Glucagon-like peptide 1 inhibits cell apoptosis and improves glucose responsiveness of freshly isolated human islets.
The peptide hormone, glucagon-like peptide 1 (GLP-1), has been shown to increase glucose-dependent insulin secretion, enhance insulin gene transcription, expand islet cell mass, and inhibit beta-cell apoptosis in animal models of diabetes. The aim of the present study was to evaluate whether GLP-1 could improve function and inhibit apoptosis in freshly isolated human islets. Human islets were cultured for 5 d in the presence, or absence, of GLP-1 (10 nm, added every 12 h) and studied for viability and expression of proapoptotic (caspase-3) and antiapoptotic factors (bcl-2) as well as glucose-dependent insulin production. We observed better-preserved three-dimensional islet morphology in the GLP-1-treated islets, compared with controls. Nuclear condensation, a feature of cell apoptosis, was inhibited by GLP-1. The reduction in the number of apoptotic cells in GLP-1-treated islets was particularly evident at d 3 (6.1% apoptotic nuclei in treated cultures vs. 15.5% in controls; P < 0.01) and at d 5 (8.9 vs. 18.9%; P < 0.01). The antiapoptotic effect of GLP-1 was associated with the down-regulation of active caspase-3 (P < 0.001) and the up-regulation of bcl-2 (P < 0.01). The effect of GLP-1 on the intracellular levels of bcl-2 and caspase-3 was observed at the mRNA and protein levels. Intracellular insulin content was markedly enhanced in islets cultured with GLP-1 vs. control (P < 0.001, at d 5), and there was a parallel GLP-1-dependent potentiation of glucose-dependent insulin secretion (P < 0.01 at d 3; P < 0.05 at d 5). Our findings provide evidence that GLP-1 added to freshly isolated human islets preserves morphology and function and inhibits cell apoptosis.
Farilla
Loredana
L
Division of Endocrinology and Diabetes and Metabolism, Cedars-Sinai Medical Center, 8723 Alden Drive, SSB #290, Los Angeles, California 90048, USA. perfettir@cshs.org.
Bulotta
Angela
A
Hirshberg
Boaz
B
Li Calzi
Sergio
S
Khoury
Nasif
N
Noushmehr
Houtan
H
Bertolotto
Cristina
C
Di Mario
Umberto
U
Harlan
David M
DM
Perfetti
Riccardo
R
D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000032:analysis / Q000235:genetics; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D015870:Gene Expression / Q000187:drug effects; D005934:Glucagon / Q000494:pharmacology*; D052216:Glucagon-Like Peptide 1; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles; D007328:Insulin / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D011498:Protein Precursors / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D005456:Fluorescent Dyes; D007211:Indoles; D007328:Insulin; D010446:Peptide Fragments; D011498:Protein Precursors; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C007293:DAPI; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D005947:Glucose