Adipose tissue transcriptomic signature highlights the pathological relevance of extracellular matrix in human obesity

Analysis of the transcriptomic signature of white adipose tissue in obese human subjects revealed increased interstitial fibrosis and an infiltration of inflammatory cells into the tissue

Interactions entre les préadipocytes et les macrophages au sein du tissu adipeux humain

Le tissu adipeux obèse produit davantage de facteurs inflammatoires notamment par sa fraction stroma vasculaire incluant les macrophages. En présence de facteurs sécrétés par les macrophages, les préadipocytes humains développent, outre une altération de leur différenciation, un état inflammatoire ainsi que des capacités accrues à proliférer et à migrer. Ces modifications phénotypiques des préadipocytes s accompagnent d un profond remodelage de leur matrice extracellulaire. Des gènes d intérêt potentiel dans l obésité ont également été identifiés : CCL5 qui jouerait un rôle dans l accumulation et la survie des macrophages du tissu adipeux et l inhibine beta A dont nous montrons l activité profibrotique dans les préadipocytes. Ainsi, au cours de l obésité, le tissu adipeux serait le site d interactions majeures entre les préadipocytes et les macrophages, contribuant probablement aux perturbations morphologiques et fonctionnelles de ce tissu, à l instar de l apparition de fibrose.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Monitoring the activation state of the insulin-like growth factor-1 receptor and its interaction with protein tyrosine phosphatase 1B using bioluminescence resonance energy transfer

ABSTRACT We have developed two bioluminescence resonance energy transfer (BRET)-based approaches to monitor 1) ligand-induced conformational changes within partially purified insulinlike growth factor-1 (IGF-1) receptors (IGF1R) and 2) IGF1R interaction with a substrate-trapping mutant of protein tyrosine phosphatase 1B (PTP1B-D181A) in living cells. In the first assay, human IGF1R fused to Renilla reniformis luciferase (Rluc) or yellow fluorescent protein (YFP) were cotransfected in human embryonic kidney (HEK)-293 cells. The chimeric receptors were then partially purified by wheat germ lectin chromatography, and BRET measurements were performed in vitro. In the second assay, BRET measurements were performed on living HEK-293 cells cotransfected with IGF1R-Rluc and YFP-PTP1B-D181A. Ligand-induced conformational changes within the IGF1R and interaction of the IGF1R with PTP1B could be detected as an energy transfer between Rluc and YFP. Doseresponse experiments with IGF-1, IGF-2, and insulin demonstrated that the effects of these ligands on BRET correlate well with their known pharmacological properties toward the IGF1R. Inhibition of IGF1R autophosphorylation by the tyrphostin AG1024 (3-bromo-5-t-butyl-4-hydroxy-benzylidenemalonitrile) resulted in the inhibition of IGF1-induced BRET signal between the IGF1R and PTP1B. In addition, an anti-IGF1R antibody known to inhibit the biological effects of IGF-1 inhibited ligandinduced BRET signal within the IGF1R, as well as between IGF1R and PTP1B. This inhibition of BRET signal paralleled the inhibition of the ligand-induced autophosphorylation of the IGF1R by this antibody. In conclusion, these BRET-based assays permit 1) the rapid evaluation of the effects of agonists or inhibitory molecules on IGF1R activation and 2) the analysis of the regulation of IGF1R-PTP1B interaction in living cells. The insulin-like growth factor-1 receptor (IGF1R) is an ubiquitously expressed plasma membrane receptor. IGF-1 and IGF-2 are high-affinity ligands for this receptor. The IGF1R is composed of two extracellular ␣-chains that bind the ligand and two extracellular transmembrane and intracellular ␤-chains that possess intrinsic tyrosine kinase activity. These chains are held together by disulfide bonds. The binding of ligands induces the autophosphorylation of the IGF1R ␤-chains on tyrosine residues and thereby stimulates the tyrosine kinase activity of the IGF1R toward intracellular substrates The IGF1R has been implicated in several physiological and pathophysiological processes. By increasing plasma levels of IGF-1, growth hormone confers on the IGF1R a major function in the transmission of its physiological effects on growth. IGF1R also represents a therapeutic target for sevThis work was supported by the Association pour la Recherche sur le Cancer (Grant 4453) and the Ligue contre le Cancer (Comité de Paris, Grants 75-02/ RS95 and R0475-75). Article, publication date, and citation information can be found a

Macrophage-secreted factors impair human adipogenesis: involvement of proinflammatory state in preadipocytes.: Human adipogenesis regulation by macrophages

Obesity is considered a chronic low-grade inflammatory state. The white adipose tissue produces a variety of inflammation-related proteins whose expression is increased in obese subjects. The nonadipose cell fraction, which includes infiltrated macrophages, is a determinant source of inflammation-related molecules within the adipose tissue. Our working hypothesis is that macrophage infiltration affects fat expansion through a paracrine action on adipocyte differentiation. Human primary preadipocytes were then differentiated in the presence of conditioned media obtained from macrophages differentiated from blood monocytes. Preadipocytes treated by macrophage-conditioned medium displayed marked reduction of adipogenesis as assessed by decreased cellular lipid accumulation and reduced gene expression of adipogenic and lipogenic markers. In addition to this effect, the activation of macrophages by lipopolysaccharides stimulated nuclear factor kappaB signaling, increased gene expression and release of proinflammatory cytokines and chemokines, and induced preadipocyte proliferation. This phenomenon was associated with increased cyclin D1 gene expression and maintenance of the fibronectin-rich matrix. Anti-TNFalpha neutralizing antibody inhibits the inflammatory state of preadipocytes positioning TNFalpha as an important mediator of inflammation in preadipocytes. Strikingly, conditioned media produced by macrophages isolated from human adipose tissue exerted comparable effects with activated macrophages, i.e. decreased adipogenesis and increased inflammatory state in the preadipocytes. These data show that macrophage-secreted factors inhibit the formation of mature adipocytes, suggesting possible role in limiting adipose tissue expansion in humans

Set-up of Z- and E-guggulsterones purification method from guggul-gum extracts by liquid chromatography and study of their activities on human preadipocytes differentiation

The rising prevalence of obesity within both industrialized and emerging societies is a major public health problem. Indeed obesity is a usual risk factor in the development of metabolic and cardiovascular diseases which nowadays rank among the highest causes of premature death. Therefore, modulating fat mass expansion represents a worldwide challenge. In this context, adipocyte differentiation, which corresponds to the cellular transition of a fibroblastic cell (the preadipocyte) to a highly specialized cell accumulating triglycerides (the adipocyte), is a decisive process in the expansion of adipose tissue during life span and consequently, in the development of obesity. Adipogenesis markers such as PPARg2, C/EBPa, lipoprotein lipase (LPL), perilipin (PLIN) and the adipokines (leptin and adinopectin) are known to be expressed throughout the different stages of adipocyte differentiation. Guggulsterones are the principal bioactive steroidal components found in the oleoresin (guggul gum) collected from the indian guggul tree, Commiphora mukul (Hook, ex Stocks) Engl. The objective of this study was to investigate the effects of the two purified diastereoisomeric forms of guggulsterones (Z- and E-) on the human preadipocytes proliferation and differentiation

The effects of purified Z- and E-guggulsterones from guggul-gum extract on human preadipocytes proliferation and differentiation through the study of gene expression of adipose markers.

The rising prevalence of obesity within both industrialized and emerging societies is a major public health problem. Indeed obesity is a usual risk factor in the development of metabolic and cardiovascular diseases which nowadays rank among the highest causes of premature death. Therefore, modulating fat mass expansion represents a worldwide challenge. In this context, adipocyte differentiation, which corresponds to the cellular transition of a fibroblastic cell (the preadipocyte) to a highly specialized cell accumulating triglycerides (the adipocyte), is a decisive process in the expansion of adipose tissue during life span and consequently, in the development of obesity. Adipogenesis markers such as PPARg2, C/EBPa, lipoprotein lipase (LPL), perilipin (PLIN) and the adipokines (leptin and adinopectin) are known to be expressed throughout the different stages of adipocyte differentiation. Guggulsterones are the principal bioactive steroidal components found in the oleoresin (guggul gum) collected from the indian guggul tree, Commiphora mukul (Hook, ex Stocks) Engl. The objective of this study was to investigate the effects of the two purified diastereoisomeric forms of guggulsterones (Z- and E-) on the human preadipocytes proliferation and differentiation