ECSS Paris 2023: OP-PN12
INTRODUCTION: Lower extremity peripheral artery disease (PAD), caused by the buildup of atherosclerotic plaque that narrows the lower extremity arteries, is a global health concern. PAD patients often experience ischemic muscular pain during exercise, which leads to a significant decline in functional capacity. Exercise training is a first-line treatment for PAD; however, the comparison of the effectiveness of different exercise training intensities on skeletal muscle adaptations is lacking. This study compared the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on endurance capacity and mRNA expression of metabolic genes in skeletal muscles of mice with PAD. METHODS: Male C57BL/6 mice underwent surgical ligation of the right common iliac artery and were then divided into three groups: sedentary (SED), MICT (40 minutes of running at 70% of maximal aerobic speed), and HIIT (8x 2.5 minutes running at 90% of maximal aerobic speed, interspersed with 2.5 minutes running at 50% of maximal aerobic speed). Mice were subjected to treadmill running 3 times/per week for 8 weeks. Maximal running distance was determined by an incremental exhaustion test. Quantitative PCR (qPCR) was performed to determine skeletal muscle mRNA expression of markers involved in the metabolism of glucose (GLUT-4, HK2, PFK), lactate (LDHA), lipid (CD36, HSL), as well as markers related to mitochondrial biogenesis and oxidative metabolism (PGC-1a, TFAM, mtND6, CS, CYTB). Analyses were performed in both non-ischemic and ischemic gastrocnemius (primarily fast-twitch fibers), and soleus (primarily slow-twitch fibers) muscles. RESULTS: At the end of the study, maximum running distance was significantly greater in both MICT and HIIT mice compared to SED (439 +/- 33.2 m in MICT vs 470.0 +/- 32.0 m in HIIT vs 311.6 +/- 21.2 m in SED, p< 0.05), with no significant difference between MICT and HIIT. In the ischemic gastrocnemius muscle, HIIT upregulated the mRNA expression of PFK, CD36, HSL, and CS (p<0.05 vs SED), while in the non-ischemic gastrocnemius, only CS expression was increased (p<0.05 vs SED). MICT did not significantly alter the mRNA levels of metabolic genes in either the ischemic or non-ischemic gastrocnemius muscle. In the ischemic soleus muscle, HIIT increased mtND6 and CYTB mRNA expression (p<0.05 vs SED). In the non-ischemic soleus, HIIT upregulated PGC-1a and CYTB while downregulating CD36 and HK2 (p<0.05 vs SED). MICT upregulated the mRNA expression of GLUT-4, LDHA, TFAM in the ischemic soleus muscle (p<0.05 vs SED), but had no impact on gene expression in the non-ischemic soleus. CONCLUSION: MICT and HIIT are equally effective in improving endurance capacity in PAD mice. However, HIIT induces greater skeletal muscle transcriptional adaptations compared to MICT in our mouse model of PAD.
Read CV Slobodan KojicECSS Paris 2023: OP-PN12
INTRODUCTION: Mitochondria serve as critical signalling hubs, integrating and relaying intracellular information to facilitate skeletal muscle adaptations to exercise. Despite known roles of mitochondrial (MITO) protein signalling and translocation between other organelles (i.e., the nucleus and cytosol), major knowledge gaps remain in our understanding of the complex muscle subcellular protein networks underlying acute responses to exercise and exercise training. METHODS: A total of 197 vastus lateralis muscle biopsies were collected from 20 untrained men and 20 untrained women (26.5 ± 5.9 y, BMI 24.9 ± 3.4 kg/m², V̇O2max 31.1 ± 5.6 mL/min/kg) pre, mid, post, and 3 h-post an acute bout of high-intensity interval exercise (HIIE) and following 8 wk HIIE training (4 sessions/wk). The acute HIIE session consisted of four 4-min workbouts based on individual maximum power output and lactate threshold, with 2-min rest. Subcellular fractionation workflows were developed to isolate MITO, nuclear (NUC) and cytosolic (CYTO) fractions from snap-frozen human muscle biopsies using differential centrifugation. Global mass spectrometry-based proteomic analysis was then performed to map acute and chronic exercise-induced changes in protein abundance and potential protein translocation between subcellular compartments. RESULTS: Proteomic and bioinformatic analysis of 591 total muscle subcellular fractions mapped acute and chronic exercise-induced dynamics of MITO, NUC, and CYTO protein abundance. We quantified 1440 total proteins in the MITO fraction, representing over 40% of all annotated MITO proteins. Differential expression analysis revealed significant changes (adjusted p<0.05 versus pre) within the MITO fraction mid (102 proteins), post (604), and 3 h-post (376) acute exercise, and following 8 weeks of training (611). HIIE acutely downregulated MITO ribosomal proteins and proteins involved in MITO fission/fusion dynamics, whereas proteins related to reactive oxygen species were upregulated. Robust upregulation of MITO proteins was observed following training, consistent with other molecular markers of MITO biogenesis (e.g., citrate synthase activity, transmission electron microscopy). In the NUC fraction, 491 total proteins were significantly regulated (216 up and 275 downregulated, respectively) across all time points, including robust regulation of auxiliary proteins linked to ribonucleotide processes. There were no sex differences in subcellular proteomes observed in response to acute and chronic exercise. CONCLUSION: These subcellular proteomic datasets represent one of the most extensive human muscle proteome analyses to date and a valuable resource of the intricate subcellular networks underlying acute exercise responses and training-induced adaptations. Collectively, these datasets highlight the overall lack of subcellular proteomic sex differences and key pathways that warrant further investigation including MITO protein translation and fission/fusion machinery.
Read CV Elizabeth ReismanECSS Paris 2023: OP-PN12
INTRODUCTION: Aging inevitably results in a decline in whole-body cardiorespiratory fitness (1). Impairments in muscle oxidative metabolism serves as key contributing factor to age-related cardiorespiratory fitness reduction, potentially driven by alterations in mitochondrial content, distribution and function (2). However, some studies suggest aging does not lead to mitochondrial impairments when high level of physical activity are maintained and there is ongoing debate in the scientific literature (3,4). This study aimed to clarify the relationship between aging, mitochondria and training by investigating muscle oxidative capacity through both in-vivo and ex-vivo technique to characterize mitochondrial function, content, and distribution in human skeletal muscle of active and sedentary older individuals. METHODS: Forty young sedentary adults (YG, n=40; 24±4 yrs) and fifty older individuals (O, n=50; 68±10 yrs) were recruited. Free-living physical activity was monitored by accelerometry and used to stratify O into active (OA) and sedentary (OS) groups. All participants completed a cycling incremental test to assess maximal pulmonary oxygen uptake (VO2peak). In-vivo vastus lateralis muscle oxidative function was estimated as oxygen uptake recovery rate constant (k) during intermittent arterial occlusions after brief exercise by near-infrared spectroscopy (5). Muscle biopsies from vastus lateralis were collected in a subsample of subjects (n=40). High-resolution respirometry was used to assess mitochondrial respiration. Immunohistochemistry analysis and Citrate Synthase activity assay were performed to determine fibre cross-sectional area (fCSA), mitochondrial content and distribution. RESULTS: YG showed higher VO2peak (35.2±7.4 ml/kg/min) compared to O (24.1±5.6 ml/kg/min, p<0.001). k was higher in YG compared to O (p<0.001), without differences between OA and OS (p=0.83). After adjusting for physical activity, age negatively correlated with VO2peak and k (both p<0.01). Mitochondrial respiration was not affected by age or physical activity. In both YG and O, type I and type II fibers differed for TOM20 (p<0.03). Markers of mitochondrial content were lower in O, compared to YG (p<0.05). OA and OS did not show any difference in the mitochondrial markers investigated (p = 0.29). CONCLUSION: Cardiorespiratory fitness and skeletal muscle oxidative capacity were negatively affected by age but the age-related decline in muscle oxidative metabolism was not preserved or restored by physical activity. Mitochondrial function did not change with age or according to physical activity level in older individuals, suggesting changes mitochondrial content and distribution during aging may disrupt mitochondrial network integrity and connectivity, potentially having a greater impact on in-vivo muscle oxidative capacity. References (1) Hawkins et al, 2003 (2) Conley et al, 2000 (3) Lanza et al, 2025 (4) Marcinek & Ferrucci, 2025 (5) Pilotto et al, 2022
Read CV chiara fellesECSS Paris 2023: OP-PN12