Figure 5.

Ketone and fatty acid oxidation. Schematic illustrates mitochondrial fatty acid and ketone oxidation pathways with associated enzymes and electron transfer proteins that increased (red fill), decreased (blue fill), or remained unchanged (gray fill) relative to CS from SL to A16 (corresponding to data in Table S2b; q < 0.05). Metabolites shown increased (red text), decreased (blue), or did not change (black) from SL to A16, or were not detected by LC/MS (gray). A, muscle and serum ketones. B, lower muscle 2-hydroxyglutarate (2-HG) correlates closely with α-KG at A16. C, muscle fatty acids and serum lipids. D, higher ADP-stimulated (OXPHOS) respiratory capacity of muscle fibers with palmitoylcarnitine + malate (fatty acid) correlates inversely with systemic respiratory exchange ratio at A16 (dotted line represents the 95% confidence interval). E, no change in muscle fiber respiration in the absence of ADP (LEAK) equates to higher palmitoylcarnitine OXPHOS coupling efficiency at A16. F, no change in muscle pyruvate- or succinate-linked OXPHOS coupling from SL to A16. See supporting Tables S1 and S2 for complete data and abbreviation listing. *, q < 0.05 versus SL in A and B; *, p < 0.05 by paired t test in D and E.