title: Different dietary energy intake affects skeletal muscle development through an Akt-dependent pathway in Dorper × Small Thin-Tailed crossbred ewe lambs.
abstract: The objective of this experiment was to investigate the mechanisms through which different levels of dietary energy affect postnatal skeletal muscle development in ewe lambs. Twelve Dorper × Small Thin-Tailed crossbred ewe lambs (100 d of age; 20 ± 0.5 kg BW) were selected randomly and divided into 2 groups in a completely randomized design. Animals were offered identical diets at 100% or 65% of ad libitum intake. Lambs were euthanized when BW in the ad libitum group reached 35 kg and the semitendinosus muscle was sampled. Final BW and skeletal muscle weight were decreased (P < 0.01) by feed restriction. Both muscle fiber size distribution and myofibril cross-sectional area were altered by feed restriction. Insulin-like growth factor 1 (IGF-1) messenger RNA (mRNA) content was decreased (P < 0.05) when lambs were underfed, whereas no difference for IGF-2 mRNA expression was observed (P > 0.05). Feed restriction altered phosphor-Akt protein abundance (P < 0.01). Moreover, the mammalian target of rapamycin (mTOR) pathway was inhibited by feed restriction, which was associated with decreased phosphor-mTOR, phosphorylated eukaryotic initiation factor 4E binding protein 1 (phosphor-4EBP1), and phosphorylated ribosomal protein S6 kinase (phosphor-S6K). Both mRNA expression of myostatin and its protein content were elevated in feed-restricted ewe lambs (P < 0.05). In addition, mRNA expression of both muscle RING finger 1 and muscle atrophy F-box was increased when ewe lambs were underfed. In summary, feed restriction in young growing ewe lambs attenuates skeletal muscle hypertrophy by inhibiting protein synthesis and increasing protein degradation, which may act through the Akt-dependent pathway.
authors: College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, Shanxi 030801, P. R. China.
authors: J X
authors: JX
authors: Zhao
authors: College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, Shanxi 030801, P. R. China.
authors: X D
authors: XD
authors: Liu
authors: College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, Shanxi 030801, P. R. China.
authors: K
authors: K
authors: Li
authors: College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, Shanxi 030801, P. R. China.
authors: W Z
authors: WZ
authors: Liu
authors: College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, Shanxi 030801, P. R. China.
authors: Y S
authors: YS
authors: Ren
authors: College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, Shanxi 030801, P. R. China. Electronic address: sxndzjx@163.com.
authors: J X
authors: JX
authors: Zhang
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004032:Diet / Q000662:veterinary*; D002149:Energy Intake; D005260:Female; D053858:Metabolic Networks and Pathways; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000254:growth & development*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism*; D012756:Sheep / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D009124:Muscle Proteins; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D000091162:AMP-Activated Protein Kinase Kinases
keywords: Akt; Feed restriction; Lamb; Skeletal muscle; mTOR