| Objective:In order to understand and monitor the incipiency and progression of DN. We investigate the level of AQP5and CTGF in patients with DM or DN, and study their correlation with well-established clinical biomarkers.Methods:33diabetic nephropathy(DN) patients and31diabetic mellitus(DM) patients were enrolled in this study. Meanwhile,20healthy subjects with matched age and sex were randomly selected from the Center for Health Promotion at the Central South University XiangYa Hospital as control subjects. Clinical data were recorded upon recruitment. Fresh urine samples(10ml) and blood samples(2ml) were collected from each patient and control subject in the morning. All samples were centrifuged within2hours after collection for20minutes at1000g. Urine supernate and serum were extracted respectively before conserving at-80℃. Serum and urine concentrations of AQP5and CTGF were analyzed by commercial ELISA kits. Urine NAG, RBP and Cr were measured by automatic biochemical analyzer.Results:1.Urinary AQP5level in DN, DM, N groups were of significant difference. Expectedly, urinary AQP5excretion level in DN and DM groups were markedly elevated as compared with N group(P<0.05). When making comparison within DN and DM groups, urine AQP5concentration was significantly higher in the former group(P<0.05).Serum AQP5was also higher in DN patients and DM patients than in control subjects (P<0.05), whereas the difference between DN and DM groups was not significant. The level of Urine AQP5and serum AQP5were not correlated in all three groups. When compared with DM and N groups, urine CTGF level were significantly higher in DN group(P <0.05), while no difference were observed between DM group and control group. There is no difference in the serum level of CTGF in all three groups.The level of Urine CTGF and serum CTGF were not correlated in all three groups as well.2. Correlation analysis of DN group showed:urinary AQP5level positively correlated with the microalbuminuria level, urinary NAG and urinary RBP (r=0.493P<0.01, r=0.487P<0.01, r=0.562P<0.01respectively). Urinary CTGF level positively correlated with only urinary NAG(r=0.379,P<0.05). Correlation analysis of DM group showed:urinary AQP5level negatively correlated with fasting blood-glucose(FBG) and glycated hemoglobins(HbAlc%)(r=-0.451, P<0.05and r=-0.366, P<0.05respectively). Urinary AQP5and CTGF has no correlation with BMI, microalbuminuria level, urinary NAG and urinary RBP. Correlation analysis between AQP5and CTGF level showed:in DN group, urinary AQP5level significantly associated with serum CTGF level(r=0.404, P<0.05).3.Receiver operator characteristic curve (ROC) analysis showed:In DN group, the area under the curve (AUC) of urinary AQP5and urinary CTGF were0.775(95%CI:0.66～0.89, P<0.01) and0.831(95%CI:0.734～0.929, P<0.01) respectively. The diagnostic accuracy of both indicators is medium.Conclusion:1. Urinary AQP5level was significantly increased in DN patients and it positively correlated with the microalbuminuria level, urinary NAG and urinary RBP, indicating urinary AQP5might be an early biomarker of diabetic nephropathy.2. There was a marked elevation in the level of urinary CTGF in the DN group. This is in accordance with previous theories that CTGF contributes to renal interstitial fibrosis.3. Urinary AQP5level and serum CTGF level showed a positive correlation, suggesting urine AQP5concentration might to some extent reflect the severity of renal interstitial fibrosis. Whether or not urinary AQP5is an earlier or more specific indicator of renal fibrosis than CTGF calls for further investigation. |
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