Exercise Heat Exposure Induced Changes In Genetic Expression Before And After Heat Acclimation In Humans

PURPOSE: To evaluate changes in genetic expression of proteins that are implicated in physiological adaptation to exercise heat exposure (Hypoxia Inducible Factor -1α [HIF-1α], Erythropoietin [EPO], and Vascular Endothelial Growth Factor [VEGF]) during systemic adaptation related to Heat Acclimation (HA) in humans. METHODS: Participants (n=18, 13 males, 5 females: 30 ± 7.34 y; 173.1 ± 7.673 cm; 76.25 ±14.17 kg) underwent two Heat Tolerance Tests (HTT 1 & 2; 120 min walking, 5 km/h, 2.0% grade, 40 °C, 40% rh) with 12-14 days between tests. Participants in experimental group (HA) underwent six heat acclimation days between tests, while the control group (CON) avoided exercise heat exposure between HTT’s. Blood was drawn pre- and post- each HTT and isolated into Peripheral Blood Mononuclear Cells, then further isolated into RNA. Then, cDNA was synthesized for Quantitative Real-Time Polymerase Chain Reaction to quantify gene expression. The data was then analyzed using the ΔΔCT to acquire fold change. RESULTS: No statistical difference in resting rectal temperature was observed before HTT2 in HA (-0.13±0.36 °C) vs. CON (-.08±0.47 °C; P=0.80). No significant changes were observed between HTT1 and HTT2 in the control group for HIF-1α, EPO, or VEGF. However, it was observed that acute EPO fold change increased 10.6x; (P=0.14) from pre- to post- in HTT1 for each group. An increased fold change was also observed in both HIF-1α and EPO between HTT1 and HTT2 (3.24x; P=0.04) & (7.19x; P=0.03) respectively in the HA group. No significant changes in VEGF were found in either group. CONCLUSION: Although the HA protocol utilized in this investigations was not stressful enough to induce observable rectal temperature changes, genetic expression of HIF-1α and EPO was significantly upregulated in response to chronic exercise heat stress. Grant Info: This publication was supported by the Mountain and Plains - Educational Research Center (MAP-ERC) Pilot Grant & the High Plains Intermountain Center for Agricultural Health & Safety (HICAHS) Pilot Grant.