The non-peptidyl low molecular weight radical scavenger IAC protects human pancreatic islets from lipotoxicity.
BACKGROUND
Chronic exposure to high free fatty acids (FFA) can lead to irreversible damage of beta-cell accounting for impaired insulin secretion. Multiple mechanisms concur in generating the damage, but activation of oxidative stress may contribute to the final toxic effect. To better understand the phenomenon of lipotoxicity in human beta-cells, we evaluated the effects of 24-h pre-culture with 1.0 mmol/l FFA on the function, survival and mRNA expression of several enzymes involved in the generation and scavenging of reactive oxygen species (ROS).


METHODS
Human islets, prepared by collagenase digestion and density gradient purification from 9 pancreases of multiorgan donors, were incubated for 24-h in the presence 1.0 mmol/l long-chain mixture (oleate:palmitate, 2:1) FFA, with or without 100 micromol/l IAC, a non-peptidyl low molecular weight radical scavenger. At the end of incubation period, insulin secretion was measured by static incubation, and mRNA expression of insulin, Cu/Zn-SOD, Mn-SOD, Catalase, Glutathione peroxidase (GSH-px) and HO-1 by quantitative Real-Time RT-PCR. Nitrotyrosine levels were determined by an ELISA technique.


RESULTS
As compared to control incubation (Ctrl, no FFA), exposure to FFA was associated with impaired insulin release and reduced insulin mRNA expression. The presence of IAC in the incubation medium increased insulin release significantly and prevented changes in mRNA expression. Exposure to FFA was associated with oxidative stress as indicated by a significant accumulation of nitrotyrosine and IAC restrained such an increase. mRNA expression of Cu/Zn-SOD, Mn-SOD, Catalase, GSH-Px, and HO-1 were all modified after FFA exposure. These changes were partially prevented in the presence of IAC.


CONCLUSIONS
In human islets 24-h exposure to high FFA causes oxidative stress associated with changes of several enzymes involved in ROS scavenging. These effects were prevented by the use of an antioxidant molecule.
D'Aleo
Valentina
V
Department of Endocrinology and Metabolism, Metabolic Unit, University of Pisa, Italy.
Del Guerra
Silvia
S
Martano
Manuela
M
Bonamassa
Barbara
B
Canistro
Donatella
D
Soleti
Antonio
A
Valgimigli
Luca
L
Paolini
Moreno
M
Filipponi
Franco
F
Boggi
Ugo
U
Del Prato
Stefano
S
Lupi
Roberto
R
D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects*; D005227:Fatty Acids / Q000633:toxicity*; D016166:Free Radical Scavengers / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005941:Glucokinase / Q000235:genetics / Q000378:metabolism; D051273:Glucose Transporter Type 2 / Q000235:genetics / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000235:genetics / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology; D008970:Molecular Weight; D018384:Oxidative Stress / Q000187:drug effects; D010455:Peptides; D010880:Piperidines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
D000975:Antioxidants; D005227:Fatty Acids; D016166:Free Radical Scavengers; D051273:Glucose Transporter Type 2; D007328:Insulin; D010455:Peptides; D010880:Piperidines; D012333:RNA, Messenger; C495680:SLC2A2 protein, human; D051028:bcl-2-Associated X Protein; C526136:bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decandioate; C002744:3-nitrotyrosine; D014443:Tyrosine; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005941:Glucokinase