FIG. 4.

Increased dosage of SirT1 suppresses GLP-1–induced β-cell proliferation. A: SirT1 protein levels were evaluated by Western blot after transfection with wild-type (WT) or dominant-negative (DN)-SirT1. GFP was used as control. B: The effect of SirT1 overexpression on β-cell proliferation was evaluated by BrdU incorporation. INS832/13 cells were transfected with WT-SirT1, DN-SirT1, or control GFP for 24 h and then incubated in the presence or absence of GLP-1 (10 nmol/L) or 10% serum for an additional 24-h period. Results represent mean ± SEM of three separate experiments carried out in triplicate. *P < 0.05 compared with the respective control.