Sirt1-mediated repression of Ucp2 expression is lost in aged BESTO islets

One possible explanation for the loss of glucose-responsive phenotypes in the aged BESTO mice is that the Sirt1 transgene is no longer overexpressed. However, we found that Sirt1 protein levels were still high in islets isolated from aged BESTO mice compared to controls, comparable to the level of overexpression in the young BESTO islets (Fig. 2A, top panels).