogen deposition. Non-conjugated dexamethasone or dexamethasone conjugated to a control IgG did not have this effect but instead exacerbated liver lipid accumulation. The low-dose anti-CD163-IgG-dexamethasone conjugate displayed no apparent systemic side effects. In conclusion, macrophage targeting by antibody-directed anti-inflammatory low-dose glucocorticoid therapy seems to be a promising approach for safe treatment of fructose-induced liver inflammation.

Nonalcoholic Fatty Liver Disease: Epidemiology, Pathogenesis, Natural History, Diagnosis, and Current Treatment Options

Nonalcoholic fatty liver disease (NAFLD) is on the rise and has become a major etiology for chronic liver disease. It is frequently associated with obesity, insulin resistance, hypertension, and dyslipidemia and is considered the hepatic manifestation of metabolic syndrome. In this review, we present a summary of the epidemiology and pathogenesis of NAFLD, and discuss the clinical evaluation and stratification of NAFLD patients into low, intermediate, and high risk with respect to liver-related outcomes. While diet and exercise are the cornerstone of treatment in all patients, the low rate of adherence and inadequacy of these recommendations necessitate pharmacologic intervention, especially in intermediate- and high-risk patients. We discuss vitamin E and pioglitazone which are often used as first-line therapy by many practitioners, with pentoxifylline and liraglutide as backup agents. Several drugs are in advanced-phase clinical trials and will likely change the landscape for management of NAFLD in the very near future.

A novel and selective melanin-concentrating hormone receptor 1 antagonist ameliorates obesity and hepatic steatosis in diet-induced obese rodent models

Melanin-concentrating hormone (MCH), a cyclic neuropeptide expressed predominantly in the lateral hypothalamus, plays an important role in the control of feeding behavior and energy homeostasis. Mice lacking MCH or MCH₁ receptor are resistant to diet-induced obesity (DIO) and MCH₁ receptor antagonists show potent anti-obesity effects in preclinical studies, indicating that MCH₁ receptor is a promising target for anti-obesity drugs. Moreover, recent studies have suggested the potential of MCH₁ receptor antagonists for treatment of non-alcoholic fatty liver disease (NAFLD). In the present study, we show the anti-obesity and anti-hepatosteatosis effect of our novel MCH₁ receptor antagonist, Compound A. Repeated oral administration of Compound A resulted in dose-dependent body weight reduction and had an anorectic effect in DIO mice. The body weight lowering effect of Compound A was more potent than that of pair-feeding. Compound A also reduced lipid content and the expression level of lipogenesis-, inflammation-, and fibrosis-related genes in the liver of DIO mice. Conversely, intracerebroventricular infusion of MCH caused induction of hepatic steatosis as well as increase in body weight in high-fat diet-fed wild type mice, but not MCH₁ receptor knockout mice. The pair-feeding study revealed the MCH-MCH₁ receptor system affects hepatic steatosis through a mechanism that is independent of body weight change. Metabolome analysis demonstrated that Compound A upregulated lipid metabolism-related molecules, such as acylcarnitines and cardiolipins, in the liver. These findings suggest that our novel MCH₁ receptor antagonist, Compound A, exerts its beneficial therapeutic effect on NAFLD and obesity through a central MCH-MCH₁ receptor pathway.

Pathogenesis of Nonalcoholic Steatohepatitis: Interactions between Liver Parenchymal and Nonparenchymal Cells

Nonalcoholic fatty liver disease (NAFLD) is the most common type of chronic liver disease in the Western countries, affecting up to 25% of the general population and becoming a major health concern in both adults and children. NAFLD encompasses the entire spectrum of fatty liver disease in individuals without significant alcohol consumption, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) and cirrhosis. NASH is a manifestation of the metabolic syndrome and hepatic disorders with the presence of steatosis, hepatocyte injury (ballooning), inflammation, and, in some patients, progressive fibrosis leading to cirrhosis. The pathogenesis of NASH is a complex process and implicates cell interactions between liver parenchymal and nonparenchymal cells as well as crosstalk between various immune cell populations in liver. Lipotoxicity appears to be the central driver of hepatic cellular injury via oxidative stress and endoplasmic reticulum (ER) stress. This review focuses on the contributions of hepatocytes and nonparenchymal cells to NASH, assessing their potential applications to the development of novel therapeutic agents. Currently, there are limited pharmacological treatments for NASH; therefore, an increased understanding of NASH pathogenesis is pertinent to improve disease interventions in the future.

Hypolactasia is associated with insulin resistance in nonalcoholic steatohepatitis

AIM

To assess lactase gene (LCT)-13910C>T polymorphisms in Brazilian non-alcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) patients in comparison with healthy controls.

METHODS

This was a transverse observational clinical study with NAFLD patients who were followed at the Hepatology Outpatient Unit of the Hospital das Clínicas, São Paulo, Brazil. The polymorphism of lactase non-persistence/lactase persistence (LCT-13910C>T) was examined by PCR-restriction fragment length polymorphism technique in 102 liver biopsy-proven NAFLD patients (steatosis in 9 and NASH in 93) and compared to those of 501 unrelated healthy volunteers. Anthropometric, clinical, biochemical and liver histology data were analyzed. Continuous variables were compared using the t or Mann-Whitney tests, and categorical data were compared with the Fisher’s exact test. Univariate logistic regression and multivariate logistic regression adjusted for gender and age were performed.

RESULTS

No differences in the LCT-13910 genotype frequencies were noted between the NAFLD patients (66.67% of the patients with steatosis were CC, 33.33% were CT, and none were TT; 55.91% of the patients with NASH were CC, 39.78% were CT, and 4.3% were TT; P = 0.941) and the healthy controls (59.12% were CC, 35.67% were CT, and 5.21% were TT) or between the steatosis and NASH patients. That is, the distribution of the lactase non-persistence/lactase persistence polymorphism (LCT-13910C>T) in the patients with NAFLD was equal to that in the general population. In the NASH patients, the univariate analysis revealed that the lactase non-persistence (low lactase activity or hypolactasia) phenotype was associated with higher insulin levels (23.47 ± 15.94 μU/mL vs 15.8 ± 8.33 μU/mL, P = 0.027) and a higher frequency of insulin resistance (91.84% vs 72.22%, P = 0.02) compared with the lactase persistence phenotype. There were no associations between the LCT genotypes and diabetes (P = 0.651), dyslipidaemia (P = 0.328), hypertension (P = 0.507) or liver histology in these patients. Moreover, in the NASH patients, hypolactasia was an independent risk factor for insulin resistance even after adjusting for gender and age [OR = 5.0 (95%CI: 1.35-20; P = 0.017)].

CONCLUSION

The LCT-13910 genotype distribution in Brazilian NAFLD patients was the same as that of the general population, but hypolactasia increased the risk of insulin resistance in the NASH patients.

p62/SQSTM1-Dr. Jekyll and Mr. Hyde that prevents oxidative stress but promotes liver cancer

p62/SQSTM1 is a multifunctional signaling hub and autophagy adaptor with many binding partners, which allow it to activate mTORC1-dependent nutrient sensing, NF-κB-mediated inflammatory responses, and the NRF2-activated antioxidant defense. p62 recognizes polyubiquitin chains via its C-terminal domain and binds to LC3 via its LIR motif, thereby promoting the autophagic degradation of ubiquitinated cargos. p62 accumulates in many human liver diseases, including nonalcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC), where it is a component of Mallory-Denk bodies and intracellular hyaline bodies. Chronic p62 elevation contributes to HCC development by preventing oncogene-induced senescence and death of cancer-initiating cells and enhancing their proliferation. In this review, we discuss p62-mediated signaling pathways and their roles in liver pathophysiology, especially NASH and HCC.

Role of Transcription Factors in Steatohepatitis and Hypertension after Ethanol: The Epicenter of Metabolism

Chronic alcohol consumption induces multi-organ damage, including alcoholic liver disease (ALD), pancreatitis and hypertension. Ethanol and ethanol metabolic products play a significant role in the manifestation of its toxicity. Ethanol metabolizes to acetaldehyde and produces reduced nicotinamide adenine dinucleotide (NADH) by cytosolic alcohol dehydrogenase. Ethanol metabolism mediated by cytochrome-P450 2E1 causes oxidative stress due to increased production of reactive oxygen species (ROS). Acetaldehyde, increased redox cellular state and ROS activate transcription factors, which in turn activate genes for lipid biosynthesis and offer protection of hepatocytes from alcohol toxicity. Sterol regulatory element binding proteins (SREBPs) and peroxisome proliferator activated-receptors (PPARs) are two key lipogenic transcription factors implicated in the development of fatty liver in alcoholic and non-alcoholic steatohepatitis. SREBP-1 is activated in the livers of chronic ethanol abusers. An increase in ROS activates nuclear factor erythroid-2-related factor-2 (Nrf2) and hypoxia inducible factor (HIF) to provide protection to hepatocytes from ethanol toxicity. Under ethanol exposure, due to increased gut permeability, there is release of gram-negative bacteria-derived lipopolysaccharide (LPS) from intestine causing activation of immune response. In addition, the metabolic product, acetaldehyde, modifies the proteins in hepatocyte, which become antigens inviting auto-immune response. LPS activates macrophages, especially the liver resident macrophages, Kupffer cells. These Kupffer cells and circulating macrophages secrete various cytokines. The level of tumor necrosis factor-α (TNFα), interleukin-1beta (IL-1β), IL-6, IL-8 and IL-12 have been found elevated among chronic alcoholics. In addition to elevation of these cytokines, the peripheral iron (Fe(2+)) is also mobilized. An increased level of hepatic iron has been observed among alcoholics. Increased ROS, IL-1β, acetaldehyde, and increased hepatic iron, all activate nuclear factor-kappa B (NF-κB) transcription factor. Resolution of increased reactive oxygen species requires increased expression of genes responsible for dismutation of increased ROS which is partially achieved by IL-6 mediated activation of signal transducers and activators of transcription 3 (STAT3). In addition to these transcription factors, activator protein-1 may also be activated in hepatocytes due to its association with resolution of increased ROS. These transcription factors are central to alcohol-mediated hepatotoxicity.

Pathogenesis of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease and a risk factor for cirrhosis and hepatocellular carcinoma. The pathological features of NASH include steatosis, hepatocyte injury, inflammation, and various degrees of fibrosis. Steatosis reflects disordered lipid metabolism. Insulin resistance and excessive fatty acid influx to the liver are two important contributing factors. Steatosis is also likely associated with lipotoxicity and cellular stresses such as oxidative stress and endoplasmic reticulum stress, which result in hepatocyte injury. Inflammation and fibrosis are frequently triggered by various signals such as proinflammatory cytokines and chemokines, released by injuried hepatocytes and activated Kupffer cells. Although much progress has been made, the pathogenesis of NASH is not fully elucidated. The purpose of this review is to discuss the current understanding of NASH pathogenesis, mainly focusing on factors contributing to steatosis, hepatocyte injury, inflammation, and fibrosis.

Metabolic Inflammation-Differential Modulation by Dietary Constituents

Obesity arises from a sustained positive energy balance which triggers a pro-inflammatory response, a key contributor to metabolic diseases such as T2D. Recent studies, focused on the emerging area of metabolic-inflammation, highlight that specific metabolites can modulate the functional nature and inflammatory phenotype of immune cells. In obesity, expanding adipose tissue attracts immune cells, creating an inflammatory environment within this fatty acid storage organ. Resident immune cells undergo both a pro-inflammatory and metabolic switch in their function. Inflammatory mediators, such as TNF-α and IL-1β, are induced by saturated fatty acids and disrupt insulin signaling. Conversely, monounsaturated and polyunsaturated fatty acids do not interrupt metabolism and inflammation to the same extent. AMPK links inflammation, metabolism and T2D, with roles to play in all and is influenced negatively by obesity. Lipid spillover results in hepatic lipotoxicity and steatosis. Also in skeletal muscle, excessive FFA can impede insulin's action and promote inflammation. Ectopic fat can also affect pancreatic β-cell function, thereby contributing to insulin resistance. Therapeutics, lifestyle changes, supplements and dietary manipulation are all possible avenues to combat metabolic inflammation and the subsequent insulin resistant state which will be explored in the current review.

Meta-analysis of lipid-traits in Hispanics identifies novel loci, population-specific effects, and tissue-specific enrichment of eQTLs

We performed genome-wide meta-analysis of lipid traits on three samples of Mexican and Mexican American ancestry comprising 4,383 individuals, and followed up significant and highly suggestive associations in three additional Hispanic samples comprising 7,876 individuals. Genome-wide significant signals were observed in or near CELSR2, ZNF259/APOA5, KANK2/DOCK6 and NCAN/MAU2 for total cholesterol, LPL, ABCA1, ZNF259/APOA5, LIPC and CETP for HDL cholesterol, CELSR2, APOB and NCAN/MAU2 for LDL cholesterol, and GCKR, TRIB1, ZNF259/APOA5 and NCAN/MAU2 for triglycerides. Linkage disequilibrium and conditional analyses indicate that signals observed at ABCA1 and LIPC for HDL cholesterol and NCAN/MAU2 for triglycerides are independent of previously reported lead SNP associations. Analyses of lead SNPs from the European Global Lipids Genetics Consortium (GLGC) dataset in our Hispanic samples show remarkable concordance of direction of effects as well as strong correlation in effect sizes. A meta-analysis of the European GLGC and our Hispanic datasets identified five novel regions reaching genome-wide significance: two for total cholesterol (FN1 and SAMM50), two for HDL cholesterol (LOC100996634 and COPB1) and one for LDL cholesterol (LINC00324/CTC1/PFAS). The top meta-analysis signals were found to be enriched for SNPs associated with gene expression in a tissue-specific fashion, suggesting an enrichment of tissue-specific function in lipid-associated loci.

Chemokine ligand 2 and paraoxonase-1 in non-alcoholic fatty liver disease: The search for alternative causative factors

The incidence and prevalence of non-alcoholic fatty liver disease (NAFLD) is constantly increasing. Despite this is apparently associated with the growing increase in obesity, insulin resistance and obesity-related metabolic disturbances their presence is not a necessary or sufficient condition to explain the accumulation of fat in the liver. Conversely, NAFLD is a predictor of other metabolic risks. NAFLD is currently the most frequent chronic liver disease but should not be considered benign or anecdotic because a considerable proportion of patients with NAFLD progress to cirrhosis and end-stage liver disease. Consequently, the search for alternative molecular mechanisms with therapeutic implications in NAFLD and associated disorders deserves a careful consideration. Mitochondria are possible targets as these organelles generate energy from nutrient oxidation. Some findings, generated in patients with extreme obesity and in murine models, support the notion that NAFLD could be a mitochondrial disease. This is plausible because mitochondrial dysfunction affects the accumulation of lipids in hepatocytes and promotes lipid peroxidation, the production of reactive oxygen species, the release of cytokines causing inflammation and cell death. Here we discuss basic research and mechanistic studies targeting the role of chemokine ligand 2 in liver inflammation and that of the paraoxonases in the oxidative stress. Their combination and association with mitochondrial dysfunction may uncover mechanisms underlying the progression of NAFLD and may help to identify novel therapeutic targets.