The relationship between brain-derived neurotrophic factor, irisin and cognitive skills of endurance athletes

The relationship of cognitive functions with brain damage markers, myokines and neurotrophic factors in amateur soccer players

Concussive and subconcussive head impatcs in sports have drawn more attention in recent years. Thus, the cognitive ability of soccer players and its relationship with circulating levels of irisin, brain-derived neurotrophic factor (BDNF), and neuron-specific enolase (NSE) were studied in this study. Fifteen amateur soccer players and 15 sedentary men volunteered to participate in this study. After evaluating the aerobic and anaerobic capacities of the participants, their cognitive performances were measured. Blood samples were obtained at rest, and the ELISA method was used to measure the concentrations of serum NSE, plasma BDNF, and irisin. There were no differences between groups in terms of cognitive abilities or serum NSE levels (P > 0.05). Plasma irisin (P = 0.019) and BDNF (P < 0.001) levels were higher in the soccer players than the sedentary subjects. There was a positive correlation between irisin and NSE (r = 0.461, P = 0.010) and BDNF (r = 0.405, P = 0.007) concentrations. General cognitive performance is maintained in amateur soccer players. This is accompanied by the unchanged NSE. However, elevated irisin and BDNF levels appear to be independent of cognitive performance.

Aerobic exercise attenuates LPS-induced cognitive dysfunction by reducing oxidative stress, glial activation, and neuroinflammation

Physical activity has been considered an important non-medication intervention in preserving mnemonic processes during aging. However, how aerobic exercise promotes such benefits for human health remains unclear. In this study, we aimed to explore the neuroprotective and anti-inflammatory effects of aerobic exercise against lipopolysaccharide (LPS)-induced amnesic C57BL/6J mice and BV-2 microglial cell models. In the in vivo experiment, the aerobic exercise training groups were allowed to run on a motorized treadmill 5 days/week for 4 weeks at a speed of 10 rpm/min, with LPS (0.1 mg/kg) intraperitoneally injected once a week for 4 weeks. We found that aerobic exercise ameliorated memory impairment and cognitive deficits among the amnesic mice. Correspondingly, aerobic exercise significantly increased the protein expressions of FNDC5, which activates target neuroprotective markers BDNF and CREB, and antioxidant markers Nrf2/HO-1, leading to inhibiting microglial-mediated neuroinflammation and reduced the expression of BACE-1 in the hippocampus and cerebral cortex of amnesic mice. We estimated that aerobic exercise inhibited neuroinflammation in part through the action of FNDC5/irisin on microglial cells. Therefore, we explored the anti-inflammatory effects of irisin on LPS-stimulated BV-2 microglial cells. In the in vitro experiment, irisin treatment blocked NF-κB/MAPK/IRF3 signaling activation concomitantly with the significantly lowered levels of the LPS-induced iNOS and COX-2 elevations and promotes the Nrf2/HO-1 expression in the LPS-stimulated BV-2 microglial cells. Together, our findings suggest that aerobic exercise can improve the spatial learning ability and cognitive functions of LPS-treated mice by inhibiting microglia-mediated neuroinflammation through its effect on the expression of BDNF/FNDC5/irisin.

Effectiveness of supplementation with date seed (Phoenix dactylifera) as a functional food on inflammatory markers, muscle damage, and BDNF following high-intensity interval training: a randomized, double-blind, placebo-controlled trial

PURPOSE

High-intensity interval training (HIIT) is one of the most effective protocols, even though acute HIIT causes inflammatory and oxidative damage. The aim of this study was to examine the effect of date seeds powder (DSP) during HIIT sessions on inflammation markers, oxidants and antioxidants, brain-derived neurotrophic factor (BDNF), exercise-induced muscle damage, and body composition.

MATERIAL AND METHODS

Thirty-six recreational runners (men and women), aged 18-35 years, were randomly assigned to consume 26 g/day of DSP or wheat bran powder during HIIT workouts for a period of 14 days. At baseline, at the end of the intervention, and 24 h after the intervention, blood samples were obtained to determine inflammatory, oxidant/antioxidant, and muscle damage markers, as well as BDNF.

RESULTS

DSP supplementation resulted in a significant downward trend in high-sensitivity C-reactive protein (Psupplement × time = 0.036), tumor necrosis factor alpha (Psupplement × time = 0.010), interleukin-6 (Psupplement × time = 0.047), malondialdehyde (Psupplement × time = 0.046), creatine kinase (Psupplement × time = 0.045), and lactate dehydrogenase (Psupplement × time = 0.040) after the intervention, as well as a significant increase in total antioxidant capacity (Psupplement × time ≤ 0.001). However, interleukin-10 (Psupplement × time = 0.523), interleukin-6/interleukin-10 (Psupplement × time = 0.061), BDNF (Psupplement × time = 0.160), and myoglobin (Psupplement × time = 0.095) levels did not change significantly in comparison to the placebo group. Moreover, analysis demonstrated that DSP supplementation over 2 weeks had no significant effect on body composition.

CONCLUSION

During the 2 weeks of the HIIT protocol, the consumption of date seed powder by participants who had engaged in moderate or high physical activity alleviated inflammation and muscle damage.

ETHICS AND DISSEMINATION

This study was approved by the Medical Ethics Committee of TBZMED (No.IR.TBZMED.REC.1399.1011).

TRIAL REGISTRATION

Iranian Registry of Clinical Trials website ( www.IRCt.ir/ , IRCT20150205020965N9).

Irisin: A bridge between exercise and neurological diseases

Exercise plays a beneficial regulating role on each organ of the body through different mechanisms and is a powerful weapon to prevent disease. Irisin is released from muscle and widely distributed in the human body, participating in the physiological processes of multiple human systems and playing a protective role in multiple human organs. The protective effect of irisin on the nervous system is particularly remarkable, which can improve cognitive function, reduce the risk of ischemic stroke and improve its prognosis. Irisin also plays a guiding role in the prevention and treatment of neurodegenerative diseases and ischemic cerebrovascular diseases. Exercise is the driving factor promoting irisin secretion, and different exercise modes, intensity, frequency, and time all affect the level of serum irisin. As a result of analyzing the effects of various exercise modes on irisin secretion, we proposed an exercise program with a higher level of irisin secretion.

Anti-Seizure and Neuronal Protective Effects of Irisin in Kainic Acid-Induced Chronic Epilepsy Model with Spontaneous Seizures

An increased level of reactive oxygen species is a key factor in neuronal apoptosis and epileptic seizures. Irisin reportedly attenuates the apoptosis and injury induced by oxidative stress. Therefore, we evaluated the effects of exogenous irisin in a kainic acid (KA)-induced chronic spontaneous epilepsy rat model. The results indicated that exogenous irisin significantly attenuated the KA-induced neuronal injury, learning and memory defects, and seizures. Irisin treatment also increased the levels of brain-derived neurotrophic factor (BDNF) and uncoupling protein 2 (UCP2), which were initially reduced following KA administration. Furthermore, the specific inhibitor of UCP2 (genipin) was administered to evaluate the possible protective mechanism of irisin. The reduced apoptosis, neurodegeneration, and spontaneous seizures in rats treated with irisin were significantly reversed by genipin administration. Our findings indicated that neuronal injury in KA-induced chronic epilepsy might be related to reduced levels of BDNF and UCP2. Moreover, our results confirmed the inhibition of neuronal injury and epileptic seizures by exogenous irisin. The protective effects of irisin may be mediated through the BDNF-mediated UCP2 level. Our results thus highlight irisin as a valuable therapeutic strategy against neuronal injury and epileptic seizures.

A Bibliometric Analysis of the Literature on Irisin from 2012-2021

Irisin is a hormone-like molecule mainly released by skeletal muscles in response to exercise, which is proposed to induce the ‘browning’ of white adipose tissue. Since its identification, irisin was reported to be closely associated with many metabolic diseases, including type 2 diabetes mellitus (T2DM), obesity, cardiovascular disease (CVD), and metabolic bone diseases. In recent years, irisin has attracted increasing research interest, and numerous studies have been published in this field. Thus, it is essential to identify the current research status of irisin and measure research hotspots and possible future trends. In this study, by utilizing two visualization software named CiteSpace and VOSviewer, we analyzed 1510 Web of Science publications on irisin published from 2012 to 2021. Our results show that the number of irisin-related articles published annually has increased significantly. China participates in the most studies, followed by the United States and Turkey. Firat University, Harvard University, and Shandong University are three major institutions with larger numbers of publications. The analysis of keywords co-occurrence indicates that insulin resistance, inflammation, and circulating irisin levels in serum are the research hotspots. Apoptosis, BDNF, and osteoporosis will likely become the focus of future research related to irisin. Overall, this study may provide helpful insights for researchers to understand the current research situation and identify the potential frontiers of irisin.

State of Knowledge on Molecular Adaptations to Exercise in Humans: Historical Perspectives and Future Directions

For centuries, regular exercise has been acknowledged as a potent stimulus to promote, maintain, and restore healthy functioning of nearly every physiological system of the human body. With advancing understanding of the complexity of human physiology, continually evolving methodological possibilities, and an increasingly dire public health situation, the study of exercise as a preventative or therapeutic treatment has never been more interdisciplinary, or more impactful. During the early stages of the NIH Common Fund Molecular Transducers of Physical Activity Consortium (MoTrPAC) Initiative, the field is well-positioned to build substantially upon the existing understanding of the mechanisms underlying benefits associated with exercise. Thus, we present a comprehensive body of the knowledge detailing the current literature basis surrounding the molecular adaptations to exercise in humans to provide a view of the state of the field at this critical juncture, as well as a resource for scientists bringing external expertise to the field of exercise physiology. In reviewing current literature related to molecular and cellular processes underlying exercise-induced benefits and adaptations, we also draw attention to existing knowledge gaps warranting continued research effort. © 2021 American Physiological Society. Compr Physiol 12:3193-3279, 2022.

Neurotrophic Factors and Brain Health in Children with Overweight and Obesity: The Role of Cardiorespiratory Fitness

ABSTRACTNeurotrophic factors and cardiorespiratory fitness are both considered important in developmental trajectories but their link to brain health remains poorly understood. The aims of the study were to examine whether levels of plasma-derived neurotrophic factors were associated with brain health indicators in children with overweight or obesity; and to test whether these associations were moderated by cardiorespiratory fitness. 100 children (41% girls) were included in this analysis. Plasma levels of brain-derived neurotrophic factor, insulin-like growth factor-1, vascular endothelial growth factor A, and epidermal growth factor were determined by XMap technology. Academic performance and executive function were assessed using validated neuropsychological tests. Hippocampal volume was measured using magnetic resonance imaging. Cardiorespiratory fitness was assessed using the 20-m Shuttle Run Test. Insulin-like growth factor-1 was positively associated with cognitive flexibility. Stratified analyses by fitness categories (i.e., unfit vs. fit) showed that brain-derived neurotrophic factor was positively associated with right posterior hippocampal volume in fit children, and epidermal growth factor was negatively associated with right hippocampal, and right anterior hippocampal volumes in their unfit peers, with a moderating role of cardiorespiratory fitness in these associations. However, all these significant associations disappeared after correction for multiple comparisons. The association between neurotrophic factors and brain health indicators in children with overweight/obesity was neither strong nor consistent. These results could help enhance our understanding of determinants of brain health in children with overweight/obesity.Trial registration: ClinicalTrials.gov identifier: NCT02295072..

Loss of association between plasma irisin levels and cognition in Alzheimer's disease

BACKGROUND

Irisin, an exercise-induced myokine, has been shown to have beneficial effects on cognitive and metabolic functions. However, previous studies assessing the levels of circulating irisin in patients with Alzheimer's disease (AD) or diabetes mellitus (DM) have provided inconsistent results. This suggests that the normal physiological action of irisin may be altered by disease-associated pathological conditions in target organs.

OBJECTIVE

To investigate the association of plasma levels of irisin with cognition and brain structures according to the presence or absence of AD and DM.

METHODS

Plasma levels of irisin, multi-domain cognition, and volumes of relevant brain regions were assessed using enzyme-linked immunoassay, neuropsychological test, and magnetic resonance imaging, respectively. We classified 107 participants by cognitive (cognitively normal [CN, n = 23], mild cognitive impairment [MCI, n = 49], and AD [n = 35]) and metabolic (non-DM [n = 75] and DM [n = 32]) states.

RESULTS

Disease state-stratified multiple regression analyses showed that plasma levels of irisin were positively associated with cognition only in participants without AD (CN plus MCI). By contrast, in participants with AD, these associations lost significance, and furthermore, higher levels of irisin indicated smaller hippocampal, superior temporal, and inferior frontal volumes. The association between plasma irisin levels and cognition was not affected by the presence of DM. Consistently, moderation analysis revealed that the relationship between plasma irisin levels and cognition or brain structures was significantly modified by the presence of AD, not that of DM.

CONCLUSION

Our findings suggest that the beneficial actions of circulating irisin on cognition may be attenuated by AD-induced pathological conditions in the brain.

Exercise Training Improves Memory Performance in Older Adults: A Narrative Review of Evidence and Possible Mechanisms

Exercise, neurotransmitters, growth factors, myokines, and potential effects on the brain.

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Brain-Derived Neurotrophic Factor and Psychophysiological Response in Youth Badminton Athletes During the Season

PURPOSE

To analyze peripheral brain-derived neurotrophic factor (BDNF) levels and psychophysiological parameters in youth badminton athletes during the season and to determine the relationship between variables.

METHODS

Fourteen young badminton athletes were assessed over the season (preseason, middle season, and final season). Serum BDNF (sBDNF) was determined during the preseason and final season. Sleep time, total physical activity, and time in vigorous activity were measured using an accelerometer. The fat-free mass, skeletal muscle mass, fat mass, handgrip strength, cardiorespiratory fitness (VO2max), and dietary intake were evaluated during the season. The Stroop Color and Word Test was employed to assess cognitive tasks. To evaluate the mood, the Brunel Mood Scale was used.

RESULTS

There  were lower sBDNF levels (-16.3% [46.8%]; P = .007) and sleep time (final season = 5.7 [1.1] vs preseason = 6.6 [1.1] h·night-1, P = .043) during the end of the season. The total calories and carbohydrate intake decreased across the season (P < .05). Conversely, better cognitive function was found in the final season with respect to the preseason (P < .05). There were significant correlations between BDNF and VO2max only in the preseason (r = .61, P = .027), but no significant relationship was found among sBDNF and cognitive performance, sleep time, and percentage of won games.

CONCLUSIONS

Youth badminton athletes decreased their sBDNF levels, sleep time, carbohydrate, and calorie intake across the season. The athletes improved in cognitive function; however, only the females improved in body composition, and the males improved their VO2max in the middle season. The sBDNF levels were positively correlated with the VO2max in the preseason, and no correlations were observed among the sBDNF and psychological parameters, sleep time, and sport performance during the season.

Combined Physical Training Increases Plasma Brain-Derived Neurotropic Factor Levels, But Not Irisin in People Living with HIV/AIDS

This study evaluated plasma levels of brain-derived neurotropic factor (BDNF), irisin, and lactate in people living with HIV/AIDS who completed a combined physical training program. Nineteen HIV+ participants (age: 39.60 ± 10.96 years; carrier time: 7.75 ± 7.88 years; time of ART: 6.41 ± 5.93 years) performed strength/aerobic training (combined physical training) in the same session for 8 weeks and levels of BDNF, irisin, and lactate were assessed. BDNF (pg/mL) was higher post-CPT (Pre: 1258.73 ± 372.30; Post: 1504.17 ± 322.30; p < 0.001). Irisin (ng/mL) showed no change (Pre: 115.61 ± 72.41; Post: 125.87 ± 81.14; p = 0.973). There was positive correlation between irisin and lactate (mmol/L) pre (r = 0.55, p = 0.04), and lactate values were higher in the group with the highest value of irisin (3.65 ± 0.69 × 2.82 ± 0.59, p = 0.02). Combined physical training results in increased basal BDNF in people living with HIV/AIDS, this finding suggests that increased concentration of BDNF may be associated with decreased chances of developing cognitive disorders or HIV-associated dementia. Further studies involving molecular mechanisms on this subject are necessary.

From Exercise to Cognitive Performance: Role of Irisin

The beneficial effects of exercise on the brain are well known. In general, exercise offers an effective way to improve cognitive function in all ages, particularly in the elderly, who are considered the most vulnerable to neurodegenerative disorders. In this regard, myokines, hormones secreted by muscle in response to exercise, have recently gained attention as beneficial mediators. Irisin is a novel exercise-induced myokine, that modulates several bodily processes, such as glucose homeostasis, and reduces systemic inflammation. Irisin is cleaved from fibronectin type III domain containing 5 (FNDC5), a transmembrane precursor protein expressed in muscle under the control of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). The FNDC5/irisin system is also expressed in the hippocampus, where it stimulates the expression of the neurotrophin brain-derived neurotrophic factor in this area that is associated with learning and memory. In this review, we aimed to discuss the role of irisin as a key mediator of the beneficial effects of exercise on synaptic plasticity and memory in the elderly, suggesting its roles within the main promoters of the beneficial effects of exercise on the brain.

New Horizon: Exercise and a Focus on Tissue-Brain Crosstalk

The world population is aging, leading to increased rates of neurodegenerative disorders. Exercise has countless health benefits and has consistently been shown to improve brain health and cognitive function. The purpose of this review is to provide an overview of exercise-induced adaptations in the brain with a focus on crosstalk between peripheral tissues and the brain. We highlight recent investigations into exercise-induced circulating factors, or exerkines, including irisin, cathepsin B, GPLD1, and ketones and the mechanisms mediating their effects in the brain.

A Single Bout of High-intensity Interval Exercise Increases Corticospinal Excitability, Brain-derived Neurotrophic Factor, and Uncarboxylated Osteolcalcin in Sedentary, Healthy Males

Exercise induces neuroplasticity in descending motor pathways facilitating motor learning, and as such it could be utilized as an intervention in neurorehabilitation, for example when re-learning motor skills after stroke. To date, however, the neurophysiological and molecular mechanisms underlying exercise-induced neuroplasticity remain largely unknown impeding the potential utilization of exercise protocols as 'motor learning boosters' in clinical and non-clinical settings. Here, we assessed corticospinal excitability, intracortical facilitation (ICF) and short-interval intracortical inhibition (SICI) using transcranial magnetic stimulation (TMS) and serum biochemical markers including brain-derived neurotrophic factor (BDNF), total and precursor cathepsin B (tCTSB, proCTSB), uncarboxylated and carboxylated osteocalcin (unOCN, cOCN) and irisin using ELISA. Measurements were carried out in sedentary, healthy males before and after a single session of high-intensity interval exercise (HIIE) or in individuals who rested and did not perform exercise (No Exercise). We found that HIIE increased corticospinal excitability, BDNF and unOCN, and decreased cOCN. We also determined that greater increases in BDNF were associated with increases in unOCN and irisin and decreases in cOCN only in participants who underwent HIIE, suggesting that unOCN and irisin may contribute to exercise-induced BDNF increases. Conversely, no changes other than a decrease in serum unOCN/tOCN were found in No Exercise participants. The present findings show that a single session of HIIE is sufficient to modulate corticospinal excitability and to increase BDNF and unOCN in sedentary, healthy males.

The Relationship between Overweight/Obesity and Executive Control in College Students: The Mediating Effect of BDNF and 5-HT

The main aim of this study was to explore the association between overweight/obesity and executive control (EC) in young adults, and to further analyze the mediating effect of brain-derived neurotrophic factor (BDNF) and serotonin (5-hydroxytryptamine (5-HT)) on the relationship between overweight/obesity and EC. A total of 449 college students aged between 18 and 20 years were recruited for the study between March and December 2019. Their height and weight were then measured professionally. Subsequently, body mass index (BMI) was calculated as weight (kg) divided by the square of height (m). The EC of the participants was then estimated using the Flanker task, while their serum BDNF levels and 5-HT levels were measured using an enzyme-linked immunosorbent assay (ELISA) kit. Finally, the multiple intermediary models in SPSS were used to analyze the mediating effect of 5-HT and BDNF between overweight/obesity and EC. The result show that the overweight/obesity of college students was positively correlated with the response of EC (p ≤ 0.005). However, it was negatively correlated with BDNF (p ≤ 0.05) and 5-HT (p ≤ 0.05). Moreover, BDNF (p ≤ 0.001) and 5-HT (p ≤ 0.001) were negatively correlated with the response of EC. The BDNF level played a partial mediating role between overweight/obesity and EC that accounted for 7.30% of the total effect value. Similarly, the 5-HT of college students played a partial mediating role between overweight/obesity and EC that accounted for 8.76% of the total effect value. Gender and age had no regulatory effect on the relationship between overweight/obesity, BDNF, 5-HT, and EC. This study provides the evidence that 5-HT and BDNF mediated the association between overweight/obesity and executive control. It is indicated that 5-HT and BDNF might be the biological pathways underpinning the link between overweight/obesity and executive control.

Preventive and Therapeutic Potential of Physical Exercise in Neurodegenerative Diseases

Significance: The prevalence and incidence of age-related neurodegenerative diseases (NDDs) tend to increase along with the enhanced average of the world life expectancy. NDDs are a major cause of morbidity and disability, affecting the health care, social and economic systems with a significant impact. Critical Issues and Recent Advances: Despite the worldwide burden of NDDs and the ongoing research efforts to increase the underlying molecular mechanisms involved in NDD pathophysiologies, pharmacological therapies have been presenting merely narrow benefits. On the contrary, absent of detrimental side effects but growing merits, regular physical exercise (PE) has been considered a prone pleiotropic nonpharmacological alternative able to modulate brain structure and function, thereby stimulating a healthier and "fitness" neurological phenotype. Future Directions: This review summarizes the state of the art of some peripheral and central-related mechanisms that underlie the impact of PE on brain plasticity as well as its relevance for the prevention and/or treatment of NDDs. Nevertheless, further studies are needed to better clarify the molecular signaling pathways associated with muscle contractions-related myokines release and its plausible positive effects in the brain. In addition, particular focus of research should address the role of PE in the modulation of mitochondrial metabolism and oxidative stress in the context of NDDs.

Understanding the Neurophysiological and Molecular Mechanisms of Exercise-Induced Neuroplasticity in Cortical and Descending Motor Pathways: Where Do We Stand?

Exercise is a promising, cost-effective intervention to augment successful aging and neurorehabilitation. Decline of gray and white matter accompanies physiological aging and contributes to motor deficits in older adults. Exercise is believed to reduce atrophy within the motor system and induce neuroplasticity which, in turn, helps preserve motor function during aging and promote re-learning of motor skills, for example after stroke. To fully exploit the benefits of exercise, it is crucial to gain a greater understanding of the neurophysiological and molecular mechanisms underlying exercise-induced brain changes that prime neuroplasticity and thus contribute to postponing, slowing, and ameliorating age- and disease-related impairments in motor function. This knowledge will allow us to develop more effective, personalized exercise protocols that meet individual needs, thereby increasing the utility of exercise strategies in clinical and non-clinical settings. Here, we review findings from studies that investigated neurophysiological and molecular changes associated with acute or long-term exercise in healthy, young adults and in healthy, postmenopausal women.

Potential exerkines for physical exercise-elicited pro-cognitive effects: Insight from clinical and animal research

A sedentary lifestyle is now known as a critical risk factor for accelerated aging-related neurodegenerative disorders. In contract, having regular physical exercise has opposite effects. Clinical findings have suggested that physical exercise can promote brain plasticity, particularly the hippocampus and the prefrontal cortex, that are important for learning and memory and mood regulations. However, the underlying mechanisms are still unclear. Animal studies reveal that the effects of physical exercise on promoting neuroplasticity could be mediated by different exerkines derived from the peripheral system and the brain itself. This book chapter summarizes the recent evidence from clinical and pre-clinical studies showing the emerging mediators for exercise-promoted brain health, including myokines secreted from skeletal muscles, adipokines from adipose tissues, and other factors secreted from the bone and liver.

An investigation into the relationship between cardiorespiratory fitness, cognition and BDNF in young healthy males

BACKGROUND

Recent investigations demonstrate that cardiorespiratory fitness may benefit brain health and plasticity with concurrent enhancements in cognitive performance; possibly via a brain-derived neurotrophic factor (BDNF)-regulated mechanism. While a number of studies have demonstrated an increase in BDNF concentration post exercise the relationship between BDNF, cardiorespiratory fitness and cognitive function requires further investigation.

OBJECTIVE

The present cross-sectional study assessed the association between cardiorespiratory fitness (VO₂max), cognitive performance and circulating BDNF concentration.

METHODS

Thirty-nine healthy male volunteers (mean age 21.7 ± 0.5 years) participated. Cognitive performance was measured by reaction time on a standard detection task and accuracy in a n-back and Continuous Paired Associative Learning (CPAL) task. Cardiorespiratory fitness was assessed using a standardised graded exercise test. Plasma and serum BDNF concentrations were assayed by ELISA.

RESULTS

A significant negative correlation between VO₂max and reaction time was demonstrated (p < 0.05). However VO₂max was not associated with circulating BDNF concentration, or performance in the n-back and CPAL tasks (p > 0.05).

CONCLUSIONS

Enhanced psychomotor speed was associated with higher cardiorespiratory fitness. In contrast to previous research no significant association between cardiorespiratory fitness and BDNF concentration was observed.

A role for FNDC5/Irisin in the beneficial effects of exercise on the brain and in neurodegenerative diseases

The beneficial effects of exercise on the brain are well known. However, the underlying molecular mechanisms are much less well understood. Interestingly, myokines, hormones secreted by muscle in response to exercise, gained attention as such beneficial mediators. In this review, we will focus on FNDC5 and its secreted form, the newly discovered myokine "irisin". We will discuss their role in the beneficial effects of exercise and its potential application in neurodegenerative disorders.

In Addition to Poor Glycemic Control, a High Level of Irisin in the Plasma Portends Early Cognitive Deficits Clinically in Chinese Patients With Type 2 Diabetes Mellitus

Background and Objectives: Irisin plays an important role in the metabolism and homeostasis of energy balance, which is involved in cognitive impairment. This study aimed to investigate the role of irisin in mild cognitive impairment (MCI) among Chinese patients with type 2 diabetes mellitus (T2DM). Methods: We recruited 133 Chinese patients with T2DM, and divided them according to the Montreal Cognitive Assessment score. Demographic data were collected and the level of irisin in the plasma was determined. In addition, the results of neuropsychological testing were examined. The concentration of irisin in the plasma was measured using an enzyme immunoassay. Results: A total of 59 patients were diagnosed with MCI and 74 patients were included as healthy-cognition controls. The level of irisin in the plasma (p = 0.043) and homeostasis model of assessment for insulin resistance (p = 0.032) in diabetic patients with MCI were higher than those observed in the healthy controls. A higher level of irisin in the plasma was associated with impaired overall cognition, specifically executive function. Linear regression analysis suggested that irisin (p = 0.017) and glycosylated hemoglobin (p = 0.036) were independent factors of diabetic MCI. Conclusions: The level of irisin in the plasma correlated with cognitive impairment in T2DM patients, particularly with executive function. These results further suggest that, in addition to poor glycemic control, a high level of irisin in the plasma portends early cognitive deficits clinically in Chinese patients with T2DM.

Irisin regulates the expression of BDNF and glycometabolism in diabetic rats

Irisin is a proteolytic product of the fibronectin type III domain-containing protein 5. The aim of the present study was to verify whether irisin is involved in the pathogenesis of diabetic mild cognitive impairment and elucidate the associated mechanisms. Diabetic rats were divided into four groups: Control, Model, Irisin (overexpression of irisin) and Irisin-short hairpin (sh)-RNA (irisin interference). The levels of irisin, brain-derived neurotrophic factor (BDNF), glycosylated hemoglobin A1c (GHbA1c) and advanced glycated end products (AGEs) in the serum were determined using ELISA. The expression of BDNF in the hippocampal tissue was evaluated by immunohistochemical analysis. Compared with the Control group, the levels of irisin and BDNF were markedly decreased in the Model and Irisin-shRNA groups, whereas those of GHbA1c and AGEs were markedly increased. However, the levels of irisin and BDNF in the Irisin group were significantly higher than those in the Model group, whereas the levels of GHbA1c and AGEs in the Irisin group were significantly lower. Irisin-shRNA significantly downregulated the expression of irisin and BDNF, and upregulated the levels of GHbA1c and AGEs, compared with those in the Model group. Rat primary hippocampal nerve cells were isolated and identified by microtubule-associated protein-2 labeling. The vitality of primary cells from diabetic rats, evaluated using a methyl thiazolyl tetrazolium assay, was markedly decreased and further reduced following the injection of irisin-shRNA, however, it was markedly improved following irisin treatment. The mRNA and protein levels of BDNF in the primary cells were evaluated by fluorogenic reverse transcription-quantitative polymerase chain reaction and western blot analyses, respectively, following the exposure of cells to different concentrations of glucose: 0 (control), 5.5, 15 and 25 mmol/l for 12, 24 and 48 h. The mRNA and protein expression levels of BDNF in the primary cells following exposure to glucose were significantly lower than those observed in the control. Further exposure to glucose led to a significant decrease in the expression of BDNF. In conclusion, irisin may regulate the expression of BDNF and glycometabolism in diabetic rats.

Exercise training increases cardiac, hepatic and circulating levels of brain-derived neurotrophic factor and irisin in young and aged rats

Background The objective of study was to examine the impacts of exercise training on cardiac, hepatic and plasma brain-derived neurotrophic factor (BDNF) and irisin levels in young and aged rats. Materials and methods Four-month-old (young) and 20-month-old (aged) female rats performed exercise training consisting of voluntary wheel running for 12 weeks. BDNF and irisin levels were analyzed in the heart, liver and plasma samples by using commercially available enzyme-linked immunosorbent assay (ELISA) kits. Results Cardiac, hepatic and plasma BDNF levels were lower in the aged sedentary rats, than in the young exercised and aged exercised rats (p < 0.05). Heart, liver and plasma irisin concentrations were lower in the aged sedentary group than in the young sedentary, young exercised and aged exercised groups (p < 0.05) and regular exercise increased irisin levels in all the analyzed tissues when compared to the sedentary counterparts (p < 0.05). Conclusions The current results show that regular exercise improves aging-induced decrease in the cardiac, hepatic and plasma BNDF and irisin levels.

Increase in Blood Levels of Growth Factors Involved in the Neuroplasticity Process by Using an Extremely Low Frequency Electromagnetic Field in Post-stroke Patients

Background: Neuroplasticity ensures the improvement of functional status in patients after stroke. The aim of this study was to evaluate the effect of extremely low-frequency electromagnetic field therapy (ELF-EMF) on brain plasticity in the rehabilitation of patients after stroke.

Methods: Forty-eight patients were divided into two groups underwent the same rehabilitation program, but in the study group, the patients additionally were exposed to a standard series of 10 ELF-EMF treatments. To determine the level of neuroplasticity, we measured the plasma level of the brain-derived neurotrophic factor (BDNF), the vascular-endothelial growth factor, as well as BDNF mRNA expression. Additionally, we determined the molecule levels for hepatocyte growth factor, stem cell factor, stromal cell-derived factor 1α, nerve growth factor β, and leukemia inhibitory factor, using 5plex cytokine panel in plasma. After 4 weeks, during which patients had undergone neurorehabilitation and neurological examinations, we assessed functional recovery using the Barthel Index, Mini-Mental State Examination (MMSE), Geriatric Depression Scale, National Institutes of Health Stroke Scale (NIHSS), and the modified Rankin Scale (mRS).

Results: We observed that ELF-EMF significantly increased growth factors and cytokine levels involved in neuroplasticity, as well as promoted an enhancement of functional recovery in post-stroke patients. Additionally, we presented evidence that these effects could be related to the increase of gene expression on the mRNA level. Moreover, a change of BDNF plasma level was positively correlated with the Barthel Index, MMSE, and negatively correlated with GDS.

Conclusion: Extremely low-frequency electromagnetic field therapy improves the effectiveness of rehabilitation of post-stroke patients by improving neuroplasticity processes.

Does iris(in) bring bad news or good news?

Irisin, a novel myokine produced in response to physical activity, promotes white-to-brown fat transdifferentiation. The name irisin referred to the ancient Greek goddess Iris, the messenger who delivered (bad) news from the gods. In mice, it has been demonstrated that irisin plays a key role in metabolic regulation, energy expenditure and glucose homeostasis. New findings from various studies carried out in both animals and humans suggest that irisin might also have other favorable effects, such as increasing bone cortical mass, preventing hepatic lipid accumulation, and improving cognitive functions, thus mediating many exercise-induced health benefits. However, data on the role and function of irisin in humans have prompted controversy, due mostly to the only recent confirmation of the presence of irisin in humans. Another strong limitation to the understanding of irisin mechanisms of action is the lack of knowledge about its receptor, which until now remains unidentified in humans and in animals. This review presents an overall analysis of the history of irisin, its expression, and its involvement in health, especially in humans. Level of Evidence Level V, review.

An update on the role of irisin in the regulation of endocrine and metabolic functions

Irisin is a novel myokine and adipokine that has gained much attention recently due to its mechanisms of action. Irisin is secreted following proteolytic cleavage of its precursor fibronectin type III domain containing 5 (FNDC5). Following its release, irisin exerts its major action by increasing the expression of mitochondrial uncoupling protein 1 (UCP 1), which facilitates the conversion of white adipose tissue (WAT) into beige adipose tissue. Irisin is distributed in various body tissues and several actions have been attributed to its presence in those tissues. It has been suggested that it plays a role in metabolic diseases, ageing, inflammation and neurogenesis. However, the circulating levels of irisin are modulated by several factors such as diet, obesity, exercise, pharmacological agents and different pathological conditions. In this review, we have discussed the mechanisms by which irisin influences the functions of different body systems and how external factors in turn affect the circulating level of irisin. In conclusion, modification of circulating irisin level may help in the management of a variety of endocrine and metabolic disorders.

Acute exercise induced BDNF-TrkB signalling is intact in the prefrontal cortex of obese, glucose-intolerant male mice

Obesity and glucose intolerance have been directly implicated in the pathology of Alzheimer's disease. It is thought that diet-induced obesity causes a reduction in neuronal plasticity through a reduction in the neurotrophin: brain-derived neurotrophic factor (BDNF). Previous work has demonstrated that acute exercise in healthy lean animals increases BDNF-TrkB signalling in the brain. However, if this effect is intact in a state of obesity remains unknown. The purpose of this study is to determine the effects of a single bout of exercise on BDNF-TrkB signalling in the prefrontal cortex and hippocampus from obese glucose intolerant mice. Male C57BL/6 mice were fed a low-fat diet (10% kcals from lard) or a high-fat diet (HFD, 60% kcals from lard) for 7 weeks. A subset of HFD mice underwent an acute bout of exercise (treadmill running: 15 m/min, 5% incline, 120 min) followed by a recovery period of 2 h, after which point the prefrontal cortex and hippocampus were collected. The HFD increased body mass and glucose intolerance (p < 0.05). Prefrontal cortex from HFD mice demonstrated lower BDNF protein content, reduced phosphorylation of the BDNF receptor (TrkB), and its downstream effector cAMP response element-binding protein (CREB), as well as PGC-1α and ERα) protein content (p < 0.05). Two hours following the acute exercise bout, TrkB and CREB phosphorylation as well as PGC-1α and ER-α protein content were recovered (p < 0.05). Our findings demonstrate for the first time that an acute bout of exercise can recover BDNF-TrkB signalling in the prefrontal cortex of obese mice.

Impact of high intensity interval exercise on executive function and brain derived neurotrophic factor in healthy college aged males

BACKGROUND

Prefrontal cortex (PFC)-dependent executive function is enhanced immediately following high intensity interval exercise (HIIE). Brain-derived neurotrophic factor (BDNF) is considered a biomarker associated with enhanced execute functioning capacity at rest and in response to exercise. However, the mechanisms responsible for the acute exercise-induced BDNF response in plasma and serum differ, and it is likely that the utilization of BDNF in plasma and/or serum as a biomarker of improved executive function following HIIE may be limited. Therefore, this study examined the impact of HIIE on the plasma and serum BDNF response to understand the efficaciousness of BDNF as a peripheral biomarker associated with improvements in PFC-dependent executive function. Thirteen healthy males (age: 23.62 ± 1.06 years) participated in a randomized, counterbalanced study, performing the Wisconsin Card Sorting Task (WCST) immediately following a 5-minute seated rest (control) and participation in a HIIE protocol administered two weeks apart. HIIE consisted of ten maximal bouts of all out pedaling on a cycle ergometer for 20 s (separated by 10 s of active recovery) against 5.5% of the subject's body weight. Whole blood was collected for the assessment of BDNF in both plasma and serum. Compared to the control session, HIIE elicited significant improvements in WCST performance, yet improvements in PFC-dependent executive function were independent of BDNF concentrations in plasma and serum. Results from this investigation demonstrate that a single session of low-volume, supramaximal HIIE significantly increases PFC-dependent executive function, thereby providing additional evidence to support the powerful benefits on HIIE on cognitive functioning.

Irisin and myostatin responses to acute high-intensity interval exercise in humans

Background The purpose of this study was to investigate irisin and myostatin responses to acute high-intensity interval exercise. Materials and methods Ten male professional kick-boxers aged between 18 and 24 years and 10 sedentary males with similar age and body weight participated in the present study. Participants performed 4 × 30-s Wingate test separated with 4 min of rest. Blood samples were taken immediately before and after exercise, and 3 and 6 h of recovery. Results and conclusion At rest, irisin levels were higher in the kick-boxers (p < 0.05). Immediately after the exercise, irisin levels were decreased in both groups (p < 0.05). A trend toward a return to baseline appeared after 3 h of recovery in the kick-boxers (p < 0.05). At rest, myostatin concentrations were not different between the groups (p > 0.05). Immediately after the exercise, myostatin levels were increased in both groups (p < 0.05). A trend toward a return to baseline appeared after 3 h of recovery in the kick-boxers (p < 0.05). Acute high-intensity interval exercise decreased irisin levels and increased myostatin levels.

The association between irisin levels, element distribution and oxidative stress markers in adolescent swimmers

The objective of this investigation was to compare irisin concentration and its relation with oxidative stress markers, antioxidant enzymes and element levels in both male adolescent swimmers and sedentary controls. Twelve male swimmers aged between 11 and 18 years, who performed regular swimming training for at least 2 years and 12 age- and gender-matched sedentary controls participated in this study. After anthropometric measurements were performed, fasting venous blood samples were taken at rest. Irisin, malondialdehyde (MDA) as a marker of oxidative stress, superoxide dismutase (SOD) as a marker of antioxidant enzyme and elements (Zn, Cu, Se, Cr, Ni, Al, Fe) were analyzed in these samples. MDA levels were lower but Zn levels and Zn/Cu ratio were higher in the swimmers than in sedentary controls (p < 0.05). There was no statistically significant difference in the irisin levels and SOD activities between the groups (p > 0.05). The results of the current study suggested that exercise training has antioxidant effects and may reduce oxidative damage. Exercise training has also limited effects on irisin levels in the adolescents.

The Alteration of Irisin-Brain-Derived Neurotrophic Factor Axis Parallels Severity of Distress Disorder in Bronchial Asthma Patients

Distress disorder (a collective term for generalized anxiety disorder and major depressive disorder) is a well-known co-morbidity of bronchial asthma. The irisin-brain-derived neurotrophic factor (BDNF) axis is a pathway that influences several neurobehavioral mechanisms involved in the pathogenesis of distress disorder. Thus, the aim of the present study was to quantify the serum irisin and BDNF concentrations in order to investigate the possible link between the irisin/BDNF axis and distress disorder in an asthma patient cohort. Data of 167 therapy-controlled asthma patients were analyzed. Demographic, anthropometric, and anamnestic data were collected, routine laboratory parameters supplemented with serum irisin and BDNF levels were determined, pulmonary function test was performed using whole-body plethysmography, and quality of life was quantified by means of the St. George's Respiratory Questionnaire (SGRQ). Correlation analysis as well as simple and multiple linear regression were used to assess the relationship between the irisin level and the Impacts score of SGRQ, which latter is indicative of the presence and severity of distress disorder. We have found a significant, positive linear relationship between the Impacts score and the reciprocal of irisin level. This association was stronger in patients whose BDNF level was higher, and it was weaker (and statistically non-significant) in patients whose BDNF level was lower. Our results indicate that higher serum irisin level together with higher serum BDNF level are associated with milder (or no) distress disorder. This finding suggests that alteration of the irisin/BDNF axis influences the presence and severity of distress disorder in asthma patients.

Long-term voluntary exercise prevents post-weaning social isolation-induced cognitive impairment in rats

This study aimed to determine the effect of exercise on locomotion, anxiety-related behavior, learning, and memory in socially isolated post-weaning rats, as well as the correlation between exercise and the concentration of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the hippocampus. Rats were randomly assigned to three groups: the control group; the social isolation group; the social isolation plus exercise (SIE) group. Social isolation conditions, with or without exercise were maintained for 90d, and then multiple behavioral tests, including the open-field test, elevated plus maze test, and Morris water maze (MWM) test were administered. Following behavioral assessment, hippocampal tissue samples were obtained for measurement of BDNF and NGF. There wasn't a significant difference in locomotor activity between the groups (P>0.05). Anxiety scores were higher in the socially isolated group (P<0.05) than in the SIE group (P<0.05). According to the probe trial session of the MWM test results, exercise training improved platform crossings' number in the socially isolated rats (P<0.05). Exercise training ameliorated social isolation-induced reduction in hippocampal BDNF and NGF content (P<0.05). These findings suggest that exercise training improves cognitive functions via increasing hippocampal BDNF and NGF concentrations in socially isolated post-weaning rats.

Irisin: A Potential Link between Physical Exercise and Metabolism-An Observational Study in Differently Trained Subjects, from Elite Athletes to Sedentary People

We compared irisin levels among groups of differently trained healthy individuals to explore the role of irisin as a physiological linker between exercise and metabolic health. Irisin and biochemical parameters of glucose and lipid metabolism were assessed in 70 healthy volunteers stratified for sport performance level into four groups: (1) 20 elite athletes of national level, (2) 20 subelite athletes of local level, (3) 20 recreational athletes, and (4) 10 sedentary subjects. All biochemical parameters were within the ranges of normality. Fasting glucose, HOMA-IR, and total cholesterol levels were inversely related to the degree of physical activity. HbA1c was higher in elite athletes compared to all the other groups (p < 0.01). A U-shaped relation between free fatty acids and the degree of physical activity was observed. All groups showed similar plasma irisin levels. After correction for the degree of insulin resistance (irisin/HOMA-IR), elite athletes showed higher levels compared to sedentary and recreational subjects (p < 0.01 and p < 0.05, resp.). In addition, the number of metabolic parameters correlated with irisin increased at increasing the training status. Our study suggests a correlation between sport performance, insulin sensitivity, and irisin levels. Irisin may be one potential mediator of the beneficial effects of exercise on metabolic profile.