Publication:

Serum concentration of beta amyloid peptide and the activity of angiotensin converting enzyme in alzheimer's disease patients: search for a potential biomarker

Background Alzheimer’s disease (AD) is a disorder that affects mainly aged population. There is still no diagnostic test for the disease. Over the past few years investigators have studied several plasma biomarkers, most frequently, plasma beta amyloid peptide (Aβ). Level of Aβ depends on balance between production and clearance, accomplished by proteases. Our purpose was to study differences in the concentrations of Aβ's (and their ratios) and also in the activity of ACE in blood serum of AD patients and control groups.

Methods We measured the blood levels of beta amyloid 40 and 42 (Aβ40 & Aβ42) and their proportions in AD patients' blood samples. We also measured the angiotensin converting enzyme (ACE) activities.

Results This study showed that amounts of Aβ40 and Aβ42 in the blood serum of AD patients were significantly lower than that in control samples. The ratio of Aβ42/Aβ40 was not significantly different from controls. With respect to age and severity of disease we observed that Aβ40 concentration was lower in AD male patients and decreased with severity of AD. We also observed that serum Aβ42 concentration was decreased by increasing the age of female patients.

Conclusions Our results indicated that the ACE activity was significantly higher in patients in comparison with normal individuals. Also, it was revealed that increase in age resulted in reduced ACE activity in females and increased activity in males. This study also showed there was a positive relationship between ACE activity and severity of disease.