Adipocyte Differentiation Medium Research Articles

OR29-02 Energy Deficient Osteoblasts Inefficiently Mineralize Developing Bone In Sheep With Hypophosphatasia

Abstract Disclosure: J.C. Bertels: None. M. McCord: None. L.G. White: None. S. Huggins: None. D. Landrock: None. E.D. Giles: None. L.J. Suva: None. D. Gaddy: None. Hypophosphatasia (HPP) is a rare genetic disorder characterized by low enzymatic activity of tissue nonspecific alkaline phosphatase (TNSALP), resulting in decreased bone mineralization, muscle weakness, and premature loss of deciduous teeth. All HPP phenotypes have been characterized in our CRISPR/Cas9 gene-edited sheep model of HPP. Previous studies identified small, abnormal mitochondria in HPP sheep cells, leading to the hypothesis that reduced bone mineralization may result from decreased osteoblast (OB) differentiation and cellular energetics. To test this idea, iliac crest bone biopsies and sternal bone marrow stromal cells (BMSCs) were harvested from 1 yr old WT and HPP sheep (n=3 per genotype). Histomorphometric analysis of bone biopsies from HPP sheep revealed increased unmineralized osteoid matrix compared to WT, indicative of decreased OB activity, whereas osteoblast and osteoclast number were unchanged. To determine whether BMSCs from HPP sheep were altered from WT in regard to differentiation capacity toward the adipocyte (AD) or OB lineage, 21 day cultures of BMSCs in OB or AD differentiation medium were performed. HPP BMSCs had significantly increased AD differentiation and similar OB differentiation compared to WT. Next, high resolution respirometry of undifferentiated and differentiating cells toward either the OB or AD lineage using Seahorse XF analysis to measure oxidative respiration and glycolysis on days 0, 7, 14 and 21 of both OB and AD differentiation was performed. Results demonstrated that both undifferentiated and differentiating HPP cells (to OB and AD) had significantly decreased oxygen consumption rates (OCR) and extracellular acidification rates (ECAR), reflective of diminished maximal and ATP-linked oxidative respiration and glycolysis. When measured, intracellular ATP levels in differentiating BMSCs, both undergoing osteoblastogenic and adiopogenic differentiation, showed a higher accumulation of ATP. Collectively, these data provide the first evidence that decreased bone mineralization in HPP sheep results from decreased BMSC and OB energetics through both oxidative respiration and glycolysis. In addition, the data demonstrate that reduced TNSALP activity also leads to enhanced bone marrow adipogenesis. Coupled with our previous results demonstrating reduced oxidative respiration and glycolysis in sheep skeletal muscle, these findings demonstrate a fundamental requirement for TNSALP activity in the maintenance of normal cellular respiration and purinergic metabolism in cells of the musculoskeletal system. Moreover, they provide important insight into the potential for targeting increased cellular respiration to alleviate the deleterious effects of HPP. Presentation: Sunday, June 18, 2023

Cydonia oblonga Miller fruit extract exerts an anti-obesity effect in 3T3-L1 adipocytes by activating the AMPK signaling pathway.

The fruit of Cydonia oblonga Miller (COM) is used traditionally in Mediterranean region medicine to prevent or treat obesity, but its mechanism of action is still unclear. Beyond a demonstrated anti-obesity effect, the fruit was tested for the mechanism of adipogenesis in 3T3-L1 preadipocytes. 3T3-L1 preadipocytes were cultured for 8 days with COM fruit extract (COME) at different concentrations (0-600 µg/mL) with adipocyte differentiation medium. The cell viability was measured using an MTT assay; triglyceride (TG) was stained with Oil Red O. The expression levels of the adipogenesis-related genes and protein expression were analyzed by reverse transcription polymerase chain reaction and Western blotting, respectively. COME inhibited intracellular TG accumulation during adipogenesis. A COME treatment in 3T3-L1 cells induced upregulation of the adenosine monophosphate-activated protein kinase (AMPK)α phosphorylation and downregulation of the adipogenic transcription factors, such as sterol regulatory element-binding protein 1c, peroxisome proliferator-activated receptor γ, and CCAAT/enhancer binding protein α. The COME treatment reduced the mRNA expression of fatty acyl synthetase, adenosine triphosphate-citrate lyase, adipocyte protein 2, and lipoprotein lipase. It increased the mRNA expression of hormone-sensitive lipase and carnitine palmitoyltransferase I in 3T3-L1 cells. COME inhibits adipogenesis via the AMPK signaling pathways. COME may be used to prevent and treat obesity.

What's up with WAT: attempting to mimic adipose tissue in vitro.

What's up with WAT: attempting to mimic adipose tissue in vitro.

\u03b1-Poly-l-lysine functions as an adipogenic inducer in 3T3-L1 preadipocytes

α-Poly-l-lysine (PLL) has been used for various purposes such as cell attachment, immunization, and molecular delivery, and is known to be cytotoxic to several cell lines. Here, we studied the effect of PLL on the adipogenesis of 3T3-L1 cells and investigated the underlying mechanism. Differentiation media containing PLL with a molecular weight (MW) greater than 4 kDa enhanced lipid droplet formation and increased adipogenic marker levels, indicating an increase in adipocyte differentiation. PLL with a molecular weight between 30 and 70 kDa was more effective than PLL of other sizes in 3T3-L1 cell differentiation. Moreover, PLL induced 3T3-L1 adipogenesis in insulin-free adipocyte differentiation medium. Incubation with insulin and PLL exhibited greater adipogenesis than insulin treatment only even at a high concentration. PLL stimulated insulin signaling and augmented the signaling pathway when it was added with insulin. While PLL did not activate the glucocorticoid receptor, which is phosphorylated by dexamethasone (DEX), it showed a positive effect on the cAMP signal pathway when preadipocytes were treated with PLL and 3-isobutyl-1-methylxanthine (IBMX). Consistent with these results, incubation with PLL and DEX without IBMX induced adipocyte differentiation. We also observed that the mitotic clonal expansion phase was the critical stage in adipogenesis for inducing the effects of PLL. These results suggest that PLL functions as an adipogenic inducer in 3T3-L1 preadipocytes and PLL has a direct effect on insulin signaling, one of the main regulatory pathways.

Basic Fibroblast Growth Factor Induces Adipogenesis in Orbital Fibroblasts: Implications for the Pathogenesis of Graves' Orbitopathy.

Basic fibroblast growth factor (bFGF) has been implicated in the pathogenesis of Graves' orbitopathy (GO). It stimulates several processes, including hyaluronan synthesis, involved in orbital tissue volume expansion and may act synergistically with platelet-derived growth factor (PDGF)-BB. PDGF-BB is known to stimulate adipogenesis in orbital fibroblasts, but the effect of bFGF on adipogenesis in orbital fibroblasts is so far unknown. This study was conducted to determine whether (i) bFGF induces adipogenesis in orbital fibroblasts, (ii) bFGF and PDGF-BB together exert an additive or synergistic effect on adipogenesis, and (iii) treatment directed at bFGF- and PDGF-BB signaling may potentially be of interest for the treatment of GO. Orbital fibroblasts from GO patients and controls were cultured in adipocyte differentiation medium with or without bFGF and/or PDGF-BB at different concentrations. Adipogenesis was determined by Oil Red O staining and messenger RNA expression of the late adipocyte differentiation markers cell death-inducing DFFA-like effector C (CIDEC) and adiponectin (ADIPOQ). To demonstrate involvement of FGF-receptor and PDGF-receptor signaling, experiments were also conducted in the presence of dasatinib (inhibitor of PDGF-receptor) or nintedanib (inhibitor of PDGF-receptor and FGF-receptor). bFGF significantly stimulated adipogenesis by orbital fibroblasts, as shown by increased Oil Red O staining and CIDEC and ADIPOQ expression after 14 days of differentiation. Furthermore, an additive effect of bFGF/PDGF-BB co-stimulation on adipogenesis was observed at the lowest concentration (12.5 ng/mL) of the growth factors tested. Nintedanib completely inhibited bFGF-, PDGF-BB-, and bFGF/PDGF-BB-induced adipogenesis, while dasatinib only fully abrogated PDGF-BB-induced adipogenesis. bFGF induces adipogenesis in orbital fibroblasts and as such may contribute to GO. The additive effect of bFGF and PDGF-BB on adipogenesis, along with the observed inhibitory effects of dasatinib and nintedanib, point at independent receptor-mediated effects. This supports the hypothesis that multi-target directed therapy might be more efficient in the treatment of GO.

Clonal derivation of white and brown adipocyte progenitor cell lines from human pluripotent stem cells

BackgroundThe role of brown fat in non-shivering thermogenesis and the discovery of brown fat depots in adult humans has made it the subject of intense research interest. A renewable source of brown adipocyte (BA) progenitors would be highly valuable for research and therapy. Directed differentiation of human pluripotent stem (hPS) cells to white or brown adipocytes is limited by lack of cell purity and scalability. Here we describe an alternative approach involving the identification of clonal self-renewing human embryonic progenitor (hEP) cell lines following partial hPS cell differentiation and selection of scalable clones.MethodsWe screened a diverse panel of hPS cell-derived clonal hEP cell lines for adipocyte markers following growth in adipocyte differentiation medium. The transcriptome of the human hES-derived clonal embryonic progenitor cell lines E3, C4ELS5.1, NP88, and NP110 representing three class of definitive adipocyte progenitors were compared to the relatively non-adipogenic line E85 and adult-derived BAT and SAT-derived cells using gene expression microarrays, RT-qPCR, metabolic analysis and immunocytochemistry. Differentiation conditions were optimized for maximal UCP1 expression.ResultsMany of the differentiated hEP cell lines expressed the adipocyte marker, FAPB4, but only a small subset expressed definitive adipocyte markers including brown adipocyte marker, UCP1. Class I cells (i.e., E3) expressed CITED1, ADIPOQ, and C19orf80 but little to no UCP1. Class II (i.e., C4ELS5.1) expressed CITED1 and UCP1 but little ADIPOQ and LIPASIN. Class III (i.e., NP88, NP110) expressed CITED1, ADIPOQ, C19orf80, and UCP1 in a similar manner as fetal BAT-derived (fBAT) cells. Differentiated NP88 and NP110 lines were closest to fBAT cells morphologically in adiponectin and uncoupling protein expression. But they were more metabolically active than fBAT cells, had higher levels of 3-hydroxybutyrate, and lacked expression of fetal/adult marker, COX7A1. The hEP BA progenitor lines were scalable to 17 passages without loss of differentiation capacity and could be readily rederived.ConclusionsTaken together, these data demonstrate that self-renewing adipocyte progenitor cells can be derived from hES cells and that they are functionally like BAT cells but with unique properties that might be advantageous for basic research and for development of cell-based treatments for metabolic diseases.

Induction of beige adipocytes by naturally occurring β3-adrenoceptor agonist p-synephrine

The prevalence of obesity and its associated diseases is increasing worldwide, and the therapeutic potential of increasing energy expenditure through differentiation or activation of beige adipocytes has attracted much interest. Therefore, we explored naturally occurring compounds that induce beige adipocytes by screening for activity to induce mRNA expression of uncoupling protein 1 (UCP1) in stromal vascular fraction (SVF) cells cultured in beige adipocyte differentiation medium. Through screening, p-synephrine, a compound isolated from Citrus unshiu Marcov., was found to be an active compound that increased UCP1 mRNA expression in a dose-dependent manner from a concentration of 3.12 µM, which induced morphological changes specific for beige adipocytes. Similar effects were also observed in SVF cells prepared from db/db obese mice. While investigating the underlying mechanism of p-synephrine-induced beige adipocyte differentiation, we found that the effects of p-synephrine were abolished by the β3-adrenoceptor antagonist SR58894. Intriguingly, p-synephrine increased UCP1 mRNA levels in SVF cells cultured in beige adipocyte differentiation medium lacking insulin to an extent different from those by the β-agonist isoprenaline. Furthermore, phosphatidylinositol 3-kinase inhibitor LY294002 decreased isoprenaline-induced UCP1 mRNA levels in the early phase of beige adipocyte differentiation and p-synephrine-induced UCP1 mRNA levels in fully differentiated beige adipocytes. Thus, p-synephrine appears to elicit signals via β3-adrenoceptor combined with some part of the insulin signaling pathway, finally resulting in efficient stimulation of beige adipocyte differentiation with the support of certain beige adipocyte differentiation-inducing factors. The present results suggest the potential of p-synephrine for prophylaxis and treatment of obesity and its associated diseases.

Oxidative stress-induced S100B accumulation converts myoblasts into brown adipocytes via an NF-κB/YY1/miR-133 axis and NF-κB/YY1/BMP-7 axis.

Muscles of sarcopenic people show hypotrophic myofibers and infiltration with adipose and, at later stages, fibrotic tissue. The origin of infiltrating adipocytes resides in fibro-adipogenic precursors and nonmyogenic mesenchymal progenitor cells, and in satellite cells, the adult stem cells of skeletal muscles. Myoblasts and brown adipocytes share a common Myf5+ progenitor cell: the cell fate depends on levels of bone morphogenetic protein 7 (BMP-7), a TGF-β family member. S100B, a Ca2+-binding protein of the EF-hand type, is expressed at relatively high levels in myoblasts from sarcopenic humans and exerts anti-myogenic effects via NF-κB-dependent inhibition of MyoD, a myogenic transcription factor acting upstream of the essential myogenic factor, myogenin. Adipogenesis requires high levels of ROS, and myoblasts of sarcopenic subjects show elevated ROS levels. Here we show that: (1) ROS overproduction in myoblasts results in upregulation of S100B levels via NF-κB activation; and (2) ROS/NF-κB-induced accumulation of S100B causes myoblast transition into brown adipocytes. S100B activates an NF-κB/Ying Yang 1 axis that negatively regulates the promyogenic and anti-adipogenic miR-133 with resultant accumulation of the brown adipogenic transcription regulator, PRDM-16. S100B also upregulates BMP-7 via NF-κB/Ying Yang 1 with resultant BMP-7 autocrine activity. Interestingly, myoblasts from sarcopenic humans show features of brown adipocytes. We also show that S100B levels and NF-κB activity are elevated in brown adipocytes obtained by culturing myoblasts in adipocyte differentiation medium and that S100B knockdown or NF-κB inhibition in myoblast-derived brown adipocytes reconverts them into fusion-competent myoblasts. At last, interstitial cells and, unexpectedly, a subpopulation of myofibers in muscles of geriatric but not young mice co-express S100B and the brown adipocyte marker, uncoupling protein-1. These results suggest that S100B is an important intracellular molecular signal regulating Myf5+ progenitor cell differentiation into fusion-competent myoblasts or brown adipocytes depending on its levels.

Enhanced Adipogenic Differentiation of Human Adipose-Derived Stem Cells in an In Vitro Microenvironment: The Preparation of Adipose-Like Microtissues Using a Three-Dimensional Culture.

The application of stem cells for cell therapy has been extensively studied in recent years. Among the various types of stem cells, human adipose tissue-derived stem cells (ASCs) can be obtained in large quantities with relatively few passages, and they possess a stable quality. ASCs can differentiate into a number of cell types, such as adipose cells and ectodermal cells. We therefore focused on the in vitro microenvironment required for such differentiation and attempted to induce the differentiation of human stem cells into microtissues using a microelectromechanical system. We first evaluated the adipogenic differentiation of human ASC spheroids in a three-dimensional (3D) culture. We then created the in vitro microenvironment using a 3D combinatorial TASCL device and attempted to induce the adipogenic differentiation of human ASCs. The differentiation of human ASC spheroids cultured in maintenance medium and those cultured in adipocyte differentiation medium was evaluated via Oil red O staining using lipid droplets based on the quantity of accumulated triglycerides. The differentiation was confirmed in both media, but the human ASCs in the 3D cultures contained higher amounts of triglycerides than those in the 2D cultures. In the short culture period, greater adipogenic differentiation was observed in the 3D cultures than in the 2D cultures. The 3D culture using the TASCL device with adipogenic differentiation medium promoted greater differentiation of human ASCs into adipogenic lineages than either a 2D culture or a culture using a maintenance medium. In summary, the TASCL device created a hospitable in vitro microenvironment and may therefore be a useful tool for the induction of differentiation in 3D culture. The resultant human ASC spheroids were "adipose-like microtissues" that formed spherical aggregation perfectly and are expected to be applicable in regenerative medicine as well as cell transplantation.

Liraglutide Induces Brown Adipocyte Specific Genes in Mice Skeletal Muscle Tissue

Obesity is a risk factor for type 2 diabetes, coronary artery disease, and stroke. Glucagon like peptide ‐1 (GLP‐1) is synthesized by the L cells of ileal mucosa and is released after nutrients ingestion to potentiate glucose stimulated insulin secretion. Liraglutide, a full agonist of the GLP‐1 receptor (GLP‐R), has long‐lasting effects due to its increased resistance to enzymatic degradation. Clinical data has demonstrated the protective effect of liraglutide on weight gain in type 2 diabetes subjects. However, the underlying mechanisms of this protective effect have not been identified. Brown adipose tissue plays a major role in control of energy balance in rodents, whether GLP‐1 activate brown fat differentiation has not been studied. C2C12 myoblasts are known to be able to differentiate into adipocytes after stimulation. By treating the undifferentiated C2C12 myoblast with 5nM liraglutide, we observed a significant induction of GLP‐1 receptor after 24 h. C2C12 cells were cultured to confluence, and then exposed to brown adipocyte differentiation medium in the presence or absence of 5nM liraglutide, the mRNA level of brown fat enriched genes including peroxisome proliferator‐activated receptor α (PPAR‐α) and cell death activator‐A (Cidea) were upregulated after 6 days of induction of differentiation compare to control cells. Induction of peroxisome proliferator‐activated receptor‐γ coactivator (PGC)‐1α mRNA was observed as early as 3 d post‐induction. In vivo study was performed by injecting C57 black/6 mice with liragludie daily for 5 weeks. Both mRNA and protein levels of uncoupling protein‐1(UCP‐1), a brown fat specific gene, are significantly induced in skeletal muscle tissue after liraglutide treatment. Lirglutide also upregulated other brown fat enriched gene including PGC‐1α, Cidea, and PPAR‐α. Our study indicates that liraglutide induces brown adipogenesis. GLP‐1 and its analogues are potential therapies for obesity and obesity related metabolic disorders.Support or Funding InformationCentral Michigan University Faculty Startup Fund.

Evaluation of Antiobesity Effect of Mangiferin in Adipogenesis-Induced Human Mesenchymal Stem Cells by Assessing Adipogenic Genes

We aimed to examine the anti-adipogenic effects of mangiferin (xanthone glucoside) and its related mechanism. Human mesenchymal stem cells (hMSCs) were cultured in Dulbecco's modified Eagle medium, after 60% confluence adipocyte differentiation was induced. Differentiation-induced hMSCs were cultured in the presence and absence of 10, 20 and 40 μmol of mangiferin from day 0 to day 10. Adipocyte differentiation and lipid accumulation were significantly decreased in 40 μmol mangiferin-treated groups when compared with the reference drugs (quercetin- and orlistat-treated groups). Using quantitative reverse transcription polymerase chain reaction, we studied the mRNA expression levels of resistin, adipocyte fatty acid-binding protein 2 (aP2), lipoprotein lipase (LPL), peroxisome proliferator-activated receptor (PPAR-γ) and tumor necrosis factor-α, in hMSCs undergoing adipocyte differentiation; treatment with mangiferin attenuated the expression of those adipogenic genes and decreased adipocyte differentiation. Mangiferin significantly inhibited hMSCs to preadipocyte differentiation within the first 2 days of treatment, indicating that the anti-adipogenic effects of mangiferin are achieved through the inhibition of differentiation and maturation. Practical Applications It is well known that various plant derived compounds presents antiobesity effect. However still there is lack of drugs for the arrest or inhibition of adipocyte differentiation from mesenchymal stem cell precursors. hMSCs treated with adipocyte differentiation medium along with mangiferin inhibits preadipocyte differentiation and maturation, via suppressing lipid accumulation. Mangiferin treatment resulted in a significant (p < 0.05) decrease in GPDH and triglyceride levels as well as an increase in LDH activity and attenuated lipid accumulation compared with untreated differentiating preadipocytes. This effect was demonstrated by the observed down-regulation of adipogenesis related genes after hMSCs underwent induced adipocyte differentiation.

On the Formation of Lipid Droplets in Human Adipocytes: The Organization of the Perilipin–Vimentin Cortex

We report on the heterogeneity and diversity of lipid droplets (LDs) in early stages of adipogenesis by elucidating the cell and molecular biology of amphiphilic and cytoskeletal proteins regulating and stabilizing the generation of LDs in human adipose cells. A plethora of distinct and differently sized LDs was detected by a brief application of adipocyte differentiation medium and additional short treatment with oleic acid. Using these cells and highly specific antibodies for LD-binding proteins of the perilipin (PLIN) family, we could distinguish between endogenously derived LDs (endogenous LDs) positive for perilipin from exogenously induced LDs (exogenous LDs) positive for adipophilin, TIP47 and S3-12. Having optimized these stimulation conditions, we used early adipogenic differentiation stages to investigate small-sized LDs and concentrated on LD-protein associations with the intermediate-sized filament (IF) vimentin. This IF protein was described earlier to surround lipid globules, showing spherical, cage-like structures. Consequently - by biochemical methods, by immunofluorescence microscopy and by electron- and immunoelectron microscopy - various stages of emerging lipid globules were revealed with perilipin as linking protein between LDs and vimentin. For this LD-PLIN-Vimentin connection, a model is now proposed, suggesting an interaction of proteins via opposed charged amino acid domains respectively. In addition, multiple sheaths of smooth endoplasmic reticulum cisternae surrounding concentrically nascent LDs are shown. Based on our comprehensive localization studies we present and discuss a novel pathway for the LD formation.

Histone Deacetylase 9 Is a Negative Regulator of Adipogenic Differentiation

Differentiation of preadipocytes into mature adipocytes capable of efficiently storing lipids is an important regulatory mechanism in obesity. Here, we examined the involvement of histone deacetylases (HDACs) and histone acetyltransferases (HATs) in the regulation of adipogenesis. We find that among the various members of the HDAC and HAT families, only HDAC9 exhibited dramatic down-regulation preceding adipogenic differentiation. Preadipocytes from HDAC9 gene knock-out mice exhibited accelerated adipogenic differentiation, whereas HDAC9 overexpression in 3T3-L1 preadipocytes suppressed adipogenic differentiation, demonstrating its direct role as a negative regulator of adipogenesis. HDAC9 expression was higher in visceral as compared with subcutaneous preadipocytes, negatively correlating with their potential to undergo adipogenic differentiation in vitro. HDAC9 localized in the nucleus, and its negative regulation of adipogenesis segregates with the N-terminal nuclear targeting domain, whereas the C-terminal deacetylase domain is dispensable for this function. HDAC9 co-precipitates with USF1 and is recruited with USF1 at the E-box region of the C/EBPα gene promoter in preadipocytes. Upon induction of adipogenic differentiation, HDAC9 is down-regulated, leading to its dissociation from the USF1 complex, whereas p300 HAT is up-regulated to allow its association with USF1 and accumulation at the E-box site of the C/EBPα promoter in differentiated adipocytes. This reciprocal regulation of HDAC9 and p300 HAT in the USF1 complex is associated with increased C/EBPα expression, a master regulator of adipogenic differentiation. These findings provide new insights into mechanisms of adipogenic differentiation and document a critical regulatory role for HDAC9 in adipogenic differentiation through a deacetylase-independent mechanism.

A stimulatory TSH receptor antibody enhances adipogenesis via phosphoinositide 3-kinase activation in orbital preadipocytes from patients with Graves' ophthalmopathy

Graves' ophthalmopathy (GO) is characterized by expanded volume of the orbital tissues associated with elevated serum levels of TSH receptor (TSHR) autoantibodies. Because previous studies have demonstrated evidence of adipogenesis within the GO orbit, we sought to determine whether M22, a human monoclonal antibody directed against TSHR, enhances adipogenesis in orbital fibroblasts from patients with GO and, if so, to identify signaling mechanisms involved. GO orbital fibroblast cultures (n=10) were treated for 10 days with bovine TSH (1 or 10·0 U/l) or M22 (1 or 10 ng/ml) in serum-free adipocyte differentiation medium. Some cultures also received a phosphoinositide 3-kinase (PI3K) inhibitor or an inhibitor of cAMP production. In other experiments, confluent cultures (n=8) were treated for between 1 and 30 min with TSH (0·1–10·0 U/l) or M22 (0·1–100 ng/ml) with measurement of cAMP production or levels of phosphorylated AKT (pAKT). We found levels of adiponectin, leptin, and TSHR mRNA to be increased in GO cultures treated for 10 days with either M22 (2·6 mean fold ±0·7; P=0·03) or TSH (13·2±5·8-fold, P=0·048). In other studies, M22 and TSH stimulated cAMP production and pAKT levels in GO cells. Inhibition of PI3K activity during 10 days in culture decreased the levels of M22-stimulated mRNA encoding adiponectin (67±12%; P=0·021), as well as adiponectin and CCAAT/enhancer-binding protein α protein levels. In conclusion, M22 is a pro-adipogenic factor in GO orbital preadipocytes. This antibody appears to act via the PI3K signaling cascade, suggesting that inhibition of PI3K signaling may represent a potential novel therapeutic approach in GO.

Depot-specific differences in the insulin response of adipose-derived stromal cells

Visceral adiposity is more strongly linked to insulin resistance than subcutaneous adiposity. High insulin levels can be mitogenic or adipogenic to adipocytes, but little is known regarding these effects of insulin on stromal cells from visceral and subcutaneous fat depots. Consequently, we measured adipogenesis and mitosis in response to elevated insulin levels in rat adipose-derived stromal cells (ADSCs) from visceral (perirenal) and subcutaneous depots. Insulin alone, at 10 μM, did not stimulate adipogenesis in naïve perirenal visceral (pvADSCs) or subcutaneous ADSCs (scADSCs), although a significant increase in proliferation occurred in both. Adipogenesis, induced using adipocyte differentiation medium (AM), resulted in greater lipid accumulation in pvADSCs, but the associated decrease in proliferation was less than in scADSCs. Omission of insulin from AM significantly reduced lipid accumulation in pvADSCs, but had little effect in scADSC, whilst proliferation was inhibited more in scADSCs than pvADSCs. Consequently, insulin is more lipogenic and less mitogenic in differentiating pvADSCs compared to scADSCs.

Differentiation and characterization in primary culture of white adipose tissue brown adipocyte-like cells

Rodent brown adipose tissue (BAT) is considered the main effector of adaptative thermogenesis as it contains a unique mitochondrial uncoupling protein, termed as uncoupling protein-1 (UCP1). The emergence of ectopic brown adipocytes in the white adipose tissue (WAT), called recruitment, might play an important role in the prevention of obesity. The recruitment phenomenon has until now been investigated mostly in vivo. This study is an attempt to mimic in vitro the recruitment phenomenon. It consisted in culturing the stroma vascular fractions of mouse BAT and WAT in a brown adipocyte differentiation medium. The multilocular cells obtained, referred to as BAT(B) and WAT(B) adipocytes, respectively, were compared. The BAT(B) and WAT(B) adipocytes were morphologically different. The expressions of UCP1, peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha), leptin and resistin mRNAs were low in WAT(B) adipocytes as compared with those in BAT(B) adipocytes. The expressions of UCP1 and PGC-1alpha proteins were, however, much higher in WAT(B) adipocytes, amounting 51% and 36% of those in BAT(B) adipocytes. The patterns of expression of UCP1, PGC-1alpha and leptin in the BAT(B) and in WAT(B) adipocytes were different with a higher relative expression of PGC-1alpha in the latter. Rosiglitazone increased UCP1 mRNA expression 4.5-fold in the BAT(B) and significantly more, 7.9-fold, in the WAT(B) adipocytes. Retinoic acid and triiodothyronine increased UCP1 mRNA expression in the BAT(B) adipocytes 1.6- and 2-fold, respectively but, surprisingly, slightly decreased UCP1 mRNA expression in the WAT(B) adipocytes. The study suggests that the nature and possibly the origin of WAT brown adipocytes is different from that of BAT brown adipocytes. It proposes an in vitro approach that could prove very useful to better characterize the WAT brown adipocyte-like cells.

Heterochromatin Protein 1γ Epigenetically Regulates Cell Differentiation and Exhibits Potential as a Therapeutic Target for Various Types of Cancers

Heterochromatin protein 1 (HP1) is a chromosomal protein that participates in both chromatin packaging and gene silencing. Three HP1 isoforms (alpha, beta, and gamma) occur in mammals, but their functional differences are still incompletely understood. In this study, we found that HP1gamma levels are decreased during adipocyte differentiation, whereas HP1alpha and beta levels are expressed constitutively during adipogenesis in cultured preadipocyte cells. In addition, ectopic overexpression of HP1gamma inhibited adipogenesis. Furthermore, we did not detect any HP1gamma protein in the differentiated cells of various normal human tissues. These results suggest that the loss of HP1gamma is required for cell differentiation to occur. On the other hand, the methylation levels of lysine 20 (K20) on histone H4 showed a significant correlation with HP1gamma expression in both these preadipocyte cells and normal tissue samples. However, all cancer tissues examined were positive for HP1gamma but were often negative for trimethylated histone H4 K20. Thus, a dissociation of the correlation between HP1gamma expression and histone H4 K20 trimethylation may reflect the malfunction of epigenetic control. Finally, suppression of HP1gamma expression restrained cell growth in various cancer-derived cell lines, suggesting that HP1gamma may be an effective target for gene therapy against various human cancers. Taken together, our results demonstrate the novel function of HP1gamma in the epigenetic regulation of both cell differentiation and cancer development.

Expression, regulation, and triglyceride hydrolase activity of Adiponutrin family members

Adiponutrin and a related protein, adipocyte triglyceride lipase (ATGL; also known as Desnutrin), were recently described as adipocyte-specific proteins with lipid hydrolase activity. Using bioinformatics, we identified three additional Adiponutrin family members (GS2, GS2-Like, and PNPLA1). Here, we report on the expression, regulation, and activity of GS2 and GS2-Like compared with Adiponutrin and Desnutrin/ATGL. GS2-Like is expressed and regulated in a manner similar to Adiponutrin; however, the absolute levels of mRNA are significantly lower than those of Adiponutrin or Desnutrin/ATGL. GS2 transcripts were identified only in humans and are highly expressed in adipose as well as other tissues. All four proteins show lipase activity in vitro, which is dependent on the presence of the active site serine for Adiponutrin, Desnutrin/ATGL, and GS2. Overexpression of Desnutrin/ATGL, GS2, and GS2-Like, but not Adiponutrin, decreases intracellular triglyceride levels. This is consistent with a function for Desnutrin/ATGL, GS2, and GS2-Like in lipolysis, but not for Adiponutrin. Consistent with previously reported data, Desnutrin/ATGL is upregulated by fasting in adipose tissue, whereas Adiponutrin is downregulated. Additionally, Adiponutrin and GS2-Like, but not Desnutrin/ATGL, are strongly induced in the liver of ob/ob mice. Our data support distinct functions for Adiponutrin and Desnutrin/ATGL and raise the possibility that GS2 may contribute significantly to lipolysis in human adipose tissue.