Adiponectin receptor agonist AdipoRon improves skeletal muscle function in aged mice

  1. Priya Balasubramanian
  2. Anne E Schaar
  3. Grace E Gustafson
  4. Alex B Smith
  5. Porsha R Howell
  6. Angela Greenman
  7. Scott Baum
  8. Ricki J Colman
  9. Dudley W Lamming
  10. Gary M Diffee
  11. Rozalyn M Anderson

  • Curated by eLife

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    Evaluation Summary:

    In this manuscript, the authors provide promising results for the treatment of age-related sarcopenia with AdipoRon, a drug that targets the receptors for adiponectin. This is a well done study using an agonist (AdipoRon) involved in lipid and mitochondrial metabolism regulation to mitigate age related muscle loss in mice.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)

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Abstract

The loss of skeletal muscle function with age, known as sarcopenia, significantly reduces independence and quality of life and can have significant metabolic consequences. Although exercise is effective in treating sarcopenia it is not always a viable option clinically, and currently, there are no pharmacological therapeutic interventions for sarcopenia. Here, we show that chronic treatment with pan-adiponectin receptor agonist AdipoRon improved muscle function in male mice by a mechanism linked to skeletal muscle metabolism and tissue remodeling. In aged mice, 6 weeks of AdipoRon treatment improved skeletal muscle functional measures in vivo and ex vivo. Improvements were linked to changes in fiber type, including an enrichment of oxidative fibers, and an increase in mitochondrial activity. In young mice, 6 weeks of AdipoRon treatment improved contractile force and activated the energy-sensing kinase AMPK and the mitochondrial regulator PGC-1a (peroxisome proliferator-activated receptor gamma coactivator one alpha). In cultured cells, the AdipoRon induced stimulation of AMPK and PGC-1a was associated with increased mitochondrial membrane potential, reorganization of mitochondrial architecture, increased respiration, and increased ATP production. Furthermore, the ability of AdipoRon to stimulate AMPK and PGC1a was conserved in nonhuman primate cultured cells. These data show that AdipoRon is an effective agent for the prevention of sarcopenia in mice and indicate that its effects translate to primates, suggesting it may also be a suitable therapeutic for sarcopenia in clinical application.

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  1. Version published to 10.7554/elife.71282 on eLife
  2. eLife

    Author Response

    Evaluation Summary:

    In this manuscript, the authors provide promising results for the treatment of age-related sarcopenia with AdipoRon, a drug that targets the receptors for adiponectin. This is a well done study using an agonist (AdipoRon) involved in lipid and mitochondrial metabolism regulation to mitigate age related muscle loss in mice.

    Thank you for these positive comments – we are excited about the potential of this agent as a means to prevent and treat sarcopenia.

    Reviewer #1 (Public Review):

    Strengths and Accomplishments:

    1. This study tests an exciting potential intervention for sarcopenia, is well supported by prior literature investigating the effects of AdipoRon in age-related metabolic diseases, and now extends these data into aging.
    1. The study uses a diversity of techniques and systems (in vitro, in vivo, and ex vivo, chronic and acute treatments, young and old mice) to investigate the effects and relevant mechanisms of AdipoRon from the level of the whole organism into the muscle fibers and further into cellular signaling pathways.
    1. Similar cellular findings across species and cell types argues for strong conservation of the downstream effects of AdipoRon.
    1. This study provides coherent and conserved downstream molecular mechanisms (e.g. PGC-1a) and physiological changes (fiber types, mitochondrial function, insulin sensitivity) that should be readily translatable into mechanistically-designed non-human primate and human clinical studies.
    1. The presentation is well organized and logical, showing the effects of chronic AdipoRon treatment in old and then young male mice, followed by acute treatment in young mice and cells, moving from clinical to physiological to cellular/molecular findings.

    We thank the reviewer for these comments and are eager to continue our work in this area – the absence of a pharmacological agent to treat sarcopenia is a major gap in geriatric and rehabilitation medicine.

    Weaknesses and Limitations:

    1. The key mouse studies are underpowered, resulting in inconclusive rotarod data in the aged group and no behavioral testing in the young group. There is no other whole-organism functional data to support the clinical relevance of the ex vivo and postmortem physiological and molecular findings.

    We acknowledge that this study is a first step toward identifying an agent to prevent and treat sarcopenia. As this reviewer will appreciate it can be challenging to overcome the natural increase in variance that occurs with age, the upshot is that the magnitude of effect needs to be quite large to find statistically significant outcomes when conducting comparisons among aged animals. We are careful to distinguish between statistically significant differences and those that are numerically different. We would argue that the absence of statistical significance does not mean that an observation is not informative or biologically meaningful. We would like to add that the data described here prompted a follow up study in male and female mice where our plans include more extensive investigation of the functional, tissue-level, and systemic outcomes of AdipoRon treatment. In addition, we have applied for funding to support a nonhuman primate study on the impact of AdipoRon on sarcopenia, physical function, and metabolism, that we anticipate will have greater translational value.

    1. The in vitro cellular use fibroblasts and immune cells, which supports an argument for broad conservation of AdipoRon mechanisms but does not directly support the primary muscle physiological findings.

    The purpose of including the cell culture experiments was to define the cellular response to AdipoRon and to determine whether indices such as gene expression that hinted at changes in metabolism were actually associated with functional differences in cellular energetics. In response to this comment and comments from the other reviewers, we have conducted experiments in differentiated C2C12 myotubes and confirm that the molecular signatures initially reported in the fibroblasts and primate PBMCs are also induced in the murine myotube culture model in response to AdipoRon. We fully acknowledge that differentiated C2C12, being “muscle like”, are a better model for interrogating the mechanisms of AdipoRon action as they relate to skeletal muscle specifically.

    1. Using different strains for young and old mice limits the interpretation of young vs old differences, which could be due to strain differences instead.

    We appreciate this point; at the time that this work was undertaken we were constrained by what was available. We would note that we see the same responses to AdipoRon in our ongoing study that was conducted in a C3B6F1 hybrid line and included mice of 6, 22, and 28 months of age. We are confident that the results described here are genuinely reflective of the actions of AdipoRon as a function of age of the treated mouse and not due to differences in mouse genetic background.

    Reviewer #2 (Public Review):

    This is a straightforward study, demonstrating utility of an agonist targeting energy metabolism pathways in aging mouse muscle. Rather than the treatment improving muscle function generally, it appears selective to muscles predominantly affected by age-related muscle loss (type II fibers). As the authors acknowledge, these results need to be replicated in females, as they only looked at male mice.

    We agree that it will be important to follow up this study using a cohort with males and females (see response to Reviewer 1 comment 1 above). Interestingly, our nonhuman primate studies have indicated that there is sex dimorphism in skeletal muscle aging. Males are bulkier and with greater gains there are apparently greater losses as the animals advance in age. The females show less of a decline in total muscle with age than males in terms of DEXA estimates of appendicular muscle bulk; however, at the cellular and molecular level it is clear that aging is having an impact. We have identified improvements in metabolic indices including fasting insulin and RER in mice treated with AdipoRon, and improvement in endurance treadmill performance that was significant in AdipoRon treated males. That study, that includes more animals and two aging time points, will allow for detailed tissue and molecular level analysis so that we can identify which processes are sensitive to aging and to AdipoRon and track those pathways against physical performance at the individual level.

    Reviewer #3 (Public Review):

    In this manuscript the authors sought to investigate whether an adiponectin-receptor agonist could reduce the incidence of sarcopenia in aged mice. The authors provide compelling evidence that AdipoRon improves skeletal muscle function in aged mice, remodels muscle fibers, and appears to improve mitochondrial function at least in vitro.

    The authors provide multiple lines of evidence for the effects of AdipoRon, from live measurements of muscle function in aged rodents, to ex-vivo muscle activity assays, to in vitro assessment of mitochondrial function and activation of pathways involved in mitochondrial remodeling.

    The experiments complement one another very well, though it is unclear why two different strains were used for young and old mice, nor why the analysis was restricted to male animals only.

    Overall, the study details a promising intervention to restore muscle function in elderly individuals and identifies a druggable pathway that can be exploited for this goal.

    We thank the reviewer for these positive remarks. We acknowledge the limitation of looking only at male mice at this stage and have undertaken a follow up study that includes both sexes. The use of AdipoRon was inspired by our work in caloric restriction where adiponectin increase is a hallmark of CR in rodents and in nonhuman primates. At the time that this work began we had access to these aged male mice from NIA but the young mice came from an internal colony. We are eager to share these data in the hope that others will be interested in testing AdipoRon as a means to prevent or treat sarcopenia and would love to see studies in rehabilitative research being undertaken too.

  3. eLife

    Evaluation Summary:

    In this manuscript, the authors provide promising results for the treatment of age-related sarcopenia with AdipoRon, a drug that targets the receptors for adiponectin. This is a well done study using an agonist (AdipoRon) involved in lipid and mitochondrial metabolism regulation to mitigate age related muscle loss in mice.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)

  4. eLife

    Reviewer #1 (Public Review):

    Strengths and Accomplishments:

    1. This study tests an exciting potential intervention for sarcopenia, is well supported by prior literature investigating the effects of AdipoRon in age-related metabolic diseases, and now extends these data into aging.
    2. The study uses a diversity of techniques and systems (in vitro, in vivo, and ex vivo, chronic and acute treatments, young and old mice) to investigate the effects and relevant mechanisms of AdipoRon from the level of the whole organism into the muscle fibers and further into cellular signaling pathways.
    3. Similar cellular findings across species and cell types argues for strong conservation of the downstream effects of AdipoRon.
    4. This study provides coherent and conserved downstream molecular mechanisms (e.g. PGC-1a) and physiological changes (fiber types, mitochondrial function, insulin sensitivity) that should be readily translatable into mechanistically-designed non-human primate and human clinical studies.
    5. The presentation is well organized and logical, showing the effects of chronic AdipoRon treatment in old and then young male mice, followed by acute treatment in young mice and cells, moving from clinical to physiological to cellular/molecular findings.

    Weaknesses and Limitations:

    1. The key mouse studies are underpowered, resulting in inconclusive rotarod data in the aged group and no behavioral testing in the young group. There is no other whole-organism functional data to support the clinical relevance of the ex vivo and postmortem physiological and molecular findings.
    2. The in vitro cellular use fibroblasts and immune cells, which supports an argument for broad conservation of AdipoRon mechanisms but does not directly support the primary muscle physiological findings.
    3. Using different strains for young and old mice limits the interpretation of young vs old differences, which could be due to strain differences instead.
  5. eLife

    Reviewer #2 (Public Review):

    This is a straightforward study, demonstrating utility of an agonist targeting energy metabolism pathways in aging mouse muscle. Rather than the treatment improving muscle function generally, it appears selective to muscles predominantly affected by age-related muscle loss (type II fibers). As the authors acknowledge, these results need to be replicated in females, as they only looked at male mice.

  6. eLife

    Reviewer #3 (Public Review):

    In this manuscript the authors sought to investigate whether an adiponectin-receptor agonist could reduce the incidence of sarcopenia in aged mice. The authors provide compelling evidence that AdipoRon improves skeletal muscle function in aged mice, remodels muscle fibers, and appears to improve mitochondrial function at least in vitro.

    The authors provide multiple lines of evidence for the effects of AdipoRon, from live measurements of muscle function in aged rodents, to ex-vivo muscle activity assays, to in vitro assessment of mitochondrial function and activation of pathways involved in mitochondrial remodeling.

    The experiments complement one another very well, though it is unclear why two different strains were used for young and old mice, nor why the analysis was restricted to male animals only.

    Overall, the study details a promising intervention to restore muscle function in elderly individuals and identifies a druggable pathway that can be exploited for this goal.

  7. Version published to 10.1101/2021.09.16.460597v1 on bioRxiv