| First Author | Matheny RW | Year | 2009 |
| Journal | Exp Biol Med (Maywood) | Volume | 234 |
| Issue | 2 | Pages | 164-70 |
| PubMed ID | 19064939 | Mgi Jnum | J:165003 |
| Mgi Id | MGI:4835871 | Doi | 10.3181/0808-RM-251 |
| Citation | Matheny RW, et al. (2009) Serum IGF-I-deficiency does not prevent compensatory skeletal muscle hypertrophy in resistance exercise. Exp Biol Med (Maywood) 234(2):164-70 |
| abstractText | The involvement of circulating insulin-like growth factor-I (IGF-I) in the skeletal muscle response to resistance exercise is currently unclear. To address this, we utilized the liver IGF-I-deficient (LID) mouse model, in which the igf1 gene has been disrupted in the hepatocytes, resulting in ~80% reduction in serum IGF-I. Twelve- to 13-month-old male LID and control (L/L) mice were subjected to 16 weeks of resistance training. Resistance exercise resulted in equal strength gains in both L/L and LID mice. Basal IGF-I mRNA levels were greater in LID muscles than in L/L, and exercise increased IGF-I mRNA in quadriceps, gastrocnemius, and plantaris muscles. LID mice had elevated tyrosine phosphorylation of IGF-IR and Stat5b, the latter possibly reflective of increased serum GH. Tyrosine phosphorylation of IGF-IR was increased, while phospho-Stat5b was reduced after resistance training of both wild-type and LID mice. These data suggest that: 1) performance and recovery in response to resistance training is normal even when there is severe deficiency of circulating IGF-I; and 2) upregulation of local IGF-I may be involved in the compensatory growth of muscle that occurs in response to resistance training. Decreased levels of p-Stat5b in exercised mice suggests that the upregulation of local IGF-I gene expression in response to exercise may be GH-independent. |
