Lower Somatostatin Expression Is an Early Event in Diabetic Retinopathy and Is Associated With Retinal Neurodegeneration

  1. Esther Carrasco, BSC1,
  2. Cristina Hernández, MD, PHD1,
  3. Adela Miralles, BSC2,
  4. Pere Huguet, MD, PHD3,
  5. Jaume Farrés, PHD4 and
  6. Rafael Simó, MD, PHD1
  1. 1Diabetes Research Unit, Institut de Recerca Hospital Universitari Vall d’Hebron, Barcelona, Spain
  2. 2Tissue Bank and Cell Therapy Center, Barcelona, Spain
  3. 3Pathology, Hospital Universitari Vall d’Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
  4. 4Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, Barcelona, Spain
  1. Address correspondence and reprint requests to Dr. Rafael Simó, Diabetes Research Unit, Institut de Recerca Hospital Universitari Vall d’Hebron, Pg. Vall d’Hebron 119-129, 08035 Barcelona, Spain. E-mail: rsimo{at}ir.vhebron.net

Abstract

OBJECTIVE—To test the hypothesis that a reduction of somatostatin (SST) in the retina exists in patients without clinically detectable diabetic retinopathy and that it is associated with retinal neurodegeneration.

RESEARCH DESIGN AND METHODS—Human diabetic postmortem eyes (n = 10) without clinically detectable retinopathy were compared with eyes (n = 10) from nondiabetic donors. SST mRNA (RT-PCR) and SST-28 immunoreactivity (confocal laser) were measured separately in neuroretina and retinal pigment epithelium (RPE). In addition, SST-28 (radioimmunoassay) was measured in the vitreous fluid. Glial fibrillar acidic protein (GFAP) was assessed by immunofluorescence and Western blot. Apoptotic cells were quantified using transferase-mediated dUTP nick-end labeling.

RESULTS—A higher expression of SST was detected in RPE than neuroretina in both groups. SST mRNA levels and SST-28 immunoreactivity were significantly lower in both RPE and the neuroretina from diabetic donors compared with nondiabetic donors. These results were in agreement with those obtained by measuring SST-28 in the vitreous fluid of the same donors. Increased GFAP and a higher degree of apoptosis were observed in diabetic retinas compared with nondiabetic retinas. These changes were most evident in patients with the higher deficit of SST.

CONCLUSIONS—Underproduction of SST is an early event in the eyes of diabetic patients and is associated with glial activation and neural death. In addition, our results suggest that RPE is an important source of SST in the human eye. The possible role of the lower production of SST in the pathogenesis of diabetic retinopathy requires further investigation.

Footnotes

  • Published ahead of print at http://care.diabetesjournals.org on 17 August 2007. DOI: 10.2337/dc07-0332.

    Additional information for this article can be found in an online appendix at http://dx.doi.org/10.2337/dc07-0332.

    A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

    The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C Section 1734 solely to indicate this fact.

    • Accepted August 9, 2007.
    • Received February 20, 2007.
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  1. doi: 10.2337/dc07-0332 Diabetes Care November 2007 vol. 30 no. 11 2902-2908
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