Browsing by Author "Troutman, Ashley"

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    High Intensity Interval Training Benefits Right Heart Function in a Rat Model of Pulmonary Arterial Hypertension
    (Office of the Vice Chancellor for Research, 2016-04-08) Troutman, Ashley; Brown, Mary Beth; Johnson, Breann; Neves, Evandro; Fisher, Amanda; Graber, Jeremy; Gladish, Brett; Presson, Robert; Petrache, Irina; Kline, Jeffrey A.; Lahm, Tim
    Pulmonary Arterial Hypertension (PAH) is a disease of progressive remodeling in pulmonary arteries that elevates pulmonary pressures and eventually leads to right ventricular (RV) failure and death. The purpose of this study was to examine the benefit and detriment of high intensity interval training (HIIT) to the RV in a monocrotaline (MCT) PAH rat model. It is hypothesized that HIIT will improve indicators of RV function without increasing myocardial inflammation or apoptosis. Male Sprague Dawley rats were injected with either MCT (40 mg/kg, n=14)) to induce mild PAH or saline for healthy controls (CON, n=9). A subgroup of MCT (n= 8) and CON rats (n=6) performed a 6 week treadmill HIIT program 5x/week using short bouts of alternating high intensity (2 min, 85-90%VO2max) and low intensity (3 min, ~30%VO2max) running for 30 min/session. Histochemistry/immunohistochemistry was performed on cryofixed or formalin-fixed/paraffin-embedded RV sections to assess indicators of inflammation (CD45+ cells), apoptosis (TUNEL), fibrosis (trichrome) and was imaged using epifluorescence or brightfield microscopy. Image quantification was performed using ImageJ. For the HIIT rats, a reduction in MCTinduced RV hypertrophy was observed, as measured echocardiographically, and by the calculated ratio of RV mass relative to LV+Septum mass. RV function was better preserved for HIIT vs. sedentary MCT, as indicated by stroke volume and cardiac index (cardiac output normalized by body weight) in echocardiography. MCT-induced RV fibrosis as measured by trichrome staining was lower for HIIT, also indicating a healthier myocardium. HIIT did not prompt greater counts per field of CD45+ cells and TUNEL+ cells in HIIT vs. sedentary MCT RV myocardium. In conclusion, in the monocrotaline rat model of PAH, HIIT appears to be a beneficial exercise approach that improves RV function without exacerbating RV inflammation or apoptosis. Future work will examine effects in other PAH models and ultimately in patients with disease.
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    Investigating Skeletal Muscle Metabolic Adaptations underlying Aerobic Fitness Gains following High Intensity Interval Training in a Rat Model of Pulmonary Arterial Hypertension
    (Office of the Vice Chancellor for Research, 2016-04-08) Talley, Mary; Troutman, Ashley; Neves, Evandro; Fisher, Amanda; Graber, Jeremy; Gladish, Brett; Presson, Robert; Petrache, Irina; Kline, Jeffrey A.; Lahm, Tim
    Rationale: In patients with pulmonary arterial hypertension (PAH) a shift from oxidative to a less efficient non-oxidative (glycolytic) metabolism in skeletal muscle is believed to contribute to the reduced exercise tolerance hallmark of the disease. As seen for other cardiopulmonary diseases, exercise training (ExT) may ameliorate this “glycolytic switch” in PAH and improve exercise capacity. Previous studies in this lab showed an improved metabolic profile of skeletal muscle in PAH rats following an ExT protocol of continuous running at moderate relative intensity, 60 minutes at 75% of maximal aerobic capacity (VO2 Max). This study tests the hypothesis in a PAH rat model that HIIT will also result in preserved aerobic capacity and attenuation of skeletal muscle glycolytic shift. Methods: Male Sprague-Dawley rats received either monocrotaline (MCT, 40 mg/kg) to induce mild PAH (n= 14), or saline, for healthy controls (n=9). After 2 wks, a 6 wkprogram of treadmill HIIT was initiated for a subset of PAH (n= 8) and healthy controls (n=6). The 30 min HIIT sessions alternated between 2 minutes at 85% VO2 max and 3 minutes at ~30% VO2 max. VO2 max was assessed at baseline, and in pre-training and post-training via analysis of expired gases. Preliminary results: MCT-induced decrement in VO2 max was attenuated by HIIT (p<0.05). Soleus muscle hypertrophy (soleus mass relative to body mass) tended to be higher (p=0.07) in HIIT vs. SED MCT. Membrane glucose transporter Glut-1, a marker of glycolytic metabolism, was evaluated in soleus cryosections with immunofluorescent staining and abundance was similar between sedentary and HIIT MCT rats (p>0.05). Western blotting of soleus homogenates for cytochromes I-V of the electron transport chain (OXPHOS), and for PGC1α, a potent stimulus for mitochondrial biogenesis, is being performed at present to further investigate potential training-induced adaptations in skeletal muscle metabolism