Regulation of IGF-I, IGFBP-4 and IGFBP-5 gene expression by loading in mouse skeletal muscle.
Gene expression of IGF-I, IGFBP-4 and IGFBP-5 was studied in hindhimb skeletal muscle of mice, which were either overloaded or unloaded for 8 days. Overloading induced a 15% hypertrophy in soleus muscle associated with a 60% increase of IGF-I transcript levels and a doubling of IGFBP-4 mRNA levels. IGFBP-5 mRNA levels were decreased to one third of the control value. Changes in IGFBPs mRNA always preceded changes in IGF-I gene expression. Unloading by hindlimb suspension resulted in atrophy of soleus muscle (20%) and phenotype change towards the fast type associated with a transient decrease of IGF-I mRNA (30%) and a sustained increase (x2) of IGFBP-5 transcript. These alterations in IGFBPs expression, in unloaded or overloaded soleus, suggest that they may play a role in skeletal muscle adaptation to changes in loading.
Awede
B
B
Unité de Physiologie Générale des Muscles, Université Catholique de Louvain, 1200, Brussels, Belgium.
Thissen
J
J
Gailly
P
P
Lebacq
J
J
D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D005786:Gene Expression Regulation; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000096:biosynthesis* / Q000235:genetics; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000096:biosynthesis* / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000235:genetics; D019736:Prostheses and Implants; D016474:Weight-Bearing
D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D009124:Muscle Proteins; D007334:Insulin-Like Growth Factor I