T-cadherin deficiency increases vascular vulnerability in T2DM through impaired NO bioactivity

Abstract

Background: Endothelial dysfunction plays a critical role in the development of type 2 diabetes (T2DM). T-cadherin (T-cad) has gained recognition as a regulator of endothelial cell (EC) function. The present study examined whether T-cad deficiency increases vascular vulnerability in T2DM.

Methods: Vascular segments were isolated from WT or T-cad knockout mice. Endothelial function, total NO accumulation, and the expression of T-cad related proteins were determined.

Results: Ach and acidified NaNO2 induced similar vasorelaxation in WT groups. T-cad KO mice exhibited normal response to acidified NaNO2, but manifested markedly reduced response to Ach. NO accumulation was also decreased in T-cad KO group. T-cad expression was reduced in WT mice fed 8 weeks of high fat diet (HFD). Furthermore, exacerbated reduction of vasorelaxation was observed in T-cad KO mice fed 8 weeks of HFD.

Conclusions: In the current study, we provide the first in vivo evidence that T-cadherin deficiency causes endothelial dysfunction in T2DM vascular segments, suggesting the involvement of T-cad deficiency in T2DM pathogenesis.

Keywords: Endothelial cell; Endothelial dysfunction; NO bioactivity; T-cadherin; T2DM; Vascular ring.

Fig. 1

T-cad mRNA and protein expression were reduced in WT mice fed 8 weeks HFD. T-cad expression as measured by Western blot and real time PCR a representative Western blots; b Western blot density analysis (n = 4); c Real time PCR analysis (n = 3).**P < 0.01 vs. WT

Fig. 2

T-cad deficiency induced endothelial dysfunction. Concentration-dependent vasorelaxation of aortic vascular rings in response to a Ach, an endothelium-dependent vasodilator, and b acidified NaNO₂, an endothelium-independent vasodilator. Top representative figures; Bottom analysis result. Each mouse aorta generated 2–3 rings, n = 8–12 rings/group. WT wild type litternates, T-cad KO T-cadherin knockout mice. *P < 0.05 vs. WT

Fig. 3

T-cad deficiency induced-endothelial dysfunction was exacerbated in T2DM. Concentration-dependent vasorelaxation of aortic vascular rings subjected to a high glucose/high fat treatment (high glucose: 25.5 m mol/l; high fat/palmitate: 300 μ mol/l) and b high fat diet alone for 8 weeks. Top representative figures; Bottom analysis result. Each mouse aorta generated 2–3 rings, n = 6–7 rings/group. WT Wild type litternates, T-cad KO T-cadherin knockout mice. **P < 0.01 vs. WT

Fig. 4

Basal NO production was significantly decreased in vascular segments from T-cad deficient animals. a NO concentration in culture medium after 8 h incubation of aortic segments from WT or T-cadherin knockout mice. b Concentration of nitric oxide in medium after Ach stimulation. Each mouse aorta generated 2 aortic segments. n = 8 segments/group. *P < 0.05 vs. WT

Fig. 5

Phosphorylation of Akt, but not eNOS, was significantly reduced in aortic tissue from T-cad KO animals. Expression of Akt, p-Akt, eNOS and p-eNOS in aortic tissues obtained from WT or T-cadherin knockout mice. Left representative Western blots. Right summary of density analysis of p-Akt/Akt (a) and p-eNOS/eNOS (b), n = 3 mice/group, *P < 0.05 vs. WT

Fig. 6

Akt inactivation increased caspase-3 activity in HUVECs. a Representative Western blots of p-Akt and Akt expression in HUVECs with or without Akt inhibitor; b Caspase-3 activity, using Ac-DEVD-pNA as substrate, n = 3, *P < 0.05 vs. WT

Fig. 7

Increased nitric oxide inactivation exacerbated endothelial dysfunction in T-cad KO mice. a Aortic nitrotyrosine content determined by ELISA; b quantitative assay of superoxide production determined by lucigenin-enhanced chemiluminescence, n = 3–4 mice/group, *P < 0.05 vs. WT, **P < 0.01 vs. WT