Dipeptidyl peptidase 4 inhibitor reduces intimal hyperplasia in rabbit autologous jugular vein graft under poor distal runoff

Reduced Function of Endothelial Nitric Oxide and Hyperpolarization in Artery Grafts with Poor Runoff

BACKGROUND

The endothelium regulates vascular tonus by releasing nitric oxide (endothelium-derived nitric oxide, EDNO) and hyperpolarizing factor (endothelium-derived hyperpolarizing factor, EDHF). In vein grafts with poor runoff, lack of function of these factors causes severe intimal hyperplasia. This study evaluated how the functions of EDNO and EDHF are altered in artery grafts under poor runoff conditions.

MATERIALS AND METHODS

The right common carotid arteries of rabbits were excised and implanted in their original positions as autogenous grafts under normal runoff conditions ("nonoccluded grafts") or poor runoff conditions ("poor runoff grafts"). Histochemical changes, acetylcholine (ACh)-induced effects on endothelium-dependent relaxation and smooth muscle cell (SMC) hyperpolarization were examined.

RESULTS

Both artery graft types displayed negligible intimal hyperplasia. In the absence and presence of an EDNO synthase inhibitor, ACh-induced relaxation was lower in grafts with poor runoff than in nonoccluded grafts. Furthermore, ACh-induced but not nonreceptor agonist A23187-induced SMC hyperpolarization was lower in the poor runoff graft group than in the nonoccluded graft group.

CONCLUSIONS

Unlike in those in vein grafts, the functions of EDNO and EDHF in autogenous carotid artery grafts under poor runoff conditions were reduced but partly maintained. In such artery grafts, intimal hyperplasia caused by surgical operation was not present. These results may explain some of the mechanisms underlying the improved patency of artery grafts compared with vein grafts.

Vasculoprotective Effects of Vildagliptin. Focus on Atherogenesis

Vildagliptin is a representative of Dipeptidyl Peptidase-4 (DPP-4) inhibitors, antihyperglycemic drugs, approved for use as monotherapy and combination therapy in type 2 diabetes mellitus. By inhibiting enzymatic decomposition, DPP-4 inhibitors increase the half-life of incretins such as GLP-1 (Glucagon-like peptide-1) and GIP (Gastric inhibitors polypeptide) and prolong their action. Some studies present results suggesting the anti-sclerotic and vasculoprotective effects of vildagliptin reaching beyond glycemic control. Vildagliptin is able to limit inflammation by suppression of the NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signaling pathway and proinflammatory agents such as TNF-α (tumor necrosis factor α), IL-1β (Interleukin-1β), and IL-8 (Interleukin 8). Moreover, vildagliptin regulates lipid metabolism; attenuates postprandial hypertriglyceridemia; and lowers serum triglycerides, apolipoprotein B, and blood total cholesterol levels. This DPP-4 inhibitor also reduces macrophage foam cell formation, which plays a key role in atheromatous plaque formation and stability. Vildagliptin reduces vascular stiffness via elevation of nitric oxide synthesis, improves vascular relaxation, and results in reduction in both systolic and diastolic blood pressure. Treatment with vildagliptin lowers the level of PAI-1 presenting possible antithrombotic effect. By affecting the endothelium, inflammation, and lipid metabolism, vildagliptin may affect the development of atherosclerosis at its various stages. The article presents a summary of the studies assessing vasculoprotective effects of vildagliptin with special emphasis on atherogenesis.

Nanofibrous vildagliptin-eluting stents enhance re-endothelialization and reduce neointimal formation in diabetes: in vitro and in vivo

BACKGROUND

The high lifetime risk of vascular disease is one of the important issues that plague patients with diabetes mellitus. Systemic oral vildagliptin administration favors endothelial recovery and inhibits smooth muscle cell (SMC) proliferation. However, the localized release of vildagliptin in the diabetic vessel damage has seldom been investigated.

RESEARCH DESIGN AND METHODS

In this work, nanofiber-eluting stents that loaded with vildagliptin, a dipeptidyl peptidase-4 enzyme (DPP-4) inhibitor, was fabricated to treat diabetic vascular disease. To prepare nanofibers, the poly (D,L)-lactide-co-glycolide (PLGA) and vildagliptin were mixed using hexafluoroisopropanol and electrospinning process. In vitro and in vivo release rates of the vildagliptin were characterized using high-performance liquid chromatography.

RESULTS

Effective vildagliptin concentrations were delivered for more than 28 days from the nanofibrous membranes coating on the surface of the stents in vitro and in vivo. The vildagliptin-eluting PLGA membranes greatly accelerated the recovery of diabetic endothelia and reduced SMC hyperplasia. The type I collagen content of the diabetic vascular intimal area that was treated by vildagliptin-eluting stents was lower than that of the non-vildagliptin-eluting group.

CONCLUSION

The experimental results revealed that stenting with vildagliptin-eluting PLGA membranes could potentially promote healing for diabetic arterial diseases.

Enhancement of Nitric Oxide Production Is Responsible for Minimal Intimal Hyperplasia of Autogenous Rabbit Arterial Grafts

BACKGROUND

Vascular endothelium induces smooth muscle cell (SMC) relaxation mainly mediated by endothelium-derived nitric oxide (EDNO) and endothelium-derived hyperpolarizing factor (EDHF). It has previously been reported that functions of these endothelium factors have been greatly impaired in vein grafts. The present study was undertaken to determine whether the functions of EDNO and EDHF might be altered in artery graft.Methods and Results:In rabbits, the right carotid artery was excised and implanted in its original position as an autogenous graft ("artery graft") and the non-operated left carotid artery served as the "control artery". Histochemical changes, acetylcholine (ACh)-induced effects on the intracellular concentration of Ca²⁺([Ca²⁺]_i) in endothelial cells, endothelium-dependent SMC hyperpolarization and relaxation, and tissue cGMP content were examined on post-operative day 28. "Artery graft" displayed a minimal amount of intimal hyperplasia. When compared with the "control artery", it exhibited greater ACh-induced, endothelium-dependent relaxation, but the reverse was true when EDNO production was blocked. In the "artery graft" (vs. the "control artery"), basal cGMP content was greater, whereas the [Ca²⁺]_iincrease in endothelial cells and the endothelium-dependent SMC-hyperpolarization induced by ACh were less.

CONCLUSIONS

It is suggested that the [Ca²⁺]_i-independent EDNO production covers the loss of function of endothelium-dependent SMC hyperpolarization and minimizes intimal hyperplasia caused by surgical operation in autogenous carotid artery graft.