Early-age feed restriction affects viability and gene expression of satellite cells isolated from the gastrocnemius muscle of broiler chicks

Background: Muscle growth depends on the fusion of proliferate satellite cells to existing myofibers. We reported previously that 0-14 day intermittent feeding led to persistent retardation in myofiber hypertrophy. However, how satellite cells respond to such nutritional insult has not been adequately elucidated. Results: One-day-old broiler chicks were allocated to control (Con, ad libitum feeding), intermittent feeding (IF, feed provided on alternate days) and re-feeding (RF, 2 days ad libitum feeding after 12 days of intermittent feeding) groups. Chickens were killed on Day 15 and satellite cells were isolated. When cultured, satellite cells from the IF group demonstrated significant retardation in proliferation and differentiation potential, while RF partly restored the proliferation rate and differentiation potential of the satellite cells. Significant up-regulation of insulin like growth factor I receptor (IGF-IR) (P< 0.05) and thyroid hormone receptor a (TRa) (P< 0.05), and down-regulation of growth hormone receptor (GHR) (P< 0.01) and IGF-I (P< 0.01) mRNA expression was observed in freshly isolated IF satellite cells when compared with Con cells. In RF cells, the mRNA expression of IGF-I was higher (P< 0.05) and of TRa was lower (P< 0.01) than in IF cells, suggesting that RF restored the mRNA expression of TRa and IGF-I, but not of GHR and IGF-IR. The Bax/Bcl-2 ratio tended to increase in the IF group, which was reversed in the RF group (P< 0.05), indicating that RF reduced the pro-apoptotic influence of IF. Moreover, no significant effect of T-3 was detected on cell survival in IF cells compared with Con (P< 0.001) or RF (P< 0.05) cells. Conclusions: These data suggest that early-age feed restriction inhibits the proliferation and differentiation of satellite cells, induces changes in mRNA expression of the GH/IGF-I and thyroid hormone receptors in satellite cells, as well as blunted sensitivity of satellite cells to T-3, and that RF partially reverses these effects. Thus, a moderate nutritional strategy for feed restriction should be chosen in early chick rearing systems.