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lilly khamsy, Laura Kowalczuk, Tatiana Favez, Catherine Martin, Francine F Behar-Cohen; The role of insulin in diabetic retinal homeostasis.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2524.
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© ARVO (1962-2015); The Authors (2016-present)
Type 2 diabetic insulin-resistant patients have high insulin circulating levels and insulin treatment is potentially aggravating the risk of retinopathy and macular edema. But the exact direct role of insulin on hydro-ionic retinal homeostasis remains incompletely understood. The aim of this study is to analyze the effect of insulin on human retinal pigment epithelium (RPE) cells in hyperglycemic conditions in vitro and after intravitreous injection in Goto Kakizaki (GK) type 2 diabetic rats.
ARPE19 cell line and human induced pluripotent stem cells derived into RPE (iPSc-RPE) were used to evaluate tight junction (TJ) rearrangement in hyperglycemic conditions in presence of insulin in vitro. Cell viability and proliferation were analyzed. Immunofluorescence of Zona occludens-1 staining was performed after 7 days of treatment in high glucose (40mM) and high insulin (10nM, 100nM) conditions following 24h FBS starvation. In parallel, transepithelial resistance (TER) measurements was performed. In vivo, insulin was injected in the vitreous of GK rats and 150kDa FITC dextran was injected intravenously one hour prior to sacrifice (n=6). Glycemia levels were recorded.
ARPE19 and iPSc-RPE cell monolayer form TJ thus maintaining a concentration gradient between apical and basal environments. We validated the presence of functional insulin receptors in our cell cultures. Insulin (10nM) induces cell proliferation. We consistently see opening of TJ in high glucose (40mM) and high insulin (10nM) conditions after 7 days of treatment compared with baseline conditions in which ARPE19 cells exhibit intact cobblestone appearance (glucose 25mM, insulin 0nM). Paradoxically TER increased in high glucose and high insulin conditions in which opening of TJ was seen. B27 supplement starvation in iPSc-RPE cultures reduced TER. Interestingly, higher insulin (100nM) levels did not induce opening of TJ, suggesting involvement of a pathway dependent on insulin receptor regulation. In vivo, insulin injected intravitreally in GK diabetic rats induced retinal vessels vasodilation and leakage. No glycemic changes resulted from intravitreal injection of insulin.
Our findings reveal that insulin in combination with high glucose impairs TJ arrangement in RPE. In vivo, high levels of insulin in the vitreous may be responsible for aggravation of macular edema.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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