Abstract
Brain-derived neurotrophic factor (BDNF) is a major orchestrator of exercise-induced brain plasticity and circulating (peripheral) BDNF may have central effects. Approximately 99% of circulating BDNF is platelet-bound, and at rest ~30% of circulating platelets are stored in the spleen. Interestingly, forearm handgrip exercise significantly elevates sympathetic outflow and has been shown to induce splenic constriction, suggesting that small muscle mass exercise could stand as a viable strategy for increasing circulating BDNF; however, the BDNF response to handgrip exercise is currently unknown.Purpose: This study examined BDNF and platelet responses to short-duration maximal (ME) and prolonged submaximal (SE) effort handgrip exercise.Methods: Healthy males (n = 18; 21.4 ± 2.1 years, BMI 25.0 ± 1.0 kg/m2) performed 10 min of ME and 30 min of SE. Blood was sampled for the determination of serum BDNF and platelet count at rest and during the last minute of exercise.Results: Compared to rest, serum BDNF significantly increased during ME (21.2%) and SE (11.2%), which displayed a non-significant trend toward an intensity-dependent response. Platelets increased in an intensity-dependent fashion compared to rest with an 8.0% increase during ME and 3.1% during SE, and these responses were significantly correlated with diastolic blood pressure responses to handgrip exercise. Further, the amount of BDNF per platelet significantly increased compared to rest during ME (13.4%) and SE (8.7%).Conclusions: Handgrip exercise evokes significant increases in serum BDNF and platelets, implicating splenic constriction as a key mechanism and confirming efficacy of this exercise model for elevating circulating BDNF.
Highlights
Brain-derived neurotrophic factor (BDNF) is recognized for its role in orchestrating activity-dependent brain plasticity (Cotman et al, 2007)
The major findings from this study were (a) serum BDNF significantly increased in response to both exercise protocols, (b) platelets significantly increased in an intensitydependent manner, with maximal effort exercise (ME) evoking a larger response compared to submaximal effort exercise (SE), and (c) the amount of BDNF per platelet significantly increased in both exercise conditions
This is the first study to demonstrate that exercise with as little muscle mass as contained in a forearm can significantly increase circulating BDNF. This appears to be sensitive to exercise intensity (p = 0.06 for differences between ME and SE). This substantial BDNF response is associated with an intensity-dependent increase in circulating platelets indicative of thrombocytosis that we interpret as being a major source of exercise-induced BDNF in a forearm handgrip model
Summary
Brain-derived neurotrophic factor (BDNF) is recognized for its role in orchestrating activity-dependent brain plasticity (Cotman et al, 2007). There is an association between CNS and circulating levels of BDNF, suggesting that peripheral levels may be important for CNS function (Angelucci et al, 2011) In support of this are findings from studies on depression and aging. The age-associated decline in circulating BDNF (Lommatzsch et al, 2005; Ziegenhorn et al, 2007) is thought to mediate hippocampal shrinkage and worsening of spatial memory (Erickson et al, 2010). Given this evidence, exploration into means by which circulating BDNF can be augmented has important implications for brain health in both clinical and healthy populations, alike
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