Mitochondrial DNA content contributes to healthy aging in Chinese: a study from nonagenarians and centenarians

Mitochondrial-derived peptides in cardiovascular disease: Novel insights and therapeutic opportunities

BACKGROUND

Mitochondria-derived peptides (MDPs) represent a recently discovered family of peptides encoded by short open reading frames (ORFs) found within mitochondrial genes. This group includes notable members including humanin (HN), mitochondrial ORF of the 12S rDNA type-c (MOTS-c), and small humanin-like peptides 1-6 (SHLP1-6). MDPs assume pivotal roles in the regulation of diverse cellular processes, encompassing apoptosis, inflammation, and oxidative stress, which are all essential for sustaining cellular viability and normal physiological functions. Their emerging significance extends beyond this, prompting a deeper exploration into their multifaceted roles and potential applications.

AIM OF REVIEW

This review aims to comprehensively explore the biogenesis, various types, and diverse functions of MDPs. It seeks to elucidate the central roles and underlying mechanisms by which MDPs participate in the onset and development of cardiovascular diseases (CVDs), bridging the connections between cell apoptosis, inflammation, and oxidative stress. Furthermore, the review highlights recent advancements in clinical research related to the utilization of MDPs in CVD diagnosis and treatment.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MDPs levels are diminished with aging and in the presence of CVDs, rendering them potential new indicators for the diagnosis of CVDs. Also, MDPs may represent a novel and promising strategy for CVD therapy. In this review, we delve into the biogenesis, various types, and diverse functions of MDPs. We aim to shed light on the pivotal roles and the underlying mechanisms through which MDPs contribute to the onset and advancement of CVDs connecting cell apoptosis, inflammation, and oxidative stress. We also provide insights into the current advancements in clinical research related to the utilization of MDPs in the treatment of CVDs. This review may provide valuable information with MDPs for CVD diagnosis and treatment.

SuperAgers and centenarians, dynamics of healthy ageing with cognitive resilience

Graceful healthy ageing and extended longevity is the most desired goal for human race. The process of ageing is inevitable and has a profound impact on the gradual deterioration of our physiology and health since it triggers the onset of many chronic conditions like dementia, osteoporosis, diabetes, arthritis, cancer, and cardiovascular disease. However, some people who lived/live more than 100 years called 'Centenarians" and how do they achieve their extended lifespans are not completely understood. Studying these unknown factors of longevity is important not only to establish a longer human lifespan but also to manage and treat people with shortened lifespans suffering from age-related morbidities. Furthermore, older adults who maintain strong cognitive function are referred to as "SuperAgers" and may be resistant to risk factors linked to cognitive decline. Investigating the mechanisms underlying their cognitive resilience may contribute to the development of therapeutic strategies that support the preservation of cognitive function as people age. The key to a long, physically, and cognitively healthy life has been a mystery to scientists for ages. Developments in the medical sciences helps us to a better understanding of human physiological function and greater access to medical care has led us to an increase in life expectancy. Moreover, inheriting favorable genetic traits and adopting a healthy lifestyle play pivotal roles in promoting longer and healthier lives. Engaging in regular physical activity, maintaining a balanced diet, and avoiding harmful habits such as smoking contribute to overall well-being. The synergy between positive lifestyle choices, access to education, socio-economic factors, environmental determinants and genetic supremacy enhances the potential for a longer and healthier life. Our article aims to examine the factors associated with healthy ageing, particularly focusing on cognitive health in centenarians. We will also be discussing different aspects of ageing including genomic instability, metabolic burden, oxidative stress and inflammation, mitochondrial dysfunction, cellular senescence, immunosenescence, and sarcopenia.

Mitochondrial DNA Copy Number Drives the Penetrance of Acute Intermittent Porphyria

No published study has investigated the mitochondrial count in patients suffering from acute intermittent porphyria (AIP). In order to determine whether mitochondrial content can influence the pathogenesis of porphyria, we measured the mitochondrial DNA (mtDNA) copy number in the peripheral blood cells of 34 patients and 37 healthy individuals. We found that all AIP patients had a low number of mitochondria, likely as a result of a protective mechanism against an inherited heme synthesis deficiency. Furthermore, we identified a close correlation between disease penetrance and decreases in the mitochondrial content and serum levels of PERM1, a marker of mitochondrial biogenesis. In a healthy individual, mitochondrial count is usually modulated to fit its ability to respond to various environmental stressors and bioenergetic demands. In AIP patients, coincidentally, the phenotype only manifests in response to endogenous and exogenous triggers factors. Therefore, these new findings suggest that a deficiency in mitochondrial proliferation could affect the individual responsiveness to stimuli, providing a new explanation for the variability in the clinical manifestations of porphyria. However, the metabolic and/or genetic factors responsible for this impairment remain to be identified. In conclusion, both mtDNA copy number per cell and mitochondrial biogenesis seem to play a role in either inhibiting or promoting disease expression. They could serve as two novel biomarkers for porphyria.

Quantifying human genome parameters in aging

Healthy human longevity is a global goal of the world health system. Determining the causes and processes influencing human longevity is the primary fundamental goal facing the scientific community. Currently, the main efforts of the scientific community are aimed at identifying the qualitative characteristics of the genome that determine the trait. At the same time, when evaluating qualitative characteristics, there are many challenges that make it difficult to establish associations. Quantitative traits are burdened with such problems to a lesser extent, but they are largely overlooked in current genomic studies of aging and longevity. Although there is a wide repertoire of quantitative trait analyses based on genomic data, most opportunities are ignored by authors, which, along with the inaccessibility of published data, leads to the loss of this important information. This review focuses on describing quantitative traits important for understanding aging and necessary for analysis in further genomic studies, and recommends the inclusion of the described traits in the analysis. The review considers the relationship between quantitative characteristics of the mitochondrial genome and aging, longevity, and age-related neurodegenerative diseases, such as the frequency of extensive mitochondrial DNA (mtDNA) deletions, mtDNA half-life, the frequency of A>G replacements in the mtDNA heavy chain, the number of mtDNA copies; special attention is paid to the mtDNA methylation sign. A separate section of this review is devoted to the correlation of telomere length parameters with age, as well as the association of telomere length with the amount of mitochondrial DNA. In addition, we consider such a quantitative feature as the rate of accumulation of somatic mutations with aging in relation to the lifespan of living organisms. In general, it may be noted that there are quite serious reasons to suppose that various quantitative characteristics of the genome may be directly or indirectly associated with certain aspects of aging and longevity. At the same time, the available data are clearly insufficient for definitive conclusions and the determination of causal relationships.

The contribution of mitochondrial DNA alterations to aging, cancer, and neurodegeneration

Mitochondrial DNA (mtDNA) is as a double-stranded molecule existing in hundreds to thousands copies in cells depending on cell metabolism and exposure to endogenous and/or environmental stressors. The coordination of mtDNA replication and transcription regulates the pace of mitochondrial biogenesis to guarantee the minimum number of organelles per cell. mtDNA inheritance follows a maternal lineage, although bi-parental inheritance has been reported in some species and in the case of mitochondrial diseases in humans. mtDNA mutations (e.g., point mutations, deletions, copy number variations) have been identified in the setting of several human diseases. For instance, sporadic and inherited rare disorders involving the nervous system as well higher risk of developing cancer and neurodegenerative conditions, including Parkinson's and Alzheimer's disease, have been associated with polymorphic mtDNA variants. An accrual of mtDNA mutations has also been identified in several tissues and organs, including heart and muscle, of old experimental animals and humans, which may contribute to the development of aging phenotypes. The role played by mtDNA homeostasis and mtDNA quality control pathways in human health is actively investigated for the possibility of developing targeted therapeutics for a wide range of conditions.

The Relationship between All-Cause Natural Mortality and Copy Number of Mitochondrial DNA in a 15-Year Follow-Up Study

We explored the relationship between the copy number of mitochondrial DNA (mtDNA-CN) and all-cause natural mortality. We examined a random population sample in 2003/2005 (n = 9360, men/women, 45-69, the HAPIEE project) and followed up for 15 years. Using a nested case-control design, we selected non-external deaths among those free from baseline cardiovascular diseases (CVD) and cancer (n = 371), and a sex- and age-stratified control (n = 785). The odds ratios (ORs) of death were 1.06 (95%CI 1.01-1.11) per one-decile decrease in mtDNA-CN independent of age, sex, metabolic factors, smoking, alcohol intake and education. The age-sex-adjusted ORs of death in the second and first tertiles of mtDNA-CN vs. the top tertile were 2.35 (95% CI 1.70-3.26) and 1.59 (1.16-2.17); an increased risk was confined to the second tertile after controlling for smoking and metabolic factors. The multivariable-adjusted OR of CVD death was 1.92 (95% CI 1.18-3.15) in tertile 2 vs. the top tertile of mtDNA-CN, and for cancer-related death the ORs were 3.66 (95% CI 2.21-6.05) and 2.29 (95% CI 1.43-3.68) in tertiles 2 and 1 vs. the top tertile. In the Siberian population cohort, the mtDNA-CN was an inverse predictor of the 15-year risk of natural mortality, due to the greatest impact of CVD and cancer-related death. The findings merit attention for exploring further the role of mtDNA in human ageing and the diversity of mortality.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Yeast Chromatin Mutants Reveal Altered mtDNA Copy Number and Impaired Mitochondrial Membrane Potential

Mitochondria are multifunctional, dynamic organelles important for stress response, cell longevity, ageing and death. Although the mitochondrion has its genome, nuclear-encoded proteins are essential in regulating mitochondria biogenesis, morphology, dynamics and function. Moreover, chromatin structure and epigenetic mechanisms govern the accessibility to DNA and control gene transcription, indirectly influencing nucleo-mitochondrial communications. Thus, they exert crucial functions in maintaining proper chromatin structure, cell morphology, gene expression, stress resistance and ageing. Here, we present our studies on the mtDNA copy number in Saccharomyces cerevisiae chromatin mutants and investigate the mitochondrial membrane potential throughout their lifespan. The mutants are arp4 (with a point mutation in the ARP4 gene, coding for actin-related protein 4-Arp4p), hho1Δ (lacking the HHO1 gene, coding for the linker histone H1), and the double mutant arp4 hho1Δ cells with the two mutations. Our findings showed that the three chromatin mutants acquired strain-specific changes in the mtDNA copy number. Furthermore, we detected the disrupted mitochondrial membrane potential in their chronological lifespan. In addition, the expression of nuclear genes responsible for regulating mitochondria biogenesis and turnover was changed. The most pronounced were the alterations found in the double mutant arp4 hho1Δ strain, which appeared as the only petite colony-forming mutant, unable to grow on respiratory substrates and with partial depletion of the mitochondrial genome. The results suggest that in the studied chromatin mutants, hho1Δ, arp4 and arp4 hho1Δ, the nucleus-mitochondria communication was disrupted, leading to impaired mitochondrial function and premature ageing phenotype in these mutants, especially in the double mutant.

The landscape of aging

Aging is characterized by a progressive deterioration of physiological integrity, leading to impaired functional ability and ultimately increased susceptibility to death. It is a major risk factor for chronic human diseases, including cardiovascular disease, diabetes, neurological degeneration, and cancer. Therefore, the growing emphasis on "healthy aging" raises a series of important questions in life and social sciences. In recent years, there has been unprecedented progress in aging research, particularly the discovery that the rate of aging is at least partly controlled by evolutionarily conserved genetic pathways and biological processes. In an attempt to bring full-fledged understanding to both the aging process and age-associated diseases, we review the descriptive, conceptual, and interventive aspects of the landscape of aging composed of a number of layers at the cellular, tissue, organ, organ system, and organismal levels.

A comparative study of Mesenchymal Stem Cells transplantation approach to antagonize age-associated ovarian hypofunction with consideration of safety and efficiency

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Mesenchymal stem cells transplantation (MSCs’) to the ovaries of POF patients could lead to effective clinical outcomes.

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Assessment of MSCs’ effect for single transplantation was performed using 3 transplantation methods.

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MSCs into ovaries by ovarian local injection was determined as the most effective route.

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This technique exerted marked effect on antagonizing age-associated ovarian hypofunction.

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Histopathological data showed that no neoplasms and obvious prosoplasia were found after MSCs transplantation.

Introduction

The transplantation of mesenchymal stem cells (MSCs) in patients with premature ovarian failure (POF) could lead to clinical improvement. The transplantation to the ovaries among other transplantation methods have been reported in various animal models, however, there is little evidence regarding the optimal method, including the clinical safety and the efficiency for the treatment of age associated ovarian hypofunction.

Objectives

To establish the most effective transplantation route of MSCs, explore the resistance to therapy, its safety and role in the natural aging process of the ovaries.

Methods

Highly purified MSCs were injected intraperitoneally, directly into the ovaries or tail-intravenously in mice animal model. The ovarian function, quantity and quality of oocytes, cell viability/apoptosis, were evaluated, applying chemiluminescence analysis (CLIA), western blotting, immunofluorescence staining, transmission electron microscope (TEM), TdT mediated dUTP Nick End Labeling (TUNEL) assay and other techniques. The organ tumorigenicity was also evaluated by long-term observation and histopathological examination. The efficiency of MSCs was further verified in non-human primates by the most effective transplantation route.

Results

The 32nd week was ultimately determined as the time point of MSCs transplantation. Our results showed that the intra-ovarian injection was the best transplantation method with a more conspicuous effect. With deeper investigations, we found that the transplanted MSCs showed an effective influence on the follicular number, promoted follicle maturation and inhibited cell apoptosis, which was further verified in non-human primates. In addition, the long-term observation and the histopathological examinations ruled out neoplasms or obvious prosoplasia after MSCs transplantation.

Conclusion

MSCs transplantation by intra-ovarian injection could within a month exert the most conspicuous anti-age-associated ovarian hypofunction effects, which may improve the quantity and quality of oocytes by changing the mitochondrial structure, regulating mitochondrial function and attenuating cell apoptosis to increase the storage of the follicle pool without a remarkable potential of tumorigenicity.

Dietary Supplements and Natural Products: An Update on Their Clinical Effectiveness and Molecular Mechanisms of Action During Accelerated Biological Aging

Accelerated biological aging, which involves the gradual decline of organ or tissue functions and the distortion of physiological processes, underlies several human diseases. Away from the earlier free radical concept, telomere attrition, cellular senescence, proteostasis loss, mitochondrial dysfunction, stem cell exhaustion, and epigenetic and genomic alterations have emerged as biological hallmarks of aging. Moreover, nutrient-sensing metabolic pathways are critical to an organism's ability to sense and respond to nutrient levels. Pharmaceutical, genetic, and nutritional interventions reverting physiological declines by targeting nutrient-sensing metabolic pathways can promote healthy aging and increase lifespan. On this basis, biological aging hallmarks and nutrient-sensing dependent and independent pathways represent evolving drug targets for many age-linked diseases. Here, we discuss and update the scientific community on contemporary advances in how dietary supplements and natural products beneficially revert accelerated biological aging processes to retrograde human aging and age-dependent human diseases, both from the clinical and preclinical studies point-of-view. Overall, our review suggests that dietary/natural products increase healthspan-rather than lifespan-effectively minimizing the period of frailty at the end of life. However, real-world setting clinical trials and basic studies on dietary supplements and natural products are further required to decisively demonstrate whether dietary/natural products could promote human lifespan.

Mitochondrial DNA copy number in human disease: the more the better?

Most of the genetic information has been lost or transferred to the nucleus during the evolution of mitochondria. Nevertheless, mitochondria have retained their own genome that is essential for oxidative phosphorylation (OXPHOS). In mammals, a gene‐dense circular mitochondrial DNA (mtDNA) of about 16.5 kb encodes 13 proteins, which constitute only 1% of the mitochondrial proteome. Mammalian mtDNA is present in thousands of copies per cell and mutations often affect only a fraction of them. Most pathogenic human mtDNA mutations are recessive and only cause OXPHOS defects if present above a certain critical threshold. However, emerging evidence strongly suggests that the proportion of mutated mtDNA copies is not the only determinant of disease but that also the absolute copy number matters. In this review, we critically discuss current knowledge of the role of mtDNA copy number regulation in various types of human diseases, including mitochondrial disorders, neurodegenerative disorders and cancer, and during ageing. We also provide an overview of new exciting therapeutic strategies to directly manipulate mtDNA to restore OXPHOS in mitochondrial diseases.

Clinical Characteristics of Mitochondrial DNA Copy Number in Osteonecrosis of the Femoral Head

Background and objectives: Alterations in mitochondrial DNA (mtDNA) have been observed and studied in various diseases. However, the clinical value of the mtDNA copy number (mtDNA-CN) alterations in osteonecrosis of the femoral head (ONFH) is poorly understood. In the present study, we investigated whether alterations in mtDNA-CNs are associated with clinicopathological parameters in ONFH. Materials and methods: MtDNA-CNs in the synovial tissue of 34 patients with ONFH and 123 control tissues (femoral neck fracture) were measured using quantitative real-time PCR. The present study then analyzed the correlation between the mtDNA-CN and the clinicopathological characteristics of ONFH and fracture patients. Results: The average mtDNA-CN (mean ± standard deviation) was 23.82 ± 22.37 and 25.04 ± 24.27 in ONFH and control tissues, respectively, and was not significantly different between the groups (p = 0.792). The mtDNA-CN was positively associated with age (27.7% vs. 45.9%, p = 0.018) and negatively associated with the erythrocyte sedimentation rate (ESR) (11.8% vs. 39.7%, p = 0.024) in all of the samples. The study also found further associations with age (22.2% vs. 68.8%, p = 0.014), gender (30.0% vs. 64.3%, p = 0.048), and ESR (0% vs. 57.7%, p = 0.043) in ONFH. Conclusions: in this study, we demonstrated that mtDNA-CN might be a significant marker for predicting clinical characteristics in ONFH.

Breastfeeding predicts blood mitochondrial DNA content in adolescents

Nutrition during early childhood is linked to metabolic programming. We hypothesized that breastfeeding has long-term consequences on the energy metabolism exemplified by mitochondrial DNA (mtDNA). As part of the third cycle of the Flemish Environment and Health Study (FLEHSIII) cohort, 303 adolescents aged 14–15 years were included. We associated breastfeeding and blood mtDNA content 14–15 years later while adjusting for confounding variables. Compared with non-breastfed adolescents, mtDNA content was 23.1% (95%CI: 4.4–45.2; p = 0.013) higher in breastfed adolescents. Being breastfed for 1–10 weeks, 11–20 weeks, and >20 weeks, was associated with a higher mtDNA content of respectively 16.0% (95%CI: −7.1–44.9; p = 0.191), 23.5% (95%CI: 0.8–51.3; p = 0.042), and 31.5% (95%CI: 4.3–65.7; p = 0.021). Our study showed a positive association between breastfeeding and mtDNA content in adolescents which gradually increased with longer periods of breastfeeding. Higher mtDNA content may be an underlying mechanism of the beneficial effects of breastfeeding on children’s metabolism.

mtDNA Copy Number Contributes to All-Cause Mortality of Lacunar Infarct in a Chinese Prospective Stroke Population

The study aimed to investigate the relationship between mtDNA copy number and the risk of all-cause mortality in stroke. One thousand four hundred eighty-four stroke patients were documented including 273 deaths (127 thrombosis, 52 lacunar, 94 hemorrhage). Patients in the third quartile had the lowest mortality rates in overall stroke and the three subtypes. The lowest quartile of mtDNA copy number (Q1 < 85.85) indicated an increased risk of all-cause mortality in stroke patients (adjusted HR, 1.52; 95% CI, 1.08-2.14; p = 0.017). In the subtype analysis, the risk of all-cause mortality appeared only in lacunar infarct, and the patients in the Q1 (< 87.76) and Q4 (> 150.61) mtDNA copy number groups showed significantly higher risks of HRs (Q1, adjusted HR, 3.87, 95% CI, 1.52-9.83; Q4, adjusted HR, 3.08, 95% CI, 1.16-8.18). Stroke patients with lacunar infarct in mtDNA copy number < 87.76 or > 150.61 were at a high risk of poor outcomes in all-cause mortality.

Low MFN2 expression related to ageing in granulosa cells is associated with assisted reproductive technology outcome

RESEARCH QUESTION

Is low MFN2 expression associated with ageing in granulosa cells as well as assisted reproductive technology (ART) outcome, and what is the underlying mechanism of action of MFN2?

DESIGN

In a prospective study, fresh granulosa cells were obtained from 161 women aged 20-40 years who underwent IVF with embryo transfer and who were divided into two groups: the diminished ovarian reserve (DOR) group (n = 51) and the control group (n = 110). Patient characteristics including age, infertility duration, body mass index, FSH, anti-Müllerian hormone (AMH), antral follicle count (AFC) and husband's semen parameters and granulosa cell MFN2 expression levels, cell apoptosis, mitochondrial membrane potential (ΔΨm) and ATP levels were analysed.

RESULTS

There were no significant differences between the DOR and control groups in terms of age, infertility duration and husband'' semen parameters; however, significant (P< 0.05) changes were found between the two groups in FSH, AMH and AFC levels. MFN2 expression was remarkably lower in granulosa cells from the DOR group and decreased in both groups as age increased. Furthermore, among young patients, MFN2 levels significantly increased in patients with pregnancy. MFN2 protein levels and cell apoptosis were lower in the MFN2 knockdown (MFN2-siRNA) group than in the control (Cy3-siRNA) group. ΔΨm and ATP levels were reduced in the MFN2-siRNA group compared with the Cy3-siRNA group.

CONCLUSIONS

Low MFN2 expression levels in granulosa cells were related to ageing, which may be involved in the clinical outcome of ART by promoting cell apoptosis and affecting mitochondrial function.

Prognostic value of mitochondrial DNA4977 deletion and mitochondrial DNA copy number in patients with stable coronary artery disease

BACKGROUND AND AIMS

Mitochondrial DNA copy number (mtDNA-CN) depletion has been recently associated with an increased cardiovascular risk. However, the integrity of mtDNA is another key aspect of the energy metabolism and mitochondrial function. We investigated the prognostic role of peripheral blood common mitochondrial deletion (mtDNA⁴⁹⁷⁷) and mtDNA-CN on long-term major adverse cardiac events (MACEs) and all-cause mortality in a cohort of patients with coronary artery disease (CAD).

METHODS

Within the Italian GENOCOR (Genetic Mapping for Assessment of Cardiovascular Risk) cohort, we studied 515 patients (450 males, 65 ± 8 years) with known or suspected stable CAD. mtDNA⁴⁹⁷⁷ deletion and mtDNA-CN were assessed in peripheral blood using qRT-PCR.

RESULTS

During a mean follow-up of 4.5 ± 1.1 years, 78 (15%) patients had MACEs (15 cardiac deaths, 17 nonfatal myocardial infarction and 46 coronary revascularizations) and 28 patients died for non-cardiac causes. Patients with high levels of mtDNA⁴⁹⁷⁷ deletion (>75th) had increased risk of MACEs (log rank = 7.2, p=0.007) and all-cause mortality (log rank = 5.7, p=0.01) compared with patients with low mtDNA⁴⁹⁷⁷ deletion (≤75th). Multivariate Cox regression analysis showed that log mtDNA⁴⁹⁷⁷ was a significant predictor of MACEs (HR = 2.17; 95% CI, 1.31-3.59; p=0.003) and all-cause mortality (HR = 2.03; 95% CI: 1.13-3.65, p=0.02). Log mtDNA-CN was not significantly associated with MACEs or all-cause mortality. However, patients with high mtDNA⁴⁹⁷⁷ deletion (>75th) and low mtDNA-CN (<25th) had significantly increased risk for MACEs (HR: 3.73; 95% CI: 1.79-7.79; p=0.0005).

CONCLUSIONS

Mitochondria DNA damage was associated with an increased risk of MACEs and all-cause mortality in patients with stable CAD, confirming the critical role of mitochondrial dysfunction in atherosclerosis.

Prevalence and correlates of chronic diseases in an elderly population: A community-based survey in Haikou

BACKGROUND

The escalating problem of multiple chronic conditions among older adults in China draws public health attention due to increasing proportion of the elderly population. This study sought to assess the prevalence of and factors associated with four chronic diseases in older adults in Haikou, the capital city of Hainan Province, China.

METHOD

In this cross-sectional study, 9432 community-dwelling elderly people aged 60 years and older living in rural or urban areas in Haikou were investigated. The interviews collected self-reported information on the presence of four major chronic diseases, as well as socio-demographic characteristics, lifestyle factors and self-reported height and weight.

FINDINGS

Overall, 31.7% (2961/9344) reported at least one of the four chronic diseases. The prevalence of hypertension, diabetes mellitus, COPD, and stroke was 26.0% (2449/9407), 8.0% (749/9371), 1.0% (95/9360), and 1.9% (175/9382), respectively. Common correlates of the four major chronic diseases were older age, being engaged in intellectual work, currently being a smoker and obesity. Gender, locality of residence, and alcohol consumptions were also found to be associated to some of the chronic conditions.

CONCLUSION

This finding indicates that multiple chronic conditions among elderly people in Haikou are prevalent and warrant special attention to reduce diseases burden and align health care services to cater the holistic elderly patients' need.

Switching off IMMP2L signaling drives senescence via simultaneous metabolic alteration and blockage of cell death

Cellular senescence is a fundamental cell fate playing a significant role throughout the natural aging process. However, the molecular determinants distinguishing senescence from other cell-cycle arrest states such as quiescence and post-mitotic state, and the specified mechanisms underlying cell-fate decisions towards senescence versus cell death in response to cellular stress stimuli remain less understood. Employing multi-omics approaches, we revealed that switching off the specific mitochondrial processing machinery involving the peptidase IMMP2L serves as the foundation of the senescence program, which was also observed during the mammalian aging process. Mechanistically, we demonstrate that IMMP2L processes and thus activates at least two substrates, mitochondrial metabolic enzyme glycerol-3-phosphate dehydrogenase (GPD2) and cell death regulator apoptosis-inducing factor (AIF). For cells destined to senesce, concerted shutdown of the IMMP2L-GPD2 and IMMP2L-AIF signaling axes collaboratively drives the senescent process by reprogramming mitochondria-associated redox status, phospholipid metabolism and signaling network, and simultaneously blocking cell death under oxidative stress conditions.

Exome-wide Association Study Identifies CLEC3B Missense Variant p.S106G as Being Associated With Extreme Longevity in East Asian Populations

Life span is a complex trait regulated by multiple genetic and environmental factors; however, the genetic determinants of extreme longevity have been largely unknown. To identify the functional coding variants associated with extreme longevity, we performed an exome-wide association study (EWAS) on a Japanese population by using an Illumina HumanExome Beadchip and a focused replication study on a Chinese population. The EWAS on two independent Japanese cohorts consisting of 530 nonagenarians/centenarians demonstrated that the G allele of CLEC3B missense variant p.S106G was associated with extreme longevity at the exome-wide level of significance (p = 2.33×10^–7, odds ratio [OR] = 1.50). The CLEC3B gene encodes tetranectin, a protein implicated in the mineralization process in osteogenesis as well as in the prognosis and metastasis of cancer. The replication study consisting of 448 Chinese nonagenarians/centenarians showed that the G allele of CLEC3B p.S106G was also associated with extreme longevity (p = .027, OR = 1.51), and the p value of this variant reached 1.87×10^–8 in the meta-analysis of Japanese and Chinese populations. In conclusion, the present study identified the CLEC3B p.S106G as a novel longevity-associated variant, raising the novel hypothesis that tetranectin, encoded by CLEC3B, plays a role in human longevity and aging.

Linkage between mitochondrial genome alterations, telomere length and aging population

We studied telomere length (TL) and mitochondrial DNA (mtDNA) copy number variations in individuals from Latvian Caucasian population in different age groups. We showed a positive correlation between TL and mtDNA copy number in individuals of up to 90 years of age; however, this correlation was not observed in the 90-100 years age group. While TL shortened with age and mtDNA content decreased with increasing age, in this study it was observed that mtDNA copy number in nonagenarians was slightly higher than in the 60-89 years age group. The presence of heteroplasmy in the mtDNA HVS-I control region did not correlate with TL and mtDNA copy number. TL and mtDNA values also did not differ between mitochondrial haplogroups. In conclusion, while both TL and mtDNA are involved in the aging process and link between these cell components exists, nonagenarians may have differences in senescence-related pathways and systems, which may function as a protective mechanism that allows them to live longer.

Demographics, phenotypic health characteristics and genetic analysis of centenarians in China

After a brief introduction to the background, significance and unique features of the centenarian population in China, we describe the Chinese Longitudinal Healthy Longevity Study (CLHLS), which is the world's largest study of centenarians, nonagenarians, octogenarians, and compatible young-old aged 65-79. Based on the CLHLS data and other relevant studies, we summarize demographic and socioeconomic characteristics as well as self-reported and objectively-tested health indicators of centenarians in China, with an emphasis on gender differences and rural/urban disparities. We then compare five-year-age-specific trajectories of physical and cognitive functions, self-reported health, and life satisfactions from ages 65-69 to 100+, concluding that good psychological resilience and optimism are keys to the exceptional longevity enjoyed by centenarians. We discuss recent findings of novel loci and pathways that are significantly associated with longevity based on the genome-wide association study (GWAS) of the CLHLS centenarian sample, which is 2.7 times as large as prior GWAS of longevity. We also highlight colleagues' and our own studies on longevity candidate genes and gene-environment interaction analyses. Finally, we discuss limitations inherent in our studies of centenarians in China and further research perspectives.

Decreased Integrity, Content, and Increased Transcript Level of Mitochondrial DNA Are Associated with Keratoconus

Oxidative stress may play an important role in the pathogenesis of keratoconus (KC). Mitochondrial DNA (mtDNA) is involved in mitochondrial function, and the mtDNA content, integrity, and transcript level may affect the generation of reactive oxygen species (ROS) and be involved in the pathogenesis of KC. We designed a case-control study to research the relationship between KC and mtDNA integrity, content and transcription. One-hundred ninety-eight KC corneas and 106 normal corneas from Chinese patients were studied. Quantitative real-time PCR was used to measure the relative mtDNA content, transcript levels of mtDNA and related genes. Long-extension PCR was used to detect mtDNA damage. ROS, mitochondrial membrane potential and ATP were measured by respective assay kit, and Mito-Tracker Green was used to label the mitochondria. The relative mtDNA content of KC corneas was significantly lower than that of normal corneas (P = 9.19×10⁻²⁴), possibly due to decreased expression of the mitochondrial transcription factor A (TFAM) gene (P = 3.26×10⁻³). In contrast, the transcript levels of mtDNA genes were significantly increased in KC corneas compared with normal corneas (NADH dehydrogenase subunit 1 [ND1]: P = 1.79×10⁻³; cytochrome c oxidase subunit 1 [COX1]: P = 1.54×10⁻³; NADH dehydrogenase subunit 1, [ND6]: P = 4.62×10⁻³). The latter may be the result of increased expression levels of mtDNA transcription-related genes mitochondrial RNA polymerase (POLRMT) (P = 2.55×10⁻⁴) and transcription factor B2 mitochondrial (TFB2M) (P = 7.88×10⁻⁵). KC corneas also had increased mtDNA damage (P = 3.63×10⁻¹⁰), higher ROS levels, and lower mitochondrial membrane potential and ATP levels compared with normal corneas. Decreased integrity, content and increased transcript level of mtDNA are associated with KC. These changes may affect the generation of ROS and play a role in the pathogenesis of KC.

Familial longevity study reveals a significant association of mitochondrial DNA copy number between centenarians and their offspring

Reduced mitochondrial function is an important cause of aging and age-related diseases. We previously revealed a relatively higher level of mitochondrial DNA (mtDNA) content in centenarians. However, it is still unknown whether such an mtDNA content pattern of centenarians could be passed on to their offspring and how it was regulated. To address these issues, we recruited 60 longevity families consisting of 206 family members (cohort 1) and explored their mtDNA copy number. The results showed that the first generation of the offspring (F1 offspring) had a higher level of mtDNA copy number than their spouses (p < 0.05) independent of a gender effect. In addition, we found a positive association of mtDNA copy number in centenarians with that in F1 offspring (r = 0.54, p = 0.0008) but not with that in F1 spouses. These results were replicated in another independent cohort consisting of 153 subjects (cohort 2). RNA sequencing analysis suggests that the single-stranded DNA-binding protein 4 was significantly associated with mtDNA copy number and was highly expressed in centenarians as well as F1 offspring versus the F1 spouses, thus likely regulates the mtDNA copy number in the long-lived family members. In conclusion, our results suggest that the pattern of high mtDNA copy number is likely inheritable, which may act as a favorable factor to familial longevity through assuring adequate energy supply.

CETP polymorphisms confer genetic contribution to centenarians of Hainan, south of China

OBJECTIVE

In this paper, we will discuss if the CETP polymorphism contributes to the centenarians in Hainan island.

METHODS

We tested the TaqIB and I405V polymorphisms of CETP gene among 276 centenarians and 301 matched healthy individuals by AS-PCR and analyzed the data with SPSS software package (Version 19.0).

RESULTS

Our data indicated that allele B1 and V have the significant differences between centenarians and healthy control groups with P < 0.001. Further analysis implied that genotypes B1B1 (P < 0.001, OR = 0.148, 95% CI = 0.095-0.230) and VV (P < 0.001 and OR = 0.353, 95% CI = 0.237-0.525) were significantly different between centenarians and matched controls. The combination of B and V, such as B1B1-II (P < 0.001, OR = 0.128, 95% CI = 0.049-0.329), B1B1-IV (P < 0.001, OR = 0.115, 95% CI = 0.056-0.237), B1B2-VV (P < 0.05, OR = 0.534, 95% CI = 0.310-0.920), and B2B2-VV (P < 0.001, OR = 0.198, 95% CI = 0.086-0.453) have significant differences between centenarians and matched healthy individuals from Hainan.

CONCLUSION

Our results implied that allele B1B1 and VV, as well as the combination B1B1-II, B1B1-IV, B1B2-VV and B2B2-VV may contribute to the longevity in centenarians of Hainan, south of China.

Correlates of Peripheral Blood Mitochondrial DNA Content in a General Population

Accumulation of mitochondrial DNA (mtDNA) mutations leads to alterations of mitochondrial biogenesis and function that might produce a decrease in mtDNA content within cells. This implies that mtDNA content might be a potential biomarker associated with oxidative stress and inflammation. However, data on correlates of mtDNA content in a general population are sparse. Our goal in the present study was to describe in a randomly recruited population sample the distribution and determinants of peripheral blood mtDNA content. From 2009 to 2013, we examined 689 persons (50.4% women; mean age = 54.4 years) randomly selected from a Flemish population (Flemish Study on Environment, Genes, and Health Outcomes). Relative mtDNA copy number as compared with nuclear DNA was measured by quantitative real-time polymerase chain reaction in peripheral blood. There was a curvilinear relationship between relative mtDNA copy number and age. mtDNA content slightly increased until the fifth decade of life and declined in older subjects (P_age² = 0.0002). mtDNA content was significantly higher in women (P = 0.007) and increased with platelet count (P < 0.0001), whereas it was inversely associated with white blood cell count (P < 0.0001). We also observed lower mtDNA content in women using estroprogestogens (P = 0.044). This study demonstrated in a general population that peripheral blood mtDNA content is significantly associated with sex and age. Blood mtDNA content is also influenced by platelet and white blood cell counts and estroprogestogen intake. Further studies are required to clarify the impact of chronic inflammation and hormone therapy on mitochondrial function.

Targeting mitochondrial DNA with a two-photon active Ru(ii) phenanthroline derivative

A novel phenanthroline Ru(ii) derivative for targeting mitochondrial DNA was designed and its potential applications in biological processes were highlighted.

The mitochondrial-derived peptide MOTS-c: a player in exceptional longevity?

Mitochondrial‐derived peptides (MDP) are encoded by functional short open reading frames in the mitochondrial DNA (mtDNA). These include humanin, and the recently discovered mitochondrial open reading frame of the 12S rRNA‐c (MOTS‐c). Although more research is needed, we suggest that the m.1382A>C polymorphism located in the MOTS‐c encoding mtDNA, which is specific for the Northeast Asian population, may be among the putative biological mechanisms explaining the high longevity of Japanese people.

Parkinson's disease as a result of aging

It is generally considered that Parkinson's disease is induced by specific agents that degenerate a clearly defined population of dopaminergic neurons. Data commented in this review suggest that this assumption is not as clear as is often thought and that aging may be critical for Parkinson's disease. Neurons degenerating in Parkinson's disease also degenerate in normal aging, and the different agents involved in the etiology of this illness are also involved in aging. Senescence is a wider phenomenon affecting cells all over the body, whereas Parkinson's disease seems to be restricted to certain brain centers and cell populations. However, reviewed data suggest that Parkinson's disease may be a local expression of aging on cell populations which, by their characteristics (high number of synaptic terminals and mitochondria, unmyelinated axons, etc.), are highly vulnerable to the agents promoting aging. The development of new knowledge about Parkinson's disease could be accelerated if the research on aging and Parkinson's disease were planned together, and the perspective provided by gerontology gains relevance in this field.

Mitochondrial DNA copy number, but not haplogroup is associated with keratoconus in Han Chinese population

Oxidative stress may play a role in the pathogenesis of keratoconus (KC). Mitochondrial DNA (mtDNA) is closely related to mitochondrion function, and variations may affect the generation of reactive oxygen species (ROS) and be involved in the pathogenesis of KC. To test whether mtDNA background and copy number confer genetic susceptibility to KC in the Han Chinese population, we performed this association study. We analyzed mtDNA sequence variations in 210 KC patients and 309 matched individuals from China, and classified each subject by haplogroup. Mitochondrial DNA copy number was measured in a subset of these subjects (193 patients and 103 controls). Comparison of matrilineal components of the cases and control populations revealed no significant difference. However, measurement of mtDNA copy number showed that KC patients had significantly lower mtDNA copy numbers than controls (P = 0.0002), even when age, gender, and mtDNA background were considered. Our results suggest that mtDNA copy number, but not haplogroup, is associated with keratoconus, and may contribute to its pathogenesis.

The mitochondrial genome in aging and senescence

Aging is characterized by a progressive decline in organism functions due to the impairment of all organs. The deterioration of both proliferative tissues in liver, skin and the vascular system, as well as of largely post-mitotic organs, such as the heart and brain could be attributed at least in part to cell senescence. In this review we examine the role of mitochondrial dysfunction and mtDNA mutations in cell aging and senescence. Specifically, we address how p53 and telomerase reverse transcriptase (TERT) activity switch their roles from cytoprotective to detrimental and also examine the role of microRNAs in cell aging. The proposed role of Reactive Oxygen Species (ROS), both as mutating agents and as signalling molecules, underlying these processes is also described.

Tissue-specific mtDNA abundance from exome data and its correlation with mitochondrial transcription, mass and respiratory activity

Eukaryotic cells contain a population of mitochondria, variable in number and shape, which in turn contain multiple copies of a tiny compact genome (mtDNA) whose expression and function is strictly coordinated with the nuclear one. mtDNA copy number varies between different cell or tissues types, both in response to overall metabolic and bioenergetics demands and as a consequence or cause of specific pathological conditions. Here we present a novel and reliable methodology to assess the effective mtDNA copy number per diploid genome by investigating off-target reads obtained by whole-exome sequencing (WES) experiments. We also investigate whether and how mtDNA copy number correlates with mitochondrial mass, respiratory activity and expression levels. Analyzing six different tissues from three age- and sex-matched human individuals, we found a highly significant linear correlation between mtDNA copy number estimated by qPCR and the frequency of mtDNA off target WES reads. Furthermore, mtDNA copy number showed highly significant correlation with mitochondrial gene expression levels as measured by RNA-Seq as well as with mitochondrial mass and respiratory activity. Our methodology makes thus feasible, at a large scale, the investigation of mtDNA copy number in diverse cell-types, tissues and pathological conditions or in response to specific treatments.