Association between large elastic artery stiffness and brain mechanical properties

Abstract

Stiffening of the large elastic arteries (i.e., the aorta and carotid arteries) occurs with aging and may play a key role in memory impairment via a diminished pressure‐dampening effect, ultimately leading to loss of neuronal tissue integrity. In this regard, changes in brain tissue viscoelastic mechanical properties, an indirect measure of neuronal tissue integrity, may reflect the impact of elastic artery stiffening on brain health. Therefore, the purpose of this pilot study was to determine whether large elastic artery stiffness is associated with total brain viscoelasticity in healthy adults across the lifespan. All measures were performed in 13 healthy participants (6 females, mean age: 38 ± 15 y; age range: 22–69 y; mean BMI: 26 ± 5 kg/m2; mean BP: 111 ± 9/68 ± 10 mmHg). Carotid artery stiffness, beta‐stiffness index and compliance were assessed using B‐mode ultrasound (Logiq e, GE) coupled with applanation tonometry (SphygmoCor, AtCor Medical Inc.) and analyzed using commercial wall‐tracking software (Cardiovascular Suite, Quipu). Aortic stiffness was assessed as carotid‐to‐femoral pulse wave velocity (PWV) using applanation tonometry. Brain tissue viscoelastic mechanical properties (shear stiffness and damping ratio) were measured using magnetic resonance elastography (MRE). MRE data were acquired using 3T magnetic resonance imaging (Magnetom Prisma, Siemens, Inc.) while the brain viscoelastic property maps were generated using a nonlinear inversion algorithm. Associations between measures of age, large elastic artery stiffness and brain viscoelastic properties were determined using linear regression. PWV significantly increased with age (F = 25.6, p < 0.05, r2 = 0.7) while total brain stiffness significantly decreased with age (F = 6.1, p < 0.05, r2 = 0.36). Carotid artery stiffness (F = 4.3, p = 0.06, r2 = 0.28) and beta‐stiffness index (F = 2.9, p = 0.11, r2 = 0.21) tended to be inversely associated with total brain stiffness, whereas carotid artery compliance tended to be positively associated with total brain stiffness (F = 2.5, p = 0.14, r2 = 0.18). No relation was observed between PWV and total brain stiffness (F = 0.9, p = 0.37, r2 = 0.08). There were no associations between any measures of arterial stiffness and damping ratio. These preliminary data confirm that aging is associated with increase in arterial stiffness and loss of brain tissue integrity. They also indicate a possible association between large artery stiffening with brain tissue integrity and suggest that preserving elasticity of the carotid artery in particular may be important for protecting brain health with aging. Future work should assess the relation between carotid artery stiffness and brain mechanical properties in a larger group of individuals.Support or Funding InformationSupported by Center for Biomedical and Brain Imaging (CBBI) Pilot Grant P20GM103653 and Center of Biomedical Research Excellence (COBRE) Pilot Grant P20GM113125.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.