Gemigliptin, a dipeptidyl peptidase-4 inhibitor, inhibits retinal pericyte injury in db/db mice and retinal neovascularization in mice with ischemic retinopathy

• Gemigliptin prevented diabetes-induced pericyte injury in db/db mice.
• Gemigliptin inhibited ischemia-induced retinal neovascularization in OIR mice.
• Gemigliptin's protective effects are independent of its effects on glucose homeostasis.
• The effects of gemigliptin may occur through a down-regulation of PAI-1.

Retinal pericyte loss and neovascularization are characteristic features of diabetic retinopathy. Gemigliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has shown robust blood-glucose lowering effects in type 2 diabetic patients, but its effects on diabetic retinopathy have not yet been reported. We evaluated the efficacy of gemigliptin on retinal vascular leakage in db/db mice, which is an animal model for type 2 diabetes, and neovascularization in oxygen-induced retinopathy (OIR) mice, which is an animal model for ischemic proliferative retinopathy. Gemigliptin (100 mg/kg/day) was orally administered to the db/db mice for 12 weeks. C57BL/6 mice on postnatal day 7 (P7) were exposed to 75% hyperoxia for 5 days, followed by exposure to room air from P12 to P17 to induce OIR. Gemigliptin (50 mg/kg/day) was intraperitoneally injected daily from P12 to P17. Retinal neovascularization was analyzed in flat-mounted retinas on P17. We determined the efficacy and possible mechanism of gemigliptin on high glucose-induced apoptosis of primary human retinal pericytes. The oral administration of gemigliptin for 4 months significantly ameliorated retinal pericyte apoptosis and vascular leakage in the db/db mice. Gemigliptin also ameliorated retinal neovascularization in the OIR mice. Gemigliptin attenuated the overexpression of plasminogen activator inhibitor-1 (PAI-1) in the retinas of diabetic and OIR mice. Gemigliptin and PAI-1 siRNA significantly inhibited pericyte apoptosis by inhibiting the overexpression of PAI-1, which is induced by high glucose. Our results suggest that gemigliptin has potent anti-angiogenic and anti-apoptotic activities via suppressing DPP-4 and PAI-1, and the results support the direct retinoprotective action of gemigliptin.