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The present study investigated the efficacy of the hepatoprotective drug matrine (Mtr) for its new application for hepatosteatosis and associated disorders in glucose homeostasis. The study was performed in two nutritional models of hepatosteatosis in mice with various abnormal glucose homeostasis: (1) high-fructose diet (HFru) induced hepatosteatosis and glucose intolerance from hepatic, and (2) hepatosteatosis and hyperglycemia induced by high-fat (HF) diet in combination with low doses of streptozotocin (STZ). Administration of Mtr (100 mg/kg every day in diet for 4 weeks) abolished HFru-induced hepatosteatosis and glucose intolerance. These effects were associated with the inhibition of HFru-stimulated de novo lipogenesis (DNL) without altering hepatic fatty acid oxidation. Further investigation revealed that HFru-induced endoplasmic reticulum (ER) stress was inhibited, whereas heat-shock protein 72 (an inducible chaperon protein) was increased by Mtr. In a type 2 diabetic model induced by HF-STZ, Mtr reduced hepatosteatosis and improved attenuated hyperglycemia. The hepatoprotective drug Mtr may be repurposed for the treatment of hepatosteatosis and associated disorders in glucose homeostasis. The inhibition of ER stress associated DNL and fatty acid influx appears to play an important role in these metabolic effects.

Background and Purpose: Matrine is a small molecule drug used in humans for the treatment of chronic viral infections and tumours in the liver with little adverse effects. The present study investigated its therapeutic efficacy for insulin resistance and hepatic steatosis in high-fat-fed mice., Experimental Approach: C57BL/J6 mice were fed a chow or high-fat diet for 10 weeks and then treated with matrine or metformin for 4 weeks. The effects on lipid metabolism and glucose tolerance were evaluated., Key Results: Our results first showed that matrine reduced glucose intolerance and plasma insulin level, hepatic triglyceride content and adiposity in high-fat-fed mice without affecting caloric intake. This reduction in hepatosteatosis was attributed to suppressed lipid synthesis and increased fatty acid oxidation. In contrast to metformin, matrine neither suppressed mitochondrial respiration nor activated AMPK in the liver. A computational docking simulation revealed HSP90, a negative regulator of HSP72, as a potential binding target of matrine. Consistent with the simulation results, matrine, but not metformin, increased the hepatic protein level of HSP72 and this effect was inversely correlated with both liver triglyceride level and glucose intolerance., Conclusions and Implications: Taken together, these results indicate that matrine may be used for the treatment of type 2 diabetes and hepatic steatosis, and the molecular action of this hepatoprotective drug involves the activation of HSP72 in the liver., (© 2015 The British Pharmacological Society.)

Hepatic steatosis is often associated with insulin resistance as a hallmark of the metabolic syndrome in the liver. The present study investigated the effects of PPARα activation induced by fenofibrate (FB) on the relationship of insulin resistance and hepatic steatosis in mice fed a high-fat (HF) diet, which increases lipid influx into the liver. Mice were fed HF diet to induce insulin resistance and hepatic steatosis with or without FB. FB activated PPARα and ameliorated HF diet-induced glucose intolerance and hepatic insulin resistance without altering either hepatic steatosis or inflammation signaling (JNK or IKK). Interestingly, FB treatment simultaneously increased fatty acid (FA) synthesis (50%) and oxidation (66%, both p<0.01) into intermediate lipid metabolites, suggesting a FA oxidation-synthesis cycling in operation. Associated with these effects, diacylglycerols (DAGs) were sequestered within the lipid droplet/ER compartment, thus reducing their deposition in the cellular membrane, which is known to impair insulin signal transduction. These findings suggest that the reduction in membrane DAGs (rather than total hepatic steatosis) may be critical for the protection by fenofibrate-induced PPARα activation against hepatic insulin resistance induced by dietary fat., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Endoplasmic reticulum (ER) stress is suggested to cause hepatic insulin resistance by increasing de novo lipogenesis (DNL) and directly interfering with insulin signaling through the activation of the c-Jun N-terminal kinase (JNK) and IκB kinase (IKK) pathway. The current study interrogated these two proposed mechanisms in a mouse model of hepatic insulin resistance induced by a high fructose (HFru) diet with the treatment of fenofibrate (FB) 100 mg/kg/day, a peroxisome proliferator-activated receptor α (PPARα) agonist known to reduce lipid accumulation while maintaining elevated DNL in the liver. FB administration completely corrected HFru-induced glucose intolerance, hepatic steatosis, and the impaired hepatic insulin signaling (pAkt and pGSK3β). Of note, both the IRE1/XBP1 and PERK/eIF2α arms of unfolded protein response (UPR) signaling were activated. While retaining the elevated DNL (indicated by the upregulation of SREBP1c, ACC, FAS, and SCD1 and [3H]H2O incorporation into lipids), FB treatment markedly increased fatty acid oxidation (indicated by induction of ACOX1, p-ACC, β-HAD activity, and [14C]palmitate oxidation) and eliminated the accumulation of diacylglycerols (DAGs), which is known to have an impact on insulin signaling. Despite the marked activation of UPR signaling, neither JNK nor IKK appeared to be activated. These findings suggest that lipid accumulation (mainly DAGs), rather than the activation of JNK or IKK, is pivotal for ER stress to cause hepatic insulin resistance. Therefore, by reducing the accumulation of deleterious lipids, activation of PPARα can ameliorate hepatic insulin resistance against increased ER stress.

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress have been implicated in hepatic steatosis and insulin resistance. The present study investigated their roles in the development of hepatic steatosis and insulin resistance during de novo lipogenesis (DNL) compared to extrahepatic lipid oversupply. Male C57BL/6J mice were fed either a high fructose (HFru) or high fat (HFat) diet to induce DNL or lipid oversupply in/to the liver. Both HFru and HFat feeding increased hepatic triglyceride within 3 days (by 3.5 and 2.4 fold) and the steatosis remained persistent from 1 week onwards (p<0.01 vs Con). Glucose intolerance (iAUC increased by ∼60%) and blunted insulin-stimulated hepatic Akt and GSK3β phosphorylation (∼40-60%) were found in both feeding conditions (p<0.01 vs Con, assessed after 1 week). No impairment of mitochondrial function was found (oxidation capacity, expression of PGC1α, CPT1, respiratory complexes, enzymatic activity of citrate synthase & β-HAD). As expected, DNL was increased (∼60%) in HFru-fed mice and decreased (32%) in HFat-fed mice (all p<0.05). Interestingly, associated with the upregulated lipogenic enzymes (ACC, FAS and SCD1), two (PERK/eIF2α and IRE1/XBP1) of three ER stress pathways were significantly activated in HFru-fed mice. However, no significant ER stress was observed in HFat-fed mice during the development of hepatic steatosis. Our findings indicate that HFru and HFat diets can result in hepatic steatosis and insulin resistance without obvious mitochondrial defects via different lipid metabolic pathways. The fact that ER stress is apparent only with HFru feeding suggests that ER stress is involved in DNL per se rather than resulting from hepatic steatosis or insulin resistance.

Peroxisome proliferator-activated receptor (PPAR)alpha and PPARgamma agonists lower lipid accumulation in muscle and liver by different mechanisms. We investigated whether benefits could be achieved on insulin sensitivity and lipid metabolism by the dual PPARalpha/gamma agonist ragaglitazar in high fat-fed rats. Ragaglitazar completely eliminated high-fat feeding-induced liver triglyceride accumulation and visceral adiposity, like the PPARalpha agonist Wy-14643 but without causing hepatomegaly. In contrast, the PPARgamma agonist rosiglitazone only slightly lessened liver triglyceride without affecting visceral adiposity. Compared with rosiglitazone or Wy-14643, ragaglitazar showed a much greater effect (79%, P < 0.05) to enhance insulin's suppression of hepatic glucose output. Whereas all three PPAR agonists lowered plasma triglyceride levels and lessened muscle long-chain acyl-CoAs, ragaglitazar and rosiglitazone had greater insulin-sensitizing action in muscle than Wy-14643, associated with a threefold increase in plasma adiponectin levels. There was a significant correlation of lipid content and insulin action in liver and particularly muscle with adiponectin levels (P < 0.01). We conclude that the PPARalpha/gamma agonist ragaglitazar has a therapeutic potential for insulin-resistant states as a PPARgamma ligand, with possible involvement of adiponectin. Additionally, it can counteract fatty liver, hepatic insulin resistance, and visceral adiposity generally associated with PPARalpha activation, but without hepatomegaly.

Background and Purpose: Non‐alcoholic steatohepatitis (NASH) is the more severe form of metabolic associated fatty liver disease (MAFLD) and no pharmacological treatment as yet been approved. Identification of novel therapeutic targets and their agents is critical to overcome the current inadequacy of drug treatment for NASH. Experimental Approach The correlation between heat shock factor 1 (HSF1) levels and the development of NASH and the target genes of HSF1 in hepatocyte were investigated by chromatin‐immunoprecipitation sequencing. The effects and mechanisms of SYSU‐3d in alleviating NASH were examined in relevant cell models and mouse models (the Ob/Ob mice, high‐fat and high‐cholesterol diet and the methionine‐choline deficient diet‐fed mice). The actions of SYSU‐3d in vivo were evaluated. Key Results: HSF1 is progressively reduced with mitochondrial dysfunction in NASH pathogenesis and activation of this transcription factor by its newly identified activator SYSU‐3d effectively inhibited all manifestations of NASH in mice. When activated, the phosphorylated HSF1 (Ser326) translocated to nucleus and bound to the promoter of PPARγ coactivator‐1α (PGC‐1α) to induce mitochondrial biogenesis. Thus, increasing mitochondrial adaptive oxidation and inhibiting oxidative stress. The deletion of HSF1 and PGC‐1α or recovery of HSF1 in HSF1‐deficiency cells showed the HSF1/PGC‐1α pathway was mainly responsible for the anti‐NASH effects of SYSU‐3d independent of AMP‐activated protein kinase (AMPK). Conclusion and Implications: Activation of HSF1 is a practical therapeutic approach for NASH treatment via the HSF1/PGC‐1α/mitochondrial pathway and SYSU‐3d can be considered as a potential candidate for the treatment of NASH. [ABSTRACT FROM AUTHOR]

Background and Purpose: Non-alcoholic hepatic fatty liver disease (NAFLD) is a manifestation of the metabolic syndrome in the liver and non-alcoholic steatohepatitis (NASH) represents its advanced stage. R17 derived from bouchardatine, shows benefits in the metabolic syndrome, but has not been tested in the liver. The present study examined the pharmacological effects of R17 in a model of NAFLD/NASH and its mode of action.Experimental Approach: The effects of R17 were examined in mice fed a high-fat (HF) diet to induce the pathological characteristics of NAFLD/NASH and in cultures of HuH7 cells. We used histological and immunohistochemical techniques along with western blotting and siRNA. Generation of ROS and apoptosis were measured.Key Results: Administration of R17 (20 mg·kg-1 , i.p. every other day) for 5 weeks reversed HF-induced hepatic triglyceride content, inflammation (inflammatory cytokines and macrophage numbers), injury (hepatocyte ballooning and apoptosis, plasma levels of alanine aminotransferase and aspartate aminotransferase), and fibrogenesis (collagen deposition and mRNA expression of fibrosis markers). In cultured cells, R17 reduced cell steatosis from both lipogenesis and fatty acid influx. The attenuated inflammation and cell injury were associated with inhibition of both endoplasmic reticulum (ER) stress and oxidative stress. Notably, R17 activated the liver kinase B1-AMP-activated protein kinase (AMPK) pathway by inhibiting activity of ATP synthase, rather than direct stimulation of AMPK.Conclusion and Implications: R17 has therapeutic potential for NAFLD/NASH. Its mode of action involves the elimination of ER and oxidative stresses, possibly via activating the LKB1-AMPK axis by inhibiting the activity of ATP synthase. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of matrine on non-alcoholic steatohepatitis (NASH) in mice induced by a methionine choline-deficient (MCD) diet and the mechanism involved. The study was performed in C57B/6J mice fed a MCD diet for 6 weeks to induce NASH with or without the treatment of matrine (100 mg/kg/day in diet). Metformin was used (250 mg/kg/day in diet) as a comparator for mechanistic investigation. Administration of matrine significantly reduced MCD-induced elevations in plasma ALT and AST but without changing body or liver fat content. Along with alleviating liver injury, matrine suppressed MCD-induced hepatic inflammation (indicated by TNFα, CD68, MCP-1, and NLRP3) and fibrosis (indicated by collagen 1, TGFβ, Smad3, and sirius-red staining). In comparison, metformin treatment did not show any clear sign of effects on these parameters indicative of NASH. Further examination of the liver showed that matrine treatment rescued the suppressed HSP72 (a chaperon protein against cytotoxicity) and blocked the induction of mTOR (a key protein in a stress pathway). In keeping with the lack of the improvement of the NASH features, metformin did not show any significant effect against MCD-induced changes in HSP72 and mTOR. Matrine protects against MCD-induced development of NASH which is refractory to metformin treatment. Its anti-NASH effects involve enhancing HSP72 and downregulating mTOR but do not rely on amelioration of hepatosteatosis. [ABSTRACT FROM AUTHOR]

The present study investigated the role of dietary cholesterol and fat in the development of nonalcoholic fatty liver disease, a common liver disease in metabolic disorders. Mice were fed a diet of regular chow (CH), chow supplemented with 0.2% w/w cholesterol (CHC), high fat (HF, 45kcal%) or HF with cholesterol (HFC) for 17weeks. While both HF and HFC groups displayed hepatic steatosis and metabolic syndrome, only HFC group developed the phenotype of liver injury, as indicated by an increase in plasma level of alanine transaminase (ALT, by 50-80%). There were ~2-fold increases in mRNA expression of tumor necrosis factor α, interleukin 1β and monocyte chemotactic protein 1 in the liver of HFC-fed mice (vs. HF) but no endoplasmic reticulum stress or oxidative stress was observed. Furthermore, cholesterol suppressed HF-induced increase of peroxisome proliferator-activated receptor γ coactivator 1α and mitochondrial transcription factor A expression and blunted fatty acid oxidation. Interestingly, after switching HFC to HF diet for 5weeks, the increases in plasma ALT and liver inflammatory markers were abolished but the blunted of mitochondrial function remained. These findings suggest that cholesterol plays a critical role in the conversion of a simple fatty liver toward nonalcoholic steatohepatitis possibly by activation of inflammatory pathways together with retarded mitochondrial function. [ABSTRACT FROM AUTHOR]

Abstract: Reducing lipid accumulation in insulin target tissues is critical for the treatment of type 2 diabetes. This study aimed to develop a biochemical assay in cells for high throughput (HTP) screening of anti-diabetic drugs by reducing lipid accumulation via different mechanisms. We designed a new method to extract triglyceride (TG) with KOH to allow biochemical quantification of TGs for HTP screening in 3T3-L1 cells. This new method was validated for its biochemical properties with identical results of TG obtained with or without KOH (r 2 =0.9978, p <0.001) and a fourfold improvement in TG extraction recovery rate (88–95%, p <0.001) as compared to the conventional chloroform/methanol extraction (12–18%). The ability of this phenotype screening to capture potential anti-diabetic drugs was verified by pharmacological agents well known to alter lipid accumulation by different mechanisms including AMPK activators, fatty acid synthesis inhibitors, PPARγ activator and several lipogenic substrates. To further demonstrate the application of this screening tool for discovery of new anti-diabetic drugs, we screened >200 new candidates selected from Chinese medicine and identified 49 compounds from different classes which reduced TG content by >50% at 1μM or >75% at 10μM. Finally, we tested two selected leads (albiflorin and oxymatrine) in vivo and confirmed their efficacy in reducing visceral adiposity, glucose intolerance and hepatic steatosis in high fat-fed or high fructose-fed mice. Our results indicate that screening for the efficacy on lipid accumulation in cells by biochemical quantification of TGs with KOH extraction is an effective tool for the identification of new anti-diabetic compounds. [Copyright &y& Elsevier]