Age-related differences in plasma BDNF levels after prolonged bed rest

Abstract

Brain-derived neurotrophic factor (BDNF) is a member of the family of neurotrophins and has been implicated in brain resistance to insults. Murine studies have demonstrated increased hippocampal concentration after acute immobilization and decreased concentration after chronic immobilization. In humans, chronic stress and sedentary lifestyle result in decreased plasma BDNF levels, but there no data exist regarding acute immobilization. The aim of our study was to evaluate age-related responses [comparing 7 younger subjects (age 23 ± 3 yr) and 8 older subjects (age 60 ± 4 yr)] of plasma BDNF before (baseline data collection, BDC) and after 14 days (BR14) of horizontal bed rest (BR). At BDC, BDNF levels were not different between the two groups (P = 0.101), although at BR14, BDNF levels were higher in older subjects (62.02 ± 18.31) than in younger subjects (34.36 ± 15.24 pg/ml) (P = 0.002). A general linear model for repeated measures showed a significant effect of BR on BDNF (P = 0.002). The BDC BDNF levels correlated with fat-free mass in both populations (ALL) (R = 0.628, P = 0.012), (older, R = 0.753, P = 0.031; younger, R = 0.772, P = 0.042), and with total cholesterol in ALL (R = 0.647, P = 0.009) and older study subjects (R = 0.805, P = 0.016). At BR14, BDNF correlated with total cholesterol (R = 0.579, P = 0.024) and age (R = 0.647, P = 0.009) in ALL. With an increase in age, the brain could become naturally less resistant to acute stressors, including the detrimental effects of prolonged bed rest, and thus the increase in BDNF in the older study group might reflect a protective overshooting of the brain to counteract the negative effects in such conditions.

Computerized cognitive training and brain derived neurotrophic factor during bed rest: mechanisms to protect individual during acute stress

“…When we designed this and the previous study [26], we hypothesized that we would have found a decrease in BDNF in people undergoing bed rest, and that this decrease would have been less important in people undergoing cognitive training, based on data coming from literature. The results were surprising, showing exactly the opposite.…”

“…We have previously demonstrated that bed rest induces an increase in plasma BDNF in adult/older, but not in young people [26]. Studies on animals [35] and on humans affected by diabetes and Alzheimer's disease [36, 37 ] seem to suggest a biphasic behaviour of BDNF with increased level in the first phase of disease and decreased level in a later phase.…”

“…BDNF might increase to protect brain form an insult; however when the stressful event overcomes a certain threshold, resulting in a brain damage, cerebral production of BDNF might decrease, with a reduction of plasma BDNF. In line with this hypothesis, we speculated that, with aging, the brain might become less resistant to acute stresses; thus, the increase in plasma BDNF would represent the effort of the brain to counteract the stress induced by bed rest [26]. …”

“…Many studies demonstrate that physical activity increases circulating BDNF in humans [18-25], however this increase is attributed to an increase in cerebral production, which accounts for 70-80% of total circulating BDNF both at rest and after physical activity [21]. We have already studied plasma BDNF modification in response to immobilization, both in young and older adults [26], demonstrating an increase of BDNF level only in the latter group. We hypothesized that this increase might represent the effort of older brain, less resistant to acute stress, to counteract bed rest negative effects.…”

Posttraumatic stress disorder eliminates association of <i>TrkB rs1187327</i> with HDL-C in Chinese Han adolescents

“…Plasma BDNF was found to be correlated with TG levels (33). In contrast, the expression of TrkB in endothelium was reduced in atherosclerotic lesions in the patients with high levels of TC, TG, LDL-C and glucose, when compared with that in the subjects with normal lipid profiles (34).…”