Contents lists are available on the ScienceDirect Mechanisms of Ageing and Development journal homepage: www.elsevier.com/locate/mechagedev. 

The Mn-superoxide dismutase single nucleotide polymorphism rs4880 and the glutathione peroxidase 1 single nucleotide polymorphism rs1050450 are associated with aging and longevity in the oldest old. 

Mette Soerensen a,b,*, Kaare Christensen a, Tinna Stevnsner c, Lene Christiansen a,b 
a Danish Aging Research Center, Epidemiology, Institute of Public Health, University of Southern Denmark, J.B. Winsloews Vej 9B, 5000 Odense C 
b Department of Biochemistry, Pharmacology and Genetics, Odense University Hospital, 5000 Odense C, Denmark 
c Danish Aging Research Center, Department of Molecular Biology, University of Aarhus, C.F. Moellers Alle 1130, 8000 Aarhus C, Denmark 

ABSTRACT 

The free radical theory of aging states that reactive oxygen species (ROS) play a key role in age-related accumulation of cellular damage and consequently influence aging and longevity. Therefore, variation in genes encoding proteins that protect against ROS could be expected to influence variation in aging and life span. The rs4880 and rs1050450 SNPs in the manganese superoxide dismutase (MnSOD) and glutathione peroxidase 1 (GPX1) genes respectively are associated with age-related diseases and appear to affect the activities of the encoded variant proteins.

In this study, we genotyped these SNPs in 1650 individuals from the Danish 1905 cohort (follow-up time: 1998-2008; age at intake: 92-93 years; number of deaths: 1589 (96.3%)) and investigated the association with aging and longevity. We found decreased mortality of individuals holding either the MnSOD rs4880 C or the GPX1 rs1050450 T alleles (hazard ratio (MnSOD(CC/CT)) = 0.91, P = 0.002 and hazard ratio (GPX1(TT/TC)) = 0.93, p = 0.008). Furthermore, a synergistic effect of the alleles was observed (hazard ratio = 0.76, p = 0.001). Finally, moderate positive associations with good self-rated health, decreased disability and increased cognitive capacity were observed. Our results thus indicate that genetic variation in MnSOD and GPX1 may be associated with aging and longevity.

2009 Elsevier Ireland Ltd. All rights reserved.

Introduction 

Genetic factors contribute to the variation in life span by approximately 25% (Herskind et al., 1996), a contribution believed to be minimal before age 60 years and most profound from age 85 years and onwards (Hjelmborg et al., 2006). The candidate genes encode proteins involved in several biological processes including the protection against oxidative stress (Christensen et al., 2006). Reactive oxygen species (ROS) are produced because approximately 23% of the oxygen atoms taken up by the mitochondria are reduced insufficiently (Valko et al., 2004). ROS can oxidize and damage nucleic acids, proteins and lipids, thereby altering their stability and function. Thus, protein modifications (such as protein carbonylation and nitration) and the formation of lipid peroxidation adducts (e.g. 4-hydroxynonenal (HNE)) can be the results of ROS damage. HNE might subsequently give rise to the exocyclic etheno adducts of adenine, cytosine and guanine in DNA. Moreover, exposure of nucleic acids to ROS can generate a wide variety of modified bases, 8-oxo-7,8-dihydroguanine (8-oxoguanine), which induces base-mispairing, being one of the most abundant. Furthermore, ROS exposure may also result in imidazol ring-opened derivatives of pyrimidines (FaPy products) and in single-strand breaks in DNA. Over time, the sum of these alterations contributes to deleterious cellular changes leading to dysfunction of mitochondria, cells and ultimately of the organism; that is, the damage-induced alterations contribute to aging and longevity (Harman, 1973; Harman, 1991). In addition, the damage-induced alterations have been associated with certain cancers and cardiovascular and neurodegenerative disorders of old age (Antonella, 1999; Vijg, 2000).

Materials and methods 

Subjects 

Study participants were the Danish 1905 cohort, which includes all Danes born in 1905 (Nybo et al., 2001a). TheHypertension (Hsueh et al., 2005), sporadic motor neuron disease (Van Landeghem et al., 1999), Parkinson's disease (Shimoda-Matsubayashi et al., 1996), and Alzheimer's disease (Wiener et al., 2007).

2.2. Genotyping
DNA was isolated from cheek swabs or blood spots using the QIAamp DNA Mini Kit (Qiagen). The Danish 1905 cohort was genotyped for the rs4880 MnSOD SNP and for the rs1050450 GPX1 SNP using Taqman technology. Rs4880 MnSOD SNP primers: 5'-GGCTGTGCTTTCTCGTCTTCA-3' (forward) and 5'-TCTGCCTGGAGCCCAGATAC-3' (reverse) and rs1050450 GPX1 SNP primers: 5'-CATCGAAGCCCTGCTGTCT-3' (forward) and 5'-CACTGCAACTGCCAAGCA-3' (reverse) were purchased from DNA Technology A/S (Denmark), while rs4880 MnSOD SNP probes: 5'-Vic-CGAGGCCGAAACCC-3' and 5'-Fam-ACCGAGGCCAAAACC-3' and rs1050450 GPX1 SNP probes: 5'-Vic-ACAGCTGGGCCCTT-3' and 5'-Fam-ACAGCTGAGCCCTT-3' were purchased from Applied Biosystems (UK). DNA was amplified in a total volume of 10 ml containing 5 ml Taqman Universal MasterMix (Applied Biosystems), 900 nM of each primer, 200 nM of each probe, and 10 ng template DNA. PCR was performed in the ABI Prism 17700 Sequence Detector (Applied Biosystems) using the conditions recommended by the manufacturer, and the PCR data were analyzed using the Sequence Detector software version 1.7 (Applied Biosystems). 37 of the 1650 cohort members could not be genotyped with certainty for the rs1050450 GPX1 SNP due to poor quality of the DNA sample.