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Diabetes. 2009 Apr;58(4):820-8. doi: 10.2337/db08-0551. Epub 2009 Jan 9.

Beta-Cell hyperplasia induced by hepatic insulin resistance: role of a liver-pancreas endocrine axis through insulin receptor A isoform.

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  • 1Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, Complutense University of Madrid, Madrid, Spain.

Abstract

OBJECTIVE:

Type 2 diabetes results from a combination of insulin resistance and impaired insulin secretion. To directly address the effects of hepatic insulin resistance in adult animals, we developed an inducible liver-specific insulin receptor knockout mouse (iLIRKO).

RESEARCH DESIGN AND METHODS:

Using this approach, we were able to induce variable insulin receptor (IR) deficiency in a tissue-specific manner (liver mosaicism).

RESULTS:

iLIRKO mice presented progressive hepatic and extrahepatic insulin resistance without liver dysfunction. Initially, iLIRKO mice displayed hyperinsulinemia and increased beta-cell mass, the extent of which was proportional to the deletion of hepatic IR. Our studies of iLIRKO suggest a cause-and-effect relationship between progressive insulin resistance and the fold increase of plasma insulin levels and beta-cell mass. Ultimately, the beta-cells failed to secrete sufficient insulin, leading to uncontrolled diabetes. We observed that hepatic IGF-1 expression was enhanced in iLIRKO mice, resulting in an increase of circulating IGF-1. Concurrently, the IR-A isoform was upregulated in hyperplastic beta-cells of iLIRKO mice and IGF-1-induced proliferation was higher than in the controls. In mouse beta-cell lines, IR-A, but not IR-B, conferred a proliferative capacity in response to insulin or IGF-1, providing a potential explanation for the beta-cell hyperplasia induced by liver insulin resistance in iLIRKO mice.

CONCLUSIONS:

Our studies of iLIRKO mice suggest a liver-pancreas endocrine axis in which IGF-1 functions as a liver-derived growth factor to promote compensatory pancreatic islet hyperplasia through IR-A.

PMID:
19136656
[PubMed - indexed for MEDLINE]
PMCID:
PMC2661585
Free PMC Article
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