59 - High Density Lipoprotein Co-localizes with Insulin in Pancreatic Islets of Normal and Diabetic Rats

Poster Board Number: 59
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Abstract Body : Background: Recent studies have implicated very low density lipoproteins in the pathogenesis of type 2 diabetic complications. In contrast, high density lipoprotein (HDL) has been shown to be protective of pancreatic beta cell. Objective: The aim of this study was to examine the distribution of HDL in pancreatic islet cells of animal models of type 1 and type 2 diabetes, including streptozotocin-induced diabetes Wistar rat, Goto-Kakizaki (GK) and Zucker diabetic fatty (ZDF) rats. The degree of co-localization with islet hormones was also investigated. Methods: Pancreatic tissue samples retrieved from normal, non-diabetic Wistar, diabetic Wistar, GK, Zucker lean (ZL) and ZDF were processed for immunohistochemistry. Additional tissues were processed for immunoelectron microscopy in order to determine the exact localization of HDL in the cytoplasmic organelles of pancreatic islet cells. All experimental procedures were in accordance with the protocols of the Research Advisory Committee Review Board of United Arab Emirates University. Results: HDL was discerned in the central and peripheral regions of pancreatic islets of Langerhans in non-diabetic Wistar, GK, ZL and ZDF rats. However, the number of HDL-positive cells was significantly lower in GK and ZDF rats when compared to Wistar controls and ZL, respectively. HDL-positive cells disappeared completely after the onset of streptozotocin-induced diabetes in Wistar rats. Co-localization study using immunofluorescence technique showed that HDL co-localizes with insulin in pancreatic beta cells, where they are located within the secretory granules. HDL does not co-localize with glucagon. Conclusion: HDL co-localizes with insulin in pancreatic beta cells of non-diabetic rats. The presence of HDL in islet cells is significantly reduced after the onset of diabetes. HDL may thus play a role in the production and release of insulin.