NEW INSIGHT INTO METFORMIN ACTION ON RETINOPATHY: POTENTIAL ADJUNCT TREATMENT IN PATIENTS WITH TYPE 1 DIABETES He, Luke 1 ; Li, Xiaoyu 2 ; Kover, Karen 1,2 ; Wilkens, Dara 2 ; Moore, Wayne V. 1,2 ; Clements, Mark A. 1,2 and Yan, Yun 1,2 1 UMKC School of Medicine, Kansas City, MO, USA 2 Children’s Mercy Hospital, Kansas City, MO, USA Diabetic retinopathy (DR) results from inflammation via microvascular insults, and is a leading cause of blindness. It has been found that TXNIP is highly induced in the diabetic retina and plays a critical role in DR pathogenesis [1]. Thioredoxin-interacting protein (TXNIP), a mediator of inflammation, reduces thioredoxin reductase activities and thus induces oxidative stress and apoptosis [2]. Metformin (dimethylbiguanide) is a potential reversing agent of TXNIP induced damage [3]. There have been some controversial statements on metformin for overweight patients with type 1 diabetes based on clinical parameters [4,5]. Our group recently found that TXNIP suppression with metformin ameliorates hyperglycemia-induced increase of reactive oxygen species (ROS) production, proinflammatory state, and early apoptosis in aortic endothelial cells [3]. However, the underlying mechanism of metformin’s effects on hyperglycemia-induced TXNIP overexpression in DR are largely unknown. METHODS Rats grouped into normal, diabetic, and diabetic with metformin treatment using streptozotocin (STZ) injection and metformin in drinking water. Three rats in each group were tested. Diabetes was induced by one intraperitonial injection of STZ, 70mg/kg. One week later, designated rats received metformin 50mg/kg/day via drinking water for four weeks. Treatment was concluded with humane euthanization. Eyes were enucleated and retinas were snap-frozen in liquid nitrogen. RNA was extracted and analyzed with qPCR for TXNIP expression. Groups were compared using one-way analysis of variance (ANOVA) and post-hoc testing via Tukey’s HSD analysis (Prism v 3.0, GraphPad Software). RESULTS FUTURE DIRECTION REFERENCES 1. Singh, L. P. (2013). "Thioredoxin Interacting Protein (TXNIP) and Pathogenesis of Diabetic Retinopathy." J Clin Exp Ophthalmol. 2013;4: Muoio, D.M., TXNIP links redox circuitry to glucose control. Cell Metab, (6): p Li, X., et al. (2015). "New Insight Into Metformin Action: Regulation of ChREBP and FOXO1 Activities in Endothelial Cells." Mol Endocrinol 29(8): Hamilton, J., et al., Metformin as an adjunct therapy in adolescents with type 1 diabetes and insulin resistance: a randomized controlled trial. Diabetes Care, (1): p Nadeau, K.J., et al., Effects of low dose metformin in adolescents with type I diabetes mellitus: a randomized, double-blinded placebo-controlled study. Pediatric Diabetes. 2015;16: Figure 2 -High glucose (HG) induces TXNIP expression in retinal tissue while metformin (Met) decreases TXNIP expression. Perform western blot to analyze TXNIP expression at the level of protein translation in diabetic rat tissue. Perform in vitro studies with primary human retinal capillary endothelial cells to dissect the mechanism of metformin action. ACKNOWLEDGEMENTS This project is supported by Children’s Mercy Hospital Physician Scientist Award and Diabetes Action research and Education Foundation to Yun Yan. and Mark, A Clements. The authors acknowledge Ms. Chaoying Zhang and Ms. Peiying Ton for their technical support. SUMMARY Hyperglycemia induces the pro-oxidant gene TXNIP expression at the mRNA level in retinal tissue. Metformin suppresses hyperglycemia-induced overexpression of TXNIP in retinal tissue. OBJECTIVE Determine the impact of hyperglycemia on TXNIP overexpression in retinal tissue in a diabetic rat model. Determine possible therapeutic effects mediated by metformin on diabetic retinopathy. Hypothesis: metformin modulates hyperglycemia induced retinal cell damage in diabetic rat model by reducing TXNIP overexpression. Figure 1 -Mechanism of TXNIP [2] CtHGHG+Met INTRODUCTION