Age-associated declines in mitochondrial biogenesis and protein quality control factors are minimized by exercise training

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.

Long-term iron supplementation combined with vitamin B6 enhances maximal oxygen uptake and promotes skeletal muscle-specific mitochondrial biogenesis in rats

Introduction

Iron is an essential micronutrient that plays a crucial role in various biological processes. Previous studies have shown that iron supplementation is related to exercise performance and endurance capacity improvements. However, the underlying mechanisms responsible for these effects are not well understood. Recent studies have suggested the beneficial impact of iron supplementation on mitochondrial function and its ability to rescue mitochondrial function under adverse stress in vitro and rodents. Based on current knowledge, our study aimed to investigate whether the changes in exercise performance resulting from iron supplementation are associated with its effect on mitochondrial function.

Methods

In this study, we orally administered an iron-based supplement to rats for 30 consecutive days at a dosage of 0.66 mg iron/kg body weight and vitamin B6 at a dosage of 0.46 mg/kg.

Results

Our findings reveal that long-term iron supplementation, in combination with vitamin B6, led to less body weight gained and increased VO2 max in rats. Besides, the treatment substantially increased Complex I- and Complex II-driven ATP production in intact mitochondria isolated from gastrocnemius and cerebellum. However, the treatment did not change basal and succinate-induced ROS production in mitochondria from the cerebellum and skeletal muscle. Furthermore, the iron intervention significantly upregulated several skeletal muscle mitochondrial biogenesis and metabolism-related biomarkers, including PGC-1α, SIRT1, NRF-2, SDHA, HSL, MTOR, and LON-P. However, it did not affect the muscular protein expression of SIRT3, FNDC5, LDH, FIS1, MFN1, eNOS, and nNOS. Interestingly, the iron intervention did not exert similar effects on the hippocampus of rats.

Discussion

In conclusion, our study demonstrates that long-term iron supplementation, in combination with vitamin B6, increases VO2 max, possibly through its positive role in regulating skeletal muscle-specific mitochondrial biogenesis and energy production in rats.

Exercise combined with postbiotics treatment results in synergistic improvement of mitochondrial function in the brain of male transgenic mice for Alzheimer's disease

BACKGROUND

It has been suggested that exercise training and postbiotic supplement could decelerate the progress of functional and biochemical deterioration in double transgenic mice overexpresses mutated forms of the genes for human amyloid precursor protein (APPsw) and presenilin 1 (m146L) (APP/PS1TG). Our earlier published data indicated that the mice performed better than controls on the Morris Maze Test parallel with decreased occurrence of amyloid-β plaques in the hippocampus. We investigated the neuroprotective and therapeutic effects of high-intensity training and postbiotic supplementation.

METHODS

Thirty-two adult APP/PS1TG mice were randomly divided into four groups: (1) control, (2) high-intensity training (3) postbiotic, (4) combined (training and postbiotic) treatment for 20 weeks. In this study, the whole hemibrain without hippocampus was used to find molecular traits explaining improved brain function. We applied qualitative RT-PCR for gene expression, Western blot for protein level, and Zymography for LONP1 activity. Disaggregation analysis of Aβ-40 was performed in the presence of Lactobacillus acidophilus and Bifidobacterium longum lysate.

RESULTS

We found that exercise training decreased Alzheimer's Disease (AD)-related gene expression (NF-kB) that was not affected by postbiotic treatment. The preparation used for postbiotic treatment is composed of tyndallized Bifidobacterium longum and Lactobacillus acidophilus. Both of the postbiotics effectively disaggregated amyloid-β/Aβ-40 aggregates by chelating Zn2+ and Cu2+ ions. The postbiotic treatment decreased endogenous human APPTG protein expression and mouse APP gene expression in the hemibrains. In addition, the postbiotic treatment elevated mitochondrial LONP1 activity as well.

CONCLUSION

Our findings revealed distinct mechanisms behind improved memory performance in the whole brain: while exercise training modulates NF-kB signaling pathway regulating immune response until postbiotic diminishes APP gene expression, disaggregates pre-existing amyloid-β plaques and activates mitochondrial protein quality control in the region of brain out of hippocampus. Using the above treatments complements and efficiently slows down the development of AD.

Mitochondrial Properties in Skeletal Muscle Fiber

Mitochondria are the primary source of energy production and are implicated in a wide range of biological processes in most eukaryotic cells. Skeletal muscle heavily relies on mitochondria for energy supplements. In addition to being a powerhouse, mitochondria evoke many functions in skeletal muscle, including regulating calcium and reactive oxygen species levels. A healthy mitochondria population is necessary for the preservation of skeletal muscle homeostasis, while mitochondria dysregulation is linked to numerous myopathies. In this review, we summarize the recent studies on mitochondria function and quality control in skeletal muscle, focusing mainly on in vivo studies of rodents and human subjects. With an emphasis on the interplay between mitochondrial functions concerning the muscle fiber type-specific phenotypes, we also discuss the effect of aging and exercise on the remodeling of skeletal muscle and mitochondria properties.

Advances in exercise to alleviate sarcopenia in older adults by improving mitochondrial dysfunction

Sarcopenia is a chronic degenerative disease affecting primarily older adults. A growing aging population is gradually increasing the number of patients suffering from sarcopenia, placing increasing financial pressure on patients' families and society in general. There is a strong link between mitochondrial dysfunction and sarcopenia pathogenesis. As a result, treating sarcopenia by improving mitochondrial dysfunction is an effective strategy. Numerous studies have demonstrated that exercise has a positive effect on mitochondrial dysfunction when treating sarcopenia. Exercise promotes mitochondrial biogenesis and mitochondrial fusion/division to add new mitochondria or improve dysfunctional mitochondria while maintaining mitochondrial calcium homeostasis, mitochondrial antioxidant defense system, and mitochondrial autophagy to promote normal mitochondrial function. Furthermore, exercise can reduce mitochondrial damage caused by aging by inhibiting mitochondrial oxidative stress, mitochondrial DNA damage, and mitochondrial apoptosis. Exercise effectiveness depends on several factors, including exercise duration, exercise intensity, and exercise form. Therefore, Moderate-intensity exercise over 4 weeks potentially mitigates sarcopenia in older adults by ameliorating mitochondrial dysfunction. HIIT has demonstrated potential as a viable approach to addressing sarcopenia in aged rats. However, further investigation is required to validate its efficacy in treating sarcopenia in older adults.

Mitochondrial transplantation as a possible therapeutic option for sarcopenia

With advancing age, the skeletal muscle phenotype is characterized by a progressive loss of mass, strength, and quality. This phenomenon, known as sarcopenia, has a negative impact on quality of life and increases the risk of morbidity and mortality in older adults. Accumulating evidence suggests that damaged and dysfunctional mitochondria play a critical role in the pathogenesis of sarcopenia. Lifestyle modifications, such as physical activity, exercise, and nutrition, as well as medical interventions with therapeutic agents, are effective in the management of sarcopenia and offer solutions to maintain and improve skeletal muscle health. Although a great deal of effort has been devoted to the identification of the best treatment option, these strategies are not sufficient to overcome sarcopenia. Recently, it has been reported that mitochondrial transplantation may be a possible therapeutic approach for the treatment of mitochondria-related pathological conditions such as ischemia, liver toxicity, kidney injury, cancer, and non-alcoholic fatty liver disease. Given the role of mitochondria in the function and metabolism of skeletal muscle, mitochondrial transplantation may be a possible option for the treatment of sarcopenia. In this review, we summarize the definition and characteristics of sarcopenia and molecular mechanisms associated with mitochondria that are known to contribute to sarcopenia. We also discuss mitochondrial transplantation as a possible option. Despite the progress made in the field of mitochondrial transplantation, further studies are needed to elucidate the role of mitochondrial transplantation in sarcopenia. KEY MESSAGES: Sarcopenia is the progressive loss of skeletal muscle mass, strength, and quality. Although the specific mechanisms that lead to sarcopenia are not fully understood, mitochondria have been identified as a key factor in the development of sarcopenia. Damaged and dysfunctional mitochondria initiate various cellular mediators and signaling pathways, which largely contribute to the age-related loss of skeletal muscle mass and strength. Mitochondrial transplantation has been reported to be a possible option for the treatment/prevention of several diseases. Mitochondrial transplantation may be a possible therapeutic option for improving skeletal muscle health and treating sarcopenia. Mitochondrial transplantation as a possible treatment option for sarcopenia.

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.

Targeting the molecular & cellular pillars of human aging with exercise

Biological aging is the main driver of age-associated chronic diseases. In 2014, the United States National Institute of Aging (NIA) sponsored a meeting between several investigators in the field of aging biology, who identified seven biological pillars of aging and a consensus review, "Geroscience: Linking Aging to Chronic Disease," was published. The pillars of aging demonstrated the conservation of aging pathways in diverse model organisms and thus represent a useful framework with which to study human aging. In this present review, we revisit the seven pillars of aging from the perspective of exercise and discuss how regular physical exercise can modulate these pillars to stave off age-related chronic diseases and maintain functional capacity.

The Role of Sirtuins in Sarcopenia and Frailty

The population of older individuals is increasing rapidly, but only a small fraction among them is able to experiences a healthy life. Due to lack of physical exercise and oxidative stress, aging leads to sarcopenia and finally end up with frailty. Sarcopenia is a component of the frailty and described as age related degenerative changes in the skeletal muscle mass, strength and quality. Though the loss of muscle strength and mass gradually seem inevitable during aging, it can be partially prevented or overcome by a deeper insight into the pathogenesis. Sirtuin protein leads to longevity across different organisms ranging from worms to mammals. Expression of sirtuin protein increases during physical exercise and thus strengthens muscle mass. Satellite cells leads to muscle repair in a SIRT1 dependent manner. In addition, SIRT1 improves insulin sensitivity and induces autophagy in the aged mice. The current paper discussed the putative role of sirtuins in sarcopenia and frailty. Moreover, it highlighted the pathways by which sirtuins can inhibit ROS production, inflammation and mitochondrial dysfunctions and therefore confers a protective role against frailty and sarcopenia. The critical role of sirtuins in the sarcopenia and frailty pathogenesis can eventually fuel the development of novel interventions by targeting sirtuins.

Effects of three modes of physical activity on physical fitness and hematological parameters in older people with sarcopenic obesity: A systematic review and meta-analysis

Objective: This systematic review and meta-analysis assessed the effects of three modes of physical activity (PA) (aerobic training [AT], resistance training [RT], and aerobic combined with resistance training [MT]) on body composition (body weight [BW], body mass index [BMI] and percentage of body fat [BF%]), muscle mass (skeletal muscle mass [SM], appendicular skeletal muscle mass [ASM] and appendicular skeletal muscle mass index [ASMI]), muscle strength (handgrip strength [HG] and knee extension strength [KES]), physical performance (gait speed [GS]) and hematological parameters (inflammatory markers, insulin-like growth factor 1 [IGF-1] and lipid profiles) in older people with sarcopenic obesity (SO).

Methods: We searched all studies for PA effects in older people with SO from six databases published from January 2010 to November 2021. Two researchers independently screened studies, extracted data according to inclusion and exclusion criteria, and assessed the quality of included studies. Pooled analyses for pre-and post- outcome measures were performed by Review Manager 5.4. We calculated a meta-analysis with a 95% confidence interval (95% CI) and the standardized mean differences (SMD).

Results: 12 studies were analyzed. There were 614 older people (84.9% female) with SO, aged 58.4 to 88.4 years. Compared with a no-PA control group, AT decreased BW (SMD = −0.64, 95% CI: −1.13 to −0.16, p = 0.009, I² = 0%) and BMI (SMD = −0.69, 95% CI: −1.18 to −0.21, p = 0.005, I² = 0%); RT improved BF% (SMD = −0.43, 95% CI: −0.63 to −0.22, p < 0.0001, I² = 38%), ASMI (SMD = 0.72, 95% CI: 0.24 to 1.21, p = 0.004, I² = 0%), ASM (SMD = −0.94, 95% CI: −1.46 to −0.42, p = 0.0004), HG (SMD = 1.06, 95% CI: 0.22 to 1.91, p = 0.01, I² = 90%) and KES (SMD = 1.06, 95% CI: 0.73 to 1.39, p < 0.00001, I² = 14%); MT improved BMI (SMD = −0.77, 95% CI: −1.26 to −0.28, p = 0.002, I² = 0%), BF% (SMD = −0.54, 95% CI: −0.83 to −0.25, p = 0.0003, I² = 0%), ASMI (SMD = 0.70, 95% CI: 0.22 to 1.19, p = 0.005, I² = 0%) and GS (SMD = 0.71, 95% CI: 0.23 to 1.18, p = 0.004, I² = 37%). PA increased IGF-1 (SMD = 0.38, 95% CI: 0.11 to 0.66, p = 0.006, I² = 0%), but had no effect on inflammatory markers and lipid profiles.

Conclusion: PA is an effective treatment to improve body composition, muscle mass, muscle strength, physical performance, and IGF-1 in older people with SO.

Ubiquitin Ligases in Longevity and Aging Skeletal Muscle

The development and prevalence of diseases associated with aging presents a global health burden on society. One hallmark of aging is the loss of proteostasis which is caused in part by alterations to the ubiquitin-proteasome system (UPS) and lysosome-autophagy system leading to impaired function and maintenance of mass in tissues such as skeletal muscle. In the instance of skeletal muscle, the impairment of function occurs early in the aging process and is dependent on proteostatic mechanisms. The UPS plays a pivotal role in degradation of misfolded and aggregated proteins. For the purpose of this review, we will discuss the role of the UPS system in the context of age-related loss of muscle mass and function. We highlight the significant role that E3 ubiquitin ligases play in the turnover of key components (e.g., mitochondria and neuromuscular junction) essential to skeletal muscle function and the influence of aging. In addition, we will briefly discuss the contribution of the UPS system to lifespan. By understanding the UPS system as part of the proteostasis network in age-related diseases and disorders such as sarcopenia, new discoveries can be made and new interventions can be developed which will preserve muscle function and maintain quality of life with advancing age.

From the Bench to the Bedside: Branched Amino Acid and Micronutrient Strategies to Improve Mitochondrial Dysfunction Leading to Sarcopenia

With extended life expectancy, the older population is constantly increasing, and consequently, so too is the prevalence of age-related disorders. Sarcopenia, the pathological age-related loss of muscle mass and function; and malnutrition, the imbalance in nutrient intake and resultant energy production, are both commonly occurring conditions in old adults. Altered nutrition plays a crucial role in the onset of sarcopenia, and both these disorders are associated with detrimental consequences for patients (e.g., frailty, morbidity, and mortality) and society (e.g., healthcare costs). Importantly, sarcopenia and malnutrition also share critical molecular alterations, such as mitochondrial dysfunction, increased oxidative stress, and a chronic state of low grade and sterile inflammation, defined as inflammageing. Given the connection between malnutrition and sarcopenia, nutritional interventions capable of affecting mitochondrial health and correcting inflammageing are emerging as possible strategies to target sarcopenia. Here, we discuss mitochondrial dysfunction, oxidative stress, and inflammageing as key features leading to sarcopenia. Moreover, we examine the effects of some branched amino acids, omega-3 PUFA, and selected micronutrients on these pathways, and their potential role in modulating sarcopenia, warranting further clinical investigation.

Age-related biochemical dysfunction in 6-OHDA model rats subject to induced- endurance exercise

Exercise can alleviate the disorders considered as the normal consequences of aging. Whether or not the treadmill endurance training affects the biochemical markers in the Parkinson's disease model rats after the 6-hydroxydopamine (6-OHDA) injection is assessed in this article. The experimental groups of N=8 rats consist of 1) Saline and Young sedentary (S-Young); 2) Saline and Old sedentary (S-Old); 3) Young and 6-OHDA without exercise (Y); 4) Young and 6-OHDA with exercise (YE); 5) Old and 6-OHDA without exercise (O); and 6) Old and 6-OHDA with exercise (OE). An 8 μg of 6-OHDA is injected into the right MFB. The rotation due to apomorphine, weight variation, and some biochemical expression are measured in the rats' striatum. Exposure to 6-OHDA: increase weight loss by (%8) and rotation by (%90), reduce the protein levels of Bdnf by (30%), Th by (43%), and Tfam by (24%), in aging rats (P<0.05). The P53 level rose after the injection compared with the same Saline group (Old rats: 27% and Young rats: 14%), the highest in the O group. The findings indicate that endurance exercise amends the mitochondrial parameters and the apomorphine-induced rotation impairments in the presence of 6-OHDA injection. These positive effects of treadmill running in unilateral 6-OHDA lesioned rat model are age-dependent and are more significant in younger rats.

Mitochondrial DNA and Exercise: Implications for Health and Injuries in Sports

Recently, several studies have highlighted the tight connection between mitochondria and physical activity. Mitochondrial functions are important in high-demanding metabolic activities, such as endurance sports. Moreover, regular training positively affects metabolic health by increasing mitochondrial oxidative capacity and regulating glucose metabolism. Exercise could have multiple effects, also on the mitochondrial DNA (mtDNA) and vice versa; some studies have investigated how mtDNA polymorphisms can affect the performance of general athletes and mtDNA haplogroups seem to be related to the performance of elite endurance athletes. Along with several stimuli, including pathogens, stress, trauma, and reactive oxygen species, acute and intense exercise also seem to be responsible for mtDNA release into the cytoplasm and extracellular space, leading to the activation of the innate immune response. In addition, several sports are characterized by a higher frequency of injuries, including cranial trauma, associated with neurological consequences. However, with regular exercise, circulating cell-free mtDNA levels are kept low, perhaps promoting cf-mtDNA removal, acting as a protective factor against inflammation.

Mitochondrial Dynamics and Mitophagy in Skeletal Muscle Health and Aging

The maintenance of mitochondrial integrity is critical for muscle health. Mitochondria, indeed, play vital roles in a wide range of cellular processes, including energy supply, Ca²⁺ homeostasis, retrograde signaling, cell death, and many others. All mitochondria-containing cells, including skeletal muscle cells, dispose of several pathways to maintain mitochondrial health, including mitochondrial biogenesis, mitochondrial-derived vesicles, mitochondrial dynamics (fusion and fission process shaping mitochondrial morphology), and mitophagy—the process in charge of the removal of mitochondria though autophagy. The loss of skeletal muscle mass (atrophy) is a major health problem worldwide, especially in older people. Currently, there is no treatment to counteract the progressive decline in skeletal muscle mass and strength that occurs with aging, a process termed sarcopenia. There is increasing data, including our own, suggesting that accumulation of dysfunctional mitochondria contributes to the development of sarcopenia. Impairments in mitochondrial dynamics and mitophagy were recently proposed to contribute to sarcopenia. This review summarizes the current state of knowledge on the role played by mitochondrial dynamics and mitophagy in skeletal muscle health and in the development of sarcopenia. We also highlight recent studies showing that enhancing mitophagy in skeletal muscle is a promising therapeutic target to prevent or even treat skeletal muscle dysfunction in the elderly.

Regulation of muscle and mitochondrial health by the mitochondrial fission protein Drp1 in aged mice

KEY POINTS

The maintenance of mitochondrial integrity is critical for skeletal muscle health. Mitochondrial dynamics play key roles in mitochondrial quality control; however, the exact role that mitochondrial fission plays in the muscle ageing process remains unclear. Here we report that both Drp1 knockdown and Drp1 overexpression late in life in mice is detrimental to skeletal muscle function and mitochondrial health. Drp1 knockdown in 18-month-old mice resulted in severe skeletal muscle atrophy, mitochondrial dysfunction, muscle degeneration/regeneration, oxidative stress and impaired autophagy. Overexpressing Drp1 in 18-month-old mice resulted in mild skeletal muscle atrophy and decreased mitochondrial quality. Our data indicate that silencing or overexpressing Drp1 late in life is detrimental to skeletal muscle integrity. We conclude that modulating Drp1 expression is unlikely to be a viable approach to counter the muscle ageing process.

ABSTRACT

Sarcopenia, the ageing-related loss of skeletal muscle mass and function, is a debilitating process negatively impacting the quality of life of afflicted individuals. Although the mechanisms underlying sarcopenia are still only partly understood, impairments in mitochondrial dynamics, and specifically mitochondrial fission, have been proposed as an underlying mechanism. Importantly, conflicting data exist in the field and both excessive and insufficient mitochondrial fission were proposed to contribute to sarcopenia. In Drosophila melanogaster, enhancing mitochondrial fission in midlife through overexpression of dynamin-1-like protein (Drp1) extended lifespan and attenuated several key hallmarks of muscle ageing. Whether a similar outcome of Drp1 overexpression is observed in mammalian muscles remains unknown. In this study, we investigated the impact of knocking down and overexpressing Drp1 protein for 4 months in skeletal muscles of late middle-aged (18 months) mice using intra-muscular injections of adeno-associated viruses expressing shRNA targeting Drp1 or full Drp1 cDNA. We report that knocking down Drp1 expression late in life triggers severe muscle atrophy, mitochondrial dysfunctions, degeneration/regeneration, oxidative stress and impaired autophagy. Drp1 overexpression late in life triggered mild muscle atrophy and decreased mitochondrial quality. Taken altogether, our results indicate that both overexpression and silencing of Drp1 in late middle-aged mice negatively impact skeletal muscle mass and mitochondrial health. These data suggest that Drp1 content must remain within a narrow physiological range to preserve muscle and mitochondrial integrity during ageing. Altering Drp1 expression is therefore unlikely to be a viable target to counter sarcopenia.

Effects of Treadmill Exercise on the Expression Level of BAX, BAD, BCL-2, BCL-XL, TFAM, and PGC-1α in the Hippocampus of Thimerosal-Treated Rats

Thimerosal (THIM) induces neurotoxic changes including neuronal death and releases apoptosis inducing factors from mitochondria to cytosol. THIM alters the expression level of factors involved in apoptosis. On the other hand, the anti-apoptotic effects of exercise have been reported. In this study, we aimed to discover the effect of three protocols of treadmill exercise on the expression level of mitochondrial transcription factor A (TFAM), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), BCL-2-associated death (BAD), BCL-2-associated X (BAX), BCL-XL, and BCL-2 (a pro-survival BCL-2 protein) in the hippocampus of control and THIM-exposed rats. Male Wistar rats were used in this research. Real-time PCR was applied to assess genes expression. The results showed that THIM increased the expression of pro-apoptotic factors (BAD and BAX), decreased the expression of anti-apoptotic factors (BCL-2 and BCL-XL), and decreased the expression of factors involved in mitochondrial biogenesis (TFAM and PGC-1α). Treadmill exercise protocols reversed the effect of THIM on all genes. In addition, treadmill exercise protocols decreased the expression of BAD and BAX, increased the expression of BCL-2, and increased the expression of TFAM and PGC-1α in control rats. In conclusion, THIM induced a pro-apoptotic effect and disturbed mitochondrial biogenesis and stability, whereas treadmill exercise reversed these effects.

Rationale for the use of metformin and exercise to counteract statin-associated side effects

INTRODUCTION

Statins are the most widely prescribed drugs for lowering low-density lipoprotein cholesterol (LDL-C) and reducing cardiovascular morbidity and mortality. They are usually well-tolerated, but have two main safety concerns: statin-associated muscle symptoms (SAMS) and new-onset type 2 diabetes (NOD).

METHODS

A PubMed search was carried out using the following key words were used: statins, statin-associated muscle symptoms, statin myalgia, statin-associated diabetes, metformin and statins, exercise and statins.

RESULTS

Mitochondrial damage and muscle atrophy are likely the central mechanisms producing SAMS, whereas decreased glucose transport, fatty acid oxidation and insulin secretion are likely involved in the development of NOD. Metformin and exercise training share many pathways that could potentially contrast SAMS and NOD. Clinical evidence also supports the combination of statins with metformin and exercise.

CONCLUSION

This combination appears attractive both from a clinical and an economical viewpoint, since all three therapies are highly cost-effective and their combination could result in diabetes and cardiovascular disease prevention.

Manifestations of Age on Autophagy, Mitophagy and Lysosomes in Skeletal Muscle

Sarcopenia is the loss of both muscle mass and function with age. Although the molecular underpinnings of sarcopenia are not fully understood, numerous pathways are implicated, including autophagy, in which defective cargo is selectively identified and degraded at the lysosome. The specific tagging and degradation of mitochondria is termed mitophagy, a process important for the maintenance of an organelle pool that functions efficiently in energy production and with relatively low reactive oxygen species production. Emerging data, yet insufficient, have implicated various steps in this pathway as potential contributors to the aging muscle atrophy phenotype. Included in this is the lysosome, the end-stage organelle possessing a host of proteolytic and degradative enzymes, and a function devoted to the hydrolysis and breakdown of defective molecular complexes and organelles. This review provides a summary of our current understanding of how the autophagy-lysosome system is regulated in aging muscle, highlighting specific areas where knowledge gaps exist. Characterization of the autophagy pathway with a particular focus on the lysosome will undoubtedly pave the way for the development of novel therapeutic strategies to combat age-related muscle loss.

Sarcopenia in Chronic Kidney Disease: Focus on Advanced Glycation End Products as Mediators and Markers of Oxidative Stress

Sarcopenia is common in chronic kidney disease (CKD), and it is independently associated with morbidity and mortality. Advanced glycation end products (AGE) are mainly known as aging products. In CKD, AGE accumulate due to increased production and reduced kidney excretion. The imbalance between oxidant/antioxidant capacities in CKD patients is one of the main factors leading to AGE synthesis. AGE can, in turn, promote CKD progression and CKD-related complications by increasing reactive oxygen species generation, inducing inflammation, and promoting fibrosis. All these derangements can further increase AGE and uremic toxin accumulation and promote loss of muscle mass and function. Since the link between AGE and sarcopenia in CKD is far from being fully understood, we revised hereby the data supporting the potential contribution of AGE as mediators of oxidative stress in the pathogenesis of sarcopenia. Understanding how AGE and oxidative stress impact the onset of sarcopenia in CKD may help to identify new potential markers of disease progression and/or therapeutic targets.

Load-matched acute and chronic exercise induce changes in mitochondrial biogenesis and metabolic markers

We investigated the effects of acute and chronic exercise, prescribed in different intensity zones, but with total load-matched on mitochondrial markers (cytochrome C oxidase subunit IV (COX-IV), mitochondrial transcription factor A (Tfam), and citrate synthase (CS) activity in skeletal muscles, heart, and liver), glycogen stores, aerobic capacity, and anaerobic index in swimming rats. For this, 2 experimental designs were performed (acute and chronic efforts). Load-matched exercises were prescribed below, above, and on the anaerobic threshold (AnT), determined by the lactate minimum test. In chronic programs, 2 training prescription strategies were assessed (monotonous and linear periodized model). Results show changes in glycogen stores but no modification in the COX-IV and Tfam contents after acute exercises. In the chronic protocols, COX-IV and Tfam proteins and CS adaptations were intensity- and tissue-dependent. Monotonous training promoted better adaptations than the periodized model. Training at 80% of the AnT improved both performance variables, emphasizing the anaerobic index, concomitant to CS and COX-IV improvement (soleus muscle). The aerobic capacity and CS activity (gastrocnemius) were increased after 120% AnT training. In conclusion, acute exercise protocol did not promote responses in mitochondrial target proteins. An intensity and tissue dependence were reported in the chronic protocols, highlighting training at 80 and 120% of the AnT. Novelty: Load-matched acute exercise did not enhance COX-IV and Tfam contents in skeletal muscles, heart, and liver. In chronic exercise, COX-IV, Tfam, and CS activity adaptations were intensity- and tissue-dependent. Monotonous training was more efficient than the periodized linear model in adaptations of target proteins and enzymatic activity.

Precision Nutrition to Activate Thermogenesis as a Complementary Approach to Target Obesity and Associated-Metabolic-Disorders

Simple Summary

Regarding the pandemic of obesity and chronic diseases associated to metabolic alterations that occur nowadays worldwide, here, we review the most recent studies related to bioactive compounds and diet derived ingredients with potential effects to augment the systemic energy expenditure. We specifically focus in two processes: the activation of thermogenesis in adipose tissue and the enhancement of the mitochondrial oxidative phosphorylation capacity in muscles. This may provide relevant information to develop diets and supplements to conduct nutritional intervention studies with the objective to ameliorate the metabolic and chronic inflammation in the course of obesity and related disorders.

Abstract

Obesity is associated to increased incidence and poorer prognosis in multiple cancers, contributing to up to 20% of cancer related deaths. These associations are mainly driven by metabolic and inflammatory changes in the adipose tissue during obesity, which disrupt the physiologic metabolic homeostasis. The association between obesity and hypercholesterolemia, hypertension, cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM) is well known. Importantly, the retrospective analysis of more than 1000 epidemiological studies have also shown the positive correlation between the excess of fatness with the risk of cancer. In addition, more important than weight, it is the dysfunctional adipose tissue the main driver of insulin resistance, metabolic syndrome and all cause of mortality and cancer deaths, which also explains why normal weight individuals may behave as “metabolically unhealthy obese” individuals. Adipocytes also have direct effects on tumor cells through paracrine signaling. Downregulation of adiponectin and upregulation of leptin in serum correlate with markers of chronic inflammation, and crown like structures (CLS) associated to the adipose tissue disfunction. Nevertheless, obesity is a preventable risk factor in cancer. Lifestyle interventions might contribute to reduce the adverse effects of obesity. Thus, Mediterranean diet interventional studies have been shown to reduce to circulation inflammatory factors, insulin sensitivity and cardiovascular function, with durable responses of up to 2 years in obese patients. Mediterranean diet supplemented with extra-virgin olive oil reduced the incidence of breast cancer compared with a control diet. Physical activity is another important lifestyle factor which may also contribute to reduced systemic biomarkers of metabolic syndrome associated to obesity. In this scenario, precision nutrition may provide complementary approaches to target the metabolic inflammation associated to “unhealthy obesity”. Herein, we first describe the different types of adipose tissue -thermogenic active brown adipose tissue (BAT) versus the energy storing white adipose tissue (WAT). We then move on precision nutrition based strategies, by mean of natural extracts derived from plants and/or diet derived ingredients, which may be useful to normalize the metabolic inflammation associated to “unhealthy obesity”. More specifically, we focus on two axis: (1) the activation of thermogenesis in BAT and browning of WAT; (2) and the potential of augmenting the oxidative capacity of muscles to dissipate energy. These strategies may be particularly relevant as complementary approaches to alleviate obesity associated effects on chronic inflammation, immunosuppression, angiogenesis and chemotherapy resistance in cancer. Finally, we summarize main studies where plant derived extracts, mainly, polyphenols and flavonoids, have been applied to increase the energy expenditure.

Exercise rescues mitochondrial coupling in aged skeletal muscle: a comparison of different modalities in preventing sarcopenia

Skeletal muscle aging is associated with a decline in motor function and loss of muscle mass- a condition known as sarcopenia. The underlying mechanisms that drive this pathology are associated with a failure in energy generation in skeletal muscle, either from age-related decline in mitochondrial function, or from disuse. To an extent, lifelong exercise is efficacious in preserving the energetic properties of skeletal muscle and thus may delay the onset of sarcopenia. This review discusses the cellular and molecular changes in skeletal muscle mitochondria during the aging process and how different exercise modalities work to reverse these changes. A key factor that will be described is the efficiency of mitochondrial coupling—ATP production relative to O₂ uptake in myocytes and how that efficiency is a main driver for age-associated decline in skeletal muscle function. With that, we postulate the most effective exercise modality and protocol for reversing the molecular hallmarks of skeletal muscle aging and staving off sarcopenia. Two other concepts pertinent to mitochondrial efficiency in exercise-trained skeletal muscle will be integrated in this review, including- mitophagy, the removal of dysfunctional mitochondrial via autophagy, as well as the implications of muscle fiber type changes with sarcopenia on mitochondrial function.

From mitochondria to sarcopenia: Role of inflammaging and RAGE-ligand axis implication

Sarcopenia is characterized by a loss of muscle mass and function that reduces mobility, diminishes quality of life, and can lead to fall-related injuries. At the intracellular level, mitochondrial population alterations are considered as key contributors to the complex etiology of sarcopenia. Mitochondrial dysfunctions lead to reactive oxygen species production, altered cellular proteostasis, and promotes inflammation. Interestingly, the receptor for advanced glycation end-products (RAGE) is a pro-inflammatory receptor involved in inflammaging. In this review, after a brief description of sarcopenia, we will describe how mitochondria and the pathways controlling mitochondrial population quality could participate to age-induced muscle mass and force loss. Finally, we will discuss the RAGE-ligand axis during aging and its possible connection with mitochondria to control inflammaging and sarcopenia.

Molecular Basis for the Therapeutic Effects of Exercise on Mitochondrial Defects

Mitochondrial dysfunction is common to many organ system disorders, including skeletal muscle. Aging muscle and diseases of muscle are often accompanied by defective mitochondrial ATP production. This manuscript will focus on the pre-clinical evidence supporting the use of regular exercise to improve defective mitochondrial metabolism and function in skeletal muscle, through the stimulation of mitochondrial turnover. Examples from aging muscle, muscle-specific mutations and cancer cachexia will be discussed. We will also examine the effects of exercise on the important mitochondrial regulators PGC-1α, and Parkin, and summarize the effects of exercise to reverse mitochondrial dysfunction (e.g., ROS production, apoptotic susceptibility, cardiolipin synthesis) in muscle pathology. This paper will illustrate the breadth and benefits of exercise to serve as "mitochondrial medicine" with age and disease.

Mitochondrial Impairment in Sarcopenia

Sarcopenia is defined by the age-related loss of skeletal muscle quality, which relies on mitochondrial homeostasis. During aging, several mitochondrial features such as bioenergetics, dynamics, biogenesis, and selective autophagy (mitophagy) are altered and impinge on protein homeostasis, resulting in loss of muscle mass and function. Thus, mitochondrial dysfunction contributes significantly to the complex pathogenesis of sarcopenia, and mitochondria are indicated as potential targets to prevent and treat this age-related condition. After a concise presentation of the age-related modifications in skeletal muscle quality and mitochondrial homeostasis, the present review summarizes the most relevant findings related to mitochondrial alterations in sarcopenia.

Intimate Relations-Mitochondria and Ageing

Mitochondrial dysfunction is associated with ageing, but the detailed causal relationship between the two is still unclear. We review the major phenomenological manifestations of mitochondrial age-related dysfunction including biochemical, regulatory and energetic features. We conclude that the complexity of these processes and their inter-relationships are still not fully understood and at this point it seems unlikely that a single linear cause and effect relationship between any specific aspect of mitochondrial biology and ageing can be established in either direction.

Substrate oxidation in primary human skeletal muscle cells is influenced by donor age

Primary human myotubes represent an alternative system to intact skeletal muscle for the study of human diseases related to changes in muscle energy metabolism. This work aimed to study if fatty acid and glucose metabolism in human myotubes in vitro were related to muscle of origin, donor gender, age, or body mass index (BMI). Myotubes from a total of 82 donors were established from three different skeletal muscles, i.e., musculus vastus lateralis, musculus obliquus internus abdominis, and musculi interspinales, and cellular energy metabolism was evaluated. Multiple linear regression analyses showed that donor age had a significant effect on glucose and oleic acid oxidation after correcting for gender, BMI, and muscle of origin. Donor BMI was the only significant contributor to cellular oleic acid uptake, whereas cellular glucose uptake did not rely on any of the variables examined. Despite the effect of age on substrate oxidation, cellular mRNA expression of pyruvate dehydrogenase kinase 4 (PDK4) and peroxisome proliferator–activated receptor gamma coactivator 1 alpha (PPARGC1A) did not correlate with donor age. In conclusion, donor age significantly impacts substrate oxidation in cultured human myotubes, whereas donor BMI affects cellular oleic acid uptake.

Effects of Long-Term Endurance Exercise and Lithium Treatment on Neuroprotective Factors in Hippocampus of Obese Rats

To investigate the effects of long-term lithium treatment and low intensity endurance exercise on brain-derived neurotrophic factor (BDNF) expression and glycogen synthase kinase 3 beta (GSK3β) activity in the hippocampus of obese rats. Fifty 10-week-old male Sprague-Dawley rats were selected. There was a control group of 10 rats (chow control group) while the other forty rats were fed on a high-fat diet for eight weeks to induce obesity. Rats were then assigned into four random groups. The rats were given 10 mg/kg lithium chloride (LiCl) dissolved in 1 mL sterile distilled water once a day, 5 times a week. The rats did 20 min of treadmill walking with an exercise intensity of 40% maximal oxygen uptake (VO₂ max) (12 m/min, slope 0%). This was performed for 20 min a day, 3 days a week. Twelve weeks of lithium treatment or endurance exercise significantly reduced body weight and body fat mass in obese rats, without showing additive effects when the treatments were given in parallel or significant toxic responses in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in blood and kidney and liver tissues. BDNF expression in the hippocampus was significantly increased both in exercise and lithium groups with synergistic effects found in the group where both exercise and lithium treatments were given in parallel. On the other hand, the decrease in GSK3β activity was shown only in the lithium treatment group, without showing additive effects when the treatments were given in parallel. Lithium and low-intensity endurance exercise for 12 weeks increased the expression of BDNF, a neuroprotective factor in the hippocampus of obese mice. Lithium treatment alone inhibited the activity of GSK3β. This can be interpreted as a positive indication of applicability of the two factors in the prevention of neurodegenerative diseases.

Effects of Aerobic and Resistance Exercise on Myokines in High Fat Diet-Induced Middle-Aged Obese Rats

The objective of this study was to analyze the effects of aerobic and resistance exercise on myokines expression in the skeletal muscle of middle-aged rats with high fat diet-induced obesity, to investigate the feasibility of using exercise training to reduce inflammation. Male 50-week-old Sprague Dawley rats were divided into normal diet, normal diet + exercise, high fat diet, and high fat diet + exercise groups. After six weeks on a high fat diet to induce obesity, a 12-week exercise program was implemented, which combined aerobic exercise (treadmill running) and resistance exercise (ladder climbing) three times a week for 75 min per session. We analyzed the protein levels of interleukins (IL) 6, 7, and 8, C-X-C motif chemokine receptor 2, and vascular endothelial growth factor in skeletal muscles by western blotting. Body weight decreased significantly during the 12-week exercise program in the exercise groups compared to the non-exercise groups (p < 0.05). The levels of all myokines analyzed were significantly lower in the skeletal muscle of the high fat diet group compared to the normal diet group (p < 0.05). After completing the 12-week exercise program, IL-7, IL-8, C-X-C motif chemokine receptor 2, and vascular endothelial growth factor expressions were significantly higher in the high fat diet + exercise group compared to the high fat diet group (p < 0.05). However, while IL-6 expression was significantly lower in the high fat diet and high fat diet + exercise groups compared to the normal diet group (p < 0.05), it was not significantly affected by exercise. In conclusion, high fat diet-induced obesity resulted in decreased myokines in the skeletal muscles, but combined exercise training of aerobic and resistance exercise increased myokines secretion in the skeletal muscle of obese rats, and is thought to help reduce inflammation.

Impacts of Aerobic Exercise on Depression-Like Behaviors in Chronic Unpredictable Mild Stress Mice and Related Factors in the AMPK/PGC-1α Pathway

This study was to study the impact of aerobic exercises on the chronic unpredictable mild stress (CUMS) in mice, and to discuss the possible mechanism from the skeletal muscle AMPK/PGC-1α energy metabolism signaling pathway. The healthy male mice were randomly divided into Control Group (CG), Model Group (MG), and Model Exercise Group (ME).Twelve stress methods were adopted for four weeks (28 days) to establish the depression model. ME was subject to aerobic training plan after the model was established. The weight of the mice was recorded weekly. After the experimental intervention, the three groups of mice were subjected to behavioral assessment tests. Western blotting, RT-PCR, and ELISA were performed to test AMPK, p-AMPK, PGC-1α, and ATP in skeletal muscle. There were no significant difference in body weight between the three groups. CUMS leaded to significant decline in behavioral scores. and the p-AMPK and PGC-1α decreased significantly. But boosted ATP content. Aerobic exercise enhanced the expressions of p-AMPK and PGC-1α, increased the ratio of p-AMPK/AMPK, boosted ATP content. And improved behavioral scores significantly. Chronic stress-induced depression-like behavior was improved significantly by Aerobic exercise. The mechanism of aerobic exercise for improving depressive symptoms in mice with chronic stress depression may be related to influence AMPK/PGC-1α pathway.

The systemic role of SIRT1 in exercise mediated adaptation

Cellular energy demands are readily changed during physical exercise resulting in adaptive responses by signaling proteins of metabolic processes, including the NAD⁺ dependent lysine deacetylase SIRT1. Regular exercise results in systemic adaptation that restores the level of SIRT1 in the kidney, liver, and brain in patients with neurodegenerative diseases, and thereby normalizes cellular metabolic processes to attenuate the severity of these diseases. In skeletal muscle, over-expression of SIRT1 results in enhanced numbers of myonuclei improves the repair process after injury and is actively involved in muscle hypertrophy by up-regulating anabolic and downregulating catabolic processes. The present review discusses the different views of SIRT1 dependent deacetylation of PGC-α.

Exercise and mitochondrial health

Mitochondrial health is an important mediator of cellular function across a range of tissues, and as a result contributes to whole-body vitality in health and disease. Our understanding of the regulation and function of these organelles is of great interest to scientists and clinicians across many disciplines within our healthcare system. Skeletal muscle is a useful model tissue for the study of mitochondrial adaptations because of its mass and contribution to whole body metabolism. The remarkable plasticity of mitochondria allows them to adjust their volume, structure and capacity under conditions such as exercise, which is useful or improving metabolic health in individuals with various diseases and/or advancing age. Mitochondria exist within muscle as a functional reticulum which is maintained by dynamic processes of biogenesis and fusion, and is balanced by opposing processes of fission and mitophagy. The sophisticated coordination of these events is incompletely understood, but is imperative for organelle function and essential for the maintenance of an interconnected organelle network that is finely tuned to the metabolic needs of the cell. Further elucidation of the mechanisms of mitochondrial turnover in muscle could offer potential therapeutic targets for the advancement of health and longevity among our ageing populations. As well, investigating exercise modalities that are both convenient and capable of inducing robust mitochondrial adaptations are useful in fostering more widespread global adherence. To this point, exercise remains the most potent behavioural therapeutic approach for the improvement of mitochondrial health, not only in muscle, but potentially also in other tissues.

Exercise is mitochondrial medicine for muscle

Mitochondria are vital organelles that provide energy for muscle function. When these organelles become dysfunctional, they produce less energy as well as excessive levels of reactive oxygen species which can trigger muscle atrophy, weakness and loss of endurance. In this review, molecular evidence is provided to show that exercise serves as a useful therapeutic countermeasure to overcome mitochondrial dysfunction, even when key regulators of organelle biogenesis are absent. These findings illustrate the complexity and compensatory nature of exercise-induced molecular signaling to transcription, as well as to post-transcriptional events within the mitochondrial synthesis and degradation (i.e. turnover) pathways. Beginning with the first bout of contractile activity, exercise exerts a medicinal effect to improve mitochondrial health and whole muscle function.

Physical Exercise and Selective Autophagy: Benefit and Risk on Cardiovascular Health

Physical exercise promotes cardiorespiratory fitness, and is considered the mainstream of non-pharmacological therapies along with lifestyle modification for various chronic diseases, in particular cardiovascular diseases. Physical exercise may positively affect various cardiovascular risk factors including body weight, blood pressure, insulin sensitivity, lipid and glucose metabolism, heart function, endothelial function, and body fat composition. With the ever-rising prevalence of obesity and other types of metabolic diseases, as well as sedentary lifestyle, regular exercise of moderate intensity has been indicated to benefit cardiovascular health and reduce overall disease mortality. Exercise offers a wide cadre of favorable responses in the cardiovascular system such as improved dynamics of the cardiovascular system, reduced prevalence of coronary heart diseases and cardiomyopathies, enhanced cardiac reserve capacity, and autonomic regulation. Ample clinical and experimental evidence has indicated an emerging role for autophagy, a conservative catabolism process to degrade and recycle cellular organelles and nutrients, in exercise training-offered cardiovascular benefits. Regular physical exercise as a unique form of physiological stress is capable of triggering adaptation while autophagy in particular selective autophagy seems to be permissive to such cardiovascular adaptation. Here in this mini-review, we will summarize the role for autophagy in particular mitochondrial selective autophagy namely mitophagy in the benefit versus risk of physical exercise on cardiovascular function.

Late life maintenance and enhancement of functional exercise capacity in low and high responding rats after low intensity treadmill training

Intrinsic exercise capacity is predictive of both lifespan and healthspan but whether adaptive exercise capacity influences the benefits achieved from aerobic training implemented later in life is not known.

AIM

To determine if exercise late in life provides any functional improvements or underlying beneficial biochemical adaptations in rats bred to have a high response to training (HRT rats) or little to no response to training (LRT rats).

METHODS

Adult (11 months) and old (22 months) female LRT and HRT rats either remained sedentary (SED) or were exercised (EXER) on a treadmill 2-3 times/week at 60% of their initial maximum running speed and distance for 4 months. At 26 months of age, exercise capacity was re-evaluated and extensor digitorum longus, gastrocnemius (GTN), and tibialis anterior (TA) muscles were excised for histological and biochemical analysis.

RESULTS

Both SED-HRT and SED-LRT rats showed decreased exercise capacity from 22 to 26 months, but with 4 months of treadmill training, EXER-HRT rats displayed a 50% improvement in exercise capacity while EXER-LRT rats maintained pre-training levels. Protein levels of antioxidant enzymes PRDX3, CuZnSOD, and PRXV were 6-fold greater in TA muscles of aged HRT rats compared to LRT rats. PGC-1α protein levels were ~2-fold greater in GTN and TA muscles of aged HRT than in LRT rats and TFAM protein was similarly elevated in GTN muscles of aged HRT rats compared with LRT rats. BNIP3 protein levels were 5-fold greater in TA muscles of aged HRT than in LRT rats while PINK1 protein content was reduced by 78% in GTN muscles of aged HRT rats compared with LRT rats.

CONCLUSION

HRT rats retained the ability to improve exercise capacity into late life and that ability was associated with inherent and adaptive changes in antioxidant enzyme levels and markers of and mitochondrial quality related to healthspan benefits in aging. Moreover, low intensity exercise prevented the age-associated decline in functional exercise capacity in LRT rats.

The balance of apoptosis and autophagy via regulation of the AMPK signal pathway in aging rat striatum during regular aerobic exercise

The objective was to analyze the effects of aerobic exercise on aging striatum stress resistance, and the adaptive mechanisms related to neurodegenerative diseases, and the occurrence, and development of neural degeneration. The 10-weeks of regular moderate-intensity aerobic exercise intervention were carried out in the aerobic exercise runner Sprague-Dawley rats. Apoptotic nuclei appeared in the striatum of aged rats, showing a tendency to relate to aging. The apoptotic index of the striatum in young, middle-aged, and old-aged rats of the aerobic exercise groups increased by 205.56%, 57%, and 68.24%. Autophagy markers Beclin l and LC 3-II expression, AMPKα1 and pAMPKα1 expression increased significantly in all age-exercise groups. The ratio of AMPKα1/pAMPKα1 increased after exercise, and the tendency of exercise to alter autophagy and cell apoptosis increased with aging. Then SirT2 mRNA was significantly upregulated in the aerobic exercise runner groups. In conclusion, we showed that the balance of autophagy and apoptosis were closely regulated by regular aerobic exercise, which affected the development of aging, and via regulation of the AMPK/SirT2 signaling pathway.

Proteomic Profile of Carbonylated Proteins Screen the Regulation of Calmodulin-Dependent Protein Kinases-AMPK-Beclin1 in Aerobic Exercise-Induced Autophagy in Middle-Aged Rat Hippocampus

BACKGROUND

Carbonylation is an oxidative modification of the proteins and a marker of oxidative stress. The accumulation of toxic carbonylated proteins might be one of the onsets of pathogenesis in hippocampal aging or neurodegeneration. Enormous evidence indicates that regular aerobic exercise might alleviate the dysfunction of carbonylated proteins, but the adaptational mechanisms in response to exercise are unclear.

OBJECTIVE

This study explored the carbonyl stress mechanism in the hippocampus using proteomics and the role of calmodulin-dependent protein kinases (CAMK)-AMP-activated protein kinase (AMPK)-Beclin1 signaling pathways in alleviating aging or improving function with regular aerobic exercise.

METHODS

Twenty-four healthy 13-month-old male Sprague-Dawley rats (average 693.21 ± 68.85 g) were randomly divided into middle-aged sedentary control group (M-SED, n = 12) and middle-aged aerobic exercise runner group (M-EX, n = 12). The M-EX group participated in regular aerobic exercise - treadmill running - with exercise intensity increasing gradually from 50-55% to 65-70% of maximum oxygen consumption (V˙O2max) over 10 weeks. The targeted proteins of oxidative modification were profiled by avidin magnetic beads and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS). Western blots were used to test for molecular targets.

RESULTS

Regular aerobic exercise restores the intersessional habituation and rescues the hippocampus morphological structure in middle-aged rats. -ESI-Q-TOF-MS screened 56 carbonylated proteins only found in M-SED and 16 carbonylated proteins only found in M-EX, indicating aerobic exercise decreased carbonyl stress. Intriguingly, Ca2+/CAMK II alpha (CAMKIIα) was carbonylated only in the M-SED group at the oxidative modification site of 4-hydroxynonenal adducts, while regular aerobic exercise alleviated CAMKIIα carbonylation. Regular aerobic exercise significantly increased the expression and phosphorylated, active levels of CAMKIIα and AMPKα1. It also upregulated the expression of Beclin1 and microtubule-associated protein1-light chain 3 in the hippocampus.

CONCLUSION

Quantification of CAMKIIα carbonylation may be a potential biomarker of the hippocampal senescence. Additionally, regular aerobic exercise-induced autophagy via the activation of CAMK-AMPK-Beclin1 signaling pathway may mitigate the hippocampal neurodegeneration or pathological changes by alleviating protein carbonylation (carbonyl stress).

Mitochondrial Adaptations in Elderly and Young Men Skeletal Muscle Following 2 Weeks of Bed Rest and Rehabilitation

The aim of the study was to evaluate the expression levels of proteins related to mitochondrial biogenesis regulation and bioenergetics in vastus lateralis muscle biopsies from 16 elderly and 7 young people subjected to 14 days of bed-rest, causing atrophy, and subsequent 14 days of exercise training. Based on quantitative immunoblot analyses, in both groups a reduction of two key regulators of mitochondrial biogenesis/remodeling and activity, namely PGC-1α and Sirt3, was revealed during bed-rest, with a subsequent up-regulation after rehabilitation, indicating an involvement of PGC-1α-Sirt3 axis in response to the treatments. A difference was observed comparing the young and elderly subjects as, for both proteins, the abundance in the elderly was more affected by immobility and less responsive to exercise. The expression levels of TOM20 and Citrate Synthase, assayed as markers of outer mitochondrial membrane and mitochondrial mass, showed a noticeable sensitivity in the elderly group, where they were affected by bed-rest and rehabilitation recalling the pattern of PGC-1α. TOM20 and CS remained unchanged in young subjects. Single OXPHOS complexes showed peculiar patterns, which were in some cases dissimilar from PGC-1α, and suggest different influences on protein biogenesis and degradation. Overall, exercise was capable to counteract the effect of immobility, when present, except for complex V, which was markedly downregulated by bed-rest, but remained unaffected after rehabilitation, maybe as result of greater extent of degradation processes over biogenesis. Phosphorylation extent of AMPK, and its upstream activator LKB1, did not change after bed-rest and rehabilitation in either young or elderly subjects, suggesting that the activation of energy-sensing LKB1-AMPK signaling pathway was “missed” due to its transient nature, or was not triggered under our conditions. Our study demonstrates that, as far as the expression of various proteins related to mitochondrial biogenesis/remodeling, adaptations to bed-rest and rehabilitation in the two populations were different. The impact of bed-rest was greater in the elderly subjects, where the pattern (decrease after bed rest and recovery following rehabilitation) was accompanied by changes of mitochondrial mass. Modifications of protein abundance were matched with data obtained from gene expression analyses of four public human datasets focusing on related genes.

Regular aerobic exercise-ameliorated troponin I carbonylation to mitigate aged rat soleus muscle functional recession

NEW FINDINGS

What is the central question of this study? What is the biological role of carbonylation in muscle age-related functional decline and how might exercise affect the carbonylation process differently compared to habitual sedentary behaviour? What is the main finding and its importance? The carbonylation of troponin I (TNNI1), tropomyosin α-1 chain and α-actinin-1 demonstrated a relationship with muscle age-related functional decline. Exercise attenuated the decline by slowing the rate of carbonylation and promoting antioxidant reactions within the muscle. As exercise demonstrated the greatest effect on TNNI1, quantification of protein carbonyls in TNNI1 may be used as a potential biomarker of muscle age-related functional decline.

ABSTRACT

This study investigated the biological role of carbonylation in muscle age-related functional decline and how regular aerobic exercise may affect the carbonylation process differently from habitual sedentary behaviour. Twenty-four healthy male Sprague-Dawley (SD) rats (mean age: 23 months) were randomly divided into an old-aged sedentary control group (O-SED) and an old-aged aerobic exercise group (O-EX). The O-EX group participated in regular aerobic exercise - treadmill running - with exercise intensity increased gradually from 50-55% to 65-70% of maximum oxygen consumption ( V ̇ O 2 max ) over 10 weeks. Rats' body weight, exercise behaviour index, morphology and oxidative stress were monitored. Avidin magnetic beads and electrospray ionization quadrupole time-of-flight mass spectrometry were used for gathering and separating carbonylated proteins while western blot tested for molecular targets. O-SED and O-EX rats both had 19 oxidative modification sites for protein carbonylation. In the O-SED group, 16 specific carbonylated proteins were identified, while 16 additional specific species were also found in the O-EX group, with all 28 species demonstrating oxidative modifications. The carbonylated proteins included troponin I (TNNI1; slow skeletal muscle), tropomyosin α1 and α-actinin 1. In particular, TNNI1 carbonylation modifications were found only in sedentary rats. Aerobic exercise increased TNNI1 and Ca²⁺ /calmodulin-dependent protein kinase IIα expression significantly. Observations suggested that quantification of TNNI1 carbonylation may be a potential biomarker of muscle age-related functional decline. Importantly, regular aerobic exercise appeared to have antioxidant effects in the muscle that reduced TNNI1 slow carbonylation and promoted Ca²⁺ /calmodulin-dependent protein kinase IIα (CAMK2) and TNNI1 expression for skeletal muscle contraction regulation, thus attenuating possible age-related skeletal muscle functional decline.

Exercise effects on physiological function during aging

The decrease in cognitive/motor functions and physical abilities severely affects the aging population in carrying out daily activities. These disabilities become a burden on individuals, families and society in general. It is known that aging conditions are ameliorated with regular exercise, which attenuates the age-associated decline in maximal oxygen uptake (VO2max), production of reactive oxygen species (ROS), decreases in oxidative damage to molecules, and functional impairment in various organs. While benefits of physical exercise are well-documented, the molecular mechanisms responsible for functional improvement and increases in health span are not well understood. Recent findings imply that exercise training attenuates the age-related deterioration in the cellular housekeeping system, which includes the proteasome, Lon protease, autophagy, mitophagy, and DNA repair systems, which beneficially impacts multiple organ functions. Accumulating evidence suggests that exercise lessens the deleterious effects of aging. However, it seems unlikely that systemic effects are mediated through a specific biomarker. Rather, complex multifactorial mechanisms are involved to maintain homeostatic functions that tend to decline with age.

Lifelong Football Training: Effects on Autophagy and Healthy Longevity Promotion

Aging is a physiological process characterized by a progressive decline of biological functions and an increase in destructive processes in cells and organs. Physical activity and exercise positively affects the expression of skeletal muscle markers involved in longevity pathways. Recently, a new mechanism, autophagy, was introduced to the adaptations induced by acute and chronic exercise as responsible of positive metabolic modification and health-longevity promotion. However, the molecular mechanisms regulating autophagy in response to physical activity and exercise are sparsely described. We investigated the long-term adaptations resulting from lifelong recreational football training on the expression of skeletal muscle markers involved in autophagy signaling. We demonstrated that lifelong football training increased the expression of messengers: RAD23A, HSPB6, RAB1B, TRAP1, SIRT2, and HSBPB1, involved in the auto-lysosomal and proteasome-mediated protein degradation machinery; of RPL1, RPL4, RPL36, MRLP37, involved in cellular growth and differentiation processes; of the Bcl-2, HSP70, HSP90, PSMD13, and of the ATG5-ATG12 protein complex, involved in proteasome promotion and autophagy processes in muscle samples from lifelong trained subjects compared to age-matched untrained controls. In conclusion, our results indicated that lifelong football training positively influence exercise-induced autophagy processes and protein quality control in skeletal muscle, thus promoting healthy aging.

Proteomic Profile of Carbonylated Proteins Screen Regulation of Apoptosis via CaMK Signaling in Response to Regular Aerobic Exercise

To research carbonylated proteins and screen molecular targets in the rat striatum on regular aerobic exercise, male Sprague-Dawley rats (13 months old, n = 24) were randomly divided into middle-aged sedentary control (M-SED) and aerobic exercise (M-EX) groups (n = 12 each). Maximum oxygen consumption (VO_2max) gradually increased from 50%-55% to 65%-70% for a total of 10 weeks. A total of 36 carbonylated proteins with modified oxidative sites were identified by Electrospray Ionization-Quadrupole-Time of Flight-Mass Spectrometer (ESI-Q-TOF-MS), including 17 carbonylated proteins unique to the M-SED group, calcium/calmodulin-dependent protein kinase type II subunit beta (CaMKIIβ), and heterogeneous nuclear ribonucleoprotein A2/B1 (Hnrnpa2b1), among others, and 19 specific to the M-EX group, ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCH-L1), and malic enzyme, among others. Regular aerobic exercise improved behavioral and stereological indicators, promoted normal apoptosis (P < 0.01), alleviated carbonylation of the CaMKIIβ and Hnrnpa2b1, but induced carbonylation of the UCH-L1, and significantly upregulated the expression levels of CaMKIIβ, CaMKIIα, and Vdac1 (p < 0.01) and Hnrnpa2b1 and UCH-L1 (p < 0.01), as well as the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin pathways (PI3K/Akt/mTOR) pathway-related genes Akt and mTOR. Regular aerobic exercise for 10 weeks (incremental for the first 6 weeks followed by constant loading for 4 weeks) enhanced carbonylation of CaMKIIβ, Hnrnpa2b1, and modulated apoptosis via activation of CaMK and phosphoinositide 3-kinase/protein kinase B/mTOR signaling. It also promoted normal apoptosis in the rat striatum, which may have protective effects in neurons.

Maintenance of Skeletal Muscle Mitochondria in Health, Exercise, and Aging

Mitochondria are critical organelles responsible for regulating the metabolic status of skeletal muscle. These organelles exhibit remarkable plasticity by adapting their volume, structure, and function in response to chronic exercise, disuse, aging, and disease. A single bout of exercise initiates signaling to provoke increases in mitochondrial biogenesis, balanced by the onset of organelle turnover carried out by the mitophagy pathway. This accelerated turnover ensures the presence of a high functioning network of mitochondria designed for optimal ATP supply, with the consequence of favoring lipid metabolism, maintaining muscle mass, and reducing apoptotic susceptibility over the longer term. Conversely, aging and disuse are associated with reductions in muscle mass that are in part attributable to dysregulation of the mitochondrial network and impaired mitochondrial function. Therefore, exercise represents a viable, nonpharmaceutical therapy with the potential to reverse and enhance the impaired mitochondrial function observed with aging and chronic muscle disuse.

Master athletes have higher miR-7, SIRT3 and SOD2 expression in skeletal muscle than age-matched sedentary controls

Regular physical exercise has health benefits and can prevent some of the ageing-associated muscle deteriorations. However, the biochemical mechanisms underlying this exercise benefit, especially in human tissues, are not well known. To investigate, we assessed this using miRNA profiling, mRNA and protein levels of anti-oxidant and metabolic proteins in the vastus lateralis muscle of master athletes aged over 65 years and age-matched controls. Master athletes had lower levels of miR-7, while mRNA or protein levels of SIRT3, SIRT1, SOD2, and FOXO1 levels were significantly higher in the vastus lateralis muscle of master athletes compared to muscles of age-matched controls. These results suggest that regular exercise results in better cellular metabolism and antioxidant capacity via maintaining physiological state of mitochondria and efficient ATP production and decreasing ageing-related inflammation as indicated by the lower level of miR-7 in master athletes.

Comparison of endoplasmic reticulum stress and mitochondrial biogenesis responses after 12 weeks of treadmill running and ladder climbing exercises in the cardiac muscle of middle-aged obese rats

The purpose of the present study was to compare the influence of aerobic exercise (AE) lasting 12 weeks to that of resistance exercise (RE) of the same duration on endoplasmic reticulum (ER) stress and mitochondrial biogenesis in the cardiac muscle of middle-aged obese rats. Obesity was induced in thirty 50-week-old male Sprague Dawley rats over 6 weeks by administration of a high-fat diet. The rats were then subjected to treadmill-running (AE) and ladder-climbing (RE) exercises 3 times per week for 12 weeks. Rats in the AE group showed significantly lower increases in body weight and intraperitoneal fat than those in the sedentary control (SC) group (P<0.05). The 12-week exercise regimes resulted in a significant increase in expression of mitochondrial biogenesis markers and levels of peroxisome proliferator-activated receptor gamma coactivator 1α in the cardiac muscle (P<0.05). Phosphorylation of PKR-like ER kinase, an ER stress marker, decreased significantly (P<0.05) after the exercise training. Although a trend for decreased C/EBP homologous protein (CHOP) expression was observed in both exercise groups, only the AE group had a statistically significant decrease (P<0.05). Levels of GRP78, an ER stress marker that protects cardiac muscle, did not significantly differ among the groups. Although only the AE group decreased body weight and fat mass, the two exercise regimes had similar effects on cardiac muscle with the exception of CHOP. Therefore, we suggest that both AE, which results in weight loss, and high-intensity RE, though not accompanied by weight loss, protect obese cardiac muscle effectively.

Exercise preconditioning diminishes skeletal muscle atrophy after hindlimb suspension in mice

The aim of the present study was to investigate whether short-term, concurrent exercise training before hindlimb suspension (HLS) prevents or diminishes both soleus and gastrocnemius atrophy and to analyze whether changes in mitochondrial molecular markers were associated. Male C57BL/6 mice were assigned to control at 13 ± 1 wk of age, 7-day HLS at 12 ± 1 wk of age (HLS), 2 wk of exercise training before 7-day HLS at 10 ± 1 wk of age (Ex+HLS), and 2 wk of exercise training at 11 ± 1 wk of age (Ex) groups. HLS resulted in a 27.1% and 21.5% decrease in soleus and gastrocnemius muscle weight-to-body weight ratio, respectively. Exercise training before HLS resulted in a 5.6% and 8.1% decrease in soleus and gastrocnemius weight-to-body weight ratio, respectively. Exercise increased mitochondrial biogenesis- and function-associated markers and slow myosin heavy chain (SMHC) expression, and reduced fiber-type transitioning marker myosin heavy chain 4 (Myh4). Ex+HLS revealed decreased reactive oxygen species (ROS) and oxidative stress compared with HLS. Our data indicated the time before an atrophic setting, particularly caused by muscle unloading, may be a useful period to intervene short-term, progressive exercise training to prevent skeletal muscle atrophy and is associated with mitochondrial biogenesis, function, and redox balance.

NEW & NOTEWORTHY Mitochondrial dysfunction is associated with disuse-induced skeletal muscle atrophy, whereas exercise is known to increase mitochondrial biogenesis and function. Here we provide evidence of short-term concurrent exercise training before an atrophic event protecting skeletal muscle from atrophy in two separate muscles with different, dominant fiber-types, and we reveal an association with the adaptive changes of mitochondrial molecular markers to exercise.