Muscles and their myokines

Dementia risk by combinations of metabolic diseases and body mass index: Japan Gerontological Evaluation Study Cohort Study

AIMS/INTRODUCTION

To compare the dementia risk associated with pre-existing diabetes, hypertension, dyslipidemia, obesity (body mass index [BMI] ≥25 kg/m2 ) and underweight (BMI <18.5 kg/m2 ) among older adults. We also explored the dementia risk associated with combinations of metabolic diseases and BMI.

MATERIALS AND METHODS

We used data from the Japan Gerontological Evaluation Study. Participants completed a health checkup in 2010 and were followed for 5.8 years on average. Dementia was measured by municipal long-term care insurance registration. Diabetes, hypertension, dyslipidemia, obesity and underweight were diagnosed by medication use or health examination results. We calculated the incidence of dementia and adjusted hazard ratios (HRs).

RESULTS

Among 3,696 participating older adults, 338 developed dementia. Adjusted HRs (95% confidence intervals) in men and women (reference: those without corresponding disease of normal weight) were as follows: 2.22 (1.26-3.90) and 2.00 (1.07-3.74) for diabetes; 0.56 (0.29-1.10) and 1.05 (0.64-1.71) for hypertension; 1.30 (0.87-1.94) and 0.73 (0.49-1.08) for dyslipidemia; 0.73 (0.42-1.28) and 0.82 (0.49-1.37) for BMI of 25-29.9 kg/m2 ; and 1.04 (0.51-2.10) and 1.72 (1.05-2.81) for underweight. Dementia risk was significantly higher in underweight men with dyslipidemia (HR 4.15, 95% CI 1.79-9.63) compared with normal-weight men without dyslipidemia, and in underweight women with hypertension (HR 3.79, 1.55-9.28) compared with normal-weight women without hypertension. Dementia incidence was highest among underweight older adults with hypertension followed by dyslipidemia.

CONCLUSIONS

Among Japanese older adults, underweight and prevalent diabetes are risk factors for developing dementia. Lower BMI is also associated with a higher incidence of dementia.

Skeletal muscle-derived cells repair peripheral nerve defects in mice

Skeletal muscle-derived cells have strong secretory function, while skeletal muscle-derived stem cells, which are included in muscle-derived cells, can differentiate into Schwann cell-like cells and other cell types. However, the effect of muscle-derived cells on peripheral nerve defects has not been reported. In this study, 5-mm-long nerve defects were created in the right sciatic nerves of mice to construct a peripheral nerve defect model. Adult female C57BL/6 mice were randomly divided into four groups. For the muscle-derived cell group, muscle-derived cells were injected into the catheter after the cut nerve ends were bridged with a polyurethane catheter. For external oblique muscle-fabricated nerve conduit and polyurethane groups, an external oblique muscle-fabricated nerve conduit or polyurethane catheter was used to bridge the cut nerve ends, respectively. For the sham group, the sciatic nerves on the right side were separated but not excised. At 8 and 12 weeks post-surgery, distributions of axons and myelin sheaths were observed, and the nerve diameter was calculated using immunofluorescence staining. The number, diameter, and thickness of myelinated nerve fibers were detected by toluidine blue staining and transmission electron microscopy. Muscle fiber area ratios were calculated by Masson’s trichrome staining of gastrocnemius muscle sections. Sciatic functional index was recorded using walking footprint analysis at 4, 8, and 12 weeks after operation. The results showed that, at 8 and 12 weeks after surgery, myelin sheaths and axons of regenerating nerves were evenly distributed in the muscle-derived cell group. The number, diameter, and myelin sheath thickness of myelinated nerve fibers, as well as gastrocnemius muscle wet weight and muscle area ratio, were significantly higher in the muscle-derived cell group compared with the polyurethane group. At 4, 8, and 12 weeks post-surgery, sciatic functional index was notably increased in the muscle-derived cell group compared with the polyurethane group. These criteria of the muscle-derived cell group were not significantly different from the external oblique muscle-fabricated nerve conduit group. Collectively, these data suggest that muscle-derived cells effectively accelerated peripheral nerve regeneration. This study was approved by the Animal Ethics Committee of Plastic Surgery Hospital, Chinese Academy of Medical Sciences (approval No. 040) on September 28, 2016.

Fibroblast growth factor 9 (FGF9) inhibits myogenic differentiation of C2C12 and human muscle cells

Osteoporosis and sarcopenia (osteosarcopenia (OS)) are twin-aging diseases. The biochemical crosstalk between muscle and bone seems to play a role in OS. We have previously shown that osteocytes produce soluble factors with beneficial effects on muscle and vice versa. Recently, enhanced FGF9 production was observed in the OmGFP66 osteogenic cell line. To test its role in myogenic differentiation, C2C12 myoblasts were treated with recombinant FGF9. FGF9 as low as 10 ng/mL inhibited myogenic differentiation, suggesting that FGF9 might be a potential inhibitory factor produced from bone cells with effects on muscle cells. FGF9 (10–50 ng/mL) significantly decreased mRNA expression of MyoG and Mhc while increasing the expression of Myostatin. Consistent with the phenotype, RT-qPCR array revealed that FGF9 (10 ng/mL) increased the expression of Icam1 while decreased the expression of Wnt1 and Wnt6 decreased, respectively. FGF9 decreased caffeine-induced Ca²⁺ release from the sarcoplasmic reticulum (SR) of C2C12 myotubes and reduced the expression of genes (i.e. Cacna1s, RyR2, Naftc3) directly associated with intracellular Ca²⁺ homeostasis. Myogenic differentiation in human skeletal muscle cells was similarly inhibited by FGF9 but required higher doses of 200 ng/mL FGF9. FGF9 was also shown to stimulate C2C12 myoblast proliferation. FGF2 and the FGF9 subfamily members FGF16 and FGF20 also inhibited C2C12 myoblast differentiation and enhanced proliferation. Intriguingly, the differentiation inhibition was independent of proliferation enhancement. These findings suggest that FGF9 may modulate myogenesis via a complex signaling mechanism.

Adipose Tissue Quality in Aging: How Structural and Functional Aspects of Adipose Tissue Impact Skeletal Muscle Quality

The interplay between adipose tissue and skeletal muscle and the impact on mobility and aging remain enigmatic. The progressive decline in mobility promoted by aging has been previously attributed to the loss of skeletal mass and function and more recently linked to changes in body fat composition and quantity. Regardless of body size, visceral and intermuscular adipose depots increase with aging and are associated with adverse health outcomes. However, the quality of adipose tissue, in particular abdominal subcutaneous as it is the largest depot, likely plays a significant role in aging outcomes, such as mobility decline, though its communication with other tissues such as skeletal muscle. In this review, we discuss the age-associated development of a pro-inflammatory profile, cellular senescence, and metabolic inflexibility in abdominal subcutaneous adipose tissue. Collectively, these facets of adipose tissue quality influence its secretory profile and crosstalk with skeletal muscle and likely contribute to the development of muscle atrophy and disability. Therefore, the identification of the key structural and functional components of adipose tissue quality—including necrosis, senescence, inflammation, self-renewal, metabolic flexibility—and adipose tissue-secreted proteins that influence mobility via direct effects on skeletal muscle are necessary to prevent morbidity/mortality in the aging population.

The vascular endothelium plays a role in insulin action

The endocrine system relies on the vasculature for delivery of hormones throughout the body, and the capillary microvasculature is the site where the hormones cross from the blood into the target tissue. Once considered an inert wall, various studies have now highlighted the functions of the capillary endothelium to regulate transport and therefore affect or maintain the interstitial environment. The role of the capillary may be clear in areas where there is a continuous endothelium, yet there also appears to be a role of endothelial cells in tissues with a sinusoidal structure. Here we focused on the most common endocrine disorder, diabetes, and several of the target organs associated with the disease, including skeletal muscle, liver and pancreas. However, it is important to note that the ability of hormones to cross the endothelium to reach their target tissue is a component of all endocrine functions. It is also a consideration in organs throughout the body and may have greater impact for larger hormones with target tissues containing a continuous endothelium. We noted that the blood levels do not always equal interstitial levels, which is what the cells are exposed to, and discussed how this may change in diseases such as obesity and insulin resistance. The capillary endothelium is, therefore, an essential and understudied aspect of endocrinology and metabolism that can be altered in disease, which may be an appropriate target for treatment.

Effect of a Very-Low-Calorie Ketogenic Diet on Circulating Myokine Levels Compared with the Effect of Bariatric Surgery or a Low-Calorie Diet in Patients with Obesity

: The preservation of muscle mass and muscle function after weight loss therapy is currently a considerable challenge in the fight against obesity. Muscle mass secretes proteins called myokines that have relevant functions in the regulation of metabolism and health. This study was aimed to evaluate whether a very low-calorie ketogenic (VLCK) diet may modulate myokine levels, in addition to changes in body composition, compared to a standard, balanced low-calorie (LC) diet or bariatric surgery in patients with obesity. Body composition, ketosis, insulin sensitivity and myokines were evaluated in 79 patients with overweight/obesity after a therapy to lose weight with a VLCK diet, a LC diet or bariatric surgery. The follow-up was 6 months. The weight loss therapies induced changes in myokine levels in association with changes in body composition and biochemical parameters. The effects on circulating myokine levels compared to those at baseline were stronger after the VLCK diet than LC diet or bariatric surgery. Differences reached statistical significance for IL-8, MMP2 and irisin. In conclusion, nutritional interventions or bariatric surgery to lose weight induces changes in circulating myokine levels, being this effect potentially most notable after following a VLCK diet.

Handgrip Strength and Pulmonary Disease in the Elderly: What is the Link?

Societies in developed countries are aging at an unprecedented rate. Considering that aging is the most significant risk factor for many chronic lung diseases (CLDs), understanding this process may facilitate the development of new interventionist approaches. Skeletal muscle dysfunction is a serious problem in older adults with CLDs, reducing their quality of life and survival. In this study, we reviewed the possible links between handgrip strength (HGS)—a simple, noninvasive, low-cost measure of muscle function—and CLDs in the elderly. Different mechanisms appear to be involved in this association, including systemic inflammation, chronic hypoxemia, physical inactivity, malnutrition, and corticosteroid use. Respiratory and peripheral myopathy, associated with muscle atrophy and a shift in muscle fiber type, also seem to be major etiological contributors to CLDs. Moreover, sarcopenic obesity, which occurs in older adults with CLDs, impairs common inflammatory pathways that can potentiate each other and further accelerate the functional decline of HGS. Our findings support the concept that the systemic effects of CLDs may be determined by HGS, and HGS is a relevant measurement that should be considered in the clinical assessment of the elderly with CLDs. These reasons make HGS a useful practical tool for indirectly evaluating functional status in the elderly. At present, early muscle reconditioning and optimal nutrition appear to be the most effective approaches to reduce the impact of CLDs and low muscle strength on the quality of life of these individuals. Nonetheless, larger in-depth studies are needed to evaluate the link between HGS and CLDs.

Physicochemical Niche Conditions and Mechanosensing by Osteocytes and Myocytes

PURPOSE OF REVIEW

Bone and muscle mass increase in response to mechanical loading and biochemical cues. Bone-forming osteoblasts differentiate into early osteocytes which ultimately mature into late osteocytes encapsulated in stiff calcified matrix. Increased muscle mass originates from muscle stem cells (MuSCs) enclosed between their plasma membrane and basal lamina. Stem cell fate and function are strongly determined by physical and chemical properties of their microenvironment, i.e., the cell niche.

RECENT FINDINGS

The cellular niche is a three-dimensional structure consisting of extracellular matrix components, signaling molecules, and/or other cells. Via mechanical interaction with their niche, osteocytes and MuSCs are subjected to mechanical loads causing deformations of membrane, cytoskeleton, and/or nucleus, which elicit biochemical responses and secretion of signaling molecules into the niche. The latter may modulate metabolism, morphology, and mechanosensitivity of the secreting cells, or signal to neighboring cells and cells at a distance. Little is known about how mechanical loading of bone and muscle tissue affects osteocytes and MuSCs within their niches. This review provides an overview of physicochemical niche conditions of (early) osteocytes and MuSCs and how these are sensed and determine cell fate and function. Moreover, we discuss how state-of-the-art imaging techniques may enhance our understanding of these conditions and mechanisms.

The Local and Systemic Interactions Between Muscle and Bone in Postmenopausal Korean Women

Despite many studies about local and systemic interactions between bone and muscle, the more dominant interaction remains unclear. We aimed to compare the association of skeletal muscle mass with bone mineral density (BMD) at the femur, which seemed more likely affected by local interaction, and the association of skeletal muscle mass with BMD at the lumbar spine (LS-BMD) and the trabecular bone score (TBS), which seemed more likely affected by systemic interaction. In 279 women, we measured the femoral neck BMD (FN-BMD), total hip BMD (TH-BMD), LS-BMD, and TBS. Appendicular skeletal muscle mass (ASM), lean mass (LM), and other LM (OLM; remaining LM excluding ASM) were measured using bioelectrical impedance analysis. ASM (β = 0.008-0.014, p < 0.001-0.014), OLM (β = 0.006-0.011, p < 0.001-0.044), and LM (β = 0.004-0.007, p < 0.001-0.020) were positively associated with FN-BMD and TH-BMD, but not with LS-BMD or TBS. The positive association of ASM, but not of OLM, was stronger than that of LM (p = 0.023). Odd ratios (ORs) with 95% confidence intervals (95% CIs) for osteoporosis were statistically significant for ASM (OR 0.74, 95% CI 0.59-0.93) and marginally significant for OLM (OR 0.80, 95% CI 0.64-1.01) in the femur, but not in the LS. The direct and indirect (through OLM) effects of ASM on BMD were 69.1-72.2% and 27.8-30.9%, respectively. In the conclusion, ASM was more positively associated with FN-BMD, but not with LS-BMD and TBS, than OLM. This suggests stronger effects of local interaction than systemic interaction between muscle and bone.

Acute Exercise Increases Plasma Levels of Muscle-Derived Microvesicles Carrying Fatty Acid Transport Proteins

CONTEXT

Microvesicles (MVs) are a class of membrane particles shed by any cell in the body in physiological and pathological conditions. They are considered to be key players in intercellular communication, and with a molecular content reflecting the composition of the cell of origin, they have recently emerged as a promising source of biomarkers in a number of diseases.

OBJECTIVE

The effects of acute exercise on the plasma concentration of skeletal muscle-derived MVs (SkMVs) carrying metabolically important membrane proteins were examined.

PARTICIPANTS

Thirteen men with obesity and type 2 diabetes mellitus (T2DM) and 14 healthy male controls with obesity exercised on a cycle ergometer for 60 minutes.

INTERVENTIONS

Muscle biopsies and blood samples-obtained before exercise, immediately after exercise, and 3 hours into recovery-were collected for the analysis of long-chain fatty acid (LCFA) transport proteins CD36 (a scavenger receptor class B protein) and fatty acid transport protein 4 (FATP4) mRNA content in muscle and for flow cytometric studies on circulating SkMVs carrying either LCFA transport protein.

RESULTS

Besides establishing a flow cytometric approach for the detection of circulating SkMVs and subpopulations carrying either CD36 or FATP4 and thereby adding proof to their existence, we demonstrated an overall exercise-induced change of SkMVs carrying these LCFA transport proteins. A positive correlation between exercise-induced changes in skeletal muscle CD36 mRNA expression and concentrations of SkMVs carrying CD36 was found in T2DM only.

CONCLUSIONS

This approach could add important real-time information about the abundance of LCFA transport proteins present on activated muscle cells in subjects with impaired glucose metabolism.

Organokines in disease

Studies have linked obesity, metabolic syndrome, type 2 diabetes, cardiovascular disease (CVD), nonalcoholic fatty liver disease (NAFLD) and dementia. Their relationship to the incidence and progression of these disease states suggests an interconnected pathogenesis involving chronic low-grade inflammation and oxidative stress. Metabolic syndrome represents comorbidities of central obesity, insulin resistance, dyslipidemia, hypertension and hyperglycemia associated with increased risk of type 2 diabetes, NAFLD, atherosclerotic CVD and neurodegenerative disease. As the socioeconomic burden for these diseases has grown signficantly with an increasing elderly population, new and alternative pharmacologic solutions for these cardiometabolic diseases are required. Adipose tissue, skeletal muscle and liver are central endocrine organs that regulate inflammation, energy and metabolic homeostasis, and the neuroendocrine axis through synthesis and secretion of adipokines, myokines, and hepatokines, respectively. These organokines affect each other and communicate through various endocrine, paracrine and autocrine pathways. The ultimate goal of this review is to provide a comprehensive understanding of organ crosstalk. This will include the roles of novel organokines in normal physiologic regulation and their pathophysiological effect in obesity, metabolic syndrome, type 2 diabetes, CVD, NAFLD and neurodegenerative disorders.

Serum Level of Musclin Is Elevated Following Severe Burn

Muscle wasting induced by severe burn worsens clinical outcomes is associated with hyperglycemia. A novel muscle-specific secretory factor, musclin, was reported to regulate glucose metabolism with a homologous sequence of natriuretic peptides. The purpose of the study was to investigate musclin expression in response to burn injury in both human and animal models. Serum was collected from 13 adult burn patients and circulating levels of musclin protein were measured via elisa. The cytokine profile was measured by Bio-Plex multiple immunoassay. Following the clinical study, we used a burn rat model with 40% TBSA to study the time course of musclin expression till day 14. Rat serum and muscle tissue sample were harvested. Finally, an in vitro study was applied to investigate whether the muscle cell C2C12 myoblast expressed musclin under 10% burn serum stimulation. Pearson analysis showed that there was a significant positive correlation of musclin expression to total body surface area of burn in patients (P &= .038). Musclin expression was significantly positively correlated with IL-4, IL-7, IL-12, and IL-13 in burn patients’ serum (P < .05). In the animal study, we found that the musclin level evaluated at 6 hours and 1 day in burn rat serum (P < .05). In vitro, musclin mRNA expression significantly increased with burn serum stimulation at 24 hours (P < .05). In conclusion, serum level of musclin elevated both in human patients and burn animals; musclin was correlated with the severity of burn injury as well as with an elevated cytokine profile in patients; burn serum-stimulated musclin expression in vitro further identified the resource of musclin expression after burn.

Effects of Exercise to Improve Cardiovascular Health

Obesity is a complex disease that affects whole body metabolism and is associated with an increased risk of cardiovascular disease (CVD) and Type 2 diabetes (T2D). Physical exercise results in numerous health benefits and is an important tool to combat obesity and its co-morbidities, including cardiovascular disease. Exercise prevents both the onset and development of cardiovascular disease and is an important therapeutic tool to improve outcomes for patients with cardiovascular disease. Some benefits of exercise include enhanced mitochondrial function, restoration and improvement of vasculature, and the release of myokines from skeletal muscle that preserve or augment cardiovascular function. In this review we will discuss the mechanisms through which exercise promotes cardiovascular health.

Muscle-bone crosstalk and potential therapies for sarco-osteoporosis

The nature of muscle-bone crosstalk has been historically considered to be only mechanical, where the muscle is the load applier while bone provides the attachment sites. However, this dogma has been challenged with the emerging notion that bone and muscle act as secretory endocrine organs affect the function of each other. Biochemical crosstalk occurs through myokines such as myostatin, irisin, interleukin (IL)-6, IL-7, IL-15, insulin-like growth factor-1, fibroblast growth factor (FGF)-2, and β-aminoisobutyric acid and through bone-derived factors including FGF23, prostaglandin E₂ , transforming growth factor β, osteocalcin, and sclerostin. Aside from the biochemical and mechanical interaction, additional factors including aging, circadian rhythm, nervous system network, nutrition intake, and exosomes also have effects on bone-muscle crosstalk. Here, we summarize the current research progress in the area, which may be conductive to identify potential novel therapies for the osteoporosis and sarcopenia, especially when they develop in parallel.

Tart Cherry Concentrate Does Not Alter the Gut Microbiome, Glycaemic Control or Systemic Inflammation in a Middle-Aged Population

Limited evidence suggests that the consumption of polyphenols may improve glycaemic control and insulin sensitivity. The gut microbiome produces phenolic metabolites and increases their bioavailability. A handful of studies have suggested that polyphenol consumption alters gut microbiome composition. There are no data available investigating such effects in polyphenol-rich Montmorency cherry (MC) supplementation. A total of 28 participants (aged 40-60 years) were randomized to receive daily MC or glucose and energy-matched placebo supplementation for 4 wk. Faecal and blood samples were obtained at baseline and at 4 wk. There was no clear effect of supplementation on glucose handling (Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and Gutt indices), although the Matsuda index decreased significantly in the MC group post-supplementation, reflecting an increase in serum insulin concentration. Contrastingly, placebo, but not MC supplementation induced a 6% increase in the Oral Glucose Insulin Sensitivity (OGIS) estimate of glucose clearance. Serum IL-6 and C reactive protein were unaltered by either supplement. The faecal bacterial microbiome was sequenced; species richness and diversity were unchanged by MC or placebo and no significant correlation existed between changes in Bacteroides and Faecalibacterium abundance and any index of insulin sensitivity. Therefore, 4 weeks of MC supplementation did not alter the gut microbiome, glycaemic control or systemic concentrations of IL-6 and CRP in a middle-aged population.

Interleukin-8 enhances myocilin expression, Akt-FoxO3 signaling and myogenic differentiation in rat skeletal muscle cells

Interleukin (IL)-8 is released both in visceral adipose tissue and in contracting skeletal muscles. In this study, we examined cellular pathways associated with muscle hypertrophy, chosen on the basis of microRNA profiling, in differentiating rat primary skeletal muscle cells (RSkMC) treated with IL-8 (1 ng/ml) for 11 days. IL-8 increased myocilin expression, Akt phosphorylation, FoxO3 dispersion throughout the cytoplasm, and reduced FoxO3 level. IL-8 decreased the expression of atrogin and MuRF1 and increased myotube length and diameter. We concluded that IL-8 present in extracellular environment of myoblasts induced to differentiation stimulates expression of myocilin, a protein important for skeletal muscle hypertrophy. This phenomenon was associated with: (a) activation of myogenic transcription, (b) increased phosphorylation and activation of PKB/Akt, leading to (c) cytoplasm distribution and degradation of a transcription factor FoxO3, (d) decreased expression of gene markers of proteolysis, atrogin and Murf1, and (e) increased myotube length and diameter. In this regard, IL-8 affects skeletal muscle cells similarly to IGF-I and can be considered as a potent anticatabolic factor for skeletal muscle.

Effect of voluntary running on expression of myokines in brains of rats with depression

This study aimed to demonstrate the histopathology and immunoexpression of exercise-derived myokines in dentate gyrus (DG), medial prefrontal cortex (mPFC) and cerebellum of depressed Wistar rats during depression and after practising voluntary running. Depression was developed by forced swimming for 2 weeks. Voluntary running was performed by voluntary running for 3 weeks. Brain sections were processed and immunostained to detect brain-derived neurotrophic factor (BDNF), macrophage migration inhibitory factor (MIF), vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6). ImageJ software was used to measure the optical density (OD). BDNF was expressed in neurons in DG, mPFC and granular and Purkinje cells in cerebellum. MIF was expressed in neurons of sub-granular zone in DG, mPFC and Purkinje cells. VEGF was expressed in many neurons in DG, mPFC and Purkinje cells. IL-6 was expressed in some neurons in DG, in neuropil of mPFC and in Purkinje cells. In depression, the OD of studied myokines significantly decreased in all examined areas. After voluntary running, the OD of myokines significantly increased in all areas. This study defines the immunohistochemical expression of myokines in brain areas in depression and after voluntary running and reveals the involvement of the mPFC and cerebellum in the pathophysiology of depression.

Use it or lose it to age: A review of bone and muscle communication

Until recently, it was assumed that the only interaction between muscle and bone is mechanical, that the muscle acts as a pulley and the bone as a lever to move the organism. A relatively new concept is that muscle, especially contracted muscle, acts as a secretory organ, regulating metabolism. An even newer concept is that bone, especially the osteocytes in bone, act as endocrine cells targeting other organs such as kidney and more recently, muscle. These two new concepts logically led to the third concept: that muscle and bone communicate via soluble factors. Crosstalk occurs through muscle factors such as myostatin, irisin, and a muscle metabolite, β-aminoisobutyric acid, BAIBA, and through bone factors such as osteocalcin, transforming growth factor beta, TGFβ, Prostaglandin E2, PGE₂ and Wnts. Some of these factors have positive and some negative effects on the opposing tissue. One feature both bone and muscle have in common is that their tissues are mechanically loaded and many of their secreted factors are regulated by load. This mechanical loading, also known as exercise, has beneficial effects on many systems leading to the hypothesis that muscle and bone factors can be responsible for the beneficial effects of exercise. Many of the characteristics of aging and diseases associated with aging such as sarcopenia and osteoporosis and neurological conditions such as Alzheimer's disease and dementia, are delayed by exercise. This beneficial effect has been ascribed to increased blood flow increasing oxygen and nutrients, but could also be due to the secretome of the musculoskeletal system as outlined in this review.

Beta-Aminoisobutyric Acid as a Novel Regulator of Carbohydrate and Lipid Metabolism

The prevalence and incidence of metabolic syndrome is reaching pandemic proportions worldwide, thus warranting an intensive search for novel preventive and treatment strategies. Recent studies have identified a number of soluble factors secreted by adipocytes and myocytes (adipo-/myokines), which link sedentary life style, abdominal obesity, and impairments in carbohydrate and lipid metabolism. In this review, we discuss the metabolic roles of the recently discovered myokine β-aminoisobutyric acid (BAIBA), which is produced by skeletal muscle during physical activity. In addition to physical activity, the circulating levels of BAIBA are controlled by the mitochondrial enzyme alanine: glyoxylate aminotransferase 2 (AGXT2), which is primarily expressed in the liver and kidneys. Recent studies have shown that BAIBA can protect from diet-induced obesity in animal models. It induces transition of white adipose tissue to a "beige" phenotype, which induces fatty acids oxidation and increases insulin sensitivity. While the exact mechanisms of BAIBA-induced metabolic effects are still not well understood, we discuss some of the proposed pathways. The reviewed data provide new insights into the connection between physical activity and energy metabolism and suggest that BAIBA might be a potential novel drug for treatment of the metabolic syndrome and its cardiovascular complications.

Mechanisms Underlying Metabolic Syndrome-Related Sarcopenia and Possible Therapeutic Measures

Although there are several reviews that report the interrelationship between sarcopenia and obesity and insulin resistance, the relation between sarcopenia and the other signs that compose the metabolic syndrome (MetS) has not been extensively revised. Here, we review the mechanisms underlying MetS-related sarcopenia and discuss the possible therapeutic measures proposed. A vicious cycle between the loss of muscle and the accumulation of intramuscular fat might be associated with MetS via a complex interplay of factors including nutritional intake, physical activity, body fat, oxidative stress, proinflammatory cytokines, insulin resistance, hormonal changes, and mitochondrial dysfunction. The enormous differences in lipid storage capacities between the two genders and elevated amounts of endogenous fat having lipotoxic effects that lead to the loss of muscle mass are discussed. The important repercussions of MetS-related sarcopenia on other illnesses that lead to increased disability, morbidity, and mortality are also addressed. Additional research is needed to better understand the pathophysiology of MetS-related sarcopenia and its consequences. Although there is currently no consensus on the treatment, lifestyle changes including diet and power exercise seem to be the best options.

Role of Myokines in Regulating Skeletal Muscle Mass and Function

Loss of skeletal muscle mass and strength has recently become a hot research topic with the extension of life span and an increasingly sedentary lifestyle in modern society. Maintenance of skeletal muscle mass is considered an essential determinant of muscle strength and function. Myokines are cytokines synthesized and released by myocytes during muscular contractions. They are implicated in autocrine regulation of metabolism in the muscle as well as in the paracrine/endocrine regulation of other tissues and organs including adipose tissue, the liver, and the brain through their receptors. Till date, secretome analysis of human myocyte culture medium has revealed over 600 myokines. In this review article, we summarize our current knowledge of major identified and characterized myokines focusing on their biological activity and function, particularly in muscle mass and function.

Blood-brain barrier permeability and physical exercise

In this narrative review, a theoretical framework on the crosstalk between physical exercise and blood-brain barrier (BBB) permeability is presented. We discuss the influence of physical activity on the factors affecting BBB permeability such as systemic inflammation, the brain renin-angiotensin and noradrenergic systems, central autonomic function and the kynurenine pathway. The positive role of exercise in multiple sclerosis and Alzheimer’s disease is described. Finally, the potential role of conditioning as well as the effect of exercise on BBB tight junctions is outlined. There is a body of evidence that regular physical exercise diminishes BBB permeability as it reinforces antioxidative capacity, reduces oxidative stress and has anti-inflammatory effects. It improves endothelial function and might increase the density of brain capillaries. Thus, physical training can be emphasised as a component of prevention programs developed for patients to minimise the risk of the onset of neuroinflammatory diseases as well as an augmentation of existing treatment. Unfortunately, despite a sound theoretical background, it remains unclear as to whether exercise training is effective in modulating BBB permeability in several specific diseases. Further research is needed as the impact of exercise is yet to be fully elucidated.

Extracellular matrix roles in cardiorenal fibrosis: Potential therapeutic targets for CVD and CKD in the elderly

Whereas hypertension, diabetes, and dyslipidemia are age-related risk factors for cardiovascular disease (CVD) and chronic kidney disease (CKD), aging alone is an independent risk factor. With advancing age, the heart and kidney gradually but significantly undergo inflammation and subsequent fibrosis, which eventually results in an irreversible decline in organ physiology. Through cardiorenal network interactions, cardiac dysfunction leads to and responds to renal injury, and both facilitate aging effects. Thus, a comprehensive strategy is needed to evaluate the cardiorenal aging network. Common hallmarks shared across systems include extracellular matrix (ECM) accumulation, along with upregulation of matrix metalloproteinases (MMPs) including MMP-9. The wide range of MMP-9 substrates, including ECM components and inflammatory cytokines, implicates MMP-9 in a variety of pathological and age-related processes. In particular, there is strong evidence that inflammatory cell-derived MMP-9 exacerbates cardiorenal aging. This review explores the potential therapeutic targets against CVD and CKD in the elderly, focusing on ECM and MMP roles.

Whole body and partial body cryotherapies - lessons from human practice and possible application for horses

Whole body and partial body cryotherapies (WBC and PBC) have been successfully used in human medicine, and currently also are being proposed in veterinary practice.

In horses, only the partial body cryotherapy provided in cryosauna is considered, due to the technical conditions. These therapies have been dedicated to human patients with rheumatic and inflammatory diseases as well as an assistance during training in athletes. The anti-inflammatory effects have been demonstrated clinically and indicated by the changes in several hematological and immunological parameters, however, various patterns have been described, depending on the protocols and the treating subjects. The numbers of white blood cells and the differential counts either increased or remained unchanged but the cytokine concentrations generally changed towards various anti-inflammatory profiles and the modifications of immunological molecules having paracrine effects have been reported.

In equine practice, local cold therapies have been successfully used, so the therapy in cryosauna, which allows for a much shorter procedure with much lower temperature seems promising.

IL-6 and the dysregulation of immune, bone, muscle, and metabolic homeostasis during spaceflight

We have previously reported that exercise-related secretion of IL-6 by peripheral blood mononuclear cells is proportionate to body weight, suggesting that IL-6 is gravisensitive and that suboptimal production of this key cytokine may contribute to homeostatic dysregulations that occur during spaceflight. This review details what is known about the role of this key cytokine in innate and adaptive immunity, hematopoiesis, and in bone, muscle and metabolic homeostasis on Earth and in the microgravity of space and suggests an experimental approach to confirm or disavow the role of IL-6 in space-related dysregulations.

Aerobic Training Efficacy in Inflammation, Neurotrophins, and Function in Chronic Stroke Persons: A Randomized Controlled Trial Protocol

BACKGROUND

Neuroinflammation is an important part of stroke pathophysiology and has both detrimental and beneficial effects after stroke. Besides that the enhancement of neurotrophins seems to be related to improvements in stroke recovery. Evidences suggest that exercise plays a role in modulating anti-inflammatory and neurotrophic effects. However, little is known about its impact in stroke survivors, mainly in chronic stroke. The purpose of this study is to investigate the efficacy of moderate-intensity treadmill exercise in changing inflammatory mediators, interleukin-6 (IL-6), soluble tumor necrosis factor receptors I and II (sTNFRI, sTNFRII), interleukin-10 (IL-10), and brain-derived neurotrophic factor (BDNF) levels in chronic stroke patients. The secondary objective is to investigate the effects of training in improve mobility and exercise capacity.

METHODS

This is a randomized controlled trial. Chronic stroke patients will be randomized to an experimental or control group, and will receive group interventions three times per week, over 12 weeks. The experimental group will receive moderate-intensity (60%-80% of maximum heart rate reserve) treadmill exercise. Control group will perform walking training on the ground (<40% of maximum heart rate reserve). Primary outcomes include IL-6, sTNFRI, sTNFRII, IL-10, and BDNF levels. Secondary outcomes include mobility and exercise capacity. Outcomes will be measured at baseline, postintervention, and at the 4-week follow-up.

DISCUSSION

The findings of this trial have the potential to provide important insights regarding the effects of an aerobic physical program in the inflammatory process and in the neuronal plasticity in stroke persons and its impact on mobility and exercise capacity.

Prepubertal skeletal muscle growth requires Pax7-expressing satellite cell-derived myonuclear contribution

The functional role of Pax7-expressing satellite cells (SCs) in postnatal skeletal muscle development beyond weaning remains obscure. Therefore, the relevance of SCs during prepubertal growth, a period after weaning but prior to the onset of puberty, has not been examined. Here, we have characterized mouse skeletal muscle growth during prepuberty and found significant increases in myofiber cross-sectional area that correlated with SC-derived myonuclear number. Remarkably, genome-wide RNA-sequencing analysis established that post-weaning juvenile and early adolescent skeletal muscle have markedly different gene expression signatures. These distinctions are consistent with extensive skeletal muscle maturation during this essential, albeit brief, developmental phase. Indelible labeling of SCs with Pax7^CreERT2/+; Rosa26^nTnG/+ mice demonstrated SC-derived myonuclear contribution during prepuberty, with a substantial reduction at puberty onset. Prepubertal depletion of SCs in Pax7^CreERT2/+; Rosa26^DTA/+ mice reduced myofiber size and myonuclear number, and caused force generation deficits to a similar extent in both fast and slow-contracting muscles. Collectively, these data demonstrate SC-derived myonuclear accretion as a cellular mechanism that contributes to prepubertal hypertrophic skeletal muscle growth.

Summary: Examination of gene expression and morphological changes in mouse skeletal muscle during prepuberty demonstrates that satellite cell-derived myonuclear accretion contributes to prepubertal hypertrophic skeletal muscle growth.

Inflammatory Markers in Anorexia Nervosa: An Exploratory Study

Inflammation has been suggested to play a pathophysiological role in anorexia nervosa (AN). In this exploratory cross-sectional study, we measured serum concentrations of 40 inflammatory markers (including cytokines, chemokines, and adhesion molecules) and brain-derived neurotrophic factor (BDNF) in people with AN (n = 27) and healthy controls (HCs) (n = 13). Many of these inflammatory markers had not been previously quantified in people with AN. Eating disorder (ED) and general psychopathology symptoms were assessed. Body mass index (BMI) and body composition data were obtained. Interleukin (IL)-6, IL-15, and vascular cell adhesion molecule (VCAM)-1 concentrations were significantly elevated and concentrations of BDNF, tumor necrosis factor (TNF)-β, and vascular endothelial growth factor (VEGF)-A were significantly lower in AN participants compared to HCs. Age, BMI, and percentage body fat mass were identified as potential confounding variables for several of these inflammatory markers. Of particular interest is that most of the quantified markers were unchanged in people with AN, despite them being severely underweight with evident body fat loss, and having clinically significant ED symptoms and severe depression and anxiety symptoms. Future research should examine the replicability of our findings and consider the effect of additional potential confounding variables, such as smoking and physical activity, on the relationship between AN and inflammation.

Myokines as Possible Therapeutic Targets in Cancer Cachexia

Cachexia is an extremely serious syndrome which occurs in most patients with different cancers, and it is characterized by systemic inflammation, a negative protein and energy balance, and involuntary loss of body mass. This syndrome has a dramatic impact on the patient's quality of life, and it is also associated with a low response to chemotherapy leading to a decrease in survival. Despite this, cachexia is still underestimated and often untreated. New research is needed in this area to understand this complex phenomenon and ultimately find treatment methods and therapeutic targets. The skeletal muscle can act as an endocrine organ. Signaling between muscles and other systems is done through myokines, cytokines, and proteins produced and released by myocytes. In this review, we would like to draw attention to some of the most important myokines that could have potential as biomarkers and therapeutic targets: myostatin, irisin, myonectin, decorin, fibroblast growth factor 21, interleukin-6, interleukin-8, and interleukin-15.

Dose of Early Therapeutic Mobility: Does Frequency or Intensity Matter?

OBJECTIVE

Investigate the feasibility of a nurse-led mobility protocol and compare the effects of once- versus twice-daily episodes of early therapeutic mobility (ETM) and low- versus moderate-intensity ETM on serum biomarkers of inflammation and selected outcomes in critically ill adults.

DESIGN

Randomized interventional study with repeated measures and blinded assessment of outcomes.

SETTING

Four adult intensive care units (ICUs) in two academic medical centers.

SUBJECTS

Fifty-four patients with > 48 hr of mechanical ventilation (MV).

INTERVENTION

Patients were assigned to once- or twice-daily ETM via sealed envelope randomization at enrollment. Intensity of (in-bed vs. out-of-bed) ETM was administered according to protocolized patient assessment.

MEASUREMENTS

Interleukins 6, 10, 8, 15, and tumor necrosis factor-α were collected from serum before and after ETM; change scores were used in the analyses. Manual muscle and handgrip strength, delirium onset, duration of MV, and ICU length of stay (LOS) were evaluated as patient outcomes.

MAIN RESULTS

Hypotheses regarding the inflammatory biomarkers were not supported based on confidence intervals. Twice-daily intervention was associated with reduced ICU LOS. Moderate-intensity (out-of-bed) ETM was associated with greater manual muscle test scores and handgrip strength and reduced occurrence of delirium.

CONCLUSION

Findings from this study suggest that nurses can provide twice-daily mobility interventions that include sitting on the edge of the bed once patients have a stable status without altering a pro-inflammatory serum biomarker profile.

Physical Exercise-Induced Myokines and Muscle-Adipose Tissue Crosstalk: A Review of Current Knowledge and the Implications for Health and Metabolic Diseases

Physical exercise has beneficial effects on metabolic diseases, and a combined therapeutic regimen of regular exercise and pharmaceutical treatment is often recommended for their clinical management. However, the mechanisms by which exercise produces these beneficial effects are not fully understood. Myokines, a group of skeletal muscle (SkM) derived peptides may play an important part in this process. Myokines are produced, expressed and released by muscle fibers under contraction and exert both local and pleiotropic effects. Myokines such as IL-6, IL-10, and IL-1ra released during physical exercise mediate its health benefits. Just as exercise seems to promote the myokine response, physical inactivity seems to impair it, and could be a mechanism to explain the association between sedentary behavior and many chronic diseases. Myokines help configure the immune-metabolic factor interface and the health promoting effects of physical exercise through the release of humoral factors capable of interacting with other tissues, mainly adipose tissue (AT). AT itself secretes proinflammatory cytokines (adipokines) as a result of physical inactivity and it is well recognized that AT inflammation can lead to the development of metabolic diseases, such as type 2 diabetes mellitus (T2DM) and atherosclerosis. On the other hand, the browning phenotype of AT has been suggested to be one of the mechanisms through which physical exercise improves body composition in overweight/obese individuals. Although, many cytokines are involved in the crosstalk between SkM and AT, in respect of these effects, it is IL-6, IL-15, irisin, and myostatin which seem to have the decisive role in this “conversation” between AT and SkM. This review article proposes to bring together the latest “state of the art” knowledge regarding Myokines and muscle-adipose tissue crosstalk. Furthermore, it is intended to particularly focus on the immune-metabolic changes from AT directly mediated by myokines.

Skeletal muscle secretion of IL-6 is muscle type specific: Ex vivo evidence

Emerging evidence indicates that skeletal muscle possesses endocrine function to secret myokines. Interleukin 6 (IL-6) is a well-characterized myokine that is involved in regulation of metabolism and muscle function. Metabolism type and contractile dynamics vary in different muscle types. It is not clear, however, if IL-6 secretion differs in different muscle types. In this study, we first established an ex vivo approach to test the inducible muscle secretion. Freshly isolated muscles were incubated in Krebs solution at 37 °C with oxygen supply. Secreted IL-6 in the incubation media was measure using Western blot and ELISA assay. We first confirmed that the IL-6 release was inducible by treating the incubated muscle with a cytokine stimulant. We demonstrated that physiological temperature (37 °C) and O₂ supply were essential for the induction of IL-6 release from the incubated muscle, suggesting it is a controlled secretion rather than a spontaneous leak. Using this approach, we found that IL-6 release was only inducible from soleus muscle but not EDL muscle. We further showed that IL-6 protein level was higher in slow oxidative muscle fibers. Moreover, we showed that EDL, although lacks of IL-6 release, surely has inducible secretory function that had different secretory pattern from soleus.

Myokines, physical activity, insulin resistance and autoimmune diseases

Myokines are peptides produced and released by myocytes of muscle fibers that influence physiology of muscle and other organs and tissues. They are involved in mediating the beneficial effects that exercise has on health. More than one hundred have been identified and among them are IL6, myostatin, irisin, mionectin and decorin. Physical inactivity leads to an altered response of the secretion of myokines and resistance to them; this leads to a pro-inflammatory state that favors sarcopenia and fat accumulation, promoting the development of cardiovascular diseases, insulin resistance, and diabetes mellitus type 2. Some myokines, including irisin, are responsible for the improvement that exercise produces in many chronic diseases such as type 2 diabetes and cardiovascular diseases, some types of cancer and many autoimmune diseases such as idiopathic inflammatory myopathy, rheumatoid arthritis, systemic lupus erythematosus and inflammatory bowel disease.

Lactate administration activates the ERK1/2, mTORC1, and AMPK pathways differentially according to skeletal muscle type in mouse

Skeletal muscle is described as an endocrine organ, constitutively or intermittently secreting bioactive molecules. The signaling pathways by which these molecules mediate changes in skeletal muscle and regulate interorgan crosstalk are only partly understood. Lactate is widely described as a signaling molecule in different cells, but the role of lactate as a signaling molecule in mature skeletal muscle has not been fully unveiled. The aim of this study was to determine the role of lactate on activation of signaling pathways in adult mouse skeletal muscle. Male mice were injected intraperitoneally with lactate or saline, and tissues were dissected after 40 min. Phosphorylation levels of relevant proteins in muscle were assessed by Western blotting. After lactate administration, we found an increase in p-ERK1/2Thr202/Tyr204 (3.5-fold; P = 0.004) and p-p70S6KThr389 (1.9-fold; P = 0.01) in quadriceps; and an increase in p-rpS6Ser235/236 in both quadriceps (6.3-fold; P = 0.01) and EDL (2.3-fold; P = 0.01), without changes in soleus. There was a tendency toward an increase in p-AMPKThr172 (1.7-fold; P = 0.08), with a significant increase in p-ACCSer79 (1.5-fold; P = 0.04) in soleus, without changes in quadriceps and EDL. These results support the hypothesis that lactate plays a role in the molecular signaling related to hypertrophy and to oxidative metabolism on adult skeletal muscle and suggest that this activation depends on the skeletal muscle type. The mechanisms that underlie the effect of lactate in mature skeletal muscles remain to be established.

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.

High levels of cerebrospinal fluid chemokines point to the presence of neuroinflammation in peripheral neuropathic pain: a cross-sectional study of 2 cohorts of patients compared with healthy controls

According to animal models, neuroinflammation is a major feature of neuropathic pain. The present findings confirm that this hypothesis is of relevance to humans.

Animal models suggest that chemokines are important mediators in the pathophysiology of neuropathic pain. Indeed, these substances have been called “gliotransmitters,” a term that illustrates the close interplay between glial cells and neurons in the context of neuroinflammation and pain. However, evidence in humans is scarce. The aim of the study was to determine a comprehensive cerebrospinal fluid (CSF) inflammatory profile of patients with neuropathic pain. Our hypothesis was that we would thereby find indications of a postulated on-going process of central neuroinflammation. Samples of CSF were collected from 2 cohorts of patients with neuropathic pain (n = 11 and n = 16, respectively) and healthy control subjects (n = 11). The samples were analyzed with a multiplex proximity extension assay in which 92 inflammation-related proteins were measured simultaneously (Proseek Multiplex Inflammation I; Olink Bioscience, Uppsala, Sweden). Univariate testing with control of false discovery rate, as well as orthogonal partial least squares discriminant analysis, were used for statistical analyses. Levels of chemokines CXCL6, CXCL10, CCL8, CCL11, CCL23 in CSF, as well as protein LAPTGF-beta-1, were significantly higher in both neuropathic pain cohorts compared with healthy controls, pointing to neuroinflammation in patients. These 6 proteins were also major results in a recent similar study in patients with fibromyalgia. The findings need to be confirmed in larger cohorts, and the question of causality remains to be settled. Because it has been suggested that prevalent comorbidities to chronic pain (eg, depression, anxiety, poor sleep, and tiredness) also are associated with neuroinflammation, it will be important to determine whether neuroinflammation is a common mediator.

Impact of muscle atrophy on bone metabolism and bone strength: implications for muscle-bone crosstalk with aging and disuse

Bone fractures in older adults are often preceded by a loss of muscle mass and strength. Likewise, bone loss with prolonged bed rest, spinal cord injury, or with exposure to microgravity is also preceded by a rapid loss of muscle mass. Recent studies using animal models in the setting of hindlimb unloading or botulinum toxin (Botox) injection also reveal that muscle loss can induce bone loss. Moreover, muscle-derived factors such as irisin and leptin can inhibit bone loss with unloading, and knockout of catabolic factors in muscle such as the ubiquitin ligase Murf1 or the myokine myostatin can reduce osteoclastogenesis. These findings suggest that therapies targeting muscle in the setting of disuse atrophy may potentially attenuate bone loss, primarily by reducing bone resorption. These potential therapies not only include pharmacological approaches but also interventions such as whole-body vibration coupled with resistance exercise and functional electric stimulation of muscle.

Bojungikgi-tang Improves Muscle and Spinal Cord Function in an Amyotrophic Lateral Sclerosis Model

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease characterized by progressive motor function impairment, dysphagia, and respiratory failure. Owing to the complexity of its pathogenic mechanisms, an effective therapy for ALS is lacking. Herbal medicines with multiple targets have good efficacy and low adverse reactions for the treatment of neurodegenerative diseases. In this study, the effects of Bojungikgi-tang (BJIGT), an herbal medicine with eight component herbs, on muscle and spinal cord function were evaluated in an ALS animal model. Animals were randomly divided into three groups: a non-transgenic group (nTg, n = 24), a hSOD1^G93A transgenic group (Tg, n = 24), and a hSOD1^G93A transgenic group in which 8-week-old mice were orally administered BJIGT (1 mg/g) once daily for 6 weeks (Tg+BJIGT, n = 24). The effects of BJIGT were evaluated using a rotarod test, foot-printing, and survival analyses based on Kaplan-Meier survival curves. To determine the biological mechanism underlying the effects of BJIGT in hSOD1^G93A mice, western blotting, transmission electron microscopy, and Bungarotoxin staining were used. BJIGT improved motor function and extended the survival duration of hSOD1^G93A mice. In addition, BJIGT had protective effects, including anti-oxidative and anti-inflammatory effects, in both the spinal cord and muscle of hSOD1^G93A mice. Our results demonstrated that BJIGT causes muscle atrophy and the denervation of neuromuscular junctions in the gastrocnemius of hSOD1^G93A mice. The components of BJIGT may alleviate the symptoms of ALS via different mechanisms, and accordingly, BJIGT treatment may be an effective therapeutic approach.

Irisin protects mitochondria function during pulmonary ischemia/reperfusion injury

Limb remote ischemic preconditioning (RIPC) is an effective means of protection against ischemia/reperfusion (IR)-induced injury to multiple organs. Many studies are focused on identifying endocrine mechanisms that underlie the cross-talk between muscle and RIPC-mediated organ protection. We report that RIPC releases irisin, a myokine derived from the extracellular portion of fibronectin domain-containing 5 protein (FNDC5) in skeletal muscle, to protect against injury to the lung. Human patients with neonatal respiratory distress syndrome show reduced concentrations of irisin in the serum and increased irisin concentrations in the bronchoalveolar lavage fluid, suggesting transfer of irisin from circulation to the lung under physiologic stress. In mice, application of brief periods of ischemia preconditioning stimulates release of irisin into circulation and transfer of irisin to the lung subjected to IR injury. Irisin, via lipid raft-mediated endocytosis, enters alveolar cells and targets mitochondria. Interaction between irisin and mitochondrial uncoupling protein 2 (UCP2) allows for prevention of IR-induced oxidative stress and preservation of mitochondrial function. Animal model studies show that intravenous administration of exogenous irisin protects against IR-induced injury to the lung via improvement of mitochondrial function, whereas in UCP2-deficient mice or in the presence of a UCP2 inhibitor, the protective effect of irisin is compromised. These results demonstrate that irisin is a myokine that facilitates RIPC-mediated lung protection. Targeting the action of irisin in mitochondria presents a potential therapeutic intervention for pulmonary IR injury.

Reduction of Movement in Neurological Diseases: Effects on Neural Stem Cells Characteristics

Both astronauts and patients affected by chronic movement-limiting pathologies face impairment in muscle and/or brain performance. Increased patient survival expectations and the expected longer stays in space by astronauts may result in prolonged motor deprivation and consequent pathological effects. Severe movement limitation can influence not only the motor and metabolic systems but also the nervous system, altering neurogenesis and the interaction between motoneurons and muscle cells. Little information is yet available about the effect of prolonged muscle disuse on neural stem cells characteristics. Our in vitro study aims to fill this gap by focusing on the biological and molecular properties of neural stem cells (NSCs). Our analysis shows that NSCs derived from the SVZ of HU mice had shown a reduced proliferation capability and an altered cell cycle. Furthermore, NSCs obtained from HU animals present an incomplete differentiation/maturation. The overall results support the existence of a link between reduction of exercise and muscle disuse and metabolism in the brain and thus represent valuable new information that could clarify how circumstances such as the absence of load and the lack of movement that occurs in people with some neurological diseases, may affect the properties of NSCs and contribute to the negative manifestations of these conditions.

Systemic inflammation as a predictor of brain aging: Contributions of physical activity, metabolic risk, and genetic risk

Inflammatory processes may contribute to risk for Alzheimer's disease (AD) and age-related brain degeneration. Metabolic and genetic risk factors, and physical activity may, in turn, influence these inflammatory processes. Some of these risk factors are modifiable, and interact with each other. Understanding how these processes together relate to brain aging will help to inform future interventions to treat or prevent cognitive decline. We used brain magnetic resonance imaging (MRI) to scan 335 older adult humans (mean age 77.3 ± 3.4 years) who remained non-demented for the duration of the 9-year longitudinal study. We used structural equation modeling (SEM) in a subset of 226 adults to evaluate whether measures of baseline peripheral inflammation (serum C-reactive protein levels; CRP), mediated the baseline contributions of genetic and metabolic risk, and physical activity, to regional cortical thickness in AD-relevant brain regions at study year 9. We found that both baseline metabolic risk and AD risk variant apolipoprotein E ε4 (APOE4), modulated baseline serum CRP. Higher baseline CRP levels, in turn, predicted thinner regional cortex at year 9, and mediated an effect between higher metabolic risk and thinner cortex in those regions. A higher polygenic risk score composed of variants in immune-associated AD risk genes (other than APOE) was associated with thinner regional cortex. However, CRP levels did not mediate this effect, suggesting that other mechanisms may be responsible for the elevated AD risk. We found interactions between genetic and environmental factors and structural brain health. Our findings support the role of metabolic risk and peripheral inflammation in age-related brain decline.

Oxidative stress: role of physical exercise and antioxidant nutraceuticals in adulthood and aging

Physical exercise is considered to be one of the beneficial factors of a proper lifestyle and is nowadays seen as an indispensable element for good health, able to lower the risk of disorders of the cardiovascular, endocrine and osteomuscular apparatus, immune system diseases and the onset of potential neoplasms. A moderate and programmed physical exercise has often been reported to be therapeutic both in the adulthood and in aging, since capable to promote fitness. Regular exercise alleviates the negative effects caused by free radicals and offers many health benefits, including reduced risk of all-cause mortality, sarcopenia in the skeletal muscle, chronic disease, and premature death in elderly people. However, physical performance is also known to induce oxidative stress, inflammation, and muscle fatigue. Many efforts have been carried out to identify micronutrients and natural compounds, also known as nutraceuticals, able to prevent or attenuate the exercise-induced oxidative stress and inflammation. The aim of this review is to discuss the benefits deriving from a constant physical activity and by the intake of antioxidant compounds to protect the body from oxidative stress. The attention will be focused mainly on three natural antioxidants, which are quercetin, resveratrol and curcumin. Their properties and activity will be described, as well as their benefits on physical activity and on aging, which is expected to increase through the years and can get favorable benefits from a constant exercise activity.

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

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