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Resistance to aerobic exercise training causes metabolic dysfunction and reveals novel exercise-regulated signaling networks

ABSTRACT: Low aerobic exercise capacity is a risk factor for diabetes and strong predictor of mortality; yet some individuals are exercise resistant, and unable to improve exercise capacity through exercise training. To test the hypothesis that resistance to aerobic exercise training underlies metabolic disease-risk, we used selective breeding for 15 generation to develop rat models of low- and high-aerobic response to training. Before exercise training, rats selected as low- and high-responders had similar exercise capacities. However, after 8-wks of treadmill training low-responders failed to improve their exercise capacity, while high-responders improved by 54%. Remarkably, low-responders to aerobic training exhibited pronounced metabolic dysfunction characterized by insulin resistance and increased adiposity, demonstrating that the exercise resistant phenotype segregates with disease risk. Low-responders had impaired exercise-induced angiogenes0is in muscle; however, mitochondrial capacity was intact and increased normally with exercise training, demonstrating that mitochondria are not limiting for aerobic adaptation or responsible for metabolic dysfunction in low-responders. Low-responders had increased stress/inflammatory signaling and altered TGFβ signaling, characterized by hyperphosphorylation of a novel exercise-regulated phosphorylation site on SMAD2. Using this powerful biological model system we have discovered key pathways for low exercise training response that may represent novel targets for the treatment of metabolic disease.

ORGANISM(S): Mus musculus Human gammaherpesvirus 8 Rattus norvegicus JC polyomavirus Betapolyomavirus macacae Homo sapiens Murid gammaherpesvirus 4 Human betaherpesvirus 5 Human alphaherpesvirus 1 Betapolyomavirus hominis human gammaherpesvirus 4 Murid betaherpesvirus 1 Human immunodeficiency virus

PROVIDER: GSE57880 | GEO | 2014/05/23

SECONDARY ACCESSION(S): PRJNA248397

REPOSITORIES: GEO

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Project description:Epidemiological studies reveal a strong link between low aerobic capacity and metabolic and cardiovascular diseases. Two-way artificial selection of rats based on low and high intrinsic exercise capacity has produced two strains that also differ in risk for metabolic syndrome (Koch LG, Britton SL. Artificial selection for intrinsic aerobic endurance running capacity in rats. Physiol Genomics 5:45-52, 2001). Here we investigated skeletal muscle characteristics and genotype-phenotype relationships behind high and low inherited aerobic exercise capacity and the link between oxygen metabolism and metabolic disease risk factors in rats derived from generation 18. This population (n=24) of high capacity runners (HCR) and low capacity runners (LCR) differed by 615% in maximal treadmill running capacity. LCR were significantly significantly heavier and had increased blood glucose, serum insulin and triglyceride concentration. HCR had higher resting metabolic rate than LCR. Capillaries/mm2 and capillary-to-fiber ratio were significantly greater in HCR rats in soleus and gastrocnemius and capillary-to-fiber ratio in extensor digitorum longus (EDL) muscle. Subsarcolemmal mitochondrial area was 96% (p<0.01) and intermyofibrillar area was 32% (p<0.05) larger in HCR soleus. Microarray results showed that 126 genes were significantly up-regulated and 113 genes were down-regulated in HCR (p<0.05). Functional clustering and unbiased correlation analysis of muscle microarray data revealed that genes up-regulated in HCR were related to mitochondria, carboxylic acid and lipid metabolism, and oxidoreductase activity. In conclusion, our data show that aerobic capacity is strongly linked to the architecture of energy transfer and corroborate the importance of oxygen metabolism as the determinant of metabolic health and complex metabolic diseases such as metabolic syndrome and type 2 diabetes. Total RNA obtained from gastrocnemius muscle was compared between rat strains of low and high inherited aerobic exercise capacity.

Project description:The molecular pathways which are activated and contribute to physiological remodeling of skeletal muscle in response to endurance exercise have not been fully characterized. We previously reported that ~800 gene transcripts are regulated following 6 weeks of supervised endurance training in young sedentary males, referred to as the training responsive transcriptome (TRT). Here we utilized this database together with data on biological variation in muscle adaptation to aerobic endurance training in both humans and a novel out-bred rodent model to study the potential regulatory molecules that coordinate this complex network of genes. We identified three DNA sequences representing RUNX1, SOX9, and PAX3 transcription factor binding sites as over-represented in the TRT. In turn, miRNA profiling indicated that several miRNAs targeting RUNX1, SOX9 and PAX3 were down-regulated by endurance training. The TRT was then examined by contrasting subjects who demonstrated the least vs. the greatest improvement in aerobic capacity (low vs. high responders), and at least 100 of the 800 TRT genes were differentially regulated, thus suggesting regulation of these genes may be important for improving aerobic capacity. In high responders, pro-angiogenic and tissue developmental networks emerged as key candidates for coordinating tissue aerobic adaptation. Beyond RNA level validation there were several DNA variants that associated with VO(2)max trainability in the HERITAGE Family Study but these did not pass conservative Bonferroni adjustment. In addition, in a rat model selected across 10 generations for high aerobic training responsiveness, we found that both the TRT and a homologous subset of the human high responder genes were regulated to a greater degree in high responder rodent skeletal muscle. This analysis provides a comprehensive map of the transcriptomic features important for aerobic exercise-induced improvements in maximal oxygen consumption. This data is from skeletal muscle post 6 weeks of endurance exercise training.

Project description:Purpose: Aerobic capacity is a strong predictor of cardiovascular mortality. To determine the relationship between inborn aerobic capacity and soleus gene expression we examined genome-wide gene expression in soleus muscle of rats artificially selected for high and low running capacity (HCR and LCR, respectively) over 16 generations. The artificial selection of LCR caused accumulation of risk factors of cardiovascular disease similar to the metabolic syndrome seen in man, whereas HCR had markedly better cardiac function. We also studied alterations in gene expression in response to exercise training in the two groups, since accumulating evidence indicates that exercise has profound beneficial effects on the metabolic syndrome. Methods:; Soleus gene expression of both sedentary and exercise trained HCR and LCR was characterized by microarray- and gene ontology analysis. Results: Although HCR and LCR had an inborn 347% difference in running capacity, only three genes were found differentially expressed in the soleus muscle between the two groups. Up-regulation of the mitochondrial enzyme leucyl-transferRNA synthetase (LARS2) was found in the sedentary LCR. Increased expression of LARS2 has been associated with a mitochondrial DNA mutation linked to maternally inherited diabetes and mitochondrial dysfunction. In line with our findings, a growing body of evidence suggests that LCR have compromised mitochondrial function. After exercise training, 58 genes were altered in the soleus muscle of HCR, in contrast to only one in the LCR group. This suggests that animals born with different levels of fitness respond different to the same type of exercise training. Adaptations to exercise in HCR seemed to be associated with increased lipid metabolism and fatty acid elongation in the mitochondria. Also, genes associated with the peroxisomes, seemed to be central in the adaptation to exercise. Conclusion: The results indicate that (i) LCR might have mitochondrial dysfunction, which may be a contributing factor of the low inborn aerobic capacity, (ii) animals born with different levels of fitness respond different to the same exercise program. Experiment Overall Design: There are 16 samples in this study.

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Resistance to aerobic exercise training causes metabolic dysfunction and reveals novel exercise-regulated signaling networks

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