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

Plasma proteomics of acute tubular injury

The kidney tubules constitute two-thirds of the cells of the kidney and account for the majority of the organ's metabolic energy expenditure. Acute tubular injury (ATI) is observed across various types of kidney diseases and may significantly contribute to progression to kidney failure. Non-invasive biomarkers of ATI may allow for early detection and drug development. Using the SomaScan proteomics platform on 434 patients with biopsy-confirmed kidney disease, we here identify plasma biomarkers associated with ATI severity. We employ regional transcriptomics and proteomics, single-cell RNA sequencing, and pathway analysis to explore biomarker protein and gene expression and enriched biological pathways. Additionally, we examine ATI biomarker associations with acute kidney injury (AKI) in the Kidney Precision Medicine Project (KPMP) (n = 44), the Atherosclerosis Risk in Communities (ARIC) study (n = 4610), and the COVID-19 Host Response and Clinical Outcomes (CHROME) study (n = 268). Our findings indicate 156 plasma proteins significantly linked to ATI with osteopontin, macrophage mannose receptor 1, and tenascin C showing the strongest associations. Pathway analysis highlight immune regulation and organelle stress responses in ATI pathogenesis.

Low serum CTRP3 is related to more severe distal symmetric polyneuropathy in type 2 diabetes patients

BACKGROUND

Distal symmetric polyneuropathy (DSPN) is one of the most common chronic complications in patients with type 2 diabetes mellitus (T2DM). Our previous study found that serum C1q tumor necrosis factor-related protein 3 (CTRP3) levels were decreased in type 2 diabetic patients. Thus, this study was designed to reveal the relationship between low serum CTRP3 and the prevalence and severity of DSPN.

METHODS

A total of 178 cases of patients with T2DM were enrolled in the study. The subjects were divided into the DSPN group (n = 89) and the non-DSPN group (n = 89). Both anthropometric parameters and neurologic symptoms were recorded. Furthermore, neurologic signs, the neuropathy symptom score (NSS), and the neuropathy disability score (NDS) were assessed. Biochemical indexes, fasting insulin, and C peptide were measured. Serum CTRP3 concentrations were assayed using the ELISA method.

RESULTS

Serum CTRP3 levels decreased significantly in the DSPN group compared with the non-DSPN group (P < 0.05). CTRP3 was negatively associated with the number of positive signs, NSS score, and NDS score in patients with DSPN (all P < 0.05). Interestingly, the higher the NSS score or NDS score, the lower were the levels of serum CTRP3 (all P < 0.05). Moreover, patients with lower CTRP3 levels (< 7.58ng/ml) had a higher rate of neurologic signs (all P < 0.05). Binary logistic regression analysis showed that CTRP3 independently predicted the occurrence of DSPN (β = -0.316, P < 0.001). ROC curve analysis revealed that the best cut-off value of CTRP3 for the prediction of DSPN was 7.55ng/ml (sensitivity 78.7%, specificity 79.8%), the area under the curve (AUC) was 0.763 (95% CI 0.689-0.838, P < 0.001).

CONCLUSION

Low serum CTRP3 could be a predictor for the occurrence and progression of DSPN in Chinese patients with T2DM.

Role of C1q/TNF-Related Protein 6 for the Evaluation of Coronary Heart Disease Associated with Type 2 Diabetes

Objective

Coronary artery disease (CAD) and type 2 diabetes (T2DM) are closely associated with increased rate of death. C1q/TNF-related protein 6 (CTRP6) is a novel adipocytokine which plays an important role in glucose and lipid metabolism. Little is known about the function of CTRP6 in CAD and T2DM patients. Herein, we aimed to study the association of CTRP6 level with CAD and T2DM.

Methods

This study included 51 CAD, 44 CAD+T2DM and 65 non-CAD+T2DM patients from Affiliated Aoyang Hospital of Jiangsu University. Serum CTRP6 concentrations were detected by ELISA. Multiple logistic regression was used to analyze the association of serum CTRP6 with CAD and T2DM.

Results

Serum CTRP6 concentrations were significantly lower in CAD patients than controls. However, there is no significant statistical difference between CAD+T2DM patients and non-CAD+T2DM patients. Serum CTRP6 was negatively correlated with low-density lipoprotein cholesterol (LDL-C) (ρ=-0.2769, p=0.028) in controls. Serum CTRP6 was positively correlated with age (ρ=0.4121, p=0.0027), systolic blood pressure (SBP) (ρ=0.4012, p=0.0035), Creatinine (ρ=0.3295, p=0.0194), uric acid (UA) (ρ=0.3386, p=0.0162), and left ventricular end diastolic diameter (LVD) (ρ=0.4277, p=0.0042) and negatively correlated with ejection fraction (EF) (ρ=-0.3237, p=0.0342) in CAD patients. Serum CTRP6 was negatively correlated with high-density lipoprotein cholesterol (HDL-C) (ρ=-0.3164, p=0.0387) in CAD+T2DM patients. Multiple logistic regression showed that the decrease of CTRP6 was significantly related to the increased prevalence of CAD. What is more, CTRP6 increased prevalence of T2DM in CAD patients.

Conclusion

Lower serum CTRP6 could be a risk factor of CAD. However, higher circulating CTRP6 associated with the increased prevalence of T2DM in CAD patients.

CTRP3 attenuates inflammation, oxidative and cell death in cisplatin induced HK-2 cells

Cisplatin has been widely studied and found to be a highly effective anti-tumor drug. It has several side effects, including acute kidney injury (AKI). Cisplatin-induced AKI can be primarily attributed to oxidative stress, inflammation, and apoptosis. The CTRP3 adipokine is a new adipokine that exhibits antioxidant, anti-inflammatory, and antiapoptotic properties. Despite this, the role of CTRP3 in AKI remain unclear. In cisplatin-induced AKI models, our findings demonstrated that CTRP3 expression was decreased in human proximal tubule epithelial cells (HK-2). In the in vitro experiments, HK-2 cells were first transfected with an overexpression plasmid of CTRP3 (pcDNA-CTRP3) or a small interfering RNA for CTRP3 (si-CTRP3) and induced by cisplatin; and cell oxidative stress, inflammation, proliferation, and apoptosis were found to be present. Overexpressing CTRP3 inhibited oxidative stress through decreasing malondialdehyde (MDA) levels and increasing the activity of SOD and CAT. The mRNA levels of SOD1 and SOD2 were increased in response to CTRP3 overexpression. Additionally, CTRP3 decreased TNF-α and MCP-1 levels. Moreover, CTRP3 overexpression increased cisplatin-induced cell activity and decreased cell apoptosis, as indicated by the elevated numbers of EdU positive cells and decreased numbers of apoptotic cells. Consistent with these results, the overexpression of CTRP3 effectively elevated the mRNA levels of Bcl-2 and reduced the mRNA levels of Bax. In contrast, inhibition of CTRP3 expression by si-CTRP3 reversed the cisplatin-induced indices. Mechanistically, we found that the overexpression of CTRP3 can increase expression of Nrf2 and inhibit the activation of MAPK phosphorylation (ERK, JNK, and p38). Furthermore, inhibition of ERK, JNK and p38 activity eliminated aggravation of cisplatin-induced inflammation and apoptosis caused by CTRP3 knockdown. Additionally, the cisplatin-induced oxidative stress and activation of MAPK phosphorylation (ERK, JNK, and p38) in HK-2 cells were reversed by Nrf2 suppression by siRNA. Collectively, these results indicated that CTRP3 may identify as a novel target for AKI treatment and protect against cisplatin-induced AKI through the Nrf2/MAPK pathway.

Obesity, chronic kidney disease progression and the role of the adipokine C1q/TNF related protein-3

INTRODUCTION AND AIMS

Obesity is a risk factor for incident chronic kidney disease (CKD). C1q/TNF related protein 3 (CTRP3) is an adipokine with multiple effects and may modulate the association between obesity and vascular diseases. The aim of the study is to explore potential links between obesity, CTRP3 levels and CKD progression.

METHODS

Patients with stage 3 and 4 CKD without previous cardiovascular events were enrolled and divided into groups according to body mass index (BMI) and sex. Demographic, clinical, analytical data and CTRP3 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 were registered).

RESULTS

81 patients were enrolled. 27 were obese and 54 non-obese. Baseline CTRP3 was similar between both groups (90.1±23.8 vs 84.5±6.2; p=0.28). Of the sum, 54 were men and 27 women, with higher CTRP3 in women (81.4±24.7 vs 106±24.7;p<0.01). During a mean follow-up of 68 months, 15 patients had a renal event. Patients in the higher CTRP3 tertile had less events but without statistical significance (p=0.07). Obese patients in the higher CTRP3 tertile significantly had less renal events (p=0.049). By multiple regression analysis CTRP3 levels could not predict renal events (HR 0.98; CI95% 0.96-1.06).

CONCLUSIONS

CTRP3 levels are higher in woman than men in patients with CKD, with similar levels between obese and non obese. Higher CTRP3 levels at baseline were associated with better renal outcomes in obese patients.

CTRP family in diseases associated with inflammation and metabolism: molecular mechanisms and clinical implication

C1q/tumor necrosis factor (TNF) related proteins (CTRPs) is a newly discovered adipokine family with conservative structure and ubiquitous distribution and is secreted by adipose tissues. Recently, CTRPs have attracted increasing attention due to the its wide-ranging effects upon inflammation and metabolism. To-date, 15 members of CTRPs (CTRP1-15) with the characteristic C1q domain have been characterized. Earlier in-depth phenotypic analyses of mouse models of CTRPs deficiency have also unveiled ample function of CTRPs in inflammation and metabolism. This review focuses on the rise of CTRPs, with a special emphasis on the latest discoveries with regards to the effects of the CTRP family on inflammation and metabolism as well as related diseases. We first introduced the structure of characteristic domain and polymerization of CTRPs to reveal its pleiotropic biological functions. Next, intimate association of CTRP family with inflammation and metabolism, as well as the involvement of CTRPs as nodes in complex molecular networks, were elaborated. With expanding membership of CTRP family, the information presented here provides new perspectives for therapeutic strategies to improve inflammatory and metabolic abnormalities.

Circulating Levels of C1q/TNF-Related Protein 3 (CTRP3) and CTRP9 in Gestational Diabetes and Their Association with Insulin Resistance and Inflammatory Cytokines

Objective

Gestational diabetes mellitus (GDM) is closely related to obesity, adipose tissue, and adipokines. Adiponectin-homologous adipokines with anti-inflammatory properties, including C1q/TNF-related protein 3 (CTRP3) and CTRP9, regulate glucose and lipid metabolism, which was measured in pregnant women with GDM with the aim to assess their circulating levels and their relation with inflammatory cytokines and other biochemical data.

Methods

Serum levels of CTRP3, CTRP9, adiponectin, tumor necrosis factor (TNF)-α, and interleukin (IL)-6 were measured in 43 subjects with GDM and 42 healthy controls by enzyme-linked immunosorbent assay.

Results

Serum levels of adiponectin and CTRP3 were lower in GDM subjects than in controls, whereas CTRP9, TNF-α, and IL-6 showed higher concentrations in subjects with GDM than in controls. In the subjects with GDM, there was a significant association of CTRP3 with homeostasis model assessment of insulin resistance (HOMA-IR), body mass index, and triglycerides, whereas CTRP9 is associated with TNF-α and HOMA-IR.

Conclusion

The differences in the assessed levels of CTRP3 and CTRP9 suggest a possible relation with the pathogenesis of GDM, in particular insulin resistance, which showed significant association with both adipokines.

Decreased Epicardial CTRP3 mRNA Levels in Patients with Type 2 Diabetes Mellitus and Coronary Artery Disease Undergoing Elective Cardiac Surgery: A Possible Association with Coronary Atherosclerosis

(1) Background: C1q TNF-related protein 3 (CTRP3) is an adipokine with anti-inflammatory and cardioprotective properties. In our study, we explored changes in serum CTRP3 and its gene expression in epicardial (EAT) and subcutaneous (SAT) adipose tissue in patients with and without coronary artery disease (CAD) and type 2 diabetes mellitus (T2DM) undergoing elective cardiac surgery. (2) Methods: SAT, EAT, and blood samples were collected at the start and end of surgery from 34 patients: (i) 11 without CAD or T2DM, (ii) 14 with CAD and without T2DM, and (iii) 9 with both CAD and T2DM. mRNA levels of CTRP3 were assessed by quantitative reverse transcription PCR. Circulating levels of CTRP3 and other factors were measured using ELISA and Luminex Multiplex commercial kits. (3) Results: Baseline plasma levels of TNF-α and IL6 did not differ among the groups and increased at the end of surgery. Baseline circulating levels of CTRP3 did not differ among the groups and decreased after surgery. In contrast, baseline CTRP3 mRNA levels in EAT were significantly decreased in CAD/T2DM group, while no differences were found for TNF-α and IL6 gene expression. (4) Conclusions: Our data suggest that decreased EAT mRNA levels of CTRP3 could contribute to higher risk of atherosclerosis in patients with CAD and T2DM.

Plasma C1q/tumor necrosis factor-related protein-3 concentrations are associated with diabetic peripheral neuropathy

INTRODUCTION

To analyze the associations of circulating C1q/tumor necrosis factor-related protein-3 (CTRP3) concentrations with several metabolic parameters and to investigate the possible role of CTRP3 in subjects with diabetic peripheral neuropathy (DPN).

RESEARCH DESIGN AND METHODS

A total of 347 participants were recruited in this study, and plasma CTRP3 concentrations were analyzed in subjects with DPN (n=172) and without DPN (non-DPN, n=175). The nerve conduction test and oral glucose tolerance test were performed, and Neuropathy Symptom Score (NSS)/Neuropathy Disability Score (NDS) and biochemical parameters were measured in all participants.

RESULTS

Plasma CTRP3 concentrations were significantly lower in patients with DPN compared with those in patients with diabetes without DPN (p<0.01), despite the comparable glucose and lipid metabolism levels in both groups. Groups with a higher plasma CTRP3 level had a faster nerve conduction velocity. In addition, plasma CTRP3 concentrations were negatively correlated with hemoglobin A1c (HbA1c), urea acid (UA), triglyceride, NSS and NDS (p<0.05) after being adjusted for age and sex. Multivariate logistic regression analysis revealed that plasma CTRP3 concentrations were significantly correlated with DPN after being controlled for age, sex, body mass index, HbA1c, blood pressure, lipid profiles, and renal function.

CONCLUSIONS

Plasma CTRP3 concentrations were significantly lower in patients with DPM and positively correlated with nerve conduction velocity. The relationship between CTRP3 levels and DPN is independent of the glucose and lipid status. Therefore, circulating CTRP3 might serve as a predictor of impairment of nerve conduction in patients with DPN.

The Role of Anti-Inflammatory Adipokines in Cardiometabolic Disorders: Moving beyond Adiponectin

The global burden of obesity has multiplied owing to its rapidly growing prevalence and obesity-related morbidity and mortality. In addition to the classic role of depositing extra energy, adipose tissue actively interferes with the metabolic balance by means of secreting bioactive compounds called adipokines. While most adipokines give rise to inflammatory conditions, the others with anti-inflammatory properties have been the novel focus of attention for the amelioration of cardiometabolic complications. This review compiles the current evidence on the roles of anti-inflammatory adipokines, namely, adiponectin, vaspin, the C1q/TNF-related protein (CTRP) family, secreted frizzled-related protein 5 (SFRP5), and omentin-1 on cardiometabolic health. Further investigations on the mechanism of action and prospective human trials may pave the way to their clinical application as innovative biomarkers and therapeutic targets for cardiovascular and metabolic disorders.

Increased circulating level of CTRP15 in patients with type 2 diabetes mellitus and its relation with inflammation and insulin resistance

Aims

Type 2 diabetes mellitus (T2DM) is a highly prevalence disease that has a close relation with secretory factors such as adipokines and myokines. C1q tumor necrosis factor-α (TNF-α)-related protein 15 (CTRP15) is a paralogue paralogue of adiponectin that has a close relation with insulin resistance and inflammation. The present study aimed to assess circulating levels of CTRP15 in patients with T2DM in comparison with controls and thier association with inflammatory cytokines.

Methods

This case-control study was performed on 80 T2DM patients and 80 controls which diagnosed according to the criteria of American Diabetes Association (ADA). Serum levels of CTRP15, adiponectin, TNF-α, and interleukin- 6 (IL-6) were determined using ELISA kits.

Results

The results indicated higher concentration of CTRP15 in T2DM patients (103.17 ± 27.99) compared to the controls (66.11 ± 20.46, p < 0.001), while adiponectin decreased considerably in the patients compared to the controls (p < 0.001). Moreover, circulating levels of IL-6 and TNF-α elevated in the patients compared to the controls (p < 0.001). CTRP15 indicated independent association with BMI and adiponectin in the controls while, in the patients it demonstrated independent association with HOMA-IR and TNF-α.

Conclusions

Higher concentration of CTRP15 in the patients and its relation with insulin resistance and inflammation suggested a relation of CTRP15 with the pathogenesis of diabetes. In addition, it seems likely that patients with T2DM had a CTRP15 resistance; however, future studies are necessary to prove this concept.

C1q/TNF-related Protein 9 Inhibits High Glucose-Induced Oxidative Stress and Apoptosis in Retinal Pigment Epithelial Cells Through the Activation of AMPK/Nrf2 Signaling Pathway

Diabetic retinopathy (DR) is one of the common complications of diabetes mellitus. C1q/TNF-related protein 9 (CTRP9) has been demonstrated to be associated with the progression of diabetes and relative complications. However, its role in DR and underlying action of mechanism are not yet well understood. In the present study, human retinal pigment epithelial ARPE-19 cells were cultured under high concentration of glucose to simulate hyperglycemia condition in vitro. Our results showed that the expression of CTRP9 was significantly decreased in high glucose (HG)–stimulated ARPE-19 cells. CTRP9 overexpression improved HG-caused reduction in cell viability of ARPE-19 cells. CTRP9 overexpression significantly attenuated HG-induced oxidative stress, as proved by decreased levels of reactive oxygen species and malondialdehyde, and increased superoxide dismutase activity. Moreover, CTRP9 also prevented apoptosis in ARPE-19 cells in response to HG stimulation with decreased caspse-3 activity and bax expression, as well as increased bcl-2 expression. In contrast, knockdown of CTRP9 aggravated HG-induced oxidative stress and apoptosis. Furthermore, CTRP9 significantly induced the activation of AMPK/Nrf2 pathway in HG-induced ARPE-19 cells. Notably, inhibiting AMPK or Nrf2 blocked the protective effect of CTRP9 on ARPE-19 cells exposed to HG stimulation. Taken together, our findings suggested a protective effect of CTRP9 on HG-induced ARPE-19 cells and a putative mechanism involving the activation of AMPK/Nrf2 signaling pathway.

Defining IL-6 levels in healthy individuals: A meta-analysis

BACKGROUND

Interleukin-6 (IL-6) is produced by and impacts different cell types in human. IL-6 is associated with different diseases and viral infections, including COVID-19. To our knowledge, no normal values were reported for IL-6 in the blood of healthy individuals. We have reviewed and performed a meta-analysis on a total of 140 studies, including 12,421 values for IL-6 in the blood of healthy adult donors. Among these studies, 83 did not report a mean value and the standard deviation. Therefore, for the statistical analysis, we used the values reported in 57 studies, which included 3166 values for IL-6.

RESULTS

The reported values for IL-6 in the blood of healthy donors varied between 0 and 43.5 pg/ml. The pooled estimate of IL-6 was 5.186 pg/ml (95% confidence interval [CI]: 4.631, 5.740). As the age increased by 1 year, IL-6 values increased by 0.05 pg/ml (95% CI: 0.02, 0.09; p < .01). Though the heterogenicity, as determined by I2 statistics, was high in our study, the differences in IL-6 values are still at the level of a few pg/ml, which might be related to the differences in the conditions that influence IL-6 production in the healthy population.

CONCLUSIONS

This is the first meta-analysis reporting the levels of IL-6 in the blood of healthy donors based on a large number of studies and donors. Therefore the 95% CI values determined in our study could well serve as a reference range for quick decision-making in clinical interventions, particularly those aiming to inhibit IL-6, especially urgent interventions, for example, COVID-19.

Spinal muscular atrophy: Broad disease spectrum and sex-specific phenotypes

Spinal muscular atrophy (SMA) is one of the major genetic disorders associated with infant mortality. More than 90% of cases of SMA result from deletions of or mutations in the Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, does not compensate for the loss of SMN1 due to predominant skipping of exon 7. The spectrum of SMA is broad, ranging from prenatal death to infant mortality to survival into adulthood. All tissues, including brain, spinal cord, bone, skeletal muscle, heart, lung, liver, pancreas, gastrointestinal tract, kidney, spleen, ovary and testis, are directly and/or indirectly affected in SMA. Accumulating evidence on impaired mitochondrial biogenesis and defects in X chromosome-linked modifying factors, coupled with the sexual dimorphic nature of many tissues, point to sex-specific vulnerabilities in SMA. Here we review the role of sex in the pathogenesis of SMA.

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.

Circulating levels of CTRP3 in patients with type 2 diabetes mellitus compared to controls: A systematic review and meta-analysis

Growing evidence suggests that adipokines may be therapeutic targets for cardiometabolic diseases such as type 2 diabetes mellitus (T2DM). C1q TNF Related Protein 3 (CTRP3) is a newly discovered adipokine which shares properties with adiponectin. The literature about the association between circulating levels of CTRP3 and T2DM has been conflicting. The present study reassessed the data on circulating CTRP3 levels in T2DM patients compared to controls through a systematic review and meta-analysis. A literature search was performed in Medline, Embase, Scopus, and Web of science to identify studies that measured circulating CTRP3 levels in T2DM patients and controls. The search identified 124 studies of which 59 were screened for title and abstract and 13 were subsequently screened at the full text stage and 12 studies included into the meta-analysis. Subgroup analyses, depending on the presence of T2DM complications, matching for BMI, age, and cut off value of fasting blood sugar and HOMA-IR, were performed. The results show that circulating CTRP3 levels are negatively associated with T2DM status (SMD: -0.837; 95% CI: (-1.656 to -0.017); p = 0.045). No publication bias was identified using the Begg's rank correlation and Egger's linear regression tests (P = 1 and P = 0.44, respectively). Meta-regression demonstrated significant association between CRTP3 levels with BMI (slope: 0.11; 95% CI: 0.04-0.19; p = 0.001) and sex (slope: -0.07; 95% CI: -0.12 to -0.01; p = 0.008). The present systematic review and meta-analysis evidences a negative association between circulating level of CTRP3 and T2DM status. BMI and sex may modify this association.

C1q/TNF-Related Protein-3 (CTRP-3) and Pigment Epithelium-Derived Factor (PEDF) Concentrations in Patients with Gestational Diabetes Mellitus: A Case-Control Study

Background: Gestational diabetes mellitus (GDM) is the most common metabolic disorder in pregnant women, defined as any degree of glucose intolerance with onset or first detected during pregnancy. Explanation of its pathogenesis is extremely important due to the possibility of preventing serious maternal and fetal complications. The aim of the study was to evaluate the concentrations of two molecules: C1q/tumor necrosis factor-related protein-3 (CTRP-3) and pigment epithelium-derived factor (PEDF) which may possibly participate in GDM development. To our knowledge, this is the first study in pregnant women with GDM evaluating CTRP-3 level. Methods: Serum CTRP-3 and PEDF concentration and clinical characteristics were detected in 172 pregnant women. These women were divided into two groups: normal glucose tolerance group (NGT, n = 54) and gestational diabetes mellitus group (GDM, n = 118). This second group was further divided into two subgroups depending on the treatment used: GDM 1—diet only (n = 75) and GDM 2—insulin treatment (n = 43). Results: Our study did not reveal any statistically significant difference between the concentration of PEDF in the control and GDM group. In our study there was a significantly higher concentration of CTRP-3 evaluated in the peripheral blood serum in patients with gestational diabetes (GDM) compared to those in the control group (8.84 vs. 4.79 ng/mL). Significantly higher values of CTRP-3 were observed in both the diet-treated subgroup and the group with insulin therapy when compared to control group (8.40 and 10.96, respectively vs. 4.79 ng/mL). Conclusion: PEDF concentration does not change in GDM, whereas an increased level of CTRP-3 may point to the key role of this adipokine in the development of GDM.

Serum levels of C1q/TNF-related protein-3 in inflammatory bowel disease patients and its inverse association with inflammatory cytokines and insulin resistance

Ulcerative colitis (UC) and Crohn's disease (CD) are two major forms of inflammatory bowel disease (IBD), which is an inflammatory disease. Studies have shown that adipose tissue and inflammation play important roles in the pathogenesis of IBD. C1q/TNF-related protein-3 (CTRP3) is a newly discovered adipokine playing a substantial role during inflammatory process, and for the first time in the present study, serum levels of this adipokine were measured in the UC and CD patients. This case-control study included 70 control, 50 UC, and 50 CD patients who were diagnosed by standard criteria. Serum levels of adiponectin, IL-6, TNF-α, TGF-β, and CTRP3 were evaluated using ELISA kits. Serum levels of IL-6, TNF-α, and TGF-β elevated in the UC and CD patients compared with the controls while adiponectin and CTRP3 diminished in the patient's groups compared with the control. Furthermore, decrease in CTRP3 serum levels was associated with the risk of UC and CD diseases. Moreover, CTRP3 indicated negative correlation with BMI, FBS, insulin, homeostasis model assessment of insulin resistance, IL-6, TNF-α, and TGF-β and also a positive correlation with adiponectin in both the UC and CD patients. For the first time, the present study demonstrated lower levels of CTRP3 in the UC and CD patients. Decreased serum levels of CTRP3 and its inverse relationship with inflammatory cytokines and TGF-β levels suggested a possible role for CTRP3 in the pathogenesis of UC and CD diseases.

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.

CTRP3 inhibits high glucose-induced oxidative stress and apoptosis in retinal pigment epithelial cells

Diabetic retinopathy (DR) is one of the most common diabetic complications and remains the leading cause of vision loss among adults. C1q/TNF-related protein 3 (CTRP3) is a member of CTRP family that has been found to be involved in the progression of diabetes mellitus and diabetic complications. However, the role of CTRP3 in DR has not been fully understood. In the present study, the results showed that CTRP3 expression was significantly decreased in DR patients compared with controls. In vitro investigations proved that overexpression of CTRP3 improved cell viability of ARPE-19 cells in response to high glucose (HG) stimulation. CTRP3 also attenuated HG-induced oxidative stress in ARPE-19 cells with decreased levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and increased superoxide dismutase (SOD) activity. Apoptotic rate was significantly decreased in CTRP3 overexpressing ARPE-19 cells. Besides, bcl-2 expression was increased, while bax expression was decreased by CTRP3 overexpression. Moreover, overexpression of CTRP3 enhanced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) pathway in HG-stimulated ARPE-19 cells, and Nrf2 knockdown reversed CTRP3-mediated oxidative stress and apoptosis. These findings suggested that CTRP3 attenuated HG-stimulated oxidative stress and apoptosis in ARPE-19 cells, which were mediated by activation of Nrf2/HO-1 pathway.

Muscle regulates mTOR dependent axonal local translation in motor neurons via CTRP3 secretion: implications for a neuromuscular disorder, spinal muscular atrophy

Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder, which causes dysfunction/loss of lower motor neurons and muscle weakness as well as atrophy. While SMA is primarily considered as a motor neuron disease, recent data suggests that survival motor neuron (SMN) deficiency in muscle causes intrinsic defects. We systematically profiled secreted proteins from control and SMN deficient muscle cells with two combined metabolic labeling methods and mass spectrometry. From the screening, we found lower levels of C1q/TNF-related protein 3 (CTRP3) in the SMA muscle secretome and confirmed that CTRP3 levels are indeed reduced in muscle tissues and serum of an SMA mouse model. We identified that CTRP3 regulates neuronal protein synthesis including SMN via mTOR pathway. Furthermore, CTRP3 enhances axonal outgrowth and protein synthesis rate, which are well-known impaired processes in SMA motor neurons. Our data revealed a new molecular mechanism by which muscles regulate the physiology of motor neurons via secreted molecules. Dysregulation of this mechanism contributes to the pathophysiology of SMA.