Genetic, epigenetic and posttranslational mechanisms of aging

Impact of sodium-glucose cotransporter-2 inhibitors on aging biomarkers and plasma ceramide levels in type 2 diabetes: beyond glycemic control

BACKGROUND

Aging is a complex biological process marked by the decline of physiological functions and heightened susceptibility to chronic illnesses, notably cardiometabolic disorders. Ceramides (Cer) are lipid derivatives linked to aging and metabolic diseases. Sodium-Glucose Cotransporter-2 inhibitors (SGLT2i), widely used in managing type 2 diabetes, have an unclear impact on aging biomarkers and Cer profiles.

OBJECTIVE

This study explored the association between SGLT2i use, plasma Cer levels (CerC16:0, CerC18:0, CerC22:0, CerC24:0, and CerC24:1), and aging biomarkers-Human Insulin-Like Growth Factor 1 (IGF-1), mammalian target of rapamycin (mTOR), 5-Methylcytosine (5MC), and Human H2AFX (Histone H2AX) in patients with type 2 diabetes mellitus (T2DM).

METHODS

In this retrospective study, 95 participants were divided into three groups: patients on SGLT2i (n = 34), patients on non-SGLT2i anti-diabetic treatments (n = 36), and healthy controls (n = 25). Plasma Cer and aging biomarkers were quantified using Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) and ELISA, respectively. Principal component analysis (PCA) assessed group-based clustering, while ANCOVA evaluated group differences with confounder adjustment.

RESULTS

SGLT2i-treated patients showed significantly lower CerC16:0, CerC22:0, and CerC24:1 levels (p < 0.01) and decreased 5MC and H2AX (p < 0.05) compared to non-SGLT2i patients. IGF-1 was significantly elevated in the SGLT2i group (p < 0.01), suggesting a possible protective effect on metabolic health. PCA distinguished control from diabetic groups but revealed overlap between SGLT2i and non-SGLT2i groups.

CONCLUSION

Beyond glucose control, SGLT2i may improve plasma Cer and aging markers in diabetic patients, supporting their broader therapeutic potential in aging and age-related diseases. Further large-scale studies are warranted to confirm these effects and underlying mechanisms.

Decoding the role of long noncoding RNAs in the healthy aging of centenarians

Aging is the largest risk factor of major human diseases. Long noncoding RNAs (lncRNAs) as the key regulatory elements have shown a strong impact on multiple biological processes as well as human disease mechanisms. However, the roles of lncRNAs in aging/healthy aging processes remain largely unknown. Centenarians are good models for healthy aging studies due to avoiding major chronic diseases and disabilities. To illustrate their ubiquitous nature in the genome and the 'secrets' of healthy aging regulation from the perspective of lncRNAs, peripheral blood samples from two regions consisting 76 centenarians (CENs), 54 centenarian-children (F1) and 41 spouses of centenarian-children (F1SP) were collected for deep RNA-seq. We identified 11 CEN-specific lncRNAs that is particularly expressed in longevous individuals. By kmers clustering, hundreds of human lncRNAs show similarities with CEN-specific lncRNAs, especially with ENST00000521663 and ENST00000444998. Using F1SP as normal elder controls (age: 59.9 ± 6.6 years), eight lncRNAs that are differentially expressed in longevous elders (CEN group, age: 102.2 ± 2.4 years) were identified as candidate aging/health aging-related lncRNAs (car-lncs). We found that the expression of eight car-lncs in human diploid fibroblasts displayed dynamic changes during cell passage and/or H2O2/rapamycin treatment; of which, overexpression either of THBS1-IT1 and THBS1-AS1, two lncRNAs that highly expressed in CENs, can remarkably decrease p16, p21 and the activity of senescent related β-galactosidase, suggesting that THBS1-IT1 and THBS1-AS1 can inhibit cellular senescence. We provided the first comprehensive analysis of lncRNA expression in longevous populations, and our results hinted that dysregulated lncRNAs in CENs are potential protective factors in healthy aging process.

lncRNA miat functions as a ceRNA to upregulate sirt1 by sponging miR-22-3p in HCC cellular senescence

Hepatocellular carcinoma (HCC) is a leading cause of cancer related deaths and lacks effective therapies. Cellular senescence acts as a barrier against cancer progression and plays an important role in tumor suppression. Senescence associated long noncoding RNAs (SAL-RNAs) are thought to be critical regulators of cancer development. Here, the long noncoding RNA (lncRNA) myocardial infarction-associated transcript (miat) was first identified as an HCC specific SALncRNA. Knockdown of miat significantly promoted cellular senescence and inhibited HCC progression. Mechanistic study revealed that SAL-miat acted as a competitive endogenous RNA (ceRNA) that upregulated the expression of sirt1 by sponging miR-22-3p. Moreover, miat downregulation activated the tumor suppressor pathway (p53/p21 and p16/pRb) and stimulated senescent cancer cells to secrete senescence-associated secretory phenotype (SASP), which contributed to inhibition of tumor cell proliferation, and resulted in the suppression of HCC tumorigenesis. Together, our study provided mechanistic insights into a critical role of miat as a miRNA sponge in HCC cellular senescence, which might offer a potential therapeutic strategy for HCC treatment.

Rn7SK small nuclear RNA is involved in cellular senescence

Rn7SK is a conserved small nuclear noncoding RNA which its function in aging has not been studied. Recently, we have demonstrated that Rn7SK overexpression reduces cell viability and is significantly downregulated in stem cells, human tumor tissues, and cell lines. In this study, we analyzed the role of Rn7SK on senescence in adipose tissue-derived mesenchymal stem cells (AD-MSCs). For this purpose, Rn7SK expression was downregulated and upregulated via transfection and transduction, respectively, in AD-MSCs and subsequently, various distinct characteristics of senescence including cell viability, proliferation, colony formation, senescence-associated β galactosidase activity, and differentiation potency was analyzed. Our results demonstrated the transient knockdown of Rn7SK in MSCs leads to delayed senescence, while its overexpressions shows opposite effects. When osteogenic differentiation was started, however, they exhibited a greater differentiation potential than the original MSCs, suggesting a potential tool for stem cell-based regenerative medicine.

Genetic Influences on Functional Capacities in Aging

PURPOSE

Older populations are characterized by great heterogeneity in functional capacities and understanding the factors underlying these differences has been a major area of research for some decades. Genetic differences arguably play an important role in the heterogeneity observed for many outcomes among older individuals. However, the role of genes in the variation and trajectories of functional capacities in older age is poorly understood. This review was conducted to explore the evidence for genetic influences on physical functional capacities in aging.

DESIGN AND METHODS

This rapid review was conducted using the following criteria: journal articles retrieved from the PubMed, Embase, AgeLine, Scopus, and Web of Science electronic databases including the key words: genetics, genotype, polymorphism, physical or functional performance, functional capacity, activities of daily living, older, and elderly. In total, 118 articles were included for initial review.

RESULTS

The heritability of objective measures of physical function ranges from 30% to 60% in studies of older twins. There is a paucity of evidence about genetic influences on functional capacities, but some candidate genes related to functional capacity have been identified.

IMPLICATIONS

No strong candidate genes exist for functional capacities. Current methodologies are beginning to generate new evidence about genetic influences on overall physical function at older ages, but the variety of measures of functional capacity makes evidence difficult to compare.

Long noncoding RNAs in aging and age-related diseases

Aging is the universal, intrinsic, genetically-controlled, evolutionarily-conserved and time-dependent intricate biological process characterised by the cumulative decline in the physiological functions and their coordination in an organism after the attainment of adulthood resulting in the imbalance of neurological, immunological and metabolic functions of the body. Various biological processes and mechanisms along with altered levels of mRNAs and proteins have been reported to be involved in the progression of aging. It is one of the major risk factors in the patho-physiology of various diseases and disorders. Recently, the discovery of pervasive transcription of a vast pool of heterogeneous regulatory noncoding RNAs (ncRNAs), including small ncRNAs (sncRNAs) and long ncRNAs (lncRNAs), in the mammalian genome have provided an alternative way to study and explore the missing links in the aging process, its mechanism(s) and related diseases in a whole new dimension. The involvement of small noncoding RNAs in aging and age-related diseases have been extensively studied and recently reviewed. However, lncRNAs, whose function is far less explored in relation to aging, have emerged as a class of major regulators of genomic functions. Here, we have described some examples of known as well as novel lncRNAs that have been implicated in the progression of the aging process and age-related diseases. This may further stimulate research on noncoding RNAs and the aging process.

DNA Damage, DNA Repair, Aging, and Neurodegeneration

Aging in mammals is accompanied by a progressive atrophy of tissues and organs, and stochastic damage accumulation to the macromolecules DNA, RNA, proteins, and lipids. The sequence of the human genome represents our genetic blueprint, and accumulating evidence suggests that loss of genomic maintenance may causally contribute to aging. Distinct evidence for a role of imperfect DNA repair in aging is that several premature aging syndromes have underlying genetic DNA repair defects. Accumulation of DNA damage may be particularly prevalent in the central nervous system owing to the low DNA repair capacity in postmitotic brain tissue. It is generally believed that the cumulative effects of the deleterious changes that occur in aging, mostly after the reproductive phase, contribute to species-specific rates of aging. In addition to nuclear DNA damage contributions to aging, there is also abundant evidence for a causative link between mitochondrial DNA damage and the major phenotypes associated with aging. Understanding the mechanistic basis for the association of DNA damage and DNA repair with aging and age-related diseases, such as neurodegeneration, would give insight into contravening age-related diseases and promoting a healthy life span.

Effect of elastin-derived peptides on the production of tissue inhibitor of metalloproteinase-1, -2, and -3 and the ratios in various endothelial cell lines

Tissue inhibitors of metalloproteinases (TIMPs) control the activity of metalloproteinases. Elastin-derived peptides (EDPs) are generated as a result of the degradation of elastin fibers. The EDPs bind to the elastin receptor and exert numerous biological effects. The aim of the present study was to compare the production of TIMP-1, TIMP-2 and TIMP-3 and their ratios in human endothelial cells (ECs) derived from three clinically important vascular localizations (coronary arteries, aorta and iliac artery), and evaluate the influence of a well-known EDP, κ-elastin. The highest concentration of TIMP-1 was identified in the aortic ECs, while the lowest concentration was observed in the ECs derived from the coronary artery. The opposite pattern was observed for TIMP-2 production. When the TIMP-3 concentration was analyzed in the three EC lines, no statistically significant differences were observed. Application of κ-elastin was found to decrease the TIMP-1 concentration in the aortic ECs, while an increase in the TIMP-1 concentration was observed in the ECs derived from the iliac artery. The most significant decrease in TIMP-2 concentration following κ-elastin administration was observed in the ECs obtained from the coronary arteries. Furthermore, the highest concentration of κ-elastin resulted in an increase in TIMP-3 production in the ECs derived from the coronary arteries. The following ratios of the TIMP concentrations were calculated: TIMP-1/TIMP-2, TIMP-1/TIMP-3 and TIMP-2/TIMP-3. Each ratio presented different values for the ECs obtained from the various localizations. In the majority of cases, the addition of κ-elastin did not significantly change these proportions. Therefore, these indicators may be characteristic features that can be used to describe ECs in various clinically important vascular localizations.

The mitochondrial free radical theory of aging

The mitochondrial free radical theory of aging is reviewed. Only two parameters currently correlate with species longevity in the right sense: the mitochondrial rate of reactive oxygen species (mitROS) production and the degree of fatty acid unsaturation of tissue membranes. Both are low in long-lived animals. In addition, the best-known manipulation that extends longevity, dietary restriction, also decreases the rate of mitROS production and oxidative damage to mtDNA. The same occurs during protein restriction as well as during methionine restriction. These two manipulations also increase maximum longevity in rodents. The decrease in mitROS generation and oxidative stress that takes place in caloric restriction seems to be due to restriction of a single dietary substance: methionine. The information available supports a mitochondrial free radical theory of aging focused on low generation of endogenous damage and low sensitivity of membranes to oxidation in long-lived animals.

Microbial-mammalian cometabolites dominate the age-associated urinary metabolic phenotype in Taiwanese and American populations

Understanding the metabolic processes associated with aging is key to developing effective management and treatment strategies for age-related diseases. We investigated the metabolic profiles associated with age in a Taiwanese and an American population. ¹H NMR spectral profiles were generated for urine specimens collected from the Taiwanese Social Environment and Biomarkers of Aging Study (SEBAS; n = 857; age 54-91 years) and the Mid-Life in the USA study (MIDUS II; n = 1148; age 35-86 years). Multivariate and univariate linear projection methods revealed some common age-related characteristics in urinary metabolite profiles in the American and Taiwanese populations, as well as some distinctive features. In both cases, two metabolites--4-cresyl sulfate (4CS) and phenylacetylglutamine (PAG)--were positively associated with age. In addition, creatine and β-hydroxy-β-methylbutyrate (HMB) were negatively correlated with age in both populations (p < 4 × 10⁻⁶). These age-associated gradients in creatine and HMB reflect decreasing muscle mass with age. The systematic increase in PAG and 4CS was confirmed using ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). Both are products of concerted microbial-mammalian host cometabolism and indicate an age-related association with the balance of host-microbiome metabolism.

Alterations in molecular status of plasma fibronectin associated with aging of normal human individuals

OBJECTIVES

Senescence, progressive deterioration of many bodily functions might be associated with age-dependent alterations of plasma fibronectin (FN) molecular status (i.e., domain, glycotope, and molecular form expressions).

DESIGN AND METHODS

FN molecular status was analyzed in 127 plasma samples of healthy individuals in groups of newborns, and subjects aged 3-14, 15-39, 41-59, and 60-82 years by FN-ELISA, lectin-FN-ELISA, and immunoblotting using a set of domain-specific monoclonal antibodies, specific lectins, and monoclonal antibody to FN, respectively.

RESULTS

During the first four decades of human life the levels of cell-binding-, carboxyl-terminal-, collagen-, heparin-, and fibrin-domains of plasma FN gradually increased. In subjects aged up to 82 years the cell-binding and carboxyl-terminal FN domain concentrations did not change, while the heparin, fibrin, and collagen domains significantly increased. The relative reactivity of plasma FN with Maackia amurensis lectin, specific to α2,3-linked sialic acid, significantly decreased after birth, reaching a stable level in the subsequent life period, whereas with Sambucus nigra lectin, specific to α2,6-linked sialic acid, it significantly decreased in the 60-82 year old group. Moreover, the appearance of 280-kDa and 320-kDa FN bands, absent in young and mature healthy individuals, was found in the groups of 41-59 and 60-82 year olds.

CONCLUSIONS

The alterations of FN molecular status throughout growth, maturation and senescence might be associated not only with disturbances in the balance of FN production rate and degradation, but concomitantly with conformational rearrangements of FN and its engagement in age-related vascular remodeling processes.

Regulation of longevity and oxidative stress by nutritional interventions: role of methionine restriction

Comparative studies indicate that long-lived mammals have low rates of mitochondrial reactive oxygen species production (mtROSp) and oxidative damage in their mitochondrial DNA (mtDNA). Dietary restriction (DR), around 40%, extends the mean and maximum life span of a wide range of species and lowers mtROSp and oxidative damage to mtDNA, which supports the mitochondrial free radical theory of aging (MFRTA). Regarding the dietary factor responsible for the life extension effect of DR, neither carbohydrate nor lipid restriction seems to modify maximum longevity. However protein restriction (PR) and methionine restriction (at least 80% MetR) increase maximum lifespan in rats and mice. Interestingly, only 7weeks of 40% PR (at least in liver) or 40% MetR (in all the studied organs, heart, brain, liver or kidney) is enough to decrease mtROSp and oxidative damage to mtDNA in rats, whereas neither carbohydrate nor lipid restriction changes these parameters. In addition, old rats also conserve the capacity to respond to 7weeks of 40% MetR with these beneficial changes. Most importantly, 40% MetR, differing from what happens during both 40% DR and 80% MetR, does not decrease growth rate and body size of rats. All the available studies suggest that the decrease in methionine ingestion that occurs during DR is responsible for part of the aging-delaying effect of this intervention likely through the decrease of mtROSp and ensuing DNA damage that it exerts. We conclude that lowering mtROS generation is a conserved mechanism, shared by long-lived species and dietary, protein, and methionine restricted animals, that decreases damage to macromolecules situated near the complex I mtROS generator, especially mtDNA. This would decrease the accumulation rate of somatic mutations in mtDNA and maybe finally also in nuclear DNA.

Effects of aging and methionine restriction applied at old age on ROS generation and oxidative damage in rat liver mitochondria

It is known that a global decrease in food ingestion (dietary restriction, DR) lowers mitochondrial ROS generation (mitROS) and oxidative stress in young immature rats. This seems to be caused by the decreased methionine ingestion of DR animals. This is interesting since isocaloric methionine restriction in the diet (MetR) also increases, like DR, rodent maximum longevity. However, it is not known if old rats maintain the capacity to lower mitROS generation and oxidative stress in response to MetR similarly to young immature animals, and whether MetR implemented at old age can reverse aging-related variations in oxidative stress. In this investigation the effects of aging and 7 weeks of MetR were investigated in liver mitochondria of Wistar rats. MetR implemented at old age decreased mitROS generation, percent free radical leak at the respiratory chain and mtDNA oxidative damage without changing oxygen consumption. Protein oxidation, lipoxidation and glycoxidation increased with age, and MetR in old rats partially or totally reversed these age-related increases. Aging increased the amount of SIRT1, and MetR decreased SIRT1 and TFAM and increased complex IV. No changes were observed in the protein amounts of PGC1, Nrf2, MnSOD, AIF, complexes I, II and III, and in the extent of genomic DNA methylation. In conclusion, treating old rats with isocaloric short-term MetR lowers mitROS production and free radical leak and oxidative damage to mtDNA, and reverses aging-related increases in protein modification. Aged rats maintain the capacity to lower mitochondrial ROS generation and oxidative stress in response to a short-term exposure to restriction of a single dietary substance: methionine.

What is lifespan regulation and why does it exist?

The development of a unified conceptual framework for the field of biogerontology has been impeded by confusing and misleading terminology. Thus, distinctions and definitions are provided for key terms (and their concepts) used in the paper: senescence, lifespan, potential lifespan, essential lifespan, and lifespan regulation. An organismal perspective is then used to examine the relationships between reproduction, lifespan regulation and senescence. The principal conclusions drawn from this examination are: (1) the inevitability of death makes physiological investments in reproduction a higher priority than somatic maintenance, (2) the race between reproduction and death creates a probabilistic window of time (essential lifespan) within which reproduction must occur, (3) the integrated network of genetic processes responsible for achieving essential lifespan (lifespan regulation) must be evolutionarily conserved and extensively regulated, (4) senescence is a stochastic byproduct of these regulated processes rather than a direct target of natural selection, and (5) genomic instability (an important stochastic component of senescence) plays no active role in lifespan regulation.

Nutritional influence on epigenetics and effects on longevity

PURPOSE OF REVIEW

This review synthesizes recently published information regarding nutrition and its impact upon epigenetically mediated mechanisms involved in longevity and aging.

RECENT FINDINGS

Recent studies enriched considerably our understanding of the relationship between aging and gene-nutrient interactions that continuously shape our phenotype. Epigenetic mechanisms play an important role in mediating between the nutrient inputs and the ensuing phenotypic changes throughout our entire life and seem to be responsible, in part, for the biological changes that occur during aging. Less is known about the epigenetic role that nutrients have in directly influencing longevity and aging. However, recent studies clearly indicated that because nutrition modulates epigenetic events associated with various diseases (e.g., cancer, obesity, and diabetes), there is at least an indirect epigenetic link between nutrition and longevity and, therefore, biologic plausibility to hypothesize the epigenetic role of nutrition in altering longevity. Apart from limited human studies, promising animal studies brought us much closer to understanding how nutrition could have such an impact upon longevity and aging.

SUMMARY

Complex epigenetic mechanisms are involved in aging and longevity, directly or indirectly via disease mechanisms. Nutrition has a strong impact upon epigenetic processes and, therefore, holds promise in having important roles in regulating longevity and aging.

Influence of elastin-derived peptides on metalloprotease production in endothelial cells

Matrix metalloproteases (MMPs) are a family of zinc-dependent endopeptidases that degrade extracellular matrix proteins. MMP-1 and MMP-2 are produced by endothelial cells and are involved in specific vascular pathologies, including atherosclerosis and aortal aneurysm. One of the most important differences between these two metalloproteases is the possibility of hydrolysis of elastin and collagen type IV by MMP-2, but not by MMP-1. Elastin-derived peptides are generated as a result of the degradation of elastin fibers. The aim of our study was to compare the production of MMP-1 and MMP-2 in cultured human arterial endothelial cells derived from vascular pathologies localized at three different sites, the coronary artery, iliac artery and aorta, measured as their concentration in cell culture medium. The second aim was to evaluate the influence of κ-elastin (at concentrations 0.1, 0.4, 1.0, 2.5 or 5.0 μg/ml) on the production of the evaluated metalloproteases in three endothelial cell lines. The production of MMP-1 was statistically significantly greater in endothelial cells derived from the aorta compared to that in the endothelium obtained from the coronary and iliac arteries. There were no statistically significant differences in the production of MMP-2 among the endothelial cell lines tested. The addition of κ-elastin at all evaluated concentrations did not statistically significantly influence the concentration of MMP-1 in the cultured coronary artery endothelium. Furthermore, no statistically significant differences were observed in the cultured iliac artery endothelium. In the cultured endothelium derived from the aorta, κ-elastin at concentrations of 0.1 and 0.4 μg/ml significantly increased the amount of MMP-1.