Plasma and urinary vascular endothelial growth factor and diabetic nephropathy in Type 2 diabetes mellitus

Serum VEGF as a predictive marker of glycemic control and diabetic nephropathy in Chinese older adults with type 2 diabetes mellitus

Objectives

Recent researches have demonstrated good correlation between vascular endothelial growth factor (VEGF) and diabetic nephropathy (DN); however, this relationship seems less clear-cut when VEGF was measured in blood samples. We tended to explore the possible association between serum VEGF and glycemic control and diabetic nephropathy severity in Chinese older adults with type 2 diabetes mellitus (T2DM).

Materials and methods

This study retrospectively enrolled 595 older T2DM adults at random. Participants were clinically grouped across the urine albumin-to-creatinine ratio (UACR) and the HbA1c tertiles by genders. Linear regressions were performed for the correlation of VEGF with HbA1c and UACR and binary logistic regressions for the odds of DN after adjusting for confounders. The receiver operating characteristic (ROC) curves were conducted for the predictive value of VEGF for DN.

Results

Both males and females with DN exhibited higher VEGF levels than non-DN (P < 0.001). Furthermore, a positive correlation of VEGF with UACR and HbA1c was presented regardless of adjusting confounding factors (P < 0.001). Serum VEGF level and fasting plasma glucose (FPG) were independent risk factors of DN in older adults of both genders (P < 0.05), while the risk prediction of DN by HbA1c only reflected in female patients (P < 0.05). The ROC curve of VEGF for DN had the area under curve (AUC) of 0.819 for males and 0.793 for females, indicating the clinical value of serum VEGF as a predictive biomarker.

Conclusions

Serum VEGF was strongly associated with UACR and HbA1c in both genders, and could be regarded as a predictive biomarker for glycemic control and diabetic nephropathy in older adults with T2DM.

Potential Role of N-Cadherin in Diagnosis and Prognosis of Diabetic Nephropathy

Diabetic nephropathy (DN) is a serious complication of diabetes affecting about half the people with diabetes and the leading cause of end stage renal disease (ESRD). Albuminuria and creatinine levels are currently the classic markers for the diagnosis of DN. However, many shortcomings are arising from the use of these markers mainly because they are not specific to DN and their levels are altered by multiple non-pathological factors. Therefore, the aim of this study is to identify better markers for the accurate and early diagnosis of DN. The study was performed on 159 subjects including 42 control subjects, 50 T2D without DN and 67 T2D subjects with DN. Our data show that circulating N-cadherin levels are significantly higher in the diabetic patients who are diagnosed with DN (842.6 ± 98.6 mg/l) compared to the diabetic patients who do not have DN (470.8 ± 111.5 mg/l) and the non-diabetic control group (412.6 ± 41.8 mg/l). We also report that this increase occurs early during the developmental stages of the disease since N-cadherin levels are significantly elevated in the microalbuminuric patients when compared to the healthy control group. In addition, we show a significant correlation between N-cadherin levels and renal markers including creatinine (in serum and urine), urea and eGFR in all the diabetic patients. In conclusion, our study presents N-cadherin as a novel marker for diabetic nephropathy that can be used as a valuable prognostic and diagnostic tool to slow down or even inhibit ESRD.

Vascular Endothelial Growth Factor (VEGF) and Neopterin Levels in Children with Steroid-sensitive and Steroid-resistant Nephrotic Syndrome

BACKGROUND

The most common glomerular disease in children is nephrotic syndrome. Steroid-resistant nephrotic syndrome tends to have a worse disease course, which bears a significant risk of chronic kidney disease in children.

OBJECTIVE

To compare VEGF and neopterin levels between children with steroid-sensitive nephrotic syndrome (SSNS), steroid-resistant nephrotic syndrome (SRNS), and also healthy (control) children.

METHODS

This cross-sectional study was conducted at H. Adam Malik General Hospital, Indonesia from January to December 2018. There were 160 children aged 1 to 8 years with confirmed nephrotic syndrome and without end-stage renal disease and systemic diseases, divided into SSNS, SRNS, and control groups. Data regarding age, gender, urine albumin creatinine ratio (UACR), serum albumin, total cholesterol, urea, creatinine, VEGF, and neopterin levels were collected. A p-value of less than 0.05 is considered statistically significant.

RESULTS

There were no differences between groups in gender (p = 0.269) and age (p = 0.375), but there was significant difference of UACR, albumin level, total cholesterol level, and VEGF level between groups, (all p< 0.001). There was a moderate positive correlation between VEGF level and UACR (r(158) = 0.439, p< 0.001) and a moderate negative correlation between neopterin level and albumin level (r(158)= -0.312, p = 0.005).

CONCLUSION

There were no differences in serum VEGF and neopterin levels between steroid-sensitive and steroid-resistant nephrotic syndrome groups. Serum VEGF level was positively correlated with UACR while serum neopterin level was negatively correlated with serum albumin level.

Panel of novel urine biomarkers for incident microalbuminuria in people with type 2 diabetes mellitus

AIM

The need to identify novel biomarkers for early diagnosis and treatment of diabetic nephropathy is widely recognized. However, only a few studies have investigated the association between biomarkers and the onset of albuminuria. In this study, we aimed to investigate a panel of biomarkers suitable for predicting microalbuminuria.

METHODS

Some 346 Japanese people with type 2 diabetes exhibiting normoalbuminuria were studied. The endpoint was defined as the onset of microalbuminuria. Thirty biomarkers were selected from among urinary biomarkers described in previous studies. A panel of biomarkers was selected using least absolute shrinkage and selection operator (LASSO). The prognostic performance of the developed panel was evaluated.

RESULTS

During a mean follow-up of 6.2 years, 45 people progressed to microalbuminuria. A composite panel of six biomarkers (monocyte chemoattractant protein-1, osteopontin, soluble human tumour necrosis factor receptor-1, tenascin C, vascular endothelial growth factor-A and kidney injury molecule-1) was developed using LASSO. Compared with the basal model comprising estimated GFR and urinary albumin-to-creatinine ratio, addition of these six biomarkers significantly increased the overall C index from 0.773 to 0.824 (P = 0.019). Net reclassification improvement and integrated discrimination improvement were estimated to be 0.412 (P = 0.049) and 0.040 (P = 0.040), respectively. Decision curve analysis also showed that the model with the six novel biomarkers had a better prognostic value for predicting the onset of microalbuminuria. The optimism was moderate or negligible according to measures.

CONCLUSIONS

The panel consisting of six novel urinary biomarkers effectively predicted incident microalbuminuria in people with type 2 diabetes.

Animal Models and Renal Biomarkers of Diabetic Nephropathy

Diabetes mellitus (DM) is the first cause of end stage chronic kidney disease (CKD). Animal models of the disease can shed light on the pathogenesis of the diabetic nephropathy (DN) and novel and earlier biomarkers of the condition may help to improve diagnosis and prognosis. This review summarizes the most important features of animal models used in the study of DN and updates the most recent progress in biomarker research.

Serum and urinary SOD3 in patients with type 2 diabetes: comparison with early chronic kidney disease patients and association with development of diabetic nephropathy

Extracellular superoxide dismutase 3 (SOD3), one member of the antioxidant defense system and a superoxide scavenger, has been noted to be downregulated in the kidneys of diabetic mice and is characterized by a heparin-binding domain that can anchor the protein to the endothelium and extracellular matrix. The association of the serum and urinary SOD3 levels with diabetic nephropathy in different stages has never been evaluated. It remains unclear how urinary SOD3 changes in different renal diseases. We recruited 98 Taiwanese patients with type 2 diabetes and 10 patients with early chronic kidney disease (CKD) into this study. Biochemical analyses were performed, including evaluation of the serum SOD3, urinary SOD3, urinary albumin, urinary vascular endothelial growth factor (VEGF), and urinary angiotensinogen (ANG). The Kruskal-Wallis rank sum test was used to compare various parameters among the three groups of patients: early CKD, diabetes alone, and diabetes with CKD. Results showed that lower serum and urinary SOD3 levels were observed in the group of patients with diabetes alone. Higher serum and urinary SOD3 levels were observed in the group of patients with diabetes and CKD, which had higher albuminuria and serum creatinine levels. The serum SOD3 levels were significantly positively correlated with renal function, according to the serum creatinine level. The urinary levels of SOD3 were significantly correlated with other urinary biomarkers such as urinary ANG and VEGF. Furthermore, albuminuria can positively predict the serum SOD3 level for the ratio of urinary albumin to urinary creatinine (ACR) >1,190.769 mg/g and the urinary SOD3 level for ACR ≥300 mg/g.

A Network Pharmacology Approach to Uncover the Mechanisms of Shen-Qi-Di-Huang Decoction against Diabetic Nephropathy

Shen-Qi-Di-Huang decoction (SQDHD), a well-known herbal formula from China, has been widely used in the treatment of diabetic nephropathy (DN). However, the pharmacological mechanisms of SQDHD have not been entirely elucidated. At first, we conducted a comprehensive literature search to identify the active constituents of SQDHD, determined their corresponding targets, and obtained known DN targets from several databases. A protein-protein interaction network was then built to explore the complex relations between SQDHD targets and those known to treat DN. Following the topological feature screening of each node in the network, 400 major targets of SQDHD were obtained. The pathway enrichment analysis results acquired from DAVID showed that the significant bioprocesses and pathways include oxidative stress, response to glucose, regulation of blood pressure, regulation of cell proliferation, cytokine-mediated signaling pathway, and the apoptotic signaling pathway. More interestingly, five key targets of SQDHD, named AKT1, AR, CTNNB1, EGFR, and ESR1, were significant in the regulation of the above bioprocesses and pathways. This study partially verified and predicted the pharmacological and molecular mechanisms of SQDHD on DN from a holistic perspective. This has laid the foundation for further experimental research and has expanded the rational application of SQDHD in clinical practice.

Advances in early biomarkers of diabetic nephropathy

Diabetic nephropathy is the main cause of chronic kidney disease, and represents the most common and serious complication of diabetes. The exact pathogenesis is complex and not elucidated. Several factors and mechanisms contribute to the development and outcome of diabetic nephropathy. An early diagnosis and intervention may slow down disease progression. A variety of biological markers associated with diabetic nephropathy were found in recent years, which was important for predicting the occurrence and development of the disease. Therefore, this article provides an overview of early biomarkers that are associated with diabetic nephropathy.

VEGF levels in plasma in relation to metabolic control, inflammation, and microvascular complications in type-2 diabetes: A cohort study

The vascular endothelial growth factor (VEGF) level in human circulation may reflect the severity of endothelial dysfunction in patients with diabetes mellitus, which leads to diabetic microvascular complications.We determined plasma VEGF levels as well as metabolic control and inflammatory factors in 26 healthy subjects and 52 type-2 diabetes mellitus (T2DM) patients with or without diabetic microvascular complications. Pearson correlation coefficient was used to evaluate the associations among those indices.The results showed that VEGF levels in plasma were positively correlated with fasting blood glucose level, glycosylated hemoglobin (HbA1c) level, type 1 helper T cell (Th1) percentage, and Th1/Th2 ratio, while they were negatively correlated with regulatory T cell percentage. Multiple linear regression analysis showed that HbA1c and Th1/Th2 ratio were the independent predictors of VEGF levels in T2DM patients.Thus, in T2DM patients with poor glycemic control as well as an elevated Th1/Th2 cell ratio, more VEGF might be released.

Therapy with atorvastatin versus rosuvastatin reduces urinary podocytes, podocyte-associated molecules, and proximal tubule dysfunction biomarkers in patients with type 2 diabetes mellitus: a pilot study

BACKGROUND

Diabetic nephropathy is a severe complication of Type 2 diabetes. Tubular lesions may play an important role in its early stages. The aim of our study was to determine if atorvastatin protects the podocytes and the proximal tubule in patients with Type 2 diabetes.

METHODS

A total of 63 patients with Type 2 diabetes completed this 6-months prospective pilot study. They were randomized to continue rosuvastatin therapy (control group) or to be administered an equipotent dose of atorvastatin (intervention group), and were assessed regarding urinary podocytes, podocyte-associated molecules, and biomarkers of proximal tubule dysfunction.

RESULTS

The patients from the intervention group presented a significant reduction in podocyturia (from 7.0 to 4.0 cells/ml, p < .05), urinary nephrin (from 1.7 to 1.3 mg/g, p < .001), urinary vascular endothelial growth factor (from 262.8 to 256.9, p < .01), urinary alpha1-microglobulin (from 10.0 to 8.3 mg/g, p < .01), urinary kidney injury molecule-1 (from 139.5 to 136.3 ng/g, p < .001), and urinary advanced glycation end-products (from 112.6 to 101.3 pg/ml, p < .001). Podocyturia correlated directly with the podocyte damage biomarkers, proximal tubule dysfunction biomarkers, albumin to creatinine ratio, and advanced glycation end-products, and inversely with the glomerular filtration rate.

CONCLUSIONS

In patients with Type 2 diabetes, atorvastatin exerts favorable effects on the kidney. There is a correlation between the evolution of the podocytes and of the proximal tubule biomarkers, supporting the hypothesis that the glomerular changes parallel proximal tubule dysfunction in the early stages of diabetic nephropathy.

Podocyturia parallels proximal tubule dysfunction in type 2 diabetes mellitus patients independently of albuminuria and renal function decline: A cross-sectional study

AIMS

Detection of podocytes in the urine of patients with type 2 diabetes may indicate severe injury to the podocytes. In the course of type 2 diabetes the proximal tubule is involved in urinary albumin processing. We studied the significance of podocyturia in relation with proximal tubule dysfunction in type 2 diabetes.

METHODS

A total of 86 patients with type 2 diabetes (34-normoalbuminuria; 30-microalbuminuria; 22-macroalbuminuria) and 28 healthy subjects were enrolled in the study and assessed concerning urinary podocytes, podocyte-associated molecules, and biomarkers of proximal tubule dysfunction. Urinary podocytes were examined in cell cultures by utilizing monoclonal antibodies against podocalyxin and synaptopodin.

RESULTS

Podocytes were detected in the urine of 10% of the healthy controls, 24% of the normoalbuminuric, 40% of the microalbuminuric, and 82% of the macroalbuminuric patients. In multivariate logistic regression analysis, urinary podocytes correlated with urinary albumin:creatinine ratio (p=0.006), urinary nephrin/creat (p=0.001), urinary vascular endothelial growth factor/creat (p=0.001), urinary kidney injury molecule-1/creat (p=0.003), cystatin C (p=0.001), urinary advanced glycation end-products (p=0.002), eGFR (p=0.001).

CONCLUSIONS

In patients with type 2 diabetes podocyturia parallels proximal tubule dysfunction independently of albuminuria and renal function decline. Advanced glycation end-products may impact the podocytes and the proximal tubule.

The role of novel biomarkers in predicting diabetic nephropathy: a review

Diabetic nephropathy (DN) is one of the microvascular complications of the kidney arising commonly from type 1 diabetes mellitus (T1DM), and occasionally from type 2 diabetes mellitus (T2DM). Microalbuminuria serves as an early indicator of DN risk and a predictor of its progression as well as cardiovascular disease risk in both T1DM and T2DM. Although microalbuminuria remains the gold standard for early detection of DN, it is not a sufficiently accurate predictor of DN risk due to some limitations. Thus, there is a paradigm shift to novel biomarkers which would help to predict DN risk early enough and possibly prevent the occurrence of end-stage kidney disease. These new biomarkers have been broadly classified into glomerular biomarkers, tubular biomarkers, biomarkers of inflammation, biomarkers of oxidative stress, and miscellaneous biomarkers which also include podocyte biomarkers, some of which are also considered as tubular and glomerular biomarkers. Although they are potentially useful for the evaluation of DN, current data still preclude the routine clinical use of majority of them. However, their validation using high-quality and large longitudinal studies is of paramount importance, as well as the subsequent development of a biomarker panel which can reliably predict and evaluate this renal microvascular disease. This paper aims to review the predictive role of these biomarkers in the evaluation of DN.

INCREASED SERUM LEVELS OF UREA AND CREATININE ARE SURROGATE MARKERS FOR DISRUPTION OF RETINAL PHOTORECEPTOR EXTERNAL LIMITING MEMBRANE AND INNER SEGMENT ELLIPSOID ZONE IN TYPE 2 DIABETES MELLITUS

PURPOSE

To evaluate the role of serum urea and creatinine as surrogate markers for disruption of retinal photoreceptor external limiting membrane (ELM) and inner segment ellipsoid zone (EZ) in Type 2 diabetic retinopathy (DR) using spectral-domain optical coherence tomography, for the first time.

METHODS

One hundred and seventeen consecutive cases of Type 2 diabetes mellitus (diabetes without retinopathy [No DR; n = 39], nonproliferative diabetic retinopathy [NPDR; n = 39], proliferative diabetic retinopathy [PDR; n = 39]) and 40 healthy control subjects were included. Serum levels of urea and creatinine were assessed using standard protocol. Spectral-domain optical coherence tomography was used to grade the disruption of ELM and EZ as follows: Grade 0, no disruption of ELM and EZ; Grade 1, ELM disrupted, EZ intact; Grade 2, ELM and EZ disrupted. Data were analyzed statistically.

RESULTS

Increase in serum levels of urea (F = 22.93) and creatinine (F = 15.82) and increased grades of disruption of ELM and EZ (γ = 116.3) were observed with increased severity of DR (P < 0.001). Increase in serum levels of urea (F = 10.45) and creatinine (F = 6.89) was observed with increased grades of disruption of ELM and EZ (P = 0.001).

CONCLUSION

Serum levels of urea and creatinine are surrogate markers for disruption of retinal photoreceptor ELM and EZ on spectral-domain optical coherence tomography in DR.

Oral subchronic exposure to silver nanoparticles causes renal damage through apoptotic impairment and necrotic cell death

Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials. Following oral exposure, AgNPs can accumulate in various organs including kidneys where they show gender specific accumulation. There is limited information on their effect on renal system following long-term animal exposure especially at the ultramicroscopic and molecular level. In this study, we have assessed the effect of 60 days oral AgNPs treatment on kidneys of female Wistar rats at doses of 50 ppm and 200 ppm that are below previously reported lowest observed adverse effect level (LOAEL). AgNPs treatment led to decrease in kidney weight and some loss of renal function as seen by increased levels of serum creatinine and early toxicity markers such as KIM-1, clusterin and osteopontin. We also observed significant mitochondrial damage, loss of brush border membranes, pronounced swelling of podocytes and degeneration of their foot processes using transmission electron microscopy (TEM). These symptoms are similar to those seen in nephrotic syndrome and 'Minimal change disease' of kidney where few changes are visible under light microscopy but significant ultrastructural damage is observed. Prolonged treatment of AgNPs also led to the activation of cell proliferative, survival and proinflammatory factors (Akt/mTOR, JNK/Stat and Erk/NF-κB pathways and IL1β, MIP2, IFN-γ, TNF-α and RANTES) and dysfunction of normal apoptotic pathway. Our study shows how long term AgNPs exposure may promote ultrastructural damage to kidney causing inflammation and expression of cell survival factors. These changes, in the long term, could lead to inhibition of the beneficial apoptotic pathway and promotion of necrotic cell death in kidneys.

Potential Role of Serum and Urinary Biomarkers in Diagnosis and Prognosis of Diabetic Nephropathy

PURPOSE OF REVIEW

Diabetic nephropathy (DN) is a progressive kidney disease caused by alterations in kidney architecture and function, and constitutes one of the leading causes of end-stage renal disease (ESRD). The purpose of this review is to summarize the state of the art of the DN-biomarker field with a focus on the new strategies that enhance the sensitivity of biomarkers to predict patients who will develop DN or are at risk of progressing to ESRD.

OBJECTIVE

In this review, we provide a description of the pathophysiology of DN and propose a panel of novel putative biomarkers associated with DN pathophysiology that have been increasingly investigated for diagnosis, to predict disease progression or to provide efficient personal treatment.

METHODS

We performed a review of the literature with PubMed and Google Scholar to collect baseline data about the pathophysiology of DN and biomarkers associated. We focused our research on new and emerging biomarkers of DN.

KEY FINDINGS

In this review, we summarized the critical signaling pathways and biological processes involved in DN and highlighted the pathogenic mediators of this disease. We next proposed a large review of the major advances that have been made in identifying new biomarkers which are more sensitive and reliable compared with currently used biomarkers. This includes information about emergent biomarkers such as functional noncoding RNAs, microRNAs, long noncoding RNAs, exosomes, and microparticles.

LIMITATIONS

Despite intensive strategies and constant investigation, no current single treatment has been able to reverse or at least mitigate the progression of DN, or reduce the morbidity and mortality associated with this disease. Major difficulties probably come from the renal disease being heterogeneous among the patients.

IMPLICATIONS

Expanding the proteomics screening, including oxidative stress and inflammatory markers, along with metabolomics approaches may further improve the prognostic value and help in identifying the patients with diabetes who are at high risk of developing kidney diseases.

Urinary podocyte-associated mRNA levels correlate with proximal tubule dysfunction in early diabetic nephropathy of type 2 diabetes mellitus

AIM

The study assessed mRNA expression of podocyte-associated molecules in urinary sediments of patients with type 2 diabetes mellitus (DM) in relation to urinary podocytes, biomarkers of podocyte injury and of proximal tubule (PT) dysfunction.

METHODS

A total of 76 patients with type 2 DM and 20 healthy subjects were enrolled in a cross-sectional study, and assessed concerning urinary podocytes, urinary mRNA of podocyte-associated genes, urinary biomarkers of podocyte damage and of PT dysfunction.

RESULTS

We found significant differences between urinary mRNA of podocyte-associated molecules in relation with albuminuria stage. In multivariable regression analysis, urinary mRNA of nephrin, podocin, alpha-actinin-4, CD2-associated protein, glomerular epithelial protein 1 (GLEPP1), ADAM 10, and NFκB correlated directly with urinary podocytes, albuminuria, urinary alpha₁-microglobulin, urinary kidney-injury molecule-1, nephrinuria, urinary vascular endothelial growth factor, urinary advanced glycation end-products (AGE), and indirectly with eGFR (p < 0.0001, R² = 0.808; p < 0.0001, R² = 0.825; p < 0.0001, R² = 0.805; p < 0.0001, R² = 0.663; p < 0.0001, R² = 0.726; p < 0.0001, R² = 0.720; p < 0.0001, R² = 0.724).

CONCLUSIONS

In patients with type 2 DM there is an association between urinary mRNA of podocyte-associated molecules, biomarkers of podocyte damage, and of PT dysfunction. GLEPP1, ADAM10, and NFκB may be considered additional candidate molecules indicative of early diabetic nephropathy. AGE could be involved in this association.

Longitudinal Changes in Measured Glomerular Filtration Rate, Renal Fibrosis and Biomarkers in a Rat Model of Type 2 Diabetic Nephropathy

BACKGROUND

Obese ZSF-1 rats display many features of human type II diabetes including nephropathy (DN). The study aimed to further understand the relevance of this model to DN, for which glomerular filtration rate (GFR), renal fibrosis and several urinary/tissue biomarkers was followed over 24 weeks in ZSF-1 rats.

METHODS

Intact/sham or uninephrectomized male and female ZSF-1 rats were studied. GFR was measured by transdermal clearance of fluorescein isothiocyanate-sinistrin. Urine was collected every 2-4 weeks for biomarker analysis. Renal tissue was examined histologically for fibrosis and for levels of inflammatory and fibrotic genes.

RESULTS

Male obese ZSF-1 rats demonstrated metabolic syndrome and proteinuria. Female counterparts were hyperlipidemic with delayed proteinuria, but were not hyperglycemic. Kidney hyperfiltration was observed in male obese rats in weeks 2-4 after surgery, and subsequently declined to levels significantly lower than controls. Tubulointerstitial/glomerular fibrosis in male obese rats was significantly elevated by week 12 post surgery and continued to expand in the ensuing weeks, particularly in uninephrectomized rats. Female rats had less severe fibrosis. Except for epidermal growth factor which decreased, the levels of several key inflammatory, injury and fibrotic factors were elevated in both tissue (mRNA) and urine (protein) of male obese rats.

CONCLUSION

Male obese ZSF-1 rats represent an important DN model, manifesting key pathophysiological features including metabolic syndrome, proteinuria, progressive tubular and glomerular fibrosis, and transient hyperfiltration followed by progressive decline in renal function. Uninephrectomy significantly accelerated disease progression. Females were less severe in disease manifestation. Several urinary and tissue biomarkers were identified in the male obese rats that tracked with disease progression.

The Promise of Mesenchymal Stem Cell Therapy for Diabetic Kidney Disease

Diabetes mellitus (DM) commonly leads to progressive chronic kidney disease despite current best medical practice. The pathogenesis of diabetic kidney disease (DKD) involves a complex network of primary and secondary mechanisms with both intra-renal and systemic components. Apart from inhibition of the renin angiotensin aldosterone system, targeting individual pathogenic mediators with drug therapy has not, thus far, been proven to have high clinical value. Stem or progenitor cell therapies offer an alternative strategy for modulating complex disease processes through suppressing multiple pathogenic pathways and promoting pro-regenerative mechanisms. Mesenchymal stem cells (MSCs) have shown particular promise based on their accessibility from adult tissues and their diverse mechanisms of action including secretion of paracrine anti-inflammatory and cyto-protective factors. In this review, the progress toward clinical translation of MSC therapy for DKD is critically evaluated. Results from animal models suggest distinct potential for systemic MSC infusion to favourably modulate DKD progression. However, only a few early phase clinical trials have been initiated and efficacy in humans remains to be proven. Key knowledge gaps and research opportunities exist in this field. These include the need to gain greater understanding of in vivo mechanism of action, to identify quantifiable biomarkers of response to therapy and to define the optimal source, dose and timing of MSC administration. Given the rising prevalence of DM and DKD worldwide, continued progress toward harnessing the inherent regenerative functions of MSCs and other progenitor cells for even a subset of those affected has potential for profound societal benefits.

Urinary Biomarkers in the Assessment of Early Diabetic Nephropathy

Diabetic nephropathy (DN) is a frequent and severe complication of diabetes mellitus (DM). Its diagnosis in incipient stages may allow prompt interventions and an improved prognosis. Towards this aim, biomarkers for detecting early DN can be used. Microalbuminuria has been proven a remarkably useful biomarker, being used for diagnosis of DN, for assessing its associated condition-mainly cardiovascular ones-and for monitoring its progression. New researches are pointing that some of these biomarkers (i.e., glomerular, tubular, inflammation markers, and biomarkers of oxidative stress) precede albuminuria in some patients. However, their usefulness is widely debated in the literature and has not yet led to the validation of a new "gold standard" biomarker for the early diagnosis of DN. Currently, microalbuminuria is an important biomarker for both glomerular and tubular injury. Other glomerular biomarkers (transferrin and ceruloplasmin) are under evaluation. Tubular biomarkers in DN seem to be of a paramount importance in the early diagnosis of DN since tubular lesions occur early. Additionally, biomarkers of inflammation, oxidative stress, podocyte biomarkers, and vascular biomarkers have been employed for assessing early DN. The purpose of this review is to provide an overview of the current biomarkers used for the diagnosis of early DN.

Serum albumin is associated with peripheral nerve function in patients with type 2 diabetes

The aim of this study is to investigate the association between serum albumin concentrations and nerve conduction (NC) parameters in Chinese patients with type 2 diabetes (T2DM). A total of 409 T2DM patients were enrolled between October 2010 and April 2014. All participants underwent nerve conduction studies. The composite Z scores for NC parameters including conduction velocity (CV), amplitude, and latency were calculated as well. Serum albumin was measured by Bromcresol Green dye-binding method. The composite Z scores of CV and amplitude increased with the increasing albumin tertiles (test for trend, both P < 0.001), while the composite Z score of latency decreased with increasing albumin tertiles (test for trend, P < 0.001). After adjusting for age, sex, duration, and HbA1c, higher serum albumin concentrations were associated with higher composite Z scores of CV (β = 0.314, P < 0.001), amplitude (β = 0.279, P < 0.001), and lower composite Z score of latency (β = -0.279, P < 0.001). When participants were stratified into albuminuria and normoalbuminuria group, we found the associations of serum albumin with composite Z scores of NC parameters remained significant only in the albuminuria group (CV Z score: β = 0.253, P = 0.002; amplitude Z score: β = 0.233, P = 0.006; latency Z score: β = -0.217 P = 0.013) after further adjustment for urinary albumin to creatinine ratio. The optimal cutoff point of serum albumin to indicate abnormal peripheral nerve function was 36.75 g/L in T2DM patients with albuminuria, with a sensitivity of 65.6 % and a specificity of 78.0 %. Serum albumin was independently associated with peripheral nerve function in T2DM patients, especially in those with albuminuria. Serum albumin could be a potential biomarker for diabetic peripheral neuropathy.

Urinary angiopoietin-2 is associated with albuminuria in patients with type 2 diabetes mellitus

Aims. To evaluate the levels of angiopoietin-1 (Ang-1), Ang-2, and vascular endothelial growth factor (VEGF) in serum and urine, and their association with albuminuria in patients with type 2 diabetes mellitus. Methods. In 113 type 2 diabetic patients with normoalbuminuria, microalbuminuria, and macroalbuminuria and 30 healthy controls, the levels of Ang-1, Ang-2, and VEGF in serum and urine were measured by enzyme-linked immunosorbent assay (ELISA). Results. Urinary and serum levels of Ang-2 were significantly higher in diabetic patients with normoalbuminuria than in healthy controls. Increased urinary Ang-2 level was positively associated with the degree of albuminuria. Urinary Ang-1 levels were significantly higher in normoalbuminuria patients and lower in macroalbuminuria patients than in controls. The levels of urinary VEGF increased in the albuminuria subgroup, though serum levels of Ang-1 and VEGF did not change. Urinary Ang-2 levels were correlated positively with albuminuria and negatively with glomerular filtration rate (GFR). Stepwise multiple regression analysis identified albuminuria (P < 0.001) and GFR (P = 0.001) as significant predictors of urinary Ang-2. Conclusions. Our data suggest that urinary Ang-2 is stepwise increased with renal damage in patients with type 2 diabetes mellitus and is associated with albuminuria.

Proximal tubule dysfunction is associated with podocyte damage biomarkers nephrin and vascular endothelial growth factor in type 2 diabetes mellitus patients: a cross-sectional study

BACKGROUND

There is an ongoing debate as to whether early diabetic nephropathy in Type 2 diabetes mellitus may be attributed to the glomerulus or to the proximal tubule. Urinary excretion of nephrin and vascular endothelial growth factor may increase even in the normoalbuminuria stage. In the course of diabetic nephropathy, the proximal tubule may be involved in the uptake of urinary nephrin and vascular endothelial growth factor.

MATERIALS AND METHODS

Two groups of consecutive Type 2 diabetes mellitus outpatients (38 normo-, 32 microalbuminuric) and 21 healthy subjects were enrolled in a cross-sectional study and evaluated concerning the relation of proximal tubule dysfunction with the podocyte biomarkers excretion, assessed by ELISA methods. The impact of advanced glycation end-products on this relation was also queried.

RESULTS

Urinary alpha1-microglobulin and kidney injury molecule-1 correlated with urinary albumin:creatinine ratio (R2 = 0.269; p < 0.001; R2 = 0.125; p < 0.001), nephrinuria (R2 = 0.529; p<0.001; R2 = 0.203; p < 0.001), urinary vascular endothelial growth factor (R2 = 0.709; p < 0.001; R2 = 0.360; p < 0.001), urinary advanced glycation end-products (R2 = 0.578; p < 0.001; R2 = 0.405; p < 0.001), serum cystatin C (R2 = 0.130; p < 0.001; R2 = 0.128; p<0.001), and glomerular filtration rate (R2 = 0.167; p < 0.001; R2 = 0.166; p < 0.001); nephrinuria and urinary vascular endothelial growth factor correlated with urinary albumin:creatinine ratio (R2 = 0.498; p < 0.001; R2 = 0.227; p<0.001), urinary advanced glycation end-products (R2 = 0.251; p < 0.001; R2 = 0.308; p < 0.001), serum cystatin C (R2 = 0.157; p < 0.001; R2 = 0.226; p < 0.001), and glomerular filtration rate (R2 = 0.087; p = 0.007; R2 = 0.218; p < 0.001).

CONCLUSIONS

In Type 2 diabetes mellitus there is an association of proximal tubule dysfunction with podocyte damage biomarkers, even in the normoalbuminuria stage. This observation suggests a potential role of the proximal tubule in urinary nephrin and urinary vascular endothelial growth factor processing in early diabetic nephropathy, a fact which could be related to advanced glycation end-products intervention. Podocyte damage and proximal tubule dysfunction biomarkers could be validated as a practical approach to the diagnosis of early diabetic nephropathy by further studies on larger cohorts.

Meta-analysis of diabetic nephropathy associated genetic variants in inflammation and angiogenesis involved in different biochemical pathways

Background

Diabetes mellitus is the most common chronic endocrine disorder, affecting an estimated population of 382 million people worldwide. It is associated with microvascular and macrovascular complications, including diabetic nephropathy (DN); primary cause of end-stage renal disease. Different inflammatory and angiogenic molecules in various pathways are important modulators in the pathogenesis and progression of diabetic nephropathy. Differential disease risk in DN may be partly attributable to genetic susceptibility. In this meta-analysis, we aimed to determine which of the previously investigated genetic variants in these pathways are significantly associated with the development of DN and to examine the functional role of these genes.

Methods

A systematic search was conducted to collect and analyze all studies published till June 2013; that investigated the association between genetic variants involved in inflammatory cytokines and angiogenesis and diabetic nephropathy. Genetic variants associated with DN were selected and analyzed by using Comprehensive Meta Analysis software. Pathway analysis of the genes with variants showing significant positive association with DN was performed using Genomatix Genome Analyzer (Genomatix, Munich, Germany).

Results

After the inclusion and exclusion criteria for this analysis, 34 studies were included in this meta-analysis. 11 genetic variants showed significant positive association with DN in a random-effects meta-analysis. These included genetic variants within or near VEGFA, CCR5, CCL2, IL-1, MMP9, EPO, IL-8, ADIPOQ and IL-10. rs1800871 (T) genetic variant in IL-10 showed protective effect for DN. Most of these eleven genetic variants were involved in GPCR signaling and receptor binding pathways whereas four were involved in chronic kidney failure. rs833061 [OR 2.08 (95% CI 1.63-2.66)] in the VEGFA gene and rs3917887 [OR 2.04 (95% CI 1.64-2.54)] in the CCL2 gene showed the most significant association with the risk of diabetic nephropathy.

Conclusions

Our results indicate that 11 genetic variants within or near VEGFA, CCR5, CCL2, IL-1, MMP9, EPO, IL-8, ADIPOQ and IL-10 showed significant positive association with diabetic nephropathy. Gene Ontology or pathway analysis showed that these genes may contribute to the pathophysiology of DN. The functional relevance of the variants and their pathways can lead to increased biological insights and development of new therapeutic targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-014-0103-8) contains supplementary material, which is available to authorized users.

VEGF and podocytes in diabetic nephropathy

Vascular endothelial growth factor-A (VEGF-A) is a protein secreted by podocytes that is necessary for survival of endothelial cells, podocytes, and mesangial cells. VEGF-A regulates slit-diaphragm signaling and podocyte shape via VEGF-receptor 2-nephrin-nck-actin interactions. Chronic hyperglycemia-induced excess podocyte VEGF-A and low endothelial nitric oxide drive the development and the progression of diabetic nephropathy. The abnormal cross-talk between VEGF-A and nitric oxide pathways is fueled by the diabetic milieu, resulting in increased oxidative stress. Recent findings on these pathogenic molecular mechanisms provide new potential targets for therapy for diabetic renal disease.

Endothelial cell-selective adhesion molecule in diabetic nephropathy

BACKGROUND

Endothelial cell-selective adhesion molecule (ESAM) contributes to the integrity of tight junctions and modulates endothelial function. ESAM has been linked to experimental diabetic nephropathy; its soluble fraction is related to atherosclerosis in humans. In this cross-sectional observational study, we describe for the first time serum ESAM in type 2 diabetic patients with different stages of chronic kidney disease (CKD) and its relationship to vascular endothelial growth factor-A (VEGF-A). Materials and methods  We included diabetic patients with different stages of CKD and controls. History, laboratory evaluation, serum ESAM and VEGF-A and urinary albumin/creatinine ratio were obtained.

RESULTS

Endothelial cell-selective adhesion molecule was higher in non-CKD diabetic patients 13.80 (6.15-18.70) ng/mL (n=45) than controls 7.30 (4.60-9.40) ng/mL (n=48), P=0.001. VEGF-A had a similar pattern: 71.3 (54.75-120.70) vs. 43.20 (30.1-65.90) pg/mL, P<0.0001. ESAM was 10.4 (5.6-17.4) ng/mL in predialysis CKD patients (n=59) and 22.35 (8.55-29.95) ng/mL in dialysis patients (n=36), P<0.001. Patients with glomerular filtration rate (GFR)<15 mL/min had the highest ESAM (P=0.003). ESAM was similar in normoalbuminuric, microalbuminuric and proteinuric patients. ESAM was directly correlated with the duration of diabetes (r(2)=0.048, P=0.009), C-reactive protein (r(2)=0.028, P=0.05), VEGF-A (r(2)=0.040, P=0.01) and inversely with HbA1C (r(2)=0.036, P=0.03), haemoglobin (r(2)=0.062, P=0.005) and albumin (r(2)=0.0·40, P=0.026). In multiple regression diabetes duration, HbA1C and VEGF-A were significant predictors of ESAM. In controls, ESAM was inversely related to VEGF (r(2)=037, P=0.01).

CONCLUSION

Endothelial cell-selective adhesion molecule and VEGF-A are higher in patients with diabetes than in controls. The highest ESAM is found in dialysis patients. ESAM correlates with diabetes duration and control, inflammation and VEGF-A in patients with diabetes, but not in controls.

Soluble serum Klotho in diabetic nephropathy: relationship to VEGF-A

OBJECTIVES

Both kidney expression and soluble serum Klotho are influenced by chronic kidney disease (CKD) and diabetes. Serum Klotho is a yet poorly explored biomarker. We describe, for the first time to our knowledge, serum Klotho in diabetic patients with CKD and its relationship to vascular endothelial growth factor A (VEGF-A).

DESIGN AND METHODS

We included 43 controls and 146 diabetic patients with different stages of CKD. Laboratory evaluation, urinary albumin/creatinine ratio (UACR), Klotho (ELISA), VEGF-A (ELISA) were performed.

RESULTS

Klotho was 0.40(0.10-1.30)ng/mL in diabetic patients without CKD and 0.80(0.30-1.30)ng/mL in controls, p=0.20; VEGF-A was higher in diabetic patients 73.85(57.32-119.00)pg/mL than in controls 43.20(30.1-65.9)pg/mL, p<0.0001. Klotho increased with CKD stage: 0.2(0.10-0.40)ng/mL in CKD 1/2, 0.60(0.20-1.1)ng/mL in CKD 3/4 and 1.45(0.425-2.90)ng/mL in dialysis patients, p<0.0001; it also increased with decreasing glomerular filtration rate (GFR). Klotho was lower in albuminuric (UACR>30 mg/g) patients 0.20(0.10-0.70)ng/mL than in normoalbuminuric (UACR<30 mg/g) ones 0.50(0.20-1.30)ng/mL, p=0.03; lowest Klotho was found in microalbuminuric (UACR 30-300 mg/g) patients, p=0.07. VEGF was lower in microalbuminuric patients but was not influenced by GFR. In diabetic patients but not in controls, Klotho correlated to VEGF-A (r=0.29, p=0.0003); in multiple regression VEGF-A was the only significant predictor of Klotho: b=0.27, 95%CI (0.01-0.04), p=0.001.

CONCLUSIONS

In diabetic patients, Klotho is decreased in early CKD and increases thereafter, paralleling reduced GFR. VEGF-A is higher in diabetic patients than in controls. Both Klotho and VEGF-A are decreased in the presence of microalbuminuria. In diabetes, Klotho strongly correlates to VEGF-A.

The effects of anti-inflammatory and anti-angiogenic DNA vaccination on diabetic nephropathy in rats

Inflammation and angiogenesis play a crucial role in the pathomechanism of diabetic nephropathy. Monocyte chemoattractant protein 1 (MCP) is a key regulator of the immune system in kidneys, and its inhibition with a dominant-negative mutant lacking the N-terminal amino acids 2-8 (7ND) reduces renal fibrosis. Angiomotin (Amot) is a novel angiogenesis modulator. We studied the effects of inhibition of Amot and MCP using DNA vaccination on incipient diabetic nephropathy in rats. Plasmid DNA (with either 7ND or human Amot) was electroporated twice into hind-limb muscles of rats with streptozotocin-induced diabetes mellitus. Sham-electroporated diabetic rats and healthy animals served as controls. After 4 months, renal histology and biochemical analyses were performed. In sham-electroporated diabetic rats, glomerular histology revealed pathological changes. 7ND and Amot treatments reduced glomerular hypertrophy and periodic acid-Schiff positivity. In both treated groups, the expression of profibrotic (transforming growth factor-β, collagen 1), proinflammatory (interleukin-6, tumor necrosis factor-α), and proangiogenic (vascular endothelial growth factor) genes in the renal cortex was lower than in the diabetic group without treatment. The mentioned renoprotective effects could be mediated via higher total antioxidant capacity and improved glycemic control. Anti-angiogenic and anti-inflammatory DNA vaccination ameliorates the progression of glomerular pathology in an animal model of diabetic nephropathy.

Circulating vascular endothelial growth factor in the normo- and/or microalbuminuric patients with type 2 diabetes mellitus

Relationship between serum vascular endothelial growth factor (VEGF) level and parameters of endothelial injury and/or dysfunction in patients with diabetes mellitus type 2 with or without microalbuminuria was investigated. Eighty-four diabetic patients were divided in two subgroups (42 each): normoalbuminuric (NAU) and microalbuminuric (MAU). Forty-two blood donors were in control group. Serum VEGF and plasma von Willebrand factor, soluble thrombomodulin, plasminogen activator inhibitor 1, thrombin-activatable fibrinolysis inhibitor (TAFI) and tissue plasminogen activator (t-PA) were measured using enzyme-linked immunosorbent assay in all subjects. VEGF was significantly higher in NAU compared to controls. The difference between MAU and controls was not statistically significant, but there was a trend toward significance. Only TAFI correlated with VEGF in MAU. An observed significant increase of serum VEGF level already in NAU suggests that serum VEGF could be a sensitive predictor of endothelial dysfunction in type 2 diabetes.

Urinary biomarkers involved in type 2 diabetes: a review

Diabetes mellitus is one of the most challenging health concerns of the 21st century. With at least 30% of the diabetic population remaining undiagnosed, effective and early diagnosis is of critical concern. Development of a diagnostic test, more convenient and reliable than those currently used, would therefore be highly beneficial. Urine as a diagnostic medium allows for non-invasive detection of biomarkers, including some associated with type 2 diabetes and its complications. This review provides a synopsis of those urinary biomarkers that potentially may provide a basis for the development of improved diagnostic tests. Three main pathways for the sourcing of potential makers are identified: kidney damage, oxidative stress and low-grade inflammation including atherosclerosis/vascular damage. This review briefly presents each pathway and some of the most relevant urinary biomarkers that may be used to monitor the development or progression of diabetes and its complications. In particular, biomarkers of renal dysfunction such as transferrin, type IV collagen and N-acetyl-beta-D-glucosaminidase might prove to be more sensitive than urinary albumin, the current gold standard, in the detection of incipient nephropathy and risk assessment of cardiovascular disease. Inflammatory markers including orosomucoid, tumour necrosis factor-alpha, transforming growth factor-beta, vascular endothelial growth factor and monocyte chemoattractant protein-1, as well as oxidative stress markers such as 8-hydroxy-2'deoxyguanosine may also be useful biomarkers for diagnosis or monitoring of diabetic complications, particularly kidney disease. However, the sensitivity of these markers compared with albumin requires further investigation.

Serum VEGF increases in diabetic polyneuropathy, particularly in the neurologically active symptomatic stage

AIM

To identify the relationship between vascular endothelial growth factor (VEGF) and diabetic polyneuropathy (DPN).

METHODS

Two hundred and twenty diabetic patients participated, 113 with DPN and 107 without DPN. All patients were also classified according to the four stages of DPN (no neuropathy: stage 0; asymptomatic neuropathy: stage 1; symptomatic neuropathy: stage 2; disabling neuropathy: stage 3). Serum VEGF concentration was measured using an enzyme-linked immunosorbent assay (ELISA) and levels between the patients with and without DPN and also between the different stages of DPN, were compared.

RESULTS

The mean serum VEGF level in all patients was 264.6 +/- 218.8 pg/ml. The mean serum VEGF level was higher in patients with DPN (310.1 +/- 224.3 pg/ml) than in the patients without DPN (216.5 +/- 204.0 pg/ml, P = 0.0014). Serum VEGF was higher in the 'symptomatic' stage (stage 2, 364.8 +/- 225.9 pg/ml) in comparison with the 'asymptomatic' (stage 1, 256.7 +/- 224.4 pg/ml, P = 0.015) and 'disabling' (stage 3, 180.3 +/- 109.4 pg/ml, P = 0.042) stages. The mean serum VEGF level in patients with diabetic retinopathy (261.1 +/- 210.6 pg/ml) and in patients with diabetic nephropathy (241.5 +/- 185.7 pg/ml) was not increased.

CONCLUSIONS

The serum VEGF level is increased in patients with DPN, particularly in patients in the neurologically active 'symptomatic' stage.

The protective effect of the RAS inhibitor on diabetic patients with nephropathy in the context of VEGF suppression

AIM

The aim of the present study was to explore whether renin angiotensin system (RAS) inhibitor can reduce the production of vascular endothelium growth factor (VEGF). Further, we sought to elucidate the correlation between VEGF level and certain clinical parameters, such as albumin excretion rate (AER), before and after treatment with angiotensin type 1 receptor blocker.

METHODS

We recruited 166 type 2 diabetic patients at various stages of diabetic nephropathy (DN) and 46 healthy control subjects for a cross-sectional study. We recruited another 42 hypertensive type 2 diabetic patients with microalbuminuria for a longitudinal study involving a 6-month irbesartan treatment protocol. Urinary VEGF (uVEGF) levels were determined using ELISA.

RESULTS

In the cross-sectional study, hypertensive type 2 diabetic patients who received RAS inhibitor presented lower uVEGF levels than those who did not receive the RAS inhibitor. Statistical analysis indicated that uVEGF level was independently correlated with the AER. In the longitudinal study involving the 6-month irbesartan treatment, we demonstrated that uVEGF levels decreased significantly in patients who achieved a 50% AER reduction (remission group, n=32). In contrast, uVEGF levels remained unchanged in patients who did not exhibit a 50% AER reduction (nonremission group, n=10). Furthermore, the change in uVEGF was significantly correlated with the change in AER (r=0.65, P<0.01) before and after 6 months of irbesartan treatment. This result held true even after we had adjusted for the decrease in average blood pressure.

CONCLUSION

The protective effect of the RAS inhibitor in DN patients is associated with the suppression of VEGF. Accordingly, it may be possible to use uVEGF as a marker of DN progression. We suggest that uVEGF may be an important target for therapeutic intervention in the context of DN.

Increased plasma urotensin-II levels are associated with diabetic retinopathy and carotid atherosclerosis in Type 2 diabetes

Human U-II (urotensin-II), the most potent vasoconstrictor peptide identified to date, is associated with cardiovascular disease. A single nucleotide polymorphism (S89N) in the gene encoding U-II (UTS2) is associated with the onset of Type 2 diabetes and insulin resistance in the Japanese population. In the present study, we have demonstrated a relationship between plasma U-II levels and the progression of diabetic retinopathy and vascular complications in patients with Type 2 diabetes. Eye fundus, IMT (intima-media thickness) and plaque score in the carotid artery, BP (blood pressure), FPG (fasting plasma glucose), HbA(1c) (glycated haemoglobin), U-II, angiogenesis-stimulating factors, such as VEGF (vascular endothelial growth factor) and heregulin-beta(1), and lipid profiles were determined in 64 patients with Type 2 diabetes and 24 non-diabetic controls. FPG, HbA(1c) and VEGF levels were significantly higher in patients with Type 2 diabetes than in non-diabetic controls. Diabetes duration, insufficient glycaemic and BP control, plasma U-II levels, IMT, plaque score and nephropathy grade increased significantly across the subjects as follows: non-diabetic controls, patients with Type 2 diabetes without retinopathy (group N), patients with Type 2 diabetes with simple (background) retinopathy (group A) and patients with Type 2 diabetes with pre-proliferative and proliferative retinopathy (group B). The prevalence of obesity and smoking, age, low-density lipoprotein, triacylglycerols (triglycerides) and heregulin-beta(1) were not significantly different among the four groups. In all subjects, U-II levels were significantly positively correlated with IMT, FPG, and systolic and diastolic BP. Multiple logistic regression analysis revealed that, of the above parameters, U-II levels alone had a significantly independent association with diabetic retinopathy. In conclusion, the results of the present study provide the first evidence that increased plasma U-II levels may be associated with the progression of diabetic retinopathy and carotid atherosclerosis in patients with Type 2 diabetes.

Vascular endothelial growth factor and diabetic nephropathy

The field of vascular endothelial growth factor (VEGF) has recently witnessed a surge of research into its role in diabetic kidney disease. Based on its credentials as a potent inducer of vasopermeability and angiogenesis, podocyte-derived VEGF is believed to participate in the glomerular capillary hyperpermeability of macromolecules that potentially underlies the pathogenesis of diabetic albuminuria. The evidence for VEGF's role is relatively straightforward in animal models of diabetes, establishing that VEGF is upregulated in the diabetic kidney, that VEGF alone reproduces some aspects of diabetic glomerulopathy, and that antagonism of VEGF attenuates diabetic albuminuria and other associated features of the podocytopathy. However, the promise shown in the animal studies has not carried over as convincingly into the realm of human studies, as some investigators find a negative or no relationship between VEGF and diabetic nephropathy, whereas others find a positive correlation between the two. If VEGF does play a role in diabetic renal disease, its observed effects and known mechanisms seem to point squarely at the podocyte as a central target of the maladaptive VEGF overactivity.

Fibrosis in diabetes complications: pathogenic mechanisms and circulating and urinary markers

Diabetes mellitus is characterized by a lack of insulin causing elevated blood glucose, often with associated insulin resistance. Over time, especially in genetically susceptible individuals, such chronic hyperglycemia can cause tissue injury. One pathological response to tissue injury is the development of fibrosis, which involves predominant extracellular matrix (ECM) accumulation. The main factors that regulate ECM in diabetes are thought to be pro-sclerotic cytokines and protease/anti-protease systems. This review will examine the key markers and regulators of tissue fibrosis in diabetes and whether their levels in biological fluids may have clinical utility.

Endothelial dysfunction and oxidative stress in type 1 and type 2 diabetic patients without clinical macrovascular complications

AIMS

To evaluate the relationship between oxidative stress and endothelial dysfunction (ED) in diabetic patients without clinical macrovascular complications.

METHODS

In 27 type 1, 56 type 2 diabetic patients and 35 healthy controls the redox state (GSH, GSSG; enzymatic method), endothelin-1 (ET-1; ELISA) and von Willebrand factor (vWF; ELISA) plasma levels, urinary vascular endothelial growth factor (VEGF; ELISA) were measured.

RESULTS

Decreased GSH levels (p<0.05, type 1 and type 2), GSH/GSSG ratio (p<0.05 type 1, p<0.001 type 2) and elevated vWF levels (p<0.001, type 1 and type 2) were observed in diabetic patients in comparison with controls. A negative correlation between GSH and vWF (p<0.02 and p<0.001, in type 1 and type 2, respectively) and GSH and BMI (p<0.02 in type 1 and type 2) was observed. ET-1 was positively correlated to age (p<0.05) and diabetes duration (p<0.03) in type 1, while vWF was correlated to systolic blood pressure (p<0.05) in type 2 diabetic patients. Urinary VEGF was higher in type 2 (p<0.05) in comparison with type 1 diabetic patients and was correlated to glycemia (p<0.05) and systolic blood pressure (p<0.05).

CONCLUSIONS

These data might indicate that markers of oxidative stress and ED are altered in diabetic patients without clinical macrovascular complications.

The relationship between vascular endothelial growth factor (VEGF) and microalbuminuria in patients with essential hypertension

OBJECTIVE

The existence of microalbuminuria (MAU) in patients with essential hypertension is a strong indicator of microvascular damage. Although endothelial dysfunction and increased vascular permeability both have a role in the development of MAU, its ethiopathogenesis in hypertensive patients is not yet clearly understood. Vascular endothelial growth factor (VEGF) is the most important regulator of pathological or physiological angiogenesis and it additionally leads to increased vascular permeability. This study aims to assess the relationship of serum VEGF levels to MAU in non-complicated, newly-diagnosed essential hypertensive patients (EHs).

METHODS

This study included 30 newly-diagnosed EHs with MAU, 46 newly-diagnosed EHs without MAU and 46 healthy controls. None of the EHs had diabetes, renal impairment or atherosclerotic diseases. Serum VEGF levels were measured using the ELISA method.

RESULTS

Serum levels of VEGF were significantly higher in EHs with MAU when compared with patients without MAU (225.15+/-109.34 pg/mL versus 166.78+/-114.35 pg/mL, p: 0.04) or controls (225.15+/-109.34 pg/mL versus 144.91+/-96.60 pg/mL, p: 0.007). On the other hand, no significant difference was observed between the non-MAU and control groups. In the univariate analysis, serum levels of VEGF, were positively correlated with systolic blood pressure (R: 0.253 p: 0.001), diastolic blood pressure (R: 0.162 p: 0.04), mean arterial pressure (R: 0.239 p: 0.002), creatinine clearance (R: 0.172 p: 0.04) and MAU (R: 0.338 p: 0.002). In the multiple linear regression analysis, VEGF levels were independently related to MAU (beta: 0.248, p: 0.02).

CONCLUSION

VEGF levels are higher in EHs in the presence of MAU. These high values may be important in the early diagnosis of vascular damage in EHs. Additionally, VEGF may increase glomerular permeability and lead to MAU in EHs.

Effect of insulin on plasma vascular endothelial growth factor in children with new-onset diabetes

CONTEXT

Considerable experimental evidence inculpates vascular endothelial growth factor (VEGF) as one of the candidate factors providing a mechanistic link between hyperglycemia and diabetic complications.

AIM

The aim of the study was to assess the effect of insulin treatment and glycemic control on plasma VEGF levels in children with new-onset diabetes.

METHODS

This prospective study assessed the changes in plasma VEGF levels after treatment of diabetes with insulin. We also aimed to ascertain whether there was any correlation between plasma VEGF levels and simultaneous random plasma glucose. The study comprised 19 children with new-onset diabetes mellitus between the ages of 3 and 18 yr. The control group comprised 55 healthy nondiabetic children with idiopathic short stature.

RESULTS

Plasma VEGF concentrations were significantly elevated in children at diagnosis of diabetes, compared with healthy controls (P < 0.0002). Plasma VEGF levels (P < 0.01) and hemoglobin A(1C) (P < 0.0001) declined in diabetic children after insulin treatment. There was a highly significant correlation between reduction in plasma VEGF levels and hemoglobin A1C levels (r = 0.65, P = 0.0037). We did not find any correlation between the simultaneous plasma glucose values and basal VEGF.

CONCLUSIONS

Presence of hyperglycemia and/ or insulin deficiency in children with new-onset of diabetes is associated with plasma VEGF elevation, even at the outset of disease, and this can be mitigated by insulin therapy.