Acute ACAT1/SOAT1 Blockade Increases MAM Cholesterol and Strengthens ER-Mitochondria Connectivity.

Cholesterol is a key component of all mammalian cell membranes. Disruptions in cholesterol metabolism have been observed in the context of various diseases, including neurodegenerative disorders such as Alzheimer's disease (AD). The genetic and pharmacological blockade of acyl-CoA:cholesterol acyltransferase 1/sterol O-acyltransferase 1 (ACAT1/SOAT1), a cholesterol storage enzyme found on the endoplasmic reticulum (ER) and enriched at the mitochondria-associated ER membrane (MAM), has been shown to reduce amyloid pathology and rescue cognitive deficits in mouse models of AD. Additionally, blocking ACAT1/SOAT1 activity stimulates autophagy and lysosomal biogenesis; however, the exact molecular connection between the ACAT1/SOAT1 blockade and these observed benefits remain unknown. Here, using biochemical fractionation techniques, we observe cholesterol accumulation at the MAM which leads to ACAT1/SOAT1 enrichment in this domain. MAM proteomics data suggests that ACAT1/SOAT1 inhibition strengthens the ER-mitochondria connection. Confocal and electron microscopy confirms that ACAT1/SOAT1 inhibition increases the number of ER-mitochondria contact sites and strengthens this connection by shortening the distance between these two organelles. This work demonstrates how directly manipulating local cholesterol levels at the MAM can alter inter-organellar contact sites and suggests that cholesterol buildup at the MAM is the impetus behind the therapeutic benefits of ACAT1/SOAT1 inhibition.

Identification of two novel ACAT1 variant associated with beta-ketothiolase deficiency in a 9-month-old boy.

OBJECTIVES: Mitochondrial acetoacetyl-CoA thiolase (beta-ketothiolase, T2) is necessary for the catabolism of ketone bodies andisoleucine. T2 deficiency is an autosomal recessive metabolic disorder caused by variant in the ACAT1 gene. In this report, we describe two novel ACAT1 variant identified in a Chinese family. CASE PRESENTATION: The 9-month-old male proband was admitted to the pediatric intensive care unit for altered consciousness. At the time of admission, the patient had acidosis, drowsiness, and respiratory failure. Both urine organic acid analyses and LC-MS/MS suggested T2 deficiency. Novel compound heterozygous variant (c.871G>C and c.1016_1017del) in the ACAT1 gene were detected in the proband by WES and verified through direct sequencing. Family analysis demonstrated that the first variant was transmitted from his father and the second variant was from his mother, indicating autosomal recessive inheritance. This report is the first to describe the association of these variant with T2 deficiency based on genetic testing. Although these variant were identified in the patient's elder sister and elder brother, they continue to be asymptomatic. CONCLUSIONS: We identified two novel ACAT1 variants associated with T2 deficiency. The identification expands the spectrum of known variant linked to the disorder.

Impact of various ß-ketothiolase genes on PHBHHx production in Cupriavidus necator H16 derivatives.

Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHHx) is a type of biopolyester of the polyhydroxyalkanoate group (PHA). Due to a wide range of properties resulting from the alteration of the (R)-3-hydroxyhexanoate (3HHx) composition, PHBHHx is getting a lot of attention as a substitute to conventional plastic materials for various applications. Cupriavidus necator H16 is the most promising PHA producer and has been genetically engineered to produce PHBHHx efficiently for many years. Nevertheless, the role of individual genes involved in PHBHHx biosynthesis is not well elaborated. C. necator H16 possesses six potential physiologically active ß-ketothiolase genes identified by transcriptome analysis, i.e., phaA, bktB, bktC (h16_A0170), h16_A0462, h16_A1528, and h16_B0759. In this study, we focused on the functionality of these genes in vivo in relation to 3HHx monomer supply. Gene deletion experiments identified BktB and H16_A1528 as important ß-ketothiolases for C6 metabolism in ß-oxidation. Furthermore, in the bktB/h16_A1528 double-deletion strain, the proportion of 3HHx composition of PHBHHx produced from sugar was very low, whereas that from plant oil was significantly higher. In fact, the proportion reached 36.2 mol% with overexpression of (R)-specifc enoyl-CoA hydratase (PhaJ) and PHA synthase. Furthermore, we demonstrated high-density production (196 g/L) of PHBHHx with high 3HHx (32.5 mol%) by fed-batch fermentation with palm kernel oil. The PHBHHx was amorphous according to the differential scanning calorimetry analysis. KEY POINTS: • Role of six ß-ketothiolases in PHBHHx biosynthesis was investigated in vivo. • Double-deletion of bktB/h16_A1528 results in high 3HHx composition with plant oil. • Amorphous PHBHHx with 32.5 mol% 3HHx was produced in high density by jar fermenter.

Installing a Green Engine To Drive an Enzyme Cascade: A Light-Powered In Vitro Biosystem for Poly(3-hydroxybutyrate) Synthesis.

Many existing in vitro biosystems harness power from the chemical energy contained in substrates and co-substrates, and light or electric energy provided from abiotic parts, leading to a compromise in atom economy, incompatibility between biological and abiotic parts, and most importantly, incapability to spatiotemporally co-regenerate ATP and NADPH. In this study, we developed a light-powered in vitro biosystem for poly(3-hydroxybutyrate) (PHB) synthesis using natural thylakoid membranes (TMs) to regenerate ATP and NADPH for a five-enzyme cascade. Through effective coupling of cofactor regeneration and mass conversion, 20 mM PHB was yielded from 50 mM sodium acetate with a molar conversion efficiency of carbon of 80.0 % and a light-energy conversion efficiency of 3.04 %, which are much higher than the efficiencies of similar in vitro PHB synthesis biosystems. This suggests the promise of installing TMs as a green engine to drive more enzyme cascades.

A dual cellular-heterogeneous catalyst strategy for the production of olefins from glucose.

Living systems provide a promising approach to chemical synthesis, having been optimized by evolution to convert renewable carbon sources, such as glucose, into an enormous range of small molecules. However, a large number of synthetic structures can still be difficult to obtain solely from cells, such as unsubstituted hydrocarbons. In this work, we demonstrate the use of a dual cellular-heterogeneous catalytic strategy to produce olefins from glucose using a selective hydrolase to generate an activated intermediate that is readily deoxygenated. Using a new family of iterative thiolase enzymes, we genetically engineered a microbial strain that produces 4.3 ± 0.4 g l-1 of fatty acid from glucose with 86% captured as 3-hydroxyoctanoic and 3-hydroxydecanoic acids. This 3-hydroxy substituent serves as a leaving group that enables heterogeneous tandem decarboxylation-dehydration routes to olefinic products on Lewis acidic catalysts without the additional redox input required for enzymatic or chemical deoxygenation of simple fatty acids.

ACAA2 is a ligand-dependent coactivator for thyroid hormone receptor ß1.

Thyroid hormones (THs) play a critical role in the metabolic phenotype of the heart; and most of the effects involve transcriptional regulation via thyroid hormone receptors (TRs). TRs ability to form combinatorial complexes with an array of partners accounts for TRs physiological flexibility in modulating gene expression. To identify proteins that associate with TRß1 in the heart we performed a pull-down assay on cardiac tissue using GST-TRß1 as bait and identified the bound proteins by LC MS/MS. ACAA2, a mitochondrial thiolase enzyme, was identified as a novel interacting protein. We confirmed ACAA2 localized to the nucleus and using a luciferase reporter assay showed ACAA2 acted as a TH-dependent coactivator for TRß1. ACAA2 showed an ability to bind to TR recognition sequences but did not alter TRß1 DNA binding ability. Thus, ACAA2 as a novel TRß1 associating protein opens a new paradigm to understanding how TH/TRs may be manipulated by energetic pathway molecules.

Bistability in fatty-acid oxidation resulting from substrate inhibition.

In this study we demonstrated through analytic considerations and numerical studies that the mitochondrial fatty-acid ß-oxidation can exhibit bistable-hysteresis behavior. In an experimentally validated computational model we identified a specific region in the parameter space in which two distinct stable and one unstable steady state could be attained with different fluxes. The two stable states were referred to as low-flux (disease) and high-flux (healthy) state. By a modular kinetic approach we traced the origin and causes of the bistability back to the distributive kinetics and the conservation of CoA, in particular in the last rounds of the ß-oxidation. We then extended the model to investigate various interventions that may confer health benefits by activating the pathway, including (i) activation of the last enzyme MCKAT via its endogenous regulator p46-SHC protein, (ii) addition of a thioesterase (an acyl-CoA hydrolysing enzyme) as a safety valve, and (iii) concomitant activation of a number of upstream and downstream enzymes by short-chain fatty-acids (SCFA), metabolites that are produced from nutritional fibers in the gut. A high concentration of SCFAs, thioesterase activity, and inhibition of the p46Shc protein led to a disappearance of the bistability, leaving only the high-flux state. A better understanding of the switch behavior of the mitochondrial fatty-acid oxidation process between a low- and a high-flux state may lead to dietary and pharmacological intervention in the treatment or prevention of obesity and or non-alcoholic fatty-liver disease.

Cloning of wheat keto-acyl thiolase 2B reveals a role of jasmonic acid in grain weight determination.

Grain weight (GW) is one of the component traits of wheat yield. Existing reports have shown that multiple phytohormones are involved in the regulation of GW in different crops. However, the potential role of jasmonic acid (JA) remains unclear. Here, we report that triticale grain weight 1 (tgw1) mutant, with marked reductions in both GW and JA content, is caused by a premature stop mutation in keto-acyl thiolase 2B (KAT-2B) involved in ß-oxidation during JA synthesis. KAT-2B overexpression increases GW in wild type and boosts yield. Additionally, KAT-2B compliments the grain defect in tgw1 and rescues the lethal phenotype of the Arabidopsis kat2 mutant in a sucrose-free medium. Despite the suppression of JA synthesis in tgw1 mutant, ABA synthesis is upregulated, which is accompanied by enhanced expression of SAG3 and reduction of chlorophyll content in leaves. Together, these results demonstrate a role of the JA synthetic gene KAT-2B in controlling GW and its potential application value for wheat improvement.

Melanoma Persister Cells Are Tolerant to BRAF/MEK Inhibitors via ACOX1-Mediated Fatty Acid Oxidation.

Emerging evidence indicates that non-mutational drug tolerance mechanisms underlie the survival of residual cancer "persister" cells. Here, we find that BRAF(V600E) mutant melanoma persister cells tolerant to BRAF/MEK inhibitors switch their metabolism from glycolysis to oxidative respiration supported by peroxisomal fatty acid ß-oxidation (FAO) that is transcriptionally regulated by peroxisome proliferator-activated receptor alpha (PPARα). Knockdown of the key peroxisomal FAO enzyme, acyl-CoA oxidase 1 (ACOX1), as well as treatment with the peroxisomal FAO inhibitor thioridazine, specifically suppresses the oxidative respiration of persister cells and significantly decreases their emergence. Consistently, a combination treatment of BRAF/MEK inhibitors with thioridazine in human-melanoma-bearing mice results in a durable anti-tumor response. In BRAF(V600E) melanoma samples from patients treated with BRAF/MEK inhibitors, higher baseline expression of FAO-related genes and PPARα correlates with patients' outcomes. These results pave the way for a metabolic strategy to overcome drug resistance.

Effects of fasting, feeding and exercise on plasma acylcarnitines among subjects with CPT2D, VLCADD and LCHADD/TFPD.

BACKGROUND: The plasma acylcarnitine profile is frequently used as a biochemical assessment for follow-up in diagnosed patients with fatty acid oxidation disorders (FAODs). Disease specific acylcarnitine species are elevated during metabolic decompensation but there is clinical and biochemical heterogeneity among patients and limited data on the utility of an acylcarnitine profile for routine clinical monitoring. METHODS: We evaluated plasma acylcarnitine profiles from 30 diagnosed patients with long-chain FAODs (carnitine palmitoyltransferase-2 (CPT2), very long-chain acyl-CoA dehydrogenase (VLCAD), and long-chain 3-hydroxy acyl-CoA dehydrogenase or mitochondrial trifunctional protein (LCHAD/TFP) deficiencies) collected after an overnight fast, after feeding a controlled low-fat diet, and before and after moderate exercise. Our purpose was to describe the variability in this biomarker and how various physiologic states effect the acylcarnitine concentrations in circulation. RESULTS: Disease specific acylcarnitine species were higher after an overnight fast and decreased by approximately 60% two hours after a controlled breakfast meal. Moderate-intensity exercise increased the acylcarnitine species but it varied by diagnosis. When analyzed for a genotype/phenotype correlation, the presence of the common LCHADD mutation (c.1528G > C) was associated with higher levels of 3-hydroxyacylcarnitines than in patients with other mutations. CONCLUSIONS: We found that feeding consistently suppressed and that moderate intensity exercise increased disease specific acylcarnitine species, but the response to exercise was highly variable across subjects and diagnoses. The clinical utility of routine plasma acylcarnitine analysis for outpatient treatment monitoring remains questionable; however, if acylcarnitine profiles are measured in the clinical setting, standardized procedures are required for sample collection to be of value.

Transcriptomic Analysis of Glioma Based on IDH Status Identifies ACAA2 as a Prognostic Factor in Lower Grade Glioma.

BACKGROUND: Glioma is the most common and lethal tumor in the central nervous system (CNS). More than 70% of WHO grade II/III gliomas were found to harbor isocitrate dehydrogenase (IDH) mutations which generated targetable metabolic vulnerabilities. Focusing on the metabolic vulnerabilities, some targeted therapies, such as NAMPT, have shown significant effects in preclinical and clinical trials. METHODS: We explored the TCGA as well as CGGA database and analyzed the RNA-seq data of lower grade gliomas (LGG) with the method of weighted correlation network analysis (WGCNA). Differential expressed genes were screened, and coexpression relationships were grouped together by performing average linkage hierarchical clustering on the topological overlap. Clinical data were used to conduct Kaplan-Meier analysis. RESULTS: In this study, we identified ACAA2 as a prognostic factor in IDH mutation lower grade glioma with the method of weighted correlation network analysis (WGCNA). The difference of ACAA2 gene expressions between the IDH wild-type (IDH-WT) group and the IDH mutant (IDH-MUT) group suggested that there may be different potential targeted therapies based on the fatty acid metabolic vulnerabilities, which promoted the personalized treatment for LGG patients.

MSC-induced lncRNA HCP5 drove fatty acid oxidation through miR-3619-5p/AMPK/PGC1α/CEBPB axis to promote stemness and chemo-resistance of gastric cancer.

Chemotherapy is the first-tier treatment regime for gastric cancer (GC) patients at advance stages. Mesenchymal stem cell (MSC) cam affect drug-resistance of GC cells in tumor microenvironment, but the detailed mechanism remains poorly understood. Present study aimed to investigate the regulation of MSC-induced long non-coding RNA (lncRNA) in GC. Dysregulated lncRNAs in GC were analyzed based on GEO data. Stemness and drug-resistance of GC cells were detected by sphere formation, colony formation, CCK-8, and flow cytometry analyses. MicroRNA (miRNA)-related pathways were analyzed by online KEGG analysis tool DAVID6.8. Molecular interactions were determined by luciferase reporter assay, pulldown, RNA immunoprecipitation (RIP), chromatin immunoprecipitation (ChIP), and co-immunoprecipitation (CoIP). Results revealed that MSC co-culture improved stemness and drug-resistance of GC cells. LncRNA histocompatibility leukocyte antigen complex P5 (HCP5) was induced in GC cells by MSC co-culture, contributing to stemness and drug-resistance. Mechanistically, HCP5 sequestered miR-3619-5p and upregulated PPARG coactivator 1 alpha (PPARGC1A), increasing transcription complex Peroxisome proliferator activated receptor (PPAR) coactivator-1α (PGC1α)/CEBPB and transcriptionally inducing carnitine palmitoyltransferase 1 (CPT1), which prompted the fatty acid oxidation (FAO) in GC cells. In conclusion, MSC-induced lncRNA HCP5 drove FAO through miR-3619-5p/AMPK/PGC1α/CEBPB axis to promote stemness and chemo-resistance of GC, indicating that targeting HCP5 was a novel approach to enhancing the efficacy of chemotherapy in GC.

Increase in omega-6 and decrease in omega-3 polyunsaturated fatty acid oxidation elevates the risk of exudative AMD development in adults with Chinese diet.

Appropriate diet is essential for the regulation of age-related macular degeneration (AMD). In particular the type of dietary polyunsaturated fatty acids (PUFA) and poor antioxidant status including carotenoid levels concomitantly contribute to AMD risk. Build-up of oxidative stress in AMD induces PUFA oxidation, and a mix of lipid oxidation products (LOPs) are generated. However, LOPs are not comprehensively evaluated in AMD. LOPs are considered biomarkers of oxidative stress but also contributes to inflammatory response. In this cross-sectional case-control study, plasma omega-6/omega-3 PUFA ratios and antioxidant status (glutathione, superoxide dismutase and catalase), and plasma and urinary LOPs (41 types) were determined to evaluate its odds-ratio in the risk of developing exudative AMD (n = 99) compared to age-gender-matched healthy controls (n = 198) in adults with Chinese diet. The odds ratio of developing exudative AMD increased with LOPs from omega-6 PUFA and decreased from those of omega-3 PUFA. These observations were associated with a high plasma omega-6/omega-3 PUFA ratio and low carotenoid levels. In short, poor PUFA and antioxidant status increased the production of omega-6 PUFA LOPs such as dihomo-isoprostane and dihomo-isofuran, and lowered omega-3 PUFA LOPs such as neuroprostanes due to the high omega-6/omega-3 PUFA ratios; they were also correlated to the risk of AMD development. These findings indicate the generation of specific LOPs is associated with the development of exudative AMD.

MicroRNA-15a Regulates the Differentiation of Intramuscular Preadipocytes by Targeting ACAA1, ACOX1 and SCP2 in Chickens.

Our previous studies showed that microRNA-15a (miR-15a) was closely related to intramuscular fat (IMF) deposition in chickens; however, its regulatory mechanism remains unclear. Here, we evaluated the expression characteristics of miR-15a and its relationship with the expression of acetyl-CoA acyltransferase 1 (ACAA1), acyl-CoA oxidase 1 (ACOX1) and sterol carrier protein 2 (SCP2) by qPCR analysis in Gushi chicken breast muscle at 6, 14, 22, and 30 weeks old, where we performed transfection tests of miR-15a mimics in intramuscular preadipocytes and verified the target gene of miR-15a in chicken fibroblasts (DF1). The miR-15a expression level at 30 weeks increased 13.5, 4.5, and 2.7-fold compared with the expression levels at 6, 14, and 22 weeks, respectively. After 6 days of induction, miR-15a over-expression significantly promoted intramuscular adipogenic differentiation and increased cholesterol and triglyceride accumulation in adipocytes. Meanwhile, 48 h after transfection with miR-15a mimics, the expression levels of ACAA1, ACOX1 and SCP2 genes decreased by 56.52%, 31.18% and 37.14% at the mRNA level in intramuscular preadipocytes. In addition, the co-transfection of miR-15a mimics and ACAA1, ACOX1 and SCP2 3'UTR (untranslated region) dual-luciferase vector significantly inhibited dual-luciferase activity in DF1 cells. Taken together, our data demonstrate that miR-15a can reduce fatty acid oxidation by targeting ACAA1, ACOX1, and SCP2, which subsequently indirectly promotes the differentiation of chicken intramuscular preadipocytes.

Mutation update on ACAT1 variants associated with mitochondrial acetoacetyl-CoA thiolase (T2) deficiency.

Mitochondrial acetoacetyl-CoA thiolase (T2, encoded by the ACAT1 gene) deficiency is an inherited disorder of ketone body and isoleucine metabolism. It typically manifests with episodic ketoacidosis. The presence of isoleucine-derived metabolites is the key marker for biochemical diagnosis. To date, 105 ACAT1 variants have been reported in 149 T2-deficient patients. The 56 disease-associated missense ACAT1 variants have been mapped onto the crystal structure of T2. Almost all these missense variants concern residues that are completely or partially buried in the T2 structure. Such variants are expected to cause T2 deficiency by having lower in vivo T2 activity because of lower folding efficiency and/or stability. Expression and activity data of 30 disease-associated missense ACAT1 variants have been measured by expressing them in human SV40-transformed fibroblasts. Only two variants (p.Cys126Ser and p.Tyr219His) appear to have equal stability as wild-type. For these variants, which are inactive, the side chains point into the active site. In patients with T2 deficiency, the genotype does not correlate with the clinical phenotype but exerts a considerable effect on the biochemical phenotype. This could be related to variable remaining residual T2 activity in vivo and has important clinical implications concerning disease management and newborn screening.

Epicardial adipose tissue GLP-1 receptor is associated with genes involved in fatty acid oxidation and white-to-brown fat differentiation: A target to modulate cardiovascular risk?

BACKGROUND: Epicardial adipose tissue (EAT) is a risk factor for cardiovascular diseases. Glucagon-like peptide 1 analogs (GLP-1A) may have beneficial cardiovascular effects and reduce EAT, possibly throughout targeting GLP-1 receptor (GLP-1R). Nevertheless, the role of EAT GLP-1R, GLP-2R and their interplay with EAT genes involved in adipogenesis and fatty acid (FA) metabolism are unknown. We analyzed whether EAT transcriptome is related to GLP-1R/GLP-2R gene expression, and GLP-1/GLP-2 plasma levels in coronary artery disease patients (CAD). METHODS: EAT was collected from 17 CAD patients undergoing CABG for microarray analysis of GLP-1R, GLP-2R and genes involved in FA metabolism and adipogenesis. EAT thickness was measured by echocardiography. GLP-1 and GLP-2 levels were quantified by ELISA in CAD and healthy subjects (CTR). RESULTS: EAT GLP-1R was directly correlated with genes promoting beta-oxidation and white-to-brown adipocyte differentiation, and inversely with pro-adipogenic genes. GLP-2R was positively correlated with genes involved in adipogenesis and lipid synthesis, and inversely with genes promoting beta-oxidation. GLP-1 and GLP-2 levels were higher in CAD than CTR and in patients with greater EAT thickness. CONCLUSIONS: GLP-1 analogs may target EAT GLP-1R and therefore reduce local adipogenesis, improve fat utilization and induce brown fat differentiation. As EAT lies in direct contiguity to myocardium and coronary arteries, the beneficial effects of GLP-1 activation may extent to the heart. The increased levels of circulating GLP-1 and GLP-2 and EAT GLP-2R may be compensatory mechanisms related to CAD and also EAT expansion, but the meaning of these observations needs to be further investigated.

Swertiamarin decreases lipid accumulation dependent on 3-ketoacyl-coA thiolase.

Natural compounds are important resources for drug discovery. Using Caenorhabditis elegans (C. elegans) models, we screened active natural compounds with lipid lowering effects. Swertiamarin was found as a potent candidate to reduce lipid content in C. elegans. Using RNAi screening, we were able to demonstrate that kat-1 (ketoacyl thiolase-1) is necessary for the lipid lowering effect of swertiamarin. Furthermore, the activity of swertiamarin was verified in high fat diet induced obese mice. Consistent with the results in C. elegans, swertiamarin ameliorated high fat diet induced lipid deposition and hyperlipidemia. These results indicate that swertiamarin exerts lipid-lowering effects through kat-1 regulation and could serve as a possible therapeutic option to improve hyperlipidemia induced comorbidities.

Activation of SIRT1 by L-serine increases fatty acid oxidation and reverses insulin resistance in C2C12 myotubes.

Silent information regulator 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, and the function is linked to cellular metabolism including mitochondrial biogenesis. Hepatic L-serine concentration is decreased significantly in fatty liver disease. We reported that the supplementation of the amino acid ameliorated the alcoholic fatty liver by enhancing L-serine-dependent homocysteine metabolism. In this study, we hypothesized that the metabolic production of NAD+ from L-serine and thus activation of SIRT1 contribute to the action of L-serine. To this end, we evaluated the effects of L-serine on SIRT1 activity and mitochondria biogenesis in C2C12 myotubes. L-Serine increased intracellular NAD+ content and led to the activation of SIRT1 as determined by p53 luciferase assay and western blot analysis of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) acetylation. L-Serine treatment increased the expression of the genes associated with mitochondrial biogenesis and enhanced mitochondrial mass and function. In addition, L-serine reversed cellular insulin resistance determined by insulin-induced phosphorylation of Akt and GLUT4 expression and membrane translocation. L-Serine-induced mitochondrial gene expression, fatty acid oxidation, and insulin sensitization were mediated by enhanced SIRT1 activity, which was verified by selective SIRT1 inhibitor (Ex-527) and siRNA directed to SIRT1. L-Serine effect on cellular NAD+ level is dependent on the L-serine metabolism to pyruvate that is subsequently converted to lactate by lactate dehydrogenase. In summary, these data suggest that L-serine increases cellular NAD+ level and thus SIRT1 activity in C2C12 myotubes.

MiR-152 Regulates Apoptosis and Triglyceride Production in MECs via Targeting ACAA2 and HSD17B12 Genes.

Mammary epithelial cells (MECs) affect milk production capacity during lactation and are critical for the maintenance of tissue homeostasis. Our previous studies have revealed that the expression of miR-152 was increased significantly in MECs of cows with high milk production. In the present study, bioinformatics analysis identified ACAA2 and HSD17B12 as the potential targets of miR-152, which were further validated by dual-luciferase repoter assay. In addition, the expressions of miR-152 was shown to be negatively correlated with levels of mRNA and protein of ACAA2, HSD17B12 genes by qPCR and western bot analysis. Furthermore, transfection with miR-152 significantly up-regulated triglyceride production, promoted proliferation and inhibited apoptosis in MECs. Furthermore, overexpression of ACAA2 and HSD17B12 could inhibit triglyceride production, cells proliferation and induce apoptosis; but sh234-ACAA2-181/sh234-HSD17B12-474 could reverse the trend. These findings suggested that miR-152 could significantly influence triglyceride production and suppress apoptosis, possibly via the expression of target genes ACAA2 and HSD17B12.

One-step fermentative production of aromatic polyesters from glucose by metabolically engineered Escherichia coli strains.

Aromatic polyesters are widely used plastics currently produced from petroleum. Here we engineer Escherichia coli strains for the production of aromatic polyesters from glucose by one-step fermentation. When the Clostridium difficile isocaprenoyl-CoA:2-hydroxyisocaproate CoA-transferase (HadA) and evolved polyhydroxyalkanoate (PHA) synthase genes are overexpressed in a D-phenyllactate-producing strain, poly(52.3 mol% 3-hydroxybutyrate (3HB)-co-47.7 mol% D-phenyllactate) can be produced from glucose and sodium 3HB. Also, various poly(3HB-co-D-phenyllactate) polymers having 11.0, 15.8, 20.0, 70.8, and 84.5 mol% of D-phenyllactate are produced from glucose as a sole carbon source by additional expression of Ralstonia eutropha ß-ketothiolase (phaA) and reductase (phaB) genes. Fed-batch culture of this engineered strain produces 13.9 g l-1 of poly(61.9 mol% 3HB-co-38.1 mol% D-phenyllactate). Furthermore, different aromatic polyesters containing D-mandelate and D-3-hydroxy-3-phenylpropionate are produced from glucose when feeding the corresponding monomers. The engineered bacterial system will be useful for one-step fermentative production of aromatic polyesters from renewable resources.