Telomere length is age-dependent and reduced in monocytes of Alzheimer patients

Telomeres are regions of repetitive DNA at the end of eukaryotic chromosomes, which prevent chromosomal instability. Telomere shortening is linked to age-related disease including Alzheimer's disease (AD) and has been reported to be reduced in leukocytes of AD patients. The aim of the present study was to measure telomere length in monocytes of patients with AD or mild cognitive impairment (MCI) compared to healthy subjects. Our data show significant shorter telomere length in AD patients (6.6 +/- 0.2 kb; p =0.05) compared to controls (7.3 +/- 0.2 kb). Telomere length of MCI patients did not differ compared to healthy subjects (7.0 +/- 0.2 kb). We observe a strong correlation between telomere length and age (p = 0.01, r = -0.38), but no association between telomere length and Mini-Mental State Examination score. In conclusion, the telomere length is age-dependent in monocytes and decreased in AD patients, which could mean that the AD pathology may contribute to telomere length shortening. The high variability of telomere lengths in individuals suggests that it will not be useful as a general biomarker for AD. However, it could become a biomarker in personalized long-term monitoring of an individuals' health. (C) 2011 Elsevier Inc. All rights reserved,