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53.44±7.42 years) were studied which resulted to observed associations between T2D and rs3758391 T-allele [46]. All in all the previous study found that rs3758391 may be associated with aging.

We investigated whether genetic variation at the SIRT1 locus correlates with the aging in a healthy Chinese population and found a meaningful divergence in genotypes distribution between aging and young, with an OR of 1.453 and 1.347 in C-allele. This indicates that carriers of the variant C-alleles of rs3758391 and rs4746720 have a high risk of aging than non-carriers. To the best of our knowledge, this is the first report of polymorphisms in the SIRT1 gene that is linked to healthy aging people. This intriguing outcome, viz. frequency of rs3758391 T-allele, was more in young than aging group in healthy Han Chinese people, was consistent with a recent work which reported that T-allele of rs3758391 in SIRT1 gene was associated with high cognitive function in Dutch people [12].

No association was detected between the SNP rs3758391 and extremely aging in German [14] and Dutch populations [12]. But in our study, we found that rs3758391 is associated with the healthy aging Chinese population. These might be because of the different genetic background in different population and the study in German and Dutch people were 85+ long-lived individuals (LLI) as against the 60+ aging people in this study. rs4746720, which was a TagSNP of SIRT1 gene in Chinese Han population, is in the 3' UTR. In some previous studies, there was only a little research about rs4746720 and this is perhaps because of the difference in selected pressure, i.e., rs4746720 is a TagSNP in Chinese population but not as a TagSNP in other populations. In our study, we found that frequency of rs4746720 T-allele frequency was a protective factor in healthy Han Chinese people.

The haplotypes employed here are likely to have captured some of the variation present in the SIRT1 genomic region for the population analyzed in this study. Four frequent SIRT1 haplotypes were identified, and haplotype 1 was found has a significant difference between aging and young groups (OR=1.63, p=0.01). Our findings suggest that certain SIRT1 gene variations may influence human aging in Chinese population. In future studies, we would compare the density of mRNA and protein of SIRT1 in the aging and control groups in order to identify the relationship between 2 SNPs and aging.

Our aim was to determine if an association exists between SIRT1 polymorphisms and healthy aging. In conclusion, this study showed that 2 SIRT1 gene polymorphisms may influence aging in healthy Han Chinese population. The use of healthy subjects excluded interference from some confounding factors such as age-related diseases, cancer and other diseases. All subjects in this study lived in the same city and all subjects were Han, so their environment and genetic background was similar, ruling out the pressure of selection interference. Since the sample size was small, this study might be considered a preliminary and initial work. The findings presented here may add a new factor to information on the multifactorial genetic contributions to aging.

Acknowledgements

We are grateful to the people who participated in this research. We thank Dr. Hong-Yu Zhou, Shao-Chen Dong, Ying Sun, Jing Liu, Lu-Lu Han for their assistance in identifying the healthy people. In addition, we thank Dr. Jia-Liang Xu for his help in preparing the paper. This

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