Disuse-associated loss of the protease Lonp1 in muscle impairs mitochondrial function and causes reduced skeletal muscle mass and strength

May combine two claims.

Overexpressing a mitochondrial-retained mutant ornithine transcarbamylase (ΔOTC) in skeletal muscle induces mitochondrial dysfunction, autophagy activation, and causes muscle loss and weakness.

“Overexpressing a mitochondrial-retained mutant ornithine transcarbamylase (ΔOTC), a known protein degraded by LONP1, in skeletal muscle induces mitochondrial dysfunction, autophagy activation, and cause muscle loss and weakness.”

May combine two claims.

Starting at 5 days following denervation, LONP1 protein expression gradually and significantly decreases in mouse gastrocnemius and tibialis anterior muscles, along with reductions in muscle weight.

“Starting at 5 days following denervation, we observed gradual and significant decreases in the protein expression of mitochondrial protease LONP1 along with apparent reductions in gastrocnemius (GC) and tibialis anterior (TA) muscle weight (Fig. 1a, b and Supplementary Fig. 1a).”

May combine two claims.

CLPP and OPA1 protein levels decrease only at later stages of denervation-induced muscle loss, whereas MFN1, MFN2, and DRP1 levels remain unchanged during denervation.

“Notably, we found decreased levels of mitochondrial protease CLPP and dynamic protein OPA1 only at later stages of denervation-induced muscle loss (Fig. 1a, b), whereas the levels of other mitochondrial dynamic proteins MFN1, MFN2, and DRP1 remained unchanged during the denervation process (Fig. 1a, b).”

May combine two claims.

LONP1 protein expression decreases in skeletal muscle after immobilization-induced muscle disuse in mice, correlating with significant muscle loss.

“We confirmed that LONP1 protein expression decreased in skeletal muscle after immobilization-induced muscle disuse (Fig. 1c, d), correlating with significant muscle loss (Supplementary Fig. 1b), whereas no decreases in the protein levels of CLPP, OPA1, MFN1, MFN2, and DRP1 were observed during the immobilization process (Fig. 1c, d and Supplementary Fig. 1c, d).”

May combine two claims.

OPA1 protein levels are not different between atrophy and non-atrophy groups and do not exhibit a significant correlation with occupation ratios.

“In contrast, the levels of OPA1 protein were not different between atrophy and non-atrophy groups, and neither exhibited a significant correlation with occupation ratios (Fig. 1g and Supplementary Fig. 1f, g).”

May combine two claims.

Relative mitochondrial area per muscle fiber area and average mitochondrial size are not different in LONP1 mKO muscle compared with WT controls.

“The quantitative EM analysis revealed that the relative mitochondrial area per muscle fiber area and average mitochondrial size were not different in LONP1 mKO muscle compared with WT controls (Supplementary Fig. 3a,b).”

May combine two claims.

Mitochondrial DNA content, Tim23 protein levels, and PGC-1α transcripts are not different in LONP1 mKO muscle relative to WT controls.

“Similarly, the mitochondrial DNA content and Tim23 protein levels, as well as PGC-1α transcripts were not different in LONP1 mKO muscle relative to WT controls (Fig. 3c and Supplementary Fig. 3c, d).”

May combine two claims.

Mice with muscle-specific knockout of Lonp1 are born at normal Mendelian ratios and are indistinguishable from WT littermates during the first 2 weeks of postnatal life.

“Mice with muscle-specific knockout of Lonp1 were born at normal Mendelian ratios and were indistinguishable from their WT littermates during the first 2 weeks of postnatal life.”

May combine two claims.

AAV-Cre-mediated deletion of LONP1 in skeletal muscle results in lower levels of LONP1 but not CLPP protein.

“Compared to Lonp1f/f muscle injected with control AAV-GFP viruses, AAV-Cre-mediated deletion of LONP1 in skeletal muscle resulted in lower levels of LONP1 but not CLPP protein (Fig. 5a).”

May combine two claims.

Acute deletion of LONP1 in mature muscle causes muscle loss and weakness.

“Acute deletion of LONP1 in mature muscle leads to autophagy activation and causes muscle loss and weakness.”

May combine two claims.

Mitochondrial autophagy is significantly increased at 2 weeks of age and becomes more dramatic at 6 weeks of age in LONP1 mKO mice.

“We found a significant increase in mitochondrial autophagy already at 2 weeks of age that became more dramatic at 6 weeks of age in LONP1 mKO mice (Fig. 4f, g and Supplementary Fig. 5e).”

May combine two claims.

LONP1 mKO mice can breed successfully and show similar survival as WT littermates at least up to 1.5 years of age.

“The LONP1 mKO mice could breed successfully and showed the similar survival as respective WT littermates at least up to 1.5 years of age.”

May combine two claims.

Ablation of LONP1 in skeletal muscle results in up-regulation of 982 genes and down-regulation of 940 genes.

“Ablation of LONP1 in skeletal muscle resulted in the up-regulation of 982 genes and the down-regulation of 940 genes.”

May combine two claims.

LONP1 mKO muscles show remarkable heterogeneity in mitochondrial structure, with disturbed mitochondrial ultrastructure and abnormal cristae organization at 2 weeks of age that persists at 6 weeks.

“However, this EM analysis of LONP1 mKO muscles revealed remarkable heterogeneity in mitochondrial structure, with many disturbed mitochondrial ultrastructure that has abnormal cristae organization already at 2 weeks of age that persisted at 6 weeks of age in LONP1 mKO mice (Fig. 3a, b).”

May combine two claims.

Histological analysis of muscles from LONP1 mKO mice reveals normal muscle architecture and absence of myofiber degeneration features such as center-nucleated fibers.

“Histological analysis of muscles revealed normal muscle architecture and absence of myofiber degeneration features such as center-nucleated fibers (Supplementary Fig. 2d).”

May combine two claims.

AAV-based LONP1 ablation in Lonp1f/f muscle causes muscle weight loss and muscle weakness.

“Consistent with the results from LONP1 mKO mice, AAV-based LONP1 ablation in Lonp1f/f muscle also caused muscle weight loss and muscle weakness (Fig. 5b–d).”

May combine two claims.

LONP1 mKO mice have a higher RER than WT controls during exercise, accompanied by reduced exercise tolerance.

“Interestingly, LONP1 mKO mice had a higher RER than WT controls during exercise, and this was accompanied by reduced exercise tolerance (Fig. 2i).”

May combine two claims.

CQ treatment leads to a reduced number of small fibers and an increased number of larger fibers in LONP1 mKO mice.

“Analysis of fiber size distribution revealed that CQ treatment led to a reduced number of small fibers and an increased number of larger fibers in LONP1 mKO mice (Supplementary Fig. 5f, g).”

May combine two claims.

At 6 weeks of age but not at 2 weeks of age, LONP1 mKO mice show a significant reduction in muscle weight and myofiber size under basal conditions.

“At 6 weeks of age but not at 2 weeks of age, LONP1 mKO mice showed a significant reduction in muscle weight and myofiber size under basal conditions (Fig. 2b–e and Supplementary Fig. 2h), they showed more pronounced myofiber atrophy and muscle loss in GC and TA muscles in response to denervation (Fig. 2b–e).”

May combine two claims.

618 mitochondrial proteins were identified, of which 81 (13%) displayed 1.2 fold changes in abundance upon LONP1 deletion compared with WT mitochondria.

“we were able to identify 618 mitochondrial proteins, of which 81 (13%) displayed 1.2 fold changes in abundance upon LONP1 deletion compared with WT mitochondria (Fig. 6c).”

• cites MitoCarta2.033Not checked yet

  Not checked in the free run.

May combine two claims.

AAV-Cre-mediated acute deletion of LONP1 in mature muscle results in muscle loss and muscle weakness.

“AAV-Cre-mediated acute deletion of LONP1 in mature muscle also results in muscle loss and muscle weakness.”

May combine two claims.

Only an early reduction in LONP1 protein, but not mitochondrial dynamic proteins, correlates with disuse-induced muscle loss.

“only an early reduction in LONP1 protein, but not mitochondrial dynamic proteins, correlates with disuse-induced muscle loss.”

May combine two claims.

Muscle loss develops in denervation-induced and hindlimb immobilization conditions.

“In parallel, muscle loss develops in these two conditions.”

May combine two claims.

Expression of atrophy-related genes, Foxo3 protein, ubiquitinated proteins content, and AKT/mTOR signaling are not different in MCK-ΔOTC muscles compared to NTG controls.

“we confirmed that the expression of atrophy-related genes, Foxo3 protein, and ubiquitinated proteins content, as well as the AKT/mTOR signaling were not different in MCK-ΔOTC muscles compared to NTG controls (Fig. 7h, i and Supplementary Fig. 9c, d).”

May combine two claims.

Both pyruvate/succinate-driven and maximal ADP-stimulated mitochondrial respiration rates are markedly reduced in MCK-ΔOTC muscles compared to NTG controls.

“Both pyruvate/succinate-driven and maximal ADP-stimulated mitochondrial respiration rates were markedly reduced in MCK-ΔOTC muscles compared to the NTG controls (Fig. 7b, c).”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the non-atrophy group, the mean occupation ratio of the supraspinatus fossa by the muscle belly was 0.76.

“Based on the occupation ratio, we divided the patients into two groups (non-atrophy group, mean ratio 0.76; atrophy group, mean ratio 0.50).”

May combine two claims.

PARK7 is a LONP1 substrate, and its knockdown reduces autophagy flux in LONP1-deficient muscle cells.

“Our mechanistic studies identified PARK7 as a LONP1 substrate, which, when knocked down, reduced autophagy flux in LONP1-deficient muscle cells.”

May combine two claims.

LONP1 affects muscle cell function without affecting PINK1 protein levels.

“our data suggest that LONP1 affects on muscle cell function without affecting PINK1 protein levels.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the atrophy group, the mean occupation ratio of the supraspinatus fossa by the muscle belly was 0.50.

“Based on the occupation ratio, we divided the patients into two groups (non-atrophy group, mean ratio 0.76; atrophy group, mean ratio 0.50).”

May combine two claims.

Loss of muscle LONP1 activates autophagy degradation program without affecting protein synthesis and ubiquitin-mediated protein degradation.

“loss of muscle LONP1 activates autophagy degradation program without affecting protein synthesis and ubiquitin-mediated protein degradation.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Disturbed mitochondrial proteostasis occurs under cellular stress conditions and is associated with aging and with a wide variety of human illnesses, including metabolic disorders, cancer, and neurodegenerative diseases.

“Disturbed mitochondrial proteostasis occurs under cellular stress conditions and is associated with aging and with a wide variety of human illnesses, including metabolic disorders, cancer, and neurodegenerative diseases1,2,4,5.”

• cites [1] Deshwal, S., Fiedler, K. U. & Langer, T. Mitochondrial proteases: multifaceted regulators of mitochondrial plasticity. Annu. Rev. Biochem. 89, 501–528 (2020). sourceNot checked yet

  Not checked in the free run.

• cites [2] Quirós, P. M., Langer, T. & López-Otín, C. New roles for mitochondrial proteases in health, ageing and disease. Nat. Rev. Mol. Cell Biol. 16, 345–359 (2015). sourceNot checked yet

  Not checked in the free run.

• cites [4] Gan, Z., Fu, T., Kelly, D. P. & Vega, R. B. Skeletal muscle mitochondrial remodeling in exercise and diseases. Cell Res. 28, 969–980 (2018). sourceNot checked yet

  Not checked in the free run.

• cites [5] Mottis, A., Herzig, S. & Auwerx, J. Mitocellular communication: Shaping health and disease. Science 366, 827–832 (2019). sourceNot checked yet

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Classified as probably not a substantial claim.

The quality of mitochondria has emerged as an important control process that regulates skeletal muscle function.

“Recently, the quality of mitochondria has emerged as important control process that regulates skeletal muscle function20–23.”

• cites [20] Chen, H. et al. Mitochondrial fusion is required for mtDNA stability in skeletal muscle and tolerance of mtDNA mutations. Cell 141, 280–289 (2010). sourceNot checked yet

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• cites [21] Pereira, R. O. et al. OPA1 deficiency promotes secretion of FGF21 from muscle that prevents obesity and insulin resistance. EMBO J. 36, 2126–2145 (2017). sourceNot checked yet

  Not checked in the free run.

• cites [22] Rodríguez-Nuevo, A. et al. Mitochondrial DNA and TLR9 drive muscle inflammation upon Opa1 deficiency. EMBO J. 37, https://doi.org/10.15252/embj.201796553 (2018). sourceNot checked yet

  Not checked in the free run.

• cites [23] Tezze, C. et al. Age-associated loss of OPA1 in muscle impacts muscle mass, metabolic homeostasis, systemic inflammation, and epithelial senescence. Cell Metab. 25, 1374–1389.e1376 (2017). sourceNot checked yet

  Not checked in the free run.

Classified as probably not a substantial claim.

Mitochondrial proteases serve as the first-line quality control by selective targeting and removal of damaged or dysfunctional mitochondrial proteins to ensure the proper functional integrity of mitochondria.

“Mitochondrial proteases serve as the first-line quality control by selective targeting and removal of damaged or dysfunctional mitochondrial proteins to ensure the proper functional integrity of mitochondria1–4.”

• cites [1] Deshwal, S., Fiedler, K. U. & Langer, T. Mitochondrial proteases: multifaceted regulators of mitochondrial plasticity. Annu. Rev. Biochem. 89, 501–528 (2020). sourceNot checked yet

  Not checked in the free run.

• cites [2] Quirós, P. M., Langer, T. & López-Otín, C. New roles for mitochondrial proteases in health, ageing and disease. Nat. Rev. Mol. Cell Biol. 16, 345–359 (2015). sourceNot checked yet

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• cites [3] Song, J., Herrmann, J. M. & Becker, T. Quality control of the mitochondrial proteome. Nat. Rev. Mol. Cell Biol. 22, 54–70 (2021). sourceNot checked yet

  Not checked in the free run.

• cites [4] Gan, Z., Fu, T., Kelly, D. P. & Vega, R. B. Skeletal muscle mitochondrial remodeling in exercise and diseases. Cell Res. 28, 969–980 (2018). sourceNot checked yet

  Not checked in the free run.

May combine two claims.

LONP1 is a major mitochondrial protease located in the mitochondrial matrix.

“LONP1, a major mitochondrial protease resides in the matrix”

• Also stated in: § Introduction · plain

  “ATP-dependent mitochondrial proteases Lon protease homolog (LONP1) and Clp protease proteolytic subunit (CLPP), stationed in the mitochondrial matrix, are the center of mitochondrial protein quality control1–4.”

• cites [1] Deshwal, S., Fiedler, K. U. & Langer, T. Mitochondrial proteases: multifaceted regulators of mitochondrial plasticity. Annu. Rev. Biochem. 89, 501–528 (2020). sourceNot checked yet

  Not checked in the free run.

• cites [2] Quirós, P. M., Langer, T. & López-Otín, C. New roles for mitochondrial proteases in health, ageing and disease. Nat. Rev. Mol. Cell Biol. 16, 345–359 (2015). sourceNot checked yet

  Not checked in the free run.

• cites [3] Song, J., Herrmann, J. M. & Becker, T. Quality control of the mitochondrial proteome. Nat. Rev. Mol. Cell Biol. 22, 54–70 (2021). sourceNot checked yet

  Not checked in the free run.

• cites [4] Gan, Z., Fu, T., Kelly, D. P. & Vega, R. B. Skeletal muscle mitochondrial remodeling in exercise and diseases. Cell Res. 28, 969–980 (2018). sourceNot checked yet

  Not checked in the free run.

Classified as probably not a substantial claim.

Skeletal muscle mass is controlled by a fine balance between protein synthesis and protein degradation processes triggered by changes in physical activity.

“Skeletal muscle mass is controlled by a fine balance between protein synthesis and protein degradation processes triggered by changes in physical activity11,14,15, yet the intrinsic muscular signaling networks driving muscle mass loss particularly during the early phase of muscle disuse remain unclear.”

• cites [11] Rüegg, M. A. & Glass, D. J. Molecular mechanisms and treatment options for muscle wasting diseases. Annu. Rev. Pharm. Toxicol. 51, 373–395 (2011). sourceNot checked yet

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• cites [14] Cohen, S., Nathan, J. A. & Goldberg, A. L. Muscle wasting in disease: molecular mechanisms and promising therapies. Nat. Rev. Drug Discov. 14, 58–74 (2015). sourceNot checked yet

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• cites [15] Egerman, M. A. & Glass, D. J. Signaling pathways controlling skeletal muscle mass. Crit. Rev. Biochem. Mol. Biol. 49, 59–68 (2014). sourceNot checked yet

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May combine two claims.

Skeletal muscle-specific ablation of LONP1 in mice results in impaired mitochondrial protein turnover, leading to mitochondrial dysfunction.

“Skeletal muscle-specific ablation of LONP1 in mice resulted in impaired mitochondrial protein turnover, leading to mitochondrial dysfunction.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Physical inactivity-associated skeletal muscle loss and weakness is a major health problem and is a common consequence of a variety of disease conditions, including bed rest, chronic illness, and neuromuscular disorders.

“Indeed, physical inactivity-associated skeletal muscle loss and weakness is a major health problem and is a common consequence of a variety of disease conditions, including bed rest, chronic illness, and neuromuscular disorders4,7,9–11, whereas exercise is effective in counteracting the effects of many chronic diseases on muscle mass and function4,12,13.”

• cites [4] Gan, Z., Fu, T., Kelly, D. P. & Vega, R. B. Skeletal muscle mitochondrial remodeling in exercise and diseases. Cell Res. 28, 969–980 (2018). sourceNot checked yet

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• cites [7] Segalés, J. et al. Sestrin prevents atrophy of disused and aging muscles by integrating anabolic and catabolic signals. Nat. Commun. 11, 189 (2020). sourceNot checked yet

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• cites [9] Wall, B. T., Dirks, M. L. & van Loon, L. J. Skeletal muscle atrophy during short-term disuse: implications for age-related sarcopenia. Ageing Res. Rev. 12, 898–906 (2013). sourceNot checked yet

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• cites [10] Moresi, V. et al. Myogenin and class II HDACs control neurogenic muscle atrophy by inducing E3 ubiquitin ligases. Cell 143, 35–45 (2010). sourceNot checked yet

  Not checked in the free run.

• cites [11] Rüegg, M. A. & Glass, D. J. Molecular mechanisms and treatment options for muscle wasting diseases. Annu. Rev. Pharm. Toxicol. 51, 373–395 (2011). sourceNot checked yet

  Not checked in the free run.

May combine two claims.

LONP1-dependent mitochondrial protein quality-control safeguards mitochondrial function and preserves skeletal muscle mass and strength.

“Thus, these findings reveal a role of LONP1-dependent mitochondrial protein quality-control in safeguarding mitochondrial function and preserving skeletal muscle mass and strength, and unravel a link between mitochondrial protein quality and muscle mass maintenance during muscle disuse.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Mutations in LONP1 have been implicated in CODAS syndrome, a human genetic disease that causes multisystem malfunctions.

“Mutations in LONP1 have been implicated in CODAS syndrome, a human genetic disease that causes multisystem malfunctions19, whereas changes in the expression levels of LONP1 under cellular stress conditions have also been reported1,2,”

• cites [19] Strauss, K. A. et al. CODAS syndrome is associated with mutations of LONP1, encoding mitochondrial AAA+ Lon protease. Am. J. Hum. Genet. 96, 121–135 (2015). sourceNot checked yet

  Not checked in the free run.

May combine two claims.

LONP1 plays a role in controlling mitochondrial function as well as skeletal muscle mass and strength in response to muscle disuse.

“Here, we demonstrate that LONP1, a major mitochondrial protease resides in the matrix, plays a role in controlling mitochondrial function as well as skeletal muscle mass and strength in response to muscle disuse.”

• AssumptionRests on an assumption: The physiological relevance of stress-induced impaired or dysregulated mitochondrial protein quality control remains unclear.
• AssumptionRests on an assumption: It has yet to be explored whether LONP1-mediated mitochondrial protein quality control plays a role in sensing skeletal muscle stress and regulating its function.

Probably not a substantial claim: may not pass S3 (load-bearing).

In mammals, several mitochondrial regulatory proteins such as aconitase (ACO), cytochrome c oxidase isoform (Cox4i1), steroidogenic acute regulatory protein (STAR), and transcription factor A (TFAM) have been identified as LONP1 substrates under basal or stress conditions.

“In mammals, several mitochondrial regulatory proteins such as aconitase (ACO), cytochrome c oxidase isoform (Cox4i1), steroidogenic acute regulatory protein (STAR), and transcription factor A (TFAM) have been identified as LONP1 substrates under basal or stress conditions2,4,16,17.”

• cites [2] Quirós, P. M., Langer, T. & López-Otín, C. New roles for mitochondrial proteases in health, ageing and disease. Nat. Rev. Mol. Cell Biol. 16, 345–359 (2015). sourceNot checked yet

  Not checked in the free run.

• cites [4] Gan, Z., Fu, T., Kelly, D. P. & Vega, R. B. Skeletal muscle mitochondrial remodeling in exercise and diseases. Cell Res. 28, 969–980 (2018). sourceNot checked yet

  Not checked in the free run.

• cites [16] Bota, D. A. & Davies, K. J. Lon protease preferentially degrades oxidized mitochondrial aconitase by an ATP-stimulated mechanism. Nat. Cell Biol. 4, 674–680 (2002). sourceNot checked yet

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• cites [17] Lu, B. et al. Phosphorylation of human TFAM in mitochondria impairs DNA binding and promotes degradation by the AAA+ Lon protease. Mol. Cell 49, 121–132 (2013). sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Changes in the expression levels of LONP1 under cellular stress conditions have been reported.

“whereas changes in the expression levels of LONP1 under cellular stress conditions have also been reported1,2,”

• cites [1] Deshwal, S., Fiedler, K. U. & Langer, T. Mitochondrial proteases: multifaceted regulators of mitochondrial plasticity. Annu. Rev. Biochem. 89, 501–528 (2020). sourceNot checked yet

  Not checked in the free run.

• cites [2] Quirós, P. M., Langer, T. & López-Otín, C. New roles for mitochondrial proteases in health, ageing and disease. Nat. Rev. Mol. Cell Biol. 16, 345–359 (2015). sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Embryonic lethality of mice with deletion of the Lonp1 gene highlights the essential role of LONP1 for life.

“The embryonic lethality of mice with deletion of the Lonp1 gene further highlighted the essential role of LONP1 for life18.”

• cites [18] Quirós, P. M. et al. ATP-dependent Lon protease controls tumor bioenergetics by reprogramming mitochondrial activity. Cell Rep. 8, 542–556 (2014). sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

LONP1 is an evolutionarily conserved serine peptidase that controls mitochondrial protein quality from yeast to human.

“LONP1 is an evolutionarily conserved serine peptidase that controls mitochondrial protein quality from yeast to human1–4.”

• cites [1] Deshwal, S., Fiedler, K. U. & Langer, T. Mitochondrial proteases: multifaceted regulators of mitochondrial plasticity. Annu. Rev. Biochem. 89, 501–528 (2020). sourceNot checked yet

  Not checked in the free run.

• cites [2] Quirós, P. M., Langer, T. & López-Otín, C. New roles for mitochondrial proteases in health, ageing and disease. Nat. Rev. Mol. Cell Biol. 16, 345–359 (2015). sourceNot checked yet

  Not checked in the free run.

• cites [3] Song, J., Herrmann, J. M. & Becker, T. Quality control of the mitochondrial proteome. Nat. Rev. Mol. Cell Biol. 22, 54–70 (2021). sourceNot checked yet

  Not checked in the free run.

• cites [4] Gan, Z., Fu, T., Kelly, D. P. & Vega, R. B. Skeletal muscle mitochondrial remodeling in exercise and diseases. Cell Res. 28, 969–980 (2018). sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Loss of LONP1 causes reduced muscle fiber size and strength.

“This caused reduced muscle fiber size and strength.”

May combine two claims.

Loss of LONP1 alters skeletal muscle mitochondrial function without affecting mitochondrial biogenesis.

“These data indicate that loss of LONP1 alters skeletal muscle mitochondrial function without affecting mitochondrial biogenesis.”

May combine two claims.

Absence of muscle LONP1 changes muscle fiber size and strength and compromises muscle performance.

“Together, these results demonstrate a change in muscle fiber size and strength in the absence of muscle LONP1 that compromises muscle performance.”

May combine two claims.

LONP1 ablation does not affect muscle protein synthesis and ubiquitin-mediated protein degradation.

“Together, these data indicate that LONP1 ablation does not affect muscle protein synthesis and ubiquitin-mediated protein degradation.”

May combine two claims.

Loss of LONP1 results in impaired muscle growth and muscle weakness.

“Thus, loss of LONP1 results in impaired muscle growth and muscle weakness.”

May combine two claims.

Down-regulation of mitochondrial LONP1, along with impaired mitochondrial protein turnover, accompanies the process of disuse-induced skeletal muscle loss.

“Thus, these data demonstrate that down-regulation of the mitochondrial LONP1, along with impaired mitochondrial protein turnover, accompanies the process of disuse-induced skeletal muscle loss.”

May combine two claims.

LONP1 mKO mice consume less fat and depend on glucose metabolism more than WT controls during exercise.

“Because a higher RER typically reflects a substrate shift in favor of carbohydrate metabolism, these data suggest that LONP1 mKO mice consume less fat and depend on glucose metabolism more than WT controls during exercise.”

May combine two claims.

Ablation of Lonp1 neither affects muscle differentiation nor development.

“These results indicate that ablation of Lonp1 neither affects muscle differentiation nor development.”

May combine two claims.

Loss of LONP1 in mature muscles also causes autophagy activation and muscle loss.

“Therefore, loss of LONP1 in mature muscles also causes autophagy activation and muscle loss.”

May combine two claims.

Loss of LONP1-dependent mitochondrial protein quality-control in skeletal muscle triggers autophagy degradation program, leading to profound impacts on muscle mass and strength.

“We found that loss of LONP1-dependent mitochondrial protein quality-control in skeletal muscle triggers autophagy degradation program, leading to profound impacts on muscle mass and strength.”

May combine two claims.

Overexpressing a mitochondrial-retained ΔOTC protein in skeletal muscle is sufficient to induce mitochondrial dysfunction, autophagy activation, and causes muscle atrophy and weakness.

“overexpressing a mitochondrial-retained ΔOTC protein in skeletal muscle is sufficient to induce mitochondrial dysfunction, autophagy activation, and causes muscle atrophy and weakness.”

May combine two claims.

Deletion of LONP1 specifically in skeletal muscle results in impaired mitochondrial protein turnover, leading to mitochondrial dysfunction and significantly reduced muscle mass and strength.

“Deletion of LONP1 specifically in skeletal muscle resulted in impaired mitochondrial protein turnover, leading to mitochondrial dysfunction and significant reduced muscle mass and strength.”

May combine two claims.

Muscle-specific overexpression of mitochondrial-retained ΔOTC protein activates autophagy and causes muscle loss, revealing physiological relevance of imbalanced mitochondrial proteostasis.

“Our findings that muscle-specific overexpressing mitochondrial-retained ΔOTC protein activates autophagy and causes muscle loss revealed an important physiological relevance of imbalanced mitochondrial proteostasis.”

May combine two claims.

ΔOTC is a known protein degraded by LONP1 and an established model for studying mitochondrial proteostasis imbalance.

“a known protein degraded by LONP1 and an established model for studying mitochondrial proteostasis imbalance38–40”

• cites [38] Zhao, Q. et al. A mitochondrial specific stress response in mammalian cells. EMBO J. 21, 4411–4419 (2002). sourceNot checked yet

  Not checked in the free run.

• cites [39] Jin, S. M. & Youle, R. J. The accumulation of misfolded proteins in the mitochondrial matrix is sensed by PINK1 to induce PARK2/Parkin-mediated mitophagy of polarized mitochondria. Autophagy 9, 1750–1757 (2013). sourceNot checked yet

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• cites [40] Bezawork-Geleta, A., Brodie, E. J., Dougan, D. A. & Truscott, K. N. LON is the master protease that protects against protein aggregation in human mitochondria through direct degradation of misfolded proteins. Sci. Rep. 5, 17397 (2015). sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Proper maintenance of mitochondria dynamics, i.e. the balance between fission and fusion, is necessary for optimal muscle mitochondrial function and fitness.

“proper maintenance of mitochondria dynamics, i.e. the balance between fission and fusion, is necessary for optimal muscle mitochondrial function and fitness20–23,43.”

• cites [20] Chen, H. et al. Mitochondrial fusion is required for mtDNA stability in skeletal muscle and tolerance of mtDNA mutations. Cell 141, 280–289 (2010). sourceNot checked yet

  Not checked in the free run.

• cites [21] Pereira, R. O. et al. OPA1 deficiency promotes secretion of FGF21 from muscle that prevents obesity and insulin resistance. EMBO J. 36, 2126–2145 (2017). sourceNot checked yet

  Not checked in the free run.

• cites [22] Rodríguez-Nuevo, A. et al. Mitochondrial DNA and TLR9 drive muscle inflammation upon Opa1 deficiency. EMBO J. 37, https://doi.org/10.15252/embj.201796553 (2018). sourceNot checked yet

  Not checked in the free run.

• cites [23] Tezze, C. et al. Age-associated loss of OPA1 in muscle impacts muscle mass, metabolic homeostasis, systemic inflammation, and epithelial senescence. Cell Metab. 25, 1374–1389.e1376 (2017). sourceNot checked yet

  Not checked in the free run.

• cites [43] Sebastián, D. et al. Mfn2 deficiency links age-related sarcopenia and impaired autophagy to activation of an adaptive mitophagy pathway. EMBO J. 35, 1677–1693 (2016). sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Most of these findings are recapitulated in skeletal myotubes, thus are cell-autonomous.

“most of these findings are recapitulated in skeletal myotubes, thus, are cell-autonomous.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Heatmap analysis of duplicate samples showed similarity between replicates.

“the heatmap analysis of the duplicate samples showed the similarity between replicates (Fig. 6d).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Mitochondrial energetic deficiency can trigger compensatory muscle fiber type switching.

“mitochondrial energetic deficiency can trigger compensatory muscle fiber type switching42.”

• cites [42] Zechner, C. et al. Total skeletal muscle PGC-1 deficiency uncouples mitochondrial derangements from fiber type determination and insulin sensitivity. Cell Metab. 12, 633–642 (2010). sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

OPA1 has important roles in regulating skeletal muscle mass and functions.

“Both transgenic and gene knockout approaches in mice have also been used to demonstrate the important roles of OPA1 in regulating skeletal muscle mass and functions23,44,45.”

• cites [23] Tezze, C. et al. Age-associated loss of OPA1 in muscle impacts muscle mass, metabolic homeostasis, systemic inflammation, and epithelial senescence. Cell Metab. 25, 1374–1389.e1376 (2017). sourceNot checked yet

  Not checked in the free run.

• cites [44] Civiletto, G. et al. Opa1 overexpression ameliorates the phenotype of two mitochondrial disease mouse models. Cell Metab. 21, 845–854 (2015). sourceNot checked yet

  Not checked in the free run.

• cites [45] Varanita, T. et al. The OPA1-dependent mitochondrial cristae remodeling pathway controls atrophic, apoptotic, and ischemic tissue damage. Cell Metab. 21, 834–844 (2015). sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Muscle LONP1 likely serves as a mitochondrial sensor sensitive to changes in physical activity levels, linking maintenance of mitochondrial protein quality and muscle mass to physical activity.

“our data suggest that muscle LONP1 likely serves as a mitochondrial sensor that is sensitive to changes in physical activity levels, linking maintenance of mitochondrial protein quality and muscle mass to physical activity.”

May combine two claims.

Genetic ablation of LONP1 in skeletal muscle results in severe mitochondrial dysfunction and causes reduced muscle fiber size and strength, leading to a precocious aging phenotype.

“Genetic ablation of LONP1 in skeletal muscle resulted in severe mitochondrial dysfunction and caused reduced muscle fiber size and strength, leading to a precocious aging phenotype.”

May combine two claims.

PARK7 mediates autophagy activation in LONP1-deficient cells, linking LONP1-dependent mitochondrial proteostasis to muscle cell autophagy.

“Thus, PARK7 mediates autophagy activation in LONP1-deficient cells, thereby linking LONP1-dependent mitochondrial proteostasis to muscle cell autophagy.”

Classified as probably not a substantial claim. May combine two claims.

PARK7 was recently shown to regulate autophagy and be degraded by LONP1.

“was recently shown to regulate autophagy and degraded by LONP134–37.”

• cites [34] Gao, H. et al. DJ-1 protects dopaminergic neurons against rotenone-induced apoptosis by enhancing ERK-dependent mitophagy. J. Mol. Biol. 423, 232–248 (2012). sourceNot checked yet

  Not checked in the free run.

• cites [35] Xue, R. et al. DJ-1 activates autophagy in the repression of cardiac hypertrophy. Arch. Biochem. Biophys. 633, 124–132 (2017). sourceNot checked yet

  Not checked in the free run.

• cites [36] Lee, D. H. et al. PARK7 modulates autophagic proteolysis through binding to the N-terminally arginylated form of the molecular chaperone HSPA5. Autophagy 14, 1870–1885 (2018). sourceNot checked yet

  Not checked in the free run.

• cites [37] Sánchez-Lanzas, R. & Castaño, J. G. Mitochondrial LonP1 protease is implicated in the degradation of unstable Parkinson’s disease-associated DJ-1/PARK 7 missense mutants. Sci. Rep. 11, 7320 (2021). sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

This LONP1 mechanism likely acts as a mitochondrial sensor of cellular stress under diverse physiological and pathophysiological circumstances.

“This LONP1 mechanism likely acts as a mitochondrial sensor of cellular stress under an array of diverse physiological and pathophysiological circumstances.”

May combine two claims.

Denervation-induced muscle disuse leads to suppressed expression of LONP1 with increased muscle autophagy and mitochondrial dysfunction.

“Our data indicate that denervation-induced muscle disuse leads to suppressed expression of LONP1 with increased muscle autophagy and mitochondrial dysfunction, which is consistent with our observations in LONP1 mKO mice.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Multiple alterations in mitochondrial function such as mitophagy and mitochondrial dynamics can lead to reduced muscle mitochondrial energetics but resistance to high-fat-diet-induced obesity.

“multiple alterations in mitochondrial function such as mitophagy and mitochondrial dynamics can lead to a surprising phenotype characterized by reduced muscle mitochondrial energetics, but remarkably, with resistance to high-fat-diet-induced obesity21,46.”

• cites [21] Pereira, R. O. et al. OPA1 deficiency promotes secretion of FGF21 from muscle that prevents obesity and insulin resistance. EMBO J. 36, 2126–2145 (2017). sourceNot checked yet

  Not checked in the free run.

• cites [46] Fu, T. et al. Mitophagy directs muscle-adipose crosstalk to alleviate dietary obesity. Cell Rep. 23, 1357–1372 (2018). sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Muscle-specific overexpression of mitochondrial-retained ΔOTC protein is sufficient to induce mitochondrial dysfunction, autophagy activation, and cause muscle loss and weakness.

“Together, these data demonstrate that muscle-specific overexpressing mitochondrial-retained ΔOTC protein is sufficient to induce mitochondrial dysfunction, autophagy activation, and cause muscle loss and weakness.”

Probably not a substantial claim: may not pass S3 (load-bearing).

All animal studies were approved by the IACUC committees at the Model Animal Research Center (MARC) of Nanjing University (Approval No. GZJ07).

“were approved by the IACUC committees at the Model Animal Research Center (MARC) of Nanjing University (Approval No. GZJ07).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Two independent samples per group were analyzed in the RNA-seq study.

“Two independent samples per group were analyzed.”

Probably not a substantial claim: may not pass S3 (load-bearing).

False discovery rate thresholds for both protein and peptide were specified at 1%.

“False discovery rate (FDR) thresholds for both protein and peptide were specified at 1%.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Arbitrary units of target mRNA were corrected to the expression of 36b4.

“Arbitrary units of target mRNA were corrected to the expression of 36b4.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The seemingly contradictory phenotype is linked to the non-cell-autonomous role of the muscle mitochondrial stress response.

“The seemingly contradictory phenotype is linked to the non-cell-autonomous role of the muscle mitochondrial stress response.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Identical acquisition parameters were set for all samples in the same experimental condition.

“Identical acquisition parameters were set for all samples in the same experimental condition.”

• Also stated in: § Measuring in vivo mitochondrial protein turnover · plain

  “Identical acquisition parameters were set for all samples in the same experimental condition.”

Classified as probably not a substantial claim.

The immobilization procedure (splint with Velcro loop) prevents knee bending.

“This procedure prevents knee bending, and the non-immobilized hindlimb served as controls.”

Classified as probably not a substantial claim.

Autophagy is critical for maintaining normal homeostasis of muscle mass in physiological and pathological conditions.

“autophagy is critical for maintaining normal homeostasis of muscle mass in physiological and pathological conditions30,47–49.”

• cites [30] Mammucari, C. et al. FoxO3 controls autophagy in skeletal muscle in vivo. Cell Metab. 6, 458–471 (2007). sourceNot checked yet

  Not checked in the free run.

• cites [47] Masiero, E. et al. Autophagy is required to maintain muscle mass. Cell Metab. 10, 507–515 (2009). sourceNot checked yet

  Not checked in the free run.

• cites [48] Castets, P. et al. Sustained activation of mTORC1 in skeletal muscle inhibits constitutive and starvation-induced autophagy and causes a severe, late-onset myopathy. Cell Metab. 17, 731–744 (2013). sourceNot checked yet

  Not checked in the free run.

• cites [49] Moresi, V. et al. Histone deacetylases 1 and 2 regulate autophagy flux and skeletal muscle homeostasis in mice. Proc. Natl Acad. Sci. USA 109, 1649–1654 (2012). sourceNot checked yet

  Not checked in the free run.

Classified as probably not a substantial claim.

Equal total protein was loaded to each lane.

“Equal total protein was loaded to each lane.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The levels of NADH dehydrogenase subunit 1 (mitochondrial DNA) were normalized to the levels of lipoprotein lipase (genomic DNA).

“The levels of NADH dehydrogenase subunit 1 (mitochondrial DNA) were normalized to the levels of lipoprotein lipase (genomic DNA).”

Classified as probably not a substantial claim.

Littermate controls were used in all cases.

“Littermate controls were used in all cases.”

Classified as probably not a substantial claim.

Informed consent was obtained from all subjects.

“Informed consent was obtained from all subjects.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Average diameters of at least 100 myotubes were measured for each condition at three points along the length of the myotube.

“Average diameters of at least 100 myotubes were measured for each condition at three points along the length of the myotube.”

Classified as probably not a substantial claim. May combine two claims.

Muscle with an occupation ratio greater than 0.60 can be considered normal or non-atrophied, while values below 0.60 suggest muscle atrophy.

“the muscle with a ratio greater than 0.60 can be considered as normal or non-atrophied, while values below 0.60 suggest muscle atrophy27.”

• cites [27] Thomazeau, H., Rolland, Y., Lucas, C., Duval, J. M. & Langlais, F. Atrophy of the supraspinatus belly. Assessment by MRI in 55 patients with rotator cuff pathology. Acta Orthop. Scand. 67, 264–268 (1996). sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Three bright field images per dish were captured, randomized, and coded.

“Three bright field images per dish were captured, randomized, and coded.”

Probably not a substantial claim: may not pass S3 (load-bearing).

PARK7 protein regulates autophagy in multiple cell types.

“PARK7 protein has been shown to regulate autophagy in multiple cell types34–36.”

• cites [34] Gao, H. et al. DJ-1 protects dopaminergic neurons against rotenone-induced apoptosis by enhancing ERK-dependent mitophagy. J. Mol. Biol. 423, 232–248 (2012). sourceNot checked yet

  Not checked in the free run.

• cites [35] Xue, R. et al. DJ-1 activates autophagy in the repression of cardiac hypertrophy. Arch. Biochem. Biophys. 633, 124–132 (2017). sourceNot checked yet

  Not checked in the free run.

• cites [36] Lee, D. H. et al. PARK7 modulates autophagic proteolysis through binding to the N-terminally arginylated form of the molecular chaperone HSPA5. Autophagy 14, 1870–1885 (2018). sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Ubiquitin-proteasome-dependent degradation is important in muscle atrophy.

“The importance of ubiquitin-proteasome-dependent degradation in muscle atrophy has been well documented11,14,15.”

• cites [11] Rüegg, M. A. & Glass, D. J. Molecular mechanisms and treatment options for muscle wasting diseases. Annu. Rev. Pharm. Toxicol. 51, 373–395 (2011). sourceNot checked yet

  Not checked in the free run.

• cites [14] Cohen, S., Nathan, J. A. & Goldberg, A. L. Muscle wasting in disease: molecular mechanisms and promising therapies. Nat. Rev. Drug Discov. 14, 58–74 (2015). sourceNot checked yet

  Not checked in the free run.

• cites [15] Egerman, M. A. & Glass, D. J. Signaling pathways controlling skeletal muscle mass. Crit. Rev. Biochem. Mol. Biol. 49, 59–68 (2014). sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Transcriptome sequencing libraries averaged 42 million paired reads per sample, with 86.9% alignment to the mouse genome (UCSC mm10).

“Transcriptome sequencing libraries averaged 42 million paired reads per sample, with 86.9% alignment to the mouse genome (UCSC mm10).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Images were taken in a double-blind manner.

“Images were taken on a FEI Tecnai G2 20 Twin electron microscope equipped with an Eagle 4k CCD digital camera (FEI; USA) in a double-blind manner.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Dysfunctional mitochondrial subdomains can be segregated from mitochondria and degraded by autophagy under stress.

“dysfunctional mitochondrial subdomains can be segregated from mitochondria and degraded by autophagy under stress54.”

• cites [54] Burman, J. L. et al. Mitochondrial fission facilitates the selective mitophagy of protein aggregates. J. Cell Biol. 216, 3231–3247 (2017). sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Respiration rates were normalized to mitochondrial protein contents or cell number.

“Respiration rates were determined and normalized to mitochondrial protein contents or cell number using the Datlab 5 software (Oroboros Inc., Innsbruck, Austria), the data were expressed as “pmol O2 s−1 mg mito protein−1” or “pmol O2 s−1 10−6 cells”.”

Probably not a substantial claim: may not pass S3 (load-bearing).

All data points were used in statistical analyses.

“All data points were used in statistical analyses.”

Classified as probably not a substantial claim.

Clinical ethical approval was obtained from the Ethical Committee of Subei People's Hospital of Jiangsu Province, Yangzhou, China (Clinical ethical approval: 2021ky-001).

“Clinical ethical approval in comply with the Declaration of Helsinki was obtained from the Ethical Committee of Subei People’s Hospital of Jiangsu Province, Yangzhou, China (Clinical ethical approval: 2021ky-001).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Blots were normalized to α-tubulin.

“Blots were normalized to α-tubulin.”

May combine two claims.

LONP1-dependent mitochondrial protein quality control safeguards mitochondrial health and skeletal muscle mass and strength, linking mitochondrial protein quality and muscle mass maintenance upon muscle disuse.

“we have revealed a role of LONP1-dependent mitochondrial protein quality control in safeguarding mitochondrial health and skeletal muscle mass and strength, unraveling an unexpected functional link between mitochondrial protein quality and muscle mass maintenance upon muscle disuse.”

Probably not a substantial claim: may not pass S3 (load-bearing).

No statistical methods were used to predetermine sample sizes.

“No statistical methods were used to predetermine sample sizes, and sample size (range from n = 3 to n = 10) are explicitly stated in the figure legends.”

Probably not a substantial claim: may not pass S3 (load-bearing).

All constructs were confirmed by DNA sequencing.

“All constructs were confirmed by DNA sequencing.”

Classified as probably not a substantial claim.

Full-thickness rotator cuff tear was confirmed by arthroscopy before supraspinatus muscle biopsies were taken.

“After confirmation for full-thickness rotator cuff tear by arthroscopy, supraspinatus muscle biopsies were taken at 2 cm proximal zone of muscle–tendon junction during rotator cuff repair surgery, cleaned, and flash frozen in liquid nitrogen for protein isolation.”

Probably not a substantial claim: may not pass S3 (load-bearing).

A previous study has reported a reproducible and reliable method to define supraspinatus muscle atrophy with MRI.

“A previous study has reported a reproducible and reliable method to define supraspinatus muscle atrophy with the help of MRI27.”

• cites [27] Thomazeau, H., Rolland, Y., Lucas, C., Duval, J. M. & Langlais, F. Atrophy of the supraspinatus belly. Assessment by MRI in 55 patients with rotator cuff pathology. Acta Orthop. Scand. 67, 264–268 (1996). sourceNot checked yet

  Not checked in the free run.