CYP2D6, NAT2 and CYP2EI genetic polymorphisms in nonagenarians

A. G. AGUNDEZ, INMACULADA RODRIGUEZ1, MANUELA OLJVERA, Josf MAR(A LADERO2, 1 A GARcfA , Jos^ M. RIBERA1, JUUO BENftEZ

Department of Pharmacology, School of Medicine, University of Extremadura, Badajoz, Spain Services of 'Geriatrics and 2Gastroenterology of the San Carlos University Hospital, Medical School, Complutense University, Madrid, Spain

Address correspondence to: J. M. Ladero.

Abstract

Background: enzymatic polymorphisms affecting the metabolic disposition of xenobiotics may modulate the rate of activation or deactivation of carcinogens and other toxic environmental chemicals. Hence, these polymorphisms may influence the risk of suffering some types of cancer and other degenerative diseases that are incompatible with

Patients: the three genotypes were determined in 41 nonagenarians (10 males, mean age 92.2 years, range 90-98) free of known malignancies or neurodegenerative diseases. The control groups comprised 217 healthy volunteers (128 males, mean age 36.3 years; SD, 12.7) for the CYP2D6 and NAT2 genotypes and 137 (116 males, mean age

Methods: after extraction of DNA from white blood cells, polymerase chain reaction and restriction fragment polymorphism methods were used to identify the allelic variants of the three genotypes. Results: we found no qualitative or quantitative difference in the mutations underlying the three genetic polymorphisms studied, nor in the expected enzymatic phenotypes. Instead, a close parallelism exists between advanced age and younger groups.

Conclusion: longevity does not seem to be related to any special configuration of these three polymorphic traits. Comparisons with younger controls may be adequate when studying the distribution of these polymorphisms in diseases affecting old people. No genetically determined differences in the activation of drugs metabolized by these enzymes are to be expected in very old people.

Keywords: longevity, CYP2D6, CYP2EI, NAT2, cytochrome P450, acetytator, polymorphisms

Introduction

Another possible link between genetic polymorph- isms and longevity is the association of several forms of cancer to genetic polymorphisms of enzymes that metabolize carcinogens [6]. There are several genetic polymorphisms, inherited as single Mendelian traits, that affect the function of enzymes involved in the activation or deactivation of environmental carcinogens. The three polymorphisms studied here have been linked to the of developing some common types of cancer [6-9] and CYP2D6 is also linked to the risk of early-onset Parkinson's disease [10]. We have studied the distribution of these enzymatic polymorphisms in a group of nonagenarians to see if there are any differences between this group and younger people that would suggest a role in determining human longevity.

these factors are under genetic control. Cardiovascular consequences of atherosclerosis and cancer are the two main causes of death in the post-reproductive period. Genetic polymorphisms affecting the structure or function of lipoproteins have been linked to erated atherosclerosis and hence to a shorter life expectancy. Modifications in the apo-AI-CIII-AIV cluster [1] may have such an effect; moreover, carriers the e4 allele of apo E rarely reach advanced ages [2, and show a higher risk of developing Alzheimer's [4]. Genes determining a moderate level of lipoprotein may be related to increased longevity [5].

Patients and methods

• Nonagenarians I 60 H • Younger controls "a e S 40- II 20- NAT2*4 NAT2*6A wirfsu Other NAT2 allelic variant

Forty-one patients over 90 (10 males, mean age years, range 90-98) in good general health, who were free of known malignancies or neurodegenerative diseases, were recruited from the San Carlos University Hospital's Geriatric Unit.

The control group for NAT2 and CYP2D6 poly- morphisms was 217 healthy subjects (128 males, mean age 36.3 years; SD, 12, 7). The control group for CYP2E1 genotype included 137 healthy volunteers (116 males, mean age 32 years; SD, 18.4). All control subjects were of the same ethnic (white Spanish) and geographic (the central area of Spain) origin.

The study was approved by the ethics committee of the San Carlos University Hospital (Madrid), under the guidelines of the 1975 Declaration of Helsinki. Patients and controls gave informed consent to be included in the study.

Figure I. Frequency of major NAT2 allelic variants in nonagenarians and younger controls. 'Other' includes any combination of mutations at positions 191, 341, 481, 590, 803 or 857 except those present in the allelic variants NAT2'6A and NAT2*5B. (For a review human NAT2 allelic variants see [24]).

venepuncture and anticoagulated in sterile glass tubes containing sodium citrate or ethylendiaminetetraacetic acid. The blood was transferred to sterile plastic vials and kept at -80°C until use. Genomic DNA samples were isolated from leucocytes as described elsewhere [11]. The analysis of the acetylator genotype was performed by using allele-specific polymerase chain reaction (PCR) amplification [12]. The identification of the CYP2D6 genotype was performed by the combined use of mutation-specific PCR and Xbal and restriction fragment polymorphism (RFLP) analyses as described elsewhere [13]. The analysis for the Rsal polymorphism at the 5'-flanking region of CYP2E1 carried out by an amplification-restriction procedure [14] with minor modifications.

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