The influence of genetic background on the induction of oxidative stress and impaired insulin secretion in mouse islets.
OBJECTIVE
We determined whether high-glucose-induced beta cell dysfunction is associated with oxidative stress in the DBA/2 mouse, a mouse strain susceptible to islet failure.


METHODS
Glucose- and non-glucose-mediated insulin secretion from the islets of DBA/2 and control C57BL/6 mice was determined following a 48-h exposure to high glucose. Flux via the hexosamine biosynthesis pathway was assessed by determining O-glycosylated protein levels. Oxidative stress was determined by measuring hydrogen peroxide levels and the expression of anti-oxidant enzymes.


RESULTS
Exposure to high glucose levels impaired glucose-stimulated insulin secretion in DBA/2 islets but not C57BL/6 islets, and this was associated with reduced islet insulin content and lower ATP levels than in C57BL/6 islets. Exposure of islets to glucosamine for 48 h mimicked the effects of high glucose on insulin secretion in the DBA/2 islets. High glucose exposure elevated O-glycosylated proteins; however, this occurred in islets from both strains, excluding a role for O-glycosylation in the impairment of DBA/2 insulin secretion. Additionally, both glucosamine and high glucose caused an increase in hydrogen peroxide in DBA/2 islets but not in C57BL/6 islets, an effect prevented by the antioxidant N-acetyl-L: -cysteine. Interestingly, while glutathione peroxidase and catalase expression was comparable between the two strains, the antioxidant enzyme manganese superoxide dismutase, which converts superoxide to hydrogen peroxide, was increased in DBA/2 islets, possibly explaining the increase in hydrogen peroxide levels.


CONCLUSIONS
Chronic high glucose culture caused an impairment in glucose-stimulated insulin secretion in DBA/2 islets, which have a genetic predisposition to failure, and this may be the result of oxidative stress.
Zraika
S
S
Department of Medicine (AH/NH), University of Melbourne, Heidelberg Repatriation Hospital, Heidelberg Heights, VIC 3081, Australia.
Aston-Mourney
K
K
Laybutt
D R
DR
Kebede
M
M
Dunlop
M E
ME
Proietto
J
J
Andrikopoulos
S
S
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D018929:Cell Culture Techniques; D002470:Cell Survival; D017931:DNA Primers; D005786:Gene Expression Regulation; D005947:Glucose / Q000494:pharmacology; D006031:Glycosylation; D006861:Hydrogen Peroxide / Q000032:analysis; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA / Q000235:genetics; D018384:Oxidative Stress / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods
D017931:DNA Primers; D007328:Insulin; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D005947:Glucose