期刊
BIOCHEMICAL JOURNAL
卷 377, 期 -, 页码 149-158出版社
PORTLAND PRESS
DOI: 10.1042/BJ20031260
关键词
diabetes; glucose; insulin; islet beta-cell; small interfering RNA (siRNA)
资金
- Diabetes UK [13/0004672] Funding Source: Medline
The importance of the insulin receptor (IR) and the insulin-like growth factor-1 receptor (IGF-lR) for glucose-regulated insulin secretion and gene expression in pancreatic islet,beta-cells is at present unresolved. Here, we have used small interfering RNAs (siRNAs) to silence the expression of each receptor selectively in clonal MIN6 beta-cells. Reduction of IR levels by > 90% completely inhibited glucose (30 mM compared with 3 mM)-induced insulin secretion, but had no effect on depolarization-stimulated secretion. IR depletion also blocked the accumulation of preproinsulin (PPI), pancreatic duodenum homoeobox-1 (PDX-1) and glucokinase (GK) mRNAs at elevated glucose concentrations, as assessed by quantitative real-time PCR analysis (TaqMan((R))). Similarly, depletion of IGF-1R inhibited glucose-induced insulin secretion but, in contrast with the effects of IR silencing, had little impact on the regulation of gene expression by glucose. More-over, loss of IGF-i=lR, but not IR, markedly inhibited glucose-stimulated increases in cytosolic and mitochondrial ATP, suggesting a role for IGF-1R in the maintenance of oxidative metabolism and in the generation of mitochondrial coupling factors. RNA silencing thus represents a useful tool for the efficient and selective inactivation of receptor tyrosine kinases in isolated,B-cells. By inhibiting glucose-stimulated insulin secretion through the inactivation of IGF-1R, this approach also demonstrates the existence of insulin-independent mechanisms whereby elevated glucose concentrations regulate PPI, PDX-1 and GK gene expression in beta-cells.
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