Decreased Brain-Derived Neurotrophic Factor Serum Concentrations in Chronic Post-Stroke Subjects

Biochemical, biomechanical and imaging biomarkers of ischemic stroke: Time for integrative thinking

Stroke is one of the leading causes of adult disability affecting millions of people worldwide. Post-stroke cognitive and motor impairments diminish quality of life and functional independence. There is an increased risk of having a second stroke and developing secondary conditions with long-term social and economic impacts. With increasing number of stroke incidents, shortage of medical professionals and limited budgets, health services are struggling to provide a care that can break the vicious cycle of stroke. Effective post-stroke recovery hinges on holistic, integrative and personalized care starting from improved diagnosis and treatment in clinics to continuous rehabilitation and support in the community. To improve stroke care pathways, there have been growing efforts in discovering biomarkers that can provide valuable insights into the neural, physiological and biomechanical consequences of stroke and how patients respond to new interventions. In this review paper, we aim to summarize recent biomarker discovery research focusing on three modalities (brain imaging, blood sampling and gait assessments), look at some established and forthcoming biomarkers, and discuss their usefulness and complementarity within the context of comprehensive stroke care. We also emphasize the importance of biomarker guided personalized interventions to enhance stroke treatment and post-stroke recovery.

Multiplexing Biosensor for the Detection of Extracellular Vesicles as Biomarkers of Tissue Damage and Recovery after Ischemic Stroke

The inflammatory, reparative and regenerative mechanisms activated in ischemic stroke patients immediately after the event cooperate in the response to injury, in the restoration of functions and in brain remodeling even weeks after the event and can be sustained by the rehabilitation treatment. Nonetheless, patients' response to treatments is difficult to predict because of the lack of specific measurable markers of recovery, which could be complementary to clinical scales in the evaluation of patients. Considering that Extracellular Vesicles (EVs) are carriers of multiple molecules involved in the response to stroke injury, in the present study, we have identified a panel of EV-associated molecules that (i) confirm the crucial involvement of EVs in the processes that follow ischemic stroke, (ii) could possibly profile ischemic stroke patients at the beginning of the rehabilitation program, (iii) could be used in predicting patients' response to treatment. By means of a multiplexing Surface Plasmon Resonance imaging biosensor, subacute ischemic stroke patients were proven to have increased expression of vascular endothelial growth factor receptor 2 (VEGFR2) and translocator protein (TSPO) on the surface of small EVs in blood. Besides, microglia EVs and endothelial EVs were shown to be significantly involved in the intercellular communications that occur more than 10 days after ischemic stroke, thus being potential tools for the profiling of patients in the subacute phase after ischemic stroke and in the prediction of their recovery.

Effects of moderate-intensity aerobic exercise on serum BDNF and motor learning in the upper-limb in patients after chronic-stroke: A randomized, controlled feasibility study with embedded health economic evaluation

BACKGROUND

Brain-derived neurotrophic factor (BDNF) promotes activity-dependent neuroplasticity and is released following aerobic-exercise.

OBJECTIVE

Feasibility and efficacy of 1.Moderate-Intensity Cycle-Ergometer-Training (MI-ET) and 2.Low-Intensity Circuit-Training (LI-CT) on BDNF-serum-concentration in chronic-stroke and consequently efficacy of motor-learning in varying BDNF-concentrations (neuroplasticity being the substrate for motor-learning) via upper-limb robotic-training (RT) in both groups.

METHODS

Randomised-control feasibility-study. 12-week, 3x/week intervention, 17 chronic-stroke-survivors randomized into: (1) MI-ET&RT or (2) LI-CT&RT. Both groups completed 40 mins MI-ET or LI-CT followed by 40 mins RT. Feasibility outcomes: (1) screening and enrollment-rates, (2) retention-rates, (3) adherence: (i) attendance-rates, (ii) training-duration, (4) adverse events. Primary clinical outcomes: 1. serum-BDNF changes pre-post training (immediate) and pre-training basal-levels over 12-weeks (long-term). 2.upper-limb performance with Action-Research-Arm-Test (ARAT). Additionally, feasibility of an embedded health economic evaluation (HEE) to evaluate health-costs and cost-effectiveness.

OUTCOMES

cost-questionnaire return-rates, cost-of-illness (COI) and Health-Utitility-Index (HUI).

RESULTS

21.5% of eligible and contactable enrolled. 10 randomized to MI-ET and 7 to LI-CT. 85% of training-sessions were completed in MI-ET (306/360) and 76.3% in LI-CT-group (165/216). 12-weeks: Drop-outs MI-ET-10%, LI-CT-43%.

CLINICAL OUTCOMES

No significant changes in immediate or long-term serum-BDNF in either group. Moderate-intensity aerobic-training did not increase serum-BDNF post-stroke. Individual but no group clinically-relevant changes in ARAT-scores. HEE outcomes at 12-weeks: 100% cost-questionnaires returned. Group-costs baseline and after treatment, consistently favouring MI-ET group. COI: (1-year-time-frame): MI-ET 67382 SD (43107) Swiss-Francs and LI-CT 95701(29473) Swiss-Francs.

CONCLUSION

The study is feasible with modifications. Future studies should compare high-intensity versus moderate-intensity aerobic-exercise combined with higher dosage arm-training.

Circulating brain-derived neurotrophic factor as a potential biomarker in stroke: a systematic review and meta-analysis

Background

Stroke, an acute cerebrovascular event, is a leading cause of disability, placing a significant psycho-socioeconomic burden worldwide. The adaptation and reorganization process following any neuronal damage is regarded as neuroplasticity. Among many factors believed to attribute to this process, Brain-derived Neurotrophic Factor (BDNF) is a neurotrophin coordinating neuroplasticity after various neurological disorders such as stroke.

Methods

We conducted a systematic search in the main electronic medical databases in January 2021. Primarily we want to compare BDNF levels between patients with stroke and healthy controls (HC). Additional aims included investigation of (1) longitudinal changes in the BDNF levels post-stroke, (2) effects of physical training, (3) repeated transcranial magnetic stimulation (rTMS), and presence of depression on BDNF levels in patients with stroke.

Results

Among 6243 reviewed records from PubMed, Web of Science, and Scopus, 62 studies were eligible for inclusion in our systematic review. Subjects with stroke, n = 1856, showed lower BDNF levels compared to HC, n = 1191 (SMD [95%CI] = − 1.04 [− 1.49 to − 0.58]). No significant difference was detected in the level of BDNF through time points past stroke. BDNF levels were lower in the patients with depression compared to non-depressed subjects (SMD [95%CI] = − 0.60 [− 1.10 to − 0.10]). Physical training had an immediate positive effect on the BDNF levels and not statistically significant effect in the long term; SMD [95%CI] = 0.49 [0.09 to 0.88]) and SMD [95%CI] = 0.02 [− 0.43 to 0.47]). Lastly, rTMS showed no effect on the level of BDNF with 0.00 SMD.

Conclusions

Our study confirms that stroke significantly decreases the level of BDNF in various domains such as cognition, affect, and motor function. As BDNF is the major representative of neuroplasticity within nervous system, it is believed that stroke has a significant impact on the CNS regeneration, which is permanent if left untreated. This effect is intensified with coexisting conditions such as depression which further decrease the BDNF level but the net impact yet needs to be discovered. We also conclude that exercise and some interventions such as different medications could effectively reverse the damage but further studies are crucial to reach the exact modality and dosage for their optimal effect.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03312-y.

Exergame training-induced neuroplasticity and cognitive improvement in institutionalized older adults: A preliminary investigation

BACKGROUND

Prior research has reported cognitive improvements in elderly individuals when mental and physical exercise are practiced simultaneously, as in exergaming. However, the molecular mechanisms driving this beneficial response remain unclear. Moreover, there is robust evidence that regular exercise increases neurotrophic factors and promotes neuroplasticity, contributing to cognitive improvement. This research aimed to assess the impact of a 6-week Xbox 360 Kinect exergame protocol on cognitive function and brain-derived neurotrophic factor (BDNF) levels in institutionalized older individuals.

METHODS

Participants living in a long-term care facility were included. The intervention (Xbox 360 Kinect exergame protocol) was conducted individually and consisted of two sessions per week (40 min each) over 6 weeks. Participants' cognitive function (Montreal Cognitive Assessment, MoCA) was evaluated before and after the intervention. Blood samples (15 ml) were collected at the same time to measure BDNF levels.

RESULTS

Although there were no changes in total MoCA scores, exergame training improved the "language" domain and demonstrated a tendency toward an improvement in the "abstraction" and "memory/delayed recall" domains. Furthermore, BDNF levels were significantly increased after the intervention.

CONCLUSION

BDNF enhancement might mediate, at least in part, the cognitive changes induced by a 6-week Xbox 360 Kinect exergame protocol in institutionalized older adults.

Assessment of BNP and BDNF results in elective endovascular cerebral aneurysm treatment

BACKGROUND

B-type natriuretic peptide (BNP) levels increase with an increase in intracranial pressure. A decrease in BNP levels has been found to be associated with patient positive prognosis. Brain-derived neurotrophic factor (BDNF) levels decrease in patients with acute stroke.

AIMS

To compare the BNP and BDNF values in serum before and after elective endovascular cerebral aneurysm treatment (ECAT).

METHODS

A total of 50 patients who underwent elective ECAT were included in the study. Exclusion criteria were determined to be history of heart failure or heart attack (n = 8), renal failure (n = 5), subarachnoid hemorrhage (n = 4), or previous aneurysm clip procedure (n = 3). Intravenous blood samples were obtained from 30 patients who underwent elective ECAT before and after treatment. After centrifugation, the BNP and BDNF values in serum were obtained with the ELISA method and compared.

RESULTS

This study included 19 female and 11 male patients, aged between 24 and 75 years. The average age of the patients was 51.27 ± 13.31 years. The median BDNF values did not change significantly after ECAT (before the endovascular procedure: 3.1 ± 1.3 pg/dl; after the endovascular procedure: 2.8 ± 0.9 pg/dl, p = 0.16). Median BNP levels decreased significantly after ECAT (before the endovascular procedure: 617.50 ± 483.11 pg/ml; after the endovascular procedure: 395.00 ± 352.15 pg/ml, p < 0.001).

CONCLUSIONS

After elective endovascular cerebral aneurysm treatment, the BNP values in serum decreased significantly, and the BDNF values in serum did not change significantly.

Brain-Derived Neurotrophic Factor as a Clinical Biomarker in Predicting the Development of Post-Stroke Depression: A Review of Evidence

Studying the relationship between brain-derived neurotrophic factor (BDNF) and post-stroke depression (PSD) may help determine the potential for depression in stroke patients at the earliest stage possible. Current research has identified changes in BDNF levels in PSD patients. Thus, this article was intended as a review of evidence with respect to changes in the expression of BDNF in patients with PSD by integrating extant findings.

We conducted a search in the electronic databases PubMed, EMBASE, and PsycINFO (all records from January 1, 2000, through October 20, 2020) using keywords: “brain-derived neurotrophic factor OR BDNF,” “post-stroke depression OR PSD,” “expression level,” “association,” and “relationship.” Returned articles were considered for inclusion in this review if they were empirical studies investigating the association between BDNF expression and PSD.

Seven original papers were selected for review and revealed inconsistent findings. Five out of seven studies reported a significant decrease in BDNF levels in PSD patients at a certain stage (most likely the early stage) of stroke after admission, whereas the other two showed contrasting findings.

Overall, this review reveals associations between changes in serum BDNF levels and depression following stroke. Whether serum BDNF levels, especially in the early phase of stroke, can be a potentially effective biomarker for predicting the risk of subsequent PSD development is still open to debate.

Resilience is an independent correlate of the course of quality of life in patients with first-ever ischemic stroke

OBJECTIVES

To explore the changes in quality of life from the acute hospitalization period to 6 months after discharge in patients with first-ever ischemic stroke and to identify the association between resilience and the course of quality of life.

DESIGN

A prospective longitudinal cohort study.

SETTING

This study was conducted in Shanghai, China.

PARTICIPANTS

Two hundred and seventeen stroke patients were recruited for an initial questionnaire survey from two tertiary hospitals from February 2017 to January 2018.

INTERVENTION

None.

MEASUREMENTS

Quality of life was measured using the Stroke Scale Quality of Life. Resilience was assessed using the Connor-Davidson Resilience Scale. Other validated measurement instruments included the modified Rankin Scale and Hospital Anxiety and Depression Scale. A multilevel model was used for the analysis of repeated measurements and to determine the association between resilience and quality of life.

RESULTS

Quality of life scores significantly improved over the 6 months after discharge (B = 7.31, p < .0001). The multilevel model indicated that resilience was positively correlated with the course of quality of life (B = .133, p < .0001), independent of stroke severity (B = -.051, p = .0006), neurological function (B = -.577, p < .0001), hospitalization days (B = .023, p = .0099), anxiety (B = -.100, p =< .0001), depression (B = -.149, p < .0001), time (B = .360, p < .0001), and the interactions of time with hospitalization days (B = -.008, p = .0002), neurological function (B = .021, p < .0024), depression (B = -.014, p = .0273), and time (B = -.031, p < .0001).

CONCLUSIONS

Resilience played an important role in predicting the self-reported course of quality of life in stroke patients. Our findings emphasized the reasonableness and importance of developing suitable resilience-targeted clinical strategies for improving prognosis in stroke patients.

Constraint Induced Movement Therapy Increases Functionality and Quality of Life after Stroke

This blind randomized clinical trial evaluated the effect of CIMT on the functionality and quality of life (QOL) of chronic hemiparetics. Thirty volunteers were divided into two groups: Control (CG) and CIMT (CIMTG); evaluated before and after 12 and 24 intervention sessions. The scales used were: adapted Fugl-Meyer Motor Assessment (FMA), Modified Ashworth, Stroke Specific Quality Of Life (SS-QOL) and the Functional Reach Test (FRT). The scores for all FMA variables in the CIMTG increased until the 24th session, differing from the pre-treatment. In the CG, the scores increased for pain, coordination/ speed and sensitivity. In the FRT there was an increase in the scores in both groups; after the 12th and 24th sessions, the result of the CIMTG was superior to the CG. For the SS-QOL in the CIMTG, the general score and most of the variables increased, as well as in the CG. Muscle tone in CIMTG was lower compared to CG after 24 sessions. Both protocols used in the study were effective, the CIMT protocol showed benefits in recovering the functionality of the paretic upper limb, in the functional range and in reducing muscle tone, with a consequent improvement in quality of life.

Aerobic exercise prescription in heart failure patients with cardiac resynchronization therapy

Exercise for heart failure patients had been shown to be beneficial in improving functional status, and was reviewed to be safe. In cases of advanced heart failure, Cardiac Resynchronization Therapy (CRT) is a promising medical option before being a heart transplant candidate. CRT itself is a biventricular pacing device, which could detect electrical aberrance in the failing heart and provide a suitable response. Studies have shown that exercise has clear benefits toward improving an overall exercise capacity of the patients. Despite its impacts, these randomized clinical trials have varying exercise regime, and until now there has not been a standardized exercise prescription for this group of patients. The nature of CRT as a pacemaker, sometimes with defibrillator, being attached to a heart failure patient, each has its own potential exercise hazards. Therefore, providing detailed exercise prescription in adjusting to the medical condition is very essential in the field of physical medicine and rehabilitation. Being classified as a high-risk patient group, exercise challenges for the complex heart failure with CRT patients will then be discussed in this literature review, with a general aim to provide a safe, effective, and targeted exercise regime.

Effects of a multimodal exercise protocol on functional outcomes, epigenetic modulation and brain-derived neurotrophic factor levels in institutionalized older adults: a quasi-experimental pilot study

Epigenetic changes have been shown to be associated with both aging process and aging-related diseases. There is evidence regarding the benefits of physical activity on the functionality, cognition, and quality of life of institutionalized older adults, however, the molecular mechanisms involved are not elucidated. The purpose of this pilot study was to investigate the effects of a multimodal exercise intervention on functional outcomes, cognitive performance, quality of life (QOL), epigenetic markers and brain-derived neurotrophic factor (BDNF) levels among institutionalized older adult individuals. Participants (n = 8) without dementia who were aged 73.38 ± 11.28 years and predominantly female (87.5%) were included in this quasi-experimental pilot study. A multimodal exercise protocol (cardiovascular capacity, strength, balance/agility and flexibility, perception and cognition) consisted of twice weekly sessions (60 minutes each) over 8 weeks. Balance (Berg Scale), mobility (Timed Up and Go test), functional capacity (Six-Minute Walk test), cognitive function (Mini-Mental State Examination) and QOL (the World Health Organization Quality of Life-BREF Scale questionnaire) were evaluated before and after the intervention. Blood sample (15 mL) was also collected before and after intervention for analysis of biomarkers global histone H3 acetylation and brain-derived neurotrophic factor levels. Significant improvements were observed in cognitive function, balance, mobility, functional capacity and QOL after the intervention. In addition, a tendency toward an increase in global histone H3 acetylation levels was observed, while brain-derived neurotrophic factor level remained unchanged. This study provided evidence that an 8-week multimodal exercise protocol has a significant effect on ameliorating functional outcomes and QOL in institutionalized older adult individuals. In addition, it was also able to promote cognitive improvement, which seems to be partially related to histone hyperacetylation status. The Ethics Research Committee of Centro Universitário Metodista-IPA, Brazil approved the current study on June 6, 2019 (approval No. 3.376.078).

Increased serum brain-derived neurotrophic factor with high-intensity interval training in stroke patients: A randomized controlled trial

BACKGROUND

Physiological adaptations of stroke patients after high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) remain unclear.

OBJECTIVE

This study determined the HIIT and MICT effects on aerobic capacity, cerebral oxygenation, peak cardiac output (CO), and serum brain-derived neurotrophic factor (BDNF) in stroke patients.

METHODS

We included 23 stroke patients with age about 55 years and stroke duration>24 months; participants completed 36 sessions of exercise training for 30min; 13 were randomly assigned to perform MICT at 60% of peak oxygen consumption (VO_2peak) and 10 to perform HIIT at alternating 80% (3min) and 40% (3min) VO_2peak. Before and after interventions, we evaluated VO_2peak, peak CO, arteriovenous oxygen difference (AV O_2diff), bilateral frontal cortex oxygenation (relative changes of oxyhemoglobin Δ[O₂Hb], deoxyhemoglobin Δ[HHb], and total hemoglobin Δ[THb] levels), serum brain-derived neurotrophic factor (BDNF) level, and fluorescent cell staining for neuron morphology and percentage of cell-bearing neurites (% neurites).

RESULTS

HIIT induced significant increases in VO_2peak (P=0.008), CO (P=0.038), Δ[HHb] (P=0.046), Δ[THb] (P=0.046), and serum BDNF level (P=0.012). The improvement in VO_2peak was significantly greater with HIIT than MICT (20.7% vs. 9.8%, P=0.031), as was AV O_2diff (P=0.041), Δ[HHb] (P=0.027), and serum BDNF level (P<0.001). HIIT facilitated neuron dendritic protrusions (greater % neurites, P=0.012) with prominent redistribution of mitochondria.

CONCLUSION

As compared with MICT, HIIT-improved aerobic capacity by increasing systemic tissue O₂ extraction in stroke patients. Increased cerebral O₂ utilization in the involved hemisphere was also identified after HIIT. These physiological adaptations may be associated with increased serum BDNF level. In vitro dendritic growth in neurons treated with serum from HIIT participants may imply significant effects on neuron activities as compared with MICT. CLINICALTRIALS.

GOV IDENTIFIER

NCT04135391.

Brain-derived neurotrophic factor levels in pediatric sickle cell disease

BACKGROUND

Children with sickle cell disease (SCD) have an increased risk of neurological complications, particularly stroke and silent cerebral infarction (SCI). Brain-derived neurotrophic factor (BDNF) is a nerve growth factor associated with neuronal survival, synaptic plasticity, elevated transcranial Doppler (TCD) velocities and increased risk of stroke in patients with SCD. The objective of this study was to analyze plasma BDNF protein levels in children with SCD participating in the Silent Cerebral Infarct Transfusion Multi-Center Clinical Trial (SIT Trial), comparing plasma samples of children with SCD and SCI to plasma samples from children with SCD without SCI, as well as healthy pediatric control participants.

PROCEDURE

Entry, exit, and longitudinal blood samples were collected from 190 SIT Trial participants with SCD and healthy pediatric controls over time. BDNF levels were measured by enzyme-linked immunosorbent assay. Sample collection was not optimized for measurements of BDNF, but factors affecting BDNF levels were accounted for in analyses.

RESULTS

BDNF levels were significantly higher in children with SCD in comparison to healthy pediatric control subjects. BDNF levels significantly increased over time in SCD participants. BDNF levels did not show any significant associations with the presence or absence of SCI or new/progressive SCI/stroke or TCD velocities.

CONCLUSIONS

Plasma BDNF levels are elevated and increase over time in children with SCD. Additional studies with more longitudinal samples are needed to address the reasons for those increased levels.

Gait turning patterns in chronic ischemic stroke males and its relationship to recovery: A cross-sectional study

INTRODUCTION

Impaired turning patterns have been considered as 1 factor which potentially leads to disability in chronic stroke patients. Mobility comprises 80% of the chief disability, and would eventually lead to falls. Expanded Timed Up and Go (ETUG) is an effective mobility assessment method. It utilizes video recording to analyze the conventional Time Up and Go (TUG) Test components, which includes turning pattern analysis.

METHODS

Six healthy males without stroke history and 21 chronic ischemic stroke males (divided into subjects with or without the presence of flexor synergy pattern subgroups) capable of independent ambulation were recruited from Neurology and Medical Rehabilitation Department outpatient clinic. ETUG tests were recorded for each subject and were analyzed thoroughly using a computer program.

RESULTS

Timed Up and Go time was significantly different between the 3 groups (P = .001). As compared to control, and synergy absent group, median turning time was highest in chronic stroke patients with presence of flexor synergy by 2786 ms (P = .002), but was not significantly different in percentage ETUG (14%, P = .939). Further analysis revealed that Brunnstrom stage and number of steps taken for turning significantly affect TUG duration. Other factors such as hemiparetic side, or body height were not significantly associated.

DISCUSSION

The presence of flexor synergy would significantly affect turning time, this would then correlate to the disability of shifting body's center of gravity, as a part of the Stroke core set of International Classification of Functioning, Disability, and Health (ICF).Therefore, stroke patients need to have early ambulatory training regarding pivoting motion rather than solely focusing on straight walking. Instead of hemiparetic side, it is possible that overall turning time is affected by coordination and orientation capability, signifying the importance of cortical plasticity.

Serum levels of insulin-like growth factor-1 and brain-derived neurotrophic factor as potential recovery biomarkers in stroke

OBJECTIVES

Our objectives were: 1) to determine whether maximal aerobic exercise increased serum neurotrophins in chronic stroke and 2) to determine the factors that predict resting and exercise-dependent levels.

METHODS

We investigated the potential predictors of resting and exercise-dependent serum insulin-like growth factor-1 and brain-derived neurotrophic factor among 35 chronic stroke patients. Predictors from three domains (demographic, disease burden, and cardiometabolic) were entered into 4 separate stepwise linear regression models with outcome variables: resting insulin-like growth factor, resting brain-derived neurotrophic factor, exercise-dependent change in insulin-like growth factor, and exercise-dependent change brain-derived neurotrophic factor.

RESULTS

Insulin-like growth factor decreased after exercise (p = 0.001) while brain-derived neurotrophic factor did not change (p = 0.38). Greater lower extremity impairment predicted higher resting brain-derived neurotrophic factor (p = 0.004, r² = 0.23). Higher fluid intelligence predicted greater brain-derived neurotrophic factor response to exercise (p = 0.01, r² = 0.18). There were no significant predictors of resting or percent change insulin-like growth factor-1.

DISCUSSION

Biomarkers have the potential to characterize an individual's potential for recovery from stroke. Neurotrophins such as insulin-like growth factor-1 and brain-derived neurotrophic factor are thought to be important in neurorehabilitation; however, the factors that modulate these biomarkers are not well understood. Resting brain-derived neurotrophic factor and percent change in brain-derived neurotrophic factor were related to physical and cognitive recovery in chronic stroke, albeit weakly. Insulin-like growth factor-1 was not an informative biomarker among chronic stroke patients. The novel finding that fluid intelligence positively correlated with exercise-induced change in brain-derived neurotrophic factor warrants further research.

A single exercise bout and locomotor learning after stroke: physiological, behavioural, and computational outcomes

KEY POINTS

Previous work demonstrated an effect of a single high-intensity exercise bout coupled with motor practice on the retention of a newly acquired skilled arm movement, in both neurologically intact and impaired adults. In the present study, using behavioural and computational analyses we demonstrated that a single exercise bout, regardless of its intensity and timing, did not increase the retention of a novel locomotor task after stroke. Considering both present and previous work, we postulate that the benefits of exercise effect may depend on the type of motor learning (e.g. skill learning, sensorimotor adaptation) and/or task (e.g. arm accuracy-tracking task, walking).

ABSTRACT

Acute high-intensity exercise coupled with motor practice improves the retention of motor learning in neurologically intact adults. However, whether exercise could improve the retention of locomotor learning after stroke is still unknown. Here, we investigated the effect of exercise intensity and timing on the retention of a novel locomotor learning task (i.e. split-belt treadmill walking) after stroke. Thirty-seven people post stroke participated in two sessions, 24 h apart, and were allocated to active control (CON), treadmill walking (TMW), or total body exercise on a cycle ergometer (TBE). In session 1, all groups exercised for a short bout (∼5 min) at low (CON) or high (TMW and TBE) intensity and before (CON and TMW) or after (TBE) the locomotor learning task. In both sessions, the locomotor learning task was to walk on a split-belt treadmill in a 2:1 speed ratio (100% and 50% fast-comfortable walking speed) for 15 min. To test the effect of exercise on 24 h retention, we applied behavioural and computational analyses. Behavioural data showed that neither high-intensity group showed greater 24 h retention compared to CON, and computational data showed that 24 h retention was attributable to a slow learning process for sensorimotor adaptation. Our findings demonstrated that acute exercise coupled with a locomotor adaptation task, regardless of its intensity and timing, does not improve retention of the novel locomotor task after stroke. We postulate that exercise effects on motor learning may be context specific (e.g. type of motor learning and/or task) and interact with the presence of genetic variant (BDNF Val66Met).

The feasibility of an acute high-intensity exercise bout to promote locomotor learning after stroke

BACKGROUND

People post-stroke can learn a novel locomotor task but require more practice to do so. Implementing an approach that can enhance locomotor learning may therefore improve post-stroke locomotor recovery. In healthy adults, an acute high-intensity exercise bout before or after a motor task may improve motor learning and has thus been suggested as a method that could be used to improve motor learning in neurorehabilitation. However, it is unclear whether an acute high-intensity exercise bout, which stroke survivors can feasibly complete in neurorehabilitation session, would generate comparable results.

OBJECTIVE

To determine a feasible, high-intensity exercise protocol that could be incorporated into a post-stroke neurorehabilitation session and would result in significant exercise-induced responses.

METHODS

Thirty-seven chronic stroke survivors participated. We allocated subjects to either a control (CON) or one of the exercise groups: treadmill walking (TMW), and total body exercise (TBE). The main exercise-induced measures were: average intensity (% max intensity) and time spent (absolute: seconds; normalized: % total time) at target exercise intensity, and magnitudes of change in serum lactate (mmol/l) and brain-derived neurotrophic factor (BDNF; ng/ml).

RESULTS

Compared to CON, both exercise groups reached and exercised longer at their target intensities and had greater responses in lactate. However, the TBE group exercised longer at target intensity and with greater lactate response than the TMW group. There were no significant BDNF responses among groups.

CONCLUSIONS

An acute high-intensity exercise bout that could be incorporated into a neurorehabilitation learning-specific session and results in substantial exercise-induced responses is feasible post-stroke.

Association of lower serum Brain-derived neurotrophic factor levels with larger infarct volumes in acute ischemic stroke

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) plays a potential role in stroke recovery, as it promotes plasticity. The aim of this study is to investigate the association between infarct volume using DWI and BDNF at admission in patients with acute ischemic stroke (AIS).

METHODS

The study population comprised consecutive patients with an AIS diagnosis who had been referred to our hospital between January 2015 and June 2016. The severity of stroke was evaluated by the National Institutes of Health Stroke Scale (NIHSS) at admission. Infarct volumes indicated by DWI were measured with MIPAV software. The relationship between median DWI infarct volume and serum BDNF level quartiles was evaluated using a semiparametric approach with univariate and multivariate quartile regression analysis.

RESULTS

In this study, 270 patients were included and met the study criteria. The median DWI infarct volumes for the serum BDNF level quartiles (lowest to highest) were 10.56, 5.13, 3.75 and 2.43ml. Nonparametric Spearman rank correlation revealed a statistically significant negative correlation between serum BDNF level and DWI infarct volume (r=-0.363; P<0.001). The median DWI infarct volume in the lowest BDNF quartile was significantly larger than those in the upper 3 quartiles (P<0.001). Further, median adjusted DWI infarct volumes (IQR) for each of the BDNF level quartiles were 7.77, 4.56, 3.75, and 2.43ml from lowest to highest quartiles.

CONCLUSIONS

Larger stroke infarct volumes using DWI are associated with lower levels of BDNF at admission. Further investigations are suggested to elucidate the role of BDNF as part of a potential neuroprotective strategy.

Assessed and Emerging Biomarkers in Stroke and Training-Mediated Stroke Recovery: State of the Art

Since the increasing update of the biomolecular scientific literature, biomarkers in stroke have reached an outstanding and remarkable revision in the very recent years. Besides the diagnostic and prognostic role of some inflammatory markers, many further molecules and biological factors have been added to the list, including tissue derived cytokines, growth factor-like molecules, hormones, and microRNAs. The literatures on brain derived growth factor and other neuroimmune mediators, bone-skeletal muscle biomarkers, cellular and immunity biomarkers, and the role of microRNAs in stroke recovery were reviewed. To date, biomarkers represent a possible challenge in the diagnostic and prognostic evaluation of stroke onset, pathogenesis, and recovery. Many molecules are still under investigation and may become promising and encouraging biomarkers. Experimental and clinical research should increase this list and promote new discoveries in this field, to improve stroke diagnosis and treatment.