Glucose induces pancreatic islet cell apoptosis that requires the BH3-only proteins Bim and Puma and multi-BH domain protein Bax.
OBJECTIVE
High concentrations of circulating glucose are believed to contribute to defective insulin secretion and beta-cell function in diabetes and at least some of this effect appears to be caused by glucose-induced beta-cell apoptosis. In mammalian cells, apoptotic cell death is controlled by the interplay of proapoptotic and antiapoptotic members of the Bcl-2 family. We investigated the apoptotic pathway induced in mouse pancreatic islet cells after exposure to high concentrations of the reducing sugars ribose and glucose as a model of beta-cell death due to long-term metabolic stress.


METHODS
Islets isolated from mice lacking molecules implicated in cell death pathways were exposed to high concentrations of glucose or ribose. Apoptosis was measured by analysis of DNA fragmentation and release of mitochondrial cytochrome c.


RESULTS
Deficiency of interleukin-1 receptors or Fas did not diminish apoptosis, making involvement of inflammatory cytokine receptor or death receptor signaling in glucose-induced apoptosis unlikely. In contrast, overexpression of the prosurvival protein Bcl-2 or deficiency of the apoptosis initiating BH3-only proteins Bim or Puma, or the downstream apoptosis effector Bax, markedly reduced glucose- or ribose-induced killing of islets. Loss of other BH3-only proteins Bid or Noxa, or the Bax-related effector Bak, had no impact on glucose-induced apoptosis.


CONCLUSIONS
These results implicate the Bcl-2 regulated apoptotic pathway in glucose-induced islet cell killing and indicate points in the pathway at which interventional strategies can be designed.
McKenzie
Mark D
MD
St. Vincent's Institute, Melbourne, Australia.
Jamieson
Emma
E
Jansen
Elisa S
ES
Scott
Clare L
CL
Huang
David C S
DC
Bouillet
Philippe
P
Allison
Janette
J
Kay
Thomas W H
TW
Strasser
Andreas
A
Thomas
Helen E
HE
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000473:pathology*; D005947:Glucose / Q000633:toxicity*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017472:Receptors, Interleukin-1 / Q000235:genetics; D012266:Ribose / Q000633:toxicity; D013312:Stress, Physiological / Q000187:drug effects; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000235:genetics
D051017:Apoptosis Regulatory Proteins; C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D008565:Membrane Proteins; C488588:PUMA protein, mouse; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1; D025521:Tumor Suppressor Proteins; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D012266:Ribose; D045304:Cytochromes c; D005947:Glucose