Figure 1.

Schematic of NAD⁺ consumption during metabolism of glucose vs. ketone bodies. Both glucose and ketone bodies lead to the formation of two molecules of acetyl-CoA which subsequently enter the citric acid cycle and participate in energy production. Although glucose provides a higher final yield of ATP, the consumption of NAD⁺ is significantly higher in this pathway (4:1). Glucose will reduce 111 molecules of NAD⁺ per 1000 molecules of ATP made, while ketone bodies reduce only 41 to produce a comparable amount of ATP. Decreased use of NAD⁺ by ketone bodies in energy production pathways could increase the amount of free NAD⁺ available as substrate for enzymes and cellular signaling processes.