Serum Levels of the Adipokine Zinc- α 2-glycoprotein Are Decreased in Patients with Hypertension

Zinc Alpha 2 Glycoprotein as an Early Biomarker of Diabetic Nephropathy in Type 2 Diabetes Mellitus Patients

Background and objectives Microalbuminuria is an early sign of diabetic nephropathy (DN). However, pathological abnormalities occur before the onset of microalbuminuria. Renal impairment progresses in about 50% of cases in type 2 diabetes mellitus (T2DM) without significant albuminuria. Diabetes mellitus (DM) is linked with obesity, metabolic syndrome, and lifestyle changes, where adipokines play an important role. Zinc alpha 2 glycoprotein (ZAGP) is an adipokine, and in this study, it was assessed as a potential biomarker for early DN as well as its progression. Materials and methods This study was a cross-sectional case-control study conducted at a tertiary hospital in northern India. T2DM patients aged 18-65 years old were included in the study and were divided into four groups based on their albuminuria level. This study included 160 participants, with 40 participants in each group. Group I included healthy volunteers, while Groups II, III, and IV were normoalbuminuric, microalbuminuric, and macroalbuminuric diabetic patients, respectively. The groups were evaluated for demographic variables, biochemical parameters, urine albumin-creatinine ratio (UACR), and serum ZAGP. Data between the groups were compared statistically. Results This study included 160 participants, with 40 participants in each group. There was a significant difference between the groups based on the serum ZAGP (p<0.001). Serum ZAGP was significantly negatively correlated with serum creatinine, glycosylated hemoglobin (HbA1c), serum cholesterol, serum triglyceride, low-density lipoprotein (LDL) cholesterol, and UACR. ZAGP was positively correlated with the estimated glomerular filtration rate (eGFR). Conclusion The present study showed that ZAGP was an early biomarker of diabetic nephropathy, and its value decreased as DN progressed. It also suggested that ZAGP, an adipokine, has an anti-inflammatory mechanism of action and its depletion worsens the disease.

Serum zinc-alpha-2 glycoprotein and insulin levels and their correlation with metabolic syndrome in patients with rosacea

BACKGROUND

Metabolic syndrome and insulin resistance may accompany rosacea. Zinc-alpha-2 glycoprotein (ZAG) is an adipokine involved in lipid, glucose, and insulin metabolism and might be associated with metabolic syndrome and insulin resistance.

AIMS

To investigate the serum ZAG levels, presence of metabolic syndrome, insulin resistance, and the correlation between ZAG levels, rosacea severity, and metabolic syndrome in patients with rosacea.

PATIENTS/METHODS

Seventy-nine patients with rosacea and 80 healthy volunteers were included. Anthropometric and demographic features, personal and family histories, clinical data, the subtype, severity, and duration of rosacea were recorded. Metabolic syndrome, insulin resistance, and dyslipidemia were evaluated in both groups. Fasting blood sugar, lipid panel, C-reactive protein, sedimentation rate, insulin, and serum ZAG levels were investigated.

RESULTS

Frequency of metabolic syndrome, systolic and diastolic blood pressures, and C-reactive protein levels were significantly higher in the rosacea group (p < 0.001 and p = 0.001, respectively). Frequency of dyslipidemia and insulin resistance did not significantly differ between the groups (p = 0.175 and 0.694, respectively). The mean serum ZAG levels were lower in the rosacea group, but no significant difference was evident. In rosacea patients with metabolic syndrome, serum ZAG levels were significantly lower (p = 0.043); however, serum ZAG levels, insulin, and the homeostasis model assessment-estimated insulin resistance values were significantly higher (p = 0.168, 0.013 and 0.001, respectively).

CONCLUSION

Metabolic syndrome, high blood pressure, and high C-reactive protein levels were associated with rosacea indicating chronic systemic inflammation. ZAG levels were associated with metabolic syndrome in patients with rosacea but not associated with rosacea subtype and disease severity.

Identification of diverse lipid-binding modes in the groove of zinc α2 glycoprotein reveals its functional versatility

ZAG is a multifunctional glycoprotein with a class I MHC-like protein fold and an α1-α2 lipid-binding groove. The intrinsic ZAG ligand is unknown. Our previous studies showed that ZAG binds the dansylated C₁₁ fatty acid, DAUDA, differently to the boron dipyrromethane C₁₆ fatty acid, C₁₆ -BODIPY. Here, the molecular basis for this difference was elucidated. Multi-wavelength analytical ultracentrifugation confirmed that DAUDA and C₁₆ -BODIPY individually bind to ZAG and compete for the same binding site. Molecular docking of lipid-binding in the structurally related Cluster of differentiation 1 proteins predicted nine conserved ligand contact residues in ZAG. Twelve mutants were accordingly created by alanine scanning site directed mutagenesis for characterisation. Mutation of Y12 caused ZAG to misfold. Mutation of K147, R157 and A158 abrogated C₁₆ -BODIPY but not DAUDA binding. L69 and T169 increased the fluorescence emission intensity of C₁₆ -BODIPY but not of DAUDA compared to wild-type ZAG and showed that C₁₆ -BODIPY binds close to T169 and L69. Distance measurements of the crystal structure revealed K147 forms a salt bridge with D83. A range of bioactive bulky lipids including phospholipids and sphingolipids displaced DAUDA from the ZAG binding site but unexpectedly did not displace C₁₆ -BODIPY. We conclude that the ZAG α1-α2 groove contains separate but overlapping sites for DAUDA and C₁₆ -BODIPY and is involved in binding to a bulkier and wider repertoire of lipids than previously reported. This work suggested that the in vivo activity of ZAG may be dictated by its lipid ligand.

Assessment of Zinc- alpha2 glycoprotein (ZAG) and Lipase Maturation Factor 1 (LMF1) concentration in children with chronic kidney disease

ZAG (zinc-alpha2-glycoprotein) - adipokine, may participate in the mechanism of malnutrition in chronic kidney disease (CKD) as cachexia factor. The transmembrane protein of the endoplasmic reticulum - lipase maturation factor 1 (LMF1) is necessary for the secretion and enzymatic activity of lipases and lowering triglycerides level. The aim of the study was to evaluate these markers - ZAG and LMF1, their potential importance in CKD in children. The study included 59 children and adolescents aged 10.7±5.0 years with CKD. Compared with healthy children, serum and urine ZAG levels were higher in children with CKD. A similar relationship was obtained in the comparison of girls and boys between the above groups. We showed a reduced serum and urine concentration of LMF1 in children with CKD. Additionally, ZAG and LMF1 levels in children below 10 years of age and above 10 were no different. There was also no correlation between these markers and serum creatinine (except negative correlation of urinary ZAG), albumin, cholesterol, triglycerides. LMF1 concentration correlated positively with vitamin D level in dialyzed patients. To conclude, elevated serum ZAG levels in children with CKD document that selective kidney damage results in the rise of ZAG concentration, however the specific role of this marker in malnutrition was not documented. Reduced serum LMF1 concentration in children with CKD, did not correlate with standard parameters used to assess lipid metabolism and severity of CKD. The usefulness of LMF1 as the marker of the lipid metabolism disturbances in children with CKD was not proven.

Changes in AZGP1 Serum Levels and Correlation With Pulse Wave Velocity After Kidney Transplantation

Background: Zinc-alpha 2-glycoprotein (AZGP1), a secreted protein with ubiquitous tissue expression, has been controversially linked to the risk of cardiovascular disease. In a cohort of kidney transplant recipients, we measured serum AZGP1 levels after transplantation over a 2 year period and tested for an association with pulse wave velocity as an important parameter indicating future cardiovascular events. Methods: Annual blood sampling and pulse wave velocity measurements were longitudinally performed in 113 kidney transplant recipients. AZGP1 was measured in serum samples using standard ELISA. Association of AZGP1 with pulse wave velocity was longitudinally assessed during follow up of 2 years by mixed longitudinal modeling. Results: AZGP1 serum levels declined significantly after kidney transplantation. This decline was dependent on allograft function as indicated by inverse correlation with eGFR. When corrected for eGFR multivariable analysis revealed an inverse correlation between AZGP1 and pulse wave velocity. This analysis further showed independent associations of older age, higher blood pressure, and higher calcium phosphate product with higher pulse wave velocity. Conclusions: Improved kidney function after transplantation leads to a decline in AZGP1 serum levels. Independent of kidney function and other cardiovascular risk factors lower AZGP1 levels are associated with higher pulse wave velocity in the 2 years after kidney transplantation. These data suggest that AZGP1 might be a potential biomarker for cardiovascular health and a target for improving cardiovascular outcome.

Development of a prediction model for mortality and cardiovascular outcomes in older adults taking into account AZGP1

Zinc-alpha 2-glycoprotein (AZGP1) is a serum protein with postulated functions in metabolism, cancer and cardiovascular disease. We developed new prediction models for mortality or cardiovascular events investigating the predictive potential of serum AZGP1 in a community-based cohort of older adults. We measured AZGP1 (μg/ml) in stored serum samples of 930 individuals of the Berlin Initiative Study, a prospective, population-based cohort of adults aged ≥ 70. We determined the prognostic potential of 20 knowledge-based predictors including AZGP1 for the outcomes of mortality or the composite endpoint of death and cardiovascular events (stroke, myocardial infarction (MI)) using Cox models; their model fit was evaluated with calibration plots, goodness-of-fit tests and c-indices. During median follow-up of 48.3 months, 70 incident strokes, 38 incident MI and 234 deaths occurred. We found no associations or correlations between AZGP1 and other candidate variables. After multivariable Cox regression with backward-selection AZGP1 remained in both models for mortality (HR = 0.44, 95%CI: 0.24–0.80) and for the composite endpoint (HR = 0.43, 95%CI: 0.23–0.82). Within newly built prediction models, we found that increased AZGP1 levels were predictive for lower risk of mortality and the composite endpoint in older adults. AZGP1 as a predictor warrants further validation in older adults.

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.

Attenuation of Weight Gain and Prevention of Associated Pathologies by Inhibiting SSAO

Obesity is a worldwide prevalent metabolic disorder that is associated with diabetes, among many other diseases. Bearing this in mind, prevention and treatment ways need to be improved. Notably, activity of the enzyme semicarbazide-sensitive amine oxidase (SSAO) is found to be elevated in overweight subjects. Moreover, SSAO inhibition has resulted in an increase of histamine activity in adipose tissue and the limitation of body fat. The current review aims to overview the risks of obesity, rationalize the molecular ways of SSAO activity, and outline the strategies of inhibiting upregulated enzyme levels. It describes the differences between SSAO inhibitors and advances the prospective agents. Based on evidence, caffeine is proposed as an effective, safe, and reliable choice to inhibit SSAO activity. Furthermore, the histamine in adipocytes has been associated with SSAO activity. Therefore, it is suggested as one of the key compounds to be studied for obesity management. To conclude, inhibiting SSAO may attenuate weight gain and prevent related diseases.

Serum ZAG and Adiponectin Levels Were Closely Related to Obesity and the Metabolically Abnormal Phenotype in Chinese Population

INTRODUCTION

To explore serum zinc-α2-glycoprotein (ZAG) and adiponectin in metabolically healthy non-obese (MHNO), metabolically healthy obesity (MHO), metabolically abnormal obesity (MAO) and metabolically abnormal diabetic obese (MADO) subjects and the relationship with metabolically phenotypes of obesity.

METHODS

Two hundred twenty-five subjects including 32 with MHNO, 40 with MHO, 104 with MAO and 49 with MADO were enrolled. Baseline clinical data and biochemical variables were collected. Serum ZAG and adiponectin levels were measured by enzyme-linked immunosorbent assay (ELISA) kits. Metabolically healthy (<3 metabolic abnormalities) or abnormal (≥3 metabolic abnormalities) subjects were classified based on the National Cholesterol Education Program-Adult Treatment Panel III (NCEP/ATP III) criteria. Obesity (body mass index ≥28 kg/m²) was recommended by China Obesity Task Force.

RESULTS

Serum ZAG levels were higher in the MHO group, but were progressively lower in MAO and MADO groups (P all<0.05). In all subjects, total cholesterol, 2-hour postprandial blood glucose and homeostasis model assessment of adiponectin were independent variables to serum ZAG levels. Compared with subjects in the highest tertile of ZAG, the odds ratio (OR) of metabolically abnormal risks of subjects in the lowest and median tertiles of ZAG were higher both in a univariate and three adjustment models (P all<0.05). Serum ZAG could discriminate the metabolically abnormal phenotype with receiver operating characteristic (ROC) curve area of 0.622 (95% CI, 0.539-0.706, P<0.05). Combination of ZAG and adiponectin had improved diagnosis value accuracy, with ROC curve area of 0.703 (95% CI, 0.629-0.776, P<0.05), and 62.7% sensitivity and 73.6% specificity.

CONCLUSION

Serum ZAG levels were higher in MHO subjects, but lower in MAO and MADO subjects. The decreased serum ZAG levels were closely related to the metabolically abnormal phenotype of obese patients. Serum ZAG, especially the combination with adiponectin might be the potential diagnostic biomarkers for metabolically abnormal obese patients.

Serum Zinc-α2-Glycoprotein Levels in Patients with or without Coronary Artery Disease in Chinese North Population

Coronary artery disease (CAD), the leading cause of morbidity and mortality, has imposed huge health and economic burdens globally. Zinc-α2-glycoprotein (ZAG) is a novel adipokine. Increasing evidence suggests the close relationship between serum ZAG levels and various cardiometabolic risk factors. However, the relationship between serum ZAG levels and CAD is still not fully clarified. We conducted this study to evaluate serum ZAG levels and its association with cardiovascular risk factors. A total of 129 patients with CAD, 99 patients with noncoronary artery disease (NCAD), and 121 controls were recruited in this retrospective study. CAD (coronary artery stenosis ≥50%) or NCAD (coronary artery stenosis <50%) patients who underwent coronary angiography were diagnosed according to the American Heart Association criteria. Serum ZAG levels were determined via commercial enzyme-linked immunosorbent assay (ELISA) kits. The results showed that serum ZAG levels in CAD and NCAD groups were significantly decreased when compared with those in the control group. Multiple stepwise regression analysis revealed that the grouping variable (control, NCAD, and CAD) was an independent determinant of serum ZAG levels (β = -0.328, P < 0.001) after controlling other confounding factors. Further multivariate ordinary logistic regression analysis demonstrated that the risk of grouping at one level higher in subjects with the lowest tertile of ZAG levels was 2.28-fold higher than those with the highest tertile levels (OR = 3.281, 95% CI 1.782-6.038, P < 0.001). The receiver-operating characteristic (ROC) curve analysis showed that serum ZAG could distinguish CAD patients (AUC = 0.706, 95% CI, 0.643-0.770, P < 0.05), NCAD patients (AUC = 0.673, 95% CI, 0.602-0.743, P < 0.05), and NCAD and CAD patients (AUC = 0.692, 95% CI, 0.633-0.750, P < 0.05) from controls. In conclusion, serum ZAG levels were significantly decreased in NCAD/CAD patients. The decreased serum ZAG levels were independently associated with the presence of NCAD/CAD. ZAG might serve as a candidate diagnostic biomarker for NCAD/CAD.

Low Serum ZAG Levels Correlate With Determinants of the Metabolic Syndrome in Chinese Subjects

Introduction: Zinc-α2-glycoprotein (ZAG) is a novel adipokine, which is involved in metabolic syndrome (MetS). This study aimed to investigate the relationship between serum ZAG and MetS in Chinese adults, who diagnosed according to the 2005 International Diabetes Federation (IDF) criteria. Methods: A group of 151 MetS patients, 84 patients with central obesity and 70 healthy controls were enrolled. General clinical information, serum samples were obtained from all subjects and serum ZAG levels were determined via the commercial ELISA kits. Results: Serum ZAG levels were the highest in the control group, then gradually decreased with the severity of the metabolic abnormalities increased (8.78 ± 1.66 μg/mL for control vs. 8.37 ± 1.52 μg/mL for central obesity vs. 7.98 ± 0.94 μg/mL for MetS, P < 0.05). It was also decreased progressively with an increasing number of the MetS components (P for trend = 0.002). Additionally, serum ZAG/fat mass ratio was calculated and the similar changes were observed in the three groups (0.85 ± 0.53 μg/mL/kg for control vs. 0.39 ± 0.10 μg/mL/kg for central obesity vs. 0.36 ± 0.08 μg/mL/kg for MetS, P < 0.05). In the multiple regression analysis, group was a strong independent factor contributing to serum ZAG levels (P < 0.001). Furthermore, compared with subjects with the highest tertile of ZAG, subjects in the lowest tertile of ZAG had 1.946-fold higher risk of MetS (95% CI 1.419-6.117, P = 0.004). This phenomenon still existed after controlling for age, gender (Model 1), ALP, AST, Cr, UA, Urea based on Model 1 (Model 2), grip strength, smoking, drinking, birth place, current address, education level, manual labor, and exercise frequency based on Model 2 (Model 3). Receiver operation characteristic (ROC) curve analysis revealed that serum ZAG might serve as a candidate biomarker for MetS (sensitivity 57.6%, specificity 70.0% and area under the curve 0.655), and serum ZAG/fat mass ratio showed improved diagnosis value accuracy, with ROC curve area of 0.951 (95% CI, 0.920-0.983, P < 0.001), and 90.7% sensitivity and 88.6% specificity. Conclusions: Serum ZAG levels were lowered in patients with MetS and central obesity. The decreased serum ZAG levels were associated with the increased risks of MetS. Serum ZAG, especially serum ZAG/fat mass ratio might be the candidate diagnostic biomarkers for MetS.

Crystal structure of zinc-α2-glycoprotein in complex with a fatty acid reveals multiple different modes of protein-lipid binding

Human zinc-α2-glycoprotein (ZAG) is a 42 kDa adipokine which regulates body fat mass and is associated with cachexia and obesity. ZAG belongs to the major histocompatibility complex class I protein family and binds long-chain polyunsaturated fatty acids in its groove formed from the α1 and α2 domains. To identify the molecular basis of its lipid-binding function, we determined the first crystal structure at 2.49 Å resolution for fatty acid-bound ZAG, where the ligand was the fluorescent 11-(dansylamino)undecanoic acid (DAUDA). The 192 kDa crystallographic asymmetric unit contained six ZAG and eight fatty acid molecules in unique conformations. Six fatty acid molecules were localised to the ZAG grooves, where their tails were bound in two distinct conformations. The carboxylate groups of three fatty acids projected out of the groove, while the fourth was hydrogen bonded with R73 inside the groove. Other ligand-residue contacts were primarily hydrophobic. A new fatty acid site was revealed for two further DAUDA molecules at the ZAG α3 domains. Following conformational changes from unbound ZAG, the α3 domains formed tetrameric β-barrel structures lined by fatty acid molecules that doubled the binding capacity of ZAG. Analytical ultracentrifugation revealed that ZAG in solution was a monomer in the absence of DAUDA, but formed small amounts of tetramers with DAUDA. By showing that ZAG binds fatty acids in different locations, we demonstrate an augmented mechanism for fatty acid binding in ZAG that is distinct from other known fatty acid binding proteins, and may be relevant to cachexia.

Serum levels of the adipokine zinc-alpha2-glycoprotein (ZAG) predict mortality in hemodialysis patients

Wasting has been associated with increased cardiovascular and all-cause mortality in chronic kidney disease (CKD). We investigated whether serum zinc-alpha2-glycoprotein (ZAG), a potent cachectic and lipid-mobilizing factor that is increased in patients with CKD, predicts clinical outcomes in patients on chronic hemodialysis. We quantified serum ZAG at baseline in a prospective cohort of 252 patients undergoing maintenance hemodialysis. Serum ZAG concentrations were inversely associated with serum albumin, creatinine, and triglycerides and, conversely, positively associated with age. Although ZAG is strongly linked to protein energy wasting (PEW) in patients with cancer, higher ZAG concentrations were not associated with PEW in our cohort. During a mean study follow-up of 954 days, 49 patients died and 62 patients experienced a cardiovascular event. Kaplan-Meier analysis revealed a significant correlation between serum ZAG concentrations and all-cause mortality and cardiovascular events. In separate multivariable Cox regression models, serum ZAG concentrations remained significantly associated with all-cause mortality and cardiovascular events after adjustment for demographic factors (age, sex, and dialysis vintage), metabolic parameters (serum albumin, prealbumin, triglycerides, cholesterol, normalized protein catabolic rate, and body mass index), and cardiovascular risk factors (diabetes, dyslipidemia, history of cardiovascular disease, smoking, and diuretic use as a proxy of residual renal function). Thus, serum ZAG appears to be a strong and independent predictor of mortality and cardiovascular events in patients with end-stage renal disease. Further studies are necessary to confirm this association and to elucidate the underlying mechanisms.

Quantitative profiling of tear proteome reveals down regulation of zinc alpha-2 glycoprotein in Aspergillus flavus keratitis patients

Corneal mycotic ulceration is predominantly due to Aspergillus and Fusarium solani infection in tropical countries. In this study, we examined the proteome profile of tear samples from A. flavus keratitis patients at various stages of infection. The proteome was profiled using 2D PAGE and the protein levels were quantified using 2D DIGE. Alpha-1-antitrypsin, apolipoprotein, haptoglobin, lactoferrin and albumin were up regulated while cystatin SA III precursor, lacrimal lipocalin precursor, lacritin precursor and Zinc alpha-2 glycoprotein (ZAG) were down regulated in tear fluid. In the case of ZAG all proteoforms were down regulated as the disease progressed from early to late stage of infection. Western blot analysis confirmed the results observed using DIGE. Further, there were no gender specific differences in the levels of ZAG expression in keratitis patient tear film. Published results show up regulation of ZAG in Fusarium keratitis patient tear indicating subtle changes in the early events of host response to these two fungal pathogens. We conclude that ZAG level could be used as an indicator of A. flavus or F. solani infection, even during the early stage of the disease.

Serum Zinc-α2-Glycoprotein Levels Were Decreased in Patients With Premature Coronary Artery Disease

Objectives: To explore serum zinc-α2-glycoprotein (ZAG) changes in patients with or without premature coronary artery disease (PCAD) and its association with several cardiovascular risk factors. Methods: A total of 3,364 patients who were undergone coronary angiography in Peking Union Medical College Hospital were screened. According to the degree of coronary artery stenosis, the number of 364 patients with PCAD (age <55 years in males and <65 years in females) and 126 age and gender matched patients without premature coronary artery disease (NPCAD) were recruited in our present study. In addition, 182 age and gender matched healthy controls were also enrolled. Serum ZAG levels were determined by enzyme-linked immunosorbent assay (ELISA) method. Results: Serum ZAG were significantly lower in the PCAD (8.03 ± 1.01 vs. 8.78 ± 1.89 μg/mL, p < 0.05) and NPCAD groups (8.28 ± 1.61 vs. 8.78 ± 1.89 μg/mL, p < 0.05), respectively, when compared with the controls. Multiple regression analysis showed that PCAD was independently associated with serum ZAG levels (B = -0.289, p = 0.002). The probability of PCAD in subjects with low tertile ZAG levels was 2.48-fold higher than those with high tertile levels after adjusting for other confounders [OR = 3.476, 95% CI 1.387-8.711, p = 0.008]. This phenomenon was more likely to be observed in male subjects with BMI <24 kg/m². The receiver operating curve (ROC) analysis showed a weak diagnostic performance of serum ZAG for PCAD (AUC = 0.659, 95% CI 0.612-0.705, p < 0.05). At the cutoff value of 7.955 μg/mL serum ZAG, the sensitivity and specificity for differentiating patients with PCAD from controls were 50.5 and 78.0%, respectively. The combination of ZAG with other clinical variables including age, gender, BMI, SBP, FBG, TC, HDL-C, Cr, and Urea had significantly improved the diagnosis accuracy with a sensitivity of 82.6%, a specificity of 95.0%, and AUC of 0.957 (95% CI, 0.940-0.975, p < 0.05). Conclusion: Serum ZAG levels were firstly found to be decreased in Chinese PCAD patients. Subjects with lower ZAG levels were more likely to have PCAD, especially for male subjects with BMI <24 kg/m². ZAG might be the potential diagnostic biomarkers for PCAD patients, and the combination of ZAG and clinical variables had higher discriminative performance.

Zinc status is associated with inflammation, oxidative stress, lipid, and glucose metabolism

A number of studies have reported that zinc plays a substantial role in the development of metabolic syndrome, taking part in the regulation of cytokine expression, suppressing inflammation, and is also required to activate antioxidant enzymes that scavenge reactive oxygen species, reducing oxidative stress. Zinc also plays a role in the correct functioning of lipid and glucose metabolism, regulating and forming the expression of insulin. In numerous studies, zinc supplementation has been found to improve blood pressure, glucose, and LDL cholesterol serum level. Deeper knowledge of zinc’s properties may help in treating metabolic syndrome, thus protecting against stroke and angina pectoris, and ultimately against death.

Serum ZAG Levels Were Associated with eGFR Mild Decrease in T2DM Patients with Diabetic Nephropathy

Objective. To investigate the changes of serum zinc-α2-glycoprotein (ZAG) in type 2 diabetes mellitus (T2DM) with eGFR mild decrease. Subjects and Methods. A total of 438 T2DM patients (61.3 ± 4.0 y) were recruited and the demographic, anthropometric, and biochemical parameters were all collected. Serum ZAG levels were determined by commercially available ELISA kits. Results. The proportion of T2DM patients with the high tertile ZAG levels was 11.9% higher in patients with mildly decreased estimated glomerular filtration rate (eGFR) (<90 mL/min/1.73 m²) than those with the low tertile ZAG levels (P = 0.038). The probability of the eGFR < 90 mL/min/1.73 m² in patients with the high ZAG levels was 94% higher than those with the low serum ZAG levels after adjusting for age, gender, and education [OR = 1.94, 95% CI (1.17-3.23), P = 0.0094]. This phenomenon was more likely to be observed in the condition of uACR ≥ 2.7 mg/mmol, WC ≥ 90 cm for men, or WC ≥ 85 cm for women. Conclusion. Serum ZAG levels were firstly found to be related with eGFR in T2DM patients. The patients with the high tertile ZAG levels were more likely to have mildly eGFR decrease, especially for female patients with higher uACR and bigger WC.

Zinc-α2-Glycoprotein Exerts Antifibrotic Effects in Kidney and Heart

Zinc-α2-glycoprotein (AZGP1) is a secreted protein synthesized by epithelial cells and adipocytes that has roles in lipid metabolism, cell cycling, and cancer progression. Our previous findings in AKI indicated a new role for AZGP1 in the regulation of fibrosis, which is a unifying feature of CKD. Using two models of chronic kidney injury, we now show that mice with genetic AZGP1 deletion develop significantly more kidney fibrosis. This destructive phenotype was rescued by injection of recombinant AZGP1. Exposure of AZGP1-deficient mice to cardiac stress by thoracic aortic constriction revealed that antifibrotic effects were not restricted to the kidney but were cardioprotective. In vitro, recombinant AZGP1 inhibited kidney epithelial dedifferentiation and antagonized fibroblast activation by negatively regulating TGF-β signaling. Patient sera with high levels of AZGP1 similarly attenuated TGF-β signaling in fibroblasts. Taken together, these findings indicate a novel role for AZGP1 as a negative regulator of fibrosis progression, suggesting that recombinant AZGP1 may have translational effect for treating fibrotic disease.

Significance of serum Zn-α2-glycoprotein for the regulation of blood pressure

Zn-α2-glycoprotein (ZAG) (molecular weight=41 kDa) is one component in the α2 fraction of human plasma, and is reported to be associated with several diseases, such as cancers and metabolic syndromes. ZAG is also considered to be an important modulator of lipid metabolism. However, little is known about the correlation of serum ZAG levels with indicators of metabolic syndrome. Serum ZAG concentrations analyzed by enzyme-linked immunoassay were positively correlated with systolic and diastolic blood pressure in 326 subjects (236 males and 90 females) aged 17-79 years who had an annual health examination. By luciferase reporter and electrophoretic mobility shift assays, the core promoter region to regulate the ZAG gene expression was found to exist between -110 and -101. The transcription factor Sp1 interacted with this region, and Sp1 knockdown experiments showed that Sp1 critically regulated ZAG expression. Furthermore, ZAG increased the active form of RhoA, which was determined by pull-down assay. Increased serum ZAG concentrations induced, at least partly, by Sp1 may cause an increase in vascular tone through the activation of RhoA and contribute to elevated blood pressure.