Abnormal platelet membrane composition in Alzheimer's-type dementia.

Area of Science:

• Neuroscience
• Biochemistry
• Cell Biology

Background:

• Previous studies indicated membrane abnormalities in Alzheimer's-type dementia (AD) platelets.
• These abnormalities were suggested to involve an increase in internal membranes.

Purpose of the Study:

• To investigate the cholesterol and phospholipid content of platelet and erythrocyte membranes in AD patients.
• To determine if lipid composition differences explain observed membrane abnormalities in AD.

Main Methods:

• Compared cholesterol and phospholipid content and ratios in platelet and erythrocyte membranes between AD patients and controls.
• Utilized fluorescence spectroscopy and electron microscopy data.
• Measured steady-state anisotropy of DPH in platelet membranes.

Main Results:

• No significant differences in total cholesterol or phospholipid content were found in platelets between AD patients and controls.
• A significantly lower cholesterol to phospholipid ratio was observed in platelets of AD patients compared to controls.
• This ratio correlated with DPH anisotropy, a measure of membrane fluidity.
• No differences were observed in erythrocyte membranes between the groups.

Conclusions:

• The findings do not support a general abnormality of membrane lipids in Alzheimer's-type dementia.
• The reduced cholesterol to phospholipid ratio in AD platelets suggests an increase in internal membrane structures.
• These internal membranes may be normal in composition but increased in quantity.