Connective tissue growth factor inhibits adipocyte differentiation

Abstract

Adipocyte differentiation is a key process implicated in the pathogenesis of obesity and insulin resistance. Its regulation is triggered by a cascade of transcription factors, including the CCAAT/enhancer binding proteins (C/EBPs) and peroxisome proliferator-activated receptor-γ (PPARγ). Growth factors such as transforming growth factor-β1 (TGF-β1) are known to inhibit adipocyte differentiation in vitro, via the C/EBP pathway, and in vivo, but whether a downstream mediator of TGF-β1, connective tissue growth factor (CTGF), also known as CCN2, has a similar role is unknown. Mouse 3T3-L1 cells were differentiated into adipocytes by using standard methods, and effects and regulation of CTGF were studied. Intervention with recombinant human CTGF during differing stages of differentiation caused an inhibition in the development of the adipocyte phenotype, according to the gene expression of the differentiation markers adiponectin and PPARγ, as well as suppression of lipid accumulation and expression of the lipogenic enzyme glycerol-3-phosphate dehydrogenase. Whereas CTGF gene expression promptly fell by 90% as 3T3-L1 preadipocytes differentiated into mature adipocytes, CTGF mRNA expression was induced by added TGF-β1. CTGF applied to cells early in the course of differentiation inhibited total cell protein levels and nuclear localization of the β-isoform of C/EBP (C/EBP-β) and, subsequently, total cell C/EBP-α levels. CTGF also inhibited the adipocyte differentiation program in primary cultures of mouse preadipocytes. Expression of CTGF mRNA was twofold higher in the central fat depots of mice compared with subcutaneous fat, suggesting a potential role for CTGF in vivo. In summary, these data show that CTGF inhibits the adipocyte differentiation program.

Connective tissue growth factor/CCN-2 is upregulated in epididymal and subcutaneous fat depots in a dietary-induced obesity model

“…We have shown previously that, like TGF-␤1, CCN-2 is downregulated during adipocyte differentiation in vitro, and in this system exogenously added CTGF was effective in the inhibition of the adipocyte differentiation program (55). Our initial observations in chow-fed mice also showed that CCN-2 expression was twofold higher in the epididymal fat depot compared with the subcutaneous fat depot (55). Because a lower level of differentiation of fat cells in the epididymal depot was associated with the development of insulin resistance, the higher basal expression of CCN-2 at this site implicated a possible role for this protein in the negative regulation of adipocyte differentiation in vivo (55).…”

“…It is a multifunctional protein produced by a variety of cells, including endothelial cells, fibroblasts, cartilaginous cells, smooth muscle cells, and fat cells (16,24,25,27,28,41,54). We have shown previously that, like TGF-␤1, CCN-2 is downregulated during adipocyte differentiation in vitro, and in this system exogenously added CTGF was effective in the inhibition of the adipocyte differentiation program (55). Our initial observations in chow-fed mice also showed that CCN-2 expression was twofold higher in the epididymal fat depot compared with the subcutaneous fat depot (55).…”

CCN2 requires TGF-β signalling to regulate CCAAT/enhancer binding proteins and inhibit fat cell differentiation

“…In some cases differing CCN family members have been shown to have balancing, and antagonistic cell and tissue effects; for example, CCN3 may suppress CCN1 and CCN2-dependent activities (Riser et al 2009;Perbal 2013). We have previously shown that rhTGF-β1 induces CCN2 in adipocyte differentiation (Tan et al 2008). Future studies will be required to examine whether the CCN family of proteins are differentially regulated in fat cell differentiation, including by TGF-β and its downstream pathways, and whether effects of differing CCN proteins are complementary or antagonistic with eachother in FCD.…”

“…This process occurs via a range of temporal transcriptional cues, ultimately resulting in a mature adipocyte characterised by a unilocular lipid droplet (McLennan et al 2004;Tan et al 2008). These morphological and functional changes result from alterations in the expression and organisation of the extracellular matrix and components of cytoskeleton in adipose tissue.…”

Adverse effects of high glucose and free fatty acid on cardiomyocytes are mediated by connective tissue growth factor

“…RNA was then reverse transcribed to cDNA using Random Hexamer Primer (Invitrogen) and SuperScript III Reverse Transcriptase (Invitrogen). The resulting cDNA was analyzed by quantitative real-time PCR using Rotor Gene 6000 (Corbett Research), using SYBR green as fluorescence dye, as described previously (44). The following sequence-specific primers were used for rat CTGF, BNP, ␤-MHC, rat and mouse ANP, and ␣-SKA and 18s mRNA expression.…”