An Oral glucose tolerance test does not affect cerebral blood flow: role of NOS

Am J Physiol Regul Integr Comp Physiol. 2023 Oct 16. doi: 10.1152/ajpregu.00169.2022. Online ahead of print.ABSTRACTAnimal data indicate that insulin triggers a robust nitric oxide synthase (NOS)-mediated dilation in cerebral arteries similar to the peripheral tissue vasodilation observed in healthy adults. Insulin's role in regulating cerebral blood flow (CBF) in humans remains unclear but may be important for understanding the links between insulin resistance, diminished CBF, and poor brain health outcomes. We tested the hypothesis an oral glucose challenge (OGTT), which increases systemic insulin and glucose, would acutely increase CBF in healthy adults due to robust NOS-mediated vasodilation, and that changes in CBF would be greater in anterior regions where NOS expression or activity may be greater. In a randomized, single-blind approach, 11 young adults (24±5 years) underwent magnetic resonance imaging (MRI) with L-NMMA or placebo, while an additional 7 participants completed a placebo visit. 4D flow MRI quantified macrovascular CBF and arterial spin labeling (ASL) quantified microvascular perfusion. Subjects completed baseline imaging with placebo (or L-NMMA), then consumed an OGTT (75g glucose) followed by MRI scans and blood sampling every 10-15 minutes for 90 minutes. Total CBF (p = 0.17) and global perfusion (p > 0.05) did not change at any time point through 60 minutes after OGTT, and no regional changes were detected. L-NMMA did not mediate any effect of OGTT...
Source: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology - Category: Physiology Authors: Source Type: research