Figure 1.

Metformin decreased NAD+ levels after 1 day of treatment and can partially be blocked by PARP inhibitors. (A) NAD+ levels of MCF7 cells that were treated with 8 mM metformin as indicated. (B) NAD+ levels of MCF7 cells that were pretreated with a PARP inhibitor (10 μM) for 1 day and treated subsequently with metformin (8 mM) for 1 or 2 additional days in the presence of the PARP inhibitor. The same number of cells was used for each sample in the NAD assay (true for all subsequent NAD+ assays). (* and # indicate significant difference between groups with p < 0.05.) Lanes labeled Con represent cells not treated with metformin and lanes labeled Met denote those treated with metformin. Lanes labeled PARP indicate cells treated with a PARP inhibitor and DMSO indicates control samples not treated with PARP inhibitor.