Urine transferrin as an early endothelial dysfunction marker in type 2 diabetic patients without nephropathy: a case control study

Background Albumin, along with other proteins, is abnormally eliminated via the urine during early stages of diabetic nephropathy. Moreover, endothelial dysfunction (ED) accompanying early diabetic nephropathy may develop even before microalbuminuria is detectable. Transferrin has a molecular weight comparable to albumin, whereas transferrinuria and microalbuminuria in a 24-h urine sample may comparably reflect early diabetic nephropathy. Whereas transferrin metabolism is related with ED during very early diabetic nephropathy has not been elucidated yet. This case–control study aimed to evaluate the relation between ED and urine transferrin, even before early diabetic nephropathy is present. Methods Patients were enrolled from two study sites in Mexico City: Ticomán General Hospital (healthy controls); and a Specialized Clinic for the Management of the Diabetic Patient (cases). All patients provided written informed consent. The primary endpoint was the correlation between urinary transferrin concentration and ED measured in type 2 diabetic patients without albuminuria. ED was evaluated by ultrasonographic validated measurements, which included carotid intima-media thickness (CIMT) and flow mediated dilation (FMD). Plasma biomarkers included glycated hemoglobin, creatinine, cholesterol and triglycerides, as well as urine albumin, transferrin and evidence of urinary tract infection. Results Sixty patients with type 2 Diabetes Mellitus (t2DM; n = 30) or without t2DM (n = 30), both negative for microalbuminuria, were recruited. The group with t2DM were older, with higher values of HbA1c and higher ED. This group also showed significant differences in urine transferrin and urine/plasma transferrin ratio, as compared with healthy controls (14.4 vs. 18.7 mg/mL, p = 0.04, and 74.2 vs. 49.5; p = 0.01; respectively). Moreover, urine transferrin correlated with higher CIMT values (r = 0.37, p = 0.04), being particularly significant for t2DM population. CIMT also correlated with time from t2DM diagnosis (r = 0.48, p < 0.001) and HbA1c (r = 0.48; p < 0.001). Conclusion Urine transferrin correlated with subclinical atherogenesis in patients with t2DM without renal failure, suggesting its potential to identify cardiovascular risk in patients at very early nephropathy stage without microalbuminuria.

VDR/Atg3 Axis Regulates Slit Diaphragm to Tight Junction Transition via p62-mediated Autophagy Pathway in Diabetic Nephropathy

Foot process effacement is an important feature of early diabetic nephropathy (DN) which is closely related to the development of albuminuria. Under certain nephrotic conditions, the integrity and function of the glomerular slit diaphragm (SD) structure were impaired and replaced by the tight junction (TJ) structure, resulting in so-called SD-TJ transition, which could partially explain the effacement of foot processes at the molecular level. However, the mechanism underlying the SD-TJ transition has not been described in DN. Here, we demonstrated that impaired autophagic flux blocked p62 mediated degradation of ZO-1 (TJ protein) and promoted podocytes injury via activation of caspase 3 and caspase 8. Interestingly, the expression of VDR in podocytes was decreased under diabetic condition which impaired autophagic flux through down-regulating Atg3. Of note, we also found that VDR abundance was negatively associated with impaired autophagic flux and SD-TJ transition in the glomeruli from human renal biopsy samples with DN. Furthermore, VDR activation improved autophagic flux and attenuated SD-TJ transition in the glomeruli of diabetic animal models. In conclusion, our data provided the novel insight that VDR/Atg3 axis deficiency resulted in SD-TJ transition and foot processes effacement via blocking p62-mediated autophagy pathway in DN.<br>

VDR/Atg3 Axis Regulates Slit Diaphragm to Tight Junction Transition via p62-mediated Autophagy Pathway in Diabetic Nephropathy

Foot process effacement is an important feature of early diabetic nephropathy (DN) which is closely related to the development of albuminuria. Under certain nephrotic conditions, the integrity and function of the glomerular slit diaphragm (SD) structure were impaired and replaced by the tight junction (TJ) structure, resulting in so-called SD-TJ transition, which could partially explain the effacement of foot processes at the molecular level. However, the mechanism underlying the SD-TJ transition has not been described in DN. Here, we demonstrated that impaired autophagic flux blocked p62 mediated degradation of ZO-1 (TJ protein) and promoted podocytes injury via activation of caspase 3 and caspase 8. Interestingly, the expression of VDR in podocytes was decreased under diabetic condition which impaired autophagic flux through down-regulating Atg3. Of note, we also found that VDR abundance was negatively associated with impaired autophagic flux and SD-TJ transition in the glomeruli from human renal biopsy samples with DN. Furthermore, VDR activation improved autophagic flux and attenuated SD-TJ transition in the glomeruli of diabetic animal models. In conclusion, our data provided the novel insight that VDR/Atg3 axis deficiency resulted in SD-TJ transition and foot processes effacement via blocking p62-mediated autophagy pathway in DN.<br>

Urine Transferrin as an Early Endothelial Dysfunction Marker in Type 2 Diabetic Patients Without Nephropathy: A Case Control Study.

Background Albumin, along with other proteins, is abnormally eliminated via the urine during early stages of diabetic nephropathy. Moreover, endothelial dysfunction (ED) accompanying early diabetic nephropathy may develop even before microalbuminuria is detectable. Transferrin has a molecular weight comparable to albumin, and transferrinuria and microalbuminuria in a 24-hour urine sample may comparably reflect early diabetic nephropathy. However, transferrin physiochemical properties may be related with ED, but these have not been elucidated yet. This case-control study was aimed to evaluate relation between ED and urinary transferrin concentration before early diabetic nephropathy is present. Methods Patients were enrolled from two study sites in Mexico City: Ticoman General Hospital to evaluate control patients; and Dr. Manuel Gonzalez Rivera Specialized Clinic for the Management of the Diabetic Patient for case patients. All patients provided written informed consent. The primary endpoint was the correlation between urinary transferrin concentration and endothelial dysfunction measured in type 2 diabetic patients without albuminuria. ED was evaluated by ultrasonographic validated measurements, which included carotid intima-media thickness (CIMT) and flow mediated dilation (FMD). A power calculation, to detect a statistical difference, with a p value of 0.05, mandated a sample of 60 patients. The patients were tested for serum biomarkers such as glycated hemoglobin, creatinine, cholesterol, triglycerides, and urinary dipstick for albuminuria and urinary tract infection; using inclusion, exclusion and elimination criteria as described. Results The group with type 2 diabetes was older and showed higher serum transferrin and lower urinary transferrin values. Likewise, the group with type 2 diabetes showed subclinical atherogenic risk characterized by lower FMD and higher CIMT and ABI values. Risk factors associated to endothelial dysfunction measured by CIMT were time from diagnosis of diabetes, insulin resistance, dyslipidemia, and male sex. Hba1c and time since diabetes diagnosis correlated both for risk associated to FMD and CIMT. CIMT was the only factor correlated with urinary transferrin values. Conclusion Urinary transferrin correlated to subclinical endothelial dysfunction measured by CIMT in type 2 diabetic patients without nephropathy and can be used to test for early nephropathy in patients without albuminuria.

Urine transferrin as an early endothelial dysfunction marker in type 2 diabetic patients without nephropathy: a case control study.

Background Albumin, along with other proteins, is abnormally eliminated via the urine during early stages of diabetic nephropathy. Moreover, endothelial dysfunction (ED) accompanying early diabetic nephropathy may develop even before microalbuminuria is detectable. Transferrin has a molecular weight comparable to albumin, and transferrinuria and microalbuminuria in a 24-hour urine sample may comparably reflect early diabetic nephropathy. However, transferrin physiochemical properties may be related with ED, but these have not been elucidated yet. This case-control study was aimed to evaluate relation between ED and urinary transferrin concentration before early diabetic nephropathy is present. Methods Patients were enrolled from two study sites in Mexico City: Ticoman General Hospital to evaluate control patients; and Dr. Manuel Gonzalez Rivera Specialized Clinic for the Management of the Diabetic Patient for case patients. All patients provided written informed consent. The primary endpoint was the correlation between urinary transferrin concentration and endothelial dysfunction measured in type 2 diabetic patients without albuminuria. ED was evaluated by ultrasonographic validated measurements, which included carotid intima-media thickness (CIMT) and flow mediated dilation (FMD). A power calculation, to detect a statistical difference, with a p value of 0.05, mandated a sample of 60 patients. The patients were tested for serum biomarkers such as glycated hemoglobin, creatinine, cholesterol, triglycerides, and urinary dipstick for albuminuria and urinary tract infection; using inclusion, exclusion and elimination criteria as described. Results The group with type 2 diabetes was older and showed higher serum transferrin and lower urinary transferrin values. Likewise, the group with type 2 diabetes showed subclinical atherogenic risk characterized by lower FMD and higher CIMT and ABI values. Risk factors associated to endothelial dysfunction measured by CIMT were time from diagnosis of diabetes, insulin resistance, dyslipidemia, and male sex. Hba1c and time since diabetes diagnosis correlated both for risk associated to FMD and CIMT. CIMT was the only factor correlated with urinary transferrin values. Conclusion Urinary transferrin correlated to subclinical endothelial dysfunction measured by CIMT in type 2 diabetic patients without nephropathy and can be used to test for early nephropathy in patients without albuminuria.