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Single swim sessions in C. elegans induce key features of mammalian exercise

View Article: PubMed Central - PubMed

ABSTRACT

Background: Exercise exerts remarkably powerful effects on metabolism and health, with anti-disease and anti-aging outcomes. Pharmacological manipulation of exercise benefit circuits might improve the health of the sedentary and the aging populations. Still, how exercised muscle signals to induce system-wide health improvement remains poorly understood. With a long-term interest in interventions that promote animal-wide health improvement, we sought to define exercise options for Caenorhabditis elegans.

Results: Here, we report on the impact of single swim sessions on C. elegans physiology. We used microcalorimetry to show that C. elegans swimming has a greater energy cost than crawling. Animals that swam continuously for 90 min specifically consumed muscle fat supplies and exhibited post-swim locomotory fatigue, with both muscle fat depletion and fatigue indicators recovering within 1 hour of exercise cessation. Quantitative polymerase chain reaction (qPCR) transcript analyses also suggested an increase in fat metabolism during the swim, followed by the downregulation of specific carbohydrate metabolism transcripts in the hours post-exercise. During a 90 min swim, muscle mitochondria matrix environments became more oxidized, as visualized by a localized mitochondrial reduction-oxidation-sensitive green fluorescent protein reporter. qPCR data supported specific transcriptional changes in oxidative stress defense genes during and immediately after a swim. Consistent with potential antioxidant defense induction, we found that a single swim session sufficed to confer protection against juglone-induced oxidative stress inflicted 4 hours post-exercise.

Conclusions: In addition to showing that even a single swim exercise bout confers physiological changes that increase robustness, our data reveal that acute swimming-induced changes share common features with some acute exercise responses reported in humans. Overall, our data validate an easily implemented swim experience as C. elegans exercise, setting the foundation for exploiting the experimental advantages of this model to genetically or pharmacologically identify the exercise-associated molecules and signaling pathways that confer system-wide health benefits.

Electronic supplementary material: The online version of this article (doi:10.1186/s12915-017-0368-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

C. elegans swim exercise increases muscle mitochondrial oxidation and induces a specific transcriptional oxidative stress response. a Relative mitochondrial oxidation level of Pmyo-3mito-roGFP-expressing animals at different time points post-exercise (higher 405/488 ratios indicate increased oxidation levels). We took confocal images of body wall muscle at both 405 nm and 488 nm excitation and used the mean fluorescence intensities of mitochondrial regions (40–50 regions per animal) to calculate the 405/488 ratios. Each point represents the 405/488 ratio average from a single animal (n = 60–63 animals); statistical significance was determined by unpaired two-tailed Student’s t test. b Heat map summarizing quantitative polymerase chain reaction results in N2 animals for commonly used stress reporter genes at different time points post-exercise (n = 5 independent trials). Expression data are presented as the log2 fold change of exercise samples relative to control samples in a color gradient from red (downregulation) to dark green (upregulation). White represents no change in expression levels. Paired two-tailed Student’s t tests were used to compare relative expressions of control versus exercise samples at each time point. See Additional file 1 and Additional file 4A–F for detailed results for each gene. c Percentage of surviving N2 animals during treatment with 3 mM juglone 4 hours post-exercise (n = 60 animals). d Average increase in percent survival during treatment with 3 mM juglone 4 hours post-exercise of N2, sod-3(tm760), sod-4(gk101), and sod-5(tm1146) exercised animals relative to control counterparts (n = 60 animals). The average increase in percent survival was calculated from all the time points between 15 and 45 min of treatment duration. Note that the reduced survival benefit of exercised sod-4 mutants was not due to a reduced swimming capacity relative to N2 and the other sod mutants. See Additional file 3B–D for detailed survival curves of sod mutants. Statistical significance in (c) and (d) determined by a log-rank test comparing control versus exercise survival curves. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. ER-UPR endoplasmic reticulum unfolded protein response, HSR heat shock response, ns, non-significant, mito-UPR mitochondrial unfolded protein response
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Fig3: C. elegans swim exercise increases muscle mitochondrial oxidation and induces a specific transcriptional oxidative stress response. a Relative mitochondrial oxidation level of Pmyo-3mito-roGFP-expressing animals at different time points post-exercise (higher 405/488 ratios indicate increased oxidation levels). We took confocal images of body wall muscle at both 405 nm and 488 nm excitation and used the mean fluorescence intensities of mitochondrial regions (40–50 regions per animal) to calculate the 405/488 ratios. Each point represents the 405/488 ratio average from a single animal (n = 60–63 animals); statistical significance was determined by unpaired two-tailed Student’s t test. b Heat map summarizing quantitative polymerase chain reaction results in N2 animals for commonly used stress reporter genes at different time points post-exercise (n = 5 independent trials). Expression data are presented as the log2 fold change of exercise samples relative to control samples in a color gradient from red (downregulation) to dark green (upregulation). White represents no change in expression levels. Paired two-tailed Student’s t tests were used to compare relative expressions of control versus exercise samples at each time point. See Additional file 1 and Additional file 4A–F for detailed results for each gene. c Percentage of surviving N2 animals during treatment with 3 mM juglone 4 hours post-exercise (n = 60 animals). d Average increase in percent survival during treatment with 3 mM juglone 4 hours post-exercise of N2, sod-3(tm760), sod-4(gk101), and sod-5(tm1146) exercised animals relative to control counterparts (n = 60 animals). The average increase in percent survival was calculated from all the time points between 15 and 45 min of treatment duration. Note that the reduced survival benefit of exercised sod-4 mutants was not due to a reduced swimming capacity relative to N2 and the other sod mutants. See Additional file 3B–D for detailed survival curves of sod mutants. Statistical significance in (c) and (d) determined by a log-rank test comparing control versus exercise survival curves. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. ER-UPR endoplasmic reticulum unfolded protein response, HSR heat shock response, ns, non-significant, mito-UPR mitochondrial unfolded protein response

Mentions: It is well known that physical exercise is associated with oxidative stress in human and mammalian muscle [20, 21]. To address whether the generation of reactive oxygen species (ROS) and an oxidative stress response in muscle are features of C. elegans swim exercise, we first took advantage of the reduction-oxidation-sensitive green fluorescent protein (roGFP), which allows for ratiometric quantification of redox changes in live cells [22]. Using a C. elegans strain that expresses roGFP specifically in the body wall muscle mitochondria [23], we determined that immediately after the swim exercise, the muscle mitochondrial matrix of swimmers was significantly more oxidized than the mitochondrial matrix in matched non-exercise controls (Fig. 3a). The increased oxidation level was maintained 1 hour after the end of exercise, but by 4 hours post-exercise the mitochondrial oxidative environment again matched control levels (Fig. 3a). Thus, as is true in mammals, acute physical exercise in C. elegans increases mitochondrial oxidation in muscle, and nematodes are able to adapt/clear elevated oxidation levels within a few hours to re-establish the mitochondrial oxidative environment to basal levels.Fig. 3


Single swim sessions in C. elegans induce key features of mammalian exercise
C. elegans swim exercise increases muscle mitochondrial oxidation and induces a specific transcriptional oxidative stress response. a Relative mitochondrial oxidation level of Pmyo-3mito-roGFP-expressing animals at different time points post-exercise (higher 405/488 ratios indicate increased oxidation levels). We took confocal images of body wall muscle at both 405 nm and 488 nm excitation and used the mean fluorescence intensities of mitochondrial regions (40–50 regions per animal) to calculate the 405/488 ratios. Each point represents the 405/488 ratio average from a single animal (n = 60–63 animals); statistical significance was determined by unpaired two-tailed Student’s t test. b Heat map summarizing quantitative polymerase chain reaction results in N2 animals for commonly used stress reporter genes at different time points post-exercise (n = 5 independent trials). Expression data are presented as the log2 fold change of exercise samples relative to control samples in a color gradient from red (downregulation) to dark green (upregulation). White represents no change in expression levels. Paired two-tailed Student’s t tests were used to compare relative expressions of control versus exercise samples at each time point. See Additional file 1 and Additional file 4A–F for detailed results for each gene. c Percentage of surviving N2 animals during treatment with 3 mM juglone 4 hours post-exercise (n = 60 animals). d Average increase in percent survival during treatment with 3 mM juglone 4 hours post-exercise of N2, sod-3(tm760), sod-4(gk101), and sod-5(tm1146) exercised animals relative to control counterparts (n = 60 animals). The average increase in percent survival was calculated from all the time points between 15 and 45 min of treatment duration. Note that the reduced survival benefit of exercised sod-4 mutants was not due to a reduced swimming capacity relative to N2 and the other sod mutants. See Additional file 3B–D for detailed survival curves of sod mutants. Statistical significance in (c) and (d) determined by a log-rank test comparing control versus exercise survival curves. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. ER-UPR endoplasmic reticulum unfolded protein response, HSR heat shock response, ns, non-significant, mito-UPR mitochondrial unfolded protein response
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Fig3: C. elegans swim exercise increases muscle mitochondrial oxidation and induces a specific transcriptional oxidative stress response. a Relative mitochondrial oxidation level of Pmyo-3mito-roGFP-expressing animals at different time points post-exercise (higher 405/488 ratios indicate increased oxidation levels). We took confocal images of body wall muscle at both 405 nm and 488 nm excitation and used the mean fluorescence intensities of mitochondrial regions (40–50 regions per animal) to calculate the 405/488 ratios. Each point represents the 405/488 ratio average from a single animal (n = 60–63 animals); statistical significance was determined by unpaired two-tailed Student’s t test. b Heat map summarizing quantitative polymerase chain reaction results in N2 animals for commonly used stress reporter genes at different time points post-exercise (n = 5 independent trials). Expression data are presented as the log2 fold change of exercise samples relative to control samples in a color gradient from red (downregulation) to dark green (upregulation). White represents no change in expression levels. Paired two-tailed Student’s t tests were used to compare relative expressions of control versus exercise samples at each time point. See Additional file 1 and Additional file 4A–F for detailed results for each gene. c Percentage of surviving N2 animals during treatment with 3 mM juglone 4 hours post-exercise (n = 60 animals). d Average increase in percent survival during treatment with 3 mM juglone 4 hours post-exercise of N2, sod-3(tm760), sod-4(gk101), and sod-5(tm1146) exercised animals relative to control counterparts (n = 60 animals). The average increase in percent survival was calculated from all the time points between 15 and 45 min of treatment duration. Note that the reduced survival benefit of exercised sod-4 mutants was not due to a reduced swimming capacity relative to N2 and the other sod mutants. See Additional file 3B–D for detailed survival curves of sod mutants. Statistical significance in (c) and (d) determined by a log-rank test comparing control versus exercise survival curves. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. ER-UPR endoplasmic reticulum unfolded protein response, HSR heat shock response, ns, non-significant, mito-UPR mitochondrial unfolded protein response
Mentions: It is well known that physical exercise is associated with oxidative stress in human and mammalian muscle [20, 21]. To address whether the generation of reactive oxygen species (ROS) and an oxidative stress response in muscle are features of C. elegans swim exercise, we first took advantage of the reduction-oxidation-sensitive green fluorescent protein (roGFP), which allows for ratiometric quantification of redox changes in live cells [22]. Using a C. elegans strain that expresses roGFP specifically in the body wall muscle mitochondria [23], we determined that immediately after the swim exercise, the muscle mitochondrial matrix of swimmers was significantly more oxidized than the mitochondrial matrix in matched non-exercise controls (Fig. 3a). The increased oxidation level was maintained 1 hour after the end of exercise, but by 4 hours post-exercise the mitochondrial oxidative environment again matched control levels (Fig. 3a). Thus, as is true in mammals, acute physical exercise in C. elegans increases mitochondrial oxidation in muscle, and nematodes are able to adapt/clear elevated oxidation levels within a few hours to re-establish the mitochondrial oxidative environment to basal levels.Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

Background: Exercise exerts remarkably powerful effects on metabolism and health, with anti-disease and anti-aging outcomes. Pharmacological manipulation of exercise benefit circuits might improve the health of the sedentary and the aging populations. Still, how exercised muscle signals to induce system-wide health improvement remains poorly understood. With a long-term interest in interventions that promote animal-wide health improvement, we sought to define exercise options for Caenorhabditis elegans.

Results: Here, we report on the impact of single swim sessions on C. elegans physiology. We used microcalorimetry to show that C. elegans swimming has a greater energy cost than crawling. Animals that swam continuously for 90&nbsp;min specifically consumed muscle fat supplies and exhibited post-swim locomotory fatigue, with both muscle fat depletion and fatigue indicators recovering within 1&nbsp;hour of exercise cessation. Quantitative polymerase chain reaction (qPCR) transcript analyses also suggested an increase in fat metabolism during the swim, followed by the downregulation of specific carbohydrate metabolism transcripts in the hours post-exercise. During a 90&nbsp;min swim, muscle mitochondria matrix environments became more oxidized, as visualized by a localized mitochondrial reduction-oxidation-sensitive green fluorescent protein reporter. qPCR data supported specific transcriptional changes in oxidative stress defense genes during and immediately after a swim. Consistent with potential antioxidant defense induction, we found that a single swim session sufficed to confer protection against juglone-induced oxidative stress inflicted 4&nbsp;hours post-exercise.

Conclusions: In addition to showing that even a single swim exercise bout confers physiological changes that increase robustness, our data reveal that acute swimming-induced changes share common features with some acute exercise responses reported in humans. Overall, our data validate an easily implemented swim experience as C. elegans exercise, setting the foundation for exploiting the experimental advantages of this model to genetically or pharmacologically identify the exercise-associated molecules and signaling pathways that confer system-wide health benefits.

Electronic supplementary material: The online version of this article (doi:10.1186/s12915-017-0368-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus