Figure 4.

The proton NMR spectrum of alanine, lactate, and ¹³C labeling patterns of glutamate from the mouse hearts with different PDK inhibitor treatments. A, sources of ¹³C label on acetyl-CoA and glutamate in the TCA cycle. The ratio of labeled pyruvate/lactate over unlabeled endogenous sources is defined as B/A. The ratio of labeled pyruvate/lactate over labeled fatty acid is defined as B/C. B, the proton spectrum of methyl group on alanine and lactate. The main doublet (center two lines, ¹²C bonded ¹H resonances) and ¹³C directly bonded satellite doublets (on two ends) are indicated. The ⁴J_CH manifests as doublets close to the ¹²C-bonded resonances around 1.33 ppm and 1.47 ppm. C and D, the ¹³C signals of label enrichment on glutamate C4 (C) and glutamate C3 (D) are shown. The coupling pattern is shown as S, singlet; D, doublet; T, triplet; Q, quartet. The subscript numbers indicate carbons of the coupling. HP, hyperpolarized [1-¹³C]pyruvate. Endo, unlabeled pyruvate derived from endogenous sources. Note that no assumption of steady state is needed for this analysis.