Liraglutide Improves the Angiogenic Capability of EPC and Promotes Ischemic Angiogenesis in Mice under Diabetic Conditions through an Nrf2-Dependent Mechanism

Abstract

The impairment in endothelial progenitor cell (EPC) functions results in dysregulation of vascular homeostasis and dysfunction of the endothelium under diabetic conditions. Improving EPC function has been considered as a promising strategy for ameliorating diabetic vascular complications. Liraglutide has been widely used as a therapeutic agent for diabetes. However, the effects and mechanisms of liraglutide on EPC dysfunction remain unclear. The capability of liraglutide in promoting blood perfusion and angiogenesis under diabetic conditions was evaluated in the hind limb ischemia model of diabetic mice. The effect of liraglutide on the angiogenic function of EPC was evaluated by cell scratch recovery assay, tube formation assay, and nitric oxide production. RNA sequencing was performed to assess the underlying mechanisms. Liraglutide enhanced blood perfusion and angiogenesis in the ischemic hindlimb of db/db mice and streptozotocin-induced type 1 diabetic mice. Additionally, liraglutide improved tube formation, cell migration, and nitric oxide production of high glucose (HG)-treated EPC. Assessment of liraglutide target pathways revealed a network of genes involved in antioxidant activity. Further mechanism study showed that liraglutide decreased the production of reactive oxygen species and increased the activity of nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 deficiency attenuated the beneficial effects of liraglutide on improving EPC function and promoting ischemic angiogenesis under diabetic conditions. Moreover, liraglutide activates Nrf2 through an AKT/GSK3β/Fyn pathway, and inhibiting this pathway abolished liraglutide-induced Nrf2 activation and EPC function improvement. Overall, these results suggest that Liraglutide represents therapeutic potential in promoting EPC function and ameliorating ischemic angiogenesis under diabetic conditions, and these beneficial effects relied on Nrf2 activation.

A Novel Angiogenesis Role of GLP-1(32-36) to Rescue Diabetic Ischemic Lower Limbs via GLP-1R-Dependent Glycolysis

“…GLP-1(9-36) could reduce elevated levels of mitochondrial-derived ROS in Alzheimer's disease model mice (54). GLP-1 (28)(29)(30)(31)(32)(33)(34)(35)(36) prevents ischemic cardiac injury by inhibiting mitochondrial trifunctional protein-α (13). It has been proposed that its Cterminal domain, VKGR amide, might contain a consensus mitochondrial targeting sequence (55).…”

“…infusion and the blood flow recovery was evaluated by using a PeriCam Perfusion Speckle Imager (PSI) at day 0, 3, 7, 14, 21, 28 days after HLI surgery (Supplementary Table . 1). GLP-1 here was used as a control for angiogenic drug (28). GLP-1 (32)(33)(34)(35)(36) treatment markedly recovered blood flow, companied with improved neovascularization in ischemic tissue (Fig.…”

“…However, they are rapidly degraded by the enzyme dipeptidyl peptidase-4 (DPP-4) after their release into the bloodstream, resulting in the formation of aminoterminally truncated peptides, such as GLP-1(9-37) and GLP-1(9-36) amide (9). GLP-1 amide can enter cells by penetrating the cell membrane, where it is internally cleaved in the C-terminal region by an intracellular endopeptidase such as neutral endopeptidase 24.11 (NEP 24.11), leading to the production of the nonapeptide GLP-1 (28)(29)(30)(31)(32)(33)(34)(35)(36) and the pentapeptide GLP-1 (32)(33)(34)(35)(36) amide (10) (Fig. 1A).…”

“…GLP-1(9-36) has also been found to reduce high glucose-induced mitochondrial ROS generation in human endothelial cells (12). GLP-1 (28)(29)(30)(31)(32)(33)(34)(35)(36) activates the AC-cAMP signaling pathway, changes the metabolic status of vascular cells, and plays a role in cardiovascular protection (13). GLP-1 (32)(33)(34)(35)(36), the major end-product of GLP-1 proteolysis in addition to the nonapeptide, has been found to decrease body weight, increase energy consumption, and reduce β-cell apoptosis in obese mice (14,15).…”

Novel Angiogenesis Role of GLP-1(32–36) to Rescue Diabetic Ischemic Lower Limbs via GLP-1R–Dependent Glycolysis in Mice

“…To investigate whether GLP-1(32-36) promotes angiogenesis and arteriogenesis in vivo, we used STZinduced T1DM mice as a murine model of unilateral HLI to examine the therapeutic potential of GLP-1(32-36) on angiogenesis and arteriogenesis according to previous protocols. 30,[44][45][46][47] The male and female mice were separately treated with GLP-1(32-36; 1 μmol/kg per d), GLP-1(7-36; 1 μmol/kg per d), or PBS by daily intraperitoneal infusion, and the blood flow recovery was evaluated by using a PeriCam Perfusion Speckle Imager at days 0, 3, 7, 14, 21, and 28 after HLI surgery (Figures S4 and S5). GLP-1(7-36) here was used as a control for angiogenic drug.…”