Selected Contribution: IGF-I antibody prevents increases in protein synthesis in epitrochlearis muscles from refed, diabetic rats.
The purpose of this study was to examine whether immune neutralization of muscle-produced insulin-like growth factor I (IGF-I) would prevent an appropriate anabolic response to refeeding in diabetic rats. Male Sprague-Dawley rats were made diabetic by partial pancreatectomy and were randomly assigned to be either control-fed, fasted, or fasted-refed (n = 7-8 per group). Diabetes decreased rates of protein synthesis and increased rates of protein degradation in incubated epitrochlearis muscles (P < 0.05). In both groups of rats, fasting lowered protein synthesis and increased proteolysis and subsequent refeeding returned both parameters to near basal values (P < 0.05). Neutralization of muscle IGF-I by the addition of IGF-I antibody to the incubation medium reduced protein synthesis an average of 22% for all groups (P < 0.05). However, rates of protein degradation were not affected. In nondiabetic rats, refeeding increased protein synthesis in both control and antibody-treated muscles (P < 0.05). Refeeding also increased protein synthesis in the control muscles from diabetic rats (P < 0.01). In contrast, muscles from diabetic rats that were incubated with anti-IGF-I did not increase protein synthesis in response to refeeding. These data suggest that immune neutralization of muscle IGF-I in hypoinsulinemic rats negated the ability of endogenous IGF-I to promote protein synthesis and thereby prevented an appropriate anabolic response.
Fedele
M J
MJ
Noll Physiological Research Center, Pennsylvania State University, University Park 16802, USA. mfedele@uic.edu
Vary
T C
TC
Farrell
P A
PA
D000818:Animals; D000906:Antibodies / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004435:Eating; D005215:Fasting; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000502:physiology*; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D010180:Pancreatectomy; D010649:Phenylalanine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D014633:Valine / Q000378:metabolism
D000906:Antibodies; D009124:Muscle Proteins; D010649:Phenylalanine; D007334:Insulin-Like Growth Factor I; D007930:Leucine; D014633:Valine