Skeletal Muscle mRNA Response to Hypobaric and Normobaric Hypoxia After Normoxic Endurance Exercise

Abstract

Background: The physiological effects of hypoxia may be influenced by how hypoxia is achieved. The purpose of this study was to determine the effects of recovery in hypobaric hypoxia (HH), normobaric hypoxia (NH), and normobaric normoxia (NN) after endurance exercise on gene expression related to mitochondrial biogenesis, myogenesis, and proteolysis. Methods: Fifteen recreationally trained subjects each cycled for 1 hour before recovering for 4 hours in NN (laboratory atmospheric conditions, 975 m), HH (depressurized to simulate 4420 m), and NH (fraction of O 2 reduced to simulate 4420 m). Muscle biopsy samples were obtained before exercise and after 4 hours of recovery. Results: Blood oxygenation (SpO 2) was lower in HH (76.02-0.58%) than NH (79.45-0.56, p < 0.001), which were both lower than in NN (96.3-0.17, p < 0.001). Heart rate was higher in HH (82-2 bpm) than NH (77-1 bpm, p < 0.001), which were both higher than in NN (67-1 bpm, p < 0.001). Mitochondrial transcription factor A (TFAM) mRNA was lower after NN than HH (p = 0.034) or NH (p = 0.005), but was not different between HH and NH (p = 0.460). Myostatin (MSTN) mRNA decreased from pre-to postexercise (p < 0.001) in all conditions and was lower in HH compared with NH (p = 0.035) and NN (p = 0.017). No other differences were noted in genes related to mitochondrial biogenesis, myogenesis, or proteolysis (p > 0.05). Conclusion: TFAM mRNA is lower with hypoxia exposure, but effected by the type of hypoxia. MSTN gene expression is lower after exposure to HH than NH or NN. These data support previous work and caution the translation of NH data obtained in a NH environment to a HH environment.

Similar Supine Heart Rate Variability Changes During 24-h Exposure to Normobaric vs. Hypobaric Hypoxia

“…As expected, HR was higher in hypoxic conditions compared to normoxia in response to the increased sympathetic activity and vagal withdrawal. Several studies have further found lower HR in NH vs. HH (Savourey et al, 2003;DiPasquale et al, 2015b;Heinzer et al, 2016;Ross et al, 2019;Aebi et al, 2020) but only during short exposures. In addition, studies examining longer exposures (>8 h) found no difference in HR (Faiss et al, 2013;Richard et al, 2014).…”

Myostatin as a Biomarker of Muscle Wasting and other Pathologies-State of the Art and Knowledge Gaps

“…Another factor that has to be taken under consideration when measuring serum myostatin is physical activity of the patients. Results of most recent studies suggest that physical exercise attenuates myostatin gene and protein expression in skeletal muscles directly after training [ 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 ], while a decrease of physical activity achieved by daily step reduction increased myostatin mRNA expression [ 135 ]. In most studies, serum myostatin levels were found to increase acutely after various exercise types (ultramarathon, aerobic, resistance and high-intensity training) [ 136 , 137 , 138 , 139 , 140 , 141 ], and decrease in the long term as a result of physical training [ 90 , 142 , 143 , 144 , 145 , 146 ].…”

The Prospective Study of Epigenetic Regulatory Profiles in Sport and Exercise Monitored Through Chromosome Conformation Signatures

“…Gene expression is affected by hot and cold climates [ 84 , 85 , 86 ] and conditions of low oxygen availability [ 87 , 88 ], though to our knowledge, the effects of such stimuli on CCSs are unknown. Heat acclimation is partially mediated by altered gene expression as an adaptation to peripheral haemodynamic load [ 89 ], and could be one example of an adaptation potentially associated with the reorganisation of specific CCSs.…”