Development of a novel enzyme-linked immunosorbent assay (ELISA) for measurement of serum CTRP1: a pilot study: measurement of serum CTRP1 in healthy donors and patients with metabolic syndrome

CTRP1: A novel player in cardiovascular and metabolic diseases

Cardiovascular diseases (CVDs) are a series of diseases induced by inflammation and lipid metabolism disorders, among others. Metabolic diseases can cause inflammation and abnormal lipid metabolism. C1q/TNF-related proteins 1 (CTRP1) is a paralog of adiponectin that belongs to the CTRP subfamily. CTRP1 is expressed and secreted in adipocytes, macrophages, cardiomyocytes, and other cells. It promotes lipid and glucose metabolism but has bidirectional effects on the regulation of inflammation. Inflammation can also inversely stimulate CTRP1 production. A vicious circle may exist between the two. This article introduces CTRP1 from the structure, expression, and different roles of CTRP1 in CVDs and metabolic diseases, to summarize the role of CTRP1 pleiotropy. Moreover, the proteins which may interact with CTRP1 are predicted through GeneCards and STRING, speculating their effects, to provide new ideas for the study of CTRP1.

CTRP1 prevents high fat diet-induced obesity and improves glucose homeostasis in obese and STZ-induced diabetic mice

BACKGROUND

C1q/tumor necrosis factor-related protein 1 (CTRP1) is an adipokine secreted by adipose tissue, related to chondrocyte proliferation, inflammation, and glucose homeostasis. However, the therapeutic effects on metabolic disorders and the underlying mechanism were unclear. Here, we investigated the functions and mechanisms of CTRP1 in treating obesity and diabetes.

METHODS

The plasmid containing human CTRP1 was delivered to mice by hydrodynamic injection, which sustained expression of CTRP1 in the liver and high protein level in the blood. High-fat diet (HFD) fed mice and STZ-induced diabetes model were used to study the effects of CTRP1 on obesity, glucose homeostasis, insulin resistance, and hepatic lipid accumulation. The lipid accumulation in liver and adipose tissue, glucose tolerance, insulin sensitivity, food intake, and energy expenditure were detected by H&E staining, Oil-Red O staining, glucose tolerance test, insulin tolerance test, and metabolic cage, respectively. The metabolic-related genes and signal pathways were determined using qPCR and western blotting.

RESULTS

With high blood circulation, CTRP1 prevented obesity, hyperglycemia, insulin resistance, and fatty liver in HFD-fed mice. CTRP1 also improved glucose metabolism and insulin resistance in obese and STZ-induced diabetic mice. The metabolic cage study revealed that CTRP1 reduced food intake and enhanced energy expenditure. The mechanistic study demonstrated that CTRP1 upregulated the protein level of leptin in blood, thermogenic gene expression in brown adipose tissue, and the gene expression responsible for lipolysis and glycolysis in white adipose tissue (WAT). CTRP1 also downregulated the expression of inflammatory genes in WAT. Overexpression of CTRP1 activated AMPK and PI3K/Akt signaling pathways and inhibited ERK signaling pathway.

CONCLUSION

These results demonstrate that CTRP1 could improve glucose homeostasis and prevent HFD-induced obesity and fatty liver through upregulating the energy expenditure and reducing food intake, suggesting CTRP1 may serve as a promising target for treating metabolic diseases.

Plasminogen Activator Inhibitor-1 and Adiponectin Are Associated With Metabolic Syndrome Components

BACKGROUND

We aimed to study the associations of adipocytokines, endothelial damage markers, and high-sensitivity C-reactive protein (hs-CRP) with metabolic syndrome (MetS) components.

METHODS

This cross-sectional study included 202 subjects categorized into MetS and No-MetS according to Harmonizing Adult Treatment Panel III.

RESULTS

Subjects with MetS showed higher levels of proinflammatory molecules but significantly lower adiponectin levels than subjects with No-MetS. Among the studied adipocytokines, plasminogen activator inhibitor-1 (PAI-1) and adiponectin showed the strongest associations with most MetS components. PAI-1 was associated with MetS (odds ratio (OR) 1.107 (1.065-1.151), P < 0.0001), whereas adiponectin was inversely associated with MetS (OR 0.710 (0.610-0.825), P < 0.0001). Following adjustment by sex, age, body mass index, and 24-hour urinary sodium excretion in a multivariate analysis, the association of PAI-1 (OR 1.090 (1.044-1.137), P < 0.0001) and adiponectin (OR 0.634 (0.519-0.775), P < 0.0001) with MetS remained significant. Multivariate analyses supported a model in which systolic blood pressure (BP) could be predicted by PAI-1, hs-CRP, and matrix metalloproteinase 2 (R2 = 0.125; P = 0.04); diastolic BP (R2 = 0.218; P = 0.0001) and glucose (R2 = 0.074; P = 0.0001) could be predicted by PAI-1; waist circumference could be predicted by PAI-1 and hs-CRP (R2 = 0.28; P = 0.016). Receiver operating characteristic curve analysis showed that a PAI-1 concentration had the best sensitivity and specificity for discriminating subjects with MetS.

CONCLUSION

PAI-1 and adiponectin rendered the most robust associations with MetS components in a general population, indicating that unfavorable adipose tissue performance is a key contributor to these metabolic anomalies. Further prospective analyses should allow establishing whether these adipocytokines can anticipate the progress of MetS and cardiovascular risk.

Novel Adipokines CTRP1, CTRP9, and FGF21 in Pediatric Type 1 and Type 2 Diabetes: A Cross-Sectional Analysis

INTRODUCTION

Pediatric obesity and diabetes has increased over the last several decades. While the role of common adipokines on metabolic parameters has been well studied in adults, the relationship of novel adipokines and hepatokines in pediatric type 1 (T1D) and type 2 diabetes (T2D) is not well understood. This study assessed novel adipokines C1q/TNF-related proteins (CTRP1 and CTRP9), and hepatokine fibroblast growth factor 21 (FGF21) in youth with T1D and T2D diabetes.

METHODS

Participants (n = 80) with T1D (n = 40) enrolled in the Pediatric Diabetes Consortium (PDC) T1D NeOn registry, and T2D (n = 40) from the PDC T2D registry. Cross-sectional analysis compared adipokines (CTRP1, CTRP9, FGF21) between T1D and T2D, and regression models assessed adipokine relationship with clinical characteristics.

RESULTS

The mean age of the participants was 14.9 ± 2 years, and 50% were female. T2D participants had a shorter diabetes duration (p = 0.0009), higher weight (p < 0.0001), and BMI (p < 0.0001) than T1D participants. CTRP9 levels were higher in T1D (13,903.6 vs. 3,608.5 pg/mL, p = 0.04) than T2D, and FGF21 levels were higher in T2D (113.1 vs. 70.6 pg/mL, p = 0.03) than T1D, with no differences in CTRP1. In regression analysis of T1D, CTRP9 was positively associated with C-peptide (p = 0.006), and FGF21 was positively associated with hemoglobin A1c (p = 0.04). In T2D, CTRP1 was positively associated with HbA1c (p < 0.001) and glucose (p = 0.004), even after controlling for age, sex, and BMI.

CONCLUSIONS

CTRP9 levels are higher in youth with T1D compared to T2D, and FGF21 levels are higher in youth with T2D than T1D. Novel adipokines are related to metabolic homeostasis in the inflammatory milieu of pediatric diabetes.

Altered adipokines in obese adolescents: a cross-sectional and longitudinal analysis across the spectrum of glycemia

Obesity and type 2 diabetes are rapidly increasing in the adolescent population. We sought to determine whether adipokines, specifically leptin, C1q/TNF-related proteins 1 (CTRP1) and CTRP9, and the hepatokine fibroblast growth factor 21 (FGF21), are associated with obesity and hyperglycemia in a cohort of lean and obese adolescents, across the spectrum of glycemia. In an observational, longitudinal study of lean and obese adolescents, we measured fasting laboratory tests, oral glucose tolerance tests, and adipokines including leptin, CTRP1, CTRP9, and FGF21. Participants completed baseline and 2-year follow-up study visits and were categorized as lean (LC, lean control; n = 30), obese normoglycemic (ONG; n = 61), and obese hyperglycemic (OHG; n = 31) adolescents at baseline and lean (n = 8), ONG (n = 18), and OHG (n = 4) at follow-up. Groups were compared using ANOVA and regression analysis, and linear mixed effects modeling was used to test for differences in adipokine levels across baseline and follow-up visits. Results showed that at baseline, leptin was higher in all obese groups (P < 0.001) compared with LC. FGF21 was higher in OHG participants compared with LC (P < 0.001) and ONG (P < 0.001) and positively associated with fasting glucose (P < 0.001), fasting insulin (P < 0.001), Homeostasis Model Assessment-Insulin Resistance Index (HOMA-IR; P < 0.001), and hemoglobin A1c (HbA1c; P = 0.01). CTRP1 was higher in OHG compared with ONG (P = 0.03). CTRP9 was not associated with obesity or hyperglycemia in this pediatric cohort. At 2 years, leptin decreased in ONG (P = 0.003) and FGF21 increased in OHG (P = 0.02), relative to lean controls. Altered adipokine levels are associated with the inflammatory milieu in obese youth with and without hyperglycemia. In adolescence, the novel adipokine CTRP1 was elevated with hyperglycemia, whereas CTRP9 was unchanged in this cohort.NEW & NOTEWORTHY Leptin is higher in obese adolescents and FGF21 is higher in obese hyperglycemic adolescents. The novel adipokine CTRP1 is higher in obese hyperglycemic adolescents, whereas CTRP9 was unchanged in this adolescent cohort.

The circulating levels of CTRP1 and CTRP5 are associated with obesity indices and carotid intima-media thickness (cIMT) value in patients with type 2 diabetes: a preliminary study

BACKGROUND

There is growing evidence that the C1qTNF-related protein (CTRP) family has a crucial role in the pathophysiology of metabolic disorders such as type 2 diabetes (T2D) and obesity. We sought to identify the association of CTRP1 and CTRP5 circulating levels with various obesity parameters such as visceral adipose tissue (VAT) thickness, visceral adiposity index (VAI), and with carotid intima-media thickness (cIMT) in patients with T2D and controls.

METHODS

This preliminary study consisted of men with T2D (n = 42) and men without T2D (n = 42). The measurement of cIMT and VAT thickness was performed using an Accuvix XQ ultrasound. Circulating levels of CTRP1, CTRP5, and adiponectin were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

CTRP-1 and CTRP1/CTRP5 ratio were markedly higher in patients with T2D compared to controls (p < 0001 and p = 0004 respectively). Interestingly, binominal logistic regression revealed that a higher circulating level of CTRP1 was associated with the presence of T2D (odds ratio [OR]: 1.009 [95% CI: 1.004-1.015]; P = .001). CTRP1 circulating levels were correlated with WHR, VAT, and HOMA-IR in the whole population study. Also, we observed that the ratio of CTRP1 to CTRP5 in plasma (β = 0.648, P = 0.005) and CTRP5 circulating levels (β = 0.444, P = 0.049) are independently associated with cIMT value.

CONCLUSIONS

Our results indicated that CTRP1 and CTRP5 concentrations were correlated with atherosclerosis in men with T2D and these adipokines might have a causal role for cardiometabolic risk in T2D.However, more studies in large sample sizes are required to clarify the role of CTRPs in T2D pathogenesis.

Aging and chronic high-fat feeding negatively affect kidney size, function, and gene expression in CTRP1-deficient mice

C1q/TNF-related protein 1 (CTRP1) is an endocrine factor with metabolic, cardiovascular, and renal functions. We previously showed that aged Ctrp1-knockout (KO) mice fed a control low-fat diet develop renal hypertrophy and dysfunction. Since aging and obesity adversely affect various organ systems, we hypothesized that aging, in combination with obesity induced by chronic high-fat feeding, would further exacerbate renal dysfunction in CTRP1-deficient animals. To test this, we fed wild-type and Ctrp1-KO mice a high-fat diet for 8 mo or longer. Contrary to our expectation, no differences were observed in blood pressure, heart function, or vascular stiffness between genotypes. Loss of CTRP1, however, resulted in an approximately twofold renal enlargement (relative to body weight), ∼60% increase in urinary total protein content, and elevated pH, and changes in renal gene expression affecting metabolism, signaling, transcription, cell adhesion, solute and metabolite transport, and inflammation. Assessment of glomerular integrity, the extent of podocyte foot process effacement, as well as renal response to water restriction and salt loading did not reveal significant differences between genotypes. Interestingly, blood platelet, white blood cell, neutrophil, lymphocyte, and eosinophil counts were significantly elevated, whereas mean corpuscular volume and hemoglobin were reduced in Ctrp1-KO mice. Cytokine profiling revealed increased circulating levels of CCL17 and TIMP-1 in KO mice. Compared with our previous study, current data suggest that chronic high-fat feeding affects renal phenotypes differently than similarly aged mice fed a control low-fat diet, highlighting a diet-dependent contribution of CTRP1 deficiency to age-related changes in renal structure and function.

Novel MicroRNA Binding Site SNPs and the Risk of Clear Cell Renal Cell Carcinoma (ccRCC): A Case-Control Study

BACKGROUND

Renal cell carcinoma represents 3% of all adult malignancies. MicroRNAs exhibit specific functions in various biological processes through their interaction with cellular mRNA involved in apoptosis and cell cycle control. Recent studies have reported the potential association of single-nucleotide polymorphisms (SNPs) in miRNA-binding sites of VHL-HIF1α pathway genes with renal cancer development and progression.

OBJECTIVE

The objective of this study is to investigate SNPs invoking an alteration in the nature of interaction with miRNA binding sites of VHL-HIF1α pathway genes.

PATIENTS & METHODS

Total 450 cases of histologically and clinically verified ccRCC and 490 controls were included in our study. Genotyping was performed using a TaqMan PCR allelic discrimination method. Kaplan-Meier method of statistical analysis was implemented to analyze the overall patient survival rate.

RESULTS

Polymorphism rs10491534 in TSC1 gene was significantly associated with risk of developing advanced ccRCC. Allele G of rs1642742 in VHL gene was significantly prevalent in ccRCC compared with control group aged 55 and older (OR = 1.5566; CI [1.1532-2.1019]). Results from the dominant model combining individuals with AG or AA genotype showed that the A allele bearers of CDCP1 rs6773576 exhibited higher risk of death compared to GG carriers (HR 3.93, 95% CI 1.76-17.21, log-rank P = 0.0033).

CONCLUSION

The present study delineated the association of miRNA binding site variants in VHL-HIF1α pathway genes with the ccRCC risk, which may affect clinical outcome.

C1q/TNF-related Protein 1, a Multifunctional Adipokine: An Overview of Current Data

The present review aimed to present the research highlights on C1q/TNF-related protein 1 (CTRP1), a member of the recently discovered family of highly conserved adiponectin paralog proteins, C1q tumor necrosis factor-related proteins. CTRP1 plays an important role in regulating body energy homeostasis and sensitivity to insulin. Studies on animal models have shown that it lowers the concentration of glucose. Elevated concentrations of CTRP1 reduce weight gain and diet-induced insulin resistance. CTRP1 limits the extent of ischemia-reperfusion injury in acute myocardial infarction. It inhibits platelet aggregation by blocking von Willebrand factor binding to collagen. In patients with chronic kidney disease, an increase in CTRP1 levels is associated with a lesser degree of disease progression. CTRP1 stimulates aldosterone synthesis in the adrenal cortex by affecting aldosterone synthase expression. In dehydration, an increase in CTRP1 concentration helps to maintain normotension. It participates in processes related to the proliferation and maturation of chondrocytes. It also promotes atherosclerosis, and a surge in its concentration is correlated with a higher cardiovascular risk in patients with coronary atherosclerosis. In vascular smooth muscle cells, it induces the expression of proinflammatory cytokines. An increase in CTRP1 levels is correlated with the progression of the neoplastic process in patients with glioblastoma.

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.

Late-onset renal hypertrophy and dysfunction in mice lacking CTRP1

Local and systemic factors that influence renal structure and function in aging are not well understood. The secretory protein C1q/TNF-related protein 1 (CTRP1) regulates systemic metabolism and cardiovascular function. We provide evidence here that CTRP1 also modulates renal physiology in an age- and sex-dependent manner. In mice lacking CTRP1, we observed significantly increased kidney weight and glomerular hypertrophy in aged male but not female or young mice. Although glomerular filtration rate, plasma renin and aldosterone levels, and renal response to water restriction did not differ between genotypes, CTRP1-deficient male mice had elevated blood pressure. Echocardiogram and pulse wave velocity measurements indicated normal heart function and vascular stiffness in CTRP1-deficient animals, and increased blood pressure was not due to greater salt retention. Paradoxically, CTRP1-deficient mice had elevated urinary sodium and potassium excretion, partially resulting from reduced expression of genes involved in renal sodium and potassium reabsorption. Despite renal hypertrophy, markers of inflammation, fibrosis, and oxidative stress were reduced in CTRP1-deficient mice. RNA sequencing revealed alterations and enrichments of genes in metabolic processes in CTRP1-deficient animals. These results highlight novel contributions of CTRP1 to aging-associated changes in renal physiology.

Circulating complement-1q tumor necrosis factor-α-related protein isoform 5 levels are low in type 2 diabetes patients and reduced by dapagliflozin

AIMS/INTRODUCTION

As a member of the tumor necrosis factor-α-related protein family, complement-1q tumor necrosis factor-α-related protein isoform 5 (CTRP5) has been found to be associated with obesity and insulin resistance (IR). Previous studies in humans and animals have reported contradictory results related to the association between CTRP5 and IR. The purpose of the present study was to explore the relationship between CTRP5 and IR through a cross-sectional study and drug intervention study of type 2 diabetes patients.

MATERIALS AND METHODS

A cross-sectional study was carried out with 118 newly diagnosed patients with type 2 diabetes and 116 healthy adults. In an interventional study, 78 individuals with newly diagnosed type 2 diabetes received sodium-glucose cotransporter 2 inhibitor (dapagliflozin) treatment for 3 months. Circulating CTRP5 concentrations were measured by enzyme-linked immunosorbent assay.

RESULTS

Serum CTRP5 concentrations were markedly reduced in patients with type 2 diabetes when compared with those of healthy individuals (P < 0.01). When considering the study population as a whole, individuals with IR (homeostasis model of assessment of IR ≥2.78) had lower CTRP5 concentrations than the individuals without IR (homeostasis model of assessment of IR <2.78; P < 0.01). Serum CTRP5 negatively correlated with age, body mass index, waist-to-hip ratio, Systolic blood pressure, triglyceride, total cholesterol, glycated hemoglobin, fasting blood glucose, 2-h blood glucose, fasting insulin and homeostasis model of assessment of IR. After 12 weeks of sodium-glucose cotransporter 2 inhibitor treatment, serum CTRP5 levels in type 2 diabetes patients were significantly reduced accompanied with ameliorated glycometabolism and IR compared with before treatment (P < 0.01).

CONCLUSIONS

CTRP5 is likely a marker for type 2 diabetes in humans.

Association of C1q/TNF-related protein-1 (CTRP1) serum levels with coronary artery disease

Objective

Complement C1q tumor necrosis factor-related proteins (CTRPs), belonging to the CTRP superfamily, are extensively involved in regulating metabolism and the immune-inflammatory response. The inflammatory process is linked to the pathogenesis of coronary artery disease (CAD). Here, we investigated the association of serum levels of CTRP1 with CAD.

Methods

Study participants were divided into two groups according to the results of coronary angiography: a control group (n = 63) and a CAD group (n = 76). The concentrations of serum CTRP1 and inflammatory cytokines were determined by enzyme-linked immunosorbent assay. Further analysis of CTRP1 levels in individuals with different severities of CAD was conducted. The CAD severity was assessed by Gensini score.

Results

Serum levels of CTRP1 were significantly higher in CAD patients than in controls (17.24 ± 1.07 versus 9.31 ± 0.56 ng/mL), and CTRP1 levels increased with increasing severity of CAD. CTRP1 levels were positively correlated with concentrations of tumor necrosis factor-α and interleukin-6. Multiple logistic regression analysis showed that CTRP1 was significantly associated with CAD.

Conclusions

Our data showed close associations of serum CTRP1 levels with the prevalence and severity of CAD, indicating that CTRP1 can be regarded as a novel and valuable biomarker for CAD.

Elevated CTRP1 Plasma Concentration Is Associated with Sepsis and Pre-Existing Type 2 Diabetes Mellitus in Critically Ill Patients

The adipokine family of C1q/TNF-like proteins (CTRP) plays a critical role in regulating systemic energy homeostasis and insulin sensitivity. It is involved in pathophysiological processes including inflammation and insulin-resistant obesity. Sepsis is associated with metabolic alterations and dysregulated adipokines, but the role of CTRP1 in critical illness and sepsis is unclear. We investigated CTRP1 plasma concentrations in 145 septic and 73 non-septic critically ill patients at admission to the medical intensive care unit (ICU) in comparison to 66 healthy controls. We also assessed associations of CTRP1 with clinical characteristics, adipokine levels, metabolic and inflammatory parameters. CTRP1 plasma concentration was significantly elevated in critically ill patients compared to healthy subjects. CTRP1 levels were significantly higher in ICU patients with sepsis. CTRP1 correlated strongly with markers of inflammatory response, renal function, liver damage and cholestasis. Furthermore, CTRP1 levels were higher in ICU patients with type 2 diabetes mellitus, and correlated with HbA1c and body mass index. This study demonstrates significantly elevated levels of CTRP1 in critically ill patients, particularly with sepsis, and links circulating CTRP1 to inflammatory and metabolic disturbances.

Obesity and chronic kidney disease progression-the role of a new adipocytokine: C1q/tumour necrosis factor-related protein-1

Background

Obesity is a risk factor for incident chronic kidney disease (CKD) in the general population. C1q/tumour necrosis factor-related protein 1 (CTRP1) is a new adipokine with multiple vascular and metabolic effects and may modulate the association between obesity and vascular diseases. The aim of the study is to explore potential links between obesity, CTRP1 levels and CKD progression.

Methods

Patients with Stages 3 and 4 CKD without previous cardiovascular events were enrolled and divided into two groups according to body mass index (BMI). Demographic, clinical and analytical data and CTRP1 levels were collected at baseline. During follow-up, renal events [defined as dialysis initiation, serum creatinine doubling or a 50% decrease in estimated glomerular filtration rate (Modification of Diet in Renal Disease)] were registered.

Results

A total of 71 patients with CKD were divided into two groups: 25 obese (BMI >30 kg/m²) and 46 non-obese. CTRP1 in plasma at baseline was higher in obese patients [median (interquartile range) 360 (148) versus 288 (188) ng/mL, P = 0.041]. No significant association was found between CTRP1 levels and CKD stage, presence of diabetes, aldosterone and renin levels, or blood pressure. Obese patients had higher systolic blood pressure (P = 0.018) and higher high-sensitivity C-reactive protein (P = 0.019) and uric acid (P = 0.003) levels, without significant differences in the percentage of diabetic patients or albuminuria. During a mean follow-up of 65 months, 14 patients had a renal event. Patients with CTRP1 in the lowest tertile had more renal events, both in the overall sample (log rank: 5.810, P = 0.016) and among obese patients (log rank: 5.405, P = 0.020). Higher CTRP1 levels were associated with slower renal progression (hazard ratio 0.992, 95% confidence interval 0.986–0.998; P = 0.001) in a model adjusted for obesity, aspirin, albuminuria and renal function.

Conclusions

CTRP1 levels are higher in obese than in non-obese patients with CKD. High CTRP1 levels may have a renal protective role since they were associated with slower kidney disease progression. Interventional studies are needed to explore this hypothesis.

Increased maternal C1q/TNF-related protein-1 (CTRP-1) serum levels in pregnancies with preeclampsia

Objective: Metabolic changes and inflammation are involved in the pathogenesis of preeclampsia. Complement C1q tumor necrosis factor-related protein-1 (CTRP-1) is a pleiotropic molecule that possesses insulin-sensitizing effects and is also involved in lipid metabolism and inflammatory responses. The aim of the study was to investigate CTRP-1 levels in pregnancies with preeclampsia.Material and methods: Serum concentrations of CTRP-1 were measured in 29 pregnant women with early-onset preeclampsia (EOPE), 24 pregnant women with late-onset preeclampsia (LOPE), and 26 women with uncomplicated pregnancies using an enzyme-linked immunosorbent assay method.Results: Patients with both EOPE and LOPE had significantly higher serum concentrations of CTRP-1 compared to the healthy controls (p < .001). However, no significant difference was found between the EOPE and LOPE groups regarding CTRP-1 levels (p = 1.000). Correlation analysis showed that CTRP-1 levels were positively correlated with systolic blood pressure (p < .001), diastolic blood pressure (p < .001), and mean UtA PI (p < .001) but negatively correlated with gestational age at delivery (p = .001) and birth weight (p < .001).Conclusions: Serum CTRP-1 levels were significantly higher in patients with both EOPE and LOPE than in healthy pregnant women.

C1QTNF1 attenuates angiotensin II-induced cardiac hypertrophy via activation of the AMPKa pathway

RATIONALE

Complement C1q tumor necrosis factor related proteins (C1QTNFs) have been reported to have diverse biological influence on the cardiovascular system. C1QTNF1 is a member of the CTRP superfamily. C1QTNF1 is expressed in the myocardium; however, its function in myocytes has not yet been investigated.

OBJECTIVE

To systematically investigate the roles of C1QTNF1 in angiotensin II (Ang II)-induced cardiac hypertrophy.

METHODS AND RESULTS

C1QTNF1 knock-out mice were used with the aim of determining the role of C1QTNF1 in cardiac hypertrophy in the adult heart. Data from experiments showed that C1QTNF1 was up-regulated during cardiac hypertrophic processes, which were triggered by increased reactive oxygen species. C1QTNF1 deficiency accelerated cardiac hypertrophy, fibrosis, inflammation responses, and oxidative stress with deteriorating cardiac dysfunction in the Ang II-induced cardiac hypertrophy mouse model. We identified C1QTNF1 as a negative regulator of cardiomyocyte hypertrophy in Ang II-stimulated neonatal rat cardiomyocytes using the recombinant human globular domain of C1QTNF1 and C1QTNF1 siRNA. Injection of the recombinant human globular domain of C1QTNF1 also suppressed the Ang II-induced cardiac hypertrophic response in vivo. The anti-hypertrophic effects of C1QTNF1 rely on AMPKa activation, which inhibits mTOR P70S6K phosphorylation. An AMPKa inhibitor abrogated the anti-hypertrophic effects of the recombinant human globular domain of C1QTNF1 both in vivo and vitro. Moreover, C1QTNF1-mediated AMPKa activation was triggered by the inhibition of PDE1-4, which subsequently activated the cAMP/PKA/LKB1 pathway.

CONCLUSION

Our results demonstrated that C1QTNF1 improves cardiac function and inhibits cardiac hypertrophy and fibrosis by increasing and activating AMPKa, suggesting that C1QTNF1 could be a therapeutic target for cardiac hypertrophy and heart failure.

Serum levels of C1q/tumor necrosis factor-related protein-1 in children with Kawasaki disease

BackgroundTo investigate the serum C1q/tumor necrosis factor-related protein-1 (CTRP1) levels in children with acute Kawasaki disease (KD), as well as the relationship between CTRP1 levels and laboratory variables.MethodsEighty-seven children with KD and 38 healthy controls (HCs) were included in this study. General characteristics were obtained from all subjects. Serum CTRP1 levels in all subjects and serum tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) levels in KD patients were measured using enzyme-linked immunosorbent assay.ResultsCompared with the HC group, serum CTRP1 levels were significantly elevated in the KD group. Significantly higher serum TNF-α, IL-1β, IL-6, and CTRP1 levels were observed in patients with KD with coronary artery lesions (KD-CALs) than in patients with KD without CALs (KD-NCALs). Serum CTRP1 levels were positively correlated with white blood cell counts (WBC), percentage of neutrophils (N%), thrombin time (TT), procalcitonin (Pct), TNF-α, IL-1β, and IL-6 levels. Meanwhile, CTRP1 levels were negatively correlated with the percentage of leukomonocytes (L%) in KD patients. Furthermore, serum CTRP1 levels were positively correlated with the time point of intravenous immunoglobulin (IVIG), WBC, N%, TNF-α, IL-1β, and IL-6 levels in the KD-CAL group.ConclusionCTRP1 may participate in the process of vasculitis and blood coagulation during the acute phase of KD.

C1qTNF-related protein 1 improve insulin resistance by reducing phosphorylation of serine 1101 in insulin receptor substrate 1

C1qTNF-related protein 1 (CTRP1) is independently associated with type 2 diabetes. However, the relationship between CTRP1 and insulin resistance is still not established. This study aimed to explore the role of CTRP1 under the situation of insulin resistance in adipose tissue. Plasma CTRP1 level was investigated in type 2 diabetic subjects (n = 35) and non-diabetic subjects (n = 35). The relationship between CTRP1 and phosphorylation of multi insulin receptor substrate 1 (IRS-1) serine (Ser) sites was further explored. Our data showed that Plasma CTRP1 was higher and negative correlation with insulin resistance in diabetic subjects (r = -0.283, p = 0.018). Glucose utilisation test revealed that the glucose utilisation rate of mature adipocytes was improved by CTRP1 in the presence of insulin. CTRP1 was not only related to IRS-1 protein, but also negatively correlated with IRS-1 Ser1101 phosphorylation (r = -0.398, p = 0.031). Furthermore, Phosphorylation levels of IRS-1 Ser1101 were significantly lower after incubation with 40 ng/mL CTRP1 in mature adipocytes than those with no intervention (p < 0.05). There was no significant correlation between CTRP1 and other IRS-1 serine sites (Ser302, Ser307, Ser612, Ser636/639, and Ser789). Collectively, our results suggested that CTRP1 might improve insulin resistance by reducing the phosphorylation of IRS-1 Ser1101, induced in the situation of insulin resistance as a feedback adipokine.

C1q/TNF-related protein 1 prevents neointimal formation after arterial injury

BACKGROUND AND AIMS

Obesity contributes to the progression of vascular disorders. C1q/TNF-related protein (CTRP) 1 is a circulating adipokine, which is upregulated in obese complications including coronary artery disease. Here, we investigated the role of CTRP1 in regulation of vascular remodeling after mechanical injury and evaluated its potential mechanism.

METHODS

Mice were subjected to wire-induced injury of left femoral arteries. An adenoviral vector encoding CTRP1 (Ad-CTRP1) or β-galactosidase as a control was injected into the jugular vein of mice 3 days prior to surgery.

RESULTS

Systemic administration of Ad-CTRP1 to wild-type mice led to reduction of the neointimal thickening after wire-induced arterial injury and the number of bromodeoxyuridine-positive cells in injured vessels as compared with treatment with control vectors. Treatment of vascular smooth muscle cells (VSMCs) with CTRP1 protein attenuated proliferative activity and ERK phosphorylation in response to PDGF-BB. CTRP1 treatment increased cyclic AMP (cAMP) levels in VSMCs, and inhibition of adenylyl cyclase reversed the inhibitory effect of CTRP1 on VSMC growth and ERK phosphorylation. Antagonization of sphingosine-1-phosphaterote (S1P) receptor 2 blocked the effects of CTRP1 on cAMP production and VSMC growth. Furthermore, CTRP1-knockout mice had enhanced neointimal thickening following injury and increased numbers of proliferating cells in neointima compared to control WT mice.

CONCLUSIONS

These findings indicate that CTRP1 functions to prevent the development of pathological vascular remodeling by reducing VSMC growth through the cAMP-dependent pathway.

Adipocyte C1QTNF5 expression is BMI-dependently related to early adipose tissue dysfunction and systemic CTRP5 serum levels in obese children

BACKGROUND/OBJECTIVES

The recently identified adipocytokine C1QTNF5 (encodes for CTRP5) has been demonstrated to inhibit pro-metabolic insulin signaling in adipocytes. We hypothesized that adipocyte C1QTNF5 expression in subcutaneous (sc) adipose tissue (AT) would correlate with the degree of obesity, systemic CTRP5 serum levels, and early AT and metabolic dysfunction in children.

SUBJECTS/METHODS

Sc AT samples were obtained from 33 healthy Caucasian lean children aged 10.06±4.84 years and 42 overweight and obese children aged 13.34±3.12 years. C1QTNF5 expression in sc AT as well as in investigated cell lines was assessed by quantitative real-time PCR. Systemic CTRP5 levels were assessed by ELISA.

RESULTS

C1QTNF5 expression in sc adipocytes increased with body mass index (BMI) standard deviation score (SDS; R=0.48, P<0.001), body fat percentage (R=0.4, P=0.004), adipocyte number (R=0.69, P<0.001) and systemic CTRP5 serum levels (R=0.28, P=0.025) whereas expression in the stromal vascular fraction (SVF) was inversely correlated with BMI SDS (R=-0.24, P=0.04). Multiple regression analysis confirmed that BMI SDS was the strongest independent predictor for C1QTNF5 expression in sc adipocytes. SVF C1QTNF5 levels strongly correlated with SVF CD31 expression (R=0.54, P<0.001) indicating expression by endothelial cells. Primary human endothelial cells demonstrated stronger expression compared with human Simpson-Golahbi-Behmel syndrome pre-adipocytes and adipocytes. Adipocyte C1QTNF5 expression levels were BMI-dependently related to fasting insulin (R=0.3, P=0.03) and leptin serum levels (R=0.5, P<0.001). Sc AT samples containing crown-like structures (CLS) demonstrated increased adipocyte C1QTNF5 expression compared to CLS-negative samples (P=0.03). Functionally, tumor necrosis factor (TNF)α caused a fourfold induction of C1QTNF5 in human adipocytes (P<0.001) and a 50% reduction in primary human endothelial cells (P<0.001).

CONCLUSIONS

In children adipocyte C1QTNF5 expression is already strongly related to the degree of obesity and is associated with obesity-related AT alterations, systemic CTRP5 serum levels as well as circulating markers of metabolic disease and is positively regulated by TNFα in vitro.

Loss of CTRP1 disrupts glucose and lipid homeostasis

C1q/TNF-related protein 1 (CTRP1) is a conserved plasma protein of the C1q family with notable metabolic and cardiovascular functions. We have previously shown that CTRP1 infusion lowers blood glucose and that transgenic mice with elevated circulating CTRP1 are protected from diet-induced obesity and insulin resistance. Here, we used a genetic loss-of-function mouse model to address the requirement of CTRP1 for metabolic homeostasis. Despite similar body weight, food intake, and energy expenditure, Ctrp1 knockout (KO) mice fed a low-fat diet developed insulin resistance and hepatic steatosis. Impaired glucose metabolism in Ctrp1 KO mice was associated with increased hepatic gluconeogenic gene expression and decreased skeletal muscle glucose transporter glucose transporter 4 levels and AMP-activated protein kinase activation. Loss of CTRP1 enhanced the clearance of orally administered lipids but did not affect intestinal lipid absorption, hepatic VLDL-triglyceride export, or lipoprotein lipase activity. In contrast to triglycerides, hepatic cholesterol levels were reduced in Ctrp1 KO mice, paralleling the reduced expression of cholesterol synthesis genes. Contrary to expectations, when challenged with a high-fat diet to induce obesity, Ctrp1 KO mice had increased physical activity and reduced body weight, adiposity, and expression of lipid synthesis and fibrotic genes in adipose tissue; these phenotypes were linked to elevated FGF-21 levels. Due in part to increased hepatic AMP-activated protein kinase activation and reduced expression of lipid synthesis genes, Ctrp1 KO mice fed a high-fat diet also had reduced liver and serum triglyceride and cholesterol levels. Taken together, these results provide genetic evidence to establish the significance of CTRP1 to systemic energy metabolism in different metabolic and dietary contexts.

Adipocytes, aldosterone and obesity-related hypertension

Understanding the mechanisms linking obesity with hypertension is important in the current obesity epidemic as it may improve therapeutic interventions. Plasma aldosterone levels are positively correlated with body mass index and weight loss in obese patients is reported to be accompanied by decreased aldosterone levels. This suggests a relationship between adipose tissue and the production/secretion of aldosterone. Aldosterone is synthesized principally by the adrenal glands, but its production may be regulated by many factors, including factors secreted by adipocytes. In addition, studies have reported local synthesis of aldosterone in extra-adrenal tissues, including adipose tissue. Experimental studies have highlighted a role for adipocyte-secreted aldosterone in the pathogenesis of obesity-related cardiovascular complications via the mineralocorticoid receptor. This review focuses on how aldosterone secretion may be influenced by adipose tissue and the importance of these mechanisms in the context of obesity-related hypertension.

Serum levels of C1q/TNF-related protein-1 (CTRP-1) are closely associated with coronary artery disease

Background

Complement C1q tumor necrosis factor related proteins (CTRPs) have been proved to have diverse biological influences on cardiovascular system. CTRP 1 is a member of the CTRP superfamily, however, the relevance with coronary artery disease (CAD) are seldom explored. This study was designed to investigate the correlation between serum levels of CTRP 1 and CAD.

Methods

CTRP 1 levels of 150 CAD patients and 50 non-CAD subjects were determined by enzymelinked immunosorbent assay. Further analysis of CTRP 1 levels in different stages and lesion vessels of CAD were conducted.

Results

Serum levels of CTRP 1 in CAD patients were significantly elevated, and it was increased with the severity of CAD. CTRP 1 level in acute myocardial infarction group was much higher than that in stable/unstable angina and non-CAD groups. And significant differences of CTRP 1 were also found between single-vessel disease and triple-vessel disease. Multiple logistic regression analysis showed that CTRP 1 was an independent risk factor of the occurrence of myocardial infarction.

Conclusions

Increased serum CTRP 1 levels were closely associated with the prevalence and severity of CAD, it might be regarded as a marker for myocardial infarction.

Circulating CTRP1 Levels in Type 2 Diabetes and Their Association with FGF21

The goal of this study was to investigate whether circulating C1q/TNF-α-related protein 1 (CTRP1) levels are associated with diabetes. In addition, relationships between CTRP1 and other diabetes-related cytokines were elucidated, including adiponectin and fibroblast growth factor 21 (FGF21). A total of 178 subjects (78 men and 100 women) aged 29-70 years (mean age, 46.1 years) were randomly selected. The sera from a normal glucose tolerance group (n = 68) and a prediabetes/type 2 diabetes group (n = 110) were collected; then, circulating levels of CTRP1, adiponectin, and FGF21 were determined via enzyme-linked immunosorbent assay in all sera. Subjects with either prediabetes or diabetes exhibited higher circulating CTRP1 levels than healthy subjects. Sera analysis revealed that CTRP1 was positively correlated with age, body mass index, fasting blood glucose, and circulating FGF21 levels. However, CTRP1 was negatively correlated with total cholesterol and total circulating adiponectin levels in univariate analysis. In addition, multivariate analysis found that CTRP1 was independently associated with age, fasting blood glucose, and circulating FGF21 levels. CTRP1 was correlated with homeostasis model assessment-β (HOMA-β), but no correlation was observed with HOMA-insulin resistance. In conclusion, circulating CTRP1 levels are increased in subjects with type 2 diabetes and are positively associated with circulating FGF21 levels.

C1q/TNF-related protein-1 functions to protect against acute ischemic injury in the heart

Obesity is associated with an increased risk of cardiovascular disease. C1q/TNF-related protein (CTRP)-1 is a poorly characterized adipokine that is up-regulated in association with ischemic heart disease. We investigated the role of CTRP1 in myocardial ischemia injury. CTRP1-knockout mice showed increased myocardial infarct size, cardiomyocyte apoptosis, and proinflammatory gene expression after I/R compared with wild-type (WT) mice. In contrast, systemic delivery of CTRP1 attenuated myocardial damage after I/R in WT mice. Treatment of cardiomyocytes with CTRP1 led to reduction of hypoxia-reoxygenation-induced apoptosis and lipopolysaccharide-stimulated expression of proinflammatory cytokines, which was reversed by inhibition of sphingosine-1-phosphate (S1P) signaling. Treatment of cardiomyocytes with CTRP1 also resulted in the increased production of cAMP, which was blocked by suppression of S1P signaling. The antiapoptotic and anti-inflammatory actions of CTRP1 were cancelled by inhibition of adenylyl cyclase or knockdown of adiponectin receptor 1. Furthermore, blockade of S1P signaling reversed CTRP1-mediated inhibition of myocardial infarct size, apoptosis, and inflammation after I/R in vivo. These data indicate that CTRP1 protects against myocardial ischemic injury by reducing apoptosis and inflammatory response through activation of the S1P/cAMP signaling pathways in cardiomyocytes, suggesting that CTRP1 plays a crucial role in the pathogenesis of ischemic heart disease.

Circulating level of CTRP1 in patients with nonalcoholic fatty liver disease (NAFLD): is it through insulin resistance?

Nonalcoholic fatty liver disease (NAFLD) is considered as one of the most common liver diseases. It is robustly linked to obesity and insulin resistance and is regarded as hepatic manifestation of metabolic syndrome (MetS). Adipokines are involved in the pathophysiology of liver diseases. The aim of this study was to evaluate the plasma concentrations of CTRP1 (complement-C1q TNF-related protein 1) in 22 patients with NAFLD, 22 patients with type 2 diabetes mellitus (T2DM), 22 patients with NAFLD+T2DM and 21 healthy controls, as well as their correlation with the level of metabolic and hepatic parameters. Plasma concentration of CTRP1 was measured with ELISA method. Plasma concentration of CTRP1 in patients with NAFLD, T2DM and NAFLD+T2DM were significantly higher than healthy subjects (p<0.0001). Moreover, we observed significant positive correlations between plasma level of CTRP1 and fasting blood glucose (FBG) (p<0.001), homeostasis model assessment of insulin resistance (HOMA-IR) (p<0.001), body mass index (BMI) (p = 0.001), alanine amino transferase (ALT) (p = 0.002), gamma glutamyl transferase (γ-GT) (p<0.001) and liver stiffness (LS) (p<0.001). Our results indicate the strong association of CTRP1 with insulin resistance in NAFLD. Also, it seems that CTRP1 can be considered as an emerging biomarker for NAFLD, however, more studies are necessary to unravel the role of CTRP1 in NAFLD pathogenesis.

The association of circulating levels of complement-C1q TNF-related protein 5 (CTRP5) with nonalcoholic fatty liver disease and type 2 diabetes: a case-control study

BACKGROUND

It is well-established that nonalcoholic fatty liver disease (NAFLD) is associated with type 2 diabetes mellitus (T2DM). Complement-C1q TNF-related protein 5 (CTRP5) is a novel adipokine involved in the regulation of lipid and glucose metabolism. We aimed to assess plasma levels of CTRP5 in patients with NAFLD (n = 22), T2DM (n = 22) and NAFLD with T2DM (NAFLD + T2DM) (n = 22) in comparison with healthy subjects (n = 21) and also to study the association between CTRP5 levels and NAFLD and diabetes-related parameters.

METHODS

All subjects underwent anthropometric assessment, biochemical evaluation and liver stiffness (LS) measurement. Insulin resistance (IR) was determined by the homeostasis model assessment (HOMA). Plasma CTRP5 levels were measured by enzyme-linked immunosorbent assay.

RESULTS

We found significantly lower plasma levels of CTRP5 in patients with NAFLD + T2DM, NAFLD and T2DM (122.52 ± 1.92, 124.7 ± 1.82 and 118.31 ± 1.99 ng/ml, respectively) in comparison with controls (164.96 ± 2.95 ng/ml). In the whole study population, there was a significant negative correlations between CTRP5 and body mass index (r = -0.337; p = 0.002), fasting blood glucose (FBG) (r = -0.488; p < 0.001), triglyceride (TG) (r = -0.245; p = 0.031), HOMA-IR (r = -0.492; p < 0.001), insulin(r = -0.338; p = 0.002), LS (r = -0.544; p < 0.001), alanine aminotransferase (ALT) (r = -0.251; p = 0.027), waist-to-hip ratio (WHR) (r = -0.352; p = 0.002) and waist circumference (WC) (r = -0.357; p = 0.001). After adjustment for BMI, decrease in circulating levels of CTRP5 remained as a significant risk factor for NAFLD, T2DM and NAFLD + T2DM. The receiver operating characteristic (ROC) curves of circulating CTRP5 in predicting NAFLD and T2DM demonstrated an area under the curve (AUC) of 0.763 in T2DM, and 0.659 in NAFLD + T2DM.

CONCLUSIONS

It appears that the decreased levels of CTRP5 contribute to the increased risk of T2DM and NAFLD.

Association of circulating C1q/TNF-related protein 1 levels with coronary artery disease in men

OBJECTIVE

Obesity is a major risk factor for cardiovascular disease. Recent evidence demonstrates that dysregulation of fat-derived hormones, also known as adipokines, is linked with the pathogenesis of obesity-related disorders including coronary artery disease (CAD). Here, we investigated whether circulating level of an adipokine C1q/TNF-related protein (CTRP) 1 is associated with the prevalence of CAD.

METHODS AND RESULTS

Consecutive 76 male CAD patients were enrolled from inpatients that underwent coronary angiography. Sixty four healthy male subjects served as controls. Plasma CTRP1 concentration was determined by enzyme-linked immunosorbent assay. CTRP1 levels were correlated positively with systolic blood pressure (BP) and triglyceride levels, and negatively with HDL cholesterol levels in all subjects. Plasma levels of CTRP1 were significantly higher in CAD patients than in control subjects (CAD: 443.3±18.6 ng/ml, control: 307.8±21.5 ng/ml, p<0.001). Multiple logistic regression analysis with body mass index, systolic BP, glucose, total cholesterol, HDL cholesterol, triglyceride, adiponectin and CTRP1 revealed that CTRP1 levels, together with systolic BP and HDL cholesterol, correlated with CAD.

CONCLUSIONS

Our data indicate the close association of high CTRP1 levels with CAD prevalence, suggesting that CTRP1 represents a novel biomarker for CAD.

Metabolic function of the CTRP family of hormones

Maintaining proper energy balance in mammals entails intimate crosstalk between various tissues and organs. These inter-organ communications are mediated, to a great extent, by secreted hormones that circulate in blood. Regulation of the complex metabolic networks by secreted hormones (e.g., insulin, glucagon, leptin, adiponectin, FGF21) constitutes an important mechanism governing the integrated control of whole-body metabolism. Disruption of hormone-mediated metabolic circuits frequently results in dysregulated energy metabolism and pathology. As part of an effort to identify novel metabolic hormones, we recently characterized a highly conserved family of 15 secreted proteins, the C1q/TNF-related proteins (CTRP1-15). While related to adiponectin in sequence and structural organization, each CTRP has its own unique tissue expression profile and non-redundant function in regulating sugar and/or fat metabolism. Here, we summarize the current understanding of the physiological functions of CTRPs, emphasizing their metabolic roles. Future studies using gain-of-function and loss-of-function mouse models will provide greater mechanistic insights into the critical role CTRPs play in regulating systemic energy homeostasis.

Circulating complement-C1q TNF-related protein 1 levels are increased in patients with type 2 diabetes and are associated with insulin sensitivity in Chinese subjects

Background

Complement-C1q TNF-related protein 1 (CTRP1), a member of the CTRP superfamily, possesses anti-inflammatory and anti-diabetic effects in mice. However, the clinical relevance of CTRP1 has been seldom explored. The current study aimed to investigate the association of circulating CTRP1 and type 2 diabetes mellitus (T2DM) in a Chinese population.

Design and Methods

Serum CTRP1 and adiponectin levels of 96 T2DM patients and 85 healthy subjects were determined by ELISA, and their associations with adiposity, glucose and lipid profiles were studied. In a subgroup of this study, the 75-g oral glucose tolerance test (OGTT) was performed in 20 healthy and 20 T2DM subjects to evaluate the relationship among serum levels of CTRP1 and adiponectin, insulin secretion and insulin sensitivity.

Results

Serum CTRP1 levels were significantly increased in patients with T2DM, compared with healthy controls (p<0.001). Similar to adiponectin, serum levels of CTRP1 were significantly correlated to several parameters involved in glucose metabolism and insulin resistance, and independently associated with fasting glucose levels (p<0.05) after BMI and gender adjustments. Furthermore, CTRP1 levels were positively correlated to insulin secretion, while negatively to insulin sensitivity, as measured by OGTT.

Conclusion

CTRP1 is a novel adipokine associated with T2DM in humans. The paradoxical increase of serum CTRP1 levels in T2DM subjects may be due to a compensatory response to the adverse glucose and lipid metabolism, which warrants further investigation.

Elevated circulating levels of CTRP1, a novel adipokine, in diabetic patients

Complement C1q tumor necrosis factor-related protein 1 (CTRP1), an adipose tissue-derived adipokine has been shown to decrease blood glucose levels and to improve metabolism of glucose in mice. In addition, CTRP1 has exhibited significant association with BMI, adiponectin and TNF-α in diabetic animal models. However, there are no published studies addressing CTRP1 levels in type 2 diabetic patients. Therefore, it was of interest to evaluate plasma CTRP1 levels and associated clinical parameters and biomarkers in patients with type 2 diabetes. 135 subjects were recruited to this study, including 62 type 2 diabetic patients (DM group) and 73 healthy subjects (control group). We measured biochemical parameters, CTRP1, TNF-α and adiponectin using enzyme-linked immunosorbent assay (ELISA). Plasma CTRP1 levels showed a significant difference between the DM group and the control group (646.3 ± 154.4 ng/mL vs. 442.6 ± 165.4 ng/mL, p < 0.01). In addition, CTRP1 was strongly positively associated with BMI, glucose levels, HbA1c, HOMA-IR and TNF-α in diabetic patients. CTRP1 showed negative correlation with adiponectin. In Multivariate regression analysis, CTRP1 was strongly independently associated with diabetes when CTRP1 levels were analyzed by both as a continuous variable and quartile (OR: 1.009, 95% CI: 1.004-1.015, p < 0.05; OR: 2.443, 95% CI: 1.379-4.182, p < 0.01, respectively). Increased plasma CTRP1 was independently associated with type 2 diabetes. Profiling of plasma adipokines such as CTRP1 is particularly important to obtain a greater understanding of their contribution to the type 2 diabetic state.

Effects of a combined aerobic and resistance exercise program on C1q/TNF-related protein-3 (CTRP-3) and CTRP-5 levels

OBJECTIVE

To examine the effect of a combined exercise program on C1q/tumor necrosis factor-related protein (CTRP) 3 and CTRP-5 levels and novel adiponectin paralogs suggested to be links between metabolism and inflammation and to evaluate sex differences and association with cardiometabolic risk factors in humans with use of a newly developed ELISA.

RESEARCH DESIGN AND METHODS

This cross-sectional study explored the implications of CTRP-3 and CTRP-5 on cardiometabolic parameters in 453 nondiabetic Korean adults. In addition, we evaluated the impact of a 3-month combined exercise program on CTRP-3 and CTRP-5 levels in 76 obese women. The exercise program consisted of 45 min of aerobic exercise at an intensity of 60-75% of the age-predicted maximum heart rate (300 kcal/session) and 20 min of resistance training (100 kcal/session) five times per week.

RESULTS

Both CTRP-3 and CTRP-5 concentrations were significantly higher in women (P<0.001) than in men (P=0.030). In a multiple stepwise regression analysis, CTRP-3 levels were independently associated with age, sex, and triglyceride, LDL cholesterol, adiponectin, and retinol-binding protein 4 (RBP4) levels (R2=0.182). After 3 months of a combined exercise program, cardiometabolic risk factors, including components of metabolic syndrome, insulin resistance, and RBP4 levels, decreased significantly. In particular, CTRP-3 levels decreased significantly (median [interquartile range] 444.3 [373.8-535.0] to 374.4 [297.2-435.9], P<0.001), whereas CTRP-5 levels were slightly increased (34.1 [28.6-44.3] to 38.4 [29.8-55.1], P=0.048).

CONCLUSIONS

A 3-month combined exercise program significantly decreased CTRP-3 levels and modestly increased CTRP-5 levels in obese Korean women.