Cardiorespiratory fitness is associated with increased middle cerebral arterial compliance and decreased cerebral blood flow in young healthy adults: A pulsed ASL MRI study

Cardiorespiratory fitness is thought to have beneficial effects on systemic vascular health, in part, by decreasing arterial stiffness. However, in the absence of non-invasive methods, it remains unknown whether this effect extends to the cerebrovasculature. The present study uses a novel pulsed arterial spin labelling (pASL) technique to explore the relationship between cardiorespiratory fitness and arterial compliance of the middle cerebral arteries (MCAC). Other markers of cerebrovascular health, including resting cerebral blood flow (CBF) and cerebrovascular reactivity to CO2 (CVRCO2) were also investigated. Eleven healthy males aged 21 ± 2 years with varying levels of cardiorespiratory fitness (maximal oxygen uptake ([Formula: see text]O2MAX) 38–76 ml/min/kg) underwent MRI scanning at 3 Tesla. Higher [Formula: see text]O2MAX was associated with greater MCAC (R2 = 0.64, p < 0.01) and lower resting grey matter CBF (R2 = 0.75, p < 0.01). However, [Formula: see text]O2MAX was not predictive of global grey matter BOLD-based CVR (R2 = 0.47, p = 0.17) or CBF-based CVR (R2 = 0.19, p = 0.21). The current experiment builds upon the established benefits of exercise on arterial compliance in the systemic vasculature, by showing that increased cardiorespiratory fitness is associated with greater cerebral arterial compliance in early adulthood.

The major cerebral arteries proximal to the Circle of Willis contribute to cerebrovascular resistance in humans

Cerebral autoregulation ensures constant cerebral blood flow during periods of increased blood pressure by increasing cerebrovascular resistance. However, whether this increase in resistance occurs at the level of major cerebral arteries as well as at the level of smaller pial arterioles is still unknown in humans. Here, we measure cerebral arterial compliance, a measure that is inversely related to cerebrovascular resistance, with our novel non-invasive magnetic resonance imaging-based measurement, which employs short inversion time pulsed arterial spin labelling to map arterial blood volume at different phases of the cardiac cycle. We investigate the differential response of the cerebrovasculature during post exercise ischemia (a stimulus which leads to increased cerebrovascular resistance because of increases in blood pressure and sympathetic outflow). During post exercise ischemia in eight normotensive men (30.4 ± 6.4 years), cerebral arterial compliance decreased in the major cerebral arteries at the level of and below the Circle of Willis, while no changes were measured in arteries above the Circle of Willis. The reduction in arterial compliance manifested as a reduction in the arterial blood volume during systole. This study provides the first evidence that in humans the major cerebral arteries may play an important role in increasing cerebrovascular resistance.