Vascular Endothelial Growth Factor–Mediated Islet Hypervascularization and Inflammation Contribute to Progressive Reduction of β-Cell Mass

  1. Fatima Bosch1,2,3
  1. 1Center of Animal Biotechnology and Gene Therapy, Universitat Autònoma de Barcelona, Barcelona, Spain
  2. 2Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, Barcelona, Spain
  3. 3Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
  1. Corresponding author: Fatima Bosch, fatima.bosch{at}uab.es.
  1. E.A. and V.J. contributed equally to this work.

  • Deceased.

Abstract

Type 2 diabetes (T2D) results from insulin resistance and inadequate insulin secretion. Insulin resistance initially causes compensatory islet hyperplasia that progresses to islet disorganization and altered vascularization, inflammation, and, finally, decreased functional β-cell mass and hyperglycemia. The precise mechanism(s) underlying β-cell failure remain to be elucidated. In this study, we show that in insulin-resistant high-fat diet-fed mice, the enhanced islet vascularization and inflammation was parallel to an increased expression of vascular endothelial growth factor A (VEGF). To elucidate the role of VEGF in these processes, we have genetically engineered β-cells to overexpress VEGF (in transgenic mice or after adeno-associated viral vector-mediated gene transfer). We found that sustained increases in β-cell VEGF levels led to disorganized, hypervascularized, and fibrotic islets, progressive macrophage infiltration, and proinflammatory cytokine production, including tumor necrosis factor-α and interleukin-1β. This resulted in impaired insulin secretion, decreased β-cell mass, and hyperglycemia with age. These results indicate that sustained VEGF upregulation may participate in the initiation of a process leading to β-cell failure and further suggest that compensatory islet hyperplasia and hypervascularization may contribute to progressive inflammation and β-cell mass loss during T2D.

Footnotes

  • Received February 8, 2012.
  • Accepted May 29, 2012.

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  1. Diabetes vol. 61 no. 11 2851-2861
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