De Souza CT, Gasparetti AL, Pereira-da-Silva M, Araújo EP, Carvalheira JB, Saad MJA, Boschero AC, Carneiro EM, Velloso LA. Peroxisome proliferator-activated receptor gamma coactivator-1-dependent uncoupling protein-2 expression in pancreatic islets of rats: a novel pathway for neural control of insulin secretion.
Diabetologia 2003;
46:1522-31. [PMID:
14576981 DOI:
10.1007/s00125-003-1222-5]
[Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2003] [Revised: 07/24/2003] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS
Sympathetic inputs inhibit insulin secretion through alpha2-adrenergic receptors coupled with Gi protein. High adrenergic tonus generated by exposure of homeothermic animals to cold reduces insulin secretion. In this study we evaluate the participation of UCP-2 in cold-induced regulation of insulin secretion.
METHODS
Static insulin secretion studies, western blotting and immunohistochemistry were used in this investigation.
RESULTS
Exposure of rats to cold during 8 days promoted 60% ( n=15, p<0.05) reduction of basal serum insulin levels concentration accompanied by reduction of the area under insulin curve during i.p. GTT (50%, n=15, p<0.05). Isolated islets from cold-exposed rats secreted 57% ( n=6, p<0.05) less insulin following a glucose challenge. Previous sympathectomy, partially prevented the effect of cold exposure upon insulin secretion. Islets isolated from cold-exposed rats expressed 51% ( n=6, p<0.5) more UCP-2 than islets from control rats, while the inhibition of UCP-2 expression by antisense oligonucleotide treatment partially restored insulin secretion of islets obtained from cold-exposed rats. Cold exposure also induced an increase of 69% ( n=6, p<0.05) in PGC-1 protein content in pancreatic islets. Inhibition of islet PGC-1 expression by antisense oligonucleotide abrogated cold-induced UCP-2 expression and partially restored insulin secretion in islets exposed to cold.
CONCLUSION/INTERPRETATION
Our data indicate that sympathetic tonus generated by exposure of rats to cold induces the expression of PGC-1, which participates in the control of UCP-2 expression in pancreatic islets. Increased UCP-2 expression under these conditions could reduce the beta-cell ATP/ADP ratio and negatively regulate insulin secretion.
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