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.

Regulation of circulating CTRP-2/CTRP-9 and GDF-8/GDF-15 by intralipids and insulin in healthy control and polycystic ovary syndrome women following chronic exercise training.

BACKGROUND: Polycystic ovary syndrome (PCOS) is associated with obesity, diabetes, and insulin resistance. The circulating C1Q/TNF-related proteins (CTRP-2, CTRP-9) and growth differentiation factors (GDF-8, GDF-15) contribute to glucose and lipid homeostasis. The effects of intralipids and insulin infusion on CTRP-2, CTRP-9, GDF-8 and GDF-15 in PCOS and control subjects before and after chronic exercise training were examined. METHODS: Ten PCOS and nine healthy subjects were studied at baseline status and after moderate-intensity chronic exercise training (1 h exercise, 3 times per week, 8 weeks). All participants were infused with 1.5 mL/min of saline or intralipids (20%) for 5 h, and during the last 2 h of saline or intralipids infusion hyperinsulinemic-euglycemic clamp (HIEC) was performed. CTRP-2, CTRP-9, GDF-8 and GDF-15 levels were measured at 0, 3 and 5 h. RESULTS: Intralipids dramatically increased CTRP-2 levels in PCOS (P = 0.02) and control (P = 0.004) subjects, which was not affected by insulin infusion or by exercise. Intralipids alone had no effects on CTRP-9, GDF-8, or GDF-15. Insulin increased the levels of GDF-15 in control subjects (P = 0.05) during the saline study and in PCOS subjects (P = 0.04) during the intralipid infusion. Insulin suppressed CTRP9 levels during the intralipid study in both PCOS (P = 0.04) and control (P = 0.01) subjects. Exercise significantly reduced fasting GDF-8 levels in PCOS (P = 0.03) and control (P = 0.04) subjects; however, intralipids infusion after chronic exercise training increased GDF-8 levels in both PCOS (P = 0.003) and control (P = 0.05) subjects and insulin infusion during intralipid infusion reduced the rise of GDF-8 levels. CONCLUSION: This study showed that exogenous lipids modulate CTRP-2, which might have a physiological role in lipid metabolism. Since chronic exercise training reduced fasting GDF-8 levels; GDF-8 might have a role in humoral adaptation to exercise. GDF-15 and CTRP-9 levels are responsive to insulin, and thus they may play a role in insulin responses.

Low Complement C1q/TNF-related Protein-13 Levels are Associated with Childhood Obesity But not Binge Eating Disorder

Objective: C1q/tumor necrosis factor-related proteins (CTRPs) are recently described members of the adipokine family. CTRP-13, a new member of this family, has been shown to increase insulin sensitivity and had an anorexigenic effect on food intake in experimental studies. The aim was to investigate serum CTRP-13 levels in children with obesity, and its relationship with other adipokines, metabolic parameters, or binge eating disorder (BED). Methods: A cross-sectional study was conducted with 105 pubertal children attending a single center. Clinical (metabolic syndrome, BED) and biochemical (glucose, insulin, lipids, leptin, adiponectin, CTRP-13 levels) parameters were assessed. Results: Sixty children with obesity [24 males (40%); median age 14.7 (13.0-16.4) years] and 45 healthy controls [15 males (33.3%); median age 15.2 (14.1-16.5) years] were included. Serum adiponectin and CTRP-13 levels were significantly lower in children with obesity than controls (7.1 vs 20.1 µg/mL, p<0.001; 64.7 vs 103.8 ng/mL, p<0.001, respectively). CTRP-13 levels correlated negatively with body mass index (Spearman rho=-0.230, p=0.018) and positively with high-density lipoprotein-cholesterol levels (Spearman rho=0.218, p=0.026). There was no significant difference in serum CTRP-13 concentrations in terms of the presence of metabolic syndrome or BED. Conclusion: Childhood obesity seems to be causing dysregulation in adipokine production and function, including the down-regulation of CTRP-13. The positive correlation between CTRP-13 and HDL-C levels suggested a possible effect of this adipokine on lipid metabolism. Thus CTRP-13 may be a novel biomarker for dyslipidemia in childhood obesity.

The C1q/TNF-related proteins (CTRPs) in pathogenesis of obesity-related metabolic disorders: Focus on type 2 diabetes and cardiovascular diseases.

The growing evidence has been tried to explain and characterize C1q/TNF- related proteins (CTRPs) family as the potential diagnostic or therapeutic targets of obesity-related metabolic disorders such as insulin resistance, type 2 diabetes (T2D), and cardiovascular disorders. However, the underlying mechanism is still obscure. Unraveling the signaling pathways downstream of CTRP family members is of great interest and could certainly be beneficial for finding new insights into therapeutic strategies for improving metabolic abnormalities. This review focused on the role of CTRP members in the initiation and development of obesity-related metabolic disorders with a focus on T2D and cardiovascular diseases. Here we summarize and discuss the role of CTRPs in the regulation of insulin signaling, inflammatory pathways, and energy metabolism, and other signaling pathways pertinent to the pathogenesis of T2D and cardiovascular diseases. We also review available clinical studies to better elucidate the roles of these potential molecules in the initiation and development of the afore-mentioned disorders.

Clinical value of monitoring serum CTRP3 and Lp-PLA2 levels in patients with coronary heart disease / 中华检验医学杂志

Objective:To investigate the clinical value of monitoring serum complement C1q/tumor necrosis factors-associated protein 3 (CTRP3) and lipoprotein-associated phospholipase A2(Lp-PLA2) levels in patients with coronary heart disease, especially patients with acute myocardial infarction (AMI).Methods:This case-control study included 99 patients with angina pectoris aged (60.4±10.4) years, 105 patients with AMI aged (61.7±14.3) years, and 60 healthy individuals aged (43.6±9.5) years. Serum CTRP3 was detected by ELISA, and Lp-PLA2 was detected by automatic biochemical analyzer. Logistic regression analysis was performed to determine the correlation between CTRP3, Lp-PLA2 in angina pectoris and AMI patients. The diagnostic efficiency of each index was analyzed by receiver operating characteristic (ROC) curve.Results:Serum Lp-PLA2 was significantly higher in AMI group than in angina pectoris group ([313.1±68.1] U/L vs [205.8±71.4] U/L, P<0.001), while CTRP3 was significantly lower in AMI group than in angina pectoris group ([64.2±18.5] μg/L vs [84.8±25.0] μg/L, P<0.001). Logistic regression showed that serum CTRP3 was negatively correlated with AMI ( OR=0.964, 95% CI 0.935-0.993, P=0.019), and Lp-PLA2 was positively correlated with AMI ( OR=1.020, 95% CI 1.008-1.032, P=0.001). ROC analysis showed that the AUC (95% CI) of AMI diagnosed by CTRP3 was 0.753 (0.685-0.821), P<0.001; the AUC (95% CI) of AMI diagnosed by Lp-PLA2 was 0.884 (0.833-0.935), P<0.001; the AUC (95% CI) of diagnosis efficacy by combined indices was 0.910 (0.870-0.950), P<0.001. Conclusions:Lower serum CTRP3 and higher serum Lp-PLA2 levels are associated with increased risk for AMI. Combined detection of both indices can improve the diagnostic efficacy of AMI.

RXFP1 is Targeted by Complement C1q Tumor Necrosis Factor-Related Factor 8 in Brain Cancer.

The relaxin-like RXFP1 ligand-receptor system has important functions in tumor growth and tissue invasion. Recently, we have identified the secreted protein, CTRP8, a member of the C1q/tumor necrosis factor-related protein (CTRP) family, as a novel ligand of the relaxin receptor, RXFP1, with functions in brain cancer. Here, we review the role of CTRP members in cancers cells with particular emphasis on CTRP8 in glioblastoma.