New insights into the role of mitochondria in aging: mitochondrial dynamics and more

Delayed and diminished postprandial lactate shuttling in healthy older men and women

Lactate, a product of glycolysis, is formed under aerobic conditions. Extensive work has shown lactate flux in young and exercising humans; however, the effect of age is not known. We tested the hypothesis that postprandial lactate shuttling (PLS) would be diminished in older adults. We used [3-13C]lactate and [6,6-2H]glucose tracers, an oral glucose tolerance test (OGTT), and arterialized blood sampling to determine postprandial lactate rates of appearance (Ra), disappearance (Rd), and oxidation (Rox) in 15 young (28.1 ± 1.4 yr) and 13 older (70.6 ± 2.4 yr) healthy men and women. In young participants, fasting blood [lactate] (≈0.5 mM) rose after the glucose challenge, peaked at 15 min, dipped to a nadir at 30 min, and rose again peaking at 60 min (≈1.0 mM). Initial responses in lactate Ra of older participants were delayed and diminished until 90 min rising by 0.83 mg·kg-1·min-1. Lactate Rox was higher throughout the entire trial in young participants by a difference of ∼0.5 mg·kg-1·min-1. Initial peaks in lactate Ra and concentration in all volunteers demonstrated the presence of an enteric PLS following an OGTT. Notably, in the systemic, but not enteric, PLS phase, lactate Ra correlated highly with glucose Rd (r2 = 0.92). Correspondence of second peaks in lactate Ra and concentration and glucose Rd shows dependence of lactate Ra on glucose Rd. Although results show both enteric and systemic PLS phases in young and older study cohorts, metabolic responses were delayed and diminished in healthy older individuals.NEW & NOTEWORTHY We used isotope tracers, an oral glucose tolerance test, and arterialized blood sampling to determine postprandial lactate flux rates in healthy young and older men and women. Lactate rates of appearance and oxidation and the lactate-pyruvate exchange were delayed and diminished in both enteric and systemic postprandial lactate shuttle phases in older participants.

Mitochondrial protein deacetylation by SIRT3 in osteoclasts promotes bone resorption with aging in female mice

OBJECTIVES

The mitochondrial deacetylase sirtuin-3 (SIRT3) is necessary for the increased bone resorption and enhanced function of mitochondria in osteoclasts that occur with advancing age; how SIRT3 drives bone resorption remains elusive.

METHODS

To determine the role of SIRT3 in osteoclast mitochondria, we used mice with conditional loss of Sirt3 in osteoclast lineage and mice with germline deletion of either Sirt3 or its known target Pink1.

RESULTS

SIRT3 stimulates mitochondrial quality in osteoclasts in a PINK1-independent manner, promoting mitochondrial activity and osteoclast maturation and function, thereby contributing to bone loss in female but not male mice. Quantitative analyses of global proteomes and acetylomes revealed that deletion of Sirt3 dramatically increased acetylation of osteoclast mitochondrial proteins, particularly ATPase inhibitory factor 1 (ATPIF1), an essential protein for mitophagy. Inhibition of mitophagy via mdivi-1 recapitulated the effect of deletion of Sirt3 or Atpif1 in osteoclast formation and mitochondrial function.

CONCLUSIONS

Decreasing mitophagic flux in osteoclasts may be a promising pharmacotherapeutic approach to treat osteoporosis in older adults.

Mitochondrial Structure and Function in Human Heart Failure

Despite clinical and scientific advancements, heart failure is the major cause of morbidity and mortality worldwide. Both mitochondrial dysfunction and inflammation contribute to the development and progression of heart failure. Although inflammation is crucial to reparative healing following acute cardiomyocyte injury, chronic inflammation damages the heart, impairs function, and decreases cardiac output. Mitochondria, which comprise one third of cardiomyocyte volume, may prove a potential therapeutic target for heart failure. Known primarily for energy production, mitochondria are also involved in other processes including calcium homeostasis and the regulation of cellular apoptosis. Mitochondrial function is closely related to morphology, which alters through mitochondrial dynamics, thus ensuring that the energy needs of the cell are met. However, in heart failure, changes in substrate use lead to mitochondrial dysfunction and impaired myocyte function. This review discusses mitochondrial and cristae dynamics, including the role of the mitochondria contact site and cristae organizing system complex in mitochondrial ultrastructure changes. Additionally, this review covers the role of mitochondria-endoplasmic reticulum contact sites, mitochondrial communication via nanotunnels, and altered metabolite production during heart failure. We highlight these often-neglected factors and promising clinical mitochondrial targets for heart failure.

MICOS Complex Loss Governs Age-Associated Murine Mitochondrial Architecture and Metabolism in the Liver, While Sam50 Dictates Diet Changes

The liver, the largest internal organ and a metabolic hub, undergoes significant declines due to aging, affecting mitochondrial function and increasing the risk of systemic liver diseases. How the mitochondrial three-dimensional (3D) structure changes in the liver across aging, and the biological mechanisms regulating such changes confers remain unclear. In this study, we employed Serial Block Face-Scanning Electron Microscopy (SBF-SEM) to achieve high-resolution 3D reconstructions of murine liver mitochondria to observe diverse phenotypes and structural alterations that occur with age, marked by a reduction in size and complexity. We also show concomitant metabolomic and lipidomic changes in aged samples. Aged human samples reflected altered disease risk. To find potential regulators of this change, we examined the Mitochondrial Contact Site and Cristae Organizing System (MICOS) complex, which plays a crucial role in maintaining mitochondrial architecture. We observe that the MICOS complex is lost during aging, but not Sam50. Sam50 is a component of the sorting and assembly machinery (SAM) complex that acts in tandem with the MICOS complex to modulate cristae morphology. In murine models subjected to a high-fat diet, there is a marked depletion of the mitochondrial protein SAM50. This reduction in Sam50 expression may heighten the susceptibility to liver disease, as our human biobank studies corroborate that Sam50 plays a genetically regulated role in the predisposition to multiple liver diseases. We further show that changes in mitochondrial calcium dysregulation and oxidative stress accompany the disruption of the MICOS complex. Together, we establish that a decrease in mitochondrial complexity and dysregulated metabolism occur with murine liver aging. While these changes are partially be regulated by age-related loss of the MICOS complex, the confluence of a murine high-fat diet can also cause loss of Sam50, which contributes to liver diseases. In summary, our study reveals potential regulators that affect age-related changes in mitochondrial structure and metabolism, which can be targeted in future therapeutic techniques.

Infectious viruses and neurodegenerative diseases: The mitochondrial defect hypothesis

Global attention is riveted on neurodegenerative diseases due to their unresolved aetiologies and lack of efficacious therapies. Two key factors implicated include mitochondrial impairment and microglial ageing. Several viral infections, including Herpes simplex virus-1 (HSV-1), human immunodeficiency virus (HIV) and Epstein-Barr virus, are linked to heightened risk of these disorders. Surprisingly, numerous studies indicate viruses induce these aforementioned precipitating events. Epstein-Barr virus, Hepatitis C Virus, HIV, respiratory syncytial virus, HSV-1, Japanese Encephalitis Virus, Zika virus and Enterovirus 71 specifically impact mitochondrial function, leading to mitochondrial malfunction. These vital organelles govern various cell activities and, under specific circumstances, trigger microglial ageing. This article explores the role of viral infections in elucidating the pathogenesis of neurodegenerative ailments. Various viruses instigate microglial ageing via mitochondrial destruction, causing senescent microglia to exhibit activated behaviour, thereby inducing neuroinflammation and contributing to neurodegeneration.

3D Mitochondrial Structure in Aging Human Skeletal Muscle: Insights into MFN-2 Mediated Changes

Age-related atrophy of skeletal muscle, is characterized by loss of mass, strength, endurance, and oxidative capacity during aging. Notably, bioenergetics and protein turnover studies have shown that mitochondria mediate this decline in function. Although exercise has been the only therapy to mitigate sarcopenia, the mechanisms that govern how exercise serves to promote healthy muscle aging are unclear. Mitochondrial aging is associated with decreased mitochondrial capacity, so we sought to investigate how aging affects mitochondrial structure and potential age-related regulators. Specifically, the three-dimensional (3D) mitochondrial structure associated with morphological changes in skeletal muscle during aging requires further elucidation. We hypothesized that aging causes structural remodeling of mitochondrial 3D architecture representative of dysfunction, and this effect is mitigated by exercise. We used serial block-face scanning electron microscopy to image human skeletal tissue samples, followed by manual contour tracing using Amira software for 3D reconstruction and subsequent analysis of mitochondria. We then applied a rigorous in vitro and in vivo exercise regimen during aging. Across 5 human cohorts, we correlate differences in magnetic resonance imaging, mitochondria 3D structure, exercise parameters, and plasma immune markers between young (under 50 years) and old (over 50 years) individuals. We found that mitochondria we less spherical and more complex, indicating age-related declines in contact site capacity. Additionally, aged samples showed a larger volume phenotype in both female and male humans, indicating potential mitochondrial swelling. Concomitantly, muscle area, exercise capacity, and mitochondrial dynamic proteins showed age-related losses. Exercise stimulation restored mitofusin 2 (MFN2), one such of these mitochondrial dynamic proteins, which we show is required for the integrity of mitochondrial structure. Furthermore, we show that this pathway is evolutionarily conserved as Marf, the MFN2 ortholog in Drosophila, knockdown alters mitochondrial morphology and leads to the downregulation of genes regulating mitochondrial processes. Our results define age-related structural changes in mitochondria and further suggest that exercise may mitigate age-related structural decline through modulation of mitofusin 2.

The current insights of mitochondrial hormesis in the occurrence and treatment of bone and cartilage degeneration

It is widely acknowledged that aging, mitochondrial dysfunction, and cellular phenotypic abnormalities are intricately associated with the degeneration of bone and cartilage. Consequently, gaining a comprehensive understanding of the regulatory patterns governing mitochondrial function and its underlying mechanisms holds promise for mitigating the progression of osteoarthritis, intervertebral disc degeneration, and osteoporosis. Mitochondrial hormesis, referred to as mitohormesis, represents a cellular adaptive stress response mechanism wherein mitochondria restore homeostasis and augment resistance capabilities against stimuli by generating reactive oxygen species (ROS), orchestrating unfolded protein reactions (UPRmt), inducing mitochondrial-derived peptides (MDP), instigating mitochondrial dynamic changes, and activating mitophagy, all prompted by low doses of stressors. The varying nature, intensity, and duration of stimulus sources elicit divergent degrees of mitochondrial stress responses, subsequently activating one or more signaling pathways to initiate mitohormesis. This review focuses specifically on the effector molecules and regulatory networks associated with mitohormesis, while also scrutinizing extant mechanisms of mitochondrial dysfunction contributing to bone and cartilage degeneration through oxidative stress damage. Additionally, it underscores the potential of mechanical stimulation, intermittent dietary restrictions, hypoxic preconditioning, and low-dose toxic compounds to trigger mitohormesis, thereby alleviating bone and cartilage degeneration.

Sit4 Genetically Interacts with Vps27 to Regulate Mitochondrial Function and Lifespan in Saccharomyces cerevisiae

The Sit4 protein phosphatase plays a key role in orchestrating various cellular processes essential for maintaining cell viability during aging. We have previously shown that SIT4 deletion promotes vacuolar acidification, mitochondrial derepression, and oxidative stress resistance, increasing yeast chronological lifespan. In this study, we performed a proteomic analysis of isolated vacuoles and yeast genetic interaction analysis to unravel how Sit4 influences vacuolar and mitochondrial function. By employing high-resolution mass spectrometry, we show that sit4Δ vacuolar membranes were enriched in Vps27 and Hse1, two proteins that are part of the endosomal sorting complex required for transport-0. In addition, SIT4 exhibited a negative genetic interaction with VPS27, as sit4∆vps27∆ double mutants had a shortened lifespan compared to sit4∆ and vps27∆ single mutants. Our results also show that Vps27 did not increase sit4∆ lifespan by improving protein trafficking or vacuolar sorting pathways. However, Vps27 was critical for iron homeostasis and mitochondrial function in sit4∆ cells, as sit4∆vps27∆ double mutants exhibited high iron levels and impaired mitochondrial respiration. These findings show, for the first time, cross-talk between Sit4 and Vps27, providing new insights into the mechanisms governing chronological lifespan.

Transketolase drives the development of aortic dissection by impairing mitochondrial bioenergetics

AIM

Aortic dissection (AD) is a disease with rapid onset but with no effective therapeutic drugs yet. Previous studies have suggested that glucose metabolism plays a critical role in the progression of AD. Transketolase (TKT) is an essential bridge between glycolysis and the pentose phosphate pathway. However, its role in the development of AD has not yet been elucidated. In this study, we aimed to explore the role of TKT in AD.

METHODS

We collected AD patients' aortic tissues and used high-throughput proteome sequencing to analyze the main factors influencing AD development. We generated an AD model using BAPN in combination with angiotensin II (Ang II) and pharmacological inhibitors to reduce TKT expression. The effects of TKT and its downstream mediators on AD were elucidated using human aortic vascular smooth muscle cells (HAVSMCs).

RESULTS

We found that glucose metabolism plays an important role in the development of AD and that TKT is upregulated in patients with AD. Western blot and immunohistochemistry confirmed that TKT expression was upregulated in mice with AD. Reduced TKT expression attenuated AD incidence and mortality, maintained the structural integrity of the aorta, aligned elastic fibers, and reduced collagen deposition. Mechanistically, TKT was positively associated with impaired mitochondrial bioenergetics by upregulating AKT/MDM2 expression, ultimately contributing to NDUFS1 downregulation.

CONCLUSION

Our results provide new insights into the role of TKT in mitochondrial bioenergetics and AD progression. These findings provide new intervention options for the treatment of AD.

Microphysiological systems for human aging research

Recent advances in microphysiological systems (MPS), also known as organs-on-a-chip (OoC), enable the recapitulation of more complex organ and tissue functions on a smaller scale in vitro. MPS therefore provide the potential to better understand human diseases and physiology. To date, numerous MPS platforms have been developed for various tissues and organs, including the heart, liver, kidney, blood vessels, muscle, and adipose tissue. However, only a few studies have explored using MPS platforms to unravel the effects of aging on human physiology and the pathogenesis of age-related diseases. Age is one of the risk factors for many diseases, and enormous interest has been devoted to aging research. As such, a human MPS aging model could provide a more predictive tool to understand the molecular and cellular mechanisms underlying human aging and age-related diseases. These models can also be used to evaluate preclinical drugs for age-related diseases and translate them into clinical settings. Here, we provide a review on the application of MPS in aging research. First, we offer an overview of the molecular, cellular, and physiological changes with age in several tissues or organs. Next, we discuss previous aging models and the current state of MPS for studying human aging and age-related conditions. Lastly, we address the limitations of current MPS and present future directions on the potential of MPS platforms for human aging research.

Mitochondrial quality control in liver fibrosis: Epigenetic hallmarks and therapeutic strategies

BACKGROUND AND AIM

Mitochondrial quality control (MQC) plays a significant role in the progression of liver fibrosis, with key processes such as mitochondrial fission, fusion, mitophagy and biogenesis maintaining mitochondrial homeostasis. To understand the molecular mechanisms underlying epigenetic regulation of mitochondrial quality control in liver fibrosis, with the aim of uncovering novel therapeutic targets for treating, mitigating, and potentially reversing liver fibrosis, in light of the most recent advances in this field.

METHODS

We searched PubMed, Web of Science, and Scopus for published manuscripts using terms "mitochondrial quality control" "mitochondrial fission" "mitochondrial fusion" "mitochondrial biogenesis" "mitophagy" "liver fibrosis" "epigenetic regulation" "DNA methylation" "RNA methylation" "histone modification" and "non-coding RNA". Manuscripts were collated, studied and carried forward for discussion where appropriate.

RESULTS

Mitochondrial fission, fusion, biogenesis, and mitophagy regulate the homeostasis of mitochondria, and the imbalance of mitochondrial homeostasis can induce liver fibrosis. Epigenetic regulation, including DNA methylation, RNA methylation, histone modifications, and non-coding RNAs, plays a significant role in regulating the processes of mitochondrial homeostasis.

CONCLUSION

Mitochondrial quality control and epigenetic mechanisms are intricately linked to the pathogenesis of liver fibrosis. Understanding these molecular interactions provides insight into potential therapeutic strategies. Further research is necessary to translate these findings into clinical applications, with a focus on developing epigenetic drugs to ameliorate liver fibrosis by modulating MQC and epigenetic pathways.

Fibrinogen in mice cerebral microvessels induces blood-brain barrier dysregulation with aging via a dynamin-related protein 1-dependent pathway

We previously reported evidence that oxidative stress during aging leads to adverse protein profile changes of brain cortical microvessels (MVs: end arterioles, capillaries, and venules) that affect mRNA/protein stability, basement membrane integrity, and ATP synthesis capacity in mice. As an extension of our previous study, we also found that proteins which comprise the blood-brain barrier (BBB) and regulate mitochondrial quality control were also significantly decreased in the mice's cortical MVs with aging. Interestingly, the neuroinflammatory protein fibrinogen (Fgn) was increased in mice brain MVs, which corresponds with clinical reports indicating that the plasma Fgn concentration increased progressively with aging. In this study, protein-protein interaction network analysis indicated that high expression of Fgn is linked with downregulated expression of both BBB- and mitochondrial fission/fusion-related proteins in mice cortical MVs with aging. To investigate the mechanism of Fgn action, we observed that 2 mg/mL or higher concentration of human plasma Fgn changed cell morphology, induced cytotoxicity, and increased BBB permeability in primary human brain microvascular endothelial cells (HBMECs). The BBB tight junction proteins were significantly decreased with increasing concentration of human plasma Fgn in primary HBMECs. Similarly, the expression of phosphorylated dynamin-related protein 1 (pDRP1) and other mitochondrial fission/fusion-related proteins were also significantly reduced in Fgn-treated HBMECs. Interestingly, DRP1 knockdown by shRNA(h) resulted in the reduction of both BBB- and mitochondrial fission/fusion-related proteins in HBMECs. Our results suggest that elevated Fgn downregulates DRP1, leading to mitochondrial-dependent endothelial and BBB dysfunction in the brain microvasculature.

Role of Quercetin in DNA Repair: Possible Target to Combat Drug Resistance in Diabetes

Diabetes Mellitus (DM) is referred to as hyperglycemia in either fasting or postprandial phases. Oxidative stress, which is defined by an excessive amount of reactive oxygen species (ROS) production, increased exposure to external stress, and an excessive amount of the cellular defense system against them, results in cellular damage. Increased DNA damage is one of the main causes of genomic instability, and genetic changes are an underlying factor in the emergence of cancer. Through covalent connections with DNA and proteins, quercetin has been demonstrated to offer protection against the creation of oxidative DNA damage. It has been found that quercetin shields DNA from possible oxidative stress-related harm by reducing the production of ROS. Therefore, Quercetin helps to lessen DNA damage and improve the ability of DNA repair mechanisms. This review mainly focuses on the role of quercetin in repairing DNA damage and compensating for drug resistance in diabetic patients. Data on the target topic was obtained from major scientific databases, including SpringerLink, Web of Science, Google Scholar, Medline Plus, PubMed, Science Direct, and Elsevier. In preclinical studies, quercetin guards against DNA deterioration by regulating the degree of lipid peroxidation and enhancing the antioxidant defense system. By reactivating antioxidant enzymes, decreasing ROS levels, and decreasing the levels of 8-hydroxydeoxyguanosine, Quercetin protects DNA from oxidative damage. In clinical studies, it was found that quercetin supplementation was related to increased antioxidant capacity and decreased risk of type 2 diabetes mellitus in the experimental group as compared to the placebo group. It is concluded that quercetin has a significant role in DNA repair in order to overcome drug resistance in diabetes.

Effects of regular exercise on vascular function with aging: Does sex matter?

Vascular aging, featuring endothelial dysfunction and large elastic artery stiffening, is a major risk factor for the development of age-associated cardiovascular diseases (CVDs). Vascular aging is largely mediated by an excessive production of reactive oxygen species (ROS) and increased inflammation leading to reduced bioavailability of the vasodilatory molecule nitric oxide and remodeling of the arterial wall. Other cellular mechanisms (i.e., mitochondrial dysfunction, impaired stress response, deregulated nutrient sensing, cellular senescence), termed "hallmarks" or "pillars" of aging, may also contribute to vascular aging. Gonadal aging, which largely impacts women but also impacts some men, modulates the vascular aging process. Regular physical activity, including both aerobic and resistance exercise, is a first-line strategy for reducing CVD risk with aging. Although exercise is an effective intervention to counter vascular aging, there is considerable variation in the vascular response to exercise training with aging. Aerobic exercise improves large elastic artery stiffening in both middle-aged/older men and women and enhances endothelial function in middle-aged/older men by reducing oxidative stress and inflammation and preserving nitric oxide bioavailability; however, similar aerobic exercise training improvements are not consistently observed in estrogen-deficient postmenopausal women. Sex differences in adaptations to exercise may be related to gonadal aging and declines in estrogen in women that influence cellular-molecular mechanisms, disconnecting favorable signaling in the vasculature induced by exercise training. The present review will summarize the current state of knowledge on vascular adaptations to regular aerobic and resistance exercise with aging, the underlying mechanisms involved, and the moderating role of biological sex.

Defining Mitochondrial Cristae Morphology Changes Induced by Aging in Brown Adipose Tissue

Mitochondria are required for energy production and even give brown adipose tissue (BAT) its characteristic color due to their high iron content and abundance. The physiological function and bioenergetic capacity of mitochondria are connected to the structure, folding, and organization of its inner-membrane cristae. During the aging process, mitochondrial dysfunction is observed, and the regulatory balance of mitochondrial dynamics is often disrupted, leading to increased mitochondrial fragmentation in aging cells. Therefore, it is hypothesized that significant morphological changes in BAT mitochondria and cristae will be present with aging. A quantitative 3D electron microscopy approach is developed to map cristae network organization in mouse BAT to test this hypothesis. Using this methodology, the 3D morphology of mitochondrial cristae is investigated in adult (3-month) and aged (2-year) murine BAT tissue via serial block face-scanning electron microscopy (SBF-SEM) and 3D reconstruction software for manual segmentation, analysis, and quantification. Upon investigation, an increase is found in mitochondrial volume, surface area, and complexity and decreased sphericity in aged BAT, alongside significant decreases in cristae volume, area, perimeter, and score. Overall, these data define the nature of the mitochondrial structure in murine BAT across aging.

Investigating the Mitoprotective Effects of S1P Receptor Modulators Ex Vivo Using a Novel Semi-Automated Live Imaging Set-Up

In multiple sclerosis (MS), mitochondrial alterations appear to contribute to disease progression. The sphingosine-1-phosphate receptor modulator siponimod is approved for treating secondary progressive MS. Its preceding compound fingolimod was shown to prevent oxidative stress-induced alterations in mitochondrial morphology. Here, we assessed the effects of siponimod, compared to fingolimod, on neuronal mitochondria in oxidatively stressed hippocampal slices. We have also advanced the model of chronic organotypic hippocampal slices for live imaging, enabling semi-automated monitoring of mitochondrial alterations. The slices were prepared from B6.Cg-Tg(Thy1-CFP/COX8A)S2Lich/J mice that display fluorescent neuronal mitochondria. They were treated with hydrogen peroxide (oxidative stress paradigm) ± 1 nM siponimod or fingolimod for 24 h. Afterwards, mitochondrial dynamics were investigated. Under oxidative stress, the fraction of motile mitochondria decreased and mitochondria were shorter, smaller, and covered smaller distances. Siponimod partly prevented oxidatively induced alterations in mitochondrial morphology; for fingolimod, a similar trend was observed. Siponimod reduced the decrease in mitochondrial track displacement, while both compounds significantly increased track speed and preserved motility. The novel established imaging and analysis tools are suitable for assessing the dynamics of neuronal mitochondria ex vivo. Using these approaches, we showed that siponimod at 1 nM partially prevented oxidatively induced mitochondrial alterations in chronic brain slices.

The mediating role of inflammaging between mitochondrial dysfunction and sarcopenia in aging: a review

Sarcopenia, characterized by the insidious reduction of skeletal muscle mass and strength, detrimentally affects the quality of life in elderly cohorts. Present therapeutic strategies are confined to physiotherapeutic interventions, signaling a critical need for elucidation of the etiological underpinnings to facilitate the development of innovative pharmacotherapies. Recent scientific inquiries have associated mitochondrial dysfunction and inflammation with the etiology of sarcopenia. Mitochondria are integral to numerous fundamental cellular processes within muscle tissue, including but not limited to apoptosis, autophagy, signaling via reactive oxygen species, and the maintenance of protein equilibrium. Deviations in mitochondrial dynamics, coupled with compromised oxidative capabilities, autophagic processes, and protein equilibrium, result in disturbances to muscular architecture and functionality. Mitochondrial dysfunction is particularly detrimental as it diminishes oxidative phosphorylation, escalates apoptotic activity, and hinders calcium homeostasis within muscle cells. Additionally, deleterious feedback loops of deteriorated respiration, exacerbated oxidative injury, and diminished quality control mechanisms precipitate the acceleration of muscular senescence. Notably, mitochondria exhibiting deficient energetic metabolism are pivotal in precipitating the shift from normative muscle aging to a pathogenic state. This analytical review meticulously examines the complex interplay between mitochondrial dysfunction, persistent inflammation, and the pathogenesis of sarcopenia. It underscores the imperative to alleviate inflammation and amend mitochondrial anomalies within geriatric populations as a strategy to forestall and manage sarcopenia. An initial overview provides a succinct exposition of sarcopenia and its clinical repercussions. The discourse then progresses to an examination of the direct correlation between mitochondrial dysfunction and the genesis of sarcopenia. Concomitantly, it accentuates potential synergistic effects between inflammatory responses and mitochondrial insufficiencies during the aging of skeletal muscle, thereby casting light upon emergent therapeutic objectives. In culmination, this review distills the prevailing comprehension of the mitochondrial and inflammatory pathways implicated in sarcopenia and delineates extant lacunae in knowledge to orient subsequent scientific inquiry.

Mitochondrial temperature homeostasis resists external metabolic stresses

Based on studies with a fluorescent reporter dye, Mito Thermo Yellow (MTY), and the genetically encoded gTEMP ratiometric fluorescent temperature indicator targeted to mitochondria, the temperature of active mitochondria in four mammalian and one insect cell line was estimated to be up to 15°C above that of the external environment to which the cells were exposed. High mitochondrial temperature was maintained in the face of a variety of metabolic stresses, including substrate starvation or modification, decreased ATP demand due to inhibition of cytosolic protein synthesis, inhibition of the mitochondrial adenine nucleotide transporter and, if an auxiliary pathway for electron transfer was available via the alternative oxidase, even respiratory poisons acting downstream of oxidative phosphorylation (OXPHOS) complex I. We propose that the high temperature of active mitochondria is an inescapable consequence of the biochemistry of OXPHOS and is homeostatically maintained as a primary feature of mitochondrial metabolism.

Lipocalin-2 induces mitochondrial dysfunction in renal tubular cells via mTOR pathway activation

Mitochondrial dysfunction is a critical process in renal epithelial cells upon kidney injury. While its implication in kidney disease progression is established, the mechanisms modulating it remain unclear. Here, we describe the role of Lipocalin-2 (LCN2), a protein expressed in injured tubular cells, in mitochondrial dysfunction. We show that LCN2 expression decreases mitochondrial mass and function and induces mitochondrial fragmentation. Importantly, while LCN2 expression favors DRP1 mitochondrial recruitment, DRP1 inhibition antagonizes LCN2's effect on mitochondrial shape. Remarkably, LCN2 promotes mitochondrial fragmentation independently of its secretion or transport iron activity. Mechanistically, intracellular LCN2 expression increases mTOR activity, and rapamycin inhibits LCN2's effect on mitochondrial shape. In vivo, Lcn2 gene inactivation prevents mTOR activation and mitochondrial length decrease observed upon ischemia-reperfusion-induced kidney injury (IRI) in Lcn2+/+ mice. Our data identify LCN2 as a key regulator of mitochondrial dynamics and further elucidate the mechanisms leading to mitochondrial dysfunction.

Defining Mitochondrial Cristae Morphology Changes Induced by Aging in Brown Adipose Tissue

Mitochondria are required for energy production and even give brown adipose tissue (BAT) its characteristic color due to their high iron content and abundance. The physiological function and bioenergetic capacity of mitochondria are connected to the structure, folding, and organization of its inner-membrane cristae. During the aging process, mitochondrial dysfunction is observed, and the regulatory balance of mitochondrial dynamics is often disrupted, leading to increased mitochondrial fragmentation in aging cells. Therefore, we hypothesized that significant morphological changes in BAT mitochondria and cristae would be present with aging. We developed a quantitative three-dimensional (3D) electron microscopy approach to map cristae network organization in mouse BAT to test this hypothesis. Using this methodology, we investigated the 3D morphology of mitochondrial cristae in adult (3-month) and aged (2-year) murine BAT tissue via serial block face-scanning electron microscopy (SBF-SEM) and 3D reconstruction software for manual segmentation, analysis, and quantification. Upon investigation, we found increases in mitochondrial volume, surface area, and complexity and decreased sphericity in aged BAT, alongside significant decreases in cristae volume, area, perimeter, and score. Overall, these data define the nature of the mitochondrial structure in murine BAT across aging.

Abstract Figure

Alleviation of ischemic brain injury by exercise preconditioning is associated with modulation of autophagy and mitochondrial dynamics in cerebral cortex of female aged mice

Evidence from clinical studies and preclinical studies supports that exercise preconditioning can not only reduce the risk of stroke but also improve brain tissue and functional outcome after stroke. It has been demonstrated that autophagy and mitochondrial dynamics are involved in ischemic stroke. However, it is still unclear whether exercise preconditioning-induced neuroprotection against stroke is associated with modulation of autophagy and mitochondrial dynamics. Although age and sex interactively affect ischemic stroke risk, incidence, and outcome, studies based on young male animals are most often used to explore the role of exercise preconditioning in the prevention of ischemic stroke. In the current study, we examined whether exercise preconditioning could modulate autophagy and mitochondrial dynamics in a brain ischemia and reperfusion (I/R) model of female aged mice. The results showed that exercise preconditioning reduced infarct volume and improved neurological deficits. Additionally, increased levels of autophagy-related proteins LC3-II/LC3-I, LC3-II, p62, Atg7, and mitophagy-related proteins Bnip3L and Parkin, as well as increased levels of mitochondrial fusion modulator Mfn2 and mitochondrial fission modulator Drp1 in the ischemic cortex of female aged mice at 12 h after I/R were present. Our results could contribute to a better understanding of exercise preconditioning-induced neuroprotection against ischemic stroke for the elderly.

AZD5438 a GSK-3a/b and CDK inhibitor is antiapoptotic modulates mitochondrial activity and protects human neurons from mitochondrial toxins

We previously reported that kenpaullone, which inhibits GSK-3a/b and CDKs inhibited CCCP mediated mitochondrial depolarisation and augments the mitochondrial network. To investigate the actions of this class of drug further, we compared the ability of kenpaullone, alsterpaullone, 1-azakenapaullone, AZD5438, AT7519 (CDK and GSK-3a/b inhibitors) and dexpramipexole and olesoxime (mitochondrial permeability transition pore inhibitors) to prevent CCCP mediated mitochondrial depolarisation and found that AZD5438 and AT7519, were the most effective. Furthermore, treatment with AZD5438 alone increased the complexity of the mitochondrial network. We also found that AZD5438 prevented the rotenone induced decrease in PGC-1alpha and TOM20 levels and that it mediated powerful anti-apoptotic effects and promoted glycolytic respiration. Importantly, experiments in human iPSC derived cortical and midbrain neurons showed AZD5438 mediated significant protective effects, preventing the neuronal cell death, and collapse in the neurite and mitochondrial network associated with rotenone treatment. These results suggest drugs that target GSK-3a/b and CDKs should be developed and assessed further as they may have significant therapeutic potential.

Boosting mitochondrial function and metabolism in aging female germ cells with dual ROCK/ROS inhibition

The decline in oocyte quality with age is an irreversible process that results in low fertility. Reproductive aging causes an increase in oocyte aneuploidy leading to a decrease in embryo quality and an increase in the incidence of miscarriage and congenital defects. Here, we show that the dysfunction associated with aging is not limited to the oocyte, as oocyte granulosa cells also show a range of defects related to mitochondrial activity. The addition of Y-27632 and Vitamin C combination drugs to aging germ cells was effective in enhancing the quality of aging cells. We observed that supplement treatment significantly decreased the production of reactive oxygen species (ROS) and restored the balance of mitochondrial membrane potential. Supplementation treatment reduces excessive mitochondrial fragmentation in aging cells by upregulating mitochondrial fusion. Moreover, it regulated the energy metabolism within cells, favoring oxygen respiration and reducing anaerobic respiration, thereby increasing cellular ATP production. In an experiment with aged mice, supplement treatment improved the maturation of oocytes in vitro and prevented the buildup of ROS in aging oocytes in culture. Additionally, this treatment resulted in an increased concentration of anti-mullerian hormone (AMH) in the culture medium. By improving mitochondrial metabolism in aging females, supplement treatment has the potential to increase quality of oocytes during in vitro fertilization.

MicroRNA-19b-3p dysfunction of mesenchymal stem cell-derived exosomes from patients with abdominal aortic aneurysm impairs therapeutic efficacy

Senescence of vascular smooth muscle cells (VSMCs) contributes to the formation of abdominal aortic aneurysm (AAA). Although mesenchymal stem cell exosomes (MSC-EXO) have been confirmed to restrict the development of AAA, their biological activity depends largely on the physiological state of the MSCs. This study aimed to compare the effects of adipose-derived MSC-EXO from healthy donors (HMEXO) and AAA patients (AMEXO) on senescence of VSMCs in AAA and explore the underlying mechanisms. An ApoE-/- mouse model of AAA was used to investigate the therapeutic effects of HMEXO, AMEXO or miR-19b-3p-AMEXO on AAA development. This in vitro model of AAA was established by treating VSMCs with Ang II (Angiotensin II). The senescence of VSMCs was determined by senescence-associated β-galactosidase (SA-β-gal) staining. The morphology of mitochondria in VSMCs was examined by MitoTracker staining. HMEXO exhibited superior capacity compared with AMEXO to inhibit VSMC senescence and attenuate AAA formation in Ang II-treated ApoE-/- mice. In vitro, both AMEXO and HMEXO inhibited Ang II-induced VSMC senescence via downregulation of mitochondrial fission. Notably, compared with HMEXO, the ability of AMEXO to inhibit VSMC senescence was significantly decreased. miRNA sequencing and the expression of miR-19b-3p was significantly decreased in AMEXO compared with HMEXO. Luciferase assay suggested that MST4 (Mammalian sterile-20-like kinase 4) is a potential target of miR-19b-3p. Mechanistically, miR-19b-3p in HMEXO ameliorated VSMC senescence by inhibiting mitochondrial fission via regulation of the MST4/ERK/Drp1 signaling pathway. Overexpression of miR-19b-3p in AMEXO improved their beneficial effect on AAA formation. Our study reveals that MSC-exosomal miR-19b-3p exerts protective effects against Ang II-induced AAA and VSMC senescence via regulation of the MST4/ERK/Drp1 pathway. The pathological state of AAA patients alters the miRNA components of AMEXO and impairs their therapeutic benefits.

Pterostilbene Attenuates High-Intensity Swimming Exercise-Induced Glucose Absorption Dysfunction Associated with the Inhibition of NLRP3 Inflammasome-Induced IECs Pyroptosis

The study investigated the effect of pterostilbene (PTE) on intestinal glucose absorption and its underlying mechanisms in high-intensity swimming exercise (HISE)-treated mice. Male C57BL/6 mice were treated with PTE for 4 weeks and performed high-intensity swimming training in the last week. Intestinal epithelial cells (IECs) were pretreated with 0.5 and 1.0 μM PTE for 24 h before being incubated in hypoxia/reoxygenation condition. Intestinal glucose absorption was detected by using an oral glucose tolerance test and d-xylose absorption assay, and the levels of factors related to mitochondrial function and pyroptosis were measured via western blot analyses, cell mito stress test, and quantitative real-time polymerase chain reaction. In vivo and in vitro, the results showed that PTE attenuated HISE-induced intestinal glucose absorption dysfunction and pyroptosis in mice intestine. Moreover, PTE inhibited NLRP3 inflammasome and the mitochondrial homeostasis as well as the ROS accumulation in IEC in vitro. Additionally, knockdown of SIRT3, a major regulator of mitochondria function, by siRNA or inhibiting its activity by 3-TYP abolished the effects of PTE on pyroptosis, mitochondrial homeostasis, and ROS generation of IEC in vitro. Our results revealed that PTE could alleviate HISE-induced intestinal glucose absorption dysfunction associated with the inhibition of NLRP3 inflammasome-induced IECs pyroptosis.

Pleiotropic and multi-systemic actions of physical exercise on PGC-1α signaling during the aging process

Physical training is a potent therapeutic approach for improving mitochondrial health through peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) signaling pathways. However, comprehensive information regarding the physical training impact on PGC-1α in the different physiological systems with advancing age is not fully understood. This review sheds light on the frontier-of-knowledge data regarding the chronic effects of exercise on the PGC-1α signaling pathways in rodents and humans. We address the molecular mechanisms involved in the different tissues, clarifying the precise biological action of PGC-1α, restricted to the aged cell type. Distinct exercise protocols (short and long-term) and modalities (aerobic and resistance exercise) increase the transcriptional and translational PGC-1α levels in adipose tissue, brain, heart, liver, and skeletal muscle in animal models, suggesting that this versatile molecule induces pleiotropic responses. However, PGC-1α function in some human tissues (adipose tissue, heart, and brain) remains challenging for further investigations. PGC-1α is not a simple transcriptional coactivator but supports a biochemical environment of mitochondrial dynamics, controlling physiological processes (primary metabolism, tissue remodeling, autophagy, inflammation, and redox balance). Acting as an adaptive mechanism, the long-term effects of PGC-1α following exercise may reflect the energy demand to coordinate multiple organs and contribute to cellular longevity.

Mitochondrial Dysfunction in CD4+ T Effector Memory RA+ Cells

Human ageing is accompanied by poor responses to infection and decreased vaccine efficacy. While the causes of this can be attributed to defects in the immune system that increase with age, it is unknown whether mitochondrial dysfunction may also contribute to these phenomena. This study aims to assess mitochondrial dysfunction in CD4+ terminal effector memory T cells re-expressing CD45RA (TEMRA) cells and other CD4+ memory T cell subtypes, which are increased in number in the elderly population, with respect to how their metabolic responses to stimulation are altered compared to CD4+ naïve T cells. In this study, we show that CD4+ TEMRA cells exhibit altered mitochondrial dynamics compared to CD4+ naïve cells and CD4+ central and effector memory cells, with a 25% reduction in OPA1 expression. CD4+ TEMRA and memory cells show increased upregulation of Glucose transporter 1 following stimulation and higher levels of mitochondrial mass compared to CD4+ naïve T cells. Additionally, TEMRA cells exhibit a decrease in mitochondrial membrane potential compared to other CD4+ memory cell subsets by up to 50%. By comparing young to aged individuals, more significant mitochondria mass and lower membrane potential were observed in CD4+ TEMRA of young individuals. In conclusion, we suggest that CD4+ TEMRA cells may be impaired with respect to their metabolic response to stimulation, possibly contributing to impaired responses to infection and vaccination.

Emerging role of TAK1 in the regulation of skeletal muscle mass

Maintenance of skeletal muscle mass and strength throughout life is crucial for heathy living and longevity. Several signaling pathways have been implicated in the regulation of skeletal muscle mass in adults. TGF-β-activated kinase 1 (TAK1) is a key protein, which coordinates the activation of multiple signaling pathways. Recently, it was discovered that TAK1 is essential for the maintenance of skeletal muscle mass and myofiber hypertrophy following mechanical overload. Forced activation of TAK1 in skeletal muscle causes hypertrophy and attenuates denervation-induced muscle atrophy. TAK1-mediated signaling in skeletal muscle promotes protein synthesis, redox homeostasis, mitochondrial health, and integrity of neuromuscular junctions. In this article, we have reviewed the role and potential mechanisms through which TAK1 regulates skeletal muscle mass and growth. We have also proposed future areas of research that could be instrumental in exploring TAK1 as therapeutic target for improving muscle mass in various catabolic conditions and diseases.

Resistance training prevents dynamics and mitochondrial respiratory dysfunction in vastus lateralis muscle of ovariectomized rats

To investigate whether ovariectomy affects mitochondrial respiratory function, gene expression of the biogenesis markers and mitochondrial dynamics of the vastus lateralis muscle, female Wistar rats divided into ovariectomized (OVX) and intact (INT) groups were kept sedentary (SED) or submitted to resistance training (RT) performed for thirteen weeks on a vertical ladder in which animals climbed with a workload apparatus. RT sessions were performed with four climbs with 65, 85, 95, and 100 % of the rat's previous maximum workload. Mitochondrial Respiratory Function data were obtained by High-resolution respirometry. Gene expression of FIS1, MFN1 and PGC1-α was evaluated by real-time PCR. There was a decrease on oxidative phosphorylation capacity in OVX-SED compared to other groups. Trained groups presented increase on oxidative phosphorylation capacity when compared to sedentary groups. For respiratory control ratio (RCR), OVX-SED presented lower values when compared to INT-SED and to trained groups. Trained groups presented RCR values higher compared to INT-SED. Exercise increased the values of FIS1, MFN1 and PGC1-α expression compared to OVX-SED. Our results demonstrated that in the absence of ovarian hormones, there is a great decrease in oxidative phosphorylation and electron transfer system capacities of sedentary animals. RT was able to increase the expression of genes related to mitochondrial dynamics markers, reversing the condition determined by ovariectomy.

Aging, aerobic exercise, and cardiovascular health: Barriers, alternative strategies and future directions

Age-associated cardiovascular (CV) dysfunction, namely arterial dysfunction, is a key antecedent to the development of CV disease (CVD). Arterial dysfunction with aging is characterized by impaired vascular endothelial function and stiffening of the large elastic arteries, each of which is an independent predictor of CVD. These processes are largely mediated by an excess production of reactive oxygen species (ROS) and an increase in chronic, low-grade inflammation that ultimately leads to a reduction in bioavailability of the vasodilatory molecule nitric oxide. Additionally, there are other fundamental aging mechanisms that may contribute to excessive ROS and inflammation termed the "hallmarks of aging"; these additional mechanisms of arterial dysfunction may represent therapeutic targets for improving CV health with aging. Aerobic exercise is the most well-known and effective intervention to prevent and treat the effects of aging on CV dysfunction. However, the majority of mid-life and older (ML/O) adults do not meet recommended exercise guidelines due to traditional barriers to aerobic exercise, such as reduced leisure time, motivation, or access to fitness facilities. Therefore, it is a biomedical research priority to develop and implement time- and resource-efficient alternative strategies to aerobic exercise to reduce the burden of CVD in ML/O adults. Alternative strategies that mimic or are inspired by aerobic exercise, that target pathways specific to the fundamental mechanisms of aging, represent a promising approach to accomplish this goal.

Minoxidil Regulates Aging-Like Phenotypes in Rat Cortical Astrocytes In Vitro

Mainly due to the slanted focus on the mechanism and regulation of neuronal aging, research on astrocyte aging and its modulation during brain aging is scarce. In this study, we established aged astrocyte culture model by long-term culturing. Cellular senescence was confirmed through SA-β-gal staining as well as through the examination of morphological, molecular, and functional markers. RNA sequencing and functional analysis of astrocytes were performed to further investigate the detailed characteristics of the aged astrocyte model. Along with aged phenotypes, decreased astrocytic proliferation, migration, mitochondrial energetic function and support for neuronal survival and differentiation has been observed in aged astrocytes. In addition, increased expression of cytokines and chemokine-related factors including plasminogen activator inhibitor -1 (PAI-1) was observed in aged astrocytes. Using the RNA sequencing results, we searched potential drugs that can normalize the dysregulated gene expression pattern observed in long-term cultured aged astrocytes. Among several candidates, minoxidil, a pyrimidine-derived anti-hypertensive and anti-pattern hair loss drug, normalized the increased number of SA-β-gal positive cells and nuclear size in aged astrocytes. In addition, minoxidil restored up-regulated activity of PAI-1 and increased mitochondrial superoxide production in aged astrocytes. We concluded that long term culture of astrocytes can be used as a reliable model for the study of astrocyte senescence and minoxidil can be a plausible candidate for the regulation of brain aging.

Alzheimer's disease: the hypotheses, known and unknown connections between UV-radiation, mtDNA haplotypes and life span - a review

Alzheimer's disease (AD) is the most common neurodegenerative disease with controversial etiology. One theory claims that AD is due to brain aging affecting mainly the functions of mitochondria, therefore, the factors leading to mitochondrial ageing should lead to the development of Alzheimer's disease. Another theory is that different mitochondrial DNA haplogroups can be predisposition for the onset of the condition. Here we focused on the possible connection between AD and UV radiation using the data on the monthly UV index in Europe, its correlation with mortality rate due to AD and mitochondrial DNA haplogroups distribution. If a link between the two theories is proved, it will mean that UV radiation is a risk factor not only for skin cancer but also for a large group of neurodegenerative diseases amongst which is the Alzheimer's disease.

Mitochondrial defects in pancreatic beta-cell dysfunction and neurodegenerative diseases: Pathogenesis and therapeutic applications

Mitochondria malfunction is linked to the development of β-cell failure and a variety of neurodegenerative disorders. Pancreatic β-cells are normally configured to detect glucose and other food secretagogues in order to adjust insulin exocytosis and maintain glucose homeostasis. As a result of the increased glucose level, mitochondria metabolites and nucleotides are produced, which operate in concert with cytosolic Ca²⁺ to stimulate insulin secretion. Furthermore, mitochondria are the primary generators of adenosine triphosphate (ATP), reactive oxygen species (ROS), and apoptosis regulation. Mitochondria are concentrated in synapses, and any substantial changes in synaptic mitochondria location, shape, quantity, or function might cause oxidative stress, resulting in faulty synaptic transmission, a symptom of various degenerative disorders at an early stage. However, a greater understanding of the role of mitochondria in the etiology of β-cell dysfunction and neurodegenerative disorder should pave the way for a more effective approach to addressing these health issues. This review looks at the widespread occurrence of mitochondria depletion in humans, and its significance to mitochondria biogenesis in signaling and mitophagy. Proper understanding of the processes might be extremely beneficial in ameliorating the rising worries about mitochondria biogenesis and triggering mitophagy to remove depleted mitochondria, therefore reducing disease pathogenesis.

Repurposing SGLT-2 Inhibitors to Target Aging: Available Evidence and Molecular Mechanisms

Caloric restriction promotes longevity in multiple animal models. Compounds modulating nutrient-sensing pathways have been suggested to reproduce part of the beneficial effect of caloric restriction on aging. However, none of the commonly studied caloric restriction mimetics actually produce a decrease in calories. Sodium-glucose cotransporter 2 inhibitors (SGLT2-i) are a class of drugs which lower glucose by promoting its elimination through urine, thus inducing a net loss of calories. This effect promotes a metabolic shift at the systemic level, fostering ketones and fatty acids utilization as glucose-alternative substrates, and is accompanied by a modulation of major nutrient-sensing pathways held to drive aging, e.g., mTOR and the inflammasome, overall resembling major features of caloric restriction. In addition, preliminary experimental data suggest that SGLT-2i might also have intrinsic activities independent of their systemic effects, such as the inhibition of cellular senescence. Consistently, evidence from both preclinical and clinical studies have also suggested a marked ability of SGLT-2i to ameliorate low-grade inflammation in humans, a relevant driver of aging commonly referred to as inflammaging. Considering also the amount of data from clinical trials, observational studies, and meta-analyses suggesting a tangible effect on age-related outcomes, such as cardiovascular diseases, heart failure, kidney disease, and all-cause mortality also in patients without diabetes, here we propose a framework where at least part of the benefit provided by SGLT-2i is mediated by their ability to blunt the drivers of aging. To support this postulate, we synthesize available data relative to the effect of this class on: 1- animal models of healthspan and lifespan; 2- selected molecular pillars of aging in preclinical models; 3- biomarkers of aging and especially inflammaging in humans; and 4- COVID-19-related outcomes. The burden of evidence might prompt the design of studies testing the potential employment of this class as anti-aging drugs.

Mitochondrial-targeted antioxidant supplementation for improving age-related vascular dysfunction in humans: A study protocol

Background: Cardiovascular disease (CVD) is the leading cause of death worldwide and aging is the primary risk factor for the development of CVD. The increased risk of CVD with aging is largely mediated by the development of vascular dysfunction. Excessive production of mitochondrial reactive oxygen species (mtROS) is a key mechanism of age-related vascular dysfunction. Therefore, establishing the efficacy of therapies to reduce mtROS to improve vascular function with aging is of high biomedical importance. Previously, in a small, randomized, crossover-design pilot clinical trial, our laboratory obtained initial evidence that chronic oral supplementation with the mitochondrial-targeted antioxidant MitoQ improves vascular function in healthy older adults. Here, we describe the protocol for an ongoing R01-funded phase IIa clinical trial to establish the efficacy of MitoQ as a therapy to improve vascular function in older adults (ClinicalTrials.gov Identifier: NCT04851288).

Outcomes: The primary outcome of the study is nitric oxide (NO)-mediated endothelium-dependent dilation (EDD) as assessed by brachial artery flow-mediated dilation (FMDBA). Secondary outcomes include mtROS-mediated suppression of EDD, aortic stiffness as measured by carotid-femoral pulse wave velocity, carotid compliance and β-stiffness index, and intima media thickness. Other outcomes include the assessment of endothelial mitochondrial health and oxidative stress in endothelial cells obtained by endovascular biopsy; the effect of altered circulating factors following MitoQ treatment on endothelial cell NO bioavailability and whole cell and mitochondrial reactive oxygen species production ex vivo; and circulating markers of oxidative stress, antioxidant status, and inflammation.

Methods: We are conducting a randomized, placebo-controlled, double-blind, parallel group, phase IIa clinical trial in 90 (45/group) healthy older men and women 60 years of age or older. Participants complete baseline testing and are then randomized to either 3 months of oral MitoQ (20 mg; once daily) or placebo supplementation. Outcome measures are assessed at the midpoint of treatment, i.e., 6 weeks, and again at the conclusion of treatment.

Discussion: This study is designed to establish the efficacy of chronic supplementation with the mitochondrial-targeted antioxidant MitoQ for improving vascular endothelial function and reducing large elastic artery stiffness in older adults, and to investigate the mechanisms by which MitoQ supplementation improves endothelial function.

Premature aging is associated with higher levels of 8-oxoguanine and increased DNA damage in the Polg mutator mouse

Mitochondrial dysfunction plays an important role in the aging process. However, the mechanism by which this dysfunction causes aging is not fully understood. The accumulation of mutations in the mitochondrial genome (or "mtDNA") has been proposed as a contributor. One compelling piece of evidence in support of this hypothesis comes from the Polg^D257A/D257A mutator mouse (Polg^mut/mut ). These mice express an error-prone mitochondrial DNA polymerase that results in the accumulation of mtDNA mutations, accelerated aging, and premature death. In this paper, we have used the Polg^mut/mut model to investigate whether the age-related biological effects observed in these mice are triggered by oxidative damage to the DNA that compromises the integrity of the genome. Our results show that mutator mouse has significantly higher levels of 8-oxoguanine (8-oxoGua) that are correlated with increased nuclear DNA (nDNA) strand breakage and oxidative nDNA damage, shorter average telomere length, and reduced mtDNA integrity. Based on these results, we propose a model whereby the increased level of reactive oxygen species (ROS) associated with the accumulation of mtDNA mutations in Polg^mut/mut mice results in higher levels of 8-oxoGua, which in turn lead to compromised DNA integrity and accelerated aging via increased DNA fragmentation and telomere shortening. These results suggest that mitochondrial play a central role in aging and may guide future research to develop potential therapeutics for mitigating aging process.

2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-Glucoside improves female ovarian aging

Reduced fertility associated with normal aging may reflect the over-maturity of oocytes. It is increasingly important to reduce aging-induced infertility since recent trends show people marrying at later ages. 2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-glucoside (THSG), a polyphenol extracted from Polygonum multiflorum, has been reported to have anti-inflammatory and anti-aging properties. To evaluate whether THSG can reduce aging-related ovarian damage in a female mouse model of aging, THSG was administered by gavage at a dose of 10 mg/kg twice weekly, starting at 4 weeks of age in a group of young mice. In addition, the effect of THSG in a group of aged mice was also studied in mice starting at 24 weeks of age. The number of oocytes in the THSG-fed group was higher than in the untreated control group. Although the percentage of secondary polar bodies (PB2) decreased during aging in the THSG-fed group, it decreased much more slowly than in the age-matched control group. THSG administration increased the quality of ovaries in young mice becoming aged. Western blotting analyses also indicated that CYP19, PR-B, and ER-β expressions were significantly increased in 36-week-old mice. THSG also increased oocyte numbers in aged mice compared to mice without THSG fed. Studies of qPCR and immunohistochemistry (IHC) analyses of ovaries in the aged mice groups were conducted. THSG increased gene expression of anti-Müllerian hormone (AMH), a biomarker of oocyte number, and protein accumulation in 40-week-old mice. THSG increased the expression of pgc1α and atp6, mitochondrial biogenesis-related genes, and their protein expression. THSG also attenuated the fading rate of CYP11a and CYP19 associated with sex hormone synthesis. And THSG maintains a high level of ER-β expression, thereby enhancing the sensitivity of estrogen. Our findings indicated that THSG increased or extended gene expression involved in ovarian maintenance and rejuvenation in young and aged mice. On the other hand, THSG treatments significantly maintained oocyte quantity and quality in both groups of young and aged mice compared to each age-matched control group. In conclusion, THSG can delay aging-related menopause, and the antioxidant properties of THSG may make it suitable for preventing aging-induced infertility.

Simple to Complex: The Role of Actin and Microtubules in Mitochondrial Dynamics in Amoeba, Yeast, and Mammalian Cells

Mitochondria are complex organelles that provide energy for the cell in the form of adenosine triphosphate (ATP) and have very specific structures. For most organisms, this is a reticular or tubular mitochondrial network, while others have singular oval-shaped organelles. Nonetheless, maintenance of this structure is dependent on the mitochondrial dynamics, fission, fusion, and motility. Recently, studies have shown that the cytoskeleton has a significant role in the regulation of mitochondrial dynamics. In this review, we focus on microtubules and actin filaments and look at what is currently known about the cytoskeleton’s role in mitochondrial dynamics in complex models like mammals and yeast, as well as what is known in the simple model system, Dictyostelium discoideum. Understanding how the cytoskeleton is involved in mitochondrial dynamics increases our understanding of mitochondrial disease, especially neurodegenerative diseases. Increases in fission, loss of fusion, and fragmented mitochondria are seen in several neurodegenerative diseases such as Parkinson’s, Alzheimer’s, and Huntington’s disease. There is no known cure for these diseases, but new therapeutic strategies using drugs to alter mitochondrial fusion and fission activity are being considered. The future of these therapeutic studies is dependent on an in-depth understanding of the mechanisms of mitochondrial dynamics. Understanding the cytoskeleton’s role in dynamics in multiple model organisms will further our understanding of these mechanisms and could potentially uncover new therapeutic targets for these neurodegenerative diseases.

Cellular and mitochondrial quality control mechanisms in maintaining homeostasis in ageing

Aging is a natural process in all living organisms defined as destruction of cell function as a result of long-term accumulation of damages. Autophagy is a cellular house safeguard pathway which responsible for degrading damaged cellular organelles. Moreover, it maintains cellular homeostasis, control lifetime, and longevity. Damaged mitochondrial accumulation is a characteristic of aging which associated with neurodegeneration. Mitochondria functions as a principal energy source via supplying ATP through oxidative phosphorylation which serves as fuel for neuronal function. Mitophagy and mitochondrial specific autophagy plays an important role in maintenance of neuronal health via the removal of dysfunctional and aged mitochondria. The mitochondrial QC system involves different strategies for protecting against mitochondrial dysfunction and maintaining healthy mitochondria in cells. Mitochondrial function protection could be a strategy for the promotion of neuroprotection. Mitophagy, could be an effective target for drug discovery. Therefore, further detailed studies for mechanism of mitophagy will advance our mitochondrial phenotype knowledge and understanding to disease pathogenesis. This review mainly focuses on ageing mediated mechanism of autophagy and mitophagy for maintaining the cellular homeostasis and longevity.

Mitochondrial dysfunction in diabetic tubulopathy

Diabetic kidney disease (DKD) is a devastating microvascular complication associated with diabetes mellitus. Recently, the major focus of glomerular lesions of DKD has partly shifted to diabetic tubulopathy because of renal insufficiency and prognosis of patients is closely related to tubular atrophy and interstitial fibrosis. Indeed, the proximal tubule enriching in mitochondria for its high energy demand and dependence on aerobic metabolism has given us pause to focus primarily on the mitochondria-centric view of early diabetic tubulopathy. Multiple studies suggest that diabetes condition directly damages renal tubules, resulting in mitochondria dysfunction, including decreased bioenergetics, overproduction of mitochondrial reactive oxygen species (mtROSs), defective mitophagy and dynamics disturbances, which in turn trigger a series of metabolic abnormalities. However, the precise mechanism underlying mitochondrial dysfunction of renal tubules is still in its infancy. Understanding tubulointerstitial's pathobiology would facilitate the search for new biomarkers of DKD. In this Review, we summarize the current literature and postulate that the potential effects of mitochondrial dysfunction may accelerate initiation of early-stage diabetic tubulopathy, as well as their potential therapeutic strategies.

High-content high-throughput imaging reveals distinct connections between mitochondrial morphology and functionality for OXPHOS complex I, III, and V inhibitors

Cells can adjust their mitochondrial morphology by altering the balance between mitochondrial fission and fusion to adapt to stressful conditions. The connection between a chemical perturbation, changes in mitochondrial function, and altered mitochondrial morphology is not well understood. Here, we made use of high-throughput high-content confocal microscopy to assess the effects of distinct classes of oxidative phosphorylation (OXPHOS) complex inhibitors on mitochondrial parameters in a concentration and time resolved manner. Mitochondrial morphology phenotypes were clustered based on machine learning algorithms and mitochondrial integrity patterns were mapped. In parallel, changes in mitochondrial membrane potential (MMP), mitochondrial and cellular ATP levels, and viability were microscopically assessed. We found that inhibition of MMP, mitochondrial ATP production, and oxygen consumption rate (OCR) using sublethal concentrations of complex I and III inhibitors did not trigger mitochondrial fragmentation. Instead, complex V inhibitors that suppressed ATP and OCR but increased MMP provoked a more fragmented mitochondrial morphology. In agreement, complex V but not complex I or III inhibitors triggered proteolytic cleavage of the mitochondrial fusion protein, OPA1. The relation between increased MMP and fragmentation did not extend beyond OXPHOS complex inhibitors: increasing MMP by blocking the mPTP pore did not lead to OPA1 cleavage or mitochondrial fragmentation and the OXPHOS uncoupler FCCP was associated with OPA1 cleavage and MMP reduction. Altogether, our findings connect vital mitochondrial functions and phenotypes in a high-throughput high-content confocal microscopy approach that help understanding of chemical-induced toxicity caused by OXPHOS complex perturbing chemicals.

Mitochondrial structural variations in the process of mitophagy

Mitochondrion is one of significant organelles inside cells because it serves as a hub for energy management and intracellular signaling. Internal/external damages on mitochondria would lead to mitochondrial stresses with the malfunctions, accompanying with the changes of morphological structure and abnormal local environments (pH values). Mitophagy is capable of degradation of damaged mitochondrial segments to restore its normal metabolism, dynamics, and biogenesis. The dynamic structural visualization and pH quantification can be helpful for the understanding of mitochondrial functions as well as the diagnosis of disorders linking with this process. In this work, we use confocal laser scanning microscopy, STED super-resolution nanoscopy and fluorescence lifetime imaging microscopy, in conjunction with a mitochondrial probe to image the dynamic changes in the mitochondrial morphology and microenvironmental pH values during mitophagy in live cells, in particular, the structural changes of mitochondrial cristae beyond optical diffraction can be distinguished by STED nanoscopy with/without treatment by CCCP, which will provide a new view for the diagnosis and personalized treatment of mitochondrial dysfunction-related diseases.

Relationship of superoxide dismutase to rotator cuff injury/tear in a rat model

Rotator cuff degeneration is one of the several factors that lead to rotator cuff tears. Oxidative stress and superoxide dismutase have been reported to be related to rotator cuff degeneration; however, the precise mechanism still remains unclear. In this study, we investigated the relationship of oxidative stress and superoxide dismutase to the degeneration of the rotator cuff using rat models. Eighty-four rats were used to create a collagenase-induced rotator cuff injury model (injury model) and a rotator cuff tear model (tear model). The controls were administered saline and had only a deltoid incision, respectively. We evaluated degeneration morphology of the rotator cuff using a degeneration score; dihydroethidium fluorescence intensity, which detects oxidative stress; gene expression; and superoxide dismutase activity. The rotator cuffs in the injury and tear models significantly increased degeneration scores and dihydroethidium fluorescence intensity. On the other hand, gene expression of superoxide dismutase isoform, superoxide dismutase 1, and superoxide dismutase activity were significantly decreased in the injury model but showed no significant difference in the tear model. These findings suggested that superoxide dismutase might not be associated with rotator cuff degeneration after tear but may be involved in degenerative rotator cuff without tear. However, we found that rotator cuff degeneration involves oxidative stress both with and without tear. Based on these findings, it is presumed that different treatments may be appropriate, depending on the state of rotator cuff degeneration, because the mechanisms of the degeneration may be different.

Is It Good to Have a Stiff Aorta with Aging? Causes and Consequences

Aortic stiffness increases with advancing age, more than doubling during the human life span, and is a robust predictor of cardiovascular disease (CVD) clinical events independent of traditional risk factors. The aorta increases in diameter and length to accommodate growing body size and cardiac output in youth, but in middle and older age the aorta continues to remodel to a larger diameter, thinning the pool of permanent elastin fibers, increasing intramural wall stress and resulting in the transfer of load bearing onto stiffer collagen fibers. Whereas aortic stiffening in early middle age may be a compensatory mechanism to normalize intramural wall stress and therefore theoretically "good" early in the life span, the negative clinical consequences of accelerated aortic stiffening beyond middle age far outweigh any earlier physiological benefit. Indeed, aortic stiffness and the loss of the "windkessel effect" with advancing age result in elevated pulsatile pressure and flow in downstream microvasculature that is associated with subclinical damage to high-flow, low-resistance organs such as brain, kidney, retina, and heart. The mechanisms of aortic stiffness include alterations in extracellular matrix proteins (collagen deposition, elastin fragmentation), increased arterial tone (oxidative stress and inflammation-related reduced vasodilators and augmented vasoconstrictors; enhanced sympathetic activity), arterial calcification, vascular smooth muscle cell stiffness, and extracellular matrix glycosaminoglycans. Given the rapidly aging population of the United States, aortic stiffening will likely contribute to substantial CVD burden over the next 2-3 decades unless new therapeutic targets and interventions are identified to prevent the potential avalanche of clinical sequelae related to age-related aortic stiffness.

Effect of oligonol, a lychee-derived polyphenol, on skeletal muscle in ovariectomized rats by regulating body composition, protein turnover, and mitochondrial quality signaling

Oligonol is a low‐molecular‐weight polyphenol product derived from lychee (Litchi chinensis Sonn.) fruits. This study was focused on the effects of oligonol on the skeletal muscle of ovariectomized rats. We randomly divided female Sprague–Dawley rats into three groups: a sham surgery control group (Sham), an ovariectomy (OVX) group, and an OVX group treated with oligonol (OVX + Oligonol). Oligonol was intraperitoneally administrated at 30 mg/kg daily for 6 weeks. Oligonol treatment after OVX decreased body weight and fat mass, regulated lipid metabolism in skeletal muscle, without loss of lean mass and bone. Bone turnover was not affected by oligonol. In protein synthesis and degradation, oligonol increased the levels of the mammalian target of rapamycin and its downstream targets, eukaryotic initiation factor 4E‐binding protein 1 and 70‐kDa ribosomal protein S6 kinase, and it stimulated the expression of ubiquitin‐proteasome pathway proteins, the forkhead box transcription factors of the class O and the muscle ring‐finger protein‐1. Moreover, oligonol treatment enhanced mitochondrial biogenesis and dynamics. Thus, our results indicated that oligonol treatment had beneficial effects on the skeletal muscle in an estrogen‐deficiency rat model.

Glyphosate and AMPA exposure in relation to markers of biological aging in an adult population-based study

BACKGROUND/AIM

Glyphosate, a broad-spectrum herbicide, and its main metabolite aminomethylphosphonic acid (AMPA) are persistent in the environment. Studies showed associations between glyphosate or AMPA exposure and several adverse cellular processes, including metabolic alterations and oxidative stress.

OBJECTIVE

To determine the association between glyphosate and AMPA exposure and biomarkers of biological aging.

METHODS

We examined glyphosate and AMPA exposure, mtDNA content and leukocyte telomere length in 181 adults, included in the third cycle of the Flemish Environment and Health Study (FLEHSIII). DNA was isolated from leukocytes and the relative mtDNA content and telomere length were determined using qPCR. Urinary glyphosate and AMPA concentrations were measured by Gas Chromatography-Tandem Mass Spectrometry (GC-MS-MS). We used multiple linear regression models to associate mtDNA content and leukocyte telomere length with glyphosate or AMPA exposure while adjusting for confounding variables.

RESULTS

A doubling in urinary AMPA concentration was associated with 5.19% (95% CI: 0.49 to 10.11; p = 0.03) longer leukocyte telomere length, while no association was observed with urinary glyphosate concentration. No association between mtDNA content and urinary glyphosate nor AMPA levels was observed.

CONCLUSIONS

This study showed that AMPA exposure may be associated with telomere biology in adults.

Role of Lysosomal Acidification Dysfunction in Mesenchymal Stem Cell Senescence

Mesenchymal stem cell (MSC) transplantation has been widely used as a potential treatment for a variety of diseases. However, the contradiction between the low survival rate of transplanted cells and the beneficial therapeutic effects has affected its clinical use. Lysosomes as organelles at the center of cellular recycling and metabolic signaling, play essential roles in MSC homeostasis. In the first part of this review, we summarize the role of lysosomal acidification dysfunction in MSC senescence. In the second part, we summarize some of the potential strategies targeting lysosomal proteins to enhance the therapeutic effect of MSCs.

Increasing Inhibition of the Rat Brain 2-Oxoglutarate Dehydrogenase Decreases Glutathione Redox State, Elevating Anxiety and Perturbing Stress Adaptation

Specific inhibitors of mitochondrial 2-oxoglutarate dehydrogenase (OGDH) are administered to animals to model the downregulation of the enzyme as observed in neurodegenerative diseases. Comparison of the effects of succinyl phosphonate (SP, 0.02 mmol/kg) and its uncharged precursor, triethyl succinyl phosphonate (TESP, 0.02 and 0.1 mmol/kg) reveals a biphasic response of the rat brain metabolism and physiology to increasing perturbation of OGDH function. At the low (TE)SP dose, glutamate, NAD+, and the activities of dehydrogenases of 2-oxoglutarate and malate increase, followed by their decreases at the high TESP dose. The complementary changes, i.e., an initial decrease followed by growth, are demonstrated by activities of pyruvate dehydrogenase and glutamine synthetase, and levels of oxidized glutathione and citrulline. While most of these indicators return to control levels at the high TESP dose, OGDH activity decreases and oxidized glutathione increases, compared to their control values. The first phase of metabolic perturbations does not cause significant physiological changes, but in the second phase, the ECG parameters and behavior reveal decreased adaptability and increased anxiety. Thus, lower levels of OGDH inhibition are compensated by the rearranged metabolic network, while the increased levels induce a metabolic switch to a lower redox state of the brain, associated with elevated stress of the animals.