Dietary free oleic and linoleic acid enhances neutrophil function and modulates the inflammatory response in rats

Effects of omega fatty acids on the short-term postprandial satiety related peptides in rats

We aimed to assess the effects of omega fatty acids on time depending on responses of satiety hormones. Sixty adult rats were randomly divided into 4 groups; linoleic acid (LA), α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) groups. For each fatty acid, the dose of 400 mg/kg was applied by oral gavage. Blood samples were taken after the 15, 30, 60 and 120 minutes. Ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), peptide YY (PYY), leptin and insulin hormones were analyzed by ELISA. We observed the significant increases (p<0.05) of the levels of CCK between n-3 (ALA, at 60th min; EPA, at 30th and 60th min and DHA, at 60 min) and n-6 (LA) supplemented rats. The highest GLP-1 levels were in ALA (0.70 ng/mL) and DHA (0.67 ng/mL) supplemented groups at 60th and 120th min indicating n-3 fatty acids efficiency on satiety compared to LA. It seems that ALA at 60th min and EPA at 120th min could provide the highest satiety effect with the highest insulin response, while the efficiency of LA supplementation on insulin-induced satiety diminished. The only significant change in AUC values among all hormones was in the CCK of the ALA group (p=0.004). The level of leptin increased in DHA and EPA supplemented rats (p=0.140). Our results showed that dietary omega fatty acids influenced the releasing of hormones in different ways possibly depending on chain length or saturation degree. Comprehensive studies need to be addressed for each fatty acid on satiety-related peptide hormones.

Eicosapentaenoic acid-rich oil supplementation activates PPAR-γ and delays skin wound healing in type 1 diabetic mice

Delayed wound healing is a devastating complication of diabetes and supplementation with fish oil, a source of anti-inflammatory omega-3 (ω-3) fatty acids including eicosapentaenoic acid (EPA), seems an appealing treatment strategy. However, some studies have shown that ω-3 fatty acids may have a deleterious effect on skin repair and the effects of oral administration of EPA on wound healing in diabetes are unclear. We used streptozotocin-induced diabetes as a mouse model to investigate the effects of oral administration of an EPA-rich oil on wound closure and quality of new tissue formed. Gas chromatography analysis of serum and skin showed that EPA-rich oil increased the incorporation of ω-3 and decreased ω-6 fatty acids, resulting in reduction of the ω-6/ω-3 ratio. On the tenth day after wounding, EPA increased production of IL-10 by neutrophils in the wound, reduced collagen deposition, and ultimately delayed wound closure and impaired quality of the healed tissue. This effect was PPAR-γ-dependent. EPA and IL-10 reduced collagen production by fibroblasts in vitro. In vivo, topical PPAR-γ-blockade reversed the deleterious effects of EPA on wound closure and on collagen organization in diabetic mice. We also observed a reduction in IL-10 production by neutrophils in diabetic mice treated topically with the PPAR-γ blocker. These results show that oral supplementation with EPA-rich oil impairs skin wound healing in diabetes, acting on inflammatory and non-inflammatory cells.

Sex-Specific Differences in Lysine, 3-Hydroxybutyric Acid and Acetic Acid in Offspring Exposed to Maternal and Postnatal High Linoleic Acid Diet, Independent of Diet

BACKGROUND

Linoleic acid (LA) is an essential polyunsaturated fatty acid (PUFA) that is required for foetal growth and development. Excess intake of LA can be detrimental for metabolic health due to its pro-inflammatory properties; however, the effect of a diet high in LA on offspring metabolites is unknown. In this study, we aimed to determine the role of maternal or postnatal high linoleic acid (HLA) diet on plasma metabolites in adult offspring.

METHODS

Female Wistar Kyoto (WKY) rats were fed with either low LA (LLA) or HLA diet for 10 weeks prior to conception and during gestation/lactation. Offspring were weaned at postnatal day 25 (PN25), treated with either LLA or HLA diets and sacrificed at PN180. Metabolite analysis was performed in plasma samples using Nuclear Magnetic Resonance.

RESULTS

Maternal and postnatal HLA diet did not alter plasma metabolites in male and female adult offspring. There was no specific clustering among different treatment groups as demonstrated by principal component analysis. Interestingly, there was clustering among male and female offspring independent of maternal and postnatal dietary intervention. Lysine was higher in female offspring, while 3-hydroxybutyric acid and acetic acid were significantly higher in male offspring.

CONCLUSION

In summary, maternal or postnatal HLA diet did not alter the plasma metabolites in the adult rat offspring; however, differences in metabolites between male and female offspring occurred independently of dietary intervention.

Anti-Diabetic Effects of Isolated Lipids from Natural Sources through Modulation of Angiogenesis

BACKGROUND

Aberrant angiogenesis plays a fateful role in the development of diabetes and diabetic complications. Lipids, as a diverse group of biomacromolecules, are able to relieve diabetes through the modulation of angiogenesis.

OBJECTIVE

Owing to the present remarkable anti-diabetic effects with no or few side effects of lipids, the aim of this study was to assess the state-of-the-art research on anti-diabetic effects of lipids via the modulation of angiogenesis.

METHODS

To study the effects of lipids in diabetes via modulation of angiogenesis, we have searched the electronic databases including Scopus, PubMed, and Cochrane.

RESULTS

The promising anti-diabetic effects of lipids were reported in several studies. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil (FO) were reported to significantly induce neovasculogenesis in high glucose (HG)-mediated endothelial progenitor cells (EPCs) neovasculogenic dysfunction in type 2 diabetic mice. Linoleic acid, mono-epoxy-tocotrienol-α (MeT3α), and ginsenoside Rg1 facilitate wound closure and vessel formation. N-Palmitoylethanolamine (PEA), α-linolenic acid (ALA), omega-3 (ω3) lipids from flaxseed (FS) oil, ω-3 polyunsaturated fatty acids (PUFA), lipoic acid, taurine, and zeaxanthin (Zx) are effective in diabetic retinopathy via suppression of angiogenesis. Lysophosphatidic acid, alkyl-glycerophosphate, crocin, arjunolic acid, α-lipoic acid, and FS oil are involved in the management of diabetes and its cardiac complications. Furthermore, in two clinical trials, R-(+)-lipoic acid (RLA) in combination with hyperbaric oxygenation therapy (HBOT) for treatment of chronic wound healing in DM patients, as well as supplementation with DHA plus antioxidants along with intravitreal ranibizumab were investigated for its effects on diabetic macular edema.

CONCLUSION

Proof-of-concept studies presented here seem to well shed light on the anti-diabetic effects of lipids via modulation of angiogenesis.

Long Chain Fatty Acids as Modulators of Immune Cells Function: Contribution of FFA1 and FFA4 Receptors

Long-chain fatty acids are molecules that act as metabolic intermediates and constituents of membranes; however, their novel role as signaling molecules in immune function has also been demonstrated. The presence of free fatty acid (FFA) receptors on immune cells has contributed to the understanding of this new role of long-chain fatty acids (LCFAs) in immune function, showing their role as anti-inflammatory or pro-inflammatory molecules and elucidating their intracellular mechanisms. The FFA1 and FFA4 receptors, also known as GPR40 and GPR120, respectively, have been described in macrophages and neutrophils, two key cells mediating innate immune response. Ligands of the FFA1 and FFA4 receptors induce the release of a myriad of cytokines through well-defined intracellular signaling pathways. In this review, we discuss the cellular responses and intracellular mechanisms activated by LCFAs, such as oleic acid, linoleic acid, palmitic acid, docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA), in T-cells, macrophages, and neutrophils, as well as the role of the FFA1 and FFA4 receptors in immune cells.

Repair function of essential oil from Crocodylus Siamensis (Schneider, 1801) on the burn wound healing via up-regulated growth factor expression and anti-inflammatory effect

ETHNOPHARMACOLOGICAL RELEVANCE

Crocodile oil has been used by traditional physicians around the world to treat wound healing and inflammation. However, the scientific rationale and mechanism behind its use in vivo has not been fully researched.

AIMS OF THE STUDY

We mainly investigated the mechanism during crocodile oil treatment of up-regulated growth factor expression and anti-inflammatory on burn wound healing in rats.

MATERIALS AND METHODS

The moisture and nitric oxide (NO) levels in the skin of rats were analyzed in the first 14 days after burn and the changes of the structure of the skin tissues in the wound healing were studied by hematoxylin-eosin (H.E.) staining within 21 days after scald. The inflammatory factor on burn wound healing in rats was dected by ELISA kits and Q-PCR. the expression of a variety of growth factors (TGF-β1, VEGE-α, EGF) and PCNA in the skin tissue after burns was evaluated using immunohistochemistry. The down-regulated phosphorylation of p38 MAPK in the wound healing was confirmed by Western-blot analysis. In addition, TEM was used to observe the ultrastructure of scalded skin.

RESULTS

This study showed that crocodile oil could significantly reduce the protein and mRNA levels of TNF-α, IL-1β and IL-6. And it was found that the phosphorylation of p38 MAPK was down-regulated in the wound healing (p < 0.05). Meanwhile, crocodile oil can promote the expression of a variety of growth factors (TGF-β1, VEGE-α, EGF) and PCNA in the skin tissue after burns, and promote the repair of collagen fibers in the dermis, preventing the production of melanin and maintain the appearance of repaired skin.

Maternal dietary linoleic acid altered intestinal barrier function in domestic pigeons (Columba livia)

Linoleic acid (LA) is predominantly essential for poultry. Poultry lacking LA show retarded growth and reduced disease resistance. Intestinal barrier function plays an important role in pigeon squab growth, whereas research on the effects of LA on intestinal health in altrices is scant. Considering that squabs are fed by their parents, the study aimed to explore the effects of maternal dietary LA on intestinal morphology, tight junction proteins, immune cytokines and microbial flora in squabs. A completely randomised design with a control group, 1 % LA supplementation group, 2 % LA supplementation group and 4 % LA supplementation group was used. Six squabs from each treatment were randomly sampled at 21 d post-hatching. The results indicated that LA supplementation improved intestinal morphology, as reflected by increased villus height, villus area and the ratio of villi to crypts. Also, 1 % LA supplementation elevated the density of goblet cells in the intestine and strengthened tight junctions by up-regulating claudin-3 and occludin gene expression but down-regulating claudin-2 gene expression. Moreover, 1 % LA supplementation reduced the secretion of proinflammatory cytokines and partly increased anti-inflammatory cytokines. The intestinal microbial diversity in the 1 % LA supplementation group was higher than that in the other groups. As beneficial bacteria, Butyrivibrio was the biomarker of 1 % LA supplementation. However, excessive (4 %) LA supplementation led to adverse impacts on intestinal immunity and microbiota. In conclusion, maternal dietary LA might alter intestinal barrier function in pigeon squabs in a dose-dependent manner. Supplementation with 1 % LA was suggested in parental pigeons.

Oleic acid-based nanosystems for mitigating acute respiratory distress syndrome in mice through neutrophil suppression: how the particulate size affects therapeutic efficiency

Background

Oleic acid (OA) is reported to show anti-inflammatory activity toward activated neutrophils. It is also an important material in nanoparticles for increased stability and cellular internalization. We aimed to evaluate the anti-inflammatory activity of injectable OA-based nanoparticles for treating lung injury. Different sizes of nanocarriers were prepared to explore the effect of nanoparticulate size on inflammation inhibition.

Results

The nanoparticles were fabricated with the mean diameters of 105, 153, and 225 nm. The nanocarriers were ingested by isolated human neutrophils during a 5-min period, with the smaller sizes exhibiting greater uptake. The size reduction led to the decrease of cell viability and the intracellular calcium level. The OA-loaded nanosystems dose-dependently suppressed the superoxide anion and elastase produced by the stimulated neutrophils. The inhibition level was comparable for the nanoparticles of different sizes. In the ex vivo biodistribution study, the pulmonary accumulation of nanoparticles increased following the increase of particle size. The nanocarriers were mainly excreted by the liver and bile clearance. Mice were exposed to intratracheal lipopolysaccharide (LPS) to induce acute respiratory distress syndrome (ARDS), like lung damage. The lipid-based nanocarriers mitigated myeloperoxidase (MPO) and cytokines more effectively as compared to OA solution. The larger nanoparticles displayed greater reduction on MPO, TNF-α, and IL-6 than the smaller ones. The histology confirmed the decreased pulmonary neutrophil recruitment and lung-architecture damage after intravenous administration of larger nanoparticles.

Conclusions

Nanoparticulate size, an essential property governing the anti-inflammatory effect and lung-injury therapy, had different effects on activated neutrophil inhibition and in vivo therapeutic efficacy.

Oleic acid and hydroxytyrosol present in olive oil promote ROS and inflammatory response in normal cultures of murine dermal fibroblasts through the NF-κB and NRF2 pathways

Few studies have evaluated the effects of olive oil on normal tissues like skin and its components. Hence, we investigated whether olive oil could increase the production of ROS and oxidative damage in murine dermal fibroblast cultures in a short-term exposition. In addition, we evaluated the role of oleic acid and hydroxytyrosol, which are the two most important components of olive oil, in the associated mechanisms of action, and the metabolism of long-chain fatty acids from olive oil. To study this, neonatal murine dermal fibroblasts (NMDF) were incubated with olive oil, oleic acid, or hydroxytyrosol for 24 or 72 h. The NMDF incubated with olive oil or oleic acid showed an increase in the production of ROS after 24 h, lipid peroxidation, and protein carbonylation after 72 h, as well as increased expression of nuclear factor-kappa B (NF-κB) p65 and cyclooxygenase-2 (COX-2) after 72 h. However, NMDF treated with olive oil or hydroxytyrosol demonstrated an increase in the expression of nuclear factor-erythroid2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1) after 72 h. In addition, NMDF treated with olive oil also showed an increase in the protein expression of diacylglycerol acyltransferase1 (DGAT1), which promotes triacylglycerol synthesis, and in the levels of triacylglycerols. The microscopic analysis showed Nile red-positive lipid droplets inside olive oil-treated NMDF after 72 h. Moreover, gas chromatography-mass spectrometry demonstrated high levels of oleic acid in the olive oil-treated NMDF after 72 h. In conclusion, oleic acid present in the olive oil promotes the production of ROS and oxidative damage in murine dermal fibroblasts, which leads to NF-κB p65 and COX-2 expression, while hydroxytyrosol promotes NRF2 and HO-1 expression. In addition, NMDF area capable of absorbing long-chain fatty acids derived from olive oil, which promotes the synthesis and the accumulation of triacylglycerols into cytoplasm of NMDF through DGAT1 activation.

The Influence of Dietary Fatty Acids on Immune Responses

Diet-derived fatty acids (FAs) are essential sources of energy and fundamental structural components of cells. They also play important roles in the modulation of immune responses in health and disease. Saturated and unsaturated FAs influence the effector and regulatory functions of innate and adaptive immune cells by changing membrane composition and fluidity and by acting through specific receptors. Impaired balance of saturated/unsaturated FAs, as well as n-6/n-3 polyunsaturated FAs has significant consequences on immune system homeostasis, contributing to the development of many allergic, autoimmune, and metabolic diseases. In this paper, we discuss up-to-date knowledge and the clinical relevance of the influence of dietary FAs on the biology, homeostasis, and functions of epithelial cells, macrophages, dendritic cells, neutrophils, innate lymphoid cells, T cells and B cells. Additionally, we review the effects of dietary FAs on the pathogenesis of many diseases, including asthma, allergic rhinitis, food allergy, atopic dermatitis, rheumatoid arthritis, multiple sclerosis as well as type 1 and 2 diabetes.

Oral administration of EPA-rich oil impairs collagen reorganization due to elevated production of IL-10 during skin wound healing in mice

Wound healing is an essential process for organism survival. Some fatty acids have been described as modulators of wound healing. However, the role of omega-3 fatty acids is unclear. In the present work, we investigate the effects of oral administration of eicosapentaenoic acid (EPA)-rich oil on wound healing in mice. After 4 weeks of EPA-rich oil supplementation (2 g/kg of body weight), mice had increased serum concentrations of EPA (20:5ω-3) (6-fold) and docosahexaenoic acid (DHA; 22:6ω-3) (33%) in relation to control mice. Omega-3 fatty acids were also incorporated into skin in the EPA fed mice. The wound healing process was delayed at the 3rd and 7th days after wounding in mice that received EPA-rich oil when compared to control mice but there was no effect on the total time required for wound closure. Collagen reorganization, that impacts the quality of the wound tissue, was impaired after EPA-rich oil supplementation. These effects were associated with an increase of M2 macrophages (twice in relation to control animals) and interleukin-10 (IL-10) concentrations in tissue in the initial stages of wound healing. In the absence of IL-10 (IL-10-/- mice), wound closure and organization of collagen were normalized even when EPA was fed, supporting that the deleterious effects of EPA-rich oil supplementation were due to the excessive production of IL-10. In conclusion, oral administration of EPA-rich oil impairs the quality of wound healing without affecting the wound closure time likely due to an elevation of the anti-inflammatory cytokine IL-10.

Omega-9 Oleic Acid, the Main Compound of Olive Oil, Mitigates Inflammation during Experimental Sepsis

The Mediterranean diet, rich in olive oil, is beneficial, reducing the risk of cardiovascular diseases and cancer. Olive oil is mostly composed of the monounsaturated fatty acid omega-9. We showed omega-9 protects septic mice modulating lipid metabolism. Sepsis is initiated by the host response to infection with organ damage, increased plasma free fatty acids, high levels of cortisol, massive cytokine production, leukocyte activation, and endothelial dysfunction. We aimed to analyze the effect of omega-9 supplementation on corticosteroid unbalance, inflammation, bacterial elimination, and peroxisome proliferator-activated receptor (PPAR) gamma expression, an omega-9 receptor and inflammatory modulator. We treated mice for 14 days with omega-9 and induced sepsis by cecal ligation and puncture (CLP). We measured systemic corticosterone levels, cytokine production, leukocyte and bacterial counts in the peritoneum, and the expression of PPAR gamma in both liver and adipose tissues during experimental sepsis. We further studied omega-9 effects on leukocyte rolling in mouse cremaster muscle-inflamed postcapillary venules and in the cerebral microcirculation of septic mice. Here, we demonstrate that omega-9 treatment is associated with increased levels of the anti-inflammatory cytokine IL-10 and decreased levels of the proinflammatory cytokines TNF-α and IL-1β in peritoneal lavage fluid of mice with sepsis. Omega-9 treatment also decreased systemic corticosterone levels. Neutrophil migration from circulation to the peritoneal cavity and leukocyte rolling on the endothelium were decreased by omega-9 treatment. Omega-9 also decreased bacterial load in the peritoneal lavage and restored liver and adipose tissue PPAR gamma expression in septic animals. Our data suggest a beneficial anti-inflammatory role of omega-9 in sepsis, mitigating leukocyte rolling and leukocyte influx, balancing cytokine production, and controlling bacterial growth possibly through a PPAR gamma expression-dependent mechanism. The significant reduction of inflammation detected after omega-9 enteral injection can further contribute to the already known beneficial properties facilitated by unsaturated fatty acid-enriched diets.

Fatty and hydroxycarboxylic acid receptors: The missing link of immune response and metabolism in cattle

Fatty and hydroxycarboxylic acids are one of the main intermediates of energy metabolism in ruminants and critical in the milk production of cattle. High production demands on a dairy farm can induce nutritional imbalances and metabolism disorders, which have been widely associated with the onset of sterile inflammatory processes and increased susceptibility to infections. The literature suggests that short-chain fatty acids (SCFA), long-chain fatty acids (LCFA) and hydroxycarboxylic acids are relevant modulators of the host innate inflammatory response. For instance, increased SCFA and lactate levels are associated with subacute ruminal acidosis (SARA) and the activation of pro-inflammatory processes mediated by diverse leukocyte and vascular endothelial cells. As such, free LCFA and the ketone body β-hydroxybutyrate are significantly increased in the plasma 1-2 weeks postpartum, coinciding with the time period in which cows are more susceptible to acquiring infectious diseases that the host innate immune system should actively oppose. Today, many of these pro-inflammatory responses can be related to the activation of specific G protein-coupled receptors, including GPR41/FFA3 and GPR43/FFA2 for SCFA; GPR40/FFA1 and GPR120/FFA4 for LCFA, GPR109A/HCA2 for ketone body β-hydroxybutyrate, and GPR81/HCA₁ for lactate, all expressed in different bovine tissues. The activation of these receptors modulates the release of intracellular granules [e.g., metalloproteinase-9 (MMP-9) and lactoferrin], radical oxygen species (ROS) production, chemotaxis, and the production of relevant pro-inflammatory mediators. The article aimed to review the role of natural ligands and receptors and the resulting impact on the host innate immune reaction of cattle and, further, to address the most recent evidence supporting a potential connection to metabolic disorders.

Wound Healing and Omega-6 Fatty Acids: From Inflammation to Repair

Wound healing is an evolutionarily conserved process that is essential for species survival. Wound healing involves a series of biochemical and cellular events that are tightly controlled, divided into 3 concomitant and overlapping phases: inflammation, proliferation, and remodelling. Poor wound healing or a chronic wound represents a silent epidemic that affects billions of people worldwide. Considering the involvement of immune cells in its resolution, recent studies are focused on investigating the roles of immune nutrients such as amino acids, minerals, and fatty acids on wound healing. Among the fatty acids, much attention has been given to omega-6 (ω-6) fatty acids since they can modulate cell migration and proliferation, phagocytic capacity, and production of inflammatory mediators. The present review summarizes current knowledge about the role of ω-6 fatty acids in the wound healing context.

Topical electrophilic nitro-fatty acids potentiate cutaneous inflammation

Endogenous electrophilic fatty acids mediate anti-inflammatory responses by modulating metabolic and inflammatory signal transduction and gene expression. Nitro-fatty acids and other electrophilic fatty acids may thus be useful for the prevention and treatment of immune-mediated diseases, including inflammatory skin disorders. In this regard, subcutaneous (SC) injections of nitro oleic acid (OA-NO₂), an exemplary nitro-fatty acid, inhibit skin inflammation in a model of allergic contact dermatitis (ACD). Given the nitration of unsaturated fatty acids during metabolic and inflammatory processes and the growing use of fatty acids in topical formulations, we sought to further study the effect of nitro-fatty acids on cutaneous inflammation. To accomplish this, the effect of topically applied OA-NO₂ on skin inflammation was evaluated using established murine models of contact hypersensitivity (CHS). In contrast to the effects of subcutaneously injected OA-NO₂, topical OA-NO₂ potentiated hapten-dependent inflammation inducing a sustained neutrophil-dependent inflammatory response characterized by psoriasiform histological features, increased angiogenesis, and an inflammatory infiltrate that included neutrophils, inflammatory monocytes, and γδ T cells. Consistent with these results, HPLC-MS/MS analysis of skin from psoriasis patients displayed a 56% increase in nitro-conjugated linoleic acid (CLA-NO₂) levels in lesional skin compared to non-lesional skin. These results suggest that nitro-fatty acids in the skin microenvironment are products of cutaneous inflammatory responses and, in high local concentrations, may exacerbate inflammatory skin diseases.

Autophagy-Dependent Generation of Free Fatty Acids Is Critical for Normal Neutrophil Differentiation

Neutrophils are critical and short-lived mediators of innate immunity that require constant replenishment. Their differentiation in the bone marrow requires extensive cytoplasmic and nuclear remodeling, but the processes governing these energy-consuming changes are unknown. While previous studies show that autophagy is required for differentiation of other blood cell lineages, its function during granulopoiesis has remained elusive. Here, we have shown that metabolism and autophagy are developmentally programmed and essential for neutrophil differentiation in vivo. Atg7-deficient neutrophil precursors had increased glycolytic activity but impaired mitochondrial respiration, decreased ATP production, and accumulated lipid droplets. Inhibiting autophagy-mediated lipid degradation or fatty acid oxidation alone was sufficient to cause defective differentiation, while administration of fatty acids or pyruvate for mitochondrial respiration rescued differentiation in autophagy-deficient neutrophil precursors. Together, we show that autophagy-mediated lipolysis provides free fatty acids to support a mitochondrial respiration pathway essential to neutrophil differentiation.

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Autophagy is critical for neutrophil differentiation in vivo

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Differentiating neutrophils shift from glycolysis to fatty acid oxidation

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By degrading lipid droplets, autophagy provides fatty acids, enabling this shift

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Fatty acids restore energy metabolism and differentiation in Atg7^–/– granulopoiesis

Electrophilic nitro-fatty acids suppress allergic contact dermatitis in mice

BACKGROUND

Reactions between nitric oxide (NO), nitrite (NO2-), and unsaturated fatty acids give rise to electrophilic nitro-fatty acids (NO₂ -FAs), such as nitro oleic acid (OA-NO₂ ) and nitro linoleic acid (LNO₂ ). Endogenous electrophilic fatty acids (EFAs) mediate anti-inflammatory responses by modulating metabolic and inflammatory signal transduction reactions. Hence, there is considerable interest in employing NO₂ -FAs and other EFAs for the prevention and treatment of inflammatory disorders. Thus, we sought to determine whether OA-NO₂ , an exemplary nitro-fatty acid, has the capacity to inhibit cutaneous inflammation.

METHODS

We evaluated the effect of OA-NO₂ on allergic contact dermatitis (ACD) using an established model of contact hypersensitivity in C57Bl/6 mice utilizing 2,4-dinitrofluorobenzene as the hapten.

RESULTS

We found that subcutaneous (SC) OA-NO₂ injections administered 18 h prior to sensitization and elicitation suppresses ACD in both preventative and therapeutic models. In vivo SC OA-NO₂ significantly inhibits pathways that lead to inflammatory cell infiltration and the production of inflammatory cytokines in the skin. Moreover, OA-NO₂ is capable of enhancing regulatory T-cell activity. Thus, OA-NO₂ treatment results in anti-inflammatory effects capable of inhibiting ACD by inducing immunosuppressive responses.

CONCLUSION

Overall, these results support the development of OA-NO₂ as a promising therapeutic for ACD and provides new insights into the role of electrophilic fatty acids in the control of cutaneous immune responses potentially relevant to a broad range of allergic and inflammatory skin diseases.

Oral Administration of Linoleic Acid Induces New Vessel Formation and Improves Skin Wound Healing in Diabetic Rats

Introduction

Impaired wound healing has been widely reported in diabetes. Linoleic acid (LA) accelerates the skin wound healing process in non-diabetic rats. However, LA has not been tested in diabetic animals.

Objectives

We investigated whether oral administration of pure LA improves wound healing in streptozotocin-induced diabetic rats.

Methods

Dorsal wounds were induced in streptozotocin-induced type-1 diabetic rats treated or not with LA (0.22 g/kg b.w.) for 10 days. Wound closure was daily assessed for two weeks. Wound tissues were collected at specific time-points and used to measure fatty acid composition, and contents of cytokines, growth factors and eicosanoids. Histological and qPCR analyses were employed to examine the dynamics of cell migration during the healing process.

Results

LA reduced the wound area 14 days after wound induction. LA also increased the concentrations of cytokine-induced neutrophil chemotaxis (CINC-2αβ), tumor necrosis factor-α (TNF-α) and leukotriene B₄ (LTB₄), and reduced the expression of macrophage chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1 (MIP-1). These results together with the histological analysis, which showed accumulation of leukocytes in the wound early in the healing process, indicate that LA brought forward the inflammatory phase and improved wound healing in diabetic rats. Angiogenesis was induced by LA through elevation in tissue content of key mediators of this process: vascular-endothelial growth factor (VEGF) and angiopoietin-2 (ANGPT-2).

Conclusions

Oral administration of LA hastened wound closure in diabetic rats by improving the inflammatory phase and angiogenesis.

Contractile function recovery in severely injured gastrocnemius muscle of rats treated with either oleic or linoleic acid

NEW FINDINGS

What is the central question of this study? Oleic and linoleic acids modulate fibroblast proliferation and myogenic differentiation in vitro. However, their in vivo effects on muscle regeneration have not yet been examined. We investigated the effects of either oleic or linoleic acid on a well-established model of muscle regeneration after severe laceration. What is the main finding and its importance? We found that linoleic acid increases fibrous tissue deposition and impairs muscle regeneration and recovery of contractile function, whereas oleic acid has the opposite effects in severely injured gastrocnemius muscle, suggesting that linoleic acid has a harmful effect and oleic acid a potential therapeutic effect on muscle regeneration. Oleic and linoleic acids control fibroblast proliferation and myogenic differentiation in vitro; however, there was no study in skeletal muscle in vivo. The aim of this study was to evaluate the effects of either oleic or linoleic acid on the fibrous tissue content (collagen deposition) of muscle and recovery of contractile function in rat gastrocnemius muscle after being severely injured by laceration. Rats were supplemented with either oleic or linoleic acid for 4 weeks after laceration [0.44 g (kg body weight)^-1 day^-1 ]. Muscle injury led to an increase in oleic-to-stearic acid and palmitoleic-to-palmitic acid ratios, suggesting an increase in Δ⁹ desaturase activity. Increased fibrous tissue deposition and reduced isotonic and tetanic specific forces and resistance to fatigue were observed in the injured muscle. Supplementation with linoleic acid increased the content of eicosadienoic (20:2, n-6) and arachidonic (20:4, n-6) acids, reduced muscle mass and fibre cross-sectional areas, increased fibrous tissue deposition and further reduced the isotonic and tetanic specific forces and resistance to fatigue induced by laceration. Supplementation with oleic acid increased the content of docosahexaenoic acid (22:6, n-3) and abolished the increase in fibrous tissue area and the decrease in isotonic and tetanic specific forces and resistance to fatigue induced by muscle injury. We concluded that supplementation with linoleic acid impairs muscle regeneration and increases fibrous tissue deposition, resulting in impaired recovery of contractile function. Oleic acid supplementation reduced fibrous tissue deposition and improved recovery of contractile function, attenuating the tissue damage caused by muscle injury.

Production of vegetable oil blends and structured lipids and their effect on wound healing

<p>Two oil blends (sunflower/canola oils 85/15 (BL1) and canola/linseed oils 70/30 (BL2)), were prepared and enzymatically interesterified to be applied to surgically-induced wounds in rats. Following surgery, the animals were submitted to the Treatment with Physiological Saline (TPS) (control group), Blends (TBL), and Structured Lipids (TSL). The control group (TPS) received physiological saline solution for 15 days. In TBL, BL1 was administered during the inflammation phase (days 0-3) and BL2 in the tissue formation and remodeling phase (days 4-15). In TSL, Structured Lipid 1 (SL1) and Structured Lipid 2 (SL2) were used instead of BL1 and BL2, respectively. The aim of this study was to compare wound closure evolution among rats treated with the blends or structured lipids versus control rats treated with physiological saline. The wound healing process was evaluated by measuring the wound areas along the treatments and the concentrations of cytokines. An increase in the areas of wounds treated with the blends and structured lipids in the inflammatory phase was observed, followed by a steeper closure curve compared to wounds treated with physiological saline. The changes observed during the inflammatory phase suggest a potential therapeutic application in cutaneous wound healing which should be further investigated.</p>

Seed oil of Joannesia princeps improves cutaneous wound closure in experimental mice

Joannesia princeps (Cotieira) is a well known medicinal plant in Brazil, however, the therapeutic effects of oil obtained from its seeds have still not been demonstrated. The beneficial effects of J. princeps seed oil on cutaneous wound healing on the back of experimental mice were investigated. An excisional lesion in male Swiss mice (n=20 per group) was topically treated with mineral oil or J. princeps seed oil once a day beginning on the day of lesion until the third day after wounding. Animals were killed and lesions collected after 14 days. Murine skin fibroblast cultures were treated with J. princeps seed oil and fibroblast activity was evaluated. In the in vivo assay, J. princeps seed oil increased wound contraction and migratory tongue length, but reduced neutrophil and macrophage number when compared with the control group. Blood vessel number, collagen deposition, and VEGF levels were increased in treated lesions when compared with control lesions. However, J. princeps seed oil reduced myofibroblast density and carbonyl protein levels when compared with the control group. In the in vitro assay, treatment with J. princeps seed oil increased fibroblast migration and proliferation, but reduced myofibroblastic differentiation in vitro. In conclusion, J. princeps seed oil accelerates wound closure increasing angiogenesis, keratinocyte migration, and fibroblast activity while reducing inflammatory response and oxidative damage.

Interferon-α2b against microbes through promoting biosynthesis of unsaturated fatty acids

Interferon (IFN) family is a large group of cytokines involved in innate immune response against various microorganisms. However, whether IFN functions in antimicrobial property by metabolic pathways is largely unknown. In the present study, GC-MS-based metabolome is investigated in humoral fluid of zebrafish (Danio rerio) which are exposed to three doses of IFN-α2b, designed as IFN-L, IFN-M, and IFN-H. Out of 67 compounds identified, 19, 28, and 29 differential abundances of metabolites are identified in the three groups compared with control, respectively. A total of 41 differential metabolites constructed IFN-dependent metabolome, in which 13 overlap among the three doses of IFN-α2b groups. These overlapped metabolites show that decreased alanine asparate and glutamate metabolic pathway, arginine and proline metabolic pathway, and increased purine metabolism form a characteristic feature in response to IFN-α2b. Further dose-related metabolites indicate that biosynthesis of unsaturated fatty acids is enriched only in IFN-M and IFN-H, which is related to high protection against bacterial infection. Exogenous fatty acids, especially unsaturated linoleic acid, may elevate the survival ability of zebrafish infected with extracellular pathogenic V. alginolyticus and intracellular pathogenic Edwardsiella tarda. These results disclose an unknown mechanism by which IFN-α2b protects host from microbial infections. Our findings highlight the ways to understand action of IFN in content of metabolic regulation.

Oleic acid modulates mRNA expression of liver X receptor (LXR) and its target genes ABCA1 and SREBP1c in human neutrophils

PURPOSE

Regulation of liver X receptors (LXRs) is essential for cholesterol homeostasis and inflammation. The present study was conducted to determine whether oleic acid (OA) could regulate mRNA expression of LXRα and LXRα-regulated genes and to assess the potential promotion of oxidative stress by OA in neutrophils.

METHODS

Human neutrophils were treated with OA at different doses and LXR target gene expression, oxidative stress production, lipid efflux and inflammation state were analyzed.

RESULTS

We describe that mRNA synthesis of both LXRα and ABCA1 (a reverse cholesterol transporter) was induced by OA in human neutrophils. This fatty acid enhanced the effects of LXR ligands on ABCA1 and LXR expression, but it decreased the mRNA levels of sterol regulatory element-binding protein 1c (a transcription factor that regulates the synthesis of triglycerides). Although OA elicited a slight oxidative stress in the short term (15-30 min) in neutrophils, it is unlikely that this is relevant for the modulation of transcription in our experimental conditions, which involve longer incubation time (i.e., 6 h). Of physiological importance is our finding that OA depresses intracellular lipid levels and that markers of inflammation, such as ERK1/2 and p38 mitogen-activated protein kinase phosphorylation, were decreased by OA treatment. In addition, 200 μM OA reduced the migration of human neutrophils, another marker of the inflammatory state. However, OA did not affect lipid peroxidation induced by pro-oxidant agents.

CONCLUSIONS

This work presents for the first time evidence that human neutrophils are highly sensitive to OA and provides novel data in support of a protective role of this monounsaturated acid against the activation of neutrophils during inflammation.

Fatty acids increase hepatitis B virus X protein stabilization and HBx-induced inflammatory gene expression

The protein level of human hepatitis B virus (HBV) in infection is variable, depending on patient context. We previously reported that HBV X protein (HBx) induces hepatic lipid accumulation and inflammation. Here, we show that abnormal levels of hepatic fatty acids increase HBx protein stability during HBV expression, resulting in the potentiation of HBx-induced inflammation. Reactive oxygen species, Ca(2+) signaling and expression levels of various lipid metabolic genes were investigated in HBx-expressing cells and in HBx transgenic mice. Fatty acids, including palmitate, stearate and oleate, increased HBx protein stability by preventing proteasome-dependent degradation. Hepatic inflammation induced by a high fat diet (HFD) and HBx was measured based on the expression of interleukin-6 and tumor necrosis factor α. In addition, the protein level of HBx increased in HFD-HBx transgenic mice. Reactive oxygen species production and intracellular Ca(2+) signal activation play critical roles in fatty-acid-induced HBx stabilization. Abnormal levels of hepatic fatty acids resulted in synergistic induction of HBx protein and liver inflammatory gene expression through HBx protein stabilization. These results indicate that different fatty acid levels in the liver might affect HBV-induced pathogenesis.

Dietary oils modify the host immune response and colonic tissue damage following Citrobacter rodentium infection in mice

Inflammatory bowel disease is an intestinal inflammatory disorder of multifactorial origin, in which diets that favor high n-6 and low n-3 fatty acids have been implicated. The present study addressed whether dietary n-6 and n-3 fatty acids alter colonic mucosal response to Citrobacter rodentium (C. rodentium) infection. Mice were fed diets identical except for fatty acids, with an energy percentage of 15% 18:2n-6 and <0.06% 18:3n-3, 4.2% 18:2n-6 and 1.9% 18:3n-3, or 1.44% 20:5n-3, 4.9% 22:6n-3, 0.32% 18:2n-6, and 0.12% 18:3n-3 from safflower, canola, or fish oil, respectively for 3 wk before infection. Dietary oils had no effect on colonic C. rodentium growth but altered colon 20:4n-6/(20:5n-3+22:6n-3) with 9.40 ± 0.06, 1.94 ± 0.08, and 0.32 ± 0.03% in colon phosphatidylcholine and 3.82 ± 0.18, 1.14 ± 0.02, and 0.30 ± 0.02% in phosphatidylethanolamine of mice fed safflower, canola, or fish oil, respectively. At 10 days postinfection, histological damage, F4/80-positive macrophages, and myeloperoxidase-positive neutrophils in colonic mucosa were higher in infected mice fed safflower than fish oil. Colon gene transcripts for macrophage inflammatory protein 2, keratinocyte cytokine, and monocyte chemoattractant protein 1 expression were significantly higher in infected mice fed safflower than canola or fish oil; IFN-γ, IL-6, and IL-17A expression were significantly elevated in mice fed safflower rather than fish oil; and IL-10 was significantly higher in mice fed fish oil rather than canola or safflower oil. This study demonstrates that oils high in 18:2n-6 with minimal n-3 fatty acids exacerbate mucosal immune response, whereas oils high in n-3 fatty acids attenuate mucosal immune response to C. rodentium. These studies implicate dietary oils as environmental modifiers of intestinal inflammation in response to infection.

Medium-chain fatty acid-sensing receptor, GPR84, is a proinflammatory receptor

G protein-coupled receptor 84 (GPR84) is a putative receptor for medium-chain fatty acids (MCFAs), whose pathophysiological roles have not yet been clarified. Here, we show that GPR84 was activated by MCFAs with the hydroxyl group at the 2- or 3-position more effectively than nonhydroxylated MCFAs. We also identified a surrogate agonist, 6-n-octylaminouracil (6-OAU), for GPR84. These potential ligands and the surrogate agonist, 6-OAU, stimulated [(35)S]GTP binding and accumulated phosphoinositides in a GPR84-dependent manner. The surrogate agonist, 6-OAU, internalized GPR84-EGFP from the cell surface. Both the potential ligands and 6-OAU elicited chemotaxis of human polymorphonuclear leukocytes (PMNs) and macrophages and amplified LPS-stimulated production of the proinflammatory cytokine IL-8 from PMNs and TNFα from macrophages. Furthermore, the intravenous injection of 6-OAU raised the blood CXCL1 level in rats, and the inoculation of 6-OAU into the rat air pouch accumulated PMNs and macrophages in the site. Our results indicate a proinflammatory role of GPR84, suggesting that the receptor may be a novel target to treat chronic low grade inflammation associated-disease.

Sunflower oil supplementation has proinflammatory effects and does not reverse insulin resistance in obesity induced by high-fat diet in C57BL/6 mice

High consumption of polyunsaturated fatty acids, such as sunflower oil has been associated to beneficial effects in plasma lipid profile, but its role on inflammation and insulin resistance is not fully elucidated yet. We evaluated the effect of sunflower oil supplementation on inflammatory state and insulin resistance condition in HFD-induced obese mice. C57BL/6 male mice (8 weeks) were divided in four groups: (a) control diet (CD), (b) HFD, (c) CD supplemented with n-6 (CD + n-6), and (d) HFD supplemented with n-6 (HFD + n-6). CD + n-6 and HFD + n-6 were supplemented with sunflower oil by oral gavage at 2 g/Kg of body weight, three times per week. CD and HFD were supplemented with water instead at the same dose. HFD induced whole and muscle-specific insulin resistance associated with increased inflammatory markers in insulin-sensitive tissues and macrophage cells. Sunflower oil supplementation was not efficient in preventing or reducing these parameters. In addition, the supplementation increased pro-inflammatory cytokine production by macrophages and tissues. Lipid profile, on the other hand, was improved with the sunflower oil supplementation in animals fed HFD. In conclusion, sunflower oil supplementation improves lipid profile, but it does not prevent or attenuate insulin resistance and inflammation induced by HFD in C57BL/6 mice.

G-protein-coupled receptors as fat sensors

PURPOSE OF REVIEW

It has been demonstrated that fatty acids (FAs) are physiological ligands of G-protein-coupled receptors (GPRs). Activation of the GPRs (40, 41, 43, 84, 119 and 120) by FAs or synthetic agonists modulates several responses. In this review, we discuss the current knowledge on the actions of FA-activated GPRs and their relevance in normal and pathological conditions.

RECENT FINDINGS

Studies have shown that FA-activated GPRs modulate hormone secretion (incretin, insulin and glucagon), activation of leukocytes and several aspects of metabolism.

SUMMARY

Understanding GPR actions and their involvement in the development of insulin-resistance, β-cell failure, dyslipidemia and inflammation associated with obesity, type 2 diabetes, metabolic syndrome and cardiovascular diseases is important for the comprehension of the mechanisms underlying these pathological conditions and for the establishment of new and effective interventions.

Fatty acids as biocompounds: their role in human metabolism, health and disease--a review. Part 1: classification, dietary sources and biological functions

BACKGROUND

Fatty acids are substantial components of lipids and cell membranes in the form of phospholipids. This review consists of two parts. The present part aims at describing fatty acid classification, dietary sources and biological functions. The second part will focus on fatty acid physiological roles and applications in human health and disease.

RESULTS

In humans, not all fatty acids can be produced endogenously due to the absence of certain desaturases. Thus, specific fatty acids termed essential (linoleic, alpha-linolenic) need to be taken from the diet. Other fatty acids whose synthesis depends on essential fatty acid intake include eicosapentaenoic acid and docosahexaenoic acid, found in oily fish. Dietary sources of saturated fatty acids are animal products (butter, lard) and tropical plant oils (coconut, palm), whereas sources of unsaturated fatty acids are vegetable oils (such as olive, sunflower, and soybean oils) and marine products (algae and fish oils). Saturated fatty acids have been related to adverse health effects, whereas unsaturated fatty acids, especially monounsaturated and n-3 polyunsaturated, are thought to be protective. In addition, trans fatty acids have been shown to have negative effects on health, whereas conjugated fatty acids might be beneficial. Lastly, fatty acids are the main components of lipid classes (triacylglycerols, phospholipids, cholesteryl esters, non-esterified fatty acids).

CONCLUSION

Fatty acids are important biocompounds which take part in complex metabolic pathways, thus having major biological roles. They are obtained from various dietary sources which determine the type of fat consumed and consequently health outcome.

Lamin B receptor regulates the growth and maturation of myeloid progenitors via its sterol reductase domain: implications for cholesterol biosynthesis in regulating myelopoiesis

Lamin B receptor (LBR) is a bifunctional nuclear membrane protein with N-terminal lamin B and chromatin-binding domains plus a C-terminal sterol Δ(14) reductase domain. LBR expression increases during neutrophil differentiation, and deficient expression disrupts neutrophil nuclear lobulation characteristic of Pelger-Huët anomaly. Thus, LBR plays a critical role in regulating myeloid differentiation, but how the two functional domains of LBR support this role is currently unclear. We previously identified abnormal proliferation and deficient functional maturation of promyelocytes (erythroid, myeloid, and lymphoid [EML]-derived promyelocytes) derived from EML-ic/ic cells, a myeloid model of ichthyosis (ic) bone marrow that lacks Lbr expression. In this study, we provide new evidence that cholesterol biosynthesis is important to myeloid cell growth and is supported by the sterol reductase domain of Lbr. Cholesterol biosynthesis inhibitors caused growth inhibition of EML cells that increased in EML-derived promyelocytes, whereas cells lacking Lbr exhibited complete growth arrest at both stages. Lipid production increased during wild-type neutrophil maturation, but ic/ic cells exhibited deficient levels of lipid and cholesterol production. Ectopic expression of a full-length Lbr in EML-ic/ic cells rescued both nuclear lobulation and growth arrest in cholesterol starvation conditions. Lipid production also was rescued, and a deficient respiratory burst was corrected. Expression of just the C-terminal sterol reductase domain of Lbr in ic/ic cells also improved each of these phenotypes. Our data support the conclusion that the sterol Δ(14) reductase domain of LBR plays a critical role in cholesterol biosynthesis and that this process is essential to both myeloid cell growth and functional maturation.