Protein kinase B/Akt signalling is required for palmitate-induced beta-cell lipotoxicity.
OBJECTIVE
This study was conducted to clarify cell death and survival signals in pancreatic beta-cell lipotoxicity.


METHODS
Rat insulinoma INS-1 cells, with or without expression of dominant-negative mutant of Akt (K179M), were cultured with palmitate (C16:0) or oleate (C18:1) and cell numbers were determined by 0.2% eosin dye exclusion assay. The Akt activity was determined by anti-3'-phospho-inositide-dependent protein kinase (Akt)/protein kinase B (PKB) or anti-phospho-Akt (Serine 473) immunoblotting, and nuclear protein nuclear factor-kB (NF-kappaB)-binding activity was by supershift analysis.


RESULTS
Twenty-four hours treatment with palmitate increased the INS-1 cell number at 0.1-0.2 mM but decreased the cell number at 0.5-1 mM. Oleate did not affect cell number at 0.1-1.0 mM. Palmitate dose-dependently increased phosphorylation of 473th serine in Akt/PKB. The K179M form of Akt/PKB abolished palmitate-induced cell proliferation at the low dose and death at the high dose. Nuclear protein NF-kappaB binding was enhanced at 0.2 and 0.5 mM of palmitate but decreased at 1.0 mM.


CONCLUSIONS
Results suggest that Akt/PKB signalling is involved in palmitate-induced cell death and survival of pancreatic beta cell.
Higa
M
M
Second Department of Internal Medicine, Faculty of Medicine, University of the Ryukyus, Okinawa, Japan.
Shimabukuro
M
M
Shimajiri
Y
Y
Takasu
N
N
Shinjyo
T
T
Inaba
T
T
D000818:Animals; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D024202:Electrophoretic Mobility Shift Assay; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000633:toxicity; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D007340:Insulinoma / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D019301:Oleic Acid / Q000494:pharmacology / Q000633:toxicity; D019308:Palmitic Acid / Q000494:pharmacology* / Q000633:toxicity; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D014280:Triglycerides / Q000378:metabolism
D004791:Enzyme Inhibitors; D016328:NF-kappa B; D014280:Triglycerides; D019301:Oleic Acid; D019308:Palmitic Acid; D051057:Proto-Oncogene Proteins c-akt