Mild mitochondrial uncoupling induces 3T3-L1 adipocyte de-differentiation by a PPARγ-independent mechanism, whereas TNFα-induced de-differentiation is PPARγ dependent

Abstract

Impairment of mitochondrial activity affects lipid-metabolizing tissues and mild mitochondrial uncoupling has been proposed as a possible strategy to fight obesity and associated diseases. In this report, we characterized the 3T3-L1-adipocyte `de-differentiation' induced by carbonyl cyanide (p-trifluoromethoxy)-phenylhydrazone (FCCP), a mitochondrial uncoupler. We found a decrease in triglyceride (TG) content in adipocytes incubated with this molecule. We next analyzed the expression of genes encoding adipogenic markers and effectors and compared the differentially expressed genes in adipocytes treated with FCCP or TNFα (a cytokine known to induce adipocyte de-differentiation). Furthermore, a significant decrease in the transcriptional activity of PPARγ and C/EBPα transcription factors was found in adipocytes with impaired mitochondrial activity. However, although these modifications were also found in TNFα-treated adipocytes, rosiglitazone and 9-cis retinoic acid (PPARγ and RXR ligands) were unable to prevent triglyceride loss in FCCP-treated cells. Metabolic assays also revealed that TG reduction could be mediated by a downregulation of lipid synthesis rather than an upregulation of fatty acid oxidation. Finally, lipolysis stimulated by the uncoupler also seems to contribute to the TG reduction, a process associated with perilipin A downregulation. These results highlight some new mechanisms that might potentially be involved in adipocyte de-differentiation initiated by a mitochondrial uncoupling.

A novel chemical uncoupler ameliorates obesity and related phenotypes in mice with diet-induced obesity by modulating energy expenditure and food intake

“…We investigated in vivo whether changes in the expression of genes involved in metabolism were at least partially mediated by cellautonomous effects in adipocytes. Consistent with the action of positive uncouplers described in a previous report [43], CZ5 enhanced Pgc-1α expression and reduced Leptin expression in adipocytes via incubation during differentiation (ESM Fig. 6).…”

Mesodermal developmental gene Tbx15 impairs adipocyte differentiation and mitochondrial respiration

“…In mature adipocytes, fat accumulation can be regulated by modulation of mitochondrial respiration in vitro and in vivo. Mild mitochondrial uncoupling by FCCP in 3T3-L1 cells decreases triglyceride content, without affecting PPARγ and C/EBPα expression (35). In mice, low doses of the mitochondrial uncoupling agent 2,4-dinitrophenol enhances tissue respiratory rates and decreases body weight (36), and ectopic expression of the uncoupling protein 1 (UCP1) in WAT protects Fig.…”

Adipose Tissue Inflammation and Insulin Resistance

“…While brown adipose tissue ( BAT) converts mitochondrial energy into heat during adaptative thermogenesis, characterization of WAT mitochondria function is still incipient (Forner et al, 2009;De Pauw et al, 2009). A recent in vivo proteomics analysis in mice WAT and BAT shows that there are quantitative and qualitative differences between the mitochondria from both tissues: BAT mitochondria are more similar to muscle mitochondria and WAT mitochondria express proteins associated with anabolic functions and proteins involved in the degradation of xenobiotics (Forner et al, 2009).…”

“…A recent in vivo proteomics analysis in mice WAT and BAT shows that there are quantitative and qualitative differences between the mitochondria from both tissues: BAT mitochondria are more similar to muscle mitochondria and WAT mitochondria express proteins associated with anabolic functions and proteins involved in the degradation of xenobiotics (Forner et al, 2009). Recent studies suggest that mitochondrial biogenesis and metabolism are implicated in the regulation of various processes in WAT, such as pre-adipocytes proliferation, adipogenesis, carbohydrate and lipid metabolism, adipocyte de-differentiation, TAG accumulation and acquirement of BATlike characteristics (De Pauw et al, 2009;Forner et al, 2009;Tedesco et al, 2010;Bordicchia et al, 2012;Koponen et al, 2012) and impaired mitochondrial biogenesis contributes to the onset of obesity and related metabolic disorders, such as insulin resistance (Tedesco et al, 2010).WAT mitochondrial biogenesis in mice is correlated with the up-regulation of genes involved in fatty acid oxidation and mitochondrial electron transport activity, boosting WAT catabolism (Granneman et al, 2005). Indeed, it was demonstrated that mitochondrial proliferation and remodeling are enhanced in 3T3-L1 cells during adipogenesis and the use of insulin sensitizers, such as rosiglitazone, leads to significant alterations in mitochondrial morphology and augmentation of the expression of several mitochondrial proteins (Wilson-Fritch et al, 2003).…”