Skeletal muscle mitochondrial DNA copy number and mitochondrial DNA deletion mutation frequency as predictors of physical performance in older men and women

Unacylated Ghrelin Counteracts Contractile and Mitochondrial Dysfunction in Cancer Cachexia

Background

Cancer cachexia is a complex metabolic syndrome that severely impacts patient mobility, treatment strategies, and quality of life. However, no treatments are available to mitigate the debilitating consequences of cancer cachexia. Unacylated ghrelin (UnAG), the main circulating form of ghrelin, enhances muscle growth and mitochondrial function in various diseases, but its effects in cancer cachexia remain to be tested.

Methods

Male C57Bl6/N mice were assigned to one of three treatment groups: non-tumor-bearing (NTB), tumor-bearing (TB), or tumor-bearing treated with unacylated ghrelin (TB+UnAG). Over four weeks, we monitored body weight, food intake, and tumor size. We assessed muscle mass, contractility, mitochondrial oxygen consumption rate (OCR), and reactive oxygen species (ROS) production. Proteomic analysis was performed to elucidate the downstream effects of UnAG. Cell culture assays were performed to measure the in vitro effects of cancer cell-secreted factors and UnAG on myoblasts.

Results

Gastrocnemius and quadriceps muscle masses were reduced by 20-30% in TB mice compared to NTB controls; however, UnAG treatment prevented approximately 50% of this loss. Beyond muscle mass, UnAG enhanced the isometric maximum specific force of the extensor digitorum longus by 70% in TB mice. This improvement in muscle quality was associated with preferential upregulation of myosin heavy chain expression in TB+UnAG mice. UnAG also increased mitochondrial OCR while reducing ROS production. Mitochondrial DNA (mtDNA) copy number, which was reduced in TB mice, was restored by UnAG, while the reduced mtDNA mutation frequency in TB mice was maintained with treatment, indicating improved mtDNA integrity. Consistent with enhanced mitochondrial function, treadmill running time was significantly increased in TB+UnAG mice. Proteomic analysis revealed that UnAG downregulated proteins associated with proteolysis, while normalizing antioxidant enzyme thioredoxin and proteins involved in calcium handling. Cancer cell-conditioned medium reduced myotube width in vitro, but UnAG treatment preserved myotube structure..

Conclusion

UnAG protects against cancer cachexia by targeting multiple risk factors, including myosin heavy chain expression, mitochondrial bioenergetics, and modulation of protein degradation pathways.

Interpreting the clinical significance of multiple large-scale mitochondrial DNA deletions (MLSMD) in skeletal muscle tissue in the diagnostic evaluation of primary mitochondrial disease

Background and Objectives

Improved detection sensitivity from combined Long-Range PCR (LR-PCR), Next-Generation Sequencing (NGS), and droplet digital PCR (ddPCR) to identify multiple large-scale mtDNA deletions (MLSMD) and quantify deletion heteroplasmy have introduced clinical interpretation challenges. We sought to evaluate clinical, biochemical, and histopathological phenotypes of a large clinical cohort harboring MLSMD in muscle to better understand their significance across a range of clinical phenotypes.

Methods

A single-site retrospective study was performed of 212 diagnostic muscle biopsies obtained from patients referred for Primary Mitochondrial Disease (PMD) evaluation with muscle mitochondrial (mt)DNA sequencing performed at our institution, including electronic medical record (EMR) review of symptoms, biochemical results, and Mitochondrial Myopathy Composite Assessment Tool (MM-COAST) scores.

Results

MLSMD were identified in 50 of 212 (24%) diagnostic tissue biopsies, and were universally present. in subjects ≥50 years (n = 18/18). In 45 of 50 (90%) subjects with MLSMD, no definitive genetic etiology was identified, despite clinical whole exome sequencing (WES) and/or whole genome sequencing (WGS). MLSMD heteroplasmy levels quantified by ddPCR ranged from 0% to 33%, exceeding 10% heteroplasmy in 5/45 (11%). Subjects with MLSMD (n = 45) were more likely to demonstrate mitochondrial abnormalities on histopathology, upregulation (≥150% of control mean) of one or more electron transport chain (ETC) complex enzyme activities, and reduced citrate synthase indicative of mitochondrial depletion (<60% of control mean) relative to subjects without MLSMD (n = 155). As clinical phenotypes varied across the MLSMD cohort, Bernier diagnostic criteria major/minor symptoms were used to discriminate 13 of 45 subjects with "suspected" PMD having unrevealing WES/WGS results and 32 of 45 subjects scored as "less likely" to have PMD. Relative to the "less likely" cohort, a significantly higher frequency of biochemical and muscle histopathological abnormalities (ragged red and COX negative fibers) were observed in the "suspected" cohort, further supporting a higher index of suspicion for PMD, p < 0.05.

Discussion

MLSMD in skeletal muscle tissue were a common molecular finding (24%) in our cohort and consistently present in subjects ≥50 years. Among those with genetically undiagnosed MLSMD (n = 45), the "suspected" PMD subset (n = 13/45) represent a promising cohort for novel gene discoveries.

Age-induced changes in skeletal muscle mitochondrial DNA synthesis, quantity, and quality in genetically unique rats

Mitochondrial genomic integrity is a key element of physiological processes and health. Changes in the half-life of the mitochondrial genome are implicated in the generation and accumulation of age-induced mitochondrial DNA (mtDNA) mutations, which are implicated in skeletal muscle aging and sarcopenia. There are conflicting data on the half-life of mtDNA, and there is limited information on how aging affects half-life in skeletal muscle. We hypothesized that skeletal muscle mtDNA synthesis rates would decrease with age in both female and male rats concomitant with changes in mtDNA integrity reflected in mtDNA copy number and mutation frequency. We measured mitochondrial genome half-life using stable isotope labeling over a period of 14 days and assessed mtDNA copy number and deletion mutation frequency using digital PCR in the quadriceps muscle of 9-month-old and 26-month-old male and female OKC-HET rats. We found a significant age-related increase in mtDNA half-life, from 132 days at 9 months to 216 days at 26 months of age in OKC-HET quadriceps. Concomitant with the increase in mtDNA half-life, we found an age-related increase in mtDNA deletion mutation frequency in both male and female rats. Notably, 26-month-old female rats had a lower mutation frequency than male rats, and there were no changes in mtDNA copy number with sex, age, or mitochondrial genotype. These data reveal several key findings: (1) mtDNA turnover in rat skeletal muscle decreases with age, (2) mtDNA half-lives in skeletal muscle are approximately an order of magnitude longer than what is reported for other tissues, and (3) muscle mtDNA turnover differs significantly from the turnover of other mitochondrial macromolecules including components of the mitochondrial nucleoid. These findings provide insight into the factors driving age-induced mtDNA mutation accumulation, which contribute to losses of mitochondrial genomic integrity and may play a role in skeletal muscle dysfunction.

Chimeric mitochondrial RNA transcripts predict mitochondrial genome deletion mutations in mitochondrial genetic diseases and aging

Although it is well understood that mitochondrial DNA (mtDNA) deletion mutations cause incurable diseases and contribute to aging, little is known about the transcriptional products that arise from these DNA structural variants. We hypothesized that mitochondrial genomes containing deletion mutations express chimeric mitochondrial RNAs. To test this, we analyzed human and rat RNA sequencing data to identify, quantitate, and characterize chimeric mitochondrial RNAs. We observe increased chimeric mitochondrial RNA frequency in samples from patients with mitochondrial genetic diseases and in samples from aged humans. The spectrum of chimeric mitochondrial transcripts reflects the known pattern of mtDNA deletion mutations. To test the hypothesis that mtDNA deletions induce chimeric RNA transcripts, we treated 18 month old and 34 month old rats with guanidinopropionic acid to induce high levels of skeletal muscle mtDNA deletion mutations. With mtDNA deletion induction, we demonstrate that the chimeric mitochondrial transcript frequency also increases and correlates strongly with an orthogonal DNA-based mutation assay performed on identical samples. Further, we show that the frequency of chimeric mitochondrial transcripts predicts expression of both nuclear and mitochondrial genes central to mitochondrial function, demonstrating the utility of these events as metrics of age-induced metabolic change. Mapping and quantitation of chimeric mitochondrial RNAs provide an accessible, orthogonal approach to DNA-based mutation assays, offer a potential method for identifying mitochondrial pathology in widely accessible data sets, and open a new area of study in mitochondrial genetics and transcriptomics.

6-Gingerol improves lipid metabolism disorders in skeletal muscle by regulating AdipoR1/AMPK signaling pathway

BACKGROUND

To delve into the precise mechanisms by which 6-gingerol ameliorates lipid metabolism disorders in skeletal muscle.

METHODS

The level of triglycerides (TG) was used to evaluate lipid deposition. In skeletal muscle, transmission electron microscopy (TEM) was employed to observe mitochondrial morphology. Additionally, PCR was applied to detect mitochondrial biogenesis, and levels of malondialdehyde (MDA), catalase (CAT), glutathione, r-glutamyl cysteingl+glycine (GSH) and nicotinamide adenine dinucleotide (NADH) were measured to assess mitochondrial oxidative stress levels. In vivo, flow cytometry and immunofluorescence assays were conducted to quantify reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). Furthermore, the Seahorse XF assays was utilized to assess mitochondrial respiratory capacity. Fluorescence confocal microscopy and molecular docking were applied to analyze the binding of 6-gingerol and adiponectin receptor 1 (AdipoR1). The expression of AdipoR1, AMPK, PGC-1α and SIRT1 were detected by Western Blot.

RESULTS

In vivo, 6-gingerol could reduce body weight in mice induced by a high-fat diet, enhance metabolic profiles in plasma, decrease lipid accumulation in skeletal muscle and liver, and elevate adiponectin levels. In skeletal muscle, it could restore mitochondrial morphology, boost mitochondrial copy number and biogenesis, and mitigate oxidative stress. In vitro, 6-gingerol may directly interact with AdipoR1 to upregulate the expression of downstream proteins p-AMPK, SIRT1, and PGC-1α, leading to a reduction in lipid deposition, a decrease in ROS production, an increase in mitochondrial membrane potential, and an enhancement of mitochondrial respiratory capacity in C2C12 myotubes.

CONCLUSION

6-Gingerol ameliorated lipid metabolism in skeletal muscle by regulating the AdipoR1/AMPK signaling pathway.

Secondary mitochondrial dysfunction across the spectrum of hereditary and acquired muscle disorders

Mitochondria form a dynamic network within skeletal muscle. This network is not only responsible for producing adenosine triphosphate (ATP) through oxidative phosphorylation, but also responds through fission, fusion and mitophagy to various factors, such as increased energy demands, oxidative stress, inflammation, and calcium dysregulation. Mitochondrial dysfunction in skeletal muscle not only occurs in primary mitochondrial myopathies, but also other hereditary and acquired myopathies. As such, this review attempts to highlight the clinical and histopathologic aspects of mitochondrial dysfunction seen in hereditary and acquired myopathies, as well as discuss potential mechanisms leading to mitochondrial dysfunction and therapies to restore mitochondrial function.

Cancerous Conditions Accelerate the Aging of Skeletal Muscle via Mitochondrial DNA Damage

Skeletal muscle aging and sarcopenia result in similar changes in the levels of aging markers. However, few studies have examined cancer sarcopenia from the perspective of aging. Therefore, this study investigated aging in cancer sarcopenia and explored its causes in vitro and in vivo. In mouse aging, in vitro cachexia, and mouse cachexia models, skeletal muscles showed similar changes in aging markers including oxidative stress, fibrosis, reduced muscle differentiation potential, and telomere shortening. Furthermore, examination of mitochondrial DNA from skeletal muscle revealed a 5 kb deletion in the major arc; truncation of complexes I, IV, and V in the electron transport chain; and reduced oxidative phosphorylation (OXPHOS). The mouse cachexia model demonstrated high levels of high-mobility group box-1 (HMGB1) and tumor necrosis factor-α (TNFα) in cancer ascites. Continuous administration of neutralizing antibodies against HMGB1 and TNFα in this model reduced oxidative stress and abrogated mitochondrial DNA deletion. These results suggest that in cancer sarcopenia, mitochondrial oxidative stress caused by inflammatory cytokines leads to mitochondrial DNA damage, which in turn leads to decreased OXPHOS and the promotion of aging.

Myopathy and Ophthalmologic Abnormalities in Association With Multiple Skeletal Muscle Mitochondrial DNA Deletions

BACKGROUND

Establishing a molecular diagnosis of mitochondrial diseases due to pathogenic mitochondrial DNA (mtDNA) variants can be difficult because of varying levels of tissue heteroplasmy, and identifying these variants is important for clinical management. Here, we present clinical and molecular findings in 8 adult patients with classical features of mitochondrial ophthalmologic and/or muscle disease and multiple mtDNA deletions isolated to muscle.

METHODS

The patients were identified via a retrospective review of patients seen in both a tertiary ophthalmology center and a genetics clinic with a clinical diagnosis of chronic progressive external ophthalmoplegia, optic nerve abnormalities, and/or mitochondrial myopathy. Age at onset of symptoms ranged from 18 to 61 years. Ocular manifestations included bilateral optic neuropathy in one patient, bilateral optic disc cupping without optic neuropathy in 2 patients, ptosis in 4 patients, and ocular motility deficits in 2 patients. Five patients had generalized weakness.

RESULTS

Pathogenic variants in mtDNA were not found in the blood or buccal sample from any patient, but 7 of 8 patients had multiple mtDNA deletions identified in muscle tissue. One patient had a single mtDNA deletion identified in the muscle. Heteroplasmy was less than 15% for all of the identified deletions, with the exception of one deletion that had a heteroplasmy of 50%-60%. None of the patients were found to have a nuclear gene variant known to be associated with mitochondrial DNA maintenance.

CONCLUSIONS

mtDNA deletions were identified in adult patients with ophthalmologic and/or musle abnormalities and may underlie their clinical presentations.

Mitochondrial dysfunction, a weakest link of network of aging, relation to innate intramitochondrial immunity of DNA recognition receptors

Aging probably is the most complexed process in biology. It is manifested by a variety of hallmarks. These hallmarks weave a network of aging; however, each hallmark is not uniformly strong for the network. It is the weakest link determining the strengthening of the network of aging, or the maximum lifespan of an organism. Therefore, only improvement of the weakest link has the chance to increase the maximum lifespan but not others. We hypothesize that mitochondrial dysfunction is the weakest link of the network of aging. It may origin from the innate intramitochondrial immunity related to the activities of pathogen DNA recognition receptors. These receptors recognize mtDNA as the PAMP or DAMP to initiate the immune or inflammatory reactions. Evidence has shown that several of these receptors including TLR9, cGAS and IFI16 can be translocated into mitochondria. The potentially intramitochondrial presented pathogen DNA recognition receptors have the capacity to attack the exposed second structures of the mtDNA during its transcriptional or especially the replicational processes, leading to the mtDNA mutation, deletion, heteroplasmy colonization, mitochondrial dysfunction, and alterations of other hallmarks, as well as aging. Pre-consumption of the intramitochondrial presented pathogen DNA recognition receptors by medical interventions including development of mitochondrial targeted small molecule which can neutralize these receptors may retard or even reverse the aging to significantly improve the maximum lifespan of the organisms.

Geroscience and pathology: a new frontier in understanding age-related diseases

Geroscience, a burgeoning discipline at the intersection of aging and disease, aims to unravel the intricate relationship between the aging process and pathogenesis of age-related diseases. This paper explores the pivotal role played by geroscience in reshaping our understanding of pathology, with a particular focus on age-related diseases. These diseases, spanning cardiovascular and cerebrovascular disorders, malignancies, and neurodegenerative conditions, significantly contribute to the morbidity and mortality of older individuals. We delve into the fundamental cellular and molecular mechanisms underpinning aging, including mitochondrial dysfunction and cellular senescence, and elucidate their profound implications for the pathogenesis of various age-related diseases. Emphasis is placed on the importance of assessing key biomarkers of aging and biological age within the realm of pathology. We also scrutinize the interplay between cellular senescence and cancer biology as a central area of focus, underscoring its paramount significance in contemporary pathological research. Moreover, we shed light on the integration of anti-aging interventions that target fundamental aging processes, such as senolytics, mitochondria-targeted treatments, and interventions that influence epigenetic regulation within the domain of pathology research. In conclusion, the integration of geroscience concepts into pathological research heralds a transformative paradigm shift in our understanding of disease pathogenesis and promises breakthroughs in disease prevention and treatment.

Hallmarks of ageing in human skeletal muscle and implications for understanding the pathophysiology of sarcopenia in women and men

Ageing is a complex biological process associated with increased morbidity and mortality. Nine classic, interdependent hallmarks of ageing have been proposed involving genetic and biochemical pathways that collectively influence ageing trajectories and susceptibility to pathology in humans. Ageing skeletal muscle undergoes profound morphological and physiological changes associated with loss of strength, mass, and function, a condition known as sarcopenia. The aetiology of sarcopenia is complex and whilst research in this area is growing rapidly, there is a relative paucity of human studies, particularly in older women. Here, we evaluate how the nine classic hallmarks of ageing: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication contribute to skeletal muscle ageing and the pathophysiology of sarcopenia. We also highlight five novel hallmarks of particular significance to skeletal muscle ageing: inflammation, neural dysfunction, extracellular matrix dysfunction, reduced vascular perfusion, and ionic dyshomeostasis, and discuss how the classic and novel hallmarks are interconnected. Their clinical relevance and translational potential are also considered.

Mitochondrial disorders as a mechanism for the development of obese Sarcopenia

Obese sarcopenia is a severe and prevalent disease in an aging society. Compared to sarcopenia alone, the development and advanced stage of obesity sarcopenia is faster and more severe. Diagnosis of the cause of adipocyte accumulation is also more complicated; however, no effective pharmacological treatment is available. Chronic inflammation is one of the causes of sarcopenia, and obese patients, who are more likely to develop chronic inflammation, may simultaneously suffer from obesity and sarcopenia. Mitochondrial metabolic disorders have been more easily observed in the tissue cells of patients with obesity and sarcopenia. Mitochondrial metabolic disorders include abnormal mtDNA release, mitochondrial autophagy, and dynamic mitochondrial disorders. Therefore, this review will reveal the mechanism of development of obesity myasthenia gravis from the perspective of mitochondria and discuss the currently existing small-molecule drugs.

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.

Novel economical, accurate, sensitive, single-cell analytical method for mitochondrial DNA quantification in mtDNA mutation carriers

PURPOSE

Although a variety of analytical methods have been developed to detect mitochondrial DNA (mtDNA) heteroplasmy, there are special requirements of mtDNA heteroplasmy quantification for women carrying mtDNA mutations receiving the preimplantation genetic diagnosis (PGD) and prenatal diagnosis (PD) in clinic. These special requirements include various sample types, large sample number, long-term follow-up, and the need for detection of single-cell from biopsied embryos. Therefore, developing an economical, accurate, high-sensitive, and single-cell analytical method for mtDNA heteroplasmy is necessary.

METHODS

In this study, we developed the Sanger sequencing combined droplet digital polymerase chain reaction (ddPCR) method for mtDNA quantification and compared the results to next-generation sequencing (NGS). A total of seventeen families with twelve mtDNA mutations were recruited in this study.

RESULTS

The results showed that both Sanger sequencing and ddPCR could be used to analyze the mtDNA heteroplasmy in single-cell samples. There was no statistically significant difference in heteroplasmy levels in common samples with high heteroplasmy (≥ 5%), low heteroplasmy (< 5%), and single-cell samples, either between Sanger sequencing and NGS methods, or between ddPCR and NGS methods (P > 0.05). However, Sanger sequencing was unable to detect extremely low heteroplasmy accurately. But even in samples with extremely low heteroplasmy (0.40% and 0.92%), ddPCR was always able to quantify them. Compared to NGS, Sanger sequencing combined ddPCR analytical methods greatly reduced the cost of sequencing.

CONCLUSIONS

In conclusion, this study successfully established an economical, accurate, sensitive, single-cell analytical method based on the Sanger sequencing combined ddPCR methods for mtDNA heteroplasmy quantification in a clinical setting.

Nanopore sequencing identifies a higher frequency and expanded spectrum of mitochondrial DNA deletion mutations in human aging

Mitochondrial DNA (mtDNA) deletion mutations cause many human diseases and are linked to age-induced mitochondrial dysfunction. Mapping the mutation spectrum and quantifying mtDNA deletion mutation frequency is challenging with next-generation sequencing methods. We hypothesized that long-read sequencing of human mtDNA across the lifespan would detect a broader spectrum of mtDNA rearrangements and provide a more accurate measurement of their frequency. We employed nanopore Cas9-targeted sequencing (nCATS) to map and quantitate mtDNA deletion mutations and develop analyses that are fit-for-purpose. We analyzed total DNA from vastus lateralis muscle in 15 males ranging from 20 to 81 years of age and substantia nigra from three 20-year-old and three 79-year-old men. We found that mtDNA deletion mutations detected by nCATS increased exponentially with age and mapped to a wider region of the mitochondrial genome than previously reported. Using simulated data, we observed that large deletions are often reported as chimeric alignments. To address this, we developed two algorithms for deletion identification which yield consistent deletion mapping and identify both previously reported and novel mtDNA deletion breakpoints. The identified mtDNA deletion frequency measured by nCATS correlates strongly with chronological age and predicts the deletion frequency as measured by digital PCR approaches. In substantia nigra, we observed a similar frequency of age-related mtDNA deletions to those observed in muscle samples, but noted a distinct spectrum of deletion breakpoints. NCATS-mtDNA sequencing allows the identification of mtDNA deletions on a single-molecule level, characterizing the strong relationship between mtDNA deletion frequency and chronological aging.

Age- and time-dependent mitochondrial genotoxic and myopathic effects of beta-guanidinopropionic acid, a creatine analog, on rodent skeletal muscles

Beta-guanidinopropionic acid (GPA) is a creatine analog suggested as a treatment for hypertension, diabetes, and obesity, which manifest primarily in older adults. A notable side effect of GPA is the induction of mitochondrial DNA deletion mutations. We hypothesized that mtDNA deletions contribute to muscle aging and used the mutation promoting effect of GPA to examine the impact of mtDNA deletions on muscles with differential vulnerability to aging. Rats were treated with GPA for up to 4 months starting at 14 or 30 months of age. We examined quadriceps and adductor longus muscles as the quadriceps exhibits profound age-induced deterioration, while adductor longus is maintained. GPA decreased body and muscle mass and mtDNA copy number while increasing mtDNA deletion frequency. The interactions between age and GPA treatment observed in the quadriceps were not observed in the adductor longus. GPA had negative mitochondrial effects in as little as 4 weeks. GPA treatment exacerbated mtDNA deletions and muscle aging phenotypes in the quadriceps, an age-sensitive muscle, while the adductor longus was spared. GPA has been proposed for use in age-associated diseases, yet the pharmacodynamics of GPA differ with age and include the detrimental induction of mtDNA deletions, a mitochondrial genotoxic stress that is pronounced in muscles that are most vulnerable to aging. Further research is needed to determine if the proposed benefits of GPA on hypertension, diabetes, and obesity outweigh the detrimental mitochondrial and myopathic side effects.

Nutrition Strategies Promoting Healthy Aging: From Improvement of Cardiovascular and Brain Health to Prevention of Age-Associated Diseases

BACKGROUND

An increasing number of studies suggest that diet plays an important role in regulating aging processes and modulates the development of the most important age-related diseases.

OBJECTIVE

The aim of this review is to provide an overview of the relationship between nutrition and critical age-associated diseases.

METHODS

A literature review was conducted to survey recent pre-clinical and clinical findings related to the role of nutritional factors in modulation of fundamental cellular and molecular mechanisms of aging and their role in prevention of the genesis of the diseases of aging.

RESULTS

Studies show that the development of cardiovascular and cerebrovascular diseases, neurodegenerative diseases, cognitive impairment and dementia can be slowed down or prevented by certain diets with anti-aging action. The protective effects of diets, at least in part, may be mediated by their beneficial macro- (protein, fat, carbohydrate) and micronutrient (vitamins, minerals) composition.

CONCLUSIONS

Certain diets, such as the Mediterranean diet, may play a significant role in healthy aging by preventing the onset of certain diseases and by improving the aging process itself. This latter can be strengthened by incorporating fasting elements into the diet. As dietary recommendations change with age, this should be taken into consideration as well, when developing a diet tailored to the needs of elderly individuals. Future and ongoing clinical studies on complex anti-aging dietary interventions translating the results of preclinical investigations are expected to lead to novel nutritional guidelines for older adults in the near future.

Are Skeletal Muscle Changes during Prolonged Space Flights Similar to Those Experienced by Frail and Sarcopenic Older Adults?

Microgravity exposure causes several physiological and psychosocial alterations that challenge astronauts' health during space flight. Notably, many of these changes are mostly related to physical inactivity influencing different functional systems and organ biology, in particular the musculoskeletal system, dramatically resulting in aging-like phenotypes, such as those occurring in older persons on Earth. In this sense, sarcopenia, a syndrome characterized by the loss in muscle mass and strength due to skeletal muscle unloading, is undoubtedly one of the most critical aging-like adverse effects of microgravity and a prevalent problem in the geriatric population, still awaiting effective countermeasures. Therefore, there is an urgent demand to identify clinically relevant biological markers and to underline molecular mechanisms behind these effects that are still poorly understood. From this perspective, a lesson from Geroscience may help tailor interventions to counteract the adverse effects of microgravity. For instance, decades of studies in the field have demonstrated that in the older people, the clinical picture of sarcopenia remarkably overlaps (from a clinical and biological point of view) with that of frailty, primarily when referred to the physical function domain. Based on this premise, here we provide a deeper understanding of the biological mechanisms of sarcopenia and frailty, which in aging are often considered together, and how these converge with those observed in astronauts after space flight.

Remdesivir does not affect mitochondrial DNA copy number or deletion mutation frequency in aged male rats: A short report

Remdesivir is a leading therapy in patients with moderate to severe coronavirus 2 (SARS-CoV-2) infection; the majority of whom are older individuals. Remdesivir is a nucleoside analog that incorporates into nascent viral RNA, inhibiting RNA-directed RNA polymerases, including that of SARS-CoV-2. Less is known about remdesivir's effects on mitochondria, particularly in older adults where mitochondria are known to be dysfunctional. Furthermore, its effect on age-induced mitochondrial mutations and copy number has not been previously studied. We hypothesized that remdesivir adversely affects mtDNA copy number and deletion mutation frequency in aged rodents. To test this hypothesis, 30-month-old male F333BNF1 rats were treated with remdesivir for three months. To determine if remdesivir adversely affects mtDNA, we measured copy number and mtDNA deletion frequency in rat hearts, kidneys, and skeletal muscles using digital PCR. We found no effects from three months of remdesivir treatment on mtDNA copy number or deletion mutation frequency in 33-month-old rats. These data support the notion that remdesivir does not compromise mtDNA quality or quantity at old age in mammals. Future work should focus on examining additional tissues such as brain and liver, and extend testing to human clinical samples.

Considerations for Sex-Cognizant Research in Exercise Biology and Medicine

As the fields of kinesiology, exercise science, and human movement developed, the majority of the research focused on male physiology and extrapolated findings to females. In the medical sphere, basing practice on data developed in only males resulted in the removal of drugs from the market in the late 1990s due to severe side effects (some life-threatening) in females that were not observed in males. In response to substantial evidence demonstrating exercise-induced health benefits, exercise is often promoted as a key modality in disease prevention, management, and rehabilitation. However, much like the early days of drug development, a historical literature knowledge base of predominantly male studies may leave the exercise field vulnerable to overlooking potentially key biological differences in males and females that may be important to consider in prescribing exercise (e.g., how exercise responses may differ between sexes and whether there are optimal approaches to consider for females that differ from conventional approaches that are based on male physiology). Thus, this review will discuss anatomical, physiological, and skeletal muscle molecular differences that may contribute to sex differences in exercise responses, as well as clinical considerations based on this knowledge in athletic and general populations over the continuum of age. Finally, this review summarizes the current gaps in knowledge, highlights the areas ripe for future research, and considerations for sex-cognizant research in exercise fields.