Glypican-4 is increased in human subjects with impaired glucose tolerance and decreased in patients with newly diagnosed type 2 diabetes

Concentrations of Glypican-4, Irisin and Total Antioxidant Status in Women with Metabolic Syndrome: Influence of Physical Activity

Glypican-4 belongs to a group of poorly understood adipokines, with potential importance in people with metabolic syndrome, especially in groups of patients with glucose metabolism disorder. This study aimed to assess the effect of physical activity on serum glypican-4 and irisin levels and total antioxidant status (TAS) in plasma and saliva in women with metabolic syndrome (MetS). Seventy-two Caucasian women aged 25-60 were included in the study (36 women with MetS and 36 women without MetS (control group, CONTR)). The glypican-4 and irisin concentrations, total antioxidant status, glycemia, lipid profile, anthropometric parameters, and blood pressure were analyzed before and after 28 days of controlled physical activity. Serum glypican-4 and plasma TAS levels were higher (p = 0.006 and p = 0.043, respectively) on the 28th day than on the first day of the study only in the CONTR group. In the MetS group, 28 days of physical activity caused a reduction in body fat mass (p = 0.049) without changes in glypican-4, irisin, or TAS levels. In both groups, glypican-4 levels correlated positively with irisin levels and negatively with Waist-Hip Ratio (WHR), while irisin levels correlated positively with High-Density Lipoprotein Cholesterol (HDL-C) levels and negatively with waist circumference (WC) and WHR values on the 28th day of the study. To summarize, a 28-day moderate training, accompanied by a reduction in body fat mass, stabilized glypican-4 levels and TAS in female patients with MetS.

The role of GPLD1 in chronic diseases

Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is a specific enzyme for glycosylphosphatidylinositol (GPI) anchors, thereby exerting its biological functions by cleaving membrane-associated GPI molecules. GPLD1 is abundant in serum, with a concentration of approximately 5-10 µg/mL. Previous studies have demonstrated that GPLD1 plays a crucial role in the pathogenesis of numerous chronic diseases including disorders of lipid and glucose metabolism, cancer, and neurological disorders. In the present study, we reviewed the structure, functions, and localization of GPLD1 in chronic diseases, as well as exercise-mediated regulation of GPLD1, thus providing a theoretical support to develop GPLD1 as a new therapeutic target for chronic diseases.

Modulation of GPC-4 and GPLD1 serum levels by improving glycemic indices in type 2 diabetes: Resistance training and hawthorn extract intervention

Aims

This study was designed to investigate the effects of resistance training (RT) and hawthorn extract (Ha) on Glypican-4 (GPC-4) and Insulin-regulated glycosylphosphatidylinositol-specific phospholipase D (GPLD1) serum levels in T2DM and to examine the relationship of these variables with glycemic indexes.

Method

40 male Wistar rats were divided into five equal groups: Healthy Control (H-C), Diabetes Control (D-C), Diabetes Resistance training (D-RT), Diabetes Hawthorn (D-Ha), and Diabetes Resistance training Hawthorn (D-RT-Ha). T2DM was induced with a 4-week high-fat diet (HFD) and one dose of STZ intraperitoneal injection (35 mg/kg). 1-week after the injection, RT (with a range of 50%-100%1RM/3 day/week) and gavage of Ha extract (100 mg/kg/day) was performed for 12 weeks.

Results

The glycemic indices improvement (reducing blood glucose and increasing serum insulin level) caused by RT and/or Ha increased GPC-4 and decreased GPLD1 in the T2DM rats, but these positive changes were more effective in the combination of RT + Ha. A strong correlation was also observed between GPC-4 and GPLD1 with blood glucose and insulin.

Conclusion

The increase in serum GPC-4 levels was probably due to the direct effect of RT + Ha, and the improvement of glycemic indexes after RT and Ha. The double effect of RT + Ha can be a regulatory mechanism for GPC-4 and its related factors in controlling T2DM complications.

Circulating syndecan-1 and glypican-4 predict 12-month survival in metastatic colorectal cancer patients

Cell surface syndecans and glypicans play important roles in the development and prognosis of colorectal cancer (CRC). Their soluble forms from proteoglycan shedding can be detected in blood and have been proposed as new prognostic biomarkers in several cancer entities. However, studies on circulating syndecan-1 (SDC1) and glypican-4 (GPC4) in CRC are limited. We, therefore, evaluated the impact of plasma SDC1 and GPC4 on the prognosis of metastatic (m)CRC patients. The present study included 93 patients with mCRC. The endpoints were progression-free survival (PFS) and overall survival (OS) at 12 months. SDC1 and GPC4 levels were measured in plasma using enzyme-linked immunosorbent assays. Plasma levels of SDC1 and GPC4 were significantly correlated. Significant correlations of these two markers were also found with carcinoembryonic antigen (CEA). Kaplan-Meier curve analyses indicated that PFS and OS probabilities significantly decreased with increasing levels of SDC1 and GPC4, respectively. Multivariable Cox regression analyses showed that both markers were significantly associated with PFS and OS independently from clinicopathological characteristics including CEA. Respective adjusted hazard ratios (HR) together with corresponding 95% confidence intervals for one standard deviation change of SDC1 were 1.32 [1.02-1.84] for PFS and 1.48 [1.01-2.15] for OS. Adjusted HRs [95% confidence intervals] of GPC4 were 1.42 [1.07-1.89] for PFS and 2.40 [1.51-3.81] for OS. Results from area under the receiver operating characteristic curve analyses suggest that GPC4 and SDC1 add additional prognostic values to CEA for OS. In conclusion, we showed significant associations of circulating SDC1 and GPC4 with poor survival of mCRC patients.

Evaluation of the association of serum glypican-4 with prevalent and future kidney function

Serum glypican-4 (GPC4) has been identified as an insulin-sensitizing adipokine serving as a marker for body mass index and insulin resistance in humans. The association of circulating GPC4 with kidney function is to date largely unexplored. Therefore, we aimed to evaluate the association between serum GPC4 and prevalent as well future kidney function in a prospective cohort study. The study included 456 Caucasian coronary angiography patients. After a median follow up period of 3.4 years, data on kidney function was reassessed in all patients. Chronic kidney disease (CKD) was defined by decreased estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 or albuminuria. At baseline, serum GPC4 was significantly associated with decreased eGFR (adjusted odds ratio (OR) per standard deviation = 4.75 [2.66-8.48]; P <  0.001), albuminuria (OR = 1.49 [1.15-1.92]; P = 0.002), and, accordingly, with CKD (OR = 1.75 [1.35-2.26]; P < 0.001). GPC4 levels also significantly and independently predicted the incidence of newly diagnosed decreased eGFR (OR = 2.74 [1.82-4.14]; P < 0.001, albuminuria (OR = 1.58 [1.01-2.46]; P = 0.043, and CKD (OR = 2.16 [1.45-3.23]; P < 0.001). ROC analysis indicated an additional predictive value of GPC4 to a basic prediction model for newly diagnosed CKD and eGFR < 60 mL/min/1.73 m2. Our study, therefore, indicates that high serum GPC4 is associated with decreased prevalent and future kidney function.

Glypican-4 in pregnancy and its relation to glucose metabolism, insulin resistance and gestational diabetes mellitus status

Glypican-4 (GPC-4) is an adipokine that enhances insulin receptor signaling. Plasma concentrations were found to be elevated in patients with prediabetes but reduced in type 2 diabetes mellitus. No study on Glypican-4 in pregnancy and pregnancy-related insulin resistance has been published yet. GPC-4 levels were investigated in 59 overweight women throughout their pregnancy at the Medical University of Vienna. GPC-4 levels, fasting insulin, fasting glucose, estradiol, liver and renal parameters, and markers of bone development were assessed before the < 21st week of gestation (GW), and at GW 35-37. GPC-4 levels increased from < 21 GW (mean = 2.38 pg/ml, SD = 0.68 pg/ml) to GW 35-37 (mean = 2.96 pg/ml, SD = 0.77 pg/ml, p < 0.001). At the same time, GPC-4 levels correlated negatively with estimated glomerular filtration rate (eGFR), serum protein and serum albumin levels and were positively related to creatinine and uric acid levels at GW 35-37. Concerning glucose metabolism, GPC-4 levels were inversely related to ISSI-2, fasting insulin and HOMA-IR, however, not significantly different between women with normal glucose tolerance (NGT) and GDM (p = 0.239). In conclusion, GPC-4 levels rose significantly during pregnancy, correlated negatively with fasting insulin and HOMA-IR but might not be related to gestational diabetes mellitus status.

Galanin and glypican-4 levels depending on metabolic and cardiovascular risk factors in patients with polycystic ovary syndrome

OBJECTIVE

Galanin is a neuropeptide which has effects not only on metabolic syndrome but also on reproduction. Glypican-4 is an adipokine associated with insulin sensitivity by interacting directly with the insulin receptor. This study evaluated serum concentrations of galanin and glypican-4 in relation with the hormonal profile as well as metabolic and cardiovascular risk factors in patients with and without polycystic ovary syndrome (PCOS).

METHODS

A total of 44 women with PCOS and 44 age-matched controls were eligible. Hirsutism scores, hormonal profile, metabolic and cardiovascular risk factors as well as galanin and glypican-4 levels were evaluated in each subject.

RESULTS

Women with PCOS exhibited lower levels of galanin (20.2 pg/mL versus 26.4 pg/mL, p = 0.002) and higher concentrations of glypican-4 (3.1 ng/mL versus 2.6 ng/mL, p < 0.001) than controls. Both adipokines were correlated positively with body mass index (BMI), insulin, triglyceride and Homeostasis Model Assessment (HOMA) index; glypican-4 also showed positive correlations with fasting blood glucose, free testosterone, modified Ferriman-Gallwey scores (p < 0.05). Multiple Linear Regression analyses showed that PCOS and BMI were the best predictors affecting galanin levels with a decreasing and increasing effect respectively; however BMI was the best predictor affecting glypican-4 levels with an increasing effect (p < 0.001).

CONCLUSION

Galanin levels were lower and glypican-4 levels were higher in women with PCOS than controls. Further studies are needed to determine whether these adipokines could be used as additional markers for insulin sensitivity and lipid profile and whether they might play a role in the pathogenesis of PCOS, in which metabolic cardiovascular risks are increased.

Heparan Sulfate Proteoglycans in Diabetes

Diabetes is a complex disorder responsible for the mortality and morbidity of millions of individuals worldwide. Although many approaches have been used to understand and treat diabetes, the role of proteoglycans, in particular heparan sulfate proteoglycans (HSPGs), has only recently received attention. The HSPGs are heterogeneous, highly negatively charged, and are found in all cells primarily attached to the plasma membrane or present in the extracellular matrix (ECM). HSPGs are involved in development, cell migration, signal transduction, hemostasis, inflammation, and antiviral activity, and regulate cytokines, chemokines, growth factors, and enzymes. Hyperglycemia, accompanying diabetes, increases reactive oxygen species and upregulates the enzyme heparanase that degrades HSPGs or affects the synthesis of the HSPGs altering their structure. The modified HSPGs in the endothelium and ECM in the blood vessel wall contribute to the nephropathy, cardiovascular disease, and retinopathy seen in diabetes. Besides the blood vessel, other cells and tissues in the heart, kidney, and eye are affected by diabetes. Although not well understood, the adipose tissue, intestine, and brain also reveal HSPG changes associated with diabetes. Further, HSPGs are significantly involved in protecting the β cells of the pancreas from autoimmune destruction and could be a focus of prevention of type I diabetes. In some circumstances, HSPGs may contribute to the pathology of the disease. Understanding the role of HSPGs and how they are modified by diabetes may lead to new treatments as well as preventative measures to reduce the morbidity and mortality associated with this complex condition.

Ameliorative effects of endurance training and Matricaria chamomilla flowers hydroethanolic extract on cognitive deficit in type 2 diabetes rats

Diabetes mellitus is mainly associated with degeneration of the central nervous system, which eventually leads to cognitive deficit. Although some studies suggest that exercise can improve the cognitive decline associated with diabetes, the potential effects of endurance training (ET) accompanied by Matricaria chamomilla (M.ch) flowers extract on cognitive impairment in type 2 diabetes has been poorly understood. Forty male Wistar rats were randomized into 5 equal groups of 8: healthy-sedentary (H-sed), diabetes-sedentary (D-sed), diabetes-endurance training (D-ET), diabetes-Matricaria chamomilla. (D-M.ch), and diabetes-endurance training-Matricaria chamomilla. (D-ET-M.ch). Nicotinamide (110 mg/kg, i.p.) and Streptozotocin (65 mg/kg, i.p.) were utilized to initiate type 2 diabetes. Then, ET (5 days/week) and M.ch (200 mg/kg body weight/daily) were administered for 12 weeks. After 12 weeks of the experiment, cognitive functions were assessed using the Morris Water Maze (MWM) test and a passive avoidance paradigm using a shuttle box device. Subsequently, using crystal violet staining, neuron necrosis was examined in the CA3 area of the hippocampus. Diabetic rats showed cognitive impairment following an increase in the number of necrotic cells in region CA3 of the hippocampal tissue. Also, diabetes increased serum levels of lipid peroxidation and decreased total antioxidant capacity in serum and hippocampal tissue. ET + M.ch treatment prevented the necrosis of neurons in the hippocampal tissue. Following positive changes in hippocampal tissue and serum antioxidant enzyme levels, an improvement was observed in the cognitive impairment of the diabetic rats receiving ET + M.ch. Therefore the results showed that treatment with ET + M.ch could ameliorate memory and inactive avoidance in diabetic rats. Hence, the use of ET + M.ch interventions is proposed as a new therapeutic perspective on the death of hippocampal neurons and cognitive deficit caused by diabetes.

How Reliable are Commercially Available Glypican4 ELISA Kits?

OBJECTIVE

Glypican4 is an interesting new adipokine, which seems to play an important role in developmental processes and is potentially associated with metabolic changes in obesity and type 2 diabetes mellitus. Currently, only a few studies examined glypican4 in human blood, mainly in adults.

DESIGN, PATIENTS AND MEASUREMENTS

The aim of our study was to investigate glypican4 serum levels in lean, overweight, and obese children and adolescents, to unravel a possible association between glypican4 serum levels and parameters of obesity and insulin resistance. In order to determine a suitable method for investigating glypican4 serum levels, we validated two commercially available human glypican4 ELISA kits, using serum and plasma samples of an obese, insulin-resistant patient, and a healthy control subject, a human recombinant glypican4 protein fragment and glypican4-overexpressing cell lysate.

RESULTS

Using ELISA kit #1 we were not able to detect values above background level, apart from standard curve values. ELISA kit #2 initially seemed suitable to measure glypican4, but further validation experiments showed non-linearity of serial dilutions, no recognition of a human recombinant glypican4 protein fragment and non-linearity in the recovery of glypican4-overexpressing cell lysate. In addition, there was a considerable decrease (approx. 68%) of measured values between two experiments, performed at different time points with aliquots of the same serum sample. Contrary to that, further experiments found sample stability not to be compromised.

CONCLUSIONS

Extensive evaluation of the performance of two commercially available ELISA kits led to the conclusion that none of them is applicable for the measurement of glypican4 in human blood samples.

Proteoglycans in Obesity-Associated Metabolic Dysfunction and Meta-Inflammation

Proteoglycans are a specific subset of glycoproteins found at the cell surface and in the extracellular matrix, where they interact with a plethora of proteins involved in metabolic homeostasis and meta-inflammation. Over the last decade, new insights have emerged on the mechanism and biological significance of these interactions in the context of diet-induced disorders such as obesity and type-2 diabetes. Complications of energy metabolism drive most diet-induced metabolic disorders, which results in low-grade chronic inflammation, thereby affecting proper function of many vital organs involved in energy homeostasis, such as the brain, liver, kidney, heart and adipose tissue. Here, we discuss how heparan, chondroitin and keratan sulfate proteoglycans modulate obesity-induced metabolic dysfunction and low-grade inflammation that impact the initiation and progression of obesity-associated morbidities.

Altered adipocytokine profile predicts early stage of left ventricular remodeling in hypertensive patients with type 2 diabetes mellitus

BACKGROUND AND AIM

Adipocytokine dysfunction is considered as causative factor of target organ damage in metabolic disease. The aim of the study was to investigate whether altered adipocytokine profile predicts left ventricular (LV) remodeling in hypertensive patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 186 patients (125 hypertensive and 61 non-hypertensive individuals) with established T2DM and 20 healthy volunteers were enrolled in the study. LV remodeling was determined at baseline. Concentrations of adipocytokines were measured with ELISA at baseline.

RESULTS

The most important predictors of LV hypertrophy in T2DM patients were serum levels of omentin-1 (B-coefficient = -0.64, p = 0.001), Zinc-α2-glycoprotein [ZA2G] (B-coefficient = -0.57, p = 0.002), visfatin (B-coefficient = 0.26, p = 0.034), hs-CRP (B-coefficient = 0.38, p = 0.002), HOMA-IR (B-coefficient = 0.34, p = 0.001), age (B-coefficient = 0.31, p = 0.022), glypican-4 (B-coefficient = -0.23, p = 0.042), and male sex (B-coefficient = 0.11, p = 0.048). After entering combined depending variable (LV hypertrophy and LV diastolic dysfunction) to the model the significant predictors remained serum levels of omentin-1 (B-coefficient = -0.82, p = 0.001), ZA2G (B-coefficient = -0.54, p = 0.001) and HOMA-IR (B-coefficient = 0.44, p = 0.001). Regression analyses showed that the most influential determinants of depending variable (LV hypertrophy + LV diastolic dysfunction) in T2DM patients were omentin-1 (B-coefficient = -1.6, p = 0.001) and ZA2G (B-coefficient = -0.78, p = 0.044).

CONCLUSION

We found that serum levels of omentin-1 and ZA2G were the most important predictors for LV hypertrophy + LV diastolic dysfunction in T2DM patients. Large clinical trials are required to confirm this assumption and get clear explanation of issues unveiled.

DOCK5 regulates energy balance and hepatic insulin sensitivity by targeting mTORC1 signaling

The dedicator of cytokinesis 5 (DOCK5) is associated with obesity. However, the mechanism by which DOCK5 contributes to obesity remains completely unknown. Here, we show that hepatic DOCK5 expression significantly decreases at a state of insulin resistance (IR). Deletion of DOCK5 in mice reduces energy expenditure, promotes obesity, augments IR, dysregulates glucose metabolism, and activates the mTOR (Raptor)/S6K1 pathway under a high-fat diet (HFD). The overexpression of DOCK5 in hepatocytes inhibits gluconeogenic gene expression and increases the level of insulin receptor (InsR) and Akt phosphorylation. DOCK5 overexpression also inhibits mTOR/S6K1 phosphorylation and decreases the level of raptor protein expression. The opposite effects were observed in DOCK5-deficient hepatocytes. Importantly, in liver-specific Raptor knockout mice and associated hepatocytes, the effects of an adeno-associated virus (AAV8)- or adenovirus-mediated DOCK5 knockdown on glucose metabolism and insulin signaling are largely eliminated. Additionally, DOCK5-Raptor interaction is indispensable for the DOCK5-mediated regulation of hepatic glucose production (HGP). Therefore, DOCK5 acts as a regulator of Raptor to control hepatic insulin activity and glucose homeostasis.

Endurance exercise training restores diabetes-induced alteration in circulating Glycosylphosphatidylinositol-specific phospholipase D levels in rats

BACKGROUND

Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is responsible for cleaving membrane-associated glycosylphosphatidylinositol (GPI) molecules, which is affected by diabetes. We aimed to examine the effect of 14 weeks treadmill running on serum GPLD1 levels and its association with glycemic indexes and serum glypican-4 (GPC-4), a novel GPI-anchored adipokine, in streptozotocin-nicotinamide-induced diabetic rats.

METHODS

Thirty-six male Wister rats were randomly divided into three groups of twelve animals each, involving sedentary control (SC), sedentary diabetic (SD), and trained diabetic (TD) groups. The diabetes was induced through intraperitoneal injection of 120 mg/kg nicotinamide 15 min prior to intraperitoneal injection of 65 mg/kg streptozotocin in SD and TD groups. The TD group was exercised on a treadmill for 60 min/days, 5 days/wk at 26 m/min, and zero grade for 14 weeks. Following the experiment period, blood samples were taken from all animals and analyzed for experimental indexes via sandwich ELISA.

RESULTS

Exercise training caused a significant decrease in the elevated blood glucose levels and a significant increase in the lowered blood insulin levels in TD rats (both p < 0.001). Glucose tolerance of TD rats significantly improved following experimental protocol, as indicated by OGTT (p < 0.001). Experimental diabetes significantly increased serum GPLD1 levels (p < 0.001), while exercise training significantly decreased its levels (p < 0.001). Serum GPLD1 levels correlated directly with glycemic indexes involving FBS, 2hOGTT, and AUC of glucose (r = 0.80, r = 0.79, r = 0.79, respectively, all p < 0.001) and inversely with serum insulin levels (r = - 0.83, p < 0.001). There were no significant differences in serum GPC-4 levels among groups, and no association with GPLD1 alteration.

CONCLUSIONS

Sedentary diabetic rats have higher circulating GPLD1 compared to controls, which can be reversed by exercise training and is associated with modifying in glycemic and insulin profile.

Circulating CTRP6 Levels are Increased in Overweight or Obese Chinese Individuals and Associated with Insulin Resistance Parameters: A Pilot Study

AIMS

CTRP6, a newly discovered adipokine, has been found to be a regulator for energy homeostasis. However, the association between circulating CTRP6 and obesity in humans is still unclear.

METHODS

256 individuals, including 185 overweight/obese (OW/OB) and 71 normal weight adults, were recruited for this study. Circulating concentrations of CTRP6 and adiponectin (Adipoq) were examined by ELISA.

RESULTS

Serum CTRP6 levels in obese individuals were significantly increased compared with those in healthy individuals (506.1±134.9 vs.363.3±80.5 ng/mL, P<0.01). Conversely, serum Adipoq concentrations in OW/OB individuals were markedly decreased compared with healthy controls [20.8 (12.1-29.3) vs. 14.1 ⁽ 8.61-17.7) ^; P<0.01]. Correlation analysis revealed that there was a positive relationship between circulating CTRP6 and age, BMI, Fat%, LDL-C, TG, WHR, TC, FBG, FIns, HOMA-IR and HbA1c, but there was an inverse correlation with Adipoq and HDL-C. Logistic regression analysis revealed that high serum CTRP6 levels are markedly associated with OW/OB. Finally, ROC curve analysis showed that the cut-off value for serum CTRP6 for prediction of IR is 518 ng/mL.

CONCLUSIONS

CTRP6 may be a marker related to OW/OB.

Circulating alarin concentrations are high in patients with type 2 diabetes and increased by glucagon-like peptide-1 receptor agonist treatment: An Consort-compliant study

CONTEXT

Alarin has been reported to be relative to food intake and an increase in body weight. However, to date, no report has demonstrated the relationship between circulating alarin and diabetes in humans.

OBJECTIVE

The objective of this study is to gain insight into the possible role of alarin in humans.

DESIGN AND METHODS

164 patients with newly diagnosed type 2 diabetes mellitus (nT2DM), 112 IGT and 134 healthy subjects were recruited for this study. In an interventional study, 29 nT2DM patients were treated by a weekly GLP-1RA for 6 months. Plasma alarin concentrations were measured by ELISA.

RESULTS

Circulating alarin concentrations were significantly higher in both IGT and nT2DM subjects than in healthy individuals (0.40 ± 0.14 and 0.54 ± 0.24 vs 0.37 ± 0.10 μg/L, P < .05 or P < .01), whereas in T2DM patients, circulating alarin levels were higher than in IGT subjects. Circulating alarin positively correlated with FBG, HbA1c, HOMA-IR, AUCglucose and TNFα (P < .05 or P < .01). Multivariate logistic regression revealed that circulating alarin levels were correlated with IGT and T2DM. GLP-1RA treatment for 6 months increased circulating alarin levels in T2DM patients (from 0.34 ± 0.10 for baseline, to 0.39 ± 0.14 for 12 weeks, and finally to 0.38 ± 0.15 μg/L for 24 weeks; vs. pre-treatment P < .05).

CONCLUSIONS

These data suggest that alarin might be involved in the pathogenesis of T2DM in humans.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR-OCS-13003185 (18/03/2013 ).

C1q/TNF-related protein-6 is associated with insulin resistance and the development of diabetes in Chinese population

AIMS

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a novel adipokine and has emerged as an important mediator for lipid and glucose metabolism. However, to date, the relationship between CTRP6 and T2DM in humans has not been demonstrated. Our objective is to investigate the association of circulating CTRP6 with T2DM in a cross-sectional study.

METHODS

118 patients with newly diagnosed T2DM, 98 subjects with impaired glucose tolerant (IGT) and 132 healthy subjects were recruited for this study. OGTT were performed in 48 healthy individuals to investigate the association of CTRP6 with glucose, insulin and other adipokines. Circulating CTRP6, TNF-α and Adipoq were measured by ELISA.

RESULTS

IGT and T2DM individuals had higher serum CTRP6 levels than healthy controls (406.2 ± 136.6 and 539.1 ± 169.7 vs. 354.3 ± 117.2 ng/mL; both P < 0.01), whereas serum CTRP6 concentrations were further increased in T2DM patients compared with IGT individuals (P < 0.01). Serum CTRP6 levels were found to be related positively to BMI, WHR, FAT%, TC, TG, HbA1c, FBG, 2 h-OGTT, fasting insulin (FIns), 2 h-Ins, HOMA-IR and TNF-α, and negatively with HDL-C and Adipoq in all individuals (P < 0.05 or P < 0.01). Multivariate logistic regression analysis demonstrated that CTRP6 was correlated with both IGT and T2DM. After an oral glucose challenge, serum CTRP6 concentrations exhibited a similar change with blood glucose, insulin, TNF-α and Adipoq.

CONCLUSIONS

CTRP6 may be a metabolism- and nutrition-related adipokine and may be related to insulin resistance and T2DM.

TRIAL REGISTRATIONS

Clinical Trial Registration Number: ChiCTR-OCC-11001422. Registration name: Plasma cytokines and endothelial function in type 2 diabetes.

The response of serum Glypican-4 levels and its potential regulatory mechanism to endurance training and chamomile flowers' hydroethanolic extract in streptozotocin-nicotinamide-induced diabetic rats

AIMS

Glypican-4 (GPC-4) is a novel adipomyokine that enhances insulin signaling. Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is thought to release GPC-4 and is itself an insulin-regulated enzyme. Beneficial effects of exercise training and chamomile flowers extract (CFE) are shown through activation of PPARγ, which is a promising drug target in diabetes and associated with GPC-4 synthesis. This study investigated the effects of 14-week treadmill running and CFE on serum GPC-4, GPLD1, and insulin levels in streptozotocin-nicotinamide (STZ-NA)-induced diabetic rats.

METHODS

Thirty-two STZ-NA-induced diabetic male Wistar rats were randomly assigned to four groups: control (C), training (T), CFE treatment (CFE), and training plus CFE treatment (TCFE) groups. The training groups were exercised on treadmill 5 days/week and the treating groups were fed with 200 mg/kg/day CFE in drinking water for 14 weeks. Finally, serum GPC-4, GPLD1, and insulin levels were analyzed via sandwich ELISA.

RESULTS

Compared to the control group, serum insulin levels were significantly higher in the T, CFE, and TCFE groups (p < 0.05, p < 0.05, p < 0.01, respectively), while OGTT and serum GPLD1 levels were significantly lower in the T, CFE, and TCFE groups (all p < 0.001). Changes in serum GPC-4 levels were not significant. Serum GPLD1 levels were negatively correlated with insulin levels and HOMA-IS (both p < 0.001).

CONCLUSIONS

This study suggests that endurance training and CFE may downregulate serum GPLD1 levels in STZ-NA-induced diabetic rats, which associate with the serum insulin profile. However, the results show that endurance training and CFE may not cause serum GPC-4 adaptation in STZ-NA-induced diabetic rats.

Myonectin Predicts the Development of Type 2 Diabetes

CONTEXT

Myonectin has been identified as a myokine, expressed predominantly in skeletal muscle. However, its clinical implications are largely unknown.

OBJECTIVE

The aim of this study is to investigate the relationship between myonectin (C1q tumor necrosis factor-α-related protein isoform 15) and type 2 diabetes mellitus (T2DM) in cross-sectional and interventional studies.

DESIGN

In a separate study, oral glucose tolerance tests, a 45-minute bout of exercise, lipid infusions, and euglycemic-hyperinsulinemic clamps (EHCs) were performed to investigate the association of myonectin with homeostasis model assessment of insulin resistance (HOMA-IR) and T2DM. Circulating myonectin was measured by enzyme-linked immunosorbent assay.

PATIENTS

One hundred four newly diagnosed T2DM (nT2DM), 109 impaired glucose tolerance (IGT), and 128 healthy individuals were recruited for this study.

RESULTS

nT2DM and IGT subjects had higher circulating myonectin concentrations than normal subjects (82.3 ± 47.6 and 68.9 ± 46.6 vs. 45.2 ± 23.5 µg/L, P < 0.05 or P < 0.01). It was also found that in nT2DM individuals, circulating myonectin was higher than in IGT subjects. Plasma myonectin correlated positively with waist/hip ratio, percentage of body fat, triglyceride, fasting blood glucose, 2-hour blood glucose after glucose overload, fasting insulin, hemoglobin A1c, and HOMA-IR and negatively with the insulin sensitivity index in all of the study population. Multivariate logistic regression analysis revealed that circulating myonectin levels were significantly correlated with IGT and T2DM. A 45-minute bout of exercise did not change circulating myonectin levels in healthy, young individuals. Circulating myonectin levels were not significantly altered in response to an oral glucose challenge or EHC. In addition, acute elevated free fatty acid levels induced by lipid infusion had no effects on circulating myonectin.

CONCLUSIONS

These data suggest that myonectin may be a useful marker in predicting the development of prediabetes and diabetes.

Serum glypican 4 level in obese children and its relation to degree of obesity

OBJECTIVE

Previous adult studies have demonstrated associations of serum glypican 4 (Gpc4) and obesity parameters and insulin sensitivity. However, an association of serum Gpc4 and glucose metabolism remains contradictory. Study of serum Gpc4 in obese children has not been conducted. We aimed to determine serum Gpc4 levels in obese children with various degrees of obesity.

DESIGN, PATIENTS AND MEASUREMENTS

Up to 370 overweight and obese children, aged 6-18 years were enrolled in this cross-sectional study. Oral glucose tolerance test (OGTT) was performed with fasting serum Gpc4, lipid profiles, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) measured. Insulin sensitivity and β-cell function indices were calculated from plasma glucose and serum insulin levels derived from the OGTT. Bioelectrical impedance analysis was performed for body fat determination. Comparisons of serum Gpc4 levels among the groups of children with various degrees of obesity were performed.

RESULTS

Serum Gpc4 levels progressively increased in children with increasing body mass index standard deviation score (BMI SDS) tertiles [median (interquartile range, IQR): 2.3 (1.8, 3.2), 2.6 (1.9, 3.4) and 3.2 (2.4, 3.8) μg/L, P<.001]. There were no differences in serum Gpc4 levels among children in the different glucose metabolism categories. Log serum Gpc4 levels were positively correlated with SDSs of weight and BMI, cholesterol, AST and ALT. No associations of log serum Gpc4 and insulin sensitivity and β-cell function indices were demonstrated.

CONCLUSIONS

Serum Gpc4 levels were increased with increasing degrees of obesity. There were no differences in serum Gpc4 levels among glucose metabolism categories.

Correlation of Glypican-4 Level with Basal Active Glucagon-Like Peptide 1 Level in Patients with Type 2 Diabetes Mellitus

BACKGROUND

Previous studies have reported that glypican-4 (GPC4) regulates insulin signaling by interacting with insulin receptor and through adipocyte differentiation. However, GPC4 has not been studied with regard to its effects on clinical factors in patients with type 2 diabetes mellitus (T2DM). We aimed to identify factors associated with GPC4 level in T2DM.

METHODS

Between January 2010 and December 2013, we selected 152 subjects with T2DM and collected serum and plasma into tubes pretreated with aprotinin and dipeptidyl peptidase-4 inhibitor to preserve active gastric inhibitory polypeptide (GIP) and glucagon-like peptide 1 (GLP-1). GPC4, active GLP-1, active GIP, and other factors were measured in these plasma samples. We performed a linear regression analysis to identify factors associated with GPC4 level.

RESULTS

The subjects had a mean age of 58.1 years, were mildly obese (mean body mass index [BMI], 26.1 kg/m²), had T2DM of long-duration (mean, 101.3 months), glycated hemoglobin 7.5%, low insulin secretion, and low insulin resistance (mean homeostatic model assessment of insulin resistance [HOMA-IR], 1.2). Their mean GPC4 was 2.0±0.2 ng/mL. In multivariate analysis, GPC4 was independently associated with age (β=0.224, P=0.009), and levels of active GLP-1 (β=0.171, P=0.049) and aspartate aminotransferase (AST; β=-0.176, P=0.043) after being adjusted for other clinical factors.

CONCLUSION

GPC4 was independently associated with age, active GLP-1, and AST in T2DM patients, but was not associated with HOMA-IR and BMI, which are well known factors related to GPC4. Further study is needed to identify the mechanisms of the association between GPC4 and basal active GLP-1 levels.

Association of serum glypican-4 levels with cardiovascular risk predictors in women with polycystic ovary syndrome - a pilot study

OBJECTIVE

Glypican-4 (Gpc4) is an adipokine which interacts with the insulin receptor and affects insulin sensitivity in proteoglycans. Insulin resistance plays a crucial role in the etiology of polycystic ovary syndrome (PCOS). PCOS is associated with metabolic disturbances such as abdominal obesity, dyslipidemia and type 2 diabetes. Thus, higher levels of Gpc4 released from visceral adipose tissue in women with PCOS may suggest an increased risk of cardiovascular disease (CVD).

DESIGN

The aim of this pilot study was to determine whether the serum Gpc4 level is associated with cardiovascular risk predictors in women with PCOS.

METHODS

Sixty-two women with PCOS according to the Rotterdam criteria (20-35 years old) and 43 healthy controls were studied. Cardiovascular risk predictors such as obesity indices, fat deposits according to dual-energy X-ray absorptiometry, biochemical lipid profile parameters and Homeostasis Model Assessment were estimated.

RESULTS

The serum Gpc4 level in PCOS women was significantly higher (2.61 ± 1.17 ng/ml) than in the control group (1.55 ± 0.47 ng/ml) and correlated with waist circumference, waist-to-hip ratio, total fat and android fat deposit to gynoid fat deposit ratio only in the PCOS group.

CONCLUSION

The Gpc4 level was higher in the PCOS group and correlated with CVD risk predictors, especially fat distribution.