Association between Matrix Metalloproteinases, Their Tissue Inhibitor and White Matter Lesions in Mild Cognitive Impairment.

BACKGROUND: White matter lesions are frequently found in mild cognitive impairments and Alzheimer's disease. Matrix metalloproteinases and the tissue inhibitor of metalloproteinases are implicated in amyloid-β catabolism and blood brain barrier permeability. However, it remains unclear whether they are associated with white matter lesions in Alzheimer's disease.

OBJECTIVE: The aim of this study was to examine the association of matrix metalloproteinases and tissue inhibitor of metalloproteinases with white matter degeneration in subjects with amyloid-positive mild cognitive impairment.

METHODS: Thirty subjects with amnestic mild cognitive impairment (14 men and 16 women; mean age, 75.6 ± 5.8 years) underwent magnetic resonance imaging, 11C-Pittsburgh Compound B positron emission tomography, and 18F-fluorodeoxyglucose positron emission tomography. Levels of plasma matrix metalloproteinases and tissue inhibitor of metalloproteinases were measured using multiplex assays. All subjects had an abnormal brain amyloid burden. Subjects were divided into two groups according to the presence of white matter lesions using the Fazekas scale. Cognitive function testing results i.e., mean 11C-Pittsburgh Compound B and 18F-fluorodeoxyglucose uptake, concentrations of matrix metalloproteinases and tissue inhibitor of metalloproteinases, and matrix metalloproteinases/tissue inhibitor of metalloproteinases ratios were compared between the groups. Correlation analysis was conducted to investigate the association between Fazekas scale score and clinical and neuroimaging variables as well as concentrations of matrix metalloproteinases and tissue inhibitor of metalloproteinases.

RESULTS: Matrix metalloproteinases-2, -8, and -9 levels, matrix metalloproteinases-2/ tissue inhibitor of metalloproteinases-2, matrix metalloproteinases-8/ tissue inhibitor of metalloproteinases-1, and matrix metalloproteinases-9/tissue inhibitor of metalloproteinases-1 significantly increased and tissue inhibitor of metalloproteinases-1 and-2 levels significantly decreased in the group with white matter lesions compared with the group without white matter lesions. Matrix metalloproteinases-2, -8, and -9 levels correlated positively and tissue inhibitor of metalloproteinases-1 and -2 levels correlated negatively with Fazekas scale score.

CONCLUSION: Plasma matrix metalloproteinases-2, -8, -9 and tissue inhibitor of metalloproteinases-1 and -2 levels are associated with white matter lesions in the mild cognitive impairment stage of Alzheimer's disease.