4-Hydroxy hexenal derived from dietary n-3 polyunsaturated fatty acids induces anti-oxidative enzyme heme oxygenase-1 in multiple organs

Habitual fish consumption and healthy lifestyle behaviours may be associated with higher total serum bilirubin level and anti-inflammatory activity: a cross-sectional study

Habitual fish consumption and a healthy lifestyle are associated with lower atherosclerotic CVD (ASCVD) risk. Mildly elevated bilirubin, an end product of Hb metabolism, may be associated with anti-inflammatory effects, suppressing ASCVD risk. No data exist on the relationship between fish consumption, total serum bilirubin (TSB) and inflammation in clinical settings. We conducted a cross-sectional study between April 2019 and March 2020 in a cohort of 8292 participants (average age, 46·7 (sd 12·9) years and 58·9 % men) with no history of ASCVD and TSB concentrations < 2·0 mg/dl. Multiple stepwise regression analysis showed Hb concentrations were a solid positive determinant of TSB concentrations (β = 0·302, P< 0·0001). Fish consumption (β = 0·025, P= 0·019) and aerobic exercise (β = 0·021, P= 0·043) were statistically weak but significantly positive determinants of TSB concentrations. Cigarette smoking negatively affected TSB concentrations (β = −0·104, P< 0·0001). Moreover, with increasing fish consumption, the proportion of participants with a habit of cigarette smoking decreased, and that of participants who engaged in aerobic exercises increased (P< 0·0001 for both). Furthermore, as TSB concentrations increased, the leukocyte counts and C-reactive protein concentrations decreased (P< 0·0001 for both). In conclusion, despite the lesser relevance given to TSB concentrations than Hb concentrations, higher fish consumption and healthier lifestyle behaviours related to fish consumption habits may be additively or synergistically associated with higher TSB concentrations and anti-inflammatory activity, leading to attenuated ASCVD risk. Further investigations are needed to clarify the causal relationships between these factors.

Heme oxygenase-1: A potential therapeutic target for improving skeletal muscle atrophy

Skeletal muscle atrophy is a common muscle disease that is directly caused by an imbalance in protein synthesis and degradation. At the histological level, it is mainly characterized by a reduction in muscle mass and fiber cross-sectional area (CSA). Patients with skeletal muscle atrophy present with reduced motor ability, easy fatigue, and poor life quality. Heme oxygenase-1 (HO-1) is an inducible enzyme that catalyzes the degradation of heme and has attracted much attention for its anti-oxidation effects. In addition, there is growing evidence that HO-1 plays an important role in anti-inflammatory, anti-apoptosis, pro-angiogenesis, and maintaining skeletal muscle homeostasis, making it a potential therapeutic target for improving skeletal muscle atrophy. Here, we review the pathogenesis of skeletal muscle atrophy, the biology of HO-1 and its regulation, and the biological function of HO-1 in skeletal muscle homeostasis, with a specific focus on the role of HO-1 in skeletal muscle atrophy, aiming to observe the therapeutic potential of HO-1 for skeletal muscle atrophy.

Targeting NRF2-KEAP1 axis by Omega-3 fatty acids and their derivatives: Emerging opportunities against aging and diseases

The transcription factor NRF2 and its endogenous inhibitor KEAP1 play a crucial role in the maintenance of cellular redox homeostasis by regulating the gene expression of diverse networks of antioxidant, anti-inflammatory, and detoxification enzymes. Therefore, activation of NRF2 provides cytoprotection against numerous pathologies, including age-related diseases. An age-associated loss of NRF2 function may be a key driving force behind the aging phenotype. Recently, numerous NRF2 inducers have been identified and some of them are promising candidates to restore NRF2 transcriptional activity during aging. Emerging evidence indicates that omega-3 (n-3) polyunsaturated fatty acids (PUFAs) and their electrophilic derivatives may trigger a protective response via NRF2 activation, rescuing or maintaining cellular redox homeostasis. In this review, we provide an overview of the NRF2-KEAP1 system and its dysregulation in aging cells. We also summarize current studies on the modulatory role of n-3 PUFAs as potential agents to prevent multiple chronic diseases and restore the age-related impairment of NRF2 function.

Dynamic Role of Phospholipases A2 in Health and Diseases in the Central Nervous System

Phospholipids are major components in the lipid bilayer of cell membranes. These molecules are comprised of two acyl or alkyl groups and different phospho-base groups linked to the glycerol backbone. Over the years, substantial interest has focused on metabolism of phospholipids by phospholipases and the role of their metabolic products in mediating cell functions. The high levels of polyunsaturated fatty acids (PUFA) in the central nervous system (CNS) have led to studies centered on phospholipases A2 (PLA2s), enzymes responsible for cleaving the acyl groups at the sn-2 position of the phospholipids and resulting in production of PUFA and lysophospholipids. Among the many subtypes of PLA2s, studies have centered on three major types of PLA2s, namely, the calcium-dependent cytosolic cPLA2, the calcium-independent iPLA2 and the secretory sPLA2. These PLA2s are different in their molecular structures, cellular localization and, thus, production of lipid mediators with diverse functions. In the past, studies on specific role of PLA2 on cells in the CNS are limited, partly because of the complex cellular make-up of the nervous tissue. However, understanding of the molecular actions of these PLA2s have improved with recent advances in techniques for separation and isolation of specific cell types in the brain tissue as well as development of sensitive molecular tools for analyses of proteins and lipids. A major goal here is to summarize recent studies on the characteristics and dynamic roles of the three major types of PLA2s and their oxidative products towards brain health and neurological disorders.

Proteomic Analysis of Cardiac Adaptation to Exercise by High Resolution Mass Spectrometry

Regular exercise has many health benefits, among which is a significant reduction of cardiovascular risk. Although many beneficial effects of exercise are well described, the exact mechanisms by which exercise confers cardiovascular benefits are yet to be fully understood. In the current study, we have used high resolution mass spectrometry to determine the proteomic responses of the heart to exercise training in mice. The impact of exercise-induced oxidative stress on modifications of cardiomyocyte proteins with lipid peroxidation biomarker 4-hydroxynonenal (4-HNE) was examined as well. Fourteen male mice were randomized into the control (sedentary) group and the exercise group that was subjected to a swim exercise training program for 5 days a week for 5 months. Proteins were isolated from the left ventricular tissue, fractionated and digested for shotgun proteomics. Peptides were separated by nanoliquid chromatography and analyzed on an Orbitrap Fusion mass spectrometer using high-energy collision–induced dissociation and electron transfer dissociation fragmentation. We identified distinct ventricular protein signatures established in response to exercise training. Comparative proteomics identified 23 proteins that were upregulated and 37 proteins that were downregulated with exercise, in addition to 65 proteins that were identified only in ventricular tissue samples of exercised mice. Most of the proteins specific to exercised mice are involved in respiratory electron transport and/or implicated in glutathione conjugation. Additionally, 10 proteins were found to be modified with 4-HNE. This study provides new data on the effects of exercise on the cardiac proteome and contributes to our understanding of the molecular mechanisms underlying the beneficial effects of exercise on the heart.

Heme-oxygenase and lipid mediators in obesity and associated cardiometabolic diseases: Therapeutic implications

Obesity-mediated metabolic syndrome remains the leading cause of death worldwide. Among many potential targets for pharmacological intervention, a promising strategy involves the heme oxygenase (HO) system, specifically its inducible form, HO-1. This review collects and updates much of the current knowledge relevant to pharmacology and clinical medicine concerning HO-1 in metabolic diseases and its effect on lipid metabolism. HO-1 has pleotropic effects that collectively reduce inflammation, while increasing vasodilation and insulin and leptin sensitivity. Recent reports indicate that HO-1 with its antioxidants via the effect of bilirubin increases formation of biologically active lipid metabolites such as epoxyeicosatrienoic acid (EET), omega-3 and other polyunsaturated fatty acids (PUFAs). Similarly, HO-1and bilirubin are potential therapeutic targets in the treatment of fat-induced liver diseases. HO-1-mediated upregulation of EET is capable not only of reversing endothelial dysfunction and hypertension, but also of reversing cardiac remodeling, a hallmark of the metabolic syndrome. This process involves browning of white fat tissue (i.e. formation of healthy adipocytes) and reduced lipotoxicity, which otherwise will be toxic to the heart. More importantly, this review examines the activity of EET in biological systems and a series of pathways that explain its mechanism of action and discusses how these might be exploited for potential therapeutic use. We also discuss the link between cardiac ectopic fat deposition and cardiac function in humans, which is similar to that described in obese mice and is regulated by HO-1-EET-PGC1α signaling, a potent negative regulator of the inflammatory adipokine NOV.

Docosahexaenoic Acid (DHA) Supplementation Alters Phospholipid Species and Lipid Peroxidation Products in Adult Mouse Brain, Heart, and Plasma

The abundance of docosahexaenoic acid (DHA) in phospholipids in the brain and retina has generated interest to search for its role in mediating neurological functions. Besides the source of many oxylipins with pro-resolving properties, DHA also undergoes peroxidation, producing 4-hydroxyhexenal (4-HHE), although its function remains elusive. Despite wide dietary consumption, whether supplementation of DHA may alter the peroxidation products and their relationship to phospholipid species in brain and other body organs have not been explored sufficiently. In this study, adult mice were administered a control or DHA-enriched diet for 3 weeks, and phospholipid species and peroxidation products were examined in brain, heart, and plasma. Results demonstrated that this dietary regimen increased (n-3) and decreased (n-6) species to different extent in all major phospholipid classes (PC, dPE, PE-pl, PI and PS) examined. Besides changes in phospholipid species, DHA-enriched diet also showed substantial increases in 4-HHE in brain, heart, and plasma. Among different brain regions, the hippocampus responded to the DHA-enriched diet showing significant increase in 4-HHE. Considering the pro- and anti-inflammatory pathways mediated by the (n-6) and (n-3) polyunsaturated fatty acids, unveiling the ability for DHA-enriched diet to alter phospholipid species and lipid peroxidation products in the brain and in different body organs may be an important step forward towards understanding the mechanism(s) for this (n-3) fatty acid on health and diseases.

The Effects of the Combination of Buckwheat D-Fagomine and Fish Omega-3 Fatty Acids on Oxidative Stress and Related Risk Factors in Pre-Obese Rats

The combined supplementation of buckwheat D-fagomine (FG) and fish omega-3 polyunsaturated fatty acids (ω-3 PUFA) attenuates the development of insulin resistance in rats fed a high-fat (HF) diet. This study aimed to examine the effects of combined supplementation with FG and ω-3 PUFA on dyslipidemia, transaminases, interleukin-6, and oxidative stress. Forty-five male Sprague-Dawley rats were fed a standard diet, an HF diet, an HF diet supplemented with FG, an HF diet supplemented with ω-3 PUFA, or an HF diet supplemented with FG and ω-3 PUFA for 21 weeks. Triacylglycerol, cholesterol, aspartate aminotransferase, alanine aminotransferase, and interleukin-6 were measured. The assessment of oxidative stress included plasma antioxidant capacity, antioxidant enzyme activities, glutathione content, lipid peroxidation, and protein carbonylation. The combined supplementation with FG and ω-3 PUFA did not attenuate the slight accumulation of liver cholesterol induced by the HF diet but normalized the plasma alanine aminotransferase activity. Rats fed the HF diet supplemented with the combination showed a lower amount of plasma interleukin-6 than those fed a standard diet. The combination attenuated oxidative damage induced by the HF diet, decreased antioxidant enzyme activities, and enhanced glutathione status. The beneficial effects of the combination of FG and ω-3 PUFA on oxidative stress and related risk factors in pre-obese rats were mainly modulated by ω-3 PUFA.

Effects of Fish Oil and Grape Seed Extract Combination on Hepatic Endogenous Antioxidants and Bioactive Lipids in Diet-Induced Early Stages of Insulin Resistance in Rats

Diacylglycerols (DAG) and ceramides have been suggested as early predictors of insulin resistance. This study was aimed to examine the combined effects of fish oil (FO) and grape seed extract (GSE) on hepatic endogenous antioxidants, DAG and ceramides in diet-induced early stages of insulin resistance. Thirty-five rats were fed one of the following diets: (1) a standard diet (STD group), (2) a high-fat high-sucrose diet (HFHS group), (3) an HFHS diet enriched with FO (FO group), (4) an HFHS diet enriched with GSE (GSE group) or (5) an HFHS diet enriched with FO and GSE (FO + GSE group). In the liver, endogenous antioxidants were measured using spectrophotometric and fluorometric techniques, and non-targeted lipidomics was conducted for the assessment of DAG and ceramides. After 24 weeks, the FO + GSE group showed increased glutathione peroxidase activity, as well as monounsaturated fatty acid and polyunsaturated fatty acid-containing DAG, and long-chain fatty acid-containing ceramides abundances compared to the STD group. The FO and GSE combination induced similar activation of the antioxidant system and bioactive lipid accumulation in the liver than the HFHS diet without supplementation. In addition, the FO and GSE combination increased the abundances of polyunsaturated fatty acid-containing DAG in the liver.

Potential Adverse Public Health Effects Afforded by the Ingestion of Dietary Lipid Oxidation Product Toxins: Significance of Fried Food Sources

Exposure of polyunsaturated fatty acid (PUFA)-rich culinary oils (COs) to high temperature frying practices generates high concentrations of cytotoxic and genotoxic lipid oxidation products (LOPs) via oxygen-fueled, recycling peroxidative bursts. These toxins, including aldehydes and epoxy-fatty acids, readily penetrate into fried foods and hence are available for human consumption; therefore, they may pose substantial health hazards. Although previous reports have claimed health benefits offered by the use of PUFA-laden COs for frying purposes, these may be erroneous in view of their failure to consider the negating adverse public health threats presented by food-transferable LOPs therein. When absorbed from the gastrointestinal (GI) system into the systemic circulation, such LOPs may significantly contribute to enhanced risks of chronic non-communicable diseases (NCDs), e.g. cancer, along with cardiovascular and neurological diseases. Herein, we provide a comprehensive rationale relating to the public health threats posed by the dietary ingestion of LOPs in fried foods. We begin with an introduction to sequential lipid peroxidation processes, describing the noxious effects of LOP toxins generated therefrom. We continue to discuss GI system interactions, the metabolism and biotransformation of primary lipid hydroperoxide LOPs and their secondary products, and the toxicological properties of these agents, prior to providing a narrative on chemically-reactive, secondary aldehydic LOPs available for human ingestion. In view of a range of previous studies focused on their deleterious health effects in animal and cellular model systems, some emphasis is placed on the physiological fate of the more prevalent and toxic α,β-unsaturated aldehydes. We conclude with a description of targeted nutritional and interventional strategies, whilst highlighting the urgent and unmet clinical need for nutritional and epidemiological trials probing relationships between the incidence of NCDs, and the frequency and estimated quantities of dietary LOP intake.

Effects of Docosahexaenoic Acid and Its Peroxidation Product on Amyloid-β Peptide-Stimulated Microglia

Growing evidence suggests that docosahexaenoic acid (DHA) exerts neuroprotective effects, although the mechanism(s) underlying these beneficial effects are not fully understood. Here we demonstrate that DHA, but not arachidonic acid (ARA), suppressed oligomeric amyloid-β peptide (oAβ)-induced reactive oxygen species (ROS) production in primary mouse microglia and immortalized mouse microglia (BV2). Similarly, DHA but not ARA suppressed oAβ-induced increases in phosphorylated cytosolic phospholipase A₂ (p-cPLA₂), inducible nitric oxide synthase (iNOS), and tumor necrosis factor-α (TNF-α) in BV2 cells. LC-MS/MS assay indicated the ability for DHA to cause an increase in 4-hydroxyhexenal (4-HHE) and suppress oAβ-induced increase in 4-hydroxynonenal (4-HNE). Although oAβ did not alter the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, exogenous DHA, ARA as well as low concentrations of 4-HHE and 4-HNE upregulated this pathway and increased production of heme oxygenase-1 (HO-1) in microglial cells. These results suggest that DHA modulates ARA metabolism in oAβ-stimulated microglia through suppressing oxidative and inflammatory pathways and upregulating the antioxidative stress pathway involving Nrf2/HO-1. Understanding the mechanism(s) underlying the beneficial effects of DHA on microglia should shed light into nutraceutical therapy for the prevention and treatment of Alzheimer's disease (AD).

Yin-Yang Mechanisms Regulating Lipid Peroxidation of Docosahexaenoic Acid and Arachidonic Acid in the Central Nervous System

Phospholipids in the central nervous system (CNS) are rich in polyunsaturated fatty acids (PUFAs), particularly arachidonic acid (ARA) and docosahexaenoic acid (DHA). Besides providing physical properties to cell membranes, these PUFAs are metabolically active and undergo turnover through the “deacylation-reacylation (Land's) cycle”. Recent studies suggest a Yin-Yang mechanism for metabolism of ARA and DHA, largely due to different phospholipases A₂ (PLA₂s) mediating their release. ARA and DHA are substrates of cyclooxygenases and lipoxygenases resulting in an array of lipid mediators, which are pro-inflammatory and pro-resolving. The PUFAs are susceptible to peroxidation by oxygen free radicals, resulting in the production of 4-hydroxynonenal (4-HNE) from ARA and 4-hydroxyhexenal (4-HHE) from DHA. These alkenal electrophiles are reactive and capable of forming adducts with proteins, phospholipids and nucleic acids. The perceived cytotoxic and hormetic effects of these hydroxyl-alkenals have impacted cell signaling pathways, glucose metabolism and mitochondrial functions in chronic and inflammatory diseases. Due to the high levels of DHA and ARA in brain phospholipids, this review is aimed at providing information on the Yin-Yang mechanisms for regulating these PUFAs and their lipid peroxidation products in the CNS, and implications of their roles in neurological disorders.

Maternal Dietary Docosahexaenoic Acid Alters Lipid Peroxidation Products and (n-3)/(n-6) Fatty Acid Balance in Offspring Mice

The abundance of docosahexaenoic acid (DHA) in the mammalian brain has generated substantial interest in the search for its roles in regulating brain functions. Our recent study with a gene/stress mouse model provided evidence to support the ability for the maternal supplement of DHA to alleviate autism-associated behavior in the offspring. DHA and arachidonic acid (ARA) are substrates of enzymatic and non-enzymatic reactions, and lipid peroxidation results in the production of 4-hydroxyhexenal (4-HHE) and 4-hydroxynonenal (4-HNE), respectively. In this study, we examine whether a maternal DHA-supplemented diet alters fatty acids (FAs), as well as lipid peroxidation products in the pup brain, heart and plasma by a targeted metabolite approach. Pups in the maternal DHA-supplemented diet group showed an increase in DHA and a concomitant decrease in ARA in all brain regions examined. However, significant increases in 4-HHE, and not 4-HNE, were found mainly in the cerebral cortex and hippocampus. Analysis of heart and plasma showed large increases in DHA and 4-HHE, but a significant decrease in 4-HNE levels only in plasma. Taken together, the DHA-supplemented maternal diet alters the (n-3)/(n-6) FA ratio, and increases 4-HHE levels in pup brain, heart and plasma. These effects may contribute to the beneficial effects of DHA on neurodevelopment, as well as functional changes in other body organs.

Docosahexaenoic acid (DHA): An essential nutrient and a nutraceutical for brain health and diseases

Docosahexaenoic acid (DHA), a polyunsaturated fatty acid (PUFA) enriched in phospholipids in the brain and retina, is known to play multi-functional roles in brain health and diseases. While arachidonic acid (AA) is released from membrane phospholipids by cytosolic phospholipase A2 (cPLA2), DHA is linked to action of the Ca2+-independent iPLA2. DHA undergoes enzymatic conversion by 15-lipoxygenase (Alox 15) to form oxylipins including resolvins and neuroprotectins, which are powerful lipid mediators. DHA can also undergo non-enzymatic conversion by reacting with oxygen free radicals (ROS), which cause the production of 4-hydoxyhexenal (4-HHE), an aldehyde derivative which can form adducts with DNA, proteins and lipids. In studies with both animal models and humans, there is evidence that inadequate intake of maternal n-3 PUFA may lead to aberrant development and function of the central nervous system (CNS). What is less certain is whether consumption of n-3 PUFA is important in maintaining brain health throughout one's life span. Evidence mostly from non-human studies suggests that DHA intake above normal nutritional requirements might modify the risk/course of a number of diseases of the brain. This concept has fueled much of the present interest in DHA research, in particular, in attempts to delineate mechanisms whereby DHA may serve as a nutraceutical and confer neuroprotective effects. Current studies have revealed ability for the oxylipins to regulation of cell redox homeostasis through the Nuclear factor (erythroid-derived 2)-like 2/Antioxidant response element (Nrf2/ARE) anti-oxidant pathway, and impact signaling pathways associated with neurotransmitters, and modulation of neuronal functions involving brain-derived neurotropic factor (BDNF). This review is aimed at describing recent studies elaborating these mechanisms with special regard to aging and Alzheimer's disease, autism spectrum disorder, schizophrenia, traumatic brain injury, and stroke.

Unveiling anti-oxidative and anti-inflammatory effects of docosahexaenoic acid and its lipid peroxidation product on lipopolysaccharide-stimulated BV-2 microglial cells

BACKGROUND

Phospholipids in the central nervous system are enriched in n-3 and n-6 polyunsaturated fatty acids (PUFA), especially docosahexaenoic acid (DHA) and arachidonic acid (ARA). These PUFA can undergo enzymatic reactions to produce lipid mediators, as well as reaction with oxygen free radicals to produce 4-hydroxyhexenal (4-HHE) from DHA and 4-hydroxynonenal (4-HNE) from ARA. Recent studies demonstrated pleiotropic properties of these peroxidation products through interaction with oxidative and anti-oxidant response pathways. In this study, BV-2 microglial cells were used to investigate ability for DHA, 4-HHE, and 4-HNE to stimulate the anti-oxidant stress responses involving the nuclear factor erythroid-2-related factor 2 (Nrf2) pathway and synthesis of heme oxygenase (HO-1), as well as to mitigate lipopolysaccharide (LPS)-induced nitric oxide (NO), reactive oxygen species (ROS), and cytosolic phospholipase A₂ (cPLA₂). In addition, LC-MS/MS analysis was carried out to examine effects of exogenous DHA and LPS stimulation on endogenous 4-HHE and 4-HNE levels in BV-2 microglial cells.

METHODS

Effects of DHA, 4-HHE, and 4-HNE on LPS-induced NO production was determined using the Griess reagent. LPS-induced ROS production was measured using CM-H₂DCFDA. Western blots were used to analyze expression of p-cPLA₂, Nrf2, and HO-1. Cell viability and cytotoxicity were measured using the WST-1 assay, and cell protein concentrations were measured using the BCA protein assay kit. An ultra-high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was used to determine levels of free 4-HHE and 4-HNE in cells.

RESULTS

DHA (12.5-100 μM), 4-HHE (1.25-10 μM), and 4-HNE (1.25-10 μM) dose dependently suppressed LPS-induced production of NO, ROS, and as p-cPLA₂ in BV-2 microglial cells. With the same concentrations, these compounds could enhance Nrf2 and HO-1 expression in these cells. Based on the estimated IC₅₀ values, 4-HHE and 4-HNE were five- to tenfold more potent than DHA in inhibiting LPS-induced NO, ROS, and p-cPLA₂. LC-MS/MS analysis indicated ability for DHA (10-50 μM) to increase levels of 4-HHE and attenuate levels of 4-HNE in BV-2 microglial cells. Stimulation of cells with LPS caused an increase in 4-HNE which could be abrogated by cPLA₂ inhibitor. In contrast, bromoenol lactone (BEL), a specific inhibitor for the Ca²⁺-independent phospholipase A₂ (iPLA₂), could only partially suppress levels of 4-HHE induced by DHA or DHA + LPS.

CONCLUSIONS

This study demonstrated the ability of DHA and its lipid peroxidation products, namely, 4-HHE and 4-HNE at 1.25-10 μM, to enhance Nrf2/HO-1 and mitigate LPS-induced NO, ROS, and p-cPLA₂ in BV-2 microglial cells. In addition, LC-MS/MS analysis of the levels of 4-HHE and 4-HNE in microglial cells demonstrates that increases in production of 4-HHE from DHA and 4-HNE from LPS are mediated by different mechanisms.

Effects of saturated palmitic acid and omega-3 polyunsaturated fatty acids on Sertoli cell apoptosis

Obesity is believed to negatively affect male semen quality and is accompanied by dysregulation of free fatty acid (FFA) metabolism in plasma. However, the implication of dysregulated FFA on semen quality and the involvement of Sertoli cells remain unclear. In the present study, we report obesity decreased Sertoli cell viability through dysregulated FFAs. We observed an increased rate of apoptosis in Sertoli cells, accompanied with elevated FFA levels, in the testes of obese mice that were provided a high-fat diet (HFD). Moreover, the levels of reactive oxygen species were elevated. Furthermore, we demonstrated by in vitro assays that saturated palmitic acid (PA), which is the most common saturated FFA in plasma, led to decreased cell viability of TM4 Sertoli cells in a time- and dose-dependent manner. A similar finding was noted in primary mouse Sertoli cells. In contrast to saturated FFA, omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) protected Sertoli cells from PA-induced lipotoxicity at the physiologically relevant levels. These results indicated that the lipotoxicity of saturated fatty acids might be the cause of obesity-induced Sertoli cell apoptosis, which leads to decreased semen quality. In addition, ω-3 PUFAs could be classified as protective FFAs.

ABBREVIATIONS

FFA: free fatty acid; HFD: high-fat diet; SD: standard diet; PA: palmitic acid; PUFA: polyunsaturated fatty acid; AI: apoptotic index; MTT: 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide; ROS: reactive oxygen species; HE: Hematoxylin and eosin; WT1: Wilm Tumor 1; NAFLD: non- alcoholic fatty liver disease; DCFH-DA: 2', 7' dichlorofluorescin diacetate; 36B4: acidic ribosomal phosphoprotein P0; SD: standard deviation; EPA: eicosapentaenoic acid; PI: propidium iodide; DHA: docosahexenoic acid.

Dietary supplementation with omega-3 polyunsaturated fatty acid-rich oils protects against visible-light-induced retinal damage in vivo

Dietary ω-3 PUFA-rich oils protect against visible-light-induced retinal damage.

Fatty Acids in Nephrotic Syndrome and Chronic Kidney Disease

The role of fatty acids (FAs) in inflammation and in the related chronic diseases has been demonstrated. However, there is a lack of consistent and agreed knowledge about the role of FA profile and renal physiology and pathology, most articles focusing on the effect of polyunsaturated FAs supplementation, without considering the impact of basal FA metabolism on the efficacy of the supplementation. Here, we have summarized the specific literature concerning the assessment of circulating FA in 2 renal diseases, namely nephrotic syndrome and chronic kidney disease, also under hemodialytic treatment, and have received the most significant contributions in the last years. The effects of changes of FA profile and metabolism and the possible involvement of polyunsaturated FA metabolites in raising and modulating inflammation are discussed.

N-3 Polyunsaturated Fatty Acids Decrease the Protein Expression of Soluble Epoxide Hydrolase via Oxidative Stress-Induced P38 Kinase in Rat Endothelial Cells

N-3 polyunsaturated fatty acids (PUFAs) improve endothelial function. The arachidonic acid-derived metabolites (epoxyeicosatrienoic acids (EETs)) are part of the endothelial hyperpolarization factor and are vasodilators independent of nitric oxide. However, little is known regarding the regulation of EET concentration by docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in blood vessels. Sprague-Dawley rats were fed either a control or fish oil diet for 3 weeks. Compared with the control, the fish oil diet improved acetylcholine-induced vasodilation and reduced the protein expression of soluble epoxide hydrolase (sEH), a key EET metabolic enzyme, in aortic strips. Both DHA and EPA suppressed sEH protein expression in rat aorta endothelial cells (RAECs). Furthermore, the concentration of 4-hydroxy hexenal (4-HHE), a lipid peroxidation product of n-3 PUFAs, increased in n-3 PUFA-treated RAECs. In addition, 4-HHE treatment suppressed sEH expression in RAECs, suggesting that 4-HHE (derived from n-3 PUFAs) is involved in this phenomenon. The suppression of sEH was attenuated by the p38 kinase inhibitor (SB203580) and by treatment with the antioxidant N-acetyl-L-cysteine. In conclusion, sEH expression decreased after n-3 PUFAs treatment, potentially through oxidative stress and p38 kinase. Mild oxidative stress induced by n-3 PUFAs may contribute to their cardio-protective effect.

Dietary omega-6 fatty acid replacement selectively impairs cardiac functional recovery after ischemia in female (but not male) rats

A definitive understanding of the role of dietary lipids in determining cardioprotection (or cardiodetriment) has been elusive. Randomized trial findings have been variable and sex specificity of dietary interventions has not been determined. In this investigation the sex-selective cardiac functional effects of three diets enriched by omega-3 or omega-6 polyunsaturated fatty acids (PUFA) or enriched to an equivalent extent in saturated fatty acid components were examined in rats after an 8-wk treatment period. In females the myocardial membrane omega-6:omega-3 PUFA ratio was twofold higher than males in the omega-6 diet replacement group. In diets specified to be high in omega-3 PUFA or in saturated fat, this sex difference was not apparent. Isolated cardiomyocyte and heart Langendorff perfusion experiments were performed, and molecular measures of cell viability were assessed. Under basal conditions the contractile performance of omega-6 fed female cardiomyocytes and hearts was reduced compared with males. Omega-6 fed females exhibited impaired systolic resilience after ischemic insult. This response was associated with increased postischemia necrotic cell damage evaluated by coronary lactate dehydrogenase during reperfusion in omega-6 fed females. Cardiac and myocyte functional parameters were not different between omega-3 and saturated fat dietary groups and within these groups there were no discernible sex differences. Our data provide evidence at both the cardiac and cardiomyocyte levels that dietary saturated fatty acid intake replacement with an omega-6 (but not omega-3) enriched diet has selective adverse cardiac effect in females. This finding has potential relevance in relation to women, cardiac risk, and dietary management.

Antioxidant role of glutathione S-transferases: 4-Hydroxynonenal, a key molecule in stress-mediated signaling

4-Hydroxy-2-trans-nonenal (4HNE), one of the major end products of lipid peroxidation (LPO), has been shown to induce apoptosis in a variety of cell lines. It appears to modulate signaling processes in more than one way because it has been suggested to have a role in signaling for differentiation and proliferation. It has been known that glutathione S-transferases (GSTs) can reduce lipid hydroperoxides through their Se-independent glutathione-peroxidase activity and that these enzymes can also detoxify LPO end-products such as 4HNE. Available evidence from earlier studies together with results of recent studies in our laboratories strongly suggests that LPO products, particularly hydroperoxides and 4HNE, are involved in the mechanisms of stress-mediated signaling and that it can be modulated by the alpha-class GSTs through the regulation of the intracellular concentrations of 4HNE. We demonstrate that 4HNE induced apoptosis in various cell lines is accompanied with c-Jun-N-terminal kinase (JNK) and caspase-3 activation. Cells exposed to mild, transient heat or oxidative stress acquire the capacity to exclude intracellular 4HNE at a faster rate by inducing GSTA4-4 which conjugates 4HNE to glutathione (GSH), and RLIP76 which mediates the ATP-dependent transport of the GSH-conjugate of 4HNE (GS-HNE). The balance between formation and exclusion promotes different cellular processes - higher concentrations of 4HNE promote apoptosis; whereas, lower concentrations promote proliferation. In this article, we provide a brief summary of the cellular effects of 4HNE, followed by a review of its GST-catalyzed detoxification, with an emphasis on the structural attributes that play an important role in the interactions with alpha-class GSTA4-4. Taken together, 4HNE is a key signaling molecule and that GSTs being determinants of its intracellular concentrations, can regulate stress-mediated signaling, are reviewed in this article.

Duality of n-3 Polyunsaturated Fatty Acids on Mcp-1 Expression in Vascular Smooth Muscle: A Potential Role of 4-Hydroxy Hexenal

N-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have protective effects against atherosclerosis. Monocyte chemotactic protein (MCP)-1 is a major inflammatory mediator in the progression of atherosclerosis. However, little is known about the regulation of MCP-1 by DHA and EPA in vessels and vascular smooth muscle cells (VSMCs). In this study, we compared the effect of DHA and EPA on the expression of Mcp-1 in rat arterial strips and rat VSMCs. DHA, but not EPA, suppressed Mcp-1 expression in arterial strips. Furthermore, DHA generated 4-hydroxy hexenal (4-HHE), an end product of n-3 polyunsaturated fatty acids (PUFAs), in arterial strips as measured by liquid chromatography-tandem mass spectrometry. In addition, 4-HHE treatment suppressed Mcp-1 expression in arterial strips, suggesting 4-HHE derived from DHA may be involved in the mechanism of this phenomenon. In contrast, Mcp-1 expression was stimulated by DHA, EPA and 4-HHE through p38 kinase and the Keap1-Nuclear factor erythroid-derived 2-like 2 (Nrf2) pathway in VSMCs. In conclusion, there is a dual effect of n-3 PUFAs on the regulation of Mcp-1 expression. Further study is necessary to elucidate the pathological role of this phenomenon.

The Deleterious Effects of Oxidative and Nitrosative Stress on Palmitoylation, Membrane Lipid Rafts and Lipid-Based Cellular Signalling: New Drug Targets in Neuroimmune Disorders

Oxidative and nitrosative stress (O&NS) is causatively implicated in the pathogenesis of Alzheimer's and Parkinson's disease, multiple sclerosis, chronic fatigue syndrome, schizophrenia and depression. Many of the consequences stemming from O&NS, including damage to proteins, lipids and DNA, are well known, whereas the effects of O&NS on lipoprotein-based cellular signalling involving palmitoylation and plasma membrane lipid rafts are less well documented. The aim of this narrative review is to discuss the mechanisms involved in lipid-based signalling, including palmitoylation, membrane/lipid raft (MLR) and n-3 polyunsaturated fatty acid (PUFA) functions, the effects of O&NS processes on these processes and their role in the abovementioned diseases. S-palmitoylation is a post-translational modification, which regulates protein trafficking and association with the plasma membrane, protein subcellular location and functions. Palmitoylation and MRLs play a key role in neuronal functions, including glutamatergic neurotransmission, and immune-inflammatory responses. Palmitoylation, MLRs and n-3 PUFAs are vulnerable to the corruptive effects of O&NS. Chronic O&NS inhibits palmitoylation and causes profound changes in lipid membrane composition, e.g. n-3 PUFA depletion, increased membrane permeability and reduced fluidity, which together lead to disorders in intracellular signal transduction, receptor dysfunction and increased neurotoxicity. Disruption of lipid-based signalling is a source of the neuroimmune disorders involved in the pathophysiology of the abovementioned diseases. n-3 PUFA supplementation is a rational therapeutic approach targeting disruptions in lipid-based signalling.

Role of dietary pro-oxidants in the maintenance of health and resilience to oxidative stress

The average length of human life is increasing, but so does the incidence of age- and lifestyle-related diseases. Improving diet and lifestyle is a key strategy for lifelong health and underlying mechanisms may well include increasing resilience pathways. The purpose of this review is to highlight and evaluate novel mechanisms by which dietary pro-oxidants, including bioactive phytochemicals and fatty acids, increase reactive oxygen species (ROS) concentrations just enough to activate transcription factor activation of nuclear factor erythroid 2 related factor 2 (Nrf-2) and heat shock factor (HSF), leading to an increase in levels of antioxidant enzymes and heat shock proteins that protect against the damaging effects of ROS. An increasing number of in vivo studies have now shown that dietary pro-oxidant compounds can increase the production of such resilience products. In most studies, dietary pro-oxidants normalized levels of antioxidant enzymes that were decreased by a range of different challenges, rather than raising levels of resilience products per se. Also, it is important to consider that the antioxidant response can be different for different organs. For future studies, however, the measurement of resilience markers may significantly improve our ability to prove the efficacy by which dietary bioactives with pro-oxidant capacities improve lifelong health.