Edward F. Adolph Distinguished Lecture: Muscle as an endocrine organ: IL-6 and other myokines

Exercise-induced changes in left ventricular strain are affected by interleukin-6 activity: An exploratory analysis of a randomised-controlled trial in humans with abdominal obesity

Whilst the exercise-induced myokine interleukin-6 (IL-6) plays a beneficial role in cardiac structural adaptations, its influence on exercise-induced functional cardiac outcomes remains unknown. We hypothesised that IL-6 activity is required for exercise-induced improvements in left ventricular global longitudinal strain (LV GLS). In an exploratory study 52 individuals with abdominal obesity were randomised to 12 weeks' high-intensity exercise or no exercise in combination with IL-6 receptor inhibition (IL-6i) or placebo. LV strain and volume measurements were assessed by cardiac magnetic resonance. Exercise improved LV GLS by -5.4% [95% CI: -9.1% to -1.6%] (P = 0.007). Comparing the change from baseline in LV GLS in the exercise + placebo group (-4.8% [95% CI: -7.4% to -2.2%]; P < 0.0004) to the exercise + IL-6i group (-1.1% [95% CI: -3.8% to 1.6%]; P = 0.42), the exercise + placebo group changed -3.7% [95% CI: -7.4% to -0.02%] (P = 0.049) more than the exercise + IL6i group. However, the interaction effect between exercise and IL-6i was insignificant (4.5% [95% CI: -0.8% to 9.9%]; P = 0.09). Similarly, the exercise + placebo group improved LV global circumferential strain by -3.1% [95% CI: -6.0% to -0.1%] (P = 0.04) more compared to the exercise + IL-6i group, yet we found an insignificant interaction between exercise and IL-6i (4.2% [95% CI: -1.8% to 10.3%]; P = 0.16). There was no effect of IL-6i on exercise-induced changes to volume rates. This study underscores the importance of IL-6 in improving LV GLS in individuals with abdominal obesity suggesting a role for IL-6 in cardiac functional exercise adaptations.

Effects of Vaccinium berries (blueberries, cranberries and bilberries) on oxidative stress, inflammation, exercise performance, and recovery - a systematic review

Exercise-induced muscle damage is common in athletes and recreational exercisers and can lead to muscle soreness, weakness, and impaired muscle function. The precise mechanisms are unclear but oxidative stress and inflammation are thought to play a role. (Poly)phenols are substances abundant in Vaccinium berries that have been suggested to possess antioxidant and anti-inflammatory effects that could help improve exercise performance and/or recovery from exercise. The objective of this systematic review was to evaluate the benefits of Vaccinium berry supplementation on exercise performance and recovery, as well as on exercise-induced oxidative and inflammatory biomarkers in healthy individuals. A comprehensive search was conducted in PubMed, ProQuest Medline, Web of Science, Cochrane Library, and Scopus. Studies were included if the participants were healthy individuals who were supplemented with any Vaccinium berry or Vaccinium berry-based products in comparison to a control group. Of the 13 articles included in this review, no significant differences in the exercise performance were found and only one study reported benefits for markers of recovery. Interleukins and c-reactive protein were the most frequently reported biomarkers, but there was limited evidence that Vaccinium berry supplementation impacted them post-exercise. Most studies were of high quality and showed a low risk of bias. Vaccinium berry supplementation is not effective in modulating markers of exercise-induced inflammation and oxidative distress in healthy individuals; nevertheless, more studies are required to evaluate their effects on exercise performance and recovery in this population.

Revisiting Skeletal Muscle Dysfunction and Exercise in Chronic Obstructive Pulmonary Disease: Emerging Significance of Myokines

Skeletal muscle dysfunction (SMD) is the most significant extrapulmonary complication and an independent prognostic indicator in patients with chronic obstructive pulmonary disease (COPD). Myokines, such as interleukin (IL)-6, IL-15, myostatin, irisin, and insulin-like growth factor (IGF)-1, play important roles in skeletal muscle mitochondrial function, protein synthesis and breakdown balance, and regeneration of skeletal muscles in COPD. As the main component of pulmonary rehabilitation, exercise can improve muscle strength, muscle endurance, and exercise capacity in patients with COPD, as well as improve the prognosis of SMD and COPD by regulating the expression levels of myokines. The mechanisms by which exercise regulates myokine levels are related to microRNAs. IGF-1 expression is upregulated by decreasing the expression of miR-1 or miR-29b. Myostatin downregulation and irisin upregulation are associated with increased miR-27a expression and decreased miR-696 expression, respectively. These findings suggest that myokines are potential targets for the prevention and treatment of SMD in COPD. A comprehensive analysis of the role and regulatory mechanisms of myokines can facilitate the development of new exercise-based therapeutic approaches for patients with COPD.

Dynamic model assuming mutually inhibitory biomarkers of frailty suggests bistability with contrasting mobility phenotypes

Bistability is a fundamental biological phenomenon associated with "switch-like" behavior reflecting the capacity of a system to exist in either of two stable states. It plays a role in gene regulation, cell fate switch, signal transduction and cell oscillation, with relevance for cognition, hearing, vision, sleep, gait and voiding. Here we consider a potential role for bistability in the existence of specific frailty states or phenotypes as part of disablement pathways. We use mathematical modeling with two frailty biomarkers (insulin growth factor-1, IGF-1 and interleukin-6, IL-6), which mutually inhibit each other. In our model, we demonstrate that small variations around critical IGF-1 or IL-6 blood levels lead to strikingly different mobility outcomes. We employ deterministic modeling of mobility outcomes, calculating the average trends in population health. Our model predicts the bistability of clinical outcomes: the deterministically-computed likelihood of an individual remaining mobile, becoming less mobile, or dying over time either increases to almost 100% or decreases to almost zero. Contrary to statistical models that attempt to estimate the likelihood of final outcomes based on probabilities and correlations, our model predicts functional outcomes over time based on specific hypothesized molecular mechanisms. Instead of estimating probabilities based on stochastic distributions and arbitrary priors, we deterministically simulate model outcomes over a wide range of physiological parameter values within experimentally derived boundaries. Our study is "a proof of principle" as it is based on a major assumption about mutual inhibition of pathways that is oversimplified. However, by making such an assumption, interesting effects can be described qualitatively. As our understanding of molecular mechanisms involved in aging deepens, we believe that such modeling will not only lead to more accurate predictions, but also help move the field from using mostly studies of associations to mechanistically guided approaches.

Emerging Nonpharmacologic Interventions to Treat Diabetic Peripheral Neuropathy

Significance: Diabetic peripheral neuropathy (DPN), a complication of metabolic syndrome, type I and type II diabetes, leads to sensory changes that include slow nerve conduction, nerve degeneration, loss of sensation, pain, and gate disturbances. These complications remain largely untreatable, although tight glycemic control can prevent neuropathy progression. Nonpharmacologic approaches remain the most impactful to date, but additional advances in treatment approaches are needed. Recent Advances: This review highlights several emerging interventions, including a focus on dietary interventions and physical activity, that continue to show promise for treating DPN. We provide an overview of our current understanding of how exercise can improve aspects of DPN. We also highlight new studies in which a ketogenic diet has been used as an intervention to prevent and reverse DPN. Critical Issues: Both exercise and consuming a ketogenic diet induce systemic and cellular changes that collectively improve complications associated with DPN. Both interventions may involve similar signaling pathways and benefits but also impact DPN through unique mechanisms. Future Directions: These lifestyle interventions are critically important as personalized medicine approaches will likely be needed to identify specific subsets of neuropathy symptoms and deficits in patients, and determine the most impactful treatment. Overall, these two interventions have the potential to provide meaningful relief for patients with DPN and provide new avenues to identify new therapeutic targets.

Current risks factors and emerging biomarkers for bone stress injuries in military personnel

INTRODUCTION

Bone stress injuries (BSIs) have plagued the military for over 150 years; they afflict around 5 to 10% of military recruits, more so in women, and continue to place a medical and financial burden on defence. While the tibia generally adapts to the rigours of basic military training, the putative mechanisms for bone maladaptation are still unclear.

METHODS

This paper provides a review of the published literature on current risk factors and emerging biomarkers for BSIs in military personnel; the potential for biochemical markers of bone metabolism to monitor the response to military training; and, the association of novel biochemical 'exerkines' with bone health.

RESULTS

The primary risk factor for BSI in military (and athletic) populations is too much training, too soon. Appropriate physical preparation before training will likely be most protective, but routine biomarkers will not yet identify those at risk. Nutritional interventions will support a bone anabolic response to training, but exposure to stress, sleep loss, and medication is likely harmful to bone. Monitoring physiology using wearables-ovulation, sleep and stress-offer potential to inform prevention strategies.

CONCLUSIONS

The risk factors for BSIs are well described, but their aetiology is very complex particularly in the multi-stressor military environment. Our understanding of the skeletal responses to military training is improving as technology advances, and potential biomarkers are constantly emerging, but sophisticated and integrated approaches to prevention of BSI are warranted.

Inflammation and malnutrition in inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, has become increasingly prevalent worldwide in the past decade. The nutritional status of patients with IBD is often impaired, with malnutrition presenting as imbalanced energy or nutrient intake, including protein-energy malnutrition, disease-related malnutrition, sarcopenia, and micronutrient deficiency. Additionally, malnutrition can manifest as overweight, obesity, and sarcopenic obesity. Malnutrition can lead to disturbances in gut microbiome composition that might alter homoeostasis and cause a dysbiotic state, potentially triggering inflammatory responses. Despite the clear link between IBD and malnutrition, little is known about the pathophysiological mechanisms beyond protein-energy malnutrition and micronutrient deficiencies that could promote inflammation through malnutrition, and vice versa. This Review focuses on potential mechanisms that trigger a vicious cycle between malnutrition and inflammation, and their clinical and therapeutic implications.

Smartphone Use and Inflammation at 2-Year Follow-Up in College Students: The Mediating Role of Physical Activity

Purpose

Smartphone use could lead to being physically inactive and a greater risk for health problems, such as inflammation. However, the associations between smartphone use, physical activity (PA), and systemic low-grade inflammation remained unclear. This study aimed to examine the potential mediating effect of PA on the association between smartphone use and inflammation.

Patients and Methods

A two-year follow-up study was conducted between April 2019 and April 2021. Duration of smartphone use, smartphone dependence and PA were assessed by a self-administered questionnaire. Laboratory analysis of blood samples was performed to evaluate the levels of TNF-α, IL-6, IL-1β, and CRP as biomarkers of systemic inflammation. The correlations between smartphone use, PA, and inflammation were analyzed using Pearson correlation. Structural equation modelling was used to analyze the potential mediating effect of PA on the associations between smartphone use and inflammation.

Results

A total of 210 participants were included with a mean (standard deviation) age of 18.7 (1.0) years, 82 (39%) of whom were males. Smartphone dependence was negatively associated with the total PA level (r=-0.18, P<0.01). PA mediated the associations between the duration of smartphone use and smartphone dependence with inflammatory markers. Specifically, as PA decreased, the duration of smartphone use was more negatively associated with TNF-α (ab=-0.027; 95% CI: -0.052, -0.007) and more positively correlated to IL-6 (ab=0.020; 95% CI: 0.001, 0.046) and CRP (ab=0.038; 95% CI: 0.004, 0.086); smartphone dependency was more negatively associated with TNF-α (ab=-0.139; 95% CI: -0.288, -0.017) and more positively related to CRP (ab=0.206; 95% CI: 0.020, 0.421).

Conclusion

Our study illustrates that there are no direct associations between smartphone use and systemic low-grade inflammation, however, PA level plays a weak but significant mediating effect on the associations between smartphone use and inflammation among college students.

Dissociation of Bone Resorption and Formation in Spaceflight and Simulated Microgravity: Potential Role of Myokines and Osteokines?

The dissociation of bone formation and resorption is an important physiological process during spaceflight. It also occurs during local skeletal unloading or immobilization, such as in people with neuromuscular disorders or those who are on bed rest. Under these conditions, the physiological systems of the human body are perturbed down to the cellular level. Through the absence of mechanical stimuli, the musculoskeletal system and, predominantly, the postural skeletal muscles are largely affected. Despite in-flight exercise countermeasures, muscle wasting and bone loss occur, which are associated with spaceflight duration. Nevertheless, countermeasures can be effective, especially by preventing muscle wasting to rescue both postural and dynamic as well as muscle performance. Thus far, it is largely unknown how changes in bone microarchitecture evolve over the long term in the absence of a gravity vector and whether bone loss incurred in space or following the return to the Earth fully recovers or partly persists. In this review, we highlight the different mechanisms and factors that regulate the humoral crosstalk between the muscle and the bone. Further we focus on the interplay between currently known myokines and osteokines and their mutual regulation.

The Role of Exercise-Induced Molecular Processes and Vitamin D in Improving Cardiorespiratory Fitness and Cardiac Rehabilitation in Patients With Heart Failure

Heart failure (HF) still affects millions of people worldwide despite great advances in therapeutic approaches in the cardiovascular field. Remarkably, unlike pathological hypertrophy, exercise leads to beneficial cardiac hypertrophy characterized by normal or enhanced contractile function. Exercise-based cardiac rehabilitation improves cardiorespiratory fitness and, as a consequence, ameliorates the quality of life of patients with HF. Particularly, multiple studies demonstrated the improvement in left ventricular ejection fraction (LVEF) among patients with HF due to the various processes in the myocardium triggered by exercise. Exercise stimulates IGF-1/PI3K/Akt pathway activation involved in muscle growth in both the myocardium and skeletal muscle by regulating protein synthesis and catabolism. Also, physical activity stimulates the activation of the mitogen-activated protein kinase (MAPK) pathway which regulates cellular proliferation, differentiation and apoptosis. In addition, emerging data pointed out the anti-inflammatory effects of exercises as well. Therefore, it is of utmost importance for clinicians to accurately evaluate the patient’s condition by performing a cardiopulmonary exercise test and/or a 6-min walking test. Portable devices with the possibility to measure exercise capacity proved to be very useful in this setting as well. The aim of this review is to gather together the molecular processes triggered by the exercise and available therapies in HF settings that could ameliorate heart performance, with a special focus on strategies such as exercise-based cardiac rehabilitation.

Suppression of active phase voluntary wheel running in male rats by unilateral chronic constriction injury: Enduring therapeutic effects of a brief treatment of morphine combined with TLR4 or P2X7 antagonists

The present series of studies examine the impact of systemically administered therapeutics on peripheral nerve injury (males; unilateral sciatic chronic constriction injury [CCI])-induced suppression of voluntary wheel running, across weeks after dosing cessation. Following CCI, active phase running distance and speed are suppressed throughout the 7-week observation period. A brief course of morphine, however, increased active phase running distance and speed throughout this same period, an effect apparent only in sham rats. For CCI rats, systemic co-administration of morphine with antagonists of either P2X7 (A438079) or TLR4 ((+)-naloxone) (receptors critical to the activation of NLRP3 inflammasomes and consequent inflammatory cascades) returned running behavior of CCI rats to that of shams through 5+ weeks after dosing ceased. This is a striking difference in effect compared to our prior CCI allodynia results using systemic morphine plus intrathecal delivery of these same antagonists, wherein a sustained albeit partial suppression of neuropathic pain was observed. This may point to actions of the systemic drugs at multiple sites along the neuraxis, modulating injury-induced, inflammasome-mediated effects at the injured sciatic nerve and/or dorsal root ganglia, spinal cord, and potentially higher levels. Given that our data to date point to morphine amplifying neuroinflammatory processes put into motion by nerve injury, it is intriguing to speculate that co-administration of TLR4 and/or P2X7 antagonists can intervene in these inflammatory processes in a beneficial way. That is, that systemic administration of such compounds may suppress inflammatory damage at multiple sites, rapidly and persistently returning neuropathic animals to sham levels of response.

Unwanted Exacerbation of the Immune Response in Neurodegenerative Disease: A Time to Review the Impact

The COVID-19 pandemic imposed a series of behavioral changes that resulted in increased social isolation and a more sedentary life for many across all age groups, but, above all, for the elderly population who are the most vulnerable to infections and chronic neurodegenerative diseases. Systemic inflammatory responses are known to accelerate neurodegenerative disease progression, which leads to permanent damage, loss of brain function, and the loss of autonomy for many aged people. During the COVID-19 pandemic, a spectrum of inflammatory responses was generated in affected individuals, and it is expected that the elderly patients with chronic neurodegenerative diseases who survived SARSCoV-2 infection, it will be found, sooner or later, that there is a worsening of their neurodegenerative conditions. Using mouse prion disease as a model for chronic neurodegeneration, we review the effects of social isolation, sedentary living, and viral infection on the disease progression with a focus on sickness behavior and on the responses of microglia and astrocytes. Focusing on aging, we discuss the cellular and molecular mechanisms related to immunosenescence in chronic neurodegenerative diseases and how infections may accelerate their progression.

L-Citrulline Supplementation and Exercise in the Management of Sarcopenia

Sarcopenia is a process associated to aging. Persistent inflammation and oxidative stress in muscle favour muscle wasting and decreased ability to perform physical activity. Controlled exercise can optimize blood flux and moderate the production of reactive oxygen species. Therefore, supplements that can work as a vasodilators and control oxidative stress, might be beneficial for active elders. In this context, we have tested citrulline supplementation in a group of 44 participants aged from 60–73 years that followed a physical activity program adapted to their age and capacities. Volunteers were divided in two groups: placebo (n = 22) and citrullline supplemented (n = 22). Different physical tests and blood extractions were performed at the beginning and at the end of intervention (six weeks). Strength and endurance showed a tendency to increase in the citrulline supplemented group, with no significant differences respect to placebo. However, walking speed in the citrulline supplemented group improved significantly compared to placebo. Markers of muscle damage as well as circulating levels of testosterone, cortisol and vitamin D showed no significant changes, but a tendency to improve at the end of intervention in the supplemented group compared to placebo. Additional studies are necessary to confirm the effect of citrulline supplementation in sarcopenia delay.

Excessive downhill training leads to early onset of knee osteoarthritis

OBJECTIVE

Increased levels of pro-inflammatory cytokines are associated with the release of degradative enzymes leading to osteoarthritis (OA) development. Although physical exercise (PE) is generally recognized as beneficial for OA symptoms, excessive training workload and eccentric muscular exercise have increased OA risk. Here, we investigated the effects of excessive exercise workload and exercise type on systemic inflammation and knee joint OA.

METHODS

Mice were divided into five groups: sedentary (SED), uphill training (TRU), downhill training (TRD), excessive uphill training (ETU), and excessive downhill training (ETD) for an 8-week training intervention protocol.

RESULTS

ETD group had increased pro-inflammatory cytokines in serum, vastus lateralis (VL), and vastus medialis (VM) muscles, while ETU group mice had increased cytokine levels in the VL and VM. Total knee joint OARSI score were more significant in ETD group compared to SED and TRU groups. They were also more meaningful for the medial tibial plateau of ETD group compared to SED group. MMP-3 and cleaved Caspase-3 were higher in the ETD group than the SED and TRU group, while Adamts-5 was higher in the ETD group than the SED group. TRU group had increased PRG-4 levels compared to ETU and ETD group. ETD group had decreased total bone volume, trabecular bone volume, and cortical thickness compared to SED group.

CONCLUSION

Excessive downhill training induced a chronic pro-inflammatory state in mice and was associated with early signs of cartilage and bone degeneration that are clinical indicators of knee OA.

A research update: Significance of cytokine storm and diaphragm in COVID-19

Emerging research on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) shows that it is spreading to multiple organs in addition to the respiratory system. Though the SARS-CoV2 enters the human body by binding to ACE2 receptors on pulmonary alveolar cells, recent studies indicate that it is spreading to the central nervous system, cardiac and skeletal muscles leading to various pathological conditions in these organs. In particular, the effects of SARS-CoV-2 on triggering the cytokine storm and its consequential effects on skeletal muscles has generated a lot of discussion. The effects of this virus on muscular function especially in susceptible elderly populations is still being explored. However, its effects on diaphragm, a respiratory muscle which plays an important role in determining lung capacity are not completely explored. Currently, as new evidence on using lung ultrasounds to confirm COVID-19 diagnosis is gaining traction, it is necessary to explore the role of diaphragm in treating COVID-19 patients. This article will review the effects of cytokine storm triggered by the SARS-CoV-2 and its resultant effects on skeletal muscle with a specific focus on the diaphragm in order to identify knowledge gaps in effectively treating COVID-19 patients, especially those who are on a mechanical ventilator.

Meteorin-Like Ameliorates β Cell Function by Inhibiting β Cell Apoptosis of and Promoting β Cell Proliferation via Activating the WNT/β-Catenin Pathway

Meteorin-like (Metrnl) is a newly discovered myokine. Plasma Metrnl is decreased in subjects with newly diagnosed type 2 diabetes (T2D) and correlated with insulin resistance. This study aims to determine the effects of Metrnl on the apoptosis and proliferation of β cell. Mouse insulinoma MIN6 cells were divided into six groups: normal control, low glucose, high glucose, Vehicle, Metrnl, and Dickkopf 1 (DKK1) groups. MIN6 cells in Metrnl group were transfected with recombinant pCDH-Metrnl vector. WNT/β-catenin pathway was inhibited using DKK1. Then the apoptosis of MIN6 cells was detected using flow cytometry and TUNEL labeling. Immunofluorescence of Ki67 or Edu-594 was used to determine the β cell proliferation. db/db mice were confirmed as T2D group. Lentivirus-Metrnl was injected from the caudal vein of db/db mice once every two weeks for two times. High glucose induced the apoptosis of MIN6 cells and elevated expression of caspase 3. In addition, high glucose resulted in reduced β cell proliferation, cell viability, insulin secretion as well as decreased expression of β-catenin and TCF4. Metrnl ameliorated the above effects of high glucose. And the protecting role of Metrnl was inhibited by DKK1. T2D mice showed higher body weight and blood glucose compared with the controls. The β cell apoptosis was increased while the β cell proliferation and WNT/β-catenin pathway were inhibited in T2D mice. Metrnl treatment partly reversed the above changes in T2D mice. Metrnl ameliorates β cell function by inhibiting β cell apoptosis of and promoting β cell proliferation via activating the WNT/β-catenin pathway.

Effects of marathon race on selected myokines and sclerostin in middle-aged male amateur runners

In recent years, there has been increasing interest in the homeostatic response to extreme exercises, especially in the integrated function of muscle and bone. The aim of this study was to evaluate the effects of a marathon race on selected myokines and sclerostin in 10 male recreational runners (mean age 41 ± 7.7 years). Body composition, bone mineral density (BMD), and the serum concentration of myostatin, irisin, sclerostin, osteoprotegerin (OPG), 25-hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH), high-sensitivity interleukin-6 (hsIL-6), tumor necrosis factor α (TNFα), high-sensitivity C-reactive protein (hsCRP) and myoglobin, were determined 24 h before and 24 h and 72 h after a marathon race. Post-marathon increases were observed in the levels of myostatin (1.2-fold), OPG (1.5-fold), and PTH (1.3-fold), hsIL-6 (1.9-fold), myoglobin (4.1-fold), hsCRP (fivefold), TNFα (2.6-fold), after 24 h; and in myostatin (1.2-fold), irisin (1.1-fold), sclerostin (1.3-fold), OPG (1.3-fold), and PTH (1.4-fold), hsIL-6 (1.4-fold), TNFα (1.9-fold), after 72 h compared to the baseline level. The results show that in response to the marathon run, a complex network of endocrine interactions is initiated. Further research is needed to fully elucidate the long-term impact of prolonged high intensity exercise on the human body.

Expression of ABC transporter and scavenger receptor mRNAs in PBMCs in 100-km ultramarathon runners

BACKGROUND

Cholesterol metabolism is tightly regulated at the cellular level. This study was to measure the expression levels of ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1), scavenger receptor class B type I (SR-BI) and class A (SRA), and CD36 mRNAs in peripheral blood mononuclear cells (PBMCs) in response to 100-km ultramarathon event and determine any correlation between these ABC transporters/scavenger receptor expression levels and plasma cholesterol homeostasis.

MATERIALS AND METHODS

Twenty-six participants were enrolled. Blood was drawn from each individual 1 week prior, immediately after, and 24 hours after the race. The expression levels of ABCA1, ABCG1, SR-BI, SRA and CD36 in PBMCs were measured by using real-time quantitative reverse transcription polymerase chain reaction.

RESULTS

Plasma triglyceride levels were significantly increased immediately after the race and dropped at 24-hour post-race compared with pre-race values. The 100-km ultramarathon boosted high-density lipoprotein cholesterol (HDL-C) levels and decreased low-density lipoprotein cholesterol (LDL-C) levels 24-hour post-race. The expression levels of ABCA1, ABCG1 and SR-BI were markedly decreased, whereas that of CD36 was slightly but significantly upregulated in runners' PBMCs immediately after the race. Ultramarathon resulted in immediate large-scale stimulation of inflammatory cytokines with increased plasma interleukin-6 and tumour necrosis factor-alpha levels. Moreover, by using in vitro models with human monocytic cell lines, incubation of runners' plasma immediately after the race significantly downregulated ABCA1 and ABCG1, and upregulated CD36 expression in these cells.

CONCLUSIONS

ABCA1, ABCG1 and CD36 gene expressions in PBMCS might be associated with endurance exercise-induced plasma cholesterol homeostasis and systemic inflammatory response.

A Vicious Cycle of Osteosarcopeniain Inflammatory Bowel Diseases-Aetiology, Clinical Implications and Therapeutic Perspectives

Sarcopenia is a disorder characterized by a loss of muscle mass which leads to the reduction of muscle strength and a decrease in the quality and quantity of muscle. It was previously thought that sarcopenia was specific to ageing. However, sarcopenia may affect patients suffering from chronic diseases throughout their entire lives. A decreased mass of muscle and bone is common among patients with inflammatory bowel disease (IBD). Since sarcopenia and osteoporosis are closely linked, they should be diagnosed as mutual consequences of IBD. Additionally, multidirectional treatment of sarcopenia and osteoporosis including nutrition, physical activity, and pharmacotherapy should include both disorders, referred to as osteosarcopenia.

Non-pharmacological Strategies Against Systemic Inflammation: Molecular Basis and Clinical Evidence

Systemic inflammation is a common denominator to a variety of cardiovascular (CV) and non-CV diseases and relative risk factors, including hypertension and its control, metabolic diseases, rheumatic disorders, and those affecting the gastrointestinal tract. Besides medications, a non-pharmacological approach encompassing lifestyle changes and other complementary measures is mentioned in several updated guidelines on the management of these conditions. We performed an updated narrative review on the mechanisms behind the systemic impact of inflammation and the role of non-pharmacological, complementary measures centered on lowering systemic phlogosis for preserving or restoring a good global health. The central role of genetics in shaping the immune response is discussed in conjunction with that of the microbiome, highlighting the interdependence and mutual influences between the human genome and microbial integrity, diversity, and functions. Several plausible strategies to modulate inflammation and restore balanced crosstalk between the human genome and the microbiome are then recapitulated, including dietary measures, active lifestyle, and other potential approaches to manipulate the resident microbial community. To date, evidence from high-quality human studies is sparse to allow the unconditioned inclusion of understudied, though plausible solutions against inflammation into public health strategies for global wellness. This gap claims further focused, well-designed research targeted at unravelling the mechanisms behind future personalized medicine.

Multi-omic, Single-Cell, and Biochemical Profiles of Astronauts Guide Pharmacological Strategies for Returning to Gravity

The National Aeronautics and Space Administration (NASA) Twins Study created an integrative molecular profile of an astronaut during NASA’s first 1-year mission on the International Space Station (ISS) and included comparisons to an identical Earth-bound twin. The unique biochemical profiles observed when landing on Earth after such a long mission (e.g., spikes in interleukin-1 [IL-1]/6/10, c-reactive protein [CRP], C-C motif chemokine ligand 2 [CCL2], IL-1 receptor antagonist [IL-1ra], and tumor necrosis factor alpha [TNF-α]) opened new questions about the human body’s response to gravity and how to plan for future astronauts, particularly around initiation or resolution of inflammation. Here, single-cell, multi-omic (100-plex epitope profile and gene expression) profiling of peripheral blood mononuclear cells (PBMCs) showed changes to blood cell composition and gene expression post-flight, specifically for monocytes and dendritic cell precursors. These were consistent with flight-induced cytokine and immune system stress, followed by skeletal muscle regeneration in response to gravity. Finally, we examined these profiles relative to 6-month missions in 28 other astronauts and detail potential pharmacological interventions for returning to gravity in future missions.

Gertz et al. present a re-analysis of the landing data from the NASA Twins Study, suggesting that the biochemical signature reflects muscle regeneration after atrophy rather than a detrimental inflammatory response. This is mediated through muscle-derived IL-6 anti-inflammatory cascades. Single-cell analysis supports this role. Potential pharmacological interventions are also discussed.

Exercise as a therapeutic option for acute kidney injury: mechanisms and considerations for the design of future clinical studies

Acute kidney injury (AKI) is a known risk factor for chronic kidney disease (CKD) and end stage kidney disease (ESKD). The progression from AKI to CKD, despite being well recognised, is not completely understood, although sustained inflammation and fibrosis are implicated. A therapeutic intervention targeting the post AKI stage could reduce the progression to CKD, which has high levels of associated morbidity and mortality. Exercise has known anti-inflammatory effects with animal AKI models demonstrating its use as a therapeutic agent in abrogating renal injury. This suggests the use of an exercise rehabilitation programme in AKI patients following discharge could attenuate renal damage and improve long term patient outcomes. In this review article we outline considerations for future clinical studies of exercise in the AKI population.

The regulatory role of dietary factors in skeletal muscle development, regeneration and function

Skeletal muscle plays a crucial role in motor function, respiration, and whole-body energy homeostasis. How to regulate the development and function of skeletal muscle has become a hot research topic for improving lifestyle and extending life span. Numerous transcription factors and nutritional factors have been clarified are closely associated with the regulation of skeletal muscle development, regeneration and function. In this article, the roles of different dietary factors including green tea, quercetin, curcumin (CUR), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and resveratrol (RES) in regulating skeletal muscle development, muscle mass, muscle function, and muscle recovery have been summarized and discussed. We also reviewed the potential regulatory molecular mechanism of these factors. Based on the current findings, dietary factors may be used as a potential therapeutic agent to treat skeletal muscle dysfunction as well as its related diseases.

The effects of glucose and fatty acids on CXCL10 expression in skeletal muscle cells

Skeletal muscles produce secretory factors termed as myokines, which alter physiological functions of target tissues. We recently identified C-X-C chemokine ligand 10 (CXCL10) as a novel myokine, which is downregulated in response to exercise. In the present study, we investigated whether the nutritional changes affect CXCL10 expression in mouse skeletal muscle. Expression of CXCL10 was evaluated in mice fed a normal diet or a high fat diet for 10 weeks. In animals fed on HFD, Cxcl10 expression was significantly induced in fast-twitched muscles, and was accompanied by increased blood glucose and free fatty acid levels. In vitro experiments using C2C12 myotubes suggested that the increased levels of glucose and palmitic acids directly enhanced CXCL10 expression. Interestingly, the effect of palmitic acids was attenuated by palmitoleic acids. Considering its potent angiostatic activity, induction of CXCL10 by nutritional changes may contribute to the impairment of microvascular networks in skeletal muscles.

A selectively suppressing amino acid transporter: Sodium-coupled neutral amino acid transporter 2 inhibits cell growth and mammalian target of rapamycin complex 1 pathway in skeletal muscle cells

Sodium-coupled neutral amino acid transporter 2 (SNAT2), also known as solute carrier family 38 member 2 (SLC38A2), is expressed in the skeletal muscle. Our research previously indicated that SNAT2 mRNA expression level in the skeletal muscle was modulated by genotype and dietary protein. The aim of this study was to investigate the key role of the amino acid transporter SNAT2 in muscle cell growth, differentiation, and related signaling pathways via SNAT2 suppression using the inhibitor α-methylaminoisobutyric acid (MeAIB). The results showed that SNAT2 suppression down-regulated both the mRNA and protein expression levels of SNAT2 in C2C12 cells, inhibited cell viability and differentiation of the cell, and regulated the cell distribution in G0/G1 and S phases (P < 0.05). Meanwhile, most of the intercellular amino acid content of the cells after MeAIB co-culturing was significantly lower (P < 0.05). Furthermore, the mRNA expression levels of system L amino acid transporter 1 (LAT1), silent information regulator 1, and peroxisome proliferator-activated receptor-gamma co-activator 1 alpha, as well as the protein expression levels of amino acid transporters LAT1 and vacuolar protein sorting 34, were all down-regulated. The phosphorylated protein expression levels of mammalian target of rapamycin (mTOR), regulatory-associated protein of mTOR, 4E binding protein 1, and ribosomal protein S6 kinase 1 after MeAIB treatment were also significantly down-regulated (P < 0.05), which could contribute to the importance of SNAT2 in amino acid transportation and skeletal muscle cell sensing. In conclusion, SNAT2 suppression inhibited C2C12 cell growth and differentiation, as well as the availability of free amino acids. Although the mTOR complex 1 signaling pathway was found to be involved, its response to different nutrients requires further study.

Inflammation, physical activity, and chronic disease: An evolutionary perspective

Low-grade inflammation is emerging as a common feature of contemporary metabolic, psychiatric, and neurodegenerative diseases. Both physical inactivity and abdominal adiposity are associated with persistent systemic low-grade inflammation. Thus, the behavioral, biological, and physiological changes that cause a predisposition to obesity and other co-morbidities could have epigenetic underpinnings in addition to various evolutionary scenarios. A key assumption involves the potential for a mismatch between the human genome molded over generations, and the issue of adapting to the modern high calorie diet and common built environments promoting inactivity. This biological mismatch appears to have dire health consequences. Therefore, the goal of this article is to provide a brief overview on the importance of inflammation as part of human survival and how physical activity (PA) and physical inactivity are critical regulators of systemic inflammation. The review will highlight anti-inflammatory effects of PA and exercise training from a metabolic and systemic signaling perspective, which includes skeletal muscle to utilization of fatty acids, TLR4 signaling, and myokine/adipokine effects. The available evidence suggests that PA, regular exercise, and weight loss offer both protection against and treatment for a wide variety of chronic diseases associated with low-grade inflammation through an improved inflammatory profile.

Nonpharmacological Modulation of Chronic Inflammation in Parkinson's Disease: Role of Diet Interventions

Neuroinflammation is increasingly recognized as an important pathophysiological feature of neurodegenerative diseases such as Parkinson's disease (PD). Recent evidence suggests that neuroinflammation in PD might originate in the intestine and the bidirectional communication between the central and enteric nervous system, the so-called "gut-brain axis," has received growing attention due to its contribution to the pathogenesis of neurological disorders. Diet targets mediators of inflammation with various mechanisms and combined with dopaminergic treatment can exert various beneficial effects in PD. Food-based therapies may favorably modulate gut microbiota composition and enhance the intestinal epithelial integrity or decrease the proinflammatory response by direct effects on immune cells. Diets rich in pre- and probiotics, polyunsaturated fatty acids, phenols including flavonoids, and vitamins, such as the Mediterranean diet or a plant-based diet, may attenuate chronic inflammation and positively influence PD symptoms and even progression of the disease. Dietary strategies should be encouraged in the context of a healthy lifestyle with physical activity, which also has neuroimmune-modifying properties. Thus, diet adaptation appears to be an effective additive, nonpharmacological therapeutic strategy that can attenuate the chronic inflammation implicated in PD, potentially slow down degeneration, and thereby modify the course of the disease. PD patients should be highly encouraged to adopt corresponding lifestyle modifications, in order to improve not only PD symptoms, but also general quality of life. Future research should focus on planning larger clinical trials with dietary interventions in PD in order to obtain hard evidence for the hypothesized beneficial effects.

Muscle-Derived Extracellular Vesicles Influence Motor Neuron Regeneration Accuracy

Extracellular vesicles are lipid bilayer-enclosed extracellular structures. Although the term extracellular vesicles is quite inclusive, it generally refers to exosomes (<200 nm), and microvesicles (~100-1000 nm). Such vesicles are resistant to degradation and can contain proteins, lipids, and nucleic acids. Although it was previously thought that the primary purpose of such vesicles was to rid cells of unwanted components, it is now becoming increasingly clear that they can function as intercellular messengers, sometimes operating over long distances. As such, there is now intense interest in extracellular vesicles in fields as diverse as immunology, cell biology, cancer, and more recently, neuroscience. The influence that such extracellular vesicles might exert on peripheral nerve regeneration is just beginning to be investigated. In the current studies we show that muscle-derived extracellular vesicles significantly influence the anatomical accuracy of motor neuron regeneration in the rat femoral nerve. These findings suggest a basic cellular mechanism by which target end-organs could guide their own reinnervation following nerve injury.

Participation in school and physical education in juvenile idiopathic arthritis in a Nordic long-term cohort study

BACKGROUND

The aim of the study was to describe school attendance and participation in physical education in school among children with juvenile idiopathic arthritis (JIA).

METHODS

Consecutive cases of JIA from defined geographical areas of Finland, Sweden and Norway with disease onset in 1997 to 2000 were followed for 8 years in a multi-center cohort study, aimed to be as close to population-based as possible. Clinical characteristics and information on school attendance and participation in physical education (PE) were registered.

RESULTS

Participation in school and in PE was lowest initially and increased during the disease course. Eight years after disease onset 228/274 (83.2%) of the children reported no school absence due to JIA, while 16.8% reported absence during the last 2 months due to JIA. Full participation in PE was reported by 194/242 (80.2%), partly by 16.9%, and none by 2.9%. Lowest participation in PE was found among children with ERA and the undifferentiated categories. Absence in school and PE was associated with higher disease activity measures at the 8-year visit. School absence > 1 day at baseline predicted use of disease-modifying anti-rheumatic drugs, including biologics (DMARDs) (OR 1.2 (1.1-1.5)), and non-remission off medication (OR 1.4 (1.1-1.7) 8 years after disease onset.

CONCLUSION

School absence at baseline predicted adverse long-term outcome. In children and adolescents with JIA participation in school activities is mostly high after 8 years of disease. For the minority with low participation, special attention is warranted to promote their full potential of social interaction and improve long-term outcome.

Exercise training reduces the risk of opportunistic infections after acute exercise and improves cytokine antigen recognition

In general, acute exercise is thought to inhibit immune function and increase the risk of opportunistic infections, but there is some opposition to this due to a lack of quantitative evaluation. Therefore, we quantified the effect of exercise on immune function and observed the interaction between antigens and cytokines using an intramuscular infection with Trichinella spiralis (T. spiralis), a common parasitic infection model. C57BL/6 mice were used for a non-infection experiment and an infection (Inf) experiment. Each experiment was divided further into three groups: one control (CON) group, and an exercise pre-infection (PIE)-only group and exercise-sustained (ES) group, each of which was subjected to exercise for 7 weeks. All animals in the infection experiment were infected with T. spiralis 30 min after acute exercise. After infection, the ES and Inf-ES groups continued exercise for 7 additional weeks. The number of T. spiralis nurse cells remaining in skeletal muscles was fewer in the infected exercise groups compared with the infected control. Expression of interleukin-6 (IL-6) and interleukin-10 (IL-10) was higher in the Inf-CON group and transforming growth factor beta (TGF-β) expression was lower in the Inf-CON group than in the CON group, as measured by RT-PCR. In the infection experiment, only IL-10 had significant differences between the groups. Immunofluorescence revealed that most cytokines were specifically expressed around the antigenic nurse cells following exercise. In conclusion, exercise training does not increase the risk of opportunistic infections even after acute exercise, but rather reduces it. These results may be due to antigen-specific immune responses.

Myonectin deletion promotes adipose fat storage and reduces liver steatosis

We recently described myonectin (also known as erythroferrone) as a novel skeletal muscle-derived myokine with metabolic functions. Here, we use a genetic mouse model to determine myonectin's requirement for metabolic homeostasis. Female myonectin-deficient mice had larger gonadal fat pads and developed mild insulin resistance when fed a high-fat diet (HFD) and had reduced food intake during refeeding after an unfed period but were otherwise indistinguishable from wild-type littermates. Male mice lacking myonectin, however, had reduced physical activity when fed ad libitum and in the postprandial state but not during the unfed period. When stressed with an HFD, myonectin-knockout male mice had significantly elevated VLDL-triglyceride (TG) and strikingly impaired lipid clearance from circulation following an oral lipid load. Fat distribution between adipose and liver was also altered in myonectin-deficient male mice fed an HFD. Greater fat storage resulted in significantly enlarged adipocytes and was associated with increased postprandial lipoprotein lipase activity in adipose tissue. Parallel to this was a striking reduction in liver steatosis due to significantly reduced TG accumulation. Liver metabolite profiling revealed additional significant changes in bile acids and 1-carbon metabolism pathways. Combined, our data affirm the physiologic importance of myonectin in regulating local and systemic lipid metabolism.-Little, H. C., Rodriguez, S., Lei, X., Tan, S. Y., Stewart, A. N., Sahagun, A., Sarver, D. C., Wong, G. W. Myonectin deletion promotes adipose fat storage and reduces liver steatosis.

Does Physical Activity-Based Intervention Improve Systemic Proinflammatory Cytokine Levels in Overweight or Obese Children and Adolescents? Insights from a Meta-Analysis of Randomized Control Trials

OBJECTIVES

The purpose of this research was to conduct a meta-analysis of the role that physical activity (PA) plays in influencing the critical proinflammatory cytokine levels associated with overweight/obese children and adolescents to explore the effectiveness of exercise intervention within this population.

METHODS

With searches of the PubMed, EMBASE, and CENTRAL databases, we updated our meta-analysis up to November 2018. The randomized controlled trials (RCT) evaluated the ability of exercise training to increase the following factors in children and/or adolescents classified as obese or overweight: tumor necrosis factor (TNF)-α, interleukin (IL)-6, and C-reactive protein (CRP).

RESULTS

Eleven RCT comprising 623 children and/or adolescents who were obese or overweight (i.e., 393 with PA and 230 controls) were suitable for use in this study. The meta-analysis showed that PA in general was associated with a significant reduction of CRP levels (mean difference = -0.45 mg/L, p = 0.02) in overweight/obese children and adolescents. Based on 115 overweight and obese youths, this study suggests that PA does not significantly mitigate IL-6 levels (mean difference = -0.39 pg/mL, p = 0.08), although there was a trend towards a reduction. Additionally, no close connection was observed between PA and TNF-α levels at 0.04 pg/mL (p = 0.78). Moreover, meta-regression analysis revealed a statistical association between CPR levels and changes in BMI or changes in adiponectin; likewise, IL-6 levels dramatically impacted the effect of exercise on changes in adiponectin.

CONCLUSIONS

PA was associated with significantly reduced CRP levels, whereas there was no significant association with IL-6 or TNF-α in overweight/obese children or adolescents; however, there was a trend towards a reduction of IL-6.

Changes in the function and phenotype of resident peritoneal macrophages after housing in an enriched environment

Exposure to an enriched environment (EE) affects not only brain functions but also immune responses upon viral or bacterial infections. In this study, we examined changes in the phagocytic response and chemokine production of resident peritoneal macrophages after mice had been housed under EE conditions for 6 or 8 weeks, and then explored the possibility that EE could cause a change in the macrophage phenotype by means of flow cytometry as well as quantitative RT-PCR. The percentages of EE macrophages phagocytosing S. aureus and apoptotic neutrophils were significantly larger than those of standard environment (SE) macrophages. After coculturing with S. aureus, EE macrophages tended to produce greater amounts of chemokines such as MIP-2, KC and MCP-1 than SE ones, although the increases for MIP-2 and KC were not statistically significant. As compared with SE macrophages, EE macrophages included more CD40-positive cells (M1 marker), and expressed more mRNAs of IL-6 (M1 marker) and IRF4 (M2 marker), and less mRNA of CD38 (M1 marker), suggesting either the possibility that EE macrophages are a mixed population of M1 and M2 macrophages or the possibility that they are a unique population with a mixed M1 and M2 macrophage phenotype.

The Importance of Biophysical and Biochemical Stimuli in Dynamic Skeletal Muscle Models

Classical approaches to engineer skeletal muscle tissue based on current regenerative and surgical procedures still do not meet the desired outcome for patient applications. Besides the evident need to create functional skeletal muscle tissue for the repair of volumetric muscle defects, there is also growing demand for platforms to study muscle-related diseases, such as muscular dystrophies or sarcopenia. Currently, numerous studies exist that have employed a variety of biomaterials, cell types and strategies for maturation of skeletal muscle tissue in 2D and 3D environments. However, researchers are just at the beginning of understanding the impact of different culture settings and their biochemical (growth factors and chemical changes) and biophysical cues (mechanical properties) on myogenesis. With this review we intend to emphasize the need for new in vitro skeletal muscle (disease) models to better recapitulate important structural and functional aspects of muscle development. We highlight the importance of choosing appropriate system components, e.g., cell and biomaterial type, structural and mechanical matrix properties or culture format, and how understanding their interplay will enable researchers to create optimized platforms to investigate myogenesis in healthy and diseased tissue. Thus, we aim to deliver guidelines for experimental designs to allow estimation of the potential influence of the selected skeletal muscle tissue engineering setup on the myogenic outcome prior to their implementation. Moreover, we offer a workflow to facilitate identifying and selecting different analytical tools to demonstrate the successful creation of functional skeletal muscle tissue. Ultimately, a refinement of existing strategies will lead to further progression in understanding important aspects of muscle diseases, muscle aging and muscle regeneration to improve quality of life of patients and enable the establishment of new treatment options.

Immune and Neuroprotective Effects of Physical Activity on the Brain in Depression

Physical activity-a lifestyle factor that is associated with immune function, neuroprotection, and energy metabolism-modulates the cellular and molecular processes in the brain that are vital for emotional and cognitive health, collective mechanisms that can go awry in depression. Physical activity optimizes the stress response, neurotransmitter level and function (e.g., serotonergic, noradrenergic, dopaminergic, and glutamatergic), myokine production (e.g., interleukin-6), transcription factor levels and correlates [e.g., peroxisome proliferator-activated receptor C coactivator-1α [PGC-1α], mitochondrial density, nitric oxide pathway activity, Ca2+ signaling, reactive oxygen specie production, and AMP-activated protein kinase [AMPK] activity], kynurenine metabolites, glucose regulation, astrocytic health, and growth factors (e.g., brain-derived neurotrophic factor). Dysregulation of these interrelated processes can effectuate depression, a chronic mental illness that affects millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility in understanding chronic depression, a need remains to better understand the interrelated mechanisms that contribute to immune dysfunction and the means by which various therapeutics mitigate them. Fortunately, convergent evidence suggests that physical activity improves emotional and cognitive function in persons with depression, particularly in those with comorbid inflammation. Accordingly, the aims of this review are to (1) underscore the link between inflammatory correlates and depression, (2) explicate immuno-neuroendocrine foundations, (3) elucidate evidence of neurotransmitter and cytokine crosstalk in depressive pathobiology, (4) determine the immunomodulatory effects of physical activity in depression, (5) examine protocols used to effectuate the positive effects of physical activity in depression, and (6) highlight implications for clinicians and scientists. It is our contention that a deeper understanding of the mechanisms by which inflammation contributes to the pathobiology of depression will translate to novel and more effective treatments, particularly by identifying relevant patient populations that can benefit from immune-based therapies within the context of personalized medicine.

Multiplex Quantification Identifies Novel Exercise-regulated Myokines/Cytokines in Plasma and in Glycolytic and Oxidative Skeletal Muscle

Exercise is known to confer major health benefits, but the underlying mechanisms are not well understood. The systemic effects of exercise on multi-organ systems are thought to be partly because of myokines/cytokines secreted by skeletal muscle. The extent to which exercise alters cytokine expression and secretion in different muscle fiber types has not been systematically examined. Here, we assessed changes in 66 mouse cytokines in serum, and in glycolytic (plantaris) and oxidative (soleus) muscles, in response to sprint, endurance, or chronic wheel running. Both acute and short-term exercise significantly altered a large fraction of cytokines in both serum and muscle, twenty-three of which are considered novel exercise-regulated myokines. Most of the secreted cytokine receptors profiled were also altered by physical activity, suggesting an exercise-regulated mechanism that modulates the generation of soluble receptors found in circulation. A greater overlap in cytokine profile was seen between endurance and chronic wheel running. Between fiber types, both acute and chronic exercise induced significantly more cytokine changes in oxidative compared with glycolytic muscle. Further, changes in a subset of circulating cytokines were not matched by their changes in muscle, but instead reflected altered expression in liver and adipose tissues. Last, exercise-induced changes in cytokine mRNA and protein were only minimally correlated in soleus and plantaris. In sum, our results indicate that exercise regulates many cytokines whose pleiotropic actions may be linked to positive health outcomes. These data provide a framework to further understand potential crosstalk between skeletal muscle and other organ compartments.

Exosomes as Mediators of the Systemic Adaptations to Endurance Exercise

Habitual endurance exercise training is associated with multisystemic metabolic adaptations that lower the risk of inactivity-associated disorders such as obesity and type 2 diabetes mellitus (T2DM). Identification of complex systemic signaling networks responsible for these benefits are of great interest because of their therapeutic potential in metabolic diseases; however, specific signals that modulate the multisystemic benefits of exercise in multiple tissues and organs are only recently being discovered. Accumulated evidence suggests that muscle and other tissues have an endocrine function and release peptides and nucleic acids into the circulation in response to acute endurance exercise to mediate the multisystemic adaptations. Factors released from skeletal muscle have been termed myokines and we propose that the total of all factors released in response to endurance exercise (including peptides, nucleic acids, and metabolites) be termed, "exerkines." We propose that many of the exerkines are released within extracellular vesicles called exosomes, which regulate peripheral organ cross talk. Exosomes (30-140 nm) and larger microvesicles [MVs] (100-1000 nm) are subcategories of extracellular vesicles that are released into the circulation. Exosomes contain peptides and several nucleic acids (microRNA [miRNA], messenger RNA [mRNA], mitochondrial DNA [mtDNA]) and are involved in intercellular/tissue exchange of their contents. An acute bout of endurance exercise increases circulating exosomes that are hypothesized to mediate organ cross talk to promote systemic adaptation to endurance exercise. Further support for the role of exosomes (and possibly MVs) in mediating the systemic benefits of exercise comes from the fact that the majority of the previously reported myokines/exerkines are found in extracellular vesicles databases (Vesiclepedia and ExoCarta). We propose that exosomes isolated from athletes following exercise or exosomes bioengineered to incorporate one or many of known exerkines will be therapeutically useful in the treatment of obesity, T2DM, and other aging-associated metabolic disorders.

Myonectin Predicts the Development of Type 2 Diabetes

CONTEXT

Myonectin has been identified as a myokine, expressed predominantly in skeletal muscle. However, its clinical implications are largely unknown.

OBJECTIVE

The aim of this study is to investigate the relationship between myonectin (C1q tumor necrosis factor-α-related protein isoform 15) and type 2 diabetes mellitus (T2DM) in cross-sectional and interventional studies.

DESIGN

In a separate study, oral glucose tolerance tests, a 45-minute bout of exercise, lipid infusions, and euglycemic-hyperinsulinemic clamps (EHCs) were performed to investigate the association of myonectin with homeostasis model assessment of insulin resistance (HOMA-IR) and T2DM. Circulating myonectin was measured by enzyme-linked immunosorbent assay.

PATIENTS

One hundred four newly diagnosed T2DM (nT2DM), 109 impaired glucose tolerance (IGT), and 128 healthy individuals were recruited for this study.

RESULTS

nT2DM and IGT subjects had higher circulating myonectin concentrations than normal subjects (82.3 ± 47.6 and 68.9 ± 46.6 vs. 45.2 ± 23.5 µg/L, P < 0.05 or P < 0.01). It was also found that in nT2DM individuals, circulating myonectin was higher than in IGT subjects. Plasma myonectin correlated positively with waist/hip ratio, percentage of body fat, triglyceride, fasting blood glucose, 2-hour blood glucose after glucose overload, fasting insulin, hemoglobin A1c, and HOMA-IR and negatively with the insulin sensitivity index in all of the study population. Multivariate logistic regression analysis revealed that circulating myonectin levels were significantly correlated with IGT and T2DM. A 45-minute bout of exercise did not change circulating myonectin levels in healthy, young individuals. Circulating myonectin levels were not significantly altered in response to an oral glucose challenge or EHC. In addition, acute elevated free fatty acid levels induced by lipid infusion had no effects on circulating myonectin.

CONCLUSIONS

These data suggest that myonectin may be a useful marker in predicting the development of prediabetes and diabetes.

Acute effect of moderate-intensity concentric and eccentric exercise on cardiac effort, perceived exertion and interleukin-6 level in physically inactive males

BACKGROUND

Muscle-derived interleukin-6 (IL-6) not only enhances glucose and fat metabolism but also has an anti-inflammatory effect that can prevent the development of cardiovascular disease (CVD) and metabolic syndrome. Dynamic resistance exercise comprises a muscle shortening and a lengthening phase known as concentric and eccentric contraction respectively. We compared an acute bout of concentric exercise (CE) with eccentric exercise (EE) for the serum IL-6 concentration, myocardial oxygen consumption (MVO2) and rating of perceived exertion (RPE).

METHODS

The present non-randomized crossover study involved 24 physically inactive but apparently healthy males, aged 18-25 years with body mass index of 18.5-23 kg/m2. Each participant performed an acute bout of moderate intensity CE followed by an EE bout after two weeks of rest. Exercise bout lasted for about 45 minutes that involved brisk walking on a treadmill at ±21% gradient for approximately 30 minutes, followed by the dumbbell exercises for biceps, triceps, quadriceps and hamstring muscles. MVO2 and IL-6 were estimated by the rate pressure product (RPP) and ELISA (enzyme-linked immunosorbent assay) kit respectively. Participants told their RPE after the workout. Wilcoxon or paired-t test were applied appropriately to compare the means. P<0.05 was considered significant.

RESULTS

RPP, RPE, and serum IL-6 levels were significantly lower after EE (164.4±16.3, 12, and 1.1±0.5, respectively) than CE (191.2±22.9, 13, and 1.2±0.6, respectively). A significant, strong and positive correlation of RPE was obtained with post-exercise heart-rate and RPP.

CONCLUSIONS

Regular EE might be beneficial for individuals having a low tolerance to exertion or at risk of developing CVD.

Positive association between musclin and insulin resistance in obesity: evidence of a human study and an animal experiment

Background

Musclin is a novel skeletal muscle-derived secretory factor considered to be a potent regulator of the glucose metabolism and therefore may contribute to the pathogenesis of obesity and insulin resistance (IR).

Methods

To test this hypothesis, we examined the plasma musclin levels in overweight/obese subjects and lean controls. Rats on a high fat diet (HFD) were used as the annimal model of obesity. Radioimmunoassay and western blot were used to determine musclin levels in plasma and skeletal muscle.

Results

According to radioimmunoassays,the overweight/obese subjects exhibited elevated musclin plasma levels compared with the lean controls (89.49 ± 19.00 ng/L vs 80.39 ± 16.35 ng/L, P < 0.01). The musclin levels were positively correlated with triglyceride, fasting plasma glucose, and homeostasis model assessment of IR levels. These observations were confirmed with a high-fat diet(HFD) rat model. HFD rats also exhibited increased musclin immunoreactivity in plasma (P < 0.01) and in skeletal muscle (P < 0.05), as well as increased musclin mRNA levels in skeletal muscle (P < 0.01). Musclin incubation significantly inhibited muscles ³H-2-DG uptake in the normal diet(ND) group (P < 0.01). The protein expression of glucose transporter type 4 was significantly down regulated by 30% (P < 0.05) in the ND group after soleusmuscle was incubated with musclin compared with the control. Musclin incubation also increased the protein levels of glucose-regulated protein (GRP)78 and GRP94 by 146.8 and 54% (both P < 0.05), respectively, in ND rats.

Conclusions

Our data support the hypothesis that musclin has a strong relationship with obesity-associated IR by impairing the glucose metabolism and, at least in part, through causing endoplasmic reticulum stress.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-017-0199-x) contains supplementary material, which is available to authorized users.

Cardiovascular Response and Serum Interleukin-6 Level in Concentric Vs. Eccentric Exercise

INTRODUCTION

Cardiovascular Disease (CVD) is a leading cause of morbidity and mortality in India. Resistance exercise is strongly recommended for implementation in CVD prevention programs. Dynamic resistance exercise comprises of concentric (muscle shortening) and eccentric (muscle lengthening) phase. The contraction of skeletal muscle promotes the synthesis and secretion of cytokines and peptides from myocytes, known as 'myokines'. Interleukin-6 (IL-6) is the first myokine to be released in the blood in response to exercise.

AIM

To compare the cardiovascular response and serum IL-6 level in concentric and eccentric exercise done at same absolute workload.

MATERIALS AND METHODS

In this non-randomised crossover study 24, apparently healthy and young male adults performed an acute bout of concentric and eccentric exercise. Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Heart Rate (HR), Mean Arterial Pressure (MAP), Pulse Pressure (PP) and serum IL-6 were measured just before and immediately after exercise. Paired t-test or Wilcoxon signed-rank test were applied to compare the data within-group and in-between group.

RESULTS

SBP, HR, MAP, PP, DBP and IL-6 level increased significantly after both, concentric and eccentric exercise. The mean change in SBP, HR, MAP, PP, and IL-6 after concentric exercise (18.54±3.06, 57.21±10.73, 8.35±1.40, 15.25±5.29, 5.40±3.13 respectively) was significantly higher than after eccentric exercise (13.38±1.72, 43.25±8.34, 6.50±1.0, 10.21±3.16, 4.36±2.54 respectively). A non-significant rise in DBP was obtained after concentric exercise (3.25±2.79) as compared to eccentric exercise (3.08±1.89).

CONCLUSION

Eccentric exercise not only caused a lesser cardiovascular demand as compared to concentric exercise but also a significant increment in IL-6 level. Exercise-induced IL-6 may prevent the initiation and development of CVD. Hence, eccentric exercise training might be recommended for reducing morbidity and mortality in individuals with- or at a risk of developing CVD.

Prior voluntary wheel running attenuates neuropathic pain

Exercise is known to exert a systemic anti-inflammatory influence, but whether its effects are sufficient to protect against subsequent neuropathic pain is underinvestigated. We report that 6 weeks of voluntary wheel running terminating before chronic constriction injury (CCI) prevented the full development of allodynia for the ∼3-month duration of the injury. Neuroimmune signaling was assessed at 3 and 14 days after CCI. Prior exercise normalized ipsilateral dorsal spinal cord expression of neuroexcitatory interleukin (IL)-1β production and the attendant glutamate transporter GLT-1 decrease, as well as expression of the disinhibitory P2X4R-BDNF axis. The expression of the macrophage marker Iba1 and the chemokine CCL2 (MCP-1), and a neuronal injury marker (activating transcription factor 3), was attenuated by prior running in the ipsilateral lumbar dorsal root ganglia. Prior exercise suppressed macrophage infiltration and/or injury site proliferation, given decreased presence of macrophage markers Iba1, iNOS (M1), and Arg-1 (M2; expression was time dependent). Chronic constriction injury-driven increases in serum proinflammatory chemokines were suppressed by prior running, whereas IL-10 was increased. Peripheral blood mononuclear cells were also stimulated with lipopolysaccharide ex vivo, wherein CCI-induced increases in IL-1β, nitrite, and IL-10 were suppressed by prior exercise. Last, unrestricted voluntary wheel running, beginning either the day of, or 2 weeks after, CCI, progressively reversed neuropathic pain. This study is the first to investigate the behavioral and neuroimmune consequences of regular exercise terminating before nerve injury. This study suggests that chronic pain should be considered a component of "the diseasome of physical inactivity," and that an active lifestyle may prevent neuropathic pain.

Increased circulating levels of musclin in newly diagnosed type 2 diabetic patients

BACKGROUND

Musclin is a newly identified skeletal muscle-derived secretory factor, which has been recently characterized as a stimulator that induces insulin resistance in mice. However, the pathophysiological role of musclin in humans remains poorly understood. The aim of this study was to explore the potential correlations between musclin plasma levels and various metabolic parameters in patients with type 2 diabetes mellitus.

MATERIALS AND METHODS

In this hospital-based study, plasma samples were collected from the enrolled individuals, including 38 newly diagnosed, treatment-naive type 2 diabetes mellitus patients and 41 age- and gender-matched control subjects. Plasma musclin levels were examined by radioimmunoassay.

RESULTS

Compared with the control group, musclin plasma levels were significantly higher in untreated type 2 diabetes mellitus patients. Musclin levels in the plasma of newly diagnosed type 2 diabetes mellitus patients were positively correlated with fasting plasma glucose, haemoglobin A_1c, serum insulin, triglycerides and homeostasis model assessment of insulin resistance. Furthermore, multivariate logistic regression analysis showed that the level of musclin was associated with the presence of type 2 diabetes mellitus. Receiver operating characteristic curve analysis yielded an area under the curve for musclin of 0.718 in type 2 diabetes mellitus.

CONCLUSION

The circulating concentration of musclin was significantly increased in type 2 diabetes mellitus patients. Our results suggest that musclin has a strong relationship with insulin resistance in type 2 diabetes mellitus.

Signs of ongoing inflammation in female patients with chronic widespread pain: A multivariate, explorative, cross-sectional study of blood samples

This cross-sectional study investigates the plasma inflammatory profile of chronic widespread pain (CWP) patients compared to healthy controls (CON). Rather than analyzing a relatively few substances at a time, we used a new multiplex proximity extension assay (PEA) panel that enabled the simultaneous analysis of 92 inflammation-related proteins, mainly cytokines and chemokines.Seventeen women with CWP and 21 female CON participated and a venous blood sample was drawn from all subjects. Pain intensity and pain thresholds for pressure, heat, and cold were registered. A PEA panel (92 proteins) was used to analyze the blood samples. Multivariate data analysis by projection was used in the statistical analyses.Eleven proteins significantly differentiated the CON and CWP subjects (R = 0.58, Q = 0.37, analysis of variance of cross-validated predictive residuals P = 0.006). It was not possible to significantly regress pain thresholds within each group (CON or CWP). Positive significant correlations existed between several proteins and pain intensities in CWP, but the model reliability of the regression was poor.CWP was associated with systemic low-grade inflammation. Larger studies are needed to confirm the results and to investigate which alterations are condition-specific and which are common across chronic pain conditions. The presence of inflammation could promote the spreading of pain, a hallmark sign of CWP. As it has been suggested that prevalent comorbidities to pain (e.g., depression and anxiety, poor sleep, and tiredness) also are associated with inflammation, it will be important to determine whether inflammation may be a common mediator.

Oxidative stress and inflammation: liver responses and adaptations to acute and regular exercise

The liver is remarkably important during exercise outcomes due to its contribution to detoxification, synthesis, and release of biomolecules, and energy supply to the exercising muscles. Recently, liver has been also shown to play an important role in redox status and inflammatory modulation during exercise. However, while several studies have described the adaptations of skeletal muscles to acute and chronic exercise, hepatic changes are still scarcely investigated. Indeed, acute intense exercise challenges the liver with increased reactive oxygen species (ROS) and inflammation onset, whereas regular training induces hepatic antioxidant and anti-inflammatory improvements. Acute and regular exercise protocols in combination with antioxidant and anti-inflammatory supplementation have been also tested to verify hepatic adaptations to exercise. Although positive results have been reported in some acute models, several studies have shown an increased exercise-related stress upon liver. A similar trend has been observed during training: while synergistic effects of training and antioxidant/anti-inflammatory supplementations have been occasionally found, others reported a blunting of relevant adaptations to exercise, following the patterns described in skeletal muscles. This review discusses current data regarding liver responses and adaptation to acute and regular exercise protocols alone or combined with antioxidant and anti-inflammatory supplementation. The understanding of the mechanisms behind these modulations is of interest for both exercise-related health and performance outcomes.

Crosstalk between adipokines and myokines in fat browning

Skeletal muscle is the largest organ determining whole-body insulin sensitivity and metabolic homoeostasis. Adaptive changes of skeletal muscle in response to physical activity include adjustments in the production and secretion of muscle-derived bioactive factors, known as myokines, such as myostatin, IL-4, IL-6, IL-7 and IL-15, myonectin, follistatin-like 1 or leukaemia inhibitory factor. These myokines not only act locally in the muscle in an autocrine/paracrine manner, but also are released to the bloodstream as endocrine factors to regulate physiological processes in other tissues. Irisin, derived from the cleavage of FNDC5 protein, constitutes a myokine that induces myogenesis and fat browning (switch of white adipocytes to brown fat-like cells) together with a concomitant increase in energy expenditure. Besides being a target for irisin actions, the adipose tissue also constitutes a production site of FNDC5. Interestingly, irisin secretion from subcutaneous and visceral fat depots is decreased by long-term exercise training and fasting, suggesting a discordant regulation of FNDC5/irisin in skeletal muscle and adipose tissue. Accordingly, our group has recently reported that the adipokine leptin differentially regulates FNDC5/irisin expression in skeletal muscle and fat, confirming the crosstalk between both tissues. Moreover, irisin secretion and function are regulated by other myokines, such as follistatin or myostatin, as well as by other adipokines, including fibroblast growth factor 21 and leptin. Taken together, myokines have emerged as novel molecular mediators of fat browning and their activity can be modulated by adipokines, confirming the crosstalk between skeletal muscle and adipose tissue to regulate thermogenesis and energy expenditure.

Differential Bone Loss in Mouse Models of Colon Cancer Cachexia

Cachexia is a distinctive feature of colorectal cancer associated with body weight loss and progressive muscle wasting. Several mechanisms responsible for muscle and fat wasting have been identified, however it is not known whether the physiologic and molecular crosstalk between muscle and bone tissue may also contribute to the cachectic phenotype in cancer patients. The purpose of this study was to clarify whether tumor growth associates with bone loss using several experimental models of colorectal cancer cachexia, namely C26, HT-29, and Apc^Min/+. The effects of cachexia on bone structure and strength were evaluated with dual energy X-ray absorptiometry (DXA), micro computed tomography (μCT), and three-point bending test. We found that all models showed tumor growth consistent with severe cachexia. While muscle wasting in C26 hosts was accompanied by moderate bone depletion, no loss of bone strength was observed. However, HT-29 tumor bearing mice showed bone abnormalities including significant reductions in whole-body bone mineral density (BMD), bone mineral content (BMC), femoral trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), and trabecular thickness (Tb.Th), but no declines in strength. Similarly, cachexia in the Apc^Min/+ mice was associated with significant decreases in BMD, BMC, BV/TV, Tb.N, and Tb.Th as well as decreased strength. Our data suggest that colorectal cancer is associated with muscle wasting and may be accompanied by bone loss dependent upon tumor type, burden, stage and duration of the disease. It is clear that preserving muscle mass promotes survival in cancer cachexia. Future studies will determine whether strategies aimed at preventing bone loss can also improve outcomes and survival in colorectal cancer cachexia.

Myokines and adipokines: Involvement in the crosstalk between skeletal muscle and adipose tissue

Skeletal muscle and adipose tissue are the two largest organs in the body. Skeletal muscle is an effector organ, and adipose tissue is an organ that stores energy; in addition, they are endocrine organs that secrete cytokines, namely myokines and adipokines, respectively. Myokines consist of myostatin, interleukin (IL)-8, IL-15, irisin, fibroblast growth factor 21, and myonectin; adipokines include leptin, adiponectin, resistin, chemerin, and visfatin. Furthermore, certain cytokines, such as IL-6 and tumor necrosis factor-α, are released by both skeletal muscle and adipose tissue and exhibit a bioactive effect; thus, they are called adipo-myokines. Recently, novel myokines or adipokines were identified through the secretomic technique, which has expanded our knowledge on the previously unknown functions of skeletal muscle and adipose tissue and provide a new avenue of investigation for obesity treatment or animal production. This review focuses on the roles of and crosstalk between myokines and adipokines in skeletal muscle and adipose tissue that modulate the molecular events in the metabolic homeostasis of the whole body.