Longevity is a complex trait, which likely results from a blessed combination of genetic and non-genetic factors [38]. It is possible that the excess of environmental factors exert stronger influence on longevity than the genetic traits [39]. For example, in institutionalized or home- bound elderly, oxidative stress was reported to increase significantly [40,41], while in free living elderly it is not always elevated [42]. In addition, MTHFR C677T poly- morphism effect on homocysteine level can be minimized by folate intake. Studies attempting to assess the overall genetic influence on variations in the human life span indicated that approximately a quarter of the variation in the adult life spans could be attributed to genetic variation among individuals [43]. Thus, the strong influence of environmental factors on longevity might wipe the most likely weaker effect of genetic factors as observed in this study. However, the result which shows that number of relatives who exceeded 85 year-old was higher in the eld- erly group by approximately 25% compared to the young control group indicates the presence of genetic compo- nent to longevity in the Jordanian population. It is possi- ble that other polymorphisms are present in the region of the examined genes in the Jordanian population; this might buffer out or modulate the effect of the studied loci. Therefore, further studies are required to screen for the presence of such modifier polymorphisms in addition to direct measurement of levels and activity of gene products of the examined loci in according to subject's genetic background.

Acknowledgements

Research in Jordan University of Science and Technology, grant number 182/2007 to OK. The authors thank Dr. Karem Al-Zoubi for his comments on the manuscript.

References

Shringarpure R, Davies KJ: Protein turnover by the in aging and disease. Free Radic Biol Med

,

Kregel KC, Zhang HJ: An integrated view of oxidative stress aging: basic mechanisms, functional effects, and considerations. Am J Physiol Regul Integr Comp Physiol

(

):R

-

Tsubota K: [Oxidative stress and inflammation: hypothesis the mechanism of aging]. Nippon Ganka Gakkai Zasshi

(

):

-

discussion

Melov S, Ravenscroft J, Malik S, Gill MS, Walker DW, Clayton Wallace DC, Malfroy B, Doctrow SR, Lithgow GJ: Extension of span with superoxide dismutase/catalase mimetics.

,

(

):

-

Zelko IN, Mariani TJ, Folz RJ: Superoxide dismutase family: a comparison of the C

n-SOD (SOD

), (SOD

), and EC-SOD (SOD

) gene structures, and expression. Free Radic Biol Med

,

(

):

-

Shimoda-Matsubayashi S, Matsumine H, Kobayashi T, tori Y, Shimizu Y, Mizuno Y: Structural dimorphism in the chondrial targeting sequence in the human superoxide dismutase gene. A predictive evidence for formational change to influence mitochondrial and a study of allelic association in Parkinson's disease. chem Biophys Res Commun

,

(

):

-

Martin RC, Li Y, Liu Q, Jensen NS, Barker DF, Doll MA, Hein Manganese Superoxide Dismutase V

A Polymorphism in the Mitochondrial Targeting Sequence Associated with Reduced Enzymatic Activity in served Human Hepatocytes. DNA Cell Biol

Sutton A, Imbert A, Igoudjil A, Descatoire V, Cazanave S, Pessayre Degoul F: The manganese superoxide dismutase dimorphism modulates both mitochondrial import

NA stability. Pharmacogenet Genomics

,

(

):

-

Chan JM, Oh WK, Xie W, Regan MM, Stampfer MJ, King IB, Abe Kantoff PW: Plasma Selenium, Manganese Superoxide mutase, and Intermediate- or High-Risk Prostate Cancer. Clin Oncol

,

(

):

-

Zejnilovic J, Akev N, Yilmaz H, Isbir T: Association between ganese superoxide dismutase polymorphism and risk of cancer. Cancer Genet Cytogenet

,

(

):

-

el-Masry TM, Zahra MA, el-Tawil MM, Khalifa RA: superoxide dismutase alanine to valine polymorphism risk of neuropathy and nephropathy in Egyptian type

betic patients. Rev Diabet Stud

,

(

):

-

Aguilar B, Rojas JC, Collados MT: Metabolism of and its relationship with cardiovascular disease. J Thrombolysis

,

(

):

-

Reaching extreme age without diseases is one aspect of successful ageing [23]. In this study, elderly individuals with cardiovascular diseases, diabetes, or cognitive impairments were excluded from the current study. Previ- ous studies have shown that SOD2 -9T/C and MTHFR 677 C/T polymorphisms were associated with diabetes, cancer and cardiovascular diseases in other populations [9,10]. Thus, these polymorphisms might also associate with cer- tain diseases in the Jordanian population. Exploring this possibility is a matter of future research.

Conclusion

In this study, we investigated the contribution of the SOD2-9T/C and MTHFR 677C/T gene polymorphisms to the longevity phenotype in the Jordanian population. The

and neonatal lethality in mutant mice lacking manganese superoxide dismutase. Nat Genet

,

(

):

-

Van Remmen H, Ikeno Y, Hamilton M, Pahlavani M, Wolf N, Thorpe SR, Alderson NL, Baynes JW, Epstein CJ, Huang TT, et al.: Life-long reduction in M

OD activity results in increased DNA dam- age and higher incidence of cancer but does not accelerate aging. Physiol Genomics

,

(

):

-

Doonan R, M

lwee JJ, Matthijssens F, Walker GA, Houthoofd K, Back P, Matscheski A, Vanfleteren JR, Gems D: Against the oxida- tive damage theory of aging: superoxide dismutases protect against oxidative stress but have little or no effect on life span in Caenorhabditis elegans. Genes Dev

,

(

):

-

Paul A, Belton A, Nag S, Martin I, Grotewiel MS, Duttaroy A: Reduced mitochondrial SOD displays mortality characteris- tics reminiscent of natural aging. Mech Ageing Dev

,

(

-

):

-

Soerensen M, Christensen K, Stevnsner T, Christiansen L: The Mn- superoxide dismutase single nucleotide polymorphism rs

and the glutathione peroxidase

single nucleotide polymorphism rs

are associated with aging and lon- gevity in the oldest old. Mech Ageing Dev

,

:

Dossey L: Longevity. Altern Ther Health Med

,

(

):

-

-