Proteome-based identification of plasma proteins associated with hippocampal metabolism in early Alzheimer's disease.
METHODS
There is an urgent need for peripheral surrogates of Alzheimer's disease (AD) that accurately reflect disease state and severity as well as correlate with key features of its neuropathology. The aim of this study was to identify plasma proteins associated with known in vivo markers of disease activity. In an earlier proteomic study of plasma, we discovered a panel of 15 proteins that were differentially expressed in AD and further validated complement factor-H (CFH) and alpha-2-macroglobulin (A2M) as AD-specific plasma biomarkers. In the present study, we extended these findings by testing the associations of these plasma proteins with neuro-imaging measures of disease progression in AD. We combined (1)H-magnetic resonance spectroscopy of the hippocampus and MRI-based hippocampal volumetry with proteomic analysis of plasma in early AD and mild cognitive impairment (MCI) to achieve this goal. Using (1)H-magnetic resonance spectroscopy, we derived estimates of the hippocampal metabolite ratio N-acetylaspartate/myo-inositol (NAA/mI), a biochemical measure that is associated with cognitive decline in early AD. We also undertook a proteomic analysis of plasma in these individuals using two-dimensional gel electrophoresis (2DGE).


RESULTS
We observed that two plasma proteins previously shown to be differentially expressed in AD, complement factor-H (CFH) and alpha-2-macroglobulin (A2M) showed significant positive correlations with hippocampal NAA/mI ratio in AD.


CONCLUSIONS
The association of plasma CFH and A2M with hippocampal NAA/mI in this cohort of AD subjects suggests that these proteins may reflect disease progression in early AD. These findings warrant validation in large population-based datasets.
Thambisetty
Madhav
M
King's College London, MRC Centre for Neurodegeneration Research, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, UK.
Hye
Abdul
A
Foy
Catherine
C
Daly
Eileen
E
Glover
Amanda
A
Cooper
Allison
A
Simmons
Andrew
A
Murphy
Declan
D
Lovestone
Simon
S
D000368:Aged; D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D015415:Biomarkers / Q000097:blood; D017242:Complement Factor H / Q000032:analysis; D018450:Disease Progression; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007294:Inositol / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009929:Organ Size; D000511:alpha-Macroglobulins / Q000032:analysis*
D015415:Biomarkers; C493495:CFH protein, human; D000511:alpha-Macroglobulins; D001224:Aspartic Acid; D007294:Inositol; D017242:Complement Factor H; C000179:N-acetylaspartate