The influence of EPA and DHA on markers of inflammation in 3T3-L1 cells at different stages of cellular maturation

Fish oil-derived n-3 polyunsaturated fatty acids downregulate aquaporin 9 protein expression of liver and white adipose tissues in diabetic KK mice and 3T3-L1 adipocytes

Aquaporin 9 (AQP9) is an integral membrane protein that facilitates glycerol transport in hepatocytes and adipocytes. Glycerol is necessary as a substrate for gluconeogenesis in the physiological fasted state, suggesting that inhibiting AQP9 function may be beneficial for treating type 2 diabetes associated with fasting hyperglycemia. The n-3 polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are rich in fish oil and lower the risk of metabolic syndrome; however, the effects of EPA and DHA on AQP9 expression in obese and type 2 diabetes are unclear. The KK mouse is an animal model of obesity and type 2 diabetes because of the polymorphisms on leptin receptor gene, which results in a part of cause for obese and diabetic conditions. In this study, we determined the effect of fish oil-derived n-3 PUFA on AQP9 protein expression in the liver and white adipose tissue (WAT) of KK mice and mouse 3T3-L1 adipocytes. The expression of AQP9 protein in the liver, epididymal WAT, and inguinal WAT were markedly decreased following fish oil administration. We also demonstrated that n-3 PUFAs, such as DHA, and to a lesser extent EPA, downregulated AQP9 protein expression in 3T3-L1 adipocytes. Our results suggest that fish oil-derived n-3 PUFAs may regulate the protein expressions of AQP9 in glycerol metabolism-related organs in KK mice and 3T3-L1 adipocytes.

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

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

Different ratios of DHA/EPA reverses insulin resistance by improving adipocyte dysfunction and lipid disorders in HFD-induced IR mice

Objective: Insulin resistance (IR) is linked to the development of diabetes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular disease (CVDs). Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from fish oils (FOs) were used to investigate their potential in high-fat diet (HFD)-induced IR mice under different ratios. Methods: A total of 84 male C57BL/6J (6 weeks old) mice were fed with HFD containing 45% kcal from fat for 16 weeks to establish the IR model. The IR mice were then fed with HFD or HFD + 4% DHA/EPA with different ratios (3 : 1, 1.5 : 1, 1 : 1, 1 : 1.5, 1 : 3, respectively) for another 12 weeks. During the experiment, the CON group (n = 12) was set to feed with a basic diet containing 10% kcal from fat. Results: HFD feeding for 16 weeks reduced insulin sensitivity and accelerated hypertrophy of white adipose tissue (WAT). Different ratios of DHA/EPA except for 1 : 1 decreased the HOMA-IR index, average area of adipocytes, and serum MDA, but increased the protein expression of PI3K. All ratios of DHA/EPA increased the protein expression of IRS-1, GLUT4, and adiponectin. Moreover, dietary DHA/EPA changed serum fatty acid (FA) composition by increasing the serum concentration of n-3 PUFAs. DHA/EPA supplements also improved serum lipid profiles (TG/TC/LDL-c/HDL-c, FFA) and reduced the hepatic steatosis area. Conclusions: The results indicate that an appropriate higher ratio of DHA (1.5 : 1) in DHA/EPA supplementation is recommended for IR prevention.

Serum fatty acid profiles associated with metabolic risk in women with polycystic ovary syndrome

PURPOSE

Dyslipidemia is a feature of polycystic ovary syndrome (PCOS) that may augment metabolic disturbances. Serum fatty acids are important biomedical indicators of dyslipidemia. The aim of this study was to determine the distinct serum fatty acids in various PCOS subtypes and their association with metabolic risk in women with PCOS.

METHODS

Fatty acids in the serum of 202 women with PCOS were measured using gas chromatography-mass spectrometry. Fatty acids were compared between PCOS subtypes and correlated with glycemic parameters, adipokines, homocysteine, sex hormones, and sex hormone-binding globulin (SHBG).

RESULTS

The levels of total monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) in the reproductive subtype of PCOS were lower than those in the metabolic subtype. Docosahexaenoic acid, a PUFA, was associated with higher SHBG after correction for multiple comparisons. Eighteen species of fatty acids emerged as potential biomarkers associated with the metabolic risk factors measured, independent of body mass index (BMI). Among them, myristic acid (C14:0), palmitoleic acid (C16:1), oleic acid (C18:1n-9C), cis-vaccenic acid (C18:1n-7), and homo-gamma-linolenic acid (C20:3n-6) were the strongest lipid species that were consistently associated with metabolic risk factors, particularly insulin-related parameters in women with PCOS. As for adipokines, 16 fatty acids were positively associated with serum leptin. Among them, C16:1 and C20:3n-6were significantly associated with leptin levels.

CONCLUSION

Our data demonstrated that a distinct fatty acid profile comprising high C14:0, C16:1, C18:1n-9C, C18:1n-7, and C20:3n-6levels is associated with metabolic risk in women with PCOS, independent of BMI.

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

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

Docosahexaenoic Acid Delivery Systems, Bioavailability, Functionality, and Applications: A Review

Docosahexaenoic acid (DHA), mainly found in microalgae and fish oil, is crucial for the growth and development of visual, neurological, and brain. In addition, DHA has been found to improve metabolic disorders associated with obesity and has anti-inflammatory, anti-obesity, and anti-adipogenesis effects. However, DHA applications in food are often limited due to its low water solubility, instability, and poor bioavailability. Therefore, delivery systems have been developed to enhance the remainder of DHA activity and increase DHA homeostasis and bioavailability. This review focused on the different DHA delivery systems and the in vitro and in vivo digestive characteristics. The research progress on cardiovascular diseases, diabetes, visual, neurological/brain, anti-obesity, anti-inflammatory, food applications, future trends, and the development potential of DHA delivery systems were also reviewed. DHA delivery systems could overcome the instability of DHA in gastrointestinal digestion, improve the bioavailability of DHA, and better play the role of its functionality.

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.

Interleukin-6 mimics insulin-dependent cellular distribution of some cytoskeletal proteins and Glut4 transporter without effect on glucose uptake in 3T3-L1 adipocytes

Interleukin (IL)-6, a known proinflammatory cytokine, is released in both visceral adipose tissue and contracting skeletal muscle. In this study, we used microRNA profiling as a screening method to identify miRNA species modified by IL-6 treatment in mouse 3T3-L1 adipocytes. miRNA microarray analysis and qRT-PCR revealed increased expression of miR-146b-3p in adipocytes exposed to IL-6 (1 ng/ml) during 8-day differentiation. On the basis of ontological analysis of potential targets, selected proteins associated with cytoskeleton and transport were examined in the context of adipocyte response to insulin, using immunofluorescence and confocal microscopy. We concluded that IL-6: (i) does not affect insulin action on actin cellular distribution; (ii) modulates the effect of insulin on myosin light chain kinase (Mylk) distribution by preventing its shift toward cytoplasm; (iii) mimics the effect of insulin on dynein distribution by increasing its near-nuclear accumulation; (iv) mimics the effect of insulin on glucose transporter Glut4 distribution, especially by increasing its near-nuclear accumulation; (v) supports insulin action on early endosome marker Rab4A near-nuclear accumulation. Moreover, as IL-6 did not disturb insulin-dependent glucose uptake, our results do not confirm the IL-6-induced impairment of insulin action observed in some in vitro studies, suggesting that the effect of IL-6 is dose dependent.

Docosahexaenoic acid lessens hepatic lipid accumulation and inflammation via the AMP-activated protein kinase and endoplasmic reticulum stress signaling pathways in grass carp (Ctenopharyngodon idella)

The liver is the primary organ for frontline immune defense and lipid metabolism. Excessive lipid accumulation in the liver severely affects its metabolic homeostasis and causes metabolic diseases. Docosahexaenoic acid (DHA) is known for its beneficial effects on lipid metabolism and anti-inflammation, but its molecular mechanism remains unknown, especially in fish. In this study, we evaluated the protective effects of DHA on hepatic steatosis of grass carp (Ctenopharyngodon idella) in vivo and in vitro and mainly focused on the AMP-activated protein kinase (AMPK) and endoplasmic reticulum stress (ER stress) signaling pathway analysis. Grass carp were fed with purified diets supplemented with 0%, 0.5% and 1% DHA for 8 weeks in vivo. 1% DHA supplementation significantly decreased the liver triglyceride (TG), malondialdehyde (MDA), serum tumor necrosis factor α (TNFα) and nuclear factor kappa B (NFκB) contents. DHA administration suppressed ER stress and decreased the mRNA expressions related to hepatic inflammation and lipogenesis, accompanied by the activation of AMPK. Correspondingly, DHA activated the AMPK signaling pathway, and inhibited palmitic acid (PA)-evoked ER stress and lipid accumulation and inflammation of grass carp hepatocytes in vitro. In contrast, the inhibitor of AMPK (compound C, CC) abrogated the effects of DHA to improve PA-induced liver injury and ER stress. In conclusion, DHA inhibits ER stress in hepatocytes by the activation of AMPK and exerts protective effects on hepatic steatosis in terms of improving antioxidant ability, relieving hepatic inflammation and inhibiting hepatic lipogenesis. Our findings give a theoretical foundation for further elucidation of the beneficial role of DHA in vertebrates.

Treatment of preadipocytes with fish oil, mixed oil, or soybean oil-based lipid emulsions have differential effects on the regulation of lipogenic and lipolytic genes in mature 3T3-L1 adipocytes

The key adipose tissue characteristics are established during early development, where lipids play an essential role. Lipid emulsions used in total parenteral nutrition have different omega-(n) 6 to n-3 fatty acid ratios. A lower n-6:n-3 fatty acid decreases lipid accumulation; however, the effects of lipid emulsions with different n-6 to n-3 fatty acid ratios on the programming of preadipocytes to affect lipid accumulation in mature adipocytes is not known. This study compared the effects of Fish oil (FO), Mixed oil (MO), and Soybean oil (SO) based lipid emulsion on genes involved in adipogenesis, lipogenesis, lipolysis, and β-oxidation in 3T3-L1 adipocytes. Preadipocytes were treated with specific lipid emulsions and then differentiated to mature adipocytes in the absence of lipid emulsions. In a separate experiment, mature 3T3-L1 adipocytes were treated with lipid emulsions to investigate the effects on genes involved in lipolysis. Fatty acid composition, triacylglycerol levels, and the mRNA expression of genes involved in adipogenesis, lipogenesis, lipolysis, and β-oxidation were measured. Preadipocytes and mature adipocytes treated with FO showed higher incorporation of n-3 polyunsaturated fatty acids, lower triacylglycerol levels, and decreased mRNA expression of adipogenic and lipogenic genes, followed by MO and SO. FO and MO increased the mRNA expression of carnitine palmitoyltransferase-1, while FO decreased the mRNA expression of lipolytic genes compared to untreated cells. Our findings suggest that FO programs preadipocytes to prevent adipose tissue dysfunction in mature adipocytes; the effects of FO-based lipid emulsion were followed by MO and SO.

Metabolism in Retinopathy of Prematurity

Retinopathy of prematurity is defined as retinal abnormalities that occur during development as a consequence of disturbed oxygen conditions and nutrient supply after preterm birth. Both neuronal maturation and retinal vascularization are impaired, leading to the compensatory but uncontrolled retinal neovessel growth. Current therapeutic interventions target the hypoxia-induced neovessels but negatively impact retinal neurons and normal vessels. Emerging evidence suggests that metabolic disturbance is a significant and underexplored risk factor in the disease pathogenesis. Hyperglycemia and dyslipidemia correlate with the retinal neurovascular dysfunction in infants born prematurely. Nutritional and hormonal supplementation relieve metabolic stress and improve retinal maturation. Here we focus on the mechanisms through which metabolism is involved in preterm-birth-related retinal disorder from clinical and experimental investigations. We will review and discuss potential therapeutic targets through the restoration of metabolic responses to prevent disease development and progression.

Oxytocin stimulates lipolysis, prostaglandin E2 synthesis, and leptin secretion in 3T3-L1 adipocytes

A model of oxytocin in the regulation of metabolic status has described one of oxytocin synthesis and release from the neurohypophysis in response to leptin, to suppress further leptin release. In addition, a lipogenic role for oxytocin has been suggested, consistent with an insulinergic action. This model, however, may be incorrect. Oxytocin reduces fat mass in the absence of either leptin or leptin receptor signalling, thereby challenging the interdependence between leptin and oxytocin. An oxytocin induced production of the anti-lipolytic prostaglandin E₂ (PGE₂) might account for this. Media from 3T3-L1 differentiated adipocytes treated with oxytocin (0-50 nmol.L^-1) for 24 hrs were assayed for PGE₂, leptin, adiponectin, and glycerol. Harvested cells were analysed for lipid droplet triglyceride and cytosolic free fatty acid (FFA) by flow cytometry, and for altered expression of lipolytic and lipogenic associated gene ontology transcripts by cDNA array. Both PGE₂ and leptin secretion were significantly increased by oxytocin treatment whilst adiponectin secretion was not. A significant increase in cytosolic FFA was detected following oxytocin treatment, similar to that determined following treatment with isoproterenol (positive control). A significant increase in glycerol release to the culture media confirmed a lipolytic effect. No enrichment of lipolytic and lipogenic associated gene ontology transcripts was determined, but significant overrepresentation of chemosensory olfactory transcripts was. In conclusion, oxytocin stimulates lipolysis in 3T3-L1 adipocytes, mediated by autocrine/paracrine actions of PGE₂ and leptin. To confirm that this response is mediated solely by the oxytocin receptor, further experiments would require those effects being blocked by a specific oxytocin antagonist.

Maternal Supplementation with Polyphenols and Omega-3 Fatty Acids during Pregnancy: Prenatal Effects on Growth and Metabolism

Simple Summary

The present study aimed to determine benefits and risks of a dietary supplementation combining hydroxytyrosol and n-3 polyunsaturated fatty acids (PUFA) on prenatal development and metabolic traits in swine, a model of intrauterine growth restricted (IUGR) pregnancies. No effects were found regarding sows’ weight and adiposity. Treated sows had larger litters, with smaller fetuses. However, these animals had better development of some major organs. Fetuses from the treated group had better glycemic and lipidic indexes, but no effects on anti/prooxidant profiles were found.

Abstract

Maternal supplementation with antioxidants and n-3 PUFAs may be a promising strategy to reduce the risk of intrauterine growth restriction and preterm delivery, which may diminish the appearance of low-birth-neonates. A previous studies showed beneficial outcomes of the combination of hydroxytyrosol and linoleic acid, but there is no data of its prenatal effects. The present study aimed to determine the possible prenatal implications of such maternal supplementation at prenatal stages in swine, a model of IUGR pregnancies. Results showed effects on litter size, with treated sows having larger litters and, therefore, smaller fetuses. However, the brain/head weight ratio showed a positive effect of the treatment in development, as well as in some other major organs like lungs, spleen, or kidneys. On the other hand, treated piglets showed better glycemic and lipidemic profiles, which could explain postnatal effects. However, further research on the implications of the treatment on litter size and prenatal and postnatal development must be done before practical recommendation can be given.

Non-target metabolomic analysis reveals the therapeutic effect of Saposhnikovia divaricata decoction on collagen-induced arthritis rats

ETHNOPHARMACOLOGICAL RELEVANCE

Saposhnikovia divaricata (SD), a Chinese crude drug, has long been recognized for therapeutic effect to rheumatoid arthritis (RA). At present, the mechanisms of SD treatment in RA have not been fully understood especially on the perspective of metabolomics.

AIM OF THE STUDY

To study the pharmacodynamic effects of Saposhnikovia divaricata decoction on CIA rats, and explore the therapeutic mechanism by metabolomics methods.

MATERIALS AND METHODS

Wistar rats were randomly divided into normal group, CIA model group, dexamethasone group and SD decoction groups (10 g crude drug/kg, 5 g crude drug/kg and 2.5 g crude drug/kg of SDD). Body weight, arthritis scores, serum cytokine levels and histopathological parameters of rats were assessed. A metabolomics method based on ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOFMS) was established to collect the metabolic profiles of rats and explore the metabolic changes that occurred after SDD treatment.

RESULTS

SDD showed its protective effect on the affected joints, especially in the middle dosage group of SDD. Eighteen and 13 potential biomarkers for the SDD treatment of CIA rats were identified in the plasma and urine, respectively. SDD could regulate the disturbed metabolic pathways including tryptophan metabolism, glycerophospholipid catabolism, primary bile acid biosynthesis and fatty acid metabolism.

CONCLUSIONS

In summary, SDD treatment could effectively alleviate symptoms of RA and regulate metabolic disorders in CIA rats.

Maternal Supplementation with Polyphenols and Omega-3 Fatty Acids during Pregnancy: Effects on Growth, Metabolism, and Body Composition of the Offspring

Simple Summary

The present study aimed to determine benefits and risks of a dietary supplementation combining hydroxytyrosol and n3 polyunsaturated fatty acids (PUFA) on developmental patterns and metabolic traits of offspring in swine, a model of intrauterine growth restricted (IUGR) pregnancies. There were no deleterious effects on the reproductive traits of the sows and the postnatal features of the piglets. Piglets from the supplemented sows, in spite of a lower mean weight and corpulence at birth, showed higher average daily weight gain and fractional growth rate afterwards. Consequently, they reached higher weight and corpulence with increased muscle development and better lipidemic and fatty acids profiles than control offspring at juvenile stages.

Abstract

Maternal supplementation with antioxidants and n3 PUFAs may be a promising strategy to reduce the risk of intrauterine growth restriction and preterm delivery, which may diminish the appearance of low-birth-weight neonates. The present study aimed to determine benefits and risks of a dietary supplementation combining hydroxytyrosol, a polyphenol from olive leaves and fruits, and n3 PUFAs, from linseed oil, on developmental patterns and metabolic traits of offspring in swine, a model of IUGR pregnancies. The results obtained indicate that maternal supplementation with hydroxytyrosol and n-3 fatty acids during pregnancy has no deleterious effects on the reproductive traits of the sows (prolificacy, homogeneity of the litter, and percentage of stillborns and low-birth-weight, LBW, piglets) and the postnatal features of the piglets (growth patterns, adiposity, and metabolic traits). Conversely, in spite of a lower mean weight and corpulence at birth, piglets from the supplemented sows showed higher average daily weight gain and fractional growth rate. Thus, at juvenile stages afterwards, the offspring from the treated group reached higher weight and corpulence, with increased muscle development and better lipidemic and fatty acid profiles, in spite of similar adiposity, than offspring in the control group. However, much caution and more research are still needed before practical recommendation and use in human pregnancies.

n-3 polyunsaturated fatty acids regulate chemerin in cultured adipocytes: role of GPR120 and derived lipid mediators

Chemerin is a pro-inflammatory adipokine that is increased in obesity and associated with obesity-related comorbidities. The aim of this study was to investigate the effects of omega-3 polyunsaturated fatty acids, eicosapentaenoic and docosahexaenoic acids (EPA and DHA), on basal and tumor necrosis factor-α (TNF-α)-induced chemerin production in 3T3-L1 and human subcutaneous cultured adipocytes. The potential involvement of G protein-coupled receptor 120 (GPR120), as well as the actions of DHA-derived specialized proresolving lipid mediators (SPMs), resolvin D1 and D2 (RvD1 and RvD2) and maresin 1 (MaR1), were also evaluated. DHA significantly lowered both basal and TNF-α-stimulated chemerin production in 3T3-L1 and human adipocytes. EPA did not modify basal chemerin production, while it attenuated the induction of chemerin by TNF-α. Silencing of GPR120 using siRNA blocked the ability of DHA and EPA to reduce TNF-α-induced chemerin secretion. Interestingly, treatment with the DHA-derived SPMs RvD1, RvD2 and MaR1 also reversed the stimulatory effect of TNF-α on chemerin production in human adipocytes.

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.

DHA Modulates Immune Response and Mitochondrial Function of Atlantic Salmon Adipocytes after LPS Treatment

Adipocytes play a central role in overall energy homeostasis and are important contributors to the immune system. Fatty acids (FAs) act as signaling molecules capable to modulate adipocyte metabolism and functions. To identify the effects of two commonly used FAs in Atlantic salmon diets, primary adipocytes were cultured in the presence of oleic (OA) or docosahexaenoic (DHA) acid. DHA decreased adipocyte lipid droplet number and area compared to OA. The increase in lipid load in OA treated adipocytes was paralleled by an increase in iNOS activity and mitochondrial SOD2-GFP activity, which was probably directed to counteract increase in oxidative stress. Under lipopolysaccharide (LPS)-induced inflammation, DHA had a greater anti-inflammatory effect than OA, as evidenced by the higher SOD2 activity and the transcriptional regulation of antioxidant enzymes and pro- and anti-inflammatory markers. In addition, DHA maintained a healthy mitochondrial structure under induced inflammation while OA led to elongated mitochondria with a thin thread like structures in adipocytes exposed to LPS. Overall, DHA possess anti-inflammatory properties and protects Atlantic salmon against oxidative stress and limits lipid deposition. Furthermore, DHA plays a key role in protecting mitochondria shape and function.

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.

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

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

Docosahexaenoic acid-flurbiprofen combination ameliorates metaflammation in rats fed on high-carbohydrate high-fat diet

OBJECTIVE

Potential benefits of combining docosahexaenoic acid (DHA), an omega-3 fatty acid with flurbiprofen (Flu), a non-steroidal anti-inflammatory drug in ameliorating obesity remain to be elucidated. This study aimed to investigate the possible protective effects of DHA and Flu, either alone or in combination, against obesity-induced metaflammation and to clarify the underlying molecular mechanisms.

METHODS

Seventy-five male Wistar rats were divided into five groups: normal diet (ND) group, high-carbohydrate high-fat diet (HCHFD) control group, DHA group (HCHFD + 200 mg/kg DHA), Flu group (HCHFD + 10 mg/kg Flu), and DHA + Flu group (HCHFD + DHA + Flu). Treatments were administered orally daily for 8 consecutive weeks, parallel with the start of diets.

RESULTS

Plasma levels of glucose, insulin, and TGs were significantly reduced in DHA, Flu, and DHA + Flu treated groups, while HDL-C concentrations were significantly elevated in the same groups, compared to HCHFD control group. Only Flu and DHA + Flu groups showed a significant decrease in plasma levels of leptin, TC, and LDL-C, relative to HCHFD control group. Concentrations of phosphorylated adenosine monophosphate-activated protein kinase (pAMPK) and resolvin D1 (RvD1) in epididymal adipose tissue (EAT) were significantly increased in the three treated groups, compared with HCHFD control group. Expression of AMPK-α₁ subunit in EAT was significantly increased, whereas expression of nuclear factor kappa B (NF-κB) was significantly decreased in EAT of the three treated groups, relative to HCHFD control group.

CONCLUSIONS

Docosahexaenoic acid-flurbiprofen combination showed an ameliorative effect on obesity-associated metaflammation and its consequences in rats.

Science behind the cardio-metabolic benefits of omega-3 polyunsaturated fatty acids: biochemical effects vs. clinical outcomes

Lower incidence of cardiovascular disease (CVD) in the Greenland Inuit, Northern Canada and Japan has been attributed to their consumption of seafood rich in long chain omega-3 polyunsaturated fatty acids (LCn-3PUFA). While a large majority of pre-clinical and intervention trials have demonstrated heart health benefits of LCn-3PUFA, some studies have shown no effects or even negative effects. LCn-3PUFA have been shown to favourably modulate blood lipid levels, particularly a reduction in circulating levels of triglycerides. High density lipoprotein-cholesterol (HDL-C) levels are elevated following dietary supplementation with LCn-3PUFA. Although LCn-3PUFA have been shown to increase low-density lipoprotein-cholesterol (LDL-C) levels, the increase is primarily in the large-buoyant particles that are less atherogenic than small-dense LDL particles. The anti-inflammatory effects of LCn-3PUFA have been clearly outlined with inhibition of NFkB mediated cytokine production being the main mechanism. In addition, reduction in adhesion molecules (intercellular adhesion molecule, ICAM and vascular cell adhesion molecule 1, VCAM-1) and leukotriene production have also been demonstrated following LCn-3PUFA supplementation. Anti-aggregatory effects of LCn-3PUFA have been a subject of controversy, however, recent studies showing sex-specific effects on platelet aggregation have helped resolve the effects on hyperactive platelets. Improvements in endothelium function, blood flow and blood pressure after LCn-3PUFA supplementation add to the mechanistic explanation on their cardio-protective effects. Modulation of adipose tissue secretions including pro-inflammatory mediators and adipokines by LCn-3PUFA has re-ignited interest in their cardiovascular health benefits. The aim of this narrative review is to filter out the reasons for possible disparity between cohort, mechanistic, pre-clinical and clinical studies. The focus of the article is to provide possible explanation for the observed controversies surrounding heart health benefits of LCn-3PUFA.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Immunomodulatory Activity of Docosahexenoic Acid on RAW264.7 Cells Activation through GPR120-Mediated Signaling Pathway

In this study, we elucidated the immunomodulatory activity of docosahexaenoic acid (DHA) on protein expression in RAW264.7 cells and its molecular mechanism. The results showed that the proliferation index of RAW264.7 cells at 48 h was about 173.03 ± 7.82% after the treatment of 2.4 μM DHA. DHA could activate RAW264.7 cells by the G-protein coupled cell membrane receptor GPR120-C-Raf- mitogen-activated protein kinases (MAPKs)-nuclear factor κB (NF-κB) p65 pathway. In addition, 2.4 μM of DHA could significantly increase (P < 0.01) the mRNA and protein expression of inducible nitric oxide synthase (iNOS), which is consistent with the result of the NO release. ELISA results revealed that DHA could enhance the protein expression of cytokines IL-1β, IL-6, IL-10, IL-12, TNF-α, IFN-γ, and TGF-β. These results indicated that the immunomodulatory mechanism of RAW264.7 cells by DHA was associated with the release of NO and cytokines by stimulating the GPR120, C-Raf, and MAPKs to the NF-κB p65 pathway.

Comparison of Fatty Acid and Gene Profiles in Skeletal Muscle in Normal and Obese C57BL/6J Mice before and after Blunt Muscle Injury

Injury and obesity are two major health burdens affecting millions of people worldwide. Obesity is recognized as a state of chronic inflammation accompanied by various co-morbidities like T2D or cardiovascular diseases. There is increasing evidence that obesity impairs muscle regeneration, which is mainly due to chronic inflammation and to excessive accumulation of lipids in adipose and non-adipose tissue. To compare fatty acid profiles and changes in gene expression at different time points after muscle injury, we used an established drop tower-based model with a defined force input to damage the extensor iliotibialis anticus on the left hind limb of female C57BL/6J mice of normal weight and obese mice. Although most changes in fatty acid content in muscle tissue are diet related, levels of eicosaenoic (normal weight) and DHG-linolenic acid (obese) in the phospholipid and docosahexaenoic acid (normal weight) in the triglyceride fraction are altered after injury. Furthermore, changes in gene transcription were detected in 3829 genes in muscles of normal weight mice, whereas only 287 genes were altered in muscles of obese mice after trauma. Alterations were found within several pathways, among them notch-signaling, insulin-signaling, sonic hedgehog-signaling, apoptosis related pathways, fat metabolism related cholesterol homeostasis, fatty acid biosynthetic process, fatty acid elongation, and acyl-CoA metabolic process. We could show that genes involved in fat metabolism are affected 3 days after trauma induction mostly in normal weight but not in obese mice. The strongest effects were observed in normal weight mice for Alox5ap, the activating protein for leukotriene synthesis, and Apobec1, an enzyme substantial for LDL synthesis. In summary, we show that obesity changes the fat content of skeletal muscle and generally shows a negative impact upon blunt muscle injury on various cellular processes, among them fatty acid related metabolism, notch-, insulin-, sonic hedgehog-signaling, and apoptosis.

A diet supplemented with n-3 polyunsaturated fatty acids influences the metabomscic and endocrine response of rabbit does and their offspring

The aim of the present study was to evaluate the productive, endocrine, and metabomscic responses as well as oxidative stress of rabbit does and their offspring when fed a diet supplemented with -3 PUFA during their first productive cycle. To this aim, a total of 105 rabbit does were fed ad mscibitum from d 60 to 172 of age 2 isoenergetic and isoproteic diets differing in fatty acid composition. The control diet ( = 52 does) contained 45.9 g/kg of -3 of the total fatty acids and the enriched diet ( = 53 does) contained 149.2 g/kg of -3 of the total fatty acids. Both experimental groups had similar feed intake during rearing, pregnancy, and lactation. The enrichment of diet had no effect on ultrasonographic assessment of does on d 9 and 16 of pregnancy, with an embryonic vesicle number and fetus and placenta size similar between groups ( > 0.05). Even though there were no major effects ( > 0.05) on fertimscity, duration of gestation, and number born amscive and stillborn kits at parturition, mscive kits from enriched does were longer (71.6 ± 2.42 vs. 79.5 ± 2.13 mm; < 0.05) and tended to be heavier (42.5 ± 3.94 vs. 50.8 ± 3.47 g; = 0.07) than those from control does ( < 0.05). The 2 groups had similar milk production and mortamscity values during lactation; consequently, there were no differences between diets in ADG, mscitter weight, and number of weaned kits ( > 0.05). In enriched does, higher plasma leptin and estradiol concentrations than in control does ( < 0.05) were observed. In addition, enriched females also had lower total and high-density mscipoprotein cholesterol (HDL-c) than control females during lactation ( < 0.05). Regarding offspring, the enrichment of diet with PUFA caused a hypermscipidemic status (greater values of plasma triglycerides, total cholesterol, and HDL-c; < 0.05) at 1 d postpartum (dpp), compared with the control group, that disappeared at 32 dpp. Supplemented does before parturition and their offspring at 1 dpp had greater oxidative stress than those in the control group. In conclusion, an increase of -3 PUFA concentration in the diet of rabbit does and, consequently, of their offspring during a productive cycle alters their mscipid profile and the indicators of oxidative stress, without major endocrine modifications or improvements in the productive variables.

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.

Eicosapentaenoic acid (EPA) vs. Docosahexaenoic acid (DHA): Effects in epididymal white adipose tissue of mice fed a high-fructose diet

BACKGROUND

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been demonstrated to be beneficial for many diseases, including those associated with the metabolic syndrome (e.g. insulin resistance and hypertension). Nevertheless, not only their actions are not entirely understood, but also their only effects were not yet elucidated. Therefore, we aimed to compare the effects of EPA and DHA, alone or in combination, on the epididymal white adipose tissue (WAT) metabolism in mice fed a high-fructose diet.

METHODS

3-mo-old C57Bl/6 mice were fed a control diet (C) or a high-fructose diet (HFru). After three weeks on the diets, the HFru group was subdivided into four new groups for another five weeks: HFru, HFru+EPA, HFru+DHA, and HFru-EPA+DHA (n=10/group). Besides evaluating biometric and metabolic parameters of the animals, we measured the adipocyte area and performed molecular analyses (inflammation and lipolysis) in the epididymal WAT.

RESULTS

The HFru group showed adipocyte hypertrophy, inflammation, and uncontrolled lipolysis. The treated animals showed a reversion of adipocyte hypertrophy, inhibition of inflammation with activation of anti-inflammatory mediators, and regularization of lipolysis. Overall, the beneficial effects were more marked with DHA than EPA.

CONCLUSION

Although the whole-body metabolic effects were similar between EPA and DHA, DHA appeared to be the central actor in WAT metabolism, modulating pro and anti-inflammatory pathways and alleviating adipocytes abnormalities. Therefore, when considering fructose-induced adverse effects in WAT, the most prominent actions were observed with DHA.

Long-chain polyunsaturated fatty acids amend palmitate-induced inflammation and insulin resistance in mouse C2C12 myotubes

Intramuscular lipid accumulation results in inflammation, which is correlated with impaired insulin action in the skeletal muscle, an important organ for glucose uptake in the body. In this study, we explored the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), arachidonic acid (AA), and long-chain polyunsaturated fatty acids (PUFAs) on palmitic acid (PA)-induced inflammatory responses and insulin resistance in C2C12 myotubes. The mRNA expression of the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-α in PA-treated myotubes was suppressed by these three test long-chain PUFAs. Moreover, the addition of long-chain PUFAs decreased PA-induced insulin resistance as evidenced by increases in phosphorylated AKT and glucose uptake. In PA-treated myotubes, long-chain PUFAs improved glucose transporter 4 expression, basal glucose uptake without insulin, and the AMP-activated protein kinase pathway. Of note, the long-chain PUFAs obstructed the effects of PA on the activation of extracellular-signal-regulated kinase and protein kinase C-θ as well as nuclear factor-κB (NF-κB) and activator protein-1. The inhibitory effect of AA but not of DHA and EPA on PA-induced inflammation and impaired insulin action was cancelled in C2C12 myotubes transfected with a constitutively active mutant IκB kinase-β plasmid. These data suggest that long-chain PUFAs may be useful in the management of PA-induced inflammation and insulin resistance in myotubes. In addition to the NF-κB pathway, other mechanisms are involved in the health benefits of DHA and EPA in PA-treated myotubes.

Review: adiponectin in retinopathy

Neovascular eye diseases are a major cause of blindness including retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration in which new vessel formation is driven by hypoxia or metabolic abnormalities affecting the fuel supply. White-adipose-tissue derived adipokines such as adiponectin modulate metabolic responses. Increasing evidence shows that lack of adiponectin may result in retinal neovascularization. Activation of the adiponectin pathway may in turn restore energy metabolism, to suppress the drive for compensatory but ultimately pathological neovessels of retinopathy. In this review, we will summarize our current knowledge of the role of adiponectin in eye diseases of premature infants, diabetic patients as well as the elderly. Further investigations in this field are likely to lead to new preventative approaches for these diseases.

Reduction of circulating FABP4 level by treatment with omega-3 fatty acid ethyl esters

Background

Fatty acid-binding protein 4 (FABP4/A-FABP/aP2) mainly expressed in adipocytes is secreted and acts as an adipokine. Increased circulating FABP4 level is associated with obesity, insulin resistance and atherosclerosis. However, little is known about the modulation of serum FABP4 level by drugs including anti-dyslipidemic agents.

Methods

Patients with dyslipidemia were treated with omega-3 fatty acid ethyl esters (4 g/day; n = 14) containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 4 weeks. Serum FABP4 level was measured before and after treatment. Expression and secretion of FABP4 were also examined in mouse 3T3-L1 adipocytes treated with EPA or DHA.

Results

Treatment with omega-3 fatty acid ethyl esters significantly decreased triglycerides and serum FABP4 level (13.5 ± 1.5 vs. 11.5 ± 1.1 ng/ml, P = 0.017). Change in FABP4 level by omega-3 fatty acids was negatively correlated with change in levels of EPA + DHA (r = −0.643, P = 0.013), EPA (r = −0.540, P = 0.046) and DHA (r = −0.650, P = 0.011) but not change in the level of triglycerides or other fatty acid composition. Treatment of 3T3-L1 adipocytes with EPA or DHA had no effect on short-term (2 h) secretion of FABP4. However, gene expression and long-term (24 h) secretion of FABP4 were significantly reduced by treatment with EPA or DHA.

Conclusions

Omega-3 fatty acids decrease circulating FABP4 level, possibly by reducing expression and consecutive secretion of FABP4 in adipocytes. Reducing FABP4 level might be involved in suppression of cardiovascular events by omega-3 fatty acids.

Targeting inflammation in metabolic syndrome

The metabolic syndrome (MetS) is comprised of a cluster of closely related risk factors, including visceral adiposity, insulin resistance, hypertension, high triglyceride, and low high-density lipoprotein cholesterol; all of which increase the risk for the development of type 2 diabetes and cardiovascular disease. A chronic state of inflammation appears to be a central mechanism underlying the pathophysiology of insulin resistance and MetS. In this review, we summarize recent research which has provided insight into the mechanisms by which inflammation underlies the pathophysiology of the individual components of MetS including visceral adiposity, hyperglycemia and insulin resistance, dyslipidemia, and hypertension. On the basis of these mechanisms, we summarize therapeutic modalities to target inflammation in the MetS and its individual components. Current therapeutic modalities can modulate the individual components of MetS and have a direct anti-inflammatory effect. Lifestyle modifications including exercise, weight loss, and diets high in fruits, vegetables, fiber, whole grains, and low-fat dairy and low in saturated fat and glucose are recommended as a first line therapy. The Mediterranean and dietary approaches to stop hypertension diets are especially beneficial and have been shown to prevent development of MetS. Moreover, the Mediterranean diet has been associated with reductions in total and cardiovascular mortality. Omega-3 fatty acids and peroxisome proliferator-activated receptor α agonists lower high levels of triglyceride; their role in targeting inflammation is reviewed. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone blockers comprise pharmacologic therapies for hypertension but also target other aspects of MetS including inflammation. Statin drugs target many of the underlying inflammatory pathways involved in MetS.

Borage oil supplementation decreases lipopolysaccharide-induced inflammation and skeletal muscle wasting in mice

Schematic outline of the proposed mechanism by which borage oil supplementation prevented LPS-induced inflammation and skeletal muscle wasting in mice.

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.

Fasting and postprandial regulation of the intracellular localization of adiponectin and of adipokines secretion by dietary fat in rats

Background/Objective:

Dietary fat sources modulate fasting serum concentration of adipokines, particularly adiponectin. However, previous studies utilized obese animals in which adipose tissue function is severely altered. Thus, the present study aimed to assess the postprandial regulation of adipokine secretion in nonobese rats that consumed high-fat diet (HFD) composed of different types of fat for a short time.

Methods:

The rats were fed a control diet or a HFD containing coconut, safflower or soybean oil (rich in saturated fatty acid, monounsaturated fatty acid or polyunsaturated fatty acid, respectively) for 21 days. The serum concentrations of adiponectin, leptin, retinol, retinol-binding protein-4 (RBP-4), visfatin and resistin were determined at fasting and after refeeding. Adiponectin multimerization and intracellular localization, as well as the expression of endoplasmic reticulum (ER) chaperones and transcriptional regulators, were evaluated in epididymal white adipose tissue.

Results:

In HFD-fed rats, serum adiponectin was significantly decreased 30 min after refeeding. With coconut oil, all three multimeric forms were reduced; with safflower oil, only the high-molecular-weight (HMW) and medium-molecular-weight (MMW) forms were decreased; and with soybean oil, only the HMW form was diminished. These reductions were due not to modifications in mRNA abundance or adiponectin multimerization but rather to an increment in intracellular localization at the ER and plasma membrane. Thus, when rats consumed a HFD, the type of dietary fat differentially affected the abundance of endoplasmic reticulum resident protein 44 kDa (ERp44), sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor-γ (PPARγ) mRNAs, all of which are involved in the post-translational processing of adiponectin required for its secretion.

Leptin, RBP-4, resistin and visfatin serum concentrations did not change during fasting, whereas modest alterations were observed after refeeding.

Conclusions:

The short-term consumption of a HFD affected adiponectin localization in adipose tissue, thereby decreasing its secretion to a different magnitude depending on the dietary fat source. Evaluating the fasting serum concentration of adipokines was not sufficient to identify alterations in their secretion, whereas postprandial values provided additional information as dynamic indicators.

Ocular Surface and Tear Film Changes in Older Women Working with Computers

The aim of this work is to investigate changes in the ocular surface (OS) and tear film (TF) by means of questionnaire-based subjective symptoms, TF break-up time, Schirmer test, and TF analysis in women working with computers and to analyze the effects of the oral supplementation with antioxidants/omega 3 fatty acids (A/ω3) in the OS outcomes. Women aged 40–65 years (n = 148) were recruited at the Administrative Offices of Valencia (Spain) and distributed into two age groups, 40–52 years (AGE1; n = 87) and 53–65 years (AGE2; n = 61), and then subdivided according to being (or not) computer users (CUG; NCUG) during the workday. Homogeneous subgroups were randomly assigned (or not) to the daily intake of three pills of A/ω3 for three months. At baseline and at the end of follow-up, personalized interviews and ocular examination were done. Reflex tear samples were collected from the inferior meniscus and processed for a multiplexed particle-based flow cytometry assay to measure proinflammatory molecules. Statistics were performed using the SPSS 15.0 program. The OS pathology was clinically evident in the AGE1-CUG (33%) versus the AGE2-CUG (64%) of women. Significantly higher interleukins-1β and -6 tear levels were found in the AGE1 versus the AGE2 women employees (P = 0.006 and P = 0.001, resp.), as well as in the CUG versus the NCUG (P = 0.001 and P = 0.000, resp.). Supplementation with A/ω3 positively influenced the OS pathology as manifested by the amelioration of the clinical signs/symptoms related to computer uses. Strategies involving a safe environment and oral micronutrient supplements may be managed within eye-care standards in older women.

LipiD-QuanT: a novel method to quantify lipid accumulation in live cells

Lipid droplets (LDs) are the main storage organelles for triglycerides. Elucidation of lipid accumulation mechanisms and metabolism are essential to understand obesity and associated diseases. Adipogenesis has been well studied in murine 3T3-L1 and human Simpson-Golabi-Behmel syndrome (SGBS) preadipocyte cell lines. However, most techniques for measuring LD accumulation are either not quantitative or can be destructive to samples. Here, we describe a novel, label-free LD quantification technique (LipiD-QuanT) to monitor lipid dynamics based on automated image analysis of phase contrast microscopy images acquired during in vitro human adipogenesis. We have applied LipiD-QuanT to measure LD accumulation during differentiation of SGBS cells. We demonstrate that LipiD-QuanT is a robust, nondestructive, time- and cost-effective method compared with other triglyceride accumulation assays based on enzymatic digest or lipophilic staining. Further, we applied LipiD-QuanT to measure the effect of four potential pro- or antiobesogenic substances: DHA, rosiglitazone, elevated levels of D-glucose, and zinc oxide nanoparticles. Our results revealed that 2 µmol/l rosiglitazone treatment during adipogenesis reduced lipid production and caused a negative shift in LD diameter size distribution, but the other treatments showed no effect under the conditions used here.

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.

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.

Leptin signaling as a therapeutic target of obesity

INTRODUCTION

Leptin is a hormone with a key role in food intake and body weight homeostasis. Congenital leptin deficiency (CLD) is a rare disease that causes hyperphagia and early severe obesity. However, common obesity conditions are associated with hyperleptinemia and leptin resistance.

AREAS COVERED

The main signaling pathways activated by leptin as well as the mechanisms underlying the regulatory actions of leptin on food intake and on lipid and glucose metabolism are reviewed. The potential mechanisms involving leptin resistance and the main regulatory hormonal and nutritional factors controlling leptin production/functions are also analyzed. The pathophysiology of leptin in human obesity, and especially the trials analyzing effects of leptin replacement therapy in patients with CLD or in subjects with common obesity and in post-obese weight-reduced subjects are also summarized.

EXPERT OPINION

The use of drugs or specific bioactive food components with anti-inflammatory properties to reduce the inflammatory state associated with obesity, especially at the hypothalamus, may help to overcome leptin resistance. Research should also be focused on investigating dietary strategies, food supplements or drugs capable of avoiding or reversing the leptin fall during weight management, in order to promote sustained body weight lowering and weight loss maintenance.