A novel adipokine C1q/TNF-related protein 3 is expressed in developing skeletal muscle and controls myoblast proliferation and differentiation

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.

CTRP3 attenuates inflammation, oxidative and cell death in cisplatin induced HK-2 cells

Cisplatin has been widely studied and found to be a highly effective anti-tumor drug. It has several side effects, including acute kidney injury (AKI). Cisplatin-induced AKI can be primarily attributed to oxidative stress, inflammation, and apoptosis. The CTRP3 adipokine is a new adipokine that exhibits antioxidant, anti-inflammatory, and antiapoptotic properties. Despite this, the role of CTRP3 in AKI remain unclear. In cisplatin-induced AKI models, our findings demonstrated that CTRP3 expression was decreased in human proximal tubule epithelial cells (HK-2). In the in vitro experiments, HK-2 cells were first transfected with an overexpression plasmid of CTRP3 (pcDNA-CTRP3) or a small interfering RNA for CTRP3 (si-CTRP3) and induced by cisplatin; and cell oxidative stress, inflammation, proliferation, and apoptosis were found to be present. Overexpressing CTRP3 inhibited oxidative stress through decreasing malondialdehyde (MDA) levels and increasing the activity of SOD and CAT. The mRNA levels of SOD1 and SOD2 were increased in response to CTRP3 overexpression. Additionally, CTRP3 decreased TNF-α and MCP-1 levels. Moreover, CTRP3 overexpression increased cisplatin-induced cell activity and decreased cell apoptosis, as indicated by the elevated numbers of EdU positive cells and decreased numbers of apoptotic cells. Consistent with these results, the overexpression of CTRP3 effectively elevated the mRNA levels of Bcl-2 and reduced the mRNA levels of Bax. In contrast, inhibition of CTRP3 expression by si-CTRP3 reversed the cisplatin-induced indices. Mechanistically, we found that the overexpression of CTRP3 can increase expression of Nrf2 and inhibit the activation of MAPK phosphorylation (ERK, JNK, and p38). Furthermore, inhibition of ERK, JNK and p38 activity eliminated aggravation of cisplatin-induced inflammation and apoptosis caused by CTRP3 knockdown. Additionally, the cisplatin-induced oxidative stress and activation of MAPK phosphorylation (ERK, JNK, and p38) in HK-2 cells were reversed by Nrf2 suppression by siRNA. Collectively, these results indicated that CTRP3 may identify as a novel target for AKI treatment and protect against cisplatin-induced AKI through the Nrf2/MAPK pathway.

Single cell analysis reveals satellite cell heterogeneity for proinflammatory chemokine expression

Background: The expression of proinflammatory signals at the site of muscle injury are essential for efficient tissue repair and their dysregulation can lead to inflammatory myopathies. Macrophages, neutrophils, and fibroadipogenic progenitor cells residing in the muscle are significant sources of proinflammatory cytokines and chemokines. However, the inducibility of the myogenic satellite cell population and their contribution to proinflammatory signaling is less understood.

Methods: Mouse satellite cells were isolated and exposed to lipopolysaccharide (LPS) to mimic sterile skeletal muscle injury and changes in the expression of proinflammatory genes was examined by RT-qPCR and single cell RNA sequencing. Expression patterns were validated in skeletal muscle injured with cardiotoxin by RT-qPCR and immunofluorescence.

Results: Satellite cells in culture were able to express Tnfa, Ccl2, and Il6, within 2 h of treatment with LPS. Single cell RNA-Seq revealed seven cell clusters representing the continuum from activation to differentiation. LPS treatment led to a heterogeneous pattern of induction of C-C and C-X-C chemokines (e.g., Ccl2, Ccl5, and Cxcl0) and cytokines (e.g., Tgfb1, Bmp2, Il18, and Il33) associated with innate immune cell recruitment and satellite cell proliferation. One cell cluster was enriched for expression of the antiviral interferon pathway genes under control conditions and LPS treatment. Activation of this pathway in satellite cells was also detectable at the site of cardiotoxin induced muscle injury.

Conclusion: These data demonstrate that satellite cells respond to inflammatory signals and secrete chemokines and cytokines. Further, we identified a previously unrecognized subset of satellite cells that may act as sensors for muscle infection or injury using the antiviral interferon pathway.

Betahistine alleviates benign paroxysmal positional vertigo (BPPV) through inducing production of multiple CTRP family members and activating the ERK1/2-AKT/PPARy pathway

BACKGROUND

Betahistine is a clinical medication for the treatment of benign paroxysmal positional vertigo (BPPV). Otolin, a secreted glycoprotein with a C-terminal globular domain homologous to the immune complement C1q, has been identified as a biomarker for BPPV. However, the role of complement C1q/TNF-related proteins (CTRPs) with a C-terminal globular domain in BPPV is unclear, so we explored the change of CTRPs in betahistine treated BPPV.

METHODS

We treated BPPV patients with Betahistine (12 mg/time, 3 times/day) for 4 weeks and observed the clinical efficacy and the expression of CTRP family members in BPPV patients. Then, we constructed a vertigo mice model of vestibular dysfunction with gentamicin (150 mg/Kg) and a BPPV model of Slc26a4^loop/loop mutant mice. Adenoviral vectors for CTRP expression vector and small interfering RNA were injected via the intratympanic injection into mice and detected the expression of CTRP family members, phosphorylation levels of ERK and AKT and the expression of PPARγ. In addition, we treated mice of vestibular dysfunction with Betahistine (10 mg/Kg) and/or ERK inhibitor of SCH772984 (12 mg/Kg) and/or and PPARγ antagonist GW9662 (1 mg/Kg) for 15 days, and evaluated the accuracy of air righting reflex, the time of contact righting reflex and the scores of head tilt and swimming behavior.

RESULTS

After treatment with Betahistine, the residual dizziness duration and the score of the evaluation were reduced, and the expression of CTRP1, 3, 6, 9 and 12 were significantly increased in BPPV patients. We also found that Betahistine improved the accuracy of air righting reflex, reduced the time of contact righting reflex and the scores of head tilt and swimming behavior in gentamicin-treated mice and Slc26a4^loop/loop mutant mice. The expression levels of CTRP1, 3, 6, 9 and 12, phosphorylation levels of ERK and AKT, and PPARγ expression were significantly increased, and the scores of head tilt and swimming behavior were decreased in vestibular dysfunction mice with overexpression of CTRPs. Silencing CTRPs has the opposite effect. SCH772984 reversed the effect of Betahistine in mice with vestibular dysfunction.

CONCLUSION

Betahistine alleviates BPPV through inducing production of multiple CTRP family members and activating the ERK1/2-AKT/PPARy pathway.

CTRP3 alleviates cardiac ischemia/reperfusion injury via LAMP1/JIP2/JNK signaling pathway

Background: C1q/tumor necrosis factor-related protein 3 (CTRP3) has been reported to be a crucial regulator in myocardial infarction. Nevertheless, the potential molecular mechanism of CTRP3 in ischemia/reperfusion (I/R) injury remains largely unclear.

Methods: The cell model of myocardial I/R injury was established by oxygen-glucose deprivation/reoxygenation (OGD/R) of rat cardiomyocyte H9C2. Expression of CTRP3 and lysosomal-associated membrane protein 1 (LAMP1) was detected in H9C2 cells treated with oxygen-glucose deprivation/reoxygenation (OGD/R). H9C2 cells were transfected with overexpression plasmids of CTRP3 (pcDNA-CTRP3) and LAMP1 (pcDNA-LAMP1), or CTRP3 small interfering RNA (si-CTRP3) or/and pcDNA-LAMP1, and cell proliferation, apoptosis and oxidative stress were testified. Co-IP assay was performed to validate the relationship among CTRP3, LAMP1 and JIP2. The role of CTRP3 and LAMP1 in JIP2/JNK pathway was evaluated with Western blot assay. Furthermore, in vivo myocardial I/R injury model was constructed to investigate the effect of CTRP3.

Results: Overexpression of CTRP3 and LAMP1 both significantly promoted cell proliferation, inhibited apoptosis and the production of reactive oxygen species (ROS), malondialdehyde (MAD) and cardiac troponin (cTn-I), while silencing CTRP3 exerted the opposite effects, and LAMP1 overexpression reversed the effect of silencing CTRP3 on the aspects above. CTRP3 interacted with LAMP1, and both CTRP3 and LAMP1 bound with JIP2. SP600125 (JNK inhibitor) could restore the effects of CTRP3 or LAMP1 overexpression on the expression of JIP2 and phosphorylated-JNK (p-JNK), proliferation and apoptosis. Moreover, overexpression of CTRP3 improved cardiac I/R injury in vivo.

Conclusion: CTRP3 alleviates cardiac I/R injury by elevating LAMP1 and activating JIP2/JNK signaling pathway, which may serve as a potential therapeutic target for I/R injury.

The CTRP3-AdipoR2 Axis Regulates the Development of Experimental Autoimmune Encephalomyelitis by Suppressing Th17 Cell Differentiation

C1q/TNF-related proteins (CTRP) including CTRP3 are a group of secreted proteins which have a complement C1q-like domain in common, and play versatile roles in lipid metabolism, inflammation, tumor metastasis and bone metabolism. Previously, we showed that the expression of C1qtnf3, encoding CTRP3, is highly augmented in joints of autoimmune arthritis models and CTRP3-deficiency exacerbates collagen-induced arthritis in mice. However, the mechanisms how CTRP3-deficiency exacerbates arthritis still remain to be elucidated. In this study, we showed that CTRP3 was highly expressed in Th17 cell, a key player for the development of autoimmune diseases, and Th17 cell differentiation was augmented in C1qtnf3^–/– mice. Th17 cell differentiation, but not Th1 cell differentiation, was suppressed by CTRP3 and this suppression was abolished by the treatment with a receptor antagonist against AdipoR2, but not AdipoR1, associated with suppression of Rorc and Stat3 expression. Furthermore, AdipoR1 and AdipoR2 agonist, AdipoRon suppressed Th17 cell differentiation via AdipoR2, but not AdipoR1. The development of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis was enhanced in C1qtnf3^–/– mice associated with increase of Th17 cell population. CTRP3 inhibited MOG-induced IL-17 production from T cells by affecting both T cells and dendritic cells. These results show that CTRP3 is an endogenous regulator of Th17 differentiation, suggesting that the CTRP3-AdipoR2 axis is a good target for the treatment of Th17 cell-mediated diseases.

The adipokine C1q/TNF-related protein-3 (CTRP-3) inhibits Toll-like receptor (TLR)-induced expression of Cathelicidin antimicrobial peptide (CAMP) in adipocytes

BACKGROUND AND AIM

CAMP (Cathelicidin antimicrobial peptide) expression in adipocytes is regulated by Toll-like receptor (TLR) agonists. Secreted adipokines such as CTRP-3 have been suggested to participate in innate immune signaling in adipose tissue (AT). This study investigates whether TLR-induced CAMP expression in adipocytes is antagonized by CTRP-3.

METHODS

3T3-L1 adipocytes were co-stimulated with TLR agonists (LPS, MALP-2, Pam3CSK4, pI:C) and recombinant CTRP-3. In a SIRS model, C57BL/6 wild-type mice were intraperitoneally (ip) injected with recombinant CTRP-3 prior to LPS. CAMP expression was analyzed by real-time PCR in AT of wild-type mice and in AT and primary adipocytes from transgenic mice lacking adipocyte CTRP-3 expression. Comparative transcriptome analysis by RNA seq. was applied in CTRP-3 KO adipocytes.

RESULTS

In vitro, CTRP-3 antagonized TLR4- and TLR1/2-induced CAMP expression in adipocytes whereas TLR3- and TLR2/6-mediated induction of CAMP was not affected. in vivo, application of exogenous CTRP-3 dose-dependently antagonized LPS-induced CAMP expression in intra-abdominal AT. CAMP expression in total AT and in primary adipocytes of subcutaneous and intra-abdominal AT did not differ between wild-type mice and transgenic mice lacking adipocyte CTRP-3 expression.

CONCLUSIONS

The study suggests a hypothetical role of CAMP in host defense not only against Gram-positive bacteria sensed by TLR1/2 and TLR2/6 but also against Gram-negative bacteria sensed by TLR4 and potentially against viruses sensed by TLR3. The machinery of TLR-mediated pro-inflammatory activation of the CAMP gene in adipocytes seems to be partly modulated by secreted adipokines belonging to the growing family of C1q/TNF-related proteins such as CTRP-3.

CTRP-3 Regulates NOD1-mediated Inflammation and NOD1 Expression in Adipocytes and Adipose Tissue

The anti-inflammatory adipokine CTRP-3 might affect innate immune reactions such as NOD1. The impact of CTRP-3 on NOD1-mediated inflammation in adipocytes and monocytic cells as well as on NOD1 expression was investigated. Murine 3T3-L1 pre-adipocytes and adipocytes as well as human THP-1 monocyte-like cells were co-stimulated with the synthetic NOD1 agonist Tri-DAP and recombinant CTRP-3. Gonadal adipose tissue and primary adipocytes were obtained from a murine model carrying a knockout (KO) of CTRP-3 in adipocytes but not in stroma-vascular cells. Wildtype mice with lipopolysaccharide (LPS)-induced elevated NOD1 expression were treated with CTRP-3. Secreted inflammatory cytokines in cell supernatants were measured by ELISA and mRNA levels were quantified by RT-PCR. Pro-inflammatory chemokine and cytokine secretion (MCP-1, RANTES, TNFα) was induced by NOD1 activation in adipocytes and monocyte-like cells, and MCP-1 and RANTES release was effectively inhibited by pre-incubation of cells with CTRP-3. CTRP-3 also antagonized LPS-triggered induction of NOD1 gene expression in murine adipose tissue, whereas adipocyte CTRP-3 deficiency upregulated NOD1 expression in adipose tissue. CTRP-3 is an effective antagonist of peptidoglycan-induced, NOD1-mediated inflammation and of LPS-induced NOD1 expression. Since basal NOD1 expression is increased by adipocyte CTRP-3 deficiency, there have to be also inflammation-independent mechanisms of NOD1 expression regulation by CTRP-3.

CTRP3 ameliorates cerulein-induced severe acute pancreatitis in mice via SIRT1/NF-κB/p53 axis

Severe acute pancreatitis (SAP) is a common and life-threatening clinical acute abdominal disease. C1q/tumor necrosis factor-related protein 3 (CTRP3), a novel paralog of adiponectin, has been identified as a crucial regulator in multiple types of inflammatory disorders. However, the biological role of CTRP3 in SAP remains poorly understood. The present study aimed to characterize the role of CTRP3 in SAP and illuminate the potential mechanisms involved. In the current study, SAP mouse models were induced by seven hourly intraperitoneal injection of cerulein (50 μg/kg) and an immediate intraperitoneal injection of lipopolysaccharide (10 mg/kg) after the last cerulein administration. Histological examination and serological analysis demonstrated that SAP mouse models were successfully established. Herein, we found that CTRP3 expression was significantly decreased in the pancreatic tissues of SAP mice compared with normal control mice. Furthermore, we explored the effects of CTRP3 rescue in SAP mice and discovered that CTRP3 overexpression attenuated pathological lesions, inhibited inflammatory mediator release and repressed acinar cell apoptosis. Notably, mechanistic studies revealed that CTRP3 overexpression suppressed NF-κB p65 phosphorylation and p53 acetylation to alleviate cerulein-induced SAP in mouse models through activation of silent information regulator 1 (SIRT1), a nicotinamide adenine dinucleotide-dependent protein deacetylase. Collectively, our data indicate that CTRP3 may exert its protective effects in SAP mice via regulation of SIRT1-mediated NF-κB and p53 signaling pathways, implying a promising therapeutic strategy against SAP.

Downregulation of CTRP-3 by Weight Loss In Vivo and by Bile Acids and Incretins in Adipocytes In Vitro

The adipokine CTRP-3 (C1q/TNF-related protein-3) exerts anti-inflammatory and anti-diabetic effects. Its regulation in obesity and during weight loss is unknown. Serum and adipose tissue (AT) samples were obtained from patients (n = 179) undergoing bariatric surgery (BS). Moreover, patients (n = 131) participating in a low-calorie diet (LCD) program were studied. CTRP 3 levels were quantified by ELISA and mRNA expression was analyzed in AT and in 3T3-L1 adipocytes treated with bile acids and incretins. There was a persistent downregulation of CTRP-3 serum levels during weight loss. CTRP-3 expression was higher in subcutaneous than in visceral AT and serum levels of CTRP-3 were positively related to AT expression levels. A rapid decrease of circulating CTRP-3 was observed immediately upon BS, suggesting weight loss-independent regulatory mechanisms. Adipocytes CTRP-3 expression was inhibited by primary bile acid species and GLP 1. Adipocyte-specific CTRP-3 deficiency increased bile acid receptor expression. Circulating CTRP-3 levels are downregulated during weight loss, with a considerable decline occurring immediately upon BS. Mechanisms dependent and independent of weight loss cause the post-surgical decline of CTRP-3. The data strongly argue for regulatory interrelations of CTRP-3 with bile acids and incretin system.

Deficiency of C1q/TNF-related protein 3 (CTRP3) decreases adipose tissue weight in diet-induced obesity mice

Adipokines are important regulators of lipid and glucose metabolism. A family of adiponectin paralogs is known as C1q and tumor necrosis factor (TNF)-related proteins (CTRPs). One line of Ctrp3-deficient mice shows reduced liver size in response to obesity. We generated and characterized another line of Ctrp3 knockout (KO) mice to reveal novel physiological functions of CTRP3. Interestingly, high fat diet (HFD)-fed Ctrp3 KO mice displayed a decrease in the epididymal white adipose tissue (WAT) weight to total body weight ratio. Histologically, adipocyte size was significantly smaller in the epididymal WAT of HFD-fed Ctrp3 KO mice than wild-type (WT) controls. The expression of several genes involved in lipogenesis, lipolysis and adipogenesis in the epididymal WAT of Ctrp3 KO mice fed a HFD was decreased. The present findings provide new insight into the role of CTRP3 as adipokine in the regulation of adipose tissue in obesity.

Isolation and identification of goose skeletal muscle satellite cells and preliminary study on the function of C1q and tumor necrosis factor-related protein 3 gene

Objective

Skeletal muscle satellite cells (SMSCs) are significant for the growth, regeneration, and maintenance of skeletal muscle after birth. However, currently, few studies have been performed on the isolation, culture and inducing differentiation of goose muscle satellite cells. Previous studies have shown that C1q and tumor necrosis factor-related protein 3 (CTRP3) participated in the process of muscle growth and development, but its role in the goose skeletal muscle development is not yet clear. This study aimed to isolate, culture, and identify the goose SMSCs in vitro. Additionally, to explore the function of CTRP3 in goose SMSCs.

Methods

Goose SMSCs were isolated using 0.25% trypsin from leg muscle (LM) of 15 to 20 day fertilized goose eggs. Cell differentiation was induced by transferring the cells to differentiation medium with 2% horse serum and 1% penicillin streptomycin. Immunofluorescence staining of Desmin and Pax7 was used to identify goose SMSCs. Quantitative realtime polymerase chain reaction and western blot were applied to explore developmental expression profile of CTRP3 in LM and the regulation of CTRP3 on myosin heavy chains (MyHC), myogenin (MyoG) expression and Notch signaling pathway related genes expression.

Results

The goose SMSCs were successfully isolated and cultured. The expression of Pax7 and Desmin were observed in the isolated cells. The expression of CTRP3 decreased significantly during leg muscle development. Overexpression of CTRP3 could enhance the expression of two myogenic differentiation marker genes, MyHC and MyoG. But knockdown of CTRP3 suppressed their expression. Furthermore, CTRP3 could repress the mRNA level of Notch signaling pathway-related genes, notch receptor 1, notch receptor 2 and hairy/enhancer-of-split related with YRPW motif 1, which previously showed a negative regulation in myoblast differentiation.

Conclusion

These findings provide a useful cell model for the future research on goose muscle development and suggest that CTRP3 may play an essential role in skeletal muscle growth of goose.

C1q-tumour necrosis factor-related protein-3 exacerbates cardiac hypertrophy in mice

AIMS

C1q-tumour necrosis factor-related protein-3 (CTRP3) is an adipokine and a paralog of adiponectin. Our previous study showed that CTRP3 attenuated diabetes-related cardiomyopathy. However, the precise role of CTRP3 in cardiac hypertrophy remains unclear. This study was aimed to clarify the role of CTRP3 involved in cardiac hypertrophy.

METHODS AND RESULTS

Cardiomyocyte-specific CTRP3 overexpression was achieved using an adeno-associated virus system, and cardiac CTRP3 expression was knocked down using gene delivery of specific short hairpin RNAs in vivo. CTRP3 expression was upregulated in murine hypertrophic hearts and failing human hearts. Increased CTRP3 was mainly derived from cardiomyocytes and induced by the production of reactive oxygen species (ROS) during the hypertrophic response. CTRP3-overexpressing mice exhibited exacerbated cardiac hypertrophy and cardiac dysfunction in response to pressure overload. Conversely, Ctrp3 deficiency in the heart resulted in an alleviated hypertrophic phenotype. CTRP3 induced hypertrophy in cardiomyocytes, which could be blocked by the addition of CTRP3 antibody in the media. Detection of signalling pathways showed that pressure overload-induced activation of the transforming growth factor β-activated kinase 1 (TAK1)-c-Jun N-terminal kinase (JNK) pathway was enhanced by CTRP3 overexpression and inhibited by CTRP3 disruption. Furthermore, we found that CTRP3 lost its pro-hypertrophic effects in cardiomyocyte-specific Tak1 knockout mice. Protein kinase A (PKA) was involved in the activation of TAK1 by CTRP3.

CONCLUSION

In conclusion, our results suggest that CTRP3 promotes pressure overload-induced cardiac hypertrophy via activation of the TAK1-JNK axis.

Transcriptome for the breast muscle of Jinghai yellow chicken at early growth stages

Background

The meat quality of yellow feathered broilers is better than the quality of its production. Growth traits are important in the broiler industry. The exploration of regulation mechanisms for the skeletal muscle would help to increase the growth performance of chickens. At present, some progress has been made by researchers, but the molecular mechanisms of the skeletal muscle still remain unclear and need to be improved.

Methods

In this study, the breast muscles of fast- and slow-growing female Jinghai yellow chickens (F4F, F8F, F4S, F8S) and slow-growing male Jinghai yellow chickens (M4S, M8S) aged four and eight weeks were selected for transcriptome sequencing (RNA-seq). All analyses of differentially expressed genes (DEGs) and functional enrichment were performed. Finally, we selected nine DEGs to verify the accuracy of the sequencing by qPCR.

Results

The differential gene expression analysis resulted in 364, 219 and 111 DEGs (adjusted P-value ≤ 0.05) for the three comparison groups, F8FvsF4F, F8SvsF4S, and M8SvsM4S, respectively. Three common DEGs (ADAMTS20, ARHGAP19, and Novel00254) were found, and they were all highly expressed at four weeks of age. In addition, some other genes related to growth and development, such as ANXA1, COL1A1, MYH15, TGFB3 and ACTC1, were obtained. The most common DEGs (n = 58) were found between the two comparison groups F8FvsF4F and F8SvsF4S, and they might play important roles in the growth of female chickens. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway also showed some significant enrichment pathways, for instance, extracellular matrix (ECM)-receptor interaction, focal adhesion, cell cycle, and DNA replication. The two pathways that were significantly enriched in the F8FvsF4F group were all contained in that of F8SvsF4S. The same two pathways were ECM–receptor interaction and focal adhesion, and they had great influence on the growth of chickens. However, many differences existed between male and female chickens in regards to common DEGs and KEGG pathways. The results would help to reveal the regulation mechanism of the growth and development of chickens and serve as a guideline to propose an experimental design on gene function with the DEGs and pathways.

CTRP3 Alleviates Ox-LDL-Induced Inflammatory Response and Endothelial Dysfunction in Mouse Aortic Endothelial Cells by Activating the PI3K/Akt/eNOS Pathway

C1q/tumor necrosis factor-related protein-3 (CTRP3) is a novel, certified, adipokine that beneficially regulates metabolism and inflammation in the cardiovascular system. Atherosclerotic plaque rupturing and secondary thrombosis cause vascular disorders, such as myocardial infarction and unstable angina. However, the underlying role of CTRP3 in atherosclerosis remains unclear. In this study, we aimed to elucidate whether and how CTRP3 ameliorates inflammation and endothelial dysfunction caused by oxidized low-density lipoprotein (ox-LDL). We first confirmed that CTRP3 expression was inhibited in ApoE-/- mice, compared to normal mice. Then, pcDNA-CTRP3 and siCTRP3 were transfected into mouse aortic endothelial cells after ox-LDL stimulation, and we observed that enhanced CTRP3 remarkably downregulated CRP, TNF-α, IL-6, CD40, and CD40L. We also observed that overexpression of CTRP3 elevated cell activity and decreased lactated hydrogenase release, accompanied by a marked reduction in cell apoptosis induced by ox-LDL. Meanwhile, overexpressed CTRP3 caused a decrease in Ang II, ICAM-1, and VCAM-1 expression, and it restored the balance between ET-1 and NO. Mechanism analysis confirmed that incremental CTRP3 upregulated p-PI3K, p-Akt, and p-eNOS expression, indicating that CTRP3 facilitated activation of the PI3K/Akt/eNOS pathway. On the contrary, siCTRP3 exerted the opposite effect to this activation. Blocking these pathways using LY294002 or L-NAME attenuated the protective role of CTRP3. Overall, these results suggest that CTRP3 can efficiently inhibit the inflammatory response and endothelial dysfunction induced by ox-LDL in mouse aortic endothelial cells, perhaps by activating the PI3K/Akt/eNOS pathway, indicating a promising strategy against atherosclerosis.

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.

Adiponectin-Consideration for its Role in Skeletal Muscle Health

Adiponectin regulates metabolism through blood glucose control and fatty acid oxidation, partly mediated by downstream effects of adiponectin signaling in skeletal muscle. More recently, skeletal muscle has been identified as a source of adiponectin expression, fueling interest in the role of adiponectin as both a circulating adipokine and a locally expressed paracrine/autocrine factor. In addition to being metabolically responsive, skeletal muscle functional capacity, calcium handling, growth and maintenance, regenerative capacity, and susceptibility to chronic inflammation are all strongly influenced by adiponectin stimulation. Furthermore, physical exercise has clear links to adiponectin expression and circulating concentrations in healthy and diseased populations. Greater physical activity is generally related to higher adiponectin expression while lower adiponectin levels are found in inactive obese, pre-diabetic, and diabetic populations. Exercise training typically restores plasma adiponectin and is associated with improved insulin sensitivity. Thus, the role of adiponectin signaling in skeletal muscle has expanded beyond that of a metabolic regulator to include several aspects of skeletal muscle function and maintenance critical to muscle health, many of which are responsive to, and mediated by, physical exercise.

C1QTNF3 in the murine ovary and its function in folliculogenesis

C1q/tumor necrosis factor-related protein 3 (C1QTNF3) is a novel adipokine with modulating effects on metabolism, inflammation and the cardiovascular system. C1QTNF3 expression levels in the sera and omental adipose tissues of women with PCOS are low compared to control subjects. However, the expression and function of C1QTNF3 in the ovary has not previously been examined. Here, we assessed the expression patterns of C1qtnf3 in the ovary and explored its role in folliculogenesis. The C1qtnf3 transcript abundance was higher in large follicles than in small follicles and was under the influence of gonadotropin. C1QTNF3 was detected mainly in the granulosa cells and oocytes of growing follicles and modestly in the granulosa cells of atretic follicles and in luteal cells. Excess androgen significantly decreased C1QTNF3 expression in the ovaries in vivo and in granulosa cells in vitro. Recombinant C1QTNF3 protein accelerated the weight gain of ovarian explants and the growth of preantral follicles induced by follicle stimulating hormone (FSH) in vitro. The stimulatory effect of C1QTNF3 on ovarian growth was accompanied by the initiation of AKT, mTOR, p70S6K and 4EBP1 phosphorylation, an increase in CCND2 expression and a reduction in cleaved CASP3 levels. Moreover, the addition of C1QTNF3 accelerated proliferation and reduced activated CASP3/7 activity in granulosa cells. In vivo, the ovarian intrabursal administration of the C1QTNF3 antibody delayed gonadotropin-induced antral follicle development. Taken together, our data demonstrate that C1QTNF3 is an intraovarian factor that promotes follicle growth by accelerating proliferation, decelerating apoptosis and promoting AKT/mTOR phosphorylation.

A MicroRNA93-Interferon Regulatory Factor-9-Immunoresponsive Gene-1-Itaconic Acid Pathway Modulates M2-Like Macrophage Polarization to Revascularize Ischemic Muscle

BACKGROUND

Currently, no therapies exist for treating and improving outcomes in patients with severe peripheral artery disease (PAD). MicroRNA93 (miR93) has been shown to favorably modulate angiogenesis and to reduce tissue loss in genetic PAD models. However, the cell-specific function, downstream mechanisms, or signaling involved in miR93-mediated ischemic muscle neovascularization is not clear. Macrophages were best known to modulate arteriogenic response in PAD, and the extent of arteriogenic response induced by macrophages is dependent on greater M2 to M1 activation/polarization state. In the present study, we identified a novel mechanism by which miR93 regulates macrophage polarization to promote angiogenesis and arteriogenesis to revascularize ischemic muscle in experimental PAD.

METHODS

In vitro (macrophages, endothelial cells, skeletal muscle cells under normal and hypoxia serum starvation conditions) and in vivo experiments in preclinical PAD models (unilateral femoral artery ligation and resection) were conducted to examine the role of miR93-interferon regulatory factor-9-immunoresponsive gene-1 (IRG1)-itaconic acid pathway in macrophage polarization, angiogenesis, arteriogenesis, and perfusion recovery.

RESULTS

In vivo, compared with wild-type controls, miR106b-93-25 cluster-deficient mice (miR106b-93-25-/-) showed decreased angiogenesis and arteriogenesis correlating with increased M1-like macrophages after experimental PAD. Intramuscular delivery of miR93 in miR106b-93-25-/- PAD mice increased angiogenesis, arteriogenesis, and the extent of perfusion, which correlated with more M2-like macrophages in the proximal and distal hind-limb muscles. In vitro, miR93 promotes and sustains M2-like polarization even under M1-like polarizing conditions (hypoxia serum starvation). Delivery of bone marrow-derived macrophages from miR106b-93-25-/- to wild-type ischemic muscle decreased angiogenesis, arteriogenesis, and perfusion, whereas transfer of wild-type macrophages to miR106b-93-25-/- had the opposite effect. Systematic analysis of top differentially upregulated genes from RNA sequencing between miR106b-93-25-/- and wild-type ischemic muscle showed that miR93 regulates IRG1 function to modulate itaconic acid production and macrophage polarization. The 3' untranslated region luciferase assays performed to determine whether IRG1 is a direct target of miR93 revealed that IRG1 is not an miR93 target but that interferon regulatory factor-9, which can regulate IRG1 expression, is an miR93 target. In vitro, increased expression of interferon regulatory factor-9 and IRG1 and itaconic acid treatment significantly decreased endothelial angiogenic potential.

CONCLUSIONS

miR93 inhibits interferon regulatory factor-9 to decrease IRG1-itaconic acid production to induce M2-like polarization in ischemic muscle to enhance angiogenesis, arteriogenesis, and perfusion recovery in experimental PAD.

Akirin2 regulates proliferation and differentiation of porcine skeletal muscle satellite cells via ERK1/2 and NFATc1 signaling pathways

Akirin2, a novel nuclear factor, plays an important role in myogenesis. To investigate the role of Akirin2 in proliferation and differentiation of porcine skeletal muscle satellite cells, Akirin2 overexpression and Akirin2 silence technologies were employed. Our results showed that overexpression of Akirin2 markedly enhanced the proliferation and differentiation of porcine skeletal muscle satellite cells, whereas silencing of Akirin2 got the opposite results. Furthermore, our results showed that Akirin2 affected proliferation and differentiation of porcine skeletal muscle satellite cells through extracellular-signal regulated kinase-1/2 (ERK1/2) and NFATc1 signaling pathways. These results indicate that Akirin2 can effectively promote skeletal muscle satellite cells proliferation and differentiation, acting through ERK1/2- and NFATc1-dependent mechanisms.

C1q/TNF-related protein 3 expression and effects on adipocyte differentiation of 3T3-L1 cells

Adipose tissue-derived adipokines influence a number of organs critical for energy homeostasis and metabolism. One of the most extensively studied adipokines is adiponectin, which exerts anti-diabetic, anti-inflammatory, and anti-atherogenic functions on various cell types. CTRP3, a paralog of adiponectin, is a member of the C1q and tumor necrosis factor-related protein (CTRP) superfamily. CTRP3 reduces hepatic triglyceride levels in diet-induced obese (DIO) mice. However, the physiological role of CTRP3 in adipocytes is largely unknown. In the course of our investigation of expression profiles of CTRPs during adipocyte differentiation, we found that CTRP3 expression pattern is different from that previously reported. Therefore, we examined the effect of CTRP3 on adipogenesis using 3T3-L1 cells. The expression level of CTRP3 was markedly decreased during the differentiation of 3T3-L1 cells. Recombinant CTRP3 (rCTRP3) treatment significantly reduced intracellular lipid content and decreased expression of adipogenic marker genes such as peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer binding protein alpha (C/EBPα), adiponectin, and fatty acid binding protein 4 (FABP4) in 3T3-L1 cells. Furthermore, rCTRP3 induced the phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) and Akt in differentiated 3T3-L1 adipocytes. These results suggest that CTRP3 may negatively regulate lipid metabolism during adipocyte differentiation.

Nanofibrous polylactide composite scaffolds with electroactivity and sustained release capacity for tissue engineering

A conveniently fabricated electroactive nanofibrous composite scaffold serves as a sustained drug release system and promotes myoblast differentiation.