Abstract
BackgroundIntrauterine growth-restricted (IUGR) neonates impair postnatal skeletal muscle growth. The aim of this study was to investigate whether high nutrient intake (HNI) during the suckling period could improve muscle growth and metabolic status of IUGR pigs.MethodsTwelve pairs of IUGR and normal birth weight (NBW) pigs (7 days old) were randomly assigned to adequate nutrient intake and HNI formula milk groups. Psoas major (PM) muscle sample was obtained after 21 days of rearing.ResultsIUGR decreased cross-sectional areas (CSA) and myofiber numbers, activity of lactate dehydrogenase (LDH), and mRNA expression of insulin-like growth factor 1 (IGF-1), IGF-1 receptor (IGF-1R), mammalian target of rapamycin (mTOR), ribosomal protein s6 (RPS6), eukaryotic translation initiation factor 4E (eIF4E), protein expression of phosphorylated mTOR (P-mTOR), and phosphorylated protein kinase B (P-Akt) in the PM muscle of pigs. Irrespective of birth weight, HNI increased muscle weight and CSA, the concentration of RNA, and ratio of RNA to DNA, as well as ratio of LDH to β-hydroxy-acyl-CoA-dehydrogenase in the PM muscle of pigs. Furthermore, HNI increased percentages of MyHC IIb, mRNA expression of IGF-1, IGF-1R, Akt, mTOR, RPS6, and eIF4E, as well as protein expression of P-mTOR, P-Akt, P-RPS6, and P-eIF4E in the PM muscle of pigs.ConclusionThe present findings suggest that high nutrient intake during the suckling period could improve skeletal muscle growth and maturity, which is associated with increasing the expression of protein deposition-related genes and accelerating the development of glycolytic-type myofiber in pigs.
Highlights
Intrauterine growth-restricted (IUGR) neonates impair postnatal skeletal muscle growth
We investigated the effects of high nutrient intake (HNI) on skeletal muscle growth, metabolic status, and the expressions of muscle growth and development-related genes of IUGR pigs
Phosphorylation of mammalian target of rapamycin (mTOR) on Ser2448 is positively related to the activity of mTOR [49]. Consistent with this observation, we found that HNI resulted in an increase of the protein expressions of phosphorylated mTOR (P-mTOR) in the Psoas major (PM) muscle of pigs, suggesting that HNI during the early postnatal period enhanced the activation of elements involved in the mTOR protein synthesis pathway
Summary
Intrauterine growth-restricted (IUGR) neonates impair postnatal skeletal muscle growth. The aim of this study was to investigate whether high nutrient intake (HNI) during the suckling period could improve muscle growth and metabolic status of IUGR pigs. Epidemiological studies have demonstrated that intrauterine growth-restricted (IUGR) neonates are associated with the higher morbidity and mortality during the early life period, as well as a greater risk of the metabolic syndrome in adult life [1, 2]. Previous studies showed that IUGR had negative impacts on the growth and development of skeletal muscle in pigs, including reduced skeletal muscle mass [3] and total myofiber number [4], Postnatal muscle growth is mostly determined by the total myofiber number and fiber CSAs [9], as well as controlled by many signaling pathways in vivo [10].
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