1.Biological properties, degradation and absorption of collagen spongesin vivo
Yanyan CHI ; Yaojin LE ; Xuzhao LIU ; Qi LI ; Jing LEI ; Shunqing TANG
Chinese Journal of Tissue Engineering Research 2014;(34):5515-5519
BACKGROUND:Colagen sponges are applied for hemostatic use, wound healing, and residual cavity filing, which have great values in clinical application and scientific research.
OBJECTIVE:To investigate the biological properties, biocompatibility and biodegradability of colagen spongesin vivo.
METHODS: The spatial structure, pore diameter and porosity of colagen sponges were characterized by scanning electron microscopy. Transmission electron microscopy was used to observe the conformation of colagen sponges. The secondary structure and thermal denaturation temperature of colagen sponges were
analyzed by circular dichroism spectrum. Colagen sponges were implanted intramuscularly into the spinal cord of New Zealand rabbits to observe the degradation and absorption and histological changesin vivo.
RESULTS AND CONCLUSION: Colagen sponges had porous structure with varying pore sizes ranging
40-150 μm, the mean pore size of 100 μm, the thickness wal of 1 μm, and a porosity of approximately 95.8%. Colagen sponges had a typical porous structure and periodic light and dark zones. The solution of colagen
sponges had a weak positive band near 220 nm and an intense negative band near 206 nm, which indicated a classic triple helix. And the secondary structure and thermal stability of colagen sponges were similar to that of
liquid colagen. Colagen sponges began to degrade at 4 weeks, and remained 20% at 12 weeks. These sponges had been associated with foreign body response and inflammation within 2 weeks after implantation. With wound healing, inflammatory reactions gradualy reduced and disappeared. During the implantation and degradation of sponges, no significant fibrous capsule formed and no tissue necrosis occurred at implantation site, indicating that colagen sponges have good performance in bioactivity, biocompatibility and degradation.
2.Expression and significance of Caveolin-1, GPR30 and Vimentin in papillary thyroid carcinoma
Le ZHAO ; Cui TANG ; Lei YANG ; Xiaomei MO ; Ping ZHU ; Zhimin LIU
Chinese Journal of Immunology 2015;(11):1510-1514,1519
Objective:To investigate the expression of Caveolin-1,GPR30 and Vimentin at tumor tissues of human papillary thyroid carcinoma( PTC) patients and analyze their associations for the possible clinical implication.Methods: Immunohistochemistry was used to analyze the expression of Caveolin-1, GPR30 and Vimentin in 76 PTC and 44 normal samples.The correlations of Caveolin-1, GPR30 and Vimentin expression with one another, and with several clinicopathological indicators were statistically analyzed.Results:In PTCs,the positive expression rates of Caveolin-1,GPR30 and Vimentin were 9.21%(7/76),80.26%(61/76) and 76.32%(58/76),respectively.Caveolin-1,GPR30 and Vimentin expression had significant correlations with TNM stages(P=0.005,P<0.001,and P<0.001,respectively) and with cervical lymph node metastasis(P≤0.001 for all).Meanwhile,Caveolin-1 ex-pression had a negative correlation with GPR30(rs=-0.528,P<0.001) and Vimentin(rs=-0.572,P<0.001).GPR30 and Vimentin expression were positively correlated ( rs=0.812, P<0.001 ).Caveolin-1 under-expression was accompanied by GPR30 or Vimentin over-expression had stronger correlation with LNM ( P=0.020 for Caveolin-1/GPR30 and P=0.001 Caveolin-1/Vimentin ) than did each alone;concomitant high expression of GPR30 and Vimentin had stronger correlation with LNM( P=0.005 for GPR30/Vimentin) than did each alone.And lower expression of Caveolin-1 accompanied by higher expression of GPR30 and Vimentin was significantly as-sociated with LNM as compared with cases not showing such expressing(P<0.001).Conclusion:These results demonstrated that the evaluation of Caveolin-1 ,GPR30 and Vimentin expression may be play an important role in the development and metastasis of PTC,and their biological function may relate with each other.
3.Influence of the peri-implantitis to the microscrew-bone interface.
Yun HU ; Lei-le ZHENG ; Tian TANG ; Zhi-he ZHAO ; Jin-lin SONG ; Feng DENG
West China Journal of Stomatology 2011;29(1):17-26
OBJECTIVETo study the histological change of microscrew-bone interface, detect the relative cytokine of gingival crevicular fluid, and explore the impossible mechanism of peri-implantitis.
METHODSFour male Beagles were collected. Randomly select one side of animals jaw as the experimental group to induce the peri-implantitis, and another side as the control group. Four microscrews were implanted on each side. In the 1st, 2nd, 3rd, 4th weeks after implantation, collect peri-implant sulcular fluid (PISF) and detect tumor necrosis factor-alpha (TNF-alpha) levels before sacrificed, and the harvest tissue were observed in histological ways.
RESULTSAccording to the extension of time after implantation, the experimental group showed visible progress of interface destruction: 1st week after implantation showed large numbers inflammatory cells collected at the neck but did not undermine the cortical bone; 2nd week after implantation, cortical bone were observed angular absorption; Bone resorption continued to develop and at the 4th week, bone resorption were enlarged to the second thread of microscrew and the interface was filled with a large number of collagen fibers.
CONCLUSIONThe destruction of interface began at the neck of microscrew, and the further development was along the interface in depth. Both microscrews with peri-implantitis and the healthy controls showed the presence of TNF-alpha. Inflammation accumulation might trigger the up-regulation of TNF-alpha level, and the onset of inflammation would enhance the up-trend.
Animals ; Bone and Bones ; Dental Implants ; Dogs ; Gingival Crevicular Fluid ; Male ; Peri-Implantitis ; Tumor Necrosis Factor-alpha
4.Comparison of Risk Factors for the Progression of Coronary Lesions in Patients with Type 2 Diabetes and Non-diabetes Mellitus
Zhe-qi WEN ; Lei-le TANG ; Xing SHUI ; Jian-rui ZHENG ; Lin CHEN
Journal of Sun Yat-sen University(Medical Sciences) 2019;40(6):912-920
【Objective】Diabetes mellitus is a risk equivalent for coronary heart disease. This retrospective study was designed to investigate the risk factors of the progression of coronary lesions in patients with type 2 diabetes(T2DM)and Non- diabetes Mellitus(NDM).【Methods】 526 patients with T2DM and 425 patients with NDM at the Third Affiliated Hospital of Sun Yat-sen University between March 2001 and January 2017 who underwent coronary imaging studies(coronary angiography or coronary CTA)twice during the same period were enrolled. The effects of cardiovascular risk factors on the progression of coronary lesions were analyzed in parallel in these two types of patients.【Results】Risk factors of the progression of coronary lesions in T2DM patients included smoking(OR = 1.836,95% CI:1.030~3.371,P = 0.04),Lp(a) [OR = 1.001,95% CI:1.000~1.002,P = 0.004(baseline);OR = 1.001,95% CI:1.000~1.002,P = 0.009(re-examined)],HbA1c leve[l OR = 1.471,95% CI:1.030~2.100,P = 0.034(re-examined)],uncontrolled LDL-C(OR = 1.882,95% CI:1.091~3.245,P = 0.023),TC[OR = 2.029,95% CI:1.028~4.008,P = 0.041(re-examined)]and low HDL-C [OR = 0.017,95% CI:0.040~0.729,P = 0.017(re-examined)]. Comparative risk factors in NDM included BMI[OR =1.746,95%CI:2.462~2.712,P = 0.026(baseline);OR = 0.001,95%CI:0~0.394,P = 0.025(re-examined)],uncontrolled LDL-C(OR = 2.875,95%CI:1.669~4.952,P < 0.001)and low ApoA[OR = 0.282,95%CI:0.082~0.971,P = 0.045 (baseline);OR = 0.117,95%CI:0.038~0.835,P = 0.029(re-examined)]. Lowest level of progression was found in the group with HbA1c<6.5%[0(0~3.4)points/year vs 0.3(0~3.0)points/year vs 1.0(0~5.1)points/year,P = 0.049. 0(-0.4~2.7)points/year vs 0.6(0~4.0)points/year vs 0.9(0~4.2)points/year,P=0.029]in T2DM patients.【Conclusion】Except for achievement of LDL- C goals,there might be some differences in risk factors for progression of coronary lesions between T2DM and NDM patients. Smoking,Lp(a),TC,HDL- C and control levels of HbA1c are independent predictors in T2DM as well as BMI and ApoA in NDM. Lowering HbA1c to less than 6.5% may delay progression of lesion.
5.Predictive Effect of High Density Lipoprotein to C-reactive Protein Ratio on Progression of Chronic Kidney Disease in Non-Dialysis Patient
Lei-le TANG ; Xing-hua GUO ; Shao-min LI ; Pei-jia LIU ; Jia FANG ; Xun LIU
Journal of Sun Yat-sen University(Medical Sciences) 2022;43(2):305-315
ObjectiveTo investigate the predictive effect of high density lipoprotein (HDL) to C-reactive protein (CRP) ratio (HDL/CRP) on the progression of chronic kidney disease (CKD) in non-dialysis patients. MethodsNon-dialysis chronic kidney disease patients with at least two sets of follow-up data from the Third Affiliated Hospital of Sun Yat-sen University (Tian-he and Ling-nan districts)from 2015 to 2019 were enrolled. The baseline demographic characteristics and biochemical examination results were collected from the electronic medical record system. The patients were grouped according to the quantile of Ln(HDL/CRP). The demographic and biochemical data were compared among groups by one-way ANOVA for normal distribution continuous variables, Kruskal-Wallis rank-sum test for non-normal distribution continuous variables, and Chi-square analysis for categorical variables. The relationship between HDL/CRP and baseline eGFR was investigated by correlation analysis, univariate and multivariate linear regression analysis. The Cox survival analysis were used to investigate the predictive effect of Ln(HDL/CRP) on renal deterioration events. ResultsTotally 9 142 patients with CKD were enrolled, and 439 patients were included in the end. There were 100 patients (22.8%) with chronic glomerulonephritis, 145 patients (33%) with diabetic nephropathy, 40 patients (9.1%) with hypertensive nephropathy, and 154 patients (35.1%) with other causes. According to Ln(HDL/CRP) quartile, group Quartile4 had a lower incidence of renal deterioration than the other three groups (11% vs. 21.1% to 21.8%) and had the highest baseline eGFR level. From Quartile1 to quartile 4 groups, age, Hba1c and APOA1 levels decreased gradually. The prevalence of chronic heart failure, BMI, hemoglobin, albumin, TC, LDL, TG, APOB100 levels were different among groups. Through correlation analysis, Ln (HDL/CRP) were positively correlated with baseline eGFR(r=0.162, P=0.001). After adjusting for a variety of factors by Cox regression analysis, Ln (HDL/CRP) could be included in the final equation when defined deterioration of renal function as end point [HR=0.79, 95%CI (0.69, 0.91), P=0.001]. ConclusionHDL/CRP can reflect the severity of chronic kidney disease, and the ratio of HDL and CRP can predict the progression of chronic kidney disease in non-dialysis patient.
6.Laboratory testing of specimens from patients with viral encephalitis from some regions of China.
Zi-qian XU ; Shi-hong FU ; Yan-ping ZHANG ; Xing-le LI ; Xiao-yan GAO ; Lei WANG ; Yu-xi CAO ; Li-hong XU ; Yu JIN ; Qing TANG ; Guo-dong LIANG
Chinese Journal of Experimental and Clinical Virology 2008;22(2):98-100
OBJECTIVETo understand the viral etiology of viral encephalitis in China by detecting IgM antibody and viral RNA in the clinical samples of patients from some provinces of China by enzyme-linked immunosorbent assay and polymerase chain reaction.
METHODSerum and cerebrospinal fluid samples of 771 patients with viral encephalitis or meningitis were collected from six provinces of China and were stored at -20 degrees C or -70 degrees C. Enzyme-linked immunosorbent assays were used for detection of IgM antibody to Japanese encephalitis virus, coxsackievirus, echovirus, herpes simplex virus, measles virus, varicella-zoster virus, mumps virus, cytomegalovirus and Epstein-Barr virus. Polymerase chain reaction was applied for the detection of viral RNA of enteroviruses and seadornavirus.
RESULTSIgM antibody was detected in 567 of 771 (73.5%) cases. The most common pathogen was Japanese encephalitis virus (47.0%, 362/771), followed by mumps virus (10.6%, 82/771), enteroviruses (8.8%, 68/771), herpes simplex virus (5.7%, 44/771), measles virus (0.4%, 3/771), varicella-zoster virus (0.4%, 3/771), Epstein-Barr virus (0.4%, 3/771), and cytomegalovirus (0.3%, 2/771). Enterovirus was positive in 8 cases, seadornavirus was negative in all the cases by PCR.
CONCLUSIONAccording to the study, Japanese encephalitis was the most important encephalitis in China. Mumps virus was another important pathogen. Enteroviruses and herpes simplex virus were also important pathogens.
Adolescent ; Adult ; Aged ; Antibodies, Viral ; blood ; cerebrospinal fluid ; Child ; Child, Preschool ; China ; Encephalitis Virus, Japanese ; immunology ; Encephalitis, Viral ; blood ; cerebrospinal fluid ; virology ; Enterovirus ; genetics ; immunology ; Enzyme-Linked Immunosorbent Assay ; Female ; Humans ; Immunoglobulin M ; blood ; cerebrospinal fluid ; Male ; Meningitis, Viral ; blood ; cerebrospinal fluid ; virology ; Middle Aged ; Mumps virus ; immunology ; RNA, Viral ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Simplexvirus ; immunology ; Young Adult
7.Association between Metabolic Syndrome and Rapid Decline of Estimated Glomerular Filtration Rate in Middle-Aged and Elderly Populations
Pei-jia LIU ; Jia FANG ; Shao-min LI ; Lei-le TANG ; Xun LIU
Journal of Sun Yat-sen University(Medical Sciences) 2022;43(3):488-495
ObjectiveTo investigate the association of metabolic syndrome (MetS) and its components with rapid estimated glomerular filtration rate (eGFR) decline. MethodsThe China health and retirement longitudinal study (CHARLS) is a nationally representative cohort study focusing on physical and psychological health as well as social activities of middle-aged and elderly households. Cohort data could be obtained free of charge after application at the CHARLS website. We screened baseline data in 2011 and follow-up data in 2015 of CHARLS, selected those populations aged 45 and older, eGFR≥60 mL·min-1·(1.73m2)-1, without previous malignant tumors, heart disease, stroke and kidney disease, excluding those with missing values and outliers. Rapid eGFR decline was defined as an average annual decrease in eGFR of more than 3 mL·min-1·(1.73m2)-1. The 4400 participants enrolled were categorized into rapid eGFR decline group (770) and non-rapid eGFR decline group (3 630). Logistic regression was performed to test the association of MetS and its components with rapid decline of eGFR. ResultsCompared with subjects without MetS, in subjects with MetS, we found no association between MetS and rapid eGFR decline after controlling for confounding factors (P>0.05), with an OR (95%CI) of 0.988 (0.811~1.204). After adjustment for confounding factors, the MetS components associated with rapid eGFR decline were central obesity (OR = 0.968, 95% CI: 0.778~1.204, P = 0.767), elevated blood glucose (OR = 0.840, 95% CI: 0.715~0.986, P = 0.032), hypertension (OR = 1.087, 95% CI: 0.919~1.285, P = 0.328), decreased high-density lipoprotein cholesterol (OR = 1.085, 95% CI: 0.895~1.316, P = 0.404) and elevated triglyceride (OR = 1.110, 95% CI: 0.918~1.343, P = 0.281). ConclusionsMetS was not an independent risk factor of rapid eGFR decline in the middle-aged and elderly populations, and elevated blood glucose was associated with the reduced risk of rapid eGFR decline. The false renal benefit caused by elevated blood sugar might be related to the renal hyperperfusion and hyperfiltration in the early stage of the disease. We need further follow-up to observe the dynamic effects of the MetS and its components on renal function.
8.Phosphorylated PKM2 regulates endothelium-dependent vasodilation in diabetes.
Bin LU ; Lei TANG ; Le LI ; Xiaoyu ZHOU ; Yiping LENG ; Chengxuan QUAN
Journal of Central South University(Medical Sciences) 2023;48(5):663-670
OBJECTIVES:
Endothelium-dependent vasodilation dysfunction is the pathological basis of diabetic macroangiopathy. The utilization and adaptation of endothelial cells to high glucose determine the functional status of endothelial cells. Glycolysis pathway is the major energy source for endothelial cells. Abnormal glycolysis plays an important role in endothelium-dependent vasodilation dysfunction induced by high glucose. Pyruvate kinase isozyme type M2 (PKM2) is one of key enzymes in glycolysis pathway, phosphorylation of PKM2 can reduce the activity of pyruvate kinase and affect the glycolysis process of glucose. TEPP-46 can stabilize PKM2 in its tetramer form, reducing its dimer formation and phosphorylation. Using TEPP-46 as a tool drug to inhibit PKM2 phosphorylation, this study aims to explore the impact and potential mechanism of phosphorylated PKM2 (p-PKM2) on endothelial dependent vasodilation function in high glucose, and to provide a theoretical basis for finding new intervention targets for diabetic macroangiopathy.
METHODS:
The mice were divided into 3 groups: a wild-type (WT) group (a control group, C57BL/6 mice) and a db/db group (a diabetic group, db/db mice), which were treated with the sodium carboxymethyl cellulose solution (solvent) by gavage once a day, and a TEPP-46 group (a treatment group, db/db mice+TEPP-46), which was gavaged with TEPP-46 (30 mg/kg) and sodium carboxymethyl cellulose solution once a day. After 12 weeks of treatment, the levels of p-PKM2 and PKM2 protein in thoracic aortas, plasma nitric oxide (NO) level and endothelium-dependent vasodilation function of thoracic aortas were detected. High glucose (30 mmol/L) with or without TEPP-46 (10 μmol/L), mannitol incubating human umbilical vein endothelial cells (HUVECs) for 72 hours, respectively. The level of NO in supernatant, the content of NO in cells, and the levels of p-PKM2 and PKM2 protein were detected. Finally, the effect of TEPP-46 on endothelial nitric oxide synthase (eNOS) phosphorylation was detected at the cellular and animal levels.
RESULTS:
Compared with the control group, the levels of p-PKM2 in thoracic aortas of the diabetic group increased (P<0.05). The responsiveness of thoracic aortas in the diabetic group to acetylcholine (ACh) was 47% lower than that in the control group (P<0.05), and that in TEPP-46 treatment group was 28% higher than that in the diabetic group (P<0.05), while there was no statistically significant difference in the responsiveness of thoracic aortas to sodium nitroprusside (SNP). Compared with the control group, the plasma NO level of mice decreased in the diabetic group, while compared with the diabetic group, the phosphorylation of PKM2 in thoracic aortas decreased and the plasma NO level increased in the TEPP-46 group (both P<0.05). High glucose instead of mannitol induced the increase of PKM2 phosphorylation in HUVECs and reduced the level of NO in supernatant (both P<0.05). HUVECs incubated with TEPP-46 and high glucose reversed the reduction of NO production and secretion induced by high glucose while inhibiting PKM2 phosphorylation (both P<0.05). At the cellular and animal levels, TEPP-46 reversed the decrease of eNOS (ser1177) phosphorylation induced by high glucose (both P<0.05).
CONCLUSIONS
p-PKM2 may be involved in the process of endothelium-dependent vasodilation dysfunction in Type 2 diabetes by inhibiting p-eNOS (ser1177)/NO pathway.
Animals
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Humans
;
Mice
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Carboxymethylcellulose Sodium/pharmacology*
;
Diabetes Mellitus, Type 2/metabolism*
;
Endothelium, Vascular/metabolism*
;
Glucose/metabolism*
;
Human Umbilical Vein Endothelial Cells
;
Mice, Inbred C57BL
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Nitric Oxide/metabolism*
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Nitric Oxide Synthase Type III/metabolism*
;
Phosphorylation
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Pyruvate Kinase/metabolism*
;
Vasodilation
9.Testing and research of drilling feed force on fresh porcine femur
Chang-shu LI ; Yu-zhe BAI ; Xiang-xue KONG ; Lan CHEN ; Jian-y LI ; Zhi-jiang DU ; Le XIE ; Lei TANG
Journal of Medical Biomechanics 2014;29(6):E560-E566
Objective To record the drilling feed force on different layers of fresh porcine femur, so as to provide reference for collecting and outputting the feedback signals of drilling feed force for orthopedic virtual surgery system. Methods The biological bone drilling feed force testing system was established by modifying the universal material testing machine and adjustable speed electric drill (drill bit Φ5.0 mm). The feed forces on 6 fresh porcine femoral shafts with a total of 162 drilling markers were collected at 3 different rotate speeds (n=500, 800, 1 200 r/min) and 3 feed speeds (v=30, 50, 70 mm/min), and their variation with corresponding tissues and locations were also analyzed. Results At the same drill marker of the fresh porcine femur, the drilling feed force on bilateral cortical bone was the largest (fmax=103.63~142.59 N), while that on marrow cavity was the smallest, which was almost close to zero, and the drilling feed force on the middle part (f4,5,6=124.69 N) was larger than that at two ends (f1,2,3,7,8,9=121.84 N); the drilling feed force was smallest (f=106.04 N) at v=30 mm/min, n=1 200 r/min, while the largest drilling feed force (fmax=139.84 N) appeared at v=70 mm/min、n=500 r/min. Conclusions The modified drilling feed force testing system could efficiently collect the biological bone drilling data. The drilling feed force had a close relationship with bone structure, feed speed and rotate speed of electric drill as well. A larger bone density, smaller rotate speed of electric drill and higher feeding speed would lead to a larger drilling feed force, and vice versa. The accurate drilling feed force data and its variation tendency on porcine femoral obtained in this experiment could provide a reliable basis for force-feedback signal output in the virtual orthopedic surgery system.
10.Comparative Performance of Four Creatinine-based GFR Estimating Equations
Pei-jia LIU ; Hong-quan PENG ; Xing-hua GUO ; Lei-le TANG ; Shao-min LI ; Jia FANG ; Xun LIU
Journal of Sun Yat-sen University(Medical Sciences) 2022;43(4):621-630
ObjectiveTo assess the predictive performance of four creatinine-based equations for estimated glomerular filtration rate (eGFR): 2012 chronic kidney disease epidemiology collaboration (CKD-EPIcr) equation , 2021CKD-EPIcr equation, Xiangya equation and European kidney function consortium (EKFC) equation. MethodsA total of 198 patients with chronic kidney disease from the Third Affiliated Hospital of Sun Yat-sen University and the Kiang Wu Hospital in Macau were enrolled. We compared the GFR measured (mGFR) by iohexol plasma clearance and the eGFR calculated by four equations. The agreement between mGFR and eGFR was analyzed by Bland-Altman plots, concordance correlation coefficient (CCC), coverage probability (CP) and total deviation index (TDI). The performance of eGFR equations, including their bias, precision, root square mean error (RSME), and percentage of estimates within 30% deviation of measured GFR (P30), were evaluated. Bootstrap method (2 000 samples) was used to calculate bias, interquartile range (IQR), RSME, and 95% confidence intervals (CI) for P30. After selecting the optimal eGFR equation as the reference, we statisticlly tested other equations by ① Wilcoxon signed-rank test for bias; ② McNemar-Bowker test for P30; ③ comparing RMSE and IQR with independent samples t test after 2 000 bootstrap samples were obtained. ResultsThe median mGFR and four eGFR equations (EKFC, 2012CKD-EPIcr, 2021CKD-EPIcr and Xiangya equation) in the overall population were 56.2 mL·min-1·(1.73m2)-1, 67.1 mL·min-1·(1.73m2)-1, 73.0 mL·min-1·(1.73m2)-1, 66.9 mL·min-1·(1.73m2)-1 and 63.8 mL·min-1·(1.73m2)-1, respectively. The Bland-Altman plots showed that EKFC equation had the lowest mean difference and the narrowest 95% limit of agreement. The EKFC equation had the optimal performance on CCC, TDI and CP with values of 0.90, 24.41 and 0.50, respectively. Overall, the bias, accuracy, P30 and RSME from the EKFC equation was -0.99, 14.64, 0.80, and 14.68, respectively, with 95% CI ranging from -2.53 to 0.94, 11.82 to 17.35, 0.73 to 0.85, and 12.69 to 17.35, respectively, which were superior to those values from other three eGFR equations. The differences were statistically significant (all P < 0.05). The results in the mGFR subgroups were basically consistent with the overall trend. ConclusionsOf the four eGFR equations validated in this study, the EKFC equation comprehensively surpasses 2012CKD-EPIcr equation, 2021CKD-EPIcr equation, and Xiangya equation. With P30>75%, the EKFC equation can meet clinical diagnostic needs. Therefore, the EKFC equation is recommended for estimating GFR in a Chinese population, but more participants need be included to further support this conclusion.