SIRT2-mediated deacetylation of ACLY promotes the progression of oesophageal squamous cell carcinoma

ATP citrate lyase (ACLY), as a key enzyme in lipid metabolism, plays an important role in energy metabolism and lipid biosynthesis of a variety of tumours. Many studies have shown that ACLY is highly expressed in various tumours, and its pharmacological or gene inhibition significantly inhibits tumour growth and progression. However, the roles of ACLY in oesophageal squamous cell carcinoma (ESCC) remain unclear. Here, our data showed that ACLY inhibitor significantly attenuated cell proliferation, migration, invasion and lipid synthesis in different ESCC cell lines, whereas the proliferation, migration, invasion and lipid synthesis of ESCC cells were enhanced after ACLY overexpression. Furthermore, ACLY inhibitor dramatically suppressed tumour growth and lipid metabolism in ESCC cells xenografted tumour model, whereas ACLY overexpression displayed the opposite effect. Mechanistically, ACLY protein harboured acetylated modification and interacted with SIRT2 protein in ESCC cells. The SIRT2 inhibitor AGK2 significantly increased the acetylation level of ACLY protein and inhibited the proliferation and migration of ESCC cells, while overexpression of ACLY partially reversed the inhibitory effect of AGK2 on ESCC cells. Overall, these results suggest that targeting the SIRT2/ACLY signalling axis may be a potential therapeutic strategy for ESCC patients.

Acylphloroglucinol-monoterpene meroterpenoids from Eucalyptus tereticornis and their inhibitory activity against ATP citrate lyase

Five undescribed enantiomeric pairs of acylphloroglucinol-monoterpene meroterpenoids ((+)-/(-)-eucateretins A-E) resolved by chiral-phase HPLC were obtained from the leaves of Eucalyptus tereticornis Smith, along with nine known analogues. Their structures were elucidated by spectroscopic methods and ECD calculations. This is the first report of meroterpenoid enantiomers from this plant. Some of the isolates, (-)-eucateretin A, (+)-/(-)-eucateretins E, 7'α-eucalrobusone X, eucalrobusone X, and robustadial B, exhibited inhibitory effects on ATP citrate lyase, and 7'α-eucalrobusone X significantly suppressed the hepatocyte lipogenesis.

Preparation and identification of isoquinoline alkaloids with ATP citrate lyase inhibitory activity from Dactylicapnos scandens

Three new isoquinoline alkaloids including a morphine derivative (1), two aporphine alkaloids (2-3), together with five known alkaloids (4-8) were obtained from the extract of Dactylicapnos scandens (D.Don) Hutch. (D. scandens). Their structures and absolute configurations were elucidated by extensive spectroscopic data analysis including HRESIMS, NMR and electronic circular dichroism (ECD) and ECD calculation. Compounds 1-8 were evaluated for ATP Citrate Lyase (ACLY) inhibitory activity through an enzymatic assay. Among them, 2 and 3 showed the high ACLY inhibitory activity with an IC50 value of 10.48 ± 1.59 and 10.89 ± 4.89 μM.

Acylphloroglucinol derivatives with ATP citrate lyase inhibitory activities from Syzygium oblatum Wall

Nine undescribed acylphloroglucinol derivatives, oblatones A-I, along with three known ones, were isolated from Syzygium oblatum. Their structures were determined on the basis of extensive spectroscopic analysis, including NMR and MS data interpretation. Oblatones A and B possess an alkylated chromanone scaffold featuring a hemiketal moiety. Oblatones C and D are the first acylphloroglucinol derivatives with an α,β-unsaturated ketone lipid chain. Some of the isolates showed inhibitory effects on ATP citrate lyase in vitro. The binding mode of oblatone A was predicted by molecular docking.

[Bempedoic acid: mechanism of action]

Bempedoic acid (ETC-1002) is an oral, once-daily, small molecule with a half-life of 15-24 h. It is responsible for the inhibition of ATP citrate lyase (ACLY), a cytosolic enzyme upstream of HMG-CoA reductase. Bempedoic acid is a prodrug rapidly converted in the liver to a coenzyme A derivate, ETC-1200-CoA, by an endogenous liver very long-chain acyl-CoA synthetase-1 (ACSVL1). Since ACSVL1 is not present in the skeletal muscle, less risk of myalgia symptoms and myopathy is expected. In a Mendelian randomization study, combined exposure to variants in the ACLY, HMGCR and Niemann-Pick C1-Like 1 genes produced an additive decrease in low-density lipoprotein cholesterol levels and additive reduction in the risk of cardiovascular events. The aim of this review is to describe bempedoic acid mechanism of action, and its pharmacokinetic and pharmacodynamic characteristics.

Clerodane diterpenoids from Dodonaea viscosa and their inhibitory effects on ATP citrate lyase

Six undescribed clerodane diterpenoids, dodovisins A-F, together with nine known ones, were isolated from the aerial parts of Dodonaea viscosa (L.) Jacq. Their structures were elucidated by extensive spectroscopic techniques, X-ray crystallographic analysis, and ECD calculation. Dodovisins A and B possess a rare carbon skeleton featuring a bicyclo[6.2.0]decane motif. Dodovisins C-E represent the first clerodane diterpenoids with a 4(5 → 19)-abeo-2,4,10(1)-triene moiety. Dodovisins A, E, and strictic acid showed potent inhibitory activities against ATP citrate lyase.

PaACL silencing accelerates flower senescence and changes the proteome to maintain metabolic homeostasis in Petunia hybrida

Cytosolic acetyl-CoA is an intermediate of the synthesis of most secondary metabolites and the source of acetyl for protein acetylation. The formation of cytosolic acetyl-CoA from citrate is catalysed by ATP-citrate lyase (ACL). However, the function of ACL in global metabolite synthesis and global protein acetylation is not well known. Here, four genes, PaACLA1, PaACLA2, PaACLB1, and PaACLB2, which encode the ACLA and ACLB subunits of ACL in Petunia axillaris, were identified as the same sequences in Petunia hybrida 'Ultra'. Silencing of PaACLA1-A2 and PaACLB1-B2 led to abnormal leaf and flower development, reduced total anthocyanin content, and accelerated flower senescence in petunia 'Ultra'. Metabolome and acetylome analysis revealed that PaACLB1-B2 silencing increased the content of many downstream metabolites of acetyl-CoA metabolism and the levels of acetylation of many proteins in petunia corollas. Mechanistically, the metabolic stress induced by reduction of acetyl-CoA in PaACL-silenced petunia corollas caused global and specific changes in the transcriptome, the proteome, and the acetylome, with the effect of maintaining metabolic homeostasis. In addition, the global proteome and acetylome were negatively correlated under acetyl-CoA deficiency. Together, our results suggest that ACL acts as an important metabolic regulator that maintains metabolic homeostasis by promoting changes in the transcriptome, proteome. and acetylome.

Distinct dual roles of p-Tyr42 RhoA GTPase in tau phosphorylation and ATP citrate lyase activation upon different Aβ concentrations

Both the accumulation of Amyloid-β (Aβ) in plaques and phosphorylation of Tau protein (p-Tau) in neurofibrillary tangles have been identified as two major symptomatic features of Alzheimer's disease (AD). Despite of critical role of Aβ and p-Tau in AD progress, the interconnection of signalling pathways that Aβ induces p-Tau remains elusive. Herein, we observed that a popular AD model mouse (APP/PS1) and Aβ-injected mouse showed an increase in p-Tyr42 Rho in hippocampus of brain. Low concentrations of Aβ (1 μM) induced RhoA-mediated Ser422 phosphorylation of Tau protein (p-Ser422 Tau), but reduced the expression of ATP citrate lyase (ACL) in the HT22 hippocampal neuronal cell line. In contrast, high concentrations of Aβ (10 μM) along with high levels of superoxide production remarkably attenuated accumulation of p-Ser422 Tau, but augmented ACL expression and activated sterol regulatory element-binding protein 1 (SREBP1), leading to cellular senescence. Notably, a high concentration of Aβ (10 μM) induced nuclear localization of p-Tyr42 Rho, which positively regulated NAD kinase (NADK) expression by binding to the NADK promoter. Furthermore, severe AD patient brain showed high p-Tyr42 Rho levels. Collectively, our findings indicate that both high and low concentrations of Aβ are detrimental to neurons via distinct two p-Tyr42 RhoA-mediated signalling pathways in Ser422 phosphorylation of Tau and ACL expression.

Stressed-Out T Cells Fragment the Mind

The immune system is increasingly recognized to play an integral role in regulating stress responses. In a recent article in Cell, Fan et al. demonstrate a novel mechanism through which stress drives mitochondrial fragmentation-induced xanthine accumulation in mouse CD4⁺ T cells, subsequently acting on oligodendrocytes to induce anxiety-like behaviors.

CITRATE AND THE CONVERSION OF CARBOHYDRATE INTO FAT. THE ACTIVITIES OF CITRATE-CLEAVAGE ENZYME AND ACETATE THIOKINASE IN LIVERS OF STARVED AND RE-FED RATS

1. The activity of citrate-cleavage enzyme varies in accordance with the nutritional state of the animal. It is suppressed on starvation and restored on re-feeding after starvation. 2. The increase in enzyme activity that occurs on re-feeding starved animals depends on the diet. It is largest on diets high in carbohydrate and low in fat, and smallest on diets high in fat. Intermediate increases are obtained with balanced diets. 3. The ratio of activities of citrate-cleavage enzyme to acetate thiokinase varies from 2.5 for animals maintained on a balanced diet to 20 for animals re-fed with a diet high in carbohydrate. 4. The changes in activity of citrate-cleavage enzyme correlate with changes in the rate of fatty acid synthesis and provide evidence for the involvement of the citrate-cleavage reaction in fatty acid synthesis.

CITRATE AND THE CONVERSION OF CARBOHYDATE INTO FAT. ACTIVITIES OF CITRATE-CLEAVAGE ENZYME AND ACETATE THIOKINASE IN LIVERS OF NORMAL AND DIABETIC RATS

1. The activity of citrate-cleavage enzyme declines in alloxan-diabetes. 2. The administration of insulin elevates the activity of the enzyme in livers of normal and diabetic animals. Diets high in glucose or fructose elevate the activity of citrate-cleavage enzyme in normal animals, whereas only the diet high in fructose does so in diabetic animals. These observations parallel the effects of insulin, glucose and fructose on fatty acid synthesis in normal and diabetic animals. The effect of fructose is brought into play more rapidly and is larger than the effect of glucose. 3. With one exception acetate thiokinase shows similar changes at a lower level of activity. 4. The results indicate that insulin acts by increasing glucose utilization, and not by exerting a direct effect on citrate-cleavage enzyme or acetate thiokinase.

Demonstration of the amphiphilic character of hormone-sensitive lipase by temperature-induced phase separation in Triton X-114 and charge-shift electrophoresis

Temperature-induced phase separation in Triton X-114 (Bordier, C. (1981) J. Biol. Chem. 256, 1604-1607) and charge-shift electrophoresis (Helenius, A., and Simons, K. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 529-532) were used to examine the amphiphilic character of hormone-sensitive lipase, purified from rat adipose tissue. In contrast to ATP-citrate lyase, a reference hydrophilic protein, the lipase was shown to partition predominantly (approximately 80%) into the detergent-rich phase upon phase separation in Triton X-114. Furthermore, its electrophoretic mobility was markedly shifted anodally and cathodally upon charge-shift electrophoresis in the presence of sodium taurodeoxycholate and cetyltrimethylammonium bromide, respectively. The results demonstrate that hormone-sensitive lipase possesses detergent-binding hydrophobic domain(s) and exhibits the same amphiphilicity as typical intrinsic membrane proteins.

The configuration and location of the ribosidic linkage in the prosthetic group of citrate lyase (Klebsiella aerogenes)

The structure of the prosthetic group of citrate lyase (Klebsiella aerogenes) was studied by nuclear magnetic resonance and mass spectrometry. The spectra at 360 MHz of the nucleoside moiety (2'-ribosyladenosine) show the absence of 2'-hydroxyl proton, thus confirming the 2' position as the site of attachment of the second ribose moiety to the dephospho-CoA. This glycosidic linkage is found to be alpha(1" leads to 2') and is identical to that of poly(ADP-ribose). Studies of permethylation products by mass spectrometry support the above conclusion regarding the location of the ribosidic linkage.

Dietary energy and fat content as factors in the nutrition of developing egg strain pullets and young hens. 4. Effect on growth, hepatic lipogenic enzyme activity and body chemical composition of White Leghorn pullets from hatch to 20 weeks of age

Nine starting and rearing diets (three energy levels each with three fat levels) were fed to commercial White Leghorn chicks from hatch to 20 weeks of age. As noted in the earlier papers of this series, pullets fed the high energy rearing diets showed significant (P = 0.05) reductions in feed intake, however, average daily caloric intake was greater (P = 0.05) for pullets consuming the low energy rearing diets. Fat content of the diet had not influence on either daily feed (g.) or caloric (kcal.) intake. Energy content of the diets failed (P = 0.05) to affect parameters related to body growth and development, hepatic citrate-cleavage and "malic" enzyme activity and liver or body composition. Fat content of the diet depressed hepatic enzyme activity while no effect was noted on body weight, liver weight or body composition. The onset of sexual maturity altered lipid metabolism in the developing pullets. Significant (P = 0.05) energy level by fat level interactions were noted in only two of the 20 parameters studied in this experiment. In vitro assay of hepatic citrate-cleavage and "malic" enzyme activity proved to be of little value in predicting hepatic lipogenic activity and subsequent effects on liver and total body composition.

The prosthetic group of citrate-lyase acyl-carrier protein

The acyl carrier protein of citrate lyase contains adenine, phosphate, sugar, cysteamine, beta-alanine and pantoic acid in a molar ratio of 1:2:2:1:1:1. Peptides containing these components in the same stoichiometric relationship were isolated after proteolytic digestion of acyl carrier protein. All components were linked together in a single prosthetic group. This was released from the peptide by mild alkaline hydrolysis. Under these conditions a phosphodiester bond is cleaved which links the prosthetic group to a serine residue of the peptide. Incubation of the prosthetic-group-containing peptide with phosphodiesterase I yielded 4'-phosphopantetheine and adenylic acid. The 5'-AMP was not free but was substituted by presumably an acidic sugar residue, which was released by mild acid hydrolysis yielding free 5'-AMP. It was concluded from these results that the prosthetic group of citrate lyase acyl carrier protein consists of a substituted isomeric dephospho-CoA. This is bound to the protein by the 5'-phosphate group of adenylic acid. The 4'-phosphopantetheine residue is bound by a phosphodiester linkage to the 2' or 3' position of ribose and the remaining hydroxyl group of ribose is substituted with presumably an acidic sugar residue. The structural similarities of this prothetic group and coenzyme A are discussed and related to the catalytic properties of citrate lyase.

Lipogenesis and glyceride synthesis in the rat: response to diet and exercise

The responses of hepatic and adipose tissue malic enzyme (ME), citrate cleavage enzyme (CCE), glucose-6-phosphate dehydrogenase (G6PD), and glyceride synthetase (GS) to exercise training and exhaustive exercies and the potential of a high fat or high carbohydrate diet to modify these responses were studied in male Carworth rats. Characteristic elevation and depression of ME, CCE, and G6PD were decreased in skeletal muscle, liver, and adipose tissues of high carbohydrate-fed rats. A significant two-way diet-training interaction was indicated for hepatic ME and G6PD. This interaction resulted from an apparent training modulation of ME and C6PD responses to the high fat and high carbohydrate diets. Adipose tissue G6PD was significantly decreased by training. Exhaustive exercise performed immediately prior to sacrifice did not significantly alter ME or CCE activities in either liver or adipose tissues, but decreased adipose tissue G6PD in untrained rats. Exhaustion was also associated with decreased GS activity in muscle and liver. Physical training was associated with a significant increase in GS in muscle and adipose tissues. In contrast to glyceride synthesis, no increase in adipose tissue lipogenic potential was noted in response to training, indicating that the physically trianed rat may have an enhanced ability to store but not synthesize fatty acids.

CITRATE CLEAVAGE ENZYME IN LIVERS OF OBESE AND NONOBESE MICE

The specific activity of the citrate cleavage enzyme is 3.3 times greater in livers of obese mice than in livers of their nonobese litter mates. The difference persists during starvation. The specific activity of the acetate activating enzyme is approximately the same in the livers of both types of animals. It is proposed that a high activity of citrate cleavage enzyme is one of the factors responsible for obesity.