acyl-CoA Oxidase Activity Research Articles

Differential effects of high MUFA with high or low P/S ratio (polyunsaturated to saturated fatty acids) on improving hepatic lipolytic enzymes and mediating PPARγ related with lipoprotein lipase and hormone-sensitive lipase of white adipose tissue in diet-induced obese hamster

The aim of this study was to assess the relationship between high monounsaturated fatty acids (MUFAs) with different levels of polyunsaturated-to-saturated fatty acid (P/S) ratios and body fat loss in diet-induced obesity (DIO) models. Male Golden Syrian hamsters were randomly assigned to the control group (n=12) and obesity group (n=24) for 4 weeks of the high-fat DIO period; afterward, six hamsters from each group were killed. The remaining control hamsters were still fed a low-fat diet. For an additional 8 weeks, the remaining obesity hamsters were switched to a low-fat diet and subdivided into three subgroups (n=6/group): the obesity-control (ObC) group, high MUFA with high P/S ratio oil (HMHR) group and olive oil (OO) group. Serum insulin and leptin concentrations were measured, and hepatic fatty acid metabolic enzymes and adipose differentiation markers were determined using enzyme activities analysis, western blot and semiquantification reverse-transcription PCR. No difference was observed in the mean energy intake through all study periods. After the DIO period, the obesity group increased in weight gain and epididymal fat weight compared with the control group. DIO hamsters in the HMLR group had significant reductions in white adipose tissue deposition and plasma leptin levels, suppression in adipose peroxisome proliferator-activated receptor-γ (PPARγ) and lipoprotein lipase (LPL) mRNA expressions and increases in hepatic acyl-CoA oxidase and carnitine palmitoyltransferase-I activities and mRNA levels compared with those in the ObC group. The HMHR group had upregulated phosphorylation of hormone-sensitive lipase (HSL) relative to total HSL protein levels compared with the OO group. However, the OO group had significantly elevated hepatic de novo lipogenesis compared with the HMHR group. HMHR seemed to be beneficial in depleting white adipose tissue accumulation by decreasing adipose PPARγ and LPL mRNA expressions and mediating phosphorylation of HSL, and by improving hepatic lipolytic enzyme activities and mRNA expressions involved in β-oxidation in DIO hamsters.

FPTIII Mitigates Peroxisome-Mediated Oxidative Stress in Kidneys of Spontaneously Hypertensive Diabetic Rats

Aim: Peroxisomes are known to play a role in cellular oxidative stress during pathogenesis of diabetes and hypertension. We reported earlier that FPTIII (a farnesyl protein transferase inhibitor) attenuates ischemia-reperfusion injury and renal dysfunction in diabetic hypertensive (DH) rats. In this study, we have examined the effect of FPTIII on peroxisomal enzymes in relation to oxidative stress in kidneys of DH rats. Methods: Male Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats were treated with streptozotocin (STZ) and/or FPTIII. Activities of key peroxisomal enzymes, catalase, acyl-CoA oxidase and β-oxidation of lignoceric acid were measured in kidney homogenates. Lipid peroxidation in kidney was measured by malondialdehyde (MDA) assay. Results: Catalase activity was significantly (p < 0.01) reduced in diabetic WKY or SHR, and FPTIII markedly attenuated (p < 0.01) diabetes-induced inhibition of catalase. FPTIII also reduced STZ-induced increase in acyl-CoA oxidase activity. Fatty acid β-oxidation and lipid peroxides were significantly increased in kidneys of DH rats. FPTIII reduced (p < 0.01) diabetes and hypertension-induced increase in fatty acid oxidation and lipid peroxides. Conclusion: Our results suggest that farnesyl transferase inhibition modulates peroxisome enzyme activities and alleviates oxidative stress, thus providing a possible mechanism for reported FPTIII-mediated protection against renal dysfunction in DH rats.

Effect of dietary protamine on lipid metabolism in rats.

Protamine has been widely used as a pharmaceutical product and natural food preservative. However, few studies have been conducted to assess the beneficial function of dietary protamine. This study examined the effects of dietary salmon protamine on serum and liver lipid levels and the expression levels of genes encoding proteins involved in lipid homeostasis in the liver of rats. Groups of male Wistar rats were fed AIN93G diet containing 2% or 5% protamine. After 4 weeks of feeding these diets, markedly decreased serum and liver cholesterol (CHOL) and triacylglycerol levels were noted. Increased activity of liver carnitine palmitoyltransferase-2 and acyl-CoA oxidase, which are key enzymes of fatty acid β-oxidation in the mitochondria and peroxisomes, was found in rats fed on protamine. Furthermore, rats fed protamine showed enhanced fecal excretion of CHOL and bile acid and increased liver mRNA expression levels of ATP-binding cassette (ABC) G5 and ABCG8, which form heterodimers and play a major role in the secretion of CHOL into bile. The decrease in triacylglycerol levels in protamine-fed rats was due to the enhancement of liver β-oxidation. Furthermore, rats fed protamine exhibited decreased CHOL levels through the suppression of CHOL and bile acid absorption and the enhancement of CHOL secretion into bile. These results suggest that dietary protamine has beneficial effects that may aid in the prevention of lifestyle-related diseases such as hyperlipidemia and atherosclerosis.

Hormone Excretion and Peroxisomes of Human Immortalized Extravillous Trophoblast Cells (TCL-2) Derived from First-Trimester Placenta

We studied the hormone excretion of human immortalized extravillous trophoblast cells (TCL-2, first-trimester cells) and determined whether peroxisomes are present in TCL-2. The results of TCL-2 were compared with those of TCL-1 (third-trimester cells). Morphologically, TCL-2 cells were fibroblast-like, and the growth rate of TCL-2 was slower than that of TCL-1 during 3 days culture. Progesterone was detected in the medium of TCL-2, and its concentration was approximately one-tenth of that in TCL-1. The activity of the peroxisomal marker enzyme catalase was detected in the TCL-2 homogenate, and it was about one-third the level of that in TCL-1. Fatty acyl-CoA oxidase activity was detected in TCL-2, and it was about one-seventh the level of that in TCL-1. On the other hand, human chorionic gonadotropin (hCG) was detected in the medium of TCL-2, and its concentration after 3 days of culture was about 2-fold that in TCL-1. Using the diaminobenzidine (DAB) method, peroxisomes were found in TCL-2, but only a very small amount of catalase was detected. These results indicate that human immortalized extravillous trophoblast cells (TCL-2) synthesize, secrete hCG and progesterone, and may contain peroxisomes. Because extravillous trophoblast cells are difficult to obtain from the first-trimester placenta, TCL-2 cells are useful for the study of the physiologic functions (including peroxisomal function) of first-trimester cells.

Subacute exposure to N-ethyl perfluorooctanesulfonamidoethanol results in the formation of perfluorooctanesulfonate and alters superoxide dismutase activity in female rats

Perfluorooctanesulfonamides, such as N-ethyl perfluorooctanesulfonamidoethanol (N-EtFOSE), are large scale industrial chemicals but their disposition and toxicity are poorly understood despite significant human exposure. The hypothesis that subacute exposure to N-EtFOSE, a weak peroxisome proliferator, causes a redox imbalance in vivo was tested using the known peroxisome proliferator, ciprofibrate, as a positive control. Female Sprague-Dawley rats were treated orally with N-EtFOSE, ciprofibrate or corn oil (vehicle) for 21 days, and levels of N-EtFOSE and its metabolites as well as markers of peroxisome proliferation and oxidative stress were assessed in serum, liver and/or uterus. The N-EtFOSE metabolite profile in liver and serum was in good agreement with reported in vitro biotransformation pathways in rats and the metabolite levels decreasing in the order perfluorooctanesulfonate >> perfluorooctanesulfonamide ~ N-ethyl perfluorooctanesulfonamidoacetate >> perfluorooctanesulfonamidoethanol approximately N-EtFOSE. Although N-EtFOSE treatment significantly decreased the growth rate, increased relative liver weight and activity of superoxide dismutases (SOD) in liver and uterus (total SOD, CuZnSOD and MnSOD), a metabolic study revealed no differences in the metabolome in serum from N-EtFOSE-treated and control animals. Ciprofibrate treatment increased liver weight and peroxisomal acyl Co-A oxidase activity in the liver and altered antioxidant enzyme activities in the uterus and liver. According to NMR metabolomic studies, ciprofibrate treated animals had altered serum lipid profiles compared to N-EtFOSE-treated and control animals, whereas putative markers of peroxisome proliferation in serum were not affected. Overall, this study demonstrates the biotransformation of N-EtFOSE to PFOS in rats that is accompanied by N-EtFOSE-induced alterations in antioxidant enzyme activity.

Rats selectively bred for low aerobic capacity have reduced hepatic mitochondrial oxidative capacity and susceptibility to hepatic steatosis and injury

Fatty liver has been linked to low aerobic fitness, but the mechanisms are unknown. We previously reported a novel model in which rats were artificially selected to be high capacity runners (HCR) and low capacity runners (LCR) that in a sedentary condition have robustly different intrinsic aerobic capacities. We utilized sedentary HCR/LCR rats (generation 17; max running distance equalled 1514 +/- 91 vs. 200 +/- 12 m for HCR and LCR, respectively) to investigate if low aerobic capacity is associated with reduced hepatic mitochondrial oxidative capacity and increased susceptibility to hepatic steatosis. At 25 weeks of age, LCR livers displayed reduced mitochondrial content (reduced citrate synthase activity and cytochrome c protein) and reduced oxidative capacity (complete palmitate oxidation in hepatic mitochondria (1.15 +/- 0.13 vs. 2.48 +/- 1.1 nm g(-1) h, P < 0.0001) and increased peroxisomal activity (acyl CoA oxidase and catalase activity) compared to the HCR. The LCR livers also displayed a lipogenic phenotype with higher protein content of both sterol regulatory element binding protein-1c and acetyl CoA carboxylase. These differences were associated with hepatic steatosis in the LCR including higher liver triglycerides (6.00 +/- 0.71 vs. 4.20 +/- 0.39 nmol g(-1), P = 0.020 value), >2-fold higher percentage of hepatocytes associated with lipid droplets (54.0 +/- 9.2 vs. 22.0 +/- 3.5%, P = 0.006), and increased hepatic lipid peroxidation compared to the HCR. Additionally, in rats aged to natural death, LCR livers had significantly greater hepatic injury (fibrosis and apoptosis). We provide novel evidence that selection for low intrinsic aerobic capacity causes reduced hepatic mitochondrial oxidative capacity that increases susceptibility to both hepatic steatosis and liver injury.

Short-term oral toxicity of three biodiesels and an ultra-low sulfur diesel in male rats

Male rats were administered one of three biodiesels – soy oil methyl ester (SoME-2), canola oil methyl ester (CaME-2), and methyl ester of animal frying oil (FrAME-1) at 5, 50 and 500 mg/kg, or ultra-low sulphur diesel (ULSD) at 500 mg/kg. Control was administered the vehicle (corn oil) only. After 4-week treatment, serum methanol and formic acid were unchanged or minimally elevated in all treatment groups. Mild histopathological changes in the liver were observed in animals receiving 500 mg/kg biodiesels and ULSD but hepatomegaly, increased phase I and II drug-metabolizing enzyme activities and urinary ascorbic acid were found only in the ULSD group. The ULSD group had increased kidney weight, changes in kidney histopathology, and increased urinary albumin and N-acetylgluocosaminidase activity. Biodiesels and ULSD caused increase in hepatic acyl-CoA oxidase activity. ULSD and FrAME-1 caused decrease in serum free fatty acid while CaME-2 caused decreases in both serum triglycerides and free fatty acids. FrAME-1 produced an increase in liver protein carbonyls and ULSD caused increased liver glutathione. The results indicated that ULSD caused more histopathological and biochemical effects than biodiesels. Biodiesels produced lipid effects and oxidative stress that were feedstock-dependent. The mechanisms and significance of increased hepatic acyl-CoA oxidase activity required further study.

Alkane inducible proteins in Geobacillus thermoleovorans B23

BackgroundInitial step of β-oxidation is catalyzed by acyl-CoA dehydrogenase in prokaryotes and mitochondria, while acyl-CoA oxidase primarily functions in the peroxisomes of eukaryotes. Oxidase reaction accompanies emission of toxic by-product reactive oxygen molecules including superoxide anion, and superoxide dismutase and catalase activities are essential to detoxify them in the peroxisomes. Although there is an argument about whether primitive life was born and evolved under high temperature conditions, thermophilic archaea apparently share living systems with both bacteria and eukaryotes. We hypothesized that alkane degradation pathways in thermophilic microorganisms could be premature and useful to understand their evolution.ResultsAn extremely thermophilic and alkane degrading Geobacillus thermoleovorans B23 was previously isolated from a deep subsurface oil reservoir in Japan. In the present study, we identified novel membrane proteins (P16, P21) and superoxide dismutase (P24) whose production levels were significantly increased upon alkane degradation. Unlike other bacteria acyl-CoA oxidase and catalase activities were also increased in strain B23 by addition of alkane.ConclusionWe first suggested that peroxisomal β-oxidation system exists in bacteria. This eukaryotic-type alkane degradation pathway in thermophilic bacterial cells might be a vestige of primitive living cell systems that had evolved into eukaryotes.

Medium‐chain fatty acids ameliorate insulin resistance caused by high‐fat diets in rats

High dietary intake of saturated fat impairs insulin sensitivity and lipid metabolism. The influence of fatty acid chain length, however, is not yet fully understood, but evidence exists for different effects of saturated long-chain (LC) versus saturated medium-chain (MC) fatty acids (FA). To investigate the effects of the FA chain length, male Wistar rats were fed high-fat diets containing triacylglycerols composed of either MC- or LCFA for 4 weeks; rats fed maintenance diet served as a control. The animals underwent euglycemic hyperinsulinemic clamping or oral metabolic tolerance testing respectively; enzyme activities of mitochondrial (EC2.3.1.21 carnitine palmitoyl transferase) and peroxisomal (EC1.3.3.6 acyl-CoA oxidase) FA oxidation were measured in liver and muscle. LCFA consumption resulted in higher fasted serum insulin and glucose concentrations compared to controls, while MCFA-fed animals did not differ from controls. Insulin sensitivity was reduced by 30% in the LCFA group while the MCFA group did not differ from controls. Feeding MCFA resulted in the controls' lowered fasted and post-prandial triacylglycerol concentration compared to LCFA, while triacylglycerol concentrations in muscle were higher in both high-fat groups compared to controls. No diet-induced changes were found in acyl-CoA oxidase (ACO) activity (liver and muscle), while LCFA feeding significantly raised carnitine palmitoyltransferase activity. The chain length of saturated fatty acids in isocaloric diets affects insulin sensitivity, lipid metabolism and mitochondrial fatty acid oxidation without influencing body weight. While dietary LCFA clearly impair insulin sensitivity and lipid metabolism, MCFA seem to protect from lipotoxicity and subsequent insulin resistance without caloric restriction.

Triphenyltin alters lipid homeostasis in females of the ramshorn snail Marisa cornuarietis

Molluscs are sensitive species to the toxic effects of organotin compounds, particularly to masculinisation. Both tributyltin (TBT) and triphenyltin (TPT) have been recently shown to bind to mollusc retinoid X receptor (RXR). If RXR is involved in lipid homeostasis, exposure to TPT would have an immediate effect on endogenous lipids. To test this hypothesis, the ramshorn snail Marisa cornuarietis was exposed to environmentally relevant concentrations of TPT (30, 125, 500 ng/L as Sn) in a semi-static water regime for 7 days. Percentage of lipids and total fatty acid content decreased significantly in TPT-exposed females while the activity of peroxisomal acyl-CoA oxidase, involved in fatty acid catabolism, increased. In addition, fatty acid profiles (carbon chain length and unsaturation degree) were significantly altered in exposed females but not in males. This work highlights the ability of TPT to disrupt lipid metabolism in M. cornuarietis at environmentally realistic concentrations and the higher susceptibility of females in comparison to males.

The effects of dietary conjugated linoleic acid (CLA) on fatty acid composition and key enzymes of fatty acid oxidation in liver and muscle of geese

The objective of this study was to determine the influence of conjugated linoleic acid (CLA) on fatty acid composition and key enzymes of fatty acid oxidation in liver and muscle of geese. A total of 192 1-day-old geese were randomly assigned to 1 of 4 dietary groups, and were fed for 56 days on diets containing 2.5% soybean oil (group A, control group) or 2.0% soybean oil with 0.5% CLA (group B), 1.0% soybean oil with 1.5% CLA (group C), and 2.5 % CLA (group D). Geese fed CLA had a decreased abdominal fat percentage (AFP) (P < 0.01) compared with the control. It was observed that dietary CLA levels had a significant effect on the body weight, weight gain, feed conversion rate (FCR) (P < 0.05), and feed intake (P < 0.01). Fatty acid composition showed a significant increase of the biologically active cis-9, trans-11 and trans-10, and cis-12 CLA isomers in both liver and muscle of geese fed CLA (P < 0.01). Dietary CLA led to an increase (P < 0.01) in saturated fatty acid (SFA) and a reduction in monounsaturated fatty acid (MUFA) (P < 0.05) concentrations in both liver and muscle. In liver, dietary CLA increased (P < 0.05) acyl CoA oxidase (ACO) activity, but did not affect carnitine palmitoyltransferase-I (CPT-I) activity compared with the control. CPT-I activity was significantly increased by 2.5% dietary CLA in muscle, where ACO activity was decreased at 1.5% CLA level. The results obtained suggested that geese can successfully incorporate CLA in both liver and muscle, which could be beneficial in the human diet, through provision of bioactive fatty acids with no detrimental effects on n-3 PUFA levels.

Effects of WY-14643 on Peroxisomal Enzyme Activity and Hormone Secretion in Immortalized Human Trophoblast Cells

In our previous report, clofibric acid increased both the enzyme activities of peroxisomes (catalase and fatty acyl-CoA oxidase) and the secretion of progesterone in immortalized human extravillous trophoblast cells (TCL-1) (F. Hashimoto et al., Biochem. Pharm., 68, 313 (2004)). WY-14643 is reported to be stronger inducer of peroxisomes in rodents than clofibric acid. Therefore, the effects of WY-14643 on the activities of peroxisomal enzymes and hormone secretion in TCL-1 were studied. After incubation for 3 d with WY-14643, WY-14643 (>/=0.15 mM) suppressed the rate of increase in DNA and protein. The specific activities of catalase were increased by 0.1 mM WY-14643. The specific activities of fatty acyl-CoA oxidase were hardly changed by WY-14643. The concentration of progesterone in the medium was increased by 0.1 mM WY-14643, but human chorionic gonadotropin was decreased by 0.2 mM WY-14643. After a discontinuous Nycodenz-density gradient centrifugation of the light mitochondrial fraction of the cells, catalase activity was distributed in lower density fractions than cytochrome-c oxidase (a mitochondria marker enzyme) activity, but the distribution was not changed by WY-14643. These results suggest that WY-14643 inhibits the proliferation of trophoblast cells. The density of peroxisomes in human trophoblast cells is lower than that of mitochondria, and it is not affected by WY-14643. WY-14643 may increase the progesterone secretion. Effects of WY-14643 on metabolism of human trophoblast cells are different from those of clofibric acid.

The absorption, distribution and biological effects of a modified fatty acid in its free form and as an ethyl ester in rats

It has been demonstrated that the absorption of EPA and DHA is significantly lower for ethyl esters than for the corresponding free fatty acids. Since these fatty acids exist in nature and are catabolized by β-oxidation, we instead wanted to investigate the absorption, distribution and biological effects of a non-β-oxidizable modified fatty acid. The modified fatty acid tetradecylthioacetic acid (TTA) and the ethyl ester of TTA (EtTTA) were administered to rats for 10 days, in doses corresponding to 150 mg TTA/kg BW/day. No significant differences were found between the accumulated amounts of TTA or its Δ9 desaturated metabolite in plasma, liver, heart and epididymal white adipose tissue between EtTTA and TTA treated rats. EtTTA and TTA increased the activities of carnitine palmitoyltransferase-II and fatty acyl-CoA oxidase in liver, with no differences between the two treatment groups, but did not affect these activities in heart. EtTTA and TTA treatment decreased the plasma levels of triacylglycerols, cholesterol and phospholipids to similar extents, but no significant effects were seen in hepatic and cardiac lipid levels. EtTTA and TTA had similar effects on the fatty acid composition in plasma, liver, heart and epididymal white adipose tissue. Based on changes in fatty acid indexes it seems that these drugs had comparable stimulating effects on stearoyl-CoA desaturase and Δ6 desaturase, and reduced the Δ5 desaturase activity in liver. From the presented results we conclude that the absorption and distribution of the ethyl ester and the free form of TTA are not significantly different, and that the two administered forms of TTA have similar effects on lipid metabolism in rats.

Contaminant accumulation and biomarker responses in caged mussels, Mytilus galloprovincialis, to evaluate bioavailability and toxicological effects of remobilized chemicals during dredging and disposal operations in harbour areas

Remobilization of chemicals from contaminated sediments is a major risk associated with dredging and disposal operations in harbour areas. In this work caged mussels, Mytilus galloprovincialis, were chosen as bioindicator organisms to reveal the impact and recovery of organisms from these activities in the harbour of Piombino (Tuscany, Italy) where approximately 100,000 m 3 of sediments were removed and disposed in a local confined disposal facility (CDF). Organisms were deployed before, during and after the end of operations, selecting sites differently impacted by these activities. Temporal changes in environmental bioavailability and biological effects of pollutants were assessed by integrating analyses of trace metals and polycyclic aromatic hydrocarbons (PAHs) accumulated in tissues of caged mussels with a wide array of biomarkers reflecting exposure to specific classes of pollutants and different levels of cellular unbalance or toxicity. Such biological responses included levels of metallothioneins, activity of acyl CoA oxidase (AOX) as a marker of peroxisome proliferation, oxidative stress biomarkers (content of glutathione, enzymatic activities of catalase, glutathione S-transferases, glutathione reductase, glutathione peroxidases), total oxyradical scavenging capacity (TOSC) toward peroxyl and hydroxyl radicals, lysosomal membrane stability and genotoxic effects measured as DNA strand breaks and frequency of micronuclei. Obtained results indicated that a general disturbance was already present in the whole harbour area and especially in the inner site before the beginning of operations, when caged mussels exhibited a significant accumulation of PAHs and Pb, lower TOSC values and higher levels of both lysosomal and genotoxic damages. Bioavailability of trace metals and PAHs markedly increased during dredging activities with values up to 40 μg/g for Pb and up to 2200 ng/g for PAHs in tissues of caged mussels, a significant inhibition of antioxidant efficiency and increase of oxidative damages. While bioavailability of trace metals returned to the pre-dredging values after the end of operations, the accumulation of PAHs, oxidative effects and genotoxic damages remained elevated in mussels caged in the inner area and in front of CDF. Overall this study confirmed the utility of caged mussels to assess the remobilization of chemicals from dredged sediments and the onset of potentially harmful biological effects.

Effect of Dietary n-6/n-3 Ratio on Liver n-6/n-3 Ratio and Peroxisomal .BETA.-Oxidation Activity in Rats

The optimal dietary n-6/n-3 ratio has not been fully elucidated. To investigate the influence of the dietary n-6/n-3 ratio on this ratio in the body and on liver beta-oxidation peroxisomal activity, rats were fed diets containing fat at an n-6/n-3 ratio of 1 to 16 for 4 weeks. To investigate whether elevation of the liver peroxisomal beta-oxidation activity increases the n-6/n-3 ratio in the body, rats were fed a diet containing a peroxisome-activating agent, bezafibrate, for 2 weeks, and its influence on the liver n-6/n-3 ratio was examined. The slope of the regression line between the dietary and liver total lipid n-6/n-3 ratios was significantly smaller when the dietary n-6/n-3 ratio was 4 or greater than when it was smaller than 4. Peroxisomal beta-oxidation and acyl CoA oxidase activities were significantly lower in rats fed a diet with an n-6/n-3 ratio of 16 than in those fed a diet with a ratio of 1. The peroxisomal beta-oxidation activity in the bezafibrate-supplemented group was significantly higher than that in the control group. The serum and liver total lipid n-6/n-3 ratios were significantly higher in the 0.015% bezafibrate-supplemented group than in the control group. These findings suggest that the liver n-6/n-3 ratio might be controlled via peroxisomal beta-oxidation in rats.

Effect of acyl‐CoA oxidase activity on the accumulation of γ‐decalactone by the yeast Yarrowia lipolytica: A factorial approach

beta-Oxidation is a cyclic pathway involved in the degradation of lipids. In yeast, it occurs in peroxisomes and the first step is catalyzed by an acyl-CoA oxidase (Aoxp). The yeast Yarrowia lipolytica possesses several genes (POX) coding for Aoxps. This study is based on the factorial analysis of results obtained with the many POX derivative strains that have been constructed previously. The effect of interactions between Aoxps on the acyl-CoA oxidase (Aox) activity was important even at the second order. We then investigated the effect of Aox activity on growth and lactone production. Aox activity was correlated with acidification of the medium by cells and with cellular growth but not with lactone production, although Aox activity on short chains was inversely correlated with lactone accumulation. Due to the poor correlation between Aox activity and lactone production, the modeling of this parameter gave no satisfactory results but growth depending on Aox activity was modeled.

Assessment of biological effects of environmental pollution along the NW Mediterranean Sea using red mullets as sentinel organisms

A biomonitoring program was carried out in spring and autumn in three pollution hot-spots and sensitive areas of the NW Mediterranean Sea using red mullets ( Mullus barbatus) as sentinel organisms and a battery of biomarkers together with gonad histology. In fish from anthropogenic impacted areas (Fos-sur-mer, Cortiou, Arenzano, Delta of Ebro) lysosomal membrane destabilization occurred indicating disturbed health. There were no significant differences in metallothionein (MT) levels among stations. Peroxisomal acyl-CoA oxidase (AOX) activity was highest in fish from Cortiou. Both MT levels and AOX activities were significantly correlated with gamete development. Prevalence of melanomacrophage centers were high in Cortiou in all samplings and in Fos-sur-mer in September samplings. In conclusion, the application of a battery of biomarkers in red mullets provided relevant data for the assessment of environmental pollution in the NW Mediterranean Sea but also showed the difficulties of using native fish as sentinels. For future studies caging strategies are recommended.

Fenofibrate modulates cardiac and hepatic metabolism and increases ischemic tolerance in diet-induced obese mice

Peroxisome proliferator-activated receptors (PPARs) play an important role in the transcriptional regulation of lipid utilization and storage in several organs, including liver and heart. Our working hypothesis is that treatment of obesity/hyperlipedemia with the PPARα ligand fenofibrate leads to drainage of plasma lipids by the liver, resulting in reduced myocardial lipid supply, reduced myocardial fatty acid oxidation and improved myocardial tolerance to ischemic stress. Thus, we investigated changes in substrate utilization in heart and liver, as well as post-ischemic functional recovery in hearts from diet-induced obese (DIO) mice following long-term (11–12 weeks) treatment with fenofibrate. The present study shows that DIO mice express increased plasma lipids and glucose, as well as increased myocardial fatty acid oxidation and a concomitant decrease in glucose oxidation. The lipid-lowering effect of fenofibrate was associated with increased hepatic mitochondrial and peroxisomal fatty acid oxidation, as indicated by a more than 30% increase in hepatic palmiotyl-CoA oxidation and more than a 10-fold increase in acyl-CoA oxidase (ACO) activity. In line with an adaptation to the reduced myocardial lipid supply, isolated hearts from fenofibrate-treated DIO mice showed increased glucose oxidation and decreased fatty acid oxidation, as well as reduced ACO activity. Fenofibrate treatment also prevented the diet-induced decrease in cardiac function and improved post-ischemic functional recovery. We also found that, while fenofibrate treatment markedly increased the expression of PPARα target genes in the liver, there were no such changes in the heart. These data demonstrate that fenofibrate results in a direct activation of PPARα in the liver with increased hepatic drainage of plasma lipids, while the cardiac effect of the compound most likely is secondary to its lipid-lowering effect.

Mutation of Tyr375 to Lys375 allows medium-chain acyl-CoA dehydrogenase to acquire acyl-CoA oxidase activity

Medium-chain acyl-CoA dehydrogenase (MCAD) and acyl-CoA oxidase (ACO) are key enzymes catalyzing the rate-determining step for the β-oxidation of fatty acids. Tyr375 of MCAD is conserved in all acyl-CoA dehydrogenases and is an important residue for substrate binding. Four Tyr375 variant enzymes of rat liver MCAD were obtained through site-directed mutagenesis. Y375K was found to have intrinsic acyl-CoA oxidase activity, which was confirmed using HPLC analysis, while the wild-type and other Tyr375 variant enzymes did not show detectable oxidase activity. The kinetic parameters for the oxidase activity of Y375K variant enzyme were determined to be k cat of 320 ± 80 h − 1 and K M of 30 ± 15 μM using hexanoyl-CoA as the substrate. The oxidase activity of Y375K increased more than 200 times compared with that reported for the MCAD wild-type enzyme from mammalian sources. Molecular modeling study shows that the solvent accessible area for Y375K variant enzyme is wider than that of the wild-type enzyme, which indicates that Tyr375 may function as a switch against solvent accession. The mutation of this residue to Lys375 allows molecular oxygen to enter into the catalytic site serving as the electron acceptor for the reduced FAD cofactor.

Metabolism and short-term metabolic effects of conjugated linoleic acids in rat hepatocytes

Metabolic fate and short-term effects of a 1:1 mixture of cis-9, trans-11 and trans-10, cis-12-conjugated linoleic acids (CLA), compared to linoleic acid (LA), on lipid metabolism was investigated in rat liver. In isolated mitochondria CLA-CoA were poorer substrates than LA-CoA for carnitine palmitoyltransferase-I (CPT-I) activity. However, in digitonin-permeabilized hepatocytes, where interactions among different metabolic pathways can be simultaneously investigated, CLA induced a remarkable stimulatory effect on CPT-I activity. This stimulation can be ascribed to a reduced malonyl-CoA level in turn due to inhibition of acetyl-CoA carboxylase (ACC) activity. The ACC/malonyl-CoA/CPT-I system can therefore represent a coordinate control by which CLA may exert effects on the partitioning of fatty acids between esterification and oxidation. Moreover, the rate of oxidation to CO 2 and ketone bodies was significantly higher from CLA; peroxisomes rather than mitochondria were responsible for this difference. Interestingly, peroxisomal acyl-CoA oxidase (AOX) activity strongly increased by CLA-CoA compared to LA-CoA. CLA, metabolized by hepatocytes at a higher rate than LA, were poorer substrates for cellular and VLDL-triacylglycerol (TAG) synthesis. Overall, our results suggest that increased fatty acid oxidation with consequent decreased fatty acid availability for TAG synthesis is a potential mechanism by which CLA reduce TAG level in rat liver.