Project description: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.
Project description:Training and priming of innate immune cells involve preconditioning by PAMPs, DAMPs and/or cytokines that elicits stronger induction of inflammatory genes upon secondary challenge. Previous models distinguish training and priming based upon whether immune activation returns to baseline prior to secondary challenge. Tolerance is a protective mechanism whereby potent stimuli induce refractoriness to secondary challenge. Training and priming are important for innate memory responses that protect against infection, efficacy of vaccines, and maintaining innate immune cells in a state of readiness; tolerance prevents toxicity from excessive immune activation. Dysregulation of these processes can contribute to pathogenesis of autoimmune/inflammatory conditions, post-COVID-19 hyperinflammatory states, or sepsis- associated immunoparalysis. Training, priming and tolerance regulate similar ‘signature’ inflammatory genes such as TNF, IL6 and IL1B and utilize overlapping epigenetic mechanisms. We review how interferons (IFNs), best known for activating Jak-STAT signaling and interferon- stimulated genes, also play a key role regulating training, priming and tolerance via chromatin- mediated mechanisms. We present new data on how monocyte-to-macrophage differentiation modulates IFN-g-mediated priming, changes AP-1 and CEBP activity, and attenuates superinduction of inflammatory genes. We present a ‘training-priming continuum’ model that integrates IFN-mediated priming into current concepts about training and tolerance and proposes a central role for STAT1 and IRF1.
Project description:The goal of the endurance exercise training study in young adult rats was to perform exercise training studies in young adult (6-month-old) F344 rats, and from these rats collect multiple tissues in order to provide high quality samples for detailed analysis by chemical analysis sites. Tissues were collected from 10-12 rats sedentary control rats concurrent with the collection of the 8-week training groups. The 8-week training group and controls were from the same cohort and same age at euthanasia. For the older age group, an additional set of controls (n=5-6) were collected with the 1-2 week training group. Rats were either sedentary or underwent an exercise training program. Rats were exercised on the rodent treadmill 5 days per week using a progressive training protocol designed to exercise the rats at approximately 70% of VO2max and training was performed no earlier than 10:00 am and no later than 5:00 pm over 5 consecutive days per week. Training was initiated with the treadmill set at 70% of VO2 max and 5 degrees grade for 20 minutes. The duration of exercise was increased by one minute each day until day 31 of training (start of week 7), when a duration of 50 min was reached. Speed and grade of each training session increased in larger increments due to treadmill parameters. The highest intensity and duration of training began on day 31. This intensity was maintained for the final 10 days of the protocol to ensure steady state had been achieved. If any rats were unable to perform at least 4 days of training per week they were removed from the study and euthanized. It is important to note that the starting treadmill speed varied depending on the sex and age of the rat. The initial and maximum speeds were based on VO2max measurements obtained during the pre-training testing of the compliant rats. Rats assigned to the control group followed a schedule similar to the training group. They were placed in one lane on the treadmill for 15 minutes/day, 5 days per week. The treadmill was set at 0 m/min at an incline that corresponded to the incline being used by the training group.
Project description:Spinal cord injury (SCI) is one of the most disabling health problems facing adults today. Locomotor training has been shown to induce substantial recovery in muscle size and muscle function in both transected and contusion injury animal models of SCI. The overall objective of this study is to implement genome wide expression profiling of skeletal muscle to define the molecular pathways associated with muscle remodeling after SCI and during locomotor training (TM). We profiled rat soleus of total 36 samples including controls; 3, 8 and 14 days after SCI; 8 and 14 days after SCI with locomotor treadmill training (TM).