Oxidative stress and aging: Learning from yeast lessons

The yeast Saccharomyces cerevisiae has played a vital role in the understanding of the molecular basis of aging and the relationship of aging process with oxidative stress (non-homeostatic accumulation of Reactive Oxygen Species, ROS). The mammalian and yeast antioxidant responses are similar and over 25 % of human-degenerative disease related genes have close homologues in yeast. The reduced genetic redundancy of yeast facilitates visualization of the effect of a deleted or mutated gene. By manipulating growth conditions, yeast cells can survive only fermenting (low ROS levels) or respiring (increased ROS levels), which facilitates the elucidation of the mechanisms involved with acquisition of tolerance to oxidative stress. Furthermore, the yeast databases are the most complete of all eukaryotic models. In this work, we highlight the value of S. cerevisiae as a model to investigate the oxidative stress response and its potential impact on aging and age-related diseases.     

Neutrophil chemotaxis, phagocytosis and parameters of reactive oxygen species in human aging: cross-sectional and longitudinal studies

To assess the effect of aging on neutrophil (PMN) functions and the parameters related to reactive oxygen species (ROS), we measured the following in blood samples from 166 asymptomatic aged individuals: PMN activities including chemotaxis, phagocytosis and generation of ROS; the activity of superoxide dismutase (SOD) of blood cell; and serum lipid peroxide levels. Compared with non-aged adults, the older individuals showed markedly attenuated PMN chemotaxis, and slightly elevated serum lipid peroxide levels. Other parameters were not significantly different between the two aged groups. In contrast both to the elderly group as a whole and to the subgroup 65 to 79 years old, the subjects over greater than or equal to 80 years old showed normal PMN chemotaxis and serum lipid peroxide levels, as defined by the young adult control group. Thirty-two subjects who entered the study at ages 69 to 72 years were followed with serial assays for seven years; twenty-one of these subjects died during this observation period. There was a striking and significant difference between the survivors and nonsurvivors with regard to PMN chemotaxis and serum lipid peroxide levels; even when asymptomatic upon initial examination, the nonsurvivors showed diminished PMN chemotaxis and elevated lipid peroxide levels. It seems from both the cross-sectional and longitudinal parts of our study that PMN chemotaxis and serum lipid peroxide levels correlate with survival to advanced age.     

Genetic model for longitudinal studies of aging, health, and longevity and its potential application to incomplete data

Many longitudinal studies of aging collect genetic information only for a sub-sample of participants of the study. These data also do not include recent findings, new ideas and methodological concepts developed by distinct groups of researchers. The formal statistical analyses of genetic data ignore this additional information and therefore cannot utilize the entire research potential of the data. In this paper, we present a stochastic model for studying such longitudinal data in joint analyses of genetic and non-genetic sub-samples. The model incorporates several major concepts of aging known to date and usually studied independently. These include age-specific physiological norms, allostasis and allostatic load, stochasticity, and decline in stress resistance and adaptive capacity with age. The approach allows for studying all these concepts in their mutual connection, even if respective mechanisms are not directly measured in data (which is typical for longitudinal data available to date). The model takes into account dependence of longitudinal indices and hazard rates on genetic markers and permits evaluation of all these characteristics for carriers of different alleles (genotypes) to address questions concerning genetic influence on aging-related characteristics. The method is based on extracting genetic information from the entire sample of longitudinal data consisting of genetic and non-genetic sub-samples. Thus it results in a substantial increase in the accuracy of statistical estimates of genetic parameters compared to methods that use only information from a genetic sub-sample. Such an increase is achieved without collecting additional genetic data. Simulation studies illustrate the increase in the accuracy in different scenarios for datasets structurally similar to the Framingham Heart Study. Possible applications of the model and its further generalizations are discussed.     

Nutrition,aging and cancer: lessons from dietary intervention studies

There is convincing epidemiological and clinical evidence that, independent of aging, lifestyle and, notably, nutrition are associated with development or progression of major human cancers, including breast, prostate, colorectal tumors, and an increasingly large collection of diet-related cancers. Mechanisms underlying this association are mostly related to the distinct epigenetic effects of different dietary patterns. In this context, Mediterranean diet has been reported to significantly reduce mortality rates for various chronic illnesses, including cardiovascular diseases, neurodegenerative diseases and cancer. Although many observational studies have supported this evidence, dietary intervention studies using a Mediterranean dietary pattern or its selected food components are still limited and affected by a rather large variability in characteristics of study subjects, type and length of intervention, selected end-points and statistical analysis. Here we review data of two of our intervention studies, the MeDiet study and the DiMeSa project, aimed at assessing the effects of traditional Mediterranean diet and/or its component(s) on a large panel of both plasma and urine biomarkers. Both published and unpublished results are presented and discussed.     

Combining longitudinal studies of PSA

Prostate-specific antigen (PSA) is a biomarker commonly used to screen for prostate cancer. Several studies have examined PSA growth rates prior to prostate cancer diagnosis. However, the resulting estimates are highly variable. In this article we propose a non-linear Bayesian hierarchical model to combine longitudinal data on PSA growth from three different studies. Our model enables novel investigations into patterns of PSA growth that were previously impossible due to sample size limitations. The goals of our analysis are twofold: first, to characterize growth rates of PSA accounting for differences when combining data from different studies; second, to investigate the impact of clinical covariates such as advanced disease and unfavorable histology on PSA growth rates.     

Protein synthesis and aging: studies with cell-free mammalian systems.

A cell-free system devoid of polysomes, which translates natural mRNA, has been prepared from rat liver. It contains ribosomal subunits, ribosomes, aminoacyl-tRNA synthetases, tRNAs, and protein factors necessary for translation. Protein synthesis required an energy-generating system, mRNA, and 3 mM Mg2+ concentration, and it was inhibited by 7-methylguanylic acid. The total extent and the rate of protein synthesis were approximately 30% greater when the translating system was prepared from livers of 3-month-old rats, as compared to 30-month-old rats. A ribosome-free fraction containing the protein factors required for translation was also prepared from 3-month-old and 30-month-old rat livers and brains, by extraction with 0.5 M KCl. The high-salt extracts were analyzed for elongation factors EF-1 and EF-2 in a poly(U) translating system. Although the activity of EF-2 was similar in preparations from young and old rats, the EF-1 activity in the 3-month-old rat livers and brains was 30 to 40% greater than in 30-month-old animals. The protein synthesizing activity of high salt-washed ribosomes stripped of endogenous peptidyl-tRNA and mRNA, from livers and brains of young and old animals, was the same.     

Plasmodium falciparum clinical malaria: lessons from longitudinal studies in Senegal

Development of new antimalaria strategies and particularly vaccines, needs an in-depth understanding of the relationships between transmission, infection, immunity, morbidity and mortality. The intensive and longitudinal collection of entomological, parasitological and clinical data from the Senegalese populations of Dielmo (250-300 inhabitants), exposed to a perennial and intense transmission (about 200 infective bites/person/year) and of Ndiop (300-350 inhabitants) exposed to a seasonal transmission (about 20 infective bites/person/year), allows to respond to many questions about this subject. The acquisition of an antimalaria immunity as one gets older appears to reduce parasite density, complexity of infection, risk of new patent infection after a suppressive treatment but does not reduce the prevalence (as assessed by PCR) of infection which is commonly chronic and asymptomatic. The existence of a pyrogenic threshold effect of parasitaemia allows the individual diagnosis of malaria attacks. P. falciparum genotyping suggests that successive malaria attacks are due to distinct recently inoculated parasite populations that multiply initially without restriction, a dominant population is generally responsible of the clinical manifestations and all new populations do not trigger systematically attacks. The initial intensity of clinical manifestations does not differ perceptibly among children and adults, is not related to the duration of the attacks, does not allow the distinction between several types of attacks, is not predictive of their severity, and the clearance of parasites and manifestations is longer among youngest persons. The risk of malaria attacks is lower as one gets older and among carriers of AS haemoglobin, is higher when transmission increases and during pregnancy up to three months after delivery, and vary between children. The risk of malaria attack per infective bite is negatively related to the intensity of transmission. Because of their high sensitivity in malaria case detection, this type of small community-based studies are powerful and useful for the identification of protective immunological mechanisms as well as for testing rapidly and cheaply the clinical efficacy of any intervention such as antimalarial vaccines and drug therapy or prophylaxis. As a lot of vaccine candidates and drug combinations will be screened or tested in the perspective of the 'Roll-Back Malaria' programme, more attention must be given to longitudinal studies of this type.     

Cell replication and aging: in vitro and in vivo studies.

The relationship between human aging and cell replication has been investigated using two complementary approaches: in vitro studies of human fibroblasts derived from young and old volunteer members of the Baltimore Longitudinal Study and in vivo examinations of bone marrow cell populations from young and old mice and rats. Total proliferative capacity measured as either the onset of cell culture senescence or as in vitro life span was significantly diminished in cell cultures derived from old human donors when compared to parallel cultures established from young donors. Acute replicative abilities as measured by percent replicating cells, cell pupulation doubling time, cell number at confluency, and colony size distribution were also significantly decreased in human old cell populations. An in vivo cytogenetic technique for measuring cell replication was developed utilizing the differential staining properties of metaphase chromosomes of cells that have replicated in the presence of bromodeoxyuridine. With this technique, cell cycle times have been derived in vivo as well as in vitro. Preliminary in vivo results in both mice and rats indicate that cell replication is slowed in old animal cell populations. Further research will be directed both in vitro and in vivo at discerning the mechanisms for this impairment of cellular replication with aging.     

Biomarkers of aging in women and the rate of longitudinal changes

The purposes of this study were (1) to estimate biological age score (BAS) in Japanese healthy women based on the 4-7 years longitudinal data for physiological, hematological and biochemical examinations and (2) to examine the rate of aging changes in adult women based on the estimated BAS. The samples consisted of cross-sectional (n=981) and longitudinal (n=110) groups. Out of 31 variables examined, five variables (forced expiratory volume in 1.0 s, systolic blood pressure, mean corpuscular hemoglobin, glucose, albumin/globulin ratio) that met the following criteria: 1) significant cross-sectional correlation with age; 2) significant longitudinal change in the same direction as the cross-sectional correlation; and (3) assessment of redundancy, were selected as candidate biomarkers of aging. This variable set was then submitted into a principal component analysis, and the first principal component obtained from this analysis was used as an equation for assessing one's BAS. Individual BAS showed a high longitudinal stability of age-related changes, suggesting high predictive validity of our newly developed aging measurement equation. However, changes in the aging rate based on the estimated BAS were not constant. The mean slopes of the regression lines of BAS for the three age groups (age<45, 45相似文献   

Stochastic model for analysis of longitudinal data on aging and mortality

Aging-related changes in a human organism follow dynamic regularities, which contribute to the observed age patterns of incidence and mortality curves. An organism's 'optimal' (normal) physiological state changes with age, affecting the values of risks of disease and death. The resistance to stresses, as well as adaptive capacity, declines with age. An exposure to improper environment results in persisting deviation of individuals' physiological (and biological) indices from their normal state (due to allostatic adaptation), which, in turn, increases chances of disease and death. Despite numerous studies investigating these effects, there is no conceptual framework, which would allow for putting all these findings together, and analyze longitudinal data taking all these dynamic connections into account. In this paper we suggest such a framework, using a new version of stochastic process model of aging and mortality. Using this model, we elaborated a statistical method for analyses of longitudinal data on aging, health and longevity and tested it using different simulated data sets. The results show that the model may characterize complicated interplay among different components of aging-related changes in humans and that the model parameters are identifiable from the data.     

Fluorophores from aging human articular cartilage.

Human articular cartilages of various ages were digested with collagenase, and the fluorescence of the digests was measured as a function of age. At acidic pH, all collagenase-treated fractions were found to contain two main fluorophores with fluorescence maxima at 395 and 385 nm (excitation at 295 and 335 nm, respectively). Each fluorophore was isolated from the hydrolysate and its structure was deduced from spectral and chemical data. The 395/295 nm fluorophore was identified as pyridinoline, which is one of the non-reducible cross-linkages in collagen. The 385/335 nm fluorophore was identical to pentosidine, which was isolated from human dura mater and characterized by Sell and Monnier in 1989. Our results showed that the amount of pentosidine per collagen in human articular cartilage increases linearly with age (r = 0.929, p less than 0.005), while the amount of pyridinoline per collagen remained constant and was not correlated with age (r = 0.20). On the other hand, the amount of pentosidine per pyridinoline increased exponentially during life (r2 = 0.839, p less than 0.05).     

Enzymatic studies on the skeletal myosin A and actomyosin of aging rats.

Myosin A and actomyosin were isolated from the skeletal muscle of old and young rats. The velocity of the Ca2+ activated myosin A ATPase was increased in the case of the older animals. On the other hand the velocity of the Mg-2plus activated actomyosin ATPase was decreased in the skeletal muscle of the aging rats. At 5 X 10-5M EGTA concentration the inhibition of the Mg-2plus activated myosin B ATPase of the 1-month-old rats was two- to threefold smaller than that of the older animals. It was shown that the myosin A component of the actomyosin was responsible for the decreased troponin inhibition in the case of the 1-month-old rats. Between the ages of 1 month and 29 months the number of free myosin A SH groups decreases by 50%. The lipid peroxidation in the muscle of the 1-month-old animals.     

Morphological and functional studies during aging at mitochondrial level. Action of drugs

1. Mitochondria show morphological changes on aging: the volume density decreases and the total surface area or volume increase. 2. Biochemical studies indicated a decrease in the rate of oxygen consumption and ATP levels for increasing age. Measurements of calcium transport across the mitochondrial membrane revealed a decrease in accumulated calcium and an alteration in the uptake kinetics of the ion in older animals. 3. Theophylline and calcitonin action were also studied. In both age groups (young and old) theophylline shows an inhibitory effect on all the parameters studied (both morphological and biochemical). 4. Calcitonin showed no effect on morphological and respiratory parameters, although it increased calcium uptake into the mitochondrion to a lesser extent in the 24 month old animals.