Serum cystatin C as an indicator for early detection of diabetic nephropathy in type 2 diabetes mellitus

Augmented Intrarenal and Urinary Angiotensinogen in Diabetic Nephropathy: The Role of Isoflavones

The circulating renin-angiotensin system (RAS) is an endocrine system with key functions in maintaining blood pressure, fluid volume, and electrolytes. The RAS in the kidney (intrarenal RAS) plays a critical role in the onset and progression of kidney diseases. However, the mechanism underlying the onset and progression of diabetic nephropathy in relation to the expression and secretion of angiotensinogen (AGT) in the kidneys remains unclear. In this review, we present an overview of the intrarenal RAS and its role in diabetic nephropathy, as well as reviewing the evidence for the use of urinary AGT as a biomarker of this system in diabetic nephropathy. We also describe the roles of isoflavones in the context of diabetic nephropathy. The considered studies show that the intrarenal RAS-especially AGT-plays a diversified role in diabetic nephropathy; for instance, the increase in AGT due to oxidative stress is suppressed by polyphenols with antioxidant capacity, which is thought to affect the progression of diabetic nephropathy. Therefore, clarification of how polyphenols affect the onset and progression of diabetic nephropathy may provide insights into new treatments for this illness.

Patients With Type 2 Diabetes Mellitus and Early Diabetic Kidney Disease Exhibit Lower Computed Tomography-measured Skeletal Muscle Attenuation Values: A Propensity Score-matched Study

OBJECTIVE

To investigate the association between computed tomography-measured quality characteristics of skeletal muscle (SM) and early diagnosis of diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

This retrospective study included patients diagnosed with T2DM, with and without early DKD, between January 2019 and December 2021. To reduce potential bias, propensity score matching (PSM) was performed. The area and computed tomography attenuation values for SM and different abdominal adipose depots were measured. After PSM, logistic and multiple linear regression analyze were performed to analyse risk factors for early DKD.

RESULTS

A total of 267 patients were enrolled (mean age, 61.67 years ± 10.87; 155 men) and divided into two groups: T2DM with early DKD (n = 133); and T2DM without DKD (n = 134). After PSM, 230 patients were matched (T2DM with early DKD [n = 115]; and T2DM without DKD [n = 115]), with no statistical differences in general characteristics between the two groups (P > .05). In multivariate logistic regression analysis, high-density lipoprotein cholesterol (odds ratio [OR] 0.14; 95% confidence interval [CI] 0.04-0.49; P = .002), uric acid (OR 1.01; 95% CI 1.00-1.01; P = .006), and SM attenuation value (OR 0.94; 95% CI 0.90-0.98; P = .003) were independent risk factors for early DKD. Multiple linear regression analysis revealed significant correlations between SM attenuation value and cystatin C (β = -0.39, P = .004), urine albumin-to-creatinine ratio (β = -0.26, P = .026), and estimated glomerular filtration rate (β = 0.31 P = .009) after adjustment for confounders.

CONCLUSION

Patients with T2DM and lower SM attenuation values may exhibit a higher risk for early DKD than those with higher values, which provides a potential imaging biomarker for early DKD diagnosis.

Developing screening tools to estimate the risk of diabetic kidney disease in patients with type 2 diabetes mellitus

BACKGROUND

Diabetic kidney disease (DKD) is an important microvascular complication of diabetes mellitus (DM).

OBJECTIVE

This study aimed to develop predictive nomograms to estimate the risk of DKD in patients with type 2 diabetes mellitus (T2DM).

METHODS

The medical records of patients with T2DM in our hospital from March 2022 to March 2023 were retrospectively reviewed. The enrolled patients were randomly selected for training and validation sets in a 7:3 ratio. The models for predicting risk of DKD were virtualized by the nomograms using logistic regression analysis.

RESULTS

Among the enrolled 597 patients, 418 were assigned to the training set, while 179 were assigned to the validation set. Using the predictors included glycated hemoglobin A1c (HbA1c), high density lipoprotein cholesterol (HDL-C), presence of diabetic retinopathy (DR) and duration of diabetes (DD), we constructed a full model (model 1) for predicting DKD. And using the laboratory indexes of HbA1c, HDL-C, and cystatin C (Cys-C), we developed a laboratory-based model (model 2). The C-indexes were 0.897 for model 1 and 0.867 for model 2, respectively. The calibration curves demonstrated a good agreement between prediction and observation in the two models. The decision curve analysis (DCA) curves showed that the two models achieved a net benefit across all threshold probabilities.

CONCLUSION

We successfully constructed two prediction models to evaluate the risk of DKD in patients with T2DM. The two models exhibited good predictive performance and could be recommended for DKD screening and early detection.

Expression of urinary exosomal miRNA-615-3p and miRNA-3147 in diabetic kidney disease and their association with inflammation and fibrosis

BACKGROUND

Diabetic kidney disease (DKD) is one of the most common chronic complications of type 2 diabetes mellitus (T2DM), and it is particularly important to identify a high-quality method for evaluating disease progression. Urinary exosomes contain microRNA that might promise early diagnostic and monitoring markers of DKD. The present study aimed to identify novel exosome-related markers associated with inflammation and fibrosis to assess the progression of DKD.

METHOD

Exosomes were extracted from the urine of 83 participants to determine the expression levels of miRNA-615-3p and miRNA-3147 in 20 healthy people, 21 patients with T2DM and 42 patients with DKD, as determined by RT-qPCR. The circulating expression level of TGF-β1 was detected by ELISA. Serum Cystatin C was measured by a latex-enhanced immunoturbidimetric method. The correlation analyses were performed for all clinical and laboratory parameters.

RESULT

The expression level of urinary exosomal miRNA-615-3p in DKD patients was significantly higher than that in the control group and the T2DM group by RT-qPCR. The expression of miRNA-3147 showed an upward trend in the three groups of subjects, but it was not statistically significant. The urinary exosomal miRNA-615-3p was positively correlated with serum Cystatin C, plasma TGF-β1, creatinine, BUN, PCR and 24-h urine protein, and negatively correlated with eGFR and albumin. The diagnostic efficacy of urinary exosomal miRNA-615-3p combined with the ACR was higher than that of ACR alone.

CONCLUSIONS

Urinary exosomal miRNA-615-3p may be used as a novel biomarker for evaluating the progression of DKD, and may be involved in the process of inflammation and fibrosis in DKD. The combined diagnosis of urinary exosomal miRNA-615-3p and ACR may be used as more stable and sensitive diagnostic criteria for DKD.

Serum cystatin C for risk stratification of prediabetes and diabetes populations

BACKGROUND

The association between serum cystatin C level and vascular outcomes has not been fully elucidated in diabetes and is unclear in prediabetes. We aim to evaluate whether cystatin C level predicts future risk for mortality and vascular outcomes in prediabetes and diabetes.

METHODS

A total of 85,371 participants with prediabetes and diabetes, and available baseline cystatin C in the UK biobank were included with a 14-year follow-up. Cox hazards models were used to calculate the associations between cystatin C level, mortality (all-cause, cause-specfic mortality) and vascular outcomes (myocardial infarction [MI], stroke, end-stage renal disease [ESRD] and diabetic retinopathy [DR]). The 1136 diabetes subjects in Guangzhou Diabetic Eye Study (GDES) were included for examing the impact of cystatin C on in vivo retinal degeneration and microvascular changes by using SS-OCT and OCTA.

RESULTS

The highest cystatin C quartile had increased risks of all-cause (hazard ratio [HR], 2.02; 95% confidence interval [CI] 1.86-2.19), cardiovascular (HR, 2.29; 95% CI 1.97-2.67), cancer (HR, 1.86; 95% CI 1.65-2.10) and other-cause mortality (HR, 2.24; 95% CI 1.90-2.64), MI (HR, 1.40; 95% CI 1.26-1.55), stroke (HR, 1.88; 95% CI, 1.57-2.26), ESRD (HR, 7.33; 95% CI, 5.02-10.71), DR (HR, 1.17; 95% CI 1.03-1.32) than those in the lowest quartile. Adding cystatin C to the conventional model improved C-statistic for all-cause (0.699-0.724), cardiovascular (0.762-0.789), cancer (0.661-0.674) and other-cause mortality (0.675-0.715), MI (0.748-0.750), stroke (0.712-0.718), and ESRD (0.808-0.827). The GDES analysis identified a strong association between increased cystatin C levels and diminished retinal neural layers, as well as microvascular rarefaction in both macular and optic disc regions (all P < 0.05).

CONCLUSIONS

Serum cystatin C refines the risk stratification for mortality and vascular outcomes among patients with prediabetes or diabetes.

Exploration of Succinimide Derivative as a Multi-Target, Anti-Diabetic Agent: In Vitro and In Vivo Approaches

Diabetes mellitus (DM) is counted among one of the leading challenges in the recent era, and it is a life-threatening disorder. Compound 4-hydroxy 3-methoxy phenylacetone (compound 1) was previously isolated from Polygonum aviculare. This compound was reacted with N-benzylmaleimide to synthesize the targeted compound 3. The purpose of this research is to exhibit our developed compound 3's ability to concurrently inhibit many targets that are responsible for hyperglycemia. Compound 3 was capable of inhibiting α-amylase, α-glucosidase, and protein tyrosine phosphatase 1 B. Even so, outstanding in vitro inhibition was shown by the compound against dipeptidyl peptidase-4 (DPP-4) with an IC₅₀ value of 0.07 µM. Additionally, by using DPPH in the antioxidant activity, it exhibited good antioxidant potential. Similarly, in the in vivo activity, the experimental mice proved to be safe by treatment with compound 3. After 21 days of examination, the compound 3 activity pattern was found to be effective in experimental mice. Compound 3 decreased the excess peak of total triglycerides, total cholesterol, AST, ALT, ALP, LDL, BUN, and creatinine in the STZ-induced diabetic mice. Likewise, the histopathology of the kidneys, liver, and pancreas of the treated animals was also evaluated. Overall, the succinimde moiety, such as compound 3, can affect several targets simultaneously, and, finally, we were successful in synthesizing a multi-targeted preclinical therapy.

Correlation between serum cystatin C level and renal microvascular perfusion assessed by contrast-enhanced ultrasound in patients with diabetic kidney disease

OBJECTIVES

To investigate the relationship between serum cystatin C (CysC) levels and renal microvascular perfusion in patients with diabetic kidney disease (DKD).

METHODS

A total of 57 patients with high CysC levels and 45 patients with normal CysC levels were enrolled. Data on clinical characteristics and laboratory examination results were also collected. Contrast-enhanced ultrasound (CEUS) of the kidneys was successively performed. The time-intensity curve (TIC) and related quantitative parameters of the kidneys were obtained by CEUS and the correlations between CysC and CEUS parameters were analyzed.

RESULTS

Compared to the normal CysC group, the high CysC group had significantly lower wash-in area under the curve (WiAUC), wash-out area under the curve (WoAUC), and wash-in and wash-out area under the curve (WiWoAUC). In the normal CysC group, patients with Stage III chronic kidney disease (CKD) had higher AUCs than those with Stage I-II CKD (p < 0.05). In the high CysC group, patients with Stage IV-V CKD had lower wash-in AUC compared to patients with Stage I-II CKD (p = 0.023). The renal cortex microvascular perfusion parameters AUCs were positively correlated with the estimated glomerular filtration rate (GFR) (r = 0.280, 0.222, and 0.243), and CysC was inversely correlated with AUCs (r= -0.299, -0.251, and -0.273).

CONCLUSIONS

CEUS parameters reflected changes in renal microvascular perfusion in patients with DKD, while AUCs might be useful indicators of declining GFR in DKD patients with increased CysC.

Oxidative stress and metabolic parameters in hypertensive patients with/without diabetes mellitus in cardiovascular risk evaluation

Introduction: Hypertension and diabetes mellitus affect a large number of patients and can significantly influence their life expectancy. Changes in metabolic and oxidative stress parameters are common in these pathologies, contributing to associated complications. The aim of the study was assessment of relationship between laboratory parameters and their role in evaluation of cardiovascular risk, and possible gender-related differences in the protective factors.

Material and methods: Blood samples were collected from hypertensive patients with/without diabetes mellitus admitted to the Cardiovascular Rehabilitation Clinic in Tîrgu Mureș and controls without these pathologies. Biochemical analyses were performed on Konelab analyzer (glycemia, lipid profile, kidney function tests, zinc, hsCRP). Oxidative stress markers, such as serum malondialdehyde (MDA), oxidized (GSSG) and reduced glutathione (GSH) were evaluated using an HPLC-UV/VIS technique at GEP UMPhST. Statistical analysis was performed by GraphPad InStat3.

Results: Mean age of hypertensive patients (n=131) was 69.44 ± 9.02 years, 45.8% males, 31.3% being diabetics. 74.1% of the studied patients had zinc deficiency, 19.8% presented slightly elevated hsCRP. The control group included 24 nonhypertensive/nondiabetic patients of similar age. Average GSH was significantly lower (p=0.0002) in hypertensive patients, 1.89 ± 0.82 µg/ml, compared to the control group (3.23 ± 0.49 µg/ml), and no correlation could be observed between GSH and MDA values. GSH concentration was significantly higher in males (p=0.0395) and HDL-cholesterol significantly higher in females (p=0.0132). A negative correlation was observed between serum triglyceride and HDL-cholesterol concentration.

Conclusions: Gender differences are present in the level of protective factors against cardiovascular diseases, while oxidative stress is intensified in hypertensive/diabetic patients.

Diagnostic value of triglyceride and cystatin C ratio in diabetic kidney disease: a retrospective and prospective cohort study based on renal biopsy

Background

Currently, there is a lack of clinical indicators that can accurately distinguish diabetic kidney disease (DKD) from non-diabetic kidney disease (NDKD) in type 2 diabetes. The purpose of this study was to investigate the diagnostic value of triglyceride and cystatin C (TG/ Cys-C) ratio in DKD. Nowadays, there are few studies on the differential diagnosis of TG/ Cys-C ratio between DKD and NDKD.

Methods

The clinical data of patients with type 2 diabetes complicated with proteinuria who underwent renal biopsy from January 2013 to September 2019 in 2 hospitals in Xuzhou were retrospectively collected. According to the pathological classification of kidney, 25 patients in group DKD and 34 patients in non-diabetic kidney disease (NDKD) group were divided into two groups. The admission information and blood biochemical indexes of all patients with renal biopsy were collected, and the TG / Cys-C ratio was calculated. Logistic regression analysis was used to analyze the related factors of DKD in patients with type 2 diabetes and proteinuria. Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of TG/Cys-C ratio for DKD in patients with type 2 diabetes and proteinuria. Another 37 patients with type 2 diabetes complicated by proteinuria who were treated in the Department of Nephrology, four hospitals in Xuzhou from October 2019 to October 2021 were selected as the research objects. The TG/Cys-C value cut-off value selected in the retrospective study was selected as the boundary point and divided into two groups according to the values of greater than or equal to the tangent point and less than the tangential point. Serum triglyceride and cystatin C levels were measured and TG / Cys-C ratio was calculated. All patients underwent ultrasound-guided fine-needle renal biopsy. The positive rates of DKD diagnosis in the two groups were compared to verify the predictive value of TG / Cys-C ratio in the diagnosis of DKD.

Results

Retrospective study showed that compared with group NDKD, the DKD group had higher systolic blood pressure, higher cystatin C and creatinine, more diabetic retinopathy, longer duration of diabetes, lower hemoglobin concentration, lower glomerular filtration rate, lower cholesterol, lower triglyceride and lower TG/ Cys-C ratio (P < 0.05).Multivariate Logistic regression analysis showed that TG/Cys-C ratio (OR = 0.429, P = 0.009) was a protective factor for DKD in patients with type 2 diabetes and proteinuria. Diabetic retinopathy (OR = 7.054, P = 0.021) and systolic blood pressure (OR = 1.041, P = 0.047) were independent risk factors for DKD in patients with type 2 diabetes complicated with proteinuria. ROC curve showed that the area under the curve predicted by TG/Cys-C ratio for the diagnosis of DKD was 0.816, the sensitivity was 84%, and the specificity was 67.6%. The tangent value of TG / Cys-C ratio is 2.43. Prospective studies showed that in 37 patients with type 2 diabetes and proteinuria, 29 patients had a TG/Cys-C ratio of less than 2.43. The TG/Cys-C ratio of 8 patients was more than 2.43. Ultrasound guided fine needle aspiration biopsy revealed that 22 of the 29 patients had pathological diagnosis of DKD, sensitivity 91.67%, specificity 46.15%, positive predictive value 75.80%, and negative predictive value 75%.

Conclusion

In type 2 diabetic patients with proteinuria, the ratio of TG/Cys-C has certain predictive value for the diagnosis of DKD.

Serum Cystatin C Trajectory Is a Marker Associated With Diabetic Kidney Disease

Objective

To explore the association of the trajectory of serum Cystatin C (Cysc) with diabetic kidney disease (DKD), a retrospective cohort study of Chinese subjects was carried out.

Method

A review of 2,928 diabetes mellitus (DM) patients admitted to the clinic and ward of the Endocrinology Department, Shengjing Hospital of China Medical University from January 1, 2014 to December 31, 2014 was performed. Subsequent visits to the hospital were followed until December 31, 2020. The primary endpoint was the incidence of DKD as diagnosed by urinary albumin/creatinine ratio ≥30 mg/g and/or estimated glomerular filtration rate <60 ml/min per 1.73 m2. Healthy control subjects were identified from a health checkup database in Shengjing Hospital from 2016 to 2019. The latent class growth mixed modeling (LCGMM) method was used to analyze latent classes of serum Cysc in healthy and DM subjects. Finally, the hazard ratios (HRs) of latent classes of Cysc in DM subjects were analyzed by Cox regression analysis.

Results

A total of 805 type 2 diabetes mellitus (T2DM) and 349 healthy subjects were included in the trial. The HRs of quartiles of baseline Cysc in T2DM subjects were 7.15 [95% confidence interval (CI), 2.79 to 25.57], 2.30 (95% CI, 1.25 to 4.24), and 2.05 (95% CI, 1.14 to 3.70), respectively, for quartile 4 (Q4), Q3, and Q2 when compared with Q1. Through LCGMM, a 1-class linear model was selected for the Cysc latent class in healthy subjects. In contrast, a 3-class linear model was selected for that in DM subjects. The slopes of the three latent classes in T2DM subjects were larger than the slope in healthy subjects. The HRs of incident DKD were 3.43 (95% CI, 1.93 to 6.11) for the high-increasing class and 1.80 (95% CI, 1.17 to 2.77) for the middle-increasing class after adjusting for confounding variables.

Conclusions

Patients with T2DM had a higher velocity of increase in Cysc than healthy subjects. Patients with high baseline Cysc values and high latent increasing velocity of Cysc had a higher risk of developing DKD in later life. More attention should be paid to patients with these high-risk factors.

Correlation of Cystatin-c with Albumin Creatinine Ratio for the Diagnosis of Diabetic Nephropathy in Patients with Type 2 Diabetes: A Cross-sectional Study in Medan Indonesia

BACKGROUND: Diabetic nephropathy (ND) is one of the main complications of chronic microvascular diabetes mellitus (DM) and the leading cause of the end-stage renal disease (ESRD), accounting for nearly half of all ND cases with ESRD incidence in developed countries. Recently, cystatin C serum has been considered as a new biomarker for the diagnosis of kidney damage. Cystatin-C is an appropriate marker for GFR measurement because it is not affected by age, weight, gender, and protein intake. Early detection of abnormal renal function is essential to slow progression to a further stage of nephropathy or the final stage of kidney disease. AIM: The aim of the study was to analyze the correlation between cystatin-C and ACR to early detection of nephropathy complications. MATERIALS AND METHODS: This study uses an observational analytical research design with a cross-sectional approach. The research was conducted on patients with type 2 diabetes mellitus (T2DM) who were visiting the primary health service in Medan that met the inclusion and exclusion criteria. The sample count was 89 respondents. The sampling method is done through consecutive sampling. The source of this research data is primary data, including the results of cystatin-c examination and albumin. Data analysis used Spearman correlation using SPSS for Windows software. RESULTS: There was a significant relationship between cystatin-C levels and albuminuria (p<0.05). CONCLUSION: Diabetic nephropathy is a clinical syndrome characterized by persistent albuminuria and progressive decline of renal function, cystatin-C and albuminuria levels can be used as early detection of nephropathy complications.

Establishment and Validation of a Nomogram Model for Prediction of Diabetic Nephropathy in Type 2 Diabetic Patients with Proteinuria

PURPOSE

To establish and validate the nomogram model for predicting diabetic nephropathy (DN) in type 2 diabetes mellitus (T2DM) patients with proteinuria.

METHODS

A total of 102 patients with T2DM and proteinuria who underwent renal biopsy were included in this study. According to pathological classification of the kidney, the patients were divided into two groups, namely, a DN group (52 cases) and a non-diabetic renal disease (NDRD) group (50 cases). The clinical data were collected, and the factors associated with diabetic nephropathy (DN) were analyzed with multivariate logistic regression. A nomogram model for predicting DN risk was constructed by using R4.1 software. Receiver operator characteristic (ROC) curves were generated, and the K-fold cross-validation method was used for validation. A consistency test was performed by generating the correction curve.

RESULTS

Systolic blood pressure (SBP), diabetic retinopathy (DR), hemoglobin (Hb), fasting plasma glucose (FPG) and triglyceride/cystatin C (TG/Cys-C) ratio were independent factors for DN in T2DM patients with proteinuria (P<0.05). The nomogram model had good prediction efficiency. If the total score of the nomogram exceeds 200, the probability of DN is as high as 95%. The area under the ROC curve was 0.9412 (95% confidence interval (CI) = 0.8981-0.9842). The 10-fold cross-validation showed that the prediction accuracy of the model was 0.8427. The Hosmer-Lemeshow (H-L) test showed that there was no significant difference between the predicted value and the actual observed value (X ² = 6.725, P = 0.567). The calibration curve showed that the fitting degree of the DN nomogram prediction model was good.

CONCLUSION

The nomogram model constructed in the present study improves the diagnostic efficiency of DN in T2DM patients with proteinuria, and it has a high clinical value.

Cisplatin's potential for type 2 diabetes repositioning by inhibiting CDKN1A, FAS, and SESN1

Cisplatin is a DNA-damaging chemotherapeutic agent used for treating cancer. Based on cDNA dataset analysis, we investigated how cisplatin modified gene expression and observed cisplatin-induced dysregulation and system-level variations relating to insulin resistance and type 2 diabetes mellitus (T2DM). T2DM is a multifactorial disease affecting 462 million people in the world, and drug-induced T2DM is a serious issue. To understand this etiology, we designed an integrative, system-level study to identify associations between cisplatin-induced differentially expressed genes (DEGs) and T2DM. From a list of differential expressed genes, cisplatin downregulated the cyclin-dependent kinase inhibitor 1 (CDKN1A), tumor necrosis factor (FAS), and sestrin-1 (SESN1) genes responsible for modifying signaling pathways, including the p53, JAK-STAT, FOXO, MAPK, mTOR, P13-AKT, Toll-like receptor (TLR), adipocytokine, and insulin signaling pathways. These enriched pathways were expressively associated with the disease. We observed significant gene signatures, including SMAD3, IRS, PDK1, PRKAA1, AKT, SOS, RAS, GRB2, MEK1/2, and ERK, interacting with source genes. This study revealed the value of system genetics for identifying the cisplatin-induced genetic variants responsible for the progression of T2DM. Also, by cross-validating gene expression data for T2DM islets, we found that downregulating IRS and PRK families is critical in insulin and T2DM signaling pathways. Cisplatin, by inhibiting CDKN1A, FAS, and SESN1, promotes IRS and PRK activity in a similar way to rosiglitazone (a popular drug used for T2DM treatment). Our integrative, network-based approach can help in understanding the drug-induced pathophysiological mechanisms of diabetes.

The association between cystatin C and COPD: a meta-analysis and systematic review

BACKGROUND

In recent years, many studies have discovered that cystatin C (Cys C) may play an important role in respiratory diseases, especially in chronic obstructive pulmonary disease (COPD). However, the findings of these studies were inconsistent. This systematic review and meta-analysis aimed to assess the relationship between serum Cys C and COPD.

METHODS

We conducted a systematic literature search in PubMed, Embase, Web of Science, Wanfang databases, and the China National Knowledge Infrastructure. The standardized mean difference (SMD), Fisher's Z-value and 95% confidence interval (CI) were calculated to investigate the effect sizes. Subgroup analyses were performed on disease status, ethnicity, assay method, and study design. Sensitivity was performed, and publication bias was assessed.

RESULTS

A total of 15 studies, including 4079 COPD patients and 5949 controls, were included in this meta-analysis. The results showed that serum Cys C levels in patients with COPD were significantly higher than those in controls (SMD = 0.99, 95% CI =0.62-1.37, P < 0.001), especially in AECOPD (SMD = 1.59, 95% CI =1.05-2.13, P < 0.001), and there were statistically different among AECOPD and SCOPD (SMD = 0.35, 95% CI =0.10-0.59, P = 0.005). The serum Cys C levels were negatively correlated with FEV1%pre (Z = - 0.45, 95%CI = -0.58--0.32, P = 0.011) and FEV1/FVC (Z = - 0.32, 95%CI = -0.50--0.14, P = 0.006). The serum Cys C levels were independent of ethnicity, assay method, and study design.

CONCLUSION

Serum Cys C levels were associated with COPD and COPD exacerbation, and they were inversely correlated with FEV1%pre and FEV1/FVC.