The effect of GLP-1 receptor agonist Lixisenatide on experimental diabetic retinopathy
Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are effective treatments for type 2 diabetes, effectively lowering glucose without weight gain and with low risk for hypoglycemia. However, their influence on the retinal neurovascular unit remains unclear. In this study we analyzed the effects of the GLP-1 RA lixisenatide in a rat model of type-1 like diabetic retinopathy.  Vasculo- and neuroprotective effects were assessed in experimental diabetic retinopathy and high glucose-cultivated C. elegans, respectively. In STZ-diabetic Wistar rats acellular capillaries and pericytes (quantitative retinal morphometry), neuroretinal function (mfERG), macroglia (GFAP western blot) and microglia (immunohistochemistry) quantification, methylglyoxal (LC-MS/MS) and retinal gene expressions (RNA-sequencing) were determined. The antioxidant properties of lixisenatide were tested in C. elegans. Lixisenatide had no effect on glucose metabolism. Lixisenatide preserved the retinal vasculature and neuroretinal function. The macro- and microglial activation was mitigated. Lixisenatide normalized some gene expression changes in diabetic animals to control levels. Ets2 was identified as a regulator of inflammatory genes. In C. elegans lixisenatide showed the antioxidative property. In summary, these data suggest that lixisenatide has a protective effect on the diabetic retina, most likely due to a combination of neuroprotective, anti-inflammatory and antioxidative effects of lixisenatide on the neurovascular unit. Overall design: First to investigate gene expression changes in whole retinae from rat with hyperglycemia but not hyperinsulinemia. And second, to identify differences and underlying signalling pathways induced by the treatment with the GLP1 receptor agonist Lixisenatide