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-1α, PPARγ, 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-1α), peroxisome proliferator-activated receptor gamma (PPARγ) 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.