Figure 3. Effects of Leu (0.5 mM or 10 mM), KIC (0.5 mM or 10 mM), and HMB (50 μM) on (A–B) oxygen consumption rate (OCR) of C2C12 myotubes and (C) protein expression of AMPKα and PGC-α. (A) Represents mitochondrial OCR curves obtained from different conditions. (B) Basal, basal respiration; H+ leak; ATP, ATP production; Max, maximum respiration; SRC, spare respiration capacity; and NMR, non-mitochondrial respiration of C2C12 myotubes under different treatments, respectively. Results are expressed as mean ± SEM. Different letters (a, b, c) indicated significant differences (P < 0.05). CON, control; HMB, β-hydroxy-β-methyl butyrate; KIC, α-ketoisocaproate; Leu, leucine.