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

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 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.

Osthole ameliorates early diabetic kidney damage by suppressing oxidative stress, inflammation and inhibiting TGF-β1/Smads signaling pathway

BACKGROUND

Osthole is a natural active ingredient extracted from the traditional Chinese medicine Cnidium monnieri. It has been demonstrated to have anti-inflammatory, anti-fibrotic, and anti-hyperglycemic properties. However, its effect on diabetic kidney disease (DKD) remains uncertain. This study aims to assess the preventive and therapeutic effects of osthole on DKD and investigate its underlying mechanisms.

METHODS

A streptozotocin/high-fat and high-sucrose diet induced Type 2 diabetic rat model was established. Metformin served as the positive drug control. Diabetic rats were treated with metformin or three different doses of osthole for 8 weeks. Throughout the treatment period, the progression of DKD was assessed by monitoring increases in urinary protein, serum creatinine, urea nitrogen, and uric acid, along with scrutinizing kidney pathology. Enzyme-linked immunosorbent assay (ELISA) was employed to detect inflammatory factors and oxidative stress levels. At the same time, immunohistochemical staining was utilized to evaluate changes in alpha-smooth muscle actin, fibronectin, E-cadherin, and apoptosis. The alterations in TGF-β1/Smads signaling pathway were ascertained through western blot and immunofluorescence. Furthermore, we constructed a high glucose-stimulated HBZY-1 cells model to uncover its molecular protective mechanism.

RESULTS

Osthole significantly reduced fasting blood glucose, insulin resistance, serum creatinine, uric acid, blood urea nitrogen, urinary protein excretion, and glomerular mesangial matrix deposition in diabetic rats. Additionally, significant improvements were observed in inflammation, oxidative stress, apoptosis, and fibrosis levels. The increase of ROS, apoptosis and hypertrophy in HBZY-1 cells induced by high glucose was reduced by osthole. Immunofluorescence and western blot results demonstrated that osthole down-regulated the TGF-β1/Smads signaling pathway and related protein expression.

CONCLUSION

Our findings indicate that osthole exhibits potential preventive and therapeutic effects on DKD. It deserves further investigation as a promising drug for preventing and treating DKD.

Characterizing the Dynamic Expression of C1q/TNF-α-Related Protein 6 (CTRP6) during Pregnancy in Humans and Mice with Gestational Diabetes Mellitus

AIM

C1q/TNF-related protein 6 (CTRP6) is a novel adipokine involved in insulin resistance. Thus, we aim to investigate the expression profile of CTRP6 in the plasma, adipose tissue and placenta of GDM patients and mice.

METHODS

Chinese Han pregnant women (GDM n = 9, control n = 10) with a scheduled caesarean section delivery were recruited. A number of high-fat diet (HFD) induced-pregnancy C57BL/6 mice were chosen as an animal model of GDM. Circulating levels of CTRP6 and adiponectin were examined by ELISA. CTRP6 expression in adipose tissue and placenta were detected by real-time qPCR and WB.

RESULT

Plasma CTRP6 levels were decreased during the first and second trimesters in mice, as well as the second and third trimesters in patients, while they were increased at delivery in GDM patients and mice. Plasma CTRP6 levels were significantly correlated with WBC, systolic pressure, diastolic pressure and fasting blood glucose. Moreover, CTRP6 mRNA expression in the subcutaneous (sWAT) and omental white adipose tissue (oWAT), as well as in the placenta, was significantly higher in GDM human patients at cesarean delivery. Furthermore, the mRNA expression of Ctrp6 was increased in the sWAT and visceral WAT (vWAT), whilst decreased in the interscapular brown adipose tissue (iBAT), of GDM mice at cesarean delivery.

CONCLUSION

Dynamically expressed CTRP6 may be served as a candidate target for treatment of GDM.

C1q/TNF-Related Proteins 1, 6 and 8 Are Involved in Corneal Epithelial Wound Closure by Targeting Relaxin Receptor RXFP1 In Vitro

Inadequate wound healing of ocular surface injuries can lead to permanent visual impairment. The relaxin ligand-receptor system has been demonstrated to promote corneal wound healing through increased cell migration and modulation of extracellular matrix formation. Recently, C1q/tumor necrosis factor-related protein (CTRP) 8 was identified as a novel interaction partner of relaxin receptor RXFP1. Additional data also suggest a role for CTRP1 and CTRP6 in RXFP1-mediated cAMP signaling. However, the role of CTRP1, CTRP6 and CTRP8 at the ocular surface remains unclear. In this study, we investigated the effects of CTRP1, CTRP6, and CTRP8 on epithelial ocular surface wound closure and their dependence on the RXFP1 receptor pathway. CTRP1, CTRP6, and CTRP8 expression was analyzed by RT-PCR and immunohistochemistry in human tissues and cell lines derived from the ocular surface and lacrimal apparatus. In vitro ocular surface wound modeling was performed using scratch assays. We analyzed the effects of recombinant CTRP1, CTRP6, and CTRP8 on cell proliferation and migration in human corneal and conjunctival epithelial cell lines. Dependence on RXFP1 signaling was established by inhibiting ligand binding to RXFP1 using a specific anti-RXFP1 antibody. We detected the expression of CTRP1, CTRP6, and CTRP8 in human tissue samples of the cornea, conjunctiva, meibomian gland, efferent tear ducts, and lacrimal gland, as well as in human corneal, conjunctival, and meibomian gland epithelial cell lines. Scratch assays revealed a dose-dependent increase in the closure rate of surface defects in human corneal epithelial cells after treatment with CTRP1, CTRP6, and CTRP8, but not in conjunctival epithelial cells. Inhibition of RXFP1 fully attenuated the effect of CTRP8 on the closure rate of surface defects in human corneal epithelial cells, whereas the CTRP1 and CTRP6 effects were not completely suppressed. Conclusions: Our findings demonstrate a novel role for CTRP1, CTRP6, and CTRP8 in corneal epithelial wound closure and suggest an involvement of the relaxin receptor RXFP1 signaling pathway. This could be a first step toward new approaches for pharmacological and therapeutic intervention.

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.

Extracellular matrix and synapse formation

The extracellular matrix (ECM) is a complex molecular network distributed throughout the extracellular space of different tissues as well as the neuronal system. Previous studies have identified various ECM components that play important roles in neuronal maturation and signal transduction. ECM components are reported to be involved in neurogenesis, neuronal migration, and axonal growth by interacting or binding to specific receptors. In addition, the ECM is found to regulate synapse formation, the stability of the synaptic structure, and synaptic plasticity. Here, we mainly reviewed the effects of various ECM components on synapse formation and briefly described the related diseases caused by the abnormality of several ECM components.

Effects of Ziyin Qianyang Formula on Renal Fibrosis through the TGF-β1/Smads Signaling Pathway in Spontaneously Hypertensive Rats

OBJECTIVE

The aim of the study is to explore the effects and mechanisms of action of Ziyin Qianyang Formula (ZYQYF) on renal fibrosis in spontaneously hypertensive rats (SHRs).

METHODS

Forty SHRs were randomly divided into a model group, Ziyin Qianyang Formula regular-dose and high-dose groups (ZYQYF-R, 20 g/kg; ZYQYF-H, 40 g/kg), and a western medicine group (enalapril 10 mg/kg), and 10 Sprague-Dawley rats were selected as the normal group. The rats received continuous gavage administration for 6 weeks and systolic blood pressure (SBP) measurements were obtained every fortnight. The serum levels of urea, serum creatinine (sCr), and uric acid (UA) were measured; the pathological morphology and collagen content of the kidneys were observed by hematoxylin-eosin (HE) and Masson staining; and the serum Ang II level was measured by an enzyme-linked immunosorbent assay (ELISA). Transforming growth factor (TGF)-β1, Smad-2, Smad-3, and Smad-7 protein and mRNA expressions in kidney tissues was evaluated by western blotting and reverse transcription-polymerase chain reaction.

RESULTS

The ZYQYF-H group showed significantly a lower renal weight and renal weight/body weight than the model group. The enalapril and ZYQYF-H groups showed significantly lower SBP than other groups after 6 weeks of administration. The ZYQYF-H group showed better improvement than the ZYQYF-R and enalapril groups in glomerular and tubular morphology and better reductions in inflammatory cell infiltration and collagen volumetric fraction. The ZYQYF-H group also showed better reductions in serum UA and Ang II levels; collagen-I, collagen-III, and p-Smad2/Smad-2 protein expression; and Smad-2 mRNA expression and a better increase in Smad-7 protein and mRNA expression than the enalapril group. Besides, the degree of renal function and fibrosis improvement was positively correlated with the dose of ZYQYF.

CONCLUSION

ZYQYF can significantly reduce SHR blood pressure, protect renal function and structure, and improve renal fibrosis by regulating Smad proteins through TGF-β1.

CTRP6 suppresses neutrophil extracellular traps formation to ameliorate sepsis-induced lung injury through inactivation of ERK pathway

BACKGROUND

Septic lung injury is associated with excessive neutrophil activation, while neutrophil extracellular traps formation contributes to inflammatory lung injury in sepsis. C1q/tumor necrosis factor-related protein-6 (CTRP6) is a paralog of adiponectin and exerts anti- inflammatory and antioxidant properties. The role of CTRP6 in sepsis-associated inflammatory lung injury was investigated in this study.

METHODS

Mice were injected with lipopolysaccharides (LPS) intraperitoneally to establish the mouse sepsis model. They were first tail-vein injected with adenovirus-mediated overexpression CTRP6 (Ad-CTRP6) and then subjected to the LPS injection. Pathological changes in lungs were detected by hematoxylin and eosin staining. Inflammation cytokine levels in bronchoalveolar lavage fluid were assessed by qRT-PCR and ELISA. Flow cytometry was used to detect the number of neutrophils in bronchoalveolar lavage fluid, and immunofluorescence was performed to assess neutrophil extracellular traps.

RESULTS

Lipopolysaccharides induced pulmonary congestion, interstitial edema, and alveolar wall thickening in the lungs, as well as upregulated lung histology score and wet/dry weight ratio. CTRP6 was reduced in lung tissues of septic mice. Injection with Ad-CTRP6 ameliorated extensive histopathological changes in LPS-induced mice and decreased lung histology score and wet/dry weight ratio. Overexpression of CTRP6 reduced the levels of TNF-α, IL-6, and IL-1β in septic mice. Injection with Ad-CTRP6 also decreased the number of neutrophils and downregulated Cit-H3 and myeloperoxidase polymers in septic mice. Protein expression of p-ERK in septic mice was reduced by overexpression of CTRP6.

CONCLUSION

CTRP6 attenuated septic lung injury, exerted anti-inflammatory effect, and suppressed neutrophil extracellular traps formation against sepsis through inactivation of extracellular signal-regulated kinase signaling.

TGF-β1 and Mechanical-Stretch Induction of Lysyl-Oxidase and Matrix-Metalloproteinase Expression in Synovial Fibroblasts Requires NF-κB Pathways

The imbalance in the expression of matrix metalloproteinases (MMPs) and lysyl oxidases (LOXs) in synovial fibroblasts (SFs) caused by mechanical injury and inflammatory response prevents injured anterior cruciate ligaments (ACLs) from self-healing. However, research on the effect of growth factors on SFs on regulating the microenvironment is limited. In this study, mechanical injury and exogenous transform growth factor-β1 (TGF-β1) were employed to mimic a joint-cavity microenvironment with ACL trauma. The function of the NF-κB transcription factor was further studied. The study found that the gene expression of LOXs (except LOXL-1), MMP-1, -2, and -3 in SFs was promoted by the combination of injurious mechanical stretching and TGF-β1 and that the upregulation of MMPs was higher than that of LOXs. In addition, MMP-2 activity induced by the combination of injurious stretch and TGF-β1 was inhibited by NF-κB inhibitors such as Bay11-7082 and Bay11-7085. The findings concluded that the synovium was an important regulator of the knee joint-cavity microenvironment after ACL injury and that the NF-κB pathway mediated the regulation of MMP-2 in SFs via mechanical factors and TGF-β1.

Tamsulosin attenuates high glucose- induced injury in glomerular endothelial cells

Diabetic nephropathy (DN) is a common complication of diabetes. Tamsulosin is a selective α1-AR antagonist. α1-AR is expressed widely in kidney tissues and has displayed its various physiological functions. However, whether Tamsulosin has affects DN is unknown. To our knowledge, this is the first time it has been examined whether Tamsulosin possesses a beneficial effect in high glucose-challenged glomerular endothelial cells (GECs). Firstly, we found that Tamsulosin reduced high glucose-induced expressions of TNF-α, IL-6, and IL-8. Secondly, Tamsulosin alleviated high glucose-induced expressions of MMP-2 and MMP-9. Thirdly, Tamsulosin inhibited the expressions of VCAM-1 and ICAM-1. Importantly, our results indicate that Tamsulosin inhibited high glucose-induced expressions of fibrosis factors such as Col-1 and TGF-β1. Additionally, we found that Tamsulosin ameliorated oxidative stress via reducing the generation of ROS and preventing the activation of p38. Mechanistically, we found that Tamsulosin attenuated high glucose-induced activation of NF-κB. Based on these findings, we conclude that Tamsulosin could attenuate high glucose-induced injury in GECs through alleviating oxidative stress and inflammatory response.

TGF-β1 Signaling: Immune Dynamics of Chronic Kidney Diseases

Chronic kidney disease (CKD) is a major cause of morbidity and mortality worldwide, imposing a great burden on the healthcare system. Regrettably, effective CKD therapeutic strategies are yet available due to their elusive pathogenic mechanisms. CKD is featured by progressive inflammation and fibrosis associated with immune cell dysfunction, leading to the formation of an inflammatory microenvironment, which ultimately exacerbating renal fibrosis. Transforming growth factor β1 (TGF-β1) is an indispensable immunoregulator promoting CKD progression by controlling the activation, proliferation, and apoptosis of immunocytes via both canonical and non-canonical pathways. More importantly, recent studies have uncovered a new mechanism of TGF-β1 for de novo generation of myofibroblast via macrophage-myofibroblast transition (MMT). This review will update the versatile roles of TGF-β signaling in the dynamics of renal immunity, a better understanding may facilitate the discovery of novel therapeutic strategies against CKD.

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.

Anti-fibrotic properties of an adiponectin paralog protein, C1q/TNF-related protein 6 (CTRP6), in diffuse gastric adenocarcinoma

Patients with advanced gastric cancer, especially diffuse-type gastric cancer, which is often accompanied by stromal fibrosis, commonly exhibit a poor prognosis. This study was designed to unravel the potential roles of C1q/TNF-related protein 6 (CTRP6) in the fibrotic cancer microenvironment of diffuse-type gastric adenocarcinoma. A total of 49 diffuse-type gastric cancer samples were evaluated in this study, and 23 of these samples exhibited focal CTRP6 immunoreactivity. CTRP6 immunoreactivity was found to be correlated with favorable survival outcomes, in terms of both overall and relapse-free survival rates, but this trend did not reach significance (P = 0.15). By contrast, CTRP6 immunoreactivity was significantly correlated with relapse-free survival rates in patients with diffuse-type gastric cancer at a distal site (P = 0.028). Notably, most gastric cancer cells at the cancer invasive front were CTRP6 negative, especially in areas of robust fibrosis. Double immunohistochemical staining demonstrated an inverse expression profile for CTRP6 and the activated fibroblast marker alpha smooth muscle actin (α-sma) in stromal and gastric cancer cells at the cancer invasion front. The addition of recombinant CTRP6 protein attenuated the TGF-β-induced α-sma expression in cultured human fibroblasts but did not alter the proliferation rate or Matrigel-invasion activity of the cultured gastric cancer cells. In addition, CTRP6 did not affect the viability of normal human gastric epithelial cells. This study suggests that CTRP6 may have potential application in combating stromal fibrosis in diffuse-type gastric cancers.

Role of the CTRP6/AMPK pathway in kidney fibrosis through the promotion of fatty acid oxidation

CTRP6, a newly identified adiponectin analogue, has been shown to be involved in inflammation, diabetes and cardiovascular diseases. Recently, increasing evidence has shown that CTRP6 plays a critical role in fibrotic diseases, such as myocardial fibrosis and skin fibrosis. FAO, an important energy source for kidney proximal tubular cells, also participates in the process of fibrosis. Therefore, our study aimed to investigate the effect of CTRP6 on mediating FAO in kidney fibrosis and the underlying associated mechanism. Firstly, the activity of CTRP6 and the key enzymes of FAO (CPT1A, ACOX1) were tested in vivo and vitro. Next, the regulatory effect of CTRP6/AMPK on FAO was accessed in animal models and in cell lines. Additionally, we explored the effect of exogenous recombinant CTRP6 on renal tubular epithelial cell differentiation. Decreased CTRP6 and p-AMPK were detected in UUO-induced kidney fibrosis and in TGF-β1-treated HK-2 cells. We also observed that defective FAO occurred during kidney fibrosis. Moreover, the human CTRP6 peptide could inhibit the ECM deposition and promote the phosphorylation of AMPK by promoting FAO. However, the inhibitory effects of CTRP6 on TGF-β1-induced ECM deposition and the protective effects of CTRP6 on FAO could be abolished by compound C, a selective inhibitor of AMPK. Compound C also reversed the CTRP6-mediated upregulation of p-AMPK. The mediation of FAO by CTRP6 plays a key role in kidney fibrosis by regulating TGF-β1-induced renal tubular epithelial cell differentiation by promoting FAO, which is mediated via AMPK activation.

Knockdown of CTRP6 inhibits high glucose-induced oxidative stress, inflammation and extracellular matrix accumulation in mesangial cells through regulating the Akt/NF-κB pathway

C1qTNF-related protein 6 (CTRP6) is a member of the CTRP family and exerts a key role in the progression of diabetes mellitus. However, the role of CTRP6 in diabetic nephropathy remains unknown. The present study was designed to examine the roles of CTRP6 in diabetic nephropathy and explore the potential molecular mechanisms. Our results showed that the expression level of CTRP6 was significantly increased in high glucose (HG)-stimulated glomerular mesangial cells (MCs). The following loss/gain-of-function assays demonstrated that CTRP6 knockdown significantly inhibited HG-induced reactive oxygen species (ROS) production in MCs. CTRP6 knockdown caused significant decreases in tumour necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 production levels in HG-induced MCs. Moreover, knockdown of CTRP6 inhibited HG-stimulated extracellular matrix (ECM) accumulation in MCs characterized by decreased expression and production levels of fibronectin (FN) and collagen IV (Col IV). Furthermore, CTRP6 knockdown suppressed HG-induced the activation of Akt/NF-κB pathway in MCs, while overexpression of CTRP6 exhibited the opposite effects. Treatment with LY294002, an inhibitor of Akt, reversed the induction effects of CTRP6 overexpression on ROS production, inflammation and ECM accumulation in MCs. In conclusion, these findings demonstrated that CTRP6 knockdown inhibits HG-induced ROS production, inflammation and ECM accumulation in MCs, which were mediated by the inactivation of the Akt/NF-κB pathway. The roles of CTRP6 in diabetic nephropathy provided evidence for its therapeutic potential for the treatment of diabetic nephropathy.

Rhubarb and Astragalus Capsule Attenuates Renal Interstitial Fibrosis in Rats with Unilateral Ureteral Obstruction by Alleviating Apoptosis through Regulating Transforming Growth Factor beta1 (TGF-β1)/p38 Mitogen-Activated Protein Kinases (p38 MAPK) Pathway

BACKGROUND Rhubarb and astragalus capsule (RAC) has been used in the clinical treatment of chronic kidney disease for decades. However, the mechanism of RAC has not been fully elucidated. This study aimed to investigate the protective effect and mechanisms of RAC on unilateral ureteral obstruction (UUO)-induced renal interstitial fibrosis. MATERIAL AND METHODS The main components of RAC are detected by high-performance liquid phase (HPLC). A rat model of UUO was established, and a subset of rats underwent treatment with RAC. Renal function and renal pathology were examined at 14 days and 21 days after the UUO operation. Renal cell apoptosis was detected by TUNEL staining. The levels of Bcl-2 and Bax in the kidney were examined by western blotting, and the levels of collagen I, alpha-SMA, transforming growth factor (TGF)-ß1, and p38 MAPK in the kidneys were detected by immunohistochemistry. RESULTS High-performance liquid phase chromatography showed that RAC contained 1.12 mg/g aloe-emodin, 2.25 mg/g rhein, 1.75 mg/g emodin, and 4.50 mg/g chrysophanol. Administration of RAC significantly decreased the levels of urinary N-acetyl-ß-D-glucosaminidase (NAG), serum blood urea nitrogen (BUN), and creatinine (Scr) and also reduced renal tissue damages and interstitial fibrosis induced by UUO in rats. Moreover, the increased levels of collagen I, alpha-SMA, TGF-ß1, p38 MAPK, and the Bax/Bcl-2 ratio, as well as cell apoptosis in the kidney, were induced by UUO, and were all found deceased by RAC treatment. CONCLUSIONS RAC can improve the renal interstitial fibrosis induced by UUO, and the mechanism may be related to inhibition of renal tubular cell apoptosis via TGF-ß1/p38 MAPK pathway.

Circulating levels of C1q/TNF-α-related protein 6 (CTRP6) in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders affecting females of reproductive age. It has been associated with cardiometabolic disorders including diabetes mellitus and cardiovascular disorders, and increases the risk of developing fecundity pathologies including recurrent pregnancy loss (RPL) and infertility. C1q/tumor necrosis factor-α-related protein-6 (CTRP6) is a novel adipokine involved in glucose and lipid metabolism, host inflammation, and organogenesis. In the present study, we aimed to determine the association of serum CTRP6 levels with some components of metabolic syndrome in PCOS patients (infertile PCOS [inf-PCOS] and PCOS-RPL). This case-control study included 120 PCOS patients (60 inf-PCOS and 60 PCOS-RPL) and 60 healthy controls. Serum high-sensitivity C-reactive protein (hs-CRP) and homocysteine were measured using commercial kits, while adiponectin and CTRP6 levels were assessed using ELISA technique. Inf-PCOS and PCOS-RPL individuals had higher levels of serum CTRP6 than controls (546.15 ± 125.02 ng/ml and 534.04 ± 144.19 ng/ml vs. 440.16 ± 159.24 ng/ml; both p < .001). Moreover, serum adiponectin levels were significantly reduced, while fasting insulin, homeostasis model assessment of insulin resistance, free testosterone, and hs-CRP levels were significantly elevated in PCOS group, when compared with controls. Furthermore, serum CTRP6 positively associated with body mass index in all subjects. It showed an inverse correlation with adiponectin in PCOS group and subgroups. However, it had a direct association with hs-CRP in PCOS group and inf-PCOS subgroup, but not PCOS-RPL subgroup. These findings unravel a probable role of CTRP6 in PCOS pathogenesis, which poses a possibility to be a good diagnostic target. However, further investigation is needed.

C1q/TNF-related protein 6 (CTRP6) attenuates renal ischaemia-reperfusion injury through the activation of PI3K/Akt signalling pathway

C1q/TNF-related protein 6 (CTRP6) is a member of the CTRP family that has been reported to exhibit a nephroprotective effect. However, the role of CTRP6 in renal ischaemia/reperfusion (I/R) injury (IRI) remains unclear. In the present study, we aimed to explore the protective effect of CTRP6 in renal IRI and the potential mechanism. We found that CTRP6 expression was markedly decreased in the kidneys of mice subjected to I/R and HK-2 cells in response to hypoxia/reoxygenation (H/R) stimulation. Recombinant CTRP6 protein protected against renal I/R injury by the reduction of blood urea nitrogen (BUN) and creatinine levels. The increased production of ROS and malondialdehyde (MDA), as well the decreased activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) caused by H/R induction were mitigated by CTRP6 in HK-2 cells. The caspase-3 activity and apoptotic rate were both decreased in CTRP6-overexpressing HK-2 cells. In addition, we also found that knockdown of CTRP6 aggravated H/R-caused oxidative stress and cell apoptosis in HK-2 cells. Moreover, CTRP6 overexpression enhanced the H/R-stimulated activation of PI3K/Akt pathway in HK-2 cells. Inhibition of PI3K reversed the nephroprotective effects of CTRP6 in HK-2 cells. Taken together, CTRP6 exerted protective effects against H/R-caused oxidative injury in HK-2 cells via activating the PI3K/Akt pathway.

Salusin-α mitigates diabetic nephropathy via inhibition of the Akt/mTORC1/p70S6K signaling pathway in diabetic rats

Salusin-α is a bioactive peptide that protects against atherosclerosis and hepatosteatosis. Serum salusin-α level is declined in patients suffering with renal insufficiency. However, it is still undefined whether salusin-α plays a role in diabetic nephropathy. The present study was designed to investigate the potential roles of salusin-α in diabetic renal disease. Herein, we demonstrated that the salusin-α levels in both plasma and kidney tissues from diabetic rats were obviously downregulated. Exogenous administration of salusin-α eliminated the typical characteristics of diabetic nephropathy. Salusin-α treatment decreased renal fibrosis, which was related with reduced epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells. Injection of salusin-α suppressed the production of reactive oxygen species (ROS) via attenuation of NADPH oxidase subunits protein expressions and recovery of the antioxidant system. Mechanistically, the activated Akt/mTORC1/p70S6K signaling pathway in diabetic nephropathy was counteracted by salusin-α treatment. Our results demonstrated that salusin-α exerted protective effect against diabetic nephropathy via reduced oxidative stress and fibrosis, dependent on inactivation of the Akt/mTORC1/p70S6K signaling cascade. Salusin-α may be considered as a promising target for the treatment of diabetic nephropathy.

Inhibition of CTRP6 prevented survival and migration in hepatocellular carcinoma through inactivating the AKT signaling pathway

C1qTNF-related proteins (CTRPs) are a member of the adiponectin paralogs family, which are implicated in regulation of various biological processes. Recently, CTRP6 was found upregulated in human hepatocellular carcinomas (HCC). However, the specific roles and molecular mechanisms of CTRP6 in HCC remain unclear. Here, we investigated the effects of CTRP6 on the vitality, apoptosis, migration, and invasion of HCC cells. Firstly, we measured the levels of CTRP6 in HCC tissues and cell lines. Our results showed that CTRP6 was markedly upregulated in HCC tissues and Hep3B cells. Then, the CTRP6 siRNA was transfected into Hep3B cells. Cell counting kit-8 (CCK-8) assay and flow cytometry analysis revealed that silencing CTRP6-induced cell viability inhibition, and apoptosis. The wound-healing and transwell assay showed that CTRP6 deficiency suppressed the migration and invasion of Hep3B cells. Meanwhile, the AKT phosphorylation level was reduced by CTRP6 silencing. Next, Hep3B cells were pretreated with insulin-like growth factor-1 (IGF-1) (an activator of AKT), and then transfected with CTRP6 siRNA, and the cell vitality, apoptosis, migration, and invasion were measured again. We found that all these alterations caused by CTRP6 inhibition could be reversed by IGF-1 treatment. Taken together, CTRP6 suppression blocked cell survival, migration, and invasion and promoted cell apoptosis through inactivating the AKT signaling pathway. Our findings present a novel potential molecular target for HCC therapy.