Figure 4. Metformin inhibition of complex I requires an intact mitochondrial inner membrane potential.
(A) Complex I (2 mM malate, 10 mM pyruvate)-driven oxygen consumption rate of saponin permeabilized Control-HCT 116 p53−/− cells over time. At t = 5 min permeabilized cells were treated with either 10 mM ADP to induce respiration with an intact mitochondrial membrane potential or (B) 10 µM CCCP to induce respiration in absence of mitochondrial membrane potential. At t = 12 min 1 mM metformin was added to cells. At t = 48 min antimycin A was added. (C) Complex I (2 mM malate, 10 mM pyruvate)-driven oxygen consumption rate of saponin-permeabilized Control-HCT 116 p53−/− cells. At t = 5 min permeabilized cells were treated with either 10 mM ADP to induce respiration with an intact mitochondrial membrane potential or (D) 10 µM CCCP to induce respiration in absence of mitochondrial membrane potential. At t = 15 min, 1 μM rotenone was added to cells. At t = 25 min antimycin A was added. (E) Mitochondrial membrane potential measured by TMRE staining of Control-HCT116 p53−/− cells or (F) NDI1-HCT 116 p53−/− in the presence of 1 mM Metformin, 10 µM CCCP or 2.5 µM Oligomycin A. Error bars are SEM (n = 4). * indicates significance p<0.05.