(A) In vivo cardiac 13C spectrum recorded after the injection and metabolism of hyperpolarized [1-13C]butyrate in the fed and fasted state (n=6 in both groups). (B) A sum spectrum with expansion to show the downstream metabolites of the co-injection experiments with both HP butyrate and pyruvate (n=7 in both groups). (C-E) The normalized signals relative to the injected substrate [1-13C]butyrate associated with metabolites of [1-13C]butyrate in the 4 experimental conditions. (F & G) Relative ratios of acetoacetate and glutamate to that of acetylcarnitine. The signals of glutamate and acetoacetate demonstrate the competition between pyruvate and butyrate for the production of acetyl-CoA as well as the impact of pyruvate on pseudoketogenesis. (&) Two way ANOVA reports a significant overall effect of the factor of nutritional state on the ratios of acetoacetate to butyrate and glutamate to butyrate. Error bars indicate +/- SEM.