Control of adipocyte differentiation

Transcriptome Analysis Revealed Potential Genes of Skeletal Muscle Thermogenesis in Mashen Pigs and Large White Pigs under Cold Stress

Pigs are susceptible to cold stress due to the absence of brown fat caused by the partial deletion of uncoupling protein 1 during their evolution. Some local pig breeds in China exhibit potential cold adaptability, but research has primarily focused on fat and intestinal tissues. Skeletal muscle plays a key role in adaptive thermogenesis in mammals, yet the molecular mechanism of cold adaptation in porcine skeletal muscle remains poorly understood. This study investigated the cold adaptability of two pig breeds, Mashen pigs (MS) and Large White pigs (LW), in a four-day cold (4 °C) or normal temperature (25 °C) environment. We recorded phenotypic changes and collected blood and longissimus dorsi muscle for transcriptome sequencing. Finally, the PRSS8 gene was randomly selected for functional exploration in porcine skeletal muscle satellite cells. A decrease in body temperature and body weight in both LW and MS pigs under cold stress, accompanied by increased shivering frequency and respiratory frequency, were observed. However, the MS pigs demonstrated stable physiological homeostasis, indicating a certain level of cold adaptability. The LW pigs primarily responded to cold stress by regulating their heat production and glycolipid energy metabolism. The MS pigs exhibited a distinct response to cold stress, involving the regulation of heat production, energy metabolism pathways, and robust mitochondrial activity, as well as a stronger immune response. Furthermore, the functional exploration of PRSS8 in porcine skeletal muscle satellite cells revealed that it affected cellular energy metabolism and thermogenesis by regulating ERK phosphorylation. These findings shed light on the diverse transcriptional responses of skeletal muscle in LW and MS pigs under cold stress, offering valuable insights into the molecular mechanisms underlying cold adaptation in pigs.

Lipid metabolism mRNA expression and cellularity of intramuscular adipocytes within the Longissimus muscle of Angus- and Wagyu-sired cattle fed for a similar days on feed or body weight endpoint

This study investigates intramuscular (IM) adipocyte development in the Longissimus muscle (LM) between Wagyu- and Angus-sired steers compared at a similar age and days on feed (D) endpoint or similar body weight (B) endpoint by measuring IM adipocyte cell area and lipid metabolism mRNA expression. Angus-sired steers (AN, n = 6) were compared with steers from two different Wagyu sires (WA), selected for either growth (G) or marbling (M), to be compared at a similar days on feed (DOF; 258 ± 26.7 d; WA-GD, n = 5 and WA-MD, n = 5) in Exp. 1 or body weight (BW; 613 ± 18.0 kg; WA-GB, n = 4 and WA-MB, n = 5) in Exp. 2, respectively. In Exp. 1, WA-MD steers had a greater (P ≤ 0.01) percentage of IM fat in the LM compared with AN and WA-GD steers. In Exp. 2, WA-MB steers had a greater (P ≤ 0.01) percentage of IM fat in the LM compared with AN and WA-GB steers. The distribution of IM adipocyte area was unimodal at all biopsy collections, with IM adipocyte area becoming progressively larger as cattle age (P ≤ 0.01) and BW increased (P ≤ 0.01). Peroxisome proliferator activated receptor delta (PPARd) was upregulated earlier for WA-MD and WA-MB cattle compared with other steers at a similar DOF and BW (P ≤ 0.02; treatment × biopsy interaction). Peroxisome proliferator activated receptor gamma was upregulated (PPARg) at a lesser BW for WA-MB steers (P = 0.09; treatment × biopsy interaction), while WA-MD steers had a greater (P ≤ 0.04) overall mean PPARg mRNA expression compared with other steers. Glycerol-3-phosphate acyltransferase, lipin 1, and hormone sensitive lipase demonstrated mRNA expression patterns similar to PPARg and PPARd or CCAAT enhancer binding protein beta, which emphasizes their importance in marbling development and growth. Additionally, WA-MD and WA-MB steers often had a greater early mRNA expression of fatty acid transporters (fatty acid transport protein 1; P < 0.02; treatment × biopsy interaction) and binding proteins (fatty acid binding protein 4) compared with other steers. Cattle with a greater marbling propensity appear to upregulate adipogenesis at a younger chronological and physiological maturity through PPARd, PPARg, and possibly adipogenic regulating compounds, lysophosphatidic acid, and diacylglycerol. These genes and compounds could be used as potential markers for marbling propensity of cattle in the future.

Integrins control epithelial stem cell proliferation in the Drosophila ovary by modulating the Notch pathway

Cell proliferation and differentiation show a remarkable inverse relationship. The temporal coupling between cell cycle withdrawal and differentiation of stem cells (SCs) is crucial for epithelial tissue growth, homeostasis and regeneration. Proliferation vs. differentiation SC decisions are often controlled by the surrounding microenvironment, of which the basement membrane (BM; a specialized form of extracellular matrix surrounding cells and tissues), is one of its main constituents. Years of research have shown that integrin-mediated SC-BM interactions regulate many aspects of SC biology, including the proliferation-to-differentiation switch. However, these studies have also demonstrated that the SC responses to interactions with the BM are extremely diverse and depend on the cell type and state and on the repertoire of BM components and integrins involved. Here, we show that eliminating integrins from the follicle stem cells (FSCs) of the Drosophila ovary and their undifferentiated progeny increases their proliferation capacity. This results in an excess of various differentiated follicle cell types, demonstrating that cell fate determination can occur in the absence of integrins. Because these phenotypes are similar to those found in ovaries with decreased laminin levels, our results point to a role for the integrin-mediated cell-BM interactions in the control of epithelial cell division and subsequent differentiation. Finally, we show that integrins regulate proliferation by restraining the activity of the Notch/Delta pathway during early oogenesis. Our work increases our knowledge of the effects of cell-BM interactions in different SC types and should help improve our understanding of the biology of SCs and exploit their therapeutic potential.

Regulatory roles of fibronectin and integrin α5 in reorganization of the actin cytoskeleton and completion of adipogenesis

Cellular differentiation is characterized by changes in cell morphology that are largely determined by actin dynamics. We previously showed that depolymerization of the actin cytoskeleton triggers the differentiation of preadipocytes into mature adipocytes as a result of inhibition of the transcriptional coactivator activity of megakaryoblastic leukemia 1 (MKL1). The extracellular matrix (ECM) influences cell morphology via interaction with integrins, and reorganization of the ECM is associated with cell differentiation. Here we show that interaction between actin dynamics and ECM rearrangement plays a key role in adipocyte differentiation. We found that depolymerization of the actin cytoskeleton precedes disruption and degradation of fibrillar fibronectin (FN) structures at the cell surface after the induction of adipogenesis in cultured preadipocytes. A FN matrix suppressed both reorganization of the actin cytoskeleton into the pattern characteristic of adipocytes and terminal adipocyte differentiation, and these inhibitory effects were overcome by knockdown of integrin α5 (ITGα5). Peroxisome proliferator–activated receptor γ was required for down-regulation of FN during adipocyte differentiation, and MKL1 was necessary for the expression of ITGα5. Our findings suggest that cell-autonomous down-regulation of FN-ITGα5 interaction contributes to reorganization of the actin cytoskeleton and completion of adipocyte differentiation.

Importance of the Microenvironment and Mechanosensing in Adipose Tissue Biology

The expansion of adipose tissue is an adaptive mechanism that increases nutrient buffering capacity in response to an overall positive energy balance. Over the course of expansion, the adipose microenvironment undergoes continual remodeling to maintain its structural and functional integrity. However, in the long run, adipose tissue remodeling, typically characterized by adipocyte hypertrophy, immune cells infiltration, fibrosis and changes in vascular architecture, generates mechanical stress on adipose cells. This mechanical stimulus is then transduced into a biochemical signal that alters adipose function through mechanotransduction. In this review, we describe the physical changes occurring during adipose tissue remodeling, and how they regulate adipose cell physiology and promote obesity-associated dysfunction in adipose tissue.

Towards an understanding of the mechanoreciprocity process in adipocytes and its perturbation with aging

Adipose tissue (AT) is a complex organ, with multiple functions that are essential for maintaining metabolic health. A feature of AT is its capability to expand in response to physiological challenges, such as pregnancy and aging, and during chronic states of positive energy balance occurring throughout life. AT grows through adipogenesis and/or an increase in the size of existing adipocytes. One process that is required for healthy AT growth is the remodeling of the extracellular matrix (ECM), which is a necessary step to restore mechanical homeostasis and maintain tissue integrity and functionality. While the relationship between mechanobiology and adipogenesis is now well recognized, less is known about the role of adipocyte mechanosignaling pathways in AT growth. In this review article, we first summarize evidence linking ECM remodelling to AT expansion and how its perturbation is associated to a metabolically unhealthy phenotype. Subsequently, we highlight findings suggesting that molecules involved in the dynamic, bidirectional process (mechanoreciprocity) enabling adipocytes to sense changes in the mechanical properties of the ECM are interconnected to pathways regulating lipid metabolism. Finally, we discuss processes through which aging may influence the ability of adipocytes to appropriately respond to alterations in ECM composition.

A Brief Overview of Oxidative Stress in Adipose Tissue with a Therapeutic Approach to Taking Antioxidant Supplements

One of the leading causes of obesity associated with oxidative stress (OS) is excessive consumption of nutrients, especially fast-foods, and a sedentary lifestyle, characterized by the ample accumulation of lipid in adipose tissue (AT). When the body needs energy, the lipid is broken down into glycerol (G) and free fatty acids (FFA) during the lipolysis process and transferred to various tissues in the body. Materials secreted from AT, especially adipocytokines (interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α)) and reactive oxygen species (ROS), are impressive in causing inflammation and OS of AT. There are several ways to improve obesity, but researchers have highly regarded the use of antioxidant supplements due to their neutralizing properties in removing ROS. In this review, we have examined the AT response to OS to antioxidant supplements focusing on animal studies. The results are inconsistent due to differences in the study duration and diversity in animals (strain, age, and sex). Therefore, there is a need for different studies, especially in humans.

Emerging Roles for the INK4a/ARF (CDKN2A) Locus in Adipose Tissue: Implications for Obesity and Type 2 Diabetes

Besides its role as a cell cycle and proliferation regulator, the INK4a/ARF (CDKN2A) locus and its associated pathways are thought to play additional functions in the control of energy homeostasis. Genome-wide association studies in humans and rodents have revealed that single nucleotide polymorphisms in this locus are risk factors for obesity and related metabolic diseases including cardiovascular complications and type-2 diabetes (T2D). Recent studies showed that both p16^INK4a-CDK4-E2F1/pRB and p19^ARF-P53 (p14^ARF in humans) related pathways regulate adipose tissue (AT) physiology and adipocyte functions such as lipid storage, inflammation, oxidative activity, and cellular plasticity (browning). Targeting these metabolic pathways in AT emerged as a new putative therapy to alleviate the effects of obesity and prevent T2D. This review aims to provide an overview of the literature linking the INK4a/ARF locus with AT functions, focusing on its mechanisms of action in the regulation of energy homeostasis.

β-actin contributes to open chromatin for activation of the adipogenic pioneer factor CEBPA during transcriptional reprograming

Adipogenesis is regulated by a cascade of signals that drive transcriptional reprogramming in adipocytes. Here, we report that nuclear actin regulates the chromatin states that establish tissue- specific expression during adipogenesis. To study the role of β-actin in adipocyte differentiation, we conducted RNA sequencing on wild-type and β-actin knockout mouse embryonic fibroblasts (MEFs) after reprograming to adipocytes. We found that β-actin depletion affects induction of several adipogenic genes during transcriptional reprograming. This impaired regulation of adipogenic genes is linked to reduced expression of the pioneer factor Cebpa and is rescued by reintroducing NLS-tagged β-actin. ATAC-Seq in knockout MEFs revealed that actin-dependent reduction of Cebpa expression correlates with decreased chromatin accessibility and loss of chromatin association of the ATPase Brg1. This, in turn, impairs CEBPB's association with its Cebpa promoter-proximal binding site during adipogenesis. We propose a role for the nuclear β-actin pool in maintaining open chromatin for transcriptional reprogramming during adipogenic differentiation.

The insulin-PI3K-Rac1 axis contributes to terminal adipocyte differentiation through regulation of actin cytoskeleton dynamics

Adipocyte differentiation is accompanied by a pronounced change in the actin cytoskeleton characterized by the reorganization of filamentous (F)-actin stress fibers into cortical F-actin structures. We previously showed that depolymerization of F-actin stress fibers induced by inactivation of RhoA-ROCK (Rho-associated kinase) signaling acts as a trigger for adipocyte differentiation. The relevance and underlying mechanism of the formation of cortical F-actin structures from depolymerized actin during adipocyte differentiation have remained unclear, however. We have now examined the mechanistic relation between actin dynamics and adipogenic induction. Transient exposure to the actin-depolymerizing agent latrunculin A (LatA) supported the formation of adipocyte-associated cortical actin structures and the completion of terminal adipocyte differentiation in the presence of insulin, whereas long-term exposure to LatA prevented such actin reorganization as well as terminal adipogenesis. Moreover, these effects of insulin were prevented by inhibition of phosphatidylinositol 3-kinase (PI3K)-Rac1 signaling and the actin-related protein 2/3 (Arp2/3) complex which is a critical component of the cortical actin networks. Our findings thus suggest that the insulin-PI3K-Rac1 axis leads to the formation of adipocyte-associated cortical actin structures which is essential for the completion of adipocyte differentiation.

Gene expression identifies metabolic and functional differences between intramuscular and subcutaneous adipocytes in cattle

Background

This study used a genome-wide screen of gene expression to better understand the metabolic and functional differences between commercially valuable intramuscular fat (IMF) and commercially wasteful subcutaneous (SC) fat depots in Bos taurus beef cattle.

Results

We confirmed many findings previously made at the biochemical level and made new discoveries. The fundamental lipogenic machinery, such as ACACA and FASN encoding the rate limiting Acetyl CoA carboxylase and Fatty Acid synthase were expressed at 1.6–1.8 fold lower levels in IMF, consistent with previous findings. The FA elongation pathway including the rate limiting ELOVL6 was also coordinately downregulated in IMF compared to SC as expected. A 2-fold lower expression in IMF of ACSS2 encoding Acetyl Coenzyme A synthetase is consistent with utilisation of less acetate for lipogenesis in IMF compared to SC as previously determined using radioisotope incorporation. Reduced saturation of fat in the SC depot is reflected by 2.4 fold higher expression of the SCD gene encoding the Δ9 desaturase enzyme. Surprisingly, CH25H encoding the cholesterol 25 hydroxylase enzyme was ~ 36 fold upregulated in IMF compared to SC. Moreover, its expression in whole muscle tissue appears representative of the proportional representation of bovine marbling adipocytes. This suite of observations prompted quantification of a set of oxysterols (oxidised forms of cholesterol) in the plasma of 8 cattle exhibiting varying IMF. Using Liquid Chromatography-Mass Spectrometry (LC-MS) we found the levels of several oxysterols were significantly associated with multiple marbling measurements across the musculature, but (with just one exception) no other carcass phenotypes.

Conclusions

These data build on our molecular understanding of ruminant fat depot biology and suggest oxysterols represent a promising circulating biomarker for cattle marbling.

Secreted protein acidic and rich in cysteine and bioenergetics: Extracellular matrix, adipocytes remodeling and skeletal muscle metabolism

The extracellular matrix (ECM) remodeling plays important roles in both adipocytes shape/expansion remodeling and the skeletal muscle (SM) metabolism. Secreted protein acidic and rich in cysteine (SPARC) is expressed in divers tissues including adipose tissue (AT) and SM where it impacts a variety of remodeling as well as metabolic functions. SPARC, also known as osteonectin or BM-40, is a glycoprotein associated with the ECM. Numerous researches attempted to elucidate the implications of SPARC in these two key metabolic tissues under different conditions. Whereas SPARC deficiency tends to shape the remodeling of the adipocytes and the fat distribution, this deficiency decreases SM metabolic properties. On the other hand, SPARC seems to be an enhancer of the metabolism and a mediator of the exercise-induced adaptation in the SM and as well as an adipogenesis inhibitor. Some findings about the SPARC effects on AT and SM seem "contradictory" in terms of tissue development and energy profile therefore highlighting the mechanistic role of SPARC in both is a priority. Yet, within this review, we expose selected researches and compare the results. We conclude with explanations to "reconcile" the different observations, hypothesize the feedback and regulatory character of SPARC and put its roles within the energetic and structural maps of both adipocytes and myocytes in homeostasis and in situations such as obesity or exercise. These properties explain the modifications and the remodeling seen in AT and SM undergoing adaptive changes (obesity, exercise, etc.) and represent a starting point for precise therapeutic targeting of SPARC-related pathways is conditions such as obesity, sarcopenia and diabetes.

Adipose cell size changes are associated with a drastic actin remodeling

Adipose tissue plays a major role in regulating whole-body insulin sensitivity and energy metabolism. To accommodate surplus energy, the tissue rapidly expands by increasing adipose cell size (hypertrophy) and cell number (hyperplasia). Previous studies have shown that enlarged, hypertrophic adipocytes are less responsive to insulin, and that adipocyte size could serve as a predictor for the development of type 2 diabetes. In the present study, we demonstrate that changes in adipocyte size correlate with a drastic remodeling of the actin cytoskeleton. Expansion of primary adipocytes following 2 weeks of high-fat diet (HFD)-feeding in C57BL6/J mice was associated with a drastic increase in filamentous (F)-actin as assessed by fluorescence microscopy, increased Rho-kinase activity, and changed expression of actin-regulating proteins, favoring actin polymerization. At the same time, increased cell size was associated with impaired insulin response, while the interaction between the cytoskeletal scaffolding protein IQGAP1 and insulin receptor substrate (IRS)-1 remained intact. Reversed feeding from HFD to chow restored cell size, insulin response, expression of actin-regulatory proteins and decreased the amount of F-actin filaments. Together, we report a drastic cytoskeletal remodeling during adipocyte expansion, a process which could contribute to deteriorating adipocyte function.

Adhesion G-protein coupled receptor 56 is required for 3T3-L1 adipogenesis

Obesity-associated conditions represent major global health and financial burdens and understanding processes regulating adipogenesis could lead to novel intervention strategies. This study shows that adhesion G-protein coupled receptor 56 (GPR56) gene transcripts are reduced in abdominal visceral white adipose tissue derived from obese Zucker rats versus lean controls. Immunostaining in 3T3-L1 preadipocytes reveals both mitotic cell restricted surface and low level general expression patterns of Gpr56. Gpr56 transcripts are differentially expressed in 3T3-L1 cells during adipogenesis. Transient knockdown (KD) of Gpr56 in 3T3-L1 cells dramatically inhibits differentiation through reducing the accumulation of both neutral cellular lipids (56%) and production of established adipogenesis Pparγ ₂ (60-80%), C/ebpα (40-78%) mediator, and Ap2 (56-80%) marker proteins. Furthermore, genome editing of Gpr56 in 3T3-L1 cells created CW2.2.4 and RM4.2.5.5 clones (Gpr56 ^-/- cells) with compound heterozygous deletion frameshift mutations which abolish adipogenesis. Genome edited cells have sustained levels of the adipogenesis inhibitor β-catenin, reduced proliferation, reduced adhesion, altered profiles, and or abundance of extracellular matrix component gene transcripts for fibronectin, types I, III, and IV collagens and loss of actin stress fibers. β-catenin KD alone is insufficient to restore adipogenesis in Gpr56 ^-/- cells. Together these data show that Gpr56 is required for adipogenesis in 3T3-L1 cells. This report is the first demonstration that Gpr56 participates in regulation of the adipogenesis developmental program. Modulation of the levels of this protein and/or its biological activity may represent a novel target for development of therapeutic agents for the treatment of obesity.

In Vitro Models for Study of Brown Adipocyte Biology

Brown adipocytes are the key cell type in brown adipose tissue (BAT) that express the genes required for heat production through the process of thermogenesis. Brown adipocyte cell culture models are important for researching the molecular pathways that control cell autonomous processes. In vitro tools for the study of brown adipocytes include BAT explant cultures and BAT primary cultures that are first proliferated and then differentiated. A number of stable brown preadipocyte cell lines have been generated by the expression transforming factors such as SV40 T antigen. The application of these cell lines reduces the requirement for animal tissue which is needed for primary culture and explants. Furthermore, brown adipocyte cell lines that effectively recapitulate the properties of brown adipocytes permit large-scale experimental procedures that are generally unfeasible with primary cultures that undergo a restricted number of cell divisions. Cell lines are valuable for applications such as large-scale endogenous protein expression, ChIP assay, and procedures requiring antibiotic selection over several cell divisions including stable exogenous gene expression and CRISR/Cas9 gene editing.

Anti-obesity activity of OBEX is regulated by activation of thermogenesis and decreasing adiposity gain

The incidence of obesity has been increasing dramatically worldwide over the past decades, thus requiring novel and effective therapeutic approaches. OBEX is an oral nutritional supplement composed of antioxidants with antiobesity activity. The effects of OBEX have been tested in vivo and in vitro. In vivo, OBEX reduces weight gain by decreasing adiposity gain and increasing energy expenditure in high fat diet-fed mice through the activation of thermogenesis in brown adipose tissue (BAT) independent of eating behaviors. In vitro analysis with 3T3-F442A cells revealed anti-proliferative and anti-differentiation effects of OBEX. In addition, OBEX induced a clear reduction of the lipid load in mature adipocytes obtained from 3T3-F442A cells. Overall, our findings suggest that OBEX has a protective effect against an obesogenic environment.

Adipocyte biology: It is time to upgrade to a new model

Globally, the obesity pandemic is profoundly affecting quality of life and economic productivity, but efforts to address this, especially on a pharmacological level, have generally proven unsuccessful to date, serving as a stark demonstration that our understanding of adipocyte biology and pathophysiology is incomplete. To deliver better insight into adipocyte function and obesity, we need improved adipocyte models with a high degree of fidelity in representing the in vivo state and with a diverse range of experimental applications. Adipocyte cell lines, especially 3T3-L1 cells, have been used extensively over many years, but these are limited in terms of relevance and versatility. In this review, I propose that primary adipose-derived stromal/stem cells (ASCs) present a superior model with which to study adipocyte biology ex vivo. In particular, ASCs afford us the opportunity to study adipocytes from different, functionally distinct, adipose depots and to investigate, by means of in vivo/ex vivo studies, the effects of many different physiological and pathophysiological factors, such as age, body weight, hormonal status, diet and nutraceuticals, as well as disease and pharmacological treatments, on the biology of adipocytes and their precursors. This study will give an overview of the characteristics of ASCs and published studies utilizing ASCs, to highlight the areas where our knowledge is lacking. More comprehensive studies in primary ASCs will contribute to an improved understanding of adipose tissue, in healthy and dysfunctional states, which will enhance our efforts to more successfully manage and treat obesity.

Transplantation of Adipose Tissue-Derived Stromal Cells Increases Mass and Functional Capacity of Damaged Skeletal Muscle

The regenerating skeletal muscle environment is capable of inducing uncommitted progenitors to terminally differentiate. The aim of this work was to determine whether adipose tissue-derived stromal cells were able to participate in muscle regeneration and to characterize the effect on muscle mass and functional capacities after transplantation of these cells. Adipose tissue stromal cells labeled with Adv cyto LacZ from 3-day-old primary cultures (SVF1) were autotransplanted into damaged tibialis anterior muscles. Fifteen days later, β-galactosidase staining of regenerated fibers was detected, showing participation of these cells in muscle regeneration. Two months after SVF1 cell transfer, muscles were heavier, showed a significantly larger fiber section area, and developed a significantly higher maximal force compared with damaged control muscles. These results are similar to those previously obtained after satellite cell transplantation. However, SVF1 transfer also generated a small amount of adipose tissue localized along the needle course. To minimize these adipose contaminants, we transferred cells from 7-day-old secondary cultures of the SVF1, containing only a small proportion of already engaged preadipocytes (SVF2). Under these conditions, no adipose tissue was observed in regenerated muscle but there was also no effect on muscle performances compared with damaged control muscles. This result provides further evidence for the existence of progenitor cells in the stromal fraction of freshly isolated adipose tissue cells, which, under our conditions, keep some of their pluripotent properties in primary cultures.

A new synthetic matrix metalloproteinase inhibitor reduces human mesenchymal stem cell adipogenesis

Development of adipose tissue requires the differentiation of less specialized cells, such as human mesenchymal stem cells (hMSCs), into adipocytes. Since matrix metalloproteinases (MMPs) play critical roles in the cell differentiation process, we conducted investigations to determine if a novel mercaptosulfonamide-based MMP inhibitor (MMPI), YHJ-7-52, could affect hMSC adipogenic differentiation and lipid accumulation. Enzyme inhibition assays, adipogenic differentiation experiments, and quantitative PCR methods were employed to characterize this inhibitor and determine its effect upon adipogenesis. YHJ-7-52 reduced lipid accumulation in differentiated cells by comparable amounts as a potent hydroxamate MMPI, GM6001. However, YHJ-7-82, a non-inhibitory structural analog of YHJ-7-52, in which the zinc-binding thiol group is replaced by a hydroxyl group, had no effect on adipogenesis. The two MMPIs (YHJ-7-52 and GM6001) were also as effective in reducing lipid accumulation in differentiated cells as T0070907, an antagonist of peroxisome-proliferator activated receptor gamma (PPAR-gamma), at a similar concentration. PPAR-gamma is a typical adipogenic marker and a key regulatory protein for the transition of preadiopocyte to adipocyte. Moreover, MMP inhibition was able to suppress lipid accumulation in cells co-treated with Troglitazone, a PPAR-gamma agonist. Our results indicate that MMP inhibitors may be used as molecular tools for adipogenesis and obesity treatment research.

Potential role of marine algae extract on 3T3-L1 cell proliferation and differentiation: an in vitro approach

Background

From ancient times, marine algae have emerged as alternative medicine and foods, contains the rich source of natural products like proteins, vitamins, and secondary metabolites, especially Chlorella vulgaris (C. vulgaris) contains numerous anti-inflammatory, antioxidants and wound healing substances. Type 2 diabetes mellitus is closely associated with adipogenesis and their factors. Hence, we aimed to investigate the chemical constituents and adipogenic modulatory properties of C. vulgaris in 3T3-L1 pre-adipocytes.

Results

We analysed chemical constituents in ethanolic extract of C. vulgaris (EECV) by LC–MS. Results revealed that the EECV contains few triterpenoids and saponin compounds. Further, the effect of EECV on lipid accumulation along with genes and proteins expressions which are associated with adipogenesis and lipogenesis were evaluated using oil red O staining, qPCR and western blot techniques. The data indicated that that EECV treatment increased differentiation and lipid accumulation in 3T3-L1 cells, which indicates positive regulation of adipogenic and lipogenic activity. These increases were associated with up-regulation of PPAR-γ2, C/EBP-α, adiponectin, FAS, and leptin mRNA and protein expressions. Also, EECV treatments increased the concentration of glycerol releases as compared with control cells. Troglitazone is a PPAR-γ agonist that stimulates the PPAR-γ2, adiponectin, and GLUT-4 expressions. Similarly, EECV treatments significantly upregulated PPAR-γ2, adiponectin, GLUT-4 expressions and glucose utilization. Further, EECV treatment decreased AMPK-α expression as compared with control and metformin treated cells.

Conclusion

The present research findings confirmed that the EECV effectively modulates the lipid accumulation and differentiation in 3T3-L1 cells through AMPK-α mediated signalling pathway.

Structural analysis and anti-obesity effect of a pectic polysaccharide isolated from Korean mulberry fruit Oddi (Morus alba L.)

A water-soluble polysaccharide JS-MP-1 was isolated from Korean mulberry fruits Oddi (Morus alba L.). Sugar linkage analysis and NMR data confirmed that it is a rhamnogalacturonan type I (RG I) polymer carrying arabinan and arabinogalactan (AG II) side chains. JS-MP-1 reduced dose-dependently the viability of 3T3-L1 pre-adipocyte cells, significantly stimulated the cleavage of caspases 9 and 3 and poly (ADP-ribose) polymerase (PARP) and decreased the ratio of Bcl-2 to Bax expression level that led to mitochondrial dysfunction and apoptosis in pre-adipocyte cells. The apoptotic death was mediated by stimulation of MAPKs (ERK and p38) signalling pathway. These results suggest that JS-MP-1 is able to reduce the number of fat cells and the mass of adipose tissue via inhibition of pre-adipocyte proliferation and thus JS-MP-1 itself or a crude aqueous Oddi extract containing this polysaccharide can be used as functional ingredient of health-beneficial food supplements for the treatment or prevention of obesity disorders.

The Bone Marrow-Derived Stromal Cells: Commitment and Regulation of Adipogenesis

Bone marrow (BM) microenvironment represents an important compartment of bone that regulates bone homeostasis and the balance between bone formation and bone resorption depending on the physiological needs of the organism. Abnormalities of BM microenvironmental dynamics can lead to metabolic bone diseases. BM stromal cells (also known as skeletal or mesenchymal stem cells) [bone marrow stromal stem cell (BMSC)] are multipotent stem cells located within BM stroma and give rise to osteoblasts and adipocytes. However, cellular and molecular mechanisms of BMSC lineage commitment to adipocytic lineage and regulation of BM adipocyte formation are not fully understood. In this review, we will discuss recent findings pertaining to identification and characterization of adipocyte progenitor cells in BM and the regulation of differentiation into mature adipocytes. We have also emphasized the clinical relevance of these findings.

7,8-Dihydroxyflavone inhibits adipocyte differentiation via antioxidant activity and induces apoptosis in 3T3-L1 preadipocyte cells

AIMS

Anti-obesity effects of a natural plant flavonoid 7,8-dihydroxyflavone (7,8-DHF) were evaluated using 3T3-L1 preadipocyte cells.

MAIN METHODS

The cell viability was determined using MTT assay. Effects of 7,8-DHF on intracellular lipid droplets and intracellular reactive oxygen species (ROS) were measured using a 2,7-dichlorofluorescein diacetate (DCF-DA) assay and Oil Red O staining method, respectively. Apoptotic cell death was monitored by annexin V-FITC/PI double staining and by a TUNEL assay. Antioxidant enzyme mRNA levels and protein expression of adipogenic transcription factors were determined by real-time PCR and Western blotting, respectively.

KEY FINDINGS

Whereas the cell viability of 3T3-L1 preadipocytes was not affected by lower concentrations of 7,8-DHF (<20 μM), higher concentrations of 7,8-DHF (>20 μM) induced apoptotic cell death. 7,8-DHF (<20 μM) significantly reduced the intracellular lipid droplets and the expression of major adipogenic transcription factors, such as CCAAT/enhancer-binding protein-α (C/EBP-α), C/EBP-β, and peroxisome proliferator activated receptor-γ (PPAR-γ). 7,8-DHF treatment also dose-dependently reduced the intracellular ROS level, attenuated MAPK pathway activation, and increased the expression of antioxidant enzymes, such as Mn-superoxide dismutase (Mn-SOD), catalase (CAT), and heme oxygenase-1 (HO-1).

SIGNIFICANCE

The results of this study indicated that 7,8-DHF inhibits the adipogenesis of 3T3-L1 preadipocyte cells by down-regulating the expression of adipogenic transcription factors, reduces lipid accumulation, and attenuates ROS accumulation by inducing antioxidant enzymes in differentiated 3T3-L1 cells, suggesting for the first time that 7,8-DHF has an anti-obesity effect in vitro via its anti-oxidant activity.

Effect of thyroglobulin gene polymorphisms on growth, carcass composition and meat quality traits in Chinese beef cattle

The thyroglobulin (TG) gene has been studied as an important gene related to fat deposition, since not only does TG gene locate in a quantitative trait locus with an effect on fat deposition, but also it encodes the precursor of thyroid hormones which have crucial biological functions in energy metabolism. In the present study, we identified four novel SNPs at the 5' flanking region of the bovine TG gene. Association analysis indicated that the G275A, G277C, G280A and C281G SNPs were significantly associated with average daily gain (ADG, P < 0.01 for G275A and G277C, P < 0.05 for G280A and C281G). Five haplotypes for the 4 SNPs were constructed and their effects on growth, carcass composition and meat quality traits were evaluated. The results showed no significant effect of haplotype on ADG. Meanwhile, no significant association was found between 4 SNPs and other growth, carcass composition and meat quality traits including intramuscular fat. Bioinformatics analysis showed that 4 SNPs may results in potential transcription factor binding site changes. Results of this study suggest that TG gene-specific SNPs may be a useful marker for growth traits in marker assisted selection programs in beef cattle.

Mest and Sfrp5 are biomarkers for healthy adipose tissue

Obesity depends on a close interplay between genetic and environmental factors. However, it is unknown how these factors interact to cause changes in the obese condition during the progression of obesity from the neonatal to the aged individual. We have utilized Mest and Sfrp5 genes, two genes highly correlated with adipose tissue expansion in diet-induced obesity, to characterize the obese condition during development of 2 genetic models of obesity. A model for the early onset of obesity was presented by leptin-deficient mice (ob/ob), whereas late onset of obesity was induced with high-fat diet (HFD) consumption in C57BL/6J mice with inherent risk of obesity (DIO). We correlated obese and diabetic phenotypes with Mest and Sfrp5 gene expression profiles in subcutaneous fat during pre-weaning, pre-adulthood and adulthood. A rapid development of obesity began in ob/ob mice immediately after weaning at 21 days of age, whereas the obesity of DIO mice was not evident until after 2 months of age. Even after 5 months of HFD treatment, the adiposity index of DIO mice was lower than in ob/ob mice at 2 months of age. In both obesity models, the expression of Mest and Sfrp5 genes increased in parallel with fat mass expansion; however, gene expression proceeded to decrease when the adiposity reached a plateau. The reduction in the expression of genes of caveolae structure and glucose metabolism were also suppressed in the aging adipose tissue. The analysis of fat mass and adipocyte size suggests that reduction in Mest and Sfrp5 is more sensitive to the age of the fat than its morphology. The balance of factors controlling fat deposition can be evaluated in part by the differential expression profiles of Mest and Sfrp5 genes with functions linked to fat deposition as long as there is an active accumulation of fat mass.

Peptide derived from desalinated boiled tuna extract inhibits adipogenesis through the downregulation of C/EBP-α and PPAR-γ in 3T3-L1 adipocytes

Recently, obesity has increased due to a variety of reasons, including the availability of 'fast food' and high-fat diets. Developing anti-obesity functional drugs and foods from natural sources may offer solutions to this global concern. Generally, tuna is a high-protein, low-fat and low-calorie food with various bioactive effects. It may improve memory, reduce cholesterol levels and positively affect the development of brain cells. In this study, we screened the anti-obesity potential of peptides derived from tuna protein. We then observed protein bands by the Coomassie blue staining of a sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gel. The protein mixture was concentrated and desalted using in-gel trypsin digestion and a C18 nano column and Poros R2 reversed-phase preparation, prior to quadrupole time-of-flight mass spectrometry (Q-TOF MS/MS). We screened the peptides for their ability to affect adipogenesis in 3T3-L1 adipocytes. We also measured glucose uptake, triglyceride levels and lipid droplets using Oil Red O staining. As a result, we confirmed that one peptide inhibited adipocyte differentiation. We also observed the expression of obesity-related genes by western blot analysis and reverse transcription-polymerase chain reaction. The peptide from the tuna extract significantly reduced the expression levels of CCAAT/enhancer-binding protein α (C/EBP-α) and peroxisome proliferator-activated receptor-γ (PPAR-γ) adipocyte marker genes. Thus, our data suggest that this peptide from boiled tuna extract reduces lipid components and adipogenesis in 3T3-L1 cells, and these characteristics may be of value in the development of anti-obesity foods.

Promoting effect of triterpenoid compound from Agrimonia pilosa Ledeb on preadipocytes differentiation via up-regulation of PPARγ expression

Background:

Agrimonia Pilosa Ledeb (APL), a traditional Chinese medicine, has been reported a variety of biological activities, including treating T2DM.

Objective:

Triterpenoid compound (TC) was collected from APL. The aim of this study was to investigate the effects of TC on 3T3-L1 preadipocytes differentiation and genes related to differentiation and IR.

Materials and Methods:

Column chromatography was used to collect TC from ALP. 3T3-L1 cell differentiation was induced typically in the presence of various concentrations of TC or pioglitazone. Oil red O staining and measurement of intracellular TG content were performed on the seventh day of differentiation. Then quantitative polymerase chain reaction (Q-PCR) was used to test the expressions of three transcription factors (PPARγ, CCAAT enhancer binding protein-α (C/EBP-α), and sterol regulatory element-binding protein 1 (SREBP-1)) and the target genes of PPARγ including glucose transporter (GLUT4), lipoprotein lipase (LPL), fat acid binding protein (AP2), and adiponectin in 3T3-L1 cells.

Results:

At the concentration of 5, 25 and 125 μg/mL, TC significantly promoted triglyceride accumulation. Further study showed that TC could promote the expression of PPARγ, C/EBPα and ADD1/SREBP1 significantly at 125 μg/mL. As for downstream genes controlled by PPARγ, TC at 25 and 125 μg/mL could significantly promote the expression of GLUT4 and adiponectin. However, the expression of aP2 related to lipid metabolism and adiposity in the TC group was significantly lower than that in the pioglitazone group.

Conclusion:

TC could promote preadipocytes differentiation through activating PPARγ and downstream controlled genes. TC has the ideal insulin sensitization with lower adipogenic action than classical TZDs in vitro. So TC from Agrimonia Pilosa Ledeb has a good prospect as a natural drug for IR and T2DM.

Sphingosine-1-phosphate inhibits differentiation of C3H10T1/2 cells into adipocyte

Mesenchymal stem cells (MSCs) can differentiate into a number of cell types, including adipocytes and osteoblasts. MSC differentiation into adipocytes inhibits osteogenic differentiation and vice versa. Therefore, understanding the mechanisms of MSC differentiation at the signaling level can lead to the development of novel therapeutic strategies toward tissue regeneration. Sphingosine-1-phosphate (S1P) is a signaling molecule that regulates many cellular responses, including cellular differentiation. However, the effects of S1P on MSC differentiation are largely unknown. The purpose of study was to investigate whether S1P drives MSCs toward either adipogenic or osteogenic differentiation, and if so, to clarify the underlying signaling mechanisms for such differentiation. We found that S1P inhibited adipogenic differentiation of C3H10T1/2 multipotent stem cells, while promoting their osteogenic differentiation. During adipogenic differentiation, S1P suppressed the cAMP accumulation in a Gi-protein-dependent manner. The Gi-dependent S1P signaling suppressed C/EBPβ expression, which is essential for adipogenic differentiation. Furthermore, S1P did not affect cAMP-independent adipogenic differentiation. These findings suggest that S1P suppresses cAMP accumulation, leading to inhibition of C/EBPβ expression, thereby resulting in decreased adipogenic differentiation of C3H10T1/2 cells. Thus, our findings provide novel molecular mechanisms as regards how S1P inhibits adipogenic differentiation of C3H10T1/2 cells, indicating a potential beneficial role for regeneration and repair of tissues.

Relationship of adipocyte size with adiposity and metabolic risk factors in Asian Indians

Background

Enlargement of adipocyte is associated with their dysfunction and alterations in metabolic functions.

Objectives

We evaluated the association of adipocyte size of subcutaneous and omental adipose tissue with body composition and cardiovascular risk factors in Asian Indians.

Methodology

Eighty (40 males and 40 females) non-diabetic adult subjects undergoing elective abdominal surgery were included. Pre-surgery evaluation included anthropometric measurements, % body fat by bioimpedance, abdominal fat area at L_2–3 level (computed tomography) and biochemical investigations (fasting blood glucose and insulin, lipids and hsCRP). During surgery, about 5 grams each of omental and subcutaneous adipose tissue was obtained for adipocyte size determination.

Results

Females had higher BMI, % body fat, skinfold thickness, total and subcutaneous abdominal fat area as compared to males. Overweight was present in 42.5% and 67.5%, and abdominal obesity in 5% and 52.5% males and females, respectively. Subcutaneous adipocyte size was significantly higher than omental adipocyte size. Omental adipocyte size correlated more strongly than subcutaneous adipocyte size with measures of adiposity (BMI, waist circumference, %BF), total and subcutaneous abdominal fat area and biochemical measures (fasting glucose, total cholesterol, triglycerides and HOMA-IR), the correlations being stronger in females. The correlation of adipocyte size with metabolic parameters was attenuated after adjusting for measures of adiposity.

Conclusion

Omental adipocyte size, though smaller than the subcutaneous adipocyte size, was more closely related to measures of adiposity and metabolic parameters. However, the relationship was not independent of measures of adiposity.

Adipose tissues as endocrine target organs

In the context of obesity, white adipocyte hypertrophy and adipose tissue macrophage infiltration result in the production of pro-inflammatory adipocytokines inducing insulin resistance locally but also in distant organs and contributing to low grade inflammatory status associated with the metabolic syndrome. Visceral adipose tissue is believed to play a prominent role. Brown and beige adipose tissues are capable of energy dissipation, but also of cytokine production and their role in dysmetabolic syndrome is emerging. This review focuses on metabolic and inflammatory changes in these adipose depots and contribution to metabolic syndrome. Also we will review surgical and pharmacological procedures to target adiposity as therapeutic interventions to treat obesity-associated disorders.

Characteristic expression of extracellular matrix in subcutaneous adipose tissue development and adipogenesis; comparison with visceral adipose tissue

Adipose tissue is a connective tissue specified for energy metabolism and endocrines, but functional differences between subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) have not been fully elucidated. To reveal the physiological role of SAT, we characterized in vivo tissue development and in vitro adipocyte differentiation. In a DNA microarray analysis of SAT and VAT in Wistar rats, functional annotation clusters of extracellular matrix (ECM)-related genes were found in SAT, and major ECM molecules expressed in adipose tissues were profiled. In a histological analysis and quantitative expression analysis, ECM expression patterns could be classified into two types: (i) a histogenesis-correlated type such as type IV and XV collagen, and laminin subunits, (ii) a high-SAT expression type such as type I, III, and V collagen and minor characteristic collagens. Type (i) was related to basal membrane and up-regulated in differentiated 3T3-L1 cells and in histogenesis at depot-specific timings. In contrast, type (ii) was related to fibrous forming and highly expressed in 3T3-L1 preadipocytes. Exceptionally, fibronectin was abundant in developed adipose tissue, although it was highly expressed in 3T3-L1 preadipocytes. The present study showed that adipose tissues site-specifically regulate molecular type and timing of ECM expression, and suggests that these characteristic ECM molecules provide a critical microenvironment, which may affect bioactivity of adipocyte itself and interacts with other tissues. It must be important to consider the depot-specific property for the treatment of obesity-related disorders, dermal dysfunction and for the tissue regeneration.

Preventive effects of siRNA targeting PPARγ gene on steroid-induced osteonecrosis in rabbits

PURPOSES/AIM: Glucocorticoid steroids can induce expression of PPARγ gene and enhance adipogenesis by bone marrow mesenchymal stem cells (BMSCs), which may result in osteonecrosis of the femoral head. Currently, there are no medications available to prevent steroid-induced osteonecrosis. We hypothesized that siRNA targeting PPARγ gene may prevent steroid-induced adipogenesis and osteonecrosis in rabbit. The purpose of this study was to evaluate the preventive effects of siRNA targeting PPARγ gene on steroid-induced adipogenesis and osteonecrosis.

METHODS

Forty-eight healthy New Zealand rabbits were randomized into four groups with Group M treated with dexamethasone only, Group S with dexamethasone and a recombinant adenovirus shuttle vector carrying siRNA targeting PPARγ gene, Group Con with dexamethasone and a vector carrying irrelative sequence, and Group N with no treatment serving as control. Expressions of the PPARγ, osteocalcin and Runx2 genes, as well as histopathologic changes were evaluated.

RESULTS

The levels of PPARγ gene expression were decreased while the levels of osteocalcin and Runx2 gene expression were increased in rabbits treated with dexamethasone and recombinant adenovirus shuttle vector carrying siRNA targeting PPARγ gene (Group S), compared to rabbits treated either with dexamethasone alone (Group M) or with both dexamethasone and a vector carrying irrelative sequence (Group Con). The marrow necrosis, adipocyte hypertrophy and proliferation, diminished hematopoiesis, thinner and sparse trabeculae, and increased empty osteocyte lacunae in the femoral head were observed in Group M and Group Con rabbits. However, no such changes were seen in Group S rabbits that were treated with dexamethasone and a recombinant adenovirus shuttle vector carrying siRNA targeting PPARγ gene.

CONCLUSION

siRNA targeting PPARγ gene can inhibit adipogenic differentiation of BMSCs and prevent steroid-induced osteonecrosis in rabbit. The inhibition of bone-marrow adipogenesis and concomitant enhancement of osteogenesis with RNAi may provide a novel approach to the prevention of steroid-induced osteonecrosis.

Transdifferentiation between bone and fat on bone metabolism

The transdifferentiation of bone and fat is a new insight in studying the increasingly bone marrow fat in the process of osteoporosis of elderly or menopause crowd which is increasing in prevalence. The loss of bone mass in osteoporosis is multifactorially determined and includes genetic, hormonal and environmental determinants. Although it has long been considered whether the transdifferentiation process does exist in vivo and whether it could be find in the same individual, interaction between skeleton and adipose tissue has been proved pre-clinically and clinically by increasing evidence. Here we focus on the current understanding of the transdifferentiation between bone and fat, the molecular interactions and future clinical implications of recent studies linking the transdifferentiation to bone metabolism diseases. Furthermore, a set of recommendations of bone and fat transdifferentiation on bone metabolism are also presented to facilitate evaluation of this magic process.

Regulation of MKL1 via actin cytoskeleton dynamics drives adipocyte differentiation

Cellular differentiation is regulated through activation and repression of defined transcription factors. A hallmark of differentiation is a pronounced change in cell shape, which is determined by dynamics of the actin cytoskeleton. Here we show that regulation of the transcriptional coactivator MKL1 (megakaryoblastic leukemia 1) by actin cytoskeleton dynamics drives adipocyte differentiation mediated by peroxisome proliferator-activated receptor γ (PPARγ), a master transcriptional regulator of adipogenesis. Induction of adipocyte differentiation results in disruption of actin stress fibres through downregulation of RhoA-ROCK signalling. The consequent rapid increase in monomeric G-actin leads to the interaction of G-actin with MKL1, which prevents nuclear translocation of MKL1 and allows expression of PPARγ followed by adipogenic differentiation. Moreover, we found that MKL1 and PPARγ act in a mutually antagonistic manner in the adipocytic differentiation programme. Our findings thus provide new mechanistic insight into the relation between the dynamics of cell shape and transcriptional regulation during cellular differentiation.

Biomaterials for adipose tissue engineering

There is high clinical need for an adequate reconstruction of soft tissue defects as found after tumor resections, deep burns or severe trauma. A promising solution for these defects is adipose tissue engineering, with adult stem cells of the adipose tissue, implanted on 3D biomaterials. These adipogenic precursor cells survive ischemia better than mature adipocytes and have the potency to proliferate and differentiate into fat cells after transplantation. They can be yielded from excised adipose tissue or liposuction material. When preadipocytes are seeded on carriers for the generation of adipose tissue, chemical composition, mechanical stability and 3D architecture of the construct are crucial factors. They ensure cellular penetration into the construct, sufficient proliferation on the material and full differentiation inside the construct after transplantation. In hydrogels, it is especially the use and combination of growth factors that determine the overall outcome of the applied biopolymer. Over recent years, in vivo trials in particular have allowed significant insights into the potential, the perspectives, but also the current difficulties and draw-backs in adipose tissue engineering. This review focuses on the main strategies in adipose tissue regeneration, compares the various materials that have been used as carrier matrices so far and considers them in light of the challenges they have yet to meet.

Pharmacologic agents for type 2 diabetes therapy and regulation of adipogenesis

The close link between type 2 diabetes and excess body weight highlights the need to consider the effects on weight of different treatments used for correction of hyperglycaemia. Indeed, specific currently available diabetes therapies can cause weight gain, including insulin and its analogues, sulphonylureas, and thiazolidinediones, while others, such as metformin and the GLP-1 receptor agonists, can promote weight loss. Excess body weight in patients with diabetes is largely due to expansion of adipose tissue, and these drugs could interfere with the mechanisms underlying the expansion and differentiation of adipocyte precursors. Almost all anti-diabetes drugs could also potentially affect adipocyte metabolism directly, by modulating lipogenesis, lipolysis, and fat oxidation. This review will examine the available evidence for specific effects of various anti-diabetes drugs on adipose tissue development and function with the ultimate goal of increasing our understanding of how pharmacological agents can modulate energy balance and body fat.

Production of a composite hyaluronic acid/gelatin blood plasma gel for hydrogel-based adipose tissue engineering applications

Standard approaches to soft-tissue reconstruction include autologous adipose tissue transplantation, but most of the transferred adipose tissue is generally reabsorbed in a short time. To overcome this problem, long lasting implantable hydrogel materials that can support tissue regeneration must be produced. The purpose of this study was to evaluate the suitability of composite 3D natural origin scaffolds for reconstructive surgery applications through in vitro tests. The Young's modulus of the glutaraldehyde crosslinked hyaluronic acid/gelatin (HA/G) plasma gels, composed of human platelet-poor plasma, gelatin and human umbilical cord hyaluronic acid, was determined as 3.5 kPa, close to that of soft tissues. The composite HA/G plasma gels had higher porosity than plain plasma gels (72.5% vs. 63.86%). Human adipose tissue derived stem cells (AD-MSCs) were isolated from human lipoaspirates and characterized with flow cytometry, and osteogenic and adipogenic differentiation. Cell proliferation assay of AD-MSCs on the HA/G plasma gels revealed the nontoxic nature of these constructs. Adipogenic differentiation was distinctly better on HA/G plasma gels than on plain plasma gels. The results showed that the HA/G plasma gel with its suitable pore size, mechanical properties and excellent cell growth and adipogenesis supporting properties can serve as a useful scaffold for adipose tissue engineering applications.

Cell adhesion and mechanical stimulation in the regulation of mesenchymal stem cell differentiation

Stem cells have been shown to have the potential to provide a source of cells for applications to tissue engineering and organ repair. The mechanisms that regulate stem cell fate, however, mostly remain unclear. Mesenchymal stem cells (MSCs) are multipotent progenitor cells that are isolated from bone marrow and other adult tissues, and can be differentiated into multiple cell lineages, such as bone, cartilage, fat, muscles and neurons. Although previous studies have focused intensively on the effects of chemical signals that regulate MSC commitment, the effects of physical/mechanical cues of the microenvironment on MSC fate determination have long been neglected. However, several studies provided evidence that mechanical signals, both direct and indirect, played important roles in regulating a stem cell fate. In this review, we summarize a number of recent studies on how cell adhesion and mechanical cues influence the differentiation of MSCs into specific lineages. Understanding how chemical and mechanical cues in the microenvironment orchestrate stem cell differentiation may provide new insights into ways to improve our techniques in cell therapy and organ repair.

Unraveling the mode of action of an obesogen: mechanistic analysis of the model obesogen tributyltin in the 3T3-L1 cell line

Obesogenic compounds are chemicals that have an influence on obesity development. This study was designed to unravel the molecular mechanisms of the model obesogen TBT, using microarray analysis in the 3T3-L1 in vitro system, and to evaluate the use of toxicogenomics for obesogen screening. The microarray results revealed enrichment of Gene Ontology terms involved in energy and fat metabolism after 10 days of TBT exposure. Pathway analysis unveiled PPAR signalling pathway as the sole pathway significantly enriched after 1 day and the most significantly enriched pathway after 10 days of exposure. To our knowledge, this is the first study delivering an in depth mechanistic outline of the mode of action of TBT as an obesogen, combining effects on both cell physiological and gene expression level. Furthermore, our results show that combining transcriptomics with 3T3-L1 cells is a promising tool for screening of potential obesogenic compounds.

Macrophage-induced adipose tissue dysfunction and the preadipocyte: should I stay (and differentiate) or should I go?

Adipose tissue can be regarded as a multidepot organ responsible for metabolic homeostasis by managing sophisticated energy transactions as well as by producing bioactive molecules that regulate insulin sensitivity and immune and vascular responses. Chronic nutrient excess expands adipose tissue, and concomitant variations in its cellular and matrix remodeling can affect the extent of the metabolic dysfunction that is associated with obesity. Preadipocytes, also termed adipose progenitor cells, play a pivotal role in determining whether a dysfunctional hypertrophic state arises as opposed to a hyperplastic process in which mature adipocytes remain relatively responsive. Obesity is associated with infiltration of macrophages, and these immune cells have been shown to communicate with preadipocytes to influence how they differentiate, survive, and proliferate. Understanding macrophage-preadipocyte interactions and their effect on adipose remodeling mechanisms may identify potential therapeutic molecular targets to improve adipose tissue function, even in the face of obesity.

Adipose tissue engineering with cells in engineered matrices

Tissue engineering has shown promise for the development of constructs to facilitate large volume soft tissue augmentation in reconstructive and cosmetic plastic surgery. This article reviews the key progress to date in the field of adipose tissue engineering. In order to effectively design a soft tissue substitute, it is critical to understand the native tissue environment and function. As such, the basic physiology of adipose tissue is described and the process of adipogenesis is discussed. In this article, we have focused on tissue engineering using a cell-seeded scaffold approach, where engineered extracellular matrix substitutes are seeded with exogenous cells that may contribute to the regenerative response. The strengths and limitations of each of the possible cell sources for adipose tissue engineering, including adipose-derived stem cells, are detailed. We briefly highlight some of the results from the major studies to date, involving a range of synthetic and naturally derived scaffolds. While these studies have shown that adipose tissue regeneration is possible, more research is required to develop optimized constructs that will facilitate safe, predictable and long-term augmentation in clinical applications.

Mulberry leaf extract increases adiponectin in murine 3T3-L1 adipocytes

We have previously shown that mulberry leaf extract (MA) causes blood glucose levels to decrease in rats with streptozotocin-induced diabetes while enhancing glucose uptake by isolated fat cells. We hypothesized that the antidiabetic activity of MA is mediated via enhancement of adiponectin secretion and adipogenesis, which consequently decreases blood glucose. In the present study, we aimed to elucidate the molecular basis for the observed antidiabetic activity using murine 3T3-L1 preadipocyte cultures. We found that treatment of differentiating 3T3-L1 cells with MA at concentrations of 5, 15, and 45 μg/mL increased expression of adiponectin messenger RNA from 1.4-fold (control) to 1.5-, 1.95-, and 2.2-fold above basal values, respectively, while causing adiponectin secretion to increase from 70 ± 7.4 ng/mL to 100 ± 1.4, 138 ± 2.0, and 176 ± 21.4 ng/mL, respectively. Furthermore, we observed an increase in both lipid accumulation and messenger RNA expression of transcription factors, such as CCAAT/enhancer-binding protein α and peroxisome proliferator-activated receptor γ; and of the fatty acid-binding protein aP2 in differentiated 3T3-L1 cells pretreated with MA. Our findings indicate that the stimulatory effects of mulberry leaf extract on adipocyte proliferation and differentiation likely occur through up-regulation of adipogenic transcription factors and downstream gene expression. Such effects of mulberry leaf extract on adiponectin secretion and adipocyte activity may account for, at least in part, the antidiabetic effects of consumption of beverages containing mulberry leaves.

The small leucine-rich proteoglycan, biglycan, is highly expressed in adipose tissue of Psammomys obesus and is associated with obesity and type 2 diabetes

We have previously demonstrated that the small leucine-rich proteoglycan decorin may play a role in adipose tissue homeostasis and the pathophysiology of obesity. Biglycan is highly similar in structure to decorin, therefore we hypothesized it would have a similar expression profile and role to decorin in adipose tissue. Real time polymerase chain reaction was used to measure biglycan mRNA levels in adipose tissue from normal glucose tolerant and impaired glucose tolerant and type 2 diabetic (T2D) Psammomys obesus. Biglycan mRNA was found to be highly expressed in adipose tissue, and gene expression was significantly higher in visceral compared to subcutaneous adipose tissue, with elevated levels in obese, T2D compared to lean normal glucose tolerant P. obesus (P < 0.04). Biglycan mRNA was predominantly expressed by stromal/vascular cells of fractionated adipose tissue (P = 0.023). Biglycan expression in adipose tissue, particularly in the obese state, was markedly upregulated. Collectively, our data suggest that the small leucine-rich proteoglycan family proteins biglycan and decorin may play a role in the development of obesity and T2D, possibly by facilitating expansion of adipose tissue mass.

ECM roles in the function of metabolic tissues

All metazoan cells produce and/or interact with tissue-specific extracellular matrices (ECMs). Such ECMs play important structural roles not only in connective tissues, but in all tissues in which they provide support and anchorage for cells. However, in addition to such structural roles it has become increasingly clear that the tissue-specific microenvironments formed by the ECM play instructional roles that inform the proper phenotypes and functional behaviors of specialized cell types, and recent in vivo and in vitro studies suggest that ECM components also affect metabolic function. This review summarizes data that provide insights into the roles of the ECM in informing the proper development and functioning of highly specialized cells of metabolic tissues, such as adipocytes and islet β cells.