Adipocyte-specific Genes Research Articles

Anti-obesity effect of taurine through inhibition of adipogenesis in white fat tissue but not in brown fat tissue in a high-fat diet-induced obese mouse model.

This study was conducted to evaluate the anti-obesity effects of long-term taurine supplementation in a mild obese ICR mouse model and to study the mechanism by which taurine induces weight loss. Three groups of male ICR mice were fed a normal chow diet, a high-fat diet (HFD), or an HFD supplemented with 2% taurine in drinking water for 28weeks. Body weight was measured every week. Metabolic, behavioral, and physiological monitoring were carried out using PhenoMaster at 28weeks. Interscapular brown fat (BAT), inguinal white fat tissue (WAT), and quadriceps muscle were analyzed and compared to assess the change of gene expression related to adipogenesis. Taurine supplementation showed the trend of anti-obesity effect in ICR mice fed an HFD for 28weeks. HFD-fed mice did not show significant difference of oxygen consumption (VO2), energy expenditure (EE), respiratory exchange rate (RER), and locomotive activity compared with those of normal chow diet fed mice. The expression of adipogenesis-related genes such as PPAR-α, PPAR-γ, C/EBP-α, C/EBP-β, and AP2 increased in BAT and WAT, but not in muscle tissue. Taurine supplementation showed the downregulation of these genes in WAT but not in BAT or muscle. Consistently, the expression of taurine transporter (TauT) and adipocyte-specific genes such as adiponectin, leptin, and IL-6 was regulated in a similar pattern by taurine supplementation. Long-term taurine supplementation causes weight loss, most likely by inhibiting adipogenesis in WAT. TauT expression may be involved in the expression of various genes regulated by taurine supplementation.

Allicin induces beige-like adipocytes via KLF15 signal cascade

Under specific conditions, white adipose tissue (WAT) depots are readily converted to a brown-like state, which is associated with weight loss. However, whether diet-derived factors directly induce browning of white adipocytes has yet to be established. Thus, we investigated the effects of allicin, one of the major components of garlic, on brown-like adipocyte formation in inguinal WAT (iWAT), and prevention of obesity and related complications in animal models. Allicin significantly increased mRNA and/or protein expression of brown adipocyte markers including uncoupling protein 1 (UCP1) in differentiated mouse embryonic fibroblast cell line 3T3-L1 and differentiated iWAT stromal vascular cells (SVC), suggesting that allicin induced brown-like adipocyte formation in vitro. Concomitantly, allicin markedly enhanced the protein expression of KLF-15 and its interaction with UCP-1 promoter region. Such changes were absent in cells lacking KLF-15, suggesting the critical role of KLF15 in allicin action. Allicin also induced brown-like adipogenesis in vivo along with the appearance of multilocular adipocytes, increased UCP1 expression and increased lipid oxidation. In summary, our data suggest that allicin potentially prevents obesity and associated metabolic disorders such as type 2 diabetes mellitus by enhancing the expression of brown adipocyte-specific genes, including UCP-1, through KLF15 signal cascade.

Lipogenesis inhibition and adipogenesis regulation via PPARγ pathway in 3T3-L1 cells by Zingiber cassumunar Roxb. rhizome extracts

Zingiber cassumunar (ZC) is used by tribal people in northern Thailand in traditional remedies for anti-obesity and in food recipes. Extracts from this plant have been studied for several pharmacological effects including anti-obesity, but with no clear evidence on cellular mechanism of activity. This study aim to investigate the lipolytic and anti-adipogenic activity of crude extracts from ZC on in vitro cultures of the mouse adipocyte cell-model, 3T3-L1. Dry rhizome powder was extracted with absolute ethanol and boiled-water. On the exposed pre-adipocytes to the extracts, cytotoxicity was not detected by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Lipid content and glycerol release were assessed using Oil Red-O and a commercial Adipolysis Assay kits respectively. The extracts exhibited no significant lipolytic activity on the exposed mature-adipocytes, in serial dilutions ranging from 1 to 800 µg/ml. However, anti-lipogenic activity was presented. All extracts significantly reduced the lipid content of exposed differentiating-adipocytes. This anti-lipogenic activity was confirmed by the expression of selected genes, determined by using real-time PCR techniques, in four groups namely: adipocyte differentiation genes, glucose uptake genes, lipid metabolism genes and fatty acid oxidation genes. 1H NMR spectrum of the extracts exhibited the prominent olefinic protons of phenylbutanoids, the group of compounds previously proved with several bioactivities. This study provided evidences of mechanisms that apparently verify the traditional use of ZC to prevent obesity.

Adipocyte DIO2 Expression Increases in Human Obesity but Is Not Related to Systemic Insulin Sensitivity.

Deiodinase type II (D2), encoded by DIO2, catalyzes the conversion of T4 to bioactive T3. T3 not only stimulates adaptive thermogenesis but also affects adipose tissue (AT) lipid accumulation, mitochondrial function, inflammation, and potentially systemic metabolism. Although better defined in brown AT, the precise role of DIO2 expression in white AT remains largely unknown, with data derived only from whole fat. Therefore, the purpose of this study was to determine whether subcutaneous (SAT) and visceral (VAT) adipocyte-specific gene expression of DIO2 differs between obese and lean patients and whether these differences relate to alterations in mitochondrial function, fatty acid flux, inflammatory cytokines/adipokines, and ultimately insulin sensitivity. Accordingly, adipocytes of 73 obese and 21 lean subjects were isolated and subjected to gene expression analyses. Our results demonstrate that obese compared to lean human individuals have increased adipocyte-specific DIO2 expression in both SAT and VAT. Although higher DIO2 was strongly related to reduced fatty acid synthesis/oxidation and mitochondrial function, we found no relationship to proinflammatory cytokines or insulin resistance and no difference based on diabetic status. Our results suggest that adipocyte-derived DIO2 may play a role in weight maintenance but is likely not a major contributor to obesity-related insulin resistance.

Small Proliferative Adipocytes, Newly Identified Adipose Progenitor, as the Precursors of Beige Cells

We previously identified proliferative cells in adipose tissue expressing adipocyte specific genes and preadipocyte specific genes, which were named small proliferative adipocytes (SPA). Furthermore, we found that SPA specifically express proliferin (PLF) and have superior potential for adipogenic differentiation as compared to stromal vascular cells (SVC). In this study, we investigated the role of SPA. A comparison between differentiated SPA (D-SPA) and differentiated SVC (D-SVC) revealed that UCP1 and PLF were strongly expressed in D-SPA. Therefore, we speculated that SPA might be progenitor of beige cells. The real time PCR analyses and the immunohistochemical studies revealed that beige cells associated genes, including UCP1, PPARα and PGC1α were significantly increased in D-SPA. Treatment with pioglitazone and CL316234, a specific β3-adrenergic receptor agonist, converted cultured SPA into cell clusters like beige cells which expressed UCP1 and activation of mitochondrial function confirmed by MitoRed stain. Furthermore, PLF was expressed in beige cells induced by continuous injection of CL316243. In conclusion, since D-SPA were found to express UCP1 and PLF, which were detected in beige cells, but not WAT, SPA were considered to be a progenitor of beige cells. There might be two lineages of cells in adipose tissue; adipose progenitor cells in SVC and WAT (PLF-), and SPA and beige cells (PLF+). The combination of pioglitazone and CL316423 produced an additive effect of inducing browning in SPA. Disclosure K. Taguchi: None. K. Kajita: None. M. Fuwa: None. M. Asano: None. Y. Kitada: None. T. Ikeda: None. T. Ishizuka: None. H. Morita: None.

The potential of brown adipogenesis and browning in porcine bone marrow-derived mesenchymal stem cells1.

Brown adipocyte lineage commitment and differentiation are under complex regulation. Brown adipocytes are derived from mesenchymal stem cells (MSC). Whether porcine bone marrow-derived MSC (BM-MSC) possess the potential to differentiate into brown adipocytes remains unclear. In the current study, we evaluated the ability of porcine BM-MSC to differentiate into brown adipocytes and browning of differentiated adipocytes. We found that similar to rodent models, bone morphogenetic protein 7 (BMP7) was able to trigger the commitment of BM-MSC to the brown adipocyte lineage by elevating expression of marker genes, nrf-1, tfam, zic1, and pgc-1α (P < 0.05). The expression of brown adipocyte-specific genes, prdm16, dio2, and cidea, was significantly induced (P < 0.05) in BMP7-treated porcine BM-MSC after hormonal induction of adipogenesis. The UCP2 and UCP3 protein levels in BMP7-treated porcine BM-MSC were higher than the control group after hormonal induction of adipogenesis, accompanied by increased mitochondrial DNA copy number and mitochondria-specific gene expression (P < 0.05). Furthermore, acute norepinephrine stimulation potentiated brown adipocyte-specific mRNA expression (P < 0.05) in differentiated adipocytes. Similarly, UCP2 and UCP3 protein levels were increased in differentiated adipocytes upon acute norepinephrine stimulation. In addition, mitochondrial DNA copy number and mitochondria-specific gene expression were also significantly increased (P < 0.05) in differentiated adipocytes after acute norepinephrine exposure. Taken together, these results demonstrate for the first time that porcine BM-MSC are able to commit to the brown adipocyte lineage and differentiate into brown adipocytes. Differentiated adipocytes derived from porcine BM-MSC have the developmental potential to transdifferentiate into brown-like adipocytes upon norepinephrine stimulation.

MicroRNA-200b regulates preadipocyte proliferation and differentiation by targeting KLF4

MicroRNAs (miRNAs) are small, non-coding RNAs that affect the post-transcriptional regulation of a variety of biological pathways. A previous study found out that miR-200b was important in the metabolism of obesity, but the mechanism of miR-200b regulateing adipogenesis is not fully understood.. In the present study, we observed that miR200b expression decreased both in obese mice and during the process of 3T3-L1 adipogenic differentiation. Overexpression of miR-200b promoted adipocyte proliferation by regulating the expression of cell cycle-regulated factors.Furthermore, overexpression of miR-200b reduced lipid accumulation and triglyceride content in adipocytes, and accompanied by a marked decrease in the expression of adipocyte-specific genes involved in fatty acid synthesis. Luciferase activity assays confirmed that miR-200b regulated adipocyte differentiation by directly targeting KLF4, and miR-200b suppressed the expression of KLF4 in both mRNA level and protein level. Moreover, the expression levels of downstream genes of KLF4, such as C/EBPβ, C/EBPα, KLF5 and PPARγ, were decreased in 3T3-L1 cells by miR-200b overexpression. Taken together, these results indicate that miR-200b may be involved in adipogenesis and could be a target for therapeutic intervention in obesity and metabolic syndrome.

Inhibition of cell growth by cellular differentiation into adipocyte-like cells in dexamethasone sensitive cancer cell lines

ABSTRACTThe stress responses in human body lead to secretion of cortisol hormone. The present study investigated the cellular responses on cell growth and cellular differentiation into adipocytes by exposure of synthetic stress hormone, dexamethasone (DEX) in various human cancer and normal cells. After prolonged exposure of cells with 1 μg/ml DEX for 2 weeks, population doubling time (PDT) was significantly (P < .05) increased by inhibited cell growth in A-549 and MCF-7 cancer cells, and was unchanged in MDA-MB-231 cancer cells, normal MRC-5 fibroblasts, umbilical cord matrix-derived mesenchymal stem cells (UCMSCs) and dental papilla tissue-derived mesenchymal stem cells (DSCs). Whereas, PDT was significantly (P < .05) decreased in U87-MG cancer cells by increased cell growth. Glucose uptake was significantly (P < .05) increased in all the cancer cell lines compared to that in normal cell lines. Further, adiposome-like vesicles were noted in A-549 and MCF-7 cancer cells indicating retarded cell growth by DEX treatment, and the vesicles were stained with Oil-Red O solution. Further, the expression of adipocyte-specific genes such as glucose transporter type 4 (GLUT4), glucocorticoid receptors β (GRβ) and peroxisome proliferator-activated receptor γ (PPARγ) were significantly (P < .05) increased in A-549 and MCF-7 with lipid vesicles. The level of telomerase activity was found to be significantly (P < .05) downregulated in DEX-treated A-549 and MCF-7 cancer cells. Our results have clearly shown that DEX treatment induces inhibition of cell growth by differentiating into adipocyte-like cells in dexamethasone sensitive cancer cells.

Actin depolymerization enhances adipogenic differentiation in human stromal stem cells

Human stromal stem cells (hMSCs) differentiate into adipocytes that play a role in skeletal tissue homeostasis and whole body energy metabolism. During adipocyte differentiation, hMSCs exhibit significant changes in cell morphology suggesting changes in cytoskeletal organization. Here, we examined the effect of direct modulation of actin microfilament dynamics on adipocyte differentiation. Stabilizing actin filaments in hMSCs by siRNA-mediated knock down of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) or treating the cells by Phalloidin reduced adipocyte differentiation as evidenced by decreased number of mature adipocytes and decreased adipocyte specific gene expression (ADIPOQ, LPL, PPARG, FABP4). In contrast, disruption of actin cytoskeleton by Cytochalasin D enhanced adipocyte differentiation. Follow up studies revealed that the effects of CFL1 on adipocyte differentiation depended on the activity of LIM domain kinase 1 (LIMK1) which is the major upstream kinase of CFL1. Inhibiting LIMK by its specific chemical inhibitor LIMKi inhibited the phosphorylation of CFL1 and actin polymerization, and enhanced the adipocyte differentiation. Moreover, treating hMSCs by Cytochalasin D inhibited ERK and Smad2 signaling and this was associated with enhanced adipocyte differentiation. On the other hand, Phalloidin enhanced ERK and Smad2 signaling, but inhibited adipocyte differentiation which was rescued by ERK specific chemical inhibitor U0126. Our data provide a link between restructuring of hMSCs cytoskeleton and hMSCs lineage commitment and differentiation.

Telmisartan reverses antiretroviral-induced adipocyte toxicity and insulin resistance in vitro.

Background:Antiretroviral therapy in HIV-positive patients leads to insulin resistance which is central to the pathogenesis of various metabolic abnormalities and cardiovascular disease seen in this patient group. We have investigated the dose–response relationship of telmisartan, an antihypertensive, on adipocytes in vitro in order to determine whether it may have metabolic beneficial effects.Methods:Using in vitro chronic toxicity models (3T3-F442A murine and primary human adipocytes), we evaluated the effects of different concentrations of telmisartan on adipocyte differentiation and adipogenic gene expression using lipid accumulation assays and real-time polymerase chain reaction, respectively. Adipokine secretion and expression of insulin signalling mediators were evaluated using enzyme-linked immunosorbent assays.Results:Telmisartan partially reversed the deleterious effects of antiretrovirals on adipocyte lipid accumulation, expression of adipogenic regulators (peroxisome proliferator receptor-gamma and lipin 1), adipokine secretion and expression of the insulin signalling mediator pAktSer473. The metabolic effects of telmisartan followed a non-monotonic response with the maximal effect observed at 5 µM in the primary human adipocyte model.Conclusion:Telmisartan has beneficial metabolic effects in adipocytes in vitro, but its potential to reduce antiretroviral-induced cardiometabolic disease in HIV-infected individuals needs to be evaluated in a well-designed adequately powered clinical trial.

Nonthermal plasma treated solution inhibits adipocyte differentiation and lipogenesis in 3T3-L1 preadipocytes via ER stress signal suppression

The accumulation and differentiation of adipocytes contribute to the development of obesity and metabolic diseases. It is well-known that interactions of transcription factors such as peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), and endoplasmic reticulum (ER) stress are required for adipogenesis. Recently, use of nonthermal atmospheric plasma (NTP) is expanding from the biomedical field into various other fields. In this study, we investigated whether nonthermal plasma-treated solution (NTS) has an inhibitory effect on adipogenesis and elucidated its mechanisms. Our results demonstrated that NTS significantly inhibited pre-adipocyte differentiation into adipocytes based on Oil Red O staining and triglyceride accumulation. Moreover, NTS treatment suppressed the mRNA and protein expression levels of key adipogenic transcription factors, and adipocyte-specific genes. NTS also down-regulated endoplasmic reticulum stress-related proteins. Consistent with in vitro studies, an animal study using a mouse model of diet-induced obesity showed that NTS treatment reduced body weight and fat, ER stress/UPR, triglyceride, and adipogenic marker level without altering food intake. These findings indicate that NTS inhibits adipogenic differentiation, and provide a mechanistic explanation of the inhibitory effect of NTS on adipogenesis. Taken together, our results suggest that NTS might be useful to treat obesity and obesity-related diseases.

Effects of the oligostilbenes from Iris lactea Pall. var. chinensis (Fisch.) Koidz on the adipocytes differentiation of 3T3-L1 cells.

The dried seeds of Iris lactea Pall. var. chinensis (Fisch.) Koidz, an important traditional Chinese medicine, are regarded to have effects of clearing heat, eliminating dampness and pharyngitis and so on. It has been used in the treatment of jaundice, diarrhea, leucorrhea and carbuncles. Previous phytochemical studies of Iris species showed the presence of flavones, isoflavones, triterpenes and stilbenes. In our previous research, we isolated five known oligostilbenes, vitisin A, vitisin B, vitisin C, vitisin D, and cis-vitisin A were successfully isolated from Iris lactea for the first time. The aim of this study was to assess the effects of these oligostilbenes on the differentiation and adipogenes in 3T3-L1 cells. Our results showed that vitisin A, vitisin B, cis-vitisin A significantly inhibited adipocytes differentiation and reduced lipid accumulation in 3T3-L1 cells. In addition, vitisin A, vitisin B, cis-vitisin A strongly suppressed the expression levels of adipocyte-specific genes including peroxisome proliferator activated receptor-γ (PPARγ), CCAAT/enhancer binding protein-α (C/EBPα) and adipocyte fatty acid binding protein 4 (FABP4). In contrast, vitisin C and vitisin D significantly promoted adipogenesis and increased intracellular lipid accumulation, while the two oligostilbenes markedly increased the expression of adipocyte marker genes. In the present study, we found that vitisin A, vitisin B and cis-vitisin A inhibit the adipogenesis and adipocytes differentiation by their influence on the expression of PPARγ, which leads to subsequenet downregulation of PPARγ mediated adipocyte-specific gene during adipogenesis.

MicroRNA-200a regulates adipocyte differentiation in the domestic yak Bos grunniens

The domestic yak (Bos grunniens) is a culturally important animal that lives at high altitude and is farmed by Tibetan herders for its meat, milk, and other animal by-products. Within the animal, adipose tissue is an important store and source of energy and is used to maintain adequate body temperature during the extended cold seasons. Exploring the biomolecular role of microRNAs (miRNAs) in the regulation of growth, development, and metabolism of yak adipocytes may provide valuable insights into the physiology of adipogenesis in the yak. This study investigated whether and how miR-200a (a miRNA recently reported to promote adipogenesis in ST2 bone marrow stromal cells) regulates adipocyte differentiation in the yak. Expression levels of miR-200a gradually increased during day 0 to day 8 of adipocyte differentiation, and transfection of adipocytes with miR-200a enhanced lipid accumulation and triglyceride content compared to control (un-transfected) adipocytes. We additionally verified (using qRT-PCR analysis) that miR-200a increased the expression of adipocyte-specific genes involved in lipogenic transcription (PPARγ, ELVOL, and C/EBPα), fatty acid synthesis (ACC, ACS, SCD, and FAS), and fatty acid transport (DGAT, LPL, and FABP4). We also found that transfection of adipocytes with miR-200a resulted in suppression of the levels of noncanonical Wnt signaling transcription factors (Wnt5a, TAK1, and NLK). These results indicate that miRNA-200a plays an important role in promoting yak adipocyte differentiation that may operate via the suppression of noncanonical Wnt signaling.

Multiple intracellular signaling pathways orchestrate adipocytic differentiation of human bone marrow stromal stem cells

Bone marrow adipocyte formation plays a role in bone homeostasis and whole body energy metabolism. However, the transcriptional landscape and signaling pathways associated with adipocyte lineage commitment and maturation are not fully delineated. Thus, we performed global gene expression profiling during adipocyte differentiation of human bone marrow stromal (mesenchymal) stem cells (hMSCs) and identified 2,589 up-regulated and 2,583 down-regulated mRNA transcripts. Pathway analysis on the up-regulated gene list untraveled enrichment in multiple signaling pathways including insulin receptor signaling, focal Adhesion, metapathway biotransformation, a number of metabolic pathways e.g. selenium metabolism, Benzo(a)pyrene metabolism, fatty acid, triacylglycerol, ketone body metabolism, tryptophan metabolism, and catalytic cycle of mammalian flavin-containing monooxygenase (FMOs). On the other hand, pathway analysis on the down-regulated genes revealed significant enrichment in pathways related to cell cycle regulation. Based on these data, we assessed the effect of pharmacological inhibition of FAK signaling using PF-573228, PF-562271, and InsR/IGF-1R using NVP-AEW541 and GSK-1904529A on adipocyte differentiation. hMSCs exposed to FAK or IGF-1R/InsR inhibitors exhibited fewer adipocyte formation (27–58% inhibition, P<0005). Concordantly, the expression of adipocyte-specific genes AP2, AdipoQ, and CEBPα was significantly reduced. On the other hand, we did not detect significant effects on cell viability as a result of FAK or IGF-1R/InsR inhibition. Our data identified FAK and insulin signaling as important intracellular signaling pathways relevant to bone marrow adipogenesis.

Inhibition of Adipocyte Differentiation by Anthocyanins Isolated from the Fruit of Vitis coignetiae Pulliat is Associated with the Activation of AMPK Signaling Pathway

Anthocyanins are naturally occurring water-soluble polyphenolic pigments in plants that have been shown to protect against cardiovascular diseases, and certain cancers, as well as other chronic human disorders. However, the anti-obesity effects of anthocyanins are not fully understood. In this study, we investigated the effects of anthocyanins isolated from the fruit of Vitis coignetiae Pulliat on the adipogenesis of 3T3-L1 preadipocytes. Our data indicated that anthocyanins attenuated the terminal differentiation of 3T3-L1 preadipocytes, as confirmed by a decrease in the number of lipid droplets, lipid content, and triglyceride production. During this process, anthocyanins effectively enhanced the activation of the AMP-activated protein kinase (AMPK); however, this phenomenon was inhibited by the co-treatment of compound C, an inhibitor of AMPK. Anthocyanins also inhibited the expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein a and b, and sterol regulatory element-binding protein-1c. In addition, anthocyanins were found to potently inhibit the expression of adipocyte-specific genes, including adipocyte fatty acid-binding protein, leptin, and fatty acid synthase. These results indicate that anthocyanins have potent anti-obesity effects due to the inhibition of adipocyte differentiation and adipogenesis, and thus may have applications as a potential source for an anti-obesity functional food agent.

Adipogenic genes expression in relation to hepatic steatosis in the liver of two duck species

Some studies have shown that expression of peroxisome proliferator-activated receptor gamma (PPARG), a key regulator of adipogenesis, and of some adipocyte-specific genes or adipokines are expressed in hepatic steatosis, leading to the concept of ‘adipogenic hepatic steatosis’ or ‘hepatic adiposis.’ Most of these studies were conducted in genetic obese mouse models or after manipulation of gene expression. The relevance of this concept to other species and more physiological models was here addressed in ducks which are able to develop hepatic steatosis after overfeeding. The expression of PPARG and other adipocyte-specific genes was thus analyzed in the liver of ducks fed ad libitum or overfed and compared with those observed in adipose tissues. Pekin (Anas platyrhynchos) and Muscovy ducks (Cairina moschata) were analyzed, as metabolic responses to overfeeding differ according to these two species, Muscovy ducks having a greater ability to synthesize and store lipids in the liver than Pekin ducks. Our results indicate that adipocyte-specific genes are expressed in the liver of ducks, PPARG and fatty acid-binding protein 4 being upregulated and adiponectin and leptin receptor downregulated by overfeeding. However, these expression levels are much lower than those observed in adipose tissue suggesting that fatty liver cells are not transformed to adipocytes, although some hepato-specific functions are decreased in fatty liver when compared with normal liver.

Modulation of Adipocyte Differentiation and Proadipogenic Gene Expression by Sulforaphane, Genistein, and Docosahexaenoic Acid as a First Step to Counteract Obesity

Obesity is characterized by excess body fat accumulation due to an increase in the size and number of differentiated mature adipocytes. Adipocyte differentiation is regulated by genetic and environmental factors, and its inhibition could represent a strategy for obesity prevention and treatment. The current study was designed with two aims: (i) to evaluate the changes in the expression of adipogenic markers (C/EBPα, PPARγ variant 1 and variant 2, and GLUT4) in 3T3-L1 murine preadipocytes at four stages of the differentiation process and (ii) to compare the effectiveness of sulforaphane, genistein, and docosahexaenoic acid in reducing lipid accumulation and modulating C/EBPα, PPARγ1, PPARγ2, and GLUT4 mRNA expression in mature adipocytes. All bioactive compounds were shown to suppress adipocyte differentiation, although with different effectiveness. These results set the stage for further studies considering natural food constituents as important agents in preventing or treating obesity.

BRD4 regulates adiponectin gene induction by recruiting the P-TEFb complex to the transcribed region of the gene

We previously reported that induction of the adipocyte-specific gene adiponectin (Adipoq) during 3T3-L1 adipocyte differentiation is closely associated with epigenetic memory histone H3 acetylation on the transcribed region of the gene. We used 3T3-L1 adipocytes and Brd4 heterozygous mice to investigate whether the induction of Adipoq during adipocyte differentiation is regulated by histone acetylation and the binding protein bromodomain containing 4 (BRD4) on the transcribed region. Depletion of BRD4 by shRNA and inhibition by (+)-JQ1, an inhibitor of BET family proteins including BRD4, reduced Adipoq expression and lipid droplet accumulation in 3T3-L1 adipocytes. Additionally, the depletion and inhibition of BRD4 reduced the expression of many insulin sensitivity-related genes, including genes related to lipid droplet accumulation in adipocytes. BRD4 depletion reduced P-TEFb recruitment and histone acetylation on the transcribed region of the Adipoq gene. The expression levels of Adipoq and fatty acid synthesis-related genes and the circulating ADIPOQ protein level were lower in Brd4 heterozygous mice than in wild-type mice at 21 days after birth. These findings indicate that BRD4 regulates the Adipoq gene by recruiting P-TEFb onto acetylated histones in the transcribed region of the gene and regulates adipocyte differentiation by regulating the expression of genes related to insulin sensitivity.

Role of adipose tissue in melanoma cancer microenvironment and progression.

An epidemiological association between excess weight and increased risk of cancer has been described in melanoma, for which the physiopathological mechanisms are still unknown. The study of tumor microenvironment and of the role of adipocytes in cancer development, progression and metastasis has recently received great interest. However, the role of peritumoral adipocytes has been characterized only in a few types of cancer, and in melanoma it still remains to be defined. We investigated the interactions between adipocytes and melanoma cells using an in vitro co-culture system. We studied the morphological and functional properties of 3T3-L1 adipocytes before and after co-culture with A375 melanoma cells, in order to assess the role of adipocytes on melanoma migration. Morphological analysis showed that after 6 days of co-culture 3T3-L1 adipocytes were reduced in number and size. Moreover, we observed the appearance of dedifferentiated cells with a fibroblast-like phenotype that were not present in controls and that had lost the expression of some adipocyte-specific genes, and increased the expression of collagen, metalloproteinases and genes typical of dedifferentiation processes. Through the Matrigel Invasion Test, as well the Scratch Test, it was possible to observe that co-culture with adipocytes induced in melanoma cells increased migratory capacity, as compared with controls. In particular, the increase in migration observed in co-culture was suppressed after adding the protein SFRP-5 in the medium, supporting the involvement of the Wnt5a pathway. The activation of this pathway was further characterized by immunofluorescence and western blot analysis, showing in melanocytes in co-culture the activation of β-catenin and LEF-1, two transcription factors involved in migration processes, neo-angiogenesis and metastasis. These data allow us to hypothesize a dedifferentiation process of adipocytes toward fibroblast-like cells, which can promote migration of melanoma cells through activation of Wnt5a and the intracellular pathways of β-catenin and LEF-1.

Extracellular calcium modulates brown adipocyte differentiation and identity

Brown adipocytes are important in regulating non-shivering thermogenesis, whole body glucose and lipid homeostasis. Increasing evidence supports an important role of metabolites as well as macro- and micronutrients in brown adipocyte differentiation and function. Calcium is one of the most abundant ions in the body regulating multiple cellular processes. We observed that increasing extracellular calcium concentration during brown adipocyte differentiation blocks lipid accumulation and suppresses induction of major adipogenic transcription factors such as PPARγ and C/EBPα. In contrast, the depletion of calcium in the medium enhances adipogenesis and expression of brown adipocyte selective genes, such as UCP1. Mechanistically, we show that elevated extracellular calcium inhibits C/EBPβ activity through hyperactivation of ERK, a process that is independent of intracellular calcium levels and reversibly halts differentiation. Moreover, increased extracellular calcium solely after the induction phase of differentiation specifically suppresses gene expression of UCP1, PRDM16 and PGC1-α. Notably, depleting extracellular calcium provokes opposite effects. Together, we show that modulating extracellular calcium concentration controls brown adipocyte differentiation and thermogenic gene expression, highlighting the importance of tissue microenvironment on brown adipocyte heterogeneity and function.