N-3 PUFA Supplementation Triggers PPAR-α Activation and PPAR-α/NF-κB Interaction: Anti-Inflammatory Implications in Liver Ischemia-Reperfusion Injury

Dietary supplementation with the n-3 polyunsaturated fatty acids (n-3 PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to rats preconditions the liver against ischemia-reperfusion (IR) injury, with reduction of the enhanced nuclear factor-κB (NF-κB) functionality occurring in the early phase of IR injury, and recovery of IR-induced pro-inflammatory cytokine response. The aim of the present study was to test the hypothesis that liver preconditioning by n-3 PUFA is exerted through peroxisone proliferator-activated receptor α (PPAR-α) activation and interference with NF-κB activation. For this purpose we evaluated the formation of PPAR-α/NF-κBp65 complexes in relation to changes in PPAR-α activation, IκB-α phosphorylation and serum levels and expression of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in a model of hepatic IR-injury (1 h of ischemia and 20 h of reperfusion) or sham laparotomy (controls) in male Sprague Dawley rats. Animals were previously supplemented for 7 days with encapsulated fish oil (General Nutrition Corp., Pittsburg, PA) or isovolumetric amounts of saline (controls). Normalization of IR-altered parameters of liver injury (serum transaminases and liver morphology) was achieved by dietary n-3 PUFA supplementation. EPA and DHA suppression of the early IR-induced NF-κB activation was paralleled by generation of PPAR-α/NF-κBp65 complexes, in concomitance with normalization of the IR-induced IκB-α phosphorylation. PPAR-α activation by n-3 PUFA was evidenced by enhancement in the expression of the PPAR-α-regulated Acyl-CoA oxidase (Acox) and Carnitine-Palmitoyl-CoA transferase I (CPT-I) genes. Consistent with these findings, normalization of IR-induced expression and serum levels of NF-κB-controlled cytokines IL-lβ and TNF-α was observed at 20 h of reperfusion. Taken together, these findings point to an antagonistic effect of PPAR-α on NF-κB-controlled transcription of pro-inflammatory mediators. This effect is associated with the formation of PPAR-α/NF-κBp65 complexes and enhanced cytosolic IκB-α stability, as major preconditioning mechanisms induced by n-3 PUFA supplementation against IR liver injury

Prevention of liver steatosis through fish oil supplementation: correlation of oxidative stress with insulin resistance and liver fatty acid content

Non-alcoholic fatty liver disease (NAFLD) is triggered by a nutritional-metabolic alteration characterized by triacylglicerides acumulation, insulin resistance (IR), oxidative stress and depletion of polyunsaturated fatty acid (PUFA). The n-3 PUFA, such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, would be hepatoprotective against the development of NAFLD by stimulating lipolysis and inhibit lipogenesis. So, fish oil supplementation (EPA + DHA) prevents HFDinduced NAFLD. In this context, the aim of this study is to evaluate the correlation between liver oxidative stress with IR and levels of PUFA in supplemented mice. Male mice C57BL/6J (n=9) were fed for 12th week: a) control diet (20% protein, 70% carbohydrate, 10% lipids), b) control diet and fish oil supplementation (200 mg EPA+DHA/kg/day), c) high fat diet (20% protein, 20% carbohydrate, 60% lipids), and d) high fat diet and fish oil supplementation. Liver steatosis (histology), insulin resistance (HOMA), liver oxidative stress (GSH/GSSG, carbonyl protein and 8-isoprostanes) and liver fatty acid content were evaluated. The significant decrease in liver oxidative stress parameters (p<0.05, ANOVA followed by Newman Keuls test) were correlated (Pearson test) with HOMA and levels of PUFA, along with the hepatoprotection observed. It concludes that prevention of NAFLD by supplementation with fish oil (EPA+DHA) is dependent of the prevention of liver oxidative stress, IR and PUFA depletion.La enfermedad por hígado graso no alcohólica (EHGNA) está provocada por una alteración metabólico-nutricional caracterizada por la acumulación de triacilglicéridos, resistencia a la insulina, estrés oxidativo y disminución de ácidos grasos poliinsaturados (AGPI). Los AGPI ω-3, como los ácidos eicosapentaenoico (EPA) y docosahexaenoico (DHA), serían hepatoprotectores contra la EHGNA al estimular la lipolisis e inhibir la lipogénesis hepática. La suplementación con aceite de pescado (EPA + DHA) previene la esteatosis hepática inducida por una dieta alta en grasas. En este contexto, el objetivo de este estudio es evaluar la correlación entre el estrés oxidativo hepático, la resistencia a la insulina y los niveles de AGPI ω-3 en ratones suplementados. Ratones machos C57BL/6J (n=9) alimentados durante 12 semanas con: a) dieta control (20% proteína, 70% hidratos de carbono, 10% lípidos), b) dieta control y suplementación con 200 mg de EPA+DHA/kg/día, c) dieta alta en grasa (20% proteína, 20% hidratos de carbono, 60% lípidos), y d) dieta alta en grasas más EPA+DHA. Se evaluaron la esteatosis hepática (histología), resistencia a la insulina (HOMA), estrés oxidativo hepático (GSH/GSSG, proteínas carboniladas y 8-isoprostanos) y el contenido de ácidos grasos hepáticos. La disminución significativa en los parámetros hepáticos de estrés oxidativo (p <0,05, ANOVA seguido de Newman-Keuls) se correlacionó positivamente (test de Pearson) con el HOMA y los niveles de AGPI ω-3, junto con la hepatoprotección observada. Se concluye que la prevención de EHGNA por suplementación con EPA+DHA, se acompaña de una correlación inversa entre el estrés oxidativo y la resistencia a la insulina y la disminución de AGPI ω-3 hepáticos