Regulation and function of collagenous repeat containing sequence of 26-kDa protein gene product "cartonectin"

BGM, a Newly Synthesised Boron Compound, Induces Apoptosis and Reduces Oxidative Stress by Inhibiting Lipogenesis in 3T3-L1 Adipocytes via PPARγ and CTRP3

Obesity is a chronic disease associated with increased morbidity and mortality. The rapidly increasing prevalence of obesity makes it a global health problem, while treatment options remain limited. Given the potential of boron in the treatment of obesity, the aim of this study is to investigate the anti-adipogenic activity of the newly synthesised boron glycine monoester compound (BGM) using 3T3-L1 adipocytes by analysing lipid accumulation, CTRP3 and PPARy gene expression, oxidative stress and apoptotic effects. 3T3-L1 fibroblast cells (ATCC® CL-173) were transformed into adipocyte cells in vitro. Fat accumulation in the 3T3-L1 adipocyte cells was detected by Oil Red O staining. Gene expression levels were determined with qPCR. Biochemical analyzes were performed using spectrophotometric method (CAT, ALP and ACP) and ELISA kit (TAS, TOS, NADP-IDH). Apoptosis studies were performed on the muse cell nalyser using the Muse Annexin V & Dead Cell Assay Kit. When BGM-treated cells were compared to control adipocyte cells, lipid accumulation decreased in a dose-dependent manner. BGM-treated adipocyte cells had higher CTRP3 expression levels and lower PPAR-γ gene expression levels compared to control adipocyte cells (p < 0.001). While BGM application increased the TAS level, it showed an antioxidant effect by regulating the activity of oxidative metabolism enzymes (p < 0.001). BGM application increased total apoptosis by 1.5-fold. These results show that BGM is a potential therapeutic agent for obesity by regulating the expression of genes related to adipogenesis and lipogenesis in adipocyte cells and by affecting the activity of enzymes of oxidative metabolism and apoptosis.

CTRP3 protects against uric acid-induced endothelial injury by inhibiting inflammation and oxidase stress in rats

Hyperuricemia, which contributes to vascular endothelial damage, plays a key role in multiple cardiovascular diseases. This study was designed to investigate whether C1q/tumor necrosis factor (TNF)-related protein 3 (CTRP3) has a protective effect on endothelial damage induced by uric acid and its underlying mechanisms. Animal models of hyperuricemia were established in Sprague-Dawley (SD) rats through the consumption of 10% fructose water for 12 weeks. Then, the rats were given a single injection of Ad-CTRP3 or Ad-GFP. The animal experiments were ended two weeks later. In vitro, human umbilical vein endothelial cells (HUVECs) were first infected with Ad-CTRP3 or Ad-GFP. Then, the cells were stimulated with 10 mg/dL uric acid for 48 h after pretreatment with or without a Toll-like receptor 4 (TLR4)-specific inhibitor. Hyperuricemic rats showed disorganized intimal structures, increased endothelial apoptosis rates, increased inflammatory responses and oxidative stress, which were accompanied by reduced CTRP3 and elevated TLR4 protein levels in the thoracic aorta. In contrast, CTRP3 overexpression decreased TLR4 protein levels and ameliorated inflammatory responses and oxidative stress, thereby improving the morphology and apoptosis of the aortic endothelium in rats with hyperuricemia. Similarly, CTRP3 overexpression decreased TLR4-mediated inflammation, reduced oxidative stress, and rescued endothelial damage induced by uric acid in HUVECs. In conclusion, CTRP3 ameliorates uric acid-induced inflammation and oxidative stress, which in turn protects against endothelial injury, possibly by inhibiting TLR4-mediated inflammation and downregulating oxidative stress.

New Insights Into Implications of CTRP3 in Obesity, Metabolic Dysfunction, and Cardiovascular Diseases: Potential of Therapeutic Interventions

Adipose tissue, as the largest endocrine organ, secretes many biologically active molecules circulating in the bloodstream, collectively termed adipocytokines, which not only regulate the metabolism but also play a role in pathophysiological processes. C1q tumor necrosis factor (TNF)-related protein 3 (CTRP3) is a member of C1q tumor necrosis factor-related proteins (CTRPs), which is a paralog of adiponectin. CTRP3 has a wide range of effects on glucose/lipid metabolism, inflammation, and contributes to cardiovascular protection. In this review, we comprehensively discussed the latest research on CTRP3 in obesity, diabetes, metabolic syndrome, and cardiovascular diseases.

C1q-tumour necrosis factor-related protein-3 exacerbates cardiac hypertrophy in mice

AIMS

C1q-tumour necrosis factor-related protein-3 (CTRP3) is an adipokine and a paralog of adiponectin. Our previous study showed that CTRP3 attenuated diabetes-related cardiomyopathy. However, the precise role of CTRP3 in cardiac hypertrophy remains unclear. This study was aimed to clarify the role of CTRP3 involved in cardiac hypertrophy.

METHODS AND RESULTS

Cardiomyocyte-specific CTRP3 overexpression was achieved using an adeno-associated virus system, and cardiac CTRP3 expression was knocked down using gene delivery of specific short hairpin RNAs in vivo. CTRP3 expression was upregulated in murine hypertrophic hearts and failing human hearts. Increased CTRP3 was mainly derived from cardiomyocytes and induced by the production of reactive oxygen species (ROS) during the hypertrophic response. CTRP3-overexpressing mice exhibited exacerbated cardiac hypertrophy and cardiac dysfunction in response to pressure overload. Conversely, Ctrp3 deficiency in the heart resulted in an alleviated hypertrophic phenotype. CTRP3 induced hypertrophy in cardiomyocytes, which could be blocked by the addition of CTRP3 antibody in the media. Detection of signalling pathways showed that pressure overload-induced activation of the transforming growth factor β-activated kinase 1 (TAK1)-c-Jun N-terminal kinase (JNK) pathway was enhanced by CTRP3 overexpression and inhibited by CTRP3 disruption. Furthermore, we found that CTRP3 lost its pro-hypertrophic effects in cardiomyocyte-specific Tak1 knockout mice. Protein kinase A (PKA) was involved in the activation of TAK1 by CTRP3.

CONCLUSION

In conclusion, our results suggest that CTRP3 promotes pressure overload-induced cardiac hypertrophy via activation of the TAK1-JNK axis.

Hypoxia-inducible factor-1 alpha maintains mouse articular cartilage through suppression of NF-κB signaling

HIF-1α, an essential transcription factor under hypoxic condition, is indispensable for chondrocytes during skeletal development but its expression and roles in articular chondrocytes are yet to be revealed. We examined HIF-1α protein expression and the hypoxic condition during mouse osteoarthritis (OA) development using state of the art hypoxic probes and found that its expression decreased as OA progressed, coinciding with the change in hypoxic conditions in articular cartilage. Gain- and loss-of-function of HIF-1α in cell culture experiments showed that HIF-1α suppressed catabolic genes such as Mmp13 and Hif2a. We confirmed these anticatabolic effects by measuring glycosaminoglycan release from wild type and conditional knock-out mice femoral heads cultured ex vivo. We went on to surgically induce OA in mice with chondrocyte-specific deletion of Hif1a and found that the development of OA was exacerbated. Increased expression of catabolic factors and activation of NF-κB signalling was clearly evident in the knock-out mice. By microarray analysis, C1qtnf3 was identified as a downstream molecule of HIF-1α, and experiments showed it exerted anti-catabolic effects through suppression of NF-κB. We conclude that HIF-1α has an anti-catabolic function in the maintenance of articular cartilage through suppression of NF-κB signalling.

High molecular weight, but not total, CTRP3 levels are associated with serum triglyceride levels

C1q/TNF-related protein 3 (CTRP3) is a relatively novel adipose tissue-derived cytokine (adipokine) which has been linked to improved glucose regulation and insulin sensitivity. However, the relationship between circulating CTRP3 levels and diabetes is controversial. CTRP3 can circulate in different oligomeric complexes: trimeric, hexameric, and high molecular weight (HMW) oligomeric complexes. However, the concentration of the different oligomeric complexes in human disease states has not been previously investigated. Therefore, the purpose of this study was to compare the levels of different oligomeric complexes of CTRP3 between type 2 diabetic and nondiabetic individuals. Additionally, the association between the oligomeric complexes and other serum factors was examined. CTRP3 primarily circulates in the HMW complex (>50%) and the hexametric multimer, with no CTRP3 detected in the trimeric complex or as a monomer. Further, no differences were observed in total, hexameric, or HMW CTRP3 levels regardless of diabetic status. Surprisingly, HMW CTRP3 was found to be positively correlated with circulating triglyceride levels. Combined, these data suggest that CTRP3 is associated with triglyceride regulation, not diabetic status. These data may explain some of the discrepancies in the literature as elevated triglyceride levels are often detected in patients with obesity and type 2 diabetes.

Short-Term Impact of Laparoscopic Sleeve Gastrectomy on Serum Cartonectin and Vaspin Levels in Obese Subjects

BACKGROUND

Cartonectin is a potent anti-inflammatory adipokine that might be implicated in metabolism and energy storage. Our objective was to evaluate the influence of weight reduction following laparoscopic sleeve gastrectomy (LSG) on serum cartonectin and vaspin levels.

SUBJECTS AND METHODS

Thirty-two individuals (29 female and 3 male) with morbid obesity underwent LSG. Anthropometric indices, lipid profile, fasting serum concentrations of glucose, insulin, vaspin, and cartonectin were measured prior and 3 months after LSG. Insulin sensitivity was determined using the homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Following LSG, circulating cartonectin level increased significantly while serum vaspin was significantly decreased. The percentage change of serum cartonectin level correlated negatively with the percentage changes in body mass index, waist circumference, and waist-hip ratio and positively with percentage changes in LDL-C, triglycerides, and HOMA-IR after adjustment for age and sex. Moreover, the changes in vaspin concentration positively correlated with the changes in insulin level and HOMA-IR after adjustment for age and sex. In a multiple stepwise linear regression model, the changes in waist circumference explained 13% variability of changes in cartonectin level while the changes in HOMA-IR and LDL-C were responsible for 31% of the variability in changes of vaspin level.

CONCLUSION

LSG-induced weight loss rapidly increases serum cartonectin level and decreases the serum vaspin level in morbidly obese subjects. The changes in cartonictin level seem to be influenced by the changes of waist circumference while the changes of HOMA-IR and LDL-C might be determinant factors of the changes in vaspin level.

Decreased CTRP3 Plasma Concentrations Are Associated with Sepsis and Predict Mortality in Critically Ill Patients

C1q/ tumor necrosis factor (TNF)-like protein 3 (CTRP3) represents a novel member of the adipokine family that exerts favorable metabolic actions in humans. However, the role of CTRP3 in critical illness and sepsis is currently unknown. Upon admission to the medical intensive care unit (ICU), we investigated CTRP3 plasma concentrations in 218 critically ill patients (145 with sepsis, 73 without sepsis). Results were compared with 66 healthy controls. CTRP3 plasma levels were significantly decreased in critically ill patients, when compared to healthy controls. In particular, low CTRP3 levels were highly associated with the presence of sepsis. CTRP3 levels were neither associated with obesity nor diabetes. In critically ill patients, CTRP3 plasma concentrations were inversely correlated with inflammatory cytokines and classical sepsis markers. Among a wide group of adipokines, CTRP3 only correlated with circulating resistin. Low CTRP3 plasma levels were associated with the overall mortality, and CTRP3 levels below 620.6 ng/mL indicated a particularly increased mortality risk in ICU patients. Our study demonstrates for the first time the role of circulating CTRP3 as a biomarker in critically ill patients that might facilitate diagnosis of sepsis as well as prognosis prediction. The association between low CTRP3 and increased inflammation warrants further pathophysiological investigations.

C1q/TNF-related protein-3 and glucose homeostasis

Adipokines are cytokines produced by adipocytes that may mediate inflammatory processes, whilst adipocyte-derived proteins may have the converse effect. C1q/TNF-related protein-3 or CTRP3 is a novel adipokine that is expressed and released by most types of human tissues including adipose tissue. This adipokine, considered as an adiponectin, can normalize blood glucose by several mechanisms. In addition, it can modulate the expression/secretion of other cytokine and adipokines leading to lower insulin resistance in peripheral tissues. Beneficial effects of CTRP3 against hyperglycemia-induced complications in the kidney and eye have been reported. In this review, we have presented the latest findings on the in vitro and in vivo hypoglycemic effects of CTRP3, followed by the findings on the preventive/therapeutic effects of CTRP3 adipokines against diabetes related complications.

The cartonectin levels at different stages of chronic kidney disease and related factors

Introduction: Cartonectin was defined as a new adipokine released from rat and human adipocyte tissues, which is also known as CORS 26 or CTRP3 protein. Although there are several studies investigating the effects of cartonectin with obesity, anti-inflammatory mechanisms, and cardioprotective effects, there is no study about the effects of cartonectin in patients with chronic kidney disease yet. We aimed to investigate cartonectin levels in predialysis and dialysis patient groups, in other words, at different stages of chronic kidney disease, by comparing with the control group. In addition, we aimed to discuss the probable causes of the differences between the patient groups that would be determined, together with the factors that might be effective.

Methods: A total of 150 patients, including 47 hemodialysis patients, 73 predialysis CKD patients, and 30 healthy individuals were enrolled in the study. Serum cartonectin levels were determined by using enzyme-linked immunosorbent assay (ELISA) method.

Findings: Serum cartonectin levels were found to be significantly higher in the hemodialysis patient group compared to predialysis group and healthy individuals (p < 0.01). Furthermore, serum cartonectin levels were found to be negatively correlated with GFR, BMI, glucose, LDL, and platelet levels, whereas a positive correlation was observed with creatinine levels.

Discussion: In our study, we found that the cartonectin levels increased as GFR decreased and were significantly higher in hemodialysis patients. Cartonectin is structurally closely related to adiponectin. It is remarkable that the level of cartonectin is also high in hemodialysis patients, like adiponectin.

Melatonin improves cardiac function in a mouse model of heart failure with preserved ejection fraction

Melatonin has been shown to inhibit myocardial infarction-induced apoptosis, its function in heart failure with preserved ejection fraction (HFpEF) has not been investigated. This study aimed to investigate whether melatonin attenuates obesity-related HFpEF. Male mice were fed a high-fat diet (HFD) from weaning to 6 months of age to induce HFpEF. The mice were orally administered melatonin (50 mg/kg) by 3 weeks. Diastolic function was significantly improved by melatonin supplementation in mice fed an HFD. Melatonin attenuated obesity-induced myocardial oxidative stress and apoptosis and promoted the secretion of C1q/tumour necrosis factor-related protein 3 (CTRP3) by adipose tissue. And depletion of circulating CTRP3 largely abolished melatonin-mediated cardio-protection. Melatonin-mediated secretion of adipocyte-derived CTRP3 activated NF-E2-related factor 2 (Nrf2), which were largely abrogated by knocking down CTRP3 in adipocytes or Nrf2 in cardiomyocytes. Nrf2 activation was mediated by miR-200a, and a miR-200a antagomir offset the effects of melatonin-conditioned medium on Nrf2 expression. Our results indicate that melatonin can be used to treat and prevent obesity-related HFpEF.

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Melatonin attenuates obesity-related heart failure with preserved ejection fraction.

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Melatonin attenuates obesity-induced myocardial injury via adipose tissue-derived CTRP3.

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Melatonin-mediated secretion of adipocyte-derived CTRP3 activates Nrf2 by miR-200a.

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.

CTRP3 promotes energy production by inducing mitochondrial ROS and up-expression of PGC-1α in vascular smooth muscle cells

C1q/tumor necrosis factor-related protein-3 (CTRP3) is an adipokine with modulation effects on metabolism and inflammation. Adenosine triphosphate (ATP) exerts multiple biological effects in vascular smooth muscle cells (VSMCs) and energy imbalance is involved in vascular diseases. This study aimed to explore the effect of CTRP3 on energy production and its underlying mechanism in VSMCs. Our results indicated that exogenous CTRP3 increased ATP synthesis and the protein expression of oxidative phosphorylation (OXPHOS)-related molecules, including peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, sirtuin-3 (SIRT3), complex I, II, III, and V in cultured VSMCs. Depletion of endogenous CTRP3 by small interfering RNA (siRNA) reduced ATP synthesis and the expression of those molecules. PGC-1α knockdown abrogated CTRP3-induced ATP production and OXPHOS-related protein expression. Furthermore, CTRP3 increased mitochondrial reactive oxygen species (ROS) production and mitochondrial membrane potential level. Pretreatment with N-acetyl-L-cysteine, a reactive oxygen species scavenger, and cyanidem-chlorophenylhydrazone, an uncoupler of OXPHOS, suppressed CTRP3-induced ROS production, PGC-1α expression and ATP synthesis. In conclusion, CTRP3 modulates mitochondrial energy production through targets of ROS and PGC-1α in VSMCs.

C1q and tumor necrosis factor-related protein 3 is present in human cord blood and is associated with fetal growth

BACKGROUND

To determine the presence of C1q and tumor necrosis factor-related protein 3 (CTRP3) in cord blood and its relationship with fetal growth among Chinese newborns.

METHODS

This pilot study recruited 126 infants (small for gestational age [SGA], n=34; appropriate for gestational age [AGA], n=60; large for gestational age [LGA], n=32); cord blood CTRP3 levels were measured, and fetal growth parameters were collected.

RESULTS

Median (25-75th percentile) CTRP3 levels in the SGA, AGA, and LGA groups were 297.2 (236.4-360.2), 297.5 (261.0-369.9), and 368.6 (298.5-507.1) ng/ml, respectively (P=0.01). LGA infants had higher CTRP3 levels than AGA infants (multiple linear regression analysis; P=0.01). The CTRP3 levels were positively correlated with birth weight (r=0.25, P<0.01), Ponderal index (r=0.28, P<0.01), and placental weight (r=0.20, P=0.03) in the total study population. In the subgroup analysis, CTRP3 levels were negatively correlated with birth length z scores (r=-0.39, P=0.03) and were positively correlated with the Ponderal index (r=0.43, P=0.02) only in the SGA group; no other significant correlations were observed. The CTRP3 levels were similar between the sexes (P=NS).

CONCLUSIONS

CTRP3 is present in cord blood and might be involved in fetal growth.

Serum Omentin Levels in Adolescent Girls With Anorexia Nervosa and Obesity

It is believed that omentin is secreted by stromal cells of adipose tissue and modulates insulin sensitivity. Data from a few studies have shown lower serum omentin in obese children and higher in anorexia nervosa. However, to date, there is lack of research on serum omentin concentrations in adolescent patients in a wide range of body mass index (BMI) and insulin resistance. In this cross-sectional study omentin-1 serum concentrations were evaluated using commercially available ELISA kit in 47 Polish girls with restrictive anorexia nervosa (AN), 50 with simple obesity (OB) and 39 healthy controls (C). The mean serum omentin-1 concentration in girls with AN was statistically significantly higher than that of C and OB girls. Statistically significant (P<0.0001) negative correlations between the serum concentrations of omentin-1 and body weight (r=−0.73), BMI (r=−0.75), standard deviation score for body mass index (BMI-SDS) (r=−0.75), insulin (r=−0.81) and HOMA-IR index (r=−0.82) were seen in the entire examined population. We conclude, that omentin-1 is the nutritional marker reflecting body weight and insulin resistance. Our findings support the hypothesized role of omentin in maintenance of body weight and regulation of appetite and suggest the adaptation of its secretion to body weight and glucose metabolism.

GLP-1 receptor agonist increases the expression of CTRP3, a novel adipokine, in 3T3-L1 adipocytes through PKA signal pathway

OBJECTIVE

To investigate the effects of Exendin-4 (Ex-4), a glucagon-like peptide-1 (GLP-1) receptor agonist, on the expression of C1q/TNF-related protein-3 (CTRP3), a novel adipokine, in 3T3-L1 adipocytes. The role of protein kinase A (PKA) signal pathway in the effects was also investigated.

METHODS

The mRNA and protein expressions of CTRP3 in 3T3-L1 adiocytes were detected by real-time polymerase chain reaction and western blot, respectively. Exendin-fragment 9-39 (Ex-9), a specific GLP-1 receptor antagonist, and H89, a selective antagonist of PKA, were used to confirm the signal pathway of Ex-4 on CTRP3.

RESULTS

2.5 or 5.0 nmol/l Ex-4 treatment for 8 h increased the expressions of CTRP3 mRNA and protein as well as PKA protein in 3T3-L1 adipocytes significantly, while Ex-9 or H89 blocked the up-regulation of CTRP3 expression induced by Ex-4 completely.

CONCLUSION

GLP-1 receptor agonist increases the expression of CTRP3 mRNA and protein in 3T3-L1 adipocytes via PKA signal pathway.

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.

Overexpression of C1q/Tumor Necrosis Factor–Related Protein-3 Promotes Phosphate-Induced Vascular Smooth Muscle Cell Calcification Both In Vivo and In Vitro

Objective—

Vascular calcification is highly correlated with increased cardiovascular morbidity and mortality. C1q/tumor necrosis factor–related protein-3 (CTRP3) is a newly identified adipokine that plays important roles in cardiovascular system. Here, we investigated the role of CTRP3 in vascular calcification and its underlying mechanism.

Approach and Results—

Adenine-induced chronic renal failure rat model was used to mimic the process of arterial medial calcification. The level of CTRP3 was elevated in serum and abdominal aorta of chronic renal failure rats. Periadventitial gene delivery of CTRP3 significantly accelerated the calcification of abdominal aorta and arterial ring. In cultured vascular smooth muscle cells (VSMCs), CTRP3 increased β-glycerophosphate–induced calcium deposition and alkaline phosphatase activity. Although CTRP3 alone was not sufficient to induce calcification in VSMCs, it upregulated the expression of osteogenic marker genes including runt-related transcription factor 2 ( Runx2 ), bone morphogenetic protein 2, and osteopontin. CTRP3 further enhanced β-glycerophosphate–induced downregulation of smooth muscle α-actin and smooth muscle 22α, while augmenting osteogenic marker expression in VSMCs induced by β-glycerophosphate. In contrast, knockdown of CTRP3 in VSMCs potently suppressed β-glycerophosphate–induced calcification. Mechanistically, knockdown of Runx2 inhibited CTRP3-promoted VSMC calcification. CTRP3 increased extracellular signal–regulated kinase 1/2 phosphorylation and reactive oxygen species production. Preincubation with U0126, an extracellular signal–regulated kinase 1/2 upstream kinase inhibitor, had no effect on CTRP3-induced reactive oxygen species production. However, pretreatment with N-acetyl- l -cysteine, a reactive oxygen species scavenger, suppressed CTRP3-induced extracellular signal–regulated kinase 1/2 phosphorylation. Both N-acetyl- l -cysteine and U0126 significantly inhibited CTRP3-induced upregulation of Runx2 and calcified nodule formation.

Conclusions—

CTRP3 promotes vascular calcification by enhancing phosphate-induced osteogenic transition of VSMC through reactive oxygen species–extracellular signal–regulated kinase 1/2–Runx2 pathway.

C1q/TNF-related protein-3 (CTRP-3) and pigment epithelium-derived factor (PEDF) concentrations in patients with type 2 diabetes and metabolic syndrome

Recent studies have suggested that a novel adipokine, C1q/tumor necrosis factor-related protein-3 (CTRP-3), a paralog of adiponectin, may play an important role in the regulation of glucose metabolism and innate immunity. Pigment epithelium-derived factor (PEDF), a multifunctional protein with antioxidant and anti-inflammatory properties, is associated with insulin resistance and metabolic syndrome. We examined circulating CTRP-3 and PEDF concentrations in 345 subjects with diverse glucose tolerance statuses. Furthermore, we evaluated the involvement of CTRP-3 and PEDF with cardiometabolic risk factors including insulin resistance, high-sensitivity C-reactive protein (hsCRP), estimated glomerular filtration rate (eGFR), and brachial-ankle pulse wave velocity (baPWV). CTRP-3 concentrations were significantly higher in patients with type 2 diabetes or prediabetes than the normal glucose tolerance group, whereas PEDF levels were not different. Subjects with metabolic syndrome showed significantly higher levels of both CTRP-3 and PEDF compared with subjects without metabolic syndrome. Both CTRP-3 and PEDF were significantly associated with cardiometabolic parameters, including waist-to-hip ratio, triglycerides, HDL-cholesterol, alanine aminotransferase, eGFR, hsCRP, and baPWV. In conclusion, circulating CTRP-3 concentrations were elevated in patients with glucose metabolism dysregulation. Both CTRP-3 and PEDF concentrations were increased in subjects with metabolic syndrome and associated with various cardiometabolic risk factors.

Establishment of an optimized PCR method using sequence-specific primers for screening multiple gene polymorphisms simultaneously

The present study aimed to explore the factors that affect polymerase chain reaction using sequence-specific primers (PCR-SSP) and to establish an optimized PCR-SSP method for detecting multiple gene polymorphisms simultaneously. The amplification system parameters, including the concentrations of Mg2+, dNTPs, pfu Taq, primers and control primers, were optimized using the designed PCR-SSP reactions. The resulting optimized reaction system was used to determine the melting temperature of the genomic DNA and the cycling parameters. The optimized PCR-SSP method was used to analyze the polymorphisms of the following genes: mutations -308A/G and -238G/A in TNF-α, -174G/C in IL-6 and C/T mutation at exon 188 of CYP2D6 *10B. The PCR-SSP amplification system was optimized; in a 20 µl reaction system, the quantities of Mg2+, dNTPs, pfu Taq, primers, control primers and genomic DNA were 3.25 µM, 0.5 mM, 2.5 units, 0.5 µM, 0.2 µM and 0.15 µg, respectively. The cycling system comprised 5 start cycles and took 15 min to melt a genomic DNA sample using a touchdown protocol. The optimized PCR-SSP is suitable for polymorphism analysis of polygenic SNPs in large genomic DNA samples and a number of different genes.

CTRP family: linking immunity to metabolism

It is well known that infectious and inflammatory diseases such as sepsis and severe inflammatory response syndrome are accompanied by metabolic alterations such as insulin resistance. Conversely, metabolic diseases such as visceral obesity and type 2 diabetes are characterized by high levels of proinflammatory cytokines. Metabolism and immunity are linked by proteins of dual function. Adiponectin, a member of the C1q/TNF-related protein (CTRP) family, has attracted much interest because of its anti-inflammatory and insulin-sensitizing effects. To date, 15 additional CTRP family members have been identified that might also play a role in metabolism and immunity. This review focuses on the biochemistry and pleiotropic physiological functions of CTRPs as new molecular mediators connecting inflammatory and metabolic diseases.

C1q/TNF-related protein-3 (CTRP-3) is secreted by visceral adipose tissue and exerts antiinflammatory and antifibrotic effects in primary human colonic fibroblasts

BACKGROUND

The adipokine CTRP-3 (C1q/TNF-related protein-3) belongs to the C1q/TNF-related protein family which antagonizes the effects of lipopolysaccharide (LPS). The aim was to investigate the antiinflammatory and antifibrotic role of CTRP-3 in Crohn's disease (CD).

METHODS

Mesenteric adipose tissue (MAT) of patients with CD or colonic cancer (CC) was resected. Human primary colonic lamina propria fibroblasts (CLPF) were isolated from controls and CD patients. Concentrations of chemokines and cytokines in the supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Expression of connective tissue growth factor (CTGF), collagen I, and collagen III was analyzed by real-time polymerase chain reaction (PCR). Recombinant CTRP-3 expressed in insect cells was used for stimulation experiments.

RESULTS

CTRP-3 is synthesized and secreted by MAT resected from patients with CD, ulcerative colitis (UC), CC, and sigma diverticulitis as well as by murine and human mature adipocytes. CTRP-3 had no effect on the basal secretion of MCSF, MIF, or RANTES in MAT of CD and control patients. LPS-stimulation (10 ng/mL) significantly increased IL-8 release in CLPF of CD patients and, to a lesser extent, in cells of controls and of fibrotic CD tissue. CTRP-3 significantly and dose-dependently reduced LPS-induced IL-8 secretion in CLPF within 8 hours after LPS exposure, whereas LPS-induced IL-6 and TNF release was not affected. CTRP-3 inhibited TGF-β production and the expression of CTGF and collagen I in CLPF, whereas collagen III expression remained unchanged.

CONCLUSIONS

CTRP-3 exerts potent antiinflammatory and antifibrotic effects in CLPF by antagonizing the LPS pathway and by targeting the TGF-β-CTGF-collagen I pathway.

C1q/TNF-related protein-3 represents a novel and endogenous lipopolysaccharide antagonist of the adipose tissue

Proteins secreted by adipocytes (adipokines) play an important role in the pathophysiology of type 2 diabetes mellitus and the associated chronic and low-grade state of inflammation. It was the aim to characterize the antiinflammatory potential of the new adipocytokine, C1q/TNF-related protein-3 (CTRP-3), which shows structural homologies to the pleiotropic adipocytokine adiponectin. mRNA and protein expression of CTRP-3 was analyzed by RT-PCR and Western blot. Recombinant CTRP-3 and small interfering RNA-based strategies were used to investigate the effect of CTRP-3 on toll-like receptor (TLR) ligand, lipopolysaccharide (LPS)-, and lauric acid-induced chemokine release of monocytes and adipocytes. Together with complex ELISA-based techniques, a designed TLR4/myeloid differentiation protein-2 fusion molecule shown to bind LPS was used to prove the ability of CTRP-3 to act as endogenous LPS antagonist. CTRP-3 is synthesized in monocytes and adipocytes. The recombinant protein dose-dependently inhibits the release of chemokines in monocytes and adipocytes that were induced by lauric acid, LPS, and other TLR ligands in vitro and ex vivo. CTRP-3 inhibits monocyte chemoattractant protein-1 release in adipocytes, whereas small interfering RNA-mediated knockdown of CTRP-3 up-regulates monocyte chemoattractant protein-1 release, reduces lipid droplet size, and decreases intracellular triglyceride concentration in adipocytes, causing a dedifferentiation into a more proinflammatory and immature phenotype. By using a designed TLR4/MD-2 fusion molecule, it is shown by different techniques that CTRP-3 specifically and effectively inhibits the binding of LPS to its receptor, TLR4/MD-2. CTRP-3 inhibits three basic and common proinflammatory pathways involved in obesity and type 2 diabetes mellitus (adipo-inflammation) by acting as an endogenous LPS antagonist of the adipose tissue.

Mutation analysis of the C1QTNF3 gene in patients with schizophrenia

We previously identified a small region on chromosome 5p13 related to schizophrenia in a Puerto Rican pedigree. We screened one of the positional candidate genes, C1QTNF3, for mutations in affected family members. The direct sequencing identified 10 sequence variants, including five shared by all affected family members. Genotyping of the shared variants in a Puerto Rican sample of 118 cases and 136 controls did not reveal either allelic or genotype association with schizophrenia.

Peritoneal fluid adipokines: ready for prime time?

BACKGROUND

Visceral adipose tissues secret a variety of adipokines; however, it is not known whether they are present in the peritoneal fluid. It was the aim of this study to investigate peritoneal fluid concentrations of novel (cartonectin, omentin) and classical adipokines (leptin, adiponectin, resistin, visfatin) in patients with ascites.

MATERIAL AND METHODS

Ninety-six patients (71 men and 25 women) undergoing paracentesis were included. Of these, 76 suffered from liver cirrhosis. Adipokines were measured by enzyme-linked immunosorbent assay or Western blot.

RESULTS

Each adipokine was detected in ascites with a broad range. Serum-ascites ratios (SAR) correlated with clinical and laboratory parameters. The main variables influencing peritoneal fluid adipokine concentrations were body mass index (BMI), local inflammation, systemic inflammation and serum adipokine concentrations. Resistin was significantly higher in patients with peritonitis and showed a positive correlation with peripheral leucocytes (white blood cell count). Leptin was correlated with the underlying disease. Visfatin correlated with peripheral white blood cell and C-reactive protein levels. Omentin expression was correlated with ascitic leucocyte count, ascitic albumin concentration and low albumin SAR. BMI was correlated positively with ascitic leptin levels and cartonectin protein levels.

CONCLUSIONS

Peritoneal fluid adipokine concentrations are characterized by individual SARs, depend on the presence of peritonitis, and correlate with underlying disease, BMI and systemic inflammation. The data open a new field of research on the role of the peritoneum and visceral adipokines in gastrointestinal diseases.

Effects of the new C1q/TNF-related protein (CTRP-3) "cartonectin" on the adipocytic secretion of adipokines

BACKGROUND

Cartonectin (collagenous repeat-containing sequence of 26-kDa protein; CORS-26) was described as a new adipokine of the C1q/TNF molecular superfamily C1q/TNF-related protein-3 (CTRP-3), secreted by the adipocytes of mice and humans. The receptor and function of cartonectin are unknown and the recombinant protein is not commercially available.

OBJECTIVE

To investigate the effects of recombinant cartonectin on the secretion of adipokines such as adiponectin, leptin, and resistin from adipocytes of human and murine origin. The effect of the BMI of the adipocyte donor was also investigated.

METHODS AND PROCEDURES

Human adipocytes from pooled lean and preobese healthy individuals and murine 3T3-L1 adipocytes were used for stimulation experiments. Recombinant cartonectin was expressed in insect H5 cells. Adipokine secretion was measured using enzyme-linked immunosorbent assay. In addition, western blot analysis and luciferase reporter gene assays were employed.

RESULTS

Cartonectin (1, 10, 50, and 250 ng/ml) in higher doses stimulates the secretion of adiponectin and resistin from murine adipocytes. This effect is not caused by an induction of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) protein expression, as confirmed by western blot analysis. Also, luciferase reporter gene assay revealed that cartonectin failed to induce luciferase activity at the peroxisome proliferator-activated receptor responsive element site containing the adiponectin/luciferase promoter fragment. Human adipocytes from lean individuals secrete higher amounts of adiponectin and leptin when compared with adipocytes of individuals with a preobesity BMI (25-30 kg/m(2)). Cartonectin failed to stimulate adiponectin or leptin secretion from human adipocytes, irrespective of the BMI value.

DISCUSSION

Cartonectin is a new adipokine that differentially regulates the secretion of classical adipokines, with marked differences between the human and the murine systems. These effects are species-dependent, while basal adipokine secretion is influenced by the BMI.

Adipose tissue as an immunological organ: Toll-like receptors, C1q/TNFs and CTRPs

Adipose tissue has long been regarded as a mostly resting tissue that is dedicated solely to energy storage and release. However, in recent years, this view has changed dramatically following new insights into the metabolic and immunological functions of preadipocytes and adipocytes. There are several lines of evidence for the involvement of adipose tissue in innate and acquired immune responses. First, adipocytes are potent producers of proinflammatory cytokines, such as interleukin-6 and tumor necrosis factor (TNF), and chemokines. Furthermore, adipocytes secrete high amounts of adipokines, such as leptin, adiponectin and resistin, that regulate monocyte/macrophage function, and also secrete molecules associated with the innate immune system, such as the C1qTNF-related protein superfamily. Finally, preadipocytes and adipocytes express a broad spectrum of functional Toll-like receptors and the former can convert into macrophage-like cells. Collectively, these data clearly establish the role of adipose tissue as a new member of the immune system.