title: Prolonged exposure to free fatty acids has cytostatic and pro-apoptotic effects on human pancreatic islets: evidence that beta-cell death is caspase mediated, partially dependent on ceramide pathway, and Bcl-2 regulated.
abstract: In an effort to better understand the phenomenon of lipotoxicity in human beta-cells, we evaluated the effects of 48-h preculture with 1.0 or 2.0 mmol/l free fatty acid (FFA) (2:1 oleate to palmitate) on the function and survival of isolated human islets and investigated some of the possible mechanisms. Compared with control islets, triglyceride content was significantly increased and insulin content and glucose-stimulated insulin release were significantly reduced in islets precultured with increased FFA concentrations. These changes were accompanied by a significant reduction of glucose utilization and oxidation. By cell death detection techniques, it was observed that exposure to FFAs induced a significant increase of the amount of dead cells. Electron microscopy showed the involvement of beta-cells, with morphological appearance compatible with the presence of apoptotic phenomena. FFA-induced islet cell death was blocked by inhibition of upstream caspases and partially prevented by inhibiton of ceramide synthesis or serine protease activity, whereas inhibition of nitric oxide synthesis had no effect. RT-PCR studies revealed no major change of iNOS and Bax mRNA expression and a marked decrease of Bcl-2 mRNA expression in the islets cultured with FFA. Thus, prolonged exposure to FFAs has cytostatic and pro-apoptotic effects on human pancreatic beta-cells. The cytostatic action is likely to be due to the FFA-induced reduction of intraislet glucose metabolism, and the proapoptotic effects are mostly caspase mediated, partially dependent on ceramide pathway, and possibly Bcl-2 regulated.
authors.affiliation: Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Lupi
authors.forename: Francesco
authors.initials: F
authors.lastname: Dotta
authors.forename: Lorella
authors.initials: L
authors.lastname: Marselli
authors.forename: Silvia
authors.initials: S
authors.lastname: Del Guerra
authors.forename: Matilde
authors.initials: M
authors.lastname: Masini
authors.forename: Carmela
authors.initials: C
authors.lastname: Santangelo
authors.forename: Giovanni
authors.initials: G
authors.lastname: Patané
authors.forename: Ugo
authors.initials: U
authors.lastname: Boggi
authors.forename: Salvatore
authors.initials: S
authors.lastname: Piro
authors.forename: Marcello
authors.initials: M
authors.lastname: Anello
authors.forename: Ettore
authors.initials: E
authors.lastname: Bergamini
authors.forename: Franco
authors.initials: F
authors.lastname: Mosca
authors.forename: Umberto
authors.initials: U
authors.lastname: Di Mario
authors.forename: Stefano
authors.initials: S
authors.lastname: Del Prato
authors.forename: Piero
authors.initials: P
authors.lastname: Marchetti
mesh_terms: D000368:Aged; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism
chemical_list: D002518:Ceramides; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D019253:Proto-Oncogene Proteins c-bcl-2; D014280:Triglycerides; D020169:Caspases; D005947:Glucose