Aged garlic extract inhibits CD36 expression in human macrophages via modulation of the PPARγ pathway

Expression of CD36 scavenger receptors on macrophages is involved in oxidized low‐density lipoprotein uptake and foam cell formation during atherosclerotic lesion development. We examined the effects of aged garlic extract (AGE), a garlic preparation enriched in water‐soluble cysteinyl moieties that increases cellular total thiols and glutathione concentrations, on CD36 expression in human monocytes/macrophages (THP‐1 cells and primary human monocytes). Compared to control, AGE (1–5 mg/mL) dose‐dependently and significantly suppressed CD36 expression up to by 61.8 ± 7.4% in THP‐1‐derived macrophages and up to 50.5 ± 7.1% in primary human macrophages, respectively. Furthermore, AGE prevented induction of CD36 expression by the peroxisome proliferator activator receptor (PPAR) γ agonist troglitazone, and decreased binding of nuclear proteins to a PPARγ response element. AGE showed a stronger inhibitory effect on CD36 expression in THP‐1 cells during simultaneous incubation with phorbol 12‐myristate 13‐acetate (PMA) compared to cells that had been pre‐incubated with PMA. Furthermore, AGE decreased CD11b expression in a dose‐dependent manner. These data indicate that AGE inhibits CD36 expression by modulating the PPARγ pathway in human macrophages and monocytes differentiation into macrophages, and suggests that the extract could be useful for the prevention of atherosclerotic lesions. Copyright © 2010 John Wiley & Sons, Ltd.     

Genistein suppresses adipogenesis of 3T3‐L1 cells via multiple signal pathways

Genistein, an isoflavone, was shown to have therapeutic effects for obesity, diabetes and cardiovascular diseases. This study investigated the effect and underlying mechanism of genistein on adipogenesis in 3T3‐L1 preadipocytes. Genistein inhibited lipid accumulation and decreased the nonesterified fatty acid (NEFA) content of 3T3‐L1 on day 6 after the induction of differentiation with methylisobutylxanthine, dexamethasone and insulin (MDI). Genistein recovered nitric oxide (NO) release suppressed by MDI and the results were consistent with the expression of endothelial NO synthase (eNOS) assayed by western blotting. Pretreatment with genistein inhibited the phosphorylation of p38 mitogen‐activated protein kinase (p38 MAPK) stimulated with 10 µg/mL of insulin. Furthermore, genistein inhibited the expression of fatty acid synthase (FAS) from 178% of the MDI group to 74%. SB203580, a p38 inhibitor, mimicked the FAS inhibition effect of genistein, suggesting that the inhibitory effect of genistein on FAS was partially via the p38 pathway. On the other hand, genistein abolished the phosphorylation of janus‐activated kinase 2 (JAK2) in response to MDI. AG490, a JAK2 inhibitor, suppressed the expression of CCAAT/enhancer binding protein alpha (C/EBPα), a marker of adipocyte differentiation. The findings suggest that genistein attenuates the differentiation of 3T3‐L1 involving multiple signal pathways. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of Ganoderma lucidum extract on adipocyte differentiation and adiponectin gene expression in the murine pre‐adipocyte cell line, 3T3‐L1

Ganoderma lucidum (G. lucidum), a traditional Chinese medicine, has been used for the treatment of various diseases including cancer and atherosclerosis. In this study, the positive effect of G. lucidum on metabolic syndrome was investigated in more detail by the use of 3T3‐L1 pre‐adipocyte cells. Treatment of 3T3‐L1 cells with G. lucidum extract (GE) significantly promoted adipocyte differentiation and adiponectin production in a dose‐dependent manner, as assessed by Oil‐Red O staining, quantitative RT‐PCR and ELISA. Treatment with GW9662, an inhibitor for peroxisome proliferator‐activated receptor‐gamma (PPARgamma), significantly attenuated GE‐dependent adipocyte differentiation and adiponectin gene expression, suggesting the involvement of PPARgamma. Moreover, a reporter gene assay using GAL4‐PPAR fusion proteins revealed that GE enhances GAL4‐PPARgamma and GAL4‐PPARalpha activities. These results indicate the presence of natural compounds possessing PPARgamma and PPARalpha activating properties in G. lucidum. Copyright © 2010 John Wiley & Sons, Ltd.     

Piperine inhibits adipocyte differentiation via dynamic regulation of histone modifications

Previously, we reported that piperine, one of the major pungent components in black pepper, attenuates adipogenesis by repressing PPARγ activity in 3T3‐L1 preadipocytes. However, the epigenetic mechanisms underlying this activity remain unexplored. Here, gene set enrichment analysis using microarray data indicated that there was significant downregulation of adipogenesis‐associated and PPARγ target genes and upregulation of genes bound with H3K27me3 in response to piperine. As shown by Gene Ontology analysis, the upregulated genes are related to lipid oxidation and polycomb repressive complex 2 (PRC2). Chromatin immunoprecipitation assays revealed that PPARγ (and its coactivators), H3K4me3, and H3K9ac were less enriched at the PPAR response element of three adipogenic genes, whereas increased accumulation of H3K9me2, H3K27me3, and Ezh2 was found, which likely led to the reduced gene expression. Further analysis using three lipolytic genes revealed the opposite enrichment pattern of H3K4me3 and H3K27me3 at the Ezh2 binding site. Treatment with GSK343, an Ezh2 inhibitor, elevated lipolytic gene expression by decreasing the enrichment of H3K27me3 during adipogenesis, which confirms that Ezh2 plays a repressive role in lipolysis. Overall, these results suggest that piperine regulates the expression of adipogenic and lipolytic genes by dynamic regulation of histone modifications, leading to the repression of adipocyte differentiation.     

Protective Effects of Turbinaria ornata and Padina pavonia against Azoxymethane‐Induced Colon Carcinogenesis through Modulation of PPAR Gamma,NF‐κB and Oxidative Stress

The aim of this study was to investigate the antiproliferative and protective effects of the brown seaweeds, Turbinaria ornata and Padina pavonia, against azoxymethane (AOM)‐induced colon carcinogenesis in mice. Both algal extracts showed anti‐proliferative effects on the human carcinoma cell line HCT‐116 in vitro, with T. ornata demonstrating a more potent effect. Male albino Swiss mice received intraperitoneal injections of AOM (10 mg/kg) once a week for two consecutive weeks and 100 mg/kg of either T. ornata or P. pavonia extracts. AOM‐induced mice exhibited alterations in the histological structure of the colon, elevated lipid peroxidation and nitric oxide, declined glutathione content and reduced activity of superoxide dismutase and glutathione peroxidase. In addition, AOM induced downregulation of peroxisome proliferator activated receptor gamma (PPARγ) and p53 mRNA expression, with concomitant upregulation of nuclear factor‐kappa B (NF‐κB) in colon tissue. Administration of either algal extract markedly alleviated the recorded alterations. In conclusion, the current study suggests that T. ornata and P. pavonia, through their antioxidant and anti‐inflammatory effects, are able to attenuate colon inflammation by downregulating NF‐κB expression. Furthermore, the protective effects of both algae against AOM‐initiated carcinogenesis were attributed, at least in part, to their ability to upregulate colonic PPARγ and p53 expression. Copyright © 2015 John Wiley & Sons, Ltd.     

Bromophenol (5‐bromo‐3,4‐dihydroxybenzaldehyde) isolated from red alga Polysiphonia morrowii inhibits adipogenesis by regulating expression of adipogenic transcription factors and AMP‐activated protein kinase activation in 3T3‐L1 adipocytes

The aim of the present study was to investigate the effect of 5‐bromo‐3,4‐dihydroxybenzaldehyde (BD) isolated from Polysiphonia morrowii on adipogenesis and differentiation of 3T3‐L1 preadipocytes into mature adipocytes and its possible mechanism of action. Levels of lipid accumulation and triglyceride were significantly lower in BD treated cells than those in untreated cells. In addition, BD treatment reduced protein expression levels of peroxisome proliferator‐activated receptor‐γ, CCAAT/enhancer‐binding proteins α, and sterol regulatory element‐binding protein 1 compared with control (no treatment). It also reduced expression levels of adiponectin, leptin, fatty acid synthase, and fatty acid binding protein 4. AMP‐activated protein kinase activation was found to be one specific mechanism involved in the effect of BD. These results demonstrate that BD possesses inhibitory effect on adipogenesis through activating AMP‐activated protein kinase signal pathway.     

Berberine inhibits SREBP‐1‐related clozapine and risperidone induced adipogenesis in 3T3‐L1 cells

Weight gain is a common and potentially serious complication associated with the treatment of second generation antipsychotics such as clozapine and risperidone. Increased peripheral adipogenesis via the SREBP‐1 pathway could be one critical mechanism responsible for antipsychotic drug‐induced weight gain. Berberine, a botanic alkaloid, has been shown in our previous studies to inhibit adipogenesis in cell and animal models. MTT was used to determine the cytotoxic effects of clozapine and risperidone in combination with berberine. Differentiation of 3T3‐L1 cells was monitored by Oil‐Red‐O staining and the expression of SREBP‐1 and related proteins was determined by real‐time RT‐PCR and western blotting. The results showed that neither clozapine nor risperidone, alone or in combination with berberine had significant effects on cell viability. Eight days treatment with 15 μm clozapine increased adipogenesis by 37.4% and 50 μm risperidone increased adipogenesis by 26.5% during 3T3‐L1 cell differentiation accompanied by increased SREBP‐1, PPARγ, C/EBPα, LDLR and Adiponectin gene expression. More importantly, the addition of 8 μm berberine diminished the induction of adipogenesis almost completely accompanied by down‐regulated mRNA and protein expression levels of SREBP‐1‐related proteins. These encouraging results may lead to the use of berberine as an adjuvant to prevent weight gain during second generation antipsychotic medication. Copyright © 2010 John Wiley & Sons, Ltd.