Platelet-Derived Growth Factor C Facilitates Malignant Behavior of Pancreatic Ductal Adenocarcinoma by Regulating SREBP1 Mediated Lipid Metabolism.

Lipid metabolism reprogramming stands as a fundamental hallmark of cancer cells. Unraveling the core regulators of lipid biosynthesis holds the potential to find promising therapeutic targets in pancreatic ductal adenocarcinoma (PDAC). Here, it is demonstrated that platelet-derived growth factor C (PDGFC) orchestrated lipid metabolism, thereby facilitated the malignant progression of PDAC. Expression of PDGFC is upregulated in PDAC cohorts and is corelated with a poor prognosis. Aberrantly high expression of PDGFC promoted proliferation and metastasis of PDAC both in vitro and in vivo. Mechanistically, PDGFC accelerated the malignant progression of PDAC by upregulating fatty acid accumulation through sterol regulatory element-binding protein 1 (SREBP1), a key transcription factor in lipid metabolism. Remarkably, Betulin, an inhibitor of SREBP1, demonstrated the capability to inhibit proliferation and metastasis of PDAC cell lines, along with attenuating the process of liver metastasis in vivo. Overall, the study underscores the pivotal role of PDGFC-mediated lipid metabolism in PDAC progression, suggesting PDGFC as a potential biomarker for PDAC metastasis. Targeting PDGFC-induced lipid metabolism emerges as a promising therapeutic strategy for metastatic PDAC, with the potential to improve clinical outcomes.

IRE1α-XBP1s axis regulates SREBP1-dependent MRP1 expression to promote chemoresistance in non-small cell lung cancer cells.

BACKGROUND: Inositol-requiring enzyme 1 (IRE1) is an endoplasmic reticulum (ER)-resident transmembrane protein that senses ER stress and mediates an essential arm of the unfolded protein response (UPR). IRE1 reduces ER stress by upregulating the expression of multiple ER chaperones through activation of X-box-binding protein 1 (XBP1). Emerging lines of evidence have revealed that IRE1-XBP1 axis serves as a multipurpose signal transducer during oncogenic transformation and cancer development. In this study, we explore how IRE1-XBP1 signaling promotes chemoresistance in lung cancer. METHODS: The expression patterns of UPR components and MRP1 were examined by Western blot. qRT-PCR was employed to determine RNA expression. The promoter activity was determined by luciferase reporter assay. Chemoresistant cancer cells were analyzed by viability, apoptosis. CUT & Tag (Cleavage under targets and tagmentation)-qPCR analysis was used for analysis of DNA-protein interaction. RESULTS: Here we show that activation of IRE1α-XBP1 pathway leads to an increase in MDR-related protein 1 (MRP1) expression, which facilitates drug extrusion and confers resistance to cytotoxic chemotherapy. At the molecular level, XBP1-induced c-Myc is necessary for SREBP1 expression, and SREBP1 binds to the MRP1 promoter to directly regulate its transcription. CONCLUSIONS: We conclude that IRE1α-XBP1 had important role in chemoresistance and appears to be a novel prognostic marker for lung cancer.

Combinatorial targeting of glutamine metabolism and lysosomal-based lipid metabolism effectively suppresses glioblastoma.

Antipsychotic drugs have been shown to have antitumor effects but have had limited potency in the clinic. Here, we unveil that pimozide inhibits lysosome hydrolytic function to suppress fatty acid and cholesterol release in glioblastoma (GBM), the most lethal brain tumor. Unexpectedly, GBM develops resistance to pimozide by boosting glutamine consumption and lipogenesis. These elevations are driven by SREBP-1, which we find upregulates the expression of ASCT2, a key glutamine transporter. Glutamine, in turn, intensifies SREBP-1 activation through the release of ammonia, creating a feedforward loop that amplifies both glutamine metabolism and lipid synthesis, leading to drug resistance. Disrupting this loop via pharmacological targeting of ASCT2 or glutaminase, in combination with pimozide, induces remarkable mitochondrial damage and oxidative stress, leading to GBM cell death in vitro and in vivo. Our findings underscore the promising therapeutic potential of effectively targeting GBM by combining glutamine metabolism inhibition with lysosome suppression.

Pharmacological inhibition of SREBP1 suppresses pancreatic cancer growth via inducing GPX4-mediated ferroptosis.

Pancreatic cancer (PC) is highly malignancy with poor survival. Ferroptosis offers a novel therapeutic target for cancer treatment and glutathione peroxidase 4 (GPX4) shields tumor cells from ferroptosis damage. Although Sterol regulatory element-binding protein 1 (SREBP1) has been implicated in the development of pancreatic cancer, its underlying mechanisms remain unclear. This research aims to explore the role of SREBP1 in ferroptosis by using its inhibitor Fatostatin. In this study, Fatostatin was found to inhibit the proliferation and clonogenicity of pancreatic cancer cell lines. This was accompanied by a reduction in intracellular lipid synthesis, increased iron accumulation, elevated levels of reactive oxygen species (ROS), and accumulation of malondialdehyde (MDA). The JASPAR database shows that there is a binding site of the SREBP1 on the promoter region of GPX4. What's more, it was verified that SREBP1 can transcriptionally regulate GPX4 by CHIP. In vivo experiments further revealed that Fatostatin could suppress the growth of subcutaneous tumors in nude mice. In conclusion, our study suggests that Fatostatin may inhibit pancreatic cancer cell proliferation by inducing ferroptosis through the SREBP1/GPX4 pathway. These findings shed light on the therapeutic potential of Fatostatin and lay the groundwork for future investigations into its mechanism of action in pancreatic cancer.

CLDN6 inhibits breast cancer growth and metastasis through SREBP1-mediated RAS palmitoylation.

BACKGROUND: Breast cancer (BC) ranks as the third most fatal malignant tumor worldwide, with a strong reliance on fatty acid metabolism. CLDN6, a candidate BC suppressor gene, was previously identified as a regulator of fatty acid biosynthesis; however, the underlying mechanism remains elusive. In this research, we aim to clarify the specific mechanism through which CLDN6 modulates fatty acid anabolism and its impact on BC growth and metastasis. METHODS: Cell function assays, tumor xenograft mouse models, and lung metastasis mouse models were conducted to evaluate BC growth and metastasis. Human palmitic acid assay, triglyceride assay, Nile red staining, and oil red O staining were employed to investigate fatty acid anabolism. Reverse transcription polymerase chain reaction (RT-PCR), western blot, immunohistochemistry (IHC) assay, nuclear fractionation, immunofluorescence (IF), immunoprecipitation and acyl-biotin exchange (IP-ABE), chromatin immunoprecipitation (ChIP), dual luciferase reporter assay, and co-immunoprecipitation (Co-IP) were applied to elucidate the underlying molecular mechanism. Moreover, tissue microarrays of BC were analyzed to explore the clinical implications. RESULTS: We identified that CLDN6 inhibited BC growth and metastasis by impeding RAS palmitoylation both in vitro and in vivo. We proposed a unique theory suggesting that CLDN6 suppressed RAS palmitoylation through SREBP1-modulated de novo palmitic acid synthesis. Mechanistically, CLDN6 interacted with MAGI2 to prevent KLF5 from entering the nucleus, thereby restraining SREBF1 transcription. The downregulation of SREBP1 reduced de novo palmitic acid synthesis, hindering RAS palmitoylation and subsequent endosomal sorting complex required for transport (ESCRT)-mediated plasma membrane localization required for RAS oncogenic activation. Besides, targeting inhibition of RAS palmitoylation synergized with CLDN6 to repress BC progression. CONCLUSIONS: Our findings provide compelling evidence that CLDN6 suppresses the palmitic acid-induced RAS palmitoylation through the MAGI2/KLF5/SREBP1 axis, thereby impeding BC malignant progression. These results propose a new insight that monitoring CLDN6 expression alongside targeting inhibition of palmitic acid-mediated palmitoylation could be a viable strategy for treating oncogenic RAS-driven BC.

Srebp-1 bridges gonad development and lipid accumulation by regulating lipogenesis in noble scallop Chlamys nobilis.

In bivalve, development of female gonad is accompanied with accumulating lipids which provided energy resource for non-feeding larvae development. As the major transcriptional regulators of lipid metabolism, Srebps play pivotal role in lipid homeostasis during oogenesis. However, little work was conducted on Srebps function in bivalves. The noble scallop Chlamys nobilis accumulated large amount of lipids in its gonad during oogenesis. Here, we identified a single Srebp gene (named Srebp-1) with a high similarity to human Srebp-1c. Disrupting Srebp-1 with Betulin (inhibiting the maturation of Srebp protein) repressed expression of lipogenic genes and de novo lipogenesis, and resulted in reduction of gonad index and lipid deposition, suggesting a crucial role of Srebp-1 for gonad development and lipid synthesis in female gonad. Additionally, scallops with Srebp-1 disruption released fewer eggs with a reduction in their lipid content and D-larvae formation, revealing an impair of fecundity caused by Srebp-1 disruption. Cold exposure stimulated lipid accumulation which required Srebp-1 to regulate de novo lipogenesis and lipid uptake, providing a crosstalk of Srebp-1 activity and environmental variation on lipid accumulation in noble scallop. Thus, our study identified Srebp-1 as a central regulator coordinating the lipid synthesis and accumulation with gonad development in noble scallop.

Fanlian Huazhuo Formula alleviates high-fat diet-induced non-alcoholic fatty liver disease by modulating autophagy and lipid synthesis signaling pathway.

BACKGROUND: Fanlian Huazhuo Formula (FLHZF) has the functions of invigorating spleen and resolving phlegm, clearing heat and purging turbidity. It has been identified to have therapeutic effects on type 2 diabetes mellitus (T2DM) in clinical application. Non-alcoholic fatty liver disease (NAFLD) is frequently diagnosed in patients with T2DM. However, the therapeutic potential of FLHZF on NAFLD and the underlying mechanisms need further investigation. AIM: To elucidate the effects of FLHZF on NAFLD and explore the underlying hepatoprotective mechanisms in vivo and in vitro. METHODS: HepG2 cells were treated with free fatty acid for 24 hours to induce lipid accumulation cell model. Subsequently, experiments were conducted with the different concentrations of freeze-dried powder of FLHZF for 24 hours. C57BL/6 mice were fed a high-fat diet for 8-week to establish a mouse model of NAFLD, and then treated with the different concentrations of FLHZF for 10 weeks. RESULTS: FLHZF had therapeutic potential against lipid accumulation and abnormal changes in biochemical indicators in vivo and in vitro. Further experiments verified that FLHZF alleviated abnormal lipid metabolism might by reducing oxidative stress, regulating the AMPKα/SREBP-1C signaling pathway, activating autophagy, and inhibiting hepatocyte apoptosis. CONCLUSION: FLHZF alleviates abnormal lipid metabolism in NAFLD models by regulating reactive oxygen species, autophagy, apoptosis, and lipid synthesis signaling pathways, indicating its potential for clinical application in NAFLD.

Inhibition of STRA6 suppresses NSCLC growth via blocking STAT3/SREBP-1c axis-mediated lipogenesis.

Dysregulation in lipid metabolism is among the most prominent metabolic alterations in cancer. Stimulated by retinoic acid 6 (STRA6), a vitamin A transporter has shown to be involved in the pathogenesis of cancers. Nevertheless, the function of STRA6 in non-small cell lung cancer (NSCLC) progression remains undefined. We obtained cancer and adjacent tissues from NSCLC patients and conducted functional experiments on STRA6 on NSCLC cell lines and mice. High STRA6 expression is correlated with poor prognosis in patients with NSCLC. Results from in vitro and in vivo animal studies showed that STRA6 knockdown suppressed the proliferation, migration, and invasion of NSCLC cells in vitro and tumor growth in vivo through regulation of lipid synthesis. Mechanistically, STRA6 activated a Janus kinase 2/signal transducer and activator of transcription 3 (JAK2-STAT3) signaling cascade which inducing the expression of STAT3 target gene. By inducing the expression of the target gene of STAT3, sterol regulatory element binding protein 1 (SREBP-1), STRA6 promotes SREBP-1-mediated adipogenesis and provides energy for NSCLC cell growth. Our study uncovers a novel STRA6/STAT3/SREBP-1 regulatory axis that enhances NSCLC metastasis by reprogramming of lipid metabolism. These results demonstrate the potential use of STRA6 as a biomarker for diagnosing NSCLC, which may therefore potentially serve as a therapeutic target for NSCLC.

STAMBPL1, transcriptionally regulated by SREBP1, promotes malignant behaviors of hepatocellular carcinoma cells via Wnt/ß-catenin signaling pathway.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. STAM binding protein-like 1 (STAMBPL1), a key member of the COP9 signalosome subunit 5/serine protease 27/proteasome 26S subunit non-ATPase 7 (JAMM) family, is closely associated with tumor development. In this work, data from GSE101728 and GSE84402 chips were analyzed, and STAMBPL1 was selected as the target factor. This study aimed to reveal the potential function of STAMBPL1 in HCC. Clinical results showed that STAMBPL1 was significantly increased in tumor tissues of HCC patients, and its expression was strongly associated with tumor size and TNM stage. Furthermore, STAMBPL1-overexpressed Hep3B2.1-7 cell line or STAMBPL1-silenced SNU-182 cell line were established using lentivirus carrying cDNA encoding STAMBPL1 mRNA or shRNA targeting STAMBPL1, respectively. STAMBPL1-overexpressed cells exhibited a pronounced enhancement of proliferation in vitro and in vivo. Exogenous expression of STAMBPL1 increased the percentage of cells in the S phase and upregulated the expressions of CyclinD1 and Survivin. As expected, STAMBPL1 knockdown exhibited completely opposite effects, resulting in impaired tumorigenicity in vitro and in vivo. Mechanistically, STAMBPL1 activated Wnt/ß-catenin pathway and increased the expression of downstream cancer-promoting genes. Interestingly, we found that STAMBPL1 was transcriptionally regulated by sterol regulatory element-binding protein 1 (SREBP1), a modulator of lipid metabolism, as evidenced by luciferase reporter and chromatin-immunoprecipitation (Ch-IP) assays. Notably, STAMBPL1 overexpression increased lipid accumulation in HCC cells and xenograft tumors. Totally our findings suggest that STAMBPL1 plays a vital role in the tumorigenicity of HCC cells. Modulation of Wnt/ß-catenin and lipid metabolism may contribute to its pro-cancer effects. STAMBPL1 may serve as a therapeutic target of HCC.

Phosphorylation of Insig-2 mediates inhibition of fatty acid synthesis by polyunsaturated fatty acids.

Insig-1 and Insig-2 are endoplasmic reticulum (ER) proteins that inhibit lipid synthesis by blocking transport of sterol regulatory element-binding proteins (SREBP-1 and SREBP-2) from ER to Golgi. In the Golgi, SREBPs are processed proteolytically to release their transcription-activating domains, which enhance the synthesis of fatty acids, triglycerides, and cholesterol. Heretofore, the two Insigs have redundant functions, and there is no rationale for two isoforms. The current data identify a specific function for Insig-2. We show that eicosapentaenoic acid (EPA), a polyunsaturated fatty acid, inhibits fatty acid synthesis in human fibroblasts and rat hepatocytes by activating adenylate cyclase, which induces protein kinase A (PKA) to phosphorylate serine-106 in Insig-2. Phosphorylated Insig-2 inhibits the proteolytic processing of SREBP-1, thereby blocking fatty acid synthesis. Phosphorylated Insig-2 does not block the processing of SREBP-2, which activates cholesterol synthesis. Insig-1 lacks serine-106 and is not phosphorylated at this site. EPA inhibition of SREBP-1 processing was reduced by the replacement of serine-106 in Insig-2 with alanine or by treatment with KT5720, a PKA inhibitor. Inhibition did not occur in mutant human fibroblasts that possess Insig-1 but lack Insig-2. These data provide an Insig-2-specific mechanism for the long-known inhibition of fatty acid synthesis by polyunsaturated fatty acids.

Hepatic miR-363 promotes nonalcoholic fatty liver disease by suppressing INSIG1.

Nonalcoholic fatty liver disease (NAFLD) constitutes one of major worldwide health problem which typically progressively results in nonalcoholic steatohepatitis (NASH) and eventually cirrhosis and liver cancer. Liver-specific deletion of INSIG1 promotes SREBP1 nuclear translocation to activate downstream lipogenic genes expression, leading to lipid accumulation. However, the underlying pathogenesis of NAFLD, and particularly involved in miRNA participation are still to be thoroughly explored. Here, we found that miR-363-3p was significantly overexpressed in high-fat, high-cholesterol (HFHC) diet mice liver tissue and fatty acid-induced steatosis cells. miR-363-3p directly targets INSIG1 to inhibit its expression, thereby facilitating the cleavage of SREBP and nuclear translocation to activate subsequent transcription of lipogenic genes in vitro and in vivo. In addition, we identified apigenin, a natural flavonoid compound, inhibited miR-363-3p expression to up-regulate INSIG1 and suppress nuclear translocation of SREBP1, thereby down-regulated lipogenic genes expression in steatosis cells and HFHC diet mice liver tissues. Taken together, our results demonstrated that miR-363-3p as a key regulator of hepatic lipid homeostasis targeted INSIG1, and apigenin alleviated NAFLD through the miR-363-3p/INSIG1/SREBP1 pathway. This indicates that reduction of miR-363-3p levels as a possible treatment of hepatic steatosis and provides a potential new therapeutic strategy for targeting miRNA to ameliorate NAFLD.

Exploring the effect and mechanism of Hippophae rhamnoides L. triterpenoid acids on improving NAFLD based on network pharmacology and experimental validation in vivo and in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Sea buckthorn (Hippophae rhamnoides L.) is a traditional Chinese medicinal and possesses a rich medical history in terms of treating gastric disorders, sputum and cough and liver injuries in oriental medicinal system. By reason of the complicated chemical constituents, the material basis and potential pharmacological mechanism of sea buckthorn acting on Non-alcoholic fatty liver disease (NAFLD) has not been clearly elucidated. AIM OF THE STUDY: To explore the pharmacological efficacy and underlying mechanism of sea buckthorn triterpenoid acid enrichment (STE) in the treatment of NAFLD. MATERIALS AND METHODS: The approaches of Network pharmacology and experiment validation in vitro and in vivo were applied in this study. Firstly, targets of triterpenoid acid compounds and NAFLD were collected from databases. The crucial targets were screened by the construction of protein-protein interaction (PPI) network. Furthermore, the potential signaling pathways and targets affected by STE was predicted by GO together with KEGG enrichment analysis. Finally, the experiment validation was carried out through high-fat feeding NAFLD mice and lipid accumulation HepG2 cell model. Lipids and liver related biochemical indicators were determined, Oil Red O and H&E staining were employed to observe fat accumulation. In addition, the expression levels of proteins of key target and signal pathway anticipated in network pharmacology were detected to elaborated its action mechanism. RESULTS: A total of 180 intersecting potential targets for enhancing NAFLD with STE were eventually identified. 6 key targets including AKT1, TNF, IL6, INS, JUN, STAT3 and TP53 were further identified and the AMPK-SREBP1 pathway was enriched. Animal experiment result showed that STE treatment could significantly reduce the levels of TG, TC, LDL-C, ALT and AST, increase the levels of HDL-C in serum, and improve lipid accumulation of epididymal fat and liver. The results of the lipid accumulation cell model indicated that STE and key compound oleanolic acid could diminish intracellular lipid levels of TG, TC, LDL-C and number of lipid droplets. Western blot results showed that the above beneficial effects could be achieved by regulating the expression of p-AMPK/AMPK, SREBP1, FAS, ACC, SCD protein. CONCLUSION: This study confirmed the effect of STE on improving NAFLD and the potential action mechanism was involved in the regulation of the AMPK-SREBP1 pathway.

Zinc finger BED-type containing 3 promotes hepatic steatosis by interacting with polypyrimidine tract-binding protein 1.

AIMS/HYPOTHESIS: The relationship between metabolic dysfunction-associated steatotic liver disease (MASLD) and type 2 diabetes mellitus, insulin resistance and the metabolic syndrome is well established. While zinc finger BED-type containing 3 (ZBED3) has been linked to type 2 diabetes mellitus and the metabolic syndrome, its role in MASLD remains unclear. In this study, we aimed to investigate the function of ZBED3 in the context of MASLD. METHODS: Expression levels of ZBED3 were assessed in individuals with MASLD, as well as in cellular and animal models of MASLD. In vitro and in vivo analyses were conducted using a cellular model of MASLD induced by NEFA and an animal model of MASLD induced by a high-fat diet (HFD), respectively, to investigate the role of ZBED3 in MASLD. ZBED3 expression was increased by lentiviral infection or tail-vein injection of adeno-associated virus. RNA-seq and bioinformatics analysis were employed to examine the pathways through which ZBED3 modulates lipid accumulation. Findings from these next-generation transcriptome sequencing studies indicated that ZBED3 controls SREBP1c (also known as SREBF1; a gene involved in fatty acid de novo synthesis); thus, co-immunoprecipitation and LC-MS/MS were utilised to investigate the molecular mechanisms by which ZBED3 regulates the sterol regulatory element binding protein 1c (SREBP1c). RESULTS: In this study, we found that ZBED3 was significantly upregulated in the liver of individuals with MASLD and in MASLD animal models. ZBED3 overexpression promoted NEFA-induced triglyceride accumulation in hepatocytes in vitro. Furthermore, the hepatocyte-specific overexpression of Zbed3 promoted hepatic steatosis. Conversely, the hepatocyte-specific knockout of Zbed3 resulted in resistance of HFD-induced hepatic steatosis. Mechanistically, ZBED3 interacts directly with polypyrimidine tract-binding protein 1 (PTBP1) and affects its binding to the SREBP1c mRNA precursor to regulate SREBP1c mRNA stability and alternative splicing. CONCLUSIONS/INTERPRETATION: This study indicates that ZBED3 promotes hepatic steatosis and serves as a critical regulator of the progression of MASLD. DATA AVAILABILITY: RNA-seq data have been deposited in the NCBI Gene Expression Omnibus ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE231875 ). MS proteomics data have been deposited to the ProteomeXchange Consortium via the iProX partner repository ( https://proteomecentral.proteomexchange.org/cgi/GetDataset?ID=PXD041743 ).

Salusin­α alleviates lipid metabolism disorders via regulation of the downstream lipogenesis genes through the LKB1/AMPK pathway.

Lipid metabolism disorders are a major cause of several chronic metabolic diseases which seriously affect public health. Salusin­α, a vasoactive peptide, has been shown to attenuate lipid metabolism disorders, although its mechanism of action has not been reported. To investigate the effects and potential mechanisms of Salusin­α on lipid metabolism, Salusin­α was overexpressed or knocked down using lentiviral vectors. Hepatocyte steatosis was induced by free fatty acid (FFA) after lentiviral transfection into HepG2 cells. The degree of lipid accumulation was assessed using Oil Red O staining and by measuring several biochemical indices. Subsequently, bioinformatics was used to analyze the signaling pathways that may have been involved in lipid metabolism disorders. Finally, semi­quantitative PCR and western blotting were used to verify the involvement of the liver kinase B1 (LKB1)/AMPK pathway. Compound C, an inhibitor of AMPK, was used to confirm this mechanism's involvement further. The results showed that Salusin­α significantly attenuated lipid accumulation, inflammation and oxidative stress. In addition, Salusin­α increased the levels of LKB1 and AMPK, which inhibited the expression of sterol regulatory element binding protein­1c, fatty acid synthase and acetyl­CoA carboxylase. The addition of Compound C abrogated the Salusin­α­mediated regulation of AMPK on downstream signaling molecules. In summary, overexpression of Salusin­α activated the LKB1/AMPK pathway, which in turn inhibited lipid accumulation in HepG2 cells. This provides insights into the potential mechanism underlying the mechanism by which Salusin­α ameliorates lipid metabolism disorders while identifying a potential therapeutic target.

SREBP-1-mediated lipogenesis confers resistance to ferroptosis and improves endothelial injury.

Atherosclerosis refers to a disease characterized by the formation of lipid plaque deposits within arterial walls, leading to reduced blood flow or blockage of blood outflow. The process of endothelial injury induced by oxidized low-density lipoprotein (ox-LDL) is considered the initial stage of atherosclerosis. Ferroptosis is a form of iron-dependent, non-apoptotic cell death, and current research suggests its association with coronary artery disease (CAD). In this study, we observed a correlation between reduced expression of SREBP-1 and the occurrence of stable CAD. Additionally, during the process of endothelial injury induced by ox-LDL, we also noted decreased expression of the SREBP-1/SCD1/FADS2 and involvement in the ferroptosis process. Mechanistically, ox-LDL induced endothelial injury by inhibiting the lipid biosynthesis process mediated by the SREBP-1/SCD1/FADS2, thereby inducing lipid peroxidation and ferroptosis. On the contrary, overexpression of SREBP-1 or supplementation with monounsaturated fatty acids counteracted iron accumulation, mitochondrial damage, and lipid peroxidation-induced ferroptosis, thereby improving endothelial injury. Our study indicated that the decreased expression of peripheral blood SREBP-1 mRNA is an independent risk factor for stable CAD. Furthermore, in endothelial cells, the lipid biosynthesis process mediated by SREBP-1 could ameliorate endothelial injury by resisting ferroptosis. The study has been registered with the Chinese Clinical Trial Registry, which serves as a primary registry in the World Health Organization International Clinical Trials Registry Platform (ChiCTR2300074315, August 3rd, 2023).

BI-7273, a BRD9 inhibitor, reduces lipid accumulation by downregulating the AKT/mTOR/SREBP1 signaling pathway.

Increases in de novo lipogenesis that disturbed lipid homeostasis and caused lipid accumulation are a major cause of NAFLD and obesity. SREBP1 is a crucial regulatory factor controlling the expression of rate-limiting enzymes of lipid synthesis. A reduction in SREBP1expression can reduce lipid accumulation. Thus, we utilized an SREBP1-luciferase-KI HEK293 cell line constructed by our lab to screen 200 kinds of epigenetic drugs for their ability to downregulate SREBP1expression. BI-7273, an inhibitor of bromodomain-containing protein 9 (BRD9), was screened and found to decrease SREBP1 expression. What is more, BI-7273 has been confirmed that it could reduce lipid accumulation in HepG2 cells by BODIPY staining, and significantly decrease the protein expression of SREBP1 and FASN. To explore the potential mechanism BI-7273 reducing lipid accumulation, RNA sequencing (RNA-seq) was performed and demonstrated that BI-7273 reduced lipid accumulation by downregulating the AKT/mTOR/SREBP1 pathway in vitro. Finally, these results were verified in NAFLD and obesity mouse model induced by high fat diet (HFD). The results indicated that BI-7273 could decrease mouse body weight and improve insulin sensitivity, but also exhibited a strong negative correlation with serum lipid levels, and also demonstrated that BI-7273 reduced lipid accumulation via AKT/mTOR/SREBP1 pathway in vivo. In conclusion, our results revealed that BI-7273 decreases lipid accumulation by downregulating the AKT/mTOR/SREBP1 pathway in vivo and in vitro. This is the first report demonstrating the protective effect of this BRD9 inhibitor against NAFLD and obesity. BRD9 may be a novel target for the discovery of effective drugs to treat lipid metabolism disorders.

Fatty acid synthesis promotes inflammasome activation through NLRP3 palmitoylation.

Despite its significance, the role of lipid metabolism in NLRP3 inflammasome remains elusive. Here, we reveal a critical role for fatty acid synthase (FASN) in NLRP3 inflammasome activation. We demonstrate that pharmacological or genetic depletion of FASN dampens NLRP3 activation in primary mouse and human macrophages and in mice. This disruption in NLRP3 activation is contingent upon FASN activity. Accordingly, abolishing cellular palmitoylation, a post-translational modification in which the FASN product palmitate is reversibly conjugated to cysteine residues of target proteins, blunts inflammasome signaling. Correspondingly, an acyl-biotin exchange assay corroborated NLRP3 palmitoylation. Mechanistically, Toll-like receptor (TLR) ligation introduces palmitoylation at NLRP3 Cys898, permitting NLRP3 translocation to dispersed trans-Golgi network (dTGN) vesicles, the site of inflammasome assembly, upon NLRP3 activation. Accordingly, the NLRP3 Cys898 mutant exhibits reduced palmitoylation, limited translocation to the dTGN compartment, and diminished inflammasome activation. These results underscore mechanistic insights through which lipid metabolism licenses NLRP3 inflammasome assembly and activation.

2-Deoxy-D-Glucose Downregulates Fatty Acid Synthase Gene Expression Via an Endoplasmic Reticulum Stress-Dependent Pathway in HeLa Cells.

Fatty acid synthase (FASN) catalyzes the rate-limiting step of cellular lipogenesis. FASN expression is upregulated in various types of cancer cells, implying that FASN is a potential target for cancer therapy. 2-Deoxy-D-glucose (2-DG) specifically targets cancer cells by inhibiting glycolysis and glucose metabolism, resulting in multiple anticancer effects. However, whether the effects of 2-DG involve lipogenic metabolism remains to be elucidated. We investigated the effect of 2-DG administration on FASN expression in HeLa human cervical cancer cells. 2-DG treatment for 24 h decreased FASN mRNA and protein levels and suppressed the activity of an exogenous rat Fasn promoter. The use of a chemical activator or inhibitors or of a mammalian expression plasmid showed that neither AMPK nor the Sp1 transcription factor is responsible for the inhibitory effect of 2-DG on FASN expression. Administration of thapsigargin, an endoplasmic reticulum (ER) stress inducer, or 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), a site 1 protease inhibitor, mimicked the inhibitory effect of 2-DG on FASN expression. 2-DG did not further decrease FASN expression in the presence of thapsigargin or AEBSF. Site 1 protease mediates activation of ATF6, an ER stress mediator, as well as sterol regulatory element-binding protein 1 (SREBP1), a robust transcription factor for FASN. Administration of 2-DG or thapsigargin for 24 h suppressed activation of ATF6 and SREBP1, as did AEBSF. We speculated that these effects of 2-DG or thapsigargin are due to feedback inhibition via increased GRP78 expression following ER stress. Supporting this, exogenous overexpression of GRP78 in HeLa cells suppressed SREBP1 activation and Fasn promoter activity. These results suggest that 2-DG suppresses FASN expression via an ER stress-dependent pathway, providing new insight into the molecular basis of FASN regulation in cancer.

STAT3 activation of SCAP-SREBP-1 signaling upregulates fatty acid synthesis to promote tumor growth.

SCAP plays a central role in controlling lipid homeostasis by activating SREBP-1, a master transcription factor in controlling fatty acid (FA) synthesis. However, how SCAP expression is regulated in human cancer cells remains unknown. Here, we revealed that STAT3 binds to the promoter of SCAP to activate its expression across multiple cancer cell types. Moreover, we identified that STAT3 also concurrently interacts with the promoter of SREBF1 gene (encoding SREBP-1), amplifying its expression. This dual action by STAT3 collaboratively heightens FA synthesis. Pharmacological inhibition of STAT3 significantly reduces the levels of unsaturated FAs and phospholipids bearing unsaturated FA chains by reducing the SCAP-SREBP-1 signaling axis and its downstream effector SCD1. Examination of clinical samples from patients with glioblastoma, the most lethal brain tumor, demonstrates a substantial co-expression of STAT3, SCAP, SREBP-1, and SCD1. These findings unveil STAT3 directly regulates the expression of SCAP and SREBP-1 to promote FA synthesis, ultimately fueling tumor progression.

Quercetin ameliorates lipid deposition in primary hepatocytes of the chicken embryo.

1. The accumulation of excessive fat plays a role in the development of non-alcoholic fatty liver disease (NAFLD) and phytogenic feed additives have the potential to ameliorate this. This study involved the isolation and culture of primary hepatocytes from chicken embryos to establish a model of hepatic steatosis induced by oleic acid/dexamethasone (OA/DEX). Lipid accumulation and cell viability were assessed using Nile Red staining, Oil Red O staining and cell count Kit -8 (CCK8) following treatment with varying concentrations of quercetin (Que). The potential mechanism by which Que exerts its effects was preliminarily investigated.2. The results indicated that OA effectively treated lipid accumulation in hepatocytes. There was no notable variance in cell proliferation between the normal and OA/DEX groups when subjected to Que treatment at concentrations of 1000 ng/ml and 10 000 ng/ml. Triglycerides and cholesterol (low and high density) decreased with Que treatment, with the most substantial reduction observed at 10 000 ng/ml.3. Gene expression levels decreased to levels similar to those in the control groups. Western blot data demonstrated that sterol regulatory element-binding protein 1 (SREBP-1) protein expression correlated with its mRNA expression level. Que mitigated lipid accumulation through the alpha serine/threonine protein kinase (AKT) and extracellular signal-regulated kinase (ERK) pathways. Expression levels of lipid-related genes (APOB, PPARα, CYP3A5 and SREBP-1) decreased to levels similar to the control groups. Western blot data demonstrated that the SREBP-1 protein expression correlated with its mRNA expression level.4. Supplementation with Que ameliorated lipid accumulation through AKT and ERK signalling pathway in OA/DEX-induced high-fat hepatocytes.