Exercise stress leads to an acute loss of mitochondrial proteins and disruption of redox control in skeletal muscle of older subjects: An underlying decrease in resilience with aging?

Signatures of cysteine oxidation on muscle structural and contractile proteins are associated with physical performance and muscle function in older adults: Study of Muscle, Mobility and Aging (SOMMA)

Oxidative stress is considered a contributor to declining muscle function and mobility during aging; however, the underlying molecular mechanisms remain poorly described. We hypothesized that greater levels of cysteine (Cys) oxidation on muscle proteins are associated with decreased measures of mobility. Herein, we applied a novel redox proteomics approach to measure reversible protein Cys oxidation in vastus lateralis muscle biopsies collected from 56 subjects in the Study of Muscle, Mobility and Aging (SOMMA), a community-based cohort study of individuals aged 70 years and older. We tested whether levels of Cys oxidation on key muscle proteins involved in muscle structure and contraction were associated with muscle function (leg power and strength), walking speed, and fitness (VO2 peak on cardiopulmonary exercise testing) using linear regression models adjusted for age, sex, and body weight. Higher oxidation levels of select nebulin Cys sites were associated with lower VO2 peak, while greater oxidation of myomesin-1, myomesin-2, and nebulin Cys sites was associated with slower walking speed. Higher oxidation of Cys sites in key proteins such as myomesin-2, alpha-actinin-2, and skeletal muscle alpha-actin were associated with lower leg power and strength. We also observed an unexpected correlation (R = 0.48) between a higher oxidation level of eight Cys sites in alpha-actinin-3 and stronger leg power. Despite this observation, the results generally support the hypothesis that Cys oxidation of muscle proteins impairs muscle power and strength, walking speed, and cardiopulmonary fitness with aging.

Randomised controlled trial combining vitamin E-functionalised chocolate with physical exercise to reduce the risk of protein-energy malnutrition in predementia aged people: study protocol for Choko-Age

OBJECTIVE

Protein-energy malnutrition and the subsequent muscle wasting (sarcopenia) are common ageing complications. It is knowing to be also associated with dementia. Our programme will test the cytoprotective functions of vitamin E combined with the cortisol-lowering effect of chocolate polyphenols (PP), in combination with muscle anabolic effect of adequate dietary protein intake and physical exercise to prevent the age-dependent decline of muscle mass and its key underpinning mechanisms including mitochondrial function, and nutrient metabolism in muscle in the elderly.

METHODS AND ANALYSIS

In 2020, a 6-month double-blind randomised controlled trial in 75 predementia older people was launched to prevent muscle mass loss, in respond to the 'Joint Programming Initiative A healthy diet for a healthy life'. In the run-in phase, participants will be stabilised on a protein-rich diet (0.9-1.0 g protein/kg ideal body weight/day) and physical exercise programme (high-intensity interval training specifically developed for these subjects). Subsequently, they will be randomised into three groups (1:1:1). The study arms will have a similar isocaloric diet and follow a similar physical exercise programme. Control group (n=25) will maintain the baseline diet; intervention groups will consume either 30 g/day of dark chocolate containing 500 mg total PP (corresponding to 60 mg epicatechin) and 100 mg vitamin E (as RRR-alpha-tocopherol) (n=25); or the high polyphenol chocolate without additional vitamin E (n=25). Muscle mass will be the primary endpoint. Other outcomes are neurocognitive status and previously identified biomolecular indices of frailty in predementia patients. Muscle biopsies will be collected to assess myocyte contraction and mitochondrial metabolism. Blood and plasma samples will be analysed for laboratory endpoints including nutrition metabolism and omics.

ETHICS AND DISSEMINATION

All the ethical and regulatory approvals have been obtained by the ethical committees of the Azienda Ospedaliera Universitaria Integrata of Verona with respect to scientific content and compliance with applicable research and human subjects' regulation. Given the broader interest of the society toward undernutrition in the elderly, we identify four main target audiences for our research activity: national and local health systems, both internal and external to the project; targeted population (the elderly); general public; and academia. These activities include scientific workshops, public health awareness campaigns, project dedicated website and publication is scientific peer-review journals.

TRIAL REGISTRATION NUMBER

NCT05343611.

Geroprotector drugs and exercise: friends or foes on healthy longevity?

Physical activity and several pharmacological approaches individually combat age-associated conditions and extend healthy longevity in model systems. It is tantalizing to extrapolate that combining geroprotector drugs with exercise could extend healthy longevity beyond any individual treatment. However, the current dogma suggests that taking leading geroprotector drugs on the same day as exercise may limit several health benefits. Here, we review leading candidate geroprotector drugs and their interactions with exercise and highlight salient gaps in knowledge that need to be addressed to identify if geroprotector drugs can have a harmonious relationship with exercise.

Signatures of Cysteine Oxidation on Muscle Structural and Contractile Proteins Are Associated with Physical Performance and Muscle Function in Older Adults: Study of Muscle, Mobility and Aging (SOMMA)

Oxidative stress is considered a contributor to declining muscle function and mobility during aging; however, the underlying molecular mechanisms remain poorly described. We hypothesized that greater levels of cysteine (Cys) oxidation on muscle proteins are associated with decreased measures of mobility. Herein, we applied a novel redox proteomics approach to measure reversible protein Cys oxidation in vastus lateralis muscle biopsies collected from 56 subjects in the Study of Muscle, Mobility and Aging (SOMMA), a community-based cohort study of individuals aged 70 years and older. We tested whether levels of Cys oxidation on key muscle proteins involved in muscle structure and contraction were associated with muscle function (leg power and strength), walking speed, and fitness (VO2 peak on cardiopulmonary exercise testing) using linear regression models adjusted for age, sex, and body weight. Higher oxidation levels of select nebulin Cys sites were associated with lower VO2 peak, while greater oxidation of myomesin-1, myomesin-2, and nebulin Cys sites was associated with slower walking speed. Higher oxidation of Cys sites in key proteins such as myomesin-2, alpha-actinin-2, and skeletal muscle alpha-actin were associated with lower leg power and strength. We also observed an unexpected correlation (r = 0.48) between a higher oxidation level of 8 Cys sites in alpha-actinin-3 and stronger leg power. Despite this observation, the results generally support the hypothesis that Cys oxidation of muscle proteins impair muscle power and strength, walking speed, and cardiopulmonary fitness with aging.

50 shades of oxidative stress: A state-specific cysteine redox pattern hypothesis

Oxidative stress is biochemically complex. Like primary colours, specific reactive oxygen species (ROS) and antioxidant inputs can be mixed to create unique "shades" of oxidative stress. Even a minimal redox module comprised of just 12 (ROS & antioxidant) inputs and 3 outputs (oxidative damage, cysteine-dependent redox-regulation, or both) yields over half a million "shades" of oxidative stress. The present paper proposes the novel hypothesis that: state-specific shades of oxidative stress, such as a discrete disease, are associated with distinct tell-tale cysteine oxidation patterns. The patterns are encoded by many parameters, from the identity of the oxidised proteins, the cysteine oxidation type, and magnitude. The hypothesis is conceptually grounded in distinct ROS and antioxidant inputs coalescing to produce unique cysteine oxidation outputs. And considers the potential biological significance of the holistic cysteine oxidation outputs. The literature supports the existence of state-specific cysteine oxidation patterns. Measuring and manipulating these patterns offer promising avenues for advancing oxidative stress research. The pattern inspired hypothesis provides a framework for understanding the complex biochemical nature of state-specific oxidative stress.

Performance benchmarking microplate-immunoassays for quantifying target-specific cysteine oxidation reveals their potential for understanding redox-regulation and oxidative stress

The antibody-linked oxi-state assay (ALISA) for quantifying target-specific cysteine oxidation can benefit specialist and non-specialist users. Specialists can benefit from time-efficient analysis and high-throughput target and/or sample n-plex capacities. The simple and accessible "off-the-shelf" nature of ALISA brings the benefits of oxidative damage assays to non-specialists studying redox-regulation. Until performance benchmarking establishes confidence in the "unseen" microplate results, ALISA is unlikely to be widely adopted. Here, we implemented pre-set pass/fail criteria to benchmark ALISA by evaluating immunoassay performance in diverse contexts. ELISA-mode ALISA assays were accurate, reliable, and sensitive. For example, the average inter-assay CV for detecting 20%- and 40%-oxidised PRDX2 or GAPDH standards was 4.6% (range: 3.6-7.4%). ALISA displayed target-specificity. Immunodepleting the target decreased the signal by ∼75%. Single-antibody formatted ALISA failed to quantify the matrix-facing alpha subunit of the mitochondrial ATP synthase. However, RedoxiFluor quantified the alpha subunit displaying exceptional performance in the single-antibody format. ALISA discovered that (1) monocyte-to-macrophage differentiation amplified PRDX2-oxidation in THP-1 cells and (2) exercise increased GAPDH-specific oxidation in human erythrocytes. The "unseen" microplate data were "seen-to-be-believed" via orthogonal visually displayed immunoassays like the dimer method. Finally, we established target (n = 3) and sample (n = 100) n-plex capacities in ∼4 h with 50-70 min hands-on time. Our work showcases the potential of ALISA to advance our understanding of redox-regulation and oxidative stress.

Peroxiredoxin 2 is required for the redox mediated adaptation to exercise

Exercise generates a site-specific increase in Reactive Oxygen Species (ROS) within muscle that promotes changes in gene transcription and mitochondrial biogenesis, required for the beneficial adaptive response. We demonstrate that Peroxiredoxin 2 (Prdx2), an abundant cytoplasmic 2-Cys peroxiredoxin, is required for the adaptive hormesis response to physiological levels of H₂O₂ in myoblasts and following exercise in C. elegans. A short bolus addition of H₂O₂ increases mitochondrial capacity and improves myogenesis of cultured myoblasts, this beneficial adaptive response was suppressed in myoblasts with decreased expression of cytoplasmic Prdxs. Moreover, a swimming exercise protocol in C. elegans increased mitochondrial content, fitness, survival and longevity in wild type (N2) worms. In contrast, prdx-2 mutant worms had decreased fitness, disrupted mitochondria, reduced survival and lifespan following exercise. Global proteomics following exercise identified distinct changes in the proteome of N2 and prdx-2 mutants. Furthermore, a redox proteomic approach to quantify reversible oxidation of specific Cysteine residues revealed a more reduced redox state in the non-exercised prdx-2 mutant strain that become oxidized following exercise. In contrast, specific Cys residues from regulatory proteins become more reduced in the N2 strain following exercise, establishing the key regulatory role of PRDX-2 in a redox signalling cascade following endogenous ROS generation. Our results demonstrate that conserved cytoplasmic 2-Cys Peroxiredoxins are required for the beneficial adaptive response to a physiological redox stress.

Reflections of an Aging Free Radical Part 2: Meeting Inspirational People

Significance: During my long career in the field of redox biology, I met many inspiring people, especially Lester Packer. Recent Advances: This special issue of Antioxidants & Redox Signaling is dedicated to Lester Packer. Critical Issues: In this short review, I explore how Lester and other pioneers helped to develop the redox biology field and how I interacted with them. Future Directions: In our research to advance the field of redox biology, we stand on the shoulders of giants, including Lester Packer.

Effect of Physical Activity/Exercise on Oxidative Stress and Inflammation in Muscle and Vascular Aging

Functional status is considered the main determinant of healthy aging. Impairment in skeletal muscle and the cardiovascular system, two interrelated systems, results in compromised functional status in aging. Increased oxidative stress and inflammation in older subjects constitute the background for skeletal muscle and cardiovascular system alterations. Aged skeletal muscle mass and strength impairment is related to anabolic resistance, mitochondrial dysfunction, increased oxidative stress and inflammation as well as a reduced antioxidant response and myokine profile. Arterial stiffness and endothelial function stand out as the main cardiovascular alterations related to aging, where increased systemic and vascular oxidative stress and inflammation play a key role. Physical activity and exercise training arise as modifiable determinants of functional outcomes in older persons. Exercise enhances antioxidant response, decreases age-related oxidative stress and pro-inflammatory signals, and promotes the activation of anabolic and mitochondrial biogenesis pathways in skeletal muscle. Additionally, exercise improves endothelial function and arterial stiffness by reducing inflammatory and oxidative damage signaling in vascular tissue together with an increase in antioxidant enzymes and nitric oxide availability, globally promoting functional performance and healthy aging. This review focuses on the role of oxidative stress and inflammation in aged musculoskeletal and vascular systems and how physical activity/exercise influences functional status in the elderly.

Redox Control of Signalling Responses to Contractile Activity and Ageing in Skeletal Muscle

Research over almost 40 years has established that reactive oxygen species are generated at different sites in skeletal muscle and that the generation of these species is increased by various forms of exercise. Initially, this was thought to be potentially deleterious to skeletal muscle and other tissues, but more recent data have identified key roles of these species in muscle adaptations to exercise. The aim of this review is to summarise our current understanding of these redox signalling roles of reactive oxygen species in mediating responses of muscle to contractile activity, with a particular focus on the effects of ageing on these processes. In addition, we provide evidence that disruption of the redox status of muscle mitochondria resulting from age-associated denervation of muscle fibres may be an important factor leading to an attenuation of some muscle responses to contractile activity, and we speculate on potential mechanisms involved.

Exercise decreases PP2A-specific reversible thiol oxidation in human erythrocytes: Implications for redox biomarkers

New readily accessible systemic redox biomarkers are needed to understand the biological roles reactive oxygen species (ROS) play in humans because overtly flawed, technically fraught, and unspecific assays severely hamper translational progress. The antibody-linked oxi-state assay (ALISA) makes it possible to develop valid ROS-sensitive target-specific protein thiol redox state biomarkers in a readily accessible microplate format. Here, we used a maximal exercise bout to disrupt redox homeostasis in a physiologically meaningful way to determine whether the catalytic core of the serine/threonine protein phosphatase PP2A is a candidate systemic redox biomarker in human erythrocytes. We reasoned that: constitutive oxidative stress (e.g., haemoglobin autoxidation) would sensitise erythrocytes to disrupted ion homeostasis as manifested by increased oxidation of the ion regulatory phosphatase PP2A. Unexpectedly, an acute bout of maximal exercise lasting ~16 min decreased PP2A-specific reversible thiol oxidation (redox ratio, rest: 0.46; exercise: 0.33) without changing PP2A content (rest: 193 pg/ml; exercise: 191 pg/ml). The need for only 3-4 μl of sample to perform ALISA means PP2A-specific reversible thiol oxidation is a capillary-fingertip blood-compatible candidate redox biomarker. Consistent with biologically meaningful redox regulation, thiol reductant-inducible PP2A activity was significantly greater (+10%) at rest compared to exercise. We establish a route to developing new readily measurable protein thiol redox biomarkers for understanding the biological roles ROS play in humans.