Animal models of nonalcoholic fatty liver disease

NASH triggers cardiometabolic HFpEF in aging mice

Both heart failure with preserved ejection fraction (HFpEF) and non-alcoholic fatty liver disease (NAFLD) develop due to metabolic dysregulation, has similar risk factors (e.g., insulin resistance, systemic inflammation) and are unresolved clinical challenges. Therefore, the potential link between the two disease is important to study. We aimed to evaluate whether NASH is an independent factor of cardiac dysfunction and to investigate the age dependent effects of NASH on cardiac function. C57Bl/6 J middle aged (10 months old) and aged mice (24 months old) were fed either control or choline deficient (CDAA) diet for 8 weeks. Before termination, echocardiography was performed. Upon termination, organ samples were isolated for histological and molecular analysis. CDAA diet led to the development of NASH in both age groups, without inducing weight gain, allowing to study the direct effect of NASH on cardiac function. Mice with NASH developed hepatomegaly, fibrosis, and inflammation. Aged animals had increased heart weight. Conventional echocardiography revealed normal systolic function in all cohorts, while increased left ventricular volumes in aged mice. Two-dimensional speckle tracking echocardiography showed subtle systolic and diastolic deterioration in aged mice with NASH. Histologic analyses of cardiac samples showed increased cross-sectional area, pronounced fibrosis and Col1a1 gene expression, and elevated intracardiac CD68+ macrophage count with increased Il1b expression. Conventional echocardiography failed to reveal subtle change in myocardial function; however, 2D speckle tracking echocardiography was able to identify diastolic deterioration. NASH had greater impact on aged animals resulting in cardiac hypertrophy, fibrosis, and inflammation.

Non-Invasive Detection of Early-Stage Fatty Liver Disease via an On-Skin Impedance Sensor and Attention-Based Deep Learning

Early-stage nonalcoholic fatty liver disease (NAFLD) is a silent condition, with most cases going undiagnosed, potentially progressing to liver cirrhosis and cancer. A non-invasive and cost-effective detection method for early-stage NAFLD detection is a public health priority but challenging. In this study, an adhesive, soft on-skin sensor with low electrode-skin contact impedance for early-stage NAFLD detection is fabricated. A method is developed to synthesize platinum nanoparticles and reduced graphene quantum dots onto the on-skin sensor to reduce electrode-skin contact impedance by increasing double-layer capacitance, thereby enhancing detection accuracy. Furthermore, an attention-based deep learning algorithm is introduced to differentiate impedance signals associated with early-stage NAFLD in high-fat-diet-fed low-density lipoprotein receptor knockout (Ldlr-/-) mice compared to healthy controls. The integration of an adhesive, soft on-skin sensor with low electrode-skin contact impedance and the attention-based deep learning algorithm significantly enhances the detection accuracy for early-stage NAFLD, achieving a rate above 97.5% with an area under the receiver operating characteristic curve (AUC) of 1.0. The findings present a non-invasive approach for early-stage NAFLD detection and display a strategy for improved early detection through on-skin electronics and deep learning.

Choline consumption reduces CVD risk via body composition modification

Despite extensive research on the relationship between choline and cardiovascular disease (CVD), conflicting findings have been reported. We aim to investigate the relationship between choline and CVD. Our analysis screened a retrospective cohort study of 14,663 participants from the National Health and Nutrition Examination Survey conducted between 2013 and 2018. Propensity score matching and restricted cubic splines was used to access the association between choline intake and the risk of CVD. A two-sample Mendelian randomization (MR) analysis was conducted to examine the potential causality. Additionally, sets of single cell RNA-sequencing data were extracted and analyzed, in order to explore the role of choline metabolism pathway in the progression and severity of the CVD and the underlying potential mechanisms involved. The adjusted odds ratios and 95% confidence intervals for stroke were 0.72 (0.53-0.98; p = 0.035) for quartile 3 and 0.54 (0.39-0.75; p < 0.001) for quartile 4. A stratified analysis revealed that the relationship between choline intake and stroke varied among different body mass index and waist circumference groups. The results of MR analysis showed that choline and phosphatidylcholine had a predominantly negative causal effect on fat percentage, fat mass, and fat-free mass, while glycine had opposite effects. Results from bioinformatics analysis revealed that alterations in the choline metabolism pathway following stroke may be associated with the prognosis. Our study indicated that the consumption of an appropriate quantity of choline in the diet may help to protect against CVD and the effect may be choline-mediated, resulting in a healthier body composition. Furthermore, the regulation of the choline metabolism pathway following stroke may be a promising therapeutic target.

A Novel TGFβ Receptor Inhibitor, IPW-5371, Prevents Diet-induced Hepatic Steatosis and Insulin Resistance in Irradiated Mice

As the number of cancer survivors increases and the risk of accidental radiation exposure rises, there is a pressing need to characterize the delayed effects of radiation exposure and develop medical countermeasures. Radiation has been shown to damage adipose progenitor cells and increase liver fibrosis, such that it predisposes patients to developing metabolic-associated fatty liver disease (MAFLD) and insulin resistance. The risk of developing these conditions is compounded by the global rise of diets rich in carbohydrates and fats. Radiation persistently increases the signaling cascade of transforming growth factor β (TGFβ), leading to heightened fibrosis as characteristic of the delayed effects of radiation exposure. We investigate here a potential radiation medical countermeasure, IPW-5371, a small molecule inhibitor of TGFβRI kinase (ALK5). We found that mice exposed to sub-lethal whole-body irradiation and chronic Western diet consumption but treated with IPW-5371 had a similar body weight, food consumption, and fat mass compared to control mice exposed to radiation. The IPW-5371 treated mice maintained lower fibrosis and fat accumulation in the liver, were more responsive to insulin and had lower circulating triglycerides and better muscle endurance. Future studies are needed to verify the improvement by IPW-5371 on the structure and function of other metabolically active tissues such as adipose and skeletal muscle, but these data demonstrate that IPW-5371 protects liver and whole-body health in rodents exposed to radiation and a Western diet, and there may be promise in using IPW-5371 to prevent the development of MAFLD.

Dietary milk polar lipids modulate gut barrier integrity and lipid metabolism in C57BL/6J mice during systemic inflammation induced by Escherichia coli lipopolysaccharide

The focus of this work is the role milk polar lipids play in affecting gut permeability, systemic inflammation, and lipid metabolism during acute and chronic inflammation induced by a single subcutaneous injection of lipopolysaccharide. Three groups of C57BL/6J mice were fed: modified AIN-93G diet with moderate level of fat (CO); CO with milk gangliosides (GG); CO with milk phospholipids (MPL). The MPL did not prevent a gut permeability increase upon LPS stress but increased the expression of tight junction proteins zonula occludens-1 and occludin in colon mucosa. The GG prevented the gut permeability increase upon LPS stress. The MPL decreased absolute and relative liver mass and decreased hepatic gene expression of acetyl-CoA carboxylase 2 and 3-hydroxy-3-methylglutaryl-CoA reductase. The GG increased hepatic gene expression of acetyl-CoA acyltransferase 2. In conclusion, milk GG protected the intestinal barrier integrity but had little effect on systemic inflammation and lipid metabolism; milk MPL, conversely, had complex effects on gut permeability, did not affect systemic inflammation, and had beneficial effect on hepatic lipid metabolism.

Implications of Microbiota and Immune System in Development and Progression of Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent type of liver disease worldwide. The exact pathophysiology behind MASLD remains unclear; however, it is thought that a combination of factors or "hits" act as precipitants for disease onset and progression. Abundant evidence supports the roles of diet, genes, metabolic dysregulation, and the intestinal microbiome in influencing the accumulation of lipids in hepatocytes and subsequent progression to inflammation and fibrosis. Currently, there is no cure for MASLD, but lifestyle changes have been the prevailing cornerstones of management. Research is now focusing on the intestinal microbiome as a potential therapeutic target for MASLD, with the spotlight shifting to probiotics, antibiotics, and fecal microbiota transplantation. In this review, we provide an overview of how intestinal microbiota interact with the immune system to contribute to the pathogenesis of MASLD and metabolic dysfunction-associated steatohepatitis (MASH). We also summarize key microbial taxa implicated in the disease and discuss evidence supporting microbial-targeted therapies in its management.

Transketolase promotes MAFLD by limiting inosine-induced mitochondrial activity

Metabolic dysfunction-associated fatty liver disease (MAFLD) has a global prevalence of about 25% and no approved therapy. Using metabolomic and proteomic analyses, we identified high expression of hepatic transketolase (TKT), a metabolic enzyme of the pentose phosphate pathway, in human and mouse MAFLD. Hyperinsulinemia promoted TKT expression through the insulin receptor-CCAAT/enhancer-binding protein alpha axis. Utilizing liver-specific TKT overexpression and knockout mouse models, we demonstrated that TKT was sufficient and required for MAFLD progression. Further metabolic flux analysis revealed that Tkt deletion increased hepatic inosine levels to activate the protein kinase A-cAMP response element binding protein cascade, promote phosphatidylcholine synthesis, and improve mitochondrial function. Moreover, insulin induced hepatic TKT to limit inosine-dependent mitochondrial activity. Importantly, N-acetylgalactosamine (GalNAc)-siRNA conjugates targeting hepatic TKT showed promising therapeutic effects on mouse MAFLD. Our study uncovers how hyperinsulinemia regulates TKT-orchestrated inosine metabolism and mitochondrial function and provides a novel therapeutic strategy for MAFLD prevention and treatment.

Comparison of Wild-Type and High-risk PNPLA3 variants in a Human Biomimetic Liver Microphysiology System for Metabolic Dysfunction-associated Steatotic Liver Disease Precision Therapy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a worldwide health epidemic with a global occurrence of approximately 30%. The pathogenesis of MASLD is a complex, multisystem disorder driven by multiple factors including genetics, lifestyle, and the environment. Patient heterogeneity presents challenges for developing MASLD therapeutics, creation of patient cohorts for clinical trials and optimization of therapeutic strategies for specific patient cohorts. Implementing pre-clinical experimental models for drug development creates a significant challenge as simple in vitro systems and animal models do not fully recapitulate critical steps in the pathogenesis and the complexity of MASLD progression. To address this, we implemented a precision medicine strategy that couples the use of our liver acinus microphysiology system (LAMPS) constructed with patient-derived primary cells. We investigated the MASLD-associated genetic variant PNPLA3 rs738409 (I148M variant) in primary hepatocytes, as it is associated with MASLD progression. We constructed LAMPS with genotyped wild type and variant PNPLA3 hepatocytes together with key non-parenchymal cells and quantified the reproducibility of the model. We altered media components to mimic blood chemistries, including insulin, glucose, free fatty acids, and immune activating molecules to reflect normal fasting (NF), early metabolic syndrome (EMS) and late metabolic syndrome (LMS) conditions. Finally, we investigated the response to treatment with resmetirom, an approved drug for metabolic syndrome-associated steatohepatitis (MASH), the progressive form of MASLD. This study using primary cells serves as a benchmark for studies using patient biomimetic twins constructed with patient iPSC-derived liver cells using a panel of reproducible metrics. We observed increased steatosis, immune activation, stellate cell activation and secretion of pro-fibrotic markers in the PNPLA3 GG variant compared to wild type CC LAMPS, consistent with the clinical characterization of this variant. We also observed greater resmetirom efficacy in PNPLA3 wild type CC LAMPS compared to the GG variant in multiple MASLD metrics including steatosis, stellate cell activation and the secretion of pro-fibrotic markers. In conclusion, our study demonstrates the capability of the LAMPS platform for the development of MASLD precision therapeutics, enrichment of patient cohorts for clinical trials, and optimization of therapeutic strategies for patient subgroups with different clinical traits and disease stages.

Insulin Resistance, Non-Alcoholic Fatty Liver Disease and Type 2 Diabetes Mellitus: Clinical and Experimental Perspective

It has been generally accepted that insulin resistance (IR) and reduced insulin secretory capacity are the basic pathogenesis of type 2 diabetes mellitus (T2DM). In addition to genetic factors, the persistence of systemic inflammation caused by obesity and the associated threat of lipotoxicity increase the risk of T2DM. In particular, the main cause of IR is obesity and subjects with T2DM have a higher body mass index (BMI) than normal subjects according to recent studies. The prevalence of T2DM with IR has increased with increasing BMI during the past three decades. According to recent studies, homeostatic model assessment of IR was increased compared to that of the 1990s. Rising prevalence of obesity in Korea have contributed to the development of IR, non-alcoholic fatty liver disease and T2DM and cutting this vicious cycle is important. My colleagues and I have investigated this pathogenic mechanism on this theme through clinical and experimental studies over 20 years and herein, I would like to summarize some of our studies with deep gratitude for receiving the prestigious 2023 Sulwon Award.

A metabolic-dysfunction associated steatotic liver acinus biomimetic induces pancreatic islet dysfunction in a coupled microphysiology system

Preclinical and clinical studies suggest that lipid-induced hepatic insulin resistance is a primary defect that predisposes to dysfunction in pancreatic islets, implicating a perturbed liver-pancreas axis underlying the comorbidity of T2DM and MASLD. To investigate this hypothesis, we developed a human biomimetic microphysiological system (MPS) coupling our vascularized liver acinus MPS (vLAMPS) with primary islets on a chip (PANIS) enabling MASLD progression and islet dysfunction to be quantitatively assessed. The modular design of this system (vLAMPS-PANIS) allows intra-organ and inter-organ dysregulation to be deconvoluted. When compared to normal fasting (NF) conditions, under early metabolic syndrome (EMS) conditions, the standalone vLAMPS exhibited characteristics of early stage MASLD, while no significant differences were observed in the standalone PANIS. In contrast, with EMS, the coupled vLAMPS-PANIS exhibited a perturbed islet-specific secretome and a significantly dysregulated glucose stimulated insulin secretion (GSIS) response implicating direct signaling from the dysregulated liver acinus to the islets. Correlations between several pairs of a vLAMPS-derived and a PANIS-derived secreted factors were significantly altered under EMS, as compared to NF conditions, mechanistically connecting MASLD and T2DM associated hepatic factors with islet-derived GLP-1 synthesis and regulation. Since vLAMPS-PANIS is compatible with patient-specific iPSCs, this platform represents an important step towards addressing patient heterogeneity, identifying complex disease mechanisms, and advancing precision medicine.

Folate Deficiency and/or the Genetic Variant Mthfr677C >T Can Drive Hepatic Fibrosis or Steatosis in Mice, in a Sex-Specific Manner

SCOPE

Disturbances in one-carbon metabolism contribute to nonalcoholic fatty liver disease (NAFLD) which encompasses steatosis, steatohepatitis, fibrosis, and cirrhosis. The goal is to examine impact of folate deficiency and the Mthfr677C >T variant on NAFLD.

METHODS AND RESULTS

This study uses the new Mthfr677C >T mouse model for the human MTHFR677C >T variant. Mthfr677CC and Mthfr677TT mice were fed control diet (CD) or folate-deficient (FD) diets for 4 months. FD and Mthfr677TT alter choline/methyl metabolites in liver and/or plasma (decreased S-adenosylmethionine (SAM):S-adenosylhomocysteine (SAH) ratio, methyltetrahydrofolate, and betaine; increased homocysteine [Hcy]). FD, with contribution from Mthfr677TT, provokes fibrosis in males. Studies of normal livers reveal alterations in plasma markers and gene expression that suggest an underlying predisposition to fibrosis induced by FD and/or Mthfr677TT in males. These changes are absent or reverse in females, consistent with the sex disparity of fibrosis. Sex-based differences in methylation potential, betaine, sphingomyelin, and trimethylamine-N-oxide (TMAO) levels may prevent fibrogenesis in females. In contrast, Mthfr677TT alters choline metabolism, dysregulates expression of lipid metabolism genes, and promotes steatosis in females.

CONCLUSION

This study suggests that folate deficiency predisposes males to fibrosis, which is exacerbated by Mthfr677TT, whereas Mthfr677TT predisposes females to steatosis, and reveal novel contributory mechanisms for these NAFLD-related disorders.

Time-Restricted Feeding Ameliorates Methionine-Choline Deficient Diet-Induced Steatohepatitis in Mice

Non-alcoholic steatohepatitis (NASH) is an inflammatory form of non-alcoholic fatty liver disease (NAFLD), closely associated with disease progression, cirrhosis, liver failure, and hepatocellular carcinoma. Time-restricted feeding (TRF) has been shown to decrease body weight and adiposity and improve metabolic outcomes; however, the effect of TRF on NASH has not yet been fully understood. We had previously reported that inositol polyphosphate multikinase (IPMK) mediates hepatic insulin signaling. Importantly, we have found that TRF increases hepatic IPMK levels. Therefore, we investigated whether there is a causal link between TRF and IPMK in a mouse model of NASH, i.e., methionine- and choline-deficient diet (MCDD)-induced steatohepatitis. Here, we show that TRF alleviated markers of NASH, i.e., reduced hepatic steatosis, liver triglycerides (TG), serum alanine transaminase (ALT) and aspartate aminotransferase (AST), inflammation, and fibrosis in MCDD mice. Interestingly, MCDD led to a significant reduction in IPMK levels, and the deletion of hepatic IPMK exacerbates the NASH phenotype induced by MCDD, accompanied by increased gene expression of pro-inflammatory chemokines. Conversely, TRF restored IPMK levels and significantly reduced gene expression of proinflammatory cytokines and chemokines. Our results demonstrate that TRF attenuates MCDD-induced NASH via IPMK-mediated changes in hepatic steatosis and inflammation.

Characteristics of contemporary drug clinical trials regarding the treatment of non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic steatohepatitis (NASH), a chronic liver disease, has no United States Food and Drug Administration (FDA) approved drugs for treatment.

OBJECTIVES

To examine fundamental characteristics of drug clinical trials for NASH treatment on the global clinical trials registry platform.

METHODS

Cross-sectional analysis of clinical trials with NASH as medical condition that are registered on ClinicalTrials.gov. Relevant trial entries registered before and on October 7th, 2022, were downloaded, deduplicated, and reviewed. NCT numbers, titles, locations, funder types, statuses, durations, study designs, subject information, conditions, interventions, outcome measures were extracted and analyzed.

RESULTS

Overall, 268 drug clinical trials were included in this study. Majority of the trials are conducted in United States (42.2 %). Most of the trials are funded by industry (67.9 %). The earliest initiated trials date back to 2001. Most trials are phase 2 (56.3 %), randomized (84.0 %), parallel assignment (78.7 %), and quadruple blind (40.3 %). The most concerned combined medical conditions are non-alcoholic fatty liver disease (NAFLD, 20.9 %). The most involved mechanisms of action drug categories are farnesoid X receptor (FXR) agonists and peroxisome proliferator-activated receptor (PPAR) agonists, with the most tested drugs being the FXR agonist EDP-305 and the Glucagon-like peptide-1 (GLP-1) agonist semaglutide.

CONCLUSION

Old drugs are further repurposed for testing in NASH treatment, novel drugs are developed to try to cure NASH. We expect that the drug clinical trials will accelerate the frontier of therapeutic development in NASH, bring an innovative and efficacious medication therapeutic approach to prevent the development and progression of NASH, or even reverse NASH.

Hepatocyte CHRNA4 mediates the MASH-promotive effects of immune cell-produced acetylcholine and smoking exposure in mice and humans

Metabolic dysfunction-associated steatohepatitis (MASH) is a leading risk factor for liver cirrhosis and hepatocellular carcinoma. Here, we report that CHRNA4, a subunit of nicotinic acetylcholine receptors (nAChRs), is an accelerator of MASH progression. CHRNA4 also mediates the MASH-promotive effects induced by smoking. Chrna4 was expressed specifically in hepatocytes and exhibited increased levels in mice and patients with MASH. Elevated CHRNA4 levels were positively correlated with MASH severity. We further revealed that during MASH development, acetylcholine released from immune cells or nicotine derived from smoking functioned as an agonist to activate hepatocyte-intrinsic CHRNA4, inducing calcium influx and activation of inflammatory signaling. The communication between immune cells and hepatocytes via the acetylcholine-CHRNA4 axis led to the production of a variety of cytokines, eliciting inflammation in liver and promoting the pathogenesis of MASH. Genetic and pharmacological inhibition of CHRNA4 protected mice from diet-induced MASH. Targeting CHRNA4 might be a promising strategy for MASH therapeutics.

Utility of ultrasonography in a mouse model of non-alcoholic steatohepatitis induced by a choline-deficient, high-fat diet and dextran sulfate sodium

Background

Nonalcoholic steatohepatitis (NASH) is a chronic progressive liver disease that can progress to cirrhosis and hepatocellular carcinoma. The prevalence of NASH is increasing year by year. However, the etiology and progression of NASH, along with the processes leading to carcinogenesis, remain poorly understood. A range of animal models are used in research, but investigators have been unable to establish a model that results in tumorigenesis from a stable disease state. The present study aimed to create a stable, low-mortality model of NASH using abdominal ultrasonography (US) to assess NASH stage and diagnose liver tumors.

Methods

Thirty-four 19-week-old male C57BL/6J mice were fed a choline-deficient, high-fat (CDHF) diet. Twenty animals were given seven courses of 0.8 % dextran sulfate sodium (DSS) for 7 days followed by 10 days of MilliQ water (CDHF+DSS group). The remaining 14 animals drank only MilliQ water (CDHF group). All animals were weighed weekly and US was performed on Days 35 and 120. After necropsy, samples were taken for biochemical analysis and histopathological evaluation.

Results

The CDHF+DSS group had significantly lower body weight on Days 35 and 120, and significantly higher liver/body weight (%) on Day 35 compared to the CDHF group. US on Days 35 and 120 revealed significantly shorter long intestine and higher colonic histological score in the CDHF+DSS group compared to the CDHF group. IL-1β and IL-6 levels in the large intestinal tissue were significantly higher in the CDHF+DSS group.

Conclusions

A stable, low-mortality model of NASH was created with a CDHF diet and intermittent 0.8 % DSS. Abdominal US can assess the degree of fatty degeneration and evaluate liver tumorigenesis without necropsy. This assessment procedure will reduce the number of mice killed unnecessarily during experiments, thereby contributing to animal welfare.

Hepatocyte CD36 protects mice from NASH diet-induced liver injury and fibrosis via blocking N1ICD production

BACKGROUND & AIMS

Fatty acid translocase CD36 (CD36/FAT) is a widely expressed membrane protein with multiple immuno-metabolic functions. Genetic CD36 deficiency is associated with increased risk of metabolic dysfunction-associated fatty liver disease (MAFLD) in patients. Liver fibrosis severity mainly affects the prognosis in patients with MAFLD, but the role of hepatocyte CD36 in liver fibrosis of MAFLD remains unclear.

METHODS

A high-fat high-cholesterol diet and a high-fat diet with high-fructose drinking water were used to induce nonalcoholic steatohepatitis (NASH) in hepatocyte-specific CD36 knockout (CD36LKO) and CD36flox/flox (LWT) mice. Human hepG2 cell line was used to investigate the role of CD36 in regulating Notch pathway in vitro.

RESULTS

Compared to LWT mice, CD36LKO mice were susceptible to NASH diet-induced liver injury and fibrosis. The analysis of RNA-sequencing data revealed that Notch pathway was activated in CD36LKO mice. LY3039478, an inhibitor of γ-secretase, inhibited Notch1 protein S3 cleavage and Notch1 intracellular domain (N1ICD) production, alleviating liver injury and fibrosis in CD36LKO mice livers. Likewise, both LY3039478 and knockdown of Notch1 inhibited the CD36KO-induced increase of N1ICD production, causing the decrease of fibrogenic markers in CD36KO HepG2 cells. Mechanistically, CD36 formed a complex with Notch1 and γ-secretase in lipid rafts, and hence CD36 anchored Notch1 in lipid rafts domains and blocked Notch1/γ-secretase interaction, inhibiting γ-secretase-mediated cleavage of Notch1 and the production of N1ICD.

CONCLUSIONS

Hepatocyte CD36 plays a key role in protecting mice from diet-induced liver injury and fibrosis, which may provide a potential therapeutic strategy for preventing liver fibrogenesis in MAFLD.

Modelling porcine NAFLD by deletion of leptin and defining the role of AMPK in hepatic fibrosis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent cause of chronic hepatic disease and results in non-alcoholic steatohepatitis (NASH), which progresses to fibrosis and cirrhosis. Although the Leptin deficient rodent models are widely used in study of metabolic syndrome and obesity, they fail to develop liver injuries as in patients.

METHODS

Due to the high similarity with humans, we generated Leptin-deficient (Leptin-/-) pigs to investigate the mechanisms and clinical trials of obesity and NAFLD caused by Leptin.

RESULTS

The Leptin-/- pigs showed increased body fat and significant insulin resistance at the age of 12 months. Moreover, Leptin-/- pig developed fatty liver, non-alcoholic steatohepatitis and hepatic fibrosis with age. Absence of Leptin in pig reduced the phosphorylation of JAK2-STAT3 and AMPK. The inactivation of JAK2-STAT3 and AMPK enhanced fatty acid β-oxidation and leaded to mitochondrial autophagy respectively, and both contributed to increased oxidative stress in liver cells. In contrast with Leptin-/- pig, although Leptin deletion in rat liver inhibited JAK2-STAT3 phosphorylation, the activation of AMPK pathway might prevent liver injury. Therefore, β-oxidation, mitochondrial autophagy and hepatic fibrosis did not occurred in Leptin-/- rat livers.

CONCLUSIONS

The Leptin-deficient pigs presents an ideal model to illustrate the full spectrum of human NAFLD. The activity of AMPK signaling pathway suggests a potential target to develop new strategy for the diagnosis and treatment of NAFLD.

Inhibition of glutathione generation in hepatic steatotic rats augments oxidative stress

Fatty liver disease has been strongly associated with a low glutathione (GSH) level in hepatocytes with increased oxidative stress, which is critically involved in the initiation and progression of the disease. The study investigated whether the GSH deficiency induced by buthionine sulfoximine (BSO), an inhibitor of γ-glutamyl cysteine synthetase, can be restored by the administration of GSH ester. We showed that mice fed a diet with cholesterol plus sodium cholate developed steatosis followed by hepatic GSH reduction. Moreover, the GSH level in the cytosol and mitochondria of steatosis plus BSO decreased than that of steatosis alone. Subsequent studies with the liver tissues and plasma of BSO plus steatosis revealed the accumulation of cholesterol in the hepatocytes, downregulating the concentration of GSH, antioxidant enzymes, and GSH metabolizing enzymes with a significant rise in reactive oxygen species (ROS), blood glucose level and plasma lipid profile. The administration of GSH ester in BSO-administered mice, prevented the depletion of GSH by upregulating the GSH concentration, antioxidant enzymes, and GSH metabolizing enzymes, followed by a reduction in ROS and plasma lipid concentration. The histopathological analysis showed a marked increase in inflammation followed by hepatocytes ballooning in BSO-induced group and steatosis control group, which was ameliorated by GSH ester administration. In conclusion, our data suggest that the restoration of GSH in the cytosol and mitochondria through the injection with GSH ester plays a principal role in maintaining the GSH level in the liver, thereby delaying the progression of fatty liver disease.

One-carbon metabolizing enzyme ALDH1L1 influences mitochondrial metabolism through 5-aminoimidazole-4-carboxamide ribonucleotide accumulation and serine depletion, contributing to tumor suppression

Tumor cells generally require large amounts of nucleotides, and thus activate de novo purine synthesis (dnPS). In the dnPS reactions, 10-formyltetrahydorofolate (10-fTHF) supplied by one-carbon metabolism is utilized as a formyl group donor. We focused on aldehyde dehydrogenase 1 family member L1 (ALDH1L1), which metabolizes 10-fTHF to tetrahydrofolate and whose expression is often attenuated in hepatocellular carcinoma (HCC). We generated ALDH1L1-expressing HuH-7 cells to perform metabolome analysis and found that intracellular levels of serine were reduced and glycine was increased. In addition, 5-aminoimidazole-4-carboxamide ribonucleotide (ZMP), a dnPS intermediate, accumulated due to the consumption of 10-fTHF by ALDH1L1, which inhibited ZMP formylation. Importantly, ALDH1L1-expressing cells showed reduced ZMP sensitivity and higher mitochondrial activity. The suppression of mitochondrial serine catabolism by ALDH1L1 expression was speculated to be closely related to this phenotype. Gene set enrichment analysis utilizing The Cancer Genome Atlas data revealed that genes related to oxidative phosphorylation were enriched in HCC patients with high ALDH1L1 expression. Moreover, drug sensitivity data analysis demonstrated that HCC cell lines with low expression of ALDH1L1 were sensitive to ZMP and cordycepin, a structural analog of ZMP and AMP. Our study revealed that ZMP and AMP analogs might be effective in the pharmacotherapy of HCC patients with low expression of ALDH1L1.

Experimental Models for Studying Structural and Functional State of the Pathological Liver (Review)

Liver pathologies remain one of the leading causes of mortality worldwide. Despite a high prevalence of liver diseases, the possibilities of diagnosing, prognosing, and treating non-alcoholic and alcoholic liver diseases still have a number of limitations and require the development of new methods and approaches. In laboratory studies, various models are used to reconstitute the pathological conditions of the liver, including cell cultures, spheroids, organoids, microfluidic systems, tissue slices. We reviewed the most commonly used in vivo, in vitro, and ex vivo models for studying non-alcoholic fatty liver disease and alcoholic liver disease, toxic liver injury, and fibrosis, described their advantages, limitations, and prospects for use. Great emphasis was placed on the mechanisms of development of pathological conditions in each model, as well as the assessment of the possibility of reconstructing various key aspects of pathogenesis for all these pathologies. There is currently no consensus on the choice of the most adequate model for studying liver pathology. The choice of a certain effective research model is determined by the specific purpose and objectives of the experiment.

Mitochondrial metabolic dysfunction and non-alcoholic fatty liver disease: new insights from pathogenic mechanisms to clinically targeted therapy

Metabolic dysfunction-associated fatty liver disease (MAFLD) is among the most widespread metabolic disease globally, and its associated complications including insulin resistance and diabetes have become threatening conditions for human health. Previous studies on non-alcoholic fatty liver disease (NAFLD) were focused on the liver's lipid metabolism. However, growing evidence suggests that mitochondrial metabolism is involved in the pathogenesis of NAFLD to varying degrees in several ways, for instance in cellular division, oxidative stress, autophagy, and mitochondrial quality control. Ultimately, liver function gradually declines as a result of mitochondrial dysfunction. The liver is unable to transfer the excess lipid droplets outside the liver. Therefore, how to regulate hepatic mitochondrial function to treat NAFLD has become the focus of current research. This review provides details about the intrinsic link of NAFLD with mitochondrial metabolism and the mechanisms by which mitochondrial dysfunctions contribute to NAFLD progression. Given the crucial role of mitochondrial metabolism in NAFLD progression, the application potential of multiple mitochondrial function improvement modalities (including physical exercise, diabetic medications, small molecule agonists targeting Sirt3, and mitochondria-specific antioxidants) in the treatment of NAFLD was evaluated hoping to provide new insights into NAFLD treatment.

iTRAQ-based quantitative proteomics analysis of the effect of ACT001 on non-alcoholic steatohepatitis in mice

ACT001 is a novel sesquiterpene lactone derivative that has been shown to have significant antitumor and anti-inflammatory effects. However, the effect of ACT001 on nonalcoholic steatohepatitis (NASH) is unknown. Methionine and choline deficient (MCD) diet induced NASH model in C57BL/6J mice. Steatosis, inflammation and fibrosis-related indices of serum and liver tissues were detected by fully automated biochemical analyzer, enzyme-linked immunosorbent assay (ELISA) kit, flow cytometry, hematoxylin and eosin (H&E), Masson and immunohistochemical staining. The results showed that ACT001 reduced serum lipid and inflammatory factor levels, attenuated hepatic steatosis, inflammation and fibrosis, and inhibited hepatic oxidative stress and activation of NOD-like receptor protein 3 (NLRP3) inflammatory vesicles in NASH mice. In addition, 381 differentially expressed proteins (DEPs), including 162 up-regulated and 219 down-regulated proteins, were identified in the MCD group and ACT001 high-dose group using isotope labeling relative and absolute quantification (iTRAQ) technique analysis. Among these DEPs, five proteins associated with NAFLD were selected for real-time fluorescence quantitative PCR (RT-qPCR) validation, and the results were consistent with proteomics. In conclusion, ACT001 has a therapeutic effect on NASH, and the results of proteomic analysis will provide new ideas for the mechanism study of ACT001 for NASH treatment.

Experimental models of fatty liver diseases: Status and appraisal

Fatty liver diseases, including alcohol-associated liver disease (ALD) and nonalcoholic fatty liver disease nonalcoholic fatty liver disease (NAFLD), affect a large number of people worldwide and become one of the major causes of end-stage liver disease, such as liver cirrhosis and hepatocellular carcinoma (HCC). Unfortunately, there are currently no approved pharmacological treatments for ALD or NAFLD. This situation highlights the urgent need to explore new intervention targets and discover effective therapeutics for ALD and NAFLD. The lack of properly validated preclinical disease models is a major obstacle to the development of clinical therapies. ALD and NAFLD models have been in the development for decades, but there are still no models that recapitulate the full spectrum of ALD and NAFLD. Throughout this review, we summarize the current in vitro and in vivo models used for research on fatty liver diseases and discuss the advantages and limitations of these models.

Loss of hepatic PPARα in mice causes hypertension and cardiovascular disease

The leading cause of death in patients with nonalcoholic fatty liver disease (NAFLD) is cardiovascular disease (CVD). However, the mechanisms are unknown. Mice deficient in hepatocyte proliferator-activated receptor-α (PPARα) (PparaHepKO) exhibit hepatic steatosis on a regular chow diet, making them prone to manifesting NAFLD. We hypothesized that the PparaHepKO mice might be predisposed to poorer cardiovascular phenotypes due to increased liver fat content. Therefore, we used PparaHepKO and littermate control mice fed a regular chow diet to avoid complications with a high-fat diet, such as insulin resistance and increased adiposity. After 30 wk on a standard diet, male PparaHepKO mice exhibited elevated hepatic fat content compared with littermates as measured by Echo MRI (11.95 ± 1.4 vs. 3.74 ± 1.4%, P < 0.05), hepatic triglycerides (1.4 ± 0.10 vs. 0.3 ± 0.01 mM, P < 0.05), and Oil Red O staining, despite body weight, fasting blood glucose, and insulin levels being the same as controls. The PparaHepKO mice also displayed elevated mean arterial blood pressure (121 ± 4 vs. 108 ± 2 mmHg, P < 0.05), impaired diastolic function, cardiac remodeling, and enhanced vascular stiffness. To determine mechanisms controlling the increase in stiffness in the aorta, we used state-of-the-art PamGene technology to measure kinase activity in this tissue. Our data suggest that the loss of hepatic PPARα induces alterations in the aortas that reduce the kinase activity of tropomyosin receptor kinases and p70S6K kinase, which might contribute to the pathogenesis of NAFLD-induced CVD. These data indicate that hepatic PPARα protects the cardiovascular system through some as-of-yet undefined mechanism.

Advancements in Research on Constructing Physiological and Pathological Liver Models and Their Applications Utilizing Bioprinting Technology

In recent decades, significant progress has been made in liver tissue engineering through the use of 3D bioprinting technology. This technology offers the ability to create personalized biological structures with precise geometric design capabilities. The complex and multifaceted nature of liver diseases underscores the need for advanced technologies to accurately mimic the physiological and mechanical characteristics, as well as organ-level functions, of liver tissue in vitro. Bioprinting stands out as a superior option over traditional two-dimensional cell culture models and animal models due to its stronger biomimetic advantages. Through the use of bioprinting, it is possible to create liver tissue with a level of structural and functional complexity that more closely resembles the real organ, allowing for more accurate disease modeling and drug testing. As a result, it is a promising tool for restoring and replacing damaged tissue and organs in the field of liver tissue engineering and drug research. This article aims to present a comprehensive overview of the progress made in liver tissue engineering using bioprinting technology to provide valuable insights for researchers. The paper provides a detailed account of the history of liver tissue engineering, highlights the current 3D bioprinting methods and bioinks that are widely used, and accentuates the importance of existing in vitro liver tissue models based on 3D bioprinting and their biomedical applications. Additionally, the article explores the challenges faced by 3D bioprinting and predicts future trends in the field. The progress of 3D bioprinting technology is poised to bring new approaches to printing liver tissue in vitro, while offering powerful tools for drug development, testing, liver disease modeling, transplantation, and regeneration, which hold great academic and practical significance.

The role of ChREBP in carbohydrate sensing and NAFLD development

Excessive sugar consumption and defective glucose sensing by hepatocytes contribute to the development of metabolic diseases including type 2 diabetes mellitus (T2DM) and nonalcoholic fatty liver disease (NAFLD). Hepatic metabolism of carbohydrates into lipids is largely dependent on the carbohydrate-responsive element binding protein (ChREBP), a transcription factor that senses intracellular carbohydrates and activates many different target genes, through the activation of de novo lipogenesis (DNL). This process is crucial for the storage of energy as triglycerides in hepatocytes. Furthermore, ChREBP and its downstream targets represent promising targets for the development of therapies for the treatment of NAFLD and T2DM. Although lipogenic inhibitors (for example, inhibitors of fatty acid synthase, acetyl-CoA carboxylase or ATP citrate lyase) are currently under investigation, targeting lipogenesis remains a topic of discussion for NAFLD treatment. In this Review, we discuss mechanisms that regulate ChREBP activity in a tissue-specific manner and their respective roles in controlling DNL and beyond. We also provide in-depth discussion of the roles of ChREBP in the onset and progression of NAFLD and consider emerging targets for NAFLD therapeutics.

Therapeutic impact of purified Trichoderma viride L-asparaginase in murine model of liver cancer and in vitro Hep-G2 cell line

BACKGROUND

Hepatocellular carcinoma (HCC) is among the common cancers, but difficult to diagnose and treat. L-asparaginase has been introduced in the treatment protocol of pediatric acute lymphoblastic leukemia (ALL) since the 1960s with a good outcome and increased survival rates to nearly 90%. Moreover, it has been found to have therapeutic potential in solid tumors. Production of glutaminase-free-L-asparaginase is of interest to avoid glutaminase-related toxicity and hypersensitivity. In the current study, an extracellular L-asparaginase that is free of L-glutaminase was purified from the culture filtrate of an endophytic fungus Trichoderma viride. The cytotoxic effect of the purified enzyme was evaluated in vitro against a panel of human tumor cell lines and in vivo against male Wister albino mice intraperitoneally injected with diethyl nitrosamine (200 mg/kg bw), followed by (after 2 weeks) oral administration of carbon tetrachloride (2 mL/kg bw). This dose was repeated for 2 months, and after that, the blood samples were collected to estimate hepatic and renal injury markers, lipid profiles, and oxidative stress parameters.

RESULTS

L-asparaginase was purified from T. viride culture filtrate with 36 purification folds, 688.1 U/mg specific activity, and 38.9% yield. The highest antiproliferative activity of the purified enzyme was observed against the hepatocellular carcinoma (Hep-G2) cell line, with an IC₅₀ of 21.2 g/mL, which was higher than that observed for MCF-7 (IC₅₀ 34.2 g/mL). Comparing the DENA-intoxicated group to the negative control group, it can be demonstrated that L-asparaginase adjusted the levels of the liver function enzymes and the hepatic injury markers that had previously changed with DENA intoxication. DENA causes kidney dysfunction and altered serum albumin and creatinine levels as well. Administration of L-asparaginase was found to improve the levels of the tested biomarkers including kidney and liver function tests. L-asparaginase treatment of the DENA-intoxicated group resulted in a significant improvement in the liver and kidney tissues to near normal similar to the healthy control group.

CONCLUSION

The results suggest that this purified T. viride L-asparaginase may be able to delay the development of liver cancer and may be used as a potential candidate for future application in medicine as an anticancer medication.

Characterization of hepatic fatty acids using magnetic resonance spectroscopy for the assessment of treatment response to metformin in an eNOS-/- mouse model of metabolic nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide. Liver biopsy remains the gold standard for diagnosis and staging of disease. There is a clinical need for noninvasive diagnostic tools for risk stratification, follow-up, and monitoring treatment response that are currently lacking, as well as preclinical models that recapitulate the etiology of the human condition. We have characterized the progression of NAFLD in eNOS^-/- mice fed a high fat diet (HFD) using noninvasive Dixon-based magnetic resonance imaging and single voxel STEAM spectroscopy-based protocols to measure liver fat fraction at 3 T. After 8 weeks of diet intervention, eNOS^-/- mice exhibited significant accumulation of intra-abdominal and liver fat compared with control mice. Liver fat fraction measured by ¹ H-MRS in vivo showed a good correlation with the NAFLD activity score measured by histology. Treatment of HFD-fed NOS3^-/- mice with metformin showed significantly reduced liver fat fraction and altered hepatic lipidomic profile compared with untreated mice. Our results show the potential of in vivo liver MRI and ¹ H-MRS to noninvasively diagnose and stage the progression of NAFLD and to monitor treatment response in an eNOS^-/- murine model that represents the classic NAFLD phenotype associated with metabolic syndrome.

Extraction, characterization, and anti-nonalcoholic steatohepatitis activity of a (1,3) (1,6)-β-D-glucan from the Polyporus umbellatus (Pers.) Fries

Nonalcoholic steatohepatitis (NASH) is a chronic liver disease characterized by inflammation and hepatic steatosis that may coincide with fibrotic activity. To date, no pharmacological agents have been approved for NASH treatment. Here, a homogeneous (1,3),(1,6)-β-D-glucan (PUP-W-1, Mw: 41.07 kDa) was successfully purified from Polyporus umbellatus (Pers.) Fries sclerotia and characterized. The analysis showed that the PUP-W-1 backbone consisted of a repeating chain of eight →3)-β-D-Glcp-(1 → units, with branched chains of four β-D-Glcp residues, joined by repeating 1,6-linkage units at the O-6 position of the backbone. The pharmacological effects of PUP-W-1 treatment in the context of NASH pathogenesis were explored using a methionine choline-deficient (MCD) diet-induced murine steatohepatitis model. The MCD model mice exhibited pronounced steatohepatitis, inflammatory activity, steatosis, stellate cell activation, and mild fibrotic activity. Treatment of the mice for three weeks with PUP-W-1 prevented the development of NASH due to the suppression of inflammation, lipid accumulation, and fibrosis. As suggested by these findings, PUP-W-1 may hold promise as a natural drug candidate or precursor for the treatment of NASH.

Myeloperoxidase-Sensitive T1 and T2 Switchable MR Imaging for Diagnosis of Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is the critical stage in the development of nonalcoholic fatty liver disease (NAFLD) from simple and reversible steatosis to irreversible cirrhosis and even hepatocellular carcinoma (HCC). Thus, the diagnosis of NASH is important for preventing the progress of NAFLD into a fatal condition. The oxidative enzyme myeloperoxidase (MPO), which is mostly produced by polymorphonuclear neutrophil granulocytes (NEU), has been identified as a key player in lipid peroxidation in inflamed tissues. Considering that the expression of MPO was much higher in NASH than in the nonalcoholic fatty liver (NAFL) with steatosis, we designed a nanoparticle platform based on ultrasmall iron oxide (USIO) nanoparticles to realize MPO-sensitive NASH diagnosis. After modification of USIO nanoparticles with amphiphilic poly(ethylene glycol) (PEG) and conjugation with 5-hydroxytryptamine (5HT), a physiological substrate for MPO, the final nanocomposite (USIO-DA-PEG-5HT) revealed MPO-mediated aggregation at the inflammatory site of NASH. Meanwhile, the intrinsic T₁-weighted magnetic resonance (MR) signal of dispersed USIO-DA-PEG-5HT nanoparticles diminishes, while the T₂-weighted MR signal is amplified owing to the aggregation effect. These USIO-DA-PEG-5HT nanoprobes offer great potential for improving NASH MR imaging diagnostic accuracy and sensitivity compared to existing molecular MR contrast agents with a single imaging modality.

Exploring the active compounds and potential mechanism of the anti-nonalcoholic fatty liver disease activity of the fraction from Schisandra chinensis fruit extract based on multi-technology integrated network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra chinensis fruit is a well-known traditional Chinese medicine (TCM) that has been used to treat various liver diseases. Our previous study revealed that its extract is effective against nonalcoholic fatty liver disease (NAFLD).

AIM OF THIS STUDY

This study aimed to elucidate the active components and explore the underlying mechanisms of action of S. chinensis fruit in the treatment of NAFLD.

MATERIALS AND METHODS

A HepG2 cell model was used to screen the anti-NAFLD activity of the fraction from S. chinensis fruit extract. Ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) was used to determine the components of the active fraction. Active compounds, potential targets, and key pathways were predicted for the active fraction treatment of NAFLD using network pharmacology. The anti-NAFLD effects of the active fraction and core active compound 3 were further validated using a high-fat diet (HFD)-induced NAFLD mouse model, intraperitoneal glucose tolerance test (IPGTT), and intraperitoneal insulin tolerance test (IPITT). Related hepatic mRNA expression was detected using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to preliminarily validate the mechanism.

RESULTS

In vitro experiments showed that the active fraction of S. chinensis fruit ethanol (EtOH) extract was mainly concentrated in the soluble fraction of petroleum ether (PET). Thirty-seven lignans were identified in this active fraction using UPLC-Q-TOF/MS. Network pharmacology studies have indicated that its anti-NAFLD effects lie in three major active lignans (3, 24, and 27) contained in PET, which may regulate the insulin resistance signaling pathway. In vivo experiments demonstrated that PET and core active compound 3 treatment significantly attenuated hepatic steatosis and reduced the levels of serum alanine transaminase (ALT), aspartate transaminase (AST), insulin, malondialdehyde (MDA), hepatic triglyceride (TG), and total cholesterol (TC) in HFD-induced mice (P < 0.05). Moreover, treatment with PET and compound 3 alleviated glucose tolerance and insulin resistance. These beneficial effects can be achieved by regulating the expression of Pik3ca, Gsk3β, Jnk1, and Tnf-α.

CONCLUSION

This study identified the main active fraction and compounds responsible for the anti-NAFLD activity of S. chinensis fruit. This mechanism may be related to regulation of the resistance pathway.

Diethyldithiocarbamate inhibits the activation of hepatic stellate cells via PPARα/FABP1 in mice with non-alcoholic steatohepatitis

Activation of hepatic stellate cells (HSCs) is the main course of liver fibrosis which is positively correlated with adverse clinical outcomes in non-alcoholic steatohepatitis (NASH). Diethyldithiocarbamate (DDC) attenuates NASH related liver fibrosis in mice, but its underlying mechanisms remains unclear. In this study, the data showed that DDC inhibited the activation of HSCs in high fat choline-deficient, L-amino acid-defined (CDAA) diet induced NASH. Double Immunofluorescence analysis showed that the baseline expression of peroxisome proliferator-activated receptor α (PPARα) is high in HSCs in normal mouse liver and notably decreases in the NASH liver, indicating that PPARα might be associated with the activation of HSCs. While, DDC upregulated PPARα in HSCs in the NASH liver. Mixture of free fatty acid was used to induce steatosis of hepatocytes. Human HSCs (LX-2 cells) were activated after co-cultured with steatotic hepatocytes, and DDC inhibited the activation of LX-2 cells. Meanwhile, DDC upregulated PPARα and FABP1, and promoted the accumulation of LDs in LX-2 cells. PPARα small interfering RNA blocked these effect of DDC. These findings suggest that PPARα is associated with the activation of HSCs in the context of NASH. DDC improves NASH related fibrosis through inhibiting the activation of HSCs via PPARα/FABP1.

IL-1β neutralization prevents diastolic dysfunction development, but lacks hepatoprotective effect in an aged mouse model of NASH

Interleukin-1β (IL-1β) is a key mediator of non-alcoholic steatohepatitis (NASH), a chronic liver disease, and of systemic inflammation-driven aging. IL-1β contributes to cardio-metabolic decline, and may promote hepatic oncogenic transformation. Therefore, IL-1β is a potential therapeutic target in these pathologies. We aimed to investigate the hepatic and cardiac effects of an IL-1β targeting monoclonal antibody in an aged mouse model of NASH. 24 months old male C57Bl/6J mice were fed with control or choline deficient (CDAA) diet and were treated with isotype control or anti-IL-1β Mab for 8 weeks. Cardiac functions were assessed by conventional-and 2D speckle tracking echocardiography. Liver samples were analyzed by immunohistochemistry and qRT-PCR. Echocardiography revealed improved cardiac diastolic function in anti-IL-1β treated mice with NASH. Marked hepatic fibrosis developed in CDAA-fed group, but IL-1β inhibition affected fibrosis only at transcriptomic level. Hepatic inflammation was not affected by the IL-1β inhibitor. PCNA staining revealed intensive hepatocyte proliferation in CDAA-fed animals, which was not influenced by neutralization of IL-1β. IL-1β inhibition increased hepatic expression of Pd-1 and Ctla4, while Pd-l1 expression increased in NASH. In conclusion, IL-1β inhibition improved cardiac diastolic function, but did not ameliorate features of NASH; moreover, even promoted hepatic immune checkpoint expression, with concomitant NASH-related hepatocellular proliferation.

P38γ modulates the lipid metabolism in non-alcoholic fatty liver disease by regulating the JAK-STAT signaling pathway

Non-alcoholic fatty liver disease (NAFLD) is a major health problem in Western countries and has become the most common cause of chronic liver disease. Although NAFLD is closely associated with obesity, inflammation, and insulin resistance, its pathogenesis remains unclear. The disease begins with excessive accumulation of triglycerides in the liver, which in turn leads to liver cell damage, steatosis, inflammation, and so on. P38γ is one of the four isoforms of P38 mitogen-activated protein kinases (P38 MAPKs) that contributes to inflammation in different diseases. In this research, we investigated the role of P38γ in NAFLD. In vivo, a NAFLD model was established by feeding C57BL/6J mice with a methionine- and choline-deficient (MCD) diet and adeno-associated virus (AAV9-shRNA-P38γ) was injected into C57BL/6J mice by tail vein for knockdown P38γ. The results indicated that the expression level of P38γ was upregulated in MCD-fed mice. Furthermore, the downregulation of P38γ significantly attenuated liver injury and lipid accumulation in mice. In vitro, mouse hepatocytes AML-12 were treated with free fatty acid (FFA). We found that P38γ was obviously increased in FFA-treated AML-12 cells, whereas knockdown of P38γ significantly suppressed lipid accumulation in FFA-treated AML-12 cells. Furthermore, P38γ regulated the Janus Kinase-Signal transducers and activators of transcription (JAK-STAT) signaling pathway. Inhibition of P38γ can inhibit the JAK-STAT signaling pathway, thereby inhibiting lipid accumulation in FFA-treated AML-12 cells. In conclusion, our results suggest that targeting P38γ contributes to the suppression of lipid accumulation in fatty liver disease.

Gut microbiota modulation in patients with non-alcoholic fatty liver disease: Effects of current treatments and future strategies

Non-alcoholic fatty liver disease (NAFLD) is frequently associated with metabolic disorders, being highly prevalent in obese and diabetic patients. Many concomitant factors that promote systemic and liver inflammation are involved in NAFLD pathogenesis, with a growing body of evidence highlighting the key role of the gut microbiota. Indeed, the gut-liver axis has a strong impact in the promotion of NAFLD and in the progression of the wide spectrum of its manifestations, claiming efforts to find effective strategies for gut microbiota modulation. Diet is among the most powerful tools; Western diet negatively affects intestinal permeability and the gut microbiota composition and function, selecting pathobionts, whereas Mediterranean diet fosters health-promoting bacteria, with a favorable impact on lipid and glucose metabolism and liver inflammation. Antibiotics and probiotics have been used to improve NAFLD features, with mixed results. More interestingly, medications used to treat NAFLD-associated comorbidities may also modulate the gut microbiota. Drugs for the treatment of type 2 diabetes mellitus (T2DM), such as metformin, glucagon-like peptide-1 (GLP-1) agonists, and sodium-glucose cotransporter (SGLT) inhibitors, are not only effective in the regulation of glucose homeostasis, but also in the reduction of liver fat content and inflammation, and they are associated with a shift in the gut microbiota composition towards a healthy phenotype. Even bariatric surgery significantly changes the gut microbiota, mostly due to the modification of the gastrointestinal anatomy, with a parallel improvement in histological features of NAFLD. Other options with promising effects in reprogramming the gut-liver axis, such as fecal microbial transplantation (FMT) and next-generation probiotics deserve further investigation for future inclusion in the therapeutic armamentarium of NAFLD.

Effect of apple vinegar on folliculogenesis and ovarian kisspeptin in a high-fat diet-induced nonalcoholic fatty liver disease in rat

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) adversely affects reproduction. We aimed to study the effect of a high-fat diet (HFD), supplemented with apple vinegar, on folliculogenesis in a rat model of NAFLD.

METHODS

Female rats were randomly divided into four groups (N = 28): Standard diet (SD), SD + vinegar, HFD, and HFD + vinegar groups. At the end of the study, biochemical tests were assessed in serum. HOMA-IR (Homeostatic model assessment-Insulin resistance) was calculated. Sex hormones were determined using an ELISA kit; ovary follicle counts were studied using histological methods. The proliferation index of granulosa cells was determined using immunohistochemistry. Kisspeptin expression in the ovary was detected using RT-PCR.

RESULTS

The HFD induced steatohepatitis and NAFLD. The ovaries in the rat model of NAFLD were atrophied. The ovaries had less count of developing follicles and corpus luteum, and more degenerated and cystic follicles in comparison with the SD group. Vinegar + HFD consumption decreased ALT, compared to the HFD group (P = 0.004). Steatohepatitis was reduced in the Vinegar + HFD group (P = 0.001). Vinegar + HFD considerably reduced HOMA-IR (p = 0.01). The HFD + vinegar diet could increase estradiol (P = 0.001), without significantly affecting progesterone or testosterone. In addition, an increase of primordial follicles as an ovarian reserve and also primary follicles were determined in the HFD + vinegar group. There were no statistical differences in the granulosa cell proliferation index in various follicle types between groups. HFD + vinegar significantly enhanced ovarian kisspeptin expression (p = 0.04).

CONCLUSIONS

The vinegar diet in a rat model of NAFLD raises estradiol, primordial, and small primary follicles, and increases ovarian kisspeptin expression indirectly. Insulin resistance and obesity were improved by apple vinegar, and anti-glycemic and anti-lipidemic effects were also determined. The supplementation of apple vinegar in NAFLD might be useful for ovary. However, it requires further investigation.

Hepatic transcriptome profiling reveals early signatures associated with disease transition from non-alcoholic steatosis to steatohepatitis

Background and aim

Non-alcoholic fatty liver disease (NAFLD) is becoming a leading cause of chronic liver disease worldwide. The molecular events that influence disease progression from non-alcoholic fatty liver (NAFL) to aggressive non-alcoholic steatohepatitis (NASH) remain incompletely understood, leading to lack of mechanism-based targeted treatment options for NASH. This study aims to identify early signatures associated with disease progression from NAFL to NASH in mice and humans.

Materials and methods

Male C57BL/6J mice were fed a high-fat, -cholesterol, and - fructose (HFCF) diet for up to 9 months. The extent of steatosis, inflammation, and fibrosis was evaluated in liver tissues. Total RNA sequencing (RNA-seq) was conducted to determine liver transcriptomic changes.

Results

After being fed the HFCF diet, mice sequentially developed steatosis, early steatohepatitis, steatohepatitis with fibrosis, and eventually spontaneous liver tumor. Hepatic RNA-seq revealed that the key signatures during steatosis progression to early steatohepatitis were pathways related to extracellular matrix organization and immune responses such as T cell migration, arginine biosynthesis, C-type lectin receptor signaling, and cytokine-cytokine receptor interaction. Genes regulated by transcription factors forkhead box M1 (FOXM1) and negative elongation factor complex member E (NELFE) were significantly altered during disease progression. This phenomenon was also observed in patients with NASH.

Conclusions

In summary, we identified early signatures associated with disease progression from NAFL to early NASH in a mouse model that recapitulated key metabolic, histologic, and transcriptomic changes seen in humans. The findings from our study may shed light on the development of novel preventative, diagnostic, and therapeutic strategies for NASH.

Epigenetic aberrations of gene expression in a rat model of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is mostly triggered by environmental and life-style factors and may involve epigenetic aberrations. However, a comprehensive documentation of the link between the dysregulated epigenome, transcriptome, and liver carcinogenesis is lacking. In the present study, Fischer-344 rats were fed a choline-deficient (CDAA, cancer group) or choline-sufficient (CSAA, healthy group) L-amino acid-defined diet. At the end of 52 weeks, transcriptomic alterations in livers of rats with HCC tumours and healthy livers were investigated by RNA sequencing. DNA methylation and gene expression were assessed by pyrosequencing and quantitative reverse-transcription PCR (qRT-PCR), respectively. We discovered 1,848 genes that were significantly differentially expressed in livers of rats with HCC tumours (CDAA) as compared with healthy livers (CSAA). Upregulated genes in the CDAA group were associated with cancer-related functions, whereas macronutrient metabolic processes were enriched by downregulated genes. Changes of highest magnitude were detected in numerous upregulated genes that govern key oncogenic signalling pathways, including Notch, Wnt, Hedgehog, and extracellular matrix degradation. We further detected perturbations in DNA methylating and demethylating enzymes, which was reflected in decreased global DNA methylation and increased global DNA hydroxymethylation. Four selected upregulated candidates, Mmp12, Jag1, Wnt4, and Smo, demonstrated promoter hypomethylation with the most profound decrease in Mmp12. MMP12 was also strongly overexpressed and hypomethylated in human HCC HepG2 cells as compared with primary hepatocytes, which coincided with binding of Ten-eleven translocation 1 (TET1). Our findings provide comprehensive evidence for gene expression changes and dysregulated epigenome in HCC pathogenesis, potentially revealing novel targets for HCC prevention/treatment.

One Carbon Metabolism and S-Adenosylmethionine in Non-Alcoholic Fatty Liver Disease Pathogenesis and Subtypes

One carbon metabolism (1CM) can be defined as the transfer of a carbon unit from one metabolite to another and its replenishment by different sources of labile methyl-group nutrients: primarily choline, methionine, betaine, and serine. This flow of carbon units allows the biosynthesis of nucleotides, amino acids, formylated methionyl-tRNA, polyamines, glutathione, phospholipids, detoxification reactions, maintenance of the redox status and the concentration of NAD, and methylation reactions including epigenetic modifications. That is, 1CM functions as a nutrient sensor and integrator of cellular metabolism. A critical process in 1CM is the synthesis of S-adenosylmethionine (SAMe), the source of essentially all the hundreds of millions of daily methyl transfer reactions in a cell. This versatility of SAMe imposes a tight control in its synthesis and catabolism. Much of our knowledge concerning 1CM has been gained from studies in the production and prevention of nonalcoholic fatty liver disease (NAFLD). Here, we discuss in detail the function of the most important enzymes for their quantitative contribution to maintaining the flux of carbon units through 1CM in the liver and discuss how alterations in their enzymatic activity contribute to the development of NAFLD. Next, we discuss NAFLD subtypes based on serum lipidomic profiles with different risk of cardiovascular disease. Among the latter, we highlight the so-called subtype A for its serum lipidomic profile phenocopying that of mice deficient in SAMe synthesis and because its high frequency (about 50% of the NAFLD patients).

A non-mitogenic FGF4 analog alleviates non-alcoholic steatohepatitis through an AMPK-dependent pathway

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) has emerged as a major liver disease increasingly in association with non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma (HCC). However, there are currently no approved therapies for treating NAFLD and NASH. Fibroblast growth factor 4 (FGF4) has recently been shown as a promising drug candidate for several metabolic diseases.

METHODS

Mice fed a high-fat diet with high fructose/glucose drinking water (HF/HFG, Western-like diet) for 21 weeks were intraperitoneally injected with non-mitogenic recombinant FGF4^△NT (rFGF4^△NT, 1.0 mg/kg body weight) every other day for 8 weeks. Primary mouse hepatocytes cultured in medium containing high glucose/palmitic acid (HG/PA) or TNFα/cyclohexane (TNFα/CHX) were treated with 1.0 μg/ml rFGF4^△NT. Changes in parameters for histopathology, lipid metabolism, inflammation, hepatocellular apoptosis and fibrosis were determined. The Caspase6 activity and AMPK pathway were assessed.

RESULTS

Administration of rFGF4^△NT significantly attenuated the Western-like diet-induced hepatic steatosis, inflammation, liver injury and fibrosis in mice. rFGF4^△NT treatment reduced fatty acid-induced lipid accumulation and lipotoxicity-induced hepatocyte apoptosis, which were associated with inhibition of Caspase6 cleavage and activation. Inhibition of AMP-activated protein kinase (AMPK) by Compound C or deficiency of Ampk abrogated rFGF4^△NT-induced hepatoprotection in primary hepatocytes and in mice with NASH.

CONCLUSION

rFGF4^△NT exerts significant protective effects on NASH via an AMPK-dependent signaling pathway. Our study indicates that FGF4 analogs may have therapeutic potential for the Western-like diet induced NASH.

Mitochondrial stress induces AREG expression and epigenomic remodeling through c-JUN and YAP-mediated enhancer activation

Nucleus–mitochondria crosstalk is essential for cellular and organismal homeostasis. Although anterograde (nucleus-to-mitochondria) pathways have been well characterized, retrograde (mitochondria-to-nucleus) pathways remain to be clarified. Here, we found that mitochondrial dysfunction triggered a retrograde signaling via unique transcriptional and chromatin factors in hepatic cells. Our transcriptomic analysis revealed that the loss of mitochondrial transcription factor A led to mitochondrial dysfunction and dramatically induced expression of amphiregulin (AREG) and other secretory protein genes. AREG expression was also induced by various mitochondria stressors and was upregulated in murine liver injury models, suggesting that AREG expression is a hallmark of mitochondrial damage. Using epigenomic and informatic approaches, we identified that mitochondrial dysfunction-responsive enhancers of AREG gene were activated by c-JUN/YAP1/TEAD axis and were repressed by chromatin remodeler BRG1. Furthermore, while mitochondrial dysfunction-activated enhancers were enriched with JUN and TEAD binding motifs, the repressed enhancers possessed the binding motifs for hepatocyte nuclear factor 4α, suggesting that both stress responsible and cell type-specific enhancers were reprogrammed. Our study revealed that c-JUN and YAP1-mediated enhancer activation shapes the mitochondrial stress-responsive phenotype, which may shift from metabolism to stress adaptation including protein secretion under such stressed conditions.

Age-Related NAFLD: The Use of Probiotics as a Supportive Therapeutic Intervention

Human aging, a natural process characterized by structural and physiological changes, leads to alterations of homeostatic mechanisms, decline of biological functions, and subsequently, the organism becomes vulnerable to external stress or damage. In fact, the elderly population is prone to develop diseases due to deterioration of physiological and biological systems. With aging, the production of reactive oxygen species (ROS) increases, and this causes lipid, protein, and DNA damage, leading to cellular dysfunction and altered cellular processes. Indeed, oxidative stress plays a key role in the pathogenesis of several chronic disorders, including hepatic diseases, such as non-alcoholic fatty liver disease (NAFLD). NAFLD, the most common liver disorder in the Western world, is characterized by intrahepatic lipid accumulation; is highly prevalent in the aging population; and is closely associated with obesity, insulin resistance, hypertension, and dyslipidemia. Among the risk factors involved in the pathogenesis of NAFLD, the dysbiotic gut microbiota plays an essential role, leading to low-grade chronic inflammation, oxidative stress, and production of various toxic metabolites. The intestinal microbiota is a dynamic ecosystem of microbes involved in the maintenance of physiological homeostasis; the alteration of its composition and function, during aging, is implicated in different liver diseases. Therefore, gut microbiota restoration might be a complementary approach for treating NAFLD. The administration of probiotics, which can relieve oxidative stress and elicit several anti-aging properties, could be a strategy to modify the composition and restore a healthy gut microbiota. Indeed, probiotics could represent a valid supplement to prevent and/or help treating some diseases, such as NAFLD, thus improving the already available pharmacological intervention. Moreover, in aging, intervention of prebiotics and fecal microbiota transplantation, as well as probiotics, will provide novel therapeutic approaches. However, the relevant research is limited, and several scientific research works need to be done in the near future to confirm their efficacy.

The potential of mecciRNA in hepatic stellate cell to regulate progression of nonalcoholic hepatitis

BACKGROUND

Nonalcoholic steatohepatitis (NASH) occupies a substantial proportion of chronic liver disease worldwide, of which pathogenesis needs further research. Recent studies have demonstrated the significant roles of circular RNAs (circRNAs) in NASH, while the function of a novel type of circRNAs, namely mitochondria-encoded circRNAs (mecciRNAs), remains elusive. Therefore, we aimed to investigate their potential to regulate the progression of NASH in this study.

METHODS

GSE134146 was used to screen for differentially expressed mecciRNAs in NASH, while GSE46300 was used to identify NASH-related genes. To establish the mecciRNA-miRNA-mRNA networks, circMINE and miRNet databases were used for predicting downstream targets. Then, consensus clustering analysis was used to determine immune subtypes of NASH. Finally, we successfully validated our findings in vitro (LPS-treated hepatic stellate cells [HSCs]) and in vivo (MCD-diet mice) NASH models.

RESULTS

We confirmed that circRNomics balance is disrupted in HSCs of NASH, while two mecciRNAs (hsa_circ_0089761 and hsa_circ_0089763) could function as competing for endogenous RNAs (ceRNAs) to regulate fibrosis-related signals. Furthermore, we constructed two ceRNA networks based on mecciRNAs for the first time. Cell and animal NASH models validated our findings that c-MYC and SMAD2/3 were upregulated in HSCs, while THBS1 and p-STAT3 were upregulated in hepatocytes. Moreover, we identified 21 core genes by overlapping the differentially expressed genes (NASH vs. Normal) with mecciRNA-targeted genes. According to their expression profiles, NASH patients could be divided in 2 different clusters, in which proinflammatory signals (TNF and IL-17 pathways) are significantly activated in Cluster 1.

CONCLUSION

We successfully established two novel mecciRNA-miRNA-mRNA networks in HSCs and hepatocytes, which were further confirmed by in vitro and in vivo models. Meanwhile, the novel immunotyping model revealed the heterogeneity of NASH, thereby might guiding treatment options. Altogether, our study brought a distinct perspective on the relationship between mecciRNAs and NASH.

The Effects of Probiotics, Prebiotics and Synbiotics in Non-Alcoholic Fat Liver Disease (NAFLD) and Non-Alcoholic Steatohepatitis (NASH): A Systematic Review

Modifications in the microbiota caused by environmental and genetic reasons can unbalance the intestinal homeostasis, deregulating the host's metabolism and immune system, intensifying the risk factors for the development and aggravation of non-alcoholic fat liver disease (NAFLD). The use of probiotics, prebiotics and synbiotics have been considered a potential and promising strategy to regulate the gut microbiota and produce beneficial effects in patients with liver conditions. For this reason, this review aimed to evaluate the effectiveness of probiotics, prebiotics, and symbiotics in patients with NAFLD and NASH. Pubmed, Embase, and Cochrane databases were consulted, and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines were followed. The clinical trials used in this study demonstrated that gut microbiota interventions could improve a wide range of markers of inflammation, glycemia, insulin resistance, dyslipidemia, obesity, liver injury (decrease of hepatic enzymes and steatosis and fibrosis). Although microbiota modulators do not play a healing role, they can work as an important adjunct therapy in pathological processes involving NAFLD and its spectrums, either by improving the intestinal barrier or by preventing the formation of toxic metabolites for the liver or by acting on the immune system.

Mouse model of NASH that replicates key features of the human disease and progresses to fibrosis stage 3

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the United States and the world; with no Food and Drug Administration-approved pharmacological treatment available, it remains an area of unmet medical need. In nonalcoholic steatohepatitis (NASH), the most important predictor of clinical outcome is the fibrosis stage. Moreover, the Food and Drug Administration recommends that clinical trials for drugs to treat this disease include patients with fibrosis stage 2 or greater. Therefore, when using animal models for investigating the pathophysiology of NAFLD and for the preclinical evaluation of new drugs, it is important that the animals develop substantial fibrosis. The aim of this study was to develop a mouse model of NAFLD that replicated the disease in humans, including obesity and progressive liver fibrosis. Agouti yellow mutant mice, which have hyperphagia, were fed a Western diet and water containing high-fructose corn syrup for 16 weeks. Mice became obese and developed glucose intolerance. Their gut microbiota showed dysbiosis with changes that replicate some of the changes described in humans with NASH. They developed NASH with activity scores of 5-6 and fibrosis, which was stage 1 after 16 weeks, and stage 3 after 12 months. Changes in liver gene expression assessed by gene-set enrichment analysis showed 90% similarity with changes in human patients with NASH. Conclusion: Ay mice, when fed a Western diet similar to that consumed by humans, develop obesity and NASH with liver histology, including fibrosis, and gene expression changes that are highly similar to the disease in humans.

Celecoxib attenuates hepatosteatosis by impairing de novo lipogenesis via Akt-dependent lipogenic pathway

Mounting evidence indicates that hepatic de novo lipogenesis is a common abnormality in non-alcoholic fatty liver disease (NAFLD) patients. We investigated whether a selective COX-2 inhibitor, celecoxib, alleviates hepatic steatosis by targeting an Akt-driven lipogenic pathway. We estimated the efficacy of celecoxib in a novel Akt-driven NAFLD mouse model established via hydrodynamic transfection of activated forms of AKT and in fructose-fed NAFLD mice that exhibited increased insulin-independent hepatic lipogenesis. AKT-transfected and insulin-stimulated human hepatoma cells were used for the in vitro experiments. Haematoxylin and eosin staining, immunohistochemistry and immunoblotting were performed for mechanistic studies. The results revealed that celecoxib ameliorated hepatic steatosis in the AKT-triggered NAFLD mice. Mechanistically, celecoxib effectively suppressed AKT/mTORC1 signalling and its downstream lipogenic cascade in the Akt-driven NAFLD mice and in vitro. Furthermore, celecoxib had limited efficacy in alleviating hepatic lipid accumulation and showed no influence on lipogenic proteins associated with hepatic lipogenesis in fructose-administered mice. This study suggests that celecoxib may be favourable for the treatment of NAFLD, especially in the subset with Akt-triggered hepatic lipogenesis.

Mitochondrial Dysfunction Plays Central Role in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a global pandemic that affects one-quarter of the world’s population. NAFLD includes a spectrum of progressive liver disease from steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis and can be complicated by hepatocellular carcinoma. It is strongly associated with metabolic syndromes, obesity, and type 2 diabetes, and it has been shown that metabolic dysregulation is central to its pathogenesis. Recently, it has been suggested that metabolic- (dysfunction) associated fatty liver disease (MAFLD) is a more appropriate term to describe the disease than NAFLD, which puts increased emphasis on the important role of metabolic dysfunction in its pathogenesis. There is strong evidence that mitochondrial dysfunction plays a significant role in the development and progression of NAFLD. Impaired mitochondrial fatty acid oxidation and, more recently, a reduction in mitochondrial quality, have been suggested to play a major role in NAFLD development and progression. In this review, we provide an overview of our current understanding of NAFLD and highlight how mitochondrial dysfunction contributes to its pathogenesis in both animal models and human subjects. Further we discuss evidence that the modification of mitochondrial function modulates NAFLD and that targeting mitochondria is a promising new avenue for drug development to treat NAFLD/NASH.