Endothelium-dependent impairments to cerebral vascular reactivity with type 2 diabetes mellitus in the Goto-Kakizaki rat

Abstract

Type 2 diabetes mellitus (T2DM) is a prevalent pathology associated with elevated cerebrovascular disease risk. We determined wall mechanics and vascular reactivity in ex vivo middle cerebral arteries (MCA) from male Goto-Kakizaki rats (GK; ~17 wk old) versus control Wistar Kyoto rats (WKY) to test the hypothesis that the diabetic environment in GK, in the absence of obesity and other comorbidities, leads to endothelial dysfunction and impaired vascular tone regulation. Dilation of MCA following challenge with acetylcholine and hypoxia was blunted in MCA from GK versus WKY, due to lower nitric oxide bioavailability and altered arachidonic acid metabolism, whereas myogenic activation and constrictor responses to serotonin were unchanged. MCA wall distensibility and cross-sectional area were not different between GK and WKY, suggesting that wall mechanics were unchanged at this age, supported by the determination that MCA dilation to sodium nitroprusside was also intact. With the use of ex vivo aortic rings as a bioassay, altered vascular reactivity determined in MCA was paralleled by relaxation responses in artery segments from GK, whereas measurements of vasoactive metabolite production indicated a loss of nitric oxide and prostacyclin bioavailability and an increased thromboxane A2 production with both methacholine challenge and hypoxia. These results suggest that endothelium-dependent dilator reactivity of MCA in GK is impaired with T2DM, and that this impairment is associated with the genesis of a prooxidant/pro-inflammatory condition with diabetes mellitus. The restriction of vascular impairments to endothelial function only, at this age and development, provide insight into the severity of multimorbid conditions of which T2DM is only one constituent.