Abstract
Background: The results from animal and human research indicate that acute intermittent hypoxia can enhance brain-derived neurotrophic factor (BDNF) plasma levels and gene expression. As BDNF is known to promote the differentiation of new neurons and the formation of synapses, it has been proposed to mediate adult neuroplasticity. Thus, the present study aimed to analyze the long-term effects of daily intermittent exposure to normobaric hypoxia (simulating high altitude exposure at approximately 4000–5000 m) over 2 weeks on BDNF levels in young adults.Methods: Twenty-eight young adults (age: 19–33 years) were randomized into a hypoxic intervention group (N = 14) or the control group (N = 14). Participants in the intervention group breathed intermittent normobaric hypoxic air at resting conditions (5 min intervals, 80–85% SpO2 measured via a finger pulse oximeter, 12 sessions for 60 min/day for 2 weeks) via a hypoxic generator. BDNF plasma and serum levels were determined at baseline and at 2 weeks after intervention using sandwich ELISAs.Results: After 2 weeks of daily intermittent hypoxic treatment (IHT), we found a significant group x time interaction effect for BDNF plasma levels based on a significant decrease in BDNF levels in the hypoxia group.Conclusion: Our results demonstrate that daily intermittent administration of hypoxic air has a significant effect on BDNF regulation in healthy young adults. Contrary to other results reporting an increase in BDNF levels under hypoxic conditions, the present data suggest that hypoxic treatment using intensive IHT can reduce BDNF plasma levels for at least 2 weeks. This finding indicates that the daily application of hypoxic air is too frequent for the aimed physiological response, namely, an increase in BDNF levels.
Highlights
Hypoxia is defined by a reduced oxygen content in air and can be divided into intermittent and chronic forms
The plasma and serum levels of brain-derived neurotrophic factor (BDNF) were analyzed in the blood samples before the onset of the intervention as well as after the intervention
A significant group x time interaction effect was observed for the BDNF plasma levels [F(1,26) = 10.742, p = 0.002, η2 = 0.292]
Summary
Hypoxia is defined by a reduced oxygen content in air and can be divided into intermittent and chronic forms. Intermittent hypoxia treatment (IHT) was first used in sports medicine to enhance human physical performance (erythropoiesis and angiogenesis) (Viscor et al, 2018). Intermittent normobaric hypoxia is not associated with positive effects only per se. The clinical syndrome of OSA leads to intermittent hypoxia as well (Burtscher et al, 2009) and is associated with numerous negative effects such as reduced cognitive performance (Yan, 2014; Malle et al, 2016). It has been proposed that low-dose intermittent hypoxia (9–16% inspired O2) with short durations can enhance positive physiological processes, whereby high-dose hypoxia (2–8% inspired O2) is associated with progressively pathological mechanisms (Navarrete-Opazo and Mitchell, 2014). The present study aimed to analyze the long-term effects of daily intermittent exposure to normobaric hypoxia (simulating high altitude exposure at approximately 4000–5000 m) over 2 weeks on BDNF levels in young adults
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