Research article

Brain type carnosinase in dementia: a pilot study

Cynthia M Balion^1,2 , Carolyn Benson^1,2 , Parminder S Raina⁴ , Alexandra Papaioannou^1,3 , Christopher Patterson^1,3 and Afisi S Ismaila⁴

¹Department of Laboratory Medicine, Hamilton Health Sciences, Hamilton, Ontario, Canada

²Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada

³Department of Medicine, McMaster University, Hamilton, Ontario, Canada

⁴Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada

author email corresponding author email

BMC Neurology 2007, 7:38doi:10.1186/1471-2377-7-38

Published:	5 November 2007

Abstract

Background

The pathological processes underlying dementia are poorly understood and so are the markers which identify them. Carnosinase is a dipeptidase found almost exclusively in brain and serum. Carnosinase and its substrate carnosine have been linked to neuropathophysiological processes.

Methods

Carnosinase activity was measured by a flourometric method in 37 patients attending a Geriatric Outpatient Clinic. There were 17 patients without dementia, 13 had Alzheimer's disease (AD) and 7 had mixed dementia (MD).

Results

The range of serum carnosinase activity for patients without dementia was 14.5 – 78.5 μmol/ml/h. There was no difference in carnosinase activity between patients without dementia (40.3 ± 15.2 μmol/ml/h) and patients with AD (44.4 ± 12.4 μmol/ml/h) or MD (26.6 ± 15 μmol/ml/h). However, levels in the MD group were significantly lower than the AD group (p = 0.01). This difference remained significant after adjusting for gender, MMSE score, exercise, but not age, one at a time and all combined. The effect of other medical conditions did not remove the significance between the AD and MD groups. The MD group, but not the AD group, demonstrated a significant trend with carnosinase activity decreasing with duration of disease (from first recorded date of diagnosis to date of blood collection) (r = -0.76, p = 0.049). There was no association with carnosinase activity and MMSE score in the AD or MD group. Both AD and MD patients on any dementia medication (donepezil, galantamine, memantine) had higher carnosinase activity compared to those not taking a dementia medication. Carnosinase activity was higher in patients who regularly exercised (n = 20) compared to those who did not exercise regularly (n = 17)(p = 0.006).

Conclusion

This exploratory study has shown altered activities of the enzyme carnosinase in patients with dementia.