Mechanisms of Ageing and Development 123 (2002) 1403(cid:2)1410 /

www.elsevier.com/locate/mechagedev

influences on human longevity by polymorphism (Tyrosine Hydroxylase gene) A relative risk approach

a b b b c a Qihua Tan , D. Bellizzi , G. Rose , S. Garasto , C. Franceschi , T. Kruse , d b d,e, J.W. Vaupel , G. De Benedictis , A.I. Yashin *

a Department of Clinical Biochemistry and Genetics, KKA, Odense University Hospital, Odense, b Cell Biology Department, University of Calabria, Rende, Italy

Department of Clinical Biochemistry and Genetics, KKA, Odense University Hospital, Odense, b Cell Biology Department, University of Calabria, Rende, Italy c Department of Experimental Pathology, University of Bologna, Bologna, Italy d Max-Planck Institute for Demographic Research, Doberaner Str. 114, 18057 Rostock, Germany e Center for Demographic Studies and Sanford Institute, Duke University, Durham, NC, USA

Received 27 February 2002; received in revised form 1 July 2002; accepted 17 July 2002

Abstract

A new method based on the recently developed relative risk approach is introduced, and applied to data from Italian centenarian study (965 subjects aged from 13 to 109 years old) for investigating influences on longevity by Tyrosine Hydroxylase (TH) gene variability. The strategic parameterization enables the model to disentangle the various ways by which HUMTHO1.STR alleles (alleles 6, 7, 8, 9, 10*, 10, as defined according to the number of repeats) may contribute in reducing or increasing the hazard of death with different patterns of influences. Among all the alleles, we have found that allele 10* (10 imperfect repeats) shows a remarkable dominant and beneficial effect that reduces the log hazard of death in an additive manner. The results confirm that HUMTHO1.STR polymorphism is involved in the modulation of human longevity. # 2002 Elsevier Science Ireland Ltd. All rights reserved.

Keywords: TH gene; Relative risk; Polymorphism; Longevity

1. Introduction

Life span is a complex trait, which is shaped by genetic, environmental, and stochastic factors. The genetic component has been intensively investi- gated by correlation studies in twins (McGue et

Increasing evidence shows that, as in model organisms, the capability to cope with stress in humans is also a leading factor in rate and quality of aging (Franceschi et al., 2000). Therefore, all the genes involved in the complex mechanisms which

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Q. Tan et al. / Mechanisms of Ageing and Development 123 (2002) 1403(cid:2)1410 /

control stress response are longevity candidate genes. The Tyrosine Hydroxylase (TH) gene (11p15.5) encodes TH, the rate-limiting enzyme in the synthesis of catecholamines, amino acid- derived molecules produced by the sympathetic nervous system in response to stress. An STR marker (HUMTHO1.STR) lies inside TH intron 1 (Polymeropoulos et al., 1991) a region which is involved in RNA alternative splicing of the TH primary transcript for generating four tissue- specific types of mRNA (Kobayashi et al., 1988). Association between HUMTHO1 variability and longevity was firstly observed (De Benedictis et al., 1998). Thereafter, gene(cid:2)environment interactions / and sex-specific genetic effects have been observed when HUMTHO1 variability was analyzed by models that combine genotypic and demographic information in the estimation of genetic influence on life span (Tan et al., 2001b). The involvement of the 11p15.5 chromosomal region in the long- evity phenotype has been confirmed by linkage disequilibrium studies carried out by analyses of two other polymorphic genes occurring in the same chromosomal region: Insulin and Insulin Growth Factor 2 (De Luca et al., 2001). However, the effects of HUMTHO1.STR allele(cid:2)allele inter- / actions on hazard of death and longevity have not been analyzed until now. The aim of the present study is to introduce an analytical method that permits to disentangle the effects of HUMTHO1.STR alleles on the longevity trait. The results confirm that this polymorphism is involved in the modulation of human longevity and that allele(cid:2)allele interaction plays an impor- / tant role.

view as far as the grandparents’ generations. All individuals gave informed consent prior to their inclusion in the study. A total of 965 subjects were collected in the new update. Among them, 210 are centenarians who were over 100 years old when blood sample was taken. In the centenarians, 68 are males and 142 are females with a female to male sex ratio about 2.1. The remaining 755 subjects cover a wide range of ages (from 13 to 99 years) with a median age of 59.

2.2. DNA analysis

DNA was extracted from blood buffy coats following standard procedures. HUMTHO1 typ- ing was carried out on PCR amplified DNA fragments (De Benedictis et al., 1998) by GEN- ESCAN software (ABIPRISM 310 Genetic Ana- lyzer, Applied Biosystem) and designated according to the repeat number.

2.3. Population survival data

The method for data analysis is based on the survival distribution function for the population from which the sample has been taken. Since subjects in the sample were born into different birth cohorts, we used in the calculation birth cohort life tables corresponding to subjects’ ages at participation. The Italian population survival data were provided by the Max-Planck Institute for Demographic Research in Rostock, Germany.

2.4. Statistical method