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

EPA and DHA differentially improve insulin resistance by reducing adipose tissue inflammation-targeting GPR120/PPARγ pathway

Insulin resistance (IR) is a global health challenge, often initiated by dysfunctional adipose tissue. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may have different effects on IR, but the mechanisms are unknown. This study aims to evaluate the protective effect of EPA and DHA against IR in a high-fat diet (HFD) mice model and investigate whether EPA and DHA alter IR modulate the G-protein-poupled receptor 120/peroxisome proliferator-activated receptor γ (GPR120/PPARγ) pathway in macrophages and adipocytes, which may affect IR in adipocytes. The findings of this study show that 4% DHA had a better effect in improving IR and reducing inflammatory cytokines in adipose tissue of mice. Additionally, in the cell experiment, the use of AH7614 (a GPR120 antagonist) inhibited the glucose consumption increase and the increasable expression of PPARγ and insulin signaling molecules mediated by DHA in adipocytes. Furthermore, GW9662 (a PPARγ antagonist) hindered the upregulation of glucose consumption and insulin signaling molecule expression induced by EPA and DHA in adipocytes. DHA exhibited significant effects in reducing the number of migrated cells and inflammation. The compounds AH7614 and GW9662 hindered the suppressive effects of EPA and DHA on macrophage-induced IR in adipocytes. These findings suggest that DHA has a stronger potential in improving IR in adipocytes through the GPR120/PPARγ pathway in macrophages, when compared to EPA.

PPAR-γ regulates the polarization of M2 macrophages to improve the microenvironment for autologous fat grafting

The unpredictable survival rate of autologous fat grafting (AFG) seriously affects its clinical application. Improving the survival rate of AFG has become an unresolved issue in plastic surgery. Peroxisome proliferator-activated receptor-γ (PPAR-γ) regulates the adipogenic differentiation of adipocytes, but the functional mechanism in AFG remains unclear. In this study, we established an animal model of AFG and demonstrated the superior therapeutic effect of PPAR-γ regulation in the process of AFG. From day 3 after fat grafting, the PPAR-γ agonist rosiglitazone group consistently showed better adipose integrity, fewer oil cysts, and fibrosis. Massive macrophage infiltration was observed after 7 days. At the same time, M2 macrophages begin to appear. At day 14, M2 macrophages gradually became the dominant cell population, which suppressed inflammation and promoted revascularization and fat regeneration. In addition, transcriptome sequencing showed that the differentially expressed genes in the Rosiglitazone group were associated with the pathways of adipose regeneration, differentiation, and angiogenesis; these results provide new ideas for clinical treatment.

Protective effects and mechanisms of Yi Qi Huo Xue Fang in cerebral ischemic stroke based on network pharmacology and experimental verification

ETHNOPHARMACOLOGICAL RELEVANCE

Yi Qi Huo Xue Fang (YQHXF) is an effective formula for treating cerebral ischemic stroke (CIS). However, its active ingredients and mechanism of action remain unclear.

AIM OF THE STUDY

This study aimed to reveal the mechanism of action of YQHXF in the treatment of ischemic stroke based on network pharmacology and experimental validation.

MATERIALS AND METHODS

This study identified the chemical components in YQHXF and the components absorbed by rat serum based on UPLC-Q-TOF/MS technology and used network pharmacology to predict key candidate targets. A protein-protein-interaction (P-P-I) network was constructed using String 11.0 database and Cytoscape, and R software for gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis. Finally, molecular docking combined with animal experiments was used to verify network pharmacology results.

RESULTS

This study identified and confirmed 36 chemical components of YQHXF and five chemical ingredients that were absorbed into the blood of rats and screened 66 key candidate targets. All targets in the P-P-I network were mainly related to inflammation and vascular processes. KEGG enrichment results revealed that these 66 key candidate targets were primarily involved in the "AGE-RAGE signaling pathway," "TNF-α signaling pathway, and "T cell receptor signaling pathway." Molecular docking results revealed that Prostaglandin-endoperoxidase synthase 2(PTGS-2), Nitric oxide synthase, endothelial (NOS3), and peroxisome proliferator-activated receptor gamma (PPARG) were more stably bound to their active ingredients. Animal experiments demonstrated that YQHXF promoted M2 polarization, inhibited M1 polarization in microglia, and promoted angiogenesis, which may be related to the PPARG pathway.

CONCLUSION

This study revealed the key active components and effective targets of YQHXF, identified the mechanism of action of YQHXF, laid the foundation for further research on YQHXF, and provided ideas for developing new drugs for CIS.

The Role of VEGF Family in Lipid Metabolism

The vascular endothelial growth factor (VEGF) family plays a major role in tumors and ophthalmic diseases. However, increasingly more data reported its potential in regulating lipids. With its biological functions mainly expressed in lymphatic vessels, some factors in the families, like VEGF-A and VEGF-C, have been proved to regulate intestinal absorption of lipids by affecting chylous ducts. Other effects, including regulating lipoprotein lipase (LPL), endothelial lipase (EL), and recombinant syndecan 1 (SDC1), have also been confirmed. However, given the scant-related studies, further research should be conducted to examine the concrete mechanisms and provide pragmatic ways to apply them in the clinic. The VEGF family may treat dyslipidemia in specific ways that are different from common methods and concurrently contribute to the treatment of other metabolic diseases, like diabetes and obesity.

Adipose endothelial cells mastering adipose tissues metabolic fate

Dynamic communication within adipose tissue depends on highly vascularized structural characteristics to maintain systemic metabolic homoeostasis. Recently, it has been noted that adipose endothelial cells (AdECs) act as essential bridges for biological information transmission between adipose-resident cells. Hence, paracrine regulators that mediate crosstalk between AdECs and adipose stromal cells were summarized. We also highlight the importance of AdECs to maintain adipocytes metabolic homoeostasis by regulating insulin sensitivity, lipid turnover and plasticity. The differential regulation of AdECs in adipose plasticity often depends on vascular density and metabolic states. Although choosing pro-angiogenic or anti-angiogenic therapies for obesity is still a matter of debate in clinical settings, the growing numbers of drugs have been confirmed to play an anti-obesity effect by affecting vascularization. Pharmacologic angiogenesis intervention has great potential as therapeutic strategies for obesity.

Chronic Low-Dose Alcohol Consumption Promotes Cerebral Angiogenesis in Mice

Chronic alcohol consumption dose-dependently affects the incidence and prognosis of ischemic stroke. We determined the influence of chronic alcohol consumption on cerebral angiogenesis under physiological conditions and following ischemic stroke. In in vitro studies, acute exposure to low-concentration ethanol significantly increased angiogenic capability and upregulated vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth factor receptor 2 (VEGFR2) in C57BL/6J mouse brain microvascular endothelial cells (MBMVECs). The increased angiogenic capability was abolished in the presence of a VEGFR2 inhibitor. In addition, the increased angiogenic capability and upregulated VEGF-A and VEGFR2 remained in chronically low-concentration ethanol-exposed MBMVECs. In in vivo studies, 8-week gavage feeding with low-dose ethanol significantly increased vessel density and vessel branches and upregulated VEGF-A and VEGFR2 in the cerebral cortex under physiological conditions. Furthermore, vessel density, vessel branches, and expression of VEGF-A and VEGFR2 in the peri-infarct cortex were significantly greater in low-dose ethanol-fed mice at 72 h of reperfusion. Although low-dose ethanol did not alter cerebral vasoreactivity and regional cerebral blood flow (rCBF) either before or during ischemia, it significantly augmented post-ischemic hyperemia during reperfusion. In contrast, exposure to high-concentration ethanol and 8-week gavage feeding with high-dose ethanol only had a mild inhibitory effect on angiogenic capability and cerebral angiogenesis, respectively. We conclude that heavy alcohol consumption may not dramatically alter cerebral angiogenesis, whereas light alcohol consumption significantly promotes cerebral angiogenesis.

Placental Angiogenesis in Mammals: A Review of the Regulatory Effects of Signaling Pathways and Functional Nutrients

Normal placental development and proper angiogenesis are essential for fetal growth during pregnancy. Angiogenesis involves the regulatory action of many angiogenic factors and a series of signal transduction processes inside and outside the cell. The obstruction of placental angiogenesis causes fetal growth restriction and serious pregnancy complications, even leading to fetal loss and pregnancy cessation. In this review, the effects of placental angiogenesis on fetal development are described, and several signaling pathways related to placental angiogenesis and their key regulatory mediators are summarized. These factors, which include vascular endothelial growth factor (VEGF)-VEGF receptor, delta-like ligand 4 (DLL-4)-Notch, Wnt, and Hedgehog, may affect the placental angiogenesis process. Moreover, the degree of vascularization depends on cell proliferation, migration, and differentiation, which is affected by the synthesis and secretion of metabolites or intermediates and mutual coordination or inhibition in these pathways. Furthermore, we discuss recent advances regarding the role of functional nutrients (including amino acids and fatty acids) in regulating placental angiogenesis. Understanding the specific mechanism of placental angiogenesis and its influence on fetal development may facilitate the establishment of new therapeutic strategies for the treatment of preterm birth, pre-eclampsia, or intrauterine growth restriction, and provide a theoretical basis for formulating nutritional regulation strategies during pregnancy.

4-Thiazolidinone-based derivatives do not affect differentiation of mouse embryo fibroblasts (3T3-L1 cell line) into adipocytes

Nowadays, diabetes mellitus type 2 (T2DM) is a serious problem in western European societies and in the United States. Thiazolidinediones (TZDs) are a broad group of compounds used to decrease insulin resistance in TDM2. To date, it has been believed that TZDs act mainly through activation of peroxisome proliferator-activated receptor gamma (PPARγ). The PPARγ receptor is important in differentiation of preadipocytes into mature adipocytes. Therefore, given the potential of structurally related thiopyrano[2,3-d]thiazoles Les-2194 and Les-3377 and 4-thiazolidinone derivative Les-3640 to interact with the PPARγ receptor, the aim of the present study was to evaluate the impact of the 4-thiazolidinone-based derivatives mentioned above on the process of 3T3-L1 cell line differentiation into adipocytes. In the first part of our study, we prove that Les-2194, Les-3377, and Les-3640 are cytotoxic to 3T3-L1 cells. In the next stage, we determine that Les-2194, Les-3377, and Les-3640 stimulate lipid accumulation (using the ORO staining method) and induce specific gene expression (Dlk1, Fabp4, Vegfa, Pai-1, Resistin, Adiponectin, and Pparγ). Our data show that rosiglitazone, pioglitazone, Les-2194, and Les-3640 at a concentration of 2 μM do not affect 3T3-L1 cell viability and do not activate the apoptotic process. Only Les-3377 decreased the number and metabolism of the cells. Although all the studied compounds influenced the expression of Dlk1, Fabp4, Vegfa, Pai-1, Resistin, Adiponectin, and Pparγ genes, none of them caused gene expression similar to that induced by rosiglitazone or pioglitazone. The ORO staining showed that rosiglitazone and pioglitazone induced lipid accumulation in the 3T3-L1 cell line, which is a marker of mature adipocytes. Only rosiglitazone increased Pparγ protein expression after 14 days of differentiation.

GPR120/FFAR4 Pharmacology: Focus on Agonists in Type 2 Diabetes Mellitus Drug Discovery

The G-protein coupled receptors (GPCRs) activated by free fatty acids (FFAs) have emerged as new and exciting drug targets, due to their plausible translation from pharmacology to medicines. This perspective aims to report recent research about GPR120/FFAR4 and its involvement in several diseases, including cancer, inflammatory conditions, and central nervous system disorders. The focus is to highlight the importance of GPR120 in Type 2 diabetes mellitus (T2DM). GPR120 agonists, useful in T2DM drug discovery, have been widely explored from a structure–activity relationship point of view. Since the identification of the first reported synthetic agonist TUG-891, the research has paved the way for the development of TUG-based molecules as well as new and different chemical entities. These molecules might represent the starting point for the future discovery of GPR120 agonists as antidiabetic drugs.

The Endocannabinoid System and PPARs: Focus on Their Signalling Crosstalk, Action and Transcriptional Regulation

Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors including PPARα, PPARγ, and PPARβ/δ, acting as transcription factors to regulate the expression of a plethora of target genes involved in metabolism, immune reaction, cell differentiation, and a variety of other cellular changes and adaptive responses. PPARs are activated by a large number of both endogenous and exogenous lipid molecules, including phyto- and endo-cannabinoids, as well as endocannabinoid-like compounds. In this view, they can be considered an extension of the endocannabinoid system. Besides being directly activated by cannabinoids, PPARs are also indirectly modulated by receptors and enzymes regulating the activity and metabolism of endocannabinoids, and, vice versa, the expression of these receptors and enzymes may be regulated by PPARs. In this review, we provide an overview of the crosstalk between cannabinoids and PPARs, and the importance of their reciprocal regulation and modulation by common ligands, including those belonging to the extended endocannabinoid system (or "endocannabinoidome") in the control of major physiological and pathophysiological functions.

Fish Oil Enriched in EPA, but Not in DHA, Reverses the Metabolic Syndrome and Adipocyte Dysfunction Induced by a High-Fat Diet

This study aimed to investigate the effects of two commercially available fish oils (FOs) containing different proportions of two omega-3 fatty acids (FA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on the metabolic and endocrine dysfunctions of white adipose tissue resulting from obesity. Male C57BL/6J mice, 8 weeks old, received a control or high-fat diet (CO and HF groups, with 9% and 59% energy from fat, respectively) for 8 weeks. The next 8 weeks, the HF group was subdivided into HF, HF+FO/E (HF+5:1 EPA:DHA), and HF+FO/D (HF+5:1 DHA:EPA). Supplementation was performed by gavage, three times a week. All groups that received the HF diet had lower food and caloric intake, but a higher fat intake, body weight (BW) gain, glucose intolerance, and a significant increase in inguinal (ING), retroperitoneal (RP), and epididymal (EPI) adipose tissues when compared to the CO group. Additionally, HF and HF+FO/D groups showed insulin resistance, adipocyte hypertrophy, increased lipolysis and secretion of TNF-α, resistin and IL-10 adipokines by ING and RP adipocytes, and adiponectin only by the HF+FO/D group in ING adipocytes. All of these effects were completely reversed in the HF+FO/E group, which also showed partial reversion in BW gain and glucose intolerance. Both the HF+FO/E and HF+FO/D groups showed a reduction in ING and RP adipose depots when compared to the HF group, but only HF+FO/E in the EPI depot. HF+FO/E, but not HF+FO/D, was able to prevent the changes triggered by obesity in TNF-α, Il-10, and resistin secretion in ING and RP depots. These results strongly suggest that different EPA:DHA ratios have different impacts on the adipose tissue metabolism, FO being rich in EPA, but not in DHA, and effective in reversing the changes induced by obesity.

Elastin-derived peptide VGVAPG decreases differentiation of mouse embryo fibroblast (3T3-L1) cells into adipocytes

Elastin is a highly elastic protein present in connective tissue. As a result of protease activity, elastin hydrolysis occurs, and during this process, elastin-derived peptides (EDPs) are released. One of the constitutively repeating elastin and EDP building sequences is the hexapeptide VGVAPG. Therefore, the aim of our research was to define the effect of VGVAPG peptide on adipogenesis in a mouse 3T3-L1 cell line. 3T3-L1 cells were differentiated according to a previously described protocol and exposed to increasing concentrations of VGVAPG or VVGPGA peptide. The obtained results showed that VGVAPG peptide does not stimulate reactive oxygen species (ROS) production, caspase-1 activation, and 3T3-L1 cell proliferation. In the second part of the experiments, it was proved that VGVAPG peptide decreased lipid accumulation as measured by oil red O staining, which was confirmed by the profile of increased expression markers of undifferentiated preadipocytes. In our experiments, 10 nM VGVAPG added for differentiating to adipocytes increased the expression of Pref-1, serpin E1, and adiponectin as compared to rosiglitazone (PPARγ agonist)-treated group and simultaneously decreased the expression of VEGF and resistin as compared to the rosiglitazone-treated group. The obtained results show that VGVAPG peptide sustains 3T3 cells in undifferentiated state.

ABBREVIATIONS

DMSO: dimethyl sulphoxide; EBP: elastin-binding protein; EDPs: elastin-derived peptides; FBS: foetal bovine serum; Glb1: gene for beta-galactosidase; LDL: low-density-lipoprotein; PAI-1 (Serpin E1): plasminogen activator inhibitor-1; PBS: phosphate-buffered saline; PPARγ: peroxisome proliferator-activated receptor gamma; Pref-1: preadipocyte factor 1; ROS: reactive oxygen species; VEGF-A: vascular endothelial growth factor-A; VGVAPG: Val-Gly-Val-Ala-Pro-Gly; β-Gal: beta-galactosidase; ORO: oil red O; IBMX: 3-isobutyl-1-methylxanthine; H2DCFDA: 2',7'-dichlorodihydrofluorescein diacetate; DMEM: Dulbecco's Modified Eagle's Medium; VVGPGA: Val-Val-Gly-Pro-Gly-Ala.

Maternal Docosahexaenoic Acid Status during Pregnancy and Its Impact on Infant Neurodevelopment

Dietary components are essential for the structural and functional development of the brain. Among these, docosahexaenoic acid, 22:6n-3 (DHA), is critically necessary for the structure and development of the growing fetal brain in utero. DHA is the major n-3 long-chain polyunsaturated fatty acid in brain gray matter representing about 15% of all fatty acids in the human frontal cortex. DHA affects neurogenesis, neurotransmitter, synaptic plasticity and transmission, and signal transduction in the brain. Data from human and animal studies suggest that adequate levels of DHA in neural membranes are required for maturation of cortical astrocyte, neurovascular coupling, and glucose uptake and metabolism. Besides, some metabolites of DHA protect from oxidative tissue injury and stress in the brain. A low DHA level in the brain results in behavioral changes and is associated with learning difficulties and dementia. In humans, the third trimester-placental supply of maternal DHA to the growing fetus is critically important as the growing brain obligatory requires DHA during this window period. Besides, DHA is also involved in the early placentation process, essential for placental development. This underscores the importance of maternal intake of DHA for the structural and functional development of the brain. This review describes DHA’s multiple roles during gestation, lactation, and the consequences of its lower intake during pregnancy and postnatally on the 2019 brain development and function.

Omega-3 Fatty Acids and Adipose Tissue: Inflammation and Browning

White adipose tissue (WAT) and brown adipose tissue (BAT) are involved in whole-body energy homeostasis and metabolic regulation. Changes to mass and function of these tissues impact glucose homeostasis and whole-body energy balance during development of obesity, weight loss, and subsequent weight regain. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs), which have known hypotriglyceridemic and cardioprotective effects, can also impact WAT and BAT function. In rodent models, these fatty acids alleviate obesity-associated WAT inflammation, improve energy metabolism, and increase thermogenic markers in BAT. Emerging evidence suggests that ω-3 PUFAs can also modulate gut microbiota impacting WAT function and adiposity. This review discusses molecular mechanisms, implications of these findings, translation to humans, and future work, especially with reference to the potential of these fatty acids in weight loss maintenance.

The effect of Faecalibacterium prausnitzii and its extracellular vesicles on the permeability of intestinal epithelial cells and expression of PPARs and ANGPTL4 in the Caco-2 cell culture model

Background and Objectives

Gut microbiota such as Faecalibacterium prausnitzii play a major role in the regulation of gut barrier, inflammation and metabolic functions. Microbiota-derived extracellular vehicles (EVs) have been recently introduced as functional units mediating the eukaryotic and prokaryotic cell-microbiota interactions. In this paper, the effect of F. prausnitzii and its EVs on mRNA expression levels of tight junction genes (ZO1 and OCLN) as well as PPARs and ANGPTL4 genes in the human epithelial colorectal adenocarcinoma (Caco-2) cell line was evaluated.

Methods

F. prausnitzii was cultured on the Brain Heart Infusion (BHI) broth medium under anaerobic conditions, and its EVs were extracted by ultracentrifugation. This bacterium and its EVs were treated on the Caco-2 cells. After 24 h, the expression of the genes encoding TJ proteins such as ZO1 and OCLN, PPARs and ANGPTL4 was evaluated by quantitative real-time PCR.

Results

Unlike F. prausnitzii, its EVs significantly increased the expression of ZO1 and OCLN genes, and PPARα, PPARγ and PPARβ/δ genes (except at a concentration of 100 µg/ml) as well as ANGPTL4 gene.

Conclusions

The results of this study demonstrated that F. prausnitzii-derived EVs increased the intestinal barrier permeability via TJs (ZO1 and OCLN) as well as PPAR-α, PPAR-γ and PPAR β/δ genes and their targeted gene (ANGPTL4) in the Caco-2 cell line. Accordingly, it is suggested that F. prausnitzii-derived EVs can be considered as a new bacterial postbiotic to cure dysbiosis-associated diseases including obesity and its related metabolic dysfunctions, according to the leaky gut hypothesis.

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.

Cytochrome P450 derived epoxidized fatty acids as a therapeutic tool against neuroinflammatory diseases

Cytochrome P450 (CYP) metabolism of arachidonic acid (ARA) produces epoxy fatty acids (EpFAs) such as epoxyeicosatrienoic acids (EETs) that are known to exert protective effects in inflammatory disorders. Endogenous EpFAs are further metabolized into corresponding diols by the soluble epoxide hydrolase (sEH). Through inhibition of sEH, many studies have demonstrated the cardioprotective and renoprotective effects of EpFAs; however, the role of sEH inhibition in modulating the pathogenesis of neuroinflammatory disorders is less well described. In this review, we discuss the current knowledge surrounding the effects of sEH inhibition and EpFA action in neuroinflammatory disorders such as Parkinson's Disease (PD), stroke, depression, epilepsy, and Alzheimer's Disease (AD), as well as the potential mechanisms that underlie the therapeutic effects of sEH inhibition.

Molecular pathway analysis associates alterations in obesity-related genes and antipsychotic-induced weight gain

OBJECTIVE

Antipsychotics often induce excessive weight gain. We hypothesised that individuals with genetic variations related to known obesity-risk genes have an increased risk of excessive antipsychotic-induced weight gain (AIWG). This hypothesis was tested in a subset of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) trial data set.

METHODS

The CATIE trial compared effects and side effects of five different antipsychotics through an 18-month period. Based on the maximum weight gain recorded, excessive weight gain was defined as >7% weight gain. Cytoscape and GeneMANIA were instrumental in composing a molecular pathway from eight selected genes linked to obesity. Genetic information on a total of 495.172 single-nucleotide polymorphisms (SNPs) were available from 765 (556 males) individuals. Enrichment test was conducted through ReactomePA and Bioconductor. A permutation test was performed, testing the generated pathway against 105 permutated pathways (p ≤ 0.05). In addition, a standard genome-wide association study (GWAS) analysis was performed.

RESULT

GWAS analysis did not detect significant differences related to excessive weight gain. The pathway generated contained 28 genes. A total of 2067 SNPs were significantly expressed (p < 0.01) within this pathway when comparing excessive weight gainers to the rest of the sample. Affected genes including PPARG and PCSK1 were not previously related to treatment-induced weight gain.

CONCLUSIONS

The molecular pathway composed from high-risk obesity genes was shown to overlap with genetics of patients who gained >7% weight gain during the CATIE trial. This suggests that genes related to obesity compose a pathway of increased risk of excessive AIWG. Further independent analyses are warranted that may confirm or clarify the possible reasoning behind.

In Vitro Effects of Eicosapentaenoic and Docosahexaenoic Acid on the Vascular Tone of a Human Saphenous Vein: Influence of Precontractile Agents

BACKGROUND

Cardiovascular effects of omega-3 polyunsaturated fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been widely reported. However, there are limited studies concerning their effects on human blood vessels. Therefore, the aim of this study was to investigate the direct vascular effects of EPA and DHA on the human saphenous vein (SV) precontracted with either prostaglandin F2α (PGF2α), or thromboxane A2 analogue (U46619), or norepinephrine (NE). Moreover, we aimed to investigate the protein expression of free fatty acid receptor 4 (FFAR4) in human SV.

METHODS

Pretreatment of human SV rings with EPA and DHA (100 μM, 30 min) was tested on vascular reactivity induced by PGF2α (10 nM to 5 μM), NE (10 nM to 100 μM), and U46619 (1 nM to 100 nM). In addition, direct relaxant effects of EPA/DHA (1-100 μM) were tested in human SV rings precontracted by PGF2α, NE, and U46619. Furthermore, the involvement of potassium channels on their vascular effects was investigated in the presence of the nonselective K⁺ channel inhibitor tetraethylammonium chloride.

RESULTS

Pretreatment with EPA and DHA resulted in a significant decrease in vascular reactivity induced by U46619 and PGF2α compared to NE. In the presence of TEA, the relaxant effects of EPA and DHA were significantly decreased in SV preparations precontracted by U46619 and PGF2α for DHA. Furthermore, FFAR-4 protein was expressed in tissue extracts of human SV.

CONCLUSIONS

Our study demonstrates that both EPA and DHA reduce the increased vascular tone elicited by contractile agents on the human SV and that the direct vasorelaxant effect is likely to involve potassium channels.

Absence of estrogen receptor beta leads to abnormal adipogenesis during early tendon healing by an up-regulation of PPARγ signalling

Achilles tendon injury is one of the challenges of sports medicine, the aetiology of which remains unknown. For a long time, estrogen receptor β (ERβ) has been known as a regulating factor of the metabolism in many connective tissues, such as bone, muscle and cartilage, but little is known about its role in tendon. Recent studies have implicated ERβ as involved in the process of tendon healing. Tendon-derived stem cells (TDSCs) are getting more and more attention in tendon physiological and pathological process. In this study, we investigated how ERβ played a role in Achilles tendon healing. Achilles tendon injury model was established to analyse how ERβ affected on healing process in vivo. Cell proliferation assay, Western blots, qRT-PCR and immunocytochemistry were performed to investigate the effect of ERβ on TDSCs. Here, we showed that ERβ deletion in mice resulted in inferior gross appearance, histological scores and, most importantly, increased accumulation of adipocytes during the early tendon healing which involved activation of peroxisome proliferator-activated receptor γ (PPARγ) signalling. Furthermore, in vitro results of ours confirmed that the abnormity might be the result of abnormal TDSC adipogenic differentiation which could be partially reversed by the treatment of ERβ agonist LY3201. These data revealed a role of ERβ in Achilles tendon healing for the first time, thereby providing a new target for clinical treatment of Achilles tendon injury.

PPAR-γ: Its ligand and its regulation by microRNAs

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

Visceral adipogenesis inhibited by Pref-1 is associated with peritoneal angiogenesis

AIM

Studies showed an increased visceral adipose tissue and peritoneal angiogenesis in peritoneal dialysis (PD) patients. However, the relationship between the visceral adipose expands and peritoneal angiogenesis remains unclear.

METHODS

Pref-1 (preadipocyte factor-1) recombinant adeno-associated virus (AAV) and control AAV were constructed. Mice were divided into four groups, mice in control and PD group were injected intraperitoneally with PBS, mice in control-AAV-PD were injected intraperitoneally with plaque-forming unit (PFU) control AAV and mice in pref-1-AAV-PD group were injected with PFU recombinant AAV. Two weeks later, control group was injected intraperitoneally with normal saline while other groups were injected intraperitoneally with 4.25% peritoneal dialysis fluid (PDF). Thirty days later, viscerall adipose tissue was collected and weighed. Pref-1 protein expression was measured by Western blot, and peritoneal permeability was measured by Evans blue. Cluster of differentiation 31(CD31) immunohistochemical staining was used to detect mesenteric blood vessel number, and vascular endothelial growth factor (VEGF) in serum were measured by enzyme-linked immunosorbent assay.

RESULTS

Pref-1 protein expression increased in pref-1-AAV-PD group. Visceral adipose expanded in PD and control-AAV-PD group while decreased in pref-1-AAV-PD group, which approves PD fluid enhance visceral adipogensis, and the process could be inhibited by Pref-1 recombinant AAV. The reduction of peritoneal vessel number and the decrease of vascular permeability as well as down-regulation of serum vascular endothelial growth factor observed in pref-1-AAV-PD group suggested peritoneal angiogenesis could be inhibited following visceral adipose tissue reduction.

CONCLUSION

Visceral adipose expands is associated with peritoneal angiogenesis in PD treatment, and prevention of visceral adipogenesis may be an alternative way to protect the validity of peritoneum. Copyright © 2019 John Wiley & Sons, Ltd.

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.

Interactions between Host PPARs and Gut Microbiota in Health and Disease

The human gastrointestinal tract is inhabited by many types of microbiota, including bacteria, viruses, and fungi. Dysregulations of their microenvironment are associated with various health problems, not only limited to gastrointestinal disorders, such as inflammatory bowel disease, but to impacts beyond the intestine. For example, intestinal microbiota can affect the liver in non-alcoholic fatty liver disease, visceral adipose tissue during adipogenesis, and the heart in atherosclerosis. The factors contributing to these pathogeneses involve the gut microbiota and the effector organs of the host, and everything in between. The nuclear receptor peroxisome proliferator-activated receptors (PPARs) are pivotal for the modulation of many of the pathogeneses mentioned above. It is, therefore, conceivable that, in the process of host-microbiota interactions, PPARs play important roles. In this review, we focus on the interactions between host PPARs in different organs and gut microbiota and their impacts on maintaining health and various diseases.

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.

IL-1β and TNFα inhibit GPR120 (FFAR4) and stimulate GPR84 (EX33) and GPR41 (FFAR3) fatty acid receptor expression in human adipocytes: implications for the anti-inflammatory action of n-3 fatty acids

Regulation of the expression of GPCR fatty acid receptor genes has been examined in human adipocytes differentiated in culture. TNFα and IL-1β induced a marked reduction in GPR120 expression, mRNA level falling 17-fold at 24 h in adipocytes incubated with TNFα. In contrast, GPR84 mRNA was dramatically increased by these cytokines (>500-fold for IL-1β at 4 h); GPR41 expression was also stimulated. Rosiglitazone did not affect GPR84 expression, but GPR120 and GPR41 expression increased. Dexamethasone, insulin, linoleic and docosahexaenoic acids (DHA), and TUG891 (GPR120 agonist) had little effect on GPR120 and GPR84 expression. TUG891 did not attenuate the pro-inflammatory actions of TNFα and IL-1β. DHA slightly countered the actions of IL-1β on CCL2, IL6 and ADIPOQ expression, though not on secretion of these adipokines. GPR120 and GP84 gene expression in human adipocytes is highly sensitive to pro-inflammatory mediators; the inflammation-induced inhibition of GPR120 expression may compromise the anti-inflammatory action of GPR120 agonists.

Fish oil as a potential activator of brown and beige fat thermogenesis

Numerous studies have shown that feeding rodents n-3 polyunsaturated fatty acids attenuates adiposity. Moreover, meta-analyses of human dietary intervention studies indicate that fish oil (eicosapentaenoic and docosahexaenoic acid) supplementation might reduce waist circumference. A recent line of research suggests that browning of white adipose depots and activation of uncoupled respiration in brown fat contributes to these effects. This mini-review summarizes the observations in rodents, highlights several mechanisms that might explain these observations and discusses the translational potential. Given the available in vivo evidence and the ability of human adipocytes to aquire a beige phenotype in response to eicosapentaenoic acid incubation, future studies should test the hypothesis that fish oil activates thermogenic brown and beige adipose tissue in humans.

Omega-3 fatty acids in obesity and metabolic syndrome: a mechanistic update

Strategies to reduce obesity have become public health priorities as the prevalence of obesity has risen in the United States and around the world. While the anti-inflammatory and hypotriglyceridemic properties of long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) are well known, their antiobesity effects and efficacy against metabolic syndrome, especially in humans, are still under debate. In animal models, evidence consistently suggests a role for n-3 PUFAs in reducing fat mass, particularly in the retroperitoneal and epididymal regions. In humans, however, published research suggests that though n-3 PUFAs may not aid weight loss, they may attenuate further weight gain and could be useful in the diet or as a supplement to help maintain weight loss. Proposed mechanisms by which n-3 PUFAs may work to improve body composition and counteract obesity-related metabolic changes include modulating lipid metabolism; regulating adipokines, such as adiponectin and leptin; alleviating adipose tissue inflammation; promoting adipogenesis and altering epigenetic mechanisms.

Effect of cilostazol on plasma levels of proprotein convertase subtilisin/kexin type 9

The protein complex proprotein convertase subtilisin/kexin type 9 (PCSK9) serves as an important target for the prevention and treatment of atherosclerosis and lipid homeostasis. This study investigated the effect of cilostazol on plasma PCSK9 concentrations. We performed a post hoc analysis of two prospective, double-blind, randomized controlled trials including 115 patients of whom 61 received cilostazol 200 mg/day and 54 received placebo for 12 weeks. Linear regression analysis was performed to determine the associations between several parameters and changes in PCSK9 levels. Use of cilostazol, but not placebo, significantly increased plasma PCSK9 concentrations, high-density lipoprotein cholesterol levels, and number of circulating endothelial progenitor cells (EPCs), and decreased triglyceride levels with a trend toward an increase in total cholesterol (TC) levels. A reduction in hemoglobin A1C and an increase in plasma vascular endothelial growth factor and adiponectin levels with cilostazol treatment were also found. Changes in the number of circulating EPCs were positively correlated and the TC concentrations were inversely correlated with changes in the PCSK9 levels. After adjusting for changes in levels of TC and numbers of circulating EPCs and history of metabolic syndrome, use of cilostazol remained independently associated with changes in plasma PCSK9 levels. In conclusion, cilostazol treatment was significantly and independently associated with an increase in plasma PCSK9 levels in patients with peripheral artery disease or at a high risk of cardiovascular disease regardless of background statin use and caused an improvement in some metabolic disorders and levels of vasculo-angiogenic biomarkers.

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.

PPARγ-mediated G-protein coupled receptor 120 signaling pathway promotes transcriptional activation of miR-143 in adipocytes

MicroRNAs (miRNAs), the small noncoding RNAs, regulate various biological processes such as adipogenesis. MicroRNA-143 (miR-143) promotes adipocyte differentiation, and is correlated with obesity in mice fed a high-fat diet. However, the transcriptional regulation of miR-143 is largely unknown. In this study, we identified that miR-143 is a target of peroxisome proliferator-activated receptor γ (PPARγ), a key transcription factor in adipogenesis. Four putative peroxisome proliferator response elements (PPREs) were identified in the miR-143 promoter region. Using chromatin immune-precipitation, we observed that PPARγ was bound with two PPRE regions of the miR-143 promoter in 3T3-L1 adipocytes. A luciferase reporter assay showed that the PPRE1 region (-1330/-1309) of the miR-143 promoter played an important role in PPARγ transcriptional activation. In addition, we determined that G-protein coupled receptor 120 (GPR 120), which functions as an omega 3 fatty acid receptor, affected miR-143 expression in adipocytes. GPR120 silencing in adipocytes inhibited the expression of PPARγ and miR-143, whereas GPR120 overexpression led to increased expressions of PPARγ and miR-143. Silencing of PPARγ inhibited the induction of miR-143 by GPR-120. These results suggested that a PPARγ-mediated GPR120 signaling pathway promotes transcriptional activation of miR-143 in adipocytes.

Suppression of Wnt Signaling and Osteogenic Changes in Vascular Smooth Muscle Cells by Eicosapentaenoic Acid

Vascular medial calcification is often observed in patients with arteriosclerosis. It is also associated with systolic hypertension, wide pulse pressure, and fluctuation of blood pressure, which results in cardiovascular events. Eicosapentaenoic acid (EPA) has been shown to suppress vascular calcification in previous animal experiments. We investigated the inhibitory effects of EPA on Wnt signaling, which is one of the important signaling pathways involved in vascular calcification. Intake of food containing 5% EPA resulted in upregulation of the mRNA expression of Klotho, an intrinsic inhibitor of Wnt signaling, in the kidneys of wild-type mice. Expression levels of β-catenin, an intracellular signal transducer in the Wnt signaling pathway, were increased in the aortas of Klotho mutant (kl/kl) mice compared to the levels in the aortas of wild-type mice. Wnt3a or BIO, a GSK-3 inhibitor that activates β-catenin signaling, upregulated mRNA levels of AXIN2 and LEF1, Wnt signaling marker genes, and RUNX2 and BMP4, early osteogenic genes, in human aorta smooth muscle cells. EPA suppressed the upregulation of AXIN2 and BMP4. The effect of EPA was cancelled by T0070907, a PPARγ inhibitor. The results suggested that EPA could suppress vascular calcification via the inhibition of Wnt signaling in osteogenic vascular smooth muscle cells via PPARγ activation.

GPR120: a critical role in adipogenesis, inflammation, and energy metabolism in adipose tissue

It is well known that adipose tissue has a critical role in the development of obesity and metabolic diseases and that adipose tissue acts as an endocrine organ to regulate lipid and glucose metabolism. Accumulating in the adipose tissue, fatty acids serve as a primary source of essential nutrients and act on intracellular and cell surface receptors to regulate biological events. G protein-coupled receptor 120 (GPR120) represents a promising target for the treatment of obesity-related metabolic disorders for its involvement in the regulation of adipogenesis, inflammation, glucose uptake, and insulin resistance. In this review, we summarize recent studies and advances regarding the systemic role of GPR120 in adipose tissue, including both white and brown adipocytes. We offer a new perspective by comparing the different roles in a variety of homeostatic processes from adipogenic development to adipocyte metabolism, and we also discuss the effects of natural and synthetic agonists that may be potential agents for the treatment of metabolic diseases.

Peroxisome proliferator‑activated receptor γ mediates porcine placental angiogenesis through hypoxia inducible factor‑, vascular endothelial growth factor‑ and angiopoietin‑mediated signaling

Peroxisome proliferator-activated receptor (PPAR) γ has been reported to be implicated in placentation in mice. Previous studies have demonstrated that PPARγ is also expressed in porcine placenta, primarily localized in vascular endothelial cells (VECs). The present study aimed to investigate the roles of PPARγ during porcine placental angiogenesis and examine the molecular mechanisms involved in its actions. VECs were incubated with the PPARγ agonist rosiglitazone and the antagonist T0070907, and their angiogenic potential was evaluated using cellular impedance, wound healing and tube formation assays. Reverse transcription-quantitative polymerase chain reaction was used to assess the mRNA expression levels of angiogenic factors, including hypoxia-inducible factors (HIFs), vascular endothelial growth factor (VEGF) isoforms, VEGF receptors (VEGFRs) and angiopoietins (Angs). The results demonstrated that the adhesive, proliferative and migratory capabilities of VECs were potentiated by rosiglitazone and suppressed by T0070907. Notably, tube formation was invariably promoted during PPARγ activation and blockade. The mRNA expression levels of HIF1α, HIF2α, VEGFR2, VEGF188 and Ang-1 were revealed to be upregulated following treatment of VECs with rosiglitazone, whereas they were downregulated following treatment with T0070907. However, the mRNA expression levels of placental growth factor and VEGF120 were consistently downregulated following PPARγ activation and blockade, whereas VEGF164 mRNA levels remained unaltered. The results of the present study suggested that PPARγ may mediate porcine placental angiogenesis, by interfering with HIF-, VEGF- and angiopoietin-mediated signaling pathways.

Probe-Dependent Negative Allosteric Modulators of the Long-Chain Free Fatty Acid Receptor FFA4

High-affinity and selective antagonists that are able to block the actions of both endogenous and synthetic agonists of G protein–coupled receptors are integral to analysis of receptor function and to support suggestions of therapeutic potential. Although there is great interest in the potential of free fatty acid receptor 4 (FFA4) as a novel therapeutic target for the treatment of type II diabetes, the broad distribution pattern of this receptor suggests it may play a range of roles beyond glucose homeostasis in different cells and tissues. To date, a single molecule, 4-methyl-N-9H-xanthen-9-yl-benzenesulfonamide (AH-7614), has been described as an FFA4 antagonist; however, its mechanism of antagonism remains unknown. We synthesized AH-7614 and a chemical derivative and demonstrated these to be negative allosteric modulators (NAMs) of FFA4. Although these NAMs did inhibit FFA4 signaling induced by a range of endogenous and synthetic agonists, clear agonist probe dependence in the nature of allosteric modulation was apparent. Although AH-7614 did not antagonize the second long-chain free fatty acid receptor, free fatty acid receptor 1, the simple chemical structure of AH-7614 containing features found in many anticancer drugs suggests that a novel close chemical analog of AH-7614 devoid of FFA4 activity, 4-methyl-N-(9H-xanthen-9-yl)benzamide (TUG-1387), will also provide a useful control compound for future studies assessing FFA4 function. Using TUG-1387 alongside AH-7614, we show that endogenous activation of FFA4 expressed by murine C3H10T1/2 mesenchymal stem cells is required for induced differentiation of these cells toward a more mature, adipocyte-like phenotype.

GPR120 in adipocytes has differential roles in the production of pro-inflammatory adipocytokines

How nutritional excess leads to inflammatory responses in metabolic syndrome is not well characterized. Here, we evaluated the effects of ω-3 polyunsaturated fatty acid specific G-protein coupled receptor 120 (GPR120) activation on inflammatory pathways in adipocytes, and the influence of this process on macrophage migration. Using 3T3-L1 adipocytes, we found that agonizing GPR120 using its synthetic ligand, GSK137647, attenuated both basal and lipopolysaccharide-induced production of interleukin-6 (IL-6) and C-C motif chemokine ligand 2 (CCL2). Moreover, the intervention reduced the phosphorylation of nuclear factor kappa B inhibitor alpha (IκBα) and nuclear translocation of nuclear factor kappa-B p65 subunit (p65). Furthermore, the silencing of GPR120 itself reduced IL-6 and CCL2 mRNA expression. Inhibition of protein kinase C (PKC) augmented the down-regulatory effect of GSK137647 on IL-6 and CCL2 mRNA. Using a luciferase assay to measure promoter activity of the IL-6 gene in mouse embryonic fibroblasts, we demonstrated that exogenous transfection of GPR120 alone reduced the promoter activity, which was augmented by GSK137647. Inhibition of PKC further reduced the promoter activity. Nevertheless, RAW 264.7 macrophages grown in conditioned medium collected from GSK137647-treated adipocytes attenuated the expressions of matrix metalloproteinases-9 and -3, and tissue inhibitor of metalloproteinase-1. Conditioned medium also inhibited the lipopolysaccharide-induced migration of these macrophages. Taken together, these findings provide critical evidence that although GPR120 is associated with a PKC-mediated pro-inflammatory pathway, the direct inhibitory effects of GPR120 on the nuclear factor kappa B pathway are anti-inflammatory. Moreover, GPR120 activity can attenuate the adipocyte-mediated enhanced production of extracellular matrix-modulating factors in macrophages and can reduce their migration by a paracrine mechanism.

Deciphering the Roles of Thiazolidinediones and PPAR in Bladder Cancer

The use of thiazolidinedione (TZD) therapy in type II diabetic patients has proven useful in the lowering of blood glucose levels. However, recent investigations have shown that there may be potential health concerns associated, including the risk of developing bladder cancer as well as complications in the cardiovasculature. TZDs are ligands for the nuclear receptor PPARγ, and activation causes lipid uptake and insulin sensitization, both of which are critical processes for diabetic patients whose bodies are unable to utilize insulin effectively. Several studies have shown that PPARγ/TZDs decrease IGF-1 levels and, thus, reduce cancer growth in carcinomas such as the pancreas, colon, liver, and prostate. However, other studies have shed light on the potential of the receptor as a biomarker for uroepithelial carcinomas, particularly due to its stimulatory effect on migration of bladder cancer cells. Furthermore, PPARγ may provide the tumor-promoting microenvironment by de novo synthesis of nutrients that are needed for bladder cancer development. In this review, we closely examine the TZD class of drugs and their effects on PPARγ in patient studies along with additional molecular factors that are positive modulators, such as protein phosphatase 5 (PP5), which may have considerable implications for bladder cancer therapy.

ω3-Polyunsaturated fatty acids for heart failure: Effects of dose on efficacy and novel signaling through free fatty acid receptor 4

Heart failure (HF) affects 5.7 million in the U.S., and despite well-established pharmacologic therapy, the 5-year mortality rate remains near 50%. Furthermore, the mortality rate for HF has not declined in years, highlighting the need for new therapeutic options. Omega-3 polyunsaturated fatty acids (ω3-PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are important regulators of cardiovascular health. However, questions of efficacy and mechanism of action have made the use of ω3-PUFAs in all cardiovascular disease (CVD) controversial. Here, we review recent studies in animal models of HF indicating that ω3-PUFAs, particularly EPA, are cardioprotective, with the results indicating a threshold for efficacy. We also examine clinical studies suggesting that ω3-PUFAs improve outcomes in patients with HF. Due to the relatively small number of clinical studies of ω3-PUFAs in HF, we discuss EPA concentration-dependency on outcomes in clinical trials of CVD to gain insight into the perceived questionable efficacy of ω3-PUFAs clinically, with the results again indicating a threshold for efficacy. Ultimately, we suggest that the main failing of ω3-PUFAs in clinical trials might be a failure to reach a therapeutically effective concentration. We also examine mechanistic studies suggesting that ω3-PUFAs signal through free fatty acid receptor 4 (Ffar4), a G-protein coupled receptor (GPR) for long-chain fatty acids (FA), thereby identifying an entirely novel mechanism of action for ω3-PUFA mediated cardioprotection. Finally, based on mechanistic animal studies suggesting that EPA prevents interstitial fibrosis and diastolic dysfunction, we speculate about a potential benefit for EPA-Ffar4 signaling in heart failure preserved with ejection fraction.

Cilostazol Enhances Mobilization of Circulating Endothelial Progenitor Cells and Improves Endothelium-Dependent Function in Patients at High Risk of Cardiovascular Disease

This is the first study to investigate the vasculoangiogenic effects of cilostazol on endothelial progenitor cells (EPCs) and flow-mediated dilatation (FMD) in patients at high risk of cardiovascular disease (CVD). This double-blind, placebo-controlled study included 71 patients (37 received 200 mg/d cilostazol and 34 received placebo for 12 weeks). Use of cilostazol, but not placebo, significantly increased circulating EPC (kinase insert domain receptor+CD34+) counts (percentage changes: 149.0% [67.9%-497.8%] vs 71.9% [−31.8% to 236.5%], P = .024) and improved triglyceride and high-density lipoprotein cholesterol levels ( P = .002 and P = .003, respectively). Plasma levels of vascular endothelial growth factor (VEGF)-A165 and FMD significantly increased (72.5% [32.9%-120.4%] vs −5.8% [−46.0% to 57.6%], P = .001; 232.8% ± 83.1% vs −46.9% ± 21.5%, P = .003, respectively) in cilostazol-treated patients. Changes in the plasma triglyceride levels significantly inversely correlated with the changes in the VEGF-A165 levels and FMD. Cilostazol significantly enhanced the mobilization of EPCs and improved endothelium-dependent function by modifying some metabolic and angiogenic markers in patients at high risk of CVD.

MicroRNA-130b promotes lung cancer progression via PPARγ/VEGF-A/BCL-2-mediated suppression of apoptosis

Background

The prognosis of non-small-cell lung cancer (NSCLC) is poor yet mechanistic understanding and therapeutic options remain limited. We investigated the biological and clinical significance of microRNA-130b and its relationship with apoptosis in NSCLC.

Methods

The level of microRNA-130b in relationship with the expression of PPARγ, VEGF-A, BCL-2 and apoptosis were analyzed in 91 lung cancer patient samples using immunohistochemistry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay on tissue microarrays. Gain and loss-of-function studies were performed to investigate the effects of microRNA-130b, peroxisome proliferator-activated receptor γ (PPARγ) or vascular endothelial growth factor-A (VEGF-A) on biological functions of lung cancer cells using in vitro and in vivo approaches.

Results

MicroRNA-130b up-regulation conferred unfavorable prognosis of lung cancer patients. Notably, microRNA-130b targeted PPARγ and inhibiting microRNA-130b markedly repressed proliferation, invasion and metastasis of lung cancer cells, leading to increased apoptosis. MicroRNA-130b-dependent biologic effects were due to suppression of PPARγ that in turn activated BCL-2, the key mediator of anti-apoptosis. Administration of microRNA-130b mimic to mouse xenografts promoted tumor growth. In vitro and in vivo, miR-130b enrichment associated with down-regulation of PPARγ, up-regulation of VEGF-A and BCL-2, and decreased apoptosis.

Conclusions

The present study demonstrates that microRNA-130b promotes lung cancer progression via PPARγ/VEGF-A/BCL-2-mediated suppression of apoptosis. Targeting microRNA-130b might have remarkable therapeutic potential for lung cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0382-3) contains supplementary material, which is available to authorized users.

Complex Pharmacology of Free Fatty Acid Receptors

G protein-coupled receptors (GPCRs) are historically the most successful family of drug targets. In recent times it has become clear that the pharmacology of these receptors is far more complex than previously imagined. Understanding of the pharmacological regulation of GPCRs now extends beyond simple competitive agonism or antagonism by ligands interacting with the orthosteric binding site of the receptor to incorporate concepts of allosteric agonism, allosteric modulation, signaling bias, constitutive activity, and inverse agonism. Herein, we consider how evolving concepts of GPCR pharmacology have shaped understanding of the complex pharmacology of receptors that recognize and are activated by nonesterified or "free" fatty acids (FFAs). The FFA family of receptors is a recently deorphanized set of GPCRs, the members of which are now receiving substantial interest as novel targets for the treatment of metabolic and inflammatory diseases. Further understanding of the complex pharmacology of these receptors will be critical to unlocking their ultimate therapeutic potential.

Disruption of the sugar-sensing receptor T1R2 attenuates metabolic derangements associated with diet-induced obesity

Sweet taste receptors (STRs) on the tongue mediate gustatory sweet sensing, but their expression in the gut, pancreas, and adipose tissue suggests a physiological contribution to whole body nutrient sensing and metabolism. However, little is known about the function and contribution of these sugar sensors during metabolic stress induced by overnutrition and subsequent obesity. Here, we investigated the effects of high-fat/low-carbohydrate (HF/LC) diet on glucose homeostasis and energy balance in mice with global disruption of the sweet taste receptor protein T1R2. We assessed body composition, energy balance, glucose homeostasis, and tissue-specific nutrient metabolism in T1R2 knockout (T1R2-KO) mice fed a HF/LC diet for 12 wk. HF/LC diet-fed T1R2-KO mice gained a similar amount of body mass as did WT mice, but had reduced fat mass and increased lean mass relative to WT mice. T1R2-KO mice were also hyperphagic and hyperactive. Ablation of the T1R2 sugar sensor protected mice from HF/LC diet-induced hyperinsulinemia and altered substrate utilization, including increased rates of glucose oxidation and decreased liver triglyceride (TG) accumulation, despite normal intestinal fat absorption. Finally, STRs (T1r2/T1r3) were upregulated in the adipose tissue of WT mice in response to HF/LC diet, and their expression positively correlated with fat mass and glucose intolerance. The chemosensory receptor T1R2, plays an important role in glucose homeostasis during diet-induced obesity through the regulation of yet to be identified molecular mechanisms that alter energy disposal and utilization in peripheral tissues.

α-Linolenic acid increases the G0/G1 switch gene 2 mRNA expression in peripheral blood mononuclear cells from obese patients: a pilot study

Background

Recent evidence has demonstrated that the G0/G1 switch gene 2 (G0S2) is an important negative regulator of the rate-limiting lipolytic enzyme adipose triglyceride lipase-mediated lipolysis. It has been revealed that α-linolenic acid (ALA), a plant-based essential omega-3 polyunsaturated fatty acids, reduces adipose tissue lipolysis. However, it is not known whether G0S2 is implicated in ALA-induced inhibition of lipolysis. The purpose of this pilot study is to investigate the effect of ALA on G0S2 gene expression in peripheral blood mononuclear cells (PBMC) of obese patients and the potential influence of G0S2 gene expression in ALA-induced inhibition of lipolysis.

Methods

A total of 26 obese patients were randomly assigned to be treated with or without ALA treatment (~4.0 g daily) for 12 weeks: the ALA-treated group (n = 14) or the untreated control group (n = 12). Plasma triglyceride (TG), free fatty acids (FFA), glycerol, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), as well as the mRNA expression levels of proliferator-activated receptor gamma (PPAR-γ), G0S2, and G protein-coupled receptor 120 (GPR120) in PBMC were repeatedly examined from fasting obese patients before and after ALA treatment.

Results

ALA significantly decreased plasma TG, FFA, glycerol, IL-6, and TNF-α levels and increased the mRNA expression levels of PPAR-γ, G0S2, and GPR120 in PBMC, compared with the untreated control group. In obese patients from the ALA-treated group, decreased plasma FFA (a biomarker for lipolysis) level was significantly correlated with increased PPAR-γ (a functional omega-3 fatty acids receptor) and G0S2 (a direct target gene of PPAR-γ) mRNA expression in PBMC, while decreased plasma FFA level was not correlated with increased GPR120 (another functional omega-3 fatty acids receptor) mRNA expression in PBMC.

Conclusion

This study shows that ALA increases G0S2 gene expression in PBMC in parallel with the decrease of plasma FFA level in obese patients. Increased G0S2 gene expression might contribute to the beneficial anti-lipolytic effect of ALA in obese patients.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Free-fatty acid receptor-4 (GPR120): Cellular and molecular function and its role in metabolic disorders

Over the last decade, a subfamily of G protein-coupled receptors that are agonized by endogenous and dietary free-fatty acids (FFA) has been discovered. These free-fatty acid receptors include FFA2 and FFA3, which are agonized by short-chained FFA, as well as FFA1 and FFA4, which are agonized by medium-to-long chained FFA. Ligands for FFA1 and FFA4 comprise the family of long chain polyunsaturated omega-3 fatty acids including α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), suggesting that many of the long-known beneficial effects of these fats may be receptor mediated. In this regard, FFA4 has gathered considerable interest due to its role in ameliorating inflammation, promoting insulin sensitization, and regulating energy metabolism in response to FFA ligands. The goal of this review is to summarize the body of evidence in regard to FFA4 signal transduction, its mechanisms of regulation, and its functional role in a variety of tissues. In addition, recent endeavors toward discovery of small molecules that modulate FFA4 activity are also presented.

Sex Differences in the Association between the Eicosapentaenoic Acid/Arachidonic Acid Ratio and the Visceral Fat Area among Patients with Type 2 Diabetes

Objective To examine the serum levels of eicosapentaenoic acid (EPA) and the ratios of docosahexaenoic acid (DHA), and the EPA/arachidonic acid (AA) and DHA/AA and to clarify their association with the areas of subcutaneous and visceral fat separately by sex among patients with type 2 diabetes. Methods The study participants included 118 men and 96 women who were hospitalized to receive treatment for type 2 diabetes. We examined the serum levels of EPA and DHA and the ratios of EPA/AA and DHA/AA, and analyzed their association with the total fat area (TFA), subcutaneous fat area (SFA), and visceral fat area (VFA), as measured by computed tomography. Results The mean age of the study participants was 62.6±13.6 years. The mean HbA1c level was 9.37±2.27%. Among men, a multivariate regression analysis adjusted for age and BMI, revealed a significant negative association between VFA and the EPA/AA ratio. When the multivariate regression analysis was adjusted for age, BMI, and HbA1c level, VFA was still found to be significantly negatively associated with the EPA/AA ratio. Although a crude analysis revealed a significant negative association between SFA and the EPA/AA ratio in women, no association was observed in multivariate regression analyses. Conclusion These results suggest the possibility that EPA inhibits the accumulation of visceral fat in men. Furthermore, there appear to be marked differences in the relationships between EPA and DHA and visceral fat accumulation.