Regulation of pancreatic beta-cell mass and proliferation by SOCS-3.
Growth hormone and prolactin are important growth factors for pancreatic beta-cells. The effects exerted by these hormones on proliferation and on insulin synthesis and secretion in beta-cells are largely mediated through the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway. Suppressors of cytokine signaling (SOCS) proteins are specific inhibitors of the JAK/STAT pathway acting through a negative-feedback loop. To investigate in vivo effects of SOCS-3 in growth hormone (GH)/prolactin signaling in beta-cells we generated transgenic mice with beta-cell-specific overexpression of SOCS-3. The relative beta-cell proliferation and volume in the mice were measured by morphometry. Beta-cell volume of transgenic female mice was reduced by over 30% compared with beta-cell volume in wild-type female mice. Stimulation of transgenic islets in vitro with GH showed a reduced tyrosine phosphorylation of STAT-5 when compared with wild-type islets. Transduction of primary islet cultures with adenoviruses expressing various SOCS proteins followed by stimulation with GH or glucagon-like peptide-1 (GLP-1) revealed that SOCS-3 inhibited GH- but not GLP-1-mediated islet cell proliferation, indicating that the decreased beta-cell volume observed in female transgenic mice could be caused by an inhibition of GH-induced beta-cell proliferation by SOCS-3. In spite of the reduced beta-cell volume the transgenic female mice exhibited enhanced glucose tolerance compared with wild-type littermates following an oral glucose-tolerance test. Together these data suggest that SOCS-3 modulates cytokine signaling in pancreatic beta-cells and therefore potentially could be a candidate target for development of new treatment strategies for diabetes.
Lindberg
K
K
Department of Signal Transduction, Novo Nordisk A/S, Bagsvaerd, Denmark.
Rønn
S G
SG
Tornehave
D
D
Richter
H
H
Hansen
J A
JA
Rømer
J
J
Jackerott
M
M
Billestrup
N
N
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D049109:Cell Proliferation; D005260:Female; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D005951:Glucose Tolerance Test; D013006:Growth Hormone / Q000378:metabolism; D017403:In Situ Hybridization; D007328:Insulin / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000502:physiology*; D053613:Janus Kinase 1; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes
D001786:Blood Glucose; D007328:Insulin; D050799:STAT5 Transcription Factor; C491411:Socs3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D052216:Glucagon-Like Peptide 1; D013006:Growth Hormone; D011505:Protein-Tyrosine Kinases; C507905:Jak1 protein, mouse; C507906:Jak1 protein, rat; D053613:Janus Kinase 1