Effect of intermittent hypoxic training on HIF gene expression in human skeletal muscle and leukocytes

Intermittent hypoxic exposure with exercise training is based on the assumption that brief exposure to hypoxia is sufficient to induce beneficial muscular adaptations mediated via hypoxia-inducible transcription factors (HIF). We previously demonstrated (Mounier et al. Med Sci Sports Exerc 38:1410–1417, 2006) that leukocytes respond to hypoxia with a marked inter-individual variability in HIF-1α mRNA. This study compared the effects of 3 weeks of intermittent hypoxic training on hif gene expression in both skeletal muscle and leukocytes. Male endurance athletes (n = 19) were divided into an Intermittent Hypoxic Exposure group (IHE) and a Normoxic Training group (NT) with each group following a similar 3-week exercise training program. After training, the amount of HIF-1α mRNA in muscle decreased only in IHE group (−24.7%, P < 0.05) whereas it remained unchanged in leukocytes in both groups. The levels of vEGF121 and vEGF165 mRNA in skeletal muscle increased significantly after training only in the NT group (+82.5%, P < 0.05 for vEGF121; +41.2%, P < 0.05 for vEGF165). In leukocytes, only the IHE group showed a significant change in vEGF165 (−28.2%, P < 0.05). The significant decrease in HIF-1α mRNA in skeletal muscle after hypoxic training suggests that transcriptional and post-transcriptional regulations of the hif-1α gene are different in muscle and leukocytes.