Natàlia Ferré

Obesity-induced insulin resistance and hepatic steatosis are alleviated by ω-3 fatty acids: a role for resolvins and protectins

Omega‐3‐polyunsaturated fatty acids (w‐3‐PUFAs) have well‐documented protective effects that are attributed not only to eicosanoid inhibition but also to the formation of novel biologically active lipid mediators (i.e., resolvins and protectins). In this study, we examined their effects on ob/ob mice, an obesity model of insulin resistance and fatty liver disease. Dietary intake ofw‐3‐PUFAs had insulin‐sensitizing actions in adipose tissue and liver and improved insulin tolerance in obese mice. Genes involved in insulin sensitivity (PPAR/γ), glucose transport (GLUT‐2/GLUT–4), and insulin receptor signaling (IRS‐1/IRS–2) were up‐regulated byw‐3‐PUFAs. Moreover,w‐3‐PUFAs increased adiponectin, an anti‐inflammatory and insulin‐sensitizing adipokine, and induced AMPK phosphorylation, a fuel‐sensing enzyme and a gatekeeper of the energy balance. Concomitantly, hepatic steatosis was alleviated byw‐3‐PUFAs. A lipidomic analysis with liquid chromatography/mass spectrome‐try/mass spectrometry revealed that w‐3‐PUFAs inhibited the formation of w‐6‐PUFA‐derived eicosanoids, while triggering the formation of w‐3‐PUFA‐derived resolvins and protectins. Moreover, representative members of these lipid mediators, namely resolvin E1 and protectin D1, mimicked the insulin‐sensitizing and antisteatotic effects of w‐3‐PUFAs and induced adiponectin expression to a similar extent that of rosigli‐tazone, a member of the thiazolidinedione family of antidiabetic drugs. Taken together, these findings uncover beneficial actions of w‐3‐PUFAs and their bioactive lipid autacoids in preventing obesity‐induced insulin resistance and hepatic steatosis.—Gonzalez‐Periz, A.,Horrillo, R., Ferre, N., Gronert, K., Dong, B., Moran‐Salvador, E.,Titos, E., Martinez‐Clemente, M.,Lopez‐Parra, M.,Arroyo, V., Claria, J. Obesity‐induced insulin resistance and hepatic steatosis are alleviated byw‐3 fatty acids: a role for resolvins and protectins. FASEB J. 23, 1946–1957 (2009)

Docosahexaenoic acid (DHA) blunts liver injury by conversion to protective lipid mediators: protectin D1 and 17S-hydroxy-DHA

Docosahexaenoic acid (DHA) is a ω‐3 essential fatty acid that reduces the incidence and severity of a number of diseases. Recently, a novel series of DHA‐derived lipid mediators with potent protective actions has been identified. In this study we demonstrate that dietary amplification of these DHA‐derived products protects the liver from necroinflammatory injury. In vitro, supplementation of hepatocytes with DHA significantly reduced hydrogen peroxide‐induced DNA damage, evaluated by the “comet assay,” and oxidative stress, determined by measurement of malondialdehyde levels. In vivo, dietary supplementation of mice with DHA ameliorated carbon tetrachloride‐induced necroinflammatory damage. In addition, hepatic cyclooxygenase‐2 expression and PGE2 levels were significantly reduced in mice fed DHA‐enriched diets. In these animals, increased hepatic formation of DHA‐derived lipid mediators (i.e., 17S‐hydroxy‐DHA (17S‐HDHA) and protectin D1) was detected by HPLC‐gas chromatography/mass spectrometry analysis. Consistent with these findings, synthetic 17‐HDHA abrogated genotoxic and oxidative damage in hepatocytes and decreased TNF‐α release and 5‐lipoxygenase expression in macrophages. In a transactivation assay, 17‐ HDHA acted in a concentration‐dependent manner as a PPARγ agonist. Taken together, these findings identify a potential role for DHA‐derived products, specifically 17S‐HDHA and protectin D1, in mediating the protective effects of dietary DHA in necroinflammatory liver injury.—González‐Périz, A., Planagumà, A., Gronert, K., Miquel, R., López‐Parra, M., Titos, E., Horrillo, R., Ferré, N., Deulofeu, R., Arroyo, V., Rodés, J., Clària, J. Docosahexaenoic acid (DHA) blunts liver injury by conversion to protective lipid mediators: protectin D1 and 17S‐hydroxy‐DHA. FASEB J. 20, E1844–E1855 (2006)

Regulation of Serum Paraoxonase Activity by Genetic, Nutritional, and Lifestyle Factors in the General Population

BACKGROUND Paraoxonase may protect lipoproteins and cell membranes from peroxidation, and alterations in the activity of this enzyme have been associated with some chronic diseases. Serum paraoxonase appears to be mainly under genetic control, but some studies suggest that environmental factors may also modulate its activity. The aim of the present study was to investigate whether diet and lifestyle affect serum paraoxonase activity. METHODS We studied a population-based sample of 388 individuals (194 women and 194 men; age range, 18-75 years) and assessed their daily dietary intake using a 3-day estimated food record. The variables studied included serum paraoxonase activity, paraoxonase polymorphisms at positions 55 and 192, age, gender, smoking status, physical exercise, body mass index, energy consumption, nutrient intake (total lipids, saturated fatty acids, beta-carotenes, vitamins C and E), and serum lipid concentrations. RESULTS Multiple linear regression analysis showed that only genetic polymorphisms, serum cholesterol, HDL-cholesterol concentrations, and cigarette smoking were significant predictors of serum paraoxonase activity. HDL-cholesterol concentrations were also related to body mass index, daily energy consumption, and saturated fatty acid intake. CONCLUSIONS The between-individual variability of serum paraoxonase activity is regulated mainly by genetic determinants. Although HDL-cholesterol and tobacco smoking may contribute to the modulation of this enzyme, the other nutritional and lifestyle factors do not seem to play a significant role.

5-Lipoxygenase Activating Protein Signals Adipose Tissue Inflammation and Lipid Dysfunction in Experimental Obesity

The presence of the so-called low-grade inflammatory state is recognized as a critical event in adipose tissue dysfunction, leading to altered secretion of adipokines and free fatty acids (FFAs), insulin resistance, and development of hepatic complications associated with obesity. This study was designed to investigate the potential contribution of the proinflammatory 5-lipoxygenase (5-LO) pathway to adipose tissue inflammation and lipid dysfunction in experimental obesity. Constitutive expression of key components of the 5-LO pathway, as well as leukotriene (LT) receptors, was detected in adipose tissue as well as in adipocyte and stromal vascular fractions. Adipose tissue from obese mice, compared with that from lean mice, exhibited increased 5-LO activating protein (FLAP) expression and LTB4 levels. Incubation of adipose tissue with 5-LO products resulted in NF-κB activation and augmented secretion of proinflammatory adipokines such as MCP-1, IL-6, and TNF-α. In addition, LTB4, but not LTD4, reduced FFA uptake in primary adipocytes, whereas 5-LO inhibition suppressed isoproterenol-induced adipose tissue lipolysis. In mice with dietary obesity, elevated FLAP expression in adipose tissue was paralleled with macrophage infiltration, increased circulating FFA levels, and hepatic steatosis, phenomena that were reversed by FLAP inhibition with Bay-X-1005. Interestingly, FLAP inhibition induced AMP-activated protein kinase phosphorylation in parallel with decreases in hormone-sensitive lipase activity and the expression and secretion of TNF-α and IL-6. Similar effects were observed in differentiated 3T3-L1 adipocytes incubated with either Bay-X-1005 or the selective LTB4 receptor antagonist U-75302. Taken together, these findings indicate that the 5-LO pathway signals the adipose tissue low-grade inflammatory state and steatogenic potential in experimental obesity.

Paraoxonase-1 is related to inflammation, fibrosis and PPAR delta in experimental liver disease.

BackgroundParaoxonase-1 (PON1) is an antioxidant enzyme synthesized by the liver. It protects against liver impairment and attenuates the production of the pro-inflammatory monocyte chemoattractant protein-1 (MCP-1). We investigated the relationships between hepatic PON1 and MCP-1 expression in rats with liver disease and explored the possible molecular mechanisms involved.MethodsCCl4 was administered for up to 12 weeks to induce liver damage. Serum and hepatic levels of PON1 and MCP-1, their gene and protein expression, nuclear transcription factors, and histological and biochemical markers of liver impairment were measured.ResultsHigh levels of PON1 and MCP-1 expression were observed at 12th week in the hepatocytes surrounding the fibrous septa and inflammatory areas. CCl4-administered rats had an increased hepatic PON1 concentration that was related to decreased gene transcription and inhibited protein degradation. Decreased PON1 gene transcription was associated with PPARδ expression. These changes were accompanied by increased hepatic MCP-1 concentration and gene expression. There were significant direct relationships between hepatic PON1 and MCP-1 concentrations (P = 0.005) and between PON1 and the amount of activated stellate cells (P = 0.001).ConclusionOur results from this experimental model suggest a hepato-protective role for PON1 against inflammation, fibrosis and liver disease mediated by MCP-1.

Time-Course Of Changes In Hepatic Lipid Peroxidation And Glutathione Metabolism In Rats With Carbon Tetrachloride-Induced Cirrhosis

1. The aims of the present study were to assess: (i) the temporal relationships between hepatic lipid peroxidation, changes in the glutathione detoxification system and the onset/development of cirrhosis in CCl4‐treated rats; and (ii) the effects of oral zinc administration on these parameters.

The continuous administration of aspirin attenuates atherosclerosis in apolipoprotein E-deficient mice

Aspirin reduces the incidence of thrombotic occlusive events. Classically this has been thought to be due to the platelet inhibitory action of aspirin but it has recently been shown that inflammation plays a predominant role in the initiation and progression of lesions in atherosclerosis. In humans, treatment with aspirin reduces cardiovascular risk and slows carotid plaque growth in a dose-dependent fashion. We have explored this issue in Apo E-deficient mice on a high-fat, high cholesterol diet which provided these animals with a continuous administration of 500 microg/day of acetylsalicylic acid in the drinking water. After 10 weeks of treatment, the size of the atherosclerotic lesion at the aortic sinus had reduced by 35%. At the end of the trial there were no significant changes in either plasma lipids or in the quantitative distribution among lipoproteins. Likewise, the total antioxidant status and the resistance of plasma to oxidation in vitro was similar and there was no change in the distribution of iron deposits and in the relative composition of plasma pro-oxidants and antioxidants, or in the concentration of plasma in ferritin. Therefore, it is our hypothesis that the antiinflammatory effect is responsible for the reduction in lesion size. We propose that antiinflammatory molecules which do not cause gastrointestinal complications should be tested in humans to determine long-term efficacy in the attenuation of atherosclerosis.

Feeding apolipoprotein E-knockout mice with cholesterol and fat enriched diets may be a model of non-alcoholic steatohepatitis

The present study was aimed (1) to investigate the effect of cholesterol and fat enriched diets on the development of steatohepatitis in apolipoprotein E-knockout mice, and (2) to study the chronological relationships between the development of hepatic alterations, hypercholesterolemia and atherosclerotic lesions in this experimental model. The study consisted of two protocols. Protocol 1 was used in 90 mice subdivided in groups of 18. For 10 weeks, each group was given a diet with different fat and cholesterol contents. Protocol 2 was used in 42 mice, subdivided in four groups. Each group was given a diet enriched with cholesterol and palm oil and they were sacrificed at 8, 13, 18 and 24 weeks of age. Results were as following. (1) Mice given high fat/high cholesterol diets developed an impairment of liver histology consisting of fat accumulation, macrophage proliferation, and inflammation. (2) These effects were modulated by the type of fat: olive oil was mainly associated with macrovesicular steatosis and cholesterol plus palm oil with severe steatohepatitis. (3) There was a chronological and quantitative relationship between liver impairment and the formation of atheromatous lesions. We conclude that apolipoprotein E-knockout mice may be a useful model for investigating the mechanisms of diet-induced steatohepatitis. (Mol Cell Biochem 268: 53–58, 2008)

5‐lipoxygenase deficiency reduces hepatic inflammation and tumor necrosis factor α–induced hepatocyte damage in hyperlipidemia‐prone ApoE‐null mice

The actual risk factors that drive hepatic inflammation during the transition from steatosis to steatohepatitis are unknown. We recently demonstrated that hyperlipidemia‐prone apolipoprotein E–deficient (ApoE−/−) mice exhibit hepatic steatosis and increased susceptibility to hepatic inflammation and advanced fibrosis. Because the proinflammatory 5‐lipoxygenase (5‐LO) pathway was found to be up‐regulated in these mice and given that 5‐LO deficiency confers cardiovascular protection to ApoE−/− mice, we determined the extent to which the absence of 5‐LO would alter liver injury in these mice. Compared with ApoE−/− mice, which showed expected hepatic steatosis and inflammation, ApoE/5‐LO double‐deficient (ApoE−/−/5‐LO−/−) mice exhibited reduced hepatic inflammation, macrophage infiltration, tumor necrosis factor α (TNF‐α), monocyte chemoattractant protein‐1 (MCP‐1) and interleukin (IL)‐18 expression, caspase‐3 and nuclear factor‐κB (NF‐κB) activities, and serum alanine aminotransferase levels in the absence of changes in hepatic steatosis. The lack of 5‐LO produced a remarkable insulin‐sensitizing effect in the adipose tissue because peroxisome proliferator‐activated receptor γ, insulin receptor substrate‐1, and adiponectin were up‐regulated, whereas c‐Jun amino‐terminal kinase phosphorylation and MCP‐1 and IL‐6 expression were down‐regulated. On the other hand, hepatocytes isolated from ApoE−/−/5‐LO−/− mice were more resistant to TNF‐α–induced apoptosis. The 5‐LO products leukotriene (LT) B4, LTD4, and 5‐HETE consistently triggered TNF‐α–induced apoptosis and compromised hepatocyte survival by suppressing NF‐κB activity in the presence of actinomycin D. Moreover, ApoE−/−/5‐LO−/− mice were protected against sustained high‐fat diet (HFD)‐induced liver injury and hepatic inflammation, macrophage infiltration and insulin resistance were significantly milder than those of ApoE−/− mice. Finally, pharmacological inhibition of 5‐LO significantly reduced hepatic inflammatory infiltrate in the HFD and ob/ob models of fatty liver disease. Conclusion: These combined data indicate that hyperlipidemic mice lacking 5‐LO are protected against hepatic inflammatory injury, suggesting that 5‐LO is involved in mounting hepatic inflammation in metabolic disease. (HEPATOLOGY 2010.)

Inhibition of hepatic cell nuclear DNA fragmentation by zinc in carbon tetrachloride-treated rats.

BACKGROUND/AIMS The aims of this study were to ascertain: 1) whether hepatic cell DNA fragmentation is increased in rats with early stages of liver disease induced by carbon tetrachloride; 2) whether the inhibition of DNA cleavage is involved in the hepatoprotective effects of zinc; and 3) if relationships exist between DNA fragmentation and the onset of fibrosis in this experimental model. METHODS Twenty-one treated rats and 23 controls were divided into two groups to receive either a standard diet or one supplemented with zinc. All the animals were sacrificed 1 week later for histological and biochemical assessments, which included a DNA fragmentation index, hepatic zinc and metallothionein concentrations, fibrosis measured by hepatic hydroxyproline concentration and plasma alanine aminotransferase activity. RESULTS Hepatic cell DNA fragmentation was increased in rats with early hepatic fibrosis and the increase was independent of hepatocytolysis, as measured by alanine aminotransferase activity. Oral zinc administration inhibited hepatic cell DNA fragmentation in the treated rats and was proportional to the hepatic concentration of the metal. The mechanism of the zinc-mediated decrease in DNA cleavage was related to an increase in the hepatic metallothionein concentration. Hepatic cell DNA fragmentation was related to hydroxyproline concentration. CONCLUSIONS Our results suggest that apoptosis may be involved in the early transformations occurring in the liver and which can lead to the initiation of cirrhosis. As such, the potential therapeutic use of zinc supplementation would warrant further investigation.