IL-6 (pg/ml)7.394.482.721.641.000.610.370.220.140.08WomenWomenMenWomen  

Fig. 1. IL-6 serum levels in elderly (A), long-lived (B) and centenarians (C) in relationship with –174 C/G locus. Women are repre- sented by circles ( Æ = C non-carriers, 1 = C carriers), and men by squares ( | = C non-carriers, ß = C carriers). Data are pre- sented as means and 95% confidence interval on a natural logarithmic scale. General linear model analysis was employed. (A.) | + ß vs. 1 + Æ : 0.773 vs. 0.333 pg/ml; F=10.05, df=1, p=0.002; | vs. ß : F=4.375, df=1, p=0.043; Æ vs. 1 : F=1.980, df=1, p=0.166; | vs. 1 + Æ : F= 10.756, p =0.006. (B.) | + ß vs. 1 + Æ : 0.903 vs. 0.822 vs. pg/ml; F=2.037, df=1, p=0.155; | vs. ß : adj F=5.75, df=1, p= 0.024; Æ vs. 1 : F=3.392, df=1, p=0.069. (C.) | + ß vs. 1 + Æ : 0.972 vs. 1.368 pg/ml; F=1.473, df=1, p=0.229; | vs. ß : F=5.12, df=1, p= 0.038; Æ vs. 1 : F=.206, df=1, p=0.652; ß vs. 1 + Æ : F=9.803, df=1, p =0.009. adj

The impact of –174 C/G locus on IL-6 serum levels was evaluated in a subgroup of 269 individuals. Data are shown in Fig. 1. In all three age groups, C– men had higher IL-6 serum levels than C+ men. Statistical analy- sis revealed that among elderly people (Fig. 1, A) C– men had the highest IL-6 serum levels, and that C+ men had the lowest IL-6 serum levels in centenarians (Fig. 1, C). In women, the impact of –174 C/G in each age group on IL-6 was not significant.

bin, a higher fasting insulin levels, and an higher insulin sensitivity [19, 20]. Accordingly, recent data suggest that C+ men may be protected from cardiovascular diseases. In particular, an under-representation of homozygotes for C allele at –174 locus has been found in a group of Swedish men having a myocardial infarction under age 40 [21]. Moreover, in middle-aged men, homozygotes for the G allele at –174 C/G locus have an increased artery intima-media thickness in the carotid bifurcation, a pre- dilection site for atherosclerosis [22]. On a demographic point of view, the decreased proportion of C– men in centenarians could be thus attributed to a higher mortal- ity of C– men for cardiovascular diseases, which are the most prominent causes of mortality among elderly in Western countries. However, the possibility cannot be excluded, that a gene variant in tight linkage disequilib- rium with IL-6 –174 C/G locus could be responsible, at least in part, for the results here presented, as well as for the above mentioned data, suggesting an association between this locus and susceptibility to diseases or pathological conditions.

Finally, a significant increase of IL-6 serum level was found in women ( U = 0.357, p= 0.001 for C+, U spearman spear- = 0.398, p= 0.0001 for C–), but not in men ( U = man spearman 0.016, p= 0.904 for C+; U = 0.202, p= 0.169 for C–). spearman

3 Discussion

The major finding reported in the present paper is that those individuals who are genetically predisposed to produce high levels of IL-6 during aging, i.e. C– men at IL-6 –174 C/G locus, have a reduced capacity to reach the extreme limits of human life-span. On the other hands, the capability of producing low levels of IL-6 throughout life-span (C+ individuals) appears to be ben- eficial for longevity, at least in men. Longitudinal studies are necessary to definitely confirm or disprove this pre- diction.

A great deal of data indicate that aging is characterized by an unbalance of proinflammatory status [18], and that inflammatory markers, IL-6 in particular, are associated with age-related diseases, and predict disability and mortality in the elderly [8, 9, 23]. Accordingly, the data presented here suggest that in an aging population, those people who have the tendency to produce ele- vated IL-6 quantities are less likely to reach the goal of longevity, and this fact is likely due to their increased proneness to develop age-related inflammatory dis- eases. If this perspective is correct, here we present a marker, the –174 C/G, which could help in identifying these “frail” individuals, far beyond the onset of any clini- cal and biochemical features.

In this investigation, we also found that women experi- ence high IL-6 serum levels later in life in respect to men, and that the age-related increase of IL-6 serum levels in women is quite independent from –174 C/G locus activ- ity. The inhibitory tone of estrogens on IL-6 gene expres- sion could explain such a gender difference [15], only if assuming that its long-term effects last until the extreme limits of human life-span.

4 Materials and methods

Intriguingly, this investigation is not the first report of a gender difference in the impact of a genetic factor on human longevity. Indeed, a similar male-specific differ- ence between young people and centenarians has been previously observed when the distribution of other germ- line variants of stress response genes (Mitochondrial DNA and Tyrosine Hydroxylase) were studied [16, 17]. Accordingly, we have proposed that men depend more on genetics than women to achieve longevity [18]. Con- versely, it can be hypothesize that female longevity depends more on environment or that in women genetic factors become important later in life.

4.1 Subjects

Blood cell DNA was collected from 700 randomly selected individuals, (482 women and 218 men), including 323 cente- narians, born and resident in Italy. All of the subjects were of Italian origin. In particular, three age groups were consid- ered: 194 randomly selected elderly people (age range 60–80 years, median age = 71, 93 men and 101 women), 183 randomly selected long-lived people (age range 81–99 years, median age = 91 years, 57 men and 126 women), and 323 centenarians (median age = 101, 68 men and 255 women). Serum was obtained from a subset of 269 individu- als (181 women and 88 men): a group of elderly people (age–range 60–80 years, median age = 73 years, 42 men and 47 women), a group of long-lived people (age-range 81–99 years, median age 94 years, 28 males and 82