Eicosapentaenoic acid and rosiglitazone increase adiponectin in an additive and PPARγ-dependent manner in human adipocytes

Targeting Lipid Metabolism in Obese Asthma: Perspectives and Therapeutic Opportunities

BACKGROUND

Obese asthma represents a unique phenotype of asthma characterized by severe symptoms, poor medication controls, increased frequency of exacerbations, and an overall diminished quality of life. Numerous factors, including the complex interactions between environment, mechanical processes, inflammatory responses, and metabolites disturbance, contribute to the onset of obese asthma.

SUMMARY

Notably, multiple metabolomics studies in the last several years have revealed the significant abnormalities in lipid metabolism among obese asthmatic patients. Several bioactive lipid messengers participate in the development of obese asthma has also been observed. Here, we present and discuss the latest advances regarding how bioactive lipid molecules contribute to the pathogenic process and mechanisms underlying obese asthma. The key roles of potentially significant effector cells and the pathways by which they respond to diverse lipid metabolites are also described. We finally summarize current lipid-related therapeutic options for the treatment of obese asthma and discuss their application prospects.

KEY MESSAGES

This review underscores the impacts of abnormal lipid metabolism in the etiopathogenesis of obese asthma and asks for further investigation to elucidate the intricate correlations among lipids, obesity, and asthma.

Therapeutic potential of adiponectin in prediabetes: strategies, challenges, and future directions

Adiponectin, an adipose-derived hormone, plays a pivotal role in glucose regulation and lipid metabolism, with a decrease in circulating adiponectin levels being linked to insulin resistance and prediabetes. This review examines the therapeutic potential of adiponectin in managing prediabetes, elucidating on multiple aspects including its role in glucose and lipid metabolism, influence on insulin sensitivity, and anti-inflammatory properties. Moreover, the paper highlights the latest strategies to augment adiponectin levels, such as gene therapy, pharmacological interventions, dietary modifications, and lifestyle changes. It also addresses the challenges encountered in translating preclinical findings into clinical practice, primarily related to drug delivery, safety, and efficacy. Lastly, the review proposes future directions, underlining the need for large-scale human trials, novel adiponectin analogs, and personalized treatment strategies to harness adiponectin's full therapeutic potential in preventing the transition from prediabetes to diabetes.

Variability in the Clinical Effects of the Omega-3 Polyunsaturated Fatty Acids DHA and EPA in Cardiovascular Disease-Possible Causes and Future Considerations

Cardiovascular disease (CVD) that includes myocardial infarction and stroke, is the leading cause of mortality worldwide. Atherosclerosis, the primary underlying cause of CVD, can be controlled by pharmacological and dietary interventions, including n-3 polyunsaturated fatty acid (PUFA) supplementation. n-3 PUFA supplementation, primarily consisting of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has shown promise in reducing atherosclerosis by modulating risk factors, including triglyceride levels and vascular inflammation. n-3 PUFAs act by replacing pro-inflammatory fatty acid types in cell membranes and plasma lipids, by regulating transcription factor activity, and by inducing epigenetic changes. EPA and DHA regulate cellular function through shared and differential molecular mechanisms. Large clinical studies on n-3 PUFAs have reported conflicting findings, causing confusion among the public and health professionals. In this review, we discuss important factors leading to these inconsistencies, in the context of atherosclerosis, including clinical study design and the differential effects of EPA and DHA on cell function. We propose steps to improve clinical and basic experimental study design in order to improve supplement composition optimization. Finally, we propose that understanding the factors underlying the poor response to n-3 PUFAs, and the development of molecular biomarkers for predicting response may help towards a more personalized treatment.

Eicosapentaenoic Acid Induces the Inhibition of Adipogenesis by Reducing the Effect of PPARγ Activator and Mediating PKA Activation and Increased COX-2 Expression in 3T3-L1 Cells at the Differentiation Stage

Obesity has received increasing attention in recent years because it is a factor in the development of non-communicable diseases. The current study aimed to analyze how representative fatty acids (FAs) such as palmitic acid, stearic acid, oleic acid, α-linolenic acid (ALA), and eicosapentaenoic acid (EPA) affected adipogenesis when/if introduced at the differentiation stage of 3T3-L1 cell culture. These FAs are assumed to be potentially relevant to the progression or prevention of obesity. EPA added during the differentiation stage reduced intracellular triacylglycerol (TAG) accumulation, as well as the expression of the established adipocyte-specific marker genes, during the maturation stage. However, no other FAs inhibited intracellular TAG accumulation. Coexistence of Δ12-prostaglandin J2, a peroxisome proliferator-activated receptor γ activator, with EPA during the differentiation stage partially attenuated the inhibitory effect of EPA on intracellular TAG accumulation. EPA increased cyclooxygenase-2 (COX-2) expression and protein kinase A (PKA) activity at the differentiation stage, which could explain the inhibitory actions of EPA. Taken together, exposure of preadipocytes to EPA only during the differentiation stage may be sufficient to finally reduce the mass of white adipose tissue through increasing COX-2 expression and PKA activity.

Chronic docosahexaenoic acid supplementation improves metabolic plasticity in subcutaneous adipose tissue of aged obese female mice

This study aimed to characterize the potential beneficial effects of chronic docosahexaenoic acid (DHA) supplementation on restoring subcutaneous white adipose tissue (scWAT) plasticity in obese aged female mice. Two-month-old female C57BL/6J mice received a control (CT) or a high fat diet (HFD) for 4 months. Then, 6-month-old diet-induced obese (DIO) mice were distributed into the DIO and the DIOMEG group (fed with a DHA-enriched HFD) up to 18 months. In scWAT, the DHA-enriched diet reduced the mean adipocyte size and reversed the upregulation of lipogenic genes induced by the HFD, reaching values even lower than those observed in CT animals. DIO mice exhibited an up-regulation of lipolytic and fatty oxidation gene expressions that was reversed in DHA-supplemented mice except for Cpt1a mRNA levels, which were higher in DIOMEG as compared to CT mice. DHA restored the increase of proinflammatory genes observed in scWAT of DIO mice. While no changes were observed in total macrophage F4/80+/CD11b+ content, the DHA treatment switched scWAT macrophages profile by reducing the M1 marker Cd11c and increasing the M2 marker CD206. These events occurred alongside with a stimulation of beige adipocyte specific genes, the restoration of UCP1 and pAKT/AKT ratio, and a recovery of the HFD-induced Fgf21 upregulation. In summary, DHA supplementation induced a metabolic remodeling of scWAT to a healthier phenotype in aged obese mice by modulating genes controlling lipid accumulation in adipocytes, reducing the inflammatory status, and inducing beige adipocyte markers in obese aged mice.

Celecoxib-mediated attenuation of non-alcoholic steatohepatitis is potentially relevant to redistributing the expression of adiponectin receptors in rats

Pharmacological inhibition of cyclooxygenase-2 (COX-2) activity ameliorated the severity of non-alcoholic steatohepatitis (NASH) rats. It is not completely understood that the role of COX-2 inhibitor celecoxib on adiponectin receptors (Adipo-R1/R2) expression in different tissues in NASH rats. Sprague-Dawley male NASH rats induced by a high-fat diet (HFD) were administrated with or without celecoxib for 8 weeks. Biochemical parameters of liver function, glucose, and lipid metabolism, and the levels of adiponectin, tumor necrosis factor-alpha (TNF-α), prostaglandin E₂ (PGE₂) in the serum or liver were collected according to the standard protocols. The mRNA and protein levels of Adipo-R1, Adipo-R2, and COX-2 in the liver, muscle, and visceral fat were performed by quantitative real-time polymerase chain reaction (q-PCR) and Western blot analysis, respectively. The results showed that celecoxib ameliorated the various clinical indicators and pathological characteristics in the NASH rats, including body weight, liver function, liver index, and redox activities in serum and hepatic samples. The serum concentrations of adiponectin and TNF-α and PGE₂ were negatively correlated. As expected, these ameliorative effects of celecoxib were associated with the gene and protein levels up-regulation of Adipo-R1, Adipo-R2 in the liver and visceral fat tissues, and seeming to be compensatory down-regulation expression in muscle tissues (P <0.05). Additionally, COX-2 protein expression was negatively correlated with serum adiponectin levels, protein expression of adiponectin receptors from the liver and visceral fat, conversely, positively correlated with those from the muscle. Our current study demonstrate that celecoxib might effectively alleviate NASH rats in a unique manner closely relevant to redistributing the expression of adiponectin receptors in the liver, visceral fat, and muscle. However, the precise molecular mechanism needs further study.

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NASH is a watershed in the progression of NAFLD.

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Finding a therapy for NASH is in urgent need.

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Pharmacological inhibition of COX-2 activity ameliorated the severity of NASH.

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Low-dose celecoxib, a COX-2 inhibitor, can improve NASH by redistributing the expression of adiponectin receptors.

Effect of Eicosapentaenoic Acid Supplementation on Murine Preadipocytes 3T3-L1 Cells Activated with Lipopolysaccharide and/or Tumor Necrosis Factor-α

The beneficial effect of n-3 fatty acids can be related to anti-inflammatory properties. The aim of the study was to analyzed the effect of eicosapentaenoic acid (EPA) on 3T3-L1 cells (murine embryonic fibroblasts‒preadipocytes) activated with inflammatory factors (IF). Cells were incubated with 50 µmol of EPA for 48 h, and then activated with lipopolysaccharide (LPS) or tumor necrosis factor-α (TNF-α). The level of cycloxygenase-2 (Prostaglandin-Endoperoxide Synthase 2, PTGS2, COX-2), cytosolic prostaglandin synthase E2 (cPGES), fatty acid binding protein 4 (FABP4), toll-like receptor 4 (TLR4), glucose receptor type 4 (GLUT-4), and cannabinoid receptor 2 (CB2) was determined using Western blot analysis. The phospholipase A2 (Pla2g4a), and prostaglandin-Endoperoxide Synthase 2 (Ptgs2) gene expression was analyzed by real-time qPCR. After EPA and IF activation, a significant decrease in the COX-2, cPGES, and TRL4 protein levels was observed. Incubation of cells with EPA and IF resulted in a decrease in Ptgs2 and an increase in the Pla2g4a gene. A significant increase in the CB2 protein was observed in adipocytes co-treated with EPA and IF. The results indicated an anti-inflammatory properties of EPA. Interestingly, the activation of the GLUT4 receptor by EPA suggests an unique role of this FA in the regulation of the adipocyte metabolism and prevention of insulin resistance.

Pectic Oligogalacturonide Facilitates the Synthesis and Activation of Adiponectin to Improve Hepatic Lipid Oxidation

SCOPE

Adiponectin (ADPN), a kind of adipokines, plays an important role in the regulation of lipid metabolism. The objective of this study is focused on the ADPN to investigate the functional mechanisms of pectin oligosaccharide (POS) from hawthorn fruit in the improvement of hepatic fatty acid oxidation.

METHOD AND RESULTS

High-fat fed mice are used in this experiment. POS is administrated with the doses of 0.25, 0.75, and 1.5 g kg^-1 diet, respectively. The results demonstrate that gene and protein expressions of ADPN synthesis regulators involved in PKA/ERK/CREB and C/EBPα/PPARγ pathways are upregulated by POS administration. POS also activates the AdiopR1/AMPKα/PGC1 and AdipoR2/PPARα signaling pathways to improve the fatty acid oxidation in the liver, which is further accelerated by the enhancement of mitochondrial functions.

CONCLUSION

POS can act as an ADPN activator to improve lipid metabolism, leading it to the applications of biomedical and functional foods for ameliorating chronic liver diseases resulted from a high-energy diet.

Effect of omega-3 fatty acids supplementation on adipokines: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Although a large body of literature reported the beneficial effects of omega-3 fatty acids (omega-3 FAs) consumption on adipokines levels, but recent findings from clinical trials are not univocal. The aim of this systematic review and meta-analysis was to evaluate the effect of omega-3 FAs supplements on adipokines.

METHODS

We searched Medline, Web of Science, Scopus, Embase, and Cochrane Library from inception to August 2020 without any particular language limitations. Outcomes were summarized as standardized mean difference (SMD) with 95% confidence intervals (CIs) estimated from Hedge's g and random effects modeling.

RESULTS

Fifty-two trials involving 4,568 participants were included. Omega-3 FAs intake was associated with a significant increase in plasma adiponectin levels (n = 43; 3,434 participants; SMD: 0.21, 95% CI: 0.04, 0.37; p = 0.01; I²= 80.14%). This meta-analysis indicates that supplementing participants with omega-3 fatty acids more than 2000 mg daily and more than 10 weeks resulted in a significant and more favorable improvement in plasma adiponectin levels. However, omega-3 FAs intake had no significant effect on leptin levels (SMD: -0.02, 95% CI: -0.20, 0.17, I²= 54.13%).

CONCLUSION

The evidence supports a beneficial effect of omega-3 FAs intake on serum adiponectin levels but does not appear to impact on leptin concentrations. Larger well-designed RCTs are still required to evaluate the effect of omega-3 FAs on leptin in specific diseases.

EPA's pleiotropic mechanisms of action: a narrative review

Treatment with icosapent ethyl 4 g/day, a highly purified and stable ethyl ester of eicosapentaenoic acid (EPA), demonstrated a significant reduction in atherosclerotic cardiovascular disease (ASCVD) events and death in REDUCE-IT. However, analyses of REDUCE-IT and meta-analyses have suggested that this clinical benefit is greater than can be achieved by triglyceride reduction alone. EPA therefore may have additional pleiotropic effects, including anti-inflammatory and anti-aggregatory mechanisms. EPA competes with arachidonic acid for cyclooxygenase and lipoxygenase, producing anti-inflammatory and anti-aggregatory metabolites rather than the more deleterious metabolites associated with arachidonic acid. Changing the EPA:arachidonic acid ratio may shift metabolic status from pro-inflammatory/pro-aggregatory to anti-inflammatory/anti-aggregatory. EPA also has antioxidant effects and increases synthesis of nitric oxide. Incorporation of EPA into phospholipid bilayers influences membrane structure and may help to prevent cardiac arrhythmias. Clinically, this may translate into improved vascular health, including regression of atherosclerotic plaque. Overall, EPA has a range of pleiotropic effects that contribute to a reduction in ASCVD.

n-3 PUFAs protect against adiposity and fatty liver by promoting browning in postnatally overfed male rats: a role for NRG4

Early-life nutrition plays an important role in regulating adult metabolism. This study evaluated the effects of early nutrition during the suckling and postweaning periods on expression of the adipocytokine Neuregulin 4 (Nrg4) and its relationship with nonalcoholic fatty liver disease (NAFLD) in adulthood. In vivo, male rats were adjusted to litter sizes of three (small litter, SL) or ten (normal litter, NL) on postnatal day 3. Pups were fed control chow (NL and SL groups) or a high-fat diet (NL-HF and SL-HF groups), and SL pups specifically were fed a fish oil diet rich in n-3 polyunsaturated fatty acids (n-3 PUFAs) (SL-FO group), from postnatal weeks 3 to 13. The results demonstrated that postnatal overnutrition increased weight, hepatic de novo lipogenesis (DNL) gene expression and NAFLD and decreased body temperature and Nrg4, Ucp1 and Pgc1a mRNA expression in adipose tissues in SL, SL-HF and NL-HF rats compared to NL rats in adulthood. The opposite trends were observed in SL-FO rats. Moreover, in vitro, recombinant NRG4 protein reduced lipid accumulation by inhibiting DNL gene expression in fatty HepG2 cells stimulated with sodium oleate. In HPAs, eicosapentaenoic acid (EPA) treatment elevated NRG4 production and caused adipocyte browning, and these effects were abrogated by PPARG antagonism. In conclusion, a postweaning n-3 PUFA diet enhanced Nrg4 expression in adipose tissues, associated with attenuation of NAFLD induced by SL rearing. Additionally, external NRG4 reduced lipogenesis in steatotic hepatocytes. Thus, white adipose tissue browning induced by n-3 PUFAs may promote NRG4 production through the PPARG pathway.

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.

Mechanisms underlying N3-PUFA regulation of white adipose tissue endocrine function

Omega-3 polyunsaturated fatty acids (N3-PUFA) are widely reported to improve obesity-associated metabolic impairments, in part, through the regulation of adipokine and cytokine secretion from white adipose tissue (WAT). However, the precise underlying molecular mechanisms by which N3-PUFA influence WAT endocrine function remain poorly described. Available evidence supports that N3-PUFA and related bioactive lipid mediators regulate several intracellular pathways that converge on two important transcription factors: PPAR-γ and NF-κB. Further, N3-PUFA signaling through GPR120 appears integral for the regulation of adipokine and cytokine production. This review collates insights from in vitro and in vivo studies using genetic and chemical inhibition of key signaling proteins to describe the pathways by which N3-PUFA regulate WAT endocrine function. Existing gaps in knowledge and opportunities to advance our understanding in this area are also highlighted.

Positive Reinforcing Mechanisms between GPR120 and PPARγ Modulate Insulin Sensitivity

G protein-coupled receptor 120 (GPR120) and PPARγ agonists each have insulin sensitizing effects. But whether these two pathways functionally interact and can be leveraged together to markedly improve insulin resistance has not been explored. Here, we show that treatment with the PPARγ agonist rosiglitazone (Rosi) plus the GPR120 agonist Compound A leads to additive effects to improve glucose tolerance and insulin sensitivity, but at lower doses of Rosi, thus avoiding its known side effects. Mechanistically, we show that GPR120 is a PPARγ target gene in adipocytes, while GPR120 augments PPARγ activity by inducing the endogenous ligand 15d-PGJ2 and by blocking ERK-mediated inhibition of PPARγ. Further, we used macrophage- (MKO) or adipocyte-specific GPR120 KO (AKO) mice to show that GRP120 has anti-inflammatory effects via macrophages while working with PPARγ in adipocytes to increase insulin sensitivity. These results raise the prospect of a safer way to increase insulin sensitization in the clinic.

Improving Metabolic Control Through Functional Foods

Background:

Functional foods are designed to have physiological benefits and reduce the risk of chronic disease beyond basic nutritional functions. Conditions related to overnutrition such as Metabolic Syndrome and Type 2 diabetes are increasingly serious concerns in Western societies. Several nutrient classes are considered to protect against these conditions and this review focuses on the latest clinical and preclinical evidence supporting their efficacy and the molecular mechanisms by which they act.

Methods:

The review searched the literature for information and data on the following functional food components and their protective effects against Metabolic Syndrome and Type 2 Diabetes: Dietary fiber; Medium-chain triglycerides and Ketone esters; ω3 Polyunsaturated fatty acids and Antioxidants.

Results:

Data from a hundred and four studies were reviewed and summarized. They indicate that dietary fiber results in the production of beneficial short chain fatty acids via intestinal microbiota, as well as increasing intestinal secretion of incretins and satiety peptides. Medium chain triglycerides and ketone esters promote thermogenesis, inhibit lipolysis and reduce inflammation. They also decrease endogenous synthesis of triglycerides and fatty acids. ω3-PUFA’s act to soften inflammation through an increase in adiponectin secretion. Antioxidants are involved in the protection of insulin sensitivity by PTP1B suppression and SIRT1 activation.

Conclusion:

Functional foods have actions that complement and/or potentiate other lifestyle interventions for reversing Metabolic Syndrome and Type 2 Diabetes. Functional foods contribute to reduced food intake by promoting satiety, less weight gain via metabolic uncoupling and improved insulin sensitivity via several distinct mechanisms.

Monounsaturated Fatty Acids in a High-Fat Diet and Niacin Protect from White Fat Dysfunction in the Metabolic Syndrome

SCOPE

Obesity is a principal causative factor of metabolic syndrome. Niacin potently regulates lipid metabolism. Replacement of saturated fatty acids by MUFAs or inclusion of omega-3 long-chain PUFAs in the diet improves plasma lipid levels. However, the potential benefits of niacin in combination with MUFAs or omega-3 long-chain PUFAs against white adipose tissue (WAT) dysfunction in the high fat diet (HFD)-induced metabolic syndrome are unknown.

METHODS AND RESULTS

Male Lep^ob/ob LDLR^-/- mice are fed a chow diet or HFDs based on milk cream (21% kcal), olive oil (21% kcal), or olive oil (20% kcal) plus 1% kcal from eicosapentaenoic and docosahexaenoic acids, including immediate-release niacin (1% w/v) in drinking water, for 8 weeks. Mice are then phenotyped. Dietary MUFAs are identified as positive regulators of adipose NAD⁺ signaling pathways by triggering NAD⁺ biosynthesis via the salvage pathway. This coexists with overexpression of genes involved in recognition of NAD⁺ and fatty acids, a surrounding lipid environment dominated by exogenous oleic acid and an alternatively activated macrophage profile, which culminate in a healthy expansion of WAT and improvement of several hallmarks that typify the metabolic syndrome.

CONCLUSION

Niacin in combination with dietary MUFAs can favor WAT homeostasis in the development of HFD-induced obesity and metabolic syndrome.

Association between plasma phospholipid omega-3 polyunsaturated fatty acids and type 2 diabetes is sex dependent: The Hunter Community Study

BACKGROUND & AIMS

Chronic inflammation drives the development of insulin resistance and type 2 diabetes. Long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) eicosapentaenoic acid (EPA, c20:5n-3) and docosahexaenoic acid (DHA, c22:6n-3) may protect against type 2 diabetes development. The aim of this current study is to determine whether LCn-3PUFA status is associated with type 2 diabetes in the Hunter Community Study.

METHODS

Men and women aged 55-85 years were randomly selected from the electoral roll and invited to participate. Participants were included in the current study if they had plasma phospholipid fatty acid composition data available and diabetes status could be determined. LCn-3PUFA status was determined by fatty acid composition of plasma phospholipids (EPA + DHA, %,w/w). Diabetes was determined according to World Health Organisation criteria. Insulin was measured in n = 251 participants and HOMA-IR calculated.

RESULTS

In total, n = 2092 (diabetes: n = 249) participants were included. After adjusting for confounders of diabetes, LCn-3PUFA status was inversely associated with diabetes in overweight/obese females (OR [95%CI]: 0.90 [0.80, 1.00], p = 0.045) but not males (p-interaction_sex = 0.041). Overweight/obese females with diabetes had significantly lower levels of DHA than those without diabetes (mean difference [95%CI]: -0.53 [-0.87, -0.20], p = 0.002), with no difference in EPA. LCn-3PUFA was inversely associated with HOMA-IR (r = -0.175, p = 0.005).

CONCLUSIONS

This study provides further evidence of a sex-dependent association between LCn-3PUFA and type 2 diabetes. Causal pathways between LCn-3PUFA and type 2 diabetes merits delineation.

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.

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.

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.

Serum adiponectin and TNFα concentrations are closely associated with epicardial adipose tissue fatty acid profiles in patients undergoing cardiovascular surgery

BACKGROUND

Epicardial adipose tissue (EAT) releases both adiponectin and TNFα, and these two adipokines play important roles in heart diseases such as coronary arterial disease. The aim of the present study was to clarify whether fatty acid (FA) profiles in EAT are linked to the serum concentration of these adipokines. The relationships between serum adipokine levels and FA profiles in patients undergoing cardiovascular surgery were analyzed.

METHODS

Patients (n = 21) undergoing cardiovascular surgery (11 males, 70.4 ± 9.0 years, BMI 26.0 ± 5.1 kg/m2) were included. EAT samples were taken. We measured clinical biochemical data and FA profiles in venous blood and EAT samples using gas chromatography. Serum adiponectin and TNFα concentrations were also measured.

RESULTS

The adiponectin and TNFα levels were not correlated with any fatty acid concentration in serum lipids. In contrast, there was a positive correlation between the serum adiponectin level and epicardial level of nervonic acid (C24:1ω9, r = 0.525, P = 0.025). In multiple regression analysis, adiponectin showed a positive association with the epicardial C24:1ω9 concentration after controlling for age and BMI, or TG, non-HDL-C, and BNP. The serum TNFα concentration was negatively correlated with the epicardial C18:3ω3, C12:0 and C18:0 content. In multiple regression analysis, the serum TNFα concentration showed a positive association with the epicardial C18:3ω3 level (β = - 0.575, P = 0.015).

CONCLUSIONS

These results suggest that there is a close relationship between epicardial FA profiles and serum levels of adiponectin and TNFα. Dietary therapy to target FA profiles may be helpful to modulate inflammation.

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.

A Randomized Double-Blinded, Placebo-Controlled Trial Investigating the Effect of Fish Oil Supplementation on Gene Expression Related to Insulin Action, Blood Lipids, and Inflammation in Gestational Diabetes Mellitus-Fish Oil Supplementation and Gestational Diabetes

Gestational diabetes mellitus (GDM) is a common complication of pregnancy, and it is mostly associated with postpartum diabetes, insulin resistance, and dyslipidemia. Fish oil (omega-3) supplementation has been shown to reduce the risk of different chronic diseases such as cardiovascular disease, type 2 diabetes, and cancers, though the evidence of its impact on gestational diabetes is scarce. Our goal in this study was to determine the effect of fish oil administration on gene expression related to insulin action, blood lipids, and inflammation in women with GDM. Participants with GDM (n = 40), aged 18–40 years, were randomized to take either 1000 mg fish oil capsules, containing 180 mg eicosapentaenoic acid and 120 mg docosahexaenoic acid (n = 20), or placebo (n = 20) twice a day for 6 weeks. Gene expression related to insulin, lipids, and inflammation was quantified in peripheral blood mononuclear cells (PBMCs) of GDM women using Reverse Transcription Polymerase Chain Reaction (RT-PCR) method. Results of RT-PCR indicated that omega-3 supplementation upregulated gene expression of peroxisome proliferator-activated receptor gamma (PPAR-γ) (P = 0.04) in PBMCs of patients with GDM, compared with the placebo. In addition, gene expression of the low-density lipoprotein receptor (LDLR) (P < 0.001), interleukin-1 (IL-1) (P = 0.007), and tumor necrosis factor alpha (TNF-α) (P = 0.01) was downregulated in PBMCs of women with GDM, following omega-3 supplementation. No significant effect of omega-3 supplementation was indicated on gene expression of IL-8 in PBMCs of patients with GDM. Overall, fish oil supplementation for 6 weeks in women with GDM significantly improved gene expression of PPAR-γ, IL-1, and TNF-α, but not gene expression of IL-8.

Rosmarinic acid attenuates cardiac fibrosis following long-term pressure overload via AMPKα/Smad3 signaling

Agonists of peroxisome proliferator-activated receptor gamma (PPAR-γ) can activate 5' AMP-activated protein kinase alpha (AMPKα) and exert cardioprotective effects. A previous study has demonstrated that rosmarinic acid (RA) can activate PPAR-γ, but its effect on cardiac remodeling remains largely unknown. Our study aimed to investigate the effect of RA on cardiac remodeling and to clarify the underlying mechanism. Mice were subjected to aortic banding to generate pressure overload induced cardiac remodeling and then were orally administered RA (100 mg/kg/day) for 7 weeks beginning 1 week after surgery. The morphological examination, echocardiography, and molecular markers were used to evaluate the effects of RA. To ascertain whether the beneficial effect of RA on cardiac fibrosis was mediated by AMPKα, AMPKα2 knockout mice were used. Neonatal rat cardiomyocytes and fibroblasts were separated and cultured to validate the protective effect of RA in vitro. RA-treated mice exhibited a similar hypertrophic response as mice without RA treatment, but had an attenuated fibrotic response and improved cardiac function after pressure overload. Activated AMPKα was essential for the anti-fibrotic effect of RA via inhibiting the phosphorylation and nuclear translocation of Smad3 in vivo and in vitro, and AMPKα deficiency abolished RA-mediated protective effects. Small interfering RNA against Ppar-γ (siPpar-γ) and GW9662, a specific antagonist of PPAR-γ, abolished RA-mediated AMPKα phosphorylation and alleviation of fibrotic response in vitro. RA attenuated cardiac fibrosis following long-term pressure overload via AMPKα/Smad3 signaling and PPAR-γ was required for the activation of AMPKα. RA might be a promising therapeutic agent against cardiac fibrosis.

Effect of different levels of feed restriction and fish oil fatty acid supplementation on fat deposition by using different techniques, plasma levels and mRNA expression of several adipokines in broiler breeder hens

Background

Reproductive hens are subjected to a restricted diet to limit the decline in fertility associated with change in body mass. However, endocrine and tissue responses to diet restriction need to be documented.

Objective

We evaluated the effect of different levels of feed restriction, with or without fish oil supplementation, on metabolic parameters and adipokine levels in plasma and metabolic tissues of reproductive hens.

Methods

We designed an in vivo protocol involving 4 groups of hens; RNS: restricted (Rt) unsupplemented, ANS: ad libitum (Ad, receiving an amount of feed 1.7 times greater than animals on the restricted diet) unsupplemented, RS: Rt supplemented, and AS: Ad supplemented. The fish oil supplement was used at 1% of the total diet composition.

Results

Hens fed with the Rt diet had a significantly (P < 0.0001) lower growth than Ad hens, while the fish oil supplementation had no effect on these parameters. Furthermore, the bioelectrical impedance analysis (BIA) and the fat ultrasonographic examinations produced similar results to the other methods that required animals to be killed (carcass analysis and weight of adipose tissue). In addition, the Rt diet significantly (P < 0.05) decreased plasma levels of triglycerides, phospholipids, glucose and ADIPOQ, and fish oil supplementation decreased plasma levels of RARRES2. We also showed a positive correlation between insulin values and ADIPOQ or NAMPT or RARRES2 values, and a negative correlation of fat percentage to RARRES2 values. Moreover, the effects of the Rt diet and fish oil supplementation on the mRNA expression depended on the factors tested and the hen age.

Conclusions

Rt diet and fish oil supplementation are able to modulate metabolic parameters and the expression of adipokines and their receptors in metabolic tissue.

The Effect of Omega-3 on Circulating Adiponectin in Adults With Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Whether consumption of omega-3 affects circulating adiponectin has not been established. The objective of this study was to evaluate the effect of omega-3 (food or supplement) on circulating adiponectin in patients with type 2 diabetes through a systematic review of meta-analyses of randomized controlled trials. PubMed, Scopus and Web of Science were searched for relevant studies through May 2016. Two researchers screened and abstracted the literature independently. Pooled estimates were obtained using the random-effects models. Overall, omega-3 increased adiponectin by 0.57 µg/mL (95% confidence interval [CI] 0.15 to 1.31; p=0.01, I-square=74.2% p for heterogeneity <0.001). The source of observed heterogeneity was explored by subgroup analyses. In subgroup analyses, adiponectin levels increased only in those who had consumed omega-3 for more than 8 weeks. This systematic review and meta-analysis of randomized, placebo-controlled clinical trials suggests that omega-3 in patients with type 2 diabetes increases circulating adiponectin. These findings support the potentially beneficial effects of dietary omega-3 in patients with type 2 diabetes on pathways related to adiponectin metabolism.

Dietary DHA/EPA Ratio Changes Fatty Acid Composition and Attenuates Diet-Induced Accumulation of Lipid in the Liver of ApoE-/- Mice

Diets containing various docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratios protect against liver damage in mice fed with a high-fat diet (HFD). However, it is unclear whether these beneficial roles of DHA and EPA are associated with alterations of fatty acid (FA) composition in the liver. This study evaluated the positive impacts of n-6/n-3 polyunsaturated fatty acids (PUFAs) containing different DHA/EPA ratios on HFD-induced liver disease and alterations of the hepatic FA composition. ApoE^-/- mice were fed with HFDs with various ratios of DHA/EPA (2 : 1, 1 : 1, and 1 : 2) and an n-6/n-3 ratio of 4 : 1 for 12 weeks. After treatment, the serum and hepatic FA compositions, serum biochemical parameters, liver injury, and hepatic lipid metabolism-related gene expression were determined. Our results demonstrated that dietary DHA/EPA changed serum and hepatic FA composition by increasing contents of n-6 and n-3 PUFAs and decreasing amounts of monounsaturated fatty acids (MUFAs) and the n-6/n-3 ratio. Among the three DHA/EPA groups, the DHA/EPA 2 : 1 group tended to raise n-3 PUFAs concentration and lower the n-6/n-3 ratio in the liver, whereas DHA/EPA 1 : 2 tended to raise n-6 PUFAs concentration and improve the n-6/n-3 ratio. DHA/EPA supplementation reduced the hepatic impairment of lipid homeostasis, oxidative stress, and the inflammatory responses in HFD-fed mice. The DHA/EPA 2 : 1 group had lower serum levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol and higher levels of adiponectin than HFD group. The DHA/EPA 1 : 2 group had elevated serum levels of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase, without significant change the expression of genes for inflammation or hepatic lipid metabolism among the three DHA/EPA groups. The results suggest that DHA/EPA-enriched diet with an n-6/n-3 ratio of 4 : 1 may reverse HFD-induced nonalcoholic fatty liver disease to some extent by increasing n-6 and n-3 PUFAs and decreasing the amount of MUFAs and the n-6/n-3 ratio.

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

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

THE EFFECT OF SHORT TERM ALPHA LIPOIC ACID ADMINISTRATION ON ADIPONECTIN AND BODY WEIGHT IN TYPE 2 DIABETES MELLITUS PATIENTS

Background

Alpha lipoic acid (ALA) acts as essential co-factor for mitochondrion respiratory enzymes. It has an increasing importance in diabetic neuropathy treatment. Its positive effects on weight gain and metabolic parameters have also been discussed. In this study, we aimed to search for the effect of ALA on weight, appetite, adiponectin and metabolic parameters in type 2 diabetes mellitus patients.

Methods

This study is designed as a randomised, double-blind, placebo controlled, prospective study. 23 type 2 diabetes mellitus patients with peripheral neuropathy (6 normal weight, 17 obese) and 21 normal weight control group were included in the study. Patients were given 600mg/day oral ALA for 6 weeks, added to their routine therapy. Body mass index (BMI), adiponectin, fasting plasma glucose, HbA1C, lipid parameters and CRP levels were tested before and after ALA treatment. Results were evaluated using SPSS 15.0 for Windows.

Results

Adiponectin levels were statistically significantly lower and CRP levels were higher in diabetes group when compared to control group. Although ALA treatment caused a slight weight loss, it was not statistically significant. Appetite scores were decreased in the diabetes group but it did not cause statistically significant weight loss. There was no significant change in metabolic parameters or adiponectin after the treatment.

Conclusions

600mg/dL ALA treatment for 6 weeks did not favor for metabolic parameters in type 2 diabetes patients. This result might be due to the dose or the duration of the treatment, genetic predisposition or dietery habits. Trial of higher doses for long terms might be needed for recovery.

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

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

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.

Curcumin and long-chain Omega-3 polyunsaturated fatty acids for Prevention of type 2 Diabetes (COP-D): study protocol for a randomised controlled trial

Background

Lifestyle interventions, including increase in physical activity and dietary counselling, have shown the ability to prevent type 2 diabetes (T2D) in high-risk state individuals, but the prevalence is still skyrocketing in Australia, in line with global prevalence. Currently, no medicines are approved by the Therapeutic Goods Administration in Australia for the management of prediabetes. Therefore, there is a need of developing a safer, biologically efficacious and cost-effective alternative for delaying the transition of individual health state from prediabetes into T2D. In the current trial we propose to evaluate the effects of curcumin and/or long-chain omega-3 polyunsaturated fatty acids on improving glycosylated haemoglobin as a primary outcome, along with secondary outcomes of glycaemic indices, lipid profile and inflammatory parameters.

Methods/design

Eighty individuals diagnosed with prediabetes, aged between 30 and 70 years, will be randomly assigned to double placebo, curcumin alone, fish oil alone or double active groups according to a computer-generated randomisation sequence for 12 weeks. At baseline and post-intervention visits participants will be asked to provide blood samples and undergo body composition measurements. A blood sample is used for estimating glycaemic profiles, lipid profiles and inflammatory parameters (C-reactive protein, whole blood cell count, adiponectin, leptin, interleukin-6). The interim visit includes review on compliance with supplements based on capsule log and capsule count, adverse events and anthropometric measurements. In addition to these procedures, participants provide self-reported questionnaires on dietary intake (using a 3-day food record), a physical activity questionnaire and medical history.

Discussion

This trial aims to determine whether curcumin and/or long-chain omega-3 polyunsaturated fatty acids affect surrogate markers of glycaemic control which is relevant to delaying T2D. To date 38 participants completed the trial. No changes have been made to the clinical protocol post recruitment. If successful, this trial will provide considerable evidence for performing a larger trial to investigate whether this combination can be administered for preventing or delaying the onset of T2D in high-risk individuals.

Trial registration

ACTRN12615000559516, registered on 29 May 2015).

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1702-9) contains supplementary material, which is available to authorized users.

Combinations of bio-active dietary constituents affect human white adipocyte function in-vitro

Background

Specific bio-active dietary compounds modulate numerous metabolic processes in adipose tissue (AT), including pre-adipocyte proliferation and differentiation. AT dysfunction, rather than an increased fat mass per se, is strongly associated with the development of insulin resistance and is characterized by impaired adipogenesis, hypertrophic adipocytes, inflammation, and impairments in substrate metabolism. A better understanding of mechanisms underlying AT dysfunction may provide new strategies for the treatment of obesity-associated metabolic diseases. Here we evaluated the role of (all-E)-lycopene (Lyc), eicosapentaenoic acid (EPA) or trans-resveratrol (Res) and combinations thereof on human white adipocyte function.

Methods

In-vitro differentiating human pre-adipocytes were treated with EPA, Lyc and Res or their combinations for 14 days. The effects on intracellular lipid droplet (LD) accumulation, secreted anti- and pro-inflammatory cyto-/adipokines (e.g. adiponectin, IL-6, IL-8/CXCL-8 and MCP-1/CCL2) and on gene expression of markers of adipocyte differentiation and substrate metabolism (e.g. PPAR-gamma, C/EBP-alpha, GLUT-4, FAS, ATGL, HSL, and PLIN-1) were measured by fluorescent microscopy (Cellomics™), multi-parametric LiquiChip® technology and quantitative RT-PCR, respectively.

Results

Treatment of differentiating adipocytes for 14 days with the combination of Lyc/Res and EPA/Res resulted in significantly inhibited LD formation (~ -25 and -20%, respectively) compared to the effects of the single compounds. These morphological changes were accompanied by increased mRNA levels of the adipogenic marker PPAR-gamma and the lipase ATGL and by decreased expression levels of lipogenic markers (LPL, FAS, GLUT-4) and the LD-covering protein PLIN-1. In addition, a blunted adipocyte secretion of pro-inflammatory cytokines (IL-6 and MCP-1) and adiponectin was observed following treatment with these compounds.

Conclusion

The combination of the dietary bio-actives Lyc and EPA with Res might influence adipocyte function by affecting the balance between adipogenic, lipogenic and lipolytic gene expression, resulting in a reduced LD storage and a less inflammatory secretion profile. Taken together, our results indicate that combinations of dietary compounds may be beneficial for the prevention and treatment of metabolic disorders via effects on human white adipocyte function.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0143-5) contains supplementary material, which is available to authorized users.

Reduced adiponectin expression after high-fat diet is associated with selective up-regulation of ALDH1A1 and further retinoic acid receptor signaling in adipose tissue

Adiponectin is an adipocyte-derived adipokine with potent antidiabetic, anti-inflammatory, and antiatherogenic activity. Long-term, high-fat diet results in gain of body weight, adiposity, further inflammatory-based cardiovascular diseases, and reduced adiponectin secretion. Vitamin A derivatives/retinoids are involved in several of these processes, which mainly take place in white adipose tissue (WAT). In this study, we examined adiponectin expression as a function of dietary high-fat and high–vitamin A conditions in mice. A decrease of adiponectin expression in addition to an up-regulation of aldehyde dehydrogenase A1 (ALDH1A1), retinoid signaling, and retinoic acid response element signaling was selectively observed in WAT of mice fed a normal–vitamin A, high-fat diet. Reduced adiponectin expression in WAT was also observed in mice fed a high–vitamin A diet. Adipocyte cell culture revealed that endogenous and synthetic retinoic acid receptor (RAR)α- and RARγ-selective agonists, as well as a synthetic retinoid X receptor agonist, efficiently reduced adiponectin expression, whereas ALDH1A1 expression only increased with RAR agonists. We conclude that reduced adiponectin expression under high-fat dietary conditions is dependent on 1) increased ALDH1A1 expression in adipocytes, which does not increase all-trans-retinoic acid levels; 2) further RAR ligand–induced, WAT-selective, increased retinoic acid response element–mediated signaling; and 3) RAR ligand–dependent reduction of adiponectin expression.—Landrier, J.-F., Kasiri, E., Karkeni, E., Mihály, J., Béke, G., Weiss, K., Lucas, R., Aydemir, G., Salles, J., Walrand, S., de Lera, A. R., Rühl, R. Reduced adiponectin expression after high-fat diet is associated with selective up-regulation of ALDH1A1 and further retinoic acid receptor signaling in adipose tissue.

Adiponectin as a target for the treatment of nonalcoholic steatohepatitis with thiazolidinediones: A systematic review

Thiazolidinediones (TZDs; pioglitazone and rosiglitazone) have provided promising results in clinical trials for nonalcoholic steatohepatitis (NASH). The main purpose of this systematic review was to summarize evidence on circulating adiponectin levels in relation to histological changes following TZD treatment in patients with histologically confirmed NASH. We performed a systematic search in PubMed, Scopus and Cochrane Library. We included four studies, published between 2006 and 2012, providing data for 187 histologically confirmed NASH adult patients (105 on TZD and 82 controls) treated for 6-12months. Significant increase in adiponectin (80-178%) after TZD treatment was observed in all included studies. Improvement in steatosis following treatment was observed in all studies. A trend towards improvement in lobular inflammation was observed in all studies after pioglitazone, but not after rosiglitazone. Trends toward improvement in ballooning and fibrosis were observed in the two studies after pioglitazone using either the highest doses or the longest duration of therapy. Overall disease activity score was improved in all studies after pioglitazone, but not after rosiglitazone. Insulin resistance and liver function tests were also improved after treatment. Despite weight gain, circulating leptin was not increased after treatment. In conclusion, parallel increases in circulating adiponectin levels and histological improvement were observed in this systematic review. These results warrant further consideration of TZDs, but even more importantly point to a key role for novel potential treatments for NASH patients such as the newer selective peroxisome proliferator activated receptor-γ modulators, which increase adiponectin without significant weight gain.

Differential secretion of adipokines from subcutaneous and visceral adipose tissue in healthy dogs: Association with body condition and response to troglitazone

This study aimed to determine the effects of body condition, fat depot, and a peroxisome proliferator-activated receptor γ-agonist (troglitazone) on secretion of adiponectin, interleukin-6 (IL6), and tumor necrosis factor-α (TNFα) from adipose tissue of healthy dogs. Subcutaneous and omental visceral adipose tissue samples were collected from 16 healthy intact female dogs, and body condition score (range 4-8/9) was determined. Concentrations of adiponectin were measured in mature adipocytes cultures and concentrations of IL6 and TNFα were measured in stromovascular cells cultures after 48 h incubation in fresh control medium, or fresh medium containing 10 µM troglitazone. Mature adipocytes and stromovascular cells of subcutaneous origin secreted higher concentrations of adiponectin and lower concentration of IL6 and TNFα, respectively, than corresponding cells of visceral origin, in both the control (P = 0.015, P = 0.004, and P = 0.016, respectively) and troglitazone-treated cultures (P <0.001, P = 0.004, and P = 0.016, respectively). Troglitazone increased adiponectin secretion from mature adipocytes in visceral (P = 0.019), but not in subcutaneous fat cultures (P = 0.4). Troglitazone decreased IL6 and TNFα secretion from stromovascular cells both in visceral (P = 0.047 and P = 0.016, respectively) and subcutaneous (P = 0.047 and P = 0.016, respectively) fat cultures. Higher body condition score was associated with lower secretion of adiponectin from mature adipocytes (P = 0.007), lower secretion of IL6 (P = 0.040) and higher secretion of TNFα (P = 0.040) from stromovascular cells. This study showed differential secretion of adipokines by subcutaneous and visceral fat depots in dogs and association between body condition and adipokine secretion. Activation of PPARγ altered adipokine secretion.

Reducing the burden of obesity-associated cancers with anti-inflammatory long-chain omega-3 polyunsaturated fatty acids

Today's world population has an unprecedented risk of dying from the consequences of being overweight and obese. Chronic diseases such as cardiovascular disease, type 2 diabetes, and cancer are often accelerated because of excessive adiposity. Various biological mechanisms are implicated in the obesity-cancer link, particularly local and systemic inflammation as well as altered growth factor signaling pathways. In order to combat obesity-induced inflammation and the resulting increases in cancer risk and progression, the identification of safe and effective mechanism-based interventions is imperative. Notably, long chain omega-3 polyunsaturated fatty acids (PUFAs) modulate the secretion of pro-inflammatory cytokines, prostaglandins and other inflammatory mediators, restore insulin sensitivity, and can prevent or delay tumorigenesis. Delineating the precise mechanisms by which omega-3 PUFAs suppress obesity-induced inflammation will help identify promising key mechanistic targets and intervention strategies to break the obesity-cancer link.

GLUT4 Expression in Adipocytes Regulates De Novo Lipogenesis and Levels of a Novel Class of Lipids With Antidiabetic and Anti-inflammatory Effects

Adipose tissue (AT) regulates systemic insulin sensitivity through multiple mechanisms, and alterations in de novo lipogenesis appear to contribute. Mice overexpressing GLUT4 in adipocytes (AG4OX) have elevated AT lipogenesis and enhanced glucose tolerance despite being obese and having elevated circulating fatty acids. Lipidomic analysis of AT identified a structurally unique class of lipids, branched fatty acid esters of hydroxy-fatty acids (FAHFAs), which were elevated in AT and serum of AG4OX mice. Palmitic acid esters of hydroxy-stearic acids (PAHSAs) are among the most upregulated FAHFA families in AG4OX mice. Eight PAHSA isomers are present in mouse and human tissues. PAHSA levels are reduced in insulin resistant people, and levels correlate highly with insulin sensitivity. PAHSAs have beneficial metabolic effects. Treatment of obese mice with PAHSAs lowers glycemia and improves glucose tolerance while stimulating glucagon-like peptide 1 and insulin secretion. PAHSAs also reduce inflammatory cytokine production from immune cells and ameliorate adipose inflammation in obesity. PAHSA isomer concentrations are altered in physiological and pathophysiological conditions in a tissue- and isomer-specific manner. The mechanisms most likely involve changes in PAHSA biosynthesis, degradation, and secretion. The discovery of PAHSAs reveals the existence of previously unknown endogenous lipids and biochemical pathways involved in metabolism and inflammation, two fundamental physiological processes.

Eicosapentaenoic acid and arachidonic acid differentially regulate adipogenesis, acquisition of a brite phenotype and mitochondrial function in primary human adipocytes

SCOPE

n-3 and n-6 PUFAs have several opposing biological effects and influence white adipose tissue (WAT) function. The recent discovery of thermogenic UCP1-expressing brite adipocytes within WAT raised the question whether n-3 and n-6 PUFAs exert differential effects on brite adipocyte formation and mitochondrial function.

METHODS AND RESULTS

Primary human preadipocytes were treated with n-3 PUFAs (eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) or n-6 PUFA (arachidonic acid, ARA) during differentiation, and adipogenesis, white and brite gene expression markers, mitochondrial content and function were analyzed at day 12 of differentiation. Adipogenesis was equally increased by n-3 and n-6 PUFAs. The n-6 PUFA ARA increased lipid droplet size and expression of the white-specific marker TCF21 while decreased mitochondrial protein expression and respiratory function. In contrast, EPA increased expression of the brown adipocyte-related genes UCP1 and CPT1B, and improved mitochondrial function of adipocytes. The opposing effects of EPA and ARA on gene expression and mitochondrial function were also observed in cells treated from day 8 to 12 of adipocyte differentiation.

CONCLUSION

EPA promotes brite adipogenesis and improves parameters of mitochondrial function, such as increased expression of CPTB1, citrate synthase activity and higher maximal respiratory capacity, while ARA reduced mitochondrial spare respiratory capacity in vitro.

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.

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.

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

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

Effect of DHA-rich fish oil on PPARγ target genes related to lipid metabolism in type 2 diabetes: A randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

The beneficial effects of omega-3 polyunsaturated fatty acids on lipid levels are well documented. However, the related molecular mechanisms are widely unknown. Omega-3 polyunsaturated fatty acids are natural ligand for peroxisome proliferator-activated receptor γ (PPARγ).

OBJECTIVE

The aim of this study was to evaluate the effect of docosahexaenoic acid (DHA)-rich fish oil supplementation on modulation of some PPARγ-responsive genes related to lipid metabolism.

METHODS

Patients with type 2 diabetes were randomly assigned to consume either DHA-rich fish oil (containing 2400 mg/d fish oil; DHA: 1450 mg and eicosapentaenoic acid: 400 mg) or placebo for 8 weeks. Lipid profile and glycemic control parameters as well as the gene expression of PPARγ, liver x receptor-a, ATP-binding cassette A1, and CD36 in peripheral blood mononuclear cells were measured at baseline and after 8 weeks.

RESULTS

DHA-rich fish oil supplementation resulted in decreased triglycerides (TG) level compared with placebo group, independently of the baseline value of TG (all patients (P = .003), hypertriglyceridemic subjects (P = .01), and normotriglyceridemic subjects (P = .02)). Moreover, a higher reduction in TG level was observed in hypertriglyceridemic subjects, comparing to normotriglyceridemic subjects with DHA-rich fish oil supplementation (P = .01). Other lipid parameters as well as the expression of PPARγ, liver x receptor-a, ATP-binding cassette A1, and CD36 were not affected by DHA-rich fish oil supplementation. Only in hypertriglyceridemic subjects, DHA-rich fish oil supplementation upregulated CD36 expression, compared with the placebo group (P = .01).

CONCLUSIONS

DHA-rich fish oil supplementation for 8 weeks increased CD36 expression in hypertriglyceridemic subjects, which might result to higher reduction in TG level, comparing with normotriglyceridemic subjects. However, this finding should be investigated in further studies.

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

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

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.