Chemerin-induced mitochondrial dysfunction in skeletal muscle

Chemerin regulates glucose and lipid metabolism by changing mitochondrial structure and function associated with androgen/androgen receptor

The adipokine chemerin contributes to exercise-induced improvements in glucose and lipid metabolism; however, the underlying mechanism remains unclear. We aimed to confirm the impact of reduced chemerin expression on exercise-induced improvement in glycolipid metabolism in male diabetic (DM) mice through exogenous chemerin administration. Furthermore, the underlying mechanism of chemerin involved in changes in muscle mitochondria function mediated by androgen/androgen receptor (AR) was explored by generating adipose-specific and global chemerin knockout (adipo-chemerin-/- and chemerin-/-) mice. DM mice were categorized into the DM, exercised DM (EDM), and EDM + chemerin supplementation groups. Adipo-chemerin-/- and chemerin-/- mice were classified in the sedentary or exercised groups and fed either a normal or high-fat diet. Exercise mice underwent a 6-wk aerobic exercise regimen. The serum testosterone and chemerin levels, glycolipid metabolism indices, mitochondrial function, and protein levels involved in mitochondrial biogenesis and dynamics were measured. Notably, exogenous chemerin reversed exercise-induced improvements in glycolipid metabolism, AR protein levels, mitochondrial biogenesis, and mitochondrial fusion in DM mice. Moreover, adipose-specific chemerin knockout improved glycolipid metabolism, enhanced exercise-induced increases in testosterone and AR levels in exercised mice, and alleviated the detrimental effects of a high-fat diet on mitochondrial morphology, biogenesis, and dynamics. Finally, similar improvements in glucose metabolism (but not lipid metabolism), mitochondrial function, and mitochondrial dynamics were observed in chemerin-/- mice. In conclusion, decreased chemerin levels affect exercise-induced improvements in glycolipid metabolism in male mice by increasing mitochondrial number and function, likely through changes in androgen/AR signaling.NEW & NOTEWORTHY Decreased chemerin levels affect exercise-induced improvements in glycolipid metabolism in male mice by increasing mitochondrial number and function, which is likely mediated by androgen/androgen receptor expression. This study is the first to report the regulatory mechanism of chemerin in muscle mitochondria.

Interaction between Selected Adipokines and Musculoskeletal and Cardiovascular Systems: A Review of Current Knowledge

Adipokines are substances secreted by adipose tissue that are receiving increasing attention. The approach to adipose tissue has changed in recent years, and it is no longer looked at as just a storage organ but its secretion and how it influences systems in the human body are also looked at. The role of adipokine seems crucial in developing future therapies for pathologies of selected systems. In this study, we look at selected adipokines, leptin, adiponectin, chemerin, resistin, omentin-1, nesfatin, irisin-1, visfatin, apelin, vaspin, heparin-binding EGF-like growth factor (HB-EGF), and TGF-β2, and how they affect systems in the human body related to physical activity such as the musculoskeletal and cardiovascular systems.

Research progress of intramuscular fat formation based on co-culture

Intramuscular fat (IMF) is closely related to the meat quality of livestock and poultry. As a new cell culture technique in vitro, cell co-culture has been gradually applied to the related research of IMF formation because it can simulate the changes of microenvironment in vivo during the process of IMF cell formation. In the co-culture model, in addition to studying the effects of skeletal muscle cells on the proliferation and differentiation of IMF, we can also consider the role of many secretion factors in the formation of IMF, thus making the cell research in vitro closer to the real level in vivo. This paper reviewed the generation and origin of IMF, summarized the existing co-culture methods and systems, and discussed the advantages and disadvantages of each method as well as the challenges faced in the establishment of the system, with emphasis on the current status of research on the formation of IMF for human and animal based on co-culture technology.

Understanding the Consequences of Fatty Bone and Fatty Muscle: How the Osteosarcopenic Adiposity Phenotype Uncovers the Deterioration of Body Composition

Adiposity is central to aging and several chronic diseases. Adiposity encompasses not just the excess adipose tissue but also body fat redistribution, fat infiltration, hypertrophy of adipocytes, and the shifting of mesenchymal stem cell commitment to adipogenesis. Bone marrow adipose tissue expansion, inflammatory adipokines, and adipocyte-derived extracellular vesicles are central to the development of osteopenic adiposity. Adipose tissue infiltration and local adipogenesis within the muscle are critical in developing sarcopenic adiposity and subsequent poorer functional outcomes. Ultimately, osteosarcopenic adiposity syndrome is the result of all the processes noted above: fat infiltration and adipocyte expansion and redistribution within the bone, muscle, and adipose tissues, resulting in bone loss, muscle mass/strength loss, deteriorated adipose tissue, and subsequent functional decline. Increased fat tissue, typically referred to as obesity and expressed by body mass index (the latter often used inadequately), is now occurring in younger age groups, suggesting people will live longer with the negative effects of adiposity. This review discusses the role of adiposity in the deterioration of bone and muscle, as well as adipose tissue itself. It reveals how considering and including adiposity in the definition and diagnosis of osteopenic adiposity, sarcopenic adiposity, and osteosarcopenic adiposity will help in better understanding the pathophysiology of each and accelerate possible therapies and prevention approaches for both relatively healthy individuals or those with chronic disease.

Cytokines and exosomal miRNAs in skeletal muscle-adipose crosstalk

Skeletal muscle and adipose tissues (ATs) are secretory organs that release secretory factors including cytokines and exosomes. These factors mediate muscle-adipose crosstalk to regulate systemic metabolism via paracrine and endocrine pathways. Myokines and adipokines are cytokines secreted by skeletal muscle and ATs, respectively. Exosomes loaded with nucleic acids, proteins, lipid droplets, and organelles can fuse with the cytoplasm of target cells to perform regulatory functions. A major regulatory component of exosomes is miRNA. In addition, numerous novel myokines and adipokines have been identified through technological innovations. These discoveries have identified new biomarkers and sparked new insights into the molecular regulation of skeletal muscle growth and adipose deposition. The knowledge may contribute to potential diagnostic and therapeutic targets in metabolic disease.

Chemokine-like receptor 1 plays a critical role in modulating the regenerative and contractile properties of muscle tissue

Musculoskeletal diseases are a leading contributor to mobility disability worldwide. Since the majority of patients with musculoskeletal diseases present with associated muscle weakness, treatment approaches typically comprise an element of resistance training to restore physical strength. The health-promoting effects of resistance exercise are mediated via complex, multifarious mechanisms including modulation of systemic and local inflammation. Here we investigated whether targeted inhibition of the chemerin pathway, which largely controls inflammatory processes via chemokine-like receptor 1 (CMKLR1), can improve skeletal muscle function. Using genetically modified mice, we demonstrate that blockade of CMKLR1 transiently increases maximal strength during growth, but lastingly decreases strength endurance. In-depth analyses of the underlying long-term adaptations revealed microscopic alterations in the number of Pax7-positive satellite cells, as well as molecular changes in genes governing myogenesis and calcium handling. Taken together, these data provide evidence of a critical role for CMKLR1 in regulating skeletal muscle function by modulating the regenerative and contractile properties of muscle tissue. CMKLR1 antagonists are increasingly viewed as therapeutic modalities for a variety of diseases (e.g., psoriasis, metabolic disorders, and multiple sclerosis). Our findings thus have implications for the development of novel drug substances that aim at targeting the chemerin pathway for musculoskeletal or other diseases.

Chemerin Overexpression in the Liver Protects against Inflammation in Experimental Non-Alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH) is marked by macrophage infiltration and inflammation. Chemerin is a chemoattractant protein and is abundant in hepatocytes. The aim of this study was to gain insight into the role of hepatocyte-produced prochemerin in NASH. Therefore, mice were infected with adeno-associated virus 8 to direct hepatic overexpression of prochemerin in a methionine–choline deficient dietary model of NASH. At the end of the study, hepatic and serum chemerin were higher in the chemerin-expressing mice. These animals had less hepatic oxidative stress, F4/80 and CC-chemokine ligand 2 (CCL2) protein, and mRNA levels of inflammatory genes than the respective control animals. In order to identify the underlying mechanisms, prochemerin was expressed in hepatocytes and the hepatic stellate cells, LX-2. Here, chemerin had no effect on cell viability, production of inflammatory, or pro-fibrotic factors. Notably, cultivation of human peripheral blood mononuclear cells (PBMCs) in the supernatant of Huh7 cells overexpressing chemerin reduced CCL2, interleukin-6, and osteopontin levels in cell media. CCL2 was also low in RAW264.7 cells exposed to Hepa1–6 cell produced chemerin. In summary, the current study showed that prochemerin overexpression had little effect on hepatocytes and hepatic stellate cells. Of note, hepatocyte-produced chemerin deactivated PBMCs and protected against inflammation in experimental NASH.

Redox Signaling and Sarcopenia: Searching for the Primary Suspect

Sarcopenia, the age-related decline in muscle mass and function, derives from multiple etiological mechanisms. Accumulative research suggests that reactive oxygen species (ROS) generation plays a critical role in the development of this pathophysiological disorder. In this communication, we review the various signaling pathways that control muscle metabolic and functional integrity such as protein turnover, cell death and regeneration, inflammation, organismic damage, and metabolic functions. Although no single pathway can be identified as the most crucial factor that causes sarcopenia, age-associated dysregulation of redox signaling appears to underlie many deteriorations at physiological, subcellular, and molecular levels. Furthermore, discord of mitochondrial homeostasis with aging affects most observed problems and requires our attention. The search for the primary suspect of the fundamental mechanism for sarcopenia will likely take more intense research for the secret of this health hazard to the elderly to be unlocked.

Sirtuin 3 deficiency accelerates Angiotensin II-induced skeletal muscle atrophy

Background: It has been reported that Angiotensin II (Ang II) induced skeletal muscle atrophy. However, the precise mechanisms remain elusive. Sirtuin 3 (SIRT3), an NAD-dependent deacetylase, plays a central role in maintaining cellular metabolic homeostasis. This work aims to determine the role of SIRT3-mediated cellular metabolism in skeletal muscle wasting. Methods and Results: Eight-week-old male wild-type (WT) and SIRT3 knockout (SIRT3 KO) mice were infused with Ang II or saline for 4 weeks. Ang II induces skeletal muscle atrophy by inducing expression of the muscle-enriched E3 ubiquitin ligase muscle RING-finger-1 (MuRF1) and atrogin-1, accompanied by a reduction in SIRT3 in skeletal muscle. SIRT3 deficiency accelerated Ang II-induced loss of lean mass and protein hyper-acetylation, while the activities of mitochondrial oxidative enzymes, such as complex I and complex V, were significantly decreased. Furthermore, SIRT3 deficiency accelerated the Ang II-induced shift from slow-twitch towards fast-twitch fibres. Similarly, the three major rate-limiting enzymes in the glycolytic pathway, hexokinase 2 (HK2), phosphofructokinase-1(PFK) and pyruvate kinase (PK), were upregulated in Ang II-treated SIRT3 KO mice. Conclusion: These studies indicate that SIRT3 deficiency augmented Ang II-induced fibre-type shifting and metabolic reprogramming.

Mitochondrial destiny in type 2 diabetes: the effects of oxidative stress on the dynamics and biogenesis of mitochondria

Background

One reason for the development of insulin resistance is the chronic inflammation in obesity.

Materials & Methods

Scientific articles in the field of knowledge on the involvement of mitochondria and mitochondrial DNA (mtDNA) in obesity and type 2 diabetes were analyzed.

Results

Oxidative stress developed during obesity contributes to the formation of peroxynitrite, which causes cytochrome C-related damage in the mitochondrial electron transfer chain and increases the production of reactive oxygen species (ROS), which is associated with the development of type 2 diabetes. Oxidative stress contributes to the nuclease activity of the mitochondrial matrix, which leads to the accumulation of cleaved fragments and an increase in heteroplasmy. Mitochondrial dysfunction and mtDNA variations during insulin resistance may be connected with a change in ATP levels, generation of ROS, mitochondrial division/fusion and mitophagy. This review discusses the main role of mitochondria in the development of insulin resistance, which leads to pathological processes in insulin-dependent tissues, and considers potential therapeutic directions based on the modulation of mitochondrial biogenesis. In this regard, the development of drugs aimed at the regulation of these processes is gaining attention.

Conclusion

Changes in the mtDNA copy number can help to protect mitochondria from severe damage during conditions of increased oxidative stress. Mitochondrial proteome studies are conducted to search for potential therapeutic targets. The use of mitochondrial peptides encoded by mtDNA also represents a promising new approach to therapy.

Induction of Chemerin on Autophagy and Apoptosis in Dairy Cow Mammary Epithelial Cells

Involution of the mammary gland is a complex process controlled by various endocrine hormones and cytokine. As a novel adipocytokine, Chemerin not only plays a pivotal role in physiological and pathological processes such as immune response and lipid metabolism, but is also involved in the regulation of programmed cell death, including autophagy and apoptosis. The purpose of the present study was to elucidate whether autophagy and apoptosis of bovine mammary epithelial cells (BMECs) was triggered by Chemerin. BMECs were cultured and treated with Chemerin in vitro. The expression of autophagosome-forming marker, microtubule-associated protein 1 light chain 3 II (LC3-II) and sequestosome-1 (SQSTM 1, best known as p62), a substrate of autophagosome degradation were detected. The result showed that Chemerin significantly decreased the expression of p62 and markedly induced the conversion of LC3-I to LC3-II. The ratio of Bcl2-associated X and B-cell lymphoma-2 (Bax/Bcl-2) and the activity of caspase-3 were up-regulated after being treated by Chemerin, and the apoptotic rate was also significantly increased. These results suggested that Chemerin promoted the occurrence of autophagy and apoptosis in BMECs. Chloroquine (CQ), which is an inhibitor of autophagy. To explore effects of Chemerin on apoptosis, we prevented Chemerin-induced autophagy by pre-adding CQ in BMECs. Interestingly, this part of the experiment helped us find that all effects of Chemerin on apoptosis of BMECs could be enhanced with the inhibition of autophagy. Our study demonstrates that Chemerin-induced autophagy and apoptosis are mutually regulated in BMECs, but the specific mechanism remains to be further researched.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

Interrelation of chemerin and TNF-α with mtDNA copy number in adipose tissues and blood cells in obese patients with and without type 2 diabetes

BACKGROUND

Inflammatory response plays a key role in the development of insulin resistance (IR) in obesity. Oxidative stress triggers the replication of the mitochondrial genome and division of the organelle. The purpose of this study was to identify the relationship of chemerin and TNF-α with mitochondrial DNA (mtDNA) copy number in subcutaneous adipose tissue (SAT) and visceral adipose tissue (mesentery of the small intestine (Mes), greater omentum (GO) and blood mononuclear cells (MNCs)) in patients with obesity with/without type 2 diabetes mellitus (T2DM).

METHODS

The study included 142 obese patients and 34 healthy donors. The samples used for the study were peripheral venous blood (MNCs) and ATs (SAT, Mes and GO). The measurement of mtDNA copy number was done by droplet digital PCR. Quantitative determination of insulin, adiponectin, TNF-α and chemerin in serum/plasma was performed by flow-through fluorometry and commercial ELISA kit. Statistical analysis and graphs were obtained in R Statistical Software (version 3.3.1).

RESULTS

The increase in body mass index (BMI) was accompanied by an increase in TNF-α production, an increase in mtDNA copy number in SAT and a decrease in mtDNA copy number in MNCs. The negative association between plasma chemerin and mtDNA copy number in the Mes, as well as between mtDNA copy number and chemerin expression in the Mes, in the group with BMI > 40 kg/m2 without T2DM demonstrates the protective effect of chemerin against the development of IR via the regulation of mtDNA copy number in adipose tissues.

CONCLUSIONS

We thus speculated the existence of a compensatory mechanism in which leads to the increased number of mtDNA copies under the influence of proinflammatory factors. Based on the obtained data, we propose that reducing mtDNA copy number in cases of morbid obesity without T2DM has a positive effect on carbohydrate metabolism, which may help maintain glucose levels within reference values. Obesity, type 2 diabetes, mtDNA, cytokines, TNF-a, chemerin.

Molecular mechanisms underlying metabolic syndrome: the expanding role of the adipocyte

The metabolic syndrome (MetS) is defined as a cluster of 3 or more metabolic and cardiovascular risk factors and represents a serious problem for public health. Altered function of adipose tissue has a significant impact on whole-body metabolism and represents a key driver for the development of these metabolic derangements, collectively referred as to MetS. In particular, increased visceral and ectopic fat deposition play a major role in the development of insulin resistance and MetS. A large body of evidence demonstrates that aging and MetS share several metabolic alterations. Of importance, molecular pathways that regulate lifespan affect key processes of adipose tissue physiology, and transgenic mouse models with adipose-specific alterations in these pathways show derangements of adipose tissue and other metabolic features of MetS, which highlights a causal link between dysfunctional adipose tissue and deleterious effects on whole-body homeostasis. This review analyzes adipose tissue-specific dysfunctions, including metabolic alterations that are related to aging, that have a significant impact on the development of MetS.-Armani, A., Berry, A., Cirulli, F., Caprio, M. Molecular mechanisms underlying metabolic syndrome: the expanding role of the adipocyte.

Sarcopenic obesity or obese sarcopenia: A cross talk between age-associated adipose tissue and skeletal muscle inflammation as a main mechanism of the pathogenesis

Sarcopenia, an age-associated decline in skeletal muscle mass coupled with functional deterioration, may be exacerbated by obesity leading to higher disability, frailty, morbidity and mortality rates. In the combination of sarcopenia and obesity, the state called sarcopenic obesity (SOB), some key age- and obesity-mediated factors and pathways may aggravate sarcopenia. This review will analyze the mechanisms underlying the pathogenesis of SOB. In obese adipose tissue (AT), adipocytes undergo hypertrophy, hyperplasia and activation resulted in accumulation of pro-inflammatory macrophages and other immune cells as well as dysregulated production of various adipokines that together with senescent cells and the immune cell-released cytokines and chemokines create a local pro-inflammatory status. In addition, obese AT is characterized by excessive production and disturbed capacity to store lipids, which accumulate ectopically in skeletal muscle. These intramuscular lipids and their derivatives induce mitochondrial dysfunction characterized by impaired β-oxidation capacity and increased reactive oxygen species formation providing lipotoxic environment and insulin resistance as well as enhanced secretion of some pro-inflammatory myokines capable of inducing muscle dysfunction by auto/paracrine manner. In turn, by endocrine manner, these myokines may exacerbate AT inflammation and also support chronic low grade systemic inflammation (inflammaging), overall establishing a detrimental vicious circle maintaining AT and skeletal muscle inflammation, thus triggering and supporting SOB development. Under these circumstances, we believe that AT inflammation dominates over skeletal muscle inflammation. Thus, in essence, it redirects the vector of processes from "sarcopenia→obesity" to "obesity→sarcopenia". We therefore propose that this condition be defined as "obese sarcopenia", to reflect the direction of the pathological pathway.

ALDH2 restores exhaustive exercise-induced mitochondrial dysfunction in skeletal muscle

BACKGROUND

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is highly expressed in heart and skeletal muscles, and is the major enzyme that metabolizes acetaldehyde and toxic aldehydes. The cardioprotective effects of ALDH2 during cardiac ischemia/reperfusion injury have been recognized. However, less is known about the function of ALDH2 in skeletal muscle. This study was designed to evaluate the effect of ALDH2 on exhaustive exercise-induced skeletal muscle injury.

METHODS

We created transgenic mice expressing ALDH2 in skeletal muscles. Male wild-type C57/BL6 (WT) and ALDH2 transgenic mice (ALDH2-Tg), 8-weeks old, were challenged with exhaustive exercise for 1 week to induce skeletal muscle injury. Animals were sacrificed 24 h post-exercise and muscle tissue was excised.

RESULTS

ALDH2-Tg mice displayed significantly increased treadmill exercise capacity compared to WT mice. Exhaustive exercise caused an increase in mRNA levels of the muscle atrophy markers, Atrogin-1 and MuRF1, and reduced mitochondrial biogenesis and fusion in WT skeletal muscles; these effects were attenuated in ALDH2-Tg mice. Exhaustive exercise also enhanced mitochondrial autophagy pathway activity, including increased conversion of LC3-I to LC3-II and greater expression of Beclin1 and Bnip3; the effects of which were mitigated by ALDH2 overexpression. In addition, ALDH2-Tg reversed the increase of an oxidative stress biomarker (4-hydroxynonenal) and decreased levels of mitochondrial antioxidant proteins, including manganese superoxide dismutase and NAD(P)H:quinone oxidoreductase 1, in skeletal muscle induced by exhaustive exercise.

CONCLUSION

ALDH2 may reverse skeletal muscle mitochondrial dysfunction due to exhaustive exercise by regulating mitochondria dynamic remodeling and enhancing the quality of mitochondria.

The chemerin production changes in obese patients with different carbohydrate metabolism state

Chemerin is a mediator of adipose tissue involved in the regulation of many processes, including lipogenesis, and inflammatory response. The role of chemerin in the development of insulin resistance has been insufficiently studied and needs detailed understanding. The aim of the study was to investigate chemerin production in obese patients with different states of carbohydrate metabolism. The study included 155 patients with a diagnosis of obesity; 34 patients with overweight. The control group 1 consisted of 43 conditionally healthy donors who did not have obesity. For comparison of the results of a study to determine the levels of tissue-specific mRNA expression of the genes IL-6, TNF-a, RARRES2, (encoding IL-6, TNF-a and chemerin) in adipose tissue introduced a control group 2 – 30 patients without obesity. Study on the relative level of mRNA expression of the genes IL-6, TNF-a and RARRES2 (encoding IL-6, TNF-a and chemerin) was carried out using real time PCR. Concentrations of IL-6, TNF-a, and chemerin were measured in serum/plasma using an enzyme-linked immunosorbent assay (ELISA). We found significant differences in the plasma level of chemerin and tissue-specific features of RARRES2 gene expression in obese patients, depending on the degree of obesity and the state of carbohydrate metabolism. Multidirectional associations of RARRES2 gene expression with TNF-a and IL-6 genes in adipose tissues of different localization are shown: in obese patients (BMI £40 kg/m2) without type 2 diabetes – negative, and type 2 diabetes – positive. Identified relationship chemerin plasma content and the expression level of its gene in biopsies with various parameters of carbohydrate and lipid metabolism, proinflammatory molecules indicate chemerin involved in metabolic and immune processes in obesity.

Transcriptome analysis of follicles reveals the importance of autophagy and hormones in regulating broodiness of Zhedong white goose

Broodiness, a maternal behavior and instinct for natural breeding in poultry, inhibits egg production and affects the poultry industry. Phenotypic and physiological factors influencing broodiness in poultry have been extensively studied, but the molecular regulation mechanism of broodiness remains unclear. Effective research strategies focusing on broodiness are hindered by limited understanding of goose developmental biology. Here we established the transcriptomes of goose follicles at egg-laying and broody stages by Illumina HiSeq platform and compared the sequenced transcriptomes of three types of follicles (small white, large white and small yellow). It was found that there were 92 up-regulated and 84 down-regulated transcription factors and 101 up-regulated and 51 down-regulated hormone-related genes. Many of these genes code for proteins involved in hormone response, follicular development, autophagy, and oxidation. Moreover, the contents of progesterone and estradiol in follicles were altered, and the autophagy levels of follicles were enhanced during the broody stage. These results suggest that hormone- and autophagy-signaling pathways are critical for controlling broodiness in the goose. We demonstrated that transcriptome analysis of egg-laying and broody Zhedong white goose follicles provided novel insights into broodiness in birds.

Redox regulation of autophagy in skeletal muscle

Autophagy is a cellular degradative pathway that involves the delivery of cytoplasmic components, including proteins and organelles, to the lysosome for degradation. Autophagy is implicated in the maintenance of skeletal muscle; increased autophagy leads to muscle atrophy while decreased autophagy leads to degeneration and weakness. A growing body of work suggests that reactive oxygen species (ROS) are important cellular signal transducers controlling autophagy. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and mitochondria are major sources of ROS generation in skeletal muscle that are likely regulating autophagy through different signaling cascades based on localization of the ROS signals. This review aims to provide insight into the redox control of autophagy in skeletal muscle. Understanding the mechanisms by which ROS regulate autophagy will provide novel therapeutic targets for skeletal muscle diseases.

Targeting VEGF-A in myeloid cells enhances natural killer cell responses to chemotherapy and ameliorates cachexia

Chemotherapy remains a mainstay of cancer treatment but its use is often limited by the development of adverse reactions. Severe loss of body weight (cachexia) is a frequent cause of death in cancer patients and is exacerbated by chemotherapy. We show that genetic inactivation of vascular endothelial growth factor (VEGF)-A in myeloid cells prevents chemotherapy-induced cachexia by inhibiting skeletal muscle loss and the lipolysis of white adipose tissue. It also improves clearance of senescent tumour cells by natural killer cells and inhibits tumour regrowth after chemotherapy. The effects depend on the chemoattractant chemerin, which is released by the tumour endothelium in response to chemotherapy. The findings define chemerin as a critical mediator of the immune response, as well as an important inhibitor of cancer cachexia. Targeting myeloid cell-derived VEGF signalling should impede the lipolysis and weight loss that is frequently associated with chemotherapy, thereby substantially improving the therapeutic outcome.

Chemerin is an adipokine often downregulated in tumours. Here the authors show that chemotherapy induces chemerin production by endothelial cells, leading to cachexia, and that VEGF ablation in myeloid cells prevents cachexia in a chemerin-dependent manner, and improves chemotherapeutic effects.

Circulating chemerin levels elevated in dilated cardiomyopathy patients with overt heart failure

BACKGROUND

Recent evidence demonstrated that the circulating concentrations of adipokine are related to the presence of heart failure secondary to ischemic heart disease and dilated cardiomyopathy (DCM). However, the plasma concentrations of chemerin in patients with DCM have yet to be investigated.

METHODS

The present study enrolled 109 DCM patients with typical symptoms of heart failure and 60 healthy controls and measured plasma concentrations of chemerin, IL-6 and TNF-α using enzyme-linked immunosorbent assay. Left ventricular end-diastolic diameter (LVEDD) and left ventricular ejection fraction (LVEF) were measured using a GE ViVid E7 ultrasonography machine.

RESULTS

Plasma chemerin, IL-6 and TNF-α concentrations were significantly higher in DCM patients compared to the control group. A correlation analysis revealed that plasma chemerin concentrations were positively correlated with the concentrations of IL-6 (R=0.270, P=0.004), TNF-α (R=0.302, P=0.001), C-reactive protein (CRP) (R=0.256, P=0.004), N-terminal pro-brain natriuretic peptide (NT-proBNP) (R=0.386, P=0.000), and LVEDD (R=0.212, P=0.027) but negatively correlated with LVEF (R=-0.543, P=0.000). Furthermore, chemerin (OR 1.102, 95% CI 1.052 to 1.153; p=0.000) was independently associated with the presence of DCM before NT-proBNP was added in the multivariable regression model.

CONCLUSIONS

The results indicate that chemerin is a novel biomarker of DCM.