Fibroblast growth factor receptor 1 is a key regulator of early adipogenic events in human preadipocytes

Adipocyte transdifferentiation and its molecular targets

According to the World Health Organization obesity is defined as the excessive accumulation of fat, which increases risk of other metabolic disorders such as insulin resistance, dyslipidemia, hypertension, cardiovascular diseases, etc. There are two types of adipose tissue, white and brown adipose tissue (BAT) and the latter has recently gathered interest of the scientific community. Discovery of BAT has opened avenues for a new therapeutic strategy for the treatment of obesity and related metabolic syndrome. BAT utilizes accumulated fatty acids for energy expenditure; hence it is seen as one of the possible alternates to the current treatment. Moreover, browning of white adipocyte on exposure to cold, as well as with some of the pharmacological agents presents exciting outcomes and indicates the feasibility of transdifferentiation. A better understanding of molecular pathways and differentiation factors, those that play a key role in transdifferentiation are of extreme importance in designing novel strategies for the treatment of obesity and associated metabolic disorders.

Plant natural products as an anti-lipid droplets accumulation agent

Recently people often suffer from unhealthy energy metabolism balance as they tend to take more energy than required. Normally, excess energy taken in is converted into triglyceride and stored in adipocyte as lipid droplets. Recent studies have suggested that irregular accumulation of triglyceride in adipocyte might be a cause of many metabolic diseases. Thus, the awareness of the detrimental effects on health of excessive lipid droplets accumulation (LDA) has urged the development or finding of drugs to counter this effect, including those from botanical origins. This review summarized recent progress in this field from the viewpoint of crude drug studies with references to their anti-LDA activity. Possible mechanisms involved in their anti-LDA effect and isolations of the relevant bioactive compounds were also discussed.

Dual-stage growth factor release within 3D protein-engineered hydrogel niches promotes adipogenesis

Engineered biomimetic microenvironments from hydrogels are an emerging strategy to achieve lineage-specific differentiation in vitro. In addition to recapitulating critical matrix cues found in the native three-dimensional (3D) niche, the hydrogel can also be designed to deliver soluble factors that are present within the native inductive microenvironment. We demonstrate a versatile materials approach for the dual-stage delivery of multiple soluble factors within a 3D hydrogel to induce adipogenesis. We use a Mixing-Induced Two-Component Hydrogel (MITCH) embedded with alginate microgels to deliver two pro-adipogenic soluble factors, fibroblast growth factor 1 (FGF-1) and bone morphogenetic protein 4 (BMP-4) with two distinct delivery profiles. We show that dual-stage delivery of FGF-1 and BMP-4 to human adipose-derived stromal cells (hADSCs) significantly increases lipid accumulation compared with the simultaneous delivery of both growth factors together. Furthermore, dual-stage growth factor delivery within a 3D hydrogel resulted in substantially more lipid accumulation compared to identical delivery profiles in 2D cultures. Gene expression analysis shows upregulation of key adipogenic markers indicative of brown-like adipocytes. These data suggest that dual-stage release of FGF-1 and BMP-4 within 3D microenvironments can promote the in vitro development of mature adipocytes.

Permanent activation of HMGA2 in lipomas mimics its temporal physiological activation linked to the gain of adipose tissue

OBJECTIVE

In this study the activation of HMGA2 and overexpression by FGF1-driven stimulation of adipose tissue derived stem cells (ADSCs) in adipose tissue tumors were analyzed. In addition, the expression of HMGA2 and PPAR-gamma mRNA were quantified in canine subcutaneous abdominal adipose tissue from normal and overweight purebred dogs.

DESIGN AND METHODS

ADSCs and adipose tissue explants stimulated with FGF1 followed by gene expression analyses of HMGA2 and p14(Arf) using Western-blot and qRT-PCR. Furthermore, canine subcutaneous white adipose tissue (WAT) were analyzed by qRT-PCR for their expression of HMGA2 and PPAR-gamma.

RESULTS

ADSCs and adipose tissue explants are able to execute a HMGA2 response upon FGF1 stimulation. FGF1 enhances proliferation of ADSCs by a HMGA2-dependent mechanism. In lipomas increase of HMGA2 is accompanied by increased expression of p14(Arf) . Furthermore, a significantly elevated level of HMGA2 in overweight dogs and a negative correlation between the expression of HMGA2 and PPAR-gamma in subcutaneous cWAT were noted.

CONCLUSIONS

These results suggest that WAT contains cells that as essential part of adipogenesis up-regulate HMGA2 resulting from growth factor stimulation. In subgroups of lipoma, constitutive activation of HMGA2 due to rearrangements replaces the temporal response triggered by growth factors.

Feeding soy protein isolate and treatment with estradiol have different effects on mammary gland morphology and gene expression in weanling male and female rats

Isoflavones are phytochemical components of soy diets that bind weakly to estrogen receptors (ERs). To study potential estrogen-like actions of soy in the mammary gland during early development, we fed weanling male and female Sprague-Dawley rats a semipurified diet with casein as the sole protein source from postnatal day 21 to 33, the same diet substituting soy protein isolate (SPI) for casein, or the casein diet supplemented with estradiol (E2) at 10 μg/kg/day. In contrast to E2, the SPI diet induced no significant change in mammary morphology. In males, there were 34 genes for which expression was changed ≥2-fold in the SPI group vs. 509 changed significantly by E2, and 8 vs. 174 genes in females. Nearly half of SPI-responsive genes in males were also E2 responsive, including adipogenic genes. Serum insulin was found to be decreased by the SPI diet in males. SPI and E2 both downregulated the expression of ERα ( Esr1) in males and females, and ERβ ( Esr2) only in males. Chromatin immunoprecipitation revealed an increased binding of ERα to the promoter of the progesterone receptor ( Pgr) and Esr1 in both SPI- and E2-treated males compared with the casein group but differential recruitment of ERβ. ER promoter binding did not correlate with differences in Pgr mRNA expression. This suggests that SPI fails to recruit appropriate co-activators at E2-inducible genes. Our results indicate that SPI behaves like a selective estrogen receptor modulator rather than a weak estrogen in the developing mammary gland.

A comparative perspective on lipid storage in animals

Lipid storage is an evolutionary conserved process that exists in all organisms from simple prokaryotes to humans. In Metazoa, long-term lipid accumulation is restricted to specialized cell types, while a dedicated tissue for lipid storage (adipose tissue) exists only in vertebrates. Excessive lipid accumulation is associated with serious health complications including insulin resistance, type 2 diabetes, cardiovascular diseases and cancer. Thus, significant advances have been made over the last decades to dissect out the molecular and cellular mechanisms involved in adipose tissue formation and maintenance. Our current understanding of adipose tissue development comes from in vitro cell culture and mouse models, as well as recent approaches to study lipid storage in genetically tractable lower organisms. This Commentary gives a comparative insight into lipid storage in uni- and multi-cellular organisms with a particular emphasis on vertebrate adipose tissue. We also highlight the molecular mechanisms and nutritional signals that regulate the formation of mammalian adipose tissue.

Protein partners of KCTD proteins provide insights about their functional roles in cell differentiation and vertebrate development

The KCTD family includes tetramerization (T1) domain containing proteins with diverse biological effects. We identified a novel member of the KCTD family, BTBD10. A comprehensive analysis of protein-protein interactions (PPIs) allowed us to put forth a number of testable hypotheses concerning the biological functions for individual KCTD proteins. In particular, we predict that KCTD20 participates in the AKT-mTOR-p70 S6k signaling cascade, KCTD5 plays a role in cytokinesis in a NEK6 and ch-TOG-dependent manner, KCTD10 regulates the RhoA/RhoB pathway. Developmental regulator KCTD15 represses AP-2α and contributes to energy homeostasis by suppressing early adipogenesis. TNFAIP1-like KCTD proteins may participate in post-replication DNA repair through PCNA ubiquitination. KCTD12 may suppress the proliferation of gastrointestinal cells through interference with GABAb signaling. KCTD9 deserves experimental attention as the only eukaryotic protein with a DNA-like pentapeptide repeat domain. The value of manual curation of PPIs and analysis of existing high-throughput data should not be underestimated.

Ceramicine B, a limonoid with anti-lipid droplets accumulation activity from Chisocheton ceramicus

The Meliaceae family of plants has been shown to contain a vast number of compounds with the potential to be developed for medicinal purposes. We have previously reported the isolation of limonoids from a plant in the Meliaceae family named Chisocheton ceramicus. Ceramicine B was identified as an active compound in inhibiting lipid droplets accumulation (LDA) in the mouse preadipocyte cell line MC3T3-G2/PA6. The presence of ceramicine B was found to inhibit the expression of glucose transporter type 4, lipoprotein lipase, and 11-beta hydroxysteroid dehydrogenase mRNA, and also adipogenic master regulator, peroxisome proliferator-activated receptor-γ, and CCAAT-enhancer-binding protein-α (C/EBPα) mRNA. However, for early adipogenic regulators, such as C/EBPβ and C/EBPδ, and intermediary adipogenic regulators, Krüppel-like factors were unaffected. Western blot analysis showed that ceramicine B was found to inhibit the phosphorylation of Forkhead box O1 (Foxo1), a key process in the insulin signaling pathway. This suggested that the mechanism of anti-LDA activity of ceramicine B was partly via the inhibition of Foxo1 phosphorylation.

bFGF promotes adipocyte differentiation in human mesenchymal stem cells derived from embryonic stem cells

In this work we describe the establishment of mesenchymal stem cells (MSCs) derived from embryonic stem cells (ESCs) and the role of bFGF in adipocyte differentiation. The totipotency of ESCs and MSCs was assessed by immunofluorescence staining and RT-PCR of totipotency factors. MSCs were successfully used to induce osteoblasts, chondrocytes and adipocytes. MSCs that differentiated into adipocytes were stimulated with and without bFGF. The OD/DNA (optical density/content of total DNA) and expression levels of the specific adipocyte genes PPARγ2 (peroxisome proliferator activated receptor γ2) and C/EBPs were higher in bFGF cells. Embryonic bodies had a higher adipocyte level compared with cells cultured in plates. These findings indicate that bFGF promotes adipocyte differentiation. MSCs may be useful cells for seeding in tissue engineering and have enormous therapeutic potential for adipose tissue engineering.

Fibroblast growth factor signaling regulates neurogenesis at multiple stages in the embryonic olfactory epithelium

Lifelong neurogenesis in the mouse olfactory epithelium (OE) is regulated by the response of stem/progenitor cells to local signals, but embryonic and adult OE progenitors appear to be quite different--with potentially different mechanisms of regulation. A recently identified progenitor unique to embryonic OE--the nestin+ radial glial-like progenitor--precedes some Mash1+ progenitors in the olfactory receptor neuron (ORN) lineage, which then gives rise to immediate neuronal precursors and immature ORNs. Neurogenic drive at each stage is governed largely by exogenous factors. Fibroblast growth factor 2 (FGF2) is believed to increase cell proliferation in both presumptive OE stem cells and immediate neuronal precursors in explants, but whether FGF2 directly acts on different target progenitors or stages in the embryonic OE is not known. Here we show that fibroblast growth factor receptor (FGFR)1 and FGFR2 are found in a variety of embryonic olfactory cells, including olfactory ensheathing cells and their precursors, and neuronal nestin+ and Mash1+ progenitors. Combining gain and loss of function for FGF2 activity in a novel in vitro clonal progenitor assay, we reveal that different colony phenotypes are formed by presumably different OE progenitors. FGF2 is essential for the survival and expansion of colony-forming cells of the OE, and also enhances the proliferation of embryonic Mash1+ progenitors, leading to long-lived enhancement of neurogenesis. Our data suggest that distinct OE progenitors yield different in vitro phenotypes with different potentials, that colony-forming activity is profoundly altered by laminin and collagen, that multiple ORNs can be produced from single colony-forming progenitors, and demonstrate a broader progenitor range of FGF action in the embryonic OE than previously demonstrated.

Antidepressant effects of fibroblast growth factor-2 in behavioral and cellular models of depression

BACKGROUND

Basic and clinical studies report that the expression of fibroblast growth factor-2 (FGF-2) is decreased in the prefrontal cortex (PFC) of depressed subjects or rodents exposed to stress and increased following antidepressant treatment. Here, we aim to determine if 1) FGF-2/fibroblast growth factor receptor (FGFR) signaling is sufficient and required for mediating an antidepressant response behaviorally and cellularly; and 2) if the antidepressant actions of FGF-2 are mediated specifically by the PFC.

METHODS

The role of FGF-2 signaling in behavioral models of depression and anxiety was tested using chronic unpredictable stress (CUS)/sucrose consumption test (SCT), forced swim test (FST), and novelty suppressed feeding test (NSFT). We also assessed the number of bromodeoxyuridine labeled dividing glial cells in the PFC as a cellular index relevant to depression (i.e., decreased by stress and increased by antidepressant treatment).

RESULTS

Chronic FGF-2 infusions (intracerebroventricular) blocked the deficit in SCT caused by CUS. Moreover, the response to antidepressant treatment in the CUS/SCT and FST was abolished upon administration of an inhibitor of FGFR activity, SU5402. These results are consistent with the regulation of proliferating cells in the PFC, a portion of which are of oligodendrocyte lineage. Lastly, subchronic infusions of FGF-2 into the PFC but not into the dorsal striatum produced antidepressant-like and anxiolytic-like effects on FST and NSFT respectively.

CONCLUSIONS

These findings demonstrate that FGF-2/FGFR signaling is sufficient and necessary for the behavioral, as well as gliogenic, actions of antidepressants and highlight the PFC as a brain region sensitive to the antidepressant actions of FGF-2.

Intrinsic regulation of hemangioma involution by platelet-derived growth factor

Infantile hemangioma is a vascular tumor that exhibits a unique natural cycle of rapid growth followed by involution. Previously, we have shown that hemangiomas arise from CD133+ stem cells that differentiate into endothelial cells when implanted in immunodeficient mice. The same clonally expanded stem cells also produced adipocytes, thus recapitulating the involuting phase of hemangioma. In the present study, we have elucidated the intrinsic mechanisms of adipocyte differentiation using hemangioma-derived stem cells (hemSCs). We found that platelet-derived growth factor (PDGF) is elevated during the proliferating phase and may inhibit adipocyte differentiation. hemSCs expressed high levels of PDGF-B and showed sustained tyrosine phosphorylation of PDGF receptors under basal (unstimulated) conditions. Inhibition of PDGF receptor signaling caused enhanced adipogenesis in hemSCs. Furthermore, exposure of hemSCs to exogenous PDGF-BB reduced the fat content and the expression of adipocyte-specific transcription factors. We also show that these autogenous inhibitory effects are mediated by PDGF receptor-β signaling. In summary, this study identifies PDGF signaling as an intrinsic negative regulator of hemangioma involution and highlights the therapeutic potential of disrupting PDGF signaling for the treatment of hemangiomas.

Identification of BMP and activin membrane-bound inhibitor (BAMBI) as a potent negative regulator of adipogenesis and modulator of autocrine/paracrine adipogenic factors

Adipose tissue dysfunction underpins the association of obesity with type 2 diabetes. Adipogenesis is required for the maintenance of adipose tissue function. It involves the commitment and subsequent differentiation of preadipocytes and is coordinated by autocrine, paracrine, and endocrine factors. We previously reported that fibroblast growth factor-1 (FGF-1) primes primary human preadipocytes and Simpson Golabi Behmel syndrome (SGBS) preadipocytes and increases adipogenesis through a cascade involving extracellular signal-related kinase 1/2 (ERK1/2). Here, we aimed to use the FGF-1 system to identify novel adipogenic regulators. Expression profiling revealed bone morphogenetic protein (BMP) and activin membrane-bound inhibitor (BAMBI) as a putative FGF-1 effector. BAMBI is a transmembrane protein and modulator of paracrine factors that regulate adipogenesis, including transforming growth factor (TGF) superfamily members (TGF-β and BMP) and Wnt. Functional investigations established BAMBI as a negative regulator of adipogenesis and modulator of the anti- and proadipogenic effects of Wnt3a, TGF-β1, and BMP-4. Further studies showed that BAMBI expression levels are decreased in a mouse model of diet-induced obesity. Collectively, these findings establish BAMBI as a novel, negative regulator of adipogenesis that can act as a nexus to integrate multiple paracrine signals to coordinate adipogenesis. Alterations in BAMBI may play a role in the (patho)physiology of obesity, and manipulation of BAMBI may present a novel therapeutic approach to improve adipose tissue function.

Obesity and breast cancer: a clinical biochemistry perspective

OBJECTIVES

To evaluate the laboratory diagnosis aspects of obesity-related health problems with special reference to postmenopausal breast cancer.

DESIGN AND METHODS

We conducted a systemic search of the literature primarily from the PubMed to obtain the relevant data.

RESULTS

Obesity is associated with the dysregulations of a number of body components such as blood constituents, extracellular matrix, and hormones/growth factors axes, which could be utilized for early diagnosis.

CONCLUSIONS

Obesity-related disorders including breast cancer have emerged as major health problems in almost all the nations. There is a need to elucidate different biochemical markers that are being used in the clinics or have the potential for such use. A precise understanding of the complex pathologies related with obesity is useful in prevention, early diagnosis and overall clinical management.

Water-soluble extract of Pacific Krill prevents triglyceride accumulation in adipocytes by suppressing PPARγ and C/EBPα expression

BACKGROUND

Pacific Krill (Euphausia pacifica) are small, red crustaceans, similar to shrimp, that flourish in the North Pacific and are eaten in Japan.

METHODS AND FINDINGS

We investigated the effect of a water-soluble extract of Pacific Krill on adipocytes and discovered that this extract suppressed triglyceride accumulation in adipocytes. Furthermore, the water-soluble extract of Pacific Krill suppressed the expression of two master regulators of adipocyte differentiation, peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT enhancer binding protein alpha (C/EBPα). C/EBPβ promotes PPARγ and C/EBPα expression, but the water-soluble extract of Pacific Krill did not inhibit the expression of C/EBPβ or C/EBPβ-mediated transcriptional activation. The Pacific Krill extract was more effective than a PPARγ antagonist in suppressing PPARγ and C/EBPα expression.

CONCLUSIONS

These results indicated that the water-soluble extract of Pacific Krill was not simply a PPARγ antagonist, but that it prevented triglyceride accumulation in adipocytes by suppression of PPARγ and C/EBPα via a pathway that is independent of C/EBPβ.

A putative role for endogenous FGF-2 in FGF-1 mediated differentiation of human preadipocytes

The defining characteristic of obesity is increased adipose tissue (AT) mass following chronic positive energy supply. AT mass is determined by adipocyte number and size, which reflect proliferation and differentiation of preadipocytes and hypertrophy of pre-existing adipocytes. The molecular pathways governing AT expansion are incompletely defined. We previously reported that FGF-1 primes proliferating primary human preadipocytes (phPA), thereby increasing adipogenesis. Here we examined whether FGF-1's adipogenic actions were due to modulation of other FGFs. Treatment of phPA with FGF-1 reduced FGF-2 mRNA/protein by 80%. To examine a putative functional role we performed siRNA knockdown studies. Following FGF-2 knockdown preadipocyte proliferation was decreased and expression of adipogenic genes (PPARγ, G3PDH and adiponectin) was increased at day 1 of differentiation. These results suggest that changes in endogenous FGF-2 levels contribute to FGF-1's early adipogenic effects and highlight the complexity of the paracrine interplay between FGFs within human AT.

Winning a won game: caffeine panacea for obesity syndemic

Over the past decades, chronic sleep reduction and a concurrent development of obesity have been recognized as a common problem in the industrialized world. Among its numerous untoward effects, there is a possibility that insomnia is also a major contributor to obesity. This attribution poses a problem for caffeine, an inexpensive, “natural” agent that is purported to improve a number of conditions and is often indicated in a long-term pharmacotherapy in the context of weight management. The present study used the “common target” approach by exploring the tentative shared molecular networks of insomnia and adiposity. It discusses caffeine targets beyond those associated with adenosine signaling machinery, phosphodiesterases, and calcium release channels. Here, we provide a view suggesting that caffeine could exert some of its effects by acting on several signaling complexes composed of HIF-1α/VEGF/IL-8 along with NO, TNF-α, IL1, and GHRH, among others. Although the relevance of these targets to the reported therapeutic effects of caffeine has remained difficult to assess, the utilization of caffeine efficacies and potencies recommend its repurposing for development of novel therapeutic approaches. Among indications mentioned, are neuroprotective, nootropic, antioxidant, proliferative, anti-fibrotic, and anti-angiogenic that appear under a variety of dissimilar diagnostic labels comorbid with obesity. In the absence of safe and efficacious antiobesity agents, caffeine remains an attractive adjuvant.

Activin a plays a critical role in proliferation and differentiation of human adipose progenitors

OBJECTIVE

Growth of white adipose tissue takes place in normal development and in obesity. A pool of adipose progenitors is responsible for the formation of new adipocytes and for the potential of this tissue to expand in response to chronic energy overload. However, factors controlling self-renewal of human adipose progenitors are largely unknown. We investigated the expression profile and the role of activin A in this process.

RESEARCH DESIGN AND METHODS

Expression of INHBA/activin A was investigated in three types of human adipose progenitors. We then analyzed at the molecular level the function of activin A during human adipogenesis. We finally investigated the status of activin A in adipose tissues of lean and obese subjects and analyzed macrophage-induced regulation of its expression.

RESULTS

INHBA/activin A is expressed by adipose progenitors from various fat depots, and its expression dramatically decreases as progenitors differentiate into adipocytes. Activin A regulates the number of undifferentiated progenitors. Sustained activation or inhibition of the activin A pathway impairs or promotes, respectively, adipocyte differentiation via the C/EBPβ-LAP and Smad2 pathway in an autocrine/paracrine manner. Activin A is expressed at higher levels in adipose tissue of obese patients compared with the expression levels in lean subjects. Indeed, activin A levels in adipose progenitors are dramatically increased by factors secreted by macrophages derived from obese adipose tissue.

CONCLUSIONS

Altogether, our data show that activin A plays a significant role in human adipogenesis. We propose a model in which macrophages that are located in adipose tissue regulate adipose progenitor self-renewal through activin A.

Mapping of the fibroblast growth factors in human white adipose tissue

CONTEXT

Fibroblast growth factors (FGFs) regulate the development of white adipose tissue (WAT). However, the secretion and cellular origin of individual FGFs in WAT as well as the influence of obesity are unknown.

OBJECTIVE

Our objective was to map FGFs in human sc WAT, the cellular source, and association with obesity.

DESIGN

Secretion, mRNA, and circulatory levels of FGFs in human abdominal sc WAT from nonobese and obese donors were examined by microarray, real-time quantitative PCR, and ELISA. The activity of FGFs in cultured human adipocytes was determined by phosphorylation assays.

RESULTS

Expression of five FGFs (FGF1, FGF2, FGF7, FGF9, and FGF18) and FGF homologous factor (FHF2) was identified in WAT. Only FGF1 was released in a time-dependent manner from sc WAT, and fat cells were the major source of FGF1 secretion. FGF1 expression increased and FGF2 decreased during adipocyte differentiation. Furthermore, FGF1 was not secreted into the circulation. Although FGF1 levels were 2-fold increased in obesity, they were unaltered by weight reduction. Only FGF1 and FGF2 induced a marked concentration-dependent phosphorylation of p44/42 in cultured human adipocytes.

CONCLUSIONS

Of the investigated FGFs, only FGF1 is secreted from sc WAT and predominantly so from the adipocyte fraction. The activity in adipocyte cultures and lack of secretion into the circulation suggest that FGF1 acts as an auto- or paracrine factor. FGF1 levels are increased in obesity but unaffected by weight reduction, suggesting a primary defect in obese individuals. In conclusion, FGF1 may play a superior role among the FGFs in sc WAT and obesity development.

Sprouty1 is a critical regulatory switch of mesenchymal stem cell lineage allocation

Development of bone and adipose tissue are linked processes arising from a common progenitor cell, but having an inverse relationship in disease conditions such as osteoporosis. Cellular differentiation of both tissues relies on growth factor cues, and we focus this study on Sprouty1 (Spry1), an inhibitor of growth factor signaling. We tested whether Spry1 can modify the development of fat cells through its activity in regulating growth factors known to be important for adipogenesis. We utilized conditional expression and genetic-null mouse models of Spry1 in adipocytes using the fatty acid binding promoter (aP2). Conditional deletion of Spry1 results in 10% increased body fat and decreased bone mass. This phenotype was rescued on Spry1 expression, which results in decreased body fat and increased bone mass. Ex vivo bone marrow experiments indicate Spry1 in bone marrow and adipose progenitor cells favors differentiation of osteoblasts at the expense of adipocytes by suppressing CEBP-beta and PPARgamma while up regulating TAZ. Age and gender-matched littermates expressing only Cre recombinase were used as controls. Spry1 is a critical regulator of adipocyte differentiation and mesenchymal stem cell (MSC) lineage allocation, potentially acting through regulation of CEBP-beta and TAZ.

DNA microarrays to define and search for genes associated with obesity

One of the major goals of this review was to identify obesity-specific gene profiles in animal models to help comprehend the pathogenic mechanisms and the prediction of the phenotypic outcomes of obesity and its associated metabolic diseases. The genomic examination of insulin-sensitive tissues, such as the adipose and hepatic tissues, has provided a wealth of information about the changes in gene expression in obesity and its associated metabolic diseases. The overexpression of genes related to inflammation, immune response, adhesion molecules, and lipid metabolism is a major characteristic of white adipose tissue, while the overexpression of the genes related to lipid metabolism, adipocyte differentiation, defense, and stress responses is noticeable in the non-alcoholic fatty liver of obese rodents. The hepatic-gene expression profiles led us to hypothesize that in obese rodents, the livers are supplied with large amounts of free fatty acids under conditions associated with obesity either through increased fatty acid biosynthesis or through decreased fatty acid oxidation, which may lead to increased mitochondrial respiratory activity. The wide list of genes that were identified in previous studies could be a source of potential therapeutic targets because most of these genes are involved in the key mechanisms of obesity development, from adipocyte differentiation to the disturbance of metabolism.

The effect of FGF-1 loaded alginate microbeads on neovascularization and adipogenesis in a vascular pedicle model of adipose tissue engineering

Engineered vascularized adipose tissue could serve as an alternative to traditional tissue reconstruction procedures. Adipose formation occurs in a coordinated fashion with neovascularization. Previous studies have shown that extracellular matrix-based materials supplemented with factors that stimulate neovascularization promote adipogenesis in a number of animal models. The present study examines the ability of fibroblast growth factor (FGF-1) delivered from alginate microbeads to induce neovascularization and adipogenesis in type I collagen gels in a vascular pedicle model of adipose tissue engineering. FGF-1 loaded microbeads stimulated greater vascular network formation in an in vitro 3D co-culture model than a single bolus of FGF-1. In in vivo studies, FGF-1 loaded beads suspended in collagen and implanted in a chamber surrounding the exposed femoral pedicle of a rat resulted in a significant increase in vascular density at 1 and 6 weeks in comparison to bolus administration of FGF-1. Staining for smooth muscle actin showed that over 48% of vessels had associated mural cells. While an increase in neovascularization was achieved, there was less than 3% adipose under any condition. These results show that delivery of FGF-1 from alginate beads stimulated a more persistent neovascularization response than bolus FGF-1 both in vitro and in vivo. However, unlike previous studies, this increased neovascularization did not result in adipogenesis. Future studies need to provide a better understanding of the relationship between neovascularization and adipogenesis in order to design advanced tissue engineering therapies.

The development and endocrine functions of adipose tissue

White adipose tissue is a mesenchymal tissue that begins developing in the fetus. Classically known for storing the body's fuel reserves, adipose tissue is now recognized as an endocrine organ. As such, the secretions from adipose tissue are known to affect several systems such as the vascular and immune systems and play major roles in metabolism. Numerous studies have shown nutrient or hormonal manipulations can greatly influence adipose tissue development. In addition, the associations between various disease states, such as insulin resistance and cardiovascular disease, and disregulation of adipose tissue seen in epidemiological and intervention studies are great. Evaluation of known adipokines suggests these factors secreted from adipose tissue play roles in several pathologies. As the identification of more adipokines and determination of their role in biological systems, and the interactions between adipocytes and other cells types continues, there is little doubt that we will gain a greater appreciation for a tissue once thought to simply store excess energy.