Lessons to learn about postmortem metabolism using the AMPKγ3R200Q mutation in the pig

The development of pork quality attributes — including color, water holding capacity, and texture — are controlled largely by the rate and extent of postmortem pH decline. In turn, pH decline is thought to follow the anaerobic degradation of glycogen to “lactic acid”. The “Hampshire effect” or Rendement Napole (RN−) pig, which has elevated muscle glycogen, propagated the widespread use of “glycolytic potential” to describe muscle's capacity for postmortem glycolysis. Since the evolution of glycolytic potential, there have been great strides in molecular and technical capabilities. Hence, it must be appreciated that the RN− pig possesses a mutation in the gene encoding the AMP-activated protein kinase (AMPK) γ3 subunit, which results in a non-conservative amino acid substitution (R200Q). AMPK, a major energy sensor in skeletal muscle, influences enzyme activity, gene and protein expression, fiber type, and mitochondrial biogenesis. The utility of glycolytic potential as indicator of ultimate pH should be reevaluated in the context of the metabolic differences between AMPKγ3 mutated and normal muscle. Understanding the metabolism and energetics in AMPKγ3 mutated muscle may provide insight into the mechanisms influencing the rate and extent of postmortem metabolism.

Research Highlights
► RN- pigs exhibit high muscle glycolytic potential and meat with low ultimate pH.
► ATP hydrolysis, not “lactic acid”, may be the source of proton load.
► RN- pigs possess a mutation in the energy sensor, AMP-activated protein kinase.
► AMP-activated protein kinase influences energetics and phenotype.
► Altered muscle energy metabolism of RN- pigs may influence postmortem pH decline.