Lack of Association between Human Longevity and Genetic Polymorphisms in Drug-Metabolizing Enzymes at the NAT2, GSTM1, and CYP2D6 Loci

Received: 4 September 1997 / Accepted: 13 December 1997

Abstract:

In this study, we explored the possible role of genetic polymorphisms of three drug-metabolizing enzymes, debrisoquine/sparteine hydroxylase (CYP2D6), glutathione S-transferase (GSTM1), and N-acetyltransferase (NAT2), as a putative genetic component of human longevity. We analyzed a total of 817 DNA samples from a centenarian and a control population (2070 years) using PCR-coupled RFLP methods. We genotyped subjects for the CYP2D6*3 (a deletion) and 2637 CYP2D6*4 (G A transition) alleles, four mutations in NAT2 [namely, NAT2*5A (C T), NAT2*6A (G A), 481 590 NAT2*7A (G A), and NAT2*14A (G A)], and for the presence or absence of GSTM1 gene deletion at 857 191. We found no significant difference at these three loci between centenarian and control subjects in terms of allelic variant frequencies, genotype distributions, or predicted phenotypes deduced from genotype combinations. By comparing the distribution of combined genotypes for the polymorphisms tested at the CYP2D6, NAT2, and GSTM1 loci, we found that none of the predicted phenotypes concerning debrisoquine hydroxylase extensive-metabolizer or poor-metabolizer phenotypes, slow or fast N-acetylation capacities, and active or defective glutathione S-transferase could be correlated with human longevity, alone or in combination.

Introduction:

The fraction of people who are living to very old age is considerably increasing. Attempts at estimating the upper limits to human longevity have failed to reach any definite conclusion (for reviews see Olshansky et al. 1990; Rattan 1995). Nevertheless, since 1992, the Chronos project at the Fondation Jean Dausset-CEPH collects DNA samples from French centenarians whose age is systematically confirmed by a birth certificate.

Interest in research on the molecular and biochemical basis of aging is growing rapidly. This is not only due to the rapidly growing fraction of elderly people but also to the realization that such persons are prone to age-associated diseases such as cardiovascular and cerebrovascular diseases, senile dementia, renal failure, osteoarthritis and osteoporosis, muscular atrophy, cataract, non-insulin-dependent diabetes (NIDDM), and cancer (Slagboom and Knook 1996). Centenarians are characterized by their capacity to have reached very old age yet have escaped these major age-associated diseases, which may result from optimal lifestyle and environmental conditions as well as from some genetically determined resistance against age-associated diseases and/or the aging process itself (Abbot et al. 1974; Schchter et al. 1993; Johnson 1997). While a genetic component for human longevity has long been postulated, the only defined genetic associations reported so far were found at the HLA (Proust et al. 1982; Takata et al. 1987) and the APOE (Schchter et al. 1994) loci.

Materials and Methods:

We compared the frequencies of polymorphic alleles of the CYP2D6, GSTM1, and NAT2 genes in centenarians and controls to test the working hypothesis that the highly variable, genetically determined xenobiotic-metabolizing capacity of humans may represent one genetic component of human longevity. We analyzed a total of 817 DNA samples using PCR-coupled RFLP methods. Centenarians had been recruited from all over France at their home or in health-care institutions, with personal informed consent, through the Chronos project at the Fondation Jean Dausset-CEPH. They were Caucasians, at least 99 years old on the day of blood collection, and had their residence in France. Controls aged 2070 years were chosen among unrelated normal individuals from the French CEPH cell bank (Dausset et al. 1990). 

Results:

We found no significant difference at these three loci between centenarian and control subjects in terms of allelic variant frequencies, genotype distributions, or predicted phenotypes deduced from genotype combinations. By comparing the distribution of combined genotypes for the polymorphisms tested at the CYP2D6, NAT2, and GSTM1 loci, we found that none of the predicted phenotypes concerningin dyes, antioxidants, pesticides, or other environmental and occupational pollutants. Three main DNA variants lacking in vitro NAT activity have been characterized in several studies from different populations (Hickman and Sim, 1991; Bell et al., 1993; Lin et al., 1994; Cascorbi et al., 1995), and at least 95% of slow acetylators can now be identified by PCR assays. A number of phenotyping analyses suggested an association between the slow-acetylator phenotype and individual susceptibility to diseases such as breast and bladder cancer (Bulowskaya et al., 1978; Cartwright et al., 1982), insulin-dependent (IDDM), and NIDDM (McLaren et al., 1977). However, recent genotyping studies failed to detect any association with NIDDM (Agundez et al., 1996) or IDDM (Mrozikiewicz et al., 1994) and NAT2 polymorphism. PCR primers used for the analysis of the NAT2, GSTM1, and CYP2D6 loci are summarized in Table 1.

Genotyping assay 

CYP2D6 locus analysis