Figure 6. Isotope tracing in ex vivo contracting muscle confirms higher nutrient flux to the TCA cycle after pulsatile weekly prednisone treatment.

(A) ¹³C incorporation into muscle metabolites was analyzed through mass resolution in an ex vivo contraction system. (B) Using either glucose, palmitate, or valine as source of ¹³C, weekly prednisone–treated muscles showed higher ¹³C incorporation than vehicle-treated muscles. In the same mass spectrometry analysis, ATP and phosphocreatine levels increased in prednisone-treated muscle. Histograms depict mean ± SEM. (stacked histograms), or single values and mean ± SEM; n = 3 mice/group. ^#P < 0.05 vs. vehicle, 2-way ANOVA; *P < 0.05 vs. vehicle, Welch’s t test (2-tailed).