C1q/TNF-related Protein-3 Research Articles

Serum levels of CTRP3 in diabetic nephropathy and its relationship with insulin resistance and kidney function.

BackgroundC1q TNF related protein 3 (CTRP3) is an adipokine secreted from adipose tissue. Previous studies have suggested that CTRP3 improves insulin sensitivity and reduces inflammation. Human studies have evaluated circulating levels of this adipokine in patients with diabetes mellitus (DM), diabetic retinopathy, metabolic syndrome, and coronary artery diseases. However, circulating levels of this adipokine in patients with diabetic nephropathy have not been evaluated. The present study aimed to assess serum levels of CTRP3 in patients with type 2 diabetes mellitus (T2DM) and diabetic nephropathy (T2DM-NP) and its relationship with metabolic and inflammatory markers.MethodsThis cross-sectional study was performed on 55 controls, 54 patients with T2DM, and 55 patients with T2DM-NP. Serum levels of CTRP3, adiponectin, TNF-α, and IL-6 were measured by ELISA technique.ResultsSerum levels of CTRP3 were significantly lower in patients with T2DM (257.61 ± 69.79 ng/mL, p < 0.001) and T2DM-NP (222.03 ± 51.99 ng/mL, p < 0.001) compared to controls (328.17 ± 80.73 ng/mL), and those with T2DM-NP compared to T2DM group. CTRP3 was independently associated with HOMA-IR (r = -0.327, p < 0.05) and adiponectin (r = 0.436, p < 0.01) in T2DM group. In T2DM-NP patients, CTRP3 independently was associated with eGFR (r = 0.428, p < 0.01) and HOMA-IR (r = -0.436, p < 0.01). Furthermore, CTRP3 revealed a ability to differentiate T2DM-NP patients from controls (area under curve (95% confidence interval): 0.881 (0.820–0.943) and p < 0.001).ConclusionDecreased serum levels of CTRP3 in patients with T2DM and diabetic nephropathy and its association with pathologic mechanism in these patients suggested a possible role for CTRP3 in pathogenesis of diabetic nephropathy; nevertheless, further studies are required in this regard.

Correlation of C1q/TNF-Related Protein-3 with Cardiac Autonomic Tone and Metabolic Parameters in Obesity.

ObjectivesThe current study aimed at investigating the correlation of circulating levels of serum C1q/TNF-related protein-3 (CTRP3) with cardiac autonomic functions and metabolic parameters in obesity.MethodsThirty drug naïve subjects newly diagnosed with obesity and body mass index (BMI) 25 - 35 kg/m2 of both genders aged 19 - 40 years, with no associated comorbidity were recruited as cases. Same number of age, gender and socioeconomic status matched subjects with BMI 19 - 23 kg/m2 were taken as controls. Autonomic function test results including heart rate variability (HRV) were recorded in both groups. Serum metabolic parameters -CTRP3, leptin, adiponectin, insulin, blood glucose, glycated hemoglobin (HbA1c), aspartate aminotransferase (AST), alanine aminotransferase (ALT), total cholesterol, low-density lipoprotein (LDL)-cholesterol, high-density lipoprotein (HDL)-cholesterol, and triglycerides were also determined and compared between the groups.ResultsSignificantly lower circulating levels of CTRP3 (P ≤ 0.001) and adiponectin (P = 0.025), and significantly higher mean of BMI (P < 0.001), fasting blood glucose (P < 0.001), LDL-cholesterol (P < 0.05), serum triglycerides (P < 0.001), insulin (P = 0.003), HOMA-IR (homeostasis model assessment of insulin resistance) (P < 0.001), and leptin (P = 0.043) were observed in the group with obesity compared to the controls. CTRP3 levels inversely correlated with serum triglyceride (r = -0.09, P < 0.001), atherogenic index (r = -0.37, P = 0.04), leptin (r = -0.39, P = 0.02), and positively with adiponectin (r = 0.42, P = 0.02) in the group with obesity. Significant reduction in the results of parasympathetic autonomic function tests (pNN50, RMSSD, excitation: inhibition (E:I) ratio, 30:15 ratio, and Valsalva ratio) and an increase in sympathovagal balance (low frequency to high frequency (LF:HF) ratio) was also observed (P < 0.05). CTRP3 levels were also positively correlated with parasympathetic indices (pNN50: r = 0.17, P < 0.05); 30:15 ratio: (r = 0.62, P < 0.01), and inversely correlated with LF: HF ratio (r = -0.35, P < 0.01) in the group with obesity.ConclusionsHigher circulating levels of CTRP3 promoted a favorable autonomic and metabolic profile in obesity. Hence, CTRP3 may be considered as a potential novel biomarker to facilitate the prognosis of obesity and its comorbidities.

The sex specific effect of alcohol consumption on circulating levels of CTRP3.

The goal of this project was to establish the effect of alcohol consumption on the circulating levels of the adipose tissue derived protein C1q TNF Related Protein 3 (CTRP3). Adipose tissue secretes several adipokines, such as adiponectin and leptin, which exert a multitude of biological effects important for human health. However, adipose tissue is extremely sensitive to alcohol consumption, leading not only to disrupted fat storage, but also to disruptions in adipokine production. Changes to adipokine secretion could have widespread biological effects and potentially contribute to alcohol-induced ailments, such as alcoholic fatty liver disease (ALD). CTRP3 has been previously demonstrated to attenuate fatty liver disease, and suppression of CTRP3 with alcohol consumption could contribute to development of and progression to alcoholic fatty liver disease. To examine the effect of ethanol consumption on circulating adipokine levels, male and female mice were fed an ethanol containing diet (Lieber-DeCarli 5% (v/v) ethanol diet) for 10-days followed by a single gavage of 5 g/kg ethanol (the NIAAA model), or for 6-weeks with no binge added (chronic model). In female mice, adiponectin levels increased ~2-fold in both models of ethanol feeding, but in male mice increased adiponectin levels were only observed after chronic ethanol feeding. On the other hand, in female mice, circulating CTRP3 levels decreased by ~75% and ~50% in the NIAAA and chronic model, respectively, with no changes observed in the male mice in either feeding model. Leptin levels were unchanged with ethanol feeding regardless of model or sex of mice. Lastly, chronic ethanol feeding led to a significant increase in mortality (~50%) in female mice, with no difference in relative ethanol consumption. These findings indicate that ethanol consumption can dysregulate adipokine secretion, but that the effects vary by sex of animal, method of ethanol consumption, and adipokine examined. These findings also indicate that female mice are more sensitive to the chronic effects of ethanol than male mice. Notably, this is the first study to document the effects of ethanol consumption on the circulating levels of CTRP3. Understanding the impact of excessive alcohol consumption on adipokine production and secretion could identify novel mechanisms of alcohol-induced human disease. However, the mechanism responsible for the increased sensitivity remains elusive.

Complement c1q tumor necrosis factor-related protein 3 a novel adipokine, protect against diabetes mellitus in young adult Egyptians

C1q/TNF-related protein-3 (CTRP3) is a novel adipokine with anti-inflammatory and a multitude of biological effects on glucose and lipid metabolism however, the influence of CTRP3 on incidence of diabetes mellitus remain unclear. This study investigated the effects of CTRP3 levels in obese and normal body weight young adults on insulin resistance and occurrence of diabetes mellitus. Subjects and methodsIn this case control study, Serum levels of CTRP3, HbA1c, Lipid profile, glucose and insulin levels were determined in 75 obese and 68 normal body weight individuals. ResultsIn obese young adults CTRP3 concentrations were decreased compared to normal body weight young adults (NBW). The association between reduction of CTRP3 concentrations and the presence of diabetes is statistically significant. CTRP3 showed significant negative correlation with BMI, HOMA-IR and triglycerides as well as positive correlations with HDL – cholesterol while there is no association between CTRP3 and BMI within the NBW group. Higher HbA1C, HOMA-IR, and risk of diabetes development within obese subjects were related to lower CTRP3 concentration. ConclusionsThis study shows that reduction of CTRP3 concentrations is likely to bring a concomitant increase in risk of diabetes in obese and normal body weight young adults. Decrease in CTRP3 concentration may have an essential role in the pathophysiology of metabolic disorders concomitant to obesity.

Transgenic overexpression of CTRP3 prevents alcohol-induced hepatic triglyceride accumulation.

This study tested the ability of a novel adipose tissue derived cytokine, C1q TNF-related protein-3 (CTRP3), to prevent alcohol-induced hepatic lipid accumulation, or alcoholic fatty liver disease (ALD). Previous work has demonstrated that CTRP3 is effective at preventing high-fat diet-induced fatty liver; however, the potential of CTRP3 to inhibit ALD has not been explored. To test the potential protective effects of CTRP3, transgenic mice overexpressing CTRP3 (Tg) or wild-type littermates (WT) were subjected to one of two different models of ALD. In the first model, known as the NIAAA model, mice were fed control or alcohol-containing liquid diets (5% vol/vol) for 10 days followed by a single gavage of ethanol (5 g/kg). In the second model, the chronic model, mice were fed control or alcohol-containing diets for 6 wk with no gavage. This study found that CTRP3 reduced triglyceride accumulation in the chronic model of alcohol consumption by ~50%, whereas no reduction was observed in the NIAAA model. Further analysis of isolated primary hepatocytes from WT and Tg mice demonstrated that CTRP3 increased oxygen consumption in the presence of fatty acids, indicating that CTRP3 increases hepatic fatty acid utilization. In conclusion, this study indicates that CTRP3 attenuates hepatic triglyceride accumulation in response to long-term chronic, but not short-term, alcohol consumption.

CTRP3 attenuates high-fat diet-induced male reproductive dysfunction in mice.

Recent studies have suggested a role for abdominal obesity in male infertility. Previous studies have found that cell apoptosis exerts an important role in obesity-related male infertility. C1q/TNF-related protein 3 (CTRP3), a paralog of adiponectin, has been proposed to exert anti-apoptotic effects and to attenuate diabetes-related cardiac injuries. However, the role of CTRP3 in high-fat diet (HFD)-induced spermatogenic impairment remains unclear. In the present study, we fed male mice an HFD for 24 weeks to induce obesity. The expression of CTRP3 was decreased by HFD feeding. Supplementation with the recombinant human globular domain of CTRP3 (0.25 μg/g/day) for 4 weeks beginning at 20 weeks of the HFD improved spermatogenic function in the HFD-fed mice, which were characterized by improved testis morphology, increased testis weight/body weight ratio, and increased sperm count, sperm viability, and sperm motility. We also found that CTRP3 infusion resulted in the attenuation of endoplasmic reticulum (ER) stress and the activation of silence information regulator 1 (SIRT1) in the testes of obese mice. Our in vitro study also suggested that CTRP3 attenuated the palmitic acid (PA)-induced reductions in sperm viability and motility via the inhibition of ER stress. Moreover, germ cell-specific Sirtuin1 knockout abolished the protective effects of CTRP3 in vivo and in vitro. In vitro studies of human sperm showed that the protective effects of CTRP3 on sperm viability and motility were abrogated by a specific inhibitor of SIRT1. Thus, our results demonstrated that CTRP3 expression protected against HFD-induced spermatogenic deficiency through the SIRT1/ER stress pathway.

The adipokine C1q TNF related protein 3 (CTRP3) is elevated in the breast milk of obese mothers.

BackgroundC1q TNF related protein 3 (CTRP3) is a relatively novel hormonal factor primarily derived from adipose tissue and has anti-diabetic properties. To determine if CTRP3 could play a role in early childhood development, the purpose of this study was to establish the presence of CTRP3 in breast milk (BM) and to determine whether CTRP3 levels were correlated with pregravid obesity status of the mother.MethodsBreast milk was collected from breast-feeding mothers who had a pregravid body mass index (BMI) classification of normal weight (BMI 18–25 kg/m2, n = 23) or obese (BMI > 30 kg/m2, n = 14). Immunoprecipitation followed by immunoblot analysis confirmed the presence of CTRP3 in BM. The concentration of CTRP3 in BM samples was determined by ELISA. Additional bioactive components were also measured by commercially available assays: ghrelin, insulin, leptin, adiponectin, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and glucose. Bioactive components in normal weight and obese mothers were compared using unpaired t-test (parametric) and Mann–Whitney U-test (non-parametric), as appropriate.ResultsThe primary findings of this study are that the adipokine CTRP3 is present in BM and CTRP3 levels are increased with pregravid obesity. Additionally, this study independently confirmed previous work that BM from obese mothers has a higher concentration of insulin and leptin. Further, no differences were observed in BM between obese and normal weight mothers in ghrelin, adiponectin, IL-6, TNF-α, or glucose levels.ConclusionThis study identified a novel factor in BM, CTRP3, and showed that BM CTRP3 levels higher in obese mothers. Because of the purported insulin sensitizing effect of CTRP3, it is possible that the elevated levels of CTRP3 in the BM of obese mothers may offset negative effects of elevated leptin and insulin levels in the BM of obese mothers. Future studies will need to be conducted to determine the relevance of CTRP3 in BM and to examine the presence of other adipose tissue-derived hormonal factors.

Expression of C1q/TNF-related protein-3 (CTRP3) in serum of patients with gestational diabetes mellitus and its relationship with insulin resistance.

In this study, the changes of insulin resistance (IR) and pancreatic β-cell function in GDM patients were observed, changes of CTRP3 level in fasting serum and relationships with plasma glucose (PG) and pancreatic β-cell function were explored at the same time, and the correlation between serum CTRP3 and body mass index (BMI) was preliminarily discussed, providing a new way to identify the pathogenesis of GDM. Data of women from 24 to 28 weeks of pregnancy were collected. 100 women were selected to form gestational diabetes mellitus (GDM) group and another 100 women were chosen to constitute normal glucose tolerance (NGT) group according to the results of oral glucose tolerance test (OGTT). They were divided into GDM overweight/obesity (GDM + OW) group, GDM non-overweight/obesity (GDM + NW) group, simple overweight (OW) group and normal body weight (NW) group, according to whether the progestational body mass index (BMI) was higher than 24 kg/m2 before pregnancy. General information of all subjects, for example, age, last menstrual period, parity, diet, weight and height, were collected, and blood samples were taken from all subjects for use in detections of total cholesterol (TC), triglyceride (TG), very low-density lipoprotein (VLDL), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and serum C1q/tumor necrosis factor-related protein-3 (CTRP3). The levels of FPG, 1 h PG, 2 h PG, fasting CP (FCP), fasting insulin (FINS), homeostasis model assessment of IR (HOMA-IR), TG and VLDL-C in the GDM group, were significantly higher than those in the NGT group. TC and LDL-C in the GDM group were greater than those in the NGT group. Compared with that in the NGT group, homeostasis model assessment of β (HOMA-β) index was lower in the GDM group. From the NGT group to the GDM group, FPG, 1 h PG, 2 h PG, FINS and FCP had rising tendencies, and the differences were of statistical significance. Pearson correlation analysis indicated that HOMA-IR was positively correlated with pre-pregnancy BMI, FPG, 2 h PG, FINS, 1 h INS, 2 h INS, FCP, 1 h CP and 2 h CP in the GDM group, HOMA-β was negatively related to FPG. In the NGT group, there was a positive correlation between HOMA-IR and pre-pregnancy BMI. The level of CTRP3 in fasting serum of the GDM group was distinctly lower than that of the NGT group. Pearson correlation analysis revealed that in the GDM group, fasting serum CTRP3 had positive correlations with HOMA-β and HDL-C, but negatively associated with pre-pregnancy BMI, FPG, 1 h PG, 2 h PG, FCP, HOMA-IR, TG and VLDL-C. In the NGT group, the fasting serum CTRP3 was negatively correlated with pre-pregnancy BMI. Multiple linear stepwise regression analysis showed FPG was an independent influencing factor for fasting serum CTRP3. With the increase of FPG, the progression of GDM IR patients is increased, and pancreatic β-cell function progressively declines. The decrease of CTRP3 level in fasting serum in GDM patients plays a metabolic role in the pathogenesis of GDM.

Low serum CTRP3 levels are associated with nonalcoholic fatty liver disease in patients with type 2 diabetes mellitus

Nonalcoholic fatty liver disease (NAFLD) commonly occurs in patients with type 2 diabetes mellitus (T2DM). C1q/TNF-related protein-3 (CTRP3) levels are decreased in type 2 diabetic patients. However, to date, it is unknown whether low CTRP3 level are correlated with the incidence of NAFLD. The aim of this study was to observe this association in Chinese patients with T2DM. Overall, 175 newly diagnosed T2DM were recruited in this study. The subjects were divided into NAFLD group (n=93) and control group (n=82). Anthropometric parameters, blood pressure, and several biochemical parameters were measured. The body composition was assessed with the bioelectrical impedance analysis (BIA) method. Insulin level was evaluated by radioimmunoassay. Levels of serum CTRP3 and interleukin-6 (IL-6) were measured by enzyme-linked immunosorbent assay. Our findings demonstrated that type 2 diabetic patients with NAFLD had lower levels of serum CTRP3 than did those without NAFLD (P=.002). Serum CTRP3 level was negatively correlated with body mass index (r=−0.271, P=.001), visceral fat area (r=−0.285, P<.001), glycosylated hemoglobin A1c (r=−0.270, P<.001), triglycerides (r=−0.267, P<.001), CRP (r=−0.222, P=.010), IL-6 (r=−0.212, P=.008), and HOMA-IR indices (r=−0.334, P<.001). When compared with the highest CTRP3 tertile, the odds ratio of the middle tertile for NAFLD incidence was 4.54 (95% CI, 1.53–13.47) and 5.80 (95% CI, 1.60–21.02) for the lowest tertile after adjustment for confounding factors. In summary, low serum CTRP3 is a strong predictor for the prevalence of NAFLD in Chinese patients with newly diagnosed T2DM.

Association of serum C1q/TNF-related protein-3 (CTRP-3) in patients with coronary artery disease

BackgroundRecent studies have demonstrated that complement C1q tumor necrosis factor related proteins (CTRPs) have diverse biological influences on the cardiovascular system. CTRP 3 is a member of the CTRP superfamily, which may play a pivotal role in the pathogenesis of coronary artery disease (CAD). Here, we investigated whether serum levels of CTRP 3 are associated with the prevalence and the severity of CAD.MethodsIn this study, 145 eligible participants were included who underwent coronary angiography. According to the result of the coronary angiography, all participants were divided into two groups: non-CAD group (n = 66) and CAD group (n = 79). The CAD group was further divided into single-vessel (n = 25), double-vessel (n = 30) and triple-vessel (n = 24) disease groups in line with different lesioned vessels of CAD. Plasma CTRP 3 concentration was determined by enzyme-linked immunosorbent assay (ELISA).ResultsSerum levels of CTRP 3 were significantly higher in CAD patients than in non-CAD patients (CAD: 56.68 ± 3.63 ng/ml, non-CAD: 44.10 ± 3.20 ng/ml, p < 0.01). Significant differences of CTRP 3 levels were also found between single-vessel group and triple-vessel group (single-vessel group: 44.80 ± 3.14 ng/ml, triple-vessel group: 75.07 ± 9.41 ng/ml, p < 0.005). Multiple logistic regression analysis revealed that CTRP 3 levels, together with HDL cholesterol and glucose, correlated with CAD.ConclusionsElevated serum CTRP 3 levels were closely related to the prevalence and severity of CAD, suggesting that it might be regarded as a novel biomarker for CAD.

C1q/TNF-Related Protein 3 (CTRP3) Function and Regulation.

As the largest endocrine organ, adipose tissue secretes many bioactive molecules that circulate in blood, collectively termed adipokines. Efforts to identify such metabolic regulators have led to the discovery of a family of secreted proteins, designated as C1q tumor necrosis factor (TNF)-related proteins (CTRPs). The CTRP proteins, adiponectin, TNF-alpha, as well as other proteins with the distinct C1q domain are collectively grouped together as the C1q/TNF superfamily. Reflecting profound biological potency, the initial characterization of these adipose tissue-derived CTRP factors finds wide-ranging effects upon metabolism, inflammation, and survival-signaling in multiple tissue types. CTRP3 (also known as CORS26, cartducin, or cartonectin) is a unique member of this adipokine family. In this review we provide a comprehensive overview of the research concerning the expression, regulation, and physiological function of CTRP3. © 2017 American Physiological Society. Compr Physiol 7:863-878, 2017.

Serum Adipokines and Metabolic Syndrome Risk Factors in Hispanic Children

Childhood obesity is a relatively new but growing epidemic in the Unites States, with 1 in 5 children currently classified as obese. Obese children are at a significantly higher risk for developing many types of cancers, cardiovascular disease, diabetes and Metabolic Syndrome (MetS). This project is focused on understanding the associations between adipose tissue health and adipose tissue‐derived secreted factors/hormones/cytokines (hereafter referred to as adipokines) and obesity and MetS in young children. Adiponectin, Leptin, and C1q TNF Related Protein 3 (CTRP3) are all adipokines which have been linked to human health, but have not been explored in children with MetS.METHODSAnthropomorphic measurements and blood collections were performed at a well child visit for Hispanic children aged 2–10 years. Lipid panel was completed at a clinical laboratory facility. Multiplex analysis (Bio‐Plex Multiplex System) was used to measure adiponectin, insulin, and leptin level. Circulating CTRP3 levels were determined by ELISA (enzyme‐linked immunosorbent assay). Risk factors for MetS were established as follows: abdominal obesity, elevated blood pressure, elevated triglycerides, low HDL and elevated plasma glucose concentrations. Pearson correlation coefficients were calculated for continuous variables and Spearman rank‐order correlation was performed for categorical variables to evaluate associations between adipokines and risk factors for MetS.RESULTSBriefly, 44 of 114 Hispanic children had 2 or more risk factors for the development of MetS. The association between Adiponectin levels, glucose, insulin, total triglyceride and Body Mass Index (BMI) trended towards significance (P&gt;0.08), whereas leptin was significantly positively associated with BMI. CTRP3 levels were not associated with any individual measure variable, but were negatively associated with the presence of 2 or more risks factors for MetS.CONCLUSIONAdipose tissue secretes many bioactive molecules that circulate in blood, and dysregulation of adipose tissue endocrine function may promote the occurrence of MetS. The data presented in this project demonstrate the association between adipokines and MetS.Support or Funding InformationThis research was supported in part National Institute On Alcohol Abuse And Alcoholism of the National Institutes of Health under Award Number R03AA023612, Tennessee Board of Regents Diversity Research Grant (2014–2015), and by the East Tennessee State University Research Development Committee (E82262).

Association of C1q/TNF-Related Protein-3 (CTRP3) and CTRP13 Serum Levels with Coronary Artery Disease in Subjects with and without Type 2 Diabetes Mellitus.

C1q/TNF-Related Protein-3 (CTRP3) and CTRP13 are two newly discovered adipokines regulating glucose and lipid metabolism. But their role in type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD) is still in infancy. The aim of this study was to investigate the associations of gene expression and serum levels of CTRP3 and CTRP13 with CAD, metabolic and inflammatory markers in patients with and without T2DM. Serum levels of CTRP3, CTRP13, adiponectin and inflammatory cytokines and their gene expression in peripheral blood mononuclear cells (PBMCs) were determined in 172 subjects categorized as group I (without T2DM and CAD), group II (with CAD but no T2DM), group III (with T2DM but no CAD) and group IV (with T2DM and CAD). Serum levels and gene expression of CTRP3, CTRP13 and adiponectin in the group I were higher compared to other groups. Inflammatory cytokines in the control group were lower than other groups too. CTRP3 serum levels have an independent association with BMI, smoking and CTRP3 gene expression; also CTRP13 serum levels has an independent association with BMI, HDL-C, insulin, HOMA-IR, HbA1c and TNF-α. Decreased serum levels of CTRP3 and CTRP13 were also associated with CAD. It appears that the decreased levels of CTRP3 and especially CTRP13 were associated with increased risk of T2DM and CAD. These findings suggest an emerging role of these adipokines in the pathogenesis of CAD, but further studies are necessary to establish this concept.

C1q/TNF-related protein-3 exerts the chondroprotective effects in IL-1β-treated SW1353 cells by regulating the FGFR1 signaling

Cartilage degeneration is known as a major cause of osteoarthritis (OA). C1q/TNF-related protein-3 (CTRP3) is an adipokine relative to chondrogenesis in vitro. However, its effect on cartilage degeneration in OA remains unclearly. In the present study, SW1353 cells were treated with IL-1β to imitate the microenvironment of OA for vitro research. Then, an obvious down-regulation of CTRP3 were validated in IL-1β-treated SW1353 cells. In addition, CTRP3 overexpression significantly attenuated the decrease in cell proliferation and increase in cell apoptosis triggered by IL-1β. Moreover, CTRP3 up-regulation significantly inhibited the expression of FGFR1, but with slight decrease in FGFR3 levels. Further analysis corroborated that FGFR1 overexpression markedly ameliorated the pro-proliferation and anti-apoptotic effects of CTRP3 elevation in cells upon IL-1β. Down-regulation of FGFR1 attenuated the increase in Ras-GTP expression caused by IL-1β stimulation. Moreover, EGFR1 elevation also abated the inhibitory effect of CTRP3 on Ras expression and the CRTP3-induced activation of PI3K/AKT in cells upon IL-1β. Furthermore, Ras inhibitor manumycin A antagonized the decrease in phosphorylation of PI3K and Akt caused by IL-1β treatment. Both Manumycin A and PI3K/Akt agonist FGF-1 attenuated the inhibitory effect of IL-1β on cell growth. Together, this research suggested that CTRP3 might protect chondrocytes against IL-1β-induced injury by suppressing the FGFR1- Ras/PI3K/Akt signaling-mediated growth inhibitory pathway, indicating a potential agent against osteoarthritis.

Divergent relationship of circulating CTRP3 levels between obesity and gender: a cross-sectional study.

C1q TNF Related Protein 3 (CTRP3) is a novel adipose tissue derived secreted factor, or adipokine, which has been linked to a number of beneficial biological effects on metabolism, inflammation, and survival signaling in a variety of tissues. However, very little is known about CTRP3 in regards to human health. The purpose of this project was to examine circulating CTRP3 levels in a clinical population, patients with symptoms requiring heart catheterization in order to identify the presence of obstructive coronary artery disease (CAD). It was hypothesized that serum CTRP3 levels would be decreased in the presence of CAD.MethodsBody mass index (BMI), diabetes status, and plasma samples were collected from 100 patients who were >30 years of age and presented at the East Tennessee State University Heart Clinic with symptoms requiring heart catheterization in order to identify the presence of cardiovascular blockages (n = 52 male, n = 48 female). Circulating CTRP3 levels were quantified using commercially available ELISA.ResultsCirculating CTRP3 levels had no relationship to the presence of CAD regardless of gender. However, circulating concentrations of CTRP3 were significantly higher in normal weight (BMI < 30) females (0.88 ± 0.12 µg/ml) compared with males (0.54 ± 0.06 µg/ml). Further, obesity (BMI > 30) resulted in an increase in circulating CTRP3 levels in male subjects (0.74 ± 0.08 µg/ml) but showed a significant decrease in female subjects (0.58 ± 0.07 µg/ml). Additionally, there was a significant reduction in circulating CTRP3 levels in female subjects who were diagnosed with Type 2 diabetes compared with patients without (0.79 ± 0.08 vs. 0.42 ± 0.10 µg/ml). There was no relationship between diabetes status and circulating CTRP3 levels in male subjects.ConclusionCirculating CTRP3 levels had a different relationship with diabetes and obesity status between male and female patients. It is possible that circulating CTRP3 levels are controlled by hormonal status, however more research is needed to explore this relationship. Nevertheless, future studies examining the relationship between CTRP3 levels and disease status should treat gender as an independent variable.

Identification of cell surface receptors for the novel adipokine CTRP3

C1q TNF Related Protein 3 (CTRP3) is a member of a family of secreted proteins that exert a multitude of biological effects throughout the body. Our initial work shows promise in the development of CTRP3‐induced cellular processes as a means to combat nonalcoholic fatty liver disease (NAFLD). Clinically, NAFLD is defined as the excessive accumulation of fat in the liver, usually due to obesity, and NAFLD effects 1 in 10 Americans. Our previous data show that when high fat fed mice are treated with CTRP3 they are protected from developing NAFLD. However, the mechanism for this effect remains unclear. The purpose of this project was to identify the unknown receptor that mediates the hepatic actions of CTRP3.METHODSWe used Ligand‐receptor glycocapture technology with TriCEPS™‐based ligand‐receptor capture (LRC‐TriCEPS; Dualsystems Biotech AG). The LRC‐TriCEPS experiment with CTRP3‐FLAG protein as ligand and Insulin as the control ligand was performed on H4IIE rat hepatoma cell line. Additional analysis using siRNA induced knockdown of the identified receptors was used to validate the findings.RESULTSInitial analysis demonstrated efficient coupling of TriCEPS to CTRP3. Further, flow cytometry analysis demonstrated successful oxidation and crosslinking of CTRP3‐TriCEPS and Insulin‐TriCEPS to the cell surface glycans. In total, an enrichment of glycopeptides of 11% (261 peptides) was observed. Under these conditions, INSR (Insulin receptor) could be identified and quantified in the control dataset. For the ligand sample two unique receptors were identified. Flow cytometry analysis with siRNA induced knockdown of these proteins confirmed that the presence of the protein is needed for CTRP3 binding to occur.CONCLUSIONThe LRC‐TriCEPS methodology was successful in identifying the receptor for CTRP3.RELEVANCEThe identification of the receptors for CTRP3 and CTRP3‐induced cellular signaling pathways are important prerequisites for the development of small molecule drug candidates that exert effects beneficial to human health.Support or Funding InformationEast Tennessee State University Research Development CommitteeNational Institute On Alcohol Abuse And Alcoholism of the National Institutes of Health under Award Number R03AA023612

Immunomodulatory roles of CTRP3 in endotoxemia and metabolic stress.

C1q/TNF‐related protein 3 (CTRP3) is a secreted hormone that modulates hepatic glucose and lipid metabolism. Its circulating levels are reduced in human and rodent models of obesity, a metabolic state accompanied by chronic low‐grade inflammation. Recent studies have demonstrated an anti‐inflammatory role for recombinant CTRP3 in attenuating LPS‐induced systemic inflammation, and its deficiency markedly exacerbates inflammation in a mouse model of rheumatoid arthritis. We used genetic mouse models to explore the immunomodulatory function of CTRP3 in response to acute (LPS challenge) and chronic (high‐fat diet) inflammatory stimuli. In a sublethal dose of LPS challenge, neither CTRP3 deficiency nor its overexpression in transgenic mice had an impact on IL‐1β, IL‐6, TNF‐α, or MIP‐2 induction at the serum protein or mRNA levels, contrary to previous findings based on recombinant CTRP3 administration. In a metabolic context, we measured 71 serum cytokine levels in wild‐type and CTRP3 transgenic mice fed a high‐fat diet or a matched control low‐fat diet. On a low‐fat diet, CTRP3 transgenic mice had elevated circulating levels of multiple chemokines (CCL11, CXCL9, CXCL10, CCL17, CX3CL1, CCL22 and sCD30). However, when obesity was induced with a high‐fat diet, CTRP3 transgenic mice had lower circulating levels of IL‐5, TNF‐α, sVEGF2, and sVEGFR3, and a higher level of soluble gp130. Contingent upon the metabolic state, CTRP3 overexpression altered chemokine levels in lean mice, and attenuated systemic inflammation in the setting of obesity and insulin resistance. These results highlight a context‐dependent immunomodulatory role for CTRP3.

Plasma C1q/TNF-Related Protein-3 (CTRP-3) and High-Mobility Group Box-1 (HMGB-1) Concentrations in Subjects with Prediabetes and Type 2 Diabetes.

Aims. To detect the association of C1q/TNF-related protein-3 (CTRP-3) and high-mobility group box-1 (HMGB-1) in subjects with prediabetes (pre-DM) and newly diagnosed type 2 diabetes (nT2DM). Methods. 224 eligible participants were included. The 75 g oral glucose tolerance test (OGTT) and several clinical parameters of metabolic disorders and cytokines were measured. All participants were divided into three groups: normal glucose tolerance (NGT, n = 62), pre-DM (n = 111), and nT2DM group (n = 56). Results. Plasma CTRP-3 concentrations were significantly lower in subjects with pre-DM and nT2DM than that of the NGT group, while plasma HMGB-1 levels were higher in pre-DM and nT2DM group compared with the NGT group (P < 0.05). A multiple linear regression analysis showed both plasma CTRP-3 and HMGB-1 concentrations were independently associated with homeostasis model assessment for insulin resistance (HOMA-IR) and interleukin-6 (IL-6) (P < 0.05 for all). Further multiple logistical regression analyses revealed that both plasma CTRP-3 and HMGB-1 levels were significantly associated with pre-DM and nT2DM after adjusting for several confounders (P < 0.001 for all). Conclusions. Circulating CTRP-3 and HMGB-1 concentrations might be promising biomarkers to predict prediabetes and type 2 diabetes.

CTRP3 deficiency reduces liver size and alters IL-6 and TGFβ levels in obese mice.

C1q/TNF-related protein 3 (CTRP3) is a secreted metabolic regulator whose circulating levels are reduced in human and rodent models of obesity and diabetes. Previously, we showed that CTRP3 infusion lowers blood glucose by suppressing gluconeogenesis and that transgenic overexpression of CTRP3 protects mice against diet-induced hepatic steatosis. Here, we used a genetic loss-of-function mouse model to further address whether CTRP3 is indeed required for metabolic homeostasis under normal and obese states. Both male and female mice lacking CTRP3 had similar weight gain when fed a control low-fat (LFD) or high-fat diet (HFD). Regardless of diet, no differences were observed in adiposity, food intake, metabolic rate, energy expenditure, or physical activity levels between wild-type (WT) and Ctrp3-knockout (KO) animals of either sex. Contrary to expectations, loss of CTRP3 in LFD- or HFD-fed male and female mice also had minimal or no impact on whole body glucose metabolism, insulin sensitivity, and fasting-induced hepatic gluconeogenesis. Unexpectedly, the liver sizes of HFD-fed Ctrp3-KO male mice were markedly reduced despite a modest increase in triglyceride content. Furthermore, liver expression of fat oxidation genes was upregulated in the Ctrp3-KO mice. Whereas the liver and adipose expression of profibrotic TGFβ1, as well as its serum levels, was suppressed in HFD-fed KO mice, circulating proinflammatory IL-6 levels were markedly increased; these changes, however, were insufficient to affect systemic metabolic outcome. We conclude that, although it is dispensable for physiological control of energy balance, CTRP3 plays a previously unsuspected role in modulating liver size and circulating cytokine levels in response to obesity.

CTRP3 Stimulates Proliferation and Anti-Apoptosis of Prostate Cells through PKC Signaling Pathways.

C1q/TNF-related protein-3 (CTRP3) is a novel adipokine with roles in multiple cellular processes. However, little is known about its function in prostate cells. This study investigated the effects and mechanisms of CTRP3 in prostate cells. We first generated and purified CTRP3 protein in HEK 293T cells. Proliferation of RWPE-1 prostate cells was evaluated by MTT analyses under treatment with different concentrations of CTRP3 for various exposure times. The results revealed maximum enhancement of proliferation with 10 μg/mL CTRP3 for 72 h. Cell apoptosis and cell cycle were determined by TUNEL staining and flow cytometry analysis. TUNEL assay showed decreased TUNEL-positive cells in RWPE-1 prostate cells treated with CTRP3, and flow cytometry showed significantly decreased apoptotic cells upon CTRP3 treatment (treated cells, 8.34±1.175 vs. controls, 20.163±0.35) (P < 0.01). Moreover, flow cytometry analysis also showed a significant decrease of cells in the G1 phase and an increase of cells in the S and G2 phase upon CTRP3 treatment (treated cells, 42.85±1.40 vs. control, 52.77±0.90; 28.41±0.57 vs. 23.49±1.13; 27.08±1.97 vs. 22.20±1.32, respectively) (all P < 0.05). Two-dimensional gel electrophoresis and mass spectrometry identified differentially expressed proteins, including cytokeratin-19, GLRX3 and DDAH1, which were upregulated in CTRP3 treated cells, and cytokeratin-17 and 14-3-3 sigma, which were downregulated. GLRX3, DDAH1 and 14-3-3 sigma were confirmed using western blot analysis. A PKC inhibitor, staurosporine, was used to inhibit PKC activity in CTRP3 treated RWPE-1 cells. Staurosporine completely abolished the CTRP3-induced increased phosphorylation of intracellular PKC substrates and CTRP3-stimulated effect by RWPE-1 cells. Our results provide the first evidence for a physiological role of the novel adipokine, CTRP3, in prostate cells. Our findings suggest that CTRP3 could improve proliferation and anti-apoptosis of prostate cells through protein kinase C signaling pathways.