Polymorphisms of Drug-Metabolizing Enzymes in Healthy Nonagenarians and Centenarians: Difference at GSTT1 Locus

*Laboratorio Epidemiologico, Ospedale Policlinico IRCCS, Milan, Italy; †Institute of Internal Medicine, University of Milan, Milan, Italy; ‡Italian National Research Centers on Aging, INRCA, Ancona, Italy; §Department of Experimental Pathology, University of Bologna, Bologna, Italy; ¶Department of Experimental Pathology and Oncology, University of Florence, Florence, Italy; iAtherosclerosis Prevention Centre, Department of Internal Medicine, University of Genoa, Genoa, Italy; and **Genetics Research Insitute, Strada della Carita` 10, 20135 Milan, Italy

Received January 5, 2001

view (1). They are the best example of successful aging, and represent a valuable model for studying the ge- netic factors impinging on survival (risk factors for cancer and other major age-related diseases) (2). In fact, some risk factors for age-related diseases are hy- porepresented in centenarians (3), whilst others are unexpectedly present in healthy centenarians at equal or even increased frequency, in comparison to controls (4–7). Nevertheless, a number of studies revealed that in centenarians important changes occur in genetic variability of loci which are not risk factors for specific diseases, but are rather responsible for modulating the individual capacity to cope with stress, such as Ty- rosine Hydroxilase and mitochondrial DNA (8, 9). In this scenario, enzymes which are involved in the me- tabolism of potentially dangerous endogenous and ex- ogenous compounds, are likely to play a major role in human longevity. A variety of polymorphisms have been reported in these genes, and have been associated with susceptibility to cancer (10) and other age-related diseases such as Parkinson disease (11). Among these candidate genes, there are Phase 1 (oxidation, activa- tion) and Phase 2 (conjugation, detoxification) drug metabolizing genes, such as cytochrome P450 genes and glutathione S-transferase enzymes (GST). Cyto- chrome P450 genes are involved in the first step of the metabolism of polycyclic aromatic hydrocarbons con- tained in tobacco smoke, whilst GST genes are involved in the detoxification of several drugs, environmental substances, and carcinogenic compounds. In particu- lar, common polymorphisms leading to complete dele- tion of the gene cause a loss of GST functional activity. Individuals with such gene deletions exhibit decreased conjugation activity, and are consequently exposed to higher internal doses of potentially toxic intermediary

Drug metabolizing enzymes are involved in the detox- ification of several drugs, environmental substances, and carcinogenic compounds, and their polymorphisms have been associated with risk for a variety of cancer. In this paper, we compared the frequency of polymor- phisms in cytochrome P450-1A1 gene (CYP1A1), a phase 1 gene (oxidation, activation), and of two polymorphisms of glutathione S-transferase enzymes (GSTM1, GSTT1), two phase 2 genes (conjugation, detoxification). Two groups were studied and compared, i.e., 94 nonagenari- ans and centenarians and 418 control subjects of younger age. A significant difference in the proportion of nonagenarians and centenarians homozygotes for a GSTT1 deletion (28%) was observed in comparison to control subjects (19%, P 5 0.03). The distribution of the other gene polymorphisms did not differ in the two groups. These findings on phase 2 drug-metabolizing en- zyme gene polymorphisms may help in disentangling gene–environmental interactions which can have a role in successful aging and longevity, as well as in cancer incidence in the oldest old. © 2001 Academic Press

Key Words: ageing; longevity; centenarians; genetics of ageing; genetics of longevity; cancer; cancer and ageing; environmental carcinogens.

A significant proportion of centenarians are in good health (category A and B, as defined by Franceschi et al., 2000) either from a physical or a cognitive point of

1 To whom correspondence should be addressed at Laboratorio Epidemiologico, Ospedale Policlinico IRCCS, Via F. Sforza 28, 20122 Milano, Italy. Fax: 139 02 55038207. E-mail: sgen@iol.it.

metabolites from xenobiotic agents. Data on the fre- quency of polymorphisms in some phase 1 genes (CYP2E1 (12), CYP2C19 (14), CYP2D6 (13, 14)) and phase 2 genes (NAT2 (13, 14), GSTM1 (13)), as well as other polymorphisms associated with cancer suscepti- bility, i.e., p53 (15, 16), did not show any difference between centenarians and the general population. In this study, we focussed our attention on other members of phase 1 gene family (CYP1A1), and phase 2 genes (GSTT1 and GSTP1) never studied before in centenar- ians, as well as on a gene which has been studied in French centenarians with negative results (GSTM1) (13). The hypothesis was that the frequency of the least favorable polymorphisms should be lower in centenar- ians than that observed in the general population.

Genotype Frequency of Drug-Metabolizing Gene Polymorphisms in Centenarians and Younger Subjects

Centenarians Control subjects (n 5 94) (n 5 418) Genes Genotypes n (%) n (%) CYP1A1 Wild typea 70 (77)b 328 (79) Heterozygous 20 (22) 81 (19) Homozygous 1 (1) 9 (2) GSTM1 Nullc 47 (53) 211 (51) Present 41 (47) 198 (49) GSTT1 Nullc 25 (28) 76 (19) Present 63 (72) 330 (82)

x2 5 0.10, P 5 0.74; GSTT1, x2 5 4.18, P 5 0.03. a “Wild type” refers to the homozygotes for the common allele (absence of the restriction site polymorphism), heterozygous refers to the presence of the polymorphism on one allele, homozygous refers to the presence of the polymorphism on both alleles. b

MATERIALS AND METHODS