Differential effects of eicosapentaenoic acid and docosahexaenoic acid in promoting the differentiation of 3T3-L1 preadipocytes

The Potential of Fish Oil Components and Manuka Honey in Tackling Chronic Wound Treatment

Chronic wounds are becoming an increasing burden on healthcare services, as they have extended healing times and are susceptible to infection, with many failing to heal, which can lead ultimately to amputation. Due to the additional rise in antimicrobial resistance and emergence of difficult-to-treat Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE pathogens), novel treatments will soon be required asides from traditional antibiotics. Many natural substances have been identified as having the potential to aid in both preventing infection and increasing the speed of wound closure processes. Manuka honey is already in some cases used as a topical treatment in the form of ointments, which in conjunction with dressings and fish skin grafts are an existing US Food and Drug Administration-approved treatment option. These existing treatment options indicate that fatty acids from fish oil and manuka honey are well tolerated by the body, and if the active components of the treatments were better understood, they could make valuable additions to topical treatment options. This review considers two prominent natural substances with established manufacturing and global distribution-marine based fatty acids (including their metabolites) and manuka honey-their function as antimicrobials and how they can aid in wound repair, two important aspects leading to resolution of chronic wounds.

Vanin1 (VNN1) in chronic diseases: Future directions for targeted therapy

Vanin1 (VNN1) is an exogenous enzyme with pantetheinase activity that mainly exerts physiological functions through enzyme catalysis products, including pantothenic acid and cysteamine. In recent years, the crosstalk between VNN1 and metabolism and oxidative stress has attracted much attention. As a result of the ability of VNN1 to affect multiple metabolic pathways and oxidative stress to exacerbate or alleviate pathological processes, it has become a key component of disease progression. This review discusses the functions of VNN1 in glucolipid metabolism, cysteamine metabolism, and glutathione metabolism to provide perspectives on VNN1-targeted therapy for chronic diseases.

The Potential of the Marine Microalga Diacronema lutheri in the Prevention of Obesity and Metabolic Syndrome in High-Fat-Fed Wistar Rats

Long-chain polyunsaturated fatty acids n-3 series (n-3 LC-PUFAs), especially eicosapentaenoic and docosahexaenoic acids, are known to exert preventive effects on obesity and metabolic syndrome. Mainly consumed in the form of fish oil, LC-PUFAs n-3 are also found in significant quantities in other sources such as certain microalgae. The aim of this study was to evaluate the effects of Diacronema lutheri (Dia), a microalga rich in n-3 LC-PUFAs, on metabolic disorders associated with obesity. Three groups of male Wistar rats (n = 6 per group) were submitted for eight weeks to a standard diet or high-fat and high-fructose diet (HF), supplemented or not with 12% of Dia (HF-Dia). Compared to HF rats, HF-Dia rats showed a 41% decrease in plasma triacylglycerol (TAG) and an increase in plasma cholesterol (+35%) as well as in high-density lipoprotein cholesterol (+51%) without change to low-density lipoprotein cholesterol levels. Although fasting glycemia did not change, glucose and insulin tolerance tests highlighted an improvement in glucose and insulin homeostasis. Dia supplementation restored body weight and fat mass, and decreased levels of liver TAG (−75%) and cholesterol (−84%). In HF-Dia rats, leptin was decreased (−30%) below the control level corresponding to a reduction of 68% compared to HF rats. Similarly, the anti-inflammatory cytokines interleukin-4 (IL-4) and IL-10 were restored up to control levels, corresponding to a 74% and 58% increase in HF rats, respectively. In contrast, the level of IL-6 remained similar in the HF and HF-Dia groups and about twice that of the control. In conclusion, these results indicated that the D. lutheri microalga may be beneficial for the prevention of weight gain and improvement in lipid and glucose homeostasis.

Valorization of Side Stream Products from Sea Cage Fattened Bluefin Tuna (Thunnus thynnus): Production and In Vitro Bioactivity Evaluation of Enriched ω-3 Polyunsaturated Fatty Acids

The valorization of side streams from fishery and aquaculture value-chains is a valuable solution to address one of the challenges of the circular economy: turning wastes into profit. Side streams produced after filleting of sea cage fattened bluefin tuna (Thunnus thynnus) were analyzed for proximate composition and fatty acid profile to evaluate the possibility of producing tuna oil (TO) as a valuable source of ω-3 polyunsaturated fatty acids (PUFA) and testing its bioactivity in vitro. Ethyl esters of total fatty acids (TFA), obtained from TO, were pre-enriched by urea complexation (PUFA-Ue) and then enriched by short path distillation (SPD) up to almost 85% of the PUFA fraction (PUFA-SPe). The bioactivity of TFA, PUFA-SPe, and ethyl esters of depleted PUFA (PUFA-SPd) were tested in vitro, through analysis of lipid metabolism genes, in gilthead sea bream (Sparus aurata) fibroblast cell line (SAF-1) exposed to oils. TFA and PUFA-SPd upregulated transcription factors (pparβ and pparγ) and lipid metabolism-related genes (D6D, fas, fabp, fatp1, and cd36), indicating the promotion of adipogenesis. PUFA-SPe treated cells were similar to control. PUFA-SPe extracted from farmed bluefin tuna side streams could be utilized in fish feed formulations to prevent excessive fat deposition, contributing to improving both the sustainability of aquaculture and the quality of its products.

Perspectives on scaling production of adipose tissue for food applications

With rising global demand for food proteins and significant environmental impact associated with conventional animal agriculture, it is important to develop sustainable alternatives to supplement existing meat production. Since fat is an important contributor to meat flavor, recapitulating this component in meat alternatives such as plant based and cell cultured meats is important. Here, we discuss the topic of cell cultured or tissue engineered fat, growing adipocytes in vitro that could imbue meat alternatives with the complex flavor and aromas of animal meat. We outline potential paths for the large scale production of in vitro cultured fat, including adipogenic precursors during cell proliferation, methods to adipogenically differentiate cells at scale, as well as strategies for converting differentiated adipocytes into 3D cultured fat tissues. We showcase the maturation of knowledge and technology behind cell sourcing and scaled proliferation, while also highlighting that adipogenic differentiation and 3D adipose tissue formation at scale need further research. We also provide some potential solutions for achieving adipose cell differentiation and tissue formation at scale based on contemporary research and the state of the field.

Co-administration of oleic and docosahexaenoic acids enhances glucose uptake rather than lipolysis in mature 3T3-L1 adipocytes cell culture

This study investigated the effect of different types of long-chain fatty acids and their combination on the triglyceride accumulation, glucose utilisation, and lipolysis in already obese adipocytes. 3T3-L1 MBX cells were first differentiated into mature adipocytes using adipogenic inducers (3-isobutyl-1-methylxanthine, dexamethasone, indomethacin, insulin, and high glucose), then 100 µM 0.1% ethanol extracts of palmitic (PA), oleic (OA), or docosahexaenoic acid (DHA) were applied for nine days. Unsaturated fatty acids decreased the intracellular lipid accumulation while maintaining glucose utilisation levels. However, unlike OA, self-administration of DHA only intensified lipolysis by 25% vs induced untreated control (IC), which may have a direct detrimental impact on the whole body’s metabolic state. DHA applied in equal proportion with PA elevated triglyceride accumulation by 10% compared to IC, but applied with OA, enhanced glucose uptake without any significant changes in the lipogenic drive and the lipolytic rate, suggesting that this unsaturated fatty acids combination may offer a considerable advantage in amelioration of obesity-related disorders.

Effect of ω-3 Polyunsaturated Fatty Acids-Derived Bioactive Lipids on Metabolic Disorders

Arachidonic acid (ARA) is an important ω-6 polyunsaturated fatty acid (PUFA), and docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and n-3 docosapentaenoic acid (n-3 DPA) are three well-known ω-3 PUFAs. These fatty acids can be metabolized into a number of bioactive lipids. Eicosanoids derived from ARA have drawn great attention because of their important and complex biofunctions. Although EPA, DHA and n-3 DPA have also shown powerful biofunctions, we have fewer studies of metabolites derived from them than those from ARA. Recently, growing research has focused on the bioaction of ω-3 PUFA-derived metabolites, which indicates their great potential for treating metabolic disorders. Most of the functional studies of these bioactive lipids focused on their anti-inflammatory effects. However, several studies elucidated their direct effects on pancreatic β cells, hepatocytes, adipocytes, skeletal muscle cells, and endothelial cells. These researches revealed the importance of studying the functions of metabolites derived from ω-3 polyunsaturated fatty acids other than themselves. The current review summarizes research into the effects of ω-3 PUFA-derived oxylipins on metabolic disorders, including diabetes, non-alcoholic fatty liver disease, adipose tissue dysfunction, and atherosclerosis.

The Marine Microalga, Tisochrysis lutea, Protects against Metabolic Disorders Associated with Metabolic Syndrome and Obesity

Long-chain polyunsaturated fatty acids n-3 series and especially docosahexaenoic acid are known to exert preventive effects on metabolic disturbances associated with obesity and decrease cardiovascular disease risk. n-3 LC-PUFAs are mainly consumed in the form of fish oil, while other sources, such as certain microalgae, may contain a high content of these fatty acids. The aim of this study was to evaluate the effects of Tisochrysis lutea (Tiso), a microalga rich in DHA, on metabolic disorders associated with obesity. Three male Wistar rat groups were submitted for eight weeks to a standard diet or high-fat and high fructose diet (HF), supplemented or not with 12% of T. lutea (HF-Tiso). The supplementation did not affect plasma alanine aminotransferase (ALAT). Bodyweight, glycemia and insulinemia decreased in HF-Tiso rats (ANOVA, p < 0.001), while total plasma cholesterol, high-density lipoprotein-cholesterol (HDL-C) increased (ANOVA, p < 0.001) without change of low-density lipoprotein-cholesterol (LDL-C) and triacylglycerol (TAG) levels. Tiso supplementation decreased fat mass and leptinemia as well as liver TAG, cholesterol and plasma tumor necrosis factor-alpha levels (ANOVA, p < 0.001) while it did not affect interleukin 6 (IL-6), IL-4 and lipopolysaccharides levels. HF-Tiso rats showed an increase of IL-10 level in abdominal adipose tissue (ANOVA, p < 0.001). In conclusion, these results indicated that DHA-rich T. lutea might be beneficial for the prevention of obesity and improvement of lipid and glucose metabolism.

Short-Term Effects of Early Menopause on Adiposity, Fatty Acids Profile and Insulin Sensitivity of a Swine Model of Female Obesity

Menopause strongly increases incidence and consequences of obesity and non-communicable diseases in women, with recent research suggesting a very early onset of changes in lipid accumulation, dyslipidemia, and insulin resistance. However, there is a lack of adequate preclinical models for its study. The present trial evaluated the usefulness of an alternative method to surgical ovariectomy, the administration of two doses of a GnRH analogue-protein conjugate (Vacsincel^®), for inducing ovarian inactivity in sows used as preclinical models of obesity and menopause. All the sows treated with the compound developed ovarian stoppage after the second dose and, when exposed to obesogenic diets during the following three months, showed changes in the patterns of fat deposition, in the fatty acids profiles at the different tissues and in the plasma concentrations of fructosamine, urea, β-hydroxibutirate, and haptoglobin when compared to obese fed with the same diet but maintaining ovarian activity. Altogether, these results indicate that menopause early augments the deleterious effects induced by overfeeding and obesity on metabolic traits, paving the way for future research on physiopathology of these conditions and possible therapeutic targets using the swine model.

Concurrent EPA and DHA Supplementation Impairs Brown Adipogenesis of C2C12 Cells

Maternal dietary supplementation of n−3 polyunsaturated fatty acids (n−3 PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), is considered to play positive roles in fetal neuro system development. However, maternal n−3 PUFAs may induce molecular reprogramming of uncommitted fetal myoblasts into adipocyte phenotype, in turn affecting lipid metabolism and energy expenditure of the offspring. The objective of this in vitro study was to investigate the combined effects of EPA and DHA on C2C12 cells undergoing brown adipogenic differentiation. C2C12 myoblasts were cultured to confluency and then treated with brown adipogenic differentiation medium with and without 50 μM EPA and 50 μM DHA. After differentiation, mRNA and protein samples were collected. Gene expression and protein levels were analyzed by real-time PCR and western blot. General Proteomics analysis was conducted using mass spectrometric evaluation. The effect of EPA and DHA on cellular oxygen consumption was measured using a Seahorse XFP Analyzer. Cells treated with n−3 PUFAs had significantly less (P < 0.05) expression of the brown adipocyte marker genes PGC1α, DIO2, and UCP3. Expression of mitochondrial biogenesis-related genes TFAM, PGC1α, and PGC1β were significantly downregulated (P < 0.05) by n−3 PUFAs treatment. Expression of mitochondrial electron transportation chain (ETC)-regulated genes were significantly inhibited (P < 0.05) by n−3 PUFAs, including ATP5J2, COX7a1, and COX8b. Mass spectrometric and western blot evaluation showed protein levels of enzymes which regulate the ETC and Krebs cycle, including ATP synthase α and β (F1F0 complex), citrate synthase, succinate CO-A ligase, succinate dehydrogenase (complex II), ubiquinol-cytochrome c reductase complex subunits (complex III), aconitate hydratase, cytochrome c, and pyruvate carboxylase were all decreased in the n−3 PUFAs group (P < 0.05). Genomic and proteomic changes were accompanied by mitochondrial dysfunction, represented by significantly reduced oxygen consumption rate, ATP production, and proton leak (P < 0.05). This study suggested that EPA and DHA may alter the BAT fate of myoblasts by inhibiting mitochondrial biogenesis and activity and induce white-like adipogenesis, shifting the metabolism from lipid oxidation to synthesis.

Caviar Extract and Its Constituent DHA Inhibits UVB-Irradiated Skin Aging by Inducing Adiponectin Production

In this study, caviar (sturgeon eggs) was used to elucidate its roles in adiponectin production and skin anti-aging. Recently, caviar has been largely used not only as a nutritional food, but also in cosmetic products. In particular, it has been reported that docosahexaenoic acid (DHA), as one of the main phospholipid components of caviar extract, induces intracellular lipid accumulation and the expression of adiponectin in adipocytes. Although adipocytes are well known to be associated with the skin dermis by secreting various factors (e.g., adiponectin), the effects of caviar extract and DHA on the skin are not well studied. Here, we demonstrate the effects of caviar extract and DHA on adipocyte differentiation and adiponectin production, resulting in a preventive role in UV-irradiated skin aging. Caviar extract and DHA enhanced adipocyte differentiation and promoted the synthesis of transcription factors controlling adipocyte differentiation and adiponectin. In addition, the mRNA expression levels of matrix metalloproteinase-1 (MMP-1) were decreased in UVB-irradiated Hs68 fibroblasts that were cultured in conditioned medium from caviar extract or DHA-treated differentiated adipocytes. Taken together, these results indicate that caviar extract and DHA induce adipocyte differentiation and adiponectin production, thereby inhibiting UVB-induced premature skin aging via the suppression of MMP-1 production.

Adipose Tissue Modification through Feeding Strategies and Their Implication on Adipogenesis and Adipose Tissue Metabolism in Ruminants

Dietary recommendations by health authorities have been advising of the importance of diminishing saturated fatty acids (SFA) consumption and replacing them by polyunsaturated fatty acids (PUFA), particularly omega-3. Therefore, there have been efforts to enhance food fatty acid profiles, helping them to meet human nutritional recommendations. Ruminant meat is the major dietary conjugated linoleic acid (CLA) source, but it also contains SFA at relatively high proportions, deriving from ruminal biohydrogenation of PUFA. Additionally, lipid metabolism in ruminants may differ from other species. Recent research has aimed to modify the fatty acid profile of meat, and other animal products. This review summarizes dietary strategies based on the n-3 PUFA supplementation of ruminant diets and their effects on meat fatty acid composition. Additionally, the role of n-3 PUFA in adipose tissue (AT) development and in the expression of key genes involved in adipogenesis and lipid metabolism is discussed. It has been demonstrated that linseed supplementation leads to an increase in α-linolenic acid (ALA) and eicosapentaenoic acid (EPA), but not in docosahexaenoic acid (DHA), whilst fish oil and algae increase DHA content. Dietary PUFA can alter AT adiposity and modulate lipid metabolism genes expression, although further research is required to clarify the underlying mechanism.

Short-Term Responses to Fatty Acids on Lipid Metabolism and Adipogenesis in Rainbow Trout (Oncorhynchus mykiss)

Fish are rich in n-3 long-chain polyunsaturated fatty acids (LC-PUFA) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Due to the increasing use of vegetable oils (VO), their proportion in diets has lowered, affecting lipid metabolism and fillet composition. Rainbow trout cultured preadipocytes were treated with representative FA found in fish oils (EPA and DHA) or VO (linoleic, LA and alpha-linolenic, ALA acids), while EPA and LA were also orally administered, to evaluate their effects on adipogenesis and lipid metabolism. In vitro, all FA increased lipid internalization, with ALA producing the highest effect, together with upregulating the FA transporter fatp1. In vivo, EPA or LA increased peroxisome proliferator-activated receptors ppara and pparb transcripts abundance in adipose tissue, suggesting elevated β-oxidation, contrary to the results obtained in liver. Furthermore, the increased expression of FA synthase (fas) and the FA translocase/cluster of differentiation (cd36) in adipose tissue indicated an enhanced uptake of lipids and lipogenesis de novo, whereas stable or low hepatic expression of genes involved in lipid transport and turnover was found. Thus, fish showed a similar tissue metabolic response to the short-term availability of EPA or LA in vivo, while in vitro VO-derived FA demonstrated greater potential inducing fat accumulation.

Eicosapentaenoic and docosapentaenoic acids lessen the expression of PPARγ/Cidec affecting adipogenesis in cultured 3T3-L1 adipocytes

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have benefits in the metabolism of adipose tissue. However, its contribution to the adipogenesis is not entirely elucidated. The study aimed to evaluate the effects of EPA and DHA on adipogenesis, especially in the PPARγ (peroxisome proliferator-activated receptor-gamma) and Cidec (cell death-inducing DFFA-like effector c) pathway. Twenty-four hours after confluence, 3T3-L1 adipocytes were treated with EPA (100 μM), DHA (50μM) and EPA (100μM) + DHA (50μM) and at the end of differentiation (day 11) the cells were collected for analysis. Cell viability analysis indicated that the concentrations used for EPA and DHA did not cause cytotoxicity in cultured 3T3l1 adipocytes. The treatments have lessened the triacylglycerol accumulation in the adipocyte cytoplasm that, compared to the control group, were EPA-32%, DHA-38%, EPA + DHA -24%. The double-labeling immunofluorescence showed a signal attenuation of protein expressions of PPARγ, CIDEC, and SREBP-1c (sterol regulatory element-binding protein). EPA and DHA had a significant impact on the expression of cleaved CASPASE 3, which increases cell apoptosis and gene expressions of Pparγ and Cidec in the treated groups. Also, there was a reduction of C/ebpα (CCAAT/enhancer-binding protein alpha), Cd36 (cluster differentiation 36), and Foxo1 (forkhead box O). In conclusion, the study determined the ability of both EPA and DHA, alone or combined, in the adipogenesis modulation in cultured 3T3-L1 adipocytes, affecting the cell differentiation, maturation, and consequently, reducing adipogenesis via PPARγ-CIDEC suppression.

The Furan Fatty Acid 9M5 Acts as a Partial Ligand to Peroxisome Proliferator-Activated Receptor gamma and Enhances Adipogenesis in 3T3-L1 Preadipocytes

A food that has been praised for its beneficial effects on overall health is fish, particularly its polyunsaturated n-3 fatty acids, including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). However, it has recently been suggested that minor fatty acids such as furan fatty acids are needed in combination with DHA and EPA to exert these positive effects of fish and fish oils. Only recently have furan fatty acids become available in quantities that allow the investigation of their biofunctional properties. In this study, the uptake and effect of the furan fatty acid 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid (9M5) as a sole component and in combination with DHA and EPA on adipogenesis were analyzed using the 3T3-L1 cell model. 9M5 is taken up and metabolized into 7M5, 5M5, and 3M5 in 3T3-L1 adipocytes during a 24-h period as shown with gas chromatography with mass spectrometry (GC/MS). Furthermore, 9M5 significantly increased lipid accumulation during the differentiation process of 3T3-L1 preadipocytes into adipocytes. In addition, the combinations of DHA + 9M5 and EPA + DHA + 9M5 also exerted a significant increase compared to control adipocytes. 3T3-L1 cells incubated with 9M5 resulted in an increased protein expression of PPARγ, C/EBPα, FABP4, and adiponectin, although not to the extent that DHA as a sole component or DHA + 9M5 did. Earlier studies have shown that DHA is a natural ligand for PPARγ, thus being a potential alternative to the antidiabetic thiazolidinediones. We show that 9M5 activates a PPARγ-responsive reporter gene and could therefore be a natural ligand for PPARγ.

N-3 fatty acids as preventive and therapeutic agents in attenuating PCOS complications

To our knowledge, in spite of several trials exploring the beneficial effect of n-3 polyunsaturated fatty acids (PUFA) on polycystic ovary syndrome (PCOS), no comprehensive evidence has investigated the effects of n-3 PUFA consumption on PCOS complications. Therefore, our aim was to conduct a review to investigate the possible effect and related mechanisms. A comprehensive systematic search was conducted in Embase, MEDLINE/PubMed, Google Scholar, and SCOPUS, to identify studies investigating n-3 fatty acids as a preventative or therapeutic agent for the attenuation of PCOS complications. Subsequently, the impact of omega-3 on PCOS, omega-3 and inflammation, omega-3 and insulin resistance, omega-3 and adipokines, omega-3 and lipid metabolism, omega-3 and endothelial function and omega-3 and hormonal factors were discussed. There are multiple mechanisms by which n-3 PUFAs may exert their beneficial effects on PCOS, including anti-obesity, glycemic and hormonal hemostasis, anti-inflammatory, regulation of adipokine production and enhancement of endothelial function.N-3 PUFAs are a promising agent in relieving complications associated with PCOS. Although most of the studies in patients with PCOS reported an improvement in most complications after administration of omega-3 supplements, there is a distinct dearth of studies investigating the dietary intake of these types of fatty acids. Moreover, favorable effects regarding the improvement of dyslipidemia, regulation of adipokines, regulation of hormonal factors and enhancement of endothelial function are limited. Therefore, more trials are warranted to investigate palatable mechanisms for clarifying the metabolic and hormonal effects of these agents in PCOS.

DPA shows comparable chemotherapy sensitizing effects as EPA upon cellular incorporation in tumor cells

Dietary supplementation with ω-3 polyunsaturated fatty acids (PUFAs) has been reported to enhance the sensitivity of tumor cells towards chemotherapy. Most enhancing effects are described for ω-3 PUFAs EPA and DHA; less evidence is available with the intermediate DPA. We studied the chemotherapy enhancing effects of EPA, DPA and DHA in murine colon C26 adenocarcinoma cells and showed that DPA displayed similar chemosensitizing effects as EPA. Moreover, EPA supplementation increased cellular DPA content. In a C26 tumor-bearing mouse model, we studied the incorporation of ω-3 PUFA in tumor and skeletal muscle after a diet with different ω-3 PUFA sources. Although little DPA was present in the fatty acid food sources, in those that contained considerable EPA concentrations, DPA levels were higher in tumor and muscle tissue. From these studies, we conclude that EPA and DPA show chemosensitizing effects and that intake of EPA or EPA-containing nutrition leads to increased cellular DPA content by elongation. These findings support the use of ω-3 PUFA containing nutritional supplementations in cancer patients during chemotherapy treatment.

Arachidonic acid exacerbates diet-induced obesity and reduces bone mineral content without impacting bone strength in growing male rats

Long-chain polyunsaturated fatty acids modulate bone mass and adipocyte metabolism. Arachidonic acid (AA, C20:4 n-6) is elevated in obesity and postulated to stimulate bone resorption. This study aimed to determine the effect of AA on bone mass, quality, and adiposity in diet-induced obesity during growth. Male Sprague-Dawley rats (n=42, 4-week) were randomized into groups fed a control diet (CTRL, AIN-93G), high-fat diet (HFD, 35% kcal fat) or HFD + AA (1% w/w diet) for 6 weeks. Body composition, bone mineral density and microarchitecture were measured using dual-energy X-ray absorptiometry and micro-computed tomography. Red blood cell fatty acid profile was measured with gas chromatography. Group differences were evaluated using repeated measures two-way analysis of variance with Tukey-Kramer post hoc testing. Total energy intake did not differ among diet groups. At week 6, HFD + AA had significantly greater body fat % (12%), body weight (6%) and serum leptin concentrations (125%) than CTRL, whereas visceral fat (mass and %, assessed with micro-computed tomography) was increased in both HFD and HFD + AA groups. HFD + AA showed reduced whole body bone mineral content and femur mid-diaphyseal cortical bone cross-sectional area than HFD and CTRL, without impairment in bone strength. Contrarily, HFD + AA had greater femur metaphyseal trabecular vBMD (35%) and bone volume fraction (5%) compared to controls. Inclusion of AA elevated leptin concentrations in male rats. The early manifestations of diet-induced obesity on bone mass were accelerated with AA. Studies of longer duration are needed to clarify the effect of AA on peak bone mass following growth cessation.

PPAR-γ: Its ligand and its regulation by microRNAs

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor superfamily. PPARs are categorized into three subtypes, PPARα, β/δ, and γ, encoded by different genes, expressed in diverse tissues and participate in various biological functions and can be activated by their metabolic derivatives in the body or dietary fatty acids. The PPAR-γ also takes parts in the regulation of energy balance, lipoprotein metabolism, insulin sensitivity, oxidative stress, and inflammatory signaling. It has been implicated in the pathology of numerous diseases including obesity, diabetes, atherosclerosis, and cancers. Among various cellular and molecular targets that are able to regulate PPAR-γ and its underlying pathways, microRNAs (miRNAs) appeared as important regulators. Given that the deregulation of these molecules via targeting PPAR-γ could affect initiation and progression of various diseases, identification of miRNAs that affects PPAR-γ could contribute to the better understanding of roles of PPAR-γ in various biological and pathological conditions. Here, we have summarized the function and various ligands of PPAR-γ and have highlighted various miRNAs involved in the regulation of PPAR-γ.

Differential Anti-Adipogenic Effects of Eicosapentaenoic and Docosahexaenoic Acids in Obesity

SCOPE

To assess the associations of plasma eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with body fat in a population-based sample and explore the mechanism of action based on browning of white adipose tissue (WAT) in high-fat-diet-induced obese (DIO) mice and 3T3-L1 adipocytes.

METHODS AND RESULTS

Plasma EPA and DHA of 1719 adults in the National Health and Nutrition Examination Survey (2003-2004) are determined by gas chromatography mass spectrometry, while total body fat is measured by dual-energy X-ray absorptiometry. DIO mice are fed a high-fat diet supplemented with EPA or DHA (1% wt/wt) for 15 weeks and 3T3-L1 preadipocytes are treated with EPA or DHA during differentiation. Plasma DHA but not EPA is associated with lower body fat mass (p_trend < 0.0001), which persists in overweight/obese subjects (p_trend = 0.02). DHA supplementation reduces inguinal WAT and exhibits a more pronounced thermogenic effect than EPA in DIO mice. In vitro, the browning process is induced after 2-day and 6-day treatment with DHA and EPA, respectively.

CONCLUSION

Plasma DHA but not EPA is inversely associated with body fat mass. The more potent anti-adipogenic effect of DHA than EPA may involve a better capability of inducing browning of WAT for DHA.

Omega-3 polyunsaturated fatty acids attenuate inflammatory activation and alter differentiation in human adipocytes

BACKGROUND

Omega-3 polyunsaturated fatty acids, specifically the fish-oil-derived eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been proposed as inflammation-resolving agents via their effects on adipose tissue.

OBJECTIVE

We proposed to determine the effects of EPA and DHA on human adipocyte differentiation and inflammatory activation in vitro.

METHODS

Primary human subcutaneous adipocytes from lean and obese subjects were treated with 100 μM EPA and/or DHA throughout differentiation (differentiation studies) or for 72 h postdifferentiation (inflammatory studies). THP-1 monocytes were added to adipocyte wells for co-culture experiments. Subcutaneous and visceral adipose explants from obese subjects were treated for 72 h with EPA and DHA. Oil Red O staining was performed on live cells. Cells were collected for mRNA analysis by quantitative polymerase chain reaction, and media were collected for protein quantification by enzyme-linked immunosorbent assay.

RESULTS

Incubation with EPA and/or DHA attenuated inflammatory response to lipopolysaccharide (LPS) and monocyte co-culture with reduction in post-LPS mRNA expression and protein levels of IL6, CCL2 and CX3CL1. Expression of inflammatory genes was also reduced in the endogenous inflammatory response in obese adipose. Both DHA and EPA reduced lipid droplet formation and lipogenic gene expression without alteration in expression of adipogenic genes or adiponectin secretion.

CONCLUSIONS

EPA and DHA attenuate inflammatory activation of in vitro human adipocytes and reduce lipogenesis.

Benefits of combination low-dose pioglitazone plus fish oil on aged type 2 diabetes mice

The elderly patients with type 2 diabetes suffer more adverse drug events than young adults due to pharmacokinetic and pharmacodynamic changes associated with aging. Reducing the risks of these medication-related problems are equally important for the clinical care of older type 2 diabetes patients. Pioglitazone is used for treating type 2 diabetes as an oral antidiabetic drug. Despite pioglitazone is used helpful insulin sensitizers, the accumulation of subcutaneous fat is considered a major adverse effect of pioglitazone therapy. We investigated to reduce the adverse effect of pioglitazone by combination with fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in aged diabetic KK mice. The accumulation of subcutaneous fat associated with high-dose pioglitazone is reduced by fish oil, suppressing lipogenesis and stimulating fatty acid β-oxidation in the liver. Our data suggest that adding fish oil to low-dose pioglitazone results in anti-diabetic efficacy similar to that of the high-dose without concomitant body weight gain.

Modulation of Insulin Resistance and the Adipocyte-Skeletal Muscle Cell Cross-Talk by LCn-3PUFA

The cross-talk between skeletal muscle and adipose tissue is involved in the development of insulin resistance (IR) in skeletal muscle, leading to the decrease in the anabolic effect of insulin. We investigated if the long chain polyunsaturated n-3 fatty acids (LCn-3PUFA), eicosapentaenoic and docosapentaenoic acids (EPA and DPA, respectively) could (1) regulate the development of IR in 3T3-L1 adipocytes and C2C12 muscle cells and (2) inhibit IR in muscle cells exposed to conditioned media (CM) from insulin-resistant adipocytes. Chronic insulin (CI) treatment of adipocytes and palmitic acid (PAL) exposure of myotubes were used to induce IR in the presence, or not, of LCn-3PUFA. EPA (50 µM) and DPA (10 µM) improved PAL-induced IR in myotubes, but had only a partial effect in adipocytes. CM from adipocytes exposed to CI induced IR in C2C12 myotubes. Although DPA increased the mRNA levels of genes involved in fatty acid (FA) beta-oxidation and insulin signaling in adipocytes, it was not sufficient to reduce the secretion of inflammatory cytokines and prevent the induction of IR in myotubes exposed to adipocyte’s CM. Treatment with DPA was able to increase the release of adiponectin by adipocytes into CM. In conclusion, DPA is able to protect myotubes from PAL-induced IR, but not from IR induced by CM from adipocytes.

Modulation of Adipocyte Differentiation and Proadipogenic Gene Expression by Sulforaphane, Genistein, and Docosahexaenoic Acid as a First Step to Counteract Obesity

Obesity is characterized by excess body fat accumulation due to an increase in the size and number of differentiated mature adipocytes. Adipocyte differentiation is regulated by genetic and environmental factors, and its inhibition could represent a strategy for obesity prevention and treatment. The current study was designed with two aims: (i) to evaluate the changes in the expression of adipogenic markers (C/EBPα, PPARγ variant 1 and variant 2, and GLUT4) in 3T3-L1 murine preadipocytes at four stages of the differentiation process and (ii) to compare the effectiveness of sulforaphane, genistein, and docosahexaenoic acid in reducing lipid accumulation and modulating C/EBPα, PPARγ1, PPARγ2, and GLUT4 mRNA expression in mature adipocytes. All bioactive compounds were shown to suppress adipocyte differentiation, although with different effectiveness. These results set the stage for further studies considering natural food constituents as important agents in preventing or treating obesity.

Maternal consumption of fish oil programs reduced adiposity in broiler chicks

Maternal intake of eicosapentaenoic acid (EPA; 20:5 n-3) and docosahexaenoic acid (22:6 n-3) has been associated with reduced adiposity in children, suggesting the possibility to program adipose development through dietary fatty acids before birth. This study determined if enriching the maternal diet in fish oil, the primary source of EPA and DHA, affected adipose development in offspring. Broiler chickens were used because they are obesity-prone, and because fatty acids provided to the embryo can be manipulated through the hen diet. Hens were fed diets supplemented (2.8% wt:wt) with corn oil (CO; n-6) or fish oil (FO; n-3) for 28 d. Chicks from both maternal diet groups were fed the same diet after hatch. Maternal FO consumption enriched chick adipose tissue in EPA and DHA and reduced adiposity by promoting more, but smaller, adipocytes. This adipocyte profile was paralleled by lower expression of the adipogenic regulator PPARG and its co-activator PPARGC1B, and elevated expression of LPL. Proteomics identified 95 differentially abundant proteins between FO and CO adipose tissue, including components of glucose metabolism, lipid droplet trafficking, and cytoskeletal organization. These results demonstrate that the maternal dietary fatty acid profile programs offspring adipose development.

Suppression of adipocyte differentiation and lipid accumulation by stearidonic acid (SDA) in 3T3-L1 cells

Background

Increased consumption of omega-3 (ω-3) fatty acids found in cold-water fish and fish oil has been reported to protect against obesity. A potential mechanism may be through reduction in adipocyte differentiation. Stearidonic acid (SDA), a plant-based ω-3 fatty acid, has been targeted as a potential surrogate for fish-based fatty acids; however, its role in adipocyte differentiation is unknown. This study was designed to evaluate the effects of SDA on adipocyte differentiation in 3T3-L1 cells.

Methods

3T3-L1 preadipocytes were differentiated in the presence of SDA or vehicle-control. Cell viability assay was conducted to determine potential toxicity of SDA. Lipid accumulation was measured by Oil Red O staining and triglyceride (TG) quantification in differentiated 3T3-L1 adipocytes. Adipocyte differentiation was evaluated by adipogenic transcription factors and lipid accumulation gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Fatty acid analysis was conducted by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS).

Results

3T3-L1 cells treated with SDA were viable at concentrations used for all studies. SDA treatment reduced lipid accumulation in 3T3-L1 adipocytes. This anti-adipogenic effect by SDA was a result of down-regulation of mRNA levels of the adipogenic transcription factors CCAAT/enhancer-binding proteins alpha and beta (C/EBPα, C/EBPβ), peroxisome proliferator-activated receptor gamma (PPARγ), and sterol-regulatory element binding protein-1c (SREBP-1c). SDA treatment resulted in decreased expression of the lipid accumulation genes adipocyte fatty-acid binding protein (AP2), fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD-1), lipoprotein lipase (LPL), glucose transporter 4 (GLUT4) and phosphoenolpyruvate carboxykinase (PEPCK). The transcriptional activity of PPARγ was found to be decreased with SDA treatment. SDA treatment led to significant EPA enrichment in 3T3-L1 adipocytes compared to vehicle-control.

Conclusion

These results demonstrated that SDA can suppress adipocyte differentiation and lipid accumulation in 3T3-L1 cells through down-regulation of adipogenic transcription factors and genes associated with lipid accumulation. This study suggests the use of SDA as a dietary treatment for obesity.

Electronic supplementary material

The online version of this article (10.1186/s12944-017-0574-7) contains supplementary material, which is available to authorized users.

DHA increases adiponectin expression more effectively than EPA at relative low concentrations by regulating PPARγ and its phosphorylation at Ser273 in 3T3-L1 adipocytes

BACKGROUND

Enhancing circulating adiponectin is considered as a potential approach for the prevention and treatment of non-communicable diseases (NCDs). Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were reported to increase adiponectin by previous studies using a mixture of them. However, their individual effects on adiponectin and the underlying mechanisms are still unclear. In the present study, we observed and compared the individual effect of DHA and EPA on adiponectin in 3T3-L1 adipocytes, and further tested whether DHA or EPA regulated adiponectin by peroxisome proliferator-activated receptor γ (PPARγ) and its phosphorylation at Ser273 to provide a plausible explanation for their distinct actions.

METHODS

Firstly, 3T3-L1 adipocytes were treated with different doses of DHA or EPA for 24 h. Secondly, 3T3-L1 adipocytes were treated with DHA or EPA in the presence or absence of GW9662. Thirdly, 3T3-L1 adipocytes were pretreated with DHA or EPA for 24 h, followed by being respectively co-incubated with tumor necrosis factor α (TNF-α) or roscovitine for another 2 h. Bovine serum albumin treatment served as the control. After treatments, cellular and secreted adiponectin, cellular PPARγ and its phosphorylation at Ser273 were determined.

RESULTS

Compared with the control, DHA increased cellular and secreted adiponectin at 50 and 100 μmol/L, while EPA increased them at 100 and 200 μmol/L. Adiponectin expressions in DHA treated groups were significantly higher than those in EPA treated groups at 50 and 100 μmol/L. Both DHA and EPA enhanced PPARγ expression, but DHA was more effective. GW9662 blocked DHA- and EPA-induced increases in PPARγ as well as adiponectin. Remarkably, an opposite regulation of PPARγ phosphorylation was detected after fatty acids treatment: DHA inhibited it but EPA stimulated it. TNF-α blocked DHA-induced decrease in PPARγ phosphorylation, which eventually led to a decrease in adiponectin. Roscovitine blocked EPA-induced increase in PPARγ phosphorylation, but the corresponding increase in adiponectin was non-significant.

CONCLUSION

DHA compared with EPA led to a greater increase in cellular and secreted adiponectin at relative low concentrations by increasing PPARγ expression and inhibiting its phosphorylation at Ser273. DHA may be more beneficial than EPA in reducing risks of NCDs.

Docosahexaenoic acid increases accumulation of adipocyte triacylglycerol through up-regulation of lipogenic gene expression in pigs

Background

Changing dietary fatty acid composition in modern diet influences the prevalence of obesity. Increasing evidences suggest favorable effects of n-3 PUFA for protecting against obesity and the metabolic syndrome. However, the regulation of n-3 PUFA in adipose is still unclear. Thus, this study addressed metabolism of different dietary fats in the adipose tissue of porcine model.

Methods

Eight-week-old cross-bred pigs were randomly assigned to three groups and fed a 2% fat diet for 30 days from either soybean oil (SBO), docosahexaenoic acid (DHA) or beef tallow. An in vitro experiment was conducted in which linoleic acid (LA), DHA or oleic acid (OA) were added to represent the major fatty acid in the SBO-, DHA- or BT- diets, respectively. Adipocytes size and lipid metabolism related genes were analyzed.

Results

Plasma triacylglycerol (TAG) was lower in DHA- than in BT-fed pigs, and the product of lipolysis, glycerol was highest in BT-fed pigs. In addition, expression of the lipolytic genes, adipose triglyceride lipase and hormone sensitive lipase was higher in BT-fed pigs and with OA treatment in vitro. DHA promoted protein kinase A activity in pigs without affecting lipolytic genes. Adipocyte cell sizes, TAG content and expression of lipogenic-related genes including, adipose differentiated related protein (ADRP) and diacylglycerol acyltransferase 1 (DGAT1) were elevated by DHA in vivo and in vitro, indicating DHA promoted adipogenesis to trap TAG in adipose tissue. Fatty acid β-oxidation genes were increased in the DHA-fed pigs.

Conclusion

This effect was partly explained by the effect of DHA to promote adipogenesis to trap TAG in adipocytes and also increase expression of genes involved in adipocyte fatty acid oxidation. Therefore, our results suggest a direct effect of DHA on adipocyte metabolism, resulting in TAG turnover and fatty acid dissipation to facilitate plasma lipid uptake from the circulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0428-3) contains supplementary material, which is available to authorized users.

A combination of dietary N-3 fatty acids and a cyclooxygenase-1 inhibitor attenuates nonalcoholic fatty liver disease in mice

We sought to determine whether a combination of purified n-3 fatty acids (n-3) and SC-560 (SC), a cyclooxygenase-1-specific inhibitor, is effective in ameliorating nonalcoholic fatty liver disease in obesity. Female wild-type mice were fed a high-fat and high-cholesterol diet (HF) supplemented with n-3 in the presence or absence of SC. Mice treated with SC alone exhibited no change in liver lipids, whereas n-3-fed mice tended to have lower hepatic lipids. Mice given n-3+SC had significantly lower liver lipids compared with HF controls indicating enhanced lipid clearance. Total and sulfated bile acids were significantly higher only in n-3+SC-treated mice compared with chow diet (CD) controls. Regarding mechanisms, the level of pregnane X receptor (PXR), a nuclear receptor regulating drug/bile detoxification, was significantly higher in mice given n-3 or n-3+SC. Studies in precision-cut liver slices and in cultured hepatoma cells showed that n-3+SC enhanced not only the expression/activation of PXR and its target genes but also the expression of farnesoid X receptor (FXR), another regulator of bile synthesis/clearance, indicating that n-3+SC can induce both PXR and FXR. The mRNA level of FGFR4 which inhibits bile formation showed a significant reduction in Huh 7 cells upon n-3 and n-3+SC treatment. PXR overexpression in hepatoma cells confirmed that n-3 or SC each induced the expression of PXR target genes and in combination had an enhanced effect. Our findings suggest that combining SC with n-3 potentiates its lipid-lowering effect, in part, by enhanced PXR and/or altered FXR/FGFR4 signaling.

GPR120 promotes adipogenesis through intracellular calcium and extracellular signal-regulated kinase 1/2 signal pathway

Numerous researches have demonstrated that GPR120 (also called FFAR4) exerts novel functions in insulin resistance and adipogenesis. However, the molecular mechanism of GPR120-mediated adipogenic differentiation is still unclear. This study was aimed to interpret the relevant function mechanism of GPR120 in the differentiation of 3T3-L1 adipocytes. The results showed that GPR120 expression was dramatically increased along with the adipogenic differentiation of 3T3-L1 adipocytes and the adipogenic ability was significantly inhibited in shGPR120-transfected cells. TUG-891, a selective agonist of GPR120, promoted the intracellular triglyceride accumulation in a dose-dependent manner and did not enhance adipogenesis in shGPR120-transfected cells. Markedly, TUG-891 increased the activation of PPARγ in a GPR120-dependent pathway as assessed by luciferase reporter assay. Furthermore, in the adipogenic differentiation process of 3T3-L1 adipocytes, TUG-891 increased the [Ca(2+)]i and phosphorylation level of ERK1/2. Pretreatment with inhibitors of either ERK1/2 (U0126) or [Ca(2+)]i (BAPTA-AM) notably attenuated the GPR120-mediated adipogenesis. These results show that GPR120 promotes adipogenesis by increasing PPARγ expression via [Ca(2+)]i and ERK1/2 signal pathway in 3T3-L1 adipocytes.

Role of n-3 Polyunsaturated Fatty Acids in Ameliorating the Obesity-Induced Metabolic Syndrome in Animal Models and Humans

The incidence of obesity and its comorbidities, such as insulin resistance and type II diabetes, are increasing dramatically, perhaps caused by the change in the fatty acid composition of common human diets. Adipose tissue plays a role as the major energy reservoir in the body. An excess of adipose mass accumulation caused by chronic positive energy balance results in obesity. The n-3 polyunsaturated fatty acids (n-3 PUFA), DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) exert numerous beneficial effects to maintain physiological homeostasis. In the current review, the physiology of n-3 PUFA effects in the body is delineated from studies conducted in both human and animal experiments. Although mechanistic studies in human are limited, numerous studies conducted in animals and models in vitro provide potential molecular mechanisms of the effects of these fatty acids. Three aspects of n-3 PUFA in adipocyte regulation are discussed: (1) lipid metabolism, including adipocyte differentiation, lipolysis and lipogenesis; (2) energy expenditure, such as mitochondrial and peroxisomal fatty acid β-oxidation; and (3) inflammation, including adipokines and specialized pro-resolving lipid mediators. Additionally, the mechanisms by which n-3 PUFA regulate gene expression are highlighted. The beneficial effects of n-3 PUFA may help to reduce the incidence of obesity and its comorbidities.

Linoelaidic acid enhances adipogenic differentiation in adipose tissue-derived stromal cells through suppression of Wnt/β-catenin signaling pathway in vitro

Obesity has become a major health problem which is related with high-trans fatty acids diet. Adipogenic differentiation of adipose tissue-derived stromal cells (ADSCs) plays an important role in the development of adipose tissue. In order to determine the effect of trans fatty acids on adipogenic differentiation in ADSCs, cells were treated with linoelaidic acid, as well as linoleic acid and linolenic acid. We found that linoelaidic acid significantly increased the lipid droplet formation and triglyceride content compared with linoleic acid and linolenic acid. Linoelaidic acid also down-regulated the levels of β-catenin in cells and inhibited the accumulation of β-catenin in cell nuclei. Lithium chloride, an activator of Wnt/β-catenin pathway, antagonized the enhancement of linoelaidic acid on adipogenesis and up-regulated the levels of β-catenin in ADSCs. These results indicated that linoelaidic acid could enhance the adipogenic differentiation in ADSCs in vitro, which is partly due to the suppression of Wnt/β-catenin pathway.

EPA prevents fat mass expansion and metabolic disturbances in mice fed with a Western diet

The impact of alpha linolenic acid (ALA), EPA, and DHA on obesity and metabolic complications was studied in mice fed a high-fat, high-sucrose (HF) diet. HF diets were supplemented with ALA, EPA, or DHA (1% w/w) and given to C57BL/6J mice for 16 weeks and to Ob/Ob mice for 6 weeks. In C57BL/6J mice, EPA reduced plasma cholesterol (-20%), limited fat mass accumulation (-23%) and adipose cell hypertrophy (-50%), and reduced plasma leptin concentration (-60%) compared with HF-fed mice. Furthermore, mice supplemented with EPA exhibited a higher insulin sensitivity (+24%) and glucose tolerance (+20%) compared with HF-fed mice. Similar effects were observed in EPA-supplemented Ob/Ob mice, although fat mass accumulation was not prevented. By contrast, in comparison with HF-fed mice, DHA did not prevent fat mass accumulation, increased plasma leptin concentration (+128%) in C57BL/6J mice, and did not improve glucose homeostasis in C57BL/6J and Ob/Ob mice. In 3T3-L1 adipocytes, DHA stimulated leptin expression whereas EPA induced adiponectin expression, suggesting that improved leptin/adiponectin balance may contribute to the protective effect of EPA. In conclusion, supplementation with EPA, but not ALA and DHA, could preserve glucose homeostasis in an obesogenic environment and limit fat mass accumulation in the early stage of weight gain.

Effects of selected bioactive food compounds on human white adipocyte function

Background

Previous studies suggest that intake of specific bioactive compounds may have beneficial clinical effects on adipose tissue partly due to their anti-inflammatory and insulin-sensitizing properties. With the overall aim to contribute to better understanding of the mechanisms of selected bioactive nutrients on fat metabolism, we investigated their role on human white adipocyte function.

Methods

The influence of the omega-3-fatty acid docosahexaenoic acid (DHA), the anthocyanin (AC) cyanidin-3-glucoside and its metabolite protocatechuic acid, and the beta-glucan metabolite propionic acid (PI) on adipokine secretion, fatty acid metabolism (lipolysis/lipogenesis) and adipocyte differentiation (lipid accumulation) was studied in human fat cells differentiated in vitro. To investigate possible synergistic, additive or antagonistic effects, DHA was also combined with AC or PI.

Results

Each compound, alone or together with DHA, suppressed basal adipocyte lipolysis compared to control treated cells. DHA alone attenuated the secretion of pro-inflammatory adipokines such as chemerin, interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1/CCL2), whereas AC suppressed only the latter two. Treatment with PI decreased IL-6, tumour necrosis factor alpha (TNFα) and adiponectin secretion. A combination of DHA and AC decreased TNFα secretion and increased insulin-stimulated lipogenesis. No effect was found on adipocyte differentiation. At the selected concentrations, none of the compounds was found to be cytotoxic.

Conclusion

The studied bioactive food compounds or their metabolites have beneficial effects in human primary fat cells measured as decreased basal lipolytic activity and secretion of inflammatory markers. A minor effect was also observed on insulin-stimulated glucose uptake albeit only with the combination of DHA and AC. Taken together, our results may link the reported health benefits of the selected bioactives on metabolic disorders such as insulin resistance, hypertension and dyslipidemia to effects on white adipocytes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0064-3) contains supplementary material, which is available to authorized users.

Nanoformulated copper/zinc superoxide dismutase reduces adipose inflammation in obesity

OBJECTIVE

An intimate association exists between oxidative stress and inflammation. Because adipose tissue (AT) inflammation is intricately linked to metabolic disorders, it was hypothesized that reducing oxidative stress would be effective in ameliorating AT inflammation in obesity.

METHODS

Wild-type mice were fed a high-fat diet (HF) for 8 weeks followed by a 2-week treatment with nanoformulated copper/zinc superoxide dismutase (NanoSOD). The mice were divided into: 1) chow diet, 2) HF, and 3) HF + NanoSOD.

RESULTS

The HF + NanoSOD-treated mice showed a significant decrease in plasma and liver triglycerides when compared with HF-fed mice. Interestingly, NanoSOD reduced the expression of macrophage and inflammatory markers in visceral AT (VAT) and stromal cells derived from VAT. Moreover, the activation of proinflammatory signaling pathways, in particular, the extracellular signal-regulated kinases, was blunted in VAT on NanoSOD treatment. However, markers of oxidative stress were not altered significantly in the HF + NanoSOD group in the experimental conditions. Pretreatment of either macrophages or adipocytes significantly reduced the inflammatory response invoked in an in vitro coculture system, further supporting the role of NanoSOD in inhibiting obesity-linked inflammation.

CONCLUSIONS

This data suggest that NanoSOD is effective not only in reducing AT macrophage accumulation and AT inflammation but also in promoting triglyceride metabolism in obesity.

The Effect of Marine Derived n-3 Fatty Acids on Adipose Tissue Metabolism and Function

Adipose tissue function is key determinant of metabolic health, with specific nutrients being suggested to play a role in tissue metabolism. One such group of nutrients are the n-3 fatty acids, specifically eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). Results from studies where human, animal and cellular models have been utilised to investigate the effects of EPA and/or DHA on white adipose tissue/adipocytes suggest anti-obesity and anti-inflammatory effects. We review here evidence for these effects, specifically focusing on studies that provide some insight into metabolic pathways or processes. Of note, limited work has been undertaken investigating the effects of EPA and DHA on white adipose tissue in humans whilst more work has been undertaken using animal and cellular models. Taken together it would appear that EPA and DHA have a positive effect on lowering lipogenesis, increasing lipolysis and decreasing inflammation, all of which would be beneficial for adipose tissue biology. What remains to be elucidated is the duration and dose required to see a favourable effect of EPA and DHA in vivo in humans, across a range of adiposity.

Fatty acids, eicosanoids and PPAR gamma

Peroxisome proliferator-activated receptor γ (PPARγ) belongs to the family of nuclear nuclear receptors and is mainly expressed in adipose tissue, hematopoietic cells and the large intestine. Contrary to other nuclear receptors that mainly bind a single specific ligand, there are numerous natural PPARγ ligands, in particular fatty acids or their derivatives called eicosanoids. PPARγ have pleiotropic functions: (i) glucose and lipid metabolism regulation, (ii) anti-inflammatory properties, (iii) oxidative stress inhibition, (iv) improvement of endothelial function. Its role has been mainly studied by the use synthetic agonists. In this review, we will focus on the effects of PPARγ mediated through fatty acids and how these have beneficial health properties.

Docosahexaenoic Acid Modulates a HER2-Associated Lipogenic Phenotype, Induces Apoptosis, and Increases Trastuzumab Action in HER2-Overexpressing Breast Carcinoma Cells

In breast cancer, lipid metabolic alterations have been recognized as potential oncogenic stimuli that may promote malignancy. To investigate whether the oncogenic nature of lipogenesis closely depends on the overexpression of HER2 protooncogene, the normal breast cell line, HB4a, was transfected with HER2 cDNA to obtain HER2-overexpressing HB4aC5.2 cells. Both cell lines were treated with trastuzumab and docosahexaenoic acid. HER2 overexpression was accompanied by an increase in the expression of lipogenic genes involved in uptake (CD36), transport (FABP4), and storage (DGAT) of exogenous fatty acids (FA), as well as increased activation of “de novo” FA synthesis (FASN). We further investigate whether this lipogenesis reprogramming might be regulated by mTOR/PPARγ pathway. Inhibition of the mTORC1 pathway markers, p70S6 K1, SREBP1, and LIPIN1, as well as an increase in DEPTOR expression (the main inhibitor of the mTOR) was detected in HB4aC5.2. Based on these results, a PPARγ selective antagonist, GW9662, was used to treat both cells lines, and the lipogenic genes remained overexpressed in the HB4aC5.2 but not HB4a cells. DHA treatment inhibited all lipogenic genes (except for FABP4) in both cell lines yet only induced death in the HB4aC5.2 cells, mainly when associated with trastuzumab. Neither trastuzumab nor GW9662 alone was able to induce cell death. In conclusion, oncogenic transformation of breast cells by HER2 overexpression may require a reprogramming of lipogenic genetic that is independent of mTORC1 pathway and PPARγ activity. This reprogramming was inhibited by DHA.

A high fat diet containing saturated but not unsaturated fatty acids enhances T cell receptor clustering on the nanoscale

Cell culture studies show that the nanoscale lateral organization of surface receptors, their clustering or dispersion, can be altered by changing the lipid composition of the membrane bilayer. However, little is known about similar changes in vivo, which can be effected by changing dietary lipids. We describe the use of a newly developed method, k-space image correlation spectroscopy, kICS, for analysis of quantum dot fluorescence to show that a high fat diet can alter the nanometer-scale clustering of the murine T cell receptor, TCR, on the surface of naive CD4(+) T cells. We found that diets enriched primarily in saturated fatty acids increased TCR nanoscale clustering to a level usually seen only on activated cells. Diets enriched in monounsaturated or n-3 polyunsaturated fatty acids had no effect on TCR clustering. Also none of the high fat diets affected TCR clustering on the micrometer scale. Furthermore, the effect of the diets was similar in young and middle aged mice. Our data establish proof-of-principle that TCR nanoscale clustering is sensitive to the composition of dietary fat.

Omega-3 fatty acids and adipose tissue function in obesity and metabolic syndrome

The n-3 long-chain polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) have been reported to improve obesity-associated metabolic disorders including chronic inflammation, insulin resistance and dyslipidaemia. Growing evidence exits about adipose tissue as a target in mediating the beneficial effects of these marine n-3 PUFAs in adverse metabolic syndrome manifestations. Therefore, in this manuscript we focus in reviewing the current knowledge about effects of marine n-3 PUFAs on adipose tissue metabolism and secretory functions. This scope includes n-3 PUFAs actions on adipogenesis, lipogenesis and lipolysis as well as on fatty acid oxidation and mitochondrial biogenesis. The effects of n-3 PUFAs on adipose tissue glucose uptake and insulin signaling are also summarized. Moreover, the roles of peroxisome proliferator-activated receptor γ (PPARγ) and AMPK activation in mediating n-3 PUFAs actions on adipose tissue functions are discussed. Finally, the mechanisms underlying the ability of n-3 PUFAs to prevent and/or ameliorate adipose tissue inflammation are also revised, focusing on the role of n-3 PUFAs-derived specialized proresolving lipid mediators such as resolvins, protectins and maresins.

Polyunsaturated fatty acid regulation of adipocyte FADS1 and FADS2 expression and function

OBJECTIVE

Polyunsaturated fatty acids (PUFAs) regulate fatty acid desaturase (FADS1, FADS2) expression in the liver; however, it is unknown whether PUFAs regulate FADS in adipocytes. This is important to study considering reports that link altered desaturase activity with adipose tissue PUFA profiles, body weight, and whole-body glucose homeostasis. Therefore, the present study aimed to determine the direct effects of PUFAs on FADS expression in differentiated 3T3-L1 adipocytes.

METHODS

Differentiated 3T3-L1 adipocytes were treated with either α-linolenic (ALA), linoleic (LA), eicosapentaenoic (EPA), or arachidonic acid (AA). Gene expression, protein abundance, and cellular PUFA content were analyzed by real-time RT-PCR, Western blotting, and gas chromatography, respectively.

RESULTS

Fads1 and Fads2 gene expression was reduced by EPA and AA, but not ALA or LA. Reductions in gene expression were reflected in FADS2 protein levels, but not FADS1. Treating cells with ALA and LA led to significant increases in the cellular content of downstream PUFAs. Neither ALA nor EPA changed docosahexaenoic acid content.

CONCLUSIONS

Differentiated 3T3-L1 adipocytes have a functional FADS pathway that can be regulated by PUFA. Therefore, this common adipocyte model is suitable to study dietary regulation of the FADS pathway.

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.

Mechanisms of enhanced insulin secretion and sensitivity with n-3 unsaturated fatty acids

The widespread acceptance that increased dietary n-3 polyunsaturated fatty acids (PUFAs), especially α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), improve health is based on extensive studies in animals, isolated cells and humans. Visceral adiposity is part of the metabolic syndrome, together with insulin resistance, dyslipidemia, hypertension and inflammation. Alleviation of metabolic syndrome requires normalization of insulin release and responses. This review assesses our current knowledge of the mechanisms that allow n-3 PUFAs to improve insulin secretion and sensitivity. EPA has been more extensively studied than either ALA or DHA. The complex actions of EPA include increased G-protein-receptor-mediated release of glucagon-like peptide 1 (GLP-1) from enteroendocrine L-cells in the intestine, up-regulation of the apelin pathway and down-regulation of other control pathways to promote insulin secretion by the pancreatic β-cells, together with suppression of inflammatory responses to adipokines, inhibition of peroxisome proliferator-activated receptor α actions and prevention of decreased insulin-like growth factor-1 secretion to improve peripheral insulin responses. The receptors involved and the mechanisms of action probably differ for ALA and DHA, with antiobesity effects predominating for ALA and anti-inflammatory effects for DHA. Modifying both GLP-1 release and the actions of adipokines by n-3 PUFAs could lead to additive improvements in both insulin secretion and sensitivity.

EPA-enriched phospholipids ameliorate cancer-associated cachexia mainly via inhibiting lipolysis

EPA-PL rescues the cancer-associated cachexia via inhibiting lipolysis.