Insulin and glucosamine infusions increase O-linked N-acetyl-glucosamine in skeletal muscle proteins in vivo.
O-linked N-acetylglucosamine (O-GlcNAc) is an abundant posttranslational modification of serine/threonine residues of nuclear and cytoplasmic proteins. We determined whether insulin or coinfusion of glucosamine (GlcN) with insulin alters O-GlcNAc of skeletal muscle proteins. Three groups of conscious fasted rats received 6-hour infusions of either saline (BAS), insulin 18 mU/kg.min and saline (INS), or insulin and GlcN 30 micromol/kg.min (GLCN) during maintenance of normoglycemia. At 6 hours, the concentrations of muscle UDP-GlcNAc, UDP-N-acetylgalactosamine (UDP-GalNAc), UDP-glucose (UDP-Glc), UDP-galactose (UDP-Gal), glycogen, and N and O-linked GlcNAc (galactosyltransferase labeling followed by beta elimination) were measured in freeze-clamped abdominis muscle. Insulin increased whole-body glucose uptake from 49 +/- 5 to 239 +/- 8 micromol/kg.min (P < .001) and glycogen in abdominis muscle from 138 +/- 11 to 370 +/- 26 mmol/kg dry weight (P < .001). Insulin increased the amount of cytosolic N - and O-linked GlcNAc by 56% from 362 +/- 30 to 564 +/- 45 dpm/microg protein . 100 min (P < .02), and O-GlcNAc from 221 +/- 16 to 339 +/- 27 dpm/microg . 100 min (P < .02). Glycogen content was positively correlated with the amount of total (r = .90, P < .005) and O-linked GlcNAc in insulin-infused animals. Coinfusion of GlcN with insulin increased muscle UDP-GlcNAc about fourfold (100 +/- 6 nmol/g) compared with insulin (27 +/- 1, P < .001) or saline (25 +/- 1, P < .001) infusion. GlcN also decreased glucose uptake over 6 hours by 30% to 168 +/- 8 micromol/kg . min (P < .001 for GLCN v INS) and muscle glycogen to 292 +/- 24 mmol/kg dry weight (P < .05 for GLCN v INS). Both total (635 +/- 60 dpm/microg . 100 min, P < .002) and O-linked GlcNAc (375 +/- 36 dpm/microg . 100 min, P < .002) in the cytosol were significantly higher in GLCN rats (635 +/- 60 dpm/microg) versus BAS rats (P < .002). As in INS rats, muscle glycogen and O-GlcNAc were positively correlated in GLCN rats (r = .54, P < .05). Variation in total and O-linked GlcNAc in GLCN rats was due both to GlcN (P < .02) and to variation in the glycogen content (P < .005).
Yki-Järvinen
H
H
Department of Medicine, University of Texas Health Science Center at San Antonio, USA.
Virkamäki
A
A
Daniels
M C
MC
McClain
D
D
Gottschalk
W K
WK
D000117:Acetylglucosamine / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002236:Carbohydrate Conformation; D005944:Glucosamine / Q000031:analogs & derivatives / Q000097:blood / Q000494:pharmacology*; D006019:Glycolysis / Q000502:physiology; D007262:Infusions, Intravenous; D007263:Infusions, Parenteral; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014531:Uridine Diphosphate Galactose / Q000097:blood
D001786:Blood Glucose; D007328:Insulin; D009124:Muscle Proteins; C026712:UDP-glucosamine; D014531:Uridine Diphosphate Galactose; D005944:Glucosamine; D000117:Acetylglucosamine