Gender-specific association of ADA genetic polymorphism with human longevity

Valerio Napolioni • Nazzareno Lucarini

Received: 19 August 2009/Accepted: 11 February 2010/Published online: 20 February 2010  Springer Science+Business Media B.V. 2010

protect from asthma and other pulmonary diseases and lead to a reduced activation of inflammatory cells and pro-inflammatory cytokines production. Moreover, the low level of adenosine may potentiate the activity of NK and other cellular effectors against tumor cells. The negligible effect of ADA genetic polymorphism in females suggest a marginal influence of genetic factors in determining longevity in this sex, confirming previous reports.

Abstract Aim of this study was to investigate whether the polymorphic ADA (Adenosine Deami- nase, EC 3.5.4.4) gene, which determines the cellular level of adenosine and plays a crucial role in the regulation of the immune system and in the control of metabolic rates, is involved in longevity. 884 unrelated healthy individuals (age range 10–106 years, 400 males and 484females) from central Italy were studied. ADA genotyping was performed by RFLP-PCR. Fre- quency distributions were compared using the chi- square test and a three-way contingency table analysis by a log linear model was applied to test independence between the variables. We found that ADA influences human life-span in a sex and age specific way. An increased frequency of ADA*2 carriers was found in males aged 80–85, and a decreased frequency in males over 85 (v2 = 13.93; df = 3; P = 0.003); significant differences among the age groups was not found in females. A strong interaction among age groups, ADA genotype and sex (G = 15.086; df = 3; P = 0.0017) was found. Males aged 80–85 could be protected from ischemic stroke by higher levels of adenosine (deter- mined by the ADA*2 allele). The decrease of ADA*2 carriers in males over 85 may depend essentially on immunological factors; reduced levels of adenosine

Introduction

During the last decade, experimental evidence has confirmed the profound impact of oxidative stress and immunosenescence on human life expectancy. Numerous epidemiological data indicate that longev- ity is largely determined by genetic factors and a number of possible associations between longevity and allelic variants of genes have been described. Long-lived individuals may lack numerous gene variants that are associated with premature mortality, and may also be carriers of protective variants (Scha¨chter 1998; Salvioli et al. 2006).

The ADA gene, encoding Adenosine Deaminase (ID 100; EC reference number EC 3.5.4.4), the enzyme that

inosine, is an excellent candidate for determining human longevity. In fact, its crucial role in the regulation of the immune system and in the control of metabolic rates is well known. Individuals carrying congenital defects of ADA are affected by severe combined immunodeficiency (SCID; OMIM 102700) characterized by the absence of functional T and B lymphocytes. In humans, ADA is located in the long arm of chromosome 20 (20q13.11) and its product is a polymorphic enzyme due to a G to A transition at nucleotide 22 of exon 1 which gives rise to an Asp (allele 1*) to Asn (allele 2*) amino acid substitution at position 8 of the mature protein. The enzymatic activity of ADA-Asn is *35% lower than that of the ADA-Asp allele (Battistuzzi et al. 1974). The fre- quency of the ADA*2 allele is estimated to be 0.06 in Westernpopulations, but is lower among individualsof African descent and higher in Southeast Asian popu- lations. The occurrence of the ADA*2 allele in at least two different genetic backgrounds, the Jewish Ashke- nazi and a large Mormon pedigree from Utah, suggests an independent recurrence of the G [ A mutation (Hirschhorn et al. 1994). Consistent with the indepen- dent recurrence of this mutation is the fact that the G- to-A transition occurs in a‘‘hotspot’’ CpG dinucleotide which is subject to a high mutation frequency.

Subjects

Eight hundred and eighty four unrelated healthy individuals randomly selected from the same geo- graphical area of central Italy were studied. Health status information obtained for all individuals indi- cated that no acute pathological condition was present. Almost all subjects up to age 65 were recruited in blood donor centers while those over 65 were recruited through family physicians or among guests in homes for the elderly. The subjects were divided into four age groups: 272 subjects\70 years (131 males and 141 females, mean age 49.8 ± 14.9), 280 subjects 80–85 years (143 males and 137 females, mean age 82.4 ± 1.6), 162 subjects 86–90 (64 males and 98 females, mean age 88.1 ± 1.5) and 170 subjects [90 years (62 males and 108 females, mean age 95.8 ± 2.5). The study was approved by the Ethical Committee of the Camerino University.

Carriers of the ADA*2 allele show reduced enzy- matic activity and consequently, a higher level of both circulating and intra-cellular adenosine, a situ- ation which may have a number of consequences. In fact, this purine nucleoside present in plasma and other extracellular fluids, is an important local hormone (like prostaglandins) which regulates immu- nological functions, blood flow, neurotransmission, smooth muscle physiology and platelet aggregation. Recent studies have also shown interesting interplays between adenosine and insulin. In the liver adenosine activates A2B receptors and counteracts the action of insulin (Yasuda et al. 2003) whereas it seems to facilitate insulin action in the adipocyte. The aden- osine deaminase complex protein (Kameoka et al. 1993) is identical to CD26, a T–cell-activating antigen and a glycoprotein present in epithelial cells of various tissues. Data also suggest that ADA and CD26 are co-localized on the surface but not inside T-cells. Cells expressing ADA and CD26 on their surface are much more resistant to the inhibitory effects of adenosine (Dong et al. 1996).

ADA genotyping