Extended Data Figure 2.

Effect of guanide/biguanide treatment on enzymes involved in pyruvate metabolism, redox regulation, and the malate-aspartate shuttle and on complex I mediated respiration. (a) Lactate enters metabolism through LDH via a redox-dependent reaction into the pyruvate pool. Pyruvate lies at the intersection of alanine influx, glycolysis, citric acid cycle and gluconeogenic flux. (b) Guanides/biguanides did not affect pyruvate carboxylase (PC) activity, compared to the known inhibitor coenzyme A, (c) and did not affect citrate synthase activity. (d) ALAT activity was also unaffected. (e) Guanides/biguanides did not affect MDH activity, (f) ASAT activity or (g) total shuttle rates. (h) Metformin had no effect on complex I mediated respiration in isolated mitochondria at concentrations less than 5 mM, and induced a slight increase in complex II respiration. Data are mean ± SEM, (n=5 technical replicates). * P<0.05, **P<0.01, ***P<0.001 by unpaired t-test.