Vasoprotective Effects of Vildagliptin in Mice Is Masked by Metformin—Overlapping Mechanisms Implied

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Preclinical and small clinical studies have demonstrated the direct cardiovascular protective effects of dipeptidyl peptidase 4 inhibitors (DPP-4Is). However, cardiovascular benefits have not been proven in large clinical trials that utilized multiple antidiabetic agents. We hypothesized that the cardiovascular protective effects of the first-line antidiabetic agent metformin (Met) affects those of DPP-4Is, so we evaluated the vasoprotective effects of vildagliptin (Vil) in combination with Met in mice. Methods: We randomly assigned C57BL6 and diabetic db/db mice (8 weeks old) to treatment with vehicle, Vil (3 mg/kg/d), Met (400 mg/kg/d), or the combination of Vil and Met. The mice were subjected to femoral artery wire injury to induce arterial remodeling. Four weeks after the injury, the femoral arteries were collected. Human umbilical vein endothelial cells (HUVECs) were used in the in vitro experiments. Results: In wild type mice, the biological parameters were similar among the groups. Both Vil and Met treatment reduced neointimal area and vascular cell proliferation to a similar extent (40% reduction) compared to that of the vehicle, and combining the two drugs did not further reduce those values. Similarly, both Vil and Met treatment reduced neointimal area in db/db mice (50% reduction) without affecting biological parameters, but no additive effect was found. In wild type mice, cotreatment with the nitric oxide (NO) synthase inhibitor completely abolished the vascular effects of both Vil and Met, suggesting that Vil and Met had common mechanisms that are dependent on endothelial NO. In HUVECs, Vil did not directly affect NO production. In contrast, glucagon like peptide (GLP)-1 did stimulate NO production. Met also stimulated NO production. However, the combination of GLP-1 and Met did not increase NO production. Conclusions: Metformin masks the vasoprotective effects of vildagliptin, possibly because of overlapping mechanisms that are dependent on endothelial NO. Disclosure H. Kushima: None. Y. Mori: None. M. Koshibu: None. M. Hiromura: None. K. Kohashi: None. M. Terasaki: None. T. Hirano: Speaker's Bureau; Self; Novo Nordisk Inc., AstraZeneca.