FOXO3A genotype is strongly associated with human longevity

Bradley J. Willcox*†‡§, Timothy A. Donlon*¶, Qimei He*, Randi Chen*†, John S. Grove*¶(cid:1), Katsuhiko Kamal H. Masaki*†‡, D. Craig Willcox*,**, Beatriz Rodriguez*†‡, and J. David Curb*†‡

*Pacific Health Research Institute, 846 South Hotel Street, Honolulu, HI 96813; †Honolulu Heart Program, Kuakini Medical Center, 347 North Kuakini Street, HPM-9, Honolulu, HI 96817; Departments of ‡Geriatric Medicine and (cid:1)Public Health Sciences and Epidemiology, John A. Burns School of Medicine, University of Hawaii at Manoa, 347 North Kuakini Street, HPM-9, Honolulu, HI 96817; ¶Cancer Research Center of Hawaii, University of Hawaii, 1236 Lauhala St # 406, Honolulu, HI 96813; and **Okinawa International University, 2-6-1 Ginowan, Ginowan, Okinawa 901-2701 Japan

Edited by Cynthia J. Kenyon, University of California, San Francisco, CA, and approved July 9, 2008 (received for review February 5, 2008)

homolog ‘‘SIRT1,’’ influences several downstream transcription events affecting lifespan, including the cellular response to stress. SIRT1 accomplishes this by regulating the FOXO (Forkhead box transcription) factors, a family of proteins that function as sensors in the IIS pathway and influence mammalian longevity (17).

component, yet little is known about its genetic antecedents. Increasing evidence from animal models suggests that the insulin/ IGF-1 signaling (IIS) pathway is an important, evolutionarily con- served biological pathway that influences aging and longevity. How- ever, to date human data have been scarce. Studies have been hampered by small sample sizes, lack of precise phenotyping, and populationstratification,amongotherchallenges.Therefore,tomore precisely assess potential genetic contributions to human longevity from genes linked to IIS signaling, we chose a large, homogeneous, long-lived population of men well-characterized for aging pheno- types, and we performed a nested-case control study of 5 candidate longevity genes. Genetic variation within the FOXO3A gene was strongly associated with human longevity. The OR for homozygous minor vs. homozygous major alleles between the cases and controls was 2.75 (P  0.00009; adjusted P >= 0.00135). Long-lived men also presented several additional phenotypes linked to healthy aging, including lower prevalence of cancer and cardiovascular disease, better self-reported health, and high physical and cognitive function, despite significantly older ages than controls. Several of these aging phenotypeswereassociatedwithFOXO3Agenotype.Long-livedmen also exhibited several biological markers indicative of greater insulin sensitivity and this was associated with homozygosity for the FOXO3A GG genotype. Further exploration of the FOXO3A gene, human longevity and other aging phenotypes is warranted in other populations.

Genetic knock-out models in mammals (and other species) have also supported the IIS hypothesis. For example, mice with a fat-specific insulin receptor knockout (FIRKO) have reduced fat mass, protected against age-related obesity, and have extended longevity (21). Many other mutations in the IIS pathway appear to impact longevity in mice. These include mutations in the IGF-1 receptor (22), IRS-1 (22), IRS-2(23), PAPP-A (24), and the Ames

The basic molecular pathway of insulin signaling is conserved through evolution, evidence of which can be seen in yeast, flies, worms, rodents, and humans (25). A key regulator of this pathway in worms is the transcription factor DAF-16 (abnormal DAuer Formation-16), which is required for the large lifespan extension produced in C. elegans by inhibiting insulin/IGF-1 signaling (16). A number of factors appear to extend lifespan in C. elegans in a DAF-16 dependent manner, such as AMP kinase (26), 14–3-3 proteins (27), the lin-4 microRNA (28), and heat shock factor (29). HomologuesofDAF-16inseveralspecieshavebeenlinkedtoaging phenotypes and longevity (30). For example, the stress responsive Jun-N-K terminal kinase (JNK) pathway appears to require FOXO to prolong lifespan in Drosophila (31), and when flies over express dFOXO, the DAF-16 ortholog, it can increase lifespan (32). The convergence of such a diverse array of signals on DAF-16/FOXO suggests that this protein may be an important, evolutionarily conserved ‘‘node’’ in a signaling network that impacts aging and longevity.

gene  insulin  healthy aging  disease  disability

uman longevity is a complex phenotype with multiple deter- minants. While non-genetic factors, including diet, physical activity, health habits, and psychosocial factors are important, up to 50% of the variation in human lifespan might be explained by genetic differences (1–5). Several studies suggest that about 25% of the variation in human lifespan in average-lived populations can be explained by genetic factors, but in populations with larger numbers of exceptional survivors, the genetic contribution to lifespan may be much higher. For example, family studies of nonagenarians and centenarians show that sibling relative risk, a common method for assessingpotentialgeneticcontributiontoacomplexphenotype(6), is particularly high and grows with increasing age of the proband (7–10). However, studies of candidate ‘‘longevity-associated’’ genes in humans, hereafter referred to as ‘‘longevity genes,’’ have gen- erally been disappointing. Few replications have been observed across populations, with the exception of the APOE gene (3).