Comparative study of fatty liver induced by methionine and choline-deficiency in C57BL/6N mice originating from three different sources

Pharmacological inhibition of p300 ameliorates steatosis, inflammation, and fibrosis in mice with non-alcoholic steatohepatitis

The histone acetyltransferase p300 plays a pivotal role in regulating gene expression and cellular phenotype through epigenetic mechanisms. It significantly influences lipid metabolism, which is a key factor in the pathogenesis of non-alcoholic steatohepatitis (NASH), by modulating the transcription of genes involved in lipid synthesis and accumulation. This study aimed to investigate the protective potential of inhibiting p300 in NASH. Male C57BL/6J mice were subjected to a methionine- and choline-deficient (MCD) diet for 4 weeks to induce NASH, and during this period, the p300 inhibitor C646 (10 mg/kg) was administered three times a week. C646 treatment reduced the elevation of p300 expression and histone H3 acetylation, leading to a decrease in liver injury markers in the serum and an improvement in the histological abnormalities observed in MCD diet-fed mice. C646 also reduced lipid accumulation by modulating de novo lipogenesis and suppressed inflammation, including cytokine overproduction and macrophage infiltration. Furthermore, C646 mitigated liver fibrosis and myofibroblast accumulation. This protective effect was achieved through the inhibition of apoptosis by reducing p53 and Bax expression and the suppression of ferroptosis by decreasing lipid peroxidation while enhancing antioxidant defenses. Additionally, C646 alleviated endoplasmic reticulum stress, as evidenced by the downregulation of unfolded protein response signaling molecules. These results highlight the potential of p300 as a therapeutic target for NASH.

The impact of stress on the behavior of C57BL/6 mice with liver injury: a comparative study

Introduction

Depressive-like behavior has been shown to be associated with liver damage. This study aimed to evaluate the impact of three different models of depression on the behavior of mice with liver injury.

Methods

During the 4 weeks of methionine/choline deficiency diet (MCD), adult C57BL/6 mice were randomly divided into four groups: MCD (no stress protocol, n = 6), chronic unpredictable mild stress (CUMS, n = 9), acute and repeated forced swim stress [aFSS (n = 9) and rFSS (n = 9)].

Results

All depression protocols induced increased anhedonia and anxiety-like behavior compared to baseline and had no impact on the severity of liver damage, according to ultrasonography. However, different protocols evoked different overall behavior patterns. After the depressive-like behavior induction protocols, animals subjected to aFSS did not exhibit anxiety-like behavior differences compared to MCD animals, while mice subjected to CUMS showed additional weight loss compared to FSS animals. All tested protocols for inducing depressive-like behavior decreased the short-term memory of mice with liver damage, as assessed by the novel object recognition test (NORT).

Discussion

Our results show that the use of all protocols seems to generate different levels of anxiety-like behavior, but only the depressive-like behavior induction procedures associate additional anhedonia and memory impairment in mice with liver injury.

6-Shogaol Ameliorates Liver Inflammation and Fibrosis in Mice on a Methionine- and Choline-Deficient Diet by Inhibiting Oxidative Stress, Cell Death, and Endoplasmic Reticulum Stress

Non-alcoholic steatohepatitis (NASH) is becoming an increasingly serious global health threat, distinguished by hepatic lipid accumulation, inflammation, and fibrosis. There is a lack of approved pharmaceutical interventions for this disease, highlighting the urgent need for effective treatment. This study explores the hepatoprotective potential of 6-shogaol, a natural compound derived from ginger, in a methionine- and choline-deficient (MCD) dietary mouse model of NASH. Male C57BL/6J mice were subjected to the MCD diet for 4 weeks to induce NASH, with concurrent intraperitoneal administration of 6-shogaol (20 mg/kg) three times a week. While 6-shogaol did not impact body weight, liver weight, or hepatic lipid accumulation, it effectively mitigated liver injury, inflammation, and fibrosis in MCD diet-fed mice. Mechanistically, 6-shogaol inhibited lipid and DNA oxidation, restored hepatic glutathione levels, and regulated the expression of pro-oxidant and antioxidant enzymes. Furthermore, 6-shogaol inhibited apoptosis and necroptosis, as indicated by a decrease in TUNEL-stained cells and downregulation of apoptosis- and necroptosis-associated proteins. Additionally, 6-shogaol alleviated endoplasmic reticulum (ER) stress, as demonstrated by decreased expression of molecules associated with unfolded protein response pathways. These findings underscore the potential of 6-shogaol as a therapeutic intervention for NASH by targeting pathways related to oxidative stress, cell death, and ER stress.

Baicalein alleviates non-alcoholic fatty liver disease in mice by ameliorating intestinal barrier dysfunction

Non-alcoholic fatty liver disease (NAFLD) is the main cause of chronic liver disease, and its pathological development is closely related to the gut-liver axis. The intestinal barrier, an important component of the gut-liver axis, can prevent gut microbes and endotoxins from entering the liver. Intestinal barrier function is impaired in patients with NAFLD. Baicalein, which is the main flavonoid in Scutellariae Radix, can improve NAFLD. However, whether baicalein alleviates NAFLD by ameliorating intestinal barrier dysfunction remains unclear. In this study, a methionine-choline deficient (MCD) diet-induced NAFLD mouse model is used. The effects of baicalein on lipid accumulation, inflammation and the intestinal barrier in MCD-fed mice were evaluated by detecting blood lipid levels, lipid accumulation, liver pathological changes, inflammatory factors, inflammatory signaling pathways, the three main short-chain fatty acids (acetate, propionate and butyrate), intestinal permeability and intestinal tight junction protein expression. Compared with the MCD-only group, baicalein intake decreased the serum and liver lipid levels. Moreover, the accumulation of lipid droplets and steatosis in the liver were also alleviated; all these results demonstrated that baicalein could alleviate NAFLD. Meanwhile, the levels of inflammatory cytokines decreased in the baicalein group. Further investigation of the mucosal permeability to 4 kDa fluorescein isothiocyanate-dextran, concentrations of short-chain fatty acids in feces, and the expression of intestinal zonula occluden 1 and claudin-1 indicated that a baicalein diet could decrease the intestinal permeability caused by a MCD diet. Moreover, the protein levels of p-NF-κB p65 and the ratio of p-NF-κB p65/NF-κB p65 increased, and IκB-α and PPARα decreased in NAFLD mice, while the administration of baicalein could alleviate these changes. The above results indicated that the mechanism of baicalein in the alleviation of NAFLD lies in the regulation of the intestinal barrier.

Dynamic changes in hepatic DNA methylation during the development of nonalcoholic fatty liver disease induced by a high-sugar diet

DNA methylation is an important epigenetic mechanism of gene expression control. The present study aimed to evaluate the temporal effect of isocaloric high-sugar diet (HSD) intake on the development of nonalcoholic fatty liver disease (NAFLD) and the role of DNA methylation in this event. Newly weaned Wistar rats were divided into eight groups and fed a standard chow diet or an HSD ad libitum for 4 weeks, 8 weeks, 15 weeks, and 18 weeks. After the experimental periods, the animals were euthanized and their livers were removed for histological analysis, gene expression of maintenance methylase (Dnmt1), de novo methylases (Dnmt3a and Dnmt3b), demethylases (Tet2 and Tet3) of DNA, and global DNA methylation. HSD intake led to the gradual development of NAFLD. HSD intake for 18 weeks was associated with downregulation of Dnmt1 expression and global DNA hypomethylation; these results were negatively correlated with more severe steatosis scores observed in these animals. The HSD consumption for 18 weeks was also associated with a decrease in Dnmt3a and Tet2 expression. Interestingly, the expression of de novo methyltransferase Dnmt3b was reduced by HSD during all experimental periods. Together, these results indicate that the downregulation of de novo DNA methylation, Dnmt3b, induced by HSD is the primary factor in the development of NAFLD. On the other hand, disease progression is associated with downregulation of maintenance DNA methylation and global DNA hypomethylation. These results suggest a link between the dynamic changes in hepatic DNA methylation and the development of NAFLD induced by an HSD intake.

Chronic Inflammation—A Link between Nonalcoholic Fatty Liver Disease (NAFLD) and Dysfunctional Adipose Tissue

Nonalcoholic fatty liver disease (NAFLD) is a new challenge in modern medicine, due to its high prevalence in the world. The pathogenesis of NAFLD is a complex dysmetabolic process, following the “multiple-hit” hypothesis that involves hepatocytes excessive accumulation of triglycerides, insulin resistance (IR), increased oxidative stress, chronic low-grade inflammatory response and lipotoxicity. In this review, we provide an overview of the interrelation of these processes, the link between systemic and local inflammation and the role of dysfunctional adipose tissue (AT) in the NAFLD development. Multiple extrahepatic triggers of the pathophysiological mechanisms of NAFLD are described: nutritional deficiency or malnutrition, unhealthy food intake, the dysfunction of the liver–gut axis, the involvement of the mesenteric adipose tissue, the role of adipokines such as adiponectin, of food intake hormone, the leptin and leptin resistance (LR) and adipose tissue’s hormone, the resistin. In addition, a wide range of intrahepatic players are involved: oxidative stress, fatty acid oxidation, endoplasmic reticulum stress, mitochondrial dysfunction, resident macrophages (Kupffer cells), neutrophils, dendritic cells (DCs), B and T lymphocytes contributing to the potential evolution of NAFLD to nonalcoholic steatohepatitis (NASH). This interdependent approach to complex dysmetabolic imbalance in NAFLD, integrating relevant studies, could contribute to a better clarification of pathogenesis and consequently the development of new personalized treatments, targeting de novo lipogenesis, chronic inflammation and fibrosis. Further studies are needed to focus not only on treatment, but also on prevention strategy in NAFLD.

A Comparison of the Gene Expression Profiles of Non-Alcoholic Fatty Liver Disease between Animal Models of a High-Fat Diet and Methionine-Choline-Deficient Diet

Non-alcoholic fatty liver disease (NAFLD) embraces several forms of liver disorders involving fat disposition in hepatocytes ranging from simple steatosis to the severe stage, namely, non-alcoholic steatohepatitis (NASH). Recently, several experimental in vivo animal models for NAFLD/NASH have been established. However, no reproducible experimental animal model displays the full spectrum of pathophysiological, histological, molecular, and clinical features associated with human NAFLD/NASH progression. Although methionine-choline-deficient (MCD) diet and high-fat diet (HFD) models can mimic histological and metabolic abnormalities of human disease, respectively, the molecular signaling pathways are extremely important for understanding the pathogenesis of the disease. This review aimed to assess the differences in gene expression patterns and NAFLD/NASH progression pathways among the most common dietary animal models, i.e., HFD- and MCD diet-fed animals. Studies showed that the HFD and MCD diet could induce either up- or downregulation of the expression of genes and proteins that are involved in lipid metabolism, inflammation, oxidative stress, and fibrogenesis pathways. Interestingly, the MCD diet model could spontaneously develop liver fibrosis within two to four weeks and has significant effects on the expression of genes that encode proteins and enzymes involved in the liver fibrogenesis pathway. However, such effects in the HFD model were found to occur after 24 weeks with insulin resistance but appear to cause less severe fibrosis. In conclusion, assessing the abnormal gene expression patterns caused by different diet types provides valuable information regarding the molecular mechanisms of NAFLD/NASH and predicts the clinical progression of the disease. However, expression profiling studies concerning genetic variants involved in the development and progression of NAFLD/NASH should be conducted.

Anti-obesity effects of Celastrus orbiculatus extract containing celastrol on canine adipocytes

From 50 to 60% of companion animals in the United States are overweight or obese and this obesity rate is rising. As obesity is associated with a number of health problems, an agent that can help weight loss in pets and assist in clinically managing obesity through veterinary prescription foods and medication would be beneficial. Many studies have shown that celastrol, a phytochemical compound found in Celastrus orbiculatus extract (COE), has anti-obesity and anti-inflammatory effects, although these effects have not yet been determined in canine or canine-derived cells. The objective of this study was to investigate the effects of celastrol on the adipogenic differentiation and lipolysis of canine adipocytes. Primary preadipocytes were isolated from the gluteal region of a beagle dog and the primary adipocytes were differentiated into mature adipocytes by adipocyte differentiation media containing isobutylmethylxanthine, dexamethasone, and insulin. In a water-soluble tetrazolium (WST) assay, the cell viability of mature adipocytes was decreased after treatment with COE (0, 0.93, 2.32, and 4.64 nM celastrol) in a concentration-dependent manner, although preadipocytes were not affected. Oil Red O (ORO) staining revealed that COE inhibited the differentiation into mature adipocytes and lipid accumulation in adipocytes. In addition, treatment with COE significantly reduced triglyceride content and increased lipolytic activities by 1.5-fold in canine adipocytes. Overall, it was concluded that COE may enhance anti-obesity activity in canine adipocytes by inhibiting lipid accumulation and increasing lipolytic activity.

Nutritional Approach Targeting Gut Microbiota in NAFLD-To Date

Non-alcoholic fatty liver disease (NAFLD) is a significant clinical and epidemiological problem that affects around 25% of the adult global population. A large body of clinical evidence highlights that NAFLD is associated with increased liver-related morbidity and mortality and an increased risk of cardiovascular disease, extrahepatic cancers, type 2 diabetes, and chronic kidney disease. Recently, a series of studies revealed the pivotal role of gut microbiota (GM) dysbiosis in NAFLD's pathogenesis. The GM plays an essential role in different metabolic pathways, including the fermentation of diet polysaccharides, energy harvest, choline regulation, and bile acid metabolism. One of the most critical factors in GM stabilization is the diet; therefore, nutritional therapyappearsto be a promising tool in NAFLD therapy. This paper aims to review the current knowledge regardingthe nutritional approach and its implications with GM and NAFLD treatment. We discuss the positive impact of probiotics, prebiotics, and symbiotics in a reverse dysbiosis state in NAFLD and show the potential beneficial effects of bioactive substances from the diet. The full description of the mechanism of action and comprehensive examination of the impact of nutritional interventions on GM modulation may, in the future, be a simple but essential tool supporting NAFLD therapy.

B Vitamins and One-Carbon Metabolism: Implications in Human Health and Disease

Vitamins B9 (folate) and B12 are essential water-soluble vitamins that play a crucial role in the maintenance of one-carbon metabolism: a set of interconnected biochemical pathways driven by folate and methionine to generate methyl groups for use in DNA synthesis, amino acid homeostasis, antioxidant generation, and epigenetic regulation. Dietary deficiencies in B9 and B12, or genetic polymorphisms that influence the activity of enzymes involved in the folate or methionine cycles, are known to cause developmental defects, impair cognitive function, or block normal blood production. Nutritional deficiencies have historically been treated with dietary supplementation or high-dose parenteral administration that can reverse symptoms in the majority of cases. Elevated levels of these vitamins have more recently been shown to correlate with immune dysfunction, cancer, and increased mortality. Therapies that specifically target one-carbon metabolism are therefore currently being explored for the treatment of immune disorders and cancer. In this review, we will highlight recent studies aimed at elucidating the role of folate, B12, and methionine in one-carbon metabolism during normal cellular processes and in the context of disease progression.

Comparative analysis of restraint stress-induced depressive-like phenotypes in C57BL/6N mice derived from three different sources

C57BL/6NKorl mice are a novel mouse stock recently developed by the National Institute of Food and Drug Safety Evaluation in Korea. Extensive research into the nature of C57BL/6NKorl mice is being conducted. However, there is no scientific evidence for the phenotypic response to restraint stress (RST), a stress paradigm for modeling depressive disorders, in rodents. In this study, we investigated the repeated RST-induced depressive-like phenotypes in C57BL/6 N mouse substrains (viz., C57BL/6NKorl mice from Korea, C57BL/6NA mice from the United States, and C57BL/6NB mice from Japan) obtained from different sources. The results showed that C57BL/6 N mice derived from various sources exposed to repeated RST resulted in depressive-like phenotypes reflected by a similar degree of behavioral modification and susceptibility to oxidative stress in a duration-dependent manner, except for the distinctive features (increased body weight (BW) and tolerance to the suppression of BW gain by exposure to repeated RST) in C57BL/6NKorl mice. Taken together, the duration-dependent alteration in depressive-like phenotypes by repeated exposure to RST observed in this study may provide valuable insights into the nature of C57BL/6NKorl mice as an alternative animal resource for better understanding of the etiology of depressive disorders and the mechanisms of antidepressant actions.

Si-Wu-Tang Alleviates Nonalcoholic Fatty Liver Disease via Blocking TLR4-JNK and Caspase-8-GSDMD Signaling Pathways

Background

Nonalcoholic fatty liver disease (NAFLD) has high global prevalence; however, the treatments of NAFLD are limited due to lack of approved drugs.

Methods

Mice were randomly assigned into three groups: Control group, NAFLD group, NAFLD plus Si-Wu-Tang group. A NAFLD mice model was established by feeding with a methionine- and choline-deficient (MCD) diet for four weeks. Si-Wu-Tang was given orally by gastric gavage at the beginning of 3rd week, and it lasted for two weeks. The treatment effects of Si-Wu-Tang were confirmed by examining the change of body weight, serum alanine aminotransferase (ALT) and aspartate transaminase (AST) levels, Oil Red O staining, and hematoxylin and eosin (H&E) staining of the liver samples and accompanied by steatosis grade scores. The expression and activation of the possible signaling proteins involved in the pathogenesis of NAFLD were determined by western blotting.

Results

Mice fed with four weeks of MCD diet displayed elevated serum levels of ALT and AST, while there was decreased body weight. The hepatic Oil Red O staining and H&E staining showed severe liver steatosis with high steatosis grade scores. All these can be improved by treating with Si-Wu-Tang for two weeks. Mechanistically, the increased hepatic TLR4 expression and its downstream JNK phosphorylation induced by MCD diet were suppressed by Si-Wu-Tang. Moreover, the upregulations of Caspase-8, gasdermin D (GSDMD), and cleaved-GSDMD in liver mediated by MCD diet were all inhibited by Si-Wu-Tang.

Conclusions

Treatment with Si-Wu-Tang improves MCD diet-induced NAFLD in part via blocking TLR4-JNK and Caspase-8-GSDMD signaling pathways, suggesting that Si-Wu-Tang has potential for clinical application in treating NAFLD.

Variations in hepatic lipid species of age-matched male mice fed a methionine-choline-deficient diet and housed in different animal facilities

Background

Non-alcoholic steatohepatitis (NASH) is a common disease and feeding mice a methionine-choline-deficient (MCD) diet is a frequently used model to study its pathophysiology. Genetic and environmental factors influence NASH development and liver lipid content, which was studied herein using C57BL/6 J mice bred in two different animal facilities.

Methods

Age-matched male C57BL/6 J mice bred in two different animal facilities (later on referred to as WT1 and WT2) at the University Hospital of Regensburg were fed identical MCD or control chows for 2 weeks. Hepatic gene and protein expression and lipid composition were determined.

Results

NASH was associated with increased hepatic triglycerides, which were actually higher in WT1 than WT2 liver in both dietary groups. Cholesterol contributes to hepatic injury but was only elevated in WT2 NASH liver. Ceramides account for insulin resistance and cell death, and ceramide species d18:1/16:0 and d18:1/18:0 were higher in the NASH liver of both groups. Saturated sphingomyelins only declined in WT1 NASH liver. Lysophosphatidylcholine concentrations were quite normal in NASH and only one of the 12 altered phosphatidylcholine species declined in NASH liver of both groups. Very few phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol species were comparably regulated in NASH liver of both animal groups. Seven of these lipid species declined and two increased in NASH. Notably, hepatic mRNA expression of proinflammatory (F4/80, CD68, IL-6, TNF and chemerin) and profibrotic genes (TGF beta and alpha SMA) was comparable in WT1 and WT2 mice.

Conclusions

Mice housed and bred in different animal facilities had comparable disease severity of NASH whereas liver lipids varied among the groups. Thus, there was no specific lipid signature for NASH in the MCD model.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-1114-4) contains supplementary material, which is available to authorized users.

The Antisteatotic and Hypolipidemic Effect of Insect Meal in Obese Zucker Rats is Accompanied by Profound Changes in Hepatic Phospholipid and 1-Carbon Metabolism

SCOPE

The hypothesis is tested that insect meal, which has a low methionine content, reduces the hepatic phosphatidylcholine (PC):phosphatidylethanolamine (PE) ratio, which is a critical determinant of hepatic lipid synthesis, by decreasing availability of the methionine metabolite S-adenosylmethionine (SAM).

METHODS AND RESULTS

Obese rats (n = 24) are randomly divided into two groups (Obese Casein and Obese Insect) of 12 rats each. In addition, lean rats (n = 12) are used as control group (LC). Groups LC and OC receive a control diet with casein as protein source, whereas in the OI group, casein is replaced isonitrogenously by insect meal, which is found to be less digestible (-12% units). Plasma and liver concentrations of lipids and hepatic expression of lipid synthesizing genes are reduced in the OI group compared to the OC group. Plasma and liver concentration of PC and the PC:PE ratio are decreased in the OI group compared to the OC group, while hepatic concentration of SAM and the hepatic SAM:S-adenosylhomocysteine (SAH) ratio is lower in the OI group than in the OC group.

CONCLUSION

The decrease of the hepatic PC:PE ratio is probably a key mechanism explaining the pronounced antisteatotic and hypolipidemic action of insect meal in obese rats.