acyl-CoA Oxidase Activity Research Articles

Responses of conventional and molecular biomarkers in turbot Scophthalmus maximus exposed to heavy fuel oil no. 6 and styrene

Several accidental spills in European coastal areas have resulted in the release of different toxic compounds into the marine environment, such as heavy fuel oil type no. 6 in the “Erika” and “Prestige” oil spills and the highly toxic styrene after the loss of the “Ievoli Sun”. There is a clear need to develop tools that might allow assessing the biological impact of these accidental spills on aquatic organisms. The aim of the present study was to determine the short-term effects and recovery after exposure of juvenile fish (Scophthalmus maximus) to heavy fuel oil no. 6 and styrene by using a battery of molecular, cell and tissue level biomarkers. Turbots were exposed to styrene for 7 days and to the diluted soluble fraction of the oil (10%) for 14 days, and then allowed to recover in clean seawater for the same time periods. cyp1a1 transcript was overexpressed in turbots after 3 and 14 days of exposure to heavy fuel oil, whereas ahr transcription was not modulated after heavy fuel oil and styrene exposure. pparα transcription level was significantly up-regulated after 3 days of treatment with styrene. Liver activity of peroxisomal acyl-CoA oxidase (AOX) was significantly induced after 14 days of oil exposure, but it was not affected by styrene. Hepatocyte lysosomal membrane stability (LMS) was significantly reduced after exposure to both treatments, indicating that the tested compounds significantly impaired fish health. Both AOX and LMS values returned to control levels after the recovery period. No differences in gamete development were observed between fuel- or styrene- exposed fish and control fish, and vitellogenin plasma levels were low, suggesting no xenoestrogenic effects of fuel oil or styrene. While styrene did not cause any increase in the prevalence of liver histopathological alterations, prevalence of extensive cell vacuolization increased after exposure to heavy fuel oil for 14 days. In conclusion, the suite of selected biomarkers proved to be useful to determine the early impact of and recovery from exposure to tested compounds in turbot.

Evaluation of hepatic and thyroid responses in male Sprague Dawley rats for up to eighty-four days following seven days of dietary exposure to potassium perfluorooctanesulfonate

In a prior 28-day dietary study in rats with 20 and 100ppm K+PFOS, activation of PPARα and CAR/PXR were concluded to be etiological factors in K+PFOS-induced hepatomegaly and hepatic tumorigenesis. The objective of this study was to evaluate persistence/resolution of K+PFOS-induced, liver-related effects in male Sprague Dawley rats following a 7-day dietary exposure to K+PFOS at 20 or 100ppm. Groups of 10 rats per treatment were observed on recovery Day(s) 1, 28, 56, and 84 following treatment. Changes consistent with hepatic PPARα and CAR/PXR activation noted on recovery Day 1 included: increased liver weight; decreased plasma cholesterol, alanine aminotransferase, and triglycerides; decreased liver DNA concentration and increased hepatocellular cytosolic CYP450 concentration; increased liver activity of acyl CoA oxidase, CYP4A, CYP2B, and CYP3A; increased liver proliferative index and decreased liver apoptotic index; decreased hepatocellular glycogen-induced vacuoles; increased centrilobular hepatocellular hypertrophy. Most effects resolved to control levels during recovery. Effects on plasma cholesterol, hepatocellular cytosolic CYP450 concentrations, liver apoptotic index, CYP3A, and centrilobular hepatocellular hypertrophy persisted through the end of the recovery period. Thyroid parameters (histology, apoptosis, and proliferation) were unaffected at all time points. Mean serum PFOS concentrations on recovery Day 1 were 39 and 140μg/mL (20ppm and 100ppm K+PFOS, respectively), decreasing to 4 and 26μg/mL by recovery Day 84. Thus, hepatic effects in male rats resulting from K+PFOS-induced activation of PPARα and CAR/PXR resolved slowly or were still present after 84-days following a 7-day dietary treatment, consistent with the slow elimination rate of PFOS.

Silibinin modulates lipid homeostasis and inhibits nuclear factor kappa B activation in experimental nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is associated with increased liver-related mortality. Disturbances in hepatic lipid homeostasis trigger oxidative stress and inflammation (ie, lipotoxicity), leading to the progression of NASH. This study aimed at identifying whether silibinin may influence the molecular events of lipotoxicity in a mouse model of NASH. Eight-week-old db/db mice were fed a methionine-choline deficient (MCD) diet for 4 weeks and treated daily with silibinin (20 mg/kg intraperitoneally) or vehicle. Liver expression and enzyme activity of stearoyl-CoA desaturase-1 and acyl-CoA oxidase, and expression of liver fatty acid-binding protein were assessed. Hepatic levels of reactive oxygen species, thiobarbituric acid-reactive substances (TBARS), 3-nitrotyrosine (3-NT), inducible nitric oxide synthase (iNOS), and nuclear factor kappa B (NFkB) activities were also determined. Silibinin administration decreased serum alanine aminotransferase and improved liver steatosis, hepatocyte ballooning, and lobular inflammation in db/db mice fed an MCD diet. Gene expression and activity of stearoyl-CoA desaturase-1 were reduced in db/db mice fed an MCD diet compared with lean controls and were increased by silibinin; moreover, silibinin treatment induced the expression and activity of acyl-CoA oxidase and the expression of liver fatty acid-binding protein. Vehicle-treated animals displayed increased hepatic levels of reactive oxygen species and TBARS, 3-NT staining, and iNOS expression; silibinin treatment markedly decreased reactive oxygen species and TBARS and restored 3-NT and iNOS to the levels of control mice. db/db mice fed an MCD diet consistently had increased NFkB p65 and p50 binding activity; silibinin administration significantly decreased the activity of both subunits. Silibinin treatment counteracts the progression of liver injury by modulating lipid homeostasis and suppressing oxidative stress-mediated lipotoxicity and NFkB activation in experimental NASH.

Catechins and Caffeine Inhibit Fat Accumulation in Mice through the Improvement of Hepatic Lipid Metabolism

To elucidate the inhibiting mechanisms of fat accumulation by catechins, caffeine, and epigallocatechin gallate (EGCG), ICR mice were fed diets containing either 0.3% catechins or 0.1% EGCG and/or 0.05% caffeine for 4 weeks. After the feeding, intraperitoneal adipose tissues weights were significantly lower in the caffeine, catechins + caffeine, and EGCG + caffeine groups compared to controls. Hepatic fatty acid synthase (FAS) activity in the catechins + caffeine group was significantly lower, and the activities of acyl-CoA oxidase (ACO) and carnitine palmitoyltransferase-II (CPT-II) were significantly higher, compared to the control group. However, these activities were not observed in the other groups. FAS mRNA expression levels in the catechins + caffeine group were significantly lower than in the control group. ACO and CPT-II mRNA levels were not different among all of the treatment groups. These findings indicate that the inhibitory effects of fat accumulation via a combination of catechins, EGCG, or caffeine were stronger collectively than by either catechins, EGCG, or caffeine alone. Moreover, it was demonstrated that the combination of catechins and caffeine induced inhibition of fat accumulation by suppression of fatty acid synthesis and upregulation of the enzymatic activities involved in β-oxidation of fatty acid in the liver, but this result was not observed by combination of EGCG and caffeine.

Cellular Oxidative Stress and Peroxisomal Enzyme Activities in Pediatric Liver Transplant Patients

Objectives: In this study, we examined the activities of key peroxisomal enzymes in peripheral blood lymphocytes (PBLs) of pediatric liver transplant patients. Subjects and Methods: Venous blood was drawn from 14 patients aged 5–16 years on FK-506 treatment and 18 healthy subjects for isolation of lymphocytes. β-Oxidation of very long chain fatty acids (VLCFAs) and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), NADPH oxidase (NOX), catalase and peroxisomal enzyme acyl CoA oxidase (ACO) were measured in cellular homogenates. Levels of malondialdehyde (MDA) were measured as an index of lipid peroxidation. Protein content and mRNA levels of catalase, peroxisomal membrane protein-70 (PMP-70) and ACO were measured using Western blotting and PCR techniques. Results: PBLs isolated from liver transplant patients showed significantly (p < 0.01) increased levels (226.9 ± 24.5 µmol/mg protein) of MDA as compared to the levels in controls (162.8 ± 19.6 µmol/mg protein), whereas enzyme activities of SOD and NOX remained unaltered in patients’ cells. Enzyme activities of catalase and GPx were markedly (p < 0.01) decreased in cells isolated from liver transplant patients. ACO activity and β-oxidation of VLCFAs in PBLs from liver transplant patients were however found to be significantly increased by 38 and 52% respectively when compared with controls. Gene expression of PMP-70 and ACO was also significantly increased (p < 0.01) in PBLs of patients. Conclusion: Our results clearly showed that peroxisomal metabolic activities are markedly altered in lymphocytes of liver transplant patients and might contribute to the development of cellular oxidative stress.

Can Hediste diversicolor (Nereidae, Polychaete) be considered a good candidate in evaluating PAH contamination? A multimarker approach

The aim of this study was to develop a preliminary characterization of the biological responses of Hediste diversicolor to polycyclic aromatic hydrocarbons (PAHs) under controlled laboratory conditions. In order to test the effects of PAH exposure, a battery of biomarkers was applied to the polychaetes by exposing them to sublethal concentrations of benzo[a]pyrene (0.1 and 0.5mgL−1) for 10d under laboratory conditions. The battery of biomarkers tested included oxidative stress biomarkers (glutathione content, enzymatic activities of catalase, glutathione S-transferases, glutathione reductase, glutathione peroxidases), total oxyradical scavenging capacity (TOSC) toward peroxyl and hydroxyl radicals and activity of acyl CoA oxidase (AOX) as a marker of peroxisome proliferation measured in the entire body; lipofuscin and neutral lipid accumulations and levels of Ca2+-ATPase activity analyzed in the intestinal epithelium; lysosomal membrane stability and genotoxic effects measured as DNA strand breaks and frequency of micronuclei in coelomocytes. Chemical analyses were also carried out to verify the polychaete’s benzo[a]pyrene (B[a]P) bioaccumulation levels after the exposure period. The results obtained indicate that B[a]P caused significant changes in most of the parameters measured in H. diversicolor. Biological responses to the organic compound were particularly significant for the biomarkers measured in the intestinal epithelium and in coelomocytes, emphasizing that these tissues were more affected during our experimental conditions. Considering the key trophic role of this benthic species in estuarine and coastal ecosystems, this study confirmed that H. diversicolor is an appropriate bioindicator of organic contamination.

Postharvest temperature influences volatile lactone production via regulation of acyl‐CoA oxidases in peach fruit

The biosynthesis of volatile compounds in plants is affected by environmental conditions. Lactones are considered to be peach-like aroma volatiles; however, no enzymes or genes associated with their biosynthesis have been characterized. White-fleshed (cv. Hujingmilu) and yellow-fleshed (cv. Jinxiu) melting peach (Prunus persica L. Batsch) fruit were used as materials in two successive seasons and responses measured to four different temperature treatments. Five major lactones accumulated during postharvest peach fruit ripening at 20 °C. Peach fruit at 5 °C, which induces chilling injury (CI), had the lowest lactone content during subsequent shelf life after removal, while 0 °C and a low-temperature conditioning (LTC) treatment alleviated development of CI and maintained significantly higher lactone contents. Expression of PpACX1 and activity of acyl-CoA oxidase (ACX) with C16-CoA tended to increase during postharvest ripening both at 20 °C and during shelf life after removal from cold storage when no CI was developed. There was a positive correlation between ACX and lactones in peach fruit postharvest. Changes in lactone production in response to temperatures are suggested to be a consequence of altered expression of PpACX1 and long-chain ACX activity.

Differential response of young and adult leaves to herbicide 2,4-dichlorophenoxyacetic acid in pea plants: role of reactive oxygen species.

In this work the differential response of adult and young leaves from pea (Pisum sativum L.) plants to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) (23 mm) applied by foliar spraying was investigated. The concentration of 2,4-D (23 mm) and the time of treatment (72 h) were previously optimized in order to visualize its toxic effects on pea plants. Under these conditions, the herbicide induced severe disturbances in mesophyll cells structure and proliferation of vascular tissue in young leaves and increased acyl-CoA oxidase (ACX), xanthine oxidase (XOD) and lipoxygenase (LOX) activities in young leaves, and only ACX and LOX in adult leaves. This situation produced reactive oxygen species (ROS) over-accumulation favoured by the absence of significant changes in the enzymatic antioxidants, giving rise to oxidative damages to proteins and membrane lipids. An increase of ethylene took place in both young and adult leaves and the induction of genes encoding the stress proteins, PRP4A and HSP 71,2, was observed mainly in young leaves. These results suggest that ROS overproduction is a key factor in the effect of high concentrations of 2,4-D, and ROS can trigger a differential response in young and adult leaves, either epinasty development in young leaves or senescence processes in adult tissues.

Role of peroxisomes in the oxidative injury induced by 2,4-dichlorophenoxyacetic acid in leaves of pea plants

The role of peroxisomes in the oxidative injury induced by the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in leaves of pea (Pisum sativum L.) plants was studied. Applications of (2,4-D) on leaves or to root substrate increased the superoxide radical production in leaf peroxisomes. Foliar application also increased H2O2 contents in leaf peroxisomes. Reactive oxygen species (ROS) overproduction was accompanied by oxidative stress, as shown by the changes in lipid peroxidation, protein carbonyls, total and protein thiols, and by the up-regulation of the activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, catalase, glucose 6-phosphate dehydrogenase and NADP+-dependent isocitrate dehydrogenase. Foliar or root 2,4-D applications also induced senescence symptoms in pea leaf peroxisomes, as shown by the decrease of protein content and glycolate oxidase and hydroxypyruvate reductase activities, and by the increase of endopeptidase, xanthine oxidase, isocitrate lyase and acyl-CoA oxidase activities as well as of 3-ketoacyl-CoA thiolase and thiol-protease protein contents. 2,4-D did not induce proliferation of pea leaf peroxisomes but induced senescence-like morphological changes in these organelles. Results suggest that peroxisomes might contribute to 2,4-D toxicity in pea leaves by overproducing cell-damaging ROS and by participating actively in 2,4-D-induced leaf senescence.

Assessment of lysosomal membrane stability and peroxisome proliferation in the head kidney of Atlantic cod ( Gadus morhua) following long-term exposure to produced water components

There is a need for sensitive biological effect methods by which to detect impacts of chronic exposure to low concentrations of contaminants. Two methods shown to be potentially useful for monitoring purposes in fish include lysosomal membrane stability and peroxisome proliferation. These biological endpoints were assessed in Atlantic cod ( Gadus morhua) head kidney following exposure to a mixture of produced water components including polycyclic aromatic hydrocarbons, phenol, and alkylphenols. Lysosomal damage of head kidney cells occurred within the first two weeks and did not recover during the entire exposure period (32 weeks). Lysosomal membrane stability was not affected by gender and was responsive at low concentrations of contamination, indicating that lysosomal membrane stability measured in the head kidney could be a useful biomarker for effects of offshore pollution. Peroxisome proliferation, measured as acyl-CoA oxidase activity in the head kidney, appeared to be a potential biomarker in male cod exposed less than 16 weeks.

Role of peroxisomes in the oxidative injury induced by 2,4-dichlorophenoxyacetic acid in leaves of pea plants

The role of peroxisomes in the oxidative injury induced by the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in leaves of pea (Pisum sativum L.) plants was studied. Applications of (2,4-D) on leaves or to root substrate increased the superoxide radical production in leaf peroxisomes. Foliar application also increased H2O2 contents in leaf peroxisomes. Reactive oxygen species (ROS) overproduction was accompanied by oxidative stress, as shown by the changes in lipid peroxidation, protein carbonyls, total and protein thiols, and by the up-regulation of the activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, catalase, glucose 6-phosphate dehydrogenase and NADP+-dependent isocitrate dehydrogenase. Foliar or root 2,4-D applications also induced senescence symptoms in pea leaf peroxisomes, as shown by the decrease of protein content and glycolate oxidase and hydroxypyruvate reductase activities, and by the increase of endopeptidase, xanthine oxidase, isocitrate lyase and acyl-CoA oxidase activities as well as of 3-ketoacyl-CoA thiolase and thiol-protease protein contents. 2,4-D did not induce proliferation of pea leaf peroxisomes but induced senescence-like morphological changes in these organelles. Results suggest that peroxisomes might contribute to 2,4-D toxicity in pea leaves by overproducing cell-damaging ROS and by participating actively in 2,4-D-induced leaf senescence.

Organ-specific effects of the auxin herbicide 2,4-D on the oxidative stress and senescence-related parameters of the stems of pea plants

Oxidative stress and senescence have been shown to participate in the toxicity mechanism of auxin herbicides in the leaves and roots of sensitive plants. However, their role in stem toxicity has not been studied yet. In this work, we report the effect of foliar or root applications of the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on the parameters of oxidative stress and senescence of stems of pea (Pisum sativum L.) plants. Contrary to their effect on the pea leaves, in the stems 2,4-D applications did not cause oxidative stress, as shown by the parameters of lipid peroxidation, protein carbonyls, and total and protein thiols. Moreover, they inhibited the superoxide radical (O 2 .− )-producing xanthine oxidase (XOD) activity and stimulated the antioxidant activities of catalase (CAT), guaiacol peroxidase (GPOX), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST) and Krebs cycle NAD+-isocitrate dehydrogenase (IDH). Applications of 2,4-D also did not induce senescence in the pea stems, as shown by the increase of proteins, the lack of stimulation of proteolytic activity, and the inhibition of senescence-related isocitrate lyase (ICL) activity. However, they stimulated the H2O2-producing acyl-CoA oxidase (ACOX) activity of fatty acid beta oxidation. Results suggest that oxidative stress and senescence are not involved in the mechanism of toxicity of 2,4-D in the stems of pea plants, and that these phenomena are not whole-plant toxicity mechanisms for auxin herbicides in susceptible plants. Results also suggest that the effect of 2,4-D on the oxidative metabolism of pea plants might be organ-specific.

Effects of 9‐cis‐retinoic acid on fatty acid oxidation induced by clofibrate in primary cultured heptocytes from newborn pigs

The experiment was conducted to investigate the effects of 9-cis-retinoic acid (RA), a ligand of the retinoid X receptors, on fatty acid oxidation induced by clofibrate in pig hepatocytes. Hepatocytes from newborn piglets were treated with or without clofibrate (0.3 mM) in the presence of RA at concentrations of 0, 2.5, 5 or 10 μM for 70 hrs. Fatty acid oxidation was determined using 14C-oleic acid, and carnitine palmitoyltransferase (CPT) and acyl-CoA oxidase (ACO) activities were assayed with enzymatic methods. Accumulations of 14C in CO2 and acid-soluble products were 1.5-fold higher in clofibrate treated cells than untreated cells (p < 0.001). Addition of RA to clofibrate untreated cells increased fatty acid oxidation at low concentration (2.5 μM) and decreased fatty acid oxidation at high concentration (10 μM), but no RA effects were detected in clofibrate treated cells. Clofibrate increased ACO activity (2-fold) and CPT malonyl-CoA inhibited (2-fold) and uninhibited (2.5-fold) activities (p < 0.01). However, RA had no effects on CPT and ACO activities in both clofibrate treated and untreated cells. These results indicate that clofibrate strongly induces fatty acid oxidation in pig primary cultured hepatocyte, but the induction was not affected by addition of RA. Supported by CSREES, USDA NRI program award 2007-35206-17897.

Wild bitter gourd extract up-regulates mRNA expression of PPARα, PPARγ and their target genes in C57BL/6J mice

Wild bitter gourd (Momordica charantia Linn. var. abbreviata ser.) was commonly used as a medicinal herb in Asia, Africa, and South America because of its anti-diabetic, antibacterial, anti-viral, and chemopreventive functions. C57BL/6J mice were orally administered with 250, 500 or 1000mg/kg BW of WBGE in 0.2mL/mouse of olive oil daily for 2 weeks. Compared to control (vehicle treated) mice, mice receiving WBGE showed significantly higher PPARα, ACO (acyl-CoA oxidase) and L-FABP (liver-fatty acid binding protein) mRNA expression, ACO activity and protein in the liver (P<0.05), as clofibrate-treated mice. WBGE treatment also resulted in significantly higher PPARγ and LPL (lipoprotein lipase) mRNA (P<0.05) in the epididymal adipose tissue. Liver triglyceride and non-esterified fatty acid concentration in WBGE treated mice were significantly lower than those of control mice (P<0.05). Plasma adiponectin level was significantly higher in mice receiving WBGE than in control mice (P<0.05), as the rosiglitazone treated mice. Results of this study demonstrated that WBGE also activates PPARα and PPARγ signaling pathway in vivo.

A Novel Series of (S)-2,7-Substituted-1,2,3,4-tetrahydroisoquinoline-3-carboxylic Acids: Peroxisome Proliferator-Activated Receptor .ALPHA./.GAMMA. Dual Agonists with Protein-Tyrosine Phosphatase 1B Inhibitory Activity

Novel 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and (S)-7-(2-{2-[(E)-2-cyclopentylvinyl]-5-methyloxazol-4-yl}ethoxy)-2-[(2E,4E)-hexadienoyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (14c) was identified as a peroxisome proliferator-activated receptor (PPAR) α/γ dual agonist. The transactivation activity of 14c was comparable to that of rosiglitazone in human PPARγ (EC50=0.14 µM) and was much higher than in human PPARα (EC50=0.20 µM). In addition, 14c, but not rosiglitazone, showed human protein-tyrosine phosphatase 1B (PTP-1B) inhibitory activity (IC50=1.85 µM). 14c showed about 10-fold stronger hypoglycemic and hypotriglyceridemic effects than rosiglitazone by repeated application for 14 d in male KK-Ay mice. Furthermore, 14c, but not rosiglitazone, increased hepatic peroxisome acyl CoA oxidase activity at 30 mg/kg/d for 7 d in male Syrian hamsters, probably due to its PPARα agonist activity. 14c did not affect plasma volume at 100 mg/kg/d for 14 d in male ICR mice, while rosiglitazone significantly increased it. In conclusion, 14c is a promising candidate for an efficacious and safe anti-diabetic drug with triple actions as a PPARα/γ dual agonist with PTP-1B inhibitory activity.

Transformed tobacco (Nicotiana tabacum) plants over-expressing a peroxisome proliferator-activated receptor gene from Xenopus laevis (xPPARα) show increased susceptibility to infection by virulent Pseudomonas syringae pathogens

Transgenic tobacco plants capable of over-expressing Xenopus PPARα (xPPARα), a transcription factor known to be required for peroxisome proliferation in animals, were recently generated. These plants (herewith referred to as PPAR-OE) were found to have increased peroxisome abundance, higher peroxisomal acyl-CoA oxidase and catalase activity and modified fatty acid metabolism. Further characterization of PPAR-OE plants revealed a higher susceptibility to virulent and a partial loss of resistance to avirulent Pseudomonas syringae pathogens, whereas the basal resistance response remained unaffected. Biochemical- and defense-related gene expression analyses showed that increased susceptibility to bacterial invasion coincided with the generalized reduction in H(2)O(2) and salicylic acid (SA) levels observed within the first 24h of bacterial contact. Decreased H(2)O(2) levels were correlated with modified activity levels of catalase and other antioxidant enzymes. A correspondence between a rapid (within 1-24 hpi; ACCO and AOC) and sustained increase (up to 6days pi; ACCO) in the expression levels of ethylene (ACCO) and jasmonic acid (AOC) biosynthetic genes and a higher susceptibility to virulent bacterial invasion was also observed in PPAR-OE plants. Conversely, no apparent differences in the short- and/or long-term expression levels of markers for the hypersensitive-response, oxidative burst and systemic-acquired resistance were observed between wild type and PPAR-OE plants. The results suggest that peroxisome proliferation could lead to increased susceptibility to bacterial pathogens in tobacco by altering the redox balance of the plant and the expression pattern of key defense signaling pathway genes.

Integrated biomarker assessment of the effects exerted by treated produced water from an onshore natural gas processing plant in the North Sea on the mussel Mytilus edulis

The biological impact of a treated produced water (PW) was investigated under controlled laboratory conditions in the blue mussel, Mytilus edulis. Mussel health status was assessed using an integrated biomarker approach in combination with chemical analysis of both water (with SPMDs), and mussel tissues. Acyl-CoA oxidase activity, neutral lipid accumulation, catalase activity, micronuclei formation, lysosomal membrane stability in digestive cells and haemocytes, cell-type composition in digestive gland epithelium, and the integrity of the digestive gland tissue were measured after 5week exposure to 0%, 0.01%, 0.1%, 0.5% and 1% PW. The suite of biomarkers employed were sensitive to treated PW exposure with significant sublethal responses found at 0.01–0.5% PW, even though individual chemical compounds of PW were at extremely low concentrations in both water and mussel tissues. The study highlights the benefits of an integrated biomarker approach for determining the potential effects of exposure to complex mixtures at low concentrations. Biomarkers were integrated in the Integrative Biological Response (IBR/n) index.

Direct effects of iodothyronines on excess fat storage in rat hepatocytes

Previous studies have demonstrated that 3,5-L-diiodothyronine (T(2)) is able to prevent lipid accumulation in the liver of rats fed a high-fat diet. Whether this effect is due to a direct action of T(2) on the liver has not been elucidated. In this study, we investigated the ability of T(2) to reduce the excess lipids in isolated hepatocytes treated with fatty acids (FFAs). The effects of T(2) were compared with those elicited by 3,3',5-L-triiodothyronine (T(3)). To mimic the fatty liver condition, primary cultures of rat hepatocytes were overloaded with lipids, by exposure to FFAs ("fatty hepatocytes"), and then treated with T(2) or T(3). Lipid content, morphometry of lipid droplets (LDs), and expression of the adipocyte differentiation-related protein (ADRP) and the peroxisome proliferator-activated receptors (PPAR-α, -γ, -δ) were evaluated. Activities of the lipolytic enzyme acyl CoA oxidase-AOX and the antioxidant enzymes superoxide dismutase-SOD and catalase-CAT were also determined. FFA-induced lipid accumulation was associated with an increase in both number/size of LDs and expression of ADRP, PPAR-γ, and PPAR-δ/β mRNAs, as well as in the activities of AOX, SOD, and CAT. The addition of T(2) or T(3) to "fatty hepatocytes" resulted in a reduction in: (i) lipid content and LD diameter; (ii) PPAR-γ and PPAR-δ expression; (iii) activities of AOX and antioxidant enzymes. These data demonstrate, for the first time, a direct action of both T(2) and T(3) in reducing the excess fat in cultured hepatocytes.

Effects of trans-10,cis-12 CLA on liver size and fatty acid oxidation under energy restriction conditions in hamsters

ObjectiveLittle evidence exists concerning the effects of trans-10,cis-12 conjugated linoleic acid (CLA) under energy restriction. Thus, the effects of this CLA isomer on adipose tissue size, liver composition, as well as on expression and activity of carnitine-palmitoyl transferase I (CPT-I) and acyl CoA oxidase (ACO), in hamsters fed an energy-restricted diet were analyzed. MethodsHamsters were fed a high-fat diet for 7 wk and then subjected to 25% energy-restricted diets supplemented with 0.5% linoleic acid or 0.5% trans-10,cis-12 CLA for 3 wk. Serum insulin, free-triiodothyronine and non-esterified fatty acid levels, liver triacylglycerol, protein and water contents, and CPT-I, ACO, and Peroxisome proliferator-activated receptor alpha (PPARα) expressions and enzyme activities were assessed. ResultsEnergy restriction reduced liver size, serum levels of insulin, free-triiodothyronine, and non-esterified fatty acid and increased CPT-I activity. Liver composition was not modified. No differences were found between both restricted groups, with the exception of CPT-I and ACO oxidative enzyme activities, which were greater in hamsters fed the CLA diet. ConclusionsEnergy restriction does not cause trans-10,cis-12 CLA to induce liver hyperplasia. Although this CLA isomer increases liver CPT-I and ACO activities, this effect does not result in reduced hepatic triacylglyerol content or decreased adipose tissue size. Consequently, this CLA isomer seems not to be a useful tool for inclusion in body weight loss strategies followed during obesity treatment.

Perfluorooctanoic acid induces peroxisomal fatty acid oxidation and cytokine expression in the liver of male Japanese medaka ( Oryzias latipes)

Widespread contamination of perfluorooctanoic acid (PFOA) in the marine environment draws a great concern over its ecotoxicological impact on marine mammals and wildlife. In the present study, male Japanese medaka ( Oryzias latipes) was adapted to seawater to mimic the marine environment and was then exposed to the nominal concentrations of 10, 50, 100 mg L −1 PFOA for 7 d. There were no impact on survival, relative liver and gonad size, and condition factor (measure of growth) at any concentration tested. Peroxisomal acyl-CoA oxidase (ACO) activity was elevated at the highest dose with a marginal significance ( P = 0.06). The increase of ACO activity was paralleled by the significant upregulation of PPAR-α expression at the same dose. PFOA induced a significant inhibition of catalase (CAT) activity at high doses with no changes of superoxide dismutase (SOD) or glutathione peroxidase (GPx) activities in the liver. These results strongly suggest that PFOA may induce peroxisomal fatty acid oxidation and impose the oxidative stress through the alteration of cellular oxidative homeostasis in the liver. PFOA increased the mRNA levels of proinflammatory cytokines such as IL-6, TNF-α and IL-1β, suggesting that it may be involved in inflammation and tissue injury. This study may contribute to understanding the mechanism of PFOA-induced hepatic toxicity in Japanese medaka and assessing the potential risk of PFOA in marine fish and wildlife. In addition, the present results obtained at the high concentrations may provide important biological endpoints relevant to situations such as environmental spills.