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Cristian Mercado, Andrew T C Tsin; Effects of insulin on vascular endothelial growth factor secretion and cell viability in human Muller glial cells. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2666. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Diabetes is a condition characterized by an inability to regulate blood glucose levels. It affects over 30 million individuals in the United States and approximately 12% of Latinos. Recent studies report that insulin, a commonly prescribed medication for diabetes management, may increase vascular endothelial growth factor (VEGF) levels in the eye. VEGF is the hallmark feature of proliferative diabetic retinopathy (PDR), a serious eye complication that leads to blindness if left untreated. In this study, we focus on the effects of insulin on VEGF secretion in MIOM1 human Muller cells.
MIO-M1 were cultured using DMEM with 10% FBS in a humidified 5% CO2 environment at 37 degrees Celsius. MIO-M1 cells were seeded in a 24 wells plate at a seeding density of 80k cells per well until confluency. Cells were treated with medium containing glucose at 5.5mM (euglycemic) or 30mM (hyperglycemic) concentrations. Immediately after, cells were treated with or without insulin (100nM) for 24 hours. After 24 hours, supernatants were collected and analyzed for vascular endothelial growth factor using ELISA. Cell viability was measured using the trypan blue exclusion method.
Our results show a significant increase in VEGF levels in conditioned media in normal (5.5mM) and high glucose concentrations (30mM) when treated with insulin (100nM) (p<0.001). Insulin treatment of 100nM increased VEGF secretion by 42% in 5.5mM and 30mM glucose after 24 hours. VEGF secretion increased with insulin treatment from (54 to 93 pg/mL) in 5.5mM glucose and (40 to 70 pg/mL) in 30mM. Additionally, insulin treatment increased the number of viable cells by 24% compared to the control (5mM without insulin; N=3) after 24-hour treatment. Cell viability also increased by 5% from insulin treatment of cells in 30mM glucose compared to the control.
Our results are consistent with previous clinical reports (Nikhil S., ARVO abstract, 2018) that insulin affects VEGF levels. Collectively, our results suggest a possible shift in the role of insulin from homeostatic maintenance to development and progression of PDR through upregulation of VEGF. Finally, our data highlight the role of extracellular glucose levels and insulin in cell viability and the development of DR.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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