Trans10, cis12 conjugated linoleic acid inhibits 3T3-L1 adipocyte adipogenesis by elevating β-catenin levels

Facile adipocyte uptake and liver/adipose tissue delivery of conjugated linoleic acid-loaded tocol nanocarriers for a synergistic anti-adipogenesis effect

Obesity is a major risk to human health. Adipogenesis is blocked by α-tocopherol and conjugated linoleic acid (CLA). However, their effect at preventing obesity is uncertain. The effectiveness of the bioactive agents is associated with their delivery method. Herein, we designed CLA-loaded tocol nanostructured lipid carriers (NLCs) for enhancing the anti-adipogenic activity of α-tocopherol and CLA. Adipogenesis inhibition by the nanocarriers was examined using an in vitro adipocyte model and an in vivo rat model fed a high fat diet (HFD). The targeting of the tocol NLCs into adipocytes and adipose tissues were also investigated. A synergistic anti-adipogenesis effect was observed for the combination of free α-tocopherol and CLA. Nanoparticles with different amounts of solid lipid were developed with an average size of 121‒151 nm. The NLCs with the smallest size (121 nm) showed greater adipocyte internalization and differentiation prevention than the larger size. The small-sized NLCs promoted CLA delivery into adipocytes by 5.5-fold as compared to free control. The nanocarriers reduced fat accumulation in adipocytes by counteracting the expression of the adipogenic transcription factors peroxisome proliferator activated receptor (PPAR)γ and CCAAT/enhancer-binding protein (C/EBP)α, and lipogenic enzymes acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). Localized administration of CLA-loaded tocol NLCs significantly reduced body weight, total cholesterol, and liver damage indicators in obese rats. The biodistribution study demonstrated that the nanoparticles mainly accumulated in liver and adipose tissues. The NLCs decreased adipocyte hypertrophy and cytokine overexpression in the groin and epididymis to a greater degree than the combination of free α-tocopherol and CLA. In conclusion, the lipid-based nanocarriers were verified to inhibit adipogenesis in an efficient and safe way.

Conjugated linoleic acid (CLA) as a functional food: Is it beneficial or not?

Conjugated linoleic acid (CLA) has attracted great attention in recent years as a popular class of functional food that is broadly used. It refers to a group of geometric and positional isomers of linoleic acid (LA) with a conjugated double bond. The main natural sources of CLA are dairy products, beef and lamb, whereas only trace amounts occur naturally in plant lipids. CLA has been shown to improve various health issues, having effects on obesity, inflammatory, anti-carcinogenicity, atherogenicity, immunomodulation, and osteosynthesis. Also, compared to studies on humans, many animal researches reveal more positive benefits on health. CLA represents a nutritional avenue to improve lifestyle diseases and metabolic syndrome. Most of these effects are attributed to the two major CLA isomers [conjugated linoleic acid cis-9,trans-11 isomer (c9,t11), and conjugated linoleic acid trans-10,cis-12 isomer (t10,c12)], and their mixture (CLA mix). In contrast, adverse effects of CLA have been also reported, such as glucose homeostasis, insulin resistance, hepatic steatosis and induction of colon carcinogenesis in humans, as well as milk fat inhibition in ruminants, lowering chicken productivity, influencing egg quality and altering growth performance in fish. This review article aims to discuss the health benefits of CLA as a nutraceutical supplement and highlight the possible mechanisms of action that may contribute to its outcome. It also outlines the feasible adverse effects of CLA besides summarizing the recent peer-reviewed publications on CLA to ensure its efficacy and safety for proper application in humans.

Crosstalk between E-Cadherin/β-Catenin and NF-κB Signaling Pathways: The Regulation of Host-Pathogen Interaction during Leptospirosis

Approximately 1 million cases of leptospirosis, an emerging infectious zoonotic disease, are reported each year. Pathogenic Leptospira species express leucine-rich repeat (LRR) proteins that are rarely expressed in non-pathogenic Leptospira species. The LRR domain-containing protein family is vital for the virulence of pathogenic Leptospira species. In this study, the biological mechanisms of an essential LRR domain protein from pathogenic Leptospira were examined. The effects of Leptospira and recombinant LRR20 (rLRR20) on the expression levels of factors involved in signal transduction were examined using microarray, quantitative real-time polymerase chain reaction, and western blotting. The secreted biomarkers were measured using an enzyme-linked immunosorbent assay. rLRR20 colocalized with E-cadherin on the cell surface and activated the downstream transcription factor β-catenin, which subsequently promoted the expression of MMP7, a kidney injury biomarker. Additionally, MMP7 inhibitors were used to demonstrate that the secreted MMP7 degrades surface E-cadherin. This feedback inhibition mechanism downregulated surface E-cadherin expression and inhibited the colonization of Leptospira. The degradation of surface E-cadherin activated the NF-κB signal transduction pathway. Leptospirosis-associated acute kidney injury is associated with the secretion of NGAL, a downstream upregulated biomarker of the NF-κB signal transduction pathway. A working model was proposed to illustrate the crosstalk between E-cadherin/β-catenin and NF-κB signal transduction pathways during Leptospira infection. Thus, rLRR20 of Leptospira induces kidney injury in host cells and inhibits the adhesion and invasion of Leptospira through the upregulation of MMP7 and NGAL.

PDGF-BB-mediated activation of CREB in vascular smooth muscle cells alters cell cycling via Rb, FoxO1 and p27kip1

INTRODUCTION & AIM

The vascular response to injury leads to the secretion of several factors, including platelet-derived growth factor (PDGF-BB). PDGF-BB stimulates smooth muscle cell (SMC) conversion to the synthetic phenotype, thereby enhancing proliferation and migration, and contributing to neointimal hyperplasia. Likewise, the cAMP response element binding protein (CREB) transcription factor has been shown to mediate SMC proliferation in response to various mitogens. We therefore investigated the contribution of CREB to PDGF-BB-dependent proliferation of SMCs with the intention of identifying signaling pathways involved both up and downstream of CREB activation.

METHODS & RESULTS

Treatments were performed on vascular SMCs from a porcine coronary artery explant model. The role of CREB was examined via adenoviral expression of a dominant-negative CREB mutant (kCREB) as well as inhibition of CREB binding protein (CBP). Involvement of the p27^kip1 pathway was determined using a constitutively expressing p27^kip1 adenoviral vector. PDGF-BB stimulated transient CREB phosphorylation on Ser-133 via ERK1/2-, PI3-kinase- and Src-dependent pathways. Expression of kCREB decreased PDGF-BB-dependent cell proliferation. PCNA expression and Rb phosphorylation were also inhibited by kCREB. These cell cycle proteins are controlled via p27^kip1 expression in response to CREB-dependent post-translational modification of FoxO1. kCREB had no effect on Cyclin D1 expression, but did prevent PDGF-BB-induced Cyclin D1 nuclear translocation. An interaction inhibitor of CBP confirmed that Cyclin D1 is downstream of PDGF-BB and CREB.

CONCLUSION

CREB phosphorylation is required for SMC proliferation in response to PDGF-BB. This phenotypic change requires CBP and is mediated by Cyclin D1 and p27^kip as a result of changes in FoxO1 activity.

Cis-9, Trans-11 Conjugated Linoleic Acid Reduces Phosphoenolpyruvate Carboxykinase Expression and Hepatic Glucose Production in HepG2 Cells

Dysregulated hepatic gluconeogenesis is a hallmark of insulin resistance and type 2 diabetes mellitus (T2DM). Although existing drugs have been proven to improve gluconeogenesis, achieving this objective with functional food is of interest, especially using conjugated linoleic acid (CLA) found in dairy products. Both cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12) isomers of CLA were tested in human (HepG2) and rat (H4IIE) hepatocytes for their potential effects on gluconeogenesis. The hepatocytes exposed for 24 h with 20 μM of c9,t11-CLA had attenuated the gluconeogenesis in both HepG2 and H4IIE by 62.5% and 80.1%, respectively. In contrast, t10,c12-CLA had no effect. Of note, in HepG2 cells, the exposure of c9,t11-CLA decreased the transcription of gluconeogenic enzymes, cytosolic phosphoenolpyruvate carboxykinase (PCK1) by 87.7%, and glucose-6-phosphatase catalytic subunit (G6PC) by 38.0%, while t10,c12-CLA increased the expression of G6PC, suggesting the isomer-specific effects of CLA on hepatic glucose production. In HepG2, the peroxisome proliferator-activated receptor (PPAR) agonist, rosiglitazone, reduced the glucose production by 72.9%. However, co-administration of c9,t11-CLA and rosiglitazone neither exacerbated nor attenuated the efficacy of rosiglitazone to inhibit glucose production; meanwhile, t10,c12-CLA abrogated the efficacy of rosiglitazone. Paradoxically, PPARγ antagonist GW 9662 also led to 70.2% reduction of glucose production and near undetectable PCK1 expression by abrogating CLA actions. Together, while the precise mechanisms by which CLA isomers modulate hepatic gluconeogenesis directly or via PPAR warrant further investigation, our findings establish that c9,t11-CLA suppresses gluconeogenesis by decreasing PEPCK on hepatocytes.

Meat, eggs, full-fat dairy, and nutritional boogeymen: Does the way in which animals are raised affect health differently in humans?

Background: Food recommendations to improve cancer prevention are generally based on epidemiologic data and remain inconsistent. These epidemiologic studies, while controversial, have generally produced results that caution against the consumption of high-fat foods, including eggs, red meat, and full-fat dairy, such as butter and cheese. Yet, limited data exist assessing the quality of individual sources of these foods and the effect each has after its consumption. This study set out to assess the impact sources of food within the same groups from animals raised differently on variables associated with health in human studies. Methods and Materials: A search was conducted through MEDLINE, Embase, and PubMed. In total, twenty-nine studies met inclusion criteria, measuring physiologic changes in humans after consuming animal products following animal diet manipulation. A meta-analysis was attempted to assess the differences between the cohorts in these studies, but was aborted due to poor study quality, vast differences in study design, and a limited number of studies. Results: Studies varied by animal, animal diet manipulation, food product, and overall design. Significant differences were present between groups eating the same food (cheese, beef, eggs, and butter) from animals raised differently, including levels of: conjugated linoleic acid, omega-3 fatty acids (alpha linoleic acid [ALA], docosahexaenoic acid [DHA], and eicosapentaenoic acid [EPA]), and inflammatory factors (triacyl glycerol [TAG], interleukin-6 [IL-6], interleukin-8 [IL-8], tumor necrosis factor [TNF], and C-reactive protein [CRP]). Lipid levels were minimally affected. Conclusions: This work highlights differences in human health markers after consumption of the same foods from animals raised differently. Overall, lipid levels remained relatively neutral, but significant changes in inflammatory and other serum markers and phospholipids were present. Future studies and dietary recommendations should consider how animals are raised, as this can produce different effects on health markers.

Coumestrol modulates Akt and Wnt/β-catenin signaling during the attenuation of adipogenesis

Coumestrol is a natural phytochemical present in plants such as red clover and soy, and has been reported to stimulate the estrogen receptor as a major phytoestrogen. While the molecular mechanisms responsible for the anti-adipogenic effects of phytoestrogens such as genistein and daidzein have been previously investigated, the effects of coumestrol on adipogenesis remain to be elucidated. We observed that coumestrol dose-dependently attenuates MDI (mixture of 3-isobutyl-1-methylxanthine, dexamethasone, and insulin)-induced lipid accumulation, consistent with an earlier study, while significantly inhibiting MDI-induced adipogenesis in the first 48 hours of differentiation, a critical time window for anti-adipogenic effects. Coumestrol treatment suppressed MDI-induced protein expression of PPARγ and C/EBPα in adipocytes, leading to the subsequent downregulation of FAS and aP2 expression. Akt and GSK3β were phosphorylated shortly after MDI stimulation, and these responses were inhibited by coumestrol treatment. Coumestrol also increased LRP6 protein expression, resulting in the recovery of β-catenin downregulation by MDI, while attenuating MDI-induced downregulation of Wnt10b. In addition, mRNA and protein expression of c-Myc and cyclin D1, target genes of β-catenin, were both recovered by coumestrol treatment. These results suggest that coumestrol inhibits adipocyte differentiation via regulation of Akt and Wnt/β-catenin signaling and may have potential for development as an agent to prevent adipogenesis.

Bioconversion of conjugated linoleic acid by Lactobacillus plantarum CGMCC8198 supplemented with Acer truncatum bunge seeds oil

Conjugated linoleic acid (CLA) isomers, c9, t11-CLA and t10, c12-CLA, have been proved to exhibit excellent biomedical properties for potential use in anti-cancer applications and in reducing obesity. Acer truncatum Bunge (ATB), which is rich in unsaturated fatty acids, including oleic acid, linoleic acid, and nervonic acid, is a new resource for edible oil. In the present study, we developed a new method for producing two CLA isomers from ATB-seed oil by fermentation using Lactobacillus plantarum CGMCC8198 (LP8198), a novel probiotics strain. Polymerase chain reaction results showed that there was a conserved linoleate isomerase (LIase) gene in LP8198, and its transcription could be induced by ATB-seed oil. Analyses by gas chromatography-mass spectrometry showed that the concentration of c9, t11-CLA and t10, c12-CLA in ATB-seed oil could be increased by about 9- and 2.25-fold, respectively, after being fermented by LP8198.

Effects of Conjugated Linoleic Acid Supplementation on the Expression Profile of miRNAs in Porcine Adipose Tissue

Conjugated linoleic acids (CLAs) play a major role in adipocyte differentiation and lipid metabolism in animals. MicroRNAs (miRNAs) appear to be involved in many biological processes in adipose tissue. However, the specific influence on miRNAs by CLA supplementation in porcine adipose tissue remains unclear. Thus, we continuously added 1.5% CLA to the pig diet from the embryo stage to the finishing period and conducted a high-throughput sequencing approach to analyse the changes in adipose tissue miRNAs. We identified 283 known porcine miRNAs, and 14 miRNAs were differentially expressed in response to CLA treatment. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the targets of the 14 differentially expressed miRNAs were involved in the Wnt signalling pathway. The CLA treatment downregulated the gene expression of PPARγ, C/EBPα, FAS, and FATP1 in both subcutaneous and abdominal fat tissues; the analysis showed that ssc-miR-21 expression was significantly correlated with PPARγ expression (p < 0.05), and speculated that ssc-miR-21 might influence adipogenesis through PPARγ. In conclusion, our study analysed the miRNA profiles in porcine adipose tissues by CLA treatment, and demonstrated that miRNAs are important regulators of fat lipogenesis. This study provides valuable information for the molecular regulatory mechanism of CLA on adipose tissue.

Invited review: The anti-inflammatory properties of dairy lipids

Dairy product consumption is often associated with negative effects because of its naturally high levels of saturated fatty acids. However, recent research has shown that dairy lipids possess putative bioactivity against chronic inflammation. Inflammation triggers the onset of several chronic diseases, including cardiovascular disease, type 2 diabetes mellitus, obesity, and cancer. This review discusses the anti-inflammatory properties of dairy lipids found in milk, yogurt, and cheese, and it examines them in relation to their implications for human health: their protective effects and their role in pathology. We also consider the effect of lipid profile alteration in dairy products-by using ruminant dietary strategies to enrich the milk, or by lipid fortification in the products. We critically review the in vivo, in vitro, ex vivo, and epidemiological studies associated with these dairy lipids and their role in various inflammatory conditions. Finally, we discuss some suggestions for future research in the study of bioactive lipids and dairy products, with reference to the novel field of metabolomics and epidemiological studies.