Sex differences in changes of protein synthesis with rapamycin treatment are minimized when metformin is added to rapamycin

Wolff, Christopher A.; Lawrence, Marcus M.; Porter, Hunter; Zhang, Qian; Reid, Justin J.; Laurin, Jaime L.; Musci, Robert V.; Linden, Melissa A.; Peelor, Frederick F.; Wren, Jonathan D.; Creery, Joseph S.; Cutler, Kyle J; Carson, Richard H.; Price, John C.; Hamilton, Karyn L.; Miller, Benjamin F.

doi:10.1007/s11357-020-00243-8

Cited by 23 publications

(22 citation statements)

References 64 publications

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“… 29 Around the time of this publication, we began to use a time-course approach to understand the incomplete renewal of some protein pools. 38 , 39 , 47 Although the paper of Zhou et al clearly demonstrated the theoretical implications of not accounting for incomplete renewal of certain protein pools, 29 we believe that a change in the dynamic protein pools is an important proteostatic outcome. 38 , 39 , 47 Therefore, we performed the present study to test the implications of the theoretical considerations posed by Zhou et al to collagen synthesis in aging skeletal muscle.…”

Section: Discussionmentioning

confidence: 82%

“…In this study, we advance the notion that in addition to protein turnover, the change in the dynamic protein pool size is also an important proteostatic outcome. Although we have previously reported dynamic protein pool sizes, 38 , 39 , 47 we have not explored whether this measurement was indicative of proteostatic maintenance.…”

Section: Discussionmentioning

confidence: 99%

“…For adult and old mice, the fraction new data were then plotted across the time points and curves were fit to the data using one-phase associations. 38 , 39 Two parameters of interest were then calculated from the curves using Graphpad Prism 9 and the one-phase association function. The software calculates rate parameter ( k , 1/day), which reflects the protein synthetic rate, and plateau fraction new ( p ), which represents the proportion of the protein pool that is actively turning over (ie, the dynamic protein pool), with 1.0 equal to 100% of the protein pool.…”

Section: Methodsmentioning

confidence: 99%

“…The software calculates rate parameter ( k , 1/day), which reflects the protein synthetic rate, and plateau fraction new ( p ), which represents the proportion of the protein pool that is actively turning over (ie, the dynamic protein pool), with 1.0 equal to 100% of the protein pool. 38 , 39 We constrained the plateau ( p ) to 1.0 when assuming the protein pool fully renews, and ≤1.0 when not assuming full renewal. The rate parameter ( k ) was therefore calculated as rise to these separate plateau values.…”

Section: Methodsmentioning

confidence: 99%

“…During differential centrifugation, the cytosolic protein fraction was saved, and protein concentration was determined by bicinchoninic acid assay (BCA) assay and prepared in Laemmli sample buffer, as described previously. 38 , 41 For quantification of protein abundance, samples were electrophoretically separated by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE) using 4%–15% TGX gels (Bio-Rad, Hercules, CA) and then transferred to a Polyvinylidene difluoride (PVDF) (Bio-Rad, Hercules, CA) membrane. Transfer efficiency and equal loading among lanes were then determined by staining membranes with Ponceau S (Sigma-Aldrich, St. Louis, MO) and imaging.…”

Section: Methodsmentioning

confidence: 99%

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A Novel Stable Isotope Approach Demonstrates Surprising Degree of Age-Related Decline in Skeletal Muscle Collagen Proteostasis

et al. 2021

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Age-related deterioration in turnover of collagen proteins accelerates extracellular matrix (ECM) fibrosis and hinders adaptation to external stimuli. This project sought to understand factors that increase skeletal muscle fibrosis with age by studying what we term the dynamic protein pool. We hypothesized that the dynamic protein pool size of muscle collagen decreases with age, thus indicating a decrease in proteostatic maintenance (i.e., ability to maintain proteostasis), and that failure to account for these changes impacts the interpretation of tracer-measured synthesis rates. We used deuterium oxide (D2O) labeling for up to 60 days in adult (6 months) and old (23 months) mice. The dynamic protein pool in adult skeletal muscle was 65% in tibialis anterior (TA), but only 28% in gastrocnemius (Gastroc). In aged muscle, the dynamic protein pool was further decreased to only 35% and 14% for TA and Gastroc, respectively. We showed that this loss in dynamic pool size was associated with increases in markers of fibrosis and decreased proteostatic maintenance. We demonstrate that aged muscle has higher rates of collagen protein synthesis and lower rates of collagen protein breakdown, which causes collagen accumulation. We further demonstrated that the normal assumption of complete protein renewal and the standard practice of taking a single sample with isotope labeling have profound impacts on interpretation of the genesis of fibrosis. Strategies to maintain muscle function with aging should focus on the dynamic protein pool with attention to methodological strategies to assess those changes.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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A Novel Stable Isotope Approach Demonstrates Surprising Degree of Age-Related Decline in Skeletal Muscle Collagen Proteostasis

et al. 2021

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Skeletal and cardiac muscle have different protein turnover responses in a model of right heart failure

et al. 2023

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Age-induced changes in skeletal muscle mitochondrial DNA synthesis, quantity, and quality in genetically unique rats

Musci,

Fuqua,

Peelor

et al. 2024

GeroScience

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Mitochondrial genomic integrity is a key element of physiological processes and health. Changes in the half-life of the mitochondrial genome are implicated in the generation and accumulation of age-induced mitochondrial DNA (mtDNA) mutations, which are implicated in skeletal muscle aging and sarcopenia. There are conflicting data on the half-life of mtDNA, and there is limited information on how aging affects half-life in skeletal muscle. We hypothesized that skeletal muscle mtDNA synthesis rates would decrease with age in both female and male rats concomitant with changes in mtDNA integrity reflected in mtDNA copy number and mutation frequency. We measured mitochondrial genome half-life using stable isotope labeling over a period of 14 days and assessed mtDNA copy number and deletion mutation frequency using digital PCR in the quadriceps muscle of 9-month-old and 26-month-old male and female OKC-HET rats. We found a significant age-related increase in mtDNA half-life, from 132 days at 9 months to 216 days at 26 months of age in OKC-HET quadriceps. Concomitant with the increase in mtDNA half-life, we found an age-related increase in mtDNA deletion mutation frequency in both male and female rats. Notably, 26-month-old female rats had a lower mutation frequency than male rats, and there were no changes in mtDNA copy number with sex, age, or mitochondrial genotype. These data reveal several key findings: (1) mtDNA turnover in rat skeletal muscle decreases with age, (2) mtDNA half-lives in skeletal muscle are approximately an order of magnitude longer than what is reported for other tissues, and (3) muscle mtDNA turnover differs significantly from the turnover of other mitochondrial macromolecules including components of the mitochondrial nucleoid. These findings provide insight into the factors driving age-induced mtDNA mutation accumulation, which contribute to losses of mitochondrial genomic integrity and may play a role in skeletal muscle dysfunction.

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Sex differences in changes of protein synthesis with rapamycin treatment are minimized when metformin is added to rapamycin

Cited by 23 publications

References 64 publications

A Novel Stable Isotope Approach Demonstrates Surprising Degree of Age-Related Decline in Skeletal Muscle Collagen Proteostasis

A Novel Stable Isotope Approach Demonstrates Surprising Degree of Age-Related Decline in Skeletal Muscle Collagen Proteostasis

Skeletal and cardiac muscle have different protein turnover responses in a model of right heart failure

Age-induced changes in skeletal muscle mitochondrial DNA synthesis, quantity, and quality in genetically unique rats

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