C1q/tumor Necrosis Factor-related Protein 6 Research Articles

CTRP6 alleviates endometrial fibrosis by regulating Smad3 pathway in intrauterine adhesion†.

Intrauterine adhesion (IUA) is manifestations of endometrial fibrosis and excessive extracellular matrix deposition. C1q/tumor necrosis factor-related protein-6 (CTRP6) is a newly identified adiponectin paralog which has been reported to modulate the fibrosis process of several diseases; however, the endometrial fibrosis function of CTRP6 remains unknown. Our study aimed to assess the role of CTRP6 in endometrial fibrosis and further explore the underlying mechanism. Here, we found that the expression of CTRP6 was downregulated in the endometrial tissues of IUA. In vitro experiments demonstrated the reduced level of CTRP6 in facilitated transforming growth factor-β1 (TGF-β1)-induced human endometrial stromal cells (HESCs). In addition, CTRP6 inhibited the expression of α-smooth muscle actin (α-SMA) and collagen I in TGF-β1-treated HESCs. Mechanistically, CTRP6 activated the AMP-activated protein kinase (AMPK) and protein kinase B (AKT) pathway in HESCs, and AMPK inhibitor (AraA) or PI3K inhibitor (LY294002) pretreatment abolished the protective effect of CTRP6 on TGF-β1-induced fibrosis. CTRP6 markedly decreased TGF-β1-induced Smad3 phosphorylation and nuclear translocation, and AMPK or AKT inhibition reversed these effects. Notably, CTRP6-overexpressing treatment alleviated the fibrosis of endometrium in vivo. Therefore, CTRP6 ameliorates endometrial fibrosis, among which AMPK and AKT are essential for the anti-fibrotic effect of CTRP6 via the Smad3 pathway. Taken together, CTRP6 may be a potential therapeutic target for the treatment of intrauterine adhesion.

Down regulation of C1q tumor necrosis factor-related protein 6 is associated with increased risk of breast cancer

C1q tumor necrosis factor-related protein 6 (CTRP6), a member of the C1q tumor necrosis factor-related protein (CTRP) family, is reported to be associated with the progression of different malignancies, however, its expression levels and role in breast cancer (BC) are yet unknown. In this study, we investigated the levels of circulating CTRP6 in BC patients and evaluated its role as a potential diagnostic biomarker in BC patients. Then we investigated the effect of recombinant CTRP6 on cellular viability in MCF-7 cells along with its effects on the expression of inflammatory cytokines, interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α) in addition to the expression of vascular endothelial growth factor (VEGF) as a marker of angiogenesis. Our results showed decreased expression of circulating CTRP6 in BC patients with an inverse correlation between CTRP6 and IL-6, TNF-α and VEGF levels. Besides, Receiver operating characteristic (ROC) curve showed that the assessment of CTRP6 levels could be used to predict BC. Moreover, treatment of MCF-7 cells with recombinant CTRP6 protein reduced cellular viability and decreased IL-6, TNF-α and VEGF expression. In conclusion, these results provide new insights into the role of CTRP6 in BC pathogenesis and suggest its potential use as a novel diagnostic biomarker of BC.

The action mechanism by which C1q/tumor necrosis factor-related protein-6 alleviates cerebral ischemia/reperfusion injury in diabetic mice.

JOURNAL/nrgr/04.03/01300535-202409000-00034/figure1/v/2024-01-16T170235Z/r/image-tiff Studies have shown that C1q/tumor necrosis factor-related protein-6 (CTRP6) can alleviate renal ischemia/reperfusion injury in mice. However, its role in the brain remains poorly understood. To investigate the role of CTRP6 in cerebral ischemia/reperfusion injury associated with diabetes mellitus, a diabetes mellitus mouse model of cerebral ischemia/reperfusion injury was established by occlusion of the middle cerebral artery. To overexpress CTRP6 in the brain, an adeno-associated virus carrying CTRP6 was injected into the lateral ventricle. The result was that oxygen injury and inflammation in brain tissue were clearly attenuated, and the number of neurons was greatly reduced. In vitro experiments showed that CTRP6 knockout exacerbated oxidative damage, inflammatory reaction, and apoptosis in cerebral cortical neurons in high glucose hypoxia-simulated diabetic cerebral ischemia/reperfusion injury. CTRP6 overexpression enhanced the sirtuin-1 signaling pathway in diabetic brains after ischemia/reperfusion injury. To investigate the mechanism underlying these effects, we examined mice with depletion of brain tissue-specific sirtuin-1. CTRP6-like protection was achieved by activating the sirtuin-1 signaling pathway. Taken together, these results indicate that CTRP6 likely attenuates cerebral ischemia/reperfusion injury through activation of the sirtuin-1 signaling pathway.

CTRP6 protects against ferroptosis to drive lung cancer progression and metastasis by destabilizing SOCS2 and augmenting the xCT/GPX4 pathway

Lung cancer is a highly heterogeneous malignancy, and despite the rapid development of chemotherapy and radiotherapy, acquired drug resistance and tumor progression still occur. Thus, it is urgent to identify novel therapeutic targets. Our research aims to screen novel biomarkers associated with the prognosis of lung carcinoma patients and explore the potential regulatory mechanisms. We obtained RNA sequencing (RNA-seq) data of lung cancer patients from public databases. Clinical signature analysis, weighted gene coexpression network analysis (WGCNA) and the random forest algorithm showed that C1q/tumor necrosis factor-related protein-6 (CTRP6) is a core gene related to lung cancer prognosis, and it was determined to promote tumor proliferation and metastasis both in vivo and in vitro. Mechanistically, silencing CTRP6 was determined to promote xCT/GPX4-involved ferroptosis through functional assays related to lipid peroxidation, Fe2+ concentration and mitochondrial ultrastructure. By performing interactive proteomics analyses in lung tumor cells, we identified the interaction between CTRP6 and suppressor of cytokine signaling 2 (SOCS2) leading to SOCS2 ubiquitination degradation, subsequently enhancing the downstream xCT/GPX4 signaling pathway. Moreover, significant correlations between CTRP6-mediated SOCS2 and ferroptosis were revealed in mouse models and clinical specimens of lung cancer. As inducing ferroptosis has been gradually regarded as an alternative strategy to treat tumors, targeting CTRP6-mediated ferroptosis could be a potential strategy for lung cancer therapy.

CTRP6 regulates M1 macrophage polarization via the PPAR-γ/NF-κB pathway and reprogramming glycolysis in recurrent spontaneous abortion

Aberrant polarization and functions of decidual macrophages are closely related to recurrent spontaneous abortion (RSA). C1q/tumor necrosis factor-related protein 6 (CTRP6) is a member of the adiponectin paralog family, and plays indispensable roles in inflammation, glucose uptake and tumor metastasis. However, the regulatory effect of CTRP6 on macrophage polarization and glycolysis in RSA and the underlying mechanisms have not been fully elucidated. In the present study, we first found that CTRP6 expression was positively correlated with the M1 macrophage marker (CD86) in decidual tissues by dual immunofluorescence analysis. In vitro experiments indicated that CTRP6 could facilitate M1 macrophage activation through the PPAR-γ/NF-κB pathway and manipulate the glycolysis of macrophages. Notably, in addition to silencing CTRP6, treatment with a PPAR-γ agonist (GW1929) inhibited M1 macrophage polarization and rescued embryo absorption in vivo. Taken together, these results identify previously unrevealed functions of CTRP6 in macrophage transformation during RSA.

C1q/tumor necrosis factor-related protein-6 exerts protective effects on myocardial ischemia-reperfusion injury through the modulation of the Akt-GSK-3β-Nrf2 signaling cascade.

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a multifunctional protein that plays a pivotal role in diverse physiological and pathological processes. To date, whether CTRP6 has a role in myocardial ischemia-reperfusion (I/R) injury remains unexplored. This work aimed to investigate the potential role and mechanism of CTRP6 in myocardial I/R injury through in vitro and in vivo experiments. CTRP6 expression was downregulated in hypoxia/reoxygenation (H/R)-treated cardiomyocytes. The apoptosis, oxidative stress, and inflammation in the H/R-treated cardiomyocytes were markedly alleviated by CTRP6 overexpression or exacerbated by CTRP6 silencing. Notably, the overexpression of CTRP6 remarkably ameliorated the myocardial injury, infarction area, cardiac apoptosis, oxidative stress, and inflammation in mice with myocardial I/R injury in vivo. Further investigation revealed that CTRP6 overexpression enhanced the activation of Nrf2 in the H/R-treated cardiomyocytes and the myocardium tissue of mice with myocardial I/R injury. CTRP6 overexpression increased the phosphorylated level of Akt and GSK-3β, and the inhibition of Akt abolished CTRP6-overexpression-elicited Nrf2 activation in the H/R-treated cardiomyocytes. Additionally, the inhibition of Akt or Nrf2 abolished the protective effects of CTRP6 overexpression on the H/R-treated cardiomyocytes. Altogether, CTRP6 had protective effects on myocardial I/R injury via the effects on the Akt-GSK-3β-Nrf2 signaling cascade. Our work recommends CTRP6 as a novel cardioprotective target for the treatment of myocardial I/R injury.

C1q/tumor necrosis factor related protein 6 (CTRP6) regulates the phenotypes of high glucose-induced gestational trophoblast cells via peroxisome proliferator-activated receptor gamma (PPARγ) signaling

ABSTRACT Multiple studies have confirmed that adipokines are compactly relevant to insulin resistance and participate in the pathogenesis of gestational diabetes mellitus (GDM). This paper aimed to study the effects of C1q/tumor necrosis factor related protein (CTRP)6 on the phenotypes of trophoblast cells, covering cell proliferation, invasion and migration, and initially explore the mechanism. High glucose was used to induce trophoblast cells to establish an in vitro model. The expression levels of CTRP6 were firstly determined, and then the effects of CTRP6 knockdown on cell viability, apoptosis, migration and invasion were assessed using CCK8, TUNEL, wound healing, Transwell assays. Moreover, the role of peroxisome proliferator-activated receptor gamma (PPARγ), probable target of CTRP6, was evaluated through co-transfection with PPARγ overexpression vector. The results of the present study revealed that CTRP6 and PPARγ were both upregulated in high glucose-induced cells. And CTRP6 knockdown could significantly elevate the abilities of cell viability, migration and invasion, and avoid cell apoptosis. In addition, PPARγ overexpression was found to restrain the protective effects of CTRP6 knockdown on the above aspects, indicating CTRP6 played a role in trophoblast cells via inhibiting PPARγ expression. In conclusion, CTRP6 regulated the viability, migration and invasion of high glucose-induced gestational trophoblast cells through PPARγ signaling.

C1QTNF6 regulates cell proliferation and apoptosis of NSCLC in vitro and in vivo.

Objectives: Lung cancer has been reported as the leading cause of cancer-associated deaths in humans, and its incidence continues to increase in the world. A growing number of studies have shown that dysregulated genes are associated with the occurrence and poor prognosis of a variety of tumors, including non-small cell lung cancer (NSCLC). C1q/tumor necrosis factor-related protein 6 (C1QTNF6), a member of the C1q/tumor necrosis factor-related protein (CTRP) family, has been revealed to play a role in carcinogenesis and cancer progression. Nevertheless, the effects and mechanisms of C1QTNF6 in NSCLC remain unrevealed. Materials and methods: MTT (3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide) and colony formation, flow cytometric and transwell assays were performed to explore the cell function. Real-time PCR (RT-PCR) and Western blot were used to analyze the mRNA and protein expression. Results: In the present study, we found that C1QTNF6 significantly promoted the proliferation of SPCA1 and A549 cells by MTT and colony formation assays. In addition, down-regulation of C1QTNF6 weakened the tumor growth in vivo. Besides, C1QTNF6 remarkably reduced apoptosis by flow cytometric analysis and TUNEL assay. Furthermore, the capability of migration and invasion was obviously enhanced on C1QTNF6 overexpression. Conclusion: Overall, our results demonstrated that inhibition of C1QTNF6 attenuated cell proliferation, migration, invasion and promoted apoptosis in vitro and in vivo of NSCLC. Based on the above results, our study provided us with a new and key perspective in understanding and treating NSCLC.

C1q/tumor necrosis factor-related protein-6 attenuates TNF-α-induced apoptosis in salivary acinar cells via AMPK/SIRT1-modulated miR-34a-5p expression.

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a newly identified adipokine involved in diverse biological processes. However, its role in salivary glands remains unknown. Here, we demonstrated that CTRP6 was mainly distributed in the nuclei, apicolateral membranes, and cytoplasm of human submandibular glands (SMGs), serous cells of parotid glands, and ducts and apicolateral membranes of serous cells in rats and mice. CTRP6 inhibited the apoptosis rate and reversed the increased levels of cleaved caspase 3, caspase 8, caspase 9, and cytochrome C and the decreased Bcl-2 expression induced by tumor necrosis factor (TNF)-α in both SMG-C6 cells and cultured human SMG tissues. Microarray analysis identified 43 differentially expressed microRNAs (miRNAs) in the SMGs of nonobese diabetic mice. miR-34a-5p was selected due to its upregulation by TNF-α, which was abolished by CTRP6. The miR-34a-5p inhibitor promoted whereas the miR-34a-5p mimic suppressed the effects of CTRP6 on TNF-α-induced apoptosis. CTRP6 increased AMP-activated protein kinase (AMPK) phosphorylation and reversed TNF-α-induced SIRT1 downregulation in salivary cells. AraA, an AMPK inhibitor, reversed the effects of CTRP6 on TNF-α-induced alterations in the levels of SIRT1, miR-34a-5p, Bcl-2, and cleaved caspase 3 in vitro and ex vivo, whereas activating AMPK by AICAR reversed the decrease in SIRT1 expression and increase in miR-34a-5p expression induced by TNF-α. Inhibition of SIRT1 by EX527 suppressed the effects of CTRP6 on TNF-α-induced changes in miR-34a-5p and apoptosis-related proteins. Our findings indicate that salivary glands are novel sites for CTRP6 synthesis and secretion. CTRP6 protects acinar cells against TNF-α-induced apoptosis via AMPK/SIRT1-modulated miR-34a-5p expression.

Knockdown of CTRP6 reduces the deposition of intramuscular and subcutaneous fat in pigs via different signaling pathways

The regulation of porcine subcutaneous (SC) and intramuscular (IM) fat deposition significantly affects pork quality and the lean meat percentage of the carcass, respectively. The adipokine C1q/tumor necrosis factor-related protein 6 (CTRP6), plays a significant role in regulating animal fat deposition. The purpose of this study was to understand the effects of CTRP6 gene knockdown in IM and SC adipocytes by RNA-seq analysis. A total of 1830 and 2936 differentially expressed genes (DEGs) were identified in SC and IM adipocytes, respectively. 844 were down- and 2092 were upregulated in SC adipocytes, while 648 were down- and 1182 were upregulated in IM adipocytes. Furthermore, 1778 DEGs were detected only in SC adipocytes, 672 DEGs only in IM adipocytes, and 1158 DEGs in both types of adipocytes. GO analysis indicated that DEGs involved in adipocyte differentiation were significantly enriched in both SC and IM adipocytes following treatment with CTRP6-siRNA. Moreover, KEGG pathway enrichment analysis revealed differences of metabolic regulation between IM and SC adipocytes. With CTRP6-silencing, the signaling pathways related to Ras and arachidonic acid metabolism were significantly enriched in IM adipocytes, while four other signaling pathways, encompassing the TNF, MAPK, p53 and adipokine pathway were specifically enriched in SC adipocytes. Interestingly, the effect of CTRP6-siRNA treatment was attenuated by the specific Ras activator ML-097 in IM adipocytes, while the specific p53 activator SJ-172550 had the corresponding effect in SC adipocytes. Altogether, we suggest that CTRP6 may be a differential regulator of the development and metabolism of IM and SC adipose tissues.

C1QTNF6 as a Novel Diagnostic and Prognostic Biomarker for Clear Cell Renal Cell Carcinoma.

Clear cell renal cell carcinoma (ccRCC) is a highly aggressive disease and ∼30% of the patients are diagnosed at the metastatic stage. Even with new targeted therapies, the average progression-free survival and overall survival (OS) rates are dismal. Thus, biomarkers for early detection and progression could improve disease outcome. The role of C1q/tumor necrosis factor (C1QTNF) family in cancer is an emerging field of research. However, the biological function of C1q/tumor necrosis factor-related protein 6 (C1QTNF6) and its prognostic value in cancer are rarely reported. This study aimed to evaluate C1QTNF6 as a potential diagnostic and prognostic biomarker for ccRCC. In this study, we enrolled 993 ccRCC samples (data from our cohort, The Cancer Genome Atlas, and Gene Expression Omnibus) with C1QTNF6 expression to explore its role and mechanism in ccRCC. The diagnostic power of C1QTNF6 was determined by receiver operating characteristic curve analysis and its prognostic value was evaluated by Kaplan-Meier analysis and Cox regression models, respectively. In addition, the gene set enrichment analysis was performed to unveil the molecular mechanism of C1QTNF6 in ccRCC. We demonstrated that C1QTNF6 was overexpressed in ccRCC, and elevated C1QTNF6 expression correlated with clinical progression. Besides, C1QTNF6 served as a new diagnostic biomarker for renal cell carcinoma. Moreover, C1QTNF6 is an independent risk factor for OS in ccRCC patients. Furthermore, C1QTNF6-related signaling pathways activated in ccRCC are mainly enriched in cell cycle, epithelial-mesenchymal transition, and angiogenesis signaling pathways. Taken together, our results provided insights in understanding the potential role of C1QTNF6 in promoting tumor growth, invasion, and metastasis, and its use as a novel cancer diagnostic and prognostic biomarker for ccRCC.

Flavone of Hippophae (H-flavone) lowers atherosclerotic risk factors via upregulation of the adipokine C1q/tumor necrosis factor-related protein 6 (CTRP6) in macrophages

In this study, we examined the mechanism of Flavone of Hippophae (H-flavone) in regulating macrophage foaming and atherosclerosis (AS) plaque formation. H-flavone treatment increased the secretion of C1q/tumor necrosis factor-related proteins 6 (CTRP6) in Ox-LDL-treated mouse peripheral blood macrophage cells (PBMC) and significantly reduced the percentage of cholesteryl ester (CE) in PBMC. Additionally, H-flavone suppressed Ox-LDL-induced cell foaming and the production of inflammatory cytokines through upregulating CTPR6 expression. Next, we further validated the inhibitory effect of H-flavone on plaque formation and inflammation in a mouse AS model. A substantial reduction in the secretion of inflammatory cytokines was observed in apoE-/- mice by H-flavone. Immunohistochemistry and Oil Red O staining results showed that H-flavone suppressed macrophage infiltration and the development of AS plaque. These effects were more pronounced in early administration. Our results suggest that H-flavone effectively inhibits macrophage foaming, inflammation and vascular plaque formation by upregulating CTRP6 and may be used to reduce AS risk.

C1QTNF6 as a novel biomarker regulates cellular behaviors in A549 cells and exacerbates the outcome of lung adenocarcinoma patients.

C1q/tumor necrosis factor-related protein 6 (C1QTNF6) is a member of the CTRP family and implicated to cardiovascular diseases, inflammatory reaction, and adipogenesis. However, the function of C1QTNF6 in lung adenocarcinoma remains unknown. We downloaded the expression profiles of C1QTNF6 from TCGA database and Oncomine dataset in order to analyze the relationship between C1QTNF6 expression level and tumorigenesis by bioinformatics methods, such as chi-square test, Kaplan-Meier, and Cox regression analysis. In addition, we performed experiments to investigate the biological function of C1QTNF6 on cancer cells in vitro. The siRNA strategy was conducted to decrease the C1QTNF6 expression and then Cell Counting Kit-8 (CCK8) assay and wound-healing and transwell assays were to determine the proliferation, migration, and invasion. Western blot and qRT-PCR were used to confirm the expression levels. Based on the TCGA database and Oncomine dataset, we found that C1QTNF6 was over expressed in lung adenocarcinoma. The statistical data also showed that the high-regulated C1QTNF6 was related to poor prognosis in patients with lung adenocarcinoma. Moreover, the capabilities of proliferation, migration, and invasion were inhibited owing to the knockdown of C1QTNF6 in lung adenocarcinoma cells. And the phosphorylation of MEK and ERK was blocked by treated si-C1QTNF6 compared with the GAPDH. In conclusion, aberrant C1QTNF6 expression was implicated in terrible prognosis accompanying with the damage of relevant cell potential in lung adenocarcinoma. C1QTNF6 might be an independent predictor of prognosis in lung adenocarcinoma.

An adiponectin paralog protein, CTRP6 decreased the proliferation and invasion activity of oral squamous cell carcinoma cells: possible interaction with laminin receptor pathway.

C1q/tumor necrosis factor-related protein-6 (CTRP6), also known as CTRP6 is identified adiponectin paralog. Although recent studies have revealed that adiponectin has an inhibitory role in carcinogenesis, the role of CTRP6 in carcinogenesis remains unclear. In this study, we found that eukaryotic recombinant CTRP6 protein bound to the cell surface membrane of cultured oral squamous cell carcinoma cells by immunofluorescence staining. Screening of CTRP6 binding protein in expression library followed by co-immunoprecipitation assay revealed that CTRP6 bound to the precursor of laminin receptor. CTRP6 disturbed the binding of laminin to the laminin receptor. Interestingly, the eukaryotic recombinant CTRP6 protein significantly suppressed the proliferation and Matrigel invasion activity of oral squamous cell carcinoma SAS cells in a dose-dependent manner. Moreover, administration of CTRP6 significantly attenuated the growth of SAS cells in xenoplant mice model. Laminin and laminin receptor are known to be overexpressed and promote the tumor growth in OSCC. Combined together, the present findings suggest that CTRP6 could repress progression of oral squamous cell carcinoma cells, putatively through disrupting the laminin-laminin receptor axis.

Localization and expression of CTRP6 in ovary and its regulation by FSH in porcine granulosa cells

C1q/tumor necrosis factor-related protein 6 (CTRP6) is a newly identified adiponectin paralog with modulating effects on metabolism and inflammation. CTRP6 transcript is detected in human ovarian tissue. However, the expression pattern and function of CTRP6 on ovary have been rarely studied. In the present study, we preliminarily examined the structure feature and function of CTRP6 in porcine granulosa cells. The results indicated that the signaling peptide of CTRP6 was located at among positions 21 and 22, and the phosphorylation sites were at 15 (Ser), 4 (Thr) and 4 (Tyr), respectively. Meanwhile, CTRP6 was extremely homologous in livestock and chiropteran. The qPCR results showed that CTRP6 was moderately expressed in porcine follicle. Immunohistochemistry manifested that CTRP6 was presented in various types of ovarian cells. Immunofluorescence revealed that CTRP6 was located in cytoplasm in primary porcine granulosa cells. ELISA results showed that the concentration of CTRP6 in the follicular fluid was gradually decreased with the growth of antral follicle. In addition FSH increased CTRP6 expression levels in a time- and dose-dependent manner in primary porcine granulosa cells, while LH had no effect on CTRP6 basal gene expression, which suggesting CTRP6 is an FSH-responsive gene in porcine granulosa cells. Our findings imply that the CTRP6 may be a candidate gene to regulate folliculogenesis and reproductive performance.

CTRP6 inhibits PDGF-BB-induced vascular smooth muscle cell proliferation and migration

Vascular smooth muscle cell (VSMC) proliferation and migration play critical roles in the development and progression of atherosclerosis. C1q/tumor necrosis factor-related protein 6 (CTRP6), a member of CTRPs family, was involved in cardiovascular diseases, inflammatory reaction and adipogenesis. However, the role of CTRP6 in VSMCs remains largely unknown. The purpose of this study is to investigate the effects of CTRP6 on VSMC proliferation and migration and explore the possible mechanism. Our results indicated that CTRP6 expression was dramatically down-regulated in human atherosclerotic tissues and in cultured VSMCs stimulated by platelet-derived growth factor-BB (PDGF-BB). In addition, CTRP6 overexpression significantly inhibited the proliferation and migration of VSMCs exposed to PDGF-BB, as well as increased expression of α-SMA and SM22α in PDGF-BB-stimulated VSMCs. Furthermore, CTRP6 overexpression efficiently prevented the activation of PI3K/Akt/mTOR in VSMCs in response to PDGF-BB. In conclusion, these findings showed that CTRP6 inhibits PDGF-BB-induced VSMC proliferation and migration, at least in part, through suppressing the PI3K/Akt/mTOR signaling pathway. Therefore, CTRP6 may be a potential target for the treatment of atherosclerosis.

CTRP6 inhibits cell proliferation and ECM expression in rat mesangial cells cultured under TGF-β1

C1q/tumor necrosis factor-related protein 6 (CTRP6), a member of CTRPs family, was involved in fibrosis. However, the biological function of CTRP6 in renal fibrosis remains elusive. This study aimed to examine the role of CTRP6 in renal fibrosis and explore the possible mechanism. Our results demonstrated that the expression of CTRP6 was significantly downregulated in renal fibrotic tissues and TGF-β1-treated NRK-49F cells. In addition, overexpression of CTRP6 inhibited the proliferation, migration, and ECM expression in TGF-β1-treated NRK-49F cells. Furthermore, overexpression of CTRP6 attenuated TGF-β-induced phosphorylation of ERK1/2 in NRK-49F cells. The ERK1/2 inhibitor U0126 enhanced the inhibitory effects of CTRP6 overexpression on cell proliferation, migration and ECM expression in TGF-β1-stimulated NRK-49F cells. In conclusion, we have demonstrated that CTRP6 suppressed ECM expression in renal fibroblasts induced by TGF-β1 through the ERK signaling pathway. Therefore, CTRP6 may be a potential therapeutic target for the treatment of renal fibrosis.

CTRP6 Regulates Porcine Adipocyte Proliferation and Differentiation by the AdipoR1/MAPK Signaling Pathway.

Intramuscular fat (IMF) and subcutaneous fat (SCF), which are modulated by adipogenesis of intramuscular and subcutaneous adipocytes, play key roles in pork quality. C1q/tumor necrosis factor-related protein 6 (CTRP6), an adipokine, plays an important role in the differentiation of 3T3-L1 cells. However, the effect and regulatory mechanisms of CTRP6 on porcine adipogenesis, and whether CTRP6 has the same effect on intramuscular and subcutaneous adipocytes, are still unknown. Here, we found that CTRP6 significantly inhibited both adipocyte proliferation assessed by proliferative marker expression, but CTRP6 decreased the proliferation rate of intramuscular adipocytes (IM) to a greater extent than subcutaneous adipocytes (SC). Moreover, CTRP6 promoted the activity of the p38 signaling pathway during the proliferation of both cell types. Nevertheless, in subcutaneous adipocytes, CTRP6 also influenced the phosphorylation of extracellular regulated protein kinases1/2 (p-Erk1/2), but not in intramuscular adipocytes. Additionally, during the differentiation of intramuscular and subcutaneous adipocytes, CTRP6 increased adipogenic genes expression and the level of p-p38, while it decreased the activity of p-Erk1/2. Interestingly, the effect of CTRP6 shRNA or CTRP6 recombinant protein was attenuated by U0126 (a special p-Erk inhibitor) or SB203580 (a special p-p38 inhibitor) in adipocytes. By target gene prediction and experimental validation, we demonstrated that CTRP6 may be a target of miR-29a in porcine adipocytes. Moreover, AdipoR1was identified as a receptor of CTRP6 in intramuscular adipocytes, but not in subcutaneous adipocytes. On the basis of the above findings, we suggest that CTRP6 was the target gene of miR-29a, inhibited intramuscular and subcutaneous adipocyte proliferation, but promoted differentiation by the mitogen-activated protein kinase (MAPK) signaling pathway. These findings indicate that CTRP6 played an essentially regulatory role in fat development.

CTRP6 inhibits fibrogenesis in TGF-β1-stimulated human dermal fibroblasts

Skin fibrosis is characterized by excessive proliferation of fibroblasts and overproduction of extracellular matrix (ECM). C1q/tumor necrosis factor-related protein 6 (CTRP6), a member of CTRPs, has been involved in the development of cardiac fibrosis. However, the function and detailed regulatory mechanism of CTRP6 in skin fibrosis remain unclear. The aim of this study was to investigate the effect of CTRP6 on the activation of human dermal fibroblasts. Our results showed that CTRP6 was lowly expressed in scar tissues and transforming growth factor-β1 (TGF-β1)-treated dermal fibroblasts. CTRP6 overexpression significantly inhibited the proliferation of dermal fibroblasts, as well as suppressed the expression of ECM in TGF-β1-treated dermal fibroblasts. Furthermore, CTRP6 overexpression markedly inhibited TGF-β1-induced phosphorylation of Smad3 in dermal fibroblasts. In conclusion, the data reported here demonstrate that CTRP6 is able to inhibit the proliferation and ECM expression in human dermal fibroblasts through suppressing the TGF-β1/Smad3 signaling pathway. These findings suggest that CTRP6 may be a potential therapeutic target for the prevention of skin fibrosis.

C1q/tumor necrosis factor-related protein-6 attenuates post-infarct cardiac fibrosis by targeting RhoA/MRTF-A pathway and inhibiting myofibroblast differentiation.

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a newly identified adiponectin paralog with modulation effects on metabolism and inflammation. However, the cardiovascular function of CTRP6 remains unknown. This study aimed to determine its role in cardiac fibrosis and explore the possible mechanism. Myocardial infarction (MI) was induced by left anterior descending coronary artery ligation in rats. CTRP6 was mainly expressed in the cytoplasm of adult rat cardiomyocytes and significantly decreased in the border and infarct zones post-MI. Adenovirus-mediated CTRP6 delivery improved cardiac function, attenuated cardiac hypertrophy, alleviated cardiac fibrosis, and inhibited myofibroblast differentiation as well as the expression of collagen I, collagen III, and connective tissue growth factor post-MI. In cultured adult rat cardiac fibroblasts (CFs), exogenous or cardiomyocyte-secreted CTRP6 inhibited, whereas knockdown of CTRP6 facilitated transforming growth factor-β1 (TGF-β1)-induced expression of α-smooth muscle actin, smooth muscle 22α, and profibrotic molecules. CTRP6 had no effect on CFs proliferation but attenuated CFs migration induced by TGF-β1. CTRP6 increased the phosphorylation of AMP-activated protein kinase (AMPK) and Akt in CFs and post-MI hearts. Pretreatment with adenine 9-β-D-arabinofuranoside (AraA), an AMPK inhibitor, or LY294002, a phosphatidylinositol-3-kinase (PI3K) inhibitor, abolished the protective effect of CTRP6 on TGF-β1-induced profibrotic response. Furthermore, CTRP6 had no effect on TGF-β1-induced Smad3 phosphorylation and nuclear translocation, whereas significantly decreased TGF-β1-induced RhoA activation and myocardin-related transcription factor-A (MRTF-A) nuclear translocation, and these effects were blocked by AMPK or Akt inhibition. In conclusion, CTRP6 attenuates cardiac fibrosis via inhibiting myofibroblast differentiation. AMPK and Akt activation are responsible for the CTRP6-mediated anti-fibrotic effect by targeting RhoA/MRTF-A pathway.