Abstract
Endothelial dysfunction in resistance arteries (RAs) leads to end-organ damage in type 2 diabetes. Remodelling of RAs in response to chronic increases in blood flow depends on the integrity of the endothelium. Since type 2 diabetes impairs endothelial sensitivity to flow and increases oxidative stress, we hypothesized that flow-induced remodelling in RAs would be impaired in diabetes. Thus, we studied the structural and functional adaptation of RAs from Zucker diabetic fatty (ZDF) and lean Zucker (LZ) rats to chronic changes in flow. Mesenteric RAs were alternatively ligated so that one artery was submitted to high flow (HF) and compared with normal-flow (NF) arteries located at distance. After 3 weeks, arteries were studied in vitro (n = 10 rats per group). Arterial diameter (468 vs. 394 +/- 8 microm) and endothelial (acetylcholine)-dependent dilation (91 +/- 8 vs. 75 +/- 6% dilation) were higher in HF than in NF arteries in LZ rats. In ZDF rats, diameter (396 +/- 9 vs. 440 +/- 17 microm) and acetylcholine-mediated dilation (42 +/- 8 vs. 75 +/- 7%) were lower in HF than in NF arteries. Nevertheless, endothelial NO synthase and NADP(H) oxidase subunits (gp91, p67) expression level and superoxide production (dihydroethidium staining) were higher in HF than in NF arteries in both strains, suggesting an efficient flow-sensing process in ZDF rats. In ZDF rats, basal oxidative stress was higher compared with LZ rats: dihydroethidium staining was higher in NF and HF arteries from ZDF rats, and acetylcholine-mediated dilation was improved by an acute antioxidant (tempol) in NF and HF arteries from ZDF rats. Thus, superoxide overproduction in ZDF rats impaired NO-dependent dilation and HF remodelling. Indeed, a chronic treatment with tempol increased HF artery diameter and endothelium-dependent dilation in ZDF rats. In type 2 diabetic rats, a chronic increase in blood flow failed to induce outward remodelling and to improve endothelium-dependent dilation, mainly because of superoxide overproduction.
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