Leptin signalling in pancreatic islets and clonal insulin-secreting cells.
Leptin is a cytokine secreted from adipose tissue at a rate commensurate with the size of the body's fat stores. In addition to its anorectic and thermogenic central actions, leptin is known to act on peripheral tissues, including the pancreatic beta-cell where it inhibits insulin secretion and reduces insulin transcript levels. However, the role of leptin signalling through its full-length receptor, OB-Rb, in the beta-cell remains unclear. In the present study, we show that leptin activates a signal transducer and activator of transcription (STAT)3 signalling mechanism in pancreatic islets and in a rat model of the pancreatic beta-cell, RINm5F. Leptin induced DNA binding to a STAT consensus oligonucleotide and resulted in transcriptional activation from STAT reporter constructs in a manner consistent with STAT3 activation. Western blot analysis confirmed activation of STAT3 in RINm5F and isolated rat islets. Conditions that mimic increased metabolic activity resulted in attenuation of leptin-mediated STAT DNA binding but had no significant effect on STAT3 tyrosine phosphorylation in RINm5F cells. In addition, leptin activated the mitogen activated protein (MAP) kinase pathway in RINm5F cells. The present study provides a framework for OB-Rb signalling mechanisms in the programming of the beta-cell by leptin and suggests that increased metabolic activity may modulate this function.
Morton
N M
NM
The Clore Laboratory, The University of Buckingham, Buckingham, Buckinghamshire, MK18 1EG, UK.
Emilsson
V
V
de Groot
P
P
Pallett
A L
AL
Cawthorne
M A
MA
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D002999:Clone Cells; D000242:Cyclic AMP / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D020738:Leptin; D008297:Male; D009765:Obesity / Q000150:complications / Q000503:physiopathology; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D007328:Insulin; D020738:Leptin; D011506:Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494088:Stat3 protein, rat; D015534:Trans-Activators; D004247:DNA; D000242:Cyclic AMP; D002118:Calcium