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Garcia-Ruiz C.,Institute of Biomedical Research of Barcelona IIBB | Baulies A.,Institute of Biomedical Research of Barcelona IIBB | Mari M.,Institute of Biomedical Research of Barcelona IIBB | Garcia-Roves P.M.,Diabetes and Obesity Laboratory | And 2 more authors.
Free Radical Research | Year: 2013

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of the metabolic syndrome and refers to a spectrum of disorders ranging from steatosis to steatohepatitis, a disease stage characterized by inflammation, fibrosis, cell death and insulin resistance (IR). Due to its association with obesity and IR the impact of NAFLD is growing worldwide. Consistent with the role of mitochondria in fatty acid (FA) metabolism, impaired mitochondrial function is thought to contribute to NAFLD and IR. Indeed, mitochondrial dysfunction and impaired mitochondrial respiratory chain have been described in patients with non-alcoholic steatohepatitis and skeletal muscle of obese patients. However, recent data have provided evidence that pharmacological and genetic models of mitochondrial impairment with reduced electron transport stimulate insulin sensitivity and protect against diet-induced obesity, hepatosteatosis and IR. These beneficial metabolic effects of impaired mitochondrial oxidative phosphorylation may be related not only to the reduction of reactive oxygen species production that regulate insulin signaling but also to decreased mitochondrial FA overload that generate specific metabolites derived from incomplete FA oxidation (FAO) in the TCA cycle. In line with the Randle cycle, reduced mitochondrial FAO rates may alleviate the repression on glucose metabolism in obesity. In addition, the redox paradox in insulin signaling and the delicate mitochondrial antioxidant balance in steatohepatitis add another level of complexity to the role of mitochondria in NAFLD and IR. Thus, better understanding the role of mitochondria in FA metabolism and glucose homeostasis may provide novel strategies for the treatment of NAFLD and IR. © 2013 Informa UK, Ltd. Source

Bejaoui M.,Institute of Biomedical Research of Barcelona IIBB | Pantazi E.,Institute of Biomedical Research of Barcelona IIBB | Calvo M.,University of Barcelona | Folch-Puy E.,Institute of Biomedical Research of Barcelona IIBB | And 6 more authors.
Oxidative Medicine and Cellular Longevity | Year: 2016

Hepatic ischemia reperfusion injury (IRI) is an inevitable clinical problem for liver surgery. Polyethylene glycols (PEGs) are water soluble nontoxic polymers that have proven their effectiveness in various in vivo and in vitro models of tissue injury. The present study aims to investigate whether the intravenous administration of a high molecular weight PEG of 35 kDa (PEG 35) could be an effective strategy for rat liver preconditioning against IRI. PEG 35 was intravenously administered at 2 and 10 mg/kg to male Sprague Dawley rats. Then, rats were subjected to one hour of partial ischemia (70%) followed by two hours of reperfusion. The results demonstrated that PEG 35 injected intravenously at 10 mg/kg protected efficiently rat liver against the deleterious effects of IRI. This was evidenced by the significant decrease in transaminases levels and the better preservation of mitochondrial membrane polarization. Also, PEG 35 preserved hepatocyte morphology as reflected by an increased F-actin/G-actin ratio and confocal microscopy findings. In addition, PEG 35 protective mechanisms were correlated with the activation of the prosurvival kinase Akt and the cytoprotective factor AMPK and the inhibition of apoptosis. Thus, PEG may become a suitable agent to attempt pharmacological preconditioning against hepatic IRI. Copyright © 2016 Mohamed Bejaoui et al. Source

Serra-Perez A.,Institute of Biomedical Research of Barcelona IIBB | Planas A.M.,Institute of Biomedical Research of Barcelona IIBB | Nunez-O'Mara A.,Cell Biology and Stem Cells Unit | Berra E.,Cell Biology and Stem Cells Unit | And 3 more authors.
Journal of Biological Chemistry | Year: 2010

Hypoxia-inducible factor (HIF) is a heterodimeric transcription factor that activates the cellular response to hypoxia. The HIF1α subunit is constantly synthesized and degraded under normoxia, but degradation is rapidly inhibited when oxygen levels drop. Oxygen-dependent hydroxylation by prolyl-4-hydroxylases (PHD) mediates HIF1α proteasome degradation. Brain ischemia limits the availability not only of oxygen but also of glucose. We hypothesized that this circumstance could have a modulating effect on HIF. We assessed the separate involvement of oxygen and glucose in HIF1α regulation in differentiated neuroblastoma cells subjected to ischemia. We report higher transcriptional activity and HIF1α expression under oxygen deprivation in the presence of glucose (OD), than in its absence (oxygen and glucose deprivation, OGD). Unexpectedly, HIF1α was not degraded at reoxygenation after an episode of OGD. This was not due to impairment of proteasome function, but was associated with lower HIF1α hydroxylation. Krebs cycle metabolites fumarate and succinate are known inhibitors of PHD, while α-ketoglutarate is a co-substrate of the reaction. Lack of HIF1α degradation in the presence of oxygen was accompanied by a very low α-ketoglutarate/fumarate ratio. Furthermore, treatment with a fumarate analogue prevented HIF1α degradation under normoxia. In all, our data suggest that postischemic metabolic alterations in Krebs cycle metabolites impair HIF1α degradation in the presence of oxygen by decreasing its hydroxylation, and highlight the involvement of metabolic pathways in HIF1α regulation besides the well known effects of oxygen. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc. Source

Martinez L.,Institute of Biomedical Research of Barcelona IIBB | Martinez L.,CIBER ISCIII | Torres S.,Institute of Biomedical Research of Barcelona IIBB | Torres S.,CIBER ISCIII | And 14 more authors.
Oncotarget | Year: 2015

Palmitic acid (PA) induces hepatocyte apoptosis and fuels de novo ceramide synthesis in the endoplasmic reticulum (ER). Myristic acid (MA), a free fatty acid highly abundant in copra/palmist oils, is a predictor of nonalcoholic steatohepatitis (NASH) and stimulates ceramide synthesis. Here we investigated the synergism between MA and PA in ceramide synthesis, ER stress, lipotoxicity and NASH. Unlike PA, MA is not lipotoxic but potentiated PA-mediated lipoapoptosis, ER stress, caspase-3 activation and cytochrome c release in primary mouse hepatocytes (PMH). Moreover, MA kinetically sustained PA-induced total ceramide content by stimulating dehydroceramide desaturase and switched the ceramide profile from decreased to increased ceramide 14:0/ceramide16:0, without changing medium and long-chain ceramide species. PMH were more sensitive to equimolar ceramide14:0/ceramide16:0 exposure, which mimics the outcome of PA plus MA treatment on ceramide homeostasis, than to either ceramide alone. Treatment with myriocin to inhibit ceramide synthesis and tauroursodeoxycholic acid to prevent ER stress ameliorated PA plus MA induced apoptosis, similar to the protection afforded by the antioxidant BHA, the pan-caspase inhibitor z-VAD-Fmk and JNK inhibition. Moreover, ruthenium red protected PMH against PA and MA-induced cell death. Recapitulating in vitro findings, mice fed a diet enriched in PA plus MA exhibited lipodystrophy, hepatosplenomegaly, increased liver ceramide content and cholesterol levels, ER stress, liver damage, inflammation and fibrosis compared to mice fed diets enriched in PA or MA alone. The deleterious effects of PA plus MA-enriched diet were largely prevented by in vivo myriocin treatment. These findings indicate a causal link between ceramide synthesis and ER stress in lipotoxicity, and imply that the consumption of diets enriched in MA and PA can cause NASH associated with lipodystrophy. Source

Ordonez R.,University of Leon | Ordonez R.,CIBER ISCIII | Fernandez A.,University of Leon | Fernandez A.,CIBER ISCIII | And 14 more authors.
Journal of Pineal Research | Year: 2015

Autophagy is a process that maintains homeostasis during stress, although it also contributes to cell death under specific contexts. Ceramides have emerged as important effectors in the regulation of autophagy, mediating the crosstalk with apoptosis. Melatonin induces apoptosis of cancer cells; however, its role in autophagy and ceramide metabolism has yet to be clearly elucidated. This study was aimed to evaluate the effect of melatonin administration on autophagy and ceramide metabolism and its possible link with melatonin-induced apoptotic cell death in hepatocarcinoma (HCC) cells. Melatonin (2 mm) transiently induced autophagy in HepG2 cells through JNK phosphorylation, characterized by increased Beclin-1 expression, p62 degradation, and LC3II and LAMP-2 colocalization, which translated in decreased cell viability. Moreover, ATG5 silencing sensitized HepG2 cells to melatonin-induced apoptosis, suggesting a dual role of autophagy in cell death. Melatonin enhanced ceramide levels through both de novo synthesis and acid sphingomyelinase (ASMase) stimulation. Serine palmitoyltransferase (SPT) inhibition with myriocin prevented melatonin-induced autophagy and ASMase inhibition with imipramine-impaired autophagy flux. However, ASMase inhibition partially protected HepG2 cells against melatonin, while SPT inhibition significantly enhanced cell death. Findings suggest a crosstalk between SPT-mediated ceramide generation and autophagy in protecting against melatonin, while specific ASMase-induced ceramide production participates in melatonin-mediated cell death. Thus, dual blocking of SPT and autophagy emerges as a potential strategy to potentiate the apoptotic effects of melatonin in liver cancer cells. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Source

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