High-fructose, medium chain trans fat diet induces liver fibrosis and elevates plasma coenzyme Q9 in a novel murine model of obesity and nonalcoholic steatohepatitis

Progress in the Study of Animal Models of Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) has recently been proposed as an alternative term to NAFLD. MASLD is a globally recognized chronic liver disease that poses significant health concerns and is frequently associated with obesity, insulin resistance, and hyperlipidemia. To better understand its pathogenesis and to develop effective treatments, it is essential to establish suitable animal models. Therefore, attempts have been made to establish modelling approaches that are highly similar to human diet, physiology, and pathology to better replicate disease progression. Here, we reviewed the pathogenesis of MASLD disease and summarised the used animal models of MASLD in the last 7 years through the PubMed database. In addition, we have summarised the commonly used animal models of MASLD and describe the advantages and disadvantages of various models of MASLD induction, including genetic models, diet, and chemically induced models, to provide directions for research on the pathogenesis and treatment of MASLD.

Partial validation of a six-month high-fat diet and fructose-glucose drink combination as a mouse model of nonalcoholic fatty liver disease

PURPOSE

The need to investigate the pathogenesis and treatment of nonalcoholic fatty liver disease (NAFLD) has led to the development of multiple mouse models. The aim of this study was to validate a fast food diet (FFD) mouse model that is introduced as being close to the human disease.

METHODS

Eight to nine weeks old male and female C57BL/6 J mice were randomly allocated to a FFD group or to a chow diet (CD) group. Every four weeks, mice were weighed, and blood samples were collected for the measurement of glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglycerides (TGs) and total cholesterol. After 25 weeks, mice were sacrificed, and liver tissue was histologically evaluated.

RESULTS

FFD mice gained more weight (p = 0.049) and presented a higher liver-to-body weight ratio (p < 0.001) compared to CD mice. FFD group presented with greater steatosis, hepatocellular ballooning and NAFLD activity score (NAS), whereas lobular inflammation and fibrosis were not significantly different compared to CD. When stratified by sex, NAS was different between FFD and CD groups in both male and female mice. Group by time interaction was significant for weight, ALT and cholesterol, but not for glucose, AST and TGs.

CONCLUSION

FFD mice presented with morphologic and biochemical features of NAFLD and with greater hepatic steatosis, hepatocellular ballooning and NAS, but not lobular inflammation and fibrosis, compared to CD mice. These results only partly validate the FFD mouse model for NAFLD, at least for a 6-month feeding period.

Regulation of Fructose Metabolism in Nonalcoholic Fatty Liver Disease

Elevations in fructose consumption have been reported to contribute significantly to an increased incidence of obesity and metabolic diseases in industrial countries. Mechanistically, a high fructose intake leads to the dysregulation of glucose, triglyceride, and cholesterol metabolism in the liver, and causes elevations in inflammation and drives the progression of nonalcoholic fatty liver disease (NAFLD). A high fructose consumption is considered to be toxic to the body, and there are ongoing measures to develop pharmaceutical therapies targeting fructose metabolism. Although a large amount of work has summarized the effects fructose exposure within the intestine, liver, and kidney, there remains a gap in our knowledge regarding how fructose both indirectly and directly influences immune cell recruitment, activation, and function in metabolic tissues, which are essential to tissue and systemic inflammation. The most recent literature demonstrates that direct fructose exposure regulates oxidative metabolism in macrophages, leading to inflammation. The present review highlights (1) the mechanisms by which fructose metabolism impacts crosstalk between tissues, nonparenchymal cells, microbes, and immune cells; (2) the direct impact of fructose on immune cell metabolism and function; and (3) therapeutic targets of fructose metabolism to treat NAFLD. In addition, the review highlights how fructose disrupts liver tissue homeostasis and identifies new therapeutic targets for treating NAFLD and obesity.

A High-Fat and High-Fructose Diet Exacerbates Liver Dysfunction by Regulating Sirtuins in a Murine Model

Metabolic dysfunction-associated steatotic liver disease (MASLD) is rapidly emerging as the most prevalent chronic liver disease, closely linked to the escalating rates of diabesity. The Western diet's abundance of fat and fructose significantly contributes to MASLD, disrupting hepatic glucose metabolism. We previously demonstrated that a high-fat and high-fructose diet (HFHFD) led to increased body and liver weight compared to the low-fat diet (LFD) group, accompanied by glucose intolerance and liver abnormalities, indicating an intermediate state between fatty liver and liver fibrosis in the HFHFD group. Sirtuins are crucial epigenetic regulators associated with energy homeostasis and play a pivotal role in these hepatic dysregulations. Our investigation revealed that HFHFD significantly decreased Sirt1 and Sirt7 gene and protein expression levels, while other sirtuins remained unchanged. Additionally, glucose 6-phosphatase (G6Pase) gene expression was reduced in the HFHFD group, suggesting a potential pathway contributing to fibrosis progression. Chromatin immunoprecipitation analysis demonstrated a significant increase in histone H3 lysine 18 acetylation within the G6Pase promoter in HFHFD livers, potentially inhibiting G6Pase transcription. In summary, HFHFD may inhibit liver gluconeogenesis, potentially promoting liver fibrosis by regulating Sirt7 expression. This study offers an epigenetic perspective on the detrimental impact of fructose on MASLD progression.

3D culture models to study pathophysiology of steatotic liver disease

Steatotic liver disease (SLD) refers to a spectrum of diseases caused by hepatic lipid accumulation. SLD has emerged as the leading cause of chronic liver disease worldwide. Despite this burden and many years, understanding the pathophysiology of this disease is challenging due to the inaccessibility to human liver specimens. Therefore, cell-based in vitro systems are widely used as models to investigate the pathophysiology of SLD. Culturing hepatic cells in monolayers causes the loss of their hepatocyte-specific phenotype and, consequently, tissue-specific function and architecture. Hence, three-dimensional (3D) culture models allow cells to mimic the in vivo microenvironment and spatial organization of the liver unit. The utilization of 3D in vitro models minimizes the drawbacks of two-dimensional (2D) cultures and aligns with the 3Rs principles to alleviate the number of in vivo experiments. This article provides an overview of liver 3D models highlighting advantages and limitations, and culminates by discussing their applications in pharmaceutical and biomedical research.

Gender Differences in the Impact of a High-Fat, High-Sugar Diet in Skeletal Muscles of Young Female and Male Mice

In the context of the increasing number of obese individuals, a major problem is represented by obesity and malnutrition in children. This condition is mainly ascribable to unbalanced diets characterized by high intakes of fat and sugar. Childhood obesity and malnutrition are not only associated with concurrent pathologies but potentially compromise adult life. Considering the strict correlation among systemic metabolism, obesity, and skeletal muscle health, we wanted to study the impact of juvenile malnutrition on the adult skeletal muscle. To this aim, 3-week-old C56BL/6 female and male mice were fed for 20 weeks on a high-fat. high-sugar diet, and their muscles were subjected to a histological evaluation. MyHCs expression, glycogen content, intramyocellular lipids, mitochondrial activity, and capillary density were analyzed on serial sections to obtain the metabolic profile. Our observations indicate that a high-fat, high-sugar diet alters the metabolic profile of skeletal muscles in a sex-dependent way and induces the increase in type II fibers, mitochondrial activity, and lipid content in males, while reducing the capillary density in females. These data highlight the sex-dependent response to nutrition, calling for the development of specific strategies and for a systematic inclusion of female subjects in basic and applied research in this field.

NADPH oxidase 1 promotes hepatic steatosis in obese mice and is abrogated by augmented skeletal muscle mass

Exercise as a lifestyle modification is a frontline therapy for nonalcoholic fatty liver disease (NAFLD), but how components of exercise attenuate steatosis is unclear. To uncouple the effect of increased muscle mass from weight loss in obesity, myostatin knockout mice were bred on a lean and obese db/db background. Myostatin deletion increases gastrocnemius (Gastrocn.) mass and reduces hepatic steatosis and hepatic sterol regulatory element binding protein 1 (Srebp1) expression in obese mice, with no impact on adiposity or body weight. Interestingly, hypermuscularity reduces hepatic NADPH oxidase 1 (Nox1) expression but not NADPH oxidase 4 (Nox4) in db/db mice. To evaluate a deterministic function of Nox1 on steatosis, Nox1 knockout mice were bred on a lean and db/db background. NOX1 deletion significantly attenuates hepatic oxidant stress, steatosis, and Srebp1 programming in obese mice to parallel hypermuscularity, with no improvement in adiposity, glucose control, or hypertriglyceridemia to suggest off-target effects. Directly assessing the role of NOX1 on SREBP1, insulin (Ins)-mediated SREBP1 expression was significantly increased in either NOX1, NADPH oxidase organizer 1 (NOXO1), and NADPH oxidase activator 1 (NOXA1) or NOX5-transfected HepG2 cells versus ?-galactosidase control virus, indicating superoxide is the key mechanistic agent for the actions of NOX1 on SREBP1. Metabolic Nox1 regulators were evaluated using physiological, genetic, and diet-induced animal models that modulated upstream glucose and insulin signaling, identifying hyperinsulinemia as the key metabolic derangement explaining Nox1-induced steatosis in obesity. GEO data revealed that hepatic NOX1 predicts steatosis in obese humans with biopsy-proven NAFLD. Taken together, these data suggest that hypermuscularity attenuates Srebp1 expression in db/db mice through a NOX1-dependent mechanism.NEW & NOTEWORTHY This study documents a novel mechanism by which changes in body composition, notably increased muscle mass, protect against fatty liver disease. This mechanism involves NADPH oxidase 1 (NOX1), an enzyme that increases superoxide and increases insulin signaling, leading to increased fat accumulation in the liver. NOX1 may represent a new early target for preventing fatty liver to stave off later liver diseases such as cirrhosis or liver cancer.

Influence of dietary sodium taurocholate on the growth performance and liver health of Nile tilapia (Oreochromis niloticus)

Bile acids (BAs) are a class of cholesterol-derived amphipathic molecules approved as new animal feed additives. However, the functional researches mainly focused on BAs mixture, and the influence of the individual BA on fishes was still limited. In the present study, Nile tilapia were fed basal diet with three levels of sodium taurocholate at 0 mg/kg (CON), 300 mg/kg (TCAL), and 600 mg/kg (TCAH) for 8 weeks. The results indicated that addition of sodium taurocholate did not significantly influence the growth performance. Instead, TCAH group had higher cholesterol accumulation with liver fibrosis. In TCAH group, the level of nuclear factor E2-related factor 2 (nrf2) signaling-associated oxidative stress factors significantly increased in the liver. Additionally, fish in TCAH group had the highest expression level of genes encoding endoplasmic reticulum (ER) stress and inflammatory cytokines in the liver. In conclusion, 300 mg/kg of sodium taurocholate did not significantly influence the growth performance of fish, while 600 mg/kg of sodium taurocholate markedly induced cholesterol accumulation and liver injury, suggesting that the application of taurocholic acid in aquafeed should be re-evaluated.

Food Insecurity and Pediatric Nonalcoholic Fatty Liver Disease Severity

OBJECTIVE

To determine the association between food insecurity and pediatric nonalcoholic fatty liver disease (NAFLD).

METHODS

Cross-sectional study of patients < 21 years of age with histologically confirmed NAFLD. The Household Food Security Survey Module was administered to determine food insecurity status. Skin lipidomics were performed to explore pathophysiologic mechanisms.

RESULTS

Seventy-three patients with histologically confirmed NAFLD completed the Household Food Security Survey Module. Of these, the majority were male (81%) and non-Hispanic (53%), with a mean age at biopsy of 13 ± 3 years. Food insecurity was seen in 42% (n = 31). Comparison of features between food insecure and food secure subgroups revealed no differences in sex, ethnicity, BMI z-score, aminotransferases, or histologic severity. However, children experiencing food insecurity presented on average 2 years before their food secure counterparts (12.3 ± 3.0 vs 14.4 ± 3.6 years, P = .015). A subset of 31 patients provided skin samples. Skin lipidomics revealed that food insecurity was associated with down-regulated features from the lipoamino acid class of lipids, previously linked to inflammation and adipocyte differentiation.

CONCLUSIONS

Food insecurity is highly prevalent in children with NAFLD and is associated with earlier presentation. Lipidomic analyses suggest a possible pathophysiologic link that warrants further exploration.

Phenotypic and metabolomic characteristics of mouse models of metabolic associated steatohepatitis

BACKGROUND

Metabolic associated steatohepatitis (MASH) is metabolic disease that may progress to cirrhosis and hepatocellular carcinoma. Mouse models of diet-induced MASH, which is characterized by the high levels of fats, sugars, and cholesterol in diets, are commonly used in research. However, mouse models accurately reflecting the progression of MASH in humans remain to be established. Studies have explored the potential use of serological metabolites as biomarkers of MASH severity in relation to human MASH.

METHODS

We performed a comparative analysis of three mouse models of diet-induced MASH in terms of phenotypic and metabolomic characteristics; MASH was induced using different diets: a high-fat diet; a Western diet; and a high-fat, high-cholesterol diet. Liver cirrhosis was diagnosed using standard clinical approaches (e.g., METAVIR score, hyaluronan level, and collagen deposition level). Mouse serum samples were subjected to nuclear magnetic resonance spectroscopy-based metabolomic profiling followed by bioinformatic analyses. Metabolomic analysis of a retrospective cohort of patients with hepatocellular carcinoma was performed; the corresponding cirrhosis scores were also evaluated.

RESULTS

Using clinically relevant quantitative diagnostic methods, the severity of MASH was evaluated. Regarding metabolomics, the number of lipoprotein metabolites increased with both diet and MASH progression. Notably, the levels of very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) significantly increased with fibrosis progression. During the development of diet-induced MASH in mice, the strongest upregulation of expression was noted for VLDL receptor. Metabolomic analysis of a retrospective cohort of patients with cirrhosis indicated lipoproteins (e.g., VLDL and LDL) as predominant biomarkers of cirrhosis.

CONCLUSIONS

Our findings provide insight into the pathophysiology and metabolomics of experimental MASH and its relevance to human MASH. The observed upregulation of lipoprotein expression reveals a feedforward mechanism for MASH development that may be targeted for the development of noninvasive diagnosis.

Phocaeicola vulgatus alleviates diet-induced metabolic dysfunction-associated steatotic liver disease progression by downregulating histone acetylation level via 3-HPAA

Diet-induced metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent metabolic disorder with limited effective interventions available. A novel approach to address this issue is through gut microbiota-based therapy. In our study, we utilized multi-omics analysis to identify Phocaeicola vulgatus (P. vulgatus) as a potential probiotic for the treatment of MASLD. Our findings from murine models clearly illustrate that the supplementation of P. vulgatus mitigates the development of MASLD. This beneficial effect is partly attributed to the metabolite 3-Hydroxyphenylacetic acid (3-HPAA) produced by P. vulgatus, which reduces the acetylation levels of H3K27 and downregulates the transcription of Squalene Epoxidase (SQLE), a rate-limiting enzyme in steroid biosynthesis that promotes lipid accumulation in liver cells. This study underscores the significant role of P. vulgatus in the development of MASLD and the critical importance of its metabolite 3-HPAA in regulating lipid homeostasis. These findings offer a promising avenue for early intervention therapy in the context of MASLD.

Sex difference in liver diseases: How preclinical models help to dissect the sex-related mechanisms sustaining NAFLD and hepatocellular carcinoma

Only a few preclinical findings are confirmed in the clinic, posing a critical issue for clinical development. Therefore, identifying the best preclinical models can help to dissect molecular and mechanistic insights into liver disease pathogenesis while being clinically relevant. In this context, the sex relevance of most preclinical models has been only partially considered. This is particularly significant in NAFLD and HCC, which have a higher prevalence in men when compared to pre-menopause women but not to those in post-menopausal status, suggesting a role for sex hormones in the pathogenesis of the diseases. This review gathers the sex-relevant findings and the available preclinical models focusing on both in vitro and in vivo studies and discusses the potential implications and perspectives of introducing the sex effect in the selection of the best preclinical model. This is a critical aspect that would help to tailor personalized therapies based on sex.

Perturbations in lipid metabolism and gut microbiota composition precede cardiac dysfunction in a mouse model of thalassemia

Cardiomyopathy is a major complication of thalassemia, yet the precise underlying molecular mechanisms remain unclear. We examined whether altered lipid metabolism is an early driving factor in the development of cardiomyopathy using the Th3/+ mouse model of thalassemia. At age 20 weeks, male and female Th3/+ mice manifested anemia and iron overload; however, only males displayed metabolic defects and altered cardiac function. Untargeted lipidomics indicated that the circulating levels of 35 lipid species were significantly altered in Th3/+ mice compared to wild-type controls: triglycerides (TGs) with saturated fatty acids (FAs; TG42:0 and TG44:0) were elevated, while TGs with unsaturated FAs (TG(18:2_20:5_18:2 and TG54:8)) were reduced. Similarly, phosphatidylcholines (PCs) with long chain FAs (palmitic (16:0) or oleic (18:1)) were increased, while PCs with polyunsaturated FAs decreased. Circulating PC(16:0_14:0), GlcCer(d18:1/24:0) correlated significantly with iron overload and cardiac hypertrophy. 16S rRNA gene profiling revealed alterations in the intestinal microbiota of Th3/+ mice. Differentially abundant bacterial genera correlated with PC(39:6), PC(18:1_22:6), GlcCer(d18:1/24:1) and CE(14:0). These results provide new knowledge on perturbations in lipid metabolism and the gut microbiota of Th3/+ mice and identify specific factors which may represent early biomarkers or therapeutic targets to prevent development of cardiomyopathy in β-thalassemia.

Lysophosphatidic acid receptor 1 antagonist (EPGN2154) causes regression of NASH in preclinical NASH models

BACKGROUND

NASH causes a tremendous health care burden in the United States. A glucagon-like peptide-1 agonist, semaglutide (Sema), treatment resulted in hepatic steatosis reduction in clinical trials of NASH. Lysophosphatidic acid receptor 1 antagonists are known to have antifibrotic effects in several organs. We tested Sema and a novel lysophosphatidic acid receptor 1 antagonist, EPGN2154, individually and in combination to evaluate their efficacy for NASH remission in preclinical models.

METHODS

In the present study, we used (1) C57Bl6/J wild-type mice fed on a high-fat, high-carbohydrate (HFHC) diet for 16 weeks and (2) leptin-deficient mice (ob/ob) fed on an Amylin liver NASH diet for 16 weeks. After 16 weeks, the mice were randomly distributed in equal numbers in (1) no-drug, (2) EPGN2154, (3) Sema, and (4) EPGN2154+Sema treatment groups for 8 additional weeks at a dosage of 10 mg/kg body weight for EPGN2154 (oral gavage, 5 days a week) and 6.17 μg/kg body weight of Sema (subcutaneous injection every alternate day, 3 days a week).

RESULTS

In the wild-type-high-fat, high-carbohydrate model, we observed the most body weight loss in the EPGN2154+Sema combination group compared to the other treatment groups. All groups led to a significant reduction in alanine transaminase levels when compared to high-fat, high-carbohydrate-fed wild type. However, no significant difference in alanine transaminase levels was observed among the treatment groups. In the ob/ob mice study, Sema did not cause body weight loss. Moreover, the EPGN2154 and the combination groups had a lower NAFLD Activity Score and incidence of advanced-stage hepatic fibrosis than the Sema group.

CONCLUSIONS

EPGN2154 demonstrated a hepato-protective effect independent of body weight loss in preclinical NASH models.

Pyruvate Oxidation Sustains B Cell Antigen-Specific Activation to Exacerbate MASH

B cells play a crucial role in the pathogenesis of metabolic dysfunction-associated steatohepatitis (MASH), a severe form of steatotic liver disease that if persistent can lead to cirrhosis, liver failure, and cancer. Chronic inflammation and fibrosis are key features of MASH that determine disease progression and outcomes. Recent advances have revealed that pathogenic B cell-derived cytokines and antibodies promote the development of MASH. However, the mechanisms through which B cells promote fibrosis and the metabolic adaptations underlying their pathogenic responses remain unclear. Here, we report that a subset of mature B cells with heightened cytokine responses accumulate in the liver and promote inflammation in MASH. To meet the increased energetic demand of effector responses, B cells increase their ATP production via oxidative phosphorylation (OXPHOS) fueled by pyruvate oxidation in a B cell receptor (BCR)-specific manner. Blocking pyruvate oxidation completely abrogated the inflammatory capacity of MASH B cells. Accordingly, the restriction of the BCR led to MASH attenuation, including reductions in steatosis, hepatic inflammation, and fibrosis. Mechanistically, BCR restriction decreased B cell maturation, activation, and effector responses in the liver, accompanied by decreased T cell- and macrophage-mediated inflammation. Notably, attenuated liver fibrosis in BCR-restricted mice was associated with lower IgG production and decreased expression of Fc-gamma receptors on hepatic stellate cells. Together, these findings indicate a key role for B cell antigen-specific responses in promoting steatosis, inflammation, and fibrosis during MASH.

Dysfunctional T Follicular Helper Cells Cause Intestinal and Hepatic Inflammation in NASH

Nonalcoholic steatohepatitis (NASH), characterized by hepatic inflammation and cellular damage, is the most severe form of nonalcoholic fatty liver disease and the fastest-growing indication for a liver transplant. The intestinal immune system is a central modulator of local and systemic inflammation. In particular, Peyer's patches (PPs) contain T follicular helper (Tfh) cells that support germinal center (GC) responses required for the generation of high-affinity intestinal IgA and the maintenance of intestinal homeostasis. However, our understanding of the mechanisms regulating mucosal immunity during the pathogenesis of NASH is incomplete. Here, using a preclinical mouse model that resembles the key features of human disease, we discovered an essential role for Tfh cells in the pathogenesis of NASH. We have found that mice fed a high-fat high-carbohydrate (HFHC) diet have an inflamed intestinal microenvironment, characterized by enlarged PPs with an expansion of Tfh cells. Surprisingly, the Tfh cells in the PPs of NASH mice showed evidence of dysfunction, along with defective GC responses and reduced IgA+ B cells. Tfh-deficient mice fed the HFHC diet showed compromised intestinal permeability, increased hepatic inflammation, and aggravated NASH, suggesting a fundamental role for Tfh cells in maintaining gut-liver homeostasis. Mechanistically, HFHC diet feeding leads to an aberrant increase in the expression of the transcription factor KLF2 in Tfh cells which inhibits its function. Thus, transgenic mice with reduced KLF2 expression in CD4 T cells displayed improved Tfh cell function and ameliorated NASH, including hepatic steatosis, inflammation, and fibrosis after HFHC feeding. Overall, these findings highlight Tfh cells as key intestinal immune cells involved in the regulation of inflammation in the gut-liver axis during NASH.

Reduction in Obesity-Related Hepatic Fibrosis by SR1664

Peroxisome-proliferator-activated receptor gamma (PPARγ) is a transcription factor with adipogenic, insulin-sensitizing, and antifibrotic properties. Strong PPARγ activators, such as the thiazolidinediones, can induce unwanted effects such as edema, weight gain, and bone loss, and therefore selective modulators of PPARγ are in development. We previously reported that one selective PPARγ modulator, SR1664, reduced toxin-induced hepatic fibrosis and the activation of hepatic stellate cells (HSCs), the main collagen-producing liver cell in fibrosis. In this study, we used a high fat and high carbohydrate (HFHC) model of hepatic steatosis and fibrosis to determine the effect of SR1664. Mice were placed on a standard chow or HFHC diet for 16 weeks, with SR1664 or control treatment for the final 4 weeks. SR1664 did not alter weight gain or fasting insulin or glucose levels. The size of lipid droplets in the HFHC group was reduced by SR1664, but there was no effect on total liver triglyceride levels. The degree of fibrosis was significantly reduced by SR1664 in mice on the HFHC diet, and this was accompanied by a decrease in activated HSC. In summary, SR1664 improved insulin sensitivity and reduced fibrosis in the HFHC diet, suggesting selective PPARγ modulation is effective in obesity-related liver fibrosis.

Fructose induced KHK-C can increase ER stress independent of its effect on lipogenesis to drive liver disease in diet-induced and genetic models of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome, and is estimated to affect one billion individuals worldwide. An increased intake of a high-fat diet (HFD) and sugar-sweetened beverages are risk-factors for NAFLD development, but how their combined intake promotes progression to a more severe form of liver injury is unknown. Here we show that fructose metabolism via ketohexokinase (KHK) C isoform leads to unresolved endoplasmic reticulum (ER) stress when coupled with a HFD intake. Conversely, a liver-specific knockdown of KHK in mice consuming fructose on a HFD is adequate to improve the NAFLD activity score and exert a profound effect on the hepatic transcriptome. Overexpression of KHK-C in cultured hepatocytes is sufficient to induce ER stress in fructose free media. Upregulation of KHK-C is also observed in mice with genetically induced obesity or metabolic dysfunction, whereas KHK knockdown in these mice improves metabolic function. Additionally, in over 100 inbred strains of male or female mice hepatic KHK expression correlates positively with adiposity, insulin resistance, and liver triglycerides. Similarly, in 241 human subjects and their controls, hepatic Khk expression is upregulated in early, but not late stages of NAFLD. In summary, we describe a novel role of KHK-C in triggering ER stress, which offers a mechanistic understanding of how the combined intake of fructose and a HFD propagates the development of metabolic complications.

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.

NAFLD-Related HCC: Focus on the Latest Relevant Preclinical Models

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and one of the deadliest cancers worldwide. Despite extensive research, the biological mechanisms underlying HCC's development and progression remain only partially understood. Chronic overeating and/or sedentary-lifestyle-associated obesity, which promote Non-Alcoholic Fatty Liver Disease (NAFLD), have recently emerged as worrying risk factors for HCC. NAFLD is characterized by excessive hepatocellular lipid accumulation (steatosis) and affects one quarter of the world's population. Steatosis progresses in the more severe inflammatory form, Non-Alcoholic Steatohepatitis (NASH), potentially leading to HCC. The incidence of NASH is expected to increase by up to 56% over the next 10 years. Better diagnoses and the establishment of effective treatments for NAFLD and HCC will require improvements in our understanding of the fundamental mechanisms of the disease's development. This review describes the pathogenesis of NAFLD and the mechanisms underlying the transition from NAFL/NASH to HCC. We also discuss a selection of appropriate preclinical models of NAFLD for research, from cellular models such as liver-on-a-chip models to in vivo models, focusing particularly on mouse models of dietary NAFLD-HCC.

In Vivo and In Vitro Models to Study Liver Fibrosis: Mechanisms and Limitations

Liver fibrosis is a common result of liver injury owing to various kinds of chronic liver diseases. A deeper understanding of the pathophysiology of liver fibrosis and identifying potential therapeutic targets of liver fibrosis is important because liver fibrosis may progress to advanced liver diseases, such as cirrhosis and hepatocellular carcinoma. Despite numerous studies, the underlying mechanisms of liver fibrosis remain unclear. Mechanisms of the development and progression of liver fibrosis differ according to etiologies. Therefore, appropriate liver fibrosis models should be selected according to the purpose of the study and the type of underlying disease. Many in vivo animal and in vitro models have been developed to study liver fibrosis. However, there are no perfect preclinical models for liver fibrosis. In this review, we summarize the current in vivo and in vitro models for studying liver fibrosis and highlight emerging in vitro models, including organoids and liver-on-a-chip models. In addition, we discuss the mechanisms and limitations of each model.

A high-trans fat, high-carbohydrate, high-cholesterol, high-cholate diet-induced nonalcoholic steatohepatitis mouse model and its hepatic immune response

Non-alcoholic fatty liver disease (NAFLD) is a chronic progressive disease that can progress to non-alcoholic steatohepatitis (NASH). Animal models are important tools for basic NASH research. Immune activation plays a key role in liver inflammation in patients with NASH. We established a high-trans fat, high-carbohydrate, and high-cholesterol, high-cholate diet-induced (HFHCCC) mouse model. C57BL/6 mice were fed a normal or HFHCCC diet for 24 weeks, and the immune response characteristics of this model were evaluated. The proportion of immune cells in mouse liver tissues was detected by immunohistochemistry and flow cytometry, Multiplex bead immunoassay and Luminex technology was used to detecte the expression of cytokines in mouse liver tissues. The results showed that mice treated with HFHCCC diet exhibited remarkably increased hepatic triglycerides (TG) content, and the increase in plasma transaminases resulted in hepatocyte injury. Biochemical results showed that HFHCCC induced elevated hepatic lipids, blood glucose, insulin; marked hepatocyte steatosis, ballooning, inflammation, and fibrosis. The proportion of innate immunity-related cells, including Kupffer cells (KCs), neutrophils, dendritic cells (DCs), natural killer T cells (NKT), and adaptive immunity-related CD3+ T cells increased; interleukin-1α (IL-1α), IL-1β, IL-2, IL-6, IL-9, and chemokines, including CCL2, CCL3, and macrophage colony stimulating factor (G-CSF) increased. The constructed model closely approximated the characteristics of human NASH and evaluation of its immune response signature, showed that the innate immune response was more pronounced than adaptive immunity. Its use as an experimental tool for understanding innate immune responses in NASH is recommended.

Fructose impairs fat oxidation: Implications for the mechanism of western diet-induced NAFLD

Increased fructose intake from sugar-sweetened beverages and highly processed sweets is a well-recognized risk factor for the development of obesity and its complications. Fructose strongly supports lipogenesis on a normal chow diet by providing both, a substrate for lipid synthesis and activation of lipogenic transcription factors. However, the negative health consequences of dietary sugar are best observed with the concomitant intake of a HFD. Indeed, the most commonly used obesogenic research diets, such as "Western diet", contain both fructose and a high amount of fat. In spite of its common use, how the combined intake of fructose and fat synergistically supports development of metabolic complications is not fully elucidated. Here we present the preponderance of evidence that fructose consumption decreases oxidation of dietary fat in human and animal studies. We provide a detailed review of the mitochondrial β-oxidation pathway. Fructose affects hepatic activation of fatty acyl-CoAs, decreases acylcarnitine production and impairs the carnitine shuttle. Mechanistically, fructose suppresses transcriptional activity of PPARα and its target CPT1α, the rate limiting enzyme of acylcarnitine production. These effects of fructose may be, in part, mediated by protein acetylation. Acetylation of PGC1α, a co-activator of PPARα and acetylation of CPT1α, in part, account for fructose-impaired acylcarnitine production. Interestingly, metabolic effects of fructose in the liver can be largely overcome by carnitine supplementation. In summary, fructose decreases oxidation of dietary fat in the liver, in part, by impairing acylcarnitine production, offering one explanation for the synergistic effects of these nutrients on the development of metabolic complications, such as NAFLD.

Fructooligosaccharides attenuate non-alcoholic fatty liver disease by remodeling gut microbiota and association with lipid metabolism

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a common liver disease highly associated with metabolic diseases and gut dysbiosis. Several clinical trials have confirmed that fructooligosaccharides (FOSs) are a viable alternative treatment for NAFLD. However, the mechanisms underlying the activities of FOSs remain unclear.

METHODS

In this study, the effects of FOSs were investigated with the use of two C57BL/6 J mouse models of NAFLD induced by a high-fat, high-cholesterol (HFHC) diet and a methionine- and choline-deficient (MCD) diet, respectively. The measured metabolic parameters included body, fat, and liver weights; and blood glucose, glucose tolerance, and serum levels of glutamate transaminase, aspartate transaminase, and triglycerides. Liver tissues were collected for histological analysis. In addition, 16 S rRNA sequencing was conducted to investigate the effects of FOSs on the composition of the gut microbiota of mice in the HFHC and MCD groups and treated with FOSs.

RESULTS

FOS treatment attenuated severe metabolic changes and hepatic steatosis caused by the HFHC and MCD diets. In addition, FOSs remodeled the structure of gut microbiota in mice fed the HFHC and MCD diets, as demonstrated by increased abundances of Bacteroidetes (phylum level), Klebsiella variicola, Lactobacillus gasseri, and Clostridium perfringens (species level); and decreased abundances of Verrucomicrobia (phylum level) and the Fissicatena group (genus level). Moreover, the expression levels of genes associated with lipid metabolism and inflammation (i.e., ACC1, PPARγ, CD36, MTTP, APOC3, IL-6, and IL-1β) were down-regulated after FOS treatment.

CONCLUSION

FOSs alleviated the pathological phenotype of NAFLD via remodeling of the gut microbiota composition and decreasing hepatic lipid metabolism, suggesting that FOSs as functional dietary supplements can potentially reduce the risk of NAFLD.

Role of liquid fructose/sucrose in regulating the hepatic transcriptome in a high-fat Western diet model of NAFLD

Nonalcoholic fatty liver disease (NAFLD), which ranges from simple steatosis to nonalcoholic steatohepatitis (NASH), is the most common chronic liver disease. Yet, the molecular mechanisms for the progression of steatosis to NASH remain largely undiscovered. Thus, there is a need for identifying specific gene and pathway changes that drive the progression of NAFLD. This study uses high-fat Western diet (HFWD) together with liquid sugar [fructose and sucrose (F/S)] feeding for 12 weeks in mice to induce obesity and examine hepatic transcriptomic changes that occur in NAFLD progression. The combination of a HFWD+F/S in the drinking water exacerbated HFWD-induced obesity, hyperinsulinemia, hyperglycemia, hepatic steatosis, inflammation, and human and murine fibrosis gene set enrichment that is consistent with progression to NASH. RNAseq analysis revealed differentially expressed genes (DEGs) associated with HFWD and HFWD+F/S dietary treatments compared to Chow-fed mice. However, liquid sugar consumption resulted in a unique set of hepatic DEGs in HFWD+F/S-fed mice, which were enriched in the complement and coagulation cascades using network and biological analysis. Cluster analysis identified Orosomucoid (ORM) as a HFWD+F/S upregulated complement and coagulation cascades gene that was also upregulated in hepatocytes treated with TNFα or free fatty acids in combination with hypoxia. ORM expression was found to correlate with NAFLD parameters in obese mice. Taken together, this study examined key genes, biological processes, and pathway changes in the liver of HFWD+F/S mice in an effort to provide insight into the molecular basis for which the addition of liquid sugar promotes the progression of NAFLD.

Fructose Induced KHK-C Increases ER Stress and Modulates Hepatic Transcriptome to Drive Liver Disease in Diet-Induced and Genetic Models of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome, and is estimated to affect one billion individuals worldwide. An increased intake of a high-fat diet (HFD) and sugar-sweetened beverages are risk-factors for NAFLD development, but how their combined intake promotes progression to a more severe form of liver injury is unknown. Here we show that fructose metabolism via ketohexokinase (KHK) C isoform increases endoplasmic reticulum (ER) stress in a dose dependent fashion, so when fructose is coupled with a HFD intake it leads to unresolved ER stress. Conversely, a liver-specific knockdown of KHK in C57BL/6J male mice consuming fructose on a HFD is adequate to improve the NAFLD activity score and exert a profound effect on the hepatic transcriptome. Overexpression of KHK-C in cultured hepatocytes is sufficient to induce ER stress in fructose free media. Upregulation of KHK-C is also observed in genetically obesity ob/ob, db/db and lipodystrophic FIRKO male mice, whereas KHK knockdown in these mice improves metabolic function. Additionally, in over 100 inbred strains of male or female mice hepatic KHK expression correlates positively with adiposity, insulin resistance, and liver triglycerides. Similarly, in 241 human subjects and their controls, hepatic Khk expression is upregulated in early, but not late stages of NAFLD. In summary, we describe a novel role of KHK-C in triggering ER stress, which offers a mechanistic understanding of how the combined intake of fructose and a HFD propagates the development of metabolic complications.

Tilianin Protects against Nonalcoholic Fatty Liver Disease in Early Obesity Mice

Non-alcoholic fatty liver disease (NAFLD) has emerged as one of the most frequent types of liver disease in pediatric populations with obesity. Tilianin has multiple biological activities including anti-inflammatory and antioxidant. Here, we aim to explore the functions and possible mechanisms of tilianin on NAFLD in obese children. A high-fat high-carbohydrate (HFHC) diet was used to feed 21-d-old mice. Tilianin was administered at a dose of 10 or 20 mg/kg daily. HFHC-fed mice gained weight, increased liver index. The liver showed hepatocyte ballooning, inflammatory infiltration, and steatosis. Elevated levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (GGT), low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) and reduced the high-density lipoprotein cholesterol (HDL-C) level were found in HFHC-fed mice. Administration of tilianin significantly reduced these impairments. We further evaluated proteins related to lipid metabolism and observed that LXRα, SREBP-1c, FAS and ACC1 expression were blunted following tilianin administration. In addition, tilianin suppressed reactive oxygen species (ROS) overproduction and lipid peroxide 4-Hydroxynonenal expression, ascribed to its oxidative stress-modulating capacity. Tilianin also reversed the increase in F4/80 expression and proinflammatory cytokine levels. Of note, tilianin administration resulted in decreased protein levels of active caspase-1 and NOD-like receptor protein 3 (NLRP3) in HFHC-fed mice. Our study suggests that tilianin may ameliorate NAFLD in early obese mice by modulating lipids metabolism, oxidative stress, and inflammation, which may in part involve inhibiting NLRP3 inflammasome activation.

An update on animal models of liver fibrosis

The development of liver fibrosis primarily determines quality of life as well as prognosis. Animal models are often used to model and understand the underlying mechanisms of human disease. Although organoids can be used to simulate organ development and disease, the technology still faces significant challenges. Therefore animal models are still irreplaceable at this stage. Currently, in vivo models of liver fibrosis can be classified into five categories based on etiology: chemical, dietary, surgical, transgenic, and immune. There is a wide variety of animal models of liver fibrosis with varying efficacy, which have different implications for proper understanding of the disease and effective screening of therapeutic agents. There is no high-quality literature recommending the most appropriate animal models. In this paper, we will describe the progress of commonly used animal models of liver fibrosis in terms of their development mechanisms, applications, advantages and disadvantages, and recommend appropriate animal models for different research purposes.

Different Types of Dietary Fat and Fructose Interactions Result in Distinct Metabolic Phenotypes in Male Mice

Fat and fructose are the two major components over-represented in the Western diet. The aim of this study was to determine the combined effects of different types of dietary fat and fructose on the development of nonalcoholic fatty liver disease (NAFLD) in a murine model. Eight-week-old male C57BL/6J mice were fed with high-fat diet enriched with saturated fat (HSF), or omega-6 polyunsaturated fat (n6HUSF), or omega-3 polyunsaturated fat (n3HUSF) with 42% of calories derived from the fat. Fructose supplementation was given via 10% fructose (w/v) in the drinking water ad libitum for 20 weeks. While both HSF and n6HUSF fed mice developed obesity, HSF fed mice exhibited severe hepatic steatosis associated with hepatomegaly and liver injury. Fructose feeding promotes the development of liver fibrosis in HSF fed mice. n6HUSF fed mice were characterized with moderate hepatic steatosis, accompanied with hypertriglyceridemia and hyperlipidemia. Notably, fructose supplementation led to remarkable glucose intolerance in n6HUSF fed mice compared to controls. Hepatic lipidomic analysis revealed that the total saturated fatty acids and total monounsaturated fatty acids were significantly increased by fructose in the free fatty acid pool in HSF fed mice. Moreover, fructose supplementation increased hepatic and plasma cholesterol levels in the HSF fed mice. Our data suggest that excess energy from HSF intake results in fat storage in the liver, likely due to impaired triglyceride secretion; whereas excess energy from n6HUSF diet is stored in the periphery. Both effects are exacerbated by fructose supplementation. n3HUSF is beneficial, even consumed with fructose.

Genetic and Diet-Induced Animal Models for Non-Alcoholic Fatty Liver Disease (NAFLD) Research

A rapidly increasing incidence of non-alcoholic fatty liver disease (NAFLD) is noted worldwide due to the adoption of western-type lifestyles and eating habits. This makes the understanding of the molecular mechanisms that drive the pathogenesis of this chronic disease and the development of newly approved treatments of utmost necessity. Animal models are indispensable tools for achieving these ends. Although the ideal mouse model for human NAFLD does not exist yet, several models have arisen with the combination of dietary interventions, genetic manipulations and/or administration of chemical substances. Herein, we present the most common mouse models used in the research of NAFLD, either for the whole disease spectrum or for a particular disease stage (e.g., non-alcoholic steatohepatitis). We also discuss the advantages and disadvantages of each model, along with the challenges facing the researchers who aim to develop and use animal models for translational research in NAFLD. Based on these characteristics and the specific study aims/needs, researchers should select the most appropriate model with caution when translating results from animal to human.

Effect of Fiber Supplementation on Systemic Inflammation and Liver Steatosis in Mice Fed with High-Carbohydrate Diets

Background: High consumption of carbohydrates can trigger metabolic and inflammatory disorders in the body. Thus, the aim of this study was to evaluate the effect of fiber supplementation on inflammation and hepatic steatosis in mice fed high-carbohydrate diets. Methods: Swiss male mice were distributed into two control groups and two experimental groups that received isocaloric diet rich in starch (55%) or rich in fructose (55%). In the last 4 weeks of the experiment, the animals received 5% fructo-oligosaccharide (FOS) supplementation via gavage, or water in the control groups. After 16 weeks, biochemical analyses, inflammatory cytokines, and histology of the liver of the animals were performed. Results: The animals that received fructose had higher weight at the end of the experiment as well as liver weight, consumed more feed, had higher levels of tumor necrosis factor (TNF) and monocyte chemoattractant protein-1 (MCP-1), and a higher degree of hepatic steatosis when compared with the animals that received starch. However, the animals that received starch showed a higher inflammatory process. FOS supplementation was efficient in reducing liver weight and hepatic steatosis degree in animals fed with fructose diet but showed more degeneration of liver tissue and high levels of inflammatory cytokines. FOS reduced the levels of urea and total cholesterol in the starch-fed animals. Conclusions: Diets rich in carbohydrates such as starch and fructose cause deleterious effects in animals, and fiber supplementation can bring beneficial effects.

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.

High-Fructose/High-Fat Diet Downregulates the Hepatic Mitochondrial Oxidative Phosphorylation Pathway in Mice Compared with High-Fat Diet Alone

Both high-fat diet (HFD) alone and high-fructose plus HFD (HFr/HFD) cause diet-induced non-alcoholic fatty liver disease in murine models. However, the mechanisms underlying their impacts on inducing different levels of liver injury are yet to be elucidated. This study employed a proteomic approach to elucidate further on this issue. Adult male C57BL/6J mice were allocated to the HFD or the HFr/HFD group. After feeding for 12 weeks, all mice were euthanized and samples were collected. The proteomic profiles in liver tissues were analyzed using liquid chromatography-tandem mass spectrometry followed by canonical pathway analysis. We demonstrated that the mitochondrial oxidative phosphorylation (OXPHOS) pathway was the most significantly downregulated canonical pathway in the HFr/HFD group when compared with the HFD group. Within the OXPHOS pathway, the HFr/HFD group demonstrated significant downregulation of complexes I and III and significant upregulation of complex IV when compared with the HFD group. Moreover, the HFr/HFD group had lower protein levels of NADH: ubiquinone oxidoreductase subunits S3, S6, A5, and A12 in complex I (p < 0.001, =0.03, <0.001, and <0.001, respectively), lower protein level of cytochrome C in complex III (p < 0.001), and higher protein level of cytochrome C oxidase subunit 2 in complex IV (p = 0.002), when compared with the HFD group. To summarize, we have demonstrated that the hepatic mitochondrial OXPHOS pathway is significantly downregulated in long-term HFr/HFD feeding when compared with long-term HFD feeding. These data support the concept that the hepatic mitochondrial OXPHOS pathway should be involved in mediating the effects of HFr/HFD on inducing more severe liver injury than HFD alone.

Attenuation by Time-Restricted Feeding of High-Fat and High-Fructose Diet-Induced NASH in Mice Is Related to Per2 and Ferroptosis

Nonalcoholic steatohepatitis (NASH) is a chronic and progressive disease whose treatment strategies are limited. Although time-restricted feeding (TRF) is beneficial for metabolic diseases without influencing caloric intake, the underlying mechanisms of TRF action in NASH and its efficacy have not yet been demonstrated. We herein showed that TRF effectively alleviated NASH, producing a reduction in liver enzymes and improvements in liver pathology. Regarding the mechanisms by which TRF mitigates NASH, we ascertained that TRF inhibited ferroptosis and the expression of the circadian gene Per2. By adopting a hepatocyte-specific Per2-knockout (Per2^△hep) mice model, we clarified the critical role of Per2 in exacerbating NASH. According to the results of our RNA-Seq analysis, the knockout of Per2 ameliorated NASH by inhibiting the onset of ferroptosis; this was manifested by diminished lipid peroxidation levels, decreased mRNA and protein levels for ferroptosis-related genes, and alleviated morphologic changes in mitochondria. Furthermore, using a ferroptosis inhibitor, we showed that ferroptosis significantly aggravated NASH and noted that this was likely achieved by regulation of the expression of peroxisome proliferator activated receptor (PPAR)α. Finally, we discerned that TRF and hepatocyte-specific knockout of Per2 promoted the expression of PPARα. Our results revealed a potential for TRF to effectively alleviate high-fat and high-fructose diet-induced NASH via the inhibition of Per2 and depicted the participation of Per2 in the progression of NASH by promoting ferroptosis, which was ultimately related to the expression of PPARα.

Moringa oleifera Improves MAFLD by Inducing Epigenetic Modifications

Background and aims. Metabolic Associated Fatty Liver Disease (MAFLD) encompasses a spectrum of diseases from simple steatosis to nonalcoholic steatohepatitis (NASH). Here, we investigated the hepatoprotective role of Moringa oleifera aqueous extract on hepatic miRNAs, genes and protein expression, as well as histological and biochemical parameters in an experimental model of NASH. Methods. Male C57BL/6J mice were fed with a high fat diet (HFD, 60% lipids, 42 gr/L sugar in water) for 16 weeks. Moringa extract was administered via gavage during the final 8 weeks. Insulin Tolerance Test (ITT) and HOMA-IR were calculated. Serum levels of insulin, resistin, leptin and PAI-1 and hepatic expression of miR-21a-5p, miR-103-3p, miR-122-5p, miR-34a-5p and SIRT1, AMPKα and SREBP1c protein were evaluated. Alpha-SMA immunohistochemistry and hematoxylin-eosin, Masson’s trichrome and sirius red staining were made. Hepatic transcriptome was analyzed using microarrays. Results. Animals treated with Moringa extract improved ITT and decreased SREBP1c hepatic protein, while SIRT1 increased. Hepatic expression of miR-21a-5p, miR-103-3p and miR-122-5p, miR34a-5p was downregulated. Hepatic histologic analysis showed in Moringa group (HF + MO) a significant decrease in inflammatory nodules, macro steatosis, fibrosis, collagen and αSMA reactivity. Analysis of hepatic transcriptome showed down expression of mRNAs implicated in DNA response to damage, endoplasmic reticulum stress, lipid biosynthesis and insulin resistance. Moringa reduced insulin resistance, de novo lipogenesis, hepatic inflammation and ER stress. Conclusions. Moringa prevented progression of liver damage in a model of NASH and improved biochemical, histological and hepatic expression of genes and miRNAs implicated in MAFLD/NASH development.

Emerging role of carboxylesterases in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a global public health problem. Carboxylesterases (CESs), as potential influencing factors of NAFLD, are very important to improve clinical outcomes. This review aims to deeply understand the role of CESs in the progression of NAFLD and proposes that CESs can be used as potential targets for NAFLD treatment. We first introduced CESs and analyzed the relationship between CESs and hepatic lipid metabolism and inflammation. Then, we further reviewed the regulation of nuclear receptors on CESs, including PXR, CAR, PPARα, HNF4α and FXR, which may influence the progression of NAFLD. Finally, we evaluated the advantages and disadvantages of existing NAFLD animal models and summarized the application of CES-related animal models in NAFLD research. In general, this review provides an overview of the relationship between CESs and NAFLD and discusses the role and potential value of CESs in the treatment and prevention of NAFLD.

Metformin treatment rescues CD8+ T-cell response to immune checkpoint inhibitor therapy in mice with NAFLD

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) represents the fastest growing underlying cause of hepatocellular carcinoma (HCC) and has been shown to impact immune effector cell function. The standard of care for the treatment of advanced HCC is immune checkpoint inhibitor (ICI) therapy, yet NASH may negatively affect the efficacy of ICI therapy in HCC. The immunologic mechanisms underlying the impact of NASH on ICI therapy remain unclear.

METHODS

Herein, using multiple murine NASH models, we analysed the influence of NASH on the CD8+ T-cell-dependent anti-PD-1 responses against liver cancer. We characterised CD8+ T cells' transcriptomic, functional, and motility changes in mice receiving a normal diet (ND) or a NASH diet.

RESULTS

NASH blunted the effect of anti-PD-1 therapy against liver cancers in multiple murine models. NASH caused a proinflammatory phenotypic change of hepatic CD8+ T cells. Transcriptomic analysis revealed changes related to NASH-dependent impairment of hepatic CD8+ T-cell metabolism. In vivo imaging analysis showed reduced motility of intratumoural CD8+ T cells. Metformin treatment rescued the efficacy of anti-PD-1 therapy against liver tumours in NASH.

CONCLUSIONS

We discovered that CD8+ T-cell metabolism is critically altered in the context of NASH-related liver cancer, impacting the effectiveness of ICI therapy - a finding which has therapeutic implications in patients with NASH-related liver cancer.

LAY SUMMARY

Non-alcoholic steatohepatitis represents the fastest growing cause of hepatocellular carcinoma. It is also associated with reduced efficacy of immunotherapy, which is the standard of care for advanced hepatocellular carcinoma. Herein, we show that non-alcoholic steatohepatitis is associated with impaired motility, metabolic function, and response to anti-PD-1 treatment in hepatic CD8+ T cells, which can be rescued by metformin treatment.

Characterization of diet based nonalcoholic fatty liver disease/nonalcoholic steatohepatitis in rodent models: Histological and biochemical outcomes

Nonalcoholic fatty liver disease (NAFLD), as the most common chronic liver disease, is rapidly increasing worldwide. This complex disorder can include simple liver steatosis to more serious stages of nonalcoholic fibrosis and steatohepatitis (NASH). One of the critical concerns in NASH research is selecting and confiding in relying on preclinical animal models and experimental methods that can accurately reflect the situation in human NASH. Recently, creating nutritional models of NASH with a closer dietary pattern in human has been providing reliable, simple, and reproducible tools that hope to create a better landscape for showing the recapitulation of disease pathophysiology. This review focuses on recent research on rodent models (mice, rats, and hamsters) in the induction of the dietary model of NAFLD /NASH. This research tries to compile the different dietary compositions of NASH, time frames required for disease development, and their impact on liver histological features as well as metabolic parameters.

Dietary fat composition shapes bile acid metabolism and severity of liver injury in a pig model of pediatric NAFLD

The objective of this study was to investigate the effect of dietary fatty acid (FA) composition on bile acid (BA) metabolism in a pig model of NAFLD, by using a multiomics approach combined with histology and serum biochemistry. Thirty 20-day-old Iberian pigs pair-housed in pens were randomly assigned to receive 1 of 3 hypercaloric diets for 10 wk: 1) lard-enriched (LAR; n = 5 pens), 2) olive oil-enriched (OLI; n = 5), and 3) coconut oil-enriched (COC; n = 5). Animals were euthanized on week 10 after blood sampling, and liver, colon, and distal ileum (DI) were collected for histology, metabolomics, and transcriptomics. Data were analyzed by multivariate and univariate statistics. Compared with OLI and LAR, COC increased primary and secondary BAs in liver, plasma, and colon. In addition, both COC and OLI reduced circulating fibroblast growth factor 19, increased hepatic necrosis, composite lesion score, and liver enzymes in serum, and upregulated genes involved in hepatocyte proliferation and DNA repair. The severity of liver disease in COC and OLI pigs was associated with increased levels of phosphatidylcholines, medium-chain triacylglycerides, trimethylamine-N-oxide, and long-chain acylcarnitines in the liver, and the expression of profibrotic markers in DI, but not with changes in the composition or size of BA pool. In conclusion, our results indicate a role of dietary FAs in the regulation of BA metabolism and progression of NAFLD. Interventions that aim to modify the composition of dietary FAs, rather than to regulate BA metabolism or signaling, may be more effective in the treatment of NAFLD.NEW & NOTEWORTHY Bile acid homeostasis and signaling is disrupted in NAFLD and may play a central role in the development of the disease. However, there are no studies addressing the impact of diet on bile acid metabolism in patients with NAFLD. In juvenile Iberian pigs, we show that fatty acid composition in high-fat high-fructose diets affects BA levels in liver, plasma, and colon but these changes were not associated with the severity of the disease.

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.

Nonalcoholic steatohepatitis and mechanisms by which it is ameliorated by activation of the CNC-bZIP transcription factor Nrf2

Non-alcoholic steatohepatitis (NASH) represents a global health concern. It is characterised by fatty liver, hepatocyte cell death and inflammation, which are associated with lipotoxicity, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, iron overload and oxidative stress. NF-E2 p45-related factor 2 (Nrf2) is a transcription factor that combats oxidative stress. Remarkably, Nrf2 is downregulated during the development of NASH, which probably accelerates disease, whereas in pre-clinical studies the upregulation of Nrf2 inhibits NASH. We now review the scientific literature that proposes Nrf2 downregulation during NASH involves its increased ubiquitylation and proteasomal degradation, mediated by Kelch-like ECH-associated protein 1 (Keap1) and/or β-transducin repeat-containing protein (β-TrCP) and/or HMG-CoA reductase degradation protein 1 (Hrd1, also called synoviolin (SYVN1)). Additionally, downregulation of Nrf2-mediated transcription during NASH may involve diminished recruitment of coactivators by Nrf2, due to increased levels of activating transcription factor 3 (ATF3) and nuclear factor-kappaB (NF-κB) p65, or competition for promoter binding due to upregulation of BTB and CNC homology 1 (Bach1). Many processes that downregulate Nrf2 are triggered by transforming growth factor-beta (TGF-β), with oxidative stress amplifying its signalling. Oxidative stress may also increase suppression of Nrf2 by β-TrCP through facilitating formation of the DSGIS-containing phosphodegron in Nrf2 by glycogen synthase kinase-3. In animal models, knockout of Nrf2 increases susceptibility to NASH, while pharmacological activation of Nrf2 by inducing agents that target Keap1 inhibits development of NASH. These inducing agents probably counter Nrf2 downregulation affected by β-TrCP, Hrd1/SYVN1, ATF3, NF-κB p65 and Bach1, by suppressing oxidative stress. Activation of Nrf2 is also likely to inhibit NASH by ameliorating lipotoxicity, inflammation, ER stress and iron overload. Crucially, pharmacological activation of Nrf2 in mice in which NASH has already been established supresses liver steatosis and inflammation. There is therefore compelling evidence that pharmacological activation of Nrf2 provides a comprehensive multipronged strategy to treat NASH.

Glycyrrhetinic acid regulates impaired macrophage autophagic flux in the treatment of non-alcoholic fatty liver disease

Macrophages are involved in hepatocyte steatosis and necroinflammation and play an important role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Impaired autophagy function (decreased autophagy or blocked autophagic flow) leads to cell damage and death and promotes NAFLD progression. The experimental and clinical research of glycyrrhetinic acid (GA) in the treatment of NAFLD has gradually attracted attention with clear pharmacological activities such as immune regulation, antiviral, antitumor, antioxidant, liver protection, and anti-inflammatory. However, the effects of GA on the STAT3-HIF-1α pathway and autophagy in macrophages are still unclear, and its mechanism of action in the treatment of NAFLD remains to be further elucidated. We constructed a NAFLD mouse model through a high-fat and high-sugar diet to investigate the therapeutic effects of GA. The results showed that GA reduced weight, improved the pathological changes and hepatic lipid deposition of liver, and abnormally elevated the levels of serum biochemical (AST, ALT, TG, T-CHO, LDL-C, and HDL-C) and inflammatory indexes (IL-1β, IL-4, IL-6, MCP-1, and TNF-α) in NAFLD mice. Further examination revealed that GA ameliorates excessive hepatic macrophage infiltration and hepatocyte apoptosis. The results of the cell experiments further elaborated that GA modulated the PA-induced macrophage STAT3-HIF-1α pathway and ameliorated impaired autophagic flux (blockade of autophagosome–lysosome fusion) and overactivation of inflammation. Excessive hepatocyte apoptosis caused by the uncontrolled release of inflammatory cytokines was also suppressed by GA.

Conclusion

This study demonstrated that GA could regulate the STAT3-HIF-1α pathway of macrophages, ameliorate the impaired autophagy flux, and reduce the excessive production of inflammatory cytokines to improve the excessive apoptosis of liver cells, thus playing a therapeutic role on NAFLD.

Corydalis saxicola Bunting Total Alkaloids ameliorate diet-induced non-alcoholic steatohepatitis by regulating hepatic PI3K/Akt and TLR4/NF-κB pathways in mice

Corydalis saxicola Bunting (Yanhuanglian), distributed in Southwest China, is mainly used for treatment of hepatitis, oral mucosal erosion, conjunctivitis, dysentery, acute abdominal pain and hemorrhoids in the folk. Corydalis saxicola Bunting Total Alkaloids (CSBTA) are the active ingredients extracted from the root of C. saxicola bunting. Non-alcoholic steatohepatitis (NASH) is the hinge between steatosis and cirrhosis in the spectrum of Non-alcoholic fatty liver disease (NAFLD), which has become one of the most common chronic liver diseases in the world. CSBTA can reduce tumors and brain diseases through anti-inflammatory and antioxidant pathways. Our study was designed to clarify the effects of CSBTA on the HFHC (High fat and high carbohydrate drinking) diet induced mice. In our research, A HFHC diet induced NASH mice model was applied to investigate the effects of CSBTA in vivo and obeticholic acid (OA) was set as positive control. Moreover, the underlying mechanisms were explored by palmitic acid (PA) and lipopolysaccharide (LPS) stimulated HepG2 cells in vitro. The in vivo study illustrated that CSBTA could alleviate mice away from the onset of NASH, and reduce intrahepatocellular lipid accumulation and hepatocyte inflammation under high fat condition. Further in vitro analysis confirmed that CSBTA attenuated inflammation and hepatic lipid accumulation by improving hepatic PI3K/Akt and suppressing hepatic TLR4/NF-κB pathways. In summary, this study demonstrated that CSBTA might be a promising compound for the treatment of NAFLD.

Crosstalk of hepatocyte nuclear factor 4a and glucocorticoid receptor in the regulation of lipid metabolism in mice fed a high-fat-high-sugar diet

Background

Hepatocyte nuclear factor 4α (HNF4α) and glucocorticoid receptor (GR), master regulators of liver metabolism, are down-regulated in fatty liver diseases. The present study aimed to elucidate the role of down-regulation of HNF4α and GR in fatty liver and hyperlipidemia.

Methods

Adult mice with liver-specific heterozygote (HET) and knockout (KO) of HNF4α or GR were fed a high-fat-high-sugar diet (HFHS) for 15 days. Alterations in hepatic and circulating lipids were determined with analytical kits, and changes in hepatic mRNA and protein expression in these mice were quantified by real-time PCR and Western blotting. Serum and hepatic levels of bile acids were quantified by LC-MS/MS. The roles of HNF4α and GR in regulating hepatic gene expression were determined using luciferase reporter assays.

Results

Compared to HFHS-fed wildtype mice, HNF4α HET mice had down-regulation of lipid catabolic genes, induction of lipogenic genes, and increased hepatic and blood levels of lipids, whereas HNF4α KO mice had fatty liver but mild hypolipidemia, down-regulation of lipid-efflux genes, and induction of genes for uptake, synthesis, and storage of lipids. Serum levels of chenodeoxycholic acid and deoxycholic acid tended to be decreased in the HNF4α HET mice but dramatically increased in the HNF4α KO mice, which was associated with marked down-regulation of cytochrome P450 7a1, the rate-limiting enzyme for bile acid synthesis. Hepatic mRNA and protein expression of sterol-regulatory-element-binding protein-1 (SREBP-1), a master lipogenic regulator, was induced in HFHS-fed HNF4α HET mice. In reporter assays, HNF4α cooperated with the corepressor small heterodimer partner to potently inhibit the transactivation of mouse and human SREBP-1C promoter by liver X receptor. Hepatic nuclear GR proteins tended to be decreased in the HNF4α KO mice. HFHS-fed mice with liver-specific KO of GR had increased hepatic lipids and induction of SREBP-1C and PPARγ, which was associated with a marked decrease in hepatic levels of HNF4α proteins in these mice. In reporter assays, GR and HNF4α synergistically/additively induced lipid catabolic genes.

Conclusions

induction of lipid catabolic genes and suppression of lipogenic genes by HNF4α and GR may mediate the early resistance to HFHS-induced fatty liver and hyperlipidemia.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-022-01654-6.

Relationship between Liver Stiffness and Steatosis in Obesity Conditions: In Vivo and In Vitro Studies

Obesity is a major risk factor for metabolic dysfunction such as non-alcoholic fatty liver disease (NAFLD). The NAFLD spectrum ranges from simple steatosis, to steatohepatitis, fibrosis, and cirrhosis. The aim of this study is to characterize the grade of steatosis being associated with overnutrition and obesity, both at the level of single hepatocyte and whole liver, and to correlate it with the hepatocyte/liver stiffness and dysfunction. For the in vivo study, 60 subjects were enrolled and grouped based on the stage of liver steatosis/fibrosis according to biochemical analyses, liver ultrasonography (USG) and acoustic radiation force impulse shear wave elastography (ARFI-SWE). For single hepatocyte analyses we employed in vitro models of moderate and severe steatosis on which to assess the single cell biomechanics by Single Cell Force Spectroscopy (SCFS) and Quantitative Phase Microscopy (QPM). Results show that in vivo liver stiffness depends mainly on the extent of fat accumulation and not on fibrosis. These results parallel the in vitro observations showing that hepatocyte stiffness and dysfunction increase with increasing fat accumulation and lipid droplet enlargement. Our findings indicate that the extent of steatosis markedly affects the biomechanical properties of both liver and single hepatocytes thus proving insights about the role of modulation of liver/hepatocyte elasticity as a physical mechanism transducing the obesity-dependent excess of plasmatic lipids towards liver steatosis and dysfunction.

The ameliorative effect of Apium graveolens & curcumin against Non-alcoholic fatty liver disease induced by high fructose-high fat diet in rats

Background

Non-alcoholic fatty liver disease (NAFLD) is a condition resulting from fat aggregates in liver cells and is associated with metabolic syndrome, obesity, and oxidative stress. The present work was designed to investigate the role of celery and curcumin against high-fructose–high-fat (HFHF) diet-induced NAFLD in rats. Thirty male rats were classified into five groups: GP1: control group (rats were fed a normal control diet), GP2: HFHF group as a positive control (rats were fed a HFHF diet) for 20 weeks, GP3: HFHF + sily group, GP4: HFHF + celery group, and GP5: HFHF + cur group (rats in 3, 4, and 5 were treated as in the HFHF group for 16 weeks, then combined treatment daily by gavage for 4 weeks with either silymarin (as a reference drug, 50 mg/kg bw) or celery (300 mg/kg bw) or curcumin (200 mg/kg bw), respectively. The progression of NAFLD was evaluated by estimating tissue serum liver enzymes, glycemic profile, lipid profile, oxidative stress markers in liver tissue, and histopathological examination. Moreover, DNA fragmentation and the released lysosomal enzymes (acid phosphatase, β-galactosidase, and N-acetyl-B-glucosaminidase) were estimated.

Results

Our results showed that HFHF administration for 16 weeks caused liver enzymes elevation, hyperglycemia, and hyperlipidemia. Furthermore, increased hepatic MDA levels along with a decline in GSH levels were observed in the HFHF group as compared to the control group. The results were confirmed by a histopathological study, which showed pathological changes in the HFHF group. DNA fragmentation was also observed, and the lysosomal enzyme activities were increased. On the other hand, oral supplementation of celery and cur improved all these changes compared with positive control groups and HFHF + sily (as a reference drug). Moreover, celery, as well as curcumin co-treatment, reduced HFHF-enhanced DNA fragmentation and inhibited elevated lysosomal enzymes. The celery combined treatment showed the most pronounced ameliorative impact, even more than silymarin did.

Conclusion

Our findings suggest that celery and curcumin consumption may exhibit ameliorative impacts against NALFD progression, while celery showed more ameliorative effect in all parameters.

Induction of Accelerated Aging in a Mouse Model

With the global increase of the elderly population, the improvement of the treatment for various aging-related diseases and the extension of a healthy lifespan have become some of the most important current medical issues. In order to understand the developmental mechanisms of aging and aging-related disorders, animal models are essential to conduct relevant studies. Among them, mice have become one of the most prevalently used model animals for aging-related studies due to their high similarity to humans in terms of genetic background and physiological structure, as well as their short lifespan and ease of reproduction. This review will discuss some of the common and emerging mouse models of accelerated aging and related chronic diseases in recent years, with the aim of serving as a reference for future application in fundamental and translational research.

Dysregulation of S-adenosylmethionine Metabolism in Nonalcoholic Steatohepatitis Leads to Polyamine Flux and Oxidative Stress

Nonalcoholic fatty liver disease (NAFLD) is the number one cause of chronic liver disease worldwide, with 25% of these patients developing nonalcoholic steatohepatitis (NASH). NASH significantly increases the risk of cirrhosis and decompensated liver failure. Past studies in rodent models have shown that glycine-N-methyltransferase (GNMT) knockout results in rapid steatosis, fibrosis, and hepatocellular carcinoma progression. However, the attenuation of GNMT in subjects with NASH and the molecular basis for its impact on the disease process is still unclear. To address this knowledge gap, we show the reduction of GNMT protein levels in the liver of NASH subjects compared to healthy controls. To gain insight into the impact of decreased GNMT in the disease process, we performed global label-free proteome studies on the livers from a murine modified amylin diet-based model of NASH. Histological and molecular characterization of the animal model demonstrate a high resemblance to human disease. We found that a reduction of GNMT leads to a significant increase in S-adenosylmethionine (AdoMet), an essential metabolite for transmethylation reactions and a substrate for polyamine synthesis. Further targeted proteomic and metabolomic studies demonstrated a decrease in GNMT transmethylation, increased flux through the polyamine pathway, and increased oxidative stress production contributing to NASH pathogenesis.

Dedicator of Cytokinesis 2 (DOCK2) Deficiency Attenuates Lung Injury Associated with Chronic High-Fat and High-Fructose Diet-Induced Obesity

Obesity is a major risk factor for lung disease development. However, little is known about the impact of chronic high-fat and high-fructose (HFHF) diet-induced obesity on lung inflammation and subsequent pulmonary fibrosis. Herein we hypothesized that dedicator of cytokinesis 2 (DOCK2) promotes a proinflammatory phenotype of lung fibroblasts (LFs) to elicit lung injury and fibrosis in chronic HFHF diet-induced obesity. An HFHF diet for 20 weeks induced lung inflammation and profibrotic changes in wild-type C57BL/6 mice. CD68 and monocyte chemoattractant protein-1 (MCP-1) expression were notably increased in the lungs of wild-type mice fed an HFHF diet. An HFHF diet further increased lung DOCK2 expression that co-localized with fibroblast-specific protein 1, suggesting a role of DOCK2 in regulating proinflammatory phenotype of LFs. Importantly, DOCK2 knockout protected mice from lung inflammation and fibrosis induced by a HFHF diet. In primary human LFs, tumor necrosis factor-α (TNF-α) and IL-1β induced DOCK2 expression concurrent with MCP-1, IL-6, and matrix metallopeptidase 2. DOCK2 knockdown suppressed TNF-α-induced expression of these molecules and activation of phosphatidylinositol 3-kinase/AKT and NF-κB signaling pathways, suggesting a mechanism of DOCK2-mediated proinflammatory and profibrotic changes in human LFs. Taken together, these findings reveal a previously unrecognized role of DOCK2 in regulating proinflammatory phenotype of LFs, potentiation of lung inflammation, and pulmonary fibrosis in chronic HFHF diet-caused obesity.