Research Paper Volume 7, Issue 10 pp 793—810

Defective mitochondrial respiration, altered dNTP pools and reduced AP endonuclease 1 activity in peripheral blood mononuclear cells of Alzheimer's disease patients

Scott Maynard1, *, , Anne-Mette Hejl2, , Thuan-Son T. Dinh1, , Guido Keijzers1, , Åse M. Hansen3,4, , Claus Desler1, , Maria Moreno-Villanueva5, , Alexander Bürkle5, , Lene J. Rasmussen1, , Gunhild Waldemar2, , Vilhelm A. Bohr1,6, ,

  • 1 Department of Cellular and Molecular Medicine, Center for Healthy Aging, University of Copenhagen, 2200 Copenhagen, Denmark
  • 2 Department of Neurology, Danish Dementia Research Centre, Rigshospitalet, University of Copenhagen, 2100 Copenhagen, Denmark
  • 3 Department of Public Health, University of Copenhagen, 1014 Copenhagen, Denmark
  • 4 The National Research Centre for the Working Environment, 2100 Copenhagen, Denmark
  • 5 Molecular Toxicology Group, University of Konstanz, D-78457 Konstanz, Germany
  • 6 Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224-6825, USA
* Present address: Danish Cancer Society Research Center, 2100 Copenhagen, Denmark

Received: August 25, 2015       Accepted: September 15, 2015       Published: October 21, 2015
How to Cite

Copyright: © 2015 Maynard et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.



Accurate biomarkers for early diagnosis of Alzheimer's disease (AD) are badly needed. Recent reports suggest that dysfunctional mitochondria and DNA damage are associated with AD development. In this report, we measured various cellular parameters, related to mitochondrial bioenergetics and DNA damage, in peripheral blood mononuclear cells (PBMCs) of AD and control participants, for biomarker discovery.


PBMCs were isolated from 53 patients with AD of mild to moderate degree and 30 age-matched healthy controls. Tests were performed on the PBMCs from as many of these participants as possible. We measured glycolysis and mitochondrial respiration fluxes using the Seahorse Bioscience flux analyzer, mitochondrial ROS production using flow cytometry, dNTP levels by way of a DNA polymerization assay, DNA strand breaks using the Fluorometric detection of Alkaline DNA Unwinding (FADU) assay, and APE1 incision activity (in cell lysates) on a DNA substrate containing an AP site (to estimate DNA repair efficiency).


In the PBMCs of AD patients, we found reduced basal mitochondrial oxygen consumption, reduced proton leak, higher dATP level, and lower AP endonuclease 1 activity, depending on adjustments for gender and/or age. CONCLUSIONS: This study reveals impaired mitochondrial respiration, altered dNTP pools and reduced DNA repair activity in PBMCs of AD patients, thus suggesting that these biochemical activities may be useful as biomarkers for AD.


AD: Alzheimer's disease; APE1: AP-endonuclease 1; BER: base excision repair; dTNPs: deoxyribonucleoside triphosphates; ECAR: extracellular acidification rate; MMSE: mini-mental state examination; OCR: oxygen consumption rate; OGG1: 8-oxoG DNA glycosylase 1; PBMC: peripheral blood mononuclear cells; ROS: reactive oxygen species.