Rate Of Β-oxidation Research Articles

Phospholipase D1 deficiency in mice causes nonalcoholic fatty liver disease via an autophagy defect.

Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of triglycerides (TG) as lipid droplets in the liver. Although lipid-metabolizing enzymes are considered important in NAFLD, the involvement of phospholipase D1 (PLD1) has not yet been studied. Here, we show that the genetic ablation of PLD1 in mice induces NAFLD due to an autophagy defect. PLD1 expression was decreased in high-fat diet-induced NAFLD. Subsequently, PLD1 deficiency led to an increase in hepatic TGs and liver weight. Autophagic flux was blocked in Pld1−/− hepatocytes, with decreased β-oxidation rate, reduced oxidation-related gene expression, and swollen mitochondria. The dynamics of autophagy was restored by treatment with the PLD product, phosphatidic acid (PA) or adenoviral PLD1 expression in Pld1−/− hepatocytes, confirming that lysosomal PA produced by PLD1 regulates autophagy. Notably, PLD1 expression in Pld1−/− liver significantly reduced hepatic lipid accumulation, compared with Pld1−/− liver. Thus, PLD1 plays an important role in hepatic steatosis via the regulation of autophagy.

The Roles of β-Oxidation and Cofactor Homeostasis in Peroxisome Distribution and Function in Arabidopsis thaliana.

Key steps of essential metabolic pathways are housed in plant peroxisomes. We conducted a microscopy-based screen for anomalous distribution of peroxisomally targeted fluorescence in Arabidopsis thaliana This screen uncovered 34 novel alleles in 15 genes affecting oil body mobilization, fatty acid β-oxidation, the glyoxylate cycle, peroxisome fission, and pexophagy. Partial loss-of-function of lipid-mobilization enzymes conferred peroxisomes clustered around retained oil bodies without other notable defects, suggesting that this microscopy-based approach was sensitive to minor perturbations, and that fatty acid β-oxidation rates in wild type are higher than required for normal growth. We recovered three mutants defective in PECTIN METHYLESTERASE31, revealing an unanticipated role in lipid mobilization for this cytosolic enzyme. Whereas mutations reducing fatty acid import had peroxisomes of wild-type size, mutations impairing fatty acid β-oxidation displayed enlarged peroxisomes, possibly caused by excess fatty acid β-oxidation intermediates in the peroxisome. Several fatty acid β-oxidation mutants also displayed defects in peroxisomal matrix protein import. Impairing fatty acid import reduced the large size of peroxisomes in a mutant defective in the PEROXISOMAL NAD+ TRANSPORTER (PXN), supporting the hypothesis that fatty acid accumulation causes pxn peroxisome enlargement. The diverse mutants isolated in this screen will aid future investigations of the roles of β-oxidation and peroxisomal cofactor homeostasis in plant development.

Acute administration of 3,5-diiodo-L-thyronine to hypothyroid rats stimulates bioenergetic parameters in liver mitochondria.

The role of 3,5-diiodo-L-thyronine (T2), initially considered only a 3,3',5-triiodo-L-thyronine (T3) catabolite, in the bioenergetic metabolism is of growing interest. In this study we investigated the acute effects (within 1h) of T2 administration to hypothyroid rats on liver mitochondria fatty acid uptake and β-oxidation rate, mitochondrial efficiency (by measuring proton leak) and mitochondrial oxidative damage (by determining H2O2 release). Fatty acid uptake into mitochondria was measured assaying carnitine palmitoyl transferase (CPT) I and II activities, and fatty acid β-oxidation using palmitoyl-CoA as a respiratory substrate. Mitochondrial fatty acid pattern was defined by gas-liquid chromatography. In hypothyroid + T2 vs hypothyroid rats we observed a raise in the serum level of nonesterified fatty acids (NEFA), in the mitochondrial CPT system activity and in the fatty acid β-oxidation rate. A parallel increase in the respiratory chain activity, mainly from succinate, occurs. When fatty acids are chelated by bovine serum albumin, a T2-induced increase in both state 3 and state 4 respiration is observed, while, when fatty acids are present, mitochondrial uncoupling occurs together with increased proton leak, responsible for mitochondrial thermogenesis. T2 administration decreases mitochondrial oxidative stress as determined by lower H2O2 production. We conclude that in rat liver mitochondria T2 acutely enhances the rate of fatty acid β-oxidation, and the activity of the downstream respiratory chain. The T2-induced increase in proton leak may contribute to mitochondrial thermogenesis and to the reduction of oxidative stress. Our results strengthen the previously reported ability of T2 to reduce adiposity, dyslipidemia and to prevent liver steatosis.

Aerobic capacity and hepatic mitochondrial lipid oxidation alters susceptibility for chronic high-fat diet-induced hepatic steatosis.

Rats selectively bred for high capacity running (HCR) or low capacity running (LCR) display divergence for intrinsic aerobic capacity and hepatic mitochondrial oxidative capacity, both factors associated with susceptibility for nonalcoholic fatty liver disease. Here, we tested if HCR and LCR rats display differences in susceptibility for hepatic steatosis after 16 wk of high-fat diets (HFD) with either 45% or 60% of kcals from fat. HCR rats were protected against HFD-induced hepatic steatosis, whereas only the 60% HFD induced steatosis in LCR rats, as marked by a doubling of liver triglycerides. Hepatic complete fatty acid oxidation (FAO) and mitochondrial respiratory capacity were all lower in LCR compared with HCR rats. LCR rats also displayed lower hepatic complete and incomplete FAO in the presence of etomoxir, suggesting a reduced role for noncarnitine palmitoyltransferase-1-mediated lipid catabolism in LCR versus HCR rats. Hepatic complete FAO and mitochondrial respiration were largely unaffected by either chronic HFD; however, 60% HFD feeding markedly reduced 2-pyruvate oxidation, a marker of tricarboxylic acid (TCA) cycle flux, and mitochondrial complete FAO only in LCR rats. LCR rats displayed lower levels of hepatic long-chain acylcarnitines than HCR rats but maintained similar levels of hepatic acetyl-carnitine levels, further supporting lower rates of β-oxidation, and TCA cycle flux in LCR than HCR rats. Finally, only LCR rats displayed early reductions in TCA cycle genes after the acute initiation of a HFD. In conclusion, intrinsically high aerobic capacity confers protection against HFD-induced hepatic steatosis through elevated hepatic mitochondrial oxidative capacity.

Acetylation and succinylation contribute to maturational alterations in energy metabolism in the newborn heart.

Dramatic maturational changes in cardiac energy metabolism occur in the newborn period, with a shift from glycolysis to fatty acid oxidation. Acetylation and succinylation of lysyl residues are novel posttranslational modifications involved in the control of cardiac energy metabolism. We investigated the impact of changes in protein acetylation/succinylation on the maturational changes in energy metabolism of 1-, 7-, and 21-day-old rabbit hearts. Cardiac fatty acid β-oxidation rates increased in 21-day vs. 1- and 7-day-old hearts, whereas glycolysis and glucose oxidation rates decreased in 21-day-old hearts. The fatty acid oxidation enzymes, long-chain acyl-CoA dehydrogenase (LCAD) and β-hydroxyacyl-CoA dehydrogenase (β-HAD), were hyperacetylated with maturation, positively correlated with their activities and fatty acid β-oxidation rates. This alteration was associated with increased expression of the mitochondrial acetyltransferase, general control of amino acid synthesis 5 like 1 (GCN5L1), since silencing GCN5L1 mRNA in H9c2 cells significantly reduced acetylation and activity of LCAD and β-HAD. An increase in mitochondrial ATP production rates with maturation was associated with the decreased acetylation of peroxisome proliferator-activated receptor-γ coactivator-1α, a transcriptional regulator for mitochondrial biogenesis. In addition, hypoxia-inducible factor-1α, hexokinase, and phosphoglycerate mutase expression declined postbirth, whereas acetylation of these glycolytic enzymes increased. Phosphorylation rather than acetylation of pyruvate dehydrogenase (PDH) increased in 21-day-old hearts, accounting for the low glucose oxidation postbirth. A maturational increase was also observed in succinylation of PDH and LCAD. Collectively, our data are the first suggesting that acetylation and succinylation of the key metabolic enzymes in newborn hearts play a crucial role in cardiac energy metabolism with maturation.

Nitrate enhances skeletal muscle fatty acid oxidation via a nitric oxide-cGMP-PPAR-mediated mechanism.

BackgroundInsulin sensitivity in skeletal muscle is associated with metabolic flexibility, including a high capacity to increase fatty acid (FA) oxidation in response to increased lipid supply. Lipid overload, however, can result in incomplete FA oxidation and accumulation of potentially harmful intermediates where mitochondrial tricarboxylic acid cycle capacity cannot keep pace with rates of β-oxidation. Enhancement of muscle FA oxidation in combination with mitochondrial biogenesis is therefore emerging as a strategy to treat metabolic disease. Dietary inorganic nitrate was recently shown to reverse aspects of the metabolic syndrome in rodents by as yet incompletely defined mechanisms.ResultsHerein, we report that nitrate enhances skeletal muscle FA oxidation in rodents in a dose-dependent manner. We show that nitrate induces FA oxidation through a soluble guanylate cyclase (sGC)/cGMP-mediated PPARβ/δ- and PPARα-dependent mechanism. Enhanced PPARβ/δ and PPARα expression and DNA binding induces expression of FA oxidation enzymes, increasing muscle carnitine and lowering tissue malonyl-CoA concentrations, thereby supporting intra-mitochondrial pathways of FA oxidation and enhancing mitochondrial respiration. At higher doses, nitrate induces mitochondrial biogenesis, further increasing FA oxidation and lowering long-chain FA concentrations. Meanwhile, nitrate did not affect mitochondrial FA oxidation in PPARα−/− mice. In C2C12 myotubes, nitrate increased expression of the PPARα targets Cpt1b, Acadl, Hadh and Ucp3, and enhanced oxidative phosphorylation rates with palmitoyl-carnitine; however, these changes in gene expression and respiration were prevented by inhibition of either sGC or protein kinase G. Elevation of cGMP, via the inhibition of phosphodiesterase 5 by sildenafil, also increased expression of Cpt1b, Acadl and Ucp3, as well as CPT1B protein levels, and further enhanced the effect of nitrate supplementation.ConclusionsNitrate may therefore be effective in the treatment of metabolic disease by inducing FA oxidation in muscle.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0221-6) contains supplementary material, which is available to authorized users.

Peroxisomal Pex11 is a pore-forming protein homologous to TRPM channels

More than 30 proteins (Pex proteins) are known to participate in the biogenesis of peroxisomes—ubiquitous oxidative organelles involved in lipid and ROS metabolism. The Pex11 family of homologous proteins is responsible for division and proliferation of peroxisomes. We show that yeast Pex11 is a pore-forming protein sharing sequence similarity with TRPM cation-selective channels. The Pex11 channel with a conductance of Λ=4.1nS in 1.0M KCl is moderately cation-selective (PK+/PCl−=1.85) and resistant to voltage-dependent closing. The estimated size of the channel's pore (r~0.6nm) supports the notion that Pex11 conducts solutes with molecular mass below 300–400Da. We localized the channel's selectivity determining sequence. Overexpression of Pex11 resulted in acceleration of fatty acids β-oxidation in intact cells but not in the corresponding lysates. The β-oxidation was affected in cells by expression of the Pex11 protein carrying point mutations in the selectivity determining sequence. These data suggest that the Pex11-dependent transmembrane traffic of metabolites may be a rate-limiting step in the β-oxidation of fatty acids. This conclusion was corroborated by analysis of the rate of β-oxidation in yeast strains expressing Pex11 with mutations mimicking constitutively phosphorylated (S165D, S167D) or unphosphorylated (S165A, S167A) protein. The results suggest that phosphorylation of Pex11 is a mechanism that can control the peroxisomal β-oxidation rate.Our results disclose an unexpected function of Pex11 as a non-selective channel responsible for transfer of metabolites across peroxisomal membrane. The data indicate that peroxins may be involved in peroxisomal metabolic processes in addition to their role in peroxisome biogenesis.

Activating PPARα prevents post-ischemic contractile dysfunction in hypertrophied neonatal hearts.

Post-ischemic contractile dysfunction is a contributor to morbidity and mortality after the surgical correction of congenital heart defects in neonatal patients. Pre-existing hypertrophy in the newborn heart can exacerbate these ischemic injuries, which may partly be due to a decreased energy supply to the heart resulting from low fatty acid β-oxidation rates. We determined whether stimulating fatty acid β-oxidation with GW7647, a peroxisome proliferator-activated receptor-α (PPARα) activator, would improve cardiac energy production and post-ischemic functional recovery in neonatal rabbit hearts subjected to volume overload-induced cardiac hypertrophy. Volume-overload cardiac hypertrophy was produced in 7-day-old rabbits via an aorto-caval shunt, after which, the rabbits were treated with or without GW7647 (3 mg/kg per day) for 14 days. Biventricular working hearts were subjected to 35 minutes of aerobic perfusion, 25 minutes of global no-flow ischemia, and 30 minutes of aerobic reperfusion. GW7647 treatment did not prevent the development of cardiac hypertrophy, but did prevent the decline in left ventricular ejection fraction in vivo. GW7647 treatment increased cardiac fatty acid β-oxidation rates before and after ischemia, which resulted in a significant increase in overall ATP production and an improved in vitro post-ischemic functional recovery. A decrease in post-ischemic proton production and endoplasmic reticulum stress, as well as an activation of sarcoplasmic reticulum calcium ATPase isoform 2 and citrate synthase, was evident in GW7647-treated hearts. Stimulating fatty acid β-oxidation in neonatal hearts may present a novel cardioprotective intervention to limit post-ischemic contractile dysfunction.

The loss of function of PhaC1 is a survival mechanism that counteracts the stress caused by the overproduction of poly‐3‐hydroxyalkanoates in Pseudomonas putidaΔfadBA

The poly-3-hydroxylkanoate (PHA)-overproducing mutant Pseudomonas putida U ΔfadBA (PpΔfadBA) lacks the genes encoding the main β-oxidation pathway (FadBA). This strain accumulates enormous amounts of bioplastics when cultured in chemically defined media containing PHA precursors (different n-alkanoic or n-aryl-alkanoic acids) and an additional carbon source. In medium containing glucose or 4-hydroxy-phenylacetate, the mutant does not accumulate PHAs and grows just as the wild type (P. putida U). However, when the carbon source is octanoate, growth is severely impaired, suggesting that in PpΔfadBA, the metabolic imbalance resulting from a lower rate of β-oxidation, together with the accumulation of bioplastics, causes severe physiological stress. Here, we show that PpΔfadBA efficiently counteracts this latter effect via a survival mechanism involving the introduction of spontaneous mutations that block PHA accumulation. Surprisingly, genetic analyses of the whole pha cluster revealed that these mutations occurred only in the gene encoding one of the polymerases (phaC1) and that the loss of PhaC1 function was enough to prevent PHA synthesis. The influence of these mutations on the structure of PhaC1 and the existence of a protein-protein (PhaC1-PhaC2) interaction that explains the functionality of the polymerization system are discussed herein.

Foetal life protein provision of mink (Neovison vison) changes the relative mRNA abundance of some hepatic enzymes regulating fat metabolism

The nutrient provision to pregnant females has high impact on the growth and metabolism of their offspring. The objective was to investigate if the expression of hepatic enzymes regulating the fat metabolism was affected in foetuses and adult female mink born by dams fed either a low or an adequate level of protein during late gestation. The relative abundances of acetyl coenzyme A carboxylase (ACC), fatty acid synthase (FAS) and carnitine palmitoyl transferase 1 (CPT1) mRNA were determined by qualitative polymerase chain reaction in the livers of F0- and F1-generation dams and in F1-generation foetuses. Low protein provision during foetal life resulted in a lower expression of FAS in foetal liver but a tendency towards increased expression in the liver of adult dams. There was a tendency towards an effect of life stage of the animal on the expression of ACC resulting in a higher expression among F1 foetuses exposed to low protein during foetal life than F0 dams fed a low protein diet during late gestation. The expression of CPT1 was significantly lower among dams exposed to low protein provision during foetal life than controls, possibly indicating a lower rate of mitochondrial β-oxidation. Further investigations are needed to clarify the consequences of these changes for the fat metabolism.

Lipid accumulation is ahead of epithelial-to-mesenchymal transition and therapeutic intervention by acetyl-CoA carboxylase 2 silence in diabetic nephropathy

ObjectiveThe study investigated the relationship between epithelial-to-mesenchymal transition (EMT) and lipotoxicity in diabetic nephropathy as well as the protective effect of acetyl-CoA carboxylase 2 (ACC2) silence. MethodsHigh glucose (30mmol/L) cultured human proximal tubular epithelial cells (HK-2 cells) were used. Triglyceride content, fatty acid β-oxidation rate, malonyl CoA content, and marker proteins of EMT, including E-cadherin (E-cad), α-smooth muscle actin (α-SMA) and transforming grow factor-β (TGF-β), were assessed. Silence of ACC2 was achieved by ACC2-shRNA lentivirus transfection. ResultsIn cultured human proximal tubular cells, high glucose induced fatty acid deposit before phenotypical and morphological changes of EMT. At 48h, more triglyceride content, more malonyl CoA content and lower fatty acid β-oxidation rate were detected. However, increased expression of TGF-β, accompanied by loss of E-cad and acquisition of α-SMA, was observed at 98h but not at 48h. The silence of ACC2 in HK-2 cells led to restored cell morphology with less lipid deposition and less malonyl-CoA content, which resulted from faster β-oxidation rate. ConclusionThe progress of lipotoxicity participates in the development of diabetic nephropathy in early stage before EMT. The manipulation of lipid metabolism might act as a promising therapeutic intervention for diabetic nephropathy.

Elaidate, an 18‐Carbon trans‐Monoenoic Fatty Acid, Inhibits β‐Oxidation in Human Peripheral Blood Macrophages

Consumption of trans-unsaturated fatty acids promotes atherosclerosis, but whether degradation of fats in macrophages is altered by trans-unsaturated fatty acids is unknown. We compared the metabolism of oleate (C18:1Δ9-10 cis; (Z)-octadec-9-enoate), elaidate (C18:Δ9-10 trans; (E)-octadec-9-enoate), and stearate (C18:0, octadecanoate) in adherent peripheral human macrophages. Metabolism was followed by measurement of acylcarnitines in cell supernatants by MS/MS, determination of cellular fatty acid content by GC/MS, and assessment of β-oxidation rates using radiolabeled fatty acids. Cells incubated for 44 h in 100 µM elaidate accumulated more unsaturated fatty acids, including both longer- and shorter-chain, and had reduced C18:0 relative to those incubated with oleate or stearate. Both C12:1 and C18:1 acylcarnitines accumulated in supernatants of macrophages exposed to trans fats. These results suggested β-oxidation inhibition one reaction proximal to the trans bond. Comparison of [1-(14)C]oleate to [1-(14)C]elaidate catabolism showed that elaidate completed the first round of fatty acid β-oxidation at rates comparable to oleate. Yet, in competitive β-oxidation assays with [9,10-(3)H]oleate, tritium release rate decreased when unlabeled oleate was replaced by the same quantity of elaidate. These data show specific inhibition of monoenoic fat catabolism by elaidate that is not shared by other atherogenic fats.

Impaired Very Long-chain Acyl-CoA β-Oxidation in Human X-linked Adrenoleukodystrophy Fibroblasts Is a Direct Consequence of ABCD1 Transporter Dysfunction

X-linked adrenoleukodystrophy (X-ALD), an inherited peroxisomal disorder, is caused by mutations in the ABCD1 gene encoding the peroxisomal ATP-binding cassette (ABC) transporter ABCD1 (adrenoleukodystrophy protein, ALDP). Biochemically, X-ALD is characterized by an accumulation of very long-chain fatty acids and partially impaired peroxisomal β-oxidation. In this study, we used primary human fibroblasts from X-ALD and Zellweger syndrome patients to investigate the peroxisomal β-oxidation defect. Our results show that the degradation of C26:0-CoA esters is as severely impaired as degradation of unesterified very long-chain fatty acids in X-ALD and is abolished in Zellweger syndrome. Interestingly, the β-oxidation rates for both C26:0-CoA and C22:0-CoA were similarly affected, although C22:0 does not accumulate in patient fibroblasts. Furthermore, we show that the β-oxidation defect in X-ALD is directly caused by ABCD1 dysfunction as blocking ABCD1 function with a specific antibody reduced β-oxidation to levels observed in X-ALD fibroblasts. By quantification of mRNA and protein levels of the peroxisomal ABC transporters and by blocking with specific antibodies, we found that residual β-oxidation activity toward C26:0-CoA in X-ALD fibroblasts is mediated by ABCD3, although the efficacy of ABCD3 appeared to be much lower than that of ABCD1. Finally, using isolated peroxisomes, we show that β-oxidation of C26:0-CoA is independent of additional CoA but requires a cytosolic factor of >10-kDa molecular mass that is resistant to N-ethylmaleimide and heat inactivation. In conclusion, our findings in human cells suggest that, in contrast to yeast cells, very long-chain acyl-CoA esters are transported into peroxisomes by ABCD1 independently of additional synthetase activity.

Silent information regulator 1 inhibition induces lipid metabolism disorders of hepatocytes and enhances hepatitis C virus replication

Hepatic steatosis is an important histopathological feature of chronic hepatitis C virus (HCV) infection. Silent information regulator 1 (SIRT1) plays key role in regulation of hepatic lipid metabolism. We investigated the possible effect of HCV replication on lipid metabolism of hepatocytes and expression of SIRT1 using Huh-7.5 cells harboring HCV replicon. The level of reactive oxygen species (ROS) and malondialdehyde (MDA), the activity of superoxide dismutase (SOD), and the value of nicotinamide adenine dinucleotide (NAD(+) )/NADH was detected. The level of triacylglycerol (TG), total cholesterol (TC) and fatty acid β-oxidation rate was detected. The activity and expression levels of SIRT1 and expression of its downstream lipid-metabolism genes were measured. In replicon cells, the level of ROS and MDA increased, SOD activity and the value of NAD(+) /NADH decreased, then the activity and expression level of mRNA and protein of SIRT1 reduced. Inhibition of SIRT1 decreased phosphorylation of forkhead box O1 (FoxO1), which not only upregulated SREBP-1c, FAS, ACC, SREBP-2, HMGR and HMGS genes and increased fatty acid synthesis; but also downregulated PPAR-α and CPT1A genes and decreased fatty acid β-oxidation. Interferon treatment restored aforementioned changes. SIRT1 activator improved lipid metabolism disorders by an increase in fatty acid β-oxidation and a decrease in TG and TC synthesis and inhibited HCV replication. HCV replication decreasing NAD(+) /NADH ratio may downregulate the activity and the expression of SIRT1, then change the expression profile of lipid metabolism-related genes, thereby cause lipid metabolism disorders of hepatocytes and promote HCV replication. Treatment with SIRT1 activator ameliorates lipid metabolic disorders and inhibits HCV replication.

Abstract IA30: Metabolic symbiosis: The contribution of adipocytes to visceral metastasis

Abstract Many tumor types (gastric, breast, colon, renal, and ovarian) grow in the anatomical vicinity of adipose tissue and are known to reprogram adjacent normal adipocytes into cancer-associated adipocytes (CAA). Clinical observations indicate that the most common, as well as the largest, site of ovarian cancer (OvCa) metastasis is the omentum, a large fat pad (20x12x3cm) positioned in front of the bowel. The omentum, which is primarily composed of adipocytes, provides energy storage and functions as an endocrine organ. Because cancer cell behavior is highly dependent on the microenvironment, and adipocytes are a major source of energy-dense fatty acids, we hypothesized that adipocytes promote OvCa omental metastasis and growth via altered lipid metabolism. To investigate this hypothesis, primary human visceral adipocytes were cultured from omental tissue specimens collected from patients who underwent surgical procedures for benign conditions. The rate of β-oxidation was assessed by a radioisotopic assay using 3H-palmitate. Sections of human serous ovarian carcinomas and corresponding omental metastases were utilized for immunohistochemistry, RT-PCR, and a reverse-phase protein array. Homozygous fatty acid binding protein 4 (FAPB4)-null mice or wild-type (WT) animals were inoculated orthotopically or intraperitoneally with mouse OvCa cells. Adipocytes were found to promote the invasion, migration, and proliferation of OvCa cells. The homing of OvCa towards adipocytes in vitro, or to the mouse omentum in vivo, was reduced by using inhibitory antibodies against interleukin (IL)-6,IL-8, or their receptors. Co-culture of OvCa cells with adipocytes resulted in cytoplasmic lipid accumulation in OvCa cells, which was a consequence of direct lipid transfer from the adipocytes. Co-injection of SKOV3ip1 OvCa cells with adipocytes enhanced tumor growth in mice, when compared to the injection of SKOV3ip1 cells alone. Moreover, lipolysis was activated in co-cultured adipocytes as evidenced by the secretion of free fatty acids and glycerol. FABP4 was found to be highly expressed in omental metastatic tissues as compared to the respective primary OvCa tumor tissue. When mouse OvCa cells were injected under the ovarian bursa of FABP4 knock-out mice the number of metastases was significantly lower than in WT mice. Treatment with a FABP4 inhibitor also induced apoptosis and inhibited migration and invasion of OvCa cells. The fatty acid translocase (FAT/CD36) was identified as the fatty acid transporter responsible for lipid accumulation in cancer cells co-cultured with adipocytes. Our results suggest that adipocytes advance the progression of OvCa through two major mechanisms: (1) They promote metastasis to the omentum via the secretion of cytokines, and (2) They support cancer cell proliferation by activating lipolysis, thereby mobilizing energy-dense fatty acids which are utilized by the cancer cells in an energy-yielding β-oxidation pathway through a FABP4 and FAT/CD36 dependent mechanism. By better understanding these mechanisms and, more generally, the biology of adipocytes in the tumor microenvironment, we will be able to identify metabolic targets and, ultimately, introduce new compounds for the treatment of cancer. Citation Format: Kristin Nieman, Andras Ladanyi, Ernst Lengyel. Metabolic symbiosis: The contribution of adipocytes to visceral metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr IA30.

Effect of an electric field on n-hexadecane microbial degradation in contaminated soil

This paper describes the development of an innovative process that combines electrokinetics and bioremediation for degrading aliphatic hydrocarbons, which are major constituents of total petroleum hydrocarbons (TPHs) in contaminated soils. Soil microcosms were spiked with a model pollutant of n-hexadecane at approximately 1.0% (v/w), and cultured with a mixture of petroleum-utilizing bacteria at about 107–108CFUg−1, before being subjected to a constant voltage gradient of 1.3Vcm−1 for 42 days. The degradation rate of n-hexadecane in electro-bioremediation was up to 53.7%, representing an increase of 20.3% compared to bioremediation without an electric field. n-Hexadecanoic acid was the sole intermediate product detected and this firmly suggested that the degradation pathway of n-hexadecane in the electric field was monoterminal oxidation. The fate of n-hexadecanoic acid was supposed to be intracellular β-oxidation, and the β-oxidation rate in electro-bioremediation was 2.2 times of that of bioremediation. The results indicate that the advantage of an electric field in n-alkane degradation is the speed-up effect on β-oxidation of the corresponding alkanoic acid. Both the monoterminal oxidation of n-hexadecane and the β-oxidation of n-hexadecanoic acid were enhanced by the electric field, which suggests electrokinetics is a good approach for aliphatic hydrocarbons remediation.

Fatty acid metabolism in European sea bass (Dicentrarchus labrax): effects of n-6 PUFA and MUFA in fish oil replaced diets

Monounsaturated fatty acids (MUFA)-rich and n-6 polyunsaturated fatty acid (n-6 PUFA)-rich vegetable oils are increasingly used as fish oil replacers for aquafeed formulation. The present study investigated the fatty acid metabolism in juvenile European sea bass (Dicentrarchus labrax, 38.4 g) fed diets containing fish oil (FO, as the control treatment) or two different vegetable oils (the MUFA-rich canola/rapeseed oil, CO; and the n-6 PUFA-rich cottonseed oil, CSO) tested individually or as a 50/50 blend (CO/CSO). The whole-body fatty acid balance method was used to deduce the apparent in vivo fatty acid metabolism. No effect on growth performance and feed utilization was recorded. However, it should be noted that the fish meal content of the experimental diets was relatively high, and thus the requirement for n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) may have likely been fulfilled even if dietary fish oil was fully replaced by vegetable oils. Overall, relatively little apparent in vivo fatty acid bioconversion was recorded, whilst the apparent in vivo β-oxidation of dietary fatty acid was largely affected by the dietary lipid source, with higher rate of β-oxidation for those fatty acids which were provided in dietary surplus. The deposition of 20:5n-3 and 22:6n-3, as % of the dietary intake, was greatest for the fish fed on the CSO diet. It has been shown that European sea bass seems to be able to efficiently use n-6 PUFA for energy substrate, and this may help in minimizing the β-oxidation of the health benefiting n-3 LC-PUFA and thus increase their deposition into fish tissues.

Genistein reduced insulin resistance index through modulating lipid metabolism in ovariectomized rats

Postmenopausal women are at higher risk for obesity and insulin resistance due to the decline of estrogen, but genistein, a phytoestrogen, may reduce the risks of these diet-related diseases. In this study, we hypothesized that supplemental genistein has beneficial effects on insulin resistance in an ovariectomized rat model by modulating lipid metabolism. Three weeks after a sham surgery (sham) or an ovariectomy (OVX), ovariectomized Sprague-Dawley rats were placed on a diet containing 0 (OVX group) or 0.1% genistein for 4 weeks. The sham rats were fed a high-fat diet containing 0% genistein and served as the control group (sham group). The ovariectomized rats showed increases in body weight and insulin resistance index, but genistein reduced insulin resistance index and the activity of hepatic fatty acid synthetase. Genistein was also associated with increased activity of succinate dehydrogenase and carnitine palmitoyltransferase and the rate of β-oxidation in the fat tissue of rats. The ovariectomized rats given genistein had smaller-sized adipocytes. Using gene-set enrichment analysis (GSEA) of microarray data, we found that a number of gene sets of fatty acid metabolism, insulin resistance, and oxidative stress were differentially expressed by OVX and reversed by genistein. This systemic approach of GSEA enables the identification of such consensus between the gene expression changes and phenotypic changes caused by OVX and genistein supplementation. Genistein treatment could help reduce insulin resistance through the amelioration of OVX-induced metabolic dysfunction, and the GSEA approach may be useful in proposing putative targets related to insulin resistance.

Estrogen receptor beta interacts and colocalizes with HADHB in mitochondria

Estrogen receptors are localized in mitochondria, but their functions in this organelle remain unclear. We previously found that ERα interacted with mitochondrial protein HADHB and affected the thiolytic cleavage activity of HADHB in β-oxidation. It is known that ERβ binds to ERα. In addition, ERβ is predominately located in mitochondria. These facts led us to speculate that ERβ may also be associated with HADHB in mitochondria. In order to test this hypothesis, we performed co-immunoprecipitation and confocal microscopy analyses with human breast cancer MCF7 cells. The results demonstrated that ERβ was indeed associated and colocalized with HADHB within mitochondria. Interestingly, in contrast to the stimulatory effect of ERα on HADHB enzyme activity observed in the previous study, silencing of ERβ enhanced the enzyme activity of HADHB in the present study, suggesting that ERβ plays an inhibitory role in HADHB enzyme activity in the breast cancer cells. Our results imply that ERα and ERβ may differentially affect cellular oxidative stress through influencing the rate of β-oxidation of fatty acids in breast cancer cells.

MitoNEET-driven alterations in adipocyte mitochondrial activity reveal a crucial adaptive process that preserves insulin sensitivity in obesity

We examined mouse models with altered adipocyte expression of mitoNEET, a protein residing in the mitochondrial outer membrane, to probe its impact on mitochondrial function and subsequent cellular responses. We found that overexpression of mitoNEET enhances lipid uptake and storage, leading to an expansion of the mass of adipose tissue. Despite the resulting massive obesity, benign aspects of adipose tissue expansion prevail, and insulin sensitivity is preserved. Mechanistically, we also found that mitoNEET inhibits mitochondrial iron transport into the matrix and, because iron is a rate-limiting component for electron transport, lowers the rate of β-oxidation. This effect is associated with a lower mitochondrial membrane potential and lower levels of reactive oxygen species-induced damage, along with increased production of adiponectin. Conversely, a reduction in mitoNEET expression enhances mitochondrial respiratory capacity through enhanced iron content in the matrix, ultimately corresponding to less weight gain on a high-fat diet. However, this reduction in mitoNEET expression also causes heightened oxidative stress and glucose intolerance. Thus, manipulation of mitochondrial function by varying mitoNEET expression markedly affects the dynamics of cellular and whole-body lipid homeostasis.