Diminished satellite cell fusion and S6K1 expression in myotubes derived from skeletal muscle of low birth weight neonatal pigs.
Low birth weight (LBWT) is consistently associated with impaired postnatal muscle growth in mammals. Satellite cell (SC)-mediated myonuclear incorporation precedes protein accumulation in the early stages of postnatal muscle development and growth. The objective of this study was to investigate proliferation and differentiation of SCs and the regulation of protein synthesis signaling in response to insulin-like growth factor (IGF)-I stimulation in SC-derived myotubes of LBWT neonatal pigs. SCs isolated fromLongissimus dorsimuscle of LBWT and NBWT pigs (3-d-old, n=8) were cultured and induced to proliferate and differentiate to myotubes in vitro. On day 3 of differentiation, myotubes were fasted in serum-free media for 3 h and treated with human recombinant R3-insulin-like growth factor-I (rh IGF-I) at 0, 25, and 50 ng × mL-1for 30 min. There was no difference in proliferation rates of SCs from LBWT and NBWT pigs. However, LBWT SC fusion was 15% lower (P≤0.05) without a difference inMyoDormyogeninmRNA expression in comparison with NBWT pigs, suggesting SCs are not intrinsically different between the two groups. IGF-Ι stimulation at physiological concentrations activated downstream effectors of mTOR similarly in myotubes from LBWT and NBWT pigs. However, abundance of ribosomal protein S6 kinase 1(S6K1) was lower in myotubes of LBWT compared to their NBWT siblings (P≤0.05). These results indicate that the modest reduction in SC fusion and S6K1 expression are not the major contributors to the impaired postnatal muscle growth of LBWT pigs.
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, 24061.
Ying
Y
Chen
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, 24061.
Haibo
H
Zhu
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, 24061.
Sydney R
SR
McCauley
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, 24061.
Lidan
L
Zhao
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, 24061.
Sally E
SE
Johnson
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, 24061.
Robert P
RP
Rhoads
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, 24061 elkadi@vt.edu.
Samer W
SW
El-Kadi
D000818:Animals; D000831:Animals, Newborn; D001724:Birth Weight; D002454:Cell Differentiation; D002459:Cell Fusion; D049109:Cell Proliferation; D005260:Female; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D061251:Primary Cell Culture; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism*; D015398:Signal Transduction; D013552:Swine
D019893:Ribosomal Protein S6 Kinases
IGF‐I; low birth weight; satellite cells; skeletal muscle growth