O-GlcNAc-selective-N-acetyl-beta-D-glucosaminidase activity and mRNA expression in muscle is related to glucosamine-induced insulin resistance.
Glucosamine (GlcN)-induced insulin resistance is associated with an increase in O-linked-N-acetylglucosaminylated modified proteins (O-GlcNAcylated proteins). The role played by O-GlcNAc-selective-N-acetyl-beta-D-glucosaminidase (O-GlcNAcase), which removes O-N-acetyl-glucosamine residues from O-GlcNAcylated proteins, has not yet been demonstrated. We investigated whether GlcN-induced whole-body insulin resistance is related to tissue O-GlcNAcase activity and mRNA expression. GlcN (30 mumol/kg/min) or physiological saline (control) was intravenously infused into Sprague-Dawley rats for 2 h. After GlcN treatment, rats were subjected to the following: intravenous glucose tolerance test, insulin tolerance test or removal of the liver, muscle and pancreas. GlcN was found to provoke hyperglycemia compared to control (8.6 +/- 0.41 vs. 4.82 +/- 0.17 mM, p < 0.001). The insulin resistance index (HOMA-IR) increased (15.76 +/- 1.47 vs. 10.14 +/- 1.41, p < 0.001) and the beta-cell function index (HOMA-beta) diminished (182.69 +/- 22.37 vs. 592.01 +/- 103, p < 0.001). Liver glucose concentration was higher in the GlcN group than in the control group (0.37 +/- 0.04 vs. 0.24 +/- 0.038 mmol/g dry weight, p < 0.001). Insulin release index (insulin/glucose) was less in the GlcN group than in the control (2.2 +/- 0.1 vs. 8 +/- 0.8 at 120 min, p < 0.001). In the GlcN group, muscle O-GlcNAcase activity diminished (0.28 +/- 0.019 vs. 0.36 +/- 0.018 nmol of p-nitrophenyl/mg protein/min, p < 0.001), and K(m) increased (1.51 +/- 0.11 vs. 1.12 +/- 0.1 mM, p < 0.001) compared to the control. In the GlcN group, O-GlcNAcase activity/mRNA expression was altered (0.6 +/- 0.07 vs. 1 +/- 0.09 of control, p < 0.05). In conclusion, O-GlcNAcase activity is posttranslationally inhibited during GlcN-induced insulin resistance.
Durán-Reyes
Genoveva
G
Unidad de Investigación Médica en Bioquímica, Centro Médico Nacional Siglo XXI, México DF, México.
Pascoe-Lira
Dalila
D
García-Macedo
Rebeca
R
Medina-Navarro
Rafael
R
Rosales-Torres
Ana María
AM
Vergara-Onofre
Marcela
M
Foyo-Niembro
Enrique
E
Gutiérrez-Rodríguez
Margarita Eugenia
ME
García-Gutiérrez
María Trinidad Adriana
MT
Valladares-Salgado
Adán
A
Kumate
Jesús
J
Cruz
Miguel
M
D000118:Acetylglucosaminidase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015971:Gene Expression Regulation, Enzymologic; D005944:Glucosamine / Q000633:toxicity*; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology*; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D001619:beta-N-Acetylhexosaminidases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; C110628:hexosaminidase C; D000118:Acetylglucosaminidase; D001619:beta-N-Acetylhexosaminidases; D005944:Glucosamine