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  • SRA regulates adipogenesis by modulating p38/JNK phosphorylation and stimulating insulin receptor gene expression and downstream signaling. 24743795

    The Steroid Receptor RNA Activator (SRA) enhances adipogenesis and increases both glucose uptake and phosphorylation of Akt and FOXO1 in response to insulin. To assess the mechanism, we differentiated ST2 mesenchymal precursor cells that did or did not overexpress SRA into adipocytes using combinations of methylisobutylxanthine, dexamethasone and insulin. These studies showed that SRA overexpression promotes full adipogenesis in part by stimulation of insulin/insulin-like growth factor-1 (IGF-1) signaling. SRA overexpression inhibited phosphorylation of p38 mitogen activated protein kinase (MAPK) and c-Jun NH2-terminal kinase (JNK) in the early differentiation of ST2 cells. Conversely, knockdown of endogenous SRA in 3T3-L1 cells increased phosphorylation of JNK. Knockdown of SRA in mature 3T3-L1 adipocytes reduced insulin receptor (IR) mRNA and protein levels, which led to decreased autophosphorylation of IRβ and decreased phosphorylation of insulin receptor substrate-1 (IRS-1) and Akt. This likely reflects a stimulatory role of SRA on IR transcription, as transfection studies showed that SRA increased expression of an IR promoter-luciferase reporter construct.
    Document Type:
    Reference
    Product Catalog Number:
    05-321
    Product Catalog Name:
    Anti-Phosphotyrosine Antibody, clone 4G10®
  • HES1 inhibits adipogenesis of porcine mesenchymal stem cells via transcriptional repression of FAD24. 23611667

    Adipogenesis, the development from preadipocytes or mesenchymal stem cells (MSCs) to mature adipocytes, is regulated by a network of signaling pathways and transcription factors. The involvement of Notch signaling and its effector HES1 in adipogenesis has been investigated in several studies with conflicting results. The underlying mechanisms remain unclear because of the lack of information about HES1 target genes during adipocyte differentiation. As a novel gene transiently up-regulated in early adipogenesis, FAD24 functions as a positive regulator of adipocyte differentiation in both preadipocytes and MSCs. In the present study, we report that the expression level of FAD24 is inversely associated with that of HES1 in porcine MSCs after adipogenic induction. Enforced overexpression of HES1 in MSCs during the early stage of adipogenesis significantly repressed the transcription of FAD24 (P < 0.01) and the other pro-adipogenic genes (P < 0.05), resulting in reduced intracellular lipid accumulation. Sequence analysis showed that porcine FAD24 harbors an evolutionarily conserved HES1 binding site in its proximal promoter region. Functional HES1, but not its dominant-negative mutant, markedly reduced the promoter activity of FAD24 (P < 0.01). Site-directed mutation and chromatin immunoprecipitation further confirmed that HES1 inhibits FAD24 transcription by direct binding to the promoter. Taken together, we identified FAD24 as a novel downstream target of HES1 during adipogenesis. Our data suggest that HES1-mediated repression of FAD24 transcription at the early stage of adipocyte differentiation may contribute to the impaired adipogenesis induced by the Notch-HES1 signaling pathway.
    Document Type:
    Reference
    Product Catalog Number:
    17-371
    Product Catalog Name:
    EZ-ChIP™
  • Impaired adipogenesis caused by a mutated thyroid hormone alpha1 receptor. 17220280

    Thyroid hormone (T3) is critical for growth, differentiation, and maintenance of metabolic homeostasis. Mice with a knock-in mutation in the thyroid hormone receptor alpha gene (TRalpha1PV) were created previously to explore the roles of mutated TRalpha1 in vivo. TRalpha1PV is a dominant negative mutant with a frameshift mutation in the carboxyl-terminal 14 amino acids that results in the loss of T3 binding and transcription capacity. Homozygous knock-in TRalpha1(PV/PV) mice are embryonic lethal, and heterozygous TRalpha1(PV/+) mice display the striking phenotype of dwarfism. These mutant mice provide a valuable tool for identifying the defects that contribute to dwarfism. Here we show that white adipose tissue (WAT) mass was markedly reduced in TRalpha1(PV/+) mice. The expression of peroxisome proliferator-activated receptor gamma (PPARgamma), the key regulator of adipogenesis, was repressed at both mRNA and protein levels in WAT of TRalpha1(PV/+) mice. Moreover, TRalpha1PV acted to inhibit the transcription activity of PPARgamma by competition with PPARgamma for binding to PPARgamma response elements and for heterodimerization with the retinoid X receptors. The expression of TRalpha1PV blocked the T3-dependent adipogenesis of 3T3-L1 cells and repressed the expression of PPARgamma. Thus, mutations of TRalpha1 severely affect adipogenesis via cross talk with PPARgamma signaling. The present study suggests that defects in adipogenesis could contribute to the phenotypic manifestation of reduced body weight in TRalpha1(PV/+) mice.
    Document Type:
    Reference
    Product Catalog Number:
    SRI-13K
    Product Catalog Name:
    Sensitive Rat Insulin RIA
  • Rho/ROCK-dependent inhibition of 3T3-L1 adipogenesis by G-protein-deamidating dermonecrotic toxins: differential regulation of Notch1, Pref1/Dlk1, and β-catenin signaling ... 22919671

    The dermonecrotic toxins from Pasteurella multocida (PMT), Bordetella (DNT), Escherichia coli (CNF1-3), and Yersinia (CNFY) modulate their G-protein targets through deamidation and/or transglutamination of an active site Gln residue, which results in activation of the G protein and its cognate downstream signaling pathways. Whereas DNT and the CNFs act on small Rho GTPases, PMT acts on the α subunit of heterotrimeric G(q), G(i), and G(12/13) proteins. We previously demonstrated that PMT potently blocks adipogenesis and adipocyte differentiation in a calcineurin-independent manner through downregulation of Notch1 and stabilization of β-catenin and Pref1/Dlk1, key proteins in signaling pathways strongly linked to cell fate decisions, including fat and bone development. Here, we report that similar to PMT, DNT, and CNF1 completely block adipogenesis and adipocyte differentiation by preventing upregulation of adipocyte markers, PPARγ and C/EBPα, while stabilizing the expression of Pref1/Dlk1 and β-catenin. We show that the Rho/ROCK inhibitor Y-27632 prevented or reversed these toxin-mediated effects, strongly supporting a role for Rho/ROCK signaling in dermonecrotic toxin-mediated inhibition of adipogenesis and adipocyte differentiation. Toxin treatment was also accompanied by downregulation of Notch1 expression, although this inhibition was independent of Rho/ROCK signaling. We further show that PMT-mediated downregulation of Notch1 expression occurs primarily through G(12/13) signaling. Our results reveal new details of the pathways involved in dermonecrotic toxin action on adipocyte differentiation, and the role of Rho/ROCK signaling in mediating toxin effects on Wnt/β-catenin and Notch1 signaling, and in particular the role of G(q) and G(12/13) in mediating PMT effects on Rho/ROCK and Notch1 signaling.
    Document Type:
    Reference
    Product Catalog Number:
    AB3511
  • Chondrogenesis, osteogenesis and adipogenesis of canine mesenchymal stem cells: a biochemical, morphological and ultrastructural study. 17922135

    Musculoskeletal diseases with osteochondrotic articular cartilage defects, such as osteoarthritis, are an increasing problem for humans and companion animals which necessitates the development of novel and improved therapeutic strategies. Canine mesenchymal stem cells (cMSCs) offer significant promise as a multipotent source for cell-based therapies and could form the basis for the differentiation and cultivation of tissue grafts to replace damaged tissue. However, no comprehensive analysis has been undertaken to characterize the ultrastructure of in vitro differentiated cMSCs. The main goal of this paper was to focus on cMSCs and to analyse their differentiation capacity. To achieve this aim, bone marrow cMSCs from three canine patients were isolated, expanded in monolayer culture and characterized with respect to their ability for osteogenic, adipogenic and chondrogenic differentiation capacities. cMSCs showed proliferative potential and were capable of osteogenic, adipogenic and chondrogenic differentiation. cMSCs treated with the osteogenic induction medium differentiated into osteoblasts, produced typical bone matrix components, beta1-integrins and upregulated the osteogenic specific transcription factor Cbfa-1. cMSCs treated with the adipogenic induction medium showed typical adipocyte morphology, produced adiponectin, collagen type I and beta1-integrins, and upregulated the adipogenic specific transcription factor PPAR-gamma. cMSCs treated with the chondrogenic induction medium exhibited a round to oval shape, produced a cartilage-specific extracellular matrix, beta1-integrins and upregulated the chondrogenic specific transcription factor Sox9. These results demonstrate, at the biochemical, morphological and ultrastructural levels, the multipotency of cMSCs and thus highlight their potential therapeutic value for cell-based tissue engineering.
    Document Type:
    Reference
    Product Catalog Number:
    MAB2015
    Product Catalog Name:
    Anti-Cartilage Proteoglycan Antibody, adult, clone EFG-4
  • Calcineurin-independent inhibition of 3T3-L1 adipogenesis by Pasteurella multocida toxin: suppression of Notch1, stabilization of beta-catenin and pre-adipocyte factor 1. 17581254

    Pasteurella multocida toxin (PMT) is a potent mitogen and a specific activator of Gq-dependent signalling pathways. PMT impairs osteoblast differentiation and causes bone loss and fat reduction in vivo. We examined the effect of PMT on cell signalling pathways involved in 3T3-L1 adipocyte differentiation. We demonstrate that PMT treatment before or together with differentiation induction factors inhibits adipogenesis and prevents upregulation of important adipocyte markers - peroxisome-proliferator-activated receptor gamma (PPARgamma) and CAATT enhancer-binding protein alpha (C/EBPalpha). Moreover, PMT completely downregulates PPARgamma and C/EBPalpha expression in mature adipocytes. Differentiation of pre-adipocytes into adipocytes requires the suppression of pre-adipocyte factor 1 (Pref1) and Wnt signalling, along with the degradation of beta-catenin. PMT prevents downregulation of Pref1 and beta-catenin under differentiation-inducing conditions. In addition, PMT treatment downregulates expression of Notch1, a protein responsible for cell fate decision and implicated in regulation of adipogenesis in 3T3-L1 cells. PMT action on adipogenesis was not reversed by cyclosporin A, an inhibitor of Galphaq-PLC-calcium-dependent calcineurin activation. Our results reveal new pathways involved in PMT action on cellular physiology and differentiation. Our study further demonstrates that the effect of PMT on Pref1/PPARgamma/C/EBPalpha expression and adipogenesis does not occur just through activation of the Galphaq-calcium-calcineurin pathway, but involves Wnt/beta-catenin and Notch1 signalling pathways, two signalling pathways strongly linked to cancer predisposition, neurological and immunological dysfunctions, and fat and bone development.
    Document Type:
    Reference
    Product Catalog Number:
    AB3511
  • Obesity-Associated MiR-342-3p Promotes Adipogenesis of Mesenchymal Stem Cells by Suppressing CtBP2 and Releasing C/EBPα from CtBP2 Binding. 25895816

    The elucidation of the molecular mechanism of adipocyte differentiation in mesenchymal stem cells is of essential importance for the development of treatments for metabolic diseases, such as obesity and diabetes.The expression levels of miR-342-3p and carboxy-terminal binding protein 2 (CtBP2) were regulated by oligonucleotide transfection. Adipogenic differentiation was induced by adipogenic medium containing indomethacin, dexamethasone and 3-isobutyl-1-methylxanthine on day 12, as determined by Oil Red O staining and triglyceride concentration assay to assess intracellular lipid accumulation. The induction of adipocyte-specific transcription factors and markers was detected by qRT-PCR and western blot. The regulation of CtBP2 expression by miR-342-3p was determined by western blot, qRT-PCR, luciferase reporter assay, ChIP assay and functional experiments.We revealed that miR-342-3p was enriched in the adipose tissue of obese mice, and its expression was significantly elevated during adipogenic differentiation in both human mesenchymal stem cells (hMSCs) and 3T3L1 cells. Using gain- and loss-of-function assays, we demonstrated that the overexpression of miR-342-3p markedly promoted the differentiation of hMSCs into an adipogenic lineage. Adipogenesis was significantly blocked by miR-342-3p downregulation. We identified and validated that CtBP2 was a direct target of miR-342-3p in this process. The effects of the inhibition of CtBP2 were similar to those of miR-342-5p overexpression on adipogenic differentiation, promoting the release of C/EBPα from CtBP2 binding.miR-342-3p is a powerful enhancer of the adipogenesis of human adipose-derived MSCs that acts by inhibiting CtBP2 and releasing the key adipogenic regulator C/EBPα from CtBP2 binding, subsequently activating the expression of adipogenic transcription factors and markers.
    Document Type:
    Reference
    Product Catalog Number:
    17-409
    Product Catalog Name:
    EZ-Magna ChIP™ G - Chromatin Immunoprecipitation Kit
  • HMGA1 overexpression in adipose tissue impairs adipogenesis and prevents diet-induced obesity and insulin resistance. 26411793

    High-Mobility-Group-A1 (HMGA1) proteins are non-histone proteins that regulate chromatin structure and gene expression during embryogenesis, tumourigenesis and immune responses. In vitro studies suggest that HMGA1 proteins may be required to regulate adipogenesis. To examine the role of HMGA1 in vivo, we generated transgenic mice overexpressing HMGA1 in adipose tissues. HMGA1 transgenic mice showed a marked reduction in white and brown adipose tissue mass that was associated with downregulation of genes involved in adipogenesis and concomitant upregulation of preadipocyte markers. Reduced adipogenesis and decreased fat mass were not associated with altered glucose homeostasis since HMGA1 transgenic mice fed a regular-chow diet exhibited normal glucose tolerance and insulin sensitivity. However, when fed a high-fat diet, overexpression of HMGA1 resulted in decreased body-weight gain, reduced fat mass, but improved insulin sensitivity and glucose tolerance. Although HMGA1 transgenic mice exhibited impaired glucose uptake in adipose tissue due to impaired adipogenesis, the increased glucose uptake observed in skeletal muscle may account for the improved glucose homeostasis. Our results indicate that HMGA1 plays an important function in the regulation of white and brown adipogenesis in vivo and suggests that impaired adipocyte differentiation and decreased fat mass is not always associated with impaired whole-body glucose homeostasis.
    Document Type:
    Reference
    Product Catalog Number:
    AB756P
    Product Catalog Name:
    Anti-Collagen Antibody, Type IV
  • Additional sex comb-like (ASXL) proteins 1 and 2 play opposite roles in adipogenesis via reciprocal regulation of peroxisome proliferator-activated receptor {gamma}. 21047783

    Our previous studies have suggested that the mammalian additional sex comb-like 1 protein functions as a coactivator or repressor of retinoic acid receptors in a cell-specific manner. Here, we investigated the roles of additional sex comb-like 1 proteins in regulating peroxisome proliferator-activated receptors (PPARs). In pulldown assays in vitro and in immunoprecipitation assays in vivo, ASXL1 and its paralog, ASXL2, interacted with PPARα and PPARγ. In 3T3-L1 preadipocyte cells, overexpression of ASXL1 inhibited the induction of PPARγ activity by rosiglitazone, as shown by transcription assays, and completely suppressed adipogenesis, as shown by Oil Red O staining. In contrast, overexpression of ASXL2 greatly enhanced rosiglitazone-induced PPARγ activity and enhanced adipogenesis. Deletion of the heterochromatin protein 1 (HP1)-binding domain from ASXL1 caused the mutant protein to enhance adipogenesis similarly to ASXL2, indicating that HP1 binding is required for the adipogenesis-suppressing activity of ASXL1. Adipocyte differentiation was associated with a gradual decrease in ASXL1 expression but did not affect ASXL2 expression. Knockdown of ASXL1 and ASXL2 had reciprocal effects on adipogenesis. In chromatin immunoprecipitation assays in 3T3-L1 cells, ASXL1 occupied the promoter of the PPARγ target gene aP2 together with HP1α and Lys-9-methylated histone H3, whereas ASXL2 occupied the aP2 promoter together with histone-lysine N-methyltransferase MLL1 and Lys-9-acetylated and Lys-4-methylated H3 histones. Finally, microarray analysis demonstrated that ASXL1 represses, whereas ASXL2 increases, the expression of adipogenic genes, most of which are PPARγ targets. These results suggest that members of the additional sex comb-like family provide complex regulation of adipogenesis via differential modulation of PPARγ activity.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple