Decreased Concentration of Irisin Is Associated with Poor Functional Outcome in Ischemic Stroke

Irisin: muscle's novel player in endoplasmic reticulum stress and disease

Irisin, an exercise-induced myokine, exhibits elevated levels during physical activity, yet its role in modulating the unfolded protein response (UPR) remains poorly understood. This comprehensive review pioneers an in-depth examination of irisin-mediated endoplasmic reticulum (ER) stress mitigation across various diseases. We provide a nuanced characterization of irisin's molecular profile, biological activity, and significance as a skeletal muscle-derived cytokine analogue. Our discussion elucidates the complex interplay between exercise, irisin signalling, and metabolic outcomes, highlighting key molecular interactions driving salutary effects. Moreover, we delineate the UPR's role as a critical ER stress countermeasure and underscore irisin's pivotal function in alleviating this stress, revealing potential therapeutic avenues for disease management. Exercise-induced release of irisin ameliorates ER stress through AMPK phosphorylation during various diseases (Icon image source: www.flaticon.com ).

Exosomal irisin from FNDC5-engineered BMSCs improves ischemic stroke via inhibiting YAP/EGR1/ACSL4-mediated ferroptosis

BACKGROUND

BMSCs-derived exosomes play an important role in ischemic stroke. Irisin and its precursor fibronectin type III domain-containing protein 5 (FNDC5) are implicated in neuroprotective effect. We aimed to clarify the role of exosomal irisin from FNDC5-overexpressed BMSCs in ischemic stroke.

METHODS

Oxygen-glucose deprivation and reoxygenation (OGD/R) neuronal cells (HT-22 and Neuro-2a cells) model and middle cerebral artery occlusion (MCAO) mice model were established. Exosomes were isolated from FNDC5-overexpressed BMSCs (BMSCs-FNDC5-exos). Cell viability was estimated with CCK-8. Fe2+, lactate dehydrogenase (LDH), glutathione (GSH) and malondialdehyde (MDA) were determined with commercial kits. Moreover, lipid reactive oxygen species (ROS) was analyzed using flow cytometry. Neurological dysfunction, infarct volume and mitochondria injury were estimated with modified neurological severity score (mNSS), TTC staining and transmission electron microscopy (TEM). Chromatin immunoprecipitation and dual luciferase assay were applied to verify the molecular interactions. Western blot, RT-qPCR and ELISA were performed for the detection of related genes and proteins.

RESULTS

YAP, EGR1 and ACSL4 were increased in OGD/R-subjected cells. Irisin from BMSCs-FNDC5-exos elevated cell viability and suppressed ferroptosis. EGR1 transcriptionally upregulated ACSL4 and promoted OGD/R-induced ferroptosis. Additionally, YAP transcriptionally upregulated EGR1 and promoted OGD/R-induced ferroptosis. EGR1 or YAP overexpression could reverse the effects of BMSCs-FNDC5-exos. EGR1 silencing or BMSCs-FNDC5-exos overturned the facilitated ferroptosis induced by YAP overexpression, meanwhile, EGR1 silencing further enhanced the effect elicited by BMSCs-FNDC5-exos. BMSCs-FNDC5-exos reduced cerebral infarction, improved neurological impairment, inhibited ferroptosis, downregulated YAP, EGR1, ACSL4 and up-regulated irisin in MCAO mice.

CONCLUSION

Exosomal irisin from FNDC5-overexpressed BMSCs improves ischemic stroke via inhibiting YAP/EGR1/ACSL4-mediated ferroptosis, which shed light on discovering new strategy against ischemic stroke.

Examining a role for irisin in treating cerebral ischemia

Stroke is a leading cause of death and disability, with ischemic stroke representing most cases. Age is the most significant nonmodifiable risk factor for stroke, and with an aging population, there is an urgent need for effective prevention and treatment strategies. Physical inactivity is a strong risk factor for stroke, and exercise has long been held as a promising approach to improve poststroke outcomes. During exercise, the myokine irisin is released as a product of a type 1 membrane protein cleavage that is encoded by the fibronectin type III domain containing 5 (FNDC5) gene. This review summarizes recent literature on irisin's role in ischemic stroke, examining central effects, stroke risk, poststroke functional outcomes, and exogenous administration. Irisin has value as a prognostic marker for risk stratification. Low levels of irisin correlate with worse outcomes and higher mortality in patients with ischemic stroke. Irisin may also be a key to the benefits of exercise, particularly for high-intensity resistance training, which significantly increases irisin levels. Beyond exercise, exogenous irisin is neuroprotective in murine models, reducing brain edema, inflammation, and apoptosis, and increasing blood-brain barrier integrity and brain-derived neurotrophic factor levels. This underscores irisin's potential to mitigate ischemic damage and promote recovery. Human trials are necessary to validate these findings and explore the feasibility of irisin-based interventions in acute stroke care. This review lays a foundation for future research to clarify irisin's therapeutic benefits, establish optimal exercise protocols, and explore exogenous irisin as a novel intervention for ischemic stroke.

Effects of Different Intensities of Endurance Training on Neurotrophin Levels and Functional and Cognitive Outcomes in Post-Ischaemic Stroke Adults: A Randomised Clinical Trial

This study aimed to examine the effects of different intensities of endurance training combined with standard neurorehabilitation on selected blood biomarkers and physical outcomes of post-stroke individuals. We randomised patients with first-episode ischaemic stroke to an experimental group that received 4 × 45 min sessions of moderate-intensity continuous training (MICT) each week and 2 × 45 min of standard rehabilitation each day or to a control group that received 4 × 45 min sessions of low-intensity continuous training (LICT) each week and 2 × 45 min of standard rehabilitation each day. We measured the following outcomes at baseline and 3 weeks after the intervention: aerobic capacity; cognitive and motor function; and blood levels of brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), vascular endothelial growth factor A (VEGF-A), insulin-like growth factor-1 (IGF-1), and irisin. We included 52 patients with a mean age of 66.1 ± 8.0 years. After 3 weeks of rehabilitation, there was a clinically significant improvement in the Rivermead Motor Assessment-arm score in the MICT group. The study showed that after 3 weeks, an intervention combining MICT with standard neurorehabilitation was significantly more beneficial in improving aerobic capacity and arm motor function than an intervention combining LICT and standard neurorehabilitation.

Understanding the Role of Irisin in Longevity and Aging: A Narrative Review

Irisin is a protein resulting from a proteolytic cleavage of fibronectin type III domain-containing protein 5 (FND5). The ability of irisin to modulate adipocyte and control glucose metabolism in human metabolic diseases gave rise to the hypothesis that irisin could have a pivotal role in aging-related diseases. Although in animal models, increased levels of irisin have been positively associated with better health outcomes, in humans, its role remains controversial. To provide an overview of the main finding on irisin in older adults, a comprehensive search was performed through the MEDLINE-PubMed, Web of Science, Scopus, and Cochrane databases for studies conducted in older adults (≥60 years) published since 2012. After grouping and analyzing the articles based on diseases associated with older adults, the main conclusion of this narrative review is that the included studies did not yield consistent evidence regarding the association between irisin and health or disease in older adults. Further studies are necessary to clarify the effective role of this protein in promoting health and longevity.

Irisin in ischemic stroke, Alzheimer's disease and depression: a Narrative Review

Irisin is a glycosylated protein formed from the hydrolysis of fibronectin type III domain-containing protein 5 (FNDC5). Irisin is widely involved in the regulation of glucose and lipid metabolism. In addition, recent studies have demonstrated that Irisin can inhibit inflammation, restrain oxidative stress and have neuroprotective effects, which suggests that Irisin may have a good therapeutic effect on central nervous system diseases. Therefore, this review summarizes the role of Irisin in central nervous system diseases, including its signal pathways and possible mechanisms, etc. Irisin may be a potential candidate drug for the treatment of central nervous system diseases.

Serum Irisin Levels are Inversely Correlated with Acute Ischaemic Stroke Incidence: Implications for Early Diagnosis in Southern China

Objective

This study aimed to examine the correlation and prognostic value of serum irisin levels in acute ischaemic stroke (AIS) and the subsequent development of hemiplegia.

Methods

This study recruited participants from the Department of Neurology and Rehabilitation Medicine at Shunde Hospital, Southern Medical University. The Fugl-Meyer Assessment was used to assess functional impairment. Serum irisin levels were measured using the enzyme-linked immunosorbent assay method. Multivariate logistic regression was employed to explore the factors related to serum irisin levels and AIS.

Results

Serum irisin levels in the AIS group were significantly lower than those in the control group. However, no significant association was observed between serum irisin and stroke severity within the AIS cohort. Multivariate logistic regression analysis revealed an inverse correlation between serum irisin levels and AIS risk, indicating that it serves as a protective factor against AIS. The increase in serum irisin levels (adjusted odds ratio (OR) 0.938, 95% confidence interval [CI]: 0.899-0.977 per 100 pg/mL increment) was associated with a decreased risk of AIS. Analysis of the receiver operating characteristic curve confirmed the diagnostic value of serum irisin for AIS, with the area under the curve being 0.591 (95% CI: 0.522-0.659, p = 0.012).

Conclusion

Serum irisin levels were significantly lower in AIS and were identified as a protective factor, suggesting that serum irisin may have diagnostic value for AIS.

FNDC5/Irisin in dementia and cognitive impairment: update and novel perspective

Epidemiological surveys show that the incidence of age-related dementia and cognitive impairment is increasing and it has been a heavy burden for society, families, and healthcare systems, making the preservation of cognitive function in an increasingly aging population a major challenge. Exercise is beneficial for brain health, and FDNC5/irisin, a new exercise-induced myokine, is thought to be a beneficial mediator to cognitive function and plays an important role in the crosstalk between skeletal muscle and brain. This review provides a critical assessment of the recent progress in both fundamental and clinical research of FDNC5/irisin in dementia and cognitive impairment-related disorders. Furthermore, we present a novel perspective on the therapeutic effectiveness of FDNC5/irisin in alleviating these conditions.

FNDC5 prevents oxidative stress and neuronal apoptosis after traumatic brain injury through SIRT3-dependent regulation of mitochondrial quality control

Mitochondrial dysfunction and oxidative stress are important mechanisms for secondary injury after traumatic brain injury (TBI), which result in progressive pathophysiological exacerbation. Although the Fibronectin type III domain-containing 5 (FNDC5) was reported to repress oxidative stress by retaining mitochondrial biogenesis and dynamics, its possible role in the secondary injury after TBI remain obscure. In present study, we observed that the level of serum irisin (the cleavage product of FNDC5) significantly correlated with the neurological outcomes of TBI patients. Knockout of FNDC5 increased the lesion volume and exacerbated apoptosis and neurological deficits after TBI in mice, while FNDC5 overexpression yielded a neuroprotective effect. Moreover, FNDC5 deficiency disrupted mitochondrial dynamics and function. Activation of Sirtuin 3 (SIRT3) alleviated FNDC5 deficiency-induced disruption of mitochondrial dynamics and bioenergetics. In neuron-specific SIRT3 knockout mice, FNDC5 failed to attenuate TBI-induced mitochondrial damage and brain injuries. Mechanically, FNDC5 deficiency led to reduced SIRT3 expression via enhanced ubiquitin degradation of transcription factor Nuclear factor erythroid 2-related factor 2 (NRF2), which contributed to the hyperacetylation and inactivation of key regulatory proteins of mitochondrial dynamics and function, including OPA1 and SOD2. Finally, engineered RVG29-conjugated nanoparticles were generated to selectively and efficiently deliver irisin to the brain of mice, which yielded a satisfactory curative effect against TBI. In conclusion, FNDC5/irisin exerts a protective role against acute brain injury by promoting SIRT3-dependent mitochondrial quality control and thus represents a potential target for neuroprotection after TBI.

Batokine in Central Nervous System Diseases

Brown adipose tissue (BAT) is a special type of fat tissue in mammals and is also a key endocrine organ in the human body. Batokine, the endocrine effector of BAT, plays a neuroprotective role and improves the prognosis by exerting anti-apoptotic and anti-inflammatory effects, as well as by improving vascular endothelial function and other mechanisms in nerve injury diseases. The present article briefly reviewed several types of batokines related to central nervous system (CNS) diseases. Following this, the potential therapeutic value and future research direction of batokines for CNS diseases were chiefly discussed from the aspects of protective mechanism and signaling pathway.

Relationship of irisin expression with metabolic alterations and cardiovascular risk in type 2 diabetes mellitus: a preliminary study

OBJECTIVE

The aim of this study was to investigate the role of irisin in type 2 diabetes mellitus and its association with metabolic alterations and obesity.

METHODS

A cross-sectional case-control study was conducted on participants treated at Centro Universitário FMABC between August 2018 and July 2019, by comparing a control group (n=14) with type 2 diabetes mellitus patients (n=16). The control group consisted of participants aged above 21 years with no chronic diseases, diabetes, smoking, or illicit drug use. The type 2 diabetes mellitus group included patients aged above 21 years, who were diagnosed with type 2 diabetes for at least 5 years (glycated hemoglobin>7%). Exclusion criteria were not willing to continue, recent hospitalization, and failure to meet inclusion criteria. Biochemical parameters included blood glucose, glycated hemoglobin, plasma irisin levels, and irisin gene expression in peripheral blood.

RESULTS

Type 2 diabetes mellitus patients exhibited significantly higher plasma glucose levels [143 (40) vs. 92 (13) mg/dL, *p<0.05] and glycated hemoglobin levels [7.1% (1.6) vs. 5.6% (0.5), *p<0.05] compared to the control group. Irisin gene expression in type 2 diabetes mellitus patients was lower 0.02288 (0.08050) than the control group 8.506e-006 (1.412e-005) (p=0.06). Correlation analysis revealed a positive association between irisin expression and body mass index in type 2 diabetes mellitus (Rho=0.5221, 95%CI -0.058 to 0.838, p=0.06), while plasma irisin showed a negative correlation with body mass index (Rho=-0.656, 95%CI -0.836 to 0.215, p=0.03). No significant correlations were found between plasma glucose or glycated hemoglobin levels and irisin expression.

CONCLUSION

The data suggests that body mass index directly influences plasma irisin levels and the regulation of irisin gene expression, possibly linking irisin to adiposity changes observed in obesity-related type 2 diabetes mellitus.

Irisin and Cardiometabolic Disorders in Obesity: A Systematic Review

Background

Overweight and obesity are global health issues, impacting a significant portion of young adults. Obesity is a complex condition influenced by genetics and environmental factors, leading to increased susceptibility to cardiovascular diseases (CVDs), hypertension, dyslipidemia, and insulin resistance. Irisin, a protein derived from the cleavage of fibronectin type III domain-containing protein 5, may have relationship with these cardiometabolic diseases.

Objective

This systematic review aims to examine the relationship between serum irisin levels and obesity, particularly in individuals predisposed to cardiovascular risk factors.

Methods

A thorough literature search was conducted in multiple databases, including "Science Direct," "Scopus," "PubMed," and "Lilacs," from July 2020. Inclusion criteria encompassed subjects with metabolic disorders (with or without obesity, BMI ≥30 kg/m2), clinical trials, and observational studies published between 2010 and June 2020. Exclusion criteria were animal studies, meta-analyses, systematic reviews, studies evaluating only healthy subjects, and those investigating disorders beyond cardiometabolic diseases.

Results

Out of 151 identified articles, 30 met the inclusion criteria. These studies, published between 2013 and 2020, assessed adults (≥21 years) and included 26 observational studies and 4 clinical trials (n = 7585 subjects). All studies examined irisin's role in obesity and CVDs, often including associated diseases such as type 2 diabetes and hypertension. Despite varying sample sizes, the samples within the articles were homogeneous. Observational studies exhibited a low risk of bias in at least 60% of the evaluated domains. Clinical trials demonstrated a low risk of bias in at least 50% of the domains. Limitations. Although the systematic review provides valuable insights, it is limited by the available literature and the varying methodologies used across studies.

Conclusion

The review suggests that irisin plays a significant role as both a preventive measure and a biomarker for comorbidities linked to obesity and cardiometabolic disorders. Future research should focus on standardized irisin measurement methods and diverse populations to further elucidate its mechanisms of action.

The efficacy of community-based exercise programs on circulating irisin level, muscle strength, cardiorespiratory endurance, and body composition for ischemic stroke: a randomized controlled trial

Objective

We investigated the changes in circulating irisin levels after community-based exercise and the association of these levels with improvements in muscle strength, cardiorespiratory endurance, and body composition in people with ischemic stroke.

Methods

Twenty participants were randomly assigned to either a control or an exercise group. The community-based exercise program (CEP) consisted of 8 weeks of 1 h sessions for 3 days a week. Irisin levels, muscle strength, cardiorespiratory endurance, and body composition were assessed before and after the intervention.

Results

Significant improvements were observed in the leg and trunk strength, peak oxygen consumption values, and body composition of the exercise group compared with the control group. In addition, circulating irisin levels were observed to have increased in the exercise group, positively correlated with muscle strength and cardiorespiratory endurance.

Conclusion

CEP might be an effective intervention to increase irisin levels and prevent a stroke-related decline in muscle function.

Unlocking the Therapeutic Potential of Irisin: Harnessing Its Function in Degenerative Disorders and Tissue Regeneration

Physical activity is well-established as an important protective factor against degenerative conditions and a promoter of tissue growth and renewal. The discovery of Fibronectin domain-containing protein 5 (FNDC5) as the precursor of Irisin in 2012 sparked significant interest in its potential as a diagnostic biomarker and a therapeutic agent for various diseases. Clinical studies have examined the correlation between plasma Irisin levels and pathological conditions using a range of assays, but the lack of reliable measurements for endogenous Irisin has led to uncertainty about its prognostic/diagnostic potential as an exercise surrogate. Animal and tissue-engineering models have shown the protective effects of Irisin treatment in reversing functional impairment and potentially permanent damage, but dosage ambiguities remain unresolved. This review provides a comprehensive examination of the clinical and basic studies of Irisin in the context of degenerative conditions and explores its potential as a therapeutic approach in the physiological processes involved in tissue repair/regeneration.

Skeletal Muscle Myokine Expression in Critical Illness, Association With Outcome and Impact of Therapeutic Interventions

Context

Muscle expresses and secretes several myokines that bring about benefits in distant organs.

Objective

We investigated the impact of critical illness on muscular expression of irisin, kynurenine aminotransferases, and amylase; association with clinical outcome; and impact of interventions that attenuate muscle wasting/weakness.

Methods

We studied critically ill patients who participated in 2 randomized controlled trials (EPaNIC/NESCI) and documented time profiles in critically ill mice. Included in the study were 174 intensive care unit (ICU) patients (day 8 ± 1) vs 19 matched controls, and 60 mice subjected to surgery/sepsis vs 60 pair-fed healthy mice. Interventions studied included 7-day neuromuscular electrical stimulation (NMES), and withholding parenteral nutrition (PN) in the first ICU week (late PN) vs early PN. The main outcome measures were FNDC5 (irisin- precursor), KYAT1, KYAT3, and amylase mRNA expression in skeletal muscle.

Results

Critically ill patients showed 34% to 80% lower mRNA expression of FNDC5, KYAT1, and amylases than controls (P < .0001). Critically ill mice showed time-dependent reductions in all mRNAs compared with healthy mice (P ≤ .04). The lower FNDC5 expression in patients was independently associated with a higher ICU mortality (P = .015) and ICU-acquired weakness (P = .012), whereas the lower amylase expression in ICU survivors was independently associated with a longer ICU stay (P = .0060). Lower amylase expression was independently associated with a lower risk of death (P = .048), and lower KYAT1 expression with a lower risk of weakness (P = .022). NMES increased FNDC5 expression compared with unstimulated muscle (P = .016), and late PN patients had a higher KYAT1 expression than early PN patients (P = .022).

Conclusion

Expression of the studied myokines was affected by critical illness and associated with clinical outcomes, with limited effects of interventions that attenuate muscle wasting or weakness.

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.

Potential Effects of Resistant Exercise on Cognitive and Muscle Functions Mediated by Myokines in Sarcopenic Obese Mice

Recently, it has been demonstrated that in sarcopenic obesity (SO), physical activity could improve cognitive functions. Moreover, previous studies suggested that muscle contraction could influence cognitive function via myokines. This study investigated the potential effects of resistant exercise on cognitive and muscle functions in SO. SO was induced by a high-fat diet treatment for 8 weeks in 8-month-old male C57BL/6J mice. Then, resistant exercise (ladder climbing) for 8 weeks was performed. Muscle and cognitive function tests and morphological analysis were conducted. The protein levels of myokines were investigated in muscle, plasma, and the hippocampus in sarcopenic obese mice. Muscle and cognitive functions were significantly elevated in the obesity-exercise group (EX) compared to the obesity-control group (OB). Interestingly, muscle function was positively correlated with cognitive function. Abnormal morphological changes in the hippocampus were ameliorated in EX compared to OB, but not in the muscle. Protein levels of cognitive function-related myokines and energy metabolism-related markers in EX were significantly elevated in both muscle and hippocampus compared to those in OB. Interestingly, the protein level of brain-derived neurotrophic factor (BDNF) in EX was simultaneously increased in all tissues including muscle, plasma, and hippocampus compared to that in OB. In conclusion, modulation of muscle-derived cognitive function-related myokines in various pathological conditions via a resistant exercise could be a possible way of relieving muscle and cognitive dysfunction.

Short-term Montreal Cognitive Assessment predicts functional outcome after endovascular therapy

Background

The previous studies have shown that cognition in patients 4–8 weeks after stroke can predict early functional outcomes after stroke. The analyses of data from the REVASCAT trial proved that stent thrombectomy improves post-morbid wiring test outcomes in patients with AIS compared with drug therapy. However, few studies focus on the relationship between cognitive impairment and functional outcomes in patients undergoing endovascular treatment.

Methods

A total of 647 participants registered from stroke centers. Stroke severity was evaluated by National Institutes of Health stroke scale (NIHSS). The functional status was estimated by modified Rankin scale (mRS). The cognitive impairment was assessed by trained neurologists at 14 (±4) and 90 (±7) days after stroke onset using the Montreal Cognitive Assessment (MoCA). A MoCA score of less than 26 was considered post-stroke cognitive impairment (PSCI).

Results

A total of 120 Patients who underwent endovascular therapy were included. The PSCI group had higher levels of age, men, educational status, atrial fibrillation, smoking, alcoholism, Alberta Stroke Program Early CT (ASPECT) score of the anterior circulation, and OTP time than the non-PSCI group (p < 0.05). In contrast, the 14-day MoCA score, 14-day NIHSS score, 3-month MoCA score, 3-month NIHSS score, 3-month mRS score, and 3-month EQ5D score were lower in those PSCI patients. The risk predictors of PSCI were age, sex, educational level, atrial fibrillation, smoking, alcoholism, ASPECT Score (anterior circulation), 14-day MoCA score, and 14-day NIHSS score. There were strong relationships between 3-month NIHSS and MoCA (r = –0.483, p < 0.001). Receiver operating characteristic (ROC) curve indicated that 14-day MoCA score, memory, abstraction, visuospatial/executive functions, attention, and language, played a significant role to predict PSCI [area under the curve (AUC) > 0.7]. It had predictive value for the 14-day visuospatial/executive functions to predict 3-month functional outcomes.

Conclusion

Early application of the MoCA in different cognitive regions could predict the PSCI and future functional outcomes, which is necessary to screen high-risk patients with poor prognosis and conduct an early intervention.

Irisin: A promising treatment for neurodegenerative diseases

The beneficial effects of exercise on human brain function have been demonstrated in previous studies. Myokines secreted by muscle have attracted increasing attention because of their bridging role between exercise and brain health. Regulated by PPARγ coactivator 1α, fibronectin type III domain-containing protein 5 releases irisin after proteolytic cleavage. Irisin, a type of myokine, is secreted during exercise, which induces white adipose tissue browning and relates to energy metabolism. Recently, irisin has been shown to exert a protective effect on the central nervous system. Irisin secretion triggers an increase in brain-derived neurotrophic factor levels in the hippocampus, contributing to the amelioration of cognition impairments. Irisin also plays an important role in the survival, differentiation, growth, and development of neurons. This review summarizes the role of irisin in neurodegenerative diseases and other neurological disorders. As a novel positive mediator of exercise in the brain, irisin may effectively prevent or decelerate the progress of neurodegenerative diseases in models and also improve cognitive functions. We place emphasis herein on the potential of irisin for prevention rather than treatment in neurodegenerative diseases. In ischemic diseases, irisin can alleviate the pathophysiological processes associated with stroke. Meanwhile, irisin has anxiolytic and antidepressant effects. The potential therapeutic effects of irisin in epilepsy and pain have been initially revealed. Due to the pleiotropic and beneficial properties of irisin, the possibility of irisin treating other neurological diseases could be gradually explored in the future.

Mechanism of CNS regulation by irisin, a multifunctional protein

Exercise not only builds up our body but also improves cognitive function. Skeletal muscle secretes myokine during exercise as a large reservoir of signaling molecules, which can be considered as a medium between exercise and brain health. Irisin is a circulating myokine derived from the Fibronectin type III domain-containing protein 5 (FNDC5). Irisin regulates energy metabolism because it can stimulate the "Browning" of white adipose tissue. It has been reported that irisin can cross the blood-brain barrier and increase the expression of a brain-derived neurotrophic factor (BDNF) in the hippocampus, which improves learning and memory. In addition, the neuroprotective effect of irisin has been verified in various disease models. Therefore, this review summarizes how irisin plays a neuroprotective role, including its signal pathway and mechanism. In addition, we will briefly discuss the therapeutic potential of irisin for neurological diseases.

Serum Irisin Levels and Its Relationship with Spasticity Severity in Chronic Stroke Patients

Objective Irisin is a myokine released from muscles by exercise and it has been shown to be a prognostic indicator in acute stroke patients. However, irisin's relationship with the chronic phase of stroke and spasticity has not been studied yet. We aimed to determine the serum level of irisin to examine its relationship with the functional status and severity of spasticity in patients with chronic stroke, and to compare these with healthy controls.

Materials and Methods A total of 70 (35 chronic stroke and 35 control patients) patients were included in the study. The blood serum irisin levels of the patients and the controls were evaluated using enzyme-linked immunosorbent assay method, their functional status was evaluated with the modified Rankin scale (mRS), and spasticity severity using the modified Ashworth scale (MAS).

Results The mean serum irisin levels of the stroke and the control groups were 6.20 ± 2.2 and 5.45 ± 2.3, respectively, and there was no statistically significant difference (p > 0.05). No significant correlation was found between the serum level of irisin and the severity of spasticity and functional status, assessed by the mRS in stroke patients.

Conclusion These results showed that irisin levels in chronic stroke patients were similar to controls, and there was no relationship between the severity of spasticity and functional status and irisin level.

Prognostic value of the systemic inflammation response index in patients with acute ischemic stroke

OBJECTIVES

Inflammation plays an essential role in acute ischemic stroke (AIS). Recent studies have recognized the systemic inflammation response index (SIRI) as a useful index to indicate inflammation status and predict the prognosis of multiple diseases. However, the relationship between SIRI and AIS prognosis is unclear. Our study is aimed to investigate the association between SIRI and the prognosis of AIS.

METHODS

Our study prospectively recruited 287 consecutive patients with first-ever stroke within 72 h after stroke. Demographic and clinical information was collected at baseline. The functional prognosis was assessed 3 months after AIS using the modified Rankin Scale (mRS). A poor outcome was defined as mRS > 2. SIRI was calculated as neutrophil × monocyte/lymphocyte count. Univariate and multivariate analyses were introduced to identify the association between SIRI and AIS prognosis. Receiver operating characteristic curve and reclassification analyses were used to evaluate the predictive value of SIRI for AIS prognosis.

RESULTS

The patients with poor prognosis account for 27.5% of all participants. After fully adjusting for all covariates, each standard deviation increment of SIRI caused 58.9% additional risk for poor prognosis after AIS. When dividing SIRI into quartiles, the fourth quartile had a 6.152 times risk than the first quartile. Moreover, after adding SIRI into established clinical risk factors, AUC showed a significant improvement (0.829 vs. 0.790, p for comparison = .016). Consistently, category-free net reclassification index (NRI, 0.761, 95% CI: 0.517-1.004, p < .001) and integrated discrimination index (IDI, 0.093, 95% CI: 0.0512-0.134, p < .001) confirmed the improvement by SIRI to predict poor prognosis of AIS, CONCLUSION: SIRI is an independent prognostic indicator for AIS. Elevated SIRI is associated with poor functional outcome of AIS. Our findings suggest the usefulness of SIRI to refine the risk stratification of unfavorable prognosis of AIS.

Plasma levels of BDNF and EGF are reduced in acute stroke patients

Stroke affects almost 14 million people worldwide each year. It is the second leading cause of death and a major cause of acquired disability. The degree of initial impairment in cognitive and motor functions greatly affects the recovery, but idiosyncratic factors also contribute. These are largely unidentified, which contributes to making accurate prediction of recovery challenging. Release of soluble regulators of neurotoxicity, neuroprotection and repair are presumably essential. Here we measured plasma levels of known regulators of neuroprotection and repair in patients with mild acute ischemic stroke and compared them to the plasma levels in healthy age and gender matched controls. We found that the levels of BDNF and EGF were substantially lower in stroke patients than in healthy controls, while the levels of bFGF and irisin did not differ between the groups. The lower levels of growth factors highlight that during the acute phase of stroke, there is a mismatch between the need for neuroprotection and repair, and the brain's ability to induce these processes. Large individual differences in growth factor levels were seen among the stroke patients, but whether these can be used as predictors of long-term prognosis remains to be investigated.

Irisin ameliorates neuroinflammation and neuronal apoptosis through integrin αVβ5/AMPK signaling pathway after intracerebral hemorrhage in mice

Background

Neuroinflammation is a crucial factor in the development of secondary brain injury after intracerebral hemorrhage (ICH). Irisin is a newly identified myokine that confers strong neuroprotective effects in experimental ischemic stroke. However, whether this myokine can exert neuroprotection effects after ICH remains unknown. This study aimed to investigate the impact of irisin treatment on neuroinflammation and neuronal apoptosis and the underlying mechanism involving integrin αVβ5/AMPK pathway after ICH.

Methods

Two hundred and eighty-five adult (8-week-old) male C57BL/6 mice were randomly assigned to sham and ICH surgery groups. ICH was induced via intrastriatal injection of autologous blood. Irisin was administered intranasally at 30 min after ICH. To elucidate the underlying mechanism, cilengitide (a selective integrin αVβ5 inhibitor) and dorsomorphin (a selective phosphorylated AMPK inhibitor) were administered before irisin treatment. The short- and long-term neurobehavior tests, brain edema, quantitative-PCR, western blotting, Fluoro-Jade C, TUNEL, and immunofluorescence staining were performed to assess the neurofunctional outcome at the level of molecular, cell, histology, and function.

Results

Endogenous irisin and its receptor, integrin αVβ5, were increased, peaked at 24 h after ICH. irisin post-treatment improved both short- and long-term neurological functions, reduced brain edema after ICH. Interestingly, integrin αVβ5 was mainly located in the microglia after ICH, and irisin post-treatment inhibited microglia/macrophage pro-inflammatory polarization and promoted anti-inflammatory polarization. Moreover, irisin treatment inhibited neutrophil infiltration and suppressed neuronal apoptotic cell death in perihematomal areas after ICH. Mechanistically, irisin post-treatment significantly increased the expression of integrin αVβ5, p-AMPK and Bcl-2, and decreased the expression of IL-1β, TNF-α, MPO, and Bax following ICH. The neuroprotective effects of irisin were abolished by both integrin αVβ5 inhibitor cilengitide and AMPK inhibitor dorsomorphin.

Conclusions

This study demonstrated that irisin post-treatment ameliorated neurological deficits, reduced brain edema, and ameliorated neuroinflammation and neuronal apoptosis, at least in part, through the integrin αVβ5/AMPK signaling pathway after ICH. Thus, irisin post-treatment may provide a promising therapeutic approach for the early management of ICH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02438-6.

Serum vaspin as a predictor of severity and prognosis in acute ischemic stroke patients

Objective: The influence of vaspin on vascular health had been investigated, yielding conflicting results. This study is intended to investigate the relation between vaspin and stroke severity and stroke outcome in a cohort Chinese patient with acute ischemic stroke (AIS).Methods: This was a prospective single-center observational study in Xinxiang, China. From 1 July 2017 to 30 November 2019, all patients with first-ever AIS were consecutively included. Serum levels of vaspin, stroke severity at (assessed by NIHSS score) admission and functional outcome (assessed by modified Rankin Scale (mRS)) at discharge were recorded. Multivariate analyses were assessed using logistic regression models.Results: Finally, 340 patients with AIS were included. The median age of those patients was 65 (interquartile range [IQR], 56-74) years and 61.8% were men. At admission, 88 patients (25.9%) experienced severe stroke (NIHSS>10) and serum levels of vaspin (median [IQR]: 0.72[0.48-0.90]ng/ml) in those patients were significantly lower than in those mild(0.92[0.70-1.19]ng/ml) and moderate stroke (0.93[0.63-1.21]ng/ml). At discharge, 113 patients (33.2%) experienced poor functional outcome (mRS >2) and vaspin serum levels in those patients were lower as compared with patients who experienced good outcome (0.71[0.45-0.98] vs. 0.91[0.71-1.19]ng/ml). In multivariate analyses, lower level of vaspin (< median) was associated with a 2.5-fold (odds ratio [OR] 2.46; 95% confidence interval [CI]: 1.75-4.45) increased risk for severe stroke and a 2.1-fold (2.03; 1.42-3.58) increased risk for poor outcome.Conclusion: In conclusion, reduced serum levels of vaspin at admission are significantly related to stroke severity and prognosis, which illustrates a predictive role of reduced vaspin in ischemic stroke.

Evaluation of an upper limb robotic rehabilitation program on motor functions, quality of life, cognition, and emotional status in patients with stroke: a randomized controlled study

OBJECTIVE

This study aims to find out whether including robotic therapy in addition to a conventional rehabilitation program affects the quality of life, motor function, cognition, and emotional status of hemiplegic patients.

DESIGN

Thirty-seven stroke patients recruited between April 2016 and April 2019 were included in the study. The patients were randomized into 2 groups (Robotic rehabilitation group-RR n:17, Control group n:20), RR was arranged to be 30-45 min, 5 days per week for 4 weeks. All patients were assessed at the beginning of therapy and the end of 4th week with Brunnstrom stages of motor recovery, Fugl-Meyer Assessment (FMA), handgrip strength, Purdue peg test, Minnesota manual dexterity test, Modified Ashworth Scale (MAS), Functional Independence Measure (FIM), Stroke Specific Quality of Life Scale (SS-QOL), Nottingham Extended Activities of Daily Living (NEADL) Scale, Montreal Cognitive Assessment (MoCA) and Center for Epidemiological Studies Depression Scale (CES- D).

RESULTS

Improvements in motor function scores, spasticity, general functioning, activities of daily living, cognitive assessment were better in the robotic group when compared to the control group but this difference was not statistically significant (p > 0.05). Improvement in the CES-D in the RR-group was better in comparison to the control group (p = 0.018).

CONCLUSION

Improvements in motor functions were observed after the treatment in both groups. Although RR group improved better in numbers, none of the outcomes except the CES-D scale were significant. Robotic rehabilitation provides a favorable alternative bringing slight benefits, and also is advantageous in terms of work power and psychological recovery, making its addition to conventional neurological rehabilitation effective and useful in patient management after stroke.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04393480.

A J-Shaped Curve Relationship Between Baseline Fasting Blood Glucose and 1-Year Stroke Recurrence in Non-diabetic Patients With Acute Cerebral Infarction in Xi'an, China: A Multicenter Observational Cohort Study

Background

The relationship between baseline fasting blood glucose (FBG) levels and 1-year stroke recurrence in non-diabetic patients with acute cerebral infarction (ACI) is unclear. We aimed to clarify this relationship in non-diabetic patients with ACI.

Methods

Baseline FBG levels and related information of the patients were collected at admission and the events of stroke recurrence were followed up 1, 3, 6, and 12 months after the patients were discharged. Baseline FBG levels were analyzed as continuous variables and quartiles (Q1–Q4). Multivariate Cox regression models and a two-piecewise linear regression model were used to investigate the relationship and determine the threshold effect between baseline FBG levels and 1-year stroke recurrence in non-diabetic patients with ACI.

Results

Overall, 1,634 non-diabetic patients with ACI were enrolled. After adjusting for potential confounding factors, the hazard is 2.24-fold higher in Q4 than those in Q2, being considered the reference in non-diabetic patients with ACI [hazard ratio (HR) = 2.24, 95%CI: 1.08–4.65, P = 0.031]. Plotting hazard ratios over baseline FBG levels suggested a J-shaped relationship for 1-year stroke recurrence. Further analysis revealed that the nadir value of baseline FBG levels is 4.6 mmol/L. The relationship was more significant in patients with atrial fibrillation than in those without (P for interaction = 0.009).

Conclusion

Lower and higher baseline FBG levels may lead to an increased risk of 1-year stroke recurrence in non-diabetic patients with ACI as shown by a J-shaped curve with a nadir value of 4.6 mmol/L.

Irisin levels in the serum and cerebrospinal fluid of patients with multiple sclerosis and the expression and distribution of irisin in experimental autoimmune encephalomyelitis

Irisin is a novel hormone-like myokine that plays an important role in central nervous system (CNS) diseases, such as cerebral ischaemia and Alzheimer's disease. However, irisin is rarely investigated in multiple sclerosis (MS), a typical inflammatory demyelinating disease of the CNS, and in experimental autoimmune encephalomyelitis (EAE), a typical model of MS. We determined the levels of irisin in the serum and cerebrospinal fluid in patients with MS. The expression and histological distribution of irisin were determined in EAE. Serum irisin levels in patients with MS and in EAE mice were increased, and the levels of FNDC5/irisin mRNA were decreased in the spinal cord and brain regardless of the onset, peak or chronic phase of EAE. Immunofluorescence staining showed co-localization of irisin and neurones. The levels of irisin fluctuated with disease progression in MS and EAE. Irisin may be involved in the pathological process of MS/EAE.

Serum Irisin as a Potential Biomarker for Cognitive Decline in Vascular Dementia

Background: Irisin, a new exercise-related myokine, has been shown to be associated with a variety of diseases including serious neurological disorders. However, whether irisin is involved in the pathogenesis of vascular dementia (VD) has not yet been reported. Our aim is to determine the serum irisin level in patients with VD and investigate its relationship with cognitive function. Methods: The subjects of the study were VD patients and controls with normal cognitive function who were hospitalized in the Neck-Shoulder and Lumbocrural Pain Hospital of Shandong First Medical University from July 2018 to June 2020. Upon admission, a cognitive function assessment was performed. Enzyme-linked immunosorbent assay (ELISA) was used to determine the concentration of irisin in serum. Results: During the study period, 187 subjects (82 controls and 105 VD patients) were included in the analysis. The serum irisin level of VD patients was significantly lower than that of the control group (p < 0.001). Spearman analysis showed that irisin was positively correlated with HLD-C and MoCA, and negatively correlated with all clinical characteristics except for HCY. Logistic regression analysis showed that after adjusting for all clinical characteristics, the serum irisin of VD patients still had a significant correlation with MoCA (β = 0.304, p = 0.029). According to receiver operating characteristic (ROC) curve analysis, the diagnostic accuracy for serum irisin levels on VD was 76% with the sensitivity and 71% with specificity respectively. Conclusions: These data indicate that a decrease in serum irisin levels is a powerful biological marker for cognitive decline in patients with VD, even after adjustment for risk factors. Further multi-center studies need to confirm this connection, which may pave the way for new treatment options.

Serum levels of irisin in postmenopausal women with osteoporotic hip fractures

OBJECTIVE

The purpose of this study was to evaluate the role of circulating serum levels of irisin in predicting hip fracture occurrence in a cohort of Chinese postmenopausal women.

METHODS

This was a cross-section and case-control study. Four hundred and thirty postmenopausal women aged 50-90 years were included (215 with hip fractures and 215 age-matched cases without fracture). Clinical features, bone mineral density (BMD) and serum biomarkers levels including irisin were measured at baseline. Cox proportional hazards regression analysis was used to assess the correlation between irisin and fracture risk.

RESULTS

The mean age of those participants was 68.7 (S.D. 11.7) and 53.0% were order than 65. The irisin serum levels were positively related to total body BMD and total hip BMD. Women with hip fractures showed lower mean serum levels of irisin compared normal control women (457.6 ± 172.6 ng/ml vs. 602.2 ng/ml; P < 0.001). The irisin levels in third and fourth quartiles were associated with the risk of hip fracture (the lowest quartile of irisin levels as the reference), and risk of fracture reduced by 67% (hazard ratio [HR] = 0.33; 95 %CI: 0.18-0.54; P < 0.001) and 84% (HR = 0.16; 95 %CI: 0.09-0.29; P < 0.001). The irisin levels in third and fourth quartiles were also associated with the risk of osteoporosis, and risk of fracture reduced by 55% (HR = 0.45; 95 %CI: 0.21-0.63; P = 0.003) and 73% (HR = 0.27; 95 %CI: 0.15-0.47; P < 0.001).

CONCLUSION

Decreased serum levels of circulating irisin are associated with high risk of osteoporosis-related hip fractures and osteoporosis.

Irisin and Vascular Inflammation: Beneficial Effects of a Healthy Lifestyle Beyond Physical Activity

Vascular inflammation is responsible for many cardiovascular diseases and endothelial dysfunction is often the first trigger. Many factors can contribute to altering vascular homeostasis and despite that some risk factors cannot be changed, some lifestyle changes might dramatically improve vascular function. In this regard, physical activity has been identified as one of the most important interventions that can positively affect endothelial dysfunction. In recent years, the discovery of irisin, a novel myokine with pleiotropic effects, has caught the attention of many researchers. This review summarizes the most relevant intervention trials, evaluating irisin modifications in subjects with or without cardiovascular risk factors assigned to physical activity programs, to improve cardiovascular risk markers.

The Prognostic Determinant of Interleukin-10 in Patients with Acute Ischemic Stroke: An Analysis from the Perspective of Disease Management

Background

In patients with ischemic stroke, the role of anti-inflammatory cytokine Interleukin-10 (IL-10) in predicting risk and outcomes is not very clear. This study is aimed at prospectively assessing the prognostic determinant value of IL-10 in patients with acute ischemic stroke in a cohort of Chinese people.

Methods

In a prospective cohort study, consecutive first-ever patients with acute ischemic stroke admitted to our hospital were included from October 2019 to October 2020. The serum level of IL-10 was measured at baseline. A structured follow-up telephone interview was performed on day 90 after admission. Logistic regression analyses were used to assess the prognostic value of IL-10 to predict the poor functional outcome (defined as a modified Rankin Scale score of 3 to 6) and mortality.

Results

The median age of the 236 enrolled patients was 65 years (interquartile range (IQR), 56-76), and 57.6% were male. There was a negative correlation between the National Institutes of Health Stroke Scale (NIHSS) score and IL-10 serum levels (r (Spearman) = −0.221, P = 0.001). Patients with elevated IL-10 levels (> the highest quartile = 5.24 pg/mL; n = 79) were at significantly lower risk of poor functional outcomes (odds ratio (OR), 0.35; 95% confidence interval (CI), 0.19 to 0.63; P < 0.001) and mortality (OR = 0.24; 95% CI = 0.11–0.52; P < 0.001) compared with patients with IL-10 levels in the lowest three quartiles.

Conclusions

Reduced serum levels of IL-10 were independently associated with both the clinical severity at admission and a poor functional prognosis in ischemic stroke patients, suggesting that the anti-inflammatory cytokine IL-10 was an important prognostic determinant.

Chemotherapy-induced toxicity in patients with testicular germ cell tumors: The impact of physical fitness and regular exercise

BACKGROUND

Testicular germ cell tumors (TGCTs) represent ∼95% of testicular malignancies and are the most common type of malignancy in young male adults. While the incidence of TGCTs has increased during the last decades, the advances in treatment, namely introducing cisplatin into the chemotherapy regimen, have made TGCTs highly curable with the 10-year survival rate exceeding 95%. However, in parallel with increased cure rates, survivors may experience acute and late adverse effects of treatment, which increase morbidity, reduce the quality of life, and can be potentially life-threatening. Chemotherapy-related toxicities include cardiovascular and metabolic diseases, secondary cancer, avascular necrosis, cognitive impairment, cancer-related fatigue, poor mental health-related quality of life, nephrotoxicity, hypogonadism, neurotoxicity, pulmonary toxicity, anxiety, and depression. These treatment-related adverse effects have emerged as important survivorship dilemmas in TGCT cancer survivors. Recently, regular physical exercise has increasingly attracted research and clinical attention as an adjunct therapy for cancer patients.

PURPOSE

Herein, we review the most common chemotherapy-related adverse effects in TGCT survivors and clinical relevance of exercise and increased cardio-respiratory fitness in modulating chemotherapy-related toxicity and quality of life in this population.

RESULTS AND CONCLUSION

Exercise has positive effects on a spectrum of physical and psychosocial outcomes during and after cancer treatment, and current guidelines on exercise prescription in chronic diseases define the recommended dose (volume and intensity) of regular exercise for cancer survivors, highlighting regular, sufficiently intensive physical activity as an essential part of patients' care.

Exercise-Linked Irisin Prevents Mortality and Enhances Cognition in a Mice Model of Cerebral Ischemia by Regulating Klotho Expression

Irisin, which can be released in the hippocampus after physical exercise, is demonstrated to have beneficial effects on neurovascular diseases. This study investigated the impact of exercise linked-irisin on mortality and cognition in a mice model of cerebral ischemia and further explored its underlying mechanism. The cerebrospinal concentrations of irisin and klotho from ischemic stroke patients were measured with an enzyme-linked immunosorbent assay (ELISA). The cognitive function of mice was evaluated by a series of behavioural experiments. The expressions of klotho, MnSOD, and FOXO3a in the hippocampus of mice were detected by Western blot. Superoxide production in the brain tissue of mice was evaluated with the dihydroethidium (DHE) dying. The results demonstrated that stroke patients showed a positive correlation between their CSF irisin concentration and klotho concentration. In addition, when mice subjected to cerebral ischemia, their cognitive function was impaired, the protein expressions of klotho, MnSOD, and FOXO3a downregulated, and the production of reactive oxygen species (ROS) increased compared with the sham group. After pretreatment with exogenous irisin, improved cognitive impairment, upregulated protein expressions of klotho, MnSOD, and FOXO3a, and reduced ROS generation were observed in mice with MCAO. However, the neuroprotective effects of irisin compromised with the evidence of severe cognitive impairment, decreased protein expressions of MnSOD and FOXO3a, and increased ROS production in klotho knockout mice. Thus, our results indicated that exercise-linked irisin could prevent mortality and improve cognitive impairment after cerebral ischemia by regulating klotho expression.

Irisin-Associated Neuroprotective and Rehabilitative Strategies for Stroke

Irisin, a newly discovered protein hormone that is secreted in response to low frequency whole body vibration (LFV), could be a promising post-stroke rehabilitation therapy for patients who are frail and cannot comply with regular rehabilitation therapy. Irisin is generated from a membrane-bound precursor protein fibronectin type III domain-containing protein 5 (FNDC5). Aside from being highly expressed in muscle, FNDC5 is highly expressed in the brain. The cleaved form of FNDC5 was found in the cerebrospinal fluid as well as in various regions of the brain. Numerous studies suggest that irisin plays a key role in brain metabolism and inflammation regulation. Both the metabolism and inflammation govern stroke outcome, and in a published study, we demonstrated that LFV therapy following middle cerebral artery occlusion significantly reduced innate immune response, improved motor function and infarct volume in reproductively senescent female rats. The observed effect of LFV therapy could be working via irisin, therefore, the current review focuses to understand various aspects of irisin including its mechanism of action on the brain.

Role of Polyphenols as Antioxidant Supplementation in Ischemic Stroke

Stroke is the second most common cause of death globally and the leading cause of death in China. The pathogenesis of cerebral ischemia injury is complex, and oxidative stress plays an important role in the fundamental pathologic progression of cerebral damage in ischemic stroke. Previous studies have preliminarily confirmed that oxidative stress should be a potential therapeutic target and antioxidant as a treatment strategy for ischemic stroke. Emerging experimental studies have demonstrated that polyphenols exert the antioxidant potential to play the neuroprotection role after ischemic stroke. This comprehensive review summarizes antioxidant effects of some polyphenols, which have the most inhibition effects on reactive oxygen species generation and oxidative stress after ischemic stroke.

Exercise Factors Released by the Liver, Muscle, and Bones Have Promising Therapeutic Potential for Stroke

Stroke is one of the leading causes of death and disability in the world. Stroke not only affects the patients, but also their families who serve as the primary caregivers. Discovering novel therapeutic targets for stroke is crucial both from a quality of life perspective as well as from a health economic perspective. Exercise is known to promote neuroprotection in the context of stroke. Indeed, exercise induces the release of blood-borne factors that promote positive effects on the brain. Identifying the factors that mediate the positive effects of exercise after ischemic stroke is crucial for the quest for novel therapies. This approach will yield endogenous molecules that normally cross the blood brain barrier (BBB) and that can mimic the effects of exercise. In this minireview, we will discuss the roles of exercise factors released by the liver such as beta-hydroxybutyrate (DBHB), by the muscle such as lactate and irisin and by the bones such as osteocalcin. We will also address their therapeutic potential in the context of ischemic stroke.

Irisin plays an important role in the outcomes of newly diagnosed prediabetes in adults in Guiyang, China

AIMS/INTRODUCTION

To explore the potential role of irisin in the outcomes of newly diagnosed prediabetes.

MATERIALS AND METHODS

Data were obtained from the Guiyang subcenter of the Risk Evaluation of cAncers in Chinese diabeTic Individuals: a lONgitudinal (REACTION) study. A total of 2,530 participants had newly diagnosed prediabetes at baseline and completed follow up. The nested 1:1 case-control study included 161 participants who developed diabetes mellitus at follow up, and 161 age- and sex-matched controls. The follow-up study included 86 matched case-control pairs. Fasting serum irisin levels were measured using enzyme-linked immunosorbent assay.

RESULTS

Baseline serum irisin levels were higher in the cases than in the controls (P = 0.002); high baseline serum irisin levels were an independent risk factor for the development of diabetes (odds ratio 1.235, 95% confidence interval 1.025-1.488). After adjustment for age, sex, body mass index, glycated hemoglobin (HbA1c), smoking, exercise, and family history of diabetes, subjects in the highest quartile of irisin levels had a higher risk of diabetes than those in the lowest quartile (odds ratio 3.065, 95% confidence interval 1.511-6.218). The extent of decrease in irisin levels during follow-up was greater in the cases than in the controls (P < 0.001). Baseline serum irisin levels were positively correlated with the extent of decrease in irisin during follow-up (r = 0.773, P < 0.001). After adjustment for confounding factors, subjects with a decrease of irisin above the median had much higher risk for diabetes (odds ratio 5.077, 95% confidence interval 2.112-12.206).

CONCLUSIONS

Irisin might play an important role in the outcomes of newly diagnosed prediabetes in adults in Guiyang, and can predict the risk for developing diabetes in these individuals.

Biomarkers of Angiogenesis and Neuroplasticity as Promising Clinical Tools for Stroke Recovery Evaluation

Several key issues impact the clinical practice of stroke rehabilitation including a patient’s medical history, stroke experience, the potential for recovery, and the selection of the most effective type of therapy. Until clinicians have answers to these concerns, the treatment and rehabilitation are rather intuitive, with standard procedures carried out based on subjective estimations using clinical scales. Therefore, there is a need to find biomarkers that could predict brain recovery potential in stroke patients. This review aims to present the current state-of-the-art stroke recovery biomarkers that could be used in clinical practice. The revision of biochemical biomarkers has been developed based on stroke recovery processes: angiogenesis and neuroplasticity. This paper provides an overview of the biomarkers that are considered to be ready-to-use in clinical practice and others, considered as future tools. Furthermore, this review shows the utility of biomarkers in the development of the concept of personalized medicine. Enhancing brain neuroplasticity and rehabilitation facilitation are crucial concerns not only after stroke, but in all central nervous system diseases.

Serum LRG1 as a novel biomarker for cardioembolic stroke

BACKGROUND

In recent years, LRG1 was found to be closely related to atrial fibrillation, heart failure, and myocardial remodeling after myocardial infarction. While its role in cerebral infarction was still controversial. We aimed to explore the value of LRG1 to identify the cardioembolic stroke.

METHODS

283 acute ischemic stroke(AIS) patients and 169 controls were enrolled. The AIS patients were divided into a CE(cardiogenic embolism) group and a non-CE group. Serum LRG1 levels were quantified by ELISA.

RESULTS

The serum LRG1 levels were decreased in the AIS patients. CE group had higher serum LRG1 levels than the non-CE group. LRG1 was an independent risk factor for cardioembolic stroke. The area under the curve (AUC) was 0.768 with a sensitivity of 72.5% and specificity of 69.5%, which was not second to BNP and LAD. The combined predictive model we designed, including LRG1, BNP, and LAD, greatly improved the prediction effect. A positive correlation was shown between LRG1 and stroke severity in the CE group. Those who experienced poor outcomes had higher serum LRG1 levels compared with good ones.

CONCLUSION

Serum LRG1 was a promising indicator to predict cardioembolic stroke, as well as stroke severity and the 3-month prognosis of it.

Irisin: A New Code Uncover the Relationship of Skeletal Muscle and Cardiovascular Health During Exercise

Exercise not only produces beneficial effects on muscle itself via various molecular pathways, but also mediates the interaction between muscles and other organs in an autocrine/paracrine manner through myokines, which plays a positive role in maintaining overall health. Irisin, an exercise-derived myokine, has been found involved in the regulation of some cardiovascular diseases. However, the relationship between irisin and cardiovascular health is not fully elucidated and there are some divergences on the regulation of irisin by exercise. In this review, we present the current knowledge on the origin and physiology of irisin, describe the regulation of irisin by acute and chronic exercises, and discuss the divergences of the related research results. Importantly, we discuss the role of irisin as a biomarker in the diagnosis of cardiovascular diseases and describe its treatment and molecular mechanism in some cardiovascular diseases. It is expected that irisin will be used as a therapeutic agent to combat cardiovascular diseases or other disorders caused by inactivity in the near future.

Irisin Contributes to Neuroprotection by Promoting Mitochondrial Biogenesis After Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating form of stroke, which poses a series of intractable challenges to clinical practice. Imbalance of mitochondrial homeostasis has been thought to be the crucial pathomechanism in early brain injury (EBI) cascade after SAH. Irisin, a protein related to metabolism and mitochondrial homeostasis, has been reported to play pivotal roles in post-stroke neuroprotection. However, whether this myokine can exert neuroprotection effects after SAH remains unknown. In the present study, we explored the protective effects of irisin and the underlying mechanisms related to mitochondrial biogenesis in a SAH animal model. Endovascular perforation was used to induce SAH, and recombinant irisin was administered intracerebroventricularly. Neurobehavioral assessments, TdT-UTP nick end labeling (TUNEL) staining, dihydroethidium (DHE) staining, immunofluorescence, western blot, and transmission electron microscopy (TEM) were performed for post-SAH assessments. We demonstrated that irisin treatment improved neurobehavioral scores, reduced neuronal apoptosis, and alleviated oxidative stress in EBI after SAH. More importantly, the administration of exogenous irisin conserved the mitochondrial morphology and promoted mitochondrial biogenesis. The protective effects of irisin were partially reversed by the mitochondrial uncoupling protein-2 (UCP-2) inhibitor. Taken together, irisin may have neuroprotective effects against SAH via improving the mitochondrial biogenesis, at least in part, through UCP-2 related targets.

Lower Serum Irisin Levels Are Associated with Increased Abdominal Aortic Calcification in Peritoneal Dialysis Patients

Introduction

Vascular calcification (VC), with the mechanisms remaining unclear, is closely related with dialysis patients' cardiovascular mortality and all-cause mortality. Irisin is a newly identified myokine. This study aims to evaluate the serum irisin levels of peritoneal dialysis (PD) patients and their relationship with VC.

Methods

This cross-sectional study enrolled stable PD patients in Peking University Third Hospital who were followed for >6 months. We used plain X-ray films of abdomen to quantitatively evaluate VC of abdominal aorta. VC was evaluated by abdominal aortic calcification (AAC) scores, and PD patients were divided into the high AAC score group (AAC score ≥4) and the low AAC score group (AAC score <4). Demographic data and laboratory indexes were collected. Serum irisin concentrations were measured by enzyme-linked immunosorbent assay.

Results

A total of 102 PD patients were enrolled in this study, and 52 patients (51.0%) were found to have a high AAC score of ≥4. Age, diabetic mellitus proportion, pulse pressure, hypercalcemia (corrected calcium >2.54 mmol/L) rate, serum ultrasensitive C reactive protein, and AAC scores were significantly higher in the high AAC score group than those of the low AAC score group (p < 0.05). The high AAC score group had lower diastolic blood pressure, serum albumin, and serum carbon dioxide combining power compared with the low AAC score group (p < 0.05). Serum irisin levels of PD patients with a high AAC score were significantly lower than those of PD patients with a low AAC score (109.7 ± 13.1 ng/mL vs. 115.9 ± 10.1 ng/mL, p = 0.010). The multivariate logistic regression analyses showed that serum irisin, diabetic mellitus, serum ultrasensitive C reactive protein, and age were independent factors influencing the occurrence of VC in PD patients.

Conclusion

Our results are the first to provide a clinical evidence of the association between serum irisin and abdominal aortic calcification in PD patients. Lower irisin levels, diabetic mellitus, higher serum ultrasensitive C reactive protein, and older age could be potential predictive factors for VC in PD patients.

The association between serum adipocyte fatty acid-binding protein and 3-month disability outcome after aneurysmal subarachnoid hemorrhage

BACKGROUND

Adipocyte fatty acid-binding protein (FABP4) is an adipokine that plays an important role in development of cardiovascular and metabolic diseases. The aim of this study was to assess the 3-month prognostic value of serum levels of FABP4 in Chinese patients with aneurysmal subarachnoid hemorrhage (aSAH) on hospital admission.

METHODS

This was a prospective observational study from a stroke treatment center in Zhengzhou, China. From October 2016 to May 2018, patients with aSAH who were hospitalized within 24 h were included. In addition, 202 age- and gender-matched healthy volunteers were assigned to the healthy control group. At admission, serum levels of FABP4 were measured, and patients' characteristics, Hunt-Hess grade, and modified Fisher grade evaluated. At 3-month follow-up, functional outcome (Glasgow Outcome Scale score; dichotomized as poor [score 1-3] or good [score 4-5]) and all-cause mortality were recorded. Univariate and multivariate logistic regression models were used to investigate the association of FABP4 with the two endpoints.

RESULTS

A total of 418 patients with aSAH were included in this study. The median age was 58 years (interquartile range, 49-66 years), and 57.9% were women. FABP4 serum levels were related to Hunt-Hess score (r[Spearman] = 0.381; P < 0.001). Patients with a poor outcome and non-survivors had significantly increased serum FABP4 levels on admission (P < 0.001 for all). In multivariate logistic regression analysis, FABP4 was an independent predictor of poor outcome and mortality, with increased risks of 7% (odds ratios 1.07, 95% confidence interval [CI] 1.02-1.13; P = 0.001) and 5% (odds ratio 1.05, 95% CI, 1.01-1.12; P = 0.003), respectively. Receiver operating characteristics to predict functional outcome and mortality were significantly different between conventional risk factors (difference area under the curve 0.024, 95% CI 0.018-0.032) and FABP4 plus conventional risk factors (area under the curve 0.015, 95%CI 0.011-0.020). After FABP4 was added to the existing risk factors, mortality was better reclassified and was associated with the net reclassification improvement statistic (P = 0.009), while poor outcome was better reclassified and associated with both the integrated discrimination improvement and net reclassification improvement statistics (P < 0.05 for all).

CONCLUSIONS

Elevated serum FABP4 levels were related to poor outcome and mortality in a cohort of patients with aSAH.

Serum Irisin: Pathogenesis and Clinical Research in Cardiovascular Diseases

Recently, muscular function/dysfunction has gained importance in the maintenance of metabolic homeostasis in cardiovascular diseases. Skeletal muscle plays a vital role in coordinating the activity and metabolism of endocrine organs by secreting many myokines, especially irisin. Irisin is a polypeptide hormone consisting of 112 amino acids secreted into the blood from muscle and adipose tissues. Serum irisin levels are associated with cardiometabolic risk factors such as obesity and insulin resistance as defined by homeostatic model assessment. Irisin reduces endothelial damage by inhibiting inflammation and oxidative stress, thus playing a key role in maintaining endothelial cell function. Unsurprisingly, low irisin levels cause endothelial dysfunction and increase the incidence of atherosclerosis. We aimed to summarize the studies on this issue since we have not found any review in the literature on the role of serum irisin levels in the process of atherosclerosis and other cardiovascular events in cardiovascular diseases.

The association between serum adiponectin and 3-month outcome after ischemic stroke

BACKGROUND

Although adiponectin is a major adipocytokine that affects the pathogenesis of various cardiovascular diseases, its clinical significance in stroke remains controversial. The purpose of this study was to assess the impact of serum adiponectin levels on functional prognosis in patients with ischemic stroke.

METHODS

This was a prospective, observational cohort study. Consecutive first-ever ischemic stroke patients without any pre-morbid handicap admitted to our hospital were identified from December 2017 to December 2018. Serum concentration of adiponectin was routinely measured within the first 24 h after admission by a commercially available sandwich ELISA. Associations between adiponectin and either clinical severity at admission, poor outcomes or mortality at 3-month after admission were analyzed using logistic regression to obtain odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

The serum level of adiponectin was obtained in 227 patients with a median value of 7.0 μg/ml, which was significantly higher (P < 0.001) than in those heathy control. Adiponectin levels were associated with moderate-to-high stroke, and risk increased by 12% (OR = 1.12; 95% CI 1.03-1.25; P = 0.002). Patients with a poor outcome and nonsurvivors had significantly increased adiponectin levels on admission (P < 0.001, all). In multivariate logistic regression analysis, adiponectin was an independent predictor of functional outcome and mortality, and risk increased by 24% (OR = 1.24, 95% CI 1.13-1.37; P < 0.001) and 31% (1.31 [1.18-1.46], P < 0.001), respectively. Kaplan-Meier analysis suggested that the patients with high serum adiponectin levels had a higher risk of death than those patients with low levels (log-rank test P < 0.001).

CONCLUSIONS

Our results show that high adiponectin is associated with stroke severity and support the hypothesis that adiponectin can be serve as a biomarker of poor outcome after stroke, independent of baseline variables. Trial registration ChiCTR-OPC-17013501. Retrospectively Registered 21 September 2017.

The Role of Myokines and Adipokines in Hypertension and Hypertension-related Complications

The cross-talk between skeletal muscle and adipose tissue has been identified to play a key role in the regulation of blood pressure and the development of hypertension. The role of different adipokines and myokines in hypertension and hypertension-related complications remains unclear. In the present study, 98 hypertensive patients and 24 normotensive controls were recruited, and additional subgroup analyses of hypertension-related complications were also performed. The levels of the circulating bone-derived factors leptin, apelin, fractalkine, brain-derived neurotrophic factor (BDNF), leukemia inhibitory factor (LIF), myostatin, fatty-acid-binding protein 3 (FABP3), irisin, follistatin-related protein 1 (FSTL1), oncostatin M, fibroblast growth factor 21 (FGF21) and musclin were measured by a protein liquid chip assay. The circulating levels of BDNF and musclin were decreased, whereas the leptin and irisin levels were increased, in hypertensive patients compared with those in the control individuals. Further logistic analysis indicated that the irisin level was positively correlated with SBP and an independent predictor for hypertension after adjustment. In nonobese subjects, the concentrations of DKK1, BDNF and FSTL1 were decreased, whereas the concentrations of leptin and irisin were increased. Irisin and DKK1 might be associated with hypertension. Additional subgroup analyses showed that irisin is significantly associated with hypertension-related stroke. In conclusion, we found that increased irisin levels are associated with hypertension and hypertension-related stroke. These findings indicate that irisin may be involved in the pathophysiology of hypertension.

Lower serum retinoic acid level for prediction of higher risk of mortality in ischemic stroke

OBJECTIVE

To explore the association between serum retinoic acid (RA) level in patients with acute ischemic stroke (AIS) and mortality risk in the 6 months after admission.

METHODS

From January 2015 through December 2016, patients admitted to 3 stroke centers in China for first-ever AIS were screened. The primary endpoint was all-cause mortality or cardiovascular disease (CVD) mortality in the 6 months after admission. The significance of serum RA level, NIH Stroke Scale score, and established risk factors in predicting mortality were determined. The integrated discrimination improvement (IDI) and net reclassification improvement (NRI) statistics were applied in statistical analysis.

RESULTS

Of the 1,530 patients enrolled, 325 died within 6 months of admission, with an all-cause mortality of 21.2% and CVD-related mortality of 13.1%. In multivariable analysis, RA levels were expressed as quartiles with the clinical variables. The results of the second to fourth quartiles (Q2-Q4) were compared with the first quartile (Q1); RA levels showed prognostic significance, with decreased all-cause and CVD mortality of 55% and 63%, respectively. After RA was added to the existing risk factors, all-cause mortality could be better reclassified, in association with only the NRI statistic (p = 0.005); CVD mortality could be better reclassified with significance, in association with both the IDI and NRI statistics (p < 0.01).

CONCLUSIONS

Low circulating levels of RA were associated with increased risk of all-cause and CVD mortality in a cohort of patients with first-incidence AIS, indicating that RA level could be a predictor independent of established conventional risk factors.