With an excess of NADH, three enzymes of the Citric Acid Cycle are inhibited (citrate synthase, isocitrate
dehydrogenase, and alpha-ketoglutarate
dehydrogenase) essentially shutting it down. Pyruvate (the end product of glycolysis) starts to accumulate, and the excess NADH drives lactate dehydrogenase to produce lactate from pyruvate in order to regenerate NAD+ and sustain life.