Molecular and phenotypic analysis of rodent models reveals conserved and species-specific modulators of human sarcopenia (original) (raw)
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PLoS ONE, 2013
Mitochondrial DNA (mtDNA) mutations lead to decrements in mitochondrial function and accelerated rates of these mutations has been linked to skeletal muscle loss (sarcopenia). The purpose of this study was to investigate the effect of mtDNA mutations on mitochondrial quality control processes in skeletal muscle from animals (young; 3-6 months and older; 8-15 months) expressing a proofreading-deficient version of mtDNA polymerase gamma (PolG). This progeroid aging model exhibits elevated mtDNA mutation rates, mitochondrial dysfunction, and a premature aging phenotype that includes sarcopenia. We found increased expression of the mitochondrial biogenesis regulator peroxisome proliferator-activated receptor gamma coactivator-1a (PGC-1a) and its target proteins, nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (Tfam) in PolG animals compared to wild-type (WT) (P,0.05). Muscle from older PolG animals displayed higher mitochondrial fission protein 1 (Fis1) concurrent with greater induction of autophagy, as indicated by changes in Atg5 and p62 protein content (P,0.05). Additionally, levels of the Tom22 import protein were higher in PolG animals when compared to WT (P,0.05). In contrast, muscle from normally-aged animals exhibited a distinctly different expression profile compared to PolG animals. Older WT animals appeared to have higher fusion (greater Mfn1/Mfn2, and lower Fis1) and lower autophagy (Beclin-1 and p62) compared to young WT suggesting that autophagy is impaired in aging muscle. In conclusion, muscle from mtDNA mutator mice display higher mitochondrial fission and autophagy levels that likely contribute to the sarcopenic phenotype observed in premature aging and this differs from the response observed in normally-aged muscle.
2021
Aging is accompanied by a loss of muscle mass and function, termed sarcopenia, which causes numerous morbidities and economic burdens in human populations. Mechanisms implicated in age-related sarcopenia include inflammation, muscle stem cell depletion, mitochondrial dysfunction and loss of motor neurons, but whether there are key drivers of sarcopenia is not yet known. To gain deeper insights into age-related sarcopenia, we performed transcriptome profiling on lower limb muscle biopsies from 72 young, old and sarcopenic subjects using bulk RNA-seq (N = 72) and single-nuclei RNA-seq (N = 17). This combined approach revealed novel changes in gene expression that occur with age and sarcopenia in multiple cell types comprising mature skeletal muscle. Notably, we found increased expression of the genes MYH8 and PDK4, and decreased expression of the gene IGFN1, in old muscle. We validated key genes in fixed human muscle tissue using digital spatial profiling. We also identified a small p...
Journal of Cachexia, Sarcopenia and Muscle
BackgroundMitochondrial dysfunction caused by mitochondrial (mtDNA) deletions have been associated with skeletal muscle atrophy and myofibre loss. However, whether such defects occurring in myofibres cause sarcopenia is unclear. Also, the contribution of mtDNA alterations in muscle stem cells (MuSCs) to sarcopenia remains to be investigated.MethodsWe expressed a dominant‐negative variant of the mitochondrial helicase, which induces mtDNA alterations, specifically in differentiated myofibres (K320Eskm mice) and MuSCs (K320Emsc mice), respectively, and investigated their impact on muscle structure and function by immunohistochemistry, analysis of mtDNA and respiratory chain content, muscle transcriptome and functional tests.ResultsK320Eskm mice at 24 months of age had higher levels of mtDNA deletions compared with controls in soleus (SOL, 0.07673% vs. 0.00015%, P = 0.0167), extensor digitorum longus (EDL, 0.0649 vs. 0.000925, P = 0.0015) and gastrocnemius (GAS, 0.09353 vs. 0.000425, P...
Muscle function decline and mitochondria changes in middle age precede sarcopenia in mice
Aging, 2018
Sarcopenia is the degenerative loss of muscle mass and strength with aging. Although a role of mitochondrial metabolism in muscle function and in the development of many diseases has been described, the role of mitochondrial topology and dynamics in the process of muscle aging is not fully understood. This work shows a time line of changes in both mitochondrial distribution and skeletal muscle function during mice lifespan. We isolated muscle fibers fromof mice of different ages. A fusion-like phenotype of mitochondria, together with a change in orientation perpendicular to the fiber axis was evident in the Adult group compared to Juvenile and Older groups. Moreover, an increase in the contact area between sarcoplasmic reticulum and mitochondria was evident in the same group. Together with the morphological changes, mitochondrial Caresting levels were reduced at age 10-14 months and significantly increased in the Older group. This was consistent with a reduced number of mitochondria...
Overlapping pathophysiological pathways between sarcopenia and chronic diseases
Dysona Life Science Journal, 2023
Sarcopenia and frailty are two geriatric syndromes that cause loss of muscle mass and function in addition to other various impairments. Sarcopenia is a specific phenotype of frailty where low grip strength, slow walking, and reduced muscle mass are observed. Since modern communities are aging more than ever, geriatric syndromes have become more prevalent and are linked to morbidity and disabilities. Several mechanisms are involved in the pathophysiology of sarcopenia, such as autophagy, protein synthesis and degradation, satellite cell activation damages, mitochondrial dysfunction, increased intracellular oxidative stress, and other factors like malnutrition, physical inactivity, and systemic inflammation that contribute to muscle weakness and degeneration. Modulating factors such as exosomes and transporters that can govern muscle loss and regeneration are involved in this pathogenetic pathway. The significance of these compounds is not theoretical since they provide a useful diagnostic tool as well as a potential treatment target. Thereby, the study of exosomes can explain the complex and intricate process of geriatric syndrome as an increasingly frequent complication of various diseases in the elderly. Therefore, this study explores the overlapping pathophysiological pathways between chronic diseases and sarcopenia by reviewing the current conception of exosome production and exosomal cargo in chronic diseases.
Ageing Research Reviews, 2010
Sarcopenia, the age-related loss of skeletal muscle mass, is a significant public health concern that continues to grow in relevance as the population ages. Certain conditions have the strong potential to coincide with sarcopenia to accelerate the progression of muscle atrophy in older adults. Among these conditions are co-morbid diseases common to older individuals such as cancer, kidney disease, diabetes, and peripheral artery disease. Furthermore, behaviors such as poor nutrition and physical inactivity are well-known to contribute to sarcopenia development. However, we argue that these behaviors are not inherent to the development of sarcopenia but rather accelerate its progression. In the present review, we discuss how these factors affect systemic and cellular mechanisms that contribute to skeletal muscle atrophy. In addition, we describe gaps in the literature concerning the role of these factors in accelerating sarcopenia progression. Elucidating biochemical pathways related to accelerated muscle atrophy may allow for improved discovery of therapeutic treatments related to sarcopenia.
Sarcopenia and Muscle Aging: A Brief Overview
Endocrinology and Metabolism
The world is facing the new challenges of an aging population, and understanding the process of aging has therefore become one of the most important global concerns. Sarcopenia is a condition which is defined by the gradual loss of skeletal muscle mass and function with age. In research and clinical practice, sarcopenia is recognized as a component of geriatric disease and is a current target for drug development. In this review we define this condition and provide an overview of current therapeutic approaches. We further highlight recent findings that describe key pathophysiological phenotypes of this condition, including alterations in muscle fiber types, mitochondrial function, nicotinamide adenine dinucleotide (NAD +) metabolism, myokines, and gut microbiota, in aged muscle compared to young muscle or healthy aged muscle. The last part of this review examines new therapeutic avenues for promising treatment targets. There is still no accepted therapy for sarcopenia in humans. Here we provide a brief review of the current state of research derived from various mouse models or human samples that provide novel routes for the development of effective therapeutics to maintain muscle health during aging.
Sarcopenia – Molecular mechanisms and open questions
Ageing Research Reviews, 2021
Sarcopenia represents a muscle-wasting syndrome characterized by progressive and generalized degenerative loss of skeletal muscle mass, quality, and strength occurring during normal aging. Sarcopenia patients are mainly suffering from the loss in muscle strength and are faced with mobility disorders reducing their quality of life and are, therefore, at higher risk for morbidity (falls, bone fracture, metabolic diseases) and mortality. Several molecular mechanisms have been described as causes for sarcopenia that refer to very different levels of muscle physiology. These mechanisms cover e. g. function of hormones (e. g. IGF-1 and Insulin), muscle fiber composition and neuromuscular drive, myo-satellite cell potential to differentiate and proliferate, inflammatory pathways as well as intracellular mechanisms in the processes of proteostasis and mitochondrial function. In this review, we describe sarcopenia as a muscle-wasting syndrome distinct from other atrophic diseases and summarize the current view on molecular causes of sarcopenia development as well as open questions provoking further research efforts for establishing efficient lifestyle and therapeutic interventions.
Skeletal muscle in aged mice reveals extensive transformation of muscle gene expression
BMC Genetics
Background: Aging leads to decreased skeletal muscle function in mammals and is associated with a progressive loss of muscle mass, quality and strength. Age-related muscle loss (sarcopenia) is an important health problem associated with the aged population. Results: We investigated the alteration of genome-wide transcription in mouse skeletal muscle tissue (rectus femoris muscle) during aging using a high-throughput sequencing technique. Analysis revealed significant transcriptional changes between skeletal muscles of mice at 3 (young group) and 24 (old group) months of age. Specifically, genes associated with energy metabolism, cell proliferation, muscle myosin isoforms, as well as immune functions were found to be altered. We observed several interesting gene expression changes in the elderly, many of which have not been reported before. Conclusions: Those data expand our understanding of the various compensatory mechanisms that can occur with age, and further will assist in the development of methods to prevent and attenuate adverse outcomes of aging.
Altered Gene Expression of Muscle Satellite Cells Contributes to Agerelated Sarcopenia in Mice
Current Aging Science, 2019
Background: During aging, muscle tissue undergoes profound changes which lead to a decline in its functional and regenerative capacity. We utilized global gene expression analysis and gene set enrichment analysis to characterize gene expression changes in aging muscle satellite cells. Method: Gene expression data; obtained from Affymetrix Mouse Genome 430 2.0 Array, for 14 mouse muscle satellite cell samples (5 young, 4 middle-aged, and 5 aged), were retrieved from public Gene Expression Omnibus repository. List of differentially expressed genes was generated based on 0.05 multiple-testing-adjusted p-value and 2-fold FC cutoff values. Functional profiling of genes was carried out using PANTHER Classification System. Results: We have found several differentially expressed genes in satellite cells derived from aged mice compared to young ones. The gene expression changes increased progressively with time, and the majority of the differentially expressed genes were upregulated during aging. While the downregulated genes could not be correlated with specific biological processes the upregulated ones could be associated with muscle differentiation-, inflammation-or fibrosis-related processes. The latter two processes encompass the senescence-associated secretory phenotype for satellite cells which alters the tissue microenvironment and contributes to inflammation and fibrosis observed in aging muscle. Conclusion: Our analysis reveals that by altering gene expression pattern and expressing inflammatory mediators and extracellular matrix components, these cells can directly contribute to muscle wasting in aged mice.