Spatial Analysis and Surname Analysis: Complementary Tools for Shedding Light on Human Longevity Patterns

Genomics landscape of mitochondrial DNA variations in patients from South Italy affected by mitochondriopathies

Mitochondrial DNA (mtDNA) is a 16,569 base pairs, double-stranded, circular molecule that contains 37 genes coding for 13 subunits of the respiratory chain plus 2 rRNAs and 22 tRNAs. Mutations in these genes have been identified in patients with a variety of disorders affecting every system in the body. The advent of next generation sequencing technologies has provided the possibility to perform the whole mitochondrial DNA sequencing, allowing the identification of disease-causing pathogenic variants in a single platform. In this study, the whole mtDNA of 100 patients from South Italy affected by mitochondrial diseases was analyzed by using an amplicon-based approach and then the enriched libraries were deeply sequenced on the ION Torrent platform (Thermofisher Scientific Waltham, MA, USA). After bioinformatics analysis and filtering, we were able to find 26 nonsynonymous variants with a MAF <1% that were associated with different pathological phenotypes, expanding the mutational spectrum of these diseases. Moreover, among the new mutations found, we have also analyzed the 3D structure of the MT-ATP6 A200T gene variation in order to confirm suspected functional alterations. This work brings light on new variants possibly associated with several mitochondriopathies in patients from South Italy and confirms that deep sequencing approach, compared to the standard methods, is a reliable and time-cost reducing strategy to detect all the variants present in the mitogenome, making the possibility to create a genomics landscape of mitochondrial DNA variations in human diseases.

Which Factors Influence Healthy Aging? A Lesson from the Longevity Village of Bama in China

A growing aging population is associated with increasing incidences of aging-related diseases and socioeconomic burdens. Hence, research into healthy longevity and aging is urgently needed. Longevity is an important phenomenon in healthy aging. The present review summarizes the characteristics of longevity in the elderly population in Bama, China, where the proportion of centenarians is 5.7-fold greater than the international standard. We examined the impact of genetic and environmental factors on longevity from multiple perspectives. We proposed that the phenomenon of longevity in this region is of high value for future investigations in healthy aging and aging-related disease and may provide guidance for fostering the establishment and maintenance of a healthy aging society.

Thymic function and survival at advance ages in nursing home residents from Southern Italy

BACKGROUND

Immunosenescence is a complex process characterized by an age-related remodelling of immune system. The prominent effects of the immunosenescence process is the thymic involution and, consequently, the decreased numbers and functions of T cells. Since thymic involution results in a collapse of the T-cell receptor (TCR) repertoire, a reliable biomarker of its activity is represented by the quantification of signal joint T-cell receptor rearrangement excision circles (sjTRECs) levels. Although it is reasonable to think that thymic function could play a crucial role on elderly survival, only a few studies investigated the relationship between an accurate measurement of human thymic function and survival at old ages.

METHODS AND FINDINGS

By quantifying the amount sjTRECs by real-time polymerase chain reaction (PCR), the decrease in thymic output in 241 nursing home residents from Calabria (Southern Italy) was evaluated to investigate the relationship between thymic function and survival at old ages. We found that low sjTREC levels were associated with a significant increased risk of mortality at older ages. Nursing home residents with lower sjTREC exhibit a near 2-fold increase in mortality risk compared to those with sjTREC levels in a normal range.

CONCLUSION

Thymic function failure is an independent predictor of mortality among elderly nursing home residents. sjTREC represents a biomarker of effective ageing as its blood levels could anticipate individuals at high risk of negative health outcomes. The identification of these subjects is crucial to manage older people's immune function and resilience, such as, for instance, to plan more efficient vaccinal campaigns in older populations.

Searching for longevity hotspots in Denmark

While existing research on regions with high prevalence of centenarians has focused on selected candidate geographical regions, we explore the existence of hotspots in the whole of Denmark.

We performed a Kulldorff spatial scan, searching for regions of birth, and of residence at age 71, where an increased percentage of the cohort born 1906-1915 became centenarians. We then compared mortality hazards for these regions to the rest of the country.

We found a birth hotspot of 222 centenarians, 1.37 times more than expected, centered on a group of rural islands. Lower mortality hazards from age 71 onwards were confined to those born within the hotspot and persisted over a period of at least 30 years. At age 71, we found two residence-based hotspots of 348 respectively 238 centenarians, 1.46 and 1.44 times the expected numbers. One hotspot, located in high-income suburbs of the Danish capital, seems driven by selective in-migration of low-mortality individuals. The other hotspot seems driven by selective migration and lower morality among those born and residing in the hotspot.

Thus, Danish centenarian hotspots do exist. The locations and interpretation depend on whether we look at place of birth or of residence late in life.

Last name analysis of mobility, gender imbalance, and nepotism across academic systems

In biology, last names have been used as proxy for genetic relatedness in pioneering studies of neutral theory and human migrations. More recently, analyzing the last name distribution of Italian academics has raised the suspicion of nepotism, with faculty hiring their relatives for academic posts. Here, we analyze three large datasets containing the last names of all academics in Italy, researchers from France, and those working at top public institutions in the United States. Through simple randomizations, we show that the US academic system is geographically well-mixed, whereas Italian academics tend to work in their native region. By contrasting maiden and married names, we can detect academic couples in France. Finally, we detect the signature of nepotism in the Italian system, with a declining trend. The claim that our tests detect nepotism as opposed to other effects is supported by the fact that we obtain different results for the researchers hired after 2010, when an antinepotism law was in effect.

Human longevity: Genetics or Lifestyle? It takes two to tango

Healthy aging and longevity in humans are modulated by a lucky combination of genetic and non-genetic factors. Family studies demonstrated that about 25 % of the variation in human longevity is due to genetic factors. The search for genetic and molecular basis of aging has led to the identification of genes correlated with the maintenance of the cell and of its basic metabolism as the main genetic factors affecting the individual variation of the aging phenotype. In addition, studies on calorie restriction and on the variability of genes associated with nutrient-sensing signaling, have shown that ipocaloric diet and/or a genetically efficient metabolism of nutrients, can modulate lifespan by promoting an efficient maintenance of the cell and of the organism. Recently, epigenetic studies have shown that epigenetic modifications, modulated by both genetic background and lifestyle, are very sensitive to the aging process and can either be a biomarker of the quality of aging or influence the rate and the quality of aging.

On the whole, current studies are showing that interventions modulating the interaction between genetic background and environment is essential to determine the individual chance to attain longevity.

The impact of nutrients on the aging rate: A complex interaction of demographic, environmental and genetic factors

Nutrition has a strong influence on the health status of the elderly, with many dietary components associated to either an increased risk of disease or to an improvement of the quality of life and to a delay of age-related pathologies. A direct effect of a reduced caloric intake on the delay of aging phenotypes is documented in several organisms. The role of nutrients in the regulation of human lifespan is not easy to disentangle, influenced by a complex interaction of nutrition with environmental and genetic factors. The individual genetic background is fundamental for mediating the effects of nutritional components on aging. Classical genetic factors able to influence nutrient metabolism are considered those belonging to insulin/insulin growth factor (INS/IGF-1) signaling, TOR signaling and Sirtuins, but also genes involved in inflammatory/immune response and antioxidant activity can have a major role. Considering the worldwide increasing interest in nutrition to prevent age related diseases and achieve a healthy aging, in this review we will discuss this complex interaction, in the light of metabolic changes occurring with aging, with the aim of shedding a light on the enormous complexity of the metabolic scenario underlying longevity phenotype.

Consanguinity and late fertility: spatial analysis reveals positive association patterns

The role of consanguinity on human complex traits is an important and controversial issue. In this work we focused on the Sardinian population and examined the effect of consanguineous unions on late female fertility. During the last century the island has been characterized by a high incidence of marriages between relatives, favoured by socio economic conditions and geographical isolation, and by high fertility despite a widespread tendency to delay reproduction. Through spatial analysis techniques, we explored the geographical heterogeneity of consanguinity and late fertility, and identified in Central-Eastern Sardinia a common area with an excess of both traits, where the traits are positively associated. We found that their association did not significantly affect women's fertility in the area, despite the expected negative role of both traits. Intriguingly, this critical zone corresponds well to areas reported by previous studies as being peculiar for a high frequency of centenarians and for lower risk in pregnancy outcome. The proposed approach can be generally exploited to identify target populations on which socioeconomic, biodemographic and genetic data can be collected at the individual level, and deeper analyses carried out to disentangle the determinants of complex biological traits and to investigate their association.

Health status and 6 years survival of 552 90+ Italian sib-ships recruited within the EU Project GEHA (GEnetics of Healthy Ageing)

In a scenario of increasing life expectancy worldwide, it is mandatory to identify the characteristics of a healthy aging phenotype, including survival predictors, and to disentangle those related to environment/lifestyle versus those related to familiarity/genetics. To this aim we comprehensively characterised a cohort of 1,160 Italian subjects of 90 years and over (90+, mean age 93 years; age range 90-106 years) followed for 6 years survival, belonging to 552 sib-ships (familiar longevity) recruited (2005-2008) within the EU-funded GEHA project in three Italian geographic areas (Northern, Central and Southern Italy) different for urban/rural and socio-economical characteristics. On the whole, the following factors emerged as significant predictors of survival after 90 years of age: absence of cognitive impairment and physical disability, high hand grip strength scores and body mass index (BMI) values, "excellent/good" self-reported health, high haemoglobin and total cholesterol levels and low creatinine levels. These parameters, excluding BMI values, were also significantly associated within sib-ships, suggesting a strong familial/genetic component. Geographical micro-heterogeneity of survival predictors emerged, such as functional and physical status being more important in Southern than in Central and Northern Italy. In conclusion, we identified modifiable survival predictors related to specific domains, whose role and importance vary according to the geographic area considered and which can help in interpreting the genetic results obtained by the GEHA project, whose major aim is the comprehensive evaluation of phenotypic and genetic data.

SPATIAL ANALYSIS OF THE APTITUDE TO LATE MATERNITY ON THE ISLAND OF SARDINIA

This study examines local heterogeneity in the aptitude of Sardinian mothers towards late reproduction, and explores its temporal persistence and association with both post-reproductive longevity and propensity to consanguineous marriage. Data on women's fertility from 1961 and birth records for 1980–1996 from Vital Statistics were analysed by means of the following indicators: the incidence of old mothers at last childbirth, female mortality (1980–2001) at 80 years of age and over and the proportion of consanguineous marriages (1930–1969). A variable kernel-smoothing method was used to create interpretable representations of the true spatial structure of the indicators, and to highlight areas of higher than expected intensity. In particular, an area of reproductive and post-reproductive longevity was identified where the traits combine with a higher tendency to relatedness. Intriguingly, this area corresponds approximately to the geographically and historically well defined central-eastern zone, which was the refuge of Sardinians during past invasions, and overlaps the Ogliastra region, which has been widely studied for its genetic homogeneity.

The genetic component of human longevity: analysis of the survival advantage of parents and siblings of Italian nonagenarians

Many epidemiological studies have shown that parents, siblings and offspring of long-lived subjects have a significant survival advantage when compared with the general population. However, how much of this reported advantage is due to common genetic factors or to a shared environment remains to be resolved.We reconstructed 202 families of nonagenarians from a population of southern Italy. To estimate the familiarity of human longevity, we compared survival data of parents and siblings of long-lived subjects to that of appropriate Italian birth cohorts. Then, to estimate the genetic component of longevity while minimizing the variability due to environment factors, we compared the survival functions of nonagenarians' siblings with those of their spouses (intrafamily control group).We found that both parents and siblings of the probands had a significant survival advantage over their Italian birth cohort counterparts. On the other hand, although a substantial survival advantage was observed in male siblings of probands with respect to the male intrafamily control group, female siblings did not show a similar advantage. In addition, we observed that the presence of a male nonagenarians in a family significantly decreased the instant mortality rate throughout lifetime for all the siblings; in the case of a female nonagenarians such an advantage persisted only for her male siblings.The methodological approach used here allowed us to distinguish the effects of environmental and genetic factors on human longevity. Our results suggest that genetic factors in males have a higher impact than in females on attaining longevity.

A novel, population-specific approach to define frailty

The description of frailty, a syndrome of the elderly due to the decline of homeostatic capacities, has opened new opportunities in the study of the biological basis of human aging. However, the noticeable heterogeneity for this trait in different geographic areas makes it difficult to use standardized methods for measuring the quality of aging in different populations. Consequently, the necessity to carry out population-specific surveys to define tools which are able to highlight groups of subjects with homogeneous aging phenotype within each population has emerged. We carried out an extensive monitoring of the status of the elderly population in Calabria, southern Italy, performing a geriatric multidimensional evaluation of 680 subjects (age range 65-108 years). Then, in order to classify the subjects, we applied a cluster analysis which considered physical, cognitive, and psychological parameters such as classification variables. We identified groups of subjects homogeneous for the aging phenotypes. The diagnostic and predictive soundness of our classification was confirmed by a 3-year longitudinal study. In fact, both Kaplan-Meier estimates of the survival functions and Cox proportional hazard models indicate higher survival chance for subjects characterized by lower frailty. The availability of operative frailty phenotypes allows a reappraisal of the biological basis of healthy aging as it regards both biomarkers correlated with the frail phenotype and the genetic variability associated with the phenotypes identified. Indeed, we found that the frailty phenotype is strongly correlated with clinical parameters associated with the nutritional status.

Epidemiological, clinical, and genetic characteristics of Paget's disease of bone in a rural area of Calabria, Southern Italy

BACKGROUND

The prevalence of Paget's disease of bone (PDB) is unknown in peninsular Southern Italy, although an elevated clinical severity of the disease was reported in patients from Campania.

AIM

This study was performed to evaluate the epidemiological and genetic characteristics of PDB in a rural area of Calabria, the southernmost region in the Italian peninsula.

SUBJECTS AND METHODS

We examined 1068 consecutive pelvic radiographs of patients older than 40 yr referred for any reason to the "Spinelli" Hospital, Belvedere Marittimo, from January 1st 2004 to December 31st 2006. In subjects with radiological findings of pelvic PDB, a 99m Technetium methylene diphosphonate bone scan and the sequence analysis of the sequestosome 1 (SQSTM1) gene were subsequently performed.

RESULTS

In the examined geographic area, the crude radiographic prevalence of pelvic PDB was 0.74% (8/1068; male:female 5:3, mean age 71.6 ± 13.1 yr) whereas the estimated overall prevalence of PDB between 0.82% and 1.21%. PDB patients from Calabria showed clinical characteristics similar to those reported in patients from Campania. The disease was also frequently complicated by osteoarthritis and the right side of the body was more affected than the left. The SQSTM1 gene analysis revealed the presence of a novel missense mutation (M401V) in exon 8 in one subject with a familial and aggressive form of PDB.

CONCLUSION

The study results confirmed that patients with PDB from rural districts of Southern Italy show an earlier onset and an increased clinical severity of the disease that appears mostly independent from the presence of germinal SQSTM1 mutations.

Gender-specific association of ADA genetic polymorphism with human longevity

Aim of this study was to investigate whether the polymorphic ADA (Adenosine Deaminase, EC 3.5.4.4) gene, which determines the cellular level of adenosine and plays a crucial role in the regulation of the immune system and in the control of metabolic rates, is involved in longevity. 884 unrelated healthy individuals (age range 10-106 years, 400 males and 484 females) from central Italy were studied. ADA genotyping was performed by RFLP-PCR. Frequency distributions were compared using the chi-square test and a three-way contingency table analysis by a log linear model was applied to test independence between the variables. We found that ADA influences human life-span in a sex and age specific way. An increased frequency of ADA*2 carriers was found in males aged 80-85, and a decreased frequency in males over 85 (chi(2) = 13.93; df = 3; P = 0.003); significant differences among the age groups was not found in females. A strong interaction among age groups, ADA genotype and sex (G = 15.086; df = 3; P = 0.0017) was found. Males aged 80-85 could be protected from ischemic stroke by higher levels of adenosine (determined by the ADA*2 allele). The decrease of ADA*2 carriers in males over 85 may depend essentially on immunological factors; reduced levels of adenosine protect from asthma and other pulmonary diseases and lead to a reduced activation of inflammatory cells and pro-inflammatory cytokines production. Moreover, the low level of adenosine may potentiate the activity of NK and other cellular effectors against tumor cells. The negligible effect of ADA genetic polymorphism in females suggest a marginal influence of genetic factors in determining longevity in this sex, confirming previous reports.