An allosteric mechanism for potent inhibition of human ATP-citrate lyase.

ATP-citrate lyase (ACLY) is a central metabolic enzyme and catalyses the ATP-dependent conversion of citrate and coenzyme A (CoA) to oxaloacetate and acetyl-CoA1-5. The acetyl-CoA product is crucial for the metabolism of fatty acids6,7, the biosynthesis of cholesterol8, and the acetylation and prenylation of proteins9,10. There has been considerable interest in ACLY as a target for anti-cancer drugs, because many cancer cells depend on its activity for proliferation2,5,11. ACLY is also a target against dyslipidaemia and hepatic steatosis, with a compound currently in phase 3 clinical trials4,5. Many inhibitors of ACLY have been reported, but most of them have weak activity5. Here we report the development of a series of low nanomolar, small-molecule inhibitors of human ACLY. We have also determined the structure of the full-length human ACLY homo-tetramer in complex with one of these inhibitors (NDI-091143) by cryo-electron microscopy, which reveals an unexpected mechanism of inhibition. The compound is located in an allosteric, mostly hydrophobic cavity next to the citrate-binding site, and requires extensive conformational changes in the enzyme that indirectly disrupt citrate binding. The observed binding mode is supported by and explains the structure-activity relationships of these compounds. This allosteric site greatly enhances the 'druggability' of ACLY and represents an attractive target for the development of new ACLY inhibitors.

Development and Validation of a Liquid Chromatography-Tandem Mass Spectrometry Method for Screening Potential Citrate Lyase Inhibitors from a Library of Marine Compounds.

Tuberculosis, a persistent illness caused by Mycobacterium tuberculosis, remains a significant global public health challenge. The widespread use of anti-tuberculosis drugs has resulted in the emergence of drug-resistant strains, which complicates treatment efforts. Addressing this issue is crucial and hinges on the development of new drugs that can effectively target the disease. This involves identifying novel therapeutic targets that can disrupt the bacterium's survival mechanisms in various environments such as granulomas and lesions. Citrate lyase, essential for the survival of Mycobacterium species at lesion sites and in granulomatous conditions, is a potential target for the treatment of tuberculosis. This manuscript aimed to construct an efficient enzyme inhibitor screening platform using ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF MS). This system can accurately identify compounds with enzyme inhibitory activity from a library of marine terpenoids and phenolic compounds. Utilizing the screened herbal enzyme inhibitors as a starting point, we analyzed their chemical structures and skillfully built a library of marine compounds based on these structures. The results showed that all of the tested compounds from the phenolics library inhibited citrate lyase by more than 50%, and a significant portion of terpenoids also demonstrated inhibition, with these active terpenoids comprising over half of the terpenoids tested. The study underscores the potential of marine-derived phenolic and terpenoid compounds as potent inhibitors of citrate lyase, indicating a promising direction for future investigations in treating tuberculosis and associated disorders.

Safety and Efficacy of Bempedoic Acid to Reduce LDL Cholesterol.

BACKGROUND: Short-term studies have shown that bempedoic acid, an inhibitor of ATP citrate lyase, reduces levels of low-density lipoprotein (LDL) cholesterol. Data are limited regarding the safety and efficacy of bempedoic acid treatment in long-term studies involving patients with hypercholesterolemia who are receiving guideline-recommended statin therapy. METHODS: We conducted a randomized, controlled trial involving patients with atherosclerotic cardiovascular disease, heterozygous familial hypercholesterolemia, or both. Patients had to have an LDL cholesterol level of at least 70 mg per deciliter while they were receiving maximally tolerated statin therapy with or without additional lipid-lowering therapy. (Maximally tolerated statin therapy was defined as the highest intensity statin regimen that a patient was able to maintain, as determined by the investigator.) Patients were randomly assigned in a 2:1 ratio to receive bempedoic acid or placebo. The primary end point was safety, and the principal secondary end point (principal efficacy end point) was the percentage change in the LDL cholesterol level at week 12 of 52 weeks. RESULTS: The trial involved 2230 patients, of whom 1488 were assigned to receive bempedoic acid and 742 to receive placebo. The mean (±SD) LDL cholesterol level at baseline was 103.2±29.4 mg per deciliter. The incidence of adverse events (1167 of 1487 patients [78.5%] in the bempedoic acid group and 584 of 742 [78.7%] in the placebo group) and serious adverse events (216 patients [14.5%] and 104 [14.0%], respectively) did not differ substantially between the two groups during the intervention period, but the incidence of adverse events leading to discontinuation of the regimen was higher in the bempedoic acid group than in the placebo group (162 patients [10.9%] vs. 53 [7.1%]), as was the incidence of gout (18 patients [1.2%] vs. 2 [0.3%]). At week 12, bempedoic acid reduced the mean LDL cholesterol level by 19.2 mg per deciliter, representing a change of -16.5% from baseline (difference vs. placebo in change from baseline, -18.1 percentage points; 95% confidence interval, -20.0 to -16.1; P<0.001). Safety and efficacy findings were consistent, regardless of the intensity of background statin therapy. CONCLUSIONS: In this 52-week trial, bempedoic acid added to maximally tolerated statin therapy did not lead to a higher incidence of overall adverse events than placebo and led to significantly lower LDL cholesterol levels. (Funded by Esperion Therapeutics; CLEAR Harmony ClinicalTrials.gov number, NCT02666664.).

Mendelian Randomization Study of ACLY and Cardiovascular Disease.

BACKGROUND: ATP citrate lyase is an enzyme in the cholesterol-biosynthesis pathway upstream of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), the target of statins. Whether the genetic inhibition of ATP citrate lyase is associated with deleterious outcomes and whether it has the same effect, per unit decrease in the low-density lipoprotein (LDL) cholesterol level, as the genetic inhibition of HMGCR is unclear. METHODS: We constructed genetic scores composed of independently inherited variants in the genes encoding ATP citrate lyase (ACLY) and HMGCR to create instruments that mimic the effect of ATP citrate lyase inhibitors and HMGCR inhibitors (statins), respectively. We then compared the associations of these genetic scores with plasma lipid levels, lipoprotein levels, and the risk of cardiovascular events and cancer. RESULTS: A total of 654,783 participants, including 105,429 participants who had major cardiovascular events, were included in the study. The ACLY and HMGCR scores were associated with similar patterns of changes in plasma lipid and lipoprotein levels and with similar effects on the risk of cardiovascular events per decrease of 10 mg per deciliter in the LDL cholesterol level: odds ratio for cardiovascular events, 0.823 (95% confidence interval [CI], 0.78 to 0.87; P = 4.0×10-14) for the ACLY score and 0.836 (95% CI, 0.81 to 0.87; P = 3.9×10-19) for the HMGCR score. Neither lifelong genetic inhibition of ATP citrate lyase nor lifelong genetic inhibition of HMGCR was associated with an increased risk of cancer. CONCLUSIONS: Genetic variants that mimic the effect of ATP citrate lyase inhibitors and statins appeared to lower plasma LDL cholesterol levels by the same mechanism of action and were associated with similar effects on the risk of cardiovascular disease per unit decrease in the LDL cholesterol level. (Funded by Esperion Therapeutics and others.).

The IKKß-USP30-ACLY Axis Controls Lipogenesis and Tumorigenesis.

BACKGROUND AND AIMS: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death that develops as a consequence of obesity, cirrhosis, and chronic hepatitis. However, the pathways along which these changes occur remain incompletely understood. APPROACH AND RESULTS: In this study, we show that the deubiquitinase USP30 is abundant in HCCs that arise in mice maintained on high-fat diets. IKKß phosphorylated and stabilized USP30, which promoted USP30 to deubiquitinate ATP citrate lyase (ACLY) and fatty acid synthase (FASN). IKKß also directly phosphorylated ACLY and facilitated the interaction between USP30 and ACLY and the latter's deubiquitination. In HCCs arising in DEN/CCl4 -treated mice, USP30 deletion attenuated lipogenesis, inflammation, and tumorigenesis regardless of diet. The combination of ACLY inhibitor and programmed death ligand 1 antibody largely suppressed chemical-induced hepatocarcinogenesis. The IKKß-USP30-ACLY axis was also found to be up-regulated in human HCCs. CONCLUSIONS: This study identifies an IKKß-USP30-ACLY axis that plays an essential and wide-spread role in tumor metabolism and may be a potential therapeutic target in HCC.

ATP citrate lyase inhibitor triggers endoplasmic reticulum stress to induce hepatocellular carcinoma cell apoptosis via p-eIF2α/ATF4/CHOP axis.

ATP citrate lyase (ACLY), a key enzyme in the metabolic reprogramming of many cancers, is widely expressed in various mammalian tissues. This study aimed to evaluate the effects and mechanisms of ACLY and its inhibitor BMS-303141 on hepatocellular carcinoma (HCC). In this study, ACLY was highly expressed in HCC tissues, especially in HepG2 and Huh7 cells, but was down-regulated in Hep3B and HCC-LM3 cells. Besides, ACLY knockdown inhibited HepG2 proliferation and clone formation, while opposite result was noticed in HCC-LM3 cells with ACLY overexpression. Moreover, ACLY knockdown impeded the migration and invasion abilities of HepG2 cells. Similarly, BMS-303141 suppressed HepG2 and Huh-7 cell proliferation. The p-eIF2α, ATF4, CHOP p-IRE1α, sXBP1 and p-PERK were activated in HepG2 cells stimulated by BMS-303141. In cells where ER stress was induced, ATF4 was involved in BMS-303141-mediated cell death procession, and ATF4 knockdown reduced HCC cell apoptosis stimulated by BMS-303141. In a mouse xenograft model, combined treatment with BMS-303141 and sorafenib reduced HepG2 tumour volume and weight. In addition, ACLY expression was associated with HCC metastasis and tumour-node-metastases staging. Survival analysis and Cox proportional hazards regression model showed that overall survival was lower in HCC patients with high ACLY expression; AFP level, TNM staging, tumour size and ACLY expression level were independent risk factors affecting their overall survival. In conclusion, ACLY might represent a promising target in which BMS-303141 could induce ER stress and activate p-eIF2α/ATF4/CHOP axis to promote apoptosis of HCC cells, and synergized with sorafenib to enhance the efficacy of HCC treatment.

Pharmacological induction of mesenchymal-epithelial transition via inhibition of H2S biosynthesis and consequent suppression of ACLY activity in colon cancer cells.

Hydrogen sulfide (H2S) is an important endogenous gaseous transmitter mediator, which regulates a variety of cellular functions in autocrine and paracrine manner. The enzymes responsible for the biological generation of H2S include cystathionine-ß-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). Increased expression of these enzymes and overproduction of H2S has been implicated in essential processes of various cancer cells, including the stimulation of metabolism, maintenance of cell proliferation and cytoprotection. Cancer cell identity is characterized by so-called "transition states". The progression from normal (epithelial) to transformed (mesenchymal) state is termed epithelial-to-mesenchymal transition (EMT) whereby epithelial cells lose their cell-to-cell adhesion capacity and gain mesenchymal characteristics. The transition process can also proceed in the opposite direction, and this process is termed mesenchymal-to-epithelial transition (MET). The current project was designed to determine whether inhibition of endogenous H2S production in colon cancer cells affects the EMT/MET balance in vitro. Inhibition of H2S biosynthesis in HCT116 human colon cancer cells was achieved either with aminooxyacetic acid (AOAA) or 2-[(4-hydroxy-6-methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one (HMPSNE). These inhibitors induced an upregulation of E-cadherin and Zonula occludens-1 (ZO-1) expression and downregulation of fibronectin expression, demonstrating that H2S biosynthesis inhibitors can produce a pharmacological induction of MET in colon cancer cells. These actions were functionally reflected in an inhibition of cell migration, as demonstrated in an in vitro "scratch wound" assay. The mechanisms involved in the action of endogenously produced H2S in cancer cells in promoting (or maintaining) EMT (or tonically inhibiting MET) relate, at least in part, in the induction of ATP citrate lyase (ACLY) protein expression, which occurs via upregulation of ACLY mRNA (via activation of the ACLY promoter). ACLY in turn, regulates the Wnt-ß-catenin pathway, an essential regulator of the EMT/MET balance. Taken together, pharmacological inhibition of endogenous H2S biosynthesis in cancer cells induces MET. We hypothesize that this may contribute to anti-cancer / anti-metastatic effects of H2S biosynthesis inhibitors.

Synthesis of new methoxy derivatives of trans 2,3-diaryl-2,3-dihydrobenzofurans and evaluation of their anti-inflammatory activity.

In the present study we synthesized new methoxy derivatives of trans 2,3-diaryl-2,3-dihydrobenzofurans, starting from suitable trans 2,3-diaryloxiranes, using regio- and stereoselective nucleophilic oxiranyl ring-opening reactions. The compounds were tested as anti-inflammatories in U937 cells. All compounds showed a significant role in inhibiting the NF-κB pathway and were able to restore normal ROS and NO level upon LPS activation. Moreover, regarding inhibition of ACLY, enantioenriched (50% ee) 7a50 showed more potency than the racemic counterpart 7arac, together with a higher reduction of prostaglandin E2 production, thus suggesting a stereoselective interaction in this pathway.

Two New Oleanane-Triterpenoid Saponins from Clinopodium gracile.

Two new oleanane-triterpenoid saponins, clinograsaponins A (1) and B (2), together with twelve known ones (3-14), were isolated from the whole herb of Clinopodium gracile (Bentham) Matsumura. Their structures were determined by spectroscopic analysis and chemical method. All the isolated compounds were evaluated for their activities against ATP-citrate lyase (ACLY) and nuclear factor kappa B (NF-κB).

Scale-Up Preparation of Crocins I and II from Gardeniajasminoides by a Two-Step Chromatographic Approach and Their Inhibitory Activity Against ATP Citrate Lyase.

Crocins are highly valuable natural compounds for treating human disorders, and they are also high-end spices and colorants in the food industry. Due to the limitation of obtaining this type of highly polar compound, the commercial prices of crocins I and II are expensive. In this study, macroporous resin column chromatography combined with high-speed counter-current chromatography (HSCCC) was used to purify crocins I and II from natural sources. With only two chromatographic steps, both compounds were simultaneously isolated from the dry fruit of Gardenia jasminoides, which is a cheap herbal medicine distributed in a number of countries. In an effort to shorten the isolation time and reduce solvent usage, forward and reverse rotations were successively utilized in the HSCCC isolation procedure. Crocins I and II were simultaneously obtained from a herbal resource with high recoveries of 0.5% and 0.1%, respectively, and high purities of 98.7% and 99.1%, respectively, by HPLC analysis. The optimized preparation method was proven to be highly efficient, convenient, and cost-effective. Crocins I and II exhibited inhibitory activity against ATP citrate lyase, and their IC50 values were determined to be 36.3 ± 6.24 and 29.7 ± 7.41 µM, respectively.

Forrestiacids†A and†B, Pentaterpene Inhibitors of ACL and Lipogenesis: Extending the Limits of Computational NMR Methods in the Structure Assignment of Complex Natural Products.

Forrestiacids A (1) and B (2) are a novel class of [4+2] type pentaterpenoids derived from a rearranged lanostane moiety (dienophile) and an abietane unit (diene). These unprecedented molecules were isolated using guidance by molecular ion networking (MoIN) from Pseudotsuga forrestii, an endangered member of the Asian Douglas Fir Family. The intermolecular hetero-Diels-Alder adducts feature an unusual bicyclo[2.2.2]octene ring system. Their structures were elucidated by spectroscopic analysis, GIAO NMR calculations and DP4+ probability analyses, electronic circular dichroism calculations, and X-ray diffraction analysis. This unique addition to the pentaterpene family represents the largest and the most complex molecule successfully assigned using computational approaches to predict accurately chemical shift values. Compounds 1 and 2 exhibited potent inhibitory activities (IC50 s <5 µM) of ATP-citrate lyase (ACL), a new drug target for the treatment of glycolipid metabolic disorders including hyperlipidemia. Validating this activity 1 effectively attenuated the de novo lipogenesis in HepG2 cells. These findings provide a new chemical class for developing potential therapeutic agents for ACL-related diseases with strong links to traditional medicines.

High-Throughput Single-Cell Mass Spectrometry Reveals Abnormal Lipid Metabolism in Pancreatic Ductal Adenocarcinoma.

Even populations of clonal cells are heterogeneous, which requires high-throughput analysis methods with single-cell sensitivity. Here, we propose a rapid, label-free single-cell analytical method based on active capillary dielectric barrier discharge ionization mass spectrometry, which can analyze multiple metabolites in single cells at a rate of 38 cells/minute. Multiple cell types (HEK-293T, PANC-1, CFPAC-1, H6c7, HeLa and iBAs) were discriminated successfully. We found evidence for abnormal lipid metabolism in pancreatic cancer cells. We also analyzed gene expression in a cancer genome atlas dataset and found that the mRNA level of a critical enzyme of lipid synthesis (ATP citrate lyase, ACLY) was upregulated in human pancreatic ductal adenocarcinoma (PDAC). Moreover, both an ACLY chemical inhibitor and a siRNA approach targeting ACLY could suppress the viability of PDAC cells. A significant reduction in lipid content in treated cells indicates that ACLY could be a potential target for treating pancreatic cancer.

Enhanced acetylation of ATP-citrate lyase promotes the progression of nonalcoholic fatty liver disease.

Hepatic steatosis is a hallmark of nonalcoholic fatty liver disease (NAFLD) and is promoted by dysregulated de novo lipogenesis. ATP-citrate lyase (ACLY) is a crucial lipogenic enzyme that is up-regulated in individuals with NAFLD. A previous study has shown that acetylation of ACLY at Lys-540, Lys-546, and Lys-554 (ACLY-3K) increases ACLY protein stability by antagonizing its ubiquitylation, thereby promoting lipid synthesis and cell proliferation in lung cancer cells. But the functional importance of this regulatory mechanism in other cellular or tissue contexts or under other pathophysiological conditions awaits further investigation. Here, we show that ACLY-3K acetylation also promotes ACLY protein stability in AML12 cells, a mouse hepatocyte cell line, and found that the deacetylase sirtuin 2 (SIRT2) deacetylates ACLY-3K and destabilizes ACLY in these cells. Of note, the livers of mice and humans with NAFLD had increased ACLY protein and ACLY-3K acetylation levels and decreased SIRT2 protein levels. Mimicking ACLY-3K acetylation by replacing the three lysines with three glutamines (ACLY-3KQ variant) promoted lipid accumulation both in high glucose-treated AML12 cells and in the livers of high-fat/high-sucrose (HF/HS) diet-fed mice. Moreover, overexpressing SIRT2 in AML12 cells inhibited lipid accumulation, which was more efficiently reversed by overexpressing the ACLY-3KQ variant than by overexpressing WT ACLY. Additionally, hepatic SIRT2 overexpression decreased ACLY-3K acetylation and its protein level and alleviated hepatic steatosis in HF/HS diet-fed mice. Our findings reveal a posttranscriptional mechanism underlying the up-regulation of hepatic ACLY in NAFLD and suggest that the SIRT2/ACLY axis is involved in NAFLD progression.

Bempedoic acid: effects on lipoprotein metabolism and atherosclerosis.

PURPOSE OF REVIEW: Bempedoic acid has emerged as a potent inhibitor of ATP-citrate lyase (ACLY), a target for the reduction of LDL cholesterol (LDL-C). We review the impact of bempedoic acid treatment on lipoprotein metabolism and atherosclerosis in preclinical models and patients with hypercholesterolemia. RECENT FINDINGS: The liver-specific activation of bempedoic acid inhibits ACLY, a key enzyme linking glucose catabolism to lipogenesis by catalyzing the formation of acetyl-CoA from mitochondrial-derived citrate for de novo synthesis of fatty acids and cholesterol. Adenosine monophosphate-activated protein kinase activation by bempedoic acid is not required for its lipid-regulating effects in vivo. Mendelian randomization of large human study cohorts has validated ACLY inhibition as a target for LDL-C lowering and atheroprotection. In rodents, bempedoic acid decreases plasma cholesterol and triglycerides, and prevents hepatic steatosis. In apolipoprotein E-deficient (Apoe) mice, LDL receptor-deficient (Ldlr) mice and LDLR-deficient miniature pigs, bempedoic acid reduces LDL-C and attenuates atherosclerosis. LDLR expression and activity are increased in primary human hepatocytes and in Apoe mouse liver treated with bempedoic acid suggesting a mechanism for LDL-C lowering, although additional pathways are likely involved. Phase 2 and 3 clinical trials revealed that bempedoic acid effectively lowers LDL-C as monotherapy, combined with ezetimibe, added to statin therapy and in statin-intolerant hypercholesterolemic patients. Treatment does not affect plasma concentrations of triglyceride or other lipoproteins. SUMMARY: The LDL-C-lowering and attenuated atherosclerosis in animal models and reduced LDL-C in hypercholesterolemic patients has validated ACLY inhibition as a therapeutic strategy. Positive results from phase 3 long-term cardiovascular outcome trials in high-risk patients are required for bempedoic acid to be approved for prevention of atherosclerosis.

Inhibition of ATP citrate lyase (ACLY) protects airway epithelia from PM2.5-induced epithelial-mesenchymal transition.

Epidemiological studies have associated ambient fine particulate matter (PM2.5) exposure with lung cancer, in which epithelial-mesenchymal transition (EMT) is an initial process. Thus, it is important to identify the key molecule or pathway involved in the PM2.5 induced EMT. Human bronchial epithelial (HBE) cells were exposed to PM2.5 (100 or 500 µg/ml) for 30 passages and analyzed by metabolomics to identify the alteration of metabolites related to PM2.5 exposure. The expression levels of EMT markers were evaluated by qRT-PCR and Western blot assays in HBE cells and murine lung tissues. Reduced epithelial markers, increased mesenchymal markers expression levels and increased capacity of metastasis were observed in PM2.5-exposed HBE cells. Metabolomics analysis suggested upregulation of citrate acid with fold change (FC) of 2.89 or 4.18 in 100 or 500 µg/ml PM2.5 treated HBE cells. For both of the in vitro and in vivo study, the up-regulation of ATP citrate lyase (ACLY) was confirmed following PM2.5 exposure. Importantly, ACLY knockdown in HBE cells reversed EMT, migration and invasion capacities in HBE cells induced by PM2.5. Taken together, our data suggest that inhibition of ACLY demonstrates a protection against PM2.5-induced EMT, providing a concern on the molecular mechanisms of PM2.5-associated pulmonary disorders.

Prevention of Diet-Induced Metabolic Dysregulation, Inflammation, and Atherosclerosis in Ldlr-/- Mice by Treatment With the ATP-Citrate Lyase Inhibitor Bempedoic Acid.

OBJECTIVE: Bempedoic acid (ETC-1002, 8-hydroxy-2,2,14,14-tetramethylpentadecanedioic acid) is a novel low-density lipoprotein cholesterol-lowering compound. In animals, bempedoic acid targets the liver where it inhibits cholesterol and fatty acid synthesis through inhibition of ATP-citrate lyase and through activation of AMP-activated protein kinase. In this study, we tested the hypothesis that bempedoic acid would prevent diet-induced metabolic dysregulation, inflammation, and atherosclerosis. APPROACH AND RESULTS: Ldlr-/- mice were fed a high-fat, high-cholesterol diet (42% kcal fat, 0.2% cholesterol) supplemented with bempedoic acid at 0, 3, 10 and 30 mg/kg body weight/day. Treatment for 12 weeks dose-dependently attenuated diet-induced hypercholesterolemia, hypertriglyceridemia, hyperglycemia, hyperinsulinemia, fatty liver and obesity. Compared to high-fat, high-cholesterol alone, the addition of bempedoic acid decreased plasma triglyceride (up to 64%) and cholesterol (up to 50%) concentrations, and improved glucose tolerance. Adiposity was significantly reduced with treatment. In liver, bempedoic acid prevented cholesterol and triglyceride accumulation, which was associated with increased fatty acid oxidation and reduced fatty acid synthesis. Hepatic gene expression analysis revealed that treatment significantly increased expression of genes involved in fatty acid oxidation while suppressing inflammatory gene expression. In full-length aorta, bempedoic acid markedly suppressed cholesteryl ester accumulation, attenuated the expression of proinflammatory M1 genes and attenuated the iNos/Arg1 ratio. Treatment robustly attenuated atherosclerotic lesion development in the aortic sinus by 44%, with beneficial changes in morphology, characteristic of earlier-stage lesions. CONCLUSIONS: Bempedoic acid effectively prevents plasma and tissue lipid elevations and attenuates the onset of inflammation, leading to the prevention of atherosclerotic lesion development in a mouse model of metabolic dysregulation.

ACLY and ACC1 Regulate Hypoxia-Induced Apoptosis by Modulating ETV4 via α-ketoglutarate.

In order to propagate a solid tumor, cancer cells must adapt to and survive under various tumor microenvironment (TME) stresses, such as hypoxia or lactic acidosis. To systematically identify genes that modulate cancer cell survival under stresses, we performed genome-wide shRNA screens under hypoxia or lactic acidosis. We discovered that genetic depletion of acetyl-CoA carboxylase (ACACA or ACC1) or ATP citrate lyase (ACLY) protected cancer cells from hypoxia-induced apoptosis. Additionally, the loss of ACLY or ACC1 reduced levels and activities of the oncogenic transcription factor ETV4. Silencing ETV4 also protected cells from hypoxia-induced apoptosis and led to remarkably similar transcriptional responses as with silenced ACLY or ACC1, including an anti-apoptotic program. Metabolomic analysis found that while α-ketoglutarate levels decrease under hypoxia in control cells, α-ketoglutarate is paradoxically increased under hypoxia when ACC1 or ACLY are depleted. Supplementation with α-ketoglutarate rescued the hypoxia-induced apoptosis and recapitulated the decreased expression and activity of ETV4, likely via an epigenetic mechanism. Therefore, ACC1 and ACLY regulate the levels of ETV4 under hypoxia via increased α-ketoglutarate. These results reveal that the ACC1/ACLY-α-ketoglutarate-ETV4 axis is a novel means by which metabolic states regulate transcriptional output for life vs. death decisions under hypoxia. Since many lipogenic inhibitors are under investigation as cancer therapeutics, our findings suggest that the use of these inhibitors will need to be carefully considered with respect to oncogenic drivers, tumor hypoxia, progression and dormancy. More broadly, our screen provides a framework for studying additional tumor cell stress-adaption mechanisms in the future.

ATP-citrate lyase: genetics, molecular biology and therapeutic target for dyslipidemia.

PURPOSE OF REVIEW: ATP-citrate lyase (ACLY) has re-emerged as a drug target for LDL cholesterol (LDL-C) lowering. We review ACLY as a therapeutic strategy, its genetics, its molecular and cellular biology, and also its inhibition. RECENT FINDINGS: ACLY is a critical enzyme linking glucose catabolism to lipogenesis by providing acetyl-CoA from mitochondrial citrate for fatty acid and cholesterol biosynthesis. Human genetic variants have been associated with enhanced growth and survival of several cancers, and with attenuated plasma triglyceride responses to dietary fish oil. In mice, liver-specific Acly deficiency protects from hepatic steatosis and dyslipidemia, whereas adipose tissue-specific Acly deletion has no phenotype, supporting therapeutic inhibition of ACLY. A lipid-regulating compound, bempedoic acid, was discovered to potently inhibit ACLY, and in animal models, it prevents dyslipidemia and attenuates atherosclerosis. Phase 2 clinical trials revealed that bempedoic acid effectively lowers LDL-C as monotherapy, combined with ezetimibe, added to statin therapy and in statin-intolerant hypercholesterolemic patients. SUMMARY: The efficacy of bempedoic acid as an LDL-C-lowering agent has validated ACLY inhibition as a therapeutic strategy. Positive results of phase 3 patient studies, together with long-term cardiovascular disease outcome trials, are required to establish ACLY as a major new target in cardiovascular medicine.

Discovery of furan carboxylate derivatives as novel inhibitors of ATP-citrate lyase via virtual high-throughput screening.

The enzyme ATP citrate lyase (ACL) catalyzes the formation of cytosolic acetyl CoA, the starting material for de novo lipid and cholesterol biosynthesis. The dysfunction and upregulation of ACL in numerous cancers makes it an attractive target for developing anticancer therapies. ACL inhibition by shRNA knockdown limits cancer cell proliferation and reduces cancer stemness. We designed and implemented a dual docking protocol to select virtual ACL inhibitors that were scored among the top 10 percentiles by both the Autodock Vina and the Glamdock algorithms. Via this in silico screens of a focused furoic acid library, we discovered four subtypes of furans and benzofurans as novel ACL inhibitors. The hit rate of our in silico protocol was 45.8% with 11 of 24 virtual hits confirmed as active in an in vitro ACL enzymatic assay. The IC50 of the most potent ACL inhibitor A1 is 4.1µM. Our results demonstrated remarkable hit rate by the dual docking approach and provided novel chemical scaffolds for the development of ACL inhibitors for the treatment of cancer.

The reduced concentration of citrate in cancer cells: An indicator of cancer aggressiveness and a possible therapeutic target.

Proliferating cells reduce their oxidative metabolism and rely more on glycolysis, even in the presence of O2 (Warburg effect). This shift in metabolism reduces citrate biosynthesis and diminishes intracellular acidity, both of which promote glycolysis sustaining tumor growth. Because citrate is the donor of acetyl-CoA, its reduced production favors a deacetylation state of proteins favoring resistance to apoptosis and epigenetic changes, both processes contributing to tumor aggressiveness. Citrate levels could be monitored as an indicator of cancer aggressiveness (as already shown in human prostate cancer) and/or could serve as a biomarker for response to therapy. Strategies aiming to increase cytosolic citrate should be developed and tested in humans, knowing that experimental studies have shown that administration of citrate and/or inhibition of ACLY arrest tumor growth, inhibit the expression of the key anti-apoptotic factor Mcl-1, reverse cell dedifferentiation and increase sensibility to cisplatin.