Effects of a high-sugar mixed meal on cerebrovascular haemodynamics in young, healthy versus middle-aged adults with cardiometabolic risk factors.

Consumption of a high-sugar mixed meal (HSMM) increases both glucose and insulin and elicits mixed vascular effects, with reduced microvascular blood flow but increased conduit artery diameter and blood flow. In this study, we sought to examine: (1) whether an HSMM elicits vascular segment-specific effects within cerebrovasculature; and (2) whether these responses differ between young healthy adults and middle-aged adults with cardiometabolic disease (CMD) risk factors. Twenty-one young, healthy adults (ages 18-39 years; 24 ± 6 years) and 20 middle-aged adults (ages 40-65 years; 55 ± 5 years) with CMD risk factors (hypertension, obesity or dyslipidaemia) underwent cerebrovascular assessments before and at 30 and 60 min after a 930 kcal HSMM. Carotid and aortic stiffness and carotid artery characteristic impedance were assessed via ultrasound and tonometry. Middle cerebral artery mean velocity, pulsatility index and resistive index were assessed via transcranial Doppler. In comparison to baseline, common carotid artery diameter increased while stiffness decreased, contributing to a decrease in carotid artery characteristic impedance in both groups following the HSMM (p < 0.05). In comparison to baseline, middle cerebral artery mean velocity, pulsatility index and resistive index increased only in young adults (p < 0.05) following the HSMM. Differential increases in cerebral pulsatility among young adults compared with middle-aged adults with CMD risk factors might reflect modest differences in upstream, extracranial artery pulsatile transmission following an HSMM, along with simultaneous, complex intracranial cerebrovascular responses that require further interrogation. Cumulatively, these data suggest that: (1) the cerebrovascular response to an HSMM might differ between segments of the extra- versus intracranial cerebrovasculature; and (2) middle-aged adults with CMD risk factors might have altered cerebrovascular responsiveness to an HSMM compared with young, healthy adults.