Conclusions
Our data demonstrate that TET2 works as an epigenetic regulator of Rosi-mediated insulin sensitization and transcriptional regulation in adipocytes.
Methods
The expression of Tet genes was assessed in the fractionated adipocytes of chow- and high fat diet-fed C57/Bl6 mice using qPCR and western blotting. The effect of Tet2 gain- or loss-of-function in fully mature 3T3-L1 adipocytes in the presence/absence of Rosiglitazone (Rosi) and TNF-α on insulin sensitivity was using the insulin-stimulated glucose uptake and insulin signaling assays. Gene expression and DNA methylation analyses of PPARγ target genes was performed in the same setting. In addition, PPARγ reporter assays, co-immunoprecipitation assays, PPARγ ChIP-PCR analyses were performed.
Results
We found that adipose expression of TET2, alone among its family members, was significantly reduced in diet-induced insulin resistance. TET2 gain-of-function was sufficient to promote insulin sensitivity while loss-of-function was necessary to facilitate insulin sensitization in response to the PPARγ agonist Rosiglitazone (Rosi) in cultured adipocytes. Consistent with this, TET2 was required for Rosi-dependent gene activation of certain PPARγ targets accompanied by changes in DNA demethylation at the promoter regions. Furthermore, TET2 was necessary to sustain PPARγ binding to target loci upon activation with Rosi via physical interaction with PPARγ. Conclusions: Our data demonstrate that TET2 works as an epigenetic regulator of Rosi-mediated insulin sensitization and transcriptional regulation in adipocytes.