Genetic Associations with Human Longevity at the APOE and ACE Loci

Francois Schachter, Laurence Faure-Delanef, Frederique Gunot, Herve Rouger, Philippe Froguel, Laurence Lesueur-Ginot & Daniel Cohen

In an effort to dissect the genetic components of longevity, we have undertaken case-control studies of populations of centenarians (n=338) and adults aged 20-70 years at several polymorphic candidate gene loci. Here we report results on two genes, chosen for their impact on cardiovascular risk, encoding apolipoprotein E (ApoE) and angiotensin-converting enzyme (ACE).

We find that the e4 allele of APOE, which promotes premature atherosclerosis, is significantly less frequent in centenarians than in controls (p<0.001), while the frequency of the 2 allele, associated previously with type III and IV hyperlipidemia, is significantly increased (p<0.01). A variant of ACE which predisposes to coronary heart disease is surprisingly more frequent in centenarians, with a significant increase of the homozygous genotype (p<0.01). These associations provide examples of genetic influences on differential survival and may point to pleiotropic age-dependent effects on longevity.

APOE has three common alleles, designated 2, 3 and 4, which code respectively for the isoforms apoE2, apoE3 and apoE4. These alleles have a major impact on total and LDL-cholesterol levels in the serum, which in turn are highly correlated with risk for atherosclerotic cardiovascular disease. The 4 allele has been associated with ischemic heart disease in several studies. An insertion (I)/deletion (D) polymorphism in the ACE gene is associated with a major gene effect on the inter-individual variability of plasma ACE concentration, and the deletion polymorphism has been identified as a risk factor for myocardial infarction.

In order to search for genetic influences on human longevity, a population of 300 French centenarians (individuals in their 100th year and beyond) was collected, to be compared with a control group of 160 French adults aged 20-70. These populations were typed by DNA amplification for alleles of APOE and ACE.

The 4 allele frequency was significantly decreased (5.2% versus 11.2%, p<0.001), while the 2 allele frequency was significantly increased (12.8% versus 6.8%, p<0.01) in the centenarian group. The p values were less than 10 for e4 and less than 10~ for 2 when data for a second control group already genotyped were pooled with the new control population. The odds ratios, a measure of the relative chance of becoming a centenarian between subjects with or without a given allele, were 2 and 0.43 for the 2 and the 4 alleles, respectively.

The ACE allele distribution was shifted in centenarians, with an increase of the DD genotype (39.6% versus 25.6%, Table 2). The p values were less than 10- when all genotyped control populations were pooled. The D allele was more frequent in centenarians than in controls (p<0.01 when all genotyped control populations are pooled).

A subset of the centenarians included in this study had been independently selected through a different protocol, on the basis of their belonging to long-lived sibships. In this subgroup, the APOE and ACE genotypes displayed the same associations with an even more marked trend (Table 3).

We typed random subsamples of our populations at two other loci. A bi-allelic marker at D4595 on 4p16.3 chromosome (the Huntington's disease region), probe 674 with Acdl, gave a frequency of 0.33 for the rare allele in controls (n=158) and centenarians (n=164). A dinucleotide repeat within the B-cell leukemia/lymphoma 2 (BCL-2) gene on chromosome 18q21.3 (GenBank accession number: M15701) with one frequentAllele and eight rare alleles gave a frequency of 0.825 and 0.838 for the frequent allele in controls (n=103) and centenarians (n=108), respectively. Thus, for both of these polymorphisms, there was no difference between controls and centenarians. 

Gender effects and interaction between loci

Our population of centenarians was mainly composed of females, with a male to female ratio of 1:8 (see Table 1), reflecting the sex differential in longevity in France.

Table 3 APOE and ACE alleles in centenarians with long-lived siblings 

Discussion

The potential overlap between cases and controls (the frequency of controls that might become centenarians) is small enough - less than 2.4% and 0.5% of women and men respectively at age 70, based on 1980 estimates taken from a Caucasian population - as to remain negligible. The frequencies found in our control group for APOE and ACE alleles agree well with those reported in French populations from Paris, Lille, and Strasbourg (for the differences reported in Tables 1 and 2 are all enhanced when controls are compared with the selected subgroup of centenarians). However, statistical significance is diminished due to the small sample size. P1 refers to the population of all the centenarians. P2 refers to the population of controls.

Table 5 Interaction between APOE and ACE in centenarians