stearoyl-CoA Desaturase Research Articles

Gain of pancreatic beta cell-specific SCD1 improves glucose homeostasis by maintaining functional beta cell mass under metabolic stress.

The key pancreatic beta cell transcription factor v-maf musculoaponeurotic fibrosarcoma oncogene homologue A (MafA) is critical for the maintenance of mature beta cell function and phenotype. The expression levels and/or activities of MafA are reduced when beta cells are chronically exposed to diabetogenic stress, such as hyperglycaemia (i.e. glucotoxicity). Interventional targets and adjuvant therapies to abate MafA loss in beta cells may provide evidence to support the effective treatment of diabetes. In this study, we aimed to investigate the function of stearoyl-CoA desaturase 1 (SCD1) in the stabilisation of MafA expression and activity in order to maintain functional beta cell mass, with a view to suppressing the development of type 2 diabetes. SCD1 expression levels were analysed in islets obtained from humans with type 2 diabetes, hyperglycaemic db/db mice, and a high-fat diet (HFD)-induced mouse model of diabetes. Pancreatic beta cell-specific Scd1 knockin (βSCD1KI) mice were generated to study the role of SCD1 in beta cell function and identity. The protein-to-protein interactions between SCD1 and MafA were detected in MIN6 and HEK293A cells. We used experiments including chromatin immunoprecipitation, cell-based ubiquitination assay and fatty acid composition analysis to investigate the specific molecular mechanism underlying the effect of SCD1 on the restoration of MafA and beta cell function under glucotoxic conditions. SCD1 expression was reduced in beta cells of humans with type 2 diabetes and in HFD-fed and db/db mice compared with healthy controls, which was attributed to glucotoxicity-induced Scd1 promoter histone deacetylation. Gain-of-function of SCD1 in beta cells improved insulin deficiency, glucose intolerance and beta cell dedifferentiation/transdifferentiation in the HFD-induced mouse model of diabetes. Mechanistically, SCD1 directly bound to the E3 ubiquitin ligase HMG-CoA reductase degradation 1 (HRD1) and stabilised nuclear MafA through interrupting MafA-HRD1 interactions in mouse islets and MIN6 cells, which inhibited the ubiquitination-mediated degradation of MafA. Moreover, the products of SCD enzyme reactions (mainly oleic acid) also alleviated glucotoxicity-mediated oxidative stress in MIN6 cells. Our findings indicate that SCD1 stabilises beta cell MafA both in desaturase-dependent and -independent manners, thus improving glucose homeostasis under metabolic stress. This provides a potential novel target for precision medicine for the treatment of diabetes.

A stearate-rich diet and oleate restriction directly inhibit tumor growth via the unfolded protein response.

Fatty acids are known to have significant effects on the properties of cancer cells. Therefore, these compounds have been incorporated into therapeutic strategies. However, few studies have examined the effects of individual fatty acids and their interactions in depth. This study analyzed the effects of various fatty acids on cancer cells and revealed that stearic acid, an abundant saturated fatty acid, had a stronger inhibitory effect on cell growth than did palmitic acid, which is also an abundant saturated fatty acid, by inducing DNA damage and apoptosis through the unfolded protein response (UPR) pathway. Intriguingly, the negative effects of stearate were reduced by the presence of oleate, a different type of abundant fatty acid. We combined a stearate-rich diet with the inhibition of stearoyl-CoA desaturase-1 to explore the impact of diet on tumor growth. This intervention significantly reduced tumor growth in both ovarian cancer models and patient-derived xenografts (PDXs), including those with chemotherapy resistance, notably by increasing stearate levels while reducing oleate levels within the tumors. Conversely, the negative effects of a stearate-rich diet were mitigated by an oleate-rich diet. This study revealed that dietary stearate can directly inhibit tumor growth through mechanisms involving DNA damage and apoptosis mediated by the UPR pathway. These results suggest that dietary interventions, which increase stearic acid levels while decreasing oleic acid levels, may be promising therapeutic strategies for cancer treatment. These results could lead to the development of new cancer treatment strategies.

Novel biomarker in hepatocellular carcinoma: Stearoyl-CoA desaturase 1

BackgroundIn recent years, more and more studies have shown that reprogramming lipid metabolism plays an important role in the occurrence and development of hepatocellular carcinoma (HCC). However, there is a lack of systematic exploration of fatty acid (FA) profiles in HCC. AimsThis study aims to systematically investigate the FA profile in HCC and assess the diagnostic potential of stearoyl-CoA desaturase 1 (SCD1) as a biomarker for HCC. MethodsThe FA profile in HCC tissues was detected by gas chromatography mass spectrometry. Abnormal FA metabolism was analyzed by qRT-PCR, Western blot. Immunohistochemical and bioinformatics analysis were used to analyze SCD1 expression and function. Receiver operating characteristic curves were used to analyze the diagnostic efficacy of SCD1, and the relationship between SCD1 and immune infiltration in HCC was analyzed by the biological information method. ResultsFAs were found to accumulate in the HCC samples, and abnormal FA metabolism in HCC related to the upregulation of the expression and activity of SCD1. The combination of SCD1 and alpha-fetoprotein produced a greater area under the receiver operating characteristic curve (0.925, P < 0.001) than SCD1 or alpha-fetoprotein alone. It also showed better sensitivity (77.5 %). Besides, high SCD1 expression was found to be related to immune infiltration in HCC. ConclusionSCD1 can serve as a reliable biomarker for HCC diagnosis.

Bisphenol B Exposure Promotes Melanoma Progression via Dysregulation of Lipid Metabolism in C57BL/6J Mice.

The increasing incidence of cancer underscore the necessity of investigating contributors such as endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA). Although BPA's risks are well-documented, comprehensive studies on its substitutes, such as bisphenol B (BPB), are limited. Dysregulated lipid metabolism is a hallmark of cancer progression. Our previous work demonstrated that BPA and bisphenol S (BPS) disrupt lipid metabolism via the peroxisome proliferator-activated receptor γ (PPARγ) pathway. We hence hypothesized that BPB might similarly perturb lipid metabolism and promote tumor growth. BPB's impact on lipid metabolism was investigated invitro and invivo using B16 melanoma cancer cells. Our findings indicate BPB exposure significantly increased lipid metabolism in B16 cells, enhancing cell proliferation and migration, and promoting tumor development in mice. Utilizing siRNA transfection or chemical inhibitor, we found that stearoyl-CoA desaturase-1 (SCD1), a key enzyme in lipid synthesis pathway, was required for BPB-induced lipid accumulation and cancer cell migration. Docking analysis revealed BPB may activate gene expression related to lipid metabolism and angiogenesis by interacting with PPARγ and hypoxia-inducible factor-1α (HIF-1α). This study illuminates BPB's potential role in advancing melanoma through lipid metabolism manipulation, highlighting the need for further research into the safety of BPA substitutes and their impact on cancer development.

Acid-exposed and hypoxic cancer cells do not overlap but are interdependent for unsaturated fatty acid resources

Cancer cells in acidic tumor regions are aggressive and a key therapeutic target, but distinguishing between acid-exposed and hypoxic cells is challenging. Here, we use carbonic anhydrase 9 (CA9) antibodies to mark acidic areas in both hypoxic and respiring tumor areas, along with an HRE-GFP reporter for hypoxia, to isolate distinct cell populations from 3D tumor spheroids. Transcriptomic analysis of CA9-positive, hypoxia-negative cells highlights enriched fatty acid desaturase activity. Inhibiting or silencing stearoyl-CoA desaturase-1 (SCD1) induces ferroptosis in CA9-positive acidic cancer cells and delays mouse tumor growth, an effect enhanced by omega-3 fatty acid supplementation. Using acid-exposed cancer cells and patient-derived tumor organoids, we show that SCD1 inhibition increases acidic cancer cell reliance on external mono-unsaturated fatty acids, depriving hypoxic cells of essential resources. This bystander effect provides unbiased evidence for a lack of full overlap between hypoxic and acidic tumor compartments, highlighting a rationale for targeting desaturase activity in cancer.

The potential role of AhR/NR4A1 in androgen-dependent prostate cancer: Focus on TCDD-induced ferroptosis.

Prostate cancer (PCa) is a complex disease with diverse molecular alterations. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that exhibits pleiotropic roles in PCa, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent ligand for AhR. While targeting ferroptosis is an innovative PCa therapeutic strategy, the impact of AhR on this process remains unclear. This study aimed to investigate the influence of AhR on lipid peroxidation and ferroptosis. Results showed that TCDD activated AhR, as evidenced by increased CYP1A1 expression, leading to reduced cell viability. TCDD caused mitochondria shrinkage, decreased the GSH/GSSG ratio, and elevated the MDA levels and lipid peroxidation. Interestingly, AhR knockdown reversed these effects, similar to the action of ferroptosis inhibitors. Mechanistically, TCDD suppressed nuclear receptor subfamily 4 group A member 1 (NR4A1) expression, in part due to AhR activation. This suppression subsequently led to a reduction in the expression of the NR4A1 downstream target stearoyl-CoA desaturase 1 (SCD1). NR4A1 overexpression counteracted the effects of TCDD. In vivo, TCDD activated AhR, downregulated NR4A1 and SCD1 expression, induced mitochondria shrinkage, and increased the MDA and 4-hydroxynonenal (4-HNE) levels. In summary, TCDD promotes ferroptosis in androgen-dependent PCa via inhibiting the NR4A1/SCD1 axis, in part dependent on AhR activation.

L-theanine enhances the improvements of EGCG on glucose and lipid metabolism disorders in obese rats

Epigallocatechin gallate (EGCG) and L-theanine (LTA) are two key bioactive components of tea that modulate nutrient metabolism. However, whether the combination of EGCG and LTA will result in synergistic benefits for glucose and lipid metabolism disorders is still unclear. Here, we treated leptin receptor-knockout (Lepr-KO) rats with EGCG and EGCG combined with LTA to examine how combined EGCG and LTA affect glucose and lipid metabolism disorders. Our data suggested that EGCG or EGCG plus LTA all significantly reduced serum triglycerides, total cholesterol, random blood glucose, and increased glucose tolerance, as well as alleviated fatty liver formation in Lepr-KO rats. Moreover, compared with EGCG alone, EGCG plus LTA significantly reduced random blood glucose and plasma triacylglycerols (TG) levels, and alleviated hepatic steatosis. Mechanistic analysis revealed that EGCG plus LTA improved glucose metabolism disorders by activating hepatic glucokinase (GCK) and glycogen synthase 2 (GYS2) expression, and inhibited fatty acid synthase (FAS) and stearoyl-CoA desaturase 1 (SCD1) for lowering hepatic TG accumulation. This study demonstrated that LTA enhances the improvements of EGCG on glucose and lipid metabolism disorders in Lepr-KO rats, especially in glycometabolism.

Lipid composition differentiates ferroptosis sensitivity between in vitro and in vivo systems.

Ferroptosis is a regulated non-apoptotic cell death process characterized by iron-dependent lipid peroxidation. This process has recently emerged as a promising approach for cancer therapy. Peroxidation of polyunsaturated fatty acid-containing phospholipids (PUFA-PLs) is necessary for the execution of ferroptosis. Ferroptosis is normally suppressed by glutathione peroxidase 4 (GPX4), which reduces lipid hydroperoxides to lipid alcohols. Some evidence indicates that GPX4 may be a useful target for drug development, yet factors that govern GPX4 inhibitor sensitivity in vivo are poorly understood. We find that pharmacological and genetic loss of GPX4 function was sufficient to induce ferroptosis in multiple adherent ("2D") cancer cell cultures. However, reducing GPX4 protein levels did not affect tumor xenograft growth when these cells were implanted in mice. Furthermore, sensitivity to GPX4 inhibition was markedly reduced when cells were cultured as spheroids ("3D"). Mechanistically, growth in 3D versus 2D conditions reduced the abundance of PUFA-PLs. 3D culture conditions upregulated the monounsaturated fatty acid (MUFA) biosynthetic gene stearoyl-CoA desaturase (SCD). SCD-derived MUFAs appear to protect against ferroptosis in 3D conditions by displacing PUFAs from phospholipids. Various structurally related long chain MUFAs can inhibit ferroptosis through this PUFA-displacement mechanism. These findings suggest that growth-condition-dependent lipidome remodeling is an important mechanism governing GPX4 inhibitor effects. This resistance mechanism may specifically limit GPX4 inhibitor effectiveness in vivo .

Stearoyl-CoA desaturase in CD4+ T cells suppresses tumor growth through activation of the CXCR3/CXCL11 axis in CD8+ T cells

BackgroundWithin the tumor microenvironment, altered lipid metabolism promotes cancer cell malignancy by activating oncogenic cascades; however, impact of lipid metabolism in CD4+ tumor-infiltrating lymphocytes (TILs) remains poorly understood. Here, we elucidated that role of stearoyl-CoA desaturase (SCD) increased by treatment with cancer-associated fibroblast (CAF) supernatant in CD4+ T cells on their subset differentiation and activity of CD8+ T cells.ResultsIn our study, we observed that CD4+ TILs had higher lipid droplet content than CD4+ splenic T cells. In tumor tissue, CAF-derived supernatant provided fatty acids to CD4+ TILs, which increased the expression of SCD and oleic acid (OA) content. Increased SCD expression by OA treatment enhanced the levels of Th1 cell markers TBX21, interleukin-2, and interferon-γ. However, SCD inhibition upregulated the expression of regulatory T (Treg) cell markers, FOXP3 and transforming growth factor-β. Comparative fatty acid analysis of genetically engineered Jurkat cells revealed that OA level was significantly higher in SCD-overexpressing cells. Overexpression of SCD increased expression of Th1 cell markers, while treatment with OA enhanced the transcriptional level of TBX21 in Jurkat cells. In contrast, palmitic acid which is higher in SCD-KO cells than other subclones enhanced the expression of Treg cell markers through upregulation of mitochondrial superoxide. Furthermore, SCD increased the secretion of the C–X–C motif chemokine ligand 11 (CXCL11) from CD4+ T cells. The binding of CXCL11 to CXCR3 on CD8+ T cells augmented their cytotoxic activity. In a mouse tumor model, the suppressive effect of CD8+ T cells on tumor growth was dependent on CXCR3 expression.ConclusionThese findings illustrate that SCD not only orchestrates the differentiation of T helper cells, but also promotes the antitumor activity of CD8+ T cells, suggesting its function in adverse tumor microenvironments.Graphical abstract

Aramchol attenuates fibrosis in mouse models of biliary fibrosis and blocks the TGFβ-induced fibroinflammatory mediators in cholangiocytes.

Fibroinflammatory cholangiopathies, such as primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC), are characterized by inflammation and biliary fibrosis, driving disease-related complications. In biliary fibrosis, cholangiocytes activated by transforming growth factor-β (TGFβ) release signals that recruit immune cells to drive inflammation and activate hepatic myofibroblasts to deposit the extracellular matrix (ECM). TGFβ regulates stearoyl-CoA desaturase (SCD), an enzyme that catalyzes the synthesis of monounsaturated fatty acids, in stimulating fibroinflammatory lipid signaling. However, the role of SCD or its inhibitor, Aramchol, has not been investigated in biliary fibrosis or TGFβ-mediated cholangiocyte activation. 10-16-week-old multi-drug resistance 2 knockout (Mdr2 -/- ) and 3,5-diethoxycarboncyl-1,4-dihydrocollidine (DDC) diet-fed mice were orally gavaged daily with Aramchol at 12.5 mg/kg/day for 4 and 3 weeks, respectively. Liver and serum were harvested for the assessment of fibrosis and inflammation. Transformed human cholangiocyte cells (H69) and mouse large biliary epithelial cells (MLEs) were used to test the effects of the SCD inhibitor, Aramchol, at varying doses on TGFβ-mediated expression of fibroinflammatory signals and were confirmed in PSC-derived cholangiocytes (PSC-Cs) using ELISA, qPCR, and Western blot analyses. Aramchol treatment of Mdr2 -/- mice with established biliary fibrosis (treatment) and DDC diet-induced (prevention) models of cholestatic injury and fibrosis demonstrated significant reductions in both measures of ECM synthesis (mRNA expression of ECM components in the liver), collagen content of the liver (picrosirius red staining and hydroxyproline content) and myofibroblast activation (αSMA staining). Il6 and Tnfa were also reduced with Aramchol in the liver. RNA-seq analysis of H69 cells showed that Aramchol co-treatment led to significant inhibition of TGFβ-induced hepatic fibrosis pathways while upregulating peroxisome proliferator-activated receptor (PPAR) signaling. SCD expression was significantly increased in TGFβ-treated H69 cells (2-fold, p<0.05). Aramchol in a dose-dependent manner significantly attenuated the increased expression of the fibrotic marker, plasminogen activator inhibitor-1 (PAI-1/SERPINE1), and hepatic stellate cell-activating genes ( VEGFA and PDGFB ) in TGFβ-activated H69 and MLEs. Aramchol also markedly reduced the expression of the inflammatory cytokine, interleukin 6 (IL6). SCD siRNA knockdown produced similar results in H69 cells. Furthermore, in PSC-Cs, the expressions of SCD, VEGFA and IL6 were significantly reduced with Aramchol. The expression of the anti-fibroinflammatory factors PPARα and -γ were modestly increased in cholangiocyte cell lines with increased expression of PPAR-responsive genes and increased nuclear binding of DNA PPAR response elements with Aramchol co-treatment compared to TGFβ only. Aramchol, an SCD inhibitor, both attenuates and prevents biliary fibrosis in mouse models of cholestatic injury and fibrosis. This effect is partially due to Aramchol inhibiting TGFβ-induced fibroinflammatory mediators in cholangiocytes by upregulating PPARα and -γ expression and activity. These findings, along with Aramchol's excellent safety profile in clinical trials, provide the rationale for assessing Aramchol in further clinical studies in patients with biliary fibrosis, particularly PSC, where a treatment is desperately needed.

Cicer arietinum phytosome ameliorates hepatosteatosis via downregulation of fatty acid synthase and stearoyl-CoA desaturase 1 in rats

BackgroundHepatosteatosis is considered a universal problematic health due to bad lifestyle. Thereby, the current study evaluates the influence of the Cicer arietinum polyunsaturated fatty acids (CAP) and newly synthesized C. arietinum polyunsaturated fatty acids phytosome (CAPP) against non-alcoholic fatty liver disease (NAFLD) persuaded through a high-fat diet (HFD) in addition to tamoxifen (TAM) in male albino rats. Forty-eight rats were separated into eight groups (6 rats/group). Rats of the control group were administered distilled water for 45 consecutive days, while phosphatidyl choline (PC), CAP, and CAPP groups administered distilled water (15 days), afterward administered PC, CAP, and CAPP, respectively (500 mg/kg b.wt), orally for 30 days. All the previous groups fed normal diet for the 45 days, while NAFLD rats feed HFD for 45 days and receive TAM (200 mg/kg b.wt, i.p) daily for 15 days, followed by administration of vehicle, PC, CAP, and CAPP orally for another 30 days.ResultsHepatosteatosis was appraised biochemically by significant increase in the concentrations of serum AST, ALT, γGT, LDH, ALP, total bilirubin, total lipid, triglycerides, fatty acid synthase (FAS), stearoyl-CoA desaturase 1 (SCD-1), and LDL-cholesterol, as well as hepatic total lipids and triglycerides. In addition, a significant decline in serum total protein, albumin, and HDL-cholesterol concentrations was observed in comparison with the control group. NAFLD induces oxidative stress by noteworthy increase in hepatic MDA, H2O2, and meaningful reduction in hepatic GSH, SOD, GST, GRD, and CAT levels as compared with the corresponding control group. Liver histological changes were noted in the NAFLD group as compared to the control. Interestingly, CAP and CAPP treatments modulate the abnormal effects of NAFLD in all the previous parameters. For the histological changes caused by NAFLD, the liver tissue appeared nearly normal after the treatment with CAP and CAPP.ConclusionCAP and CAPP administration may have a potential role in alleviating hepatosteatosis. This may relate to its downregulation against FAS, SCD-1, and oxidative stress.

STEM-08. LIPID SATURATION HOMEOSTASIS PRESENTS A TARGETABLE VULNERABILITY IN MYC-AMPLIFIED GROUP 3 MEDULLOBLASTOMA

Abstract Medulloblastoma (MB) is the most common malignant pediatric brain cancer, originating from the cerebellum. Despite advancements in standard of care (SoC), MB remains fatal for 30% of patients. Tumor relapse, spinal metastasis and treatment resistance are the most prevalent in MYC-driven Group 3 MB (G3-MB). Patients surviving SoC are faced with life-long neurocognitive and neurodevelopmental deficits. These issues highlight the urgent need for improved treatment modalities. Reprogramming of cellular lipid metabolism is an emerging hallmark of cancer and may yield novel cancer-specific therapeutic options. Here we explore the lipidome of both G3-MB and its proposed cell of origin, human neural stem cells (hNSCs) by comparing untargeted lipidomics using Liquid-Chromatography-Mass Spectrometry (LC-MS). Comparative analyses revealed a differential abundance of distinct lipid species in G3-MB, with an overall reduced saturation level of fatty acids (FAs). These findings implicate the de novo lipid synthesis (DNL) pathway. We identified the enzymes involved in DNL to be essential for MB survival in our genome-wide CRISPR KO screen. Additionally, mRNA expression of the DNL enzymes increases at relapse in our SoC-adapted murine patient-derived xenograft (PDX) model. Pharmacological and genetic targeting of the DNL enzyme Stearoyl-CoA Desaturase 1 (SCD1) selectively targets G3-MB. Furthermore, small molecule treatment of SCD1 demonstrates efficacy against G3-MB PDX models in vivo. We identified SCD expression as a prognostic marker in Group 3 and 4 MB patients and identified possible pathways for MB treatment. Overall, these findings indicate that SCD1 is a potent target for the treatment of G3-MB.

DNAR-12. STEAROYL-COA DESATURASE REGULATES DNA DAMAGE REPAIR IN GBM BY MODULATING PARP1 ACTIVITY

Abstract Glioblastoma (GBM) is the most prevalent malignant brain cancer in adults, notorious for its aggressiveness and resistance to therapy. GBM patients commonly receive radiation therapy combined with temozolomide (TMZ), which engages tumor cells to promote lethal DNA damage and subsequent cytotoxicity. Active DNA repair mechanisms, particularly in a subset population of GBM stem-like cells (GSCs), drive therapeutic resistance, thus largely contributing to the bleak prognosis of GBM. Poly (ADP-ribose) polymerases (PARPs) are essential in various cellular processes, including DNA repair. We have previously reported that fatty acid desaturation mediated by Stearoyl-CoA desaturase 1 (SCD1) plays a cytoprotective role in GSCs. Inhibiting SCD prevents tumor initiation and inhibits DNA damage repair, hence sensitizing to radiation and TMZ. Yet, the mechanistic role of SCD in DNA damage regulation remained unknown. Here, we found that the expression of both human isoforms of SCD, SCD1, and SCD5, directly correlates with PARP protein levels and subcellular localization. Downregulating SCD1/5 in GSCs resulted in significantly lower levels of PARP1, coupled with increased DNA damage, as well as reduced DNA damage repair and chromosome assembly. Conversely, cells overexpressing SCD1/5 exhibited higher PARP1 expression and lower levels of basal DNA damage compared to control GSCs. Notably, SCD1/5 overexpression also led to increased resistance to TMZ. We show that SCD1/5 regulates PARP activity by controlling PARP1 subcellular localization. In addition to decreased total levels of PARP following SCD1/5 downregulation, we also found increased PARP1 self-PARylation. Using confocal microscopy, we show that when SCD1/5 is repressed, PARylated PARP translocates from the nucleus to the cytosol, rendering it unable to bind DNA and recruit DNA-repairing machinery. In conclusion, our study provides a direct link between fatty acid metabolism and PARP1-mediated DNA damage repair.

TMET-03. ONCOGENIC STAT3 PROMOTES TUMOR GROWTH VIA STIMULATION THE SCAP- AND SREBP-1-REGULATED LIPOGENIC PATHWAY

Abstract Augmented lipogenesis is a hallmark of cancer. In addition, signal transducer and activator of transcription 3 (STAT3) is aberrantly activated and associated with poor prognosis in multiple cancers. Whether oncogenic STAT3 has an intrinsic and causal link to lipogenesis in cancer remains unclear. Here, we show that inhibition of STAT3 significantly alters the lipid profile of tumor cells, including free fatty acids and derived membrane structural phospholipids (phosphatidic acid, phosphatidylinositol, phosphatidylserine and sphingomyelin), this change results in cell death which could be rescued by lipids (oleic acid and palmitoleic acid) supplementation, while suppressing the gene and protein expression of major mediators of the lipogenic pathway including sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), SREBP-1, fatty acid synthase and stearoyl-CoA desaturase 1. Furthermore, we show that STAT3 binds the promoter of SCAP, SREBP-1a and SREBP-1c, to promote their transcription in tumor cells. Finally, targeting STAT3 in a xenograft mouse model blocked glioblastoma growth and lipogenic enzyme expression. Our study reveals a novel regulatory pathway of STAT3-SCAP/SREBP-1 involved in tumor growth in vitro and in vivo, connecting STAT3 signaling with SCAP- and SREBP-1-mediated lipogenesis.

Estimated stearoyl-CoA desaturase activity mediates the associations of total cysteine with adiposity: The Maastricht Study

BackgroundPlasma sulfur amino acids (SAAs), particularly cysteine, are associated with obesity. One proposed mechanism is the altered regulation of the stearoyl-CoA desaturase (SCD) enzyme. Changes in the SCD enzyme activity have been linked to obesity, as well as to plasma SAA concentrations. ObjectiveThis study aimed to investigate whether estimated SCD activity mediates the associations between plasma SAAs and measures of overall adiposity and specific fat depots. MethodsWe examined cross-sectional data from a subset of the Maastricht Study (n=1129, 50.7% men, 56.7% with (pre)diabetes). Concentrations of methionine, total homocysteine, cystathionine, total cysteine (tCys), total glutathione (tGSH) and taurine were measured in fasting plasma. Outcomes included measures of overall, peripheral and central adiposity, and liver fat. SCD activity was estimated by ratios of serum fatty acids as SCD16 and SCD18 indices. The associations between plasma SAAs and measures of adiposity or liver fat were examined with multiple linear regression analysis. Multiple mediation analysis was used to investigate whether the significant associations were mediated by SCD16 and SCD18 indices. ResultsPlasma tCys was positively associated with all adiposity measures (β ranged from 0.15 to 0.30). SCD16 significantly mediated all associations (proportion mediated ranged from 5.1% to 9.7%). Inconsistent mediation effects were found for SCD18. Despite a significant inverse association of plasma tGSH with all adiposity measures (β ranged from -0.08 to -0.16), no significant mediation effect was found. ConclusionsPlasma tCys may promote excessive body fat accumulation via upregulation of SCD activity.

ARMC5 selectively degrades SCAP-free SREBF1 and is essential for fatty acid desaturation in adipocytes

SREBF1 plays the central role in lipid metabolism. It has been known that full-length SREBF1 that did not associate with SCAP (SCAP-free SREBF1) is actively degraded, but its molecular mechanism and its biological meaning remain unclear. ARMC5-CUL3 complex was recently identified as E3 ubiquitin ligase of full-length SREBF. Although ARMC5 was involved in SREBF pathway in adrenocortical cells, the role of ARMC5 in adipocytes has not been investigated. In this study, adipocyte-specific Armc5 knockout mice were generated. In the white adipose tissue (WAT) of these mice, all the stearoyl-CoA desaturase (Scd) were drastically downregulated. Consistently, unsaturated fatty acids were decreased and saturated fatty acids were increased. The protein amount of full-length SREBF1 were increased, but ATAC-Seq peaks at the SREBF1-binding sites were markedly diminished around the Scd1 locus in the WAT of Armc5 knockout mice. Armc5-deficient 3T3-L1 adipocytes also exhibited downregulation of Scd. Mechanistically, disruption of Armc5 restored decreased full-length SREBF1 in CHO cells deficient for Scap. Overexpression of Scap inhibited ARMC5-mediated degradation of full-length SREBF1, and overexpression of Armc5 increased nuclear SREBF1/full-length SREBF1 ratio and SREBF1 transcriptional activity in the presence of exogenous SCAP. These results demonstrated that ARMC5 selectively removes SCAP-free SREBF1 and stimulates SCAP-mediated SREBF1 processing, hence is essential for fatty acid desaturation in vivo.

Stearoyl CoA desaturase inhibition can effectively induce apoptosis in bladder cancer stem cells

Bladder cancer stands as one of the most prevalent cancers worldwide. While our previous research confirmed the significant role of stearoyl-CoA desaturase (SCD) in bladder cancer, the underlying reasons for its abnormal overexpression remain largely unknown. Moreover, the distinct response to SCD inhibitors between cancer stem cells (CSCs) and adherent cultured cell lines lacks clear elucidation. Therefore, in this experiment, we aim to conduct an analysis and screening of the SCD transcription start site, further seeking critical transcription factors involved. Simultaneously, through experimental validation, we aim to explore the pivotal role of endoplasmic reticulum stress/unfolded protein response in drug sensitivity among cancer stem cells. Additionally, our RNA-seq and lipid metabolism analysis revealed the significant impact of nervonic acid on altering the proliferative capacity of bladder cancer cell lines.

Therapeutic Potential of Stearoyl-CoA Desaturase1 (SCD1) in Modulating the Effects of Fatty Acids on Osteoporosis.

Osteoporosis is a common skeletal disease, primarily associated with aging, that results from decreased bone density and bone volume. This reduction significantly increases the risk of fractures in osteoporosis patients compared to individuals with normal bone density. Additionally, the bone regeneration process in these patients is slow, making complete healing difficult. Along with the decline in bone volume and density, osteoporosis is characterized by an increase in marrow adipose tissue (MAT), which is fat within the bone. In this altered bone microenvironment, osteoblasts are influenced by various factors secreted by adipocytes. Notably, saturated fatty acids promote osteoclast activity, inhibit osteoblast differentiation, and induce apoptosis, further reducing osteoblast formation. In contrast, monounsaturated fatty acids inhibit osteoclast formation and mitigate the apoptosis caused by saturated fatty acids. Leveraging these properties, we aimed to investigate the effects of overexpressing stearoyl-CoA desaturase 1 (SCD1), an enzyme that converts saturated fatty acids into monounsaturated fatty acids, on osteogenic differentiation and bone regeneration in both in vivo and in vitro models. Through this novel approach, we seek to develop a stem cell-based therapeutic strategy that harnesses SCD1 to improve bone regeneration in the adipocyte-rich osteoporotic environment.

Intermittent cold stimulation acclimates broilers to acute cold stress by affecting cardiac lipid metabolism.

This study aimed to investigate whether intermittent cold stimulation can induce adaptation in broilers to acute cold stress (ACS) by regulating the lipid metabolism of hearts. CS0 were kept at normal rearing temperature, while CS3 and CS5 were exposed to 3°C for 3 and 5 hours, respectively, on alternate days lower than CS0 from 15d to 35d. On 50d, broilers in three groups were exposed to ACS at 10°C for 12 hours (Y12). The levels of corticosterone (CORT) and liothyronine (T3), mRNA and protein levels of heart AMP-activated protein kinase/mammalian target of rapamycin (AMPK/mTOR) pathway genes were assessed at 36d, 50d and Y12. At 36d, mRNA levels of AMPKα, acyl-CoA oxidase (ACO), mTOR, sterol-regulatory element binding protein (SREBP), stearoyl-coA desaturase (SCD), acetyl-coA carboxylase (ACC), fatty acid synthase (FAS) and protein level of peroxisome proliferators-activated receptor α (PPARα) in CS3 and CS5 were significantly lower than those in CS0 (p<0.05). At 50d, compared to CS0, mRNA levels of PPARα, carnitine palmitoyltransferase1 (CPT1), ACO, tuberous sclerosis complex (TSC), SREBP and SCD, as well as protein levels of p-AMPKα/AMPKα, PPARα and SREBP were significantly increased in CS5 (p<0.05). At Y12, the levels of T3 in CS3 and CS5 were significantly higher than those in CS0 (p<0.05), mRNA levels of CPT1, ACO, SREBP, SCD and protein levels of p-AMPKα/AMPKα, SREBP, and FAS were significantly higher in CS5 than in CS0 and CS3 (p<0.05). However, compared to 50d, at Y12, mRNA levels of AMPKα, CPT1 and ACO in CS3 and CS5 significantly decreased (p<0.05), while protein levels of p-AMPKα/AMPKα significantly increased (p<0.05). This study suggested that intermittent cold stimulation at 3°C lower than normal rearing temperature for 5h could help broilers adapt to the ACS by promoting heart lipid metabolism.

Exploration of potential mechanism of Sanhua Jiangzhi granules for the treatment of hyperlipidemia based on network pharmacology and experimental verification

Sanhua Jiangzhi Granules (SJG) is a traditional Chinese patent medicine known for regulating lipid metabolism. In this study, we utilized UPLC-TOF-MS to analyze the components of SJG and, in conjunction with network pharmacology, identified 125 core chemical constituents. These components were individually queried and intersected with targets related to hyperlipidemia, resulting in the identification of 312 core targets. KEGG and GO analyses suggested that the mechanism of SJG in treating hyperlipidemia may primarily involve the PPAR signaling pathway. To further validate the efficacy and underlying signaling mechanisms of SJG, we conducted experiments using 60 rats. The results indicated that SJG significantly reduced body weight, lowered serum levels of total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C), while increasing high-density lipoprotein cholesterol (HDLC) levels. Enzyme-linked immunosorbent assay (ELISA) results demonstrated that SJG decreased hepatic TC and TG levels and mitigated lipid accumulation in the liver. Hematoxylin and eosin (HE) staining indicated that SJG improved liver pathological morphology and reduced the risk of fatty liver disease. Western blot analyses showed that treatment with SJG down-regulated the expression of stearoyl-CoA desaturase (SCD), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), phospholipid transfer protein (PLTP), and fatty acid-binding protein 1 (FABP1), while up-regulating the expression of cholesterol 7α-hydroxylase (CYP7A1), carnitine palmitoyltransferase 1 (CPT-1), and PPARα by activating the PPAR signaling pathway. In conclusion, this study demonstrated that SJG activates the PPAR signaling pathway, leading to decreased body weight, lowered blood lipid levels, reduced hepatic TC and TG, and improved liver pathology in rats.