Comparisons of longissimus muscle metabolic enzymes and muscle fiber types in Korean and western pig breeds

We compared differentially expressed genes and muscle fiber types in the longissimus muscles of Korean native pigs (KNP) and the western meat-producing breeds Landrace and Yorkshire. The KNP breed exhibited a higher muscle fat content and more red meat color as determined by the a∗ (redness) value (P < 0.01) and b∗ (yellowness) value (P < 0.05) compared to the western breeds. Using differential display RT-PCR, we detected two genes that were differentially expressed in skeletal muscle among the pig breeds. These genes were identified as NADH dehydrogenase subunit 1 and ATPase subunit 6 by cloning and sequencing analysis. Both of these genes are involved oxidative phosphorylation and therefore energy metabolism. The genes were more highly expressed in the KNP breed than in the other breeds, indicating that KNPs exhibit more oxidative metabolism than do the western breeds. We also analyzed the mRNA levels of myosin heavy-chain isoforms such as type I (oxidative), type IIb (glycolytic), and types IIa and IIx (intermediate) fibers using real-time RT-PCR. The mRNA levels of oxidative and intermediate fibers were elevated in the KNP breed, whereas the glycolytic fibers were more highly expressed in the Landrace and Yorkshire pigs. These results suggest that the elevated expression of the oxidation-related metabolism genes NADH dehydrogenase and ATPase is related to meat quality as indicated by a higher content of oxidative fibers and muscle fat, as well as redder meat color.