Brain-Derived neurotrophic factor and inflammatory biomarkers are unaffected by acute and chronic intermittent hypoxic-hyperoxic exposure in geriatric patients: a randomized controlled trial

Abstract

Background Animal and human studies have shown that exposure to hypoxia can increase brain-derived neurotrophic factor (BDNF) protein transcription and reduce systematic inflammatory cytokine response. Therefore, the aim of this study was to investigate the acute and chronic effects of intermittent hypoxic-hyperoxic exposure (IHHE) prior to aerobic exercise on BDNF, interleukin-6 (IL-6), and C-reactive protein (CRP) blood levels in geriatric patients. Patients and Methods Twenty-five geriatric patients (83.1 ± 5.0 yrs, 71.1 ± 10.0 kg, 1.8 ± 0.9 m) participated in a placebo-controlled, single-blinded trial and were randomly assigned to either an intervention (IG) or control group (CG) performing an aerobic cycling training (17 sessions, 20 min·session −1 , 3 sessions·week −1 ). Prior to aerobic cycling exercise, the IG was additionally exposed to IHHE for 30 min, whereas the CG received continuous normoxic air. Blood samples were taken immediately before (pre-exercise) and 10 min (post-exercise) after the first session as well as 48 h (post-training) after the last session to determine serum (BDNF S ) and plasma BDNF (BDNF P ), IL-6, and CRP levels. Intervention effects were analyzed using a 2 x 2 analysis of covariance with repeated measures. Results were interpreted based on effect sizes with a medium effect considered as meaningful (η p 2 ≥ 0.06, d ≥ 0.5). Results CRP was moderately higher ( d = 0.51) in the CG compared to the IG at baseline. IHHE had no acute effect on BDNF S (η p 2 = 0.01), BDNF P (η p 2 < 0.01), BDNF serum/plasma-ratio (η p 2 < 0.01), IL-6 (η p 2 < 0.01), or CRP (η p 2 = 0.04). After the 6-week intervention, an interaction was found for BDNF serum/plasma-ratio (η p 2 = 0.06) but not for BDNF S (η p 2 = 0.04), BDNF P (η p 2 < 0.01), IL-6 (η p 2 < 0.01), or CRP (η p 2 < 0.01). BDNF serum/plasma-ratio increased from pre-exercise to post-training ( d = 0.67) in the CG compared to the IG ( d = 0.51). A main effect of time was found for BDNF P (η p 2 = 0.09) but not for BDNF S (η p 2 = 0.02). Wit...