Adipocyte response to conjugated linoleic acid

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.

A Mix of Natural Bioactive Compounds Reduces Fat Accumulation and Modulates Gene Expression in the Adipose Tissue of Obese Rats Fed a Cafeteria Diet

Scientists are focusing on bioactive ingredients to counteract obesity. We evaluated whether a mix containing grape seed proanthocyanidin extract (GSPE), anthocyanins, conjugated linoleic acid (CLA), and chicken feet hydrolysate (CFH) could reduce body fat mass and also determined which mechanisms in the white adipose tissue (WAT) and the brown adipose tissue (BAT) were affected by the treatment. The mix or vehicle (VH) were administered for three weeks to obese rats fed a cafeteria (CAF) diet. Biometric measures, indirect calorimetry, and gene expression in WAT and BAT were analyzed as was the histology of the inguinal WAT (IWAT). The individual compounds were also tested in the 3T3-L1 cell line. The mix treatment resulted in a significant 15% reduction in fat (25.01 ± 0.91 g) compared to VH treatment (21.19 ± 1.59 g), and the calorimetry results indicated a significant increase in energy expenditure and fat oxidation. We observed a significant downregulation of Fasn mRNA and an upregulation of Atgl and Hsl mRNA in adipose depots in the group treated with the mix. The IWAT showed a tendency of reduction in the number of adipocytes, although no differences in the total adipocyte area were found. GSPE and anthocyanins modulated the lipid content and downregulated the gene and protein levels of Fasn compared to the untreated group in 3T3-L1 cells. In conclusion, this mix is a promising treatment against obesity, reducing the WAT of obese rats fed a CAF diet, increasing energy expenditure and fat oxidation, and modifying the expression of genes involved in lipid metabolism of the adipose tissue.

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.

Fatty acid extract from CLA-enriched egg yolks can mediate transcriptome reprogramming of MCF-7 cancer cells to prevent their growth and proliferation

Background

Our previous study showed that fatty acids extract obtained from CLA-enriched egg yolks (EFA-CLA) suppressed the viability of MCF-7 cancer cell line more effectively than extract from non-enriched egg yolks (EFA). In this study, we analysed the effect of EFA-CLA and EFA on transcriptome profile of MCF-7 cells by applying the whole Human Genome Microarray technology.

Results

We found that EFA-CLA and EFA treated cells differentially regulated genes involved in cancer development and progression. EFA-CLA, compared to EFA, positively increased the mRNA expression of TSC2 and PTEN tumor suppressors as well as decreased the expression of NOTCH1, AGPS, GNA12, STAT3, UCP2, HIGD2A, HIF1A, PPKAR1A oncogenes.

Conclusions

We show for the first time that EFA-CLA can regulate genes engaged in AKT/mTOR pathway and inhibiting cell cycle progression. The observed results are most likely achieved by the combined effect of both: incorporated CLA isomers and other fatty acids in eggs organically modified through hens’ diet. Our results suggest that CLA-enriched eggs could be easily available food products with a potential of a cancer chemopreventive agent.

Electronic supplementary material

The online version of this article (doi:10.1186/s12263-016-0537-z) contains supplementary material, which is available to authorized users.

Trans-10,cis-12 conjugated linoleic acid (CLA) interferes with lipid droplet accumulation during 3T3-L1 preadipocyte differentiation

In this study, we hypothesize that the biologically active isomers of conjugated linoleic acid (CLA), cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) CLA, have different effects on early and late stages 3T3-L1 preadipocyte differentiation. Both c9-t11 and t10-c12CLA stimulated early stage pre-adipocyte differentiation (day 2), while t10-c12CLA inhibited late differentiation (day 8) as determined by lipid droplet numbers and both perilipin-1 levels and phosphorylation state. At day 8, the adipokines adiponectin, chemerin and adipsin were all reduced in t10-c12CLA treated cells versus control cells. Immunofluorescence microscopy showed perilipin-1 was present solely on lipid droplets on day 8 in t10-c12 treated 3T3-L1 cells, whereas preilipin-1 was also located in the perinuclear region in control and c9-t11 treated cells. The t10-c12CLA isomer also decreased levels of hormone-sensitive lipase and inhibited lipolysis. These findings indicate that the decrease in lipid droplets caused by t10-c12CLA is the result of an inhibition of lipid droplet production during adipogenesis rather than a stimulation of lipolysis. Additionally, treatment with Gö6976 blocked the effect of t10-c12CLA on perilipin-1 phosphorylation, implicating PKCα in perilipin-1 phosphorylation, and thus a regulator of triglyceride catabolism. These data are supported by evidence that t10-c12CLA activated PKCα. These are the first data to show that CLA isomers can affect lipid droplet dynamics in adipocytes through PKCα.

Effect of conjugated linoleic acid on blood pressure: a meta-analysis of randomized, double-blind placebo-controlled trials

Background

Numerous studies on animals evidenced that conjugated linoleic acid (CLA) could decrease blood pressure (BP) in several rat models. However, such beneficial effect is not completely supported by studies on humans.

Methods

We searched the Pubmed, Cochrane Library, and the ClinicalTrials.gov databases for relevant randomized, double-blind placebo-controlled trials up to August 2014 to perform a meta-analysis. A random-effects model was used to calculate the combined treatment effects.

Results

Eight studies with nine trials, which involved 638 participants with CLA supplementation ranging from 2.0 g/day to 6.8 g/day, were included in this meta-analysis. Compared with placebo, the pooled estimate of change was −0.03 mm Hg (95% CI: −2.29, 2.24, P = 0.98) and 0.69 mm Hg (95% CI: −1.41, 2.80, P = 0.52) in systolic and diastolic BPs, respectively. No significant heterogeneity across studies for systolic BP; however, substantial heterogeneity for diastolic BP was identified. Publication bias was not found for both systolic and diastolic BPs.

Conclusion

The findings of this meta-analysis did not support the overall favorable effect of CLA supplementation on BP regulation.