Relationship between protein O-linked glycosylation and insulin-stimulated glucose transport in rat skeletal muscle following calorie restriction or exposure to O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate.
OBJECTIVE
Protein O-linked glycosylation is regulated in vivo by the concentration of hexosamine substrates. Calorie restriction (60% of ad libitum intake) for 20 days causes decreased UDP-N-acetylhexosamine levels and increased insulin-mediated glucose transport in rat skeletal muscle. Conversely, prolonged incubation (19 h) of muscle with O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenyl-carbamate (PUGNAc; an inhibitor of N-acetyl-beta-D-glucosaminidase) is characterized by increased O-linked glycosylation and insulin resistance. We aimed to determine the calorie restriction effect on O-linked glycosylation and characterize the temporal relationship between PUGNAc-induced O-linked glycosylation and insulin resistance.


OBJECTIVE
A calorie restriction protocol characterized by decreased muscle hexosamine levels will result in a global reduction in O-linked glycosylated proteins in muscle, and PUGNAc-induced insulin resistance will coincide with increased O-linked glycosylation.


METHODS
Plantaris muscle and liver from rats (ad libitum or calorie restricted) were analysed for O-linked glycosylation using two antibodies against different O-linked N-acetylglucosamine epitopes. Also, rat epitrochlearis muscles were incubated for 8.5 h +/- 100 mum PUGNAc prior to measurement of [(3)H]-3-O-methylglucose transport and O-linked glycosylation.


RESULTS
Calorie restriction did not alter protein O-linked glycosylated levels in muscle or liver. Incubation with PUGNAc for 8.5 h resulted in increased in O-linked glycosylation but unaltered basal or insulin-stimulated glucose transport.


CONCLUSIONS
The delay between O-linked glycosylation and insulin resistance in muscle incubated with PUGNAc suggests an indirect, relatively slow mechanism for insulin resistance. The effect of calorie restriction on insulin action in muscle is unlikely to be the direct result of a global change in protein O-linked glycosylation.
Arias
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EB
Division of Kinesiology, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, MI 48109, USA.
Cartee
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GD
D000117:Acetylglucosamine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D031204:Caloric Restriction; D004591:Electrophoresis, Polyacrylamide Gel; D005947:Glucose / Q000378:metabolism; D006031:Glycosylation / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance; D008099:Liver / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010091:Oximes / Q000494:pharmacology*; D048448:Phenylcarbamates / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344; D046509:Tissue Culture Techniques; D001619:beta-N-Acetylhexosaminidases / Q000037:antagonists & inhibitors
D007328:Insulin; D009124:Muscle Proteins; D010091:Oximes; D048448:Phenylcarbamates; C068836:N-acetylglucosaminono-1,5-lactone O-(phenylcarbamoyl)oxime; D001619:beta-N-Acetylhexosaminidases; D005947:Glucose; D000117:Acetylglucosamine