Figure 1.

Muscle fiber type composition is a major determinant in fatty acid-supported mitochondrial respiration. (A), (B), (C) Representative imaging of muscle fiber typing via Myosin Heavy Chain (MyHC) immunohistochemistry in predominately glycolytic (EDL), mixed (TA), and oxidative (Soleus) muscles. Magnification 20X. Scale bar 200 μm. (D) Mitochondrial respiration (JO₂) across a continuum of ATP free energy (ΔG_ATP) and (E) respiratory conductance in predominantly glycolytic, mixed, and oxidative muscles energized with palmitoylcarnitine/malate (PC/M). (F) Heatmap of abundance of proteins involved in mitochondrial fatty acid oxidation in glycolytic (EDL) and oxidative (SOL) muscles. (G) Relative abundance of long-chain acylcarnitines (LCACs) in mixed TA muscle. (H) Digital reconstitution of mass spectroscopy-based lipid scanning (nano-DESI) of palmitoleyl-carnitine (C16:1) in mixed TA muscle and (I) immunostaining for myosin heavy chain type 2A (green) and dystrophin (white) on consecutive muscle section. For (D), (E), and (G), data is presented as Mean ± SEM; n = 3–6 and ∗P ≤ 0.05 by 2-way ANOVA. For (F), data is presented as log2 abundance; n = 6 and ∗P ≤ 0.05 of adjusted p-value calculated by Benjamini Hochberg FDR correction.