Hydroxyeicosapentaenoic acids from the Pacific krill show high ligand activities for PPARs.
ABSTRACT: PPARs regulate the expression of genes for energy metabolism in a ligand-dependent manner. PPARs can influence fatty acid oxidation, the level of circulating triglycerides, glucose uptake and insulin sensitivity. Here, we demonstrate that 5-hydroxyeicosapentaenoic acid (HEPE), 8-HEPE, 9-HEPE, 12-HEPE and 18-HEPE (hydroxylation products of EPA) obtained from methanol extracts of Pacific krill (Euphausia pacifica) can act as PPAR ligands. Two of these products, 8-HEPE and 9-HEPE, enhanced the transcription levels of GAL4-PPARs to a significantly greater extent than 5-HEPE, 12-HEPE, 18-HEPE, EPA, and EPA ethyl-ester. 8-HEPE also activated significantly higher transcription of GAL4-PPAR?, GAL4-PPAR?, and GAL4-PPAR? than EPA at concentrations greater than 4, 64, and 64 ?M, respectively. We also demonstrated that 8-HEPE increased the expression levels of genes regulated by PPARs in FaO, 3T3-F442A, and C2C12 cells. Furthermore, 8-HEPE enhanced adipogenesis and glucose uptake. By contrast, at the same concentrations, EPA showed weak or little effect, indicating that 8-HEPE was the more potent inducer of physiological effects.
Project description:PPARs regulate the expression of genes involved in lipid homeostasis. PPARs serve as molecular sensors of fatty acids, and their activation can act against obesity and metabolic syndromes. 8-Hydroxyeicosapentaenoic acid (8-HEPE) acts as a PPAR ligand and has higher activity than EPA. However, to date, the PPAR ligand activity of 8-HEPE has only been demonstrated in vitro. Here, we investigated its ligand activity in vivo by examining the effect of 8-HEPE treatment on high fat diet-induced obesity in mice. After the 4-week treatment period, the levels of plasma and hepatic triglycerides in the 8-HEPE-fed mice were significantly lower than those in the HFD-fed mice. The expression of genes regulated by PPAR? was significantly increased in 8-HEPE-fed mice compared to those that received only HFD. Additionally, the level of hepatic palmitic acid in 8-HEPE-fed mice was significantly lower than in HFD-fed mice. These results suggested that intake of 8-HEPE induced PPAR? activation and increased catabolism of lipids in the liver. We found no significant differences between EPA-fed mice and HFD-fed mice. We demonstrated that 8-HEPE has a larger positive effect on metabolic syndrome than EPA and that 8-HEPE acts by inducing PPAR? activation in the liver.
Project description:The metabolism and generation of bioactive lipid mediators are key events in the exertion of the beneficial effects of dietary omega-3 fatty acids in the regulation of allergic inflammation. Here, we found that dietary linseed oil, which contains high amounts of alpha-linolenic acid (ALA) dampened allergic rhinitis through eosinophilic production of 15-hydroxyeicosapentaenoic acid (15-HEPE), a metabolite of eicosapentaenoic acid (EPA). Lipidomic analysis revealed that 15-HEPE was particularly accumulated in the nasal passage of linseed oil-fed mice after the development of allergic rhinitis with the increasing number of eosinophils. Indeed, the conversion of EPA to 15-HEPE was mediated by the 15-lipoxygenase activity of eosinophils. Intranasal injection of 15-HEPE dampened allergic symptoms by inhibiting mast cell degranulation, which was mediated by the action of peroxisome proliferator-activated receptor gamma. These findings identify 15-HEPE as a novel EPA-derived, and eosinophil-dependent anti-allergic metabolite, and provide a preventive and therapeutic strategy against allergic rhinitis.
Project description:Resolvins are family of lipid mediators derived from omega-3 polyunsaturated fatty acids, which are generated during the resolution phase of acute inflammation. Resolvin E1 is biosynthesized from eicosapentaenoic acid via 18(R)-hydroxyeicosapentaenoic acid (18R-HEPE) in the Cox-2 and lipoxygenase mediated pathway and has proven to exhibit potent anti-inflammatory activity. We report herein the first total chemical synthesis of 18R-HEPE and demonstrate that this compound displays in vivo bioactivity by blocking neutrophil infiltration in a murine model of zymosan-induced peritonitis.
Project description:The ?-3 polyunsaturated fatty acids (PUFAs) mediate protective effects on several metabolic disorders. However, the functions of their metabolites in the early stage of nonalcoholic fatty liver disease (NAFLD) are largely unknown.Mice were fed a control diet, high-fat diet (HFD) or ?-3 PUFA-enriched HFD (?3HFD) for 4 days and phenotypes were analysed. LC-MS/MS was used to determine the eicosanoid profiles. Primary hepatocytes and peritoneal macrophages were used for the mechanism study.In short-term HFD-fed mice, the significantly increased lipid accumulation in the liver was reversed by ?-3 PUFA supplementation. Metabolomics showed that the plasma concentrations of hydroxyeicosapentaenoic acids (HEPEs) and epoxyeicosatetraenoic acids (EEQs) were reduced by a short-term HFD and markedly increased by the ?3HFD. However, HEPE/EEQ treatment had no direct protective effect on hepatocytes. ?3HFD also significantly attenuated HFD-induced adipose tissue inflammation. Furthermore, the expression of pro-inflammatory cytokines and activation of the JNK pathway induced by palmitate were suppressed by HEPEs and EEQs in macrophages. 17,18-EEQ, 5-HEPE and 9-HEPE were identified as the effective components among these metabolites, as indicated by their greater suppression of the palmitate-induced expression of inflammatory factors, chemotaxis and JNK activation compared to other metabolites in macrophages. A mixture of 17,18-EEQ, 5-HEPE and 9-HEPE significantly ameliorated the short-term HFD-induced accumulation of macrophages in adipose tissue and hepatic steatosis.17,18-EEQ, 5-HEPE and 9-HEPE may be potential approaches to prevent NAFLD in the early stage by inhibiting the inflammatory response in adipose tissue macrophages via JNK signalling.
Project description:N-3 polyunsaturated fatty acids (PUFAs) have potential cardiovascular benefit, although the mechanisms underlying this effect remain poorly understood. Fat-1 transgenic mice expressing Caenorhabditis elegans n-3 fatty acid desaturase, which is capable of producing n-3 PUFAs from n-6 PUFAs, exhibited resistance to pressure overload-induced inflammation and fibrosis, as well as reduced cardiac function. Lipidomic analysis revealed selective enrichment of eicosapentaenoic acid (EPA) in fat-1 transgenic bone marrow (BM) cells and EPA-metabolite 18-hydroxyeicosapentaenoic acid (18-HEPE) in fat-1 transgenic macrophages. BM transplantation experiments revealed that fat-1 transgenic BM cells, but not fat-1 transgenic cardiac cells, contributed to the antiremodeling effect and that the 18-HEPE-rich milieu in the fat-1 transgenic heart was generated by BM-derived cells, most likely macrophages. 18-HEPE inhibited macrophage-mediated proinflammatory activation of cardiac fibroblasts in culture, and in vivo administration of 18-HEPE reproduced the fat-1 mice phenotype, including resistance to pressure overload-induced maladaptive cardiac remodeling.
Project description:5-hydroxyeicosatetraenoic acid (5-HETE) and 5-hydroxyeicosapentaenoic acid (5-HEPE) are major metabolites produced by 5-lipoxygenase (5-LOX) from arachidonic acid (AA) and eicosapentaenoic acid (EPA). Effects of hydroxides on endothelial cells are unclear, although 5-LOX is known to increase at arteriosclerotic lesions. To investigate the effects of hydroxides on human umbilical vein endothelial cells (HUVECs), the cells were treated with 50 ?M each of AA, EPA, 5-HETE, and 5-HEPE. Treatment of HUVECs with 5-HETE and 5-HEPE, rather than with AA and EPA, increased the nuclear translocation of NF-E2 related factor 2 (Nrf2) and upregulated the expression of heme oxygenase-1 and cystine/glutamate transporter regulated by Nrf2. Reactive oxygen species (ROS) generation was markedly elevated in HUVECs after treatment with 5-HETE and 5-HEPE, and the pretreatment with ?-tocopherol abrogated ROS levels similar to those in the vehicle control. However, ROS generation was independent of Nrf2 activation induced by 5-HETE and 5-HEPE. 5-HETE was converted to 5-oxo-eicosatetraenoic acid (5-oxo-ETE) in HUVECs, and 5-oxo-ETE increased Nrf2 activation. These results suggest that 5-HETE works as an Nrf2 activator through the metabolite 5-oxo-ETE in HUVECs. Similarly, 5-HEPE works in the same way, because 5-HEPE is metabolized to 5-oxo-eicosapentaenoic acid through the same pathway as that for 5-HETE.
Project description:Eicosapentaenoic acid (EPA) has garnered attention after the success of the REDUCE-IT trial, which contradicted previous conclusions on EPA for cardiovascular disease risk. Here we first investigated EPA's preventative role on hyperglycemia and hyperinsulinemia. EPA ethyl esters prevented obesity-induced glucose intolerance, hyperinsulinemia, and hyperglycemia in C57BL/6J mice. Supporting NHANES analyses showed that fasting glucose levels of obese adults were inversely related to EPA intake. We next investigated how EPA improved murine hyperinsulinemia and hyperglycemia. EPA overturned the obesity-driven decrement in the concentration of 18-hydroxyeicosapentaenoic acid (18-HEPE) in white adipose tissue and liver. Treatment of obese inbred mice with RvE1, the downstream immunoresolvant metabolite of 18-HEPE, but not 18-HEPE itself, reversed hyperinsulinemia and hyperglycemia through the G-protein coupled receptor ERV1/ChemR23. To translate the findings, we determined if the effects of RvE1 were dependent on host genetics. RvE1's effects on hyperinsulinemia and hyperglycemia were divergent in diversity outbred mice that model human genetic variation. Secondary SNP analyses further confirmed extensive genetic variation in human RvE1/EPA-metabolizing genes. Collectively, the data suggest EPA prevents hyperinsulinemia and hyperglycemia, in part, through RvE1's activation of ERV1/ChemR23 in a host genetic manner. The studies underscore the need for personalized administration of RvE1 based on genetic/metabolic enzyme profiles.
Project description:Omega-6 and omega-3 polyunsaturated fatty acids (n-6 and n-3 PUFA) can modulate inflammatory processes. In western diets, the content of n-6 PUFA is much higher than that of n-3 PUFA, which has been suggested to promote a pro-inflammatory phenotype. The aim of this study was to analyze the effect of modulating the n-6/n-3 PUFA ratio on the formation of monohydroxylated fatty acid (HO-FAs) derived from the n-6 PUFA arachidonic acid (AA) and the n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in THP-1 macrophages by means of LC-MS. Lipid metabolites were measured in THP-1 macrophage cell pellets. The concentration of AA-derived hydroxyeicosatetraenoic acids (HETEs) was not significantly changed when incubated THP-1 macrophages in a high AA/(EPA+DHA) ratio of 19/1 vs. a low ratio AA/(EPA+DHA) of 1/1 (950.6 ± 110 ng/mg vs. 648.2 ± 92.4 ng/mg, p = 0.103). Correspondingly, the concentration of EPA-derived hydroxyeicosapentaenoic acids (HEPEs) and DHA-derived hydroxydocosahexaenoic acids (HDHAs) were significantly increased (63.9 ± 7.8 ng/mg vs. 434.4 ± 84.3 ng/mg, p = 0.012 and 84.9 ± 18.3 ng/mg vs. 439.4 ± 82.7 ng/mg, p = 0.014, respectively). Most notable was the strong increase of 18-hydroxyeicosapentaenoic acid (18-HEPE) formation in THP-1 macrophages, with levels of 170.9 ± 40.2 ng/mg protein in the high n-3 PUFA treated cells. Thus our data indicate that THP-1 macrophages prominently utilize EPA and DHA for monohydroxylated metabolite formation, in particular 18-HEPE, which has been shown to be released by macrophages to prevent pressure overload-induced maladaptive cardiac remodeling.
Project description:Polyunsaturated fatty acids (PUFA) are precursors of bioactive metabolites and mediators. In this study, the profile of hydroxyeicosatetraenoic (HETE), hydroxyeicosapentaenoic (HEPE) and hydroxydocosahexaenoic (HDHA) acids derived from arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in colon, liver, lung, spleen, muscle, heart and kidney tissue of healthy wildtype mice were characterized, and compared to profiles in organs from transgenic fat-1 mice engineered to express the Caenorhabditis elegans fat-1 gene encoding an n-3 desaturase and thereby with endogenously elevated n-3 PUFA levels. PUFAs were measured using gas chromatography. The lipid metabolites were assayed using LC-MS/MS. AA and DHA were the prominent PUFAs in wildtype and fat-1 mice. EPA levels were low in both groups even though there was a significant increase in fat-1 organs with an up to 12-fold increase in fat-1 spleen and kidney. DHA levels increased by approximately 1.5-fold in fat-1 as compared to wildtype mice. While HETEs remained the same or decreased moderately and HDHAs increased 1- to 3-fold, HEPE formation in fat-1 tissues increased from 8- (muscle) to 44-fold (spleen). These findings indicate distinct profiles of monohydroxy lipid metabolites in different organs and strong utilization of EPA for HEPE formation, by which moderate EPA supplementation might trigger formation of biologically active EPA-derived resolvins.
Project description:Peroxisome proliferator-activated receptors (PPARs) belong to the family of ligand-activated nuclear receptors. The PPAR family consists of three subtypes encoded by three separate genes: PPAR? (NR1C1), PPAR?/? (NR1C2), and PPAR? (NR1C3). PPARs are critical regulators of metabolism and exhibit tissue and cell type-specific expression patterns and functions. Specific PPAR ligands have been proposed as potential therapies for a variety of diseases such as metabolic syndrome, cancer, neurogenerative disorders, diabetes, cardiovascular diseases, endometriosis, and retinopathies. In this review, we focus on the knowledge of PPAR function in angiogenesis, a complex process that plays important roles in numerous pathological conditions for which therapeutic use of PPAR modulation has been suggested.