Age-Dependent Expression of MyHC Isoforms and Lipid Metabolism-Related Genes in the Longissimus Dorsi Muscle of Wild and Domestic Pigs

Simple Summary This comparative study found that postnatal myofiber differentiation in the longissimus dorsi muscle of wild pigs was accelerated and directed toward oxidative myofibers in which the MyHC-I, -IIa and -IIx genes were well expressed. In domestic pigs, the transformation was directed toward glycolytic myofibers in which the MyHC-IIb gene transcript was abundant. The myofiber succinate dehydrogenase (SDH) activity and lipid content reflected expression patterns of the MyHCs and not genes involved in lipid uptake and utilization (PGC-1, PPAR, LPL, and CPT-1B). MyHC myofiber characteristics reflect the effects of selection pressure and rearing conditions on the growth and lean meat content and may be valuable for establishing a balanced breeding scheme focused on improving meat quality traits. Abstract This study aimed to compare age-dependent changes in the relative expression of genes encoding myosin heavy chain (MyHC) isoforms and selected lipid metabolism-related genes in the longissimus dorsi muscle of wild pigs (WPs) and domestic pigs (DPs). Muscles sampled from postnatal day one as well as three-week-old and two-year-old animals were used in quantitative polymerase chain reaction (qPCR) assays, histological evaluations of succinate dehydrogenase (SDH) activity, and intra-myofiber lipid (IMFL) assessment. Expression of the MyHC isoforms displayed the most extensive age- and breed-dependent changes within the first three postnatal weeks. The MyHC(embry) level decreased significantly faster in the WPs than in the DPs. The relative MyHC-I and -IIa expression was significantly higher in the WPs, and MyHC-IIb was substantially higher in the DPs. The differences in MyHC expression corroborated the number of SDH-positive myofibers and IMFLs. Expression of the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1), peroxisome proliferator-activated receptor gamma (PPAR) and lipoprotein lipase (LPL) genes displayed only age-related variations. In summary, the evidence is provided for accelerated postnatal myofiber transformation directed towards oxidative myofibers in WPs. The SDH activity/staining intensity largely reflected the expression of MyHCs, and not genes involved in lipid uptake and utilization.