Methionine- and choline-deficient diet induces hepatic changes characteristic of non-alcoholic steatohepatitis

Hedan tablet ameliorated non-alcoholic steatohepatitis by moderating NF-κB and lipid metabolism-related pathways via regulating hepatic metabolites

Non-alcoholic steatohepatitis (NASH) is a severe form of fatty liver disease. If not treated, it can lead to liver damage, cirrhosis and even liver cancer. However, advances in treatment have remained relatively slow, and there is thus an urgent need to develop appropriate treatments. Hedan tablet (HDP) is used to treat metabolic syndrome. However, scientific understanding of the therapeutic effect of HDP on NASH remains limited. We used HDP to treat a methionine/choline-deficient diet-induced model of NASH in rats to elucidate the therapeutic effects of HDP on liver injury. In addition, we used untargeted metabolomics to investigate the effects of HDP on metabolites in liver of NASH rats, and further validated its effects on inflammation and lipid metabolism following screening for potential target pathways. HDP had considerable therapeutic, anti-oxidant, and anti-inflammatory effects on NASH. HDP could also alter the hepatic metabolites changed by NASH. Moreover, HDP considerable moderated NF-κB and lipid metabolism-related pathways. The present study found that HDP had remarkable therapeutic effects in NASH rats. The therapeutic efficacy of HDP in NASH mainly associated with regulation of NF-κB and lipid metabolism-related pathways via arachidonic acid metabolism, glycine-serine-threonine metabolism, as well as steroid hormone biosynthesis.

Current insights into the interplay between gut microbiota-derived metabolites and metabolic-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a prevalent and challenging disease associated with a significant health and economic burden. MAFLD has been subjected to and widely investigated in many studies; however, the underlying pathogenesis and its progression have yet to understand fully. Furthermore, precise biomarkers for diagnosing and specific drugs for treatment are yet to be discovered. Increasing evidence has proven gut microbiota as the neglected endocrine organ that regulates homeostasis and immune response. Targeting gut microbiota is an essential strategy for metabolic diseases, including MAFLD. Gut microbiota in the gut-liver axis is connected through tight bidirectional links through the biliary tract, portal vein, and systemic circulation, producing gut microbiota metabolites. This review focuses on the specific correlation between gut microbiota metabolites and MAFLD. Gut microbiota metabolites are biologically active in the host and, through subsequent changes and biological activities, provide implications for MAFLD. Based on the review studies, gut-liver axis related-metabolites including short-chain fatty acids, bile acids (BAs), lipopolysaccharide, choline and its metabolites, indole and its derivates, branched-chain amino acids, and methionine cycle derivates was associated with MAFLD and could be promising MAFLD diagnosis biomarkers, as well as the targets for MAFLD new drug discovery.

Effect of Kinins on the Hepatic Oxidative Stress in Mice Treated with a Methionine-Choline Deficient Diet

Non-alcoholic fatty liver is the leading cause of hepatic disease worldwide and ranges from simple steatosis to non-alcoholic steatohepatitis (NASH) due to cell injury, oxidative stress, and apoptosis. The kinins' role in the liver has been studied in experimental fibrosis, partial hepatectomy, and ischemia-reperfusion and is related to cell death and regeneration. We investigated its role in experimental NASH induced by a methionine-choline deficient diet for 4 weeks. After that, liver perfusion was performed, and bradykinin (BK) or des-Arg9-BK was infused. Cell death was evaluated by cathepsin-B and caspase-3 activity and oxidative stress by catalase (CAT), glutathione S-transferase, and superoxide dismutase (SOD) activities, as well as malondialdehyde and carbonylated proteins. In control livers, DABK increased CAT activity, which was reversed by antagonist DALBK. In the NASH group, kinins tend to decrease antioxidant activity, with SOD activity being significantly reduced by BK and DABK. Malondialdehyde levels increased in all NASH groups, but carbonylated protein did not. DABK significantly decreased cathepsin-B in the NASH group, while caspase-3 was increased by BK in control animals. Our results suggest that B1R and/or B2R activation did not induce oxidative stress but affected the antioxidant system, reducing SOD in the NASH group.

Gut-liver axis in the progression of nonalcoholic fatty liver disease: From the microbial derivatives-centered perspective

Nonalcoholic fatty liver disease (NAFLD) is one of the world's most common chronic liver diseases. However, its pathogenesis remains unclear. With the deepening of research, NAFLD is considered a metabolic syndrome associated with the environment, heredity, and metabolic disorders. Recently, the close relationship between the intestinal microbiome and NAFLD has been discovered, and the theory of the "gut-liver axis" has been proposed. In short, the gut bacteria directly reach the liver via the portal vein through the damaged intestinal wall or indirectly participate in the development of NAFLD through signaling pathways mediated by their components and metabolites. This review focuses on the roles of microbiota-derived lipopolysaccharide, DNA, peptidoglycan, bile acids, short-chain fatty acids, endogenous ethanol, choline and its metabolites, indole and its derivatives, and bilirubin and its metabolites in the progression of NAFLD, which may provide significative insights into the pathogenesis, diagnosis, and treatment for this highly prevalent liver disease.

The central role of the gut in intensive care

Critically ill patients undergo early impairment of their gut microbiota (GM) due to routine antibiotic therapies and other environmental factors leading to intestinal dysbiosis. The GM establishes connections with the rest of the human body along several axes representing critical inter-organ crosstalks that, once disrupted, play a major role in the pathophysiology of numerous diseases and their complications. Key players in this communication are GM metabolites such as short-chain fatty acids and bile acids, neurotransmitters, hormones, interleukins, and toxins. Intensivists juggle at the crossroad of multiple connections between the intestine and the rest of the body. Harnessing the GM in ICU could improve the management of several challenges, such as infections, traumatic brain injury, heart failure, kidney injury, and liver dysfunction. The study of molecular pathways affected by the GM in different clinical conditions is still at an early stage, and evidence in critically ill patients is lacking. This review aims to describe dysbiosis in critical illness and provide intensivists with a perspective on the potential as adjuvant strategies (e.g., nutrition, probiotics, prebiotics and synbiotics supplementation, adsorbent charcoal, beta-lactamase, and fecal microbiota transplantation) to modulate the GM in ICU patients and attempt to restore eubiosis.

Adropin’s Role in Energy Homeostasis and Metabolic Disorders

Adropin is a novel 76-amino acid-peptide that is expressed in different tissues and cells including the liver, pancreas, heart and vascular tissues, kidney, milk, serum, plasma and many parts of the brain. Adropin, encoded by the Enho gene, plays a crucial role in energy homeostasis. The literature review indicates that adropin alleviates the degree of insulin resistance by reducing endogenous hepatic glucose production. Adropin improves glucose metabolism by enhancing glucose utilization in mice, including the sensitization of insulin signaling pathways such as Akt phosphorylation and the activation of the glucose transporter 4 receptor. Several studies have also demonstrated that adropin improves cardiac function, cardiac efficiency and coronary blood flow in mice. Adropin can also reduce the levels of serum triglycerides, total cholesterol and low-density lipoprotein cholesterol. In contrast, it increases the level of high-density lipoprotein cholesterol, often referred to as the beneficial cholesterol. Adropin inhibits inflammation by reducing the tissue level of pro-inflammatory cytokines such as tumor necrosis factor alpha and interleukin-6. The protective effect of adropin on the vascular endothelium is through an increase in the expression of endothelial nitric oxide synthase. This article provides an overview of the existing literature about the role of adropin in different pathological conditions.

Liver Protein Expression in NASH Mice on a High-Fat Diet: Response to Multi-Mineral Intervention

Male MS-NASH mice were maintained on a high-fat diet for 16 weeks with and without red algae-derived minerals. Obeticholic acid (OCA) was used as a comparator in the same strain and diet. C57BL/6 mice maintained on a standard (low-fat) rodent chow diet were used as a control. At the end of the in-life portion of the study, body weight, liver weight, liver enzyme levels and liver histology were assessed. Samples obtained from individual livers were subjected to Tandem Mass Tag labeling / mass spectroscopy for protein profile determination. As compared to mice maintained on the low-fat diet, all high-fat-fed mice had increased whole-body and liver weight, increased liver enzyme (aminotransferases) levels and widespread steatosis / ballooning hepatocyte degeneration. Histological evidence for liver inflammation and collagen deposition was also present, but changes were to a lesser extent. A moderate reduction in ballooning degeneration and collagen deposition was observed with mineral supplementation. Control mice on the high-fat diet alone demonstrated multiple protein changes associated with dysregulated fat and carbohydrate metabolism, lipotoxicity and oxidative stress. Cholesterol metabolism and bile acid formation were especially sensitive to diet. In mice receiving multi-mineral supplementation along with the high-fat diet, there was reduced liver toxicity as evidenced by a decrease in levels of several cytochrome P450 enzymes and other oxidant-generating moieties. Additionally, elevated expression of several keratins was also detected in mineral-supplemented mice. The protein changes observed with mineral supplementation were not seen with OCA. Our previous studies have shown that mice maintained on a high-fat diet for up to 18 months develop end-stage liver injury including hepatocellular carcinoma. Mineral-supplemented mice were substantially protected against tumor formation and other end-state consequences of high-fat feeding. The present study identifies early (16-week) protein changes occurring in the livers of the high-fat diet-fed mice, and how the expression of these proteins is influenced by mineral supplementation. These findings help elucidate early protein changes that contribute to end-stage liver injury and potential mechanisms by which dietary minerals may mitigate such damage.

Melatonin Attenuates Inflammation, Oxidative Stress, and DNA Damage in Mice with Nonalcoholic Steatohepatitis Induced by a Methionine- and Choline-Deficient Diet

Nonalcoholic steatohepatitis (NASH) is a disease with a high incidence worldwide, but its diagnosis and treatment are poorly managed. In this study, NASH pathophysiology and DNA damage biomarkers were investigated in mice with NASH treated and untreated with melatonin (MLT). C57BL/6 mice were fed a methionine- and choline-deficient (MCD) diet for 4 weeks to develop NASH. Melatonin was administered at 20 mg/kg during the last 2 weeks. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured, and hepatic tissue was dissected for histological analysis, evaluation of lipoperoxidation, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), as well as nuclear factor-erythroid 2 (Nrf2), tumor necrosis factor alpha (TNF-α), inducible nitric oxide synthase (iNOS), and transforming growth factor beta (TGF-β) expression by immunohistochemistry. DNA damage was evaluated using Comet assay, while a micronucleus test in bone marrow was performed to assess the genomic instability associated with the disease. Melatonin decreased AST and ALT, liver inflammatory processes, balloonization, and fibrosis in mice with NASH, decreasing TNF-α, iNOS, and TGF-β, as well as oxidative stress, shown by reducing lipoperoxidation and intensifying Nrf2 expression. The SOD and GPx activities were increased, while CAT was decreased by treatment with MLT. Although the micronucleus frequency was not increased in mice with NASH, a protective effect on DNA was observed with MLT treatment in blood and liver tissues using Comet assay. As conclusions, MLT slows down the progression of NASH, reducing hepatic oxidative stress and inflammatory processes, inhibiting DNA damage via anti-inflammatory and antioxidant actions.

The Critical and Diverse Roles of CD4-CD8- Double Negative T Cells in Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS

Hepatic inflammation is a hallmark of nonalcoholic fatty liver disease (NAFLD). Double negative T (DNT) cells are a unique subset of T lymphocytes that do not express CD4, CD8, or natural killer cell markers, and studies have suggested that DNT cells play critical and diverse roles in the immune system. However, the role of intrahepatic DNT cells in NAFLD is largely unknown.

METHODS

The proportions and RNA transcription profiling of intrahepatic DNT cells were compared between C57BL/6 mice fed with control diet or methionine-choline-deficient diet for 5 weeks. The functions of DNT cells were tested in vitro and in vivo.

RESULTS

The proportion of intrahepatic DNT cells was significantly increased in mice with diet-induced NAFLD. In NAFLD mice, the proportion of intrahepatic TCRγδ⁺ DNT cells was increased along with elevated interleukin (IL) 17A; in contrast, the percentage of TCRαβ⁺ DNT cells was decreased, accompanied by reduced granzyme B (GZMB). TCRγδ⁺ DNT cell depletion resulted in lowered liver IL17A levels and significantly alleviated NAFLD. Adoptive transfer of intrahepatic TCRαβ⁺ DNT cells from control mice increased intrahepatic CD4 and CD8 T cell apoptosis and inhibited NAFLD progression. Furthermore, we revealed that adrenic acid and arachidonic acid, harmful fatty acids that were enriched in the liver of the mice with NAFLD, could induce apoptosis of TCRαβ⁺ DNT cells and inhibit their immunosuppressive function and nuclear factor kappa B (NF-κB) or AKT signaling pathway activity. However, arachidonic acid facilitated IL17A secretion by TCRγδ⁺ DNT cells, and the NF-κB signaling pathway was involved. Finally, we also confirmed the variation of intrahepatic TCRαβ⁺ DNT cells and TCRγδ⁺ DNT cells in humans.

CONCLUSIONS

During NAFLD progression, TCRγδ⁺ DNT cells enhance IL17A secretion and aggravate liver inflammation, whereas TCRαβ⁺ DNT cells decrease GZMB production and lead to weakened immunoregulatory function. Shifting of balance from TCRγδ⁺ DNT cell response to one that favors TCRαβ⁺ DNT regulation would be beneficial for the prevention and treatment of NAFLD.

Oxidative Stress in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a challenging disease caused by multiple factors, which may partly explain why it still remains an orphan of adequate therapies. This review highlights the interaction between oxidative stress (OS) and disturbed lipid metabolism. Several reactive oxygen species generators, including those produced in the gastrointestinal tract, contribute to the lipotoxic hepatic (and extrahepatic) damage by fatty acids and a great variety of their biologically active metabolites in a “multiple parallel-hit model”. This leads to inflammation and fibrogenesis and contributes to NAFLD progression. The alterations of the oxidant/antioxidant balance affect also metabolism-related organelles, leading to lipid peroxidation, mitochondrial dysfunction, and endoplasmic reticulum stress. This OS-induced damage is at least partially counteracted by the physiological antioxidant response. Therefore, modulation of this defense system emerges as an interesting target to prevent NAFLD development and progression. For instance, probiotics, prebiotics, diet, and fecal microbiota transplantation represent new therapeutic approaches targeting the gut microbiota dysbiosis. The OS and its counter-regulation are under the influence of individual genetic and epigenetic factors as well. In the near future, precision medicine taking into consideration genetic or environmental epigenetic risk factors, coupled with new OS biomarkers, will likely assist in noninvasive diagnosis and monitoring of NAFLD progression and in further personalizing treatments.

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

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

Honokiol Alleviates Methionine-Choline Deficient Diet-Induced Hepatic Steatosis and Oxidative Stress in C57BL/6 Mice by Regulating CFLAR-JNK Pathway

Background

Honokiol (HNK) has been reported to possess various beneficial effects in the context of metabolic disorders, including fatty liver, insulin resistance, and oxidative stress which are closely related to nonalcoholic steatohepatitis (NASH), however with no particular reference to CFLAR or JNK.

Methods

C57BL/6 mice were fed methionine-choline-deficient (MCD) diet and administered simultaneously with HNK (10 and 20 mg/kg once a day, ig) for 6 weeks, and NCTC1469 cells were pretreated, respectively, by oleic acid (OA, 0.5 mmol/L) plus palmitic acid (PA, 0.25 mmol/L) for 24 h, and adenovirus-down Cflar for 24 h, then exposed to HNK (10 and 20 μmol/L) for 24 h. Commercial kits, H&E, MT, ORO staining, RT-qPCR, and Western blotting were used to detect the biomarkers, hepatic histological changes, and the expression of key genes involved in NASH.

Results

The in vivo results showed that HNK suppressed the phosphorylation of JNK (pJNK) by activating CFLAR; enhanced the mRNA expression of lipid metabolism-related genes Acox, Cpt1α, Fabp5, Gpat, Mttp, Pparα, and Scd-1; and decreased the levels of hepatic TG, TC, and MDA, as well as the levels of serum ALT and AST. Additionally, HNK enhanced the protein expression of oxidative stress-related key regulatory gene NRF2 and the activities of antioxidases HO-1, CAT, and GSH-Px and decreased the protein levels of prooxidases CYP4A and CYP2E1. The in vivo effects of HNK on the expression of CLFAR, pJNK, and NRF2 were proved by the in vitro experiments. Moreover, HNK promoted the phosphorylation of IRS1 (pIRS1) in both tested cells and increased the uptake of fluorescent glucose 2-NBDG in OA- and PA-pretreated cells.

Conclusions

HNK ameliorated NASH mainly by activating the CFLAR-JNK pathway, which not only alleviated fat deposition by promoting the efflux and β-oxidation of fatty acids in the liver but also attenuated hepatic oxidative damage and insulin resistance by upregulating the expression of NRF2 and pIRS1.

Reduced Serum Cholesterol and Triglyceride Levels in a Choline-Deficient L-Amino Acid-Defined High-Fat Diet (CDAHFD)-Induced Mouse Model of Non-alcoholic Steatohepatitis (NASH)

Non-alcoholic fatty liver disease (NAFLD) or non-alcoholic seatohepatitis (NASH) is one of the major health problems world wide, because of increased abdominal obesity. To date, specific and effective medications to treat or prevent NAFLD/NASH have not been established. To identify appropriate molecular targets for that purpose, suitable animal models of NAFLD/NASH have been explored. A choline-deficient amino acid-defined high fat diet (CDAHFD)-induced mouse model of NASH has been developed. However, its relevance to human NASH, including serum lipid profiles, have not been clearly defined. In this study, we have revealed that mice fed CDAHFD showed significantly lowerd serum total cholesterol and triglyceride (TG) levels, in addition to reduced body weight (BW). Furthermore, hepatic microsomal triglyceride transfer protein (MTP) expression was significantly downregulated in CDAHFD-fed mice. Thus, the current CDAHFD-fed mouse model has points that are distinct from human NAFLD/NASH, in general, which is based upon abdominal obesity.

Resolvin D1 mitigates non-alcoholic steatohepatitis by suppressing the TLR4-MyD88-mediated NF-κB and MAPK pathways and activating the Nrf2 pathway in mice

AIMS

Resolvin D1 (RvD1), a potent endogenous lipid mediator converted from docosahexaenoic acid (DHA), has exert anti-inflammatory and antioxidant effects in many preclinical disease models, but its potential role in non-alcoholic steatohepatitis (NASH) remains elusive. This study was performed to investigate the protective effects and mechanisms of RvD1 in NASH.

MAIN METHODS

In vivo, male C57BL/6 mice were fed an MCD diet for 4 weeks to induce NASH. RvD1 was added in the last 2 weeks of the feeding period. In vitro, lipopolysaccharide (LPS)-activated RAW264.7 macrophages were pretreated with increasing concentrations of RvD1. Serum liver functional markers and hepatic oxidative stress indicators were measured biochemically. Mouse liver tissue sections were stained with hematoxylin-eosin, oil red O, and Masson's trichrome to assess the severity of steatohepatitis, steatosis and fibrosis. The qRT-PCR, immunohistochemistry and Western blotting assays were applied to analyse mechanisms underlying RvD1 protection in NASH.

KEY FINDINGS

In vivo, RvD1 significantly attenuates steatohepatitis in MCD diet-fed mice by modulating key events, including steatosis, inflammation, oxidative stress and fibrosis in the progression of NASH. In vitro, RvD1 also represses LPS-induced inflammation in RAW264.7 cells. These effects may be mainly attributed to RvD1 markedly suppressing excessive inflammatory responses via the inhibition of the TLR4-MyD88-mediated NF-κB and MAPK signalling pathways as well as enhancing antioxidation capacity via the activation of the Nrf2 pathway.

SIGNIFICANCE

These results demonstrate that RvD1 is a promising hepatoprotective agent for the therapy of NASH.

Role of oxidative stress in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common chronic liver disease worldwide and is strongly associated with the presence of oxidative stress. Disturbances in lipid metabolism lead to hepatic lipid accumulation, which affects different reactive oxygen species (ROS) generators, including mitochondria, endoplasmic reticulum, and NADPH oxidase. Mitochondrial function adapts to NAFLD mainly through the downregulation of the electron transport chain (ETC) and the preserved or enhanced capacity of mitochondrial fatty acid oxidation, which stimulates ROS overproduction within different ETC components upstream of cytochrome c oxidase. However, non-ETC sources of ROS, in particular, fatty acid β-oxidation, appear to produce more ROS in hepatic metabolic diseases. Endoplasmic reticulum stress and NADPH oxidase alterations are also associated with NAFLD, but the degree of their contribution to oxidative stress in NAFLD remains unclear. Increased ROS generation induces changes in insulin sensitivity and in the expression and activity of key enzymes involved in lipid metabolism. Moreover, the interaction between redox signaling and innate immune signaling forms a complex network that regulates inflammatory responses. Based on the mechanistic view described above, this review summarizes the mechanisms that may account for the excessive production of ROS, the potential mechanistic roles of ROS that drive NAFLD progression, and therapeutic interventions that are related to oxidative stress.

Study of Methionine Choline Deficient Diet-Induced Steatosis in Mice Using Endogenous Fluorescence Spectroscopy

Non-alcoholic fatty liver disease is a highly prevalent condition worldwide that increases the risk to develop liver fibrosis, cirrhosis, and hepatocellular carcinoma. Thus, it is imperative to develop novel diagnostic tools that together with liver biopsy help to differentiate mild and advanced degrees of steatosis. Ex-vivo liver samples were collected from mice fed a methionine-choline deficient diet for two or eight weeks, and from a control group. The degree of hepatic steatosis was histologically evaluated, and fat content was assessed by Oil-Red O staining. On the other hand, fluorescence spectroscopy was used for the assessment of the steatosis progression. Fluorescence spectra were recorded at excitation wavelengths of 330, 365, 385, 405, and 415 nm by establishing surface contact of the fiber optic probe with the liver specimens. A multi-variate statistical approach based on principal component analysis followed by quadratic discriminant analysis was applied to spectral data to obtain classifiers able to distinguish mild and moderate stages of steatosis at the different excitation wavelengths. Receiver Operating Characteristic (ROC) curves were computed to compare classifier’s performances for each one of the five excitation wavelengths and steatosis stages. Optimal sensitivity and specificity were calculated from the corresponding ROC curves using the Youden index. Intensity in the endogenous fluorescence spectra at the given wavelengths progressively increased according to the time of exposure to diet. The area under the curve of the spectra was able to discriminate control liver samples from those with steatosis and differentiate among the time of exposure to the diet for most of the used excitation wavelengths. High specificities and sensitivities were obtained for every case; however, fluorescence spectra obtained by exciting with 405 nm yielded the best results distinguishing between the mentioned classes with a total classification error of 1.5% and optimal sensitivities and specificities better than 98.6% and 99.3%, respectively.

Tangshen Formula Alleviates Hepatic Steatosis by Inducing Autophagy Through the AMPK/SIRT1 Pathway

Tangshen formula (TSF), a formula of Chinese herbal medicine, improves lipid metabolism in humans and animals with diabetic kidney disease. However, the effect and mechanism of TSF on nonalcoholic fatty liver disease (NAFLD) remain unclear. The activation of autophagy appears to be a potential mechanism for improving NAFLD. In the present study, we examined the therapeutic effect of TSF on hepatic steatosis and sought to explore whether its effect is related to activating autophagy. Here, we showed that TSF treatment significantly attenuated hepatic steatosis in both high-fat diet (HFD) and methionine choline-deficient diet (MCDD)-fed mice. Meanwhile, TSF reduced lipid accumulation in palmitate (PA)-stimulated HepG2 cells and primary mouse hepatocytes. Furthermore, TSF increased Sirtuin 1 (SIRT1) expression and promoted autophagy activation in vivo. TSF also improved PA-induced suppression of both SIRT1 expression and SIRT1-dependent autophagy, thereby alleviating intracellular lipid accumulation in vitro. In addition, TSF increased SIRT1 expression and induced autophagy in an adenosine monophosphate-activated protein kinase (AMPK)-dependent manner. Moreover, SIRT1 knockdown abolished the autophagy-inducing and lipid-lowering effects of TSF. In conclusion, TSF improved lipid accumulation and hepatic steatosis by inducing the AMPK/SIRT1 pathway-mediated autophagy.

Liver Histological Improvement After Administration of High-Dose Vitamin C in Guinea Pig with Nonalcoholic Steatohepatitis

Background: Vitamin C is a strong antioxidant, and the health effects of vitamin C megadoses have not been validated despite the apparent health benefits. Therefore, the present study sought to confirm the effects of vitamin C megadoses. Materials and Methods : Four groups of six guinea pigs were used. Each group was fed one of the following diets for three weeks: normal diet, methionine choline-deficient diet, methionine choline-deficient diet + vitamin C megadose (MCD + vit C 2.5 g/kg/day), and methionine-choline deficient diet + ursodeoxycholic acid (MCD + UDCA 30 mg/kg/day). The MCD diet was given to induce nonalcoholic steatohepatitis, and UDCA was used to treat nonalcoholic steatohepatitis. Three weeks after initial diet administration, the results of biochemical tests and liver biopsy were compared between the groups. Results: The cytoplasm state was similar in the MCD + vit C and MCD + UDCA groups, exhibiting clearing of the cytoplasm and ballooning degeneration. However, macrovesicular steatosis was not observed in the MCD + vit C group. Aspartate transaminase and alanine transaminase were elevated significantly following vitamin C administration. Conclusions: The present study confirmed that alone vitamin C megadoses are potential remedies for nonalcoholic steatohepatitis, based on the liver biopsy results of guinea pigs that were unable to synthesize vitamin C.

Inhibitory Effects of Sodium Alginate on Hepatic Steatosis in Mice Induced by a Methionine- and Choline-deficient Diet

Nonalcoholic steatohepatitis (NASH) progresses from nonalcoholic fatty liver disease (NAFLD); however, efficacious drugs for NASH treatment are lacking. Sodium alginate (SA), a soluble dietary fiber extracted from brown algae, could protect the small intestine from enterobacterial invasion. NASH pathogenesis has been suggested to be associated with enterobacterial invasion, so we examined the effect of SA on methionine- and choline-deficient (MCD) diet-induced steatohepatitis in mice (the most widely-used model of NASH). The mice (n = 31) were divided into three groups (mice fed with regular chow, MCD diet, and MCD diet premixed with 5% SA) for 4 and 8 weeks. The MCD diet increased lipid accumulation and inflammation in the liver, the NAFLD Activity Score and hepatic mRNA expression of tumor necrosis factor-α and collagen 1α1, and induced macrophage infiltration. Villus shortening, disruption of zonula occludens-1 localization and depletion of mucus production were observed in the small intestine of the MCD-group mice. SA administration improved lipid accumulation and inflammation in the liver, and impaired barrier function in the small intestine. Collectively, these results suggest that SA is useful for NASH treatment because it can prevent hepatic inflammation and fatty degeneration by maintaining intestinal barrier function.

Oxidative Stress and Antioxidant Biomarkers in Clinical and Experimental Models of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a term that covers a range of hepatic disorders involving fat deposits in the liver. NAFLD begins with simple steatosis and progresses into non-alcoholic steatohepatitis (NASH) characterised by inflammation, fibrosis, apoptosis, oxidative stress, lipid peroxidation, mitochondrial dysfunction and release of adipokines and pro-inflammatory cytokines. Oxidative stress and antioxidants are known to play a vital role in the pathogenesis and severity of NAFLD/NASH. A number of oxidative stress and antioxidant markers are employed in the assessment of the pathological state and progression of the disease. In this article, we review several biomarkers of oxidative stress and antioxidants that have been measured at clinical and experimental levels. Also included is a comprehensive description of oxidative stress, sources and contribution to the pathogenesis of NAFLD/NASH.

Silybin Alleviates Hepatic Steatosis and Fibrosis in NASH Mice by Inhibiting Oxidative Stress and Involvement with the Nf-κB Pathway

BACKGROUND AND AIM

Silybin is the major biologically active compound of silymarin, the standardized extract of the milk thistle (Silybum marianum). Increasing numbers of studies have shown that silybin can improve nonalcoholic steatohepatitis (NASH) in animal models and patients; however, the mechanisms underlying silybin's actions remain unclear.

METHODS

Male C57BL/6 mice were fed a methionine-choline deficient (MCD) diet for 8 weeks to induce the NASH model, and silybin was orally administered to the NASH mice. The effects of silybin on lipid accumulation, hepatic fibrosis, oxidative stress, inflammation-related gene expression and nuclear factor kappa B (NF-κB) activities were evaluated by biochemical analysis, immunohistochemistry, immunofluorescence, quantitative real-time PCR and western blot.

RESULTS

Silybin treatment significantly alleviated hepatic steatosis, fibrosis and inflammation in MCD-induced NASH mice. Moreover, silybin inhibited HSC activation and hepatic apoptosis and prevented the formation of MDBs in the NASH liver. Additionally, silybin partly reversed the abnormal expression of lipid metabolism-related genes in NASH. Further study showed that the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway played important roles in the silybin-derived antioxidant effect, as evidenced by the upregulation of Nrf2 target genes in the silybin treatment group. In addition, silybin significantly downregulated the expression of inflammation-related genes and suppressed the activity of NF-κB signaling.

CONCLUSIONS

Silybin was effective in preventing the MCD-induced increases in hepatic steatosis, fibrosis and inflammation. The effect was related to alteration of lipid metabolism-related gene expression, activation of the Nrf2 pathway and inhibition of the NF-κB signaling pathway in the NASH liver.

Mitochondrial role in the neonatal predisposition to developing nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a global epidemic in obese children and adults, and the onset might have fetal origins. A growing body of evidence supports the role of developmental programming, whereby the maternal environment affects fetal and infant development, altering the risk profile for disease later in life. Human and nonhuman primate studies of maternal obesity demonstrate that risk factors for pediatric obesity and NAFLD begin in utero. The pathologic mechanisms for NAFLD are multifactorial but have centered on altered mitochondrial function/dysfunction that might precede insulin resistance. Compared with the adult liver, the fetal liver has fewer mitochondria, low activity of the fatty acid metabolic enzyme carnitine palmitoyl-CoA transferase-1, and little or no gluconeogenesis. Exposure to excess maternal fuels during fetal life uniquely alters hepatic fatty acid oxidation, tricarboxylic acid cycle activity, de novo lipogenesis, and mitochondrial health. These events promote increased oxidative stress and excess triglyceride storage, and, together with altered immune function and epigenetic changes, they prime the fetal liver for NAFLD and might drive the risk for nonalcoholic steatohepatitis in the next generation.

Editor's Highlight: PCB126 Exposure Increases Risk for Peripheral Vascular Diseases in a Liver Injury Mouse Model

The liver is vital for xenobiotic and endobiotic metabolism. Previously, we demonstrated that a compromised liver worsened toxicity associated with exposure to polychlorinated biphenyls (PCBs), through disruption of energy homeostasis. However, the role of a compromised liver in defining dioxin-like PCB126 toxicity on the peripheral vasculature and associated inflammatory diseases is yet to be studied. This study investigated the effects of PCB126 on vascular inflammation linked to hepatic dysfunction utilizing a liver injury mouse model. Male C57Bl/6 mice were fed either an amino acid control diet (CD) or a methionine-choline deficient (MCD) diet in this 14-week study. Mice were exposed to PCB126 (0.5 mg/kg) and analyzed for inflammatory, calorimetric and metabolic parameters. MCD diet-fed mice demonstrated steatosis, indicative of a compromised liver. Mice fed the MCD-diet and subsequently exposed to PCB126 manifested lower body fat mass, increased liver to body weight ratio and alterations in hepatic gene expression related to lipid and carbohydrate metabolism, implicating metabolic disturbances. PCB126-induced steatosis irrespective of the diet type, but only the MCD + PCB126 group exhibited steatohepatitis and fibrosis. Furthermore, PCB126 exposure in MCD-fed mice led to increased plasma inflammatory markers such as Icam-1, plasminogen activator inhibitor-1 and proatherogenic trimethylamine-N-oxide, suggesting inflammation of the peripheral vasculature that is characteristic of atherosclerosis. Taken together, our data provide new evidence of a link between a compromised liver, PCB-mediated hepatic inflammation and vascular inflammatory markers, suggesting that environmental pollutants can promote crosstalk between different organ systems, leading to inflammatory disease pathologies.

Autophagy is involved in acetylshikonin ameliorating non-alcoholic steatohepatitis through AMPK/mTOR pathway

Acetylshikonin (AS), a naphthoquinone constituent derived from Lithospermum erythrorhizon, has been revealed various pharmacological activities including anti-oxidative, anti-inflammatory and antifertility effects. Our previous study has illuminated the effects of AS on preventing obesity and hepatic steatosis in db/db mice. However, the effects of AS and the molecular mechanisms for curing non-alcoholic steatohepatitis (NASH) have not yet been studied. Autophagy has been considered as a lysosomal degradative pathway responsible for the removal of cellular lipid droplets through a process called lipophagy, which is recognized as a potential therapeutic approach for NASH. Here we hypothesize that autophagy is involved in the beneficial effects of AS on methionine-choline deficient (MCD) diet-induced NASH of mice. In this study, we observed that AS treatment ameliorated the pathological signs of NASH, and markedly suppressed the levels of hepatic IL-1β and TNF-α cytokines, and hepatocyte apoptotic cells in MCD diet-induced mice. Moreover, immunological analyses showed that the elevated expression of the fibrotic markers including α-SMA, collegen I, collegen III and fibronectin in MCD diet-induced mice were notably down-regulated by AS treatment. Nevertheless, the beneficial effects of AS on ameliorating NASH were notably counteracted by co-administration of chloroquine, an autophagy inhibitor. Furthermore, our data suggested that AS treatment increased hepatocyte autophagy in MCD diet-induced mice via AMPK/mTOR pathway. These findings suggest that AS could be therapeutically effective in the development of NASH by ameliorating steatosis, inflammation, liver injury and fibrosis.

Role of xenobiotics in the induction and progression of fatty liver disease

Non-alcoholic fatty liver disease is a major cause of chronic liver pathology in humans. Fatty liver disease involves the accumulation of hepatocellular fat in hepatocytes that can progress to hepatitis. Steatohepatitis is categorized into alcoholic (ASH) or non-alcoholic (NASH) steatohepatitis based on the etiology of the insult. Both pathologies involve an initial steatosis followed by a progressive inflammation of the liver and eventual hepatic fibrosis (steatohepatitis) and cirrhosis. The involvement of pharmaceuticals and other chemicals in the initiation and progression of fatty liver disease has received increased study. This review will examine not only how xenobiotics initiate hepatic steatosis and steatohepatitis but also how the presence of fatty liver may modify the metabolism and pathologic effects of xenobiotics. The feeding of a high fat diet results in changes in the expression of nuclear receptors that are involved in adaptive and adverse liver effects following xenobiotic exposure. High fat diets also modulate cellular and molecular pathways involved in inflammation, metabolism, oxidative phosphorylation and cell growth. Understanding the role of hepatic steatosis and steatohepatitis on the sequelae of toxic and pathologic changes seen following xenobiotic exposure has importance in defining proper and meaningful human risk characterization of the drugs and other chemical agents.

The Effects of Betaine on the Nuclear Fractal Dimension, Chromatin Texture, and Proliferative Activity in Hepatocytes in Mouse Model of Nonalcoholic Fatty Liver Disease

The effects of betaine on hepatocytes chromatin architecture changes were examined by using fractal and gray-level co-occurrence matrix (GLCM) analysis in methionine/choline-deficient (MCD) diet-induced, nonalcoholic fatty liver disease (NAFLD). Male C57BL/6 mice were divided into groups: (1) Control: standard diet; (2) BET: standard diet and betaine supplementation through drinking water (solution 1.5%); (3) MCD group: MCD diet for 6 weeks; (4) MCD+BET: fed with MCD diet + betaine for 6 weeks. Liver tissue was collected for histopathology, immunohistochemistry, and determination of fractal dimension and GLCM parameters. MCD diet induced diffuse micro- and macrovesicular steatosis accompanied with increased Ki67-positive hepatocyte nuclei. Steatosis and Ki67 immunopositivity were less prominent in the MCD+BET group compared with the MCD group. Angular second moment (ASM) and inverse difference moment (IDM) (textural homogeneity markers) were significantly increased in the MCD+BET group versus the MCD group (p<0.001), even though no difference between the MCD and the control group was evident. Heterogeneity parameters, contrast, and correlation were significantly increased in the MCD group versus the control (p<0.001). On the other hand, betaine treatment significantly reduced correlation, contrast, and entropy compared with the MCD group (p<0.001). Betaine attenuated MCD diet-induced NAFLD by reducing fat accumulation and inhibiting hepatocyte proliferation. Betaine supplementation increased nuclear homogeneity and chromatin complexity with reduction of entropy, contrast, and correlation.

Metabolomic characteristics of cholesterol-induced non-obese nonalcoholic fatty liver disease in mice

Nonalcoholic fatty liver disease (NAFLD) in non-obese patients remains a clinical condition with unclear etiology and pathogenesis. Using a metabolomics approach in a mouse model that recapitulates almost all the characteristic features of non-obese NAFLD, we aimed to advance mechanistic understanding of this disorder. Mice fed high fat, high cholesterol, cholate (HFHCC) diet for three weeks consistently developed hepatic pathology similar to NAFLD and nonalcoholic steatohepatitis (NASH) without changes to body weight or fat pad weights. Gas- and liquid chromatography/mass spectrometry-based profiling of lipidomic and primary metabolism changes in the liver and plasma revealed that systemic mechanisms leading to steatosis and hepatitis in this non-obese NAFLD model were driven by a combination of effects directed by elevated free cholesterol, cholesterol esters and cholic acid, and associated changes to metabolism of sphingomyelins and phosphatidylcholines. These results demonstrate that mechanisms underlying cholesterol-induced non-obese NAFLD are distinct from NAFLD occurring as a consequence of metabolic syndrome. In addition, this investigation provides one of the first metabolite reference profiles for interpreting effects of dietary and hepatic cholesterol in human non-obese NAFLD/NASH patients.

Editor's Highlight: Perfluorooctane Sulfonate-Choline Ion Pair Formation: A Potential Mechanism Modulating Hepatic Steatosis and Oxidative Stress in Mice

The mechanisms underlying perfluorooctane sulfonate (PFOS)-induced steatosis remain unclear. The hypothesis that PFOS causes steatosis and other hepatic effects by forming an ion pair with choline was examined. C57BL/6 mice were fed either a control diet or a marginal methionine/choline-deficient (mMCD) diet, with and without 0.003, 0.006, or 0.012% potassium PFOS. Dietary PFOS caused a dose-dependent decrease in body weight, and increases in the relative liver weight, hepatic triglyceride concentration and serum markers of liver toxicity and oxidative stress. Some of these effects were exacerbated in mice fed the mMCD diet supplemented with 0.012% PFOS compared with those fed the control diet supplemented with 0.012% PFOS. Surprisingly, serum PFOS concentrations were higher while liver PFOS concentrations were lower in mMCD-fed mice compared with corresponding control-fed mice. To determine if supplemental dietary choline could prevent PFOS-induced hepatic effects, C57BL/6 mice were fed a control diet, or a choline supplemental diet (1.2%) with or without 0.003% PFOS. Lipidomic analysis demonstrated that PFOS caused alterations in hepatic lipid metabolism in the PFOS-fed mice compared with controls, and supplemental dietary choline prevented these PFOS-induced changes. Interestingly, dietary choline supplementation also prevented PFOS-induced oxidative damage. These studies are the first to suggest that PFOS may cause hepatic steatosis and oxidative stress by effectively reducing the choline required for hepatic VLDL production and export by forming an ion pair with choline, and suggest that choline supplementation may prevent and/or treat PFOS-induced hepatic steatosis and oxidative stress.

Can aging be 'drugged'?

The engines that drive the complex process of aging are being identified by model-organism research, thereby providing potential targets and rationale for drug studies. Several studies of small molecules have already been completed in animal models with the hope of finding an elixir for aging, with a few compounds showing early promise. What lessons can we learn from drugs currently being tested, and which pitfalls can we avoid in our search for a therapeutic for aging? Finally, we must also ask whether an elixir for aging would be applicable to everyone, or whether we age differently, thus potentially shortening lifespan in some individuals.

The Ethanol Extract from Lonicera japonica Thunb. Regresses Nonalcoholic Steatohepatitis in a Methionine- and Choline-Deficient Diet-Fed Animal Model

Nonalcoholic steatohepatitis (NASH) is characterized as fat accumulation in the hepatic tissue associated with various degrees of inflammation and progressive fibrosis. The potent anti-inflammatory and ethnopharmacological properties of Lonicera japonica Thunb. (Caprifoliaceae) make it an excellent source of novel medicinal targets for the treatment of NASH. The aim of the study was to investigate the effects of L. japonica ethanol extract (LJEE) on NASH in mice. C57BL/6J mice were fed with methionine-choline-deficient diet (MCDD) for eight weeks to promote the development of NASH. After development of the model, the mice were administered LJEE once daily via oral gavage at doses of 100, 200, or 300 mg/kg for another four weeks. Simultaneous treatments with LJEE (300 mg/kg/day) resulted in pronounced improvements in liver steatosis, ballooning degeneration, and inflammation. LJEE prevented MCDD-induced plasma level increases in aspartate aminotransferase and alanine aminotransferase. LJEE significantly reduced hepatic malondialdehyde level and ameliorated hepatic inflammation and fibrosis in MCDD-fed mice, which were associated with down-regulation of cytochrome P450 2E1 suppression of multiple proinflammatory and profibrotic genes. LJEE can prevent hepatic steatosis by reducing hepatic peroxisome acyl-CoA:diacylglycerol acyltransferase 2 expression, as well as by inducing proliferator-activated receptor α expression. In addition, the LJEE treatments caused significant reduction in the phosphorylated form of Jun N-terminal kinase along with an increase in the phosphorylated level of extra cellular signal-regulated kinase 1/2. Our study demonstrated the protective role of LJEE in ameliorating nutritional steatohepatitis.

6-gingerol protects against nutritional steatohepatitis by regulating key genes related to inflammation and lipid metabolism

Non-alcoholic fatty liver disease, including non-alcoholic steatohepatitis (NASH), appears to be increasingly common worldwide. The aim of the study was to investigate the effects of 6-gingerol ((S)-5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-3-decanone), a bioactive ingredient of plants belonging to the Zingiberaceae family, on experimental models of NASH. In HepG2 cells, 6-gingerol (100 μmol/L) treatment inhibited free fatty acids mixture (0.33 mmol/L palmitate and 0.66 mmol/L oleate)-induced triglyceride and inflammatory marker accumulations. Male C57BL/6 mice were fed with a methionine and choline-deficient (MCD) diet to induce steatohepatitis. After four weeks of MCD diet feeding, the mice were dosed orally with 6-gingerol (25, 50 or 100 mg/kg/day) once daily for another four weeks. 6-Gingerol (100 mg/kg/day) attenuated liver steatosis and necro-inflammation in MCD diet-fed mice. The expressions of inflammatory cytokine genes, including those for monocyte chemoattractant protein-1, tumor necrosis factor-α, and interleukin-6, and nuclear transcription factor (NF-κB), which were increased in the livers of MCD diet-fed mice, were attenuated by 6-gingerol. 6-Gingerol possesses a repressive property on hepatic steatosis, which is associated with induction of peroxisome proliferator-activated receptor α. Our study demonstrated the protective role of 6-gingerol in ameliorating nutritional steatohepatitis. The effect was mediated through regulating key genes related to lipid metabolism and inflammation.

Hepatoprotective and antioxidant activities of extracts from Salvia-Nelumbinis naturalis against nonalcoholic steatohepatitis induced by methionine- and choline-deficient diet in mice

BACKGROUND

Nonalcoholic steatohepatitis (NASH), the advanced stage of nonalcoholic fatty liver disease that is characterized by both steatosis and severe injury in liver, still lacks efficient treatment. The traditional Chinese formula Salvia-Nelumbinis naturalis (SNN) is effectively applied to improve the symptoms of nonalcoholic simple fatty liver (NAFL) patients. Previous studies have confirmed that SNN could reduce the liver lipid deposition and serum transaminases of NAFL experimental models. This study aims to determine whether SNN is effective for murine NASH model and investigate the underlying pharmacological mechanisms.

METHODS

C57BL/6 J mice were fed with methionine- and choline-deficient (MCD) diet for six weeks to induce NASH. Simultaneously, SNN or saline was intragastrically administered daily to the mice in the SNN or model group, respectively. A standard diet was given to the control mice. Serum biochemical indices and tumor necrosis factor-α were measured. Liver histopathology was observed, and the contents of triglycerides and lipid peroxide malondialdehyde (MDA) in liver homogenates were evaluated. The hepatic expression and/or activation of genes associated with inflammation, apoptosis, and oxidative stress were determined by quantitative RT-PCR or Western blot analysis.

RESULTS

The prominent liver steatosis displayed in the NASH model was prevented by SNN. The liver injury of NASH mice was obviously manifested by the increased levels of serum transaminases and bilirubin, as well as the lobular inflammation, elevated pro-inflammatory cytokines, and upregulated apoptosis in liver tissues. SNN administration improved the aforementioned pathological changes. The increased hepatic levels of MDA and cytochrome P450 2E1 of the model confirmed the unregulated balance of oxidative stress. The hepatic expression of nuclear factor erythroid 2-related factor 2 and its target genes decreased, whereas c-Jun N-terminal kinase activation in the model mice increased. Treating the mice with SNN significantly improved oxidative stress-related harmful factors.

CONCLUSIONS

This study shows that SNN can protect the liver from severe steatosis and damage induced by MCD diet, which suggests the potential use of SNN on the treatment of NASH patient. The results also indicate that improving the hepatic antioxidant capability of the liver may contribute to the underlying hepatoprotective mechanism.

Time-dependent changes and association between liver free fatty acids, serum lipid profile and histological features in mice model of nonalcoholic fatty liver disease

BACKGROUND AND AIMS

Methionine-choline deficient (MCD) diet duration necessary for development of non-alcoholic fatty liver disease (NAFLD) and the dynamic of lipid profile and fatty acids are not completely established. The study examined dynamics and association between liver free fatty acids (FFA), serum lipid profile and liver morphological changes on MCD diet-induced NAFLD in mice.

METHODS

Male C57BL/6 mice (n = 28) were divided into four groups (n = 7 per group): control: fed with standard chow, MCD diet-fed groups: 2, 4 or 6 weeks. After treatment, liver and blood samples were taken for histopathology, serum lipid profile, and liver FFA composition.

RESULTS

Hepatic FFA profile showed a decrease in saturated acids, arachidonic and docosahexaenoic acid, whereas proportions of docosapentaenoic, oleic and linoleic acid were increased. Total cholesterol, HDL and triglycerides progressively decreased, whereas LDL level progressively increased. Focal fatty change in the liver appeared after 2 weeks, whereas diffuse fatty change with severe inflammation and ballooned hepatocytes were evident after 6 weeks.

CONCLUSIONS

Six-week diet model may be appropriate for investigation of the role of lipotoxicity in the progression of NAFLD. Therefore, supplementation with n-3 polyunsaturated acid like DHA, rather than DPA, especially in the initial stage of fatty liver disease, may potentially have preventive effects and alleviate development of NAFLD/NASH and may also potentially reduce cardiovascular risk by moderating dyslipidemia.

Dynamics of oxidative/nitrosative stress in mice with methionine-choline-deficient diet-induced nonalcoholic fatty liver disease

Insulin resistance, oxidative stress, and proinflammatory cytokines play a key role in pathogenesis of nonalcoholic fatty liver disease (NAFLD). The aim of our study was to investigate the dynamics of oxidative/nitrosative stress in methionine-choline-deficient (MCD) diet -induced NAFLD in mice. Male C57BL/6 mice were divided into following groups: group 1: control group on standard diet; group 2: MCD diet for 2, 4, and 6 weeks (MCD2, MCD4, and MCD6, respectively). After treatment, liver and blood samples were taken for histopathology, alanine- and aspartate aminotransferase, acute phase reactants, and oxidative/nitrosative stress parameters. Liver malondialdehyde level was higher in all MCD-fed groups versus control group (p < 0.01), while nitrites + nitrates level showed a progressive increase. The activity of total superoxide dismutase and its isoenzymes was significantly lower in all MCD-fed groups (p < 0.01). Although catalase activity was significantly lower in MCD-fed animals at all intervals (p < 0.01), the lowest activity of this enzyme was evident in MCD4 group. Liver content of glutathione was lower in MCD4 (p < 0.05) and MCD6 group (p < 0.01) versus control. : Ferritin and C-reactive protein serum concentration were significantly higher only in MCD6 group. Our study suggests that MCD diet induces a progressive rise in nitrosative stress in the liver. Additionally, the most prominent decrease in liver antioxidative capacity is in the fourth week, which implies that application of antioxidants would be most suitable in this period, in order to prevent nonalcoholic steatohepatitis but not the initial NAFLD phase.

Quercetin decreases liver damage in mice with non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a frequent condition in obese patients that may progress to end-stage liver disease. This study was designed to evaluate the modulation of this condition by use of quercetin (Q), a flavonoid largely found in vegetable foods, with known anti-inflammatory and antioxidant properties, in the experimental model of non-alcoholic steatohepatitis (NASH) using a diet deficient in methionine and choline (MCD). Male C57BL6 mice were divided into four groups (n = 16): (i) Control plus vehicle (control ration plus carboxymethylcellulose 1% used as vehicle, CO + V); (ii) Control ration plus Q 50 mg/kg (CO + Q); (iii) MCD diet plus vehicle (NASH + V); and (iv) MCD diet plus Q (NASH + Q). Diets were administered for 4 weeks. At the end of the experimental period, liver alterations, bioindicators of oxidative stress and DNA damage were assessed. NASH was diagnosed in 100% of the mice that were fed the MCD diet. In addition, a significant increase in DNA damage in liver tissue from NASH + V group was observed in comparison with CO + V. The group NASH + Q showed a significant decrease in hepatic damage enzymes, lipoperoxidation, DNA damage and a lower degree of macrovesicular steatosis, ballooning and inflammatory process. These findings suggest that Q may have protective effects by improving liver integrity in NASH.

Purple grape juices prevent pentylenetetrazol-induced oxidative damage in the liver and serum of Wistar rats

Oxidative damages in hepatocytes may be caused by epilepsy and/or anticonvulsant drugs. Epilepsy is one of the most common neurological disorders, characterized by recurrent seizures, which may increase the content of reactive oxygen species. Organic and conventional grape juices are rich in polyphenols, compounds with important antioxidant activity. It is hypothesized that organic and conventional purple grape juices may have protective effect against oxidative damage induced by pentylenetetrazole (PTZ) (a standard convulsant drug) in the liver and serum of Wistar rats. Animals (n = 16 in each group) received, by gavage, saline, organic grape juice or conventional grape juice (10 μL/g of body weight) for 17 days. Subsequently, half of the rats in each group received PTZ (60 mg/kg). After 30 minutes, the animals were euthanized by decapitation. Liver and blood samples were isolated to evaluate oxidative parameters (lipid and protein oxidation, nitric oxide metabolite content, antioxidant defenses, and protein sulfhydryl content). The results of this study showed that although organic juice contains higher polyphenol content than conventional juice, both juices conferred protection against lipid and protein oxidative damage and limited the increase in PTZ-induced nitric oxide metabolite content in the liver and serum. In addition, both juices inhibited the PTZ-induced reduction in enzymatic antioxidant defenses (superoxide dismutase and catalase activities) and sulfhydryl protein content in the liver and serum. In summary, both organic and conventional grape juices were able to reduce oxidative damage induced by PTZ in the liver and serum of Wistar rats.

Disturbed one-carbon metabolism causing adverse reproductive outcomes in mice is associated with altered expression of apolipoprotein AI and inflammatory mediators PPARα, interferon-γ, and interleukin-10

Low dietary choline or deficiency of methylenetetrahydrofolate reductase (Mthfr) leads to hyperhomocysteinemia (Hhcy) and adverse reproductive outcomes. Homocysteine reduces synthesis of ApoAI, the major lipoprotein in HDL-cholesterol; ApoAI is regulated by PPARα and has antiinflammatory properties. Our aim was to determine whether pregnancy complications due to genetic or nutritional deficiencies in 1-carbon metabolism could relate to dysregulation of ApoAI and inflammatory mediators. We fed pregnant mice, with or without a deficiency of Mthfr, control or choline-deficient (ChDD) diets for 10-12 wk and examined levels of ApoAI, PPARα, IFNγ, and IL-10. ApoAI mRNA was reduced in livers of Mthfr(+/-) mice and ApoAI protein was reduced due to Mthfr deficiency or choline deficiency in liver and plasma. Placental ApoAI protein was also reduced due to Mthfr genotype or choline-deficient diet and in developmentally delayed embryos. Reduced liver PPARα expression (mRNA and protein) was observed in ChDD-fed mice and was associated with increased methylation of a CpG dinucleotide in its promoter. Hepatic IFNγ increased due to genotype, and placental IFNγ was higher in Mthfr(+/-) ChDD-fed dams compared to Mthfr(+/+) mice fed ChDD or Mthfr(+/-) mice fed CD. IL-10 was reduced in livers of ChDD-fed mice. We propose that a deficiency of dietary choline or Mthfr leads to Hhcy and reduced expression of maternal ApoAI, with reduced ApoAI transfer to embryo. Disturbances in 1-carbon metabolism also reduce maternal PPARα expression, possibly through promoter hypermethylation, and increase IFNγ and decrease IL-10 levels. This disturbance of the T helper (Th1) (IFNγ):Th2 (IL-10) ratio and the increase in inflammatory mediators may contribute to pregnancy complications.