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Temporal pattern of skeletal muscle gene expression following endurance exercise in Alaskan sled dogs

ABSTRACT: Background: Muscle responses to exercise are complex, and potentially include acute responses to exercise-induced injury as well as longer-term adaptive training responses. Using Alaskan sled dogs as an experimental model, changes in muscle gene expression were analyzed to better understand the temporal changes that occur after severe exercise. Methods: Dogs were randomly assigned to undertake in a 160 km run (n=9), or to remain at rest (n=4). Biceps femoris muscle was obtained by needle biopsy from the unexercised dogs and two dogs at each of 2, 6 and 12 hours after the exercise and from 3 dogs 24 hours after exercise. RNA was extracted and microarray analysis used to define gene transcriptional changes. Results: Nine hundred sixty three transcripts exhibited statistically significant change over time after exercise as compared to the unexercised dogs. The changes in gene expression after exercise occurred in a clear temporal pattern and included transcripts with increased expression 2 hours after exercise with a return towards resting levels by 6 hours after exercise. Other transcripts demonstrated increased expression which peaked at six hours after exercise, while other transcripts showed sustained induction or repression over the 24 hours after exercise. Increases in a number of known transcriptional regulators, including PPAR-α, CERM and CEBPD, were observed 2-hours after exercise. Pathway analysis demonstrated coordinated changes in expression of genes with known functional relationships, including genes involved in muscle remodeling and growth, intermediary metabolism and immune regulation. Conclusion: Sustained endurance exercise by Alaskan sled dogs induces coordinated changes in gene expression with a clear temporal pattern. RNA expression profiling has the potential to identify novel regulatory mechanisms and responses to exercise stimuli.

ORGANISM(S): Canis lupus familiaris

PROVIDER: GSE15117 | GEO | 2009/07/01

SECONDARY ACCESSION(S): PRJNA114867

REPOSITORIES: GEO

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Project description:Background: Muscle responses to exercise are complex, and potentially include acute responses to exercise-induced injury as well as longer-term adaptive training responses. Using Alaskan sled dogs as an experimental model, changes in muscle gene expression were analyzed to better understand the temporal changes that occur after severe exercise. Methods: Dogs were randomly assigned to undertake in a 160 km run (n=9), or to remain at rest (n=4). Biceps femoris muscle was obtained by needle biopsy from the unexercised dogs and two dogs at each of 2, 6 and 12 hours after the exercise and from 3 dogs 24 hours after exercise. RNA was extracted and microarray analysis used to define gene transcriptional changes. Results: Nine hundred sixty three transcripts exhibited statistically significant change over time after exercise as compared to the unexercised dogs. The changes in gene expression after exercise occurred in a clear temporal pattern and included transcripts with increased expression 2 hours after exercise with a return towards resting levels by 6 hours after exercise. Other transcripts demonstrated increased expression which peaked at six hours after exercise, while other transcripts showed sustained induction or repression over the 24 hours after exercise. Increases in a number of known transcriptional regulators, including PPAR-Î±, CERM and CEBPD, were observed 2-hours after exercise. Pathway analysis demonstrated coordinated changes in expression of genes with known functional relationships, including genes involved in muscle remodeling and growth, intermediary metabolism and immune regulation. Conclusion: Sustained endurance exercise by Alaskan sled dogs induces coordinated changes in gene expression with a clear temporal pattern. RNA expression profiling has the potential to identify novel regulatory mechanisms and responses to exercise stimuli. Subjects were 13 Alaskan sled dogs aged 4.5 + 2.5 years (mean + SD) and weighing 23.3 + 2.5 kg. Dogs were randomly assigned to two groups â one group of 9 dogs subsequently ran 160 km in 24 hours as 2 sessions of 80 km, separated by a 6 hour rest period. The second group consisted of four dogs housed in unheated kennels, their usual housing, for the duration of the experiment. All dogs were from the same kennel. Dogs were fed a commercial kibble (Eukanuba, Iams Company, Dayton, OH) supplemented with frozen meat during the 8 weeks preceding the study and throughout the study period. The dogâs diet was consistent before, during and after the exercise bout. All dogs had completed 1590 + 100 km of training runs in the 3 months before the study. The dogs had not exercised for 72 hors before the start of this study. Dogs in the exercise group ran as a team pulling a lightly laden sled and driver over packed snow. Ambient temperatures were -20o to -10o C with no wind. Dogs completed the two 80 km runs in 23 hours, including the 6 hour rest period. Blood samples were collected by jugular venepuncture from all dogs the day before exercise, and within a 10 minute window at 2, 6, 12, and 24 hours after completing the second run. Samples were collected into evacuated glass tubes containing a clot enhancer. Muscle samples were collected from each of two dogs within a 10 minute window at 2, 6 and 12 hours after completing exercise and from three dogs 24 hours after completing exercise. Muscle samples were collected from each of the four unexercised dogs within two hours of the other dogs initiating their exercise bout. Each dog had only one biopsy procedure performed. Muscle samples were collected from the biceps femoris muscle using a needle biopsy that yielded approximately 40-60 mg of muscle. The biopsy was performed after clipping and aseptic preparation of the skin overlying the biopsy site. The dog was anesthetized with propofol (6 mg/kg, IV, maintained as necessary with 2 mg/kg additional boluses), a cuffed orotracheal tube placed and the dog ventilated with a hand-held ventilation bag. When adequate anesthesia had been obtained a 5 mm incision was made in the skin. A sterile biopsy needle (12 g PGI EZ Core, Products group International, Inc. Lyons, CO) was then inserted through the incision and a sample of muscle collected. If necessary, repeated collections of muscle were made until a minimum of 40 mg of muscle has been collected from an individual dog. The skin incision was closed with tissue glue and an antibiotic ointment applied. The dog was monitored closely until recovery from anesthesia was complete. Carprofen (4.4 mg/kg, orally) was administered when the dog had recovered sufficiently from anesthesia to have a gag reflex.

Project description:Purpose. Insulin resistant muscle is resistant to gene expression changes induced by acute exercise. This study was undertaken to identify transcription factors that differentially respond to exercise in insulin resistance. Candidate transcription factors were identified from analysis of 5’-untranslated regions (5’-UTRs) of exercise responsive genes and from analysis of the 5’-UTRs of genes coding for proteins that differ in abundance in insulin resistance. Research design and methods. Muscle biopsies were obtained from lean and obese subjects before and after a single exercise bout. Euglycemic glucose clamps assessed insulin sensitivity. Global proteomics analysis identified differentially abundant proteins. The 5’-UTRs of genes coding for significant proteins were subjected to transcription factor enrichment analysis to identify candidate transcription factors. Q-rt-PCR to determine expression of candidate transcription factors was performed on RNA from resting and post-exercise muscle biopsies; immunoblots quantified protein abundance. Results. Obese subjects were insulin resistant compared to lean but performed exercise at the same intensity. Proteins involved in mitochondrial function, protein targeting and translation, and metabolism were among those significantly different between the groups. Transcription factor enrichment analysis of genes coding for these proteins revealed new candidate transcription factors. Q-rt-PCR analysis of RNA and immunoblot analysis from pre- and post-exercise muscle biopsies revealed several transcription and growth factors that had altered responses to exercise in insulin resistant subjects. Conclusions. These results confirm findings of an association between insulin sensitivity and transcription factor mRNA response to exercise and extend these results to show that obesity also may be a sufficient prerequisite for exercise resistance. Analysis of the muscle proteome together with determination of effects of exercise on expression of transcription factors suggests that abnormal responses of transcription factors to exercise may be responsible for differences in protein abundances in insulin resistant muscle.

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Temporal pattern of skeletal muscle gene expression following endurance exercise in Alaskan sled dogs

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