Fig. 4

Mechanisms that regenerate NAD⁺ to allow for continued metabolic flux through β-oxidation and the tricarboxylic acid cycle. First, we present a β-OH butyrate dehydrogenase 1 (BDH 1) activity and b BDH1 mRNA expression to understand the potential regeneration of NAD⁺ as acetoacetate is converted to β-OH butyrate by β-OH butyrate dehydrogenase 1. c BDH2 converts β-OH butyrate to acetoacetate and in turn reduces NAD⁺ to NADH. d By assessing the relative ratio of BDH1:BDH2 we can see that as fasting duration is extended so is the flux from acetoacetate to β-OH butyrate which will increase the regeneration of NAD+. Finally, we shown that uncoupling protein 2 expression increases with fasting duration (e), leading to decreased synthesis of ATP and decreased hepatic ATP content (f). ^a,bBars that do not share a common letter differ significantly (P < 0.05; n = 6)