Contribution of the phosphagen system to postmortem muscle metabolism in AMP-activated protein kinase γ3 R200Q pig Longissimus muscle

Pigs with the AMP-activated protein kinase γ3 R200Q (AMPKγ3R200Q) mutation generate pork with low ultimate pH (pHu). We hypothesized that reducing muscle creatine (Cr) and phosphocreatine (PCr) may accelerate postmortem ATP consumption and prevent extended pH decline in AMPKγ3R200Q longissimus muscle. Wild type and AMPKγ3R200Q pigs were assigned to control diet or diet supplemented with the creatine analog β-guanidinopropionic acid (β-GPA, 1%) for 2 wk. β-GPA reduced muscle PCr (P = 0.006) and total Cr (P < 0.0001). In general, AMPKγ3R200Q + β-GPA exhibited more rapid metabolism than control, AMPKγ3R200Q, and β-GPA treatment, evidenced by more rapid loss of ATP, more rapid increase in IMP, and decreased pH during the first 90 min postmortem. Overall, pHu was similar despite elevated glycogen (AMPKγ3R200Q), reduced total Cr (β-GPA) or both (AMPKγ3R200Q + β-GPA). Thus, reducing muscle phosphagens did not affect pHu in AMPKγ3R200Q muscle, but it hastened ATP depletion and pH decline.