The allele (A) in the promoter region of the HSP70-1 gene is unfavorable to longevity in women. Heat shock proteins (HSPs) are crucial for maintaining cell homeostasis and survival during and after various stresses, affecting the chance of health and survival at the organismal level. We investigated whether the gene pool relevant to the (A/C)110 polymorphism in the promoter region of the HSP70-1 gene changes as the population ages and survival selection occurs. A total of 591 southern Italian subjects were enrolled in the study, free of clinically manifest diseases and with normal hematological and chemical parameters. A significant age-related decrease in the frequency of allele (A)110 was observed in females. The probability ratio of 0.403 (95% confidence interval [0.163, 0.910]) computed by considering female centenarians as cases and young women (18-49 years old) as controls showed that the (A)110 allele is unfavorable to longevity in females.

Heat shock proteins (HSPs) play a crucial role in stress response as molecular chaperones, which is conserved during evolution and likely involved in mechanisms modulating human aging. HSP70-1 is a gene encoding for Hsp70 protein, one of the major inducible heat shock proteins. An A/C polymorphism lies in the HSE region of the HSP70-1 gene at 110 nt from the transcription starting site, which was analyzed by automatic DNA sequencing.

A total of 591 unrelated subjects were analyzed, including 263 males and 328 females with median ages of 57.0 and 56.5 years, respectively, with an age range of 18-109 years. The age-related trajectories of both allele (A)110 frequencies and genotypes carrying allele (A)110 were analyzed by the least squares method, showing a significant age-related decrease in the frequency of allele (A)110 in females. The odds ratio (O.R.) relevant to allele (A)110 was computed by taking carriers of allele (A)110 in the 90-109 years age class as cases and those in the 18-29 plus 30-49 years age class as controls, showing that the (A)110 allele is unfavorable to longevity in females.

In conclusion, the study shows that the allele (A)110 in the promoter region of the HSP70-1 gene is unfavorable to longevity in women. The research also suggests that HSP genes are good candidates for investigating gene factors that affect the rate and quality of human aging.Reliability of such studies: i) the homogeneity of the population, to avoid confounding factors due to population stratification; ii) the selection of the candidate gene, which should be based on strong biological hints (Tabor et al. 2002). The data presented here show that the (A/C)110 variability in the promoter region of the HSP70-1 gene is associated, in women, with the probability of survival to oldest age (O.R. = 0.403, with 95% c.i. [0.163, 0.910]). This positive association seems to be reliable and not due to population stratification, taking into account data regarding the structure and demographic history of the Calabrian population (Rose et al. 1996; Danubio et al. 1999; Baudi 2001). Moreover, the biological role of Hsp70 proteins in stress response and the link between stress response and aging ascertained in model organisms (Minois 2000) reinforce the choice of HSP70-1 gene as a candidate gene in human gene/longevity association studies. 

Results: In order to verify whether the genotypic/allelic pool changed as the population aged and selection for health or survival occurred, both female and male samples were subdivided into five age classes (18-29 years, 30-49 years, 50-69 years, 70-89 years, 90-109 years) and the (A/C)110 genotypic/allelic frequencies were estimated in each age class. Data are reported in Table 1. In each age class, and in both sexes, the observed genotypes were in agreement with those expected at Hardy-Weinberg equilibrium (P > 0.05).

Linear regression analysis was then applied to allele frequency data. In females (Figure 1), a decreasing trend of the frequency of allele (A)110 was observed with increasing age. The estimated value of the slope coefficient of the regression line, b = -0.0018, was significantly lower than zero because the 95% empirical confidence interval (c.i.) of 1 was [0.0030, 0.0005]. Moreover, the frequency of the allele (A)110 carriers (AA plus AC genotypes) showed a significant decrease with increasing age (b1 = -0.0013, 95% c.i. of 1 [-0.0027, -0.00013]). The age-related decrease of allele (A)110 indicated that this allele is unfavorable to female longevity. To check this indication, we estimated the O.R. relevant to allele (A)110 by assuming as cases the carriers of allele (A)110 in the 90-109 years age class and as controls those in the 18-29 plus 30-49 years age class (Table 1a). It should be noted that both allelic and genotypic frequency distributions were different between cases and controls (χ2 = 7.76, P = 0.005 for alleles; χ2 = 8.07, P = 0.018 for genotypes). The O.R. of 0.403 (95% c.i. [0.163, 0.910]) confirmed that the (A)110 allele is unfavorable for longevity in women.