Zhimu-Huangbai herb-pair ameliorates hepatic steatosis in mice by regulating IRE1α/XBP1s pathway to inhibit SREBP-1c.

Currently, there is a lack of validated pharmacological interventions for non-alcoholic fatty liver disease (NAFLD), which is characterized by the accumulation of hepatic triglyceride. Zhimu-Huangbai (ZH) herb-pair is a traditional Chinese medicine that regulates glucose and lipid metabolism disorders. However, the precise mechanisms underlying the preventive effects of hepatic triglyceride induced by high-fat diet (HFD) remain elusive. The study aimed to examine the impact of ZH herb-pair on NAFLD in mice and explore the underlying mechanisms, particularly its effects on endoplasmic reticulum (ER) stress and lipid metabolism. NAFLD was induced in mice using HFD, and the treated mice were orally administered ZH, metformin (Glucophage) or lovastatin. The lipid metabolism factors, ER stress markers, and the unfolded protein response (UPR) branch factors were measured using immunohistochemistry, western blotting or qRT-PCR. Co-Immunoprecipitation (CoIP) was performed to reveal the connection between SCAP and SREBP-1c. Tunicamycin (TM) and plasmid delivery were used to induce acute ER stress or crease XBP1 gain function models. The main compounds in ZH binding to IRE1α protein were studied by molecular docking and cellular thermal shift assay (CETSA). Treatment with ZH significantly ameliorated hepatic steatosis and reduced lipid synthesis process mainly inhibiting the expression of mature active form of SREBP-1c through relieving ER stress. The expression of IRE1α and XBP1s was inhibited after treatment with ZH. In addition, ZH improved the fatty liver phenotype caused by XBP1 overexpression via decreasing srebp1c transcription. In vitro experimental results suggested that the main compounds in ZH decreased cellular TG contents. Mechanistically, ZH targeted IRE1α and inhibited XBP1s mRNA expression to relieve ER stress and inhibit SREBP-1c production. ZH herb-pair can protect against NAFLD by reducing the expression of SREBP-1c, in part, via regulating IRE1α/XBP1s pathway.

Zhao W ，Wang X ，Nie W ，Jiang M ，Zhao Y ，Zhang T ，Ding Y ... -  《-》

FOXA3 induction under endoplasmic reticulum stress contributes to non-alcoholic fatty liver disease.

Chronic endoplasmic reticulum (ER) stress in the liver has been shown to play a causative role in non-alcoholic fatty liver disease (NAFLD) progression, yet the underlying molecular mechanisms remain to be elucidated. Forkhead box A3 (FOXA3), a member of the FOX family, plays critical roles in metabolic homeostasis, although its possible functions in ER stress and fatty liver progression are unknown. Adenoviral delivery, siRNA delivery, and genetic knockout mice were used to crease FOXA3 gain- or loss-of-function models. Tunicamycin (TM) and a high-fat diet (HFD) were used to induce acute or chronic ER stress in mice. Chromatin immunoprecipiation (ChIP)-seq, luciferase assay, and adenoviral-mediated downstream gene manipulations were performed to reveal the transcriptional axis involved. Key axis protein levels in livers from healthy donors and patients with NAFLD were assessed via immunohistochemical staining. FOXA3 transcription is specifically induced by XBP1s upon ER stress. FOXA3 exacerbates the excessive lipid accumulation caused by the acute ER-inducer TM, whereas FOXA3 deficiency in hepatocytes and mice alleviates it. Importantly, FOXA3 deficiency in mice reduced diet-induced chronic ER stress, fatty liver, and insulin resistance. In addition, FOXA3 suppression via siRNA or adeno-associated virus delivery ameliorated the fatty liver phenotype in HFD-fed and db/db mice. Mechanistically, ChIP-Seq analysis revealed that FOXA3 directly regulates Period1 (Per1) transcription, which in turn promotes the expression of lipogenic genes, including Srebp1c, thus enhancing lipid synthesis. Of pathophysiological significance, FOXA3, PER1, and SREBP1c levels were increased in livers of obese mice and patients with NAFLD. The present study identified FOXA3 as the bridging molecule that links ER stress and NAFLD progression. Our results highlighted the role of the XBP1s-FOXA3-PER1/Srebp1c transcriptional axis in the development of NAFLD and identified FOXA3 as a potential therapeutic target for fatty liver disease. The molecular mechanisms linking endoplasmic reticulum stress to non-alcoholic fatty liver disease (NAFLD) progression remain undefined. Herein, via in vitro and in vivo analysis, we identified Forkhead box A3 (FOXA3) as a key bridging molecule. Of pathophysiological significance, FOXA3 protein levels were increased in livers of obese mice and patients with NAFLD, indicating that FOXA3 could be a potential therapeutic target in fatty liver disease.

Liu C ，Zhou B ，Meng M ，Zhao W ，Wang D ，Yuan Y ，Zheng Y ，Qiu J ，Li Y ，Li G ，Xiong X ，Bian H ，Zhang H ，Wang H ，Ma X ，Hu C ，Xu L ，Lu Y ... -  《-》

Scutellarin ameliorates hepatic lipid accumulation by enhancing autophagy and suppressing IRE1α/XBP1 pathway.

Nonalcoholic fatty liver disease is the most prevalent liver disease characterized by excessive lipid accumulation in hepatocytes. Endoplasmic reticulum (ER) stress and autophagy play an important role in lipid accumulation. In this study, scutellarin (Scu) was examined in palmitic acid-treated HepG2 cells and C57/BL6 mice fed a high-fat diet (HFD). Scu reduced intracellular lipid content and inhibited sterol regulatory element binding protein-1c (SREBP-1c)-mediated lipid synthesis and fatty acid translocase-mediated lipid uptake in HepG2 cells. Additionally, Scu restored impaired autophagy and inhibited excessive activation of ER stress in vivo and in vitro. Moreover, Scu upregulated forkhead box O transcription factor 1-mediated autophagy by inhibiting inositol-requiring enzyme 1α (IRE1α)/X-box-binding protein 1 (XBP1) branch activation, while XBP1s overexpression exacerbated the lipid accumulation and impaired autophagy in HepG2 cells and also weakened the positive effects of Scu. Furthermore, Scu attenuated ER stress by activating autophagy, ultimately downregulating SREBP-1c-mediated lipid synthesis, and autophagy inhibitors offset these beneficial effects. Scu inhibited the crosstalk between autophagy and ER stress and downregulated saturated fatty acid-induced lipid accumulation in hepatocytes. These findings demonstrate that Scu ameliorates hepatic lipid accumulation by enhancing autophagy and suppressing ER stress via the IRE1α/XBP1 pathway.

Zhang X ，Huo Z ，Luan H ，Huang Y ，Shen Y ，Sheng L ，Liang J ，Wu F ... -  《-》

Fagopyrum dibotrys extract improves nonalcoholic fatty liver disease via inhibition of lipogenesis and endoplasmic reticulum stress in high-fat diet-fed mice.

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing, presenting a treatment challenge due to limited options. Endoplasmic reticulum (ER) stress and associated lipid metabolism disorders are main causes of NAFLD, making it important to inhibit ER stress for effective treatment. Fagopyrum dibotrys has hypolipidemic, anti-inflammatory and hepatoprotective properties, showing promise in treating NAFLD. However, its effects on ER stress in NAFLD remain unclear. This study used a high-fat diet (HFD) to establish NAFLD mouse models and supplemented with Fagopyrum dibotrys extract (FDE) to evaluate its therapeutic effect and underlying mechanisms. We showed that FDE supplementation reduced the severity of hepatic steatosis and lowered triglycerides (TG) and total cholesterol (TC) levels in NAFLD mice. At the molecular level, FDE supplementation reduced hepatic lipid deposition by downregulating lipogenic markers (SREBP-1c, SCD1) and upregulating fatty acid oxidase CPT1α expression. Additionally, FDE treatment inhibited the overexpression of ER stress markers (GRP78, CHOP, and P-EIF2α) in NAFLD mice livers, and blocked the activation of the PERK-EIF2α-CHOP pathway, demonstrating its role in maintaining ER homeostasis. Considering that activation of the PERK pathway could exacerbate lipid deposition, our findings suggest that FDE has a protective effect against hepatic steatosis in NAFLD mice by attenuating ER stress, and the potential mechanism is through inhibiting the PERK pathway.

Wang D ，Zhang D ，Zhu Z ，Zhang Y ，Wan Y ，Chen H ，Liu J ，Ma L ... -  《-》

Quercetin ameliorates HFD-induced NAFLD by promoting hepatic VLDL assembly and lipophagy via the IRE1a/XBP1s pathway.

The consumption of a quercetin-rich diet has been well-established as a feasible method against non-alcoholic fatty liver disease (NAFLD); however, the molecular mechanisms underlying the progression of NAFLD and its intervention by quercetin remain largely obscure. Male Sprague-Dawley rats fed high-fat diet (HFD), and HepG2 cells stimulated with free fatty acid, were treated with quercetin and various pharmacological reagents to explore the effect of signaling pathways involved in endoplasmic reticulum stress on very low-density lipoprotein (VLDL) assembly and lipophagy. Quercetin intake decreased hepatic TG content by 39%, with a 1.5-fold increase in VLDL, and up-regulated spliced X-box binding protein 1 (XBP1s) expression compared with the HFD group. Thapsigargin or STF-083010 (an IRE1α endonuclease inhibitor) decreased VLDL content in a dose-dependent manner, partially counteracting the protective effects of quercetin, 4-PBA or APY-29 (an IRE1α endonuclease activator). Additionally, microsomal TG-transfer protein complex expression was increased with quercetin-treated and down-regulated by STF-083010. Moreover, quercetin increased co-localization of lysosomes with lipid droplets (LDs) accompanied by decreased p62 accumulation. STF-083010 partially abolished the effect of quercetin on LDs autophagy in an mTOR-independent manner. Collectively, these findings demonstrate that hepatic VLDL assembly and lipophagy are the main targets of quercetin against NAFLD via the IRE1a/XBP1s pathway.

Zhu X ，Xiong T ，Liu P ，Guo X ，Xiao L ，Zhou F ，Tang Y ，Yao P ... -  《-》