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A Virus-acquired Host Cytokine Controls Systemic Aging by Antagonizing Apoptosis

ABSTRACT: Aging is characterized by degeneration of unique tissues. However, dissecting the interconnectedness of tissue aging remains a challenge. Here, we employ a muscle-specific DNA damage model in Drosophila to reveal secreted factors that influence systemic aging in distal tissues. Utilizing this model, we uncovered a cytokine, Diedel, that when secreted from muscle or adipose can attenuate age-related intestinal tissue degeneration by promoting proliferative homeostasis of stem cells. Diedel is both necessary and sufficient to limit tissue degeneration and extend lifespan. Secreted homologs of Diedel are also found in viruses, having been acquired from host genomes. Focusing on potential mechanistic overlap between cellular aging and viral-host cell interactions and, we found that Diedel is a functionally conserved inhibitor of apoptosis and can act as a systemic rheostat to modulate cell death during aging. These results highlight a key role for secreted antagonists of apoptosis in the systemic coordination of tissue aging.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE111248 | GEO | 2018/07/02

REPOSITORIES: GEO

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Project description:The degenerative loss of muscle associated with aging leading to muscular atrophy is called sarcopenia. Currently, practicing regular physical exercise is the only efficient way to delay the onset of sarcopenia. To identify therapeutic targets to suppress the symptoms of aging, there is a need for in vivo model organisms of accelerated muscle degeneration and atrophy. The zebrafish harbors hallmarks of aging, notably mitochondrial dysfunction, telomeres shortening and accumulation of senescent cells. Unfortunately, zebrafish aged slowly, and no specific zebrafish models of accelerated muscle atrophy associated with aging or sarcopenia are currently available. We have developed a new genetic tool to efficiently accelerate muscle fibers degeneration and muscle tissue atrophy in zebrafish larvae and adults. We used a gain-of-function strategy with a molecule that has been shown to be necessary and sufficient to induce muscle atrophy and a sarcopenia phenotype in mammals: Atrogin1 (also named Fbxo32). We report the generation, validation, and characterization of a zebrafish genetic model of accelerated muscle atrophy, the sarcofish. We demonstrated that specific expression of Atrogin1 in skeletal muscle tissue induces a muscle atrophic phenotype associated with locomotion dysfunctions in both larvae and adult fish. We identified that degradation of the myosin light chain as an event occurring before the degeneration of muscle fibers. Biological processes associated with muscle aging such as inflammation, proteolysis, apoptosis and stress response are upregulated in the sarcofish. Surprisingly, we observed a strong correlation between muscle fibers degeneration and a reduction of neuromuscular junctions in the peripheral nervous system, as well as neuronal cell bodies in the spinal cord, suggesting that muscle atrophy could underly a neurodegenerative phenotype in the central nervous system. Finally, while sarcofish larvae harbor regeneration of muscle fibers, spinal neurons and recover locomotive functions, adult sarcofish have impaired regenerative capacities as observed in mammals during muscle aging. In the future, the sarcofish could open new strategies in the fight against the sarcopenia disease to test therapeutic molecules aiming to treat or alleviate the symptoms of muscle aging.

Project description:Background: Skeletal muscle constitutes a significant portion of total body mass and is a major regulator of systemic metabolism as it serves as the major site for glucose disposal and the main reservoir for amino acids. With aging, cachexia, starvation, and myositis, there is a preferential loss of fast glycolytic muscle fibers. We previously reported a mouse model in which a constitutively-active Akt transgene is induced to express in a subset of muscle groups leading to the hypertrophy of type IIb myofibers with an accompanying increase in strength. This muscle growth protects mice in various cardio-metabolic disease models, but little is known about the underlying cellular and molecular mechanisms by which fast-twitch muscle impacts disease processes and regulates distant tissues. Purpose: In the present study, poly(A)+ tail mRNA-seq was performed to characterize the transcriptome of the hypertrophic gastrocnemius muscle from Akt1-transgenic mice. Results: Pathway analysis for the 3,481 differentially expressed genes in muscle identified enriched signaling pathways involving growth, cell cycle regulation, and inflammation. Combined metabolomics and transcriptomic analyses revealed that Akt1-induced muscle growth mediated a metabolic shift involving reductions in glycolysis and oxidative phosphorylation, but enhanced pentose phosphate pathway activation and increased branch chain amino acid accumulation. Signal peptide prediction analysis revealed 241 differentially expressed in muscle transcripts that potentially encode secreted proteins. A number of these secreted factors have signaling properties that are consistent with the myogenic, metabolic and cardiovascular-protective properties that have previously been associated with type IIb muscle growth. Conclusions: These data reveal that enhanced Akt signaling promotes the activation of the pentose phosphate and the accumulation of branched amino acids that are important for the production of nucleic acids and proteins. Numerous known and novel transcripts potentially encoding muscle secreted proteins were identified, indicating the importance of fast-twitch muscle in inter-tissue communication.

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A Virus-acquired Host Cytokine Controls Systemic Aging by Antagonizing Apoptosis

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