High-fat Diet-induced Hepatic Steatosis Research Articles

Hepatocyte-specific Nrf2 deficiency mitigates high-fat diet-induced hepatic steatosis: Involvement of reduced PPARγ expression

Non-alcoholic fatty liver disease (NAFLD) is an emerging global disease with increasing prevalence. However, the mechanism of NAFLD development is not fully understood. To elucidate the cell-specific role of nuclear factor erythroid-derived 2-like 2 (NRF2) in the pathogenesis of NAFLD, we utilized hepatocyte- and macrophage-specific Nrf2-knockout [Nrf2(L)-KO and Nrf2(Mϕ)-KO] mice to examine the progress of NAFLD induced by high-fat diet (HFD). Compared to Nrf2-LoxP littermates, Nrf2(L)-KO mice showed less liver enlargement, milder inflammation and less hepatic steatosis after HFD feeding. In contrast, Nrf2(Mϕ)-KO mice displayed no significant difference in HFD-induced hepatic steatosis from Nrf2-LoxP control mice. Mechanistic investigations revealed that Nrf2 deficiency in hepatocytes dampens the expression of peroxisome proliferator-activated receptor γ (PPARγ) and its downstream lipogenic genes in the liver and/or primary hepatocytes induced by HFD and palmitate exposure, respectively. While PPARγ agonists augmented PPARγ expression and its transcriptional activity in primary hepatocytes in a NRF2-dependent manner, forced overexpression of PPARγ1 or γ2 distinctively reversed the decreased expression of their downstream genes fatty acid binding protein 4, lipoprotein lipase and/or fatty acid synthase caused by Nrf2 deficiency. We conclude that NRF2-dependent expression of PPARγ in hepatocytes is a critical initiating process in the development of NAFLD, suggesting that inhibition of NRF2 specifically in hepatocytes may be a valuable approach to prevent the disease.

Effects of XIAP on high fat diet-induced hepatic steatosis: a mechanism involving NLRP3 inflammasome and oxidative stress.

Increasing evidence indicates that prolonged fat-rich diet (HFD) ingestion is a predisposing factor for metabolic disorder-associated system inflammation and oxidative stress injury, which contributes to the occurrence of non-alcoholic fatty liver disease (NAFLD). NACHT, LRR and PYD domains-containing protein 3 (NLRP3)-mediated inflammatory infiltration was determined to participate in NAFLD. X-linked inhibitor of apoptosis protein (XIAP) was recently confirmed as an essential regulator for apoptosis in cells. However, the role of XIAP in HFD-induced NAFLD is still not understood. Here, XIAP was characterized with respect to HFD-induced NLRP3 inflammasome activation and reactive oxygen species (ROS) generation in vivo and palmitate (PA)-treated cells in vitro. After HFD administration, hepatic injury was confirmed via histological assessment (grading and staging of NAFLD) and biochemical parameters, oxidative stress, and reduced antioxidant activity. Up-regulated hepatic dysfunction were further indicated by elevated dyslipidemia, lipid accumulation, and decreased fatty acid β-oxidation associated gene expression. Moreover, in the absence of XIAP, NLRP3 signaling activated by HFD-triggered oxidative stress was up-regulated, accompanied by reduction in antioxidants including HO-1, NQO-1, GST, SOD and Nrf2 activity. The detrimental effects of XIAP blocking on hepatic steatosis and related pathologies were also confirmed in PA-treated mouse liver cells. In contrast, overexpression of XIAP by transfection in vitro restrained PA-stimulated hepatic steatosis by suppression of oxidative stress, NLRP3 related inflammatory response, and impairment of Nrf2 activity, further alleviating abnormal metabolic disorder associated NAFLD. Taken together, the present study helped to elucidate how HFD-induced hepatic steatosis was regulated by XIAP, possibly via the inhibition of NLRP3 signaling and oxidative stress injury.

Helminthostachys zeylanica alleviates hepatic steatosis and insulin resistance in diet-induced obese mice

BackgroundObesity and its associated health conditions, type 2 diabetes mellitus (T2DM) and nonalcoholic fatty liver disease (NAFLD), are worldwide health problems. It has been shown that insulin resistance is associated with increased hepatic lipid and causes hepatic steatosis through a myriad of mechanisms, including inflammatory signaling.MethodsHelminthostachys zeylanica (HZ) is used widely as a common herbal medicine to relieve fever symptoms and inflammatory diseases in Asia. In the present study, we evaluated whether HZ has therapeutic effects on obesity, NAFLD and insulin resistance. The protective effects of HZ extract were examined using free fatty acid-induced steatosis in human HuS-E/2 cells and a high-fat diet-induced NAFLD in mice.ResultsThe major components of the HZ extract are ugonins J and K, confirmed by HPLC. Incubation of human hepatocytes, HuS-E/2 cells, with palmitate markedly increased lipid accumulation and treatment with the HZ extract significantly decreased lipid deposition and facilitated AMPK and ACC activation. After 12 weeks of a high-fat diet with HZ extract treatment, the HFD mice were protected from hyperlipidemia and hyperglycemia. HZ extract prevented body weight gain, adipose tissue expansion and adipocyte hypertrophy in the HFD mice. In addition, fat accumulation was reduced in mice livers. Moreover, the insulin sensitivity-associated index, which evaluates insulin function, was also significantly restored.ConclusionsThese results suggest that HZ has a promising pharmacological effect on high-fat diet-induced obesity, hepatic steatosis and insulin resistance, which may have the potential for clinical application.

Curcumin prevents high-fat diet-induced hepatic steatosis in ApoE\u2212/\u2212 mice by improving intestinal barrier function and reducing endotoxin and liver TLR4/NF-\u03baB inflammation

BackgroundNon-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and has become a public health concern worldwide. The hallmark of NAFLD is hepatic steatosis. Therefore, there is an urgent need to develop new therapeutic strategies that are efficacious and have minimal side effects in hepatic steatosis and NAFLD treatment. The present study aimed to investigate the effect of dietary supplement of curcumin on high-fat diet (HFD)-induced hepatic steatosis and the underlying mechanism.MethodsApoE−/− mice were fed a normal diet, high-fat diet (HFD) or HFD supplemented with curcumin (0.1% w/w) for 16 weeks. Body and liver weight, blood biochemical.parameters, and liver lipids were measured. Intestinal permeability, hepatic steatosis and mRNA and protein expressions of TLR4-related inflammatory signaling molecule were analyzed.ResultsThe administration of curcumin significantly prevented HFD-induced body weight gain and reduced liver weight. Curcumin attenuated hepatic steatosis along with improved serum lipid profile. Moreover, curcumin up-regulated the expression of intestinal tight junction protein zonula occluden-1 and occludin, which further improved gut barrier dysfunction and reduced circulating lipopolysaccharide levels. Curcumin also markedly down-regulated the protein expression of hepatic TLR4 and myeloid differentiation factor 88 (MyD88), inhibited p65 nuclear translocation and DNA binding activity of nuclear factor-κB (NF-κB) in the liver. In addition, the mRNA expression of hepatic tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) as well as the plasma levels of TNF-α and IL-1β were also lowered by curcumin treatment.ConclusionThese results indicated that curcumin protects against HFD-induced hepatic steatosis by improving intestinal barrier function and reducing endotoxin and liver TLR4/NF-κB inflammation. The ability of curcumin to inhibit hepatic steatosis portrayed its potential as effective dietry intervention for NAFLD prevention.

Activation of peroxisome proliferator-activated receptor gamma/small heterodimer partner pathway prevents high fat diet-induced obesity and hepatic steatosis in Sprague–Dawley rats fed soybean meal

Soybeans are a complete nutritional resource and soybean proteins are known to affect lipid metabolism via multiple mechanisms. Soybean meal (SBM) is produced after extraction of soybean oil and in this study, we investigated the ability whether the SBM could prevent high fat diet-induced obesity and understand the underlying mechanisms. Male Sprague–Dawley rats, aged 5 weeks, were randomly divided into three groups (n=8 each) and fed one of three diets for 28 days: Cont (AIN-93G), HFD (high fat diet with 40% of calories derived from fat) and HFD+SBM (HFD with 30% SBM). White adipose tissue weight as well as plasma and hepatic triglycerides were significantly decreased in HFD+SBM rats. Expression of hepatic SREBP-1 and its target genes was significantly decreased in HFD+SBM rats. Meanwhile, expression of SHP gene expression was significantly increased in HFD+SBM, and there was a negative correlation between SHP and SREBP-1 expression. Together these results suggest that hepatic SREBP-1 gene expression is negatively regulated by SHP. Expression of PPARG, the transcriptional factor that regulates SHP expression, was increased in HFD+SBM rats. Furthermore, expression of genes controlled by PPARG/SHP, such as those involved in hepatic gluconeogenesis, was also significantly decreased in HFD+SBM rats. Therefore, in addition to the previous findings of SBM on obesity here we show an additional mechanism which by changing the expression of genes involved in lipid metabolism via the PPARG/SHP pathway in the liver.

Liver sympathetic denervation reverses obesity-induced hepatic steatosis.

Non-alcoholic fatty liver disease, characterized in part by elevated liver triglycerides (i.e. hepatic steatosis), is a growing health problem. In this study, we found that hepatic steatosis is associated with robust hepatic sympathetic overactivity. Removal of hepatic sympathetic nerves reduced obesity-induced hepatic steatosis. Liver sympathetic innervation modulated hepatic lipid acquisition pathways during obesity. Non-alcoholic fatty liver disease (NAFLD) affects 1 in 3 Americans and is a significant risk factor for typeII diabetes mellitus, insulin resistance and hepatic carcinoma. Characterized in part by excessive hepatic triglyceride accumulation (i.e. hepatic steatosis), the incidence of NAFLD is increasing - in line with the growing obesity epidemic. The role of the autonomic nervous system in NAFLD remains unclear. Here, we show that chronic hepatic sympathetic overactivity mediates hepatic steatosis. Direct multiunit recordings of hepatic sympathetic nerve activity were obtained in high fat diet and normal chow fed male C57BL/6J mice. To reduce hepatic sympathetic nerve activity we utilized two approaches including pharmacological ablation of the sympathetic nerves and phenol-based hepatic sympathetic nerve denervation. Diet-induced NAFLD was associated with a nearly doubled firing rate of the hepatic sympathetic nerves, which was largely due to an increase in efferent nerve traffic. Furthermore, established high fat diet-induced hepatic steatosis was effectively reduced with pharmacological or phenol-based removal of the hepatic sympathetic nerves, independent of changes in body weight, caloric intake or adiposity. Ablation of liver sympathetic nerves was also associated with improvements in liver triglyceride accumulation pathways including free fatty acid uptake and de novo lipogenesis. These findings highlight an unrecognized pathogenic link between liver sympathetic outflow and hepatic steatosis and suggest that manipulation of the liver sympathetic nerves may represent a novel therapeutic strategy for NAFLD.

Broccoli extract improves high fat diet-induced obesity, hepatic steatosis and glucose intolerance in Wistar rats

Brassicaceae contain bioactive compounds with potential positive effects on metabolic syndrome. Here, we evaluated the eventual anti-obesity properties of an ethanolic broccoli extract (BE), selected by a tested ability to reduce Caenorhabditis elegans fat content. Two doses (14 and 140 mg/kg animal) of BE were evaluated in a diet-induced obesity (DIO) Wistar rat model. After 10 weeks of BE supplementation, animals exhibited reduced body weight gain and food efficiency, decreased atherogenic index of plasma and improved glucose tolerance in comparison with non-supplemented rats. BE also reduced the retroperitoneal fat mass and adipocyte size, all associated to down-regulation of Cebpa, Srebp1, Fasn and Adipoq expression in adipocytes. Finally, BE significantly decreased liver steatosis, accompanied by the up-regulation of Acot8 and Acox1, and the down-regulation of Fasn, Fatp4 and Srebf1 expression in hepatocytes. Our data provides new knowledge about the potential role of broccoli components in the prevention of metabolic syndrome.

The Combination of Mulberry Extracts and Silk Amino Acids Alleviated High Fat Diet-Induced Nonalcoholic Hepatic Steatosis by Improving Hepatic Insulin Signaling and Normalizing Gut Microbiome Dysbiosis in Rats.

Mulberry water extracts (MB) and silk amino acids (SA) are reported to improve oxidative stress and inflammation, respectively. We hypothesized whether the mixture of mulberry water extracts and silk amino acids can alleviate nonalcoholic fatty liver disease (NAFLD) induced by high fat diets. Male Sprague Dawley rats were orally provided with high fat diets containing different ratios of MB and SA (1:3, MS1:3, or 1:5, MS1:5) or cellulose (the disease-control) for 12 weeks. Rats had 200 or 600 mg/kg bw of MS1:3 and MS1:5 (MS1:3-L, MS1:3-H; MS1:5-L, and MS1:5-H). Rats in the normal-control group were fed the 20% fat diet with cellulose. Disease-control rats exhibited much greater triglyceride (TG) deposition in the liver than the normal-control rats along with increased body weight gain, visceral fat mass, serum concentrations of cholesterol, triglyceride and nonesterified fatty acid (NEFA), and insulin resistance. Disease-control rats also had liver damage with increased oxidative stress and inflammation compared to the normal-control rats. MS1:3-H and MS1:5-H were found to have greater hepatic glycogen accumulation and decreased hepatic TG, insulin resistance, and dyslipidemia, with MS1:5-H being similar to the normal-control. MS1:3-H alleviated oxidative stress with lower hepatic lipid peroxide compared to MS1:5-H whereas MS1:5-H ameliorated inflammation and hepatocyte damage better than MS1:3-H. Both MS1:3-H and MS1:5-H potentiated hepatic insulin signaling (pAkt⟶pACC) and reduced the mRNA expression of TG synthesis genes mRNA (FAS and SREBP-1c). In the gut microbiome MS1:3-H elevated the ratio of Bacteroidales to Clostridiales in the cecum better than MS1:5-H but MS1:5-H reduced the proinflammatory Turicibacterales. In conclusion, both MS1:3-H and MS1:5-H prevented liver damage induced by high fat diets, mainly by suppressing oxidative stress and inflammation, respectively. MS1:3 and MS1:5 might be used as therapeutic agent for NAFLD.

Alcohol and HBV synergistically promote hepatic steatosis

Background and aimsHepatitis virus and alcohol are the main factors leading to liver damage. Synergy between hepatitis B virus (HBV) and alcohol in promoting liver cell damage and disease progression has been reported. However, the interaction of HBV and ethanol in hepatic steatosis development has not been fully elucidated. MethodsEight-week-old male C57BL/6 mice were treated with or without HBV, ethanol, or the combination of HBV and ethanol (HBV+EtOH), followed by a three-week high-fat diet (HFD) regimen. Liver histology, serum biomarkers, and liver triglyceride levels were analysed. Furthermore, a meta-analysis of the effects of alcohol and HBV on hepatic steatosis in populations was performed. ResultsHepatic steatosis was significantly more severe in the HBV+EtOH group than in the other groups. The serum alanine aminotransferase, aspartate aminotransferase and liver triglyceride levels in the HBV+EtOH group were also significantly higher than those in the other groups. The HBeAg and HBsAg levels in the HBV+EtOH group were significantly higher than those in the pair-fed HBV-infected mice. In addition, the meta-analysis showed that alcohol consumption increased the risk of hepatic steatosis by 43% in HBV-infected patients (pooled risk ratio (RR)=1.43, P<0.01). ConclusionsAlcohol and HBV synergistically promote high-fat diet-induced hepatic steatosis in mice. In addition, alcohol consumption increases the risk of hepatic steatosis in HBV-infected patients.

Ces1d deficiency protects against high-sucrose diet-induced hepatic triacylglycerol accumulation

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Triacylglycerol accumulation in the liver is a hallmark of NAFLD. Metabolic studies have confirmed that increased hepatic de novo lipogenesis (DNL) in humans contributes to fat accumulation in the liver and to NAFLD progression. Mice deficient in carboxylesterase (Ces)1d expression are protected from high-fat diet-induced hepatic steatosis. To investigate whether loss of Ces1d can also mitigate steatosis induced by over-activated DNL, WT and Ces1d-deficient mice were fed a lipogenic high-sucrose diet (HSD). We found that Ces1d-deficient mice were protected from HSD-induced hepatic lipid accumulation. Mechanistically, Ces1d deficiency leads to activation of AMP-activated protein kinase and inhibitory phosphorylation of acetyl-CoA carboxylase. Together with our previous demonstration that Ces1d deficiency attenuated high-fat diet-induced steatosis, this study suggests that inhibition of CES1 (the human ortholog of Ces1d) might represent a novel pharmacological target for prevention and treatment of NAFLD.

Chitooligosaccharide supplementation prevents the development of high fat diet-induced non-alcoholic fatty liver disease (NAFLD) in mice via the inhibition of cluster of differentiation 36 (CD36)

Abstract The effects of (GlcN)2-3 on the development of high fat diet-induced non-alcoholic fatty liver disease in C57BL/6J mice and the potential structural-functional relationship between different singular degrees of polymerization (DPs) COSs and CD36 activity were investigated. (GlcN)2-3 was found to significantly inhibit the levels of triglyceride, low density lipid protein and total cholesterol in the serum and liver, thus reducing hepatic steatosis and, ultimately, altering lipid accumulation. This phenomenon was associated with a decrease in the mRNA and protein expressions of CD36, PXR, DGAT2, LXRα and PPARγ, which subsequently decreased the uptake of FFAs and triglyceride synthesis. Using structural analysis, (GlcN)2-3 blocked the core cavity and inhibited the translocation of FFAs in CD36. Furthermore, the molecular size and steric hindrance effect play crucial roles in the deactivation of CD36. These findings will provide a better understanding of the modulating actions of specific singular-DPs COS in high fat diet-induced hepatic steatosis.

Araçá ( Psidium cattleianum Sabine) Ameliorates Liver Damage and Reduces Hepatic Steatosis in Rats Fed with a High-fat Diet

Bioactive compounds, present in some foods, act enhancing the endogenous antioxidant system and are proposed as an effective strategy in preventing the changes induced by free radicals in some diseases, such as nonalcoholic fatty liver disease (NAFLD). There has been an increase in the number of studies carried out with the aim of finding natural antioxidant compounds present in fruits, mainly the native fruits of Brazil, because they contain a high content of these compounds. Araca (Psidium cattleianum Sabine) is a fruit that is rich in polyphenols and exhibits strong antioxidant, antiproliferative, and anti-inflammatory activities. Therefore, the present study investigated the effects of araca flour on oxidative stress, liver injury, and antioxidant defenses in high-fat diet-induced hepatic steatosis in rats. In vitro experiments showed that araca contains high concentrations of total polyphenols and exhibits strong antioxidant activity with no cytotoxicity. In vivo experiments indicated that the addition of araca to a high-fat diet inhibited the activities of alanine aminotransferase and aspartate enzymes, reduced macrovesicular steatosis, increased the paraoxonase activity, and increased the concentration of the total and reduced forms of glutathione. Therefore, our findings suggested the hepatoprotective role of araca against the progression of steatosis.

Adipose-derived autotaxin regulates inflammation and steatosis associated with diet-induced obesity

Autotaxin (ATX) is a secreted enzyme that generates the bioactive lipid lysophosphatidic acid (LPA). We generated mice with global inducible post-natal inactivation or adipose-specific loss of the Enpp2 gene encoding ATX. The animals are phenotypically unremarkable and exhibit differences in adipocyte size and adipose tissue expression of inflammatory genes after high fat feeding without gross differences in fat distribution or body mass. Surprisingly, both models of Enpp2- deficiency exhibited marked protection from high fat diet-induced hepatic steatosis. This phenotype was not associated with differences in dietary fat absorption but may be accounted for by differences in hepatic expression of genes involved in de novo synthesis of triglycerides. These findings suggest that pharmacological inhibition of ATX might be protective against hepatic steatosis.

Conophylline inhibits high fat diet-induced non-alcoholic fatty liver disease in mice.

Conophylline (CnP), a vinca alkaloid extracted from the leaves of the tropical plant Tabernaemontana divaricate, attenuates hepatic fibrosis in mice. We have previously shown that CnP inhibits non-alcoholic steatohepatitis (NASH) using a methionine-choline-deficient (MCD) diet-fed mouse model. However, little is known about the CnP mediated inhibition of hepatic steatosis in high-fat diet-induced non-alcoholic fatty liver disease (NAFLD) mouse models. CnP (0.5 and 1 μg/g/body weight) was co-administered along with a high-fat diet to male BALB/c mice. After nine weeks of administering the high-fat diet, hepatic steatosis, triglyceride, and hepatic fat metabolism-related markers were examined. Administration of a high-fat diet for 9 weeks was found to induce hepatic steatosis. CnP dose-dependently attenuated the high-fat diet-induced hepatic steatosis. The diet also attenuated hepatic peroxisome proliferator-activated receptor alpha (PPARA) mRNA levels. PPARA is known to be involved in β-oxidation. CnP upregulated the mRNA levels of hepatic PPARA and its target genes, such as carnitine palmitoyl transferase 1 (CPT1) and CPT2, in a dose-dependent manner in the liver. Furthermore, levels of hepatic β-hydroxybutyrate, which is a type of ketone body, were increased by CnP in a dose-dependent manner. Finally, CnP increased the expression of the autophagosomal marker LC3-II and decreased the expression of p62, which are known to be selectively degraded during autophagy. These results indicate that CnP inhibits hepatic steatosis through the stimulation of β-oxidation and autophagy in the liver. Therefore, CnP might prove to be a suitable therapeutic target for NAFLD.

Rhus verniciflua and Eucommia ulmoides Protects Against High-Fat Diet-Induced Hepatic Steatosis by Enhancing Anti-Oxidation and AMPK Activation.

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disorder associated with features of metabolic syndrome and oxidative stress. We examined the mechanism by which the combined extracts of Rhus verniciflua and Eucommia ulmoides extracts (ILF-RE) regulate hepatic dyslipidemia in an established NAFLD model, high-fat diet (HFD)-induced lipid dysmetabolism in rats. ILF-RE attenuated alanine aminotransferase (ALT) by 1.5% , aspartate aminotransferase (AST) by 1.5% , triglycerides by 1.5% , cholesterol by 2.0% , and lipid peroxidation by 1.5% in the NAFLD model. ILF-RE, recently shown to have anti-oxidant properties, also inhibited hepatic ROS accumulation by 1.68% and regulated ER-redox imbalance, a key phenomenon of ER stress. Due to nutrient overload stress-associated protein folding, ER stress and downstream SREBP-lipogenic transcription signaling were highly activated, and the mTORC1-AMPK axis was also disturbed, leading to hepatic steatosis. ILF-RE results in recovery from hepatic conditions induced by nutrient-based protein folding stress signaling and the ER stress-SREBP and AMPK-mTORC1-SREBP1 axes. Based on these results, ILF-RE is suggested to be a potential therapeutic strategy for hepatic steatosis and may represent a promising novel agent for the prevention and treatment of NAFLD.

MTOR Signaling in X/A-Like Cells Contributes to Lipid Homeostasis in Mice.

Gastric mechanistic target of rapamycin (mTOR) signaling is inversely associated with the expression and secretion of ghrelin, a 28-aa peptide hormone produced by gastric X/A-like cells. Ghrelin contributes to obesity and hepatic steatosis. We sought to control global lipid metabolism via the manipulation of gastric mTOR signaling in X/A-like cells. We established a ghrl-cre transgene in which the Cre enzyme is expressed in X/A-like cells under the control of the ghrelin-promoter. mTORflox/flox and tuberous sclerosis 1 (TSC1)flox/flox mice were separately bred with ghrl-cre mice to generate mTOR-ghrl-cre or TSC1-ghrl-cre mice, within which mTOR signaling was suppressed or activated, respectively. Lipid metabolism in liver and adipose depots was analyzed. Under the control of the ghrelin-promoter, the Cre enzyme was exclusively expressed in stomach X/A-like cells in adult animals. Knockout of mTOR in X/A-like cells increased circulating acyl-ghrelin and promoted hepatic lipogenesis with effects on adipose depots. Activation of mTOR signaling by deletion of its upstream inhibitor, TSC1, decreased ghrelin expression and secretion, altering lipid metabolism as evidenced by resistance to high-fat diet-induced obesity and hepatic steatosis. Both ghrelin administration and injection of rapamycin, an inhibitor of mTOR, altered the phenotypes of TSC1-ghrl-cre mice. Conclusion: Gastric mTOR signaling in X/A-like cells contributes to organism lipid homeostasis by regulating hepatic and adipose lipid metabolism. Gastric mTOR signaling may provide an alternative strategy for intervention in lipid disorders.

Dual-Specificity Phosphatase 9 Protects Against Nonalcoholic Fatty Liver Disease in Mice Through ASK1 Suppression.

Nonalcoholic fatty liver disease (NAFLD), ranging from nonalcoholic fatty liver to nonalcoholic steatohepatitis (NASH), is the leading cause of chronic liver diseases. Until now, no medications for NAFLD have been approved by relevant governmental agencies. Dual‐specificity phosphatase 9 (Dusp9) is a member of the DUSP protein family. Dusp9 is expressed in insulin‐sensitive tissues, and its expression may be modified with the development of insulin resistance (IR). However, the molecular targets and mechanisms of Dusp9 action on NAFLD and NASH remain poorly understood. In this study, using conditional liver‐specific Dusp9‐knockout (Dusp9‐CKO) mice and Dusp9‐transgenic mice, we showed that Dusp9 was a key suppressor of high‐fat diet–induced hepatic steatosis and inflammatory responses and that Dusp9 deficiency aggravated high‐fat high‐cholesterol diet–induced liver fibrosis. Dusp9 was shown to exert its effects by blocking apoptosis signal–regulating kinase 1 (ASK1) phosphorylation and the subsequent activation of p38 and c‐Jun NH2‐terminal kinase signaling. Conclusion: Hepatocyte Dusp9 prevents NAFLD and NASH progression in mice, including lipid accumulation, glucose metabolism disorders, and enhanced inflammation and liver fibrosis, in an ASK1‐dependent manner; these findings suggest that Dusp9 may be a promising therapeutic target for the treatment of NAFLD and NASH.

Effects of Rhus coriaria L. hydroalcoholic extract on the lipid and antioxidant profile in high fat diet-induced hepatic steatosis in rats

Oxidative stress is related to increased fat deposition in the liver, known as hepatic steatosis. The present study is an evaluation of the anti-oxidative and antihyperlipidemic effects of the hydroalcoholic extract of Rhus coriaria L. (HARE) in rats on a high-fat diet (HFD). Twenty male Wistar rats were divided into four groups: control, HFD, HFD + HARE 50 mg/kg/day, and HFD + HARE 250 mg/kg/day for 12 weeks. Animals were weighed weekly and treated with the HARE extract for 12 weeks by gavage. Subsequently, the histopathological changes, oxidative markers, and lipid profile were evaluated. Statistical analysis was performed using the one-way analysis of variance (ANOVA) for multiple comparisons. First, the active ingredients of the extract were determined by HPLC. Then, the levels in the serum lipid profile (TG, cholesterol, HDL, and LDL) in rats fed with the HFD + HARE were analyzed where a significant reduction was observed. The HFD proved to increase the activity of the liver enzymes, the serum lipid levels, and the malondialdehyde (MDA) level. The ferric-reducing antioxidant activity power (FRAP), catalase (CAT), and superoxide dismutase (SOD) catalytic activity were reduced in the liver homogenate of HFD rats compared to the controls. Additionally, the aforementioned liver enzymes activities were reduced in response to HARE. Evaluation of oxidative stress determined a reduction in the MDA level while a raised FRAP was confirmed. In accordance with the present results, histopathological observations have also demonstrated that HARE ameliorated grade-1 hepatic steatosis induced by HFD. Taken together, the findings of this study introduce HARE as a future potential therapeutic agent in treating hepatic steatosis and reducing oxidative damages of an HFD in the liver.

L-Fucose ameliorates high-fat diet-induced obesity and hepatic steatosis in mice

Backgroundl-Fucose (Fuc), a six-deoxy hexose monosaccharide, is present endogenously in humans and animals and has a wide range of biological functions. In the present study, we aimed to examine the effect of Fuc on obesity and hepatic steatosis in mice fed a high-fat diet (HFD).MethodsC57BL/6 mice were fed a normal chow (NC) or HFD for 18 weeks to induce obesity and fatty liver. Fuc was administered intragastrically from the 8th week to the end of the experiment (18 weeks).ResultsMetagenomic analysis showed that HFD altered the genomic profile of gut microbiota in the mice; specifically, expression of alpha-l-fucosidase, the gene responsible for Fuc generation, was markedly reduced in the HFD group compared with that in the NC group. Fuc treatment decreased body weight gain, fat accumulation, and hepatic triglyceride elevation in HFD-fed mice. In addition, Fuc decreased the levels of endotoxin-producing bacteria of the Desulfovibrionaceae family and restored HFD-induced enteric dysbiosis at both compositional and functional levels.ConclusionOur findings suggest that Fuc might be a novel strategy to treat HFD-induced obesity and fatty liver.

Acetyl-CoA Carboxylase Inhibition Reverses NAFLD and Hepatic Insulin Resistance but Promotes Hypertriglyceridemia in Rodents.

Pharmacologic inhibition of acetyl-CoA carboxylase (ACC) enzymes, ACC1 and ACC2, offers an attractive therapeutic strategy for nonalcoholic fatty liver disease (NAFLD) through simultaneous inhibition of fatty acid synthesis and stimulation of fatty acid oxidation. However, the effects of ACC inhibition on hepatic mitochondrial oxidation, anaplerosis, and ketogenesis in vivo are unknown. Here, we evaluated the effect of a liver-directed allosteric inhibitor of ACC1 and ACC2 (Compound 1) on these parameters, as well as glucose and lipid metabolism, in control and diet-induced rodent models of NAFLD. Oral administration of Compound 1 preferentially inhibited ACC enzymatic activity in the liver, reduced hepatic malonyl-CoA levels, and enhanced hepatic ketogenesis by 50%. Furthermore, administration for 6 days to high-fructose-fed rats resulted in a 20% reduction in hepatic de novo lipogenesis. Importantly, long-term treatment (21 days) significantly reduced high-fat sucrose diet-induced hepatic steatosis, protein kinase C epsilon activation, and hepatic insulin resistance. ACCi treatment was associated with a significant increase in plasma triglycerides (approximately 30% to 130%, depending on the length of fasting). ACCi-mediated hypertriglyceridemia could be attributed to approximately a 15% increase in hepatic very low-density lipoprotein production and approximately a 20% reduction in triglyceride clearance by lipoprotein lipase (P ≤ 0.05). At the molecular level, these changes were associated with increases in liver X receptor/sterol response element-binding protein-1 and decreases in peroxisome proliferator-activated receptor-α target activation and could be reversed with fenofibrate co-treatment in a high-fat diet mouse model. Conclusion: Collectively, these studies warrant further investigation into the therapeutic utility of liver-directed ACC inhibition for the treatment of NAFLD and hepatic insulin resistance.