Serum IGF-I levels and IGF-I gene splicing in muscle of healthy young males receiving rhGH.

Objective: Elevated growth hormone (GH) levels lead to increased circulating insulin-like growth factor-I (IGF-I), but the effects on localised muscle IGF-I splice variant expression is not known. The effects of rhGH administration, with or without an acute bout of high resistance exercise, were measured on serum IGF-I and on the mRNA levels of IGF-I splice variants in the vastus lateralis muscle of healthy young men.

Design: The study was a randomised double blind trial with a crossover design.

Different levels of neuroprotection by two insulin-like growth factor-I splice variants.

We compared the neuroprotective effects of a liver-type isoform of insulin-like growth factor-I (IGF-IEa) and its splice variant, mechano-growth factor (MGF), isolated from active skeletal muscle. cDNAs of these peptides were injected into the facial muscle of adult rats prior to facial nerve avulsion. This resulted in significant neuroprotection of 88% and 37%, respectively, of motoneurons compared to control plasmid and avulsion-only groups.