n3 and n6 polyunsaturated fatty acids differentially modulate prostaglandin E secretion but not markers of lipogenesis in adipocytes

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.

Fatty acid concentration of plasma, muscle, adipose and liver from beef heifers fed an encapsulated n-3 polyunsaturated fatty acid supplement

Increasing the content of polyunsaturated fat in the human diet is a priority for reducing cardiovascular disease and cancer risks. Beef has the potential to contribute to the polyunsaturated fat content in the human diet; however, ruminants cannot synthesise many long-chain fatty acids de novo; they require dietary supplementation. The objectives of the current study were to evaluate (i) the effect of a partially rumen protected n-3 long-chain polyunsaturated fatty acid (LC-PUFA) dietary supplement on the fatty acid composition of muscle (Longissimus dorsi), adipose and liver tissues of beef heifers and (ii) the usefulness of blood plasma as a predictor of tissue concentrations of specific fatty acids. Charolais crossbred heifers (n = 20) were assigned to one of two isolipid dietary treatments namely palmitic acid (control) or an n-3 LC-PUFA supplement for a 91-day period. Blood plasma and adipose tissue samples were taken to determine the temporal effect of these diets on fatty acid composition (days 0, 10, 35 and 91), while liver and muscle samples were taken following slaughter. Dietary lipid source did not influence animal growth rate or body condition score. At day 91, the percentage differences between control and n-3 LC-PUFA heifers in concentrations of eicosapentaenoic acid were +61, +176 and +133 % in liver, muscle and adipose, respectively. For docosahexaenoic acid, at the same time point, the percentage differences were +57, +73 and +138 % for liver, muscle and adipose, respectively. Medium-to-strong positive correlation coefficients were evident for liver and plasma fatty acids, in particular, there were positive relationships with concentrations of total saturated fatty acid (SFA), total n-6 PUFA and total n-3 PUFA. This trend also extended to both the ratio of PUFA to SFA (slope (β₁) = 0.56 ± 0.167, intercept (β₀) = 0.56, R² = 0.61, P < 0.05) and the ratio of n-6 to n-3 PUFA (β₁ = 0.15 ± 0.054, β₀ = 0.24, R² = 0.52, P < 0.05). A strong correlation was also detected in the ratio of n-6 to n-3 in plasma and muscle tissue of heifers fed the n-3 LC-PUFA diet (β₁ = 0.53 ± 0.089, β₀ = -0.31, R² = 0.83, P < 0.001). The results of this study show that the n-3 LC-PUFA can be readily increased through targeted supplementation and that plasma concentrations of n-3 LC-PUFA are useful predictors of their concentrations in a number of economically important tissues.

ω-3 and ω-6 Polyunsaturated Fatty Acids, Obesity and Cancer

Recently, nutraceutical bioactive compounds in foods have been discovered for their potential health benefits regarding the prevention of chronic disorders, such as cancer, and inflammatory, cardiovascular, and metabolic diseases. Dietary omega-3 polyunsaturated fatty acids (ω-3PUFAs), including alpha-linolenic acid, docosapentaenoic acid, and eicosapentaenoic acid, are mostly attractive. They are available for the customers worldwide from commonly used foods and/or as components of commercial food supplements. The anti-inflammatory and hypotriglyceridemic effects of these fatty acids are well known, whereas pro-inflammatory properties have been recognized in their dietary counterparts, the ω-6PUFAs. Both ω-3 and ω-6PUFAs contribute to the production of lipid mediators such as endocannabinoids that are notably involved in control of food intake, energy sensing, and food-related disorders. In this review, we present ω-3 and ω-6PUFAs and their derivatives, endocannabinoids; discuss the anti-obesity effects of ω-3PUFAs; their roles in inflammation and colorectal cancer development; and how their action can be co-preventative and co-therapeutic.

Combined Effects of Eicosapentaenoic Acid and Adipocyte Renin-Angiotensin System Inhibition on Breast Cancer Cell Inflammation and Migration

Obesity is a major risk factor for breast cancer (BC). Obesity-related metabolic alterations such as inflammation and overactivation of the adipose renin–angiotensin system (RAS) may contribute to the progression of BC. Clinically used antihypertensive drugs such as angiotensin-converting enzyme inhibitors (ACE-I) and dietary bioactive components such as eicosapentaenoic acid (EPA) are known for their anti-inflammatory and adipose RAS blocking properties. However, whether EPA enhances the protective effects of ACE-I in lessening adipocyte inflammation on BC cells has not been studied. We hypothesized that combined EPA and ACE-I would attenuate BC cell inflammation and migration possibly via adipose RAS inhibition. To test our hypothesis, we examined the (i) direct effects of an ACE-I (captopril (CAP)) or EPA, individually and combined, on MCF-7 and MDA-MB-231 human BC cells, and the (ii) effects of conditioned medium (CM) from human adipocytes pretreated with the abovementioned agents on BC cells. We demonstrated that CM from adipocytes pretreated with EPA with or without captopril (but not direct treatments of BC cells) significantly reduced proinflammatory cytokines expression in both BC cell lines. Additionally, cell migration was reduced in MDA-MB-231 cells in response to both direct and CM-mediated CAP and/or EPA treatments. In summary, our study provides a significant insight into added benefits of combining anti-inflammatory EPA and antihypertensive ACE-I to attenuate the effects of adipocytes on breast cancer cell migration and inflammation.

Eicosapentaenoic Acid Reduces Adiposity, Glucose Intolerance and Increases Oxygen Consumption Independently of Uncoupling Protein 1

SCOPE

Brown adipose tissue (BAT) dissipates energy through uncoupling protein 1 (UCP1) and has been proposed as an anti-obesity target. It was reported previously that a high-fat (HF) diet enriched in eicosapentaenoic acid (EPA) significantly increased UCP1 and other thermogenic markers in BAT. It is hypothesized that these effects are mediated through UCP1-dependent regulation.

METHODS AND RESULTS

Wild-type (WT) and UCP1 knockout (KO) B6 male mice were housed at thermoneutrality and fed a HF diet, without or with eicosapentaenoic acid (EPA)-enriched fish oil. HF-fed KO mice were heavier and had higher BAT lipid content than other groups. Protective effects of EPA in WT, previously observed at 22 °C (reduced adiposity, improved glucose tolerance, and increased UCP1), disappeared at thermoneutrality. Mitochondrial proteins, cytochrome c oxidase subunit 1 (COX I), COX I, II, and IV were reduced in the KO mice compared to WT. Unexpectedly, EPA attenuated weight and fat mass gain and improved glucose tolerance in the KO mice. Finally, EPA increased BAT peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α) protein and gene expression, and whole-body oxygen consumption in KO mice, consistent with increased mitochondria DNA (mtDNA)/nuclear DNA (nucDNA) ratio.

CONCLUSIONS

EPA rescued the weight gain and glucose intolerance in UCP1 KO mice at thermoneutrality, independent of UCP1; these effects may be mediated in part via increased oxygen consumption and BAT PGC1α.

Transcriptomic and microRNA analyses of gene networks regulated by eicosapentaenoic acid in brown adipose tissue of diet-induced obese mice

Brown adipose tissue (BAT) dissipates chemical energy as heat via thermogenesis and protects against obesity by increasing energy expenditure. However, regulation of BAT by dietary factors remains largely unexplored at the mechanistic level. We investigated the effect of eicosapentaenoic acid (EPA) on BAT metabolism. Male C57BL/6J (B6) mice were fed either a high-fat diet (HF, 45% kcal fat) or HF diet supplemented with EPA (HF-EPA, 6.75% kcal EPA) for 11 weeks. RNA sequencing (RNA-Seq) and microRNA (miRNA) profiling were performed on RNA from BAT using Illumina HiSeq and Illumina Genome Analyzer NextSeq, respectively. We conducted pathway analyses using ingenuity pathway analysis software (IPA®) and validated some genes and miRNAs using qPCR. We identified 479 genes that were differentially expressed (2-fold change, n = 3, P ≤ 0.05) in BAT from HF compared to HF-EPA. Genes negatively correlated with thermogenesis such as hypoxia inducible factor 1 alpha subunit inhibitor (Hif1an), were downregulated by EPA. Pathways related to thermogenesis such as peroxisome proliferator-activated receptor (PPAR) were upregulated by EPA while pathways associated with obesity and inflammation such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) were downregulated by EPA. MiRNA profiling identified nine and six miRNAs that were upregulated and downregulated by EPA, respectively (log2 fold change > 1.25, n = 3, P ≤ 0.05). Key regulatory miRNAs which were involved in thermogenesis, such as miR-455-3p and miR-129-5p were validated using qPCR. In conclusion, the depth of transcriptomic and miRNA profiling revealed novel mRNA-miRNA interaction networks in BAT which are involved in thermogenesis, and regulated by EPA.

Omega-3 polyunsaturated fatty acids reduce vascular tone and inflammation in human saphenous vein

Dietary intake of omega-3 polyunsaturated fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been reported to have beneficial cardiovascular effects. However, little is known about the effect of EPA and DHA on human vascular tone. Therefore, the aim of this study is to evaluate the effect of EPA and DHA on vascular tone of the human saphenous vein (SV) obtained from patients undergoing coronary bypass operation under normal and inflammatory conditions. Moreover, we aimed to investigate the effect of EPA and DHA on the release of inflammatory mediators from SV. Pretreatment of SV with EPA and DHA (100μM, 18h) decreased the contractile response of SV to norepinephrine (NE) under normal and inflammatory conditions. Moreover, EPA and DHA pretreatment diminished increased Monocyte Chemoattractant Protein-1 (MCP-1) and Tumor Necrosis Factor-alpha (TNF-α) release from SV under inflammatory conditions. In conclusion, our results suggest that EPA and DHA pretreatment may be beneficial to counteract graft vasospasm and vascular inflammation in SV which are important factors in graft failure development. Therefore, dietary intake of EPA and DHA may have potential clinical applications in improving coronary bypass graft patency.

Eicosapentaenoic acid regulates brown adipose tissue metabolism in high-fat-fed mice and in clonal brown adipocytes

Brown adipose tissue (BAT) plays a key role in energy expenditure through its specialized thermogenic function. Therefore, BAT activation may help prevent and/or treat obesity. Interestingly, subcutaneous white adipose tissue (WAT) also has the ability to differentiate into brown-like adipocytes and may potentially contribute to increased thermogenesis. We have previously reported that eicosapentaenoic acid (EPA) reduces high-fat (HF)-diet-induced obesity and insulin resistance in mice. Whether BAT mediates some of these beneficial effects of EPA has not been determined. We hypothesized that EPA activates BAT thermogenic program, contributing to its antiobesity effects. BAT and WAT were harvested from B6 male mice fed HF diets supplemented with or without EPA. HIB 1B clonal brown adipocytes treated with or without EPA were also used. Gene and protein expressions were measured in adipose tissues and H1B 1B cells by quantitative polymerase chain reaction and immunoblotting, respectively. Our results show that BAT from EPA-supplemented mice expressed significantly higher levels of thermogenic genes such as PRDM16 and PGC1α and higher levels of uncoupling protein 1 compared to HF-fed mice. By contrast, both WATs (subcutaneous and visceral) had undetectable levels of these markers with no up regulation by EPA. HIB 1B cells treated with EPA showed significantly higher mRNA expression of PGC1α and SIRT2. EPA treatment significantly increased maximum oxidative and peak glycolytic metabolism in H1B 1B cells. Our results demonstrate a novel and promising role for EPA in preventing obesity via activation of BAT, adding to its known beneficial anti-inflammatory effects.

Difference in fatty acid composition and related nutritional indices of meat between two lines of slow-growing chickens slaughtered at different ages

Abstract. The fatty acid profile and the related indices of the nutritional quality of breast and thigh muscles were studied in two lines of chickens – La Belle (LB) and White Plymouth Rock (WPR) – slaughtered at the age of 9 and 18 weeks. The fatty acid profile was more affected by the age than the line of the birds; however, the influence of both differed between the breast and thigh. The content of total saturated fatty acids (SFAs) increased in the thigh (P <  0.01), while that of the monounsaturated fatty acids (MUFAs) decreased with age in both muscles (P <  0.001). This corresponded to the significant decrease in C18:1 in the older chickens and the lower desaturase activity (P <  0.001). The contents of C20:4n-6, C22:5n-3 and C22:6n-3 and the total amount of polyunsaturated fatty acids (PUFAs) in breast were higher (P < 0.001) at the age of 18 weeks. A similar pattern in the individual and total PUFA was observed in the thighs. The effect of line was more visible in the breast, leading to a lower C14:0 content and C20:5n-3 and a higher C18:0 content in the WPR chickens (P <  0.001), corresponding to the higher elongase and thioesterase indices in these birds. Both atherogenic (AI) and thrombogenic (TI) indices were lowered, while the ratio of hypocholesterolemic ∕ hypercholesterolemic fatty acids (h ∕ H) and polyunsaturated ∕ saturated fatty acids (P ∕ S) increased in the breast of the birds at 18 weeks. In breast and thigh meat, the ratio of n-6 ∕ n-3 PUFA decreased in the older chickens (P <  0.001).

Hydroxytyrosol Inhibits Cannabinoid CB1 Receptor Gene Expression in 3T3-L1 Preadipocyte Cell Line

The 3T3-L1 preadipocyte cell line is a well characterized cell model for studying the adipocyte status and the molecular mechanisms involved in differentiation of these cells. 3T3-L1 preadipocytes have the ability to synthesize and degrade endocannabinoid anandamide (AEA) and their differentiation into adipocytes increases the expression of cannabinoid (CB1) and PPAR-γ receptors. Clinically, the blocking stimulation of the endocannabinoid pathway has been one of the first approaches proposed to counteract the obesity and obesity-associated diseases (such as diabetes, metabolic syndrome and cancer). In this connection, here we studied in cultured 3T3-L1 pre-adipocytes the effects of n-3-PUFA, α-Linolenic acid (OM-3), n-6-PUFA, Linoleic acid (OM-6), and hydroxytyrosol (HT) on the expression of CB1 receptor gene and the adipogenesis-related genes PPAR-γ, Fatty Acid Synthase (FAS) and Lipoprotein Lipase (LPL). HT was able to inhibit 3T3-L1 cell differentiation by down-regulating cell proliferation and CB1 receptor gene expression. HT exhibited anti-adipogenic effects, whereas OM-3 and OM-6 exerted an inhibitory action on cell proliferation associated with an induction of the preadipocytes differentiation and CB1 receptor gene expression. Moreover, the expression of FAS and LPL genes resulted increased after treatment with both HT and OM-3 and OM-6. The present study points out that the intake of molecules such as HT, contained in extra virgin olive oil, may be considered also in view of antiobesity and antineoplastic properties by acting directly on the adipose tissue and modulating CB1 receptor gene transcription.

Can metabolically healthy obesity be explained by diet, genetics, and inflammation?

A substantial proportion of obese individuals do not present cardiometabolic complications such as diabetes, hypertension, or dyslipidemia. Some, but not all, prospective studies observe similar risk of cardiovascular events and all-cause mortality among individuals with this so-called "metabolically healthy obese" (MHO) phenotype, compared to the metabolically healthy normal weight or metabolically healthy non-obese phenotypes. Compared to the metabolically unhealthy obese (MUO) phenotype, MHO is often characterized by a more favorable inflammatory profile, less visceral fat, less infiltration of macrophages into adipose tissue, and smaller adipocyte cell size. Tipping the inflammation balance in adipose tissue might be particularly important for metabolic health in the obese. While the potential role of genetic predisposition or lifestyle factors such as diet in the MHO phenotype is yet to be clarified, it is well known that diet affects inflammation profile and contributes to the functionality of adipose tissue. This review will discuss genetic predisposition and the molecular mechanisms underlying the potential effect of food on the development of the metabolic phenotype characteristic of obesity.

N-3 Polyunsaturated Fatty Acids and Inflammation in Obesity: Local Effect and Systemic Benefit

Overwhelming consensus emerges among countless evidences that obesity is characterized by a chronic low-grade inflammation in the adipose tissue (AT), which subsequently develops into a systemic inflammatory state contributing to obesity-associated diseases. N-3 Polyunsaturated fatty acids (n-3 PUFA), known as important modulators participating in inflammatory process, turn out to be an effective mitigating strategy dealing with local and systemic inflammation observed in obesity. Some of the effects of n-3 PUFA are brought about by regulation of gene expression through interacting with nuclear receptors and transcription factors; other effects are elicited by modulation of the amount and type of mediator derived from PUFAs. The metabolic effects of n-3 PUFA mainly result from their interactions with several organ systems, not limited to AT. Notably, the attenuation of inflammation in hard-hit AT, in turn, contributes to reducing circulating concentrations of proinflammatory cytokines and detrimental metabolic derivatives, which is beneficial for the function of other involved organs. The present review highlights a bridging mechanism between n-3 PUFA-mediated inflammation relief in AT and systemic benefits.

Eicosapentaenoic acid upregulates VEGF-A through both GPR120 and PPARγ mediated pathways in 3T3-L1 adipocytes

Vascular endothelial growth factor-A (VEGF-A) released from adipocytes promotes angiogenesis; and thereby ameliorates the local hypoxia-induced adipose inflammation and insulin resistance. Here, we newly found that eicosapentaenoic acid (EPA) upregulated both mRNA expression and release of VEGF-A in mature 3T3-L1 adipocytes. Silencing mRNA of G-protein coupled receptor 120 (GPR120) and specific inhibition of peroxisome proliferator-activated receptor γ (PPARγ) by GW9662 respectively attenuated the EPA-induced augmentation of VEGF-A release by adipocytes. Furthermore, transfection of GPR120 gene alone and PPARγ gene alone to HEK293 cells respectively increased the promoter activity of VEGF-A as assessed by luciferase reporter assay, which was further augmented when both genes were co-transfected. Promoter deletion analysis and chromatin immunoprecipitation assay revealed that co-transfection of GPR120 enhanced EPA-induced PPARγ binding to PPAR-response element in VEGF-A promoter region. Thus, by the synchronized activation of a membrane receptor GRP120 and a nuclear receptor PPARγ, EPA enhances VEGF-A production in adipocytes.

Arachidonic acid has a dominant effect to regulate lipogenic genes in 3T3-L1 adipocytes compared to omega-3 fatty acids

BACKGROUND

The effects of long-chain n-3 and n-6 polyunsaturated fatty acids (PUFA) on the regulation of adipocytes metabolism are well known. These fatty acids are generally consumed together in our diets; however, the metabolic regulation of adipocytes in the presence of these fatty acids when given together is not known.

OBJECTIVE

To investigate the effects of n-3 PUFA and arachidonic acid (AA), an n-6 PUFA, on the regulation of adipogenic and lipogenic genes in mature 3T3-L1 adipocytes.

METHODS

3T3-L1 adipocytes were incubated in the presence or absence of 100 µM of eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA; docosapentaenoic acid, DPA and AA, either alone or AA+n-3 PUFA; control cells received bovine serum albumin alone. The mRNA expression of adipogenic and lipogenic genes was measured. The fatty acid composition of adipocytes was analyzed using gas chromatography.

RESULTS

Individual n-3 PUFA or AA had no effect on the mRNA expression of peroxisome-proliferator-activated receptor-γ; however, AA+EPA and AA+DPA significantly increased (P<0.05) the expression compared to control cells (38 and 42%, respectively). AA and AA+EPA increased the mRNA expression of acetyl-CoA carboxylase 1 (P<0.05). AA treatment decreased the mRNA expression of stearoyl-CoA desaturase (SCD1) (P<0.01), while n-3 PUFA, except EPA, had no effect compared to control cells. AA+DHA and AA+DPA inhibited SCD1 gene expression (P<0.05) suggesting a dominant effect of AA. Fatty acids analysis of adipocytes revealed a higher accretion of AA compared to n-3 PUFA.

CONCLUSIONS

Our findings reveal that AA has a dominant effect on the regulation of lipogenic genes in adipocytes.

Nutraceuticals and regulation of adipocyte life: premises or promises

Obesity is the actual worldwide health threat, that is associated with an increased number of metabolic disorders and diseases. Following the traditional hypothesis stating that in obesity hypertrophic adipocytes trigger the adipose tissue hyperplasia, strategies to treat obesity have increased fat researches of the molecular processes that achieve adipocyte enlargement and formation that finally increase body fat mass. Moreover, a new cell type was recently identified, the "brite" adipocyte that presents a unique gene expression profile of compared to both brown and white adipocytes. Therapies against obesity, targeting these cells and their pathways, would include the induction of lipolysis and apoptosis or the inhibition of differentiation and adipogenesis. However, it should be noted that both the increase of adipocyte size and number take place in association with positive energy balance. According to the adipose tissue expansion hypothesis, adipogenesis could be related with improved metabolic health of obese people, taking back the adipose mass to a traditionally site of lipid storage. Furthermore, new perspectives in fat biology suggest that the conversion of white-to-brown adipocytes and their metabolism could be exploited for the development of therapeutic approaches against obesity-associated diseases and for the regulation of energy balance. Drugs currently available to treat obesity generally have unpleasant side effects. A novel promising approach is the usage of dietary supplements and plant products that could interfere on the life cycle of adipocyte. Here, various dietary bioactive compounds that target different stages of adipocyte life cycle and molecular and metabolic pathways are reviewed.

Potential treatment of human nonalcoholic fatty liver disease with long-chain omega-3 polyunsaturated fatty acids

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder in the Western world. Its prevalence has increased with the growing obesity epidemic, yet no definitive treatment has been developed, and optimal management remains a clinical challenge. Long-chain omega-3 polyunsaturated fatty acids (PUFAs) have recently been proposed as a potential treatment for liver inflammation associated with fat accumulation. PubMed literature and the ClinicalTrials.gov database were reviewed for the effects of omega-3 PUFA treatment on NAFLD, from mechanisms to the results of preclinical studies, human studies, and unreported ongoing clinical trials, using terms such as NAFLD, nonalcoholic steatohepatitis, omega-3 fatty acids, and fish oil. Articles published over the last 3-4 years were emphasized, and relevancy was ensured by scanning their abstracts. Preliminary studies have confirmed an ameliorative effect, yet the translation of promising early data into therapeutic interventions will have to await the results of larger, properly conducted, ongoing clinical trials.

Modulation of adipose tissue inflammation by bioactive food compounds

Adipose tissue has an important endocrine function in the regulation of whole-body metabolism. Obesity leads to a chronic low-grade inflammation of the adipose tissue, which disrupts this endocrine function and results in metabolic derangements, such as type-2 diabetes. Dietary bioactive compounds, such as polyphenols and certain fatty acids, are known to suppress both systemic and adipose tissue inflammation and have the potential to improve these obesity-associated metabolic disorders. Mechanistically, polyphenolic compounds including non-flavonoids, such as curcumin and resveratrol, and flavonoids, such as catechins (tea-polyphenols), quercetin and isoflavones, suppress nuclear factor-κB (NF-κB) and mitogen-activated protein (MAP) kinases (MAPK) pathways while activating the 5' adenosine monophosphate-activated protein kinase (AMPK) pathway in adipose tissue. Dietary polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), conjugated linoleic acid (CLA) and monounsaturated fatty acids (MUFA), such as oleic acid, also impart anti-inflammatory effects through several mechanisms. These include activation of AMPK and peroxisome proliferator-activated receptor gamma (PPAR-γ), as well as suppression of toll-like receptors (TLRs) and NF-κB pathway. This review discusses the major molecular mechanisms of dietary polyphenols and fatty acids, alone or in combination, which are responsible for adipose tissue-associated anti-inflammatory effects.

Serum phospholipid fatty acids, genetic variation in myeloperoxidase, and prostate cancer risk in heavy smokers: a gene-nutrient interaction in the carotene and retinol efficacy trial

The authors investigated associations of serum phospholipid n-3 and n-6 polyunsaturated fatty acids (PUFAs) and trans-fatty acids with prostate cancer risk, and whether myeloperoxidase G-463A (rs2333227) modified the associations in the Carotene and Retinol Efficacy Trial (CARET) (Seattle, Washington; Irvine, California; New Haven, Connecticut; San Francisco, California; Baltimore, Maryland; and Portland, Oregon, 1985-2003). Prerandomization sera were assayed for fatty acids among 641 men with incident prostate cancer (368 nonaggressive and 273 aggressive (stage III/IV or Gleason score ≥7)) and 1,398 controls. Overall, dihomo-γ-linolenic (quartiles 4 vs. 1: odds ratio (OR) = 0.66, 95% confidence interval (CI): 0.49, 0.95; P(trend) = 0.024) and docosatetraenoic (OR = 0.69, 95% CI: 0.46, 1.02; P(trend) = 0.011) acids were inversely associated with nonaggressive and aggressive prostate cancer risks, respectively. Among men with MPO GG, the genotype upregulating oxidative stress, quartiles 4 versus 1 eicosapentaenoic plus docosahexaenoic acids were suggestively associated with an increased risk of aggressive prostate cancer (OR = 1.66, 95% CI: 0.95, 2.92; P(trend) = 0.07). However, the association was the inverse among men with MPO GA/AA genotypes (P(interaction) = 0.011). Interactions were also observed for docosapentaenoic acid, total n-3 PUFAs, and arachidonic acid. MPO GA/AA vs. GG was associated with a 2-fold increase in aggressive prostate cancer risk among men with low (quartile 1) n-3 PUFAs. This study adds important evidence linking oxidative stress with prostate carcinogenesis.

Heterologous expression of C. elegans fat-1 decreases the n-6/n-3 fatty acid ratio and inhibits adipogenesis in 3T3-L1 cells

In general, a diet enriched in polyunsaturated fatty acids (PUFAs) inhibits the development of obesity and decreases adipose tissue. The specific impacts of n-3 and n-6 PUFAs on adipogenesis, however, have not been definitively determined. Traditional in vivo and in vitro supplementation studies have yielded inconsistent or even contradictory results, which likely reflect insufficiently controlled experimental systems. Caenorhabditiselegans fat-1 gene encodes an n-3 fatty acid desaturase, and its heterologous expression represents an effective method both for altering the n-6/n-3 PUFA ratio and for evaluating the biological effects of n-3 and n-6 PUFAs. We sought to determine whether a reduced n-6/n-3 ratio could influence adipogenesis in 3T3-L1 cells. Lentivirus-mediated introduction of the fat-1 gene into 3T3-L1 preadipocytes significantly reduced the n-6/n-3 ratio and inhibited preadipocyte proliferation and differentiation. In mature adipocytes, fat-1 expression reduced lipid deposition, as measured by Oil Red O staining, and induced apoptosis. Our results indicate that a reduced n-6/n-3 ratio inhibits adipogenesis through several mechanisms and that n-3 PUFAs more effectively inhibit adipogenesis (but not lipogenesis) than do n-6 PUFAs.

Eicosapentaenoic acid (EPA) efficacy for colorectal aberrant crypt foci (ACF): a double-blind randomized controlled trial

BACKGROUND

Colorectal cancer (CRC) is one of the most commonly occurring neoplasms and a leading cause of cancer death worldwide, and new preventive strategies are needed to lower the burden of this disease. Eicosapentaenoic acid (EPA), the omega-3 polyunsaturated fatty acid that is widely used in the treatment of hyperlipidemia and prevention of cardiovascular disease, has recently been suggested to have a suppressive effect on tumorigenesis and cancer cell growth. In CRC chemoprevention trials, in general, the incidence of polyps or of the cancer itself is set as the study endpoint. Although the incidence rate of CRC would be the most reliable endpoint, use of this endpoint would be unsuitable for chemoprevention trials, because of the relatively low occurrence rate of CRC in the general population and the long-term observation period that it would necessitate. Moreover, there is an ethical problem in conducting long-term trials to determine whether a test drug might be effective or harmful. Aberrant crypt foci (ACF), defined as lesions containing crypts that are larger in diameter and stain more darkly with methylene blue than normal crypts, are considered as a reliable surrogate biomarker of CRC. Thus, we devised a prospective randomized controlled trial as a preliminary study prior to a CRC chemoprevention trial to evaluate the chemopreventive effect of EPA against colorectal ACF formation and the safety of this drug, in patients scheduled for polypectomy.

METHODS

This study is a multicenter, double-blind, placebo-controlled, randomized controlled trial to be conducted in patients with both colorectal ACF and colorectal polyps scheduled for polypectomy. Eligible patients shall be recruited for the study and the number of ACF in the rectum counted at the baseline colonoscopy. Then, the participants shall be allocated randomly to either one of two groups, the EPA group and the placebo group. Patients in the EPA group shall receive oral 900-mg EPA capsules thrice daily (total daily dose, 2.7 g per day), and those in the placebo group shall receive oral placebo capsules thrice daily. After one month's treatment with EPA/placebo, colonoscopic examination and polypectomy will be performed to evaluate the formation of ACF, and the cell-proliferative activity and cell-apoptotic activity in normal colorectal mucosa and colorectal polyps.

DISCUSSION

This is the first study proposed to explore the effect of EPA against colorectal ACF formation in humans.This trial has been registered in the University hospital Medical Information Network (UMIN) Clinical Trials Registry as UMIN000008172.

n-3 and n-6 polyunsaturated fatty acids differentially regulate adipose angiotensinogen and other inflammatory adipokines in part via NF-κB-dependent mechanisms

Excessive secretion of proinflammatory adipokines has been linked to metabolic disorders. We have previously documented anti-inflammatory effects of n-3 polyunsaturated fatty acids (n-3 PUFAs) in adipose tissue; however, the mechanisms by which these fatty acids regulate adipokine secretion remain unclear. Here, we determined differential effects of eicosapentaenoic acid (EPA, n-3 PUFA) vs. arachidonic acid (AA, n-6 PUFA) on expression and secretion of angiotensinogen (Agt), interleukin 6 (IL-6) and monocyte chemotactic protein (MCP-1) in 3T3-L1 adipocytes. While both PUFAs increased intracellular Agt protein and mRNA expression, Agt secretion into culture media was increased only by AA treatment, which in turn was prevented by co-treatment with EPA. At various AA/EPA ratios, increasing AA concentrations significantly increased secretion of the above three adipokines, whereas increasing EPA dose-dependently, while lowering AA, decreased their secretion. Moreover, IL-6 and MCP-1 were more significantly reduced by EPA treatment compared to Agt (IL-6>MCP>Agt). Next, we tested whether nuclear factor-κB (NF-κB), a major proinflammatory transcription factor, was involved in regulation of these adipokines by PUFAs. EPA significantly inhibited NF-κB activation compared to control or AA treatments. Moreover, EPA attenuated tumor necrosis factor-α-induced MCP-1 and further reduced its secretion in the presence of an NF-κB inhibitor. Taken together, we reported here novel beneficial effects of EPA in adipocytes. We demonstrated direct anti-inflammatory effects of EPA, which are at least in part due to the inhibitory effects of this n-3 PUFA on the NF-κB pathway in adipocytes. In conclusion, these studies further support beneficial effects of n-3 PUFAs in adipocyte inflammation and metabolic disorders.

Overproduction of angiotensinogen from adipose tissue induces adipose inflammation, glucose intolerance, and insulin resistance

Although obesity is associated with overactivation of the white adipose tissue (WAT) renin-angiotensin system (RAS), a causal link between the latter and systemic insulin resistance is not established. We tested the hypothesis that overexpression of angiotensinogen (Agt) from WAT causes systemic insulin resistance via modulation of adipose inflammation. Glucose tolerance, systemic insulin sensitivity, and WAT inflammatory markers were analyzed in mice overexpressing Agt in the WAT (aP2-Agt mice). Proteomic studies and in vitro studies using 3T3-L1 adipocytes were performed to build a mechanistic framework. Male aP2-Agt mice exhibited glucose intolerance, insulin resistance, and lower insulin-stimulated glucose uptake by the skeletal muscle. The difference in glucose tolerance between genotypes was normalized by high-fat (HF) feeding, and was significantly improved by treatment with angiotensin-converting enzyme (ACE) inhibitor captopril. aP2-Agt mice also had higher monocyte chemotactic protein-1 (MCP-1) and lower interleukin-10 (IL-10) in the WAT, indicating adipose inflammation. Proteomic studies in WAT showed that they also had higher monoglyceride lipase (MGL) and glycerol-3-phosphate dehydrogenase levels. Treatment with angiotensin II (Ang II) increased MCP-1 and resistin secretion from adipocytes, which was prevented by cotreating with inhibitors of the nuclear factor-κB (NF-κB) pathway or nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In conclusion, we show for the first time that adipose RAS overactivation causes glucose intolerance and systemic insulin resistance. The mechanisms appear to be via reduced skeletal muscle glucose uptake, at least in part due to Ang II-induced, NADPH oxidase and NFκB-dependent increases in WAT inflammation.

Health benefits of n-3 polyunsaturated fatty acids: eicosapentaenoic acid and docosahexaenoic acid

Marine-based fish and fish oil are the most popular and well-known sources of n-3 polyunsaturated fatty acids (PUFAs), namely, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These n-3 PUFAs are known to have variety of health benefits against cardiovascular diseases (CVDs) including well-established hypotriglyceridemic and anti-inflammatory effects. Also, various studies indicate promising antihypertensive, anticancer, antioxidant, antidepression, antiaging, and antiarthritis effects. Moreover, recent studies also indicate anti-inflammatory and insulin-sensitizing effects of these fatty acids in metabolic disorders. Classically, n-3 PUFAs mediate some of these effects by antagonizing n-6 PUFA (arachidonic acid)-induced proinflammatory prostaglandin E₂ (PGE₂) formation. Another well-known mechanism by which n-3 PUFAs impart their anti-inflammatory effects is via reduction of nuclear factor-κB activation. This transcription factor is a potent inducer of proinflammatory cytokine production, including interleukin 6 and tumor necrosis factor-α, both of which are decreased by EPA and DHA. Other evidence also demonstrates that n-3 PUFAs repress lipogenesis and increase resolvins and protectin generation, ultimately leading to reduced inflammation. Finally, beneficial effects of EPA and DHA in insulin resistance include their ability to increase secretion of adiponectin, an anti-inflammatory adipokine. In summary, n-3 PUFAs have multiple health benefits mediated at least in part by their anti-inflammatory actions; thus their consumption, especially from dietary sources, should be encouraged.

Dietary lipids and their oxidized products in Alzheimer's disease

Alzheimer's disease (AD) is the commonest form of dementia in the elderly, characterized by memory dysfunction, loss of lexical access, spatial and temporal disorientation, and impaired judgment. A growing body of scientific literature addresses the implication of dietary habits in the pathogenesis of AD. This review reports recent findings concerning the modulation of AD development by dietary lipids, in animals and humans, focusing on the pathogenetic role of lipid oxidation products. Oxidative breakdown products of ω-6 polyunsaturated fatty acids (ω-6 PUFAs), and cholesterol oxidation products (oxysterols), might play a role in favoring β-amyloid deposition, a hallmark of AD's onset and progression. Conversely, ω-3 PUFAs appear to contribute to preventing and treating AD. However, high concentrations of ω-3 PUFAs can also produce oxidized derivatives reacting with important functions of nervous cells. Thus, altered balances between cholesterol and oxysterols, and between ω-3 and ω-6 PUFAs must be considered in AD's pathophysiology. The use of a diet with an appropriate ω-3/ω-6 PUFA ratio, rich in healthy oils, fish and antioxidants, such as flavonoids, but low in cholesterol-containing foods, can be a beneficial component in the clinical strategies of prevention of AD.

(n-3) Fatty acids alleviate adipose tissue inflammation and insulin resistance: mechanistic insights

Obesity is associated with the metabolic syndrome, a significant risk factor for developing type 2 diabetes and cardiovascular diseases. Chronic low-grade inflammation occurring in the adipose tissue of obese individuals is causally linked to the pathogenesis of insulin resistance and the metabolic syndrome. Although the exact trigger of this inflammatory process is unknown, adipose tissue hypoxia, endoplasmic reticular stress, and saturated fatty acid-mediated activation of innate immune processes have been identified as important processes in these disorders. Furthermore, macrophages and T lymphocytes have important roles in orchestrating this immune process. Although energy restriction leading to weight loss is the primary dietary intervention to reverse these obesity-associated metabolic disorders, other interventions targeted at alleviating adipose tissue inflammation have not been explored in detail. In this regard, (n-3) PUFA of marine origin both prevent and reverse high-fat-diet-induced adipose tissue inflammation and insulin resistance in rodents. We provide an update on the pathogenesis of adipose tissue inflammation and insulin resistance in obesity and discuss potential mechanisms by which (n-3) PUFA prevent and reverse these changes and the implications in human health.

Energy-restricted high-fat diets only partially improve markers of systemic and adipose tissue inflammation

This study aimed at investigating whether the weight loss due to energy-restricted high-fat diets is accompanied with parallel improvements in metabolic markers and adipose tissue inflammation. Eight-week-old C57BL/6J mice were given free access to a low-fat (LF) or a high-fat (45% of energy from fat-HF) diet for 6 months. Restricting intake of the HF diet by 30% (HFR) during the last 2 months of the HF feeding trial decreased fasting plasma insulin, homeostasis model assessment of insulin resistance (HOMA(IR)), and plasma triglyceride levels and improved hepatic steatosis compared to ad libitum HF feeding, indicating an improved metabolic profile. Further, analysis of gonadal white adipose tissue (GWAT) gene expression by microarray and quantitative PCR analyses demonstrated that HFR downregulated expression of genes linked to cell and focal adhesion, cytokine-cytokine receptor interaction, and endoplasmic reticulum (ER)-associated degradation pathway. However, HFR had no effect on circulating plasminogen activator inhibitor-1 (PAI-1) and nonesterified fatty acid levels, which were persistently higher in both HF and HFR groups compared to the LF group. Furthermore, HFR had a negative effect on plasma total adiponectin level. Finally, while HFR decreased GWAT monocyte chemotactic protein-1 (MCP-1), interleukin-2 (IL-2), and PAI-1 levels, it did not affect several other cytokines including granulocyte-macrophage colony-stimulating factor, interferon-γ, IL-1β, IL-6, and IL-10. In summary, energy-restricted high-fat diets improve insulin sensitivity, while only partially improving markers of systemic and adipose tissue inflammation. In conclusion, our study supports the recommended low-fat intake for overall cardiovascular health.

The Role of Phospholipase A(2)-derived Mediators in Obesity

Obesity has become an epidemic and its prevalence is increasing exponentially. A great deal of focus has been given to understanding the molecular processes that regulate obesity. The characterization of phospholipase A(2)s, especially adipose-specific PLA(2), have lead to a proposed role of their downstream products in the progression of obesity and obesity related disorders. This review summarizes recent developments in the role of PLA(2) and their downstream effects in the development of metabolic disorders.

Eicosapentaenoic acid prevents and reverses insulin resistance in high-fat diet-induced obese mice via modulation of adipose tissue inflammation

We investigated the effects of eicosapentaenoic acid (EPA) on prevention (P) and reversal (R) of high saturated-fat (HF) diet-induced obesity and glucose-insulin homeostasis. Male C57BL/6J mice were fed low-fat (LF; 10% energy from fat), HF (45% energy from fat), or a HF-EPA-P (45% energy from fat; 36 g/kg EPA) diet for 11 wk. A 4th group was initially fed HF for 6 wk followed by the HF-EPA-R diet for 5 wk. As expected, mice fed the HF diet developed obesity and glucose intolerance. In contrast, mice fed the HF-EPA-P diet maintained normal glucose tolerance despite weight gain compared with the LF group. Whereas the HF group developed hyperglycemia and hyperinsulinemia, both HF-EPA groups (P and R) exhibited normal glycemia and insulinemia. Further, plasma adiponectin concentration was lower in the HF group but was comparable in the LF and HF-EPA groups, suggesting a role of EPA in preventing and improving insulin resistance induced by HF feeding. Further analysis of adipose tissue adipokine levels and proteomic studies in cultured adipocytes indicated that dietary EPA supplementation of HF diets was associated with reduced adipose inflammation and lipogenesis and elevated markers of fatty acid oxidation. In C57BL/6J mice, EPA minimized saturated fat-induced insulin resistance and this is in part mediated by its effects on fatty acid oxidation and inflammation.

A low alpha-linolenic intake during early life increases adiposity in the adult guinea pig

Background

The composition of dietary fatty acids (FA) during early life may impact adult adipose tissue (AT) development. We investigated the effects of α-linolenic acid (ALA) intake during the suckling/weaning period on AT development and metabolic markers in the guinea pig (GP).

Methods

Newborn GP were fed a 27%-fat diet (w/w %) with high (10%-ALA group), moderate (2.4%-ALA group) or low (0.8%-ALA group) ALA content (w/w % as total FA) until they were 21 days old (d21). Then all animals were switched to a 15%-fat diet containing 2% ALA (as total FA) until 136 days of age (d136).

Results

ALA and docosapentaenoic acid measured in plasma triglycerides (TG) at d21 decreased with decreasing ALA intake. Total body fat mass was not different between groups at d21. Adipose tissue TG synthesis rates and proliferation rate of total adipose cells, as assessed by ²H₂O labelling, were unchanged between groups at d21, while hepatic de novo lipogenesis was significantly 2-fold increased in the 0.8%-ALA group. In older GP, the 0.8%-ALA group showed a significant 15-%-increased total fat mass (d79 and d107, p < 0.01) and epididymal AT weight (d136) and tended to show higher insulinemia compared to the 10%-ALA group. In addition, proliferation rate of cells in the subcutaneous AT was higher in the 0.8%-ALA (15.2 ± 1.3% new cells/5d) than in the 10%-ALA group (8.6 ± 1.7% new cells/5d, p = 0.021) at d136. AT eicosanoid profiles were not associated with the increase of AT cell proliferation.

Conclusion

A low ALA intake during early postnatal life promotes an increased adiposity in the adult GP.