Glucagon-like peptide-1 prevents beta cell glucolipotoxicity.
OBJECTIVE
We have provided evidence that glucagon-like peptide-1, a potential therapeutic agent in the treatment of diabetes, activates phosphatidylinositol-3 kinase/protein kinase B signalling in the pancreatic beta cell. Since this pathway promotes cell survival in a variety of systems, we tested whether glucagon-like peptide-1 protects beta cells against cell death induced by elevated glucose and/or non-esterified fatty acids.


METHODS
Human islets and INS832/13 cells were cultured at glucose concentrations of 5 or 25 mmol/l in the presence or absence of palmitate. Apoptosis was evaluated by monitoring DNA fragmentation and chromatin condensation. Wild-type and protein kinase B mutants were overexpressed in INS832/13 cells using adenoviruses. Nuclear factor-kappa B DNA binding was assayed by electrophoretic mobility shift assay.


RESULTS
In human pancreatic beta cells and INS832/13 cells, glucagon-like peptide-1 prevented beta cell apoptosis induced by elevated concentrations of (i) glucose (glucotoxicity), (ii) palmitate (lipotoxicity) and (iii) both glucose and palmitate (glucolipotoxicity). Overexpression of a dominant-negative protein kinase B suppressed the anti-apoptotic action of glucagon-like peptide-1 in INS832/13 cells, whereas a constitutively active protein kinase B prevented beta cell apoptosis induced by elevated glucose and palmitate. Glucagon-like peptide-1 enhanced nuclear factor-kappa B DNA binding activity and stimulated the expression of inhibitor of apoptosis protein-2 and Bcl-2, two anti-apoptotic genes under the control of nuclear factor-kappa B. Inhibition of nuclear factor-kappa B by BAY 11-7082 abolished the prevention of glucolipotoxicity by glucagon-like peptide-1.


CONCLUSIONS
The results demonstrate a potent protective effect of glucagon-like peptide-1 on beta cell gluco-, lipo- and glucolipotoxicity. This effect is mediated via protein kinase B activation and possibly its downstream target nuclear factor-kappa B.
Buteau
J
J
Molecular Nutrition Unit, Department of Nutrition, University of Montreal, CR-CHUM, Pavillon de Sève, Montreal, PQ, Canada.
El-Assaad
W
W
Rhodes
C J
CJ
Rosenberg
L
L
Joly
E
E
Prentki
M
M
D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D002478:Cells, Cultured; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D004763:Glucagon-Like Peptides; D005947:Glucose / Q000633:toxicity*; D006801:Humans; D007515:Islets of Langerhans / Q000166:cytology* / Q000187:drug effects / Q000473:pathology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D019308:Palmitic Acid / Q000633:toxicity*; D010446:Peptide Fragments / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D013450:Sulfones / Q000494:pharmacology
C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D016328:NF-kappa B; D009570:Nitriles; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D013450:Sulfones; C055453:glucagon-like peptide 1 (7-36)amide; D019308:Palmitic Acid; D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose