Docosahexaenoic acid decreases pro-inflammatory mediators in an in vitro murine adipocyte macrophage co-culture model

n-3 and n-6 Polyunsaturated Fatty Acids Modulate Macrophage-Myocyte Inflammatory Crosstalk and Improve Myocyte Insulin Sensitivity

In obesity, circulating saturated fatty acids (SFAs) and inflammatory cytokines interfere with skeletal muscle insulin signaling, leading to whole body insulin resistance. Further, obese skeletal muscle is characterized by macrophage infiltration and polarization to the inflammatory M1 phenotype, which is central to the development of local inflammation and insulin resistance. While skeletal muscle-infiltrated macrophage-myocyte crosstalk is exacerbated by SFA, the effects of other fatty acids, such as n-3 and n-6 polyunsaturated fatty acids (PUFAs), are less studied. Thus, the objective of this study was to determine the effects of long-chain n-3 and n-6 PUFAs on macrophage M1 polarization and subsequent effects on myocyte inflammation and metabolic function compared to SFA. Using an in vitro model recapitulating obese skeletal muscle cells, differentiated L6 myocytes were cultured for 24 h with RAW 264.7 macrophage-conditioned media (MCM), followed by insulin stimulation (100 nM, 20 min). MCM was generated by pre-treating macrophages for 24 h with 100 μM palmitic acid (16:0, PA-control), arachidonic acid (20:4n-6, AA), or docosahexaenoic acid (22:6n-3, DHA). Next, macrophage cultures were stimulated with a physiological dose (10 ng/mL) of lipopolysaccharide for an additional 12 h to mimic in vivo obese endotoxin levels. Compared to PA, both AA and DHA reduced mRNA expression and/or secreted protein levels of markers for M1 (TNFα, IL-6, iNOS; p < 0.05) and increased those for M2 (IL-10, TGF-β; p < 0.05) macrophage polarization. In turn, AA- and DHA-derived MCM reduced L6 myocyte-secreted cytokines (TNFα, IL-6; p < 0.05) and chemokines (MCP-1, MIP-1β; p < 0.05). Only AA-derived MCM increased L6-myocyte phosphorylation of Akt (p < 0.05), yet this was inconsistent with improved insulin signaling, as only DHA-derived MCM improved L6 myocyte glucose uptake (p < 0.05). In conclusion, dietary n-3 and n-6 PUFAs may be a useful strategy to modulate macrophage-myocyte inflammatory crosstalk and improve myocyte insulin sensitivity in obesity.

Effect of Lifelong Exposure to Dietary Plant and Marine Sources of n-3 Polyunsaturated Fatty Acids on Morphologic and Gene Expression Biomarkers of Intestinal Health in Early Life

Altered intestinal health is also associated with the incidence and severity of many chronic inflammatory conditions, which could be attenuated via dietary n-3 PUFA interventions. However, little is known about the effect of lifelong exposure to n-3 PUFA from plant and marine sources (beginning in utero via the maternal diet) on early life biomarkers of intestinal health. Harems of C57Bl/6 mice were randomly assigned to one of three isocaloric AIN-93G modified diets differing in their fat sources consisting of the following: (i) 10% safflower oil (SO, enriched in n-6 PUFA), (ii) 3% flaxseed oil + 7% safflower oil (FX, plant-based n-3 PUFA-enriched diet), or (iii) 3% menhaden fish oil + 7% safflower oil (MO, marine-based n-3 PUFA-enriched diet). Mothers remained on these diets throughout pregnancy and offspring (n = 14/diet) continued on the same parental diet until termination at 3 weeks of age. In ileum, villi:crypt length ratios were increased in both the FX and MO dietary groups compared to SO (p < 0.05). Ileum mRNA expression of critical intestinal health biomarkers was increased by both n-3 PUFA-enriched diets including Relmβ and REG3γ compared to SO (p < 0.05), whereas only the FX diet increased mRNA expression of TFF3 and Muc2 (p < 0.05) and only the MO diet increased mRNA expression of ZO-1 (p < 0.05). In the proximal colon, both the FX and MO diets increased crypt lengths compared to SO (p < 0.05), whereas only the MO diet increased goblet cell numbers compared to SO (p < 0.05). Further, the MO diet increased proximal colon mRNA expression of Relmβ and REG3γ (p < 0.05) and both MO and FX increased mRNA expression of Muc2 compared to SO (p < 0.05). Collectively, these results demonstrate that lifelong exposure to dietary n-3 PUFA, beginning in utero, from both plant and marine sources, can support intestinal health development in early life. The differential effects between plant and marine sources warrants further investigation for optimizing health.

The Preventive Mechanisms of Bioactive Food Compounds against Obesity-Induced Inflammation

Dietary patterns are promising strategies for preventing and treating obesity and its coexisting inflammatory processes. Bioactive food compounds have received considerable attention due to their actions against obesity-induced inflammation, with limited harmful side effects. They are perceived as food ingredients or dietary supplements other than those necessary to meet basic human nutritional needs and are responsible for positive changes in the state of health. These include polyphenols, unsaturated fatty acids, and probiotics. Although the exact mechanisms of bioactive food compounds' action are still poorly understood, studies have indicated that they involve the modulation of the secretion of proinflammatory cytokines, adipokines, and hormones; regulate gene expression in adipose tissue; and modify the signaling pathways responsible for the inflammatory response. Targeting the consumption and/or supplementation of foods with anti-inflammatory potential may represent a new approach to obesity-induced inflammation treatment. Nevertheless, more studies are needed to evaluate strategies for bioactive food compound intake, especially times and doses. Moreover, worldwide education about the advantages of bioactive food compound consumption is warranted to limit the consequences of unhealthy dietary patterns. This work presents a review and synthesis of recent data on the preventive mechanisms of bioactive food compounds in the context of obesity-induced inflammation.

Fatty Acids as Potent Modulators of Autophagy Activity in White Adipose Tissue

A high-fat diet is one of the causative factors of obesity. The dietary profile of fatty acids is also an important variable in developing obesity, as saturated fatty acids are more obesogenic than monounsaturated and polyunsaturated fatty acids. Overweight and obesity are inseparably connected with the excess of adipose tissue in the body, characterized by hypertrophy and hyperplasia of fat cells, which increases the risk of developing metabolic syndrome. Changes observed within hypertrophic adipocytes result in elevated oxidative stress, unfolded protein accumulation, and increased endoplasmic reticulum (ER) stress. One of the processes involved in preservation of cellular homeostasis is autophagy, which is defined as an intracellular lysosome-dependent degradation system that serves to recycle available macromolecules and eliminate damaged organelles. In obesity, activation of autophagy is increased and the process appears to be regulated by different types of dietary fatty acids. This review describes the role of autophagy in adipose tissue and summarizes the current understanding of the effects of saturated and unsaturated fatty acids in autophagy modulation in adipocytes.

Docosahexaenoic Acid Counteracts the Hypoxic-Induced Inflammatory and Metabolic Alterations in 3T3-L1 Adipocytes

Background: Hypoxia is caused by the excessive expansion of the white adipose tissue (AT) and is associated with obesity-related conditions such as insulin resistance, inflammation, and oxidative stress. Docosahexaenoic acid (DHA) is an omega-3 fatty acid reported to have beneficial health effects. However, the effects of DHA in AT against hypoxia-induced immune-metabolic perturbations in adipocytes exposed to low O₂ tension are not well known. Consequently, this study aimed to evaluate the impact of DHA on markers of inflammation, metabolism, apoptosis, and oxidative stress in 3T3-L1 cell adipocytes exposed to low O₂ tension (1% O₂) induced hypoxia. Methods: The apoptosis and reactive oxygen species (ROS) rates were evaluated. Metabolic parameters such as lactate, FFA, glycerol release, glucose uptake, and ATP content were assessed by a fluorometer. The expression of HIF-1, GLUT1 and the secretion of adipocytokines such as leptin, adiponectin, and pro-inflammatory markers was evaluated. Results: DHA-treated hypoxic cells showed significantly decreased basal free fatty acid release, lactate production, and enhanced glucose consumption. In addition, DHA-treatment of hypoxic cells caused a significant reduction in the apoptosis rate and ROS production with decreased lipid peroxidation. Moreover, DHA-treatment of hypoxic cells caused a decreased secretion of pro-inflammatory markers (IL-6, MCP-1) and leptin and increased adiponectin secretion compared with hypoxic cells. Furthermore, DHA-treatment of hypoxic cells caused significant reductions in the expression of genes related to hypoxia (HIF-1, HIF-2), anaerobic metabolism (GLUT1 and Ldha), ATP production (ANT2), and fat metabolism (FASN and PPARY). Conclusion: This study suggests that DHA can exert potential anti-obesity effects by reducing the secretion of inflammatory adipokines, oxidative stress, lipolysis, and apoptosis.

Differential Effects of Short-Chain Fatty Acids on L6 Myotube Inflammatory Mediator Production in Response to Lipopolysaccharide- or Palmitic Acid-Stimulation

Short-chain fatty acids (SCFA) produced from dietary non-digestible carbohydrate fermentation have metabolic effects in skeletal muscle; however, their effect on inflammatory mediator production is unknown. In this study, L6 myotubes were cultured with individual SCFA (acetate, propionate, and butyrate) at 0.5 mM and 2.5 mM ± 10 ng/mL lipopolysaccharide (LPS) or ± 500 µM palmitic acid (PA) for 24 h. In response to LPS, only butyrate had an effect at the lower concentration (0.5 mM), whereas at the higher concentration (2.5 mM) both propionate and butyrate reduced MCP-1, MIP-1α, and RANTES secretion (p < 0.05), and only butyrate reduced IL-6 secretion and intracellular protein levels of phospho-STAT3 (p < 0.05). In response to PA, 0.5 mM butyrate reduced protein expression of phospho-NFκB p65 and the secretion of IL-6, MIP-1α, and MCP-1, whereas all three SCFA reduced RANTES secretion (p < 0.05). At the 2.5 mM SCFA concentration combined with PA stimulation, all three SCFA reduced intracellular protein expression of phospho-NFκB p65 and phospho-STAT3 and secreted protein levels of MCP-1, IL-6, and RANTES, whereas only butyrate reduced secretion of MIP-1α (p < 0.05). Thus, SCFA exhibit differential effects on inflammatory mediator expression in response to LPS and PA stimulation, which has implications for their individual impacts on inflammation-mediated skeletal muscle dysfunction.

Resveratrol and ω-3 PUFAs Promote Human Macrophage Differentiation and Function

Monocytes differentiate into M1 and M2 macrophages, which are classically activated by microbial products such as LPS or IFN-γ and interleukins (e.g., the anti-inflammatory and T_h2 promoting IL-4), respectively. The contribution of nutrients or nutrient-based substances such as ω-3 polyunsaturated fatty acids (ω-3 PUFAs) and resveratrol (Res) on the differentiation and function of M1 and M2 macrophages was evaluated. THP-1 cells and peripheral blood mononuclear cells (PBMCs) were differentiated into M1 and M2 cells and activated with LPS/IFN-γ or IL-4/IL-13. Macrophage lineage specific surface determinants (e.g., CD11b, CD11c, CD14, CD206, CD209, CD274, HLA-DR, CCR7, CCR2) were analysed by cytofluorometry. Res and ω-3 PUFAs altered CD14, CD206, CD274 and HL-DR surface expression patterns in M1 and M2 macrophages differentiated from PBMC. LPS/IFN-γ or IL-14/IL-13 activated macrophages subpopulations, which secreted cytokines and chemokines as measured by multiplex ELISA. Res and ω-3 PUFA reduced IL-1β, IL-6, TNF-α, CXCL10/IP-10, CCL13/MCP-4 and CCL20/MIP-3α in LPS/IFN-γ activated human leukaemia THP-1 cells, which is indicative of a dampening effect on M1 macrophages. However, Res increased M1 prototypic cytokines such as IL-1β or IL-6 in macrophages derived from PBMCs and also modified the expression of IL-12p70. Collectively, Res and ω-3 PUFAs distinctly promoted the differentiation and function of M1 and M2 macrophages. We conclude that these substances strengthen the macrophage-mediated effects on the innate and adaptive immune response.

The FADS1 genotypes modify the effect of linoleic acid-enriched diet on adipose tissue inflammation via pro-inflammatory eicosanoid metabolism

PURPOSE

Fatty acid desaturase (FADS) variants associate with fatty acid (FA) and adipose tissue (AT) metabolism and inflammation. Thus, the role of FADS1 variants in the regulation of dietary linoleic acid (LA)-induced effects on AT inflammation was investigated.

METHODS

Subjects homozygotes for the TT and CC genotypes of the FADS1-rs174550 (TT, n = 25 and CC, n = 28) or -rs174547 (TT, n = 42 and CC, n = 28), were either recruited from the METabolic Syndrome In Men cohort to participate in an intervention with LA-enriched diet (FADSDIET) or from the Kuopio Obesity Surgery (KOBS) study. GC and LC-MS for plasma FA proportions and eicosanoid concentrations and AT gene expression for AT inflammatory score (AT-InSc) was determined.

RESULTS

We observed a diet-genotype interaction between LA-enriched diet and AT-InSc in the FADSDIET. In the KOBS study, interleukin (IL)1 beta mRNA expression in AT was increased in subjects with the TT genotype and highest LA proportion. In the FADSDIET, n-6/LA proportions correlated positively with AT-InSc in those with the TT genotype but not with the CC genotype after LA-enriched diet. Specifically, LA- and AA-derived pro-inflammatory eicosanoids related to CYP450/sEH-pathways correlated positively with AT-InSc in those with the TT genotype, whereas in those with the CC genotype, the negative correlations between pro-inflammatory eicosanoids and AT-InSc related to COX/LOX-pathways.

CONCLUSIONS

LA-enriched diet increases inflammatory AT gene expression in subjects with the TT genotype, while CC genotype could play a protective role against LA-induced AT inflammation. Overall, the FADS1 variant could modify the dietary LA-induced effects on AT inflammation through the differential biosynthesis of AA-derived eicosanoids.

Dietary Docosahexaenoic Acid as a Potential Treatment for Semi-acute and Chronic Particle-Induced Pulmonary Inflammation in Balb/c Mice

Acute and chronic inflammation are vital contributing factors to pulmonary diseases which can be triggered by exposure to occupational and man-made particles; however, there are no established treatments. One potential treatment shown to have anti-inflammatory capabilities is the dietary supplement docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid found in fish oil. DHA's anti-inflammatory mechanisms are unclear for particle-induced inflammation; therefore, this study evaluated DHA as a prophylactic treatment for semi-acute and chronic particle-induced inflammation in vivo. Balb/c mice were fed a control or 1% DHA diet and exposed to dispersion media, an inflammatory multi-walled carbon nanotube (MWCNT), or crystalline silica (SiO₂) either once (semi-acute) or once a week for 4 weeks (chronic). The hypothesis was that DHA will decrease pulmonary inflammatory markers in response to particle-induced inflammation. Results indicated that DHA had a trending anti-inflammatory effect in mice exposed to MWCNT. There was a general decrease in inflammatory signals within the lung lavage fluid and upregulation of M2c macrophage gene expression in the spleen tissue. In contrast, mice exposed to SiO₂ while on the DHA diet significantly increased most inflammatory markers. However, DHA stabilized the phagolysosomal membrane upon prolonged treatment. This indicated that DHA treatment may depend upon certain inflammatory particle exposures as well as the length of the exposure.

Effect of n-3 long-chain polyunsaturated fatty acid intake on the eicosanoid profile in individuals with obesity and overweight: a systematic review and meta-analysis of clinical trials

Dietary n-3 polyunsaturated fatty acids (PUFAs) present beneficial effects on counteracting inflammation status, displaying a critical anti-inflammatory role and maintaining physiological homeostasis in obesity. The primary objective of this systematic review was to evaluate the effect of n-3 PUFAs intake on the eicosanoid profile of people with obesity and overweight. The search strategy on Embase, Scopus, PubMed, Web of Science, Cochrane Library, Google Scholar and ProQuest was undertaken until November 2019 and updated January 2021. The effect size of n-3 PUFAs on prostaglandins was estimated by Glass's, type 1 in a random-effect model for the meta-analysis. Seven clinical trials met the eligible criteria and a total of 610 subjects were included in this systematic review, and four of seven studies were included in meta-analysis. The intake of n-3 PUFAs promoted an overall reduction in serum pro-inflammatory eicosanoids. Additionally, n-3 PUFAs intake significantly decreased the arachidonic acid COX-derived PG eicosanoid group levels (Glass's Δ -0⋅35; CI -0⋅62, -0⋅07, I ² 31⋅48). Subgroup analyses showed a higher effect on periods up to 8 weeks (Glass's Δ -0⋅51; CI -0⋅76, -0⋅27) and doses higher than 0⋅5 g of n-3 PUFAs (Glass's Δ -0⋅46; CI -0⋅72, -0⋅27). Dietary n-3 PUFAs intake contributes to reduce pro-inflammatory eicosanoids of people with obesity and overweight. Subgroup's analysis showed that n-3 PUFAs can reduce the overall arachidonic acid COX-derived PG when adequate dose and period are matched.

Dietary ω-3 polyunsaturated fatty acids modulate CD4+ T-cell subset markers, adipocyte antigen-presentation potential, and NLRP3 inflammasome activity in a coculture model of obese adipose tissue

OBJECTIVES

Chronic low-grade inflammation in obesity is partly driven by inflammatory cross talk between adipocytes and interferon-γ-secreting CD4⁺ T-helper (Th)1 cells, a process we have shown may be mitigated by long-chain (LC) ω-3 polyunsaturated fatty acids (PUFAs). Our objective was to study pivotal mediators of interactions between Th1 cells and adipocytes as potential mechanisms underlying the antiinflammatory effects of LC ω-3 PUFAs.

METHODS

Using an in vitro model, 3T3-L1 adipocytes were cocultured with purified splenic CD4⁺ T cells from C57BL/6 mice consuming one of two isocaloric high-fat (HF) diets (60% kcal fat), containing either 41.2% kcal from lard + 18.7% kcal from corn oil (control, HF) or 41.2% kcal from lard + 13.4% kcal from corn oil + 5.3% kcal from fish oil (HF+FO). Cocultures were stimulated for 48 h with lipopolysaccharide (10 ng/mL).

RESULTS

Compared with HF cocultures, HF+FO reduced Th1-cell markers (including secreted interferon-γ) and increased Th2-cell markers, consistent with reduced expression of genes related to major histocompatibility complex II (P < 0.05). HF+FO also blunted markers of priming and activity of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome (P < 0.05). In confirmatory work, 3T3-L1 adipocyte pretreatment with the LC ω-3 PUFA docosahexaenoic acid (100 μM, 24 h) blunted interferon-γ-induced (5 ng/mL, 24 h) expression of genes related to major histocompatibility complex II and priming and activity markers of the NLRP3 inflammasome compared with control (P < 0.05).

CONCLUSIONS

Inflammatory interactions between CD4⁺ T cells and adipocytes may provide a target for LC ω-3 PUFAs to mitigate obesity-associated inflammation.

Studying Adipocyte and Immune Cell Cross Talk Using a Co-culture System

The co-culture of adipocytes and immune cells, such as macrophages or T cells (CD4⁺ or CD8⁺ subsets), is a novel experimental approach used to study paracrine interactions (or the cross talk) between cultured cell types in isolation, in order to understand their role in obese adipose tissue (AT) inflammation and dysfunction. Here we describe the general methodologies required for the co-culture of mature adipocytes (differentiated 3T3-L1 pre-adipocyte cell line) with primary immune cell subsets purified from mouse splenic mononuclear cells using a magnetic MicroBead positive selection, wherein multiple immune cell populations can be purified sequentially from a single mouse spleen, thereby providing diversity in the types of immune cells that can be co-cultured with adipocytes. Additionally, we describe experimental procedures for co-culturing adipocytes and immune cells in two different co-culture systems, including a cell contact-dependent co-culture system, wherein the cells are in direct physical contact, and a cell contact-independent, soluble mediator-driven co-culture system wherein the cells are physically separated by a trans-well semipermeable membrane. Finally, we discuss how these co-culture models can be utilized to recapitulate the AT microenvironment in obesity by utilizing physiologically relevant ratios of adipocytes:immune cells (specifically CDllb⁺ macrophages, CD4⁺ T cells, or CD8⁺ T cells) and lipopolysaccharide stimulation that mimics endotoxin concentrations observed in obesity.

Effect of oral administration of docohexanoic acid on anemia and inflammation in hemodialysis patients: A randomized controlled clinical trial

BACKGROUND & AIMS

Docohexanoic acid (DHA), a dietary n-3 polyunsaturated fatty-acid omega-3 (n-3, PUFA), showed potential beneficial effects in reducing all-cause mortality in hemodialysis (HD) patients. This randomized trial aimed to analyze whether DHA supplementation was a modulator of erythropoietin (EPO) response and inflammation in hemodialysis (HD) patients.

METHODS

In this controlled clinical trial, 52 HD patients were randomized to either DHA supplementation (650 mg DHA/3 times/wk/post-HD session) or controls (usual care), with 8-weeks of follow-up. The primary outcome was to determine the correction of anemia measured by changes in the erythropoiesis-resistance index (ERI) to keep the hemoglobin level at recommended target value. Secondary outcomes include changes in inflammatory biomarkers: serum C-reactive protein, total homocysteine (tHcy) and expression of miR-146a. Laboratory measures were determined at baseline and at 8-weeks after the DHA supplementation or usual care in controls. Linear regression analysis was used to assess the effect of DHA supplementation, adjusting for baseline values and intervention.

RESULTS

Forty-two HD patients (men: 69%; aged:66.7 ± 15.5 yrs; DM:19%), completed this study. The DHA effect significantly decreased EPO doses (-4158.7 UI/weekly; CI95%:-8123.7 to 193,6; p = 0.04), ERI (-9.25 UI weekly/kg BW/g/dL; CI95%:-15.5 to -2.9; p = 0.006), tHcy (-5.1 μmol/L; CI95%:-9.7 to -0.3; p = 0.03), and levels of miR-146a (-1.43; CI95%:-2.7 to -0.19; p = 0.03) in regression model. No adverse effects were found.

CONCLUSION

The DHA supplementation enhances anemia management and attenuates inflammation response in this controlled trial in HD patients, when provided as coadjutant therapy together with usual medical care. REGISTERED UNDER CLINICALTRIALS.

GOV IDENTIFIER NUMBER

04536636.

Adipose and Muscle Cell Co-Culture System: A Novel In Vitro Tool to Mimic the In Vivo Cellular Environment

A co-culture system allows researchers to investigate the complex interactions between two cell types under various environments, such as those that promote differentiation and growth as well as those that mimic healthy and diseased states, in vitro. In this paper, we review the most common co-culture systems for myocytes and adipocytes. The in vitro techniques mimic the in vivo environment and are used to investigate the causal relationships between different cell lines. Here, we briefly discuss mono-culture and co-culture cell systems and their applicability to the study of communication between two or more cell types, including adipocytes and myocytes. Also, we provide details about the different types of co-culture systems and their applicability to the study of metabolic disease, drug development, and the role of secretory factors in cell signaling cascades. Therefore, this review provides details about the co-culture systems used to study the complex interactions between adipose and muscle cells in various environments, such as those that promote cell differentiation and growth and those used for drug development.

Comparison of Dietary Oils with Different Polyunsaturated Fatty Acid n-3 and n-6 Content in the Rat Model of Cutaneous Wound Healing

Dietary supplementation with polyunsaturated fatty acids (PUFA) n-3 can affect cutaneous wound healing; however, recent findings demonstrate the variable extent of their influence on the quality of healing. Here, we compare the effect of several dietary oils, containing different levels of PUFA n-3 and PUFA n-6, on wound healing in the rat model. Rats were fed the feed mixture with 8% palm oil (P), safflower oil (S), fish oil (F) or Schizochytrium microalga extract (Sch) and compared to the animals fed by control feed mixture (C). Dorsal full-thickness cutaneous excisions were performed after 52 days of feeding and skin was left to heal for an additional 12 days. Histopathological analysis of skin wounds was performed, including immune cells immunolabeling and the determination of hydroxyproline amount as well as gene expression analyses of molecules contributing to different steps of the healing. Matrix-assisted-laser-desorption-ionization mass-spectrometry-imaging (MALDI-MSI) was used to determine the amount of collagen α-1(III) chain fragment in healing samples. Treatment by Schizochytrium extract resulted in decrease in the total wound area, in contrast to the safflower oil group where the size of the wound was larger when comparing to control animals. Diet with Schizochytrium extract and safflower oils displayed a tendency to increase the number of new vessels. The number of MPO-positive cells was diminished following any of oil treatment in comparison to the control, but their highest amount was found in animals with a fish oil diet. On the other hand, the number of CD68-positive macrophages was increased, with the most significant enhancement in the fish oil and safflower oil group. Hydroxyproline concentration was the highest in the safflower oil group but it was also enhanced in all other analyzed treatments in comparison to the control. MALDI-MSI signal intensity of a collagen III fragment decreased in the sequence C > S > Sch > P > F treatment. In conclusion, we observed differences in tissue response during healing between dietary oils, with the activation of inflammation observed following the treatment with oil containing high eicosapentaenoic acid (EPA) level (fish oil) and enhanced healing features were induced by the diet with high content of docosahexaenoic acid (DHA, Schizochytrium extract).

Anti-Inflammatory and Cytotoxicity Effects of Cudrania tricuspidata Fruits Vinegar in a Co-Culture System with RAW264.7 Macrophages and 3T3-L1 Adipocytes

Vinegar has been found to have in vitro improvement effect on inflammatory biomarkers, and clinically used to improve inflammation and obesity-related diseases. This study was designed to analyze in vitro anti-inflammatory effects of Cudrania tricuspidata fruits vinegar (CTFV) in a co-culture system with macrophages and adipocytes. We analyzed the physicochemical properties and polyphenolic ingredients of CTFV, and investigated in vitro anti-inflammatory effects of CTFV in a co-culture system with macrophages and adipocytes. The cells were cultured in the presence of CTFV for 24 h in contact with each other, then, harvested. The levels of monocyte chemoattractant protein (MCP)-1, tumour necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), nitric oxide (NO), and interleukin (IL)-6 were evaluated by using the Griess reagent, western blot, or enzyme-linked immunosorbent assay assays. We found that increasing levels for NO, iNOS, TNF-α, IL-6 and MCP-1 were caused by LPS treatment and co-culture using the contact method, whereas CTFV efficaciously attenuated inflammatory response by improving inflammatory parameters including NO, iNOS, TNF-α, IL-6 and MCP-1. The present study indicates that CTFV might provide a nutraceutical product or functional food resource for improving inflammation processed via the interaction of adipocytes and macrophages.

Dietary long-chain n-3 PUFAs mitigate CD4+ T cell/adipocyte inflammatory interactions in co-culture models of obese adipose tissue

Obese adipose tissue (AT) inflammation is partly driven by accumulation of CD4⁺ T helper (Th)1 cells and reduced Th2 and T regulatory subsets, which promotes macrophage chemotaxis and ensuing AT metabolic dysfunction. This study investigated CD4⁺ T cell/adipocyte cytokine-mediated paracrine interactions (cross talk) as a target for dietary intervention to mitigate obese AT inflammation. Using an in vitro co-culture model designed to recapitulate CD4⁺ T cell accumulation in obese AT (5% of stromal vascular cellular fraction), 3T3-L1 adipocytes were co-cultured with purified splenic CD4⁺ T cells from C57Bl/6 mice consuming one of two isocaloric diets containing either 10% w/w safflower oil (control, CON) or 7% w/w safflower oil+3% w/w fish oil (FO) for 4 weeks (n=8-11/diet). The FO diet provided 1.9% kcal from the long-chain (LC) n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid and docosahexaenoic acid, a dose that can be achieved by supplementation. Co-cultures were stimulated for 48 h with lipopolysaccharide (LPS) to mimic in vivo obese endotoxin levels or with conditioned media collected from LPS-stimulated visceral AT isolated from CON-fed mice. In both stimulation conditions, FO reduced mRNA expression and/or secreted protein levels of Th1 markers (T-bet, IFN-γ) and increased Th2 markers (GATA3, IL-4), concomitant with reduced inflammatory cytokines (IL-1β, IL-6, IL-12p70, TNF-α), macrophage chemokines (MCP-1, MCP-3, MIP-1α, MIP-2) and levels of activated central regulators of inflammatory signaling (NF-κB, STAT-1, STAT-3) (P<.05). Therefore, CD4⁺ T cell/adipocyte cross talk represents a potential target for LC n-3 PUFAs to mitigate obese AT inflammation.

Apple Flavonols Mitigate Adipocyte Inflammation and Promote Angiogenic Factors in LPS- and Cobalt Chloride-Stimulated Adipocytes, in Part by a Peroxisome Proliferator-Activated Receptor-γ-Dependent Mechanism

Adipose tissue (AT) expansion induces local hypoxia, a key contributor to the chronic low-grade inflammation that drives obesity-associated disease. Apple flavonols phloretin (PT) and phlorizin (PZ) are suggested anti-inflammatory molecules but their effectiveness in obese AT is inadequately understood. Using in vitro models designed to reproduce the obese AT microenvironment, 3T3-L1 adipocytes were cultured for 24 h with PT or PZ (100 μM) concurrent with the inflammatory stimulus lipopolysaccharide (LPS; 10 ng/mL) and/or the hypoxia mimetic cobalt chloride (CoCl₂; 100 μM). Within each condition, PT was more potent than PZ and its effects were partially mediated by peroxisome proliferator-activated receptor (PPAR)-γ (p < 0.05), as tested using the PPAR-γ antagonist bisphenol A diglycidyl ether (BADGE). In LPS-, CoCl₂-, or LPS + CoCl₂-stimulated adipocytes, PT reduced mRNA expression and/or secreted protein levels of inflammatory and macrophage chemotactic adipokines, and increased that of anti-inflammatory and angiogenic adipokines, which was consistent with reduced mRNA expression of M1 polarization markers and increased M2 markers in RAW 264.7 macrophages cultured in media collected from LPS + CoCl₂-simulated adipocytes (p < 0.05). Further, within LPS + CoCl₂-stimulated adipocytes, PT reduced reactive oxygen species accumulation, nuclear factor-κB activation, and apoptotic protein expression (p < 0.05). Overall, apple flavonols attenuate critical aspects of the obese AT phenotype.

CD8+ T cell/adipocyte inflammatory cross talk and ensuing M1 macrophage polarization are reduced by fish-oil-derived n-3 polyunsaturated fatty acids, in part by a TNF-α-dependent mechanism

Obese visceral adipose tissue (AT) inflammation is driven by adipokine-mediated cross talk between CD8⁺ T cells and adipocytes, a process mitigated by long-chain (LC) n-3 polyunsaturated fatty acids (PUFA) but underlying mechanisms and ensuing effects on macrophage polarization status are unknown. Using an in vitro co-culture model that recapitulates the degree of CD8⁺ T cell infiltration reported in obese AT, 3T3-L1 adipocytes were co-cultured for 24 h with purified splenic CD8⁺ T cells from C57Bl/6 mice consuming either a 10% w/w safflower oil (control, CON) or 7% w/w safflower oil + 3% w/w fish oil (FO) diet for 4 weeks (n=8-10/diet). Co-cultured cells were in direct contact or in a contact-independent condition separated by a Transwell permeable membrane and stimulated with lipopolysaccharide (10 ng/ml) to mimic in vivo obese endotoxin levels. In contact-dependent co-cultures, FO reduced inflammatory (IL-6, TNFα, IFN-γ) and macrophage chemotactic (CCL2, CCL7, CCL3) mRNA expression and/or secreted protein, NF-κB p65 activation, ROS accumulation, NLRP3 inflammasome priming (Nlrp3, Il1β mRNA) and activation (caspase-1 activity) compared to CON (P<.05). The anti-inflammatory action of FO was reproduced by the addition of a TNF-α neutralizing antibody (1 μg/ml) to CON co-cultures (CON/anti-TNF-α), albeit to a lesser degree. Conditioned media from FO and CON/anti-TNF-α co-cultures, in turn, reduced RAW 264.7 macrophage mRNA expression of M1 polarization markers (iNos, Cd11c, Ccr2) and associated inflammatory cytokines (Il6, Tnfα, Il1β) compared to CON. These data suggest that inflammatory CD8⁺ T cell/adipocyte cross talk is partially attributable to TNF-α signaling, which can be mitigated by LC n-3 PUFA.

Treatment of obesity-related inflammation with a novel synthetic pentacyclic oleanane triterpenoids via modulation of macrophage polarization

Background

Obesity leads to the chronic inflammation in the whole body and triggers the macrophage polarization to the pro-inflammatory phenotype. Targeting macrophage polarization provides a promising therapeutic strategy for obesity-related metabolic disorders and inflammation. Here, we show that SO1989, a derivative of natural occurring compound oleanolic acid, restores the balance between M1-polarized and M2-polarized macrophages in high fat diets (HFD)-induced obese mice resulting in the improvement of adipose inflammation and the metabolic dysfunctions.

Methods

Histological analysis, magnetic cell sorting and FACS, in vitro cell model of adipose inflammation, Western blotting, HFD mice model.

Findings

SO1989 exhibits similar or even stronger activity in inhibiting inflammation and M1 polarization of macrophages both in vitro and in vivo compared to its analogue CDDO-Me, previously known as a powerful anti-inflammation chemical small molecule. In addition, SO1989 can significantly increase the level of fatty acid oxidation in macrophages which can efficiently facilitate M2 polarization of macrophages. Unlike CDDO-Me, SO1989 shows less adverse effects on obese mice.

Interpretation

Taken all together, our findings identify SO1989 as a modulator in macrophage polarization and a safer potential leading compound for pro-resolution of inflammation treatment in metabolic disorders.

Fund

Supported by grants from the National Key Research and Development Plan (2017YFA0506000, 2017YFA0205400) and National Natural Science Foundation of China (81673439) and Natural Science Fund project in Jiangsu Province (BK20161408).

Effect of n-3 long-chain polyunsaturated fatty acids on wound healing using animal models – a review

The present review summarizes results of experiments, mostly performed on rodents, regarding the effects of fish oil (FO) and its biologically active constituents, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on the healing of cutaneous wounds, but also of selected other types of injury. Structure, metabolism and functions of EPA/DHA in an organism are briefly mentioned, with an emphasis on the ability of these long-chain polyunsaturated fatty acids to modulate inflammation. Wound healing as a complex programmed sequence of cellular and molecular processes including inflammation, cell migration, angiogenesis, synthesis of provisional matrix, collagen deposition and reepithelialisation is briefly described. Markers for evaluation of the healing process include planimetry indices, tensile strength, quantification of collagen synthesis including hydroxyproline determination, histopathology/immunohistochemistry and genomic/proteomic markers. As far as effects on wound healing are concerned, the main emphasis is put on the outcomes of experiments using a dietary FO/DHA/EPA administration, but the results of experiments with a parenteral application are also mentioned, together with selected relevantin vitrostudies. An important conclusion from the above-mentioned studies is an inconsistency of FO/DHA/EPA effects on wound healing: decreased/increased collagen deposition; lower/higher counts of the inflammatory cells in the healing tissue; increased/decreased concentration of both pro- and anti-inflammatory cytokines; DHA accelerated/delayed wound healing process. Some experiments indicate superiority of DHA over EPA regarding wound healing.

Dietary Fatty Acids Differentially Regulate Secretion of Adiponectin and Interleukin-6 in Primary Canine Adipose Tissue Culture

The aim of this study was to determine the effect of n3 polyunsaturated fatty acids (PUFA) on canine adipose tissue secretion of adiponectin, interleukin-6 (IL6), and tumor necrosis factor-α (TNFα). Subcutaneous and omental visceral adipose tissue samples were collected from 16 healthy intact female dogs. Concentrations of adiponectin were measured in mature adipocyte cultures, and concentrations of IL6 and TNFα were measured in undifferentiated stromovascular cell (SVC) cultures following treatment with eicosapentaenic acid (EPA, 20:5n-3), arachidonic acid (ARA, 20:4n-6), or palmitic acid (PAM, 16:0) at 25, 50, or 100 μM. Secretion of adiponectin from mature adipocytes was higher (p < 0.001) following EPA treatment at 50 μM compared to control in subcutaneous tissue, and higher following EPA treatment compared to PAM treatment at 25 μM in both subcutaneous (p < 0.001) and visceral tissues (p = 0.010). Secretion of IL6 from SVC derived from subcutaneous tissue was lower following EPA treatment and higher following PAM treatment compared to control both at 50 μM (p = 0.001 and p = 0.041, respectively) and 100 μM (p = 0.013 and p < 0.001, respectively). These findings of stimulation of adiponectin secretion and inhibition of IL6 secretion by EPA, and stimulation of IL6 secretion by PAM, are consistent with findings of increased circulating concentrations of adiponectin and decreased circulating concentration of IL6 in dogs supplemented with dietary fish oil, and show that the effect of fish oil on circulating concentrations of adiponectin and IL6 is, at least partially, the result of local effects of EPA and PAM on adipose tissue.

Docosahexaenoic acid antagonizes the boosting effect of palmitic acid on LPS inflammatory signaling by inhibiting gene transcription and ceramide synthesis

It is well known that saturated fatty acids (SFAs) and unsaturated fatty acid, in particular omega-3 polyunsaturated fatty acids (n-3 PUFAs), have different effects on inflammatory signaling: SFAs are pro-inflammatory but n-3 PUFAs have strong anti-inflammatory properties. We have reported that palmitic acid (PA), a saturated fatty acid, robustly amplifies lipopolysaccharide (LPS) signaling to upregulate proinflammatory gene expression in macrophages. We also reported that the increased production of ceramide (CER) via sphingomyelin (SM) hydrolysis and CER de novo synthesis plays a key role in the synergistic effect of LPS and PA on proinflammatory gene expression. However, it remains unclear if n-3 PUFAs are capable of antagonizing the synergistic effect of LPS and PA on gene expression and CER production. In this study, we employed the above macrophage culture system and lipidomical analysis to assess the effect of n-3 PUFAs on proinflammatory gene expression and CER production stimulated by LPS and PA. Results showed that DHA strongly inhibited the synergistic effect of LPS and PA on proinflammatory gene expression by targeting nuclear factor kappa B (NFκB)-dependent gene transcription. Results also showed that DHA inhibited the cooperative effect of LPS and PA on CER production by targeting CER de novo synthesis, but not SM hydrolysis. Furthermore, results showed that myriocin, a specific inhibitor of serine palmitoyltransferase, strongly inhibited both LPS-PA-stimulated CER synthesis and proinflammatory gene expression, indicating that CER synthesis is associated with proinflammatory gene expression and that inhibition of CER synthesis contributes to DHA-inhibited proinflammatory gene expression. Taken together, this study demonstrates that DHA antagonizes the boosting effect of PA on LPS signaling on proinflammatory gene expression by targeting both NFκB-dependent transcription and CER de novo synthesis in macrophages.

Effects of docosahexanoic acid supplementation on inflammatory and subcutaneous adipose tissue gene expression in HIV-infected patients on combination antiretroviral therapy (cART). A sub-study of a randomized, double-blind, placebo-controlled study

BACKGROUND

Omega-3 fatty acids have the potential to decrease inflammation and modify gene transcription. Whether docosahexanoic acid (DHA) supplementation can modify systemic inflammatory and subcutaneous adipose tissue (SAT) gene expression in HIV-infected patients is unknown.

METHODS

A randomized, double-blind, placebo-controlled trial that enrolled 84 antiretroviral-treated patients who had fasting TG levels from 2.26 to 5.65 mmol/l and received DHA or placebo for 48 weeks was performed (ClinicalTrials.gov, NCT02005900). Systemic inflammatory and SAT gene expression was assessed at baseline and at week 48 in 39 patients.

RESULTS

Patients receiving DHA had a 43.9% median decline in fasting TG levels at week 4 (IQR: -31% to -56%), compared with -2.9% (-18.6% to 16.5%) in the placebo group (P < 0.0001). High sensitivity C reactive protein (hsCRP) and arachidonic acid levels significantly decreased in the DHA group. Adipogenesis-related and mitochondrial-related gene expression did not experience significant changes. Mitochondrial DNA (mtDNA) significantly decreased in the placebo group. SAT inflammation-related gene expression (Tumor necrosis factor alpha [TNF-α], and monocyte chemoattractant protein-1 [MCP-1]) significantly decreased in the DHA group.

CONCLUSIONS

DHA supplementation down-regulated inflammatory gene expression in SAT. DHA impact on markers of systemic inflammation was restricted to hsCRP and arachidonic acid.

Preventive mechanism of bioactive dietary foods on obesity-related inflammation and diseases

This review focuses on the molecular biological mechanism of obesity-induced inflammation and the reciprocal interactions between the major molecular mechanisms and a range of dietary bioactive compounds.

Integrated Immunomodulatory Mechanisms through which Long-Chain n-3 Polyunsaturated Fatty Acids Attenuate Obese Adipose Tissue Dysfunction

Obesity is a global health concern with rising prevalence that increases the risk of developing other chronic diseases. A causal link connecting overnutrition, the development of obesity and obesity-associated co-morbidities is visceral adipose tissue (AT) dysfunction, characterized by changes in the cellularity of various immune cell populations, altered production of inflammatory adipokines that sustain a chronic state of low-grade inflammation and, ultimately, dysregulated AT metabolic function. Therefore, dietary intervention strategies aimed to halt the progression of obese AT dysfunction through any of the aforementioned processes represent an important active area of research. In this connection, fish oil-derived dietary long-chain n-3 polyunsaturated fatty acids (PUFA) in the form of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been demonstrated to attenuate obese AT dysfunction through multiple mechanisms, ultimately affecting AT immune cellularity and function, adipokine production, and metabolic signaling pathways, all of which will be discussed herein.

Anti-Inflammatory Effects of Stearidonic Acid Mediated by Suppression of NF-κB and MAP-Kinase Pathways in Macrophages

Stearidonic acid (SDA, 18:4n-3) is an omega-3 polyunsaturated fatty acid present in oils derived from plants of the Boraginaceae family. In this study, we determined the anti-inflammatory effects of SDA isolated from echium oil on lipopolysaccharide (LPS)-induced inflammatory responses in RAW 264.7 macrophages. SDA significantly downregulated the levels of the inducible nitric oxide synthase (iNOS) protein, thereby suppressing the production of nitric oxide (NO) in LPS-stimulated RAW 264.7 cells. In addition, SDA inhibited the nuclear translocation and promoter activity of nuclear factor κB (NFκB) and the phosphorylation of mitogen-activated protein kinases (MAPK) such as extracellular signal regulated kinase 1/2, c-jun N terminal kinase, and p38 in LPS-stimulated RAW 264.7 cells. Our results showed that SDA exerted anti-inflammatory effects by suppressing iNOS-mediated NO production via inactivation of NFκB and MAPK signaling pathways.

Hydroxyeicosapentaenoic acids and epoxyeicosatetraenoic acids attenuate early occurrence of nonalcoholic fatty liver disease

BACKGROUND AND PURPOSE

The ω-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.

EXPERIMENTAL APPROACH

Mice were fed a control diet, high-fat diet (HFD) or ω-3 PUFA-enriched HFD (ω3HFD) 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.

KEY RESULTS

In short-term HFD-fed mice, the significantly increased lipid accumulation in the liver was reversed by ω-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 ω3HFD. However, HEPE/EEQ treatment had no direct protective effect on hepatocytes. ω3HFD 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.

CONCLUSION AND IMPLICATIONS

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.

Cholinergic activation suppresses palmitate-induced macrophage activation and improves acylation stimulating protein resistance in co-cultured adipocytes

Acylation-stimulating protein (ASP), produced through activation of the alternative complement immune system, modulates lipid metabolism. Using a trans-well co-culture cell model, the mitigating role of α7-nicotinic acetylcholine receptor (α7nAChR)-mediated cholinergic pathway on ASP resistance was evaluated. ASP signaling in adipocytes via its receptor C5L2 and signaling intermediates Gαq, Gβ, phosphorylated protein kinase C-α, and protein kinase C-ζ were markedly suppressed in the presence of TNFα or medium from palmitate-treated RAW264.7 macrophages, indicating ASP resistance. There was no direct effect of α7nAChR activation in 3T3-L1 cell culture. However, α7nAChR activation almost completely reversed the ASP resistance in adipocytes co-cultured with palmitate-treated RAW264.7 macrophages. Further, α7nAChR activation could suppress the production of pro-inflammatory molecules TNFα and interleukin-6 produced from palmitate-treated co-cultured macrophages. These results suggest that macrophages play a significant role in the pathogenesis of ASP resistance and α7nAChR activation secondarily improves adipose ASP resistance through suppression of inflammation in macrophages. Impact statement 1. Adipocyte-macrophage interaction in acylation-stimulating protein (ASP) resistance 2. Lipotoxicity induced inflammatory response in ASP resistance 3. A vicious circle between lipotoxicity and inflammatory response in ASP resistance 4. Cholinergic modulation of inflammatory response in adipocyte and macrophage.

Vegetable oil induced inflammatory response by altering TLR-NF-κB signalling, macrophages infiltration and polarization in adipose tissue of large yellow croaker (Larimichthys crocea)

High level of vegetable oil (VO) in diets could induce strong inflammatory response, and thus decrease nonspecific immunity and disease resistance in most marine fish species. The present study was conducted to investigate whether dietary VO could exert these anti-immunological effects by altering TLR-NF-κB signalling, macrophages infiltration and polarization in adipose tissue of large yellow croaker (Larimichthys crocea). Three iso-nitrogenous and iso-lipid diets with 0% (FO, fish oil, the control), 50% (FV, fish oil and vegetable oil mixed) and 100% (VO, vegetable oil) vegetable oil were fed to fish with three replicates for ten weeks. The results showed that activities of respiratory burst (RB) and alternative complement pathway (ACP), as well as disease resistance after immune challenge were significantly decreased in large yellow croaker fed VO diets compared to FO diets. Inflammatory response of experimental fish was markedly elevated by VO reflected by increase of pro-inflammatory cytokines (IL1β and TNFα) and decrease of anti-inflammatory cytokine (arginase I and IL10) genes expression. TLR-related genes expression, nucleus p65 protein, IKKα/β and IκBα phosphorylation were all significantly increased in the AT of large yellow croaker fed VO diets. Moreover, the expression of macrophage infiltration marker proteins (cluster of differentiation 68 [CD68] and colony-stimulating factor 1 receptor [CSF1R]) was significantly increased while the expression of anti-inflammatory M2 macrophage polarization marker proteins (macrophage mannose receptor 1 [MRC1] and cluster of differentiation 209 [CD209]) was significantly decreased in the AT of large yellow croaker fed VO diets. In conclusion, VO could induce inflammatory responses by activating TLR-NF-κB signalling, increasing macrophage infiltration into adipose tissue and polarization of macrophage in large yellow croaker.

ω3 Polyunsaturated Fatty Acids as Immunomodulators in Colorectal Cancer: New Potential Role in Adjuvant Therapies

Diet composition may affect the onset and progression of chronic degenerative diseases, including cancer, whose pathogenesis relies on inflammatory processes. Growing evidence indicates that diet and its components critically contribute to human health, affecting the immune system, secretion of adipokines, and metabolic pathways. Colorectal cancer (CRC) is one of the leading causes of death worldwide. Antineoplastic drugs are widely used for CRC treatment, but drug resistance and/or off-target toxicity limit their efficacy. Dietary ω3 polyunsaturated fatty acids (PUFA) have been gaining great interest in recent years as possible anti-inflammatory and anticancer agents, especially in areas such as the large bowel, where the pro-inflammatory context promotes virtually all steps of colon carcinogenesis. Growing epidemiological, experimental, and clinical evidence suggests that ω3 PUFA may play a role in several stages of CRC management exhibiting antineoplastic activity against human CRC cells, improving the efficacy of radiation and chemotherapy, ameliorating cancer-associated secondary complications, and preventing CRC recurrence. These effects are most likely related to the immunomodulatory activities of ω3 PUFA that are able to influence several aspects of the inflammatory process ranging from inflammasome activation, leukocyte recruitment, production of immune mediators to differentiation, and activation of immune cells. In this review, we will focus on the potential use of ω3 PUFA as adjuvant agents together with chemo/radiotherapy, highlighting the immunomodulatory effects most likely responsible for their beneficial effects in different stages of CRC management.

A Unique Combination of Nutritionally Active Ingredients Can Prevent Several Key Processes Associated with Atherosclerosis In Vitro

Introduction

Atherosclerosis is the underlying cause of cardiovascular disease that leads to more global mortalities each year than any other ailment. Consumption of active food ingredients such as phytosterols, omega-3 polyunsaturated fatty acids and flavanols are known to impart beneficial effects on cardiovascular disease although the combined actions of such agents in atherosclerosis is poorly understood. The aim of this study was to screen a nutritional supplement containing each of these active components for its anti-atherosclerotic effect on macrophages in vitro.

Results

The supplement attenuated the expression of intercellular adhesion molecule-1 and macrophage chemoattractant protein-1 in human and murine macrophages at physiologically relevant doses. The migratory capacity of human monocytes was also hindered, possibly mediated by eicosapentaenoic acid and catechin, while the ability of foam cells to efflux cholesterol was improved. The polarisation of murine macrophages towards a pro-inflammatory phenotype was also attenuated by the supplement.

Conclusion

The formulation was able to hinder multiple key steps of atherosclerosis development in vitro by inhibiting monocyte recruitment, foam cell formation and macrophage polarisation towards an inflammatory phenotype. This is the first time a combination these ingredients has been shown to elicit such effects and supports its further study in preclinical in vivo models.

Epigenetic regulation of gene expression and M2 macrophage polarization as new potential omega-3 polyunsaturated fatty acid targets in colon inflammation and cancer

INTRODUCTION

It has become increasingly clear that dietary habits may affect the risk/progression of chronic diseases with a pathogenic inflammatory component, such as colorectal cancer. Considerable attention has been directed toward the ability of nutritional agents to target key molecular pathways involved in these inflammatory-related diseases.

AREAS COVERED

ω-3 Polyunsaturated fatty acids (PUFA) and their oxidative metabolites have attracted considerable interest as possible anti-inflammatory and anti-cancer agents, especially in areas such as the large bowel, where the influence of orally introduced substances is high and tumors show deranged PUFA patterns. On this basis, we have analyzed pre-clinical findings that have recently revealed new insight into the molecular pathways targeted by ω-3 PUFA.

EXPERT OPINION

The findings analyzed herein demonstrate that ω-3 PUFA may exert beneficial effects by targeting the epigenetic regulation of gene expression and altering M2 macrophage polarization during the inflammatory response. These mechanisms need to be better explored in the large bowel, and further studies could better clarify their role and the potential of dietary interventions with ω-3 PUFA in the large bowel. The epigenomic mechanism is discussed in view of the potential of ω-3 PUFA to enhance the efficacy of other agents used in the therapy of colorectal cancer.

Docosahexaenoic acid attenuates adipose tissue angiogenesis and insulin resistance in high fat diet-fed middle-aged mice via a sirt1-dependent mechanism

SCOPE

Docosahexaenoic acid (DHA; C22: 6, n-3), one of PUFAs, exerts beneficial effects on inflammatory diseases, obesity and diabetes. Angiogenesis in adipose tissue has a major role in the development of obesity and its related metabolic complications. Inhibition of angiogenesis is an emerging strategy for the novel treatment for obesity. Thus, we examined the effect of DHA on angiogenesis in adipose tissues and investigated the underlying mechanisms.

METHODS AND RESULTS

In high-fat diet (HFD) fed middle-aged mice, DHA inhibited the macrophage-derived inflammation and angiogenesis in adipose tissues, reduced adipocyte size and body fat composition and improved insulin sensitivity. Moreover, DHA reversed the HFD-induced reduction of Sirt1 in adipose tissues. Interestingly, the effects of DHA were attenuated by lentivirus-mediated Sirt1 knockdown with increasing expression of markers of macrophage-derived inflammation and angiogenesis, associated with impaired insulin sensitivity.

CONCLUSION

Overall, our findings demonstrated that DHA reduced angiogenesis of adipose tissues and attenuated insulin resistance in HFD-induced obese mice via the activation of Sirt1.

Real Time Monitoring of Inhibition of Adipogenesis and Angiogenesis by (-)-Epigallocatechin-3-Gallate in 3T3-L1 Adipocytes and Human Umbilical Vein Endothelial Cells

Little is known about the effect of (−)-epigallocatechin-3-gallate (EGCG) on angiogenesis in adipocytes. We aimed to test the effect of EGCG on the expression of vascular endothelial growth factor (VEGF) in adipocytes. The levels of VEGF secretion, the expression of VEGF message ribonucleic acid (mRNA) and VEGF protein in 3T3-L1 cells were measured by enzyme linked immunosorbent assay (ELISA), real time polymerase chain reaction (PCR), and immunofluorescence staining, respectively. The xCELLigence real time cell analysis system was used to study the growth and differentiation of 3T3-L1 preadipocytes. A coculture system was used to test the effects of 3T3-L1 cells on proliferation of human umbilical vein endothelial cells (HUVECs). The conditioned media derived from 3T3-L1 cells treated with or without EGCG was used to culture the HUVECs for a tube formation assay. Peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer binding protein α (C/EBPα), two transcription factors related to both adipogenesis and angiogenesis, were examined to explore the potential mechanism. We found that all the three measurements of VEGF expression in adipocytes (mRNA, protein and secretion in media) were reduced after EGCG treatment. The growth of HUVECs co-cultured with 3T3-L1 cells was significantly increased and the conditioned media from EGCG treated 3T3-L1 adipocytes inhibited tube formation in HUVECs. Both PPARγ and C/EBPα expression in adipocytes were decreased with EGCG treatment. In conclusion, findings from this study suggest that EGCG may inhibit angiogenesis by regulating VEGF expression and secretion in adipocytes.

Fish Oil-Derived Long-Chain n-3 Polyunsaturated Fatty Acids Reduce Expression of M1-Associated Macrophage Markers in an ex vivo Adipose Tissue Culture Model, in Part through Adiponectin

Adipose tissue (AT) macrophages (ATM) play a key role in obesity-associated pathologies, and their phenotype can be influenced by the local tissue microenvironment. Interestingly, long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) and the LC n-3 PUFA-upregulated adipokine, adiponectin (Ad), may mitigate excessive ATM inflammatory M1-polarization responses. However, to what extent LC n-3 PUFA and Ad work in concert to affect macrophage phenotype has not been examined. Thus, we used an established ex vivo AT organ culture model using visceral AT from mice fed a control (CON; 10% w/w safflower oil) n-6 PUFA-rich diet or an isocaloric fish oil (FO; 3% w/w menhaden oil + 7% w/w safflower oil)-derived LC n-3 PUFA-rich diet to generate AT conditioned media (ACM). We then evaluated if CON or FO ACM affected macrophage polarization markers in a model designed to mimic acute [18 h ACM plus lipopolysaccharide (LPS) for the last 6 h] or chronic (macrophages treated with LPS-challenged CON or FO ACM for 24 h) inflammation ± Ad-neutralizing antibody and the LPS-neutralizing agent, polymyxin B. In the acute inflammation model, macrophages treated with FO ACM had decreased lipid uptake and mRNA expression of M1 markers (Nos2, Nfκb, Il6, Il18, Ccl2, and Ccl5) compared with CON ACM (p ≤ 0.05); however, these effects were largely attenuated when Ad was neutralized (p > 0.05). Furthermore, in the chronic inflammation model, macrophages treated with FO ACM had decreased mRNA expression of M1 markers (Nos2, Tnfα, Ccl2, and Il1β) and IL-6 and CCL2 secretion (p ≤ 0.05); however, some of these effects were lost when Ad was neutralized, and were further exacerbated when both Ad and LPS were neutralized. Taken together, this work shows that LC n-3 PUFA and Ad work in concert to suppress certain M1 macrophage responses. Thus, future strategies to modulate the ATM phenotype should consider the role of both LC n-3 PUFA and Ad in mitigating obese AT inflammation.

A decade of progress in adipose tissue macrophage biology

One decade has passed since seminal publications described macrophage infiltration into adipose tissue (AT) as a key contributor to inflammation and obesity-related insulin resistance. Currently, a PubMed search for 'adipose tissue inflammation' reveals over 3500 entries since these original reports. We now know that resident macrophages in lean AT are alternatively activated, M2-like, and play a role in AT homeostasis. In contrast, the macrophages in obese AT are dramatically increased in number and are predominantly classically activated, M1-like, and promote inflammation and insulin resistance. Mediators of AT macrophage (ATM) phenotype include adipokines and fatty acids secreted from adipocytes as well as cytokines secreted from other immune cells in AT. There are several mechanisms that could explain the large increase in ATMs in obesity. These include recruitment-dependent mechanisms such as adipocyte death, chemokine release, and lipolysis of fatty acids. Newer evidence also points to recruitment-independent mechanisms such as impaired apoptosis, increased proliferation, and decreased egress. Although less is known about the homeostatic function of M2-like resident ATMs, recent evidence suggests roles in AT expansion, thermoregulation, antigen presentation, and iron homeostasis. The field of immunometabolism has come a long way in the past decade, and many exciting new discoveries are bound to be made in the coming years that will expand our understanding of how AT stands at the junction of immune and metabolic co-regulation.

The therapeutic effects of docosahexaenoic acid on oestrogen/androgen-induced benign prostatic hyperplasia in rats

Benign prostatic hyperplasia (BPH) is one of the major disorders of the urinary system in elderly men. Docosahexaenoic acid (DHA) is the main component of n-3 polyunsaturated fatty acids (n-3 PUFAs) and has nerve protective, anti-inflammatory and tumour-growth inhibitory effects. Here, the therapeutic potential of DHA in treating BPH was investigated. Seal oil effectively prevented the development of prostatic hyperplasia induced by oestradiol/testosterone in a rat model by suppressing the increase of the prostatic index (PI), reducing the thickness of the peri-glandular smooth muscle layer, inhibiting the proliferation of both prostate epithelial and stromal cells, and downregulating the expression of androgen receptor (AR) and oestrogen receptor α (ERα). An in vitro study showed that DHA inhibited the growth of the human prostate stromal cell line WPMY-1 and the epithelial cell line RWPE-1 in a dose- and time-dependent manner. In both cell lines, the DHA arrested the cell cycle in the G2/M phase. In addition, DHA also reduced the expression of ERα and AR in the WPMY-1 and RWPE-1 cells. These results indicate that DHA inhibits the multiplication of prostate stromal and epithelial cells through a mechanism that may involve cell cycle arrest and the downregulation of ERα and AR expression.

Fish-oil-derived n-3 PUFAs reduce inflammatory and chemotactic adipokine-mediated cross-talk between co-cultured murine splenic CD8+ T cells and adipocytes

BACKGROUND

Obese adipose tissue (AT) inflammation is characterized by dysregulated adipokine production and immune cell accumulation. Cluster of differentiation (CD) 8+ T cell AT infiltration represents a critical step that precedes macrophage infiltration. n-3 (ω-3) Polyunsaturated fatty acids (PUFAs) exert anti-inflammatory effects in obese AT, thereby disrupting AT inflammatory paracrine signaling.

OBJECTIVE

We assessed the effect of n-3 PUFAs on paracrine interactions between adipocytes and primary CD8+ T cells co-cultured at the cellular ratio observed in obese AT.

METHODS

C57BL/6 mice were fed either a 3% menhaden fish-oil + 7% safflower oil (FO) diet (wt:wt) or an isocaloric 10% safflower oil (wt:wt) control (CON) for 3 wk, and splenic CD8+ T cells were isolated by positive selection (via magnetic microbeads) and co-cultured with 3T3-L1 adipocytes. Co-cultures were unstimulated (cells alone), T cell receptor stimulated, or lipopolysaccharide (LPS) stimulated for 24 h.

RESULTS

In LPS-stimulated co-cultures, FO reduced secreted protein concentrations of interleukin (IL)-6 (-42.6%), tumor necrosis factor α (-67%), macrophage inflammatory protein (MIP) 1α (-52%), MIP-1β (-62%), monocyte chemotactic protein (MCP) 1 (-23%), and MCP-3 (-19%) vs. CON, which coincided with a 74% reduction in macrophage chemotaxis toward secreted chemotaxins in LPS-stimulated FO-enriched co-culture-conditioned media. FO increased mRNA expression of the inflammatory signaling negative regulators monocyte chemoattractant 1-induced protein (Mcpip; +9.3-fold) and suppressor of cytokine signaling 3 (Socs3; +1.7-fold), whereas FO reduced activation of inflammatory transcription factors nuclear transcription factor κB (NF-κB) p65 and signal transducer and activator of transcription 3 (STAT3) by 27% and 33%, respectively. Finally, mRNA expression of the inflammasome components Caspase1 (-36.4%), Nod-like receptor family pyrin domain containing 3 (Nlrp3; -99%), and Il1b (-68.8%) were decreased by FO compared with CON (P ≤ 0.05).

CONCLUSION

FO exerted an anti-inflammatory and antichemotactic effect on the cross-talk between CD8+ T cells and adipocytes and has implications in mitigating macrophage-centered AT-driven components of the obese phenotype.

Interaction of differentiated human adipocytes with macrophages leads to trogocytosis and selective IL-6 secretion

Obesity leads to adipose tissue inflammation that is characterized by increased release of proinflammatory molecules and the recruitment of activated immune cells. Although macrophages are present in the highest number among the immune cells in obese adipose tissue, not much is known about their direct interaction with adipocytes. We have introduced an ex vivo experimental system to characterize the cellular interactions and the profile of secreted cytokines in cocultures of macrophages and human adipocytes differentiated from either mesenchymal stem cells or a preadipocyte cell line. As observed by time-lapse microscopy, flow, and laser-scanning cytometry, macrophages phagocytosed bites of adipocytes (trogocytosis), which led to their de novo, phagocytosis and NF-κB-dependent synthesis, then release of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1. IL-6 secretion was not accompanied by secretion of other proinflammatory cytokines, such as tumor necrosis factor (TNF)-α and IL-8, except MCP-1. LPS-induced release of TNF-α, IL-8 and MCP-1 was decreased in the presence of the differentiated adipocytes but the IL-6 level did not subside suggesting that phagocytosis-dependent IL-6 secretion may have significant regulatory function in the inflamed adipose tissue.

n-3 polyunsaturated fatty acids and mechanisms to mitigate inflammatory paracrine signaling in obesity-associated breast cancer

Globally, the prevalence of obesity is increasing which subsequently increases the risk of the development of obesity-related chronic diseases. Low-grade chronic inflammation and dysregulated adipose tissue inflammatory mediator/adipokine secretion are well-established in obesity, and these factors increase the risk of developing inflammation-associated cancer. Breast cancer is of particular interest given that increased inflammation within the subcutaneous mammary adipose tissue depot can alter the local tissue inflammatory microenvironment such that it resembles that of obese visceral adipose tissue. Therefore, in obese women with breast cancer, increased inflammatory mediators both locally and systemically can perpetuate inflammation-associated pro-carcinogenic signaling pathways, thereby increasing disease severity. Herein, we discuss some of these inflammation-associated pro-carcinogenic mechanisms of the combined obese breast cancer phenotype and offer evidence that dietary long chain n-3 polyunsaturated fatty acids (PUFA) may have utility in mitigating the severity of obesity-associated inflammation and breast cancer.