A link between sICAM-1, ACE and parietal blood flow in the aging brain

A connection between Alzheimer's disease (AD) and endothelium pathology has been inferred from measured decreases in both blood flow and metabolism in the parietal and temporal cortex. However, it is not known whether these alterations are seen in normal aging. We performed regional cerebral blood flow (rCBF) measurements in 22 AD patients and in 44 non-demented subjects during a simple test of information processing speed. Cerebrospinal fluid (CSF) levels of angiotensin-converting enzyme (ACE) and the soluble form of intercellular adhesion molecule-1 (sICAM-1) were analyzed in non-demented subjects. We found correlations between sICAM-1 and ACE (p=0.004), and sICAM (but not ACE) and CSF/plasma albumin ratio (p<0.0001). Higher concentrations of sICAM-1 (>893ng/L) and ACE (>5.22microg/L) were exclusively associated with lower parietal blood flow (p<0.001). The rCBF patterns in the AD and non-demented subjects with biomarker levels above median showed similar reductions in the temporoparietal areas. Our findings provide evidence that elevated CSF sICAM-1 and ACE are associated with lower perfusion levels in the parietal cortex of cognitively intact elderly.