That women live longer than men has been recognized. However, studies on identifying the genetic causes for this phenomenon are very limited and preliminary (30). Previously, Barbieri et al. (31) found that an exonic SNP replacing the amino acid Pro with Ala in peroxisome proliferators-activated receptor (PPAR) g-2 has different distributions between long-lived males and controls (P < 0.035), but not between female groups. Recently, it was found that an SNP (A/G)-308 in tumor necrosis factor has sex-dependent distributions, and allele A is specifically associated with male life expectancy (P < 0.019) (32). In an animal model, it has been shown that the increased expression of dFOXO is associated only with female lifespan (21). Since D. melanogaster hasBy regulating reproduction, it is uncertain whether this is sufficient to explain why FOXO1A is associated with human female longevity. In summary, this study demonstrates that FOXO1A is associated with female longevity while FOXO3A is associated with longevity in both genders. The association of both FOXO1A and FOXO3A with the human longevity trait is inherited in additive or dominant fashions. Han Chinese share the same longevity-associated haplotypes of FOXO3A with Japanese and German individuals. Although the finding that FOXO1A is not associated with male longevity has been replicated in Han Chinese and Japanese populations, the numbers of male centenarians are relatively small in both studies, so caution is needed. The association of FOXO1A and FOXO3A with human longevity needs to be validated in more ethnic groups and larger populations.

FOXO1A and FOXO3A, members of the forkhead transcription factors of the FoxO family, serve as direct downstream signaling molecules of AKT1 in insulin/insulin-like growth factor signaling pathways. In vivo, FOXO1A and FOXO3A regulate the cell cycle and growth, apoptosis, DNA damage responses, and angiogenesis (33-36). Malfunctions of FOXO1A or FOXO3A are involved in various cancers, insulin resistance, altered immune responses, and organ damage (15, 22, 37-40). In the cardiovascular system, for example, FOXO1A and/or FOXO3A are important for the onset of diabetic cardiomyopathy (41, 42), cardiac hypertrophy (43, 44), and ischemic heart disease (45, 46). It is likely that FOXO1A and FOXO3A affect longevity through multiple pathways such as insulin resistance, stress responses or proneness to disease. Earlier studies have provided several lines of evidence that both FOXO1A and FOXO3A are associated with HbA1c levels and fasting plasma insulin (12, 47, 48), suggesting that their contributions to human longevity may be due to balancing insulin sensitivity and insulin resistance through insulin/insulin-like growth factor signaling pathways. The question remains why FOXO1A is more closely associated with human female longevity.

MATERIALS AND METHODS

Study subjects: We performed the baseline survey of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) reported previously (61). In the survey, we interviewed 9093 oldest-olds aged 80-116 with a questionnaire containing 404 questions and physical tests throughout 85% of the regions of China. Among these 9093, 8441 were Han Chinese. In this study, a total of 761 centenarians (long-lived group) and 1056 unrelated younger individuals (control group) from southern China were selected and used as Population 1 for initial screening of all six SNPs. We also took 350 female centenarians and 350 younger individuals from northern China for the necessary replication of associations found in the initial screening. All participants were Han Chinese. Finger-prick blood samples from centenarians were spotted onto S&S no. 903 filter paper (Schleicher & Schuell, Germany) and stored at -48°C after the spots were completely dried. Two to three milliliters of blood were obtained from each younger individual. Written informed consent was obtained from all participants or their representative family members in cases of centenarians who were incapable of signing. BMI was calculated based on the formula (body weight/height2). The basic characteristics of the studied populations are presented in Table 1. The study protocol was approved by the Institutional Review Board, Institute of Molecular Medicine at Peking University. The study conformed to the principles outlined in the Declaration of Helsinki.

The two-tailed P-values, odds ratios, and 95% confidence intervals are presented for all association tests. Statistical power was calculated with the sampsi command in STATA (StataCorp LP) under a given sample size and significance level (α = 0.05).

SUPPLEMENTARY MATERIAL

Supplementary Material is available at HMG online. 

Genotyping of SNPs: We thank all participants and their families for their commitment and enthusiastic help in the Chinese Longitudinal Healthy Longevity Survey. Human genomic DNA was isolated from a 5-mm diameter punch-out from each blood spot or EDTA-anticoagulated blood using the proteinase K methods described previously (62). Based on the HapMap (CHBJPT), the tagging SNPs rs17630266, rs2755209, and rs2755213 were selected for FOXO1A, and rs2253310, rs2802292, and rs4946936 for FOXO3A. DNA fragments of 200-350 bp containing SNPs were amplified by PCR from 10 ng of genomic DNA from each participant, with the primShea-Drinkwater, M., Kang, S., Joyce, E., Nicoli, J., Benson, E. et al. (2012) A genome-wide scan for linkage to human exceptional longevity identifies a locus on chromosome 4. Proc. Natl Acad. Sci. USA, 109, 864– 868.

Reed, T., Dick, D.M., Uniacke, S.K., Foroud, T. and Nichols, W.C. (2010) Genome-wide scan for a healthy aging phenotype provides support for a locus near D4S1564 promoting healthy aging. J. Gerontol. A Biol. Sci. Med. Sci., 65, 171–177.