Moderate Maternal Energy Restriction During Gestation in Pigs Attenuates Fetal Skeletal Muscle Development Through Changing Myogenic Gene Expression and Myofiber Characteristics.

Maternal undernutrition during gestation influences the development of the fetus, thereby increasing the risk of metabolic syndrome in adulthood. Skeletal muscle, one of the key insulin-responsive organs, is susceptible to maternal nutritional programming. This study aimed to evaluate the effect of moderate maternal energy restriction during gestation in pigs on basic events of fetal skeletal myogenesis. Primiparous, purebred Meishan sows were fed a control (normal energy intake) or a low-energy (LE) diet from mating to day 90 of gestation. Biochemical characteristics, myogenic gene expression, and myofiber characteristics were assessed in longissimus dorsi (LD) muscle of fetuses on days 55 and 90 of gestation. Fetal weights, myofiber density, and fetal umbilical vein serum triiodothyronine (T3) concentration decreased in LE group on both days 55 and 90 of gestation. The expression and activity of creatine kinase, the messenger RNA (mRNA) expression of myosin heavy chain ( MYH/ MyHC) genes ( MYH2 and MYH4), concentration of muscular DNA and protein, and protein expression of fast-MyHC isoforms were reduced in LD muscle of LE fetuses on day 55 or 90 of gestation. Meanwhile, myogenic gene expression was reduced in LE fetuses on day 55 or 90 of gestation, indicating the downregulation of myogenesis. Additionally, the exposure to LE diet led to increased isocitrate dehydrogenase activity and slow MyHC (MYH7) mRNA expression on day 90 of gestation, suggesting the elevation of oxidative muscle metabolism. These findings suggest that moderate energy restriction during gestation attenuates fetal skeletal muscle development in pigs, resulting in the delay of skeletal muscle differentiation and maturity.