Studying Arterial Stiffness Using High-Frequency Ultrasound in Mice with Alzheimer Disease

Alzheimer disease (AD) is an irreversible, progressive brain disorder that causes slow loss of memory and thinking skills, normally leading to death in 3-9 y. The etiology of AD is not fully understood but is widely believed to be induced by the production and deposition of amyloid-β peptide in the brain. Recently, a correlation was discovered between amyloid-β deposition and atherosclerosis in the cerebral arteries of postmortem brains, indicating that amyloid-β promotes atherogenesis and that in turn atherosclerosis promotes brain amyloid-β accumulation. However, a direct measurement of arterial stiffness for AD is lacking. In the present study, the pulse wave velocity (PWV) of the carotid artery was measured non-invasively in young (3-mo-old) and middle-aged (9-mo-old) wild-type (WT) and modeled AD mice to obtain quantitative data of arterial stiffness by using a 35-MHz high-frequency dual-element transducer. Experimental results show that the PWVs were 1.6 ± 0.5 m/s for young and 2.4 ± 0.4 m/s for middle-aged WT mice and 1.7 ± 0.4 m/s for young and 3.2 ± 0.6 m/s for middle-aged AD mice. Middle-aged groups had higher PWVs (p < 0.0001), which were more pronounced in the AD mice (p < 0.001). The differences in PWVs were not caused by arterial lumen diameter, wall thickness or contents of elastin or collagen. These results imply that AD increases the stiffness of the carotid artery and introduce ultrasound as a potential tool for AD research and diagnosis.