The AGE-breaker ALT-711 restores high blood flow-dependent remodeling in mesenteric resistance arteries in a rat model of type 2 diabetes

Abstract

Flow-mediated remodeling of resistance arteries is essential for revascularization in ischemic diseases, but this is impaired in diabetes. We hypothesized that breaking advanced glycation end product (AGE) cross-links could improve remodeling in mesenteric resistance arteries in Zucker diabetic fatty (ZDF) rats compared with lean Zucker (LZ) rats. Arteries, exposed to high (HF) or normal (NF) blood flow after alternate arterial ligation in vivo, were collected after 2 weeks. In LZ rats, HF artery diameter was larger than for NF vessels, but this was not the case in ZDF rats. Endothelium-mediated dilation in ZDF rats, which was lower than in LZ rats, was further decreased in HF arteries. Treatment of rats with the AGE-breaker 4,5-dimethyl-3-phenacylthiazolium chloride (ALT-711) (3 mg/kg/day; 3 weeks) reversed diabetes-induced impairment of HF-dependent remodeling. ALT-711 also improved endothelium nitric oxide-dependent relaxation in mesenteric resistance arteries. Reactive oxygen species reduction restored relaxation in ZDF rats but not in LZ or ALT-711-treated rats. AGEs were reduced in ALT-711-treated ZDF rats compared with ZDF rats. Metalloproteinase activity, necessary for HF-dependent remodeling, was reduced in ZDF rats compared with LZ rats and restored by ALT-711. Thus, targeting AGE cross-links may provide a therapeutic potential for overcoming microvascular complications in ischemic disorders occurring in diabetes.

FIG. 1.

Changes in diameter in response to stepwise increases in pressure in HF and NF mesenteric resistance arteries isolated from LZ and ZDF rats, either left untreated (A and B) or treated (C and D) with the AGE-breaker ALT-711. E and F: Changes in arterial diameter in HF arteries compared with NF vessels are represented as a percentage of change in diameter. Means ± SEM are presented (n = 10 per group). *P < 0.05, HF vs. NF arteries. #P < 0.05, ALT-711 vs. control (untreated).

FIG. 2.

In vitro cross-sectional compliance determined in response to stepwise increases in pressure from 10 to 150 mmHg in HF and NF mesenteric resistance arteries isolated from LZ (A) and ZDF (B) rats, either treated with the AGE-breaker ALT-711 or left untreated. C: Cross-sectional area of the media. Means ± SEM are presented (n = 10 per group). #P < 0.05, ALT-711 vs. control (untreated); *P < 0.05, HF vs. NF arteries; $P < 0.05, ZDF vs. LZ.

FIG. 3.

A and C: ACh-induced relaxation in HF and NF mesenteric resistance arteries isolated from LZ and ZDF rats. B and D: Effects of NOS inhibition (l-NAME, 100 μmol/L) on ACh-induced relaxation in HF and NF mesenteric resistance arteries isolated from LZ and ZDF rats. E and F: l-NAME–mediated contraction in HF and NF mesenteric resistance arteries isolated from LZ and ZDF rats treated or not with ALT-711. $P < 0.05, ZDF vs. LZ; #P < 0.05, ALT-711 vs. control (untreated).

FIG. 4.

Effect of SOD and catalase (SOD-cat) on ACh-induced relaxation in NF (A and B) and HF (D and E) mesenteric resistance arteries isolated from LZ (A and C) and ZDF (B and D) rats. #P < 0.05, ALT-711 vs. control (untreated).

FIG. 5.

Cumulative CRCs to serotonin (5-hydroxy-tryptamine [5-HT]) (A and C) and SNP (B and D) obtained in mesenteric resistance arteries submitted to a chronic increase in blood flow for 2 weeks (HF arteries), compared with control arteries exposed to NF. Arteries were isolated from LZ and ZDF rats, either treated with ALT-711 or left untreated. Means ± SEM are presented (n = 10 per group).

FIG. 6.

Immunohistological detection of AGEs and MG-¹H in HF and NF mesenteric resistance arteries isolated from ZDF or LZ rats. Values are presented as means ± SEM, n = 8 per group. #P < 0.05, ALT-711 vs. control (untreated); $P < 0.05, ZDF vs. LZ. (A high-quality color representation of this figure is available in the online issue.)

FIG. 7.

Images showing in situ zymography obtained in arterial thin sections submitted to angiotensin II or not. Gelatinase activity was visualized as an enhanced fluorescence of a fluorogenic gelatin substrate in NF and HF arteries using confocal microscopy. Bar graph: Quantification of gelatinolytic activity was performed using image density analysis (three to four arterial sections per artery and six rats per group). Means ± SEM are presented. *P < 0.05, angiotensin II vs. control. (A high-quality color representation of this figure is available in the online issue.)

FIG. 8.

Flow-mediated outward remodeling in a rat model of type 2 diabetes. A chronic increase in blood flow induces inflammation and oxidative stress. ROS associated with NO form peroxinitrite (ONOO), which activate MMPs and extracellular matrix (ECM) digestion. NO produced by eNOS after stimulation by flow (shear stress) then is able to induce diameter enlargement. In type 2 diabetes, AGE formation increases ROS formation, which reduces NO-dependent dilation. AGEs also decrease MMP activity in ZDF rats. Consequently, diameter enlargement does not occur. Green arrows refer to the pathway induced in flow-mediated outward remodeling, and red arrows point out the possible deleterious effect of AGEs. (A high-quality color representation of this figure is available in the online issue.)