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)

Mitochondrial Bioenergetics in Resilience of Older Adults with Gynecologic Cancer: Design and Rationale of a Pilot Study

Resilience, the ability to recover and maintain function following stresses, is a critical factor influencing treatment tolerance and recovery in older adults with cancer. Despite the high incidence of gynecologic cancers in postmenopausal individuals, resilience in this population remains underexplored, even though patients commonly face compounded stress from both chemotherapy and surgery. The goal of our research is 1) to test the feasibility of cognitive and physical function assessments in older women with gynecologic cancers and 2) to discover reliable predictors that enhance clinical decision-making and guide personalized treatment strategies. Current clinical assessments focus on isolated physiological systems. As such, there is a need for a reliable predictor that captures systemic resilience more comprehensively. A reliable predictor of resilience following cancer treatment could improve clinical decision-making and identify potential targets for therapeutic intervention. Both mitochondrial bioenergetics and oxidative stress are presumably mechanistically linked to resilience of patients with gynecologic cancers because of widely known effects of chemotherapy and tumor burden on mitochondrial bioenergetics. Mitochondria generate more than 95% of cellular ATP through oxidative phosphorylation, a process essential for recovery following physiological stress. Oxidative stress disrupts excitation-contraction coupling and reduces metabolic efficiency in skeletal muscle, contributing to weakness and fatigue. In the brain, oxidative modifications have been associated with impaired neurotransmission and cognitive dysfunction. This protocol paper describes a longitudinal study design aimed at evaluating the feasibility of resilience assessment and testing mitochondria and oxidative stress as predictors of resilience in older adults diagnosed with advanced endometrial or ovarian cancer.

Low Relative Sit-to-Stand Power Is Associated With the Development of Adverse Health Outcomes: A 5-Year Longitudinal Study

BACKGROUND

Relative sit-to-stand (STS) power has emerged as a key biomarker of aging due to its strong association with adverse health outcomes such as frailty or disability. Thus, this study aimed to evaluate the association between low baseline relative STS power with the development of adverse health outcomes.

METHODS

A total of 839 community-dwelling older adults (65-91 years; 42% men) from the Toledo Study for Healthy Aging were assessed at baseline and after 5 years of follow-up. Relative STS power was assessed using the 30-s STS test and Alcazar's equation. Adverse conditions considered encompassed frailty (evaluated using the frailty trait scale 5 [FTS5] or frailty phenotype [FP]), disability in basic (BADL; Barthel index) and instrumental activities of daily living (IADL; Lawton and Brody scale), cognitive impairment (mini-mental state examination), depression (geriatric depression scale) and medication use.

RESULTS

At baseline, people with low relative STS power (461 participants) had significantly higher FTS5 (+5.9 points), FP (+0.56 criteria), disability in BADL (-0.1 points) and IADL (-0.7 points), cognitive impairment (-1.3 points) and medication use (+0.9 medications) than older adults with normal relative STS power (all p < 0.05). In contrast, no significant differences were observed at baseline in GDS (p > 0.05). Low baseline relative STS power was significantly associated with the incidence of frailty FTS5 (OR [95% CI] = 2.51 [1.26-5.03]; p = 0.009), disability in BADL (OR [95% CI] = 1.70 [1.13-2.56]; p = 0.011) and IADL (OR [95% CI] = 1.79 [1.06-3.02]; p = 0.030) and increased medication use (OR [95% CI] = 1.51 [1.10-2.07]; p = 0.011) during the follow-up. No association was found with the incidence of frailty by FP (OR [95% CI] = 1.71 [0.75-3.93]; p = 0.202), depression (OR [95% CI] = 1.29 [0.85-1.98]; p = 0.236) or cognitive impairment (OR [95% CI] = 1.38 [0.86-2.21]; p = 0.178).

CONCLUSION

Participants with low relative STS power exhibited worse baseline and 5-year follow-up values in frailty, BADL and IADL disability, cognitive impairment and medication intake. Low relative STS power was also associated with a higher probability of future frailty, disability in BADL and IADL and increased medication use.

Mechanisms of mitochondrial reactive oxygen species action in bone mesenchymal cells

Mitochondrial (mt)ROS, insufficient NAD+, and cellular senescence all contribute to the decrease in bone formation with aging. ROS can cause senescence and decrease NAD+, but it remains unknown whether these mechanisms mediate the effects of ROS in vivo. Here, we generated mice lacking the mitochondrial antioxidant enzyme Sod2 in osteoblast lineage cells targeted by Osx1-Cre and showed that Sod2ΔOsx1 mice had low bone mass. Osteoblastic cells from these mice had impaired mitochondrial respiration and attenuated NAD+ levels. Administration of an NAD+ precursor improved mitochondrial function in vitro but failed to rescue the low bone mass of Sod2ΔOsx1 mice. Single-cell RNA-sequencing of bone mesenchymal cells indicated that ROS had no significant effects on markers of senescence but disrupted parathyroid hormone signaling, iron metabolism, and proteostasis. Our data supports the rationale that treatment combinations aimed at decreasing mtROS and senescent cells and increasing NAD+ should confer additive effects in delaying age-associated osteoporosis.

From Cell Architecture to Mitochondrial Signaling: Role of Intermediate Filaments in Health, Aging, and Disease

The coordination of cytoskeletal proteins shapes cell architectures and functions. Age-related changes in cellular mechanical properties have been linked to decreased cellular and tissue dysfunction. Studies have also found a relationship between mitochondrial function and the cytoskeleton. Cytoskeleton inhibitors impact mitochondrial quality and function, including motility and morphology, membrane potential, and respiration. The regulatory properties of the cytoskeleton on mitochondrial functions are involved in the pathogenesis of several diseases. Disassembly of the axon's cytoskeleton and the release of neurofilament fragments have been documented during neurodegeneration. However, these changes can also be related to mitochondrial impairments, spanning from reduced mitochondrial quality to altered bioenergetics. Herein, we discuss recent research highlighting some of the pathophysiological roles of cytoskeleton disassembly in aging, neurodegeneration, and neuromuscular diseases, with a focus on studies that explored the relationship between intermediate filaments and mitochondrial signaling as relevant contributors to cellular health and disease.

A Mass Spectrometry-Based Proteomics Workflow for Concurrent Profiling of Protein Thiol Oxidation and Phosphorylation

Multiple types of protein posttranslational modifications (PTMs) play vital roles in the regulation of normal cellular functions and pathogenesis. Two of the most relevant and well-studied PTMs are protein thiol oxidation (redox) and phosphorylation. Both processes involve the reversible addition of a chemical group to a specific amino acid residue, altering the protein activity, stability, or interaction with other molecules. Environmental stressors are known to trigger rapid and dynamic regulation of both thiol oxidation and phosphorylation, and these PTMs on key proteins serve as molecular switches in response to external stimuli. Studies have also shown interplay between phosphorylation and redox modifications, as one PTM type can alter the conformation of a protein, thus exposing or masking the sites for another type of PTM. Such crosstalk represents a complex regulatory mechanism that fine-tunes cellular signaling pathways such as those involved in DNA damage responses (DDR). Despite significant advances in our ability to analyze the redox proteome and phosphoproteome individually, a method that allows the detection of both PTM types from the same sample is still lacking. Herein, we describe a method for simultaneous analysis of protein thiol oxidation and phosphorylation in the same sample. This integrated workflow consists of cell lysis, acetone precipitation, tryptic digestion and isobaric labeling, and subsequent enrichment of thiol-containing peptides utilizing resin-assisted capture (RAC) and phosphopeptides using immobilized metal affinity chromatography (IMAC), respectively. The immediate alkylation of samples and other measures incorporated throughout the protocol prevents artificial oxidation of nascent free thiols and preservation of phosphorylation sites to ensure accurate identification and quantification.

Exploring new frontiers in type 1 diabetes through advanced mass-spectrometry-based molecular measurements

Type 1 diabetes (T1D) is a devastating autoimmune disease for which advanced mass spectrometry (MS) methods are increasingly used to identify new biomarkers and better understand underlying mechanisms. For example, integration of MS analysis and machine learning has identified multimolecular biomarker panels. In mechanistic studies, MS has contributed to the discovery of neoepitopes, and pathways involved in disease development and identifying therapeutic targets. However, challenges remain in understanding the role of tissue microenvironments, spatial heterogeneity, and environmental factors in disease pathogenesis. Recent advancements in MS, such as ultra-fast ion-mobility separations, and single-cell and spatial omics, can play a central role in addressing these challenges. Here, we review recent advancements in MS-based molecular measurements and their role in understanding T1D.

The cellular bases of mobility from the Study of Muscle, Mobility and Aging (SOMMA)

Findings from the Study of Muscle, Mobility and Aging (SOMMA) in this issue of Aging Cell show that several biological pathways in skeletal muscle cells play an important role in determining mobility in older adults. These are based on assays in skeletal muscle biopsies obtained from participants, aged 70 years and older in SOMMA tested for association with assessments related to mobility, including muscle mass, strength, power, cardiopulmonary fitness, and 400 m walking speed. The papers show that, using mass spectrometry, oxidative modifications of proteins essential to myocellular function are associated with poorer mobility. Using RNA-seq to quantify gene expression, lower levels of expression of antioxidant enzymes located in mitochondria, autophagy, patterns of expression of genes involved in autophagy, and higher levels of RNA transcripts that increase with denervation were associated with poorer performance on tests of mobility. These results extend previous research from the Baltimore Longitudinal Study of Aging and recent studies from SOMMA showing the importance of mitochondrial energetics in mobility. Together, these findings are painting a picture of how fundamental cellular processes influence the loss of mobility with aging. They may also be a window on aging in other cells, tissues, and systems. The data collected in SOMMA are publicly available and SOMMA welcomes collaborations with scientists who are interested in research about human aging.

Autophagy gene expression in skeletal muscle of older individuals is associated with physical performance, muscle volume and mitochondrial function in the study of muscle, mobility and aging (SOMMA)

Autophagy is essential for proteostasis, energetic balance, and cell defense and is a key pathway in aging. Identifying associations between autophagy gene expression patterns in skeletal muscle and physical performance outcomes would further our knowledge of mechanisms related with proteostasis and healthy aging. Muscle biopsies were obtained from participants in the Study of Muscle, Mobility, and Aging (SOMMA). For 575 participants, RNA was sequenced and expression of 281 genes related to autophagy regulation, mitophagy, and mTOR/upstream pathways was determined. Associations between gene expression and outcomes including mitochondrial respiration in muscle fiber bundles (MAX OXPHOS), physical performance (VO2 peak, 400 m walking speed, and leg power), and thigh muscle volume, were determined using negative binomial regression models. For autophagy, key transcriptional regulators including TFE3 and NFKB-related genes (RELA, RELB, and NFKB1) were negatively associated with outcomes. On the contrary, regulators of oxidative metabolism that also promote overall autophagy, mitophagy, and pexophagy (PPARGC1A, PPARA, and EPAS1) were positively associated with multiple outcomes. In line with this, several mitophagy, fusion, and fission-related genes (NIPSNAP2, DNM1L, and OPA1) were also positively associated with outcomes. For mTOR pathway and related genes, expression of WDR59 and WDR24, both subunits of GATOR2 complex (an indirect inhibitor of mTORC1), and PRKAG3, which is a regulatory subunit of AMPK, were negatively correlated with multiple outcomes. Our study identifies autophagy and selective autophagy such as mitophagy gene expression patterns in human skeletal muscle related to physical performance, muscle volume, and mitochondrial function in older persons which may lead to target identification to preserve mobility and independence.