Novel urinary protein biomarkers predicting the development of microalbuminuria and renal function decline in type 1 diabetes

Determinants of serious health outcome-free status in middle-aged and older people with dysglycaemia: Exploratory analysis of the ORIGIN trial

AIM

To assess clinical and biochemical measurements that can identify people with dysglycaemia (i.e. diabetes or pre-diabetes) who remain free of serious outcomes during follow-up.

MATERIALS AND METHODS

We conducted exploratory analyses using data from the Outcomes Reduction with an Initial Glargine Intervention (ORIGIN) study to identify independent determinants of outcome-free status in 12 537 middle-aged and older adults with prediabetes and early type 2 diabetes from 40 countries. Serious outcome-free status was defined as the absence of major cardiovascular outcomes, kidney or retinal outcomes, peripheral artery disease, dementia, cancer, any hospitalization, or death during follow-up.

RESULTS

In total, 3328 (26.6%) participants remained free of serious outcomes during a median follow-up of 6.2 years (IQR 5.8, 6.7). Independent clinical determinants of outcome-free status included younger age, female sex, non-White ethnicity, shorter diabetes duration, absence of previous cardiovascular disease, current or former smokers, higher grip strength, Mini-Mental State Examination score, and ankle-brachial index, lower body mass index and kidney disease index, and non-use of renin-angiotensin system drugs and beta-blockers. In a subset of 8401 people with baseline measurements of 238 biomarkers, growth differentiation factor 15, kidney injury molecule-1, N-terminal pro-brain natriuretic peptide, uromodulin, C-reactive protein, factor VII and ferritin were independent determinants. The combination of clinical determinants and biomarkers best identified participants who remained outcome-free (C-statistics 0.71, 95% confidence interval 0.70-0.73; net reclassification improvement 0.55, 95% confidence interval 0.48-0.58).

CONCLUSIONS

A set of routinely measured clinical characteristics and seven protein biomarkers identify middle-aged and older people with prediabetes or early type 2 diabetes as least likely to experience serious outcomes during follow-up.

Urinary SPP1 has potential as a non-invasive diagnostic marker for focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a type of chronic glomerular nephropathy showing characteristic glomerular sclerosis, diagnosed by kidney biopsy. However, it is difficult and expensive to monitor disease progression with repeated renal biopsy in clinical practice, and thus here we explored the feasibility of urine biomarkers as non-invasive diagnostic tools. We downloaded scRNA-seq datasets of 20 urine cell samples and 3 kidney tissues and obtained two gene lists encoding extracellular proteins for bioinformatic analysis; in addition, we identified key EP-Genes by immunohistochemical staining and performed bulk RNA sequencing with 12 urine samples. We report that urine cells and kidney cells were correlated. A total of 64 EP-Genes were acquired by intersecting genes of distal tubular cluster with extracellular proteins. Function enrichment analysis showed that EP-Genes might be involved in the immune response and extracellular components. Six key EP-Genes were identified and correlated with renal function. IMC showed that key EP-Genes were located mainly in tubules. Cross verification and examination of a urine RNAseq dataset showed that SPP1 had diagnostic potential for FSGS. The presence of urine SPP1 was primarily associated with macrophage infiltration in kidney, and the pathogenesis of FSGS may be related to innate immunity. Urinary cells seemed to be strongly similar to kidney cells. In summary, SPP1 levels reflect renal function and may have potential as a biomarker for non-invasive diagnosis of FSGS.

Novel biomarkers for diabetic kidney disease

Although diabetic kidney disease (DKD) remains one of the leading causes of reduced lifespan in patients with diabetes mellitus; its prevalence has failed to decline over the past 30 years. To identify those at high risk of developing DKD and disease progression at an early stage, extensive research has been ongoing in the search for prognostic and surrogate endpoint biomarkers for DKD. Although biomarkers are not used routinely in clinical practice or prospective clinical trials, many biomarkers have been developed to improve the early identification and prognostication of patients with DKD. Novel biomarkers that capture one specific mechanism of the DKD disease process have been developed, and studies have evaluated the prognostic value of assay-based biomarkers either in small sets or in combinations involving multiple biomarkers. More recently, several studies have assessed the prognostic value of omics- based biomarkers that include proteomics, metabolomics, and transcriptomics. This review will first describe the biomarkers used in current practice and their limitations, and then summarize the current status of novel biomarkers for DKD with respect to assay- based protein biomarkers, proteomics, metabolomics, and transcriptomics.

The Most Promising Biomarkers of Allogeneic Kidney Transplant Rejection

Clinical transplantology is a constantly evolving field of medicine. Kidney transplantation has become standard clinical practice, and it has a significant impact on reducing mortality and improving the quality of life of patients. Allogenic transplantation induces an immune response, which may lead to the rejection of the transplanted organ. The gold standard for evaluating rejection of the transplanted kidney by the recipient's organism is a biopsy of this organ. However, due to the high invasiveness of this procedure, alternative diagnostic methods are being sought. Therefore, the biomarkers may play an essential predictive role in transplant rejection. A review of the most promising biomarkers for early diagnosis and prognosis prediction of allogenic kidney transplant rejection summarizes novel data on neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), C-X-C motif chemokine 10 (CXCL-10), cystatin C (CysC), osteopontin (OPN), and clusterin (CLU) and analyses the dynamics of changes of the biomarkers mentioned above in kidney diseases and the mechanism of rejection of the transplanted kidney.

Autophagy and Oxidative Balance Mediate the Effect of Carvedilol and Glibenclamide in a Rat Model of Renal Ischemia-Reperfusion Injury

BACKGROUND: Reactive oxygen species and cytokines are the main players in the development of renal ischemia-reperfusion (I/R) injury. AIM: The current study aimed to evaluate the effects of carvedilol and/or glibenclamide and the interaction between autophagy and oxidative stress. METHODS: 50 male rats were divided into five groups: Control, IR injury (IRI), carvedilol pretreated, glibenclamide pretreated, and combined carvedilol and glibenclamide pretreated. Measurements of renal blood flow (RBF), creatinine clearance, serum blood urea nitrogen (BUN), histopathological, and immunohistochemical evaluation of autophagy marker Becl-1 in the rat kidney were performed. Beclin-1and light chain 3 (LC3) Mrna expression was detected by real time polymerase chain reaction. RESULTS: IRI was associated with significant increases in BUN, tumor necrosis factor-alpha, nuclear factor κB, and histo (H) score value of Becl-1. However, there was a significant decrease in RBF, creatinine clearance, and glutathione peroxidase compared to the control group. There was significant increase in Beclin-1 and LC3 mRNA gene expression in carvedilol, glibenclamide, and combined treatment groups as compared to IRI and control groups. Combination of carvedilol and glibenclamide significantly restored IRI changes when compared with the other pretreated groups. CONCLUSION: This study suggests that carvedilol and glibenclamide are promising reno-protective drugs to reduce renal injury induced by I/R through their antioxidant and autophagy stimulation.

Urinary complement proteins and risk of end-stage renal disease: quantitative urinary proteomics in patients with type 2 diabetes and biopsy-proven diabetic nephropathy

PURPOSE

To investigate the association between urinary complement proteins and renal outcome in biopsy-proven diabetic nephropathy (DN).

METHODS

Untargeted proteomic and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional analyses and targeted proteomic analysis using parallel reaction-monitoring (PRM)-mass spectrometry was performed to determine the abundance of urinary complement proteins in healthy controls, type 2 diabetes mellitus (T2DM) patients, and patients with T2DM and biopsy-proven DN. The abundance of each urinary complement protein was individually included in Cox proportional hazards models for predicting progression to end-stage renal disease (ESRD).

RESULTS

Untargeted proteomic and functional analysis using the KEGG showed that differentially expressed urinary proteins were primarily associated with the complement and coagulation cascades. Subsequent urinary complement proteins quantification using PRM showed that urinary abundances of C3, C9, and complement factor H (CFAH) correlated negatively with annual estimated glomerular filtration rate (eGFR) decline, while urinary abundances of C5, decay-accelerating factor (DAF), and CD59 correlated positively with annual rate of eGFR decline. Furthermore, higher urinary abundance of CFAH and lower urinary abundance of DAF were independently associated with greater risk of progression to ESRD. Urinary abundance of CFAH and DAF had a larger area under the curve (AUC) than that of eGFR, proteinuria, or any pathological parameter. Moreover, the model that included CFAH or DAF had a larger AUC than that with only clinical or pathological parameters.

CONCLUSION

Urinary abundance of complement proteins was significantly associated with ESRD in patients with T2DM and biopsy-proven DN, indicating that therapeutically targeting the complement pathway may alleviate progression of DN.

The Use of 'Omics for Diagnosing and Predicting Progression of Chronic Kidney Disease: A Scoping Review

Globally, chronic kidney disease (CKD) contributes substantial morbidity and mortality. Recently, various 'omics platforms have provided insight into the molecular basis of kidney dysfunction. This scoping review is a synthesis of the current literature on the use of different 'omics platforms to identify biomarkers that could be used to detect early-stage CKD, predict disease progression, and identify pathways leading to CKD. This review includes 123 articles published from January 2007 to May 2021, following a structured selection process. The most common type of 'omic platform was proteomics, appearing in 55 of the studies and two of these included a metabolomics component. Most studies (n = 91) reported on CKD associated with diabetes mellitus. Thirteen studies that provided information on the biomarkers associated with CKD and explored potential pathways involved in CKD are discussed. The biomarkers that are associated with risk or early detection of CKD are SNPs in the MYH9/APOL1 and UMOD genes, the proteomic CKD273 biomarker panel and metabolite pantothenic acid. Pantothenic acid and the CKD273 biomarker panel were also involved in predicting CKD progression. Retinoic acid pathway genes, UMOD, and pantothenic acid provided insight into potential pathways leading to CKD. The biomarkers were mainly used to detect CKD and predict progression in high-income, European ancestry populations, highlighting the need for representative 'omics research in other populations with disparate socio-economic strata, including Africans, since disease etiologies may differ across ethnic groups. To assess the transferability of findings, it is essential to do research in diverse populations.

Development of Biomarkers and Molecular Therapy Based on Inflammatory Genes in Diabetic Nephropathy

Diabetic Nephropathy (DN) is a debilitating consequence of both Type 1 and Type 2 diabetes affecting the kidney and renal tubules leading to End Stage Renal Disease (ESRD). As diabetes is a world epidemic and almost half of diabetic patients develop DN in their lifetime, a large group of people is affected. Due to the complex nature of the disease, current diagnosis and treatment are not adequate to halt disease progression or provide an effective cure. DN is now considered a manifestation of inflammation where inflammatory molecules regulate most of the renal physiology. Recent advances in genetics and genomic technology have identified numerous susceptibility genes that are associated with DN, many of which have inflammatory functions. Based on their role in DN, we will discuss the current aspects of developing biomarkers and molecular therapy for advancing precision medicine.

BoxCar increases the depth and reproducibility of diabetic urinary proteome analysis

PURPOSE

Mass spectrometry-based proteomics performs well in high throughput detection of urinary proteins. Nonetheless, protein identification depth and reproducibility remain the challenges in diabetic urinary proteome with high complexity and broad dynamic range, especially for low-abundant proteins. As a new data acquisition strategy, the BoxCar method was reported to benefit for low-abundant protein identification. Whether it is propitious to diabetic samples with high dynamic range proteomes has not been discussed yet. We aimed to apply BoxCar method to diabetic urine sample analysis, and to compare it with standard data dependent acquisition (DDA) method on protein identification in detail.

EXPERIMENTAL DESIGN

We performed seven technical replicates analysis on two urine samples from healthy individuals and diabetic patients to evaluate protein detection of BoxCar and standard DDA methods on single sample. Further comparison of two methods was made on multiple diabetic urine samples.

RESULTS

BoxCar could increase over 20% of identified proteins and performed better quantitative reproducibility than standard DDA method either in single or multiple diabetic urinary samples. BoxCar also improved the detection of low-abundant proteins. Functional enrichment analysis of normal albuminuria or microalbuminuria samples indicated that BoxCar acquired more diabetes-related biological information.

CONCLUSIONS AND CLINICAL RELEVANCE

The study demonstrates that BoxCar could enhance the depth and reproducibility in diabetic urinary proteome analysis, which provides reference for mass spectrometry approach selection in clinical urinary proteomic research.

Serum Progranulin As a Risk Predictor in Patients with Acute Myocardial Infarction

BACKGROUND Although progranulin was recently proposed as an adipokine that may be involved in glucose metabolic and inflammatory diseases, the role of serum progranulin in cardiovascular disease is elusive and remains disputed. The aim of our research was to determine the concentration of serum progranulin in Chinese patients with cardiovascular disease, notably in acute myocardial infarction (AMI), and its relationship to other cardiometabolic risk factors. MATERIAL AND METHODS This prospective observational study included 342 Chinese AMI patients and 255 healthy control subjects. Serum progranulin concentrations and various cardiometabolic risk factor levels were investigated. We assessed the relationship between progranulin and other cardiometabolic risk factors. Logistic regression analysis was applied to evaluate risk factors in patients with AMI. RESULTS Progranulin levels were obviously elevated in AMI patients compared to control subjects (P=0.0001). Correlation analysis showed that progranulin levels were positively associated with coronary artery disease severity (r=0.380, P=0.0001), glucose (r=0.195, P=0.015), and myeloperoxidase (r=0.198, P=0.014). In logistic regression analysis, serum progranulin (Exp(B)=1.104, 95% CI=1.043-1.168, P=0.001), myeloperoxidase (Exp(B)=1.006, 95% CI=1.003-1.008, P=0.0001), and uric acid (Exp(B)=1.020, 95% CI=1.009-1.032, P=0.0001) were independent risk factors in AMI patients. CONCLUSIONS Patients with AMI had significantly higher serum progranulin concentrations than control subjects. This study suggests that serum progranulin is an independent risk predictor in Chinese patients with AMI.

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.

A Targeted Multiomics Approach to Identify Biomarkers Associated with Rapid eGFR Decline in Type 1 Diabetes

BACKGROUND

Individuals with type 1 diabetes (T1D) demonstrate varied trajectories of estimated glomerular filtration rate (eGFR) decline. The molecular pathways underlying rapid eGFR decline in T1D are poorly understood, and individual-level risk of rapid eGFR decline is difficult to predict.

METHODS

We designed a case-control study with multiple exposure measurements nested within 4 well-characterized T1D cohorts (FinnDiane, Steno, EDC, and CACTI) to identify biomarkers associated with rapid eGFR decline. Here, we report the rationale for and design of these studies as well as results of models testing associations of clinical characteristics with rapid eGFR decline in the study population, upon which "omics" studies will be built. Cases (n = 535) and controls (n = 895) were defined as having an annual eGFR decline of ≥3 and <1 mL/min/1.73 m2, respectively. Associations of demographic and clinical variables with rapid eGFR decline were tested using logistic regression, and prediction was evaluated using area under the curve (AUC) statistics. Targeted metabolomics, lipidomics, and proteomics are being performed using high-resolution mass-spectrometry techniques.

RESULTS

At baseline, the mean age was 43 years, diabetes duration was 27 years, eGFR was 94 mL/min/1.73 m2, and 62% of participants were normoalbuminuric. Over 7.6-year median follow-up, the mean annual change in eGFR in cases and controls was -5.7 and 0.6 mL/min/1.73 m2, respectively. Younger age, longer diabetes duration, and higher baseline HbA1c, urine albumin-creatinine ratio, and eGFR were significantly associated with rapid eGFR decline. The cross-validated AUC for the predictive model incorporating these variables plus sex and mean arterial blood pressure was 0.74 (95% CI: 0.68-0.79; p < 0.001).

CONCLUSION

Known risk factors provide moderate discrimination of rapid eGFR decline. Identification of blood and urine biomarkers associated with rapid eGFR decline in T1D using targeted omics strategies may provide insight into disease mechanisms and improve upon clinical predictive models using traditional risk factors.

Protective factors as biomarkers and targets for prevention and treatment of diabetic nephropathy: From current human evidence to future possibilities

Although hyperglycemia, high blood pressure and aging increase the risk of developing kidney complications, some diabetes patients exposed to these risk factors do not develop kidney disease, suggesting the presence of endogenous protective factors. There is a growing need to understand these factors determining protection of the kidney in order to improve the design of preventive strategies and to enhance the processes responsible for renoprotection. The aim of this review was to present the existing molecular and epidemiological data on factors showing protective effects in diabetic kidney disease, and to summarize the evidence regarding their potential in the area of future clinical diagnostics, therapeutics and early preventive strategies. These include transcriptomic and proteomic studies regarding the anti-inflammatory, anti-fibrotic and regenerative factors that were associated with slower progression of renal function loss. Another focus is the new evidence regarding the evaluation of alterations in the regulatory epigenome and its involvement in the risk of diabetic kidney disease. Further effort is required to validate and extend these findings, and to define their potential for clinical implementation in the future.

Autophagy and mTOR Pathways Mediate the Potential Renoprotective Effects of Vitamin D on Diabetic Nephropathy

Introduction

Not only is diabetic nephropathy (DN) the most common cause of end-stage renal disease worldwide, but it also increases the risk of mortality up to fourteen times compared to normoalbuminuric diabetic patients.

Aim

The aim of the current study was the evaluation of the renoprotective effects of vitamin D in DN and the possible interplay between autophagy and mTOR pathways.

Materials and Methods

Fifty male Wistar albino rats were divided (10/group) into control, DN group, insulin-treated DN group, vitamin D-treated DN group, and combined insulin and vitamin D-treated DN group. Assessments of systolic blood pressure, albuminuria, creatinine clearance, serum glucose, insulin, urea, creatinine, inflammatory cytokines, oxidative stress markers, and rat kidney gene expression of mTOR were performed. Histopathological and immunohistochemical assessments of autophagy marker LC3 in rat kidneys were also performed.

Results

DN was associated with significant increases in SBP, urinary albumin, serum glucose, urea, creatinine, inflammatory cytokines, MDA, and mTOR gene expression (P < 0.05). However, there was significant decrease in creatinine clearance, serum insulin, GSH, and H score value of LC3 when compared with control group (P < 0.05). The combination of insulin and vitamin D treatment significantly restored DN changes when compared with the other treated groups, except in oxidative stress markers where there was an insignificant difference between the combination-treated and insulin-treated groups (P > 0.05).

Conclusion

It has been concluded that vitamin D is a potent adjuvant therapy in treatment of DN via downregulation of mTOR gene expression, stimulation of autophagy, and antioxidant, anti-inflammatory, and hypotensive effects.

Uromodulin in mineral metabolism

PURPOSE OF REVIEW

Uromodulin (UMOD), also known as Tamm-Horsfall protein, is the most abundant protein in human urine. UMOD has multiple functions such as protection against urinary tract infections and nephrolithiasis. This review outlines recent progress made in UMOD's role in renal physiology, tubular transport, and mineral metabolism.

RECENT FINDINGS

UMOD is mostly secreted in the thick ascending limb (TAL) and to a lesser degree in the distal convoluted tubule (DCT). UMOD secretion is regulated by the calcium-sensing receptor. UMOD upregulates ion channels [e.g., renal outer medullary potassium channel, transient receptor potential cation channel subfamily V member 5, and transient receptor potential melastatin 6 (TRPM6)] and cotransporters [e.g., Na,K,2Cl cotransporter (NKCC2) and sodium-chloride cotransporter (NCC)] in the TAL and DCT. Higher serum UMOD concentrations have been associated with higher renal function and preserved renal reserve. Higher serum UMOD has also been linked to a lower risk of cardiovascular disease and diabetes mellitus.

SUMMARY

With better serum UMOD detection assays the extent of different functions for UMOD is still expanding. Urinary UMOD regulates different tubular ion channels and cotransporters. Variations of urinary UMOD secretion can so contribute to common disorders such as hypertension or nephrolithiasis.

Diabetes-induced Proteome Changes Throughout Development

BACKGROUND

Diabetes Mellitus (DM) is a multisystemic disease involving the homeostasis of insulin secretion by the pancreatic islet beta cells (β-cells). It is associated with hypertension, renal disease, and arterial and arteriolar vascular diseases.

DISCUSSION

The classification of diabetes is identified as type 1 (gene linked β-cell destruction in childhood) and type 2 (late onset associated with β-cell overload and insulin resistance in peripheral tissues. Type 1 diabetes is characterized by insulin deficiency, type 2 diabetes by both insulin deficiency and insulin resistance. The former is a genetically programmed loss of insulin secretion whereas the latter constitutes a disruption of the homeostatic relationship between the opposing activity of β- cell insulin and alpha cell (α-cell) glucagon of the Islets of Langerhans. The condition could also occur in pregnancy, as a prenatal occurring event, possibly triggered by the hormonal changes of pregnancy combined with β-cell overload. This review discusses the molecular basis of the biomolecular changes that occur with respect to glucose homeostasis and related diseases in DM. The underlying link between pancreatic, renal, and microvascular diseases in DM is based on oxidative stress and the Unfolded Protein Response (UPR).

CONCLUSION

Studying proteome changes in diabetes can deepen our understanding of the biomolecular basis of disease and help us acquire more efficient therapies.

Potential value of serum Progranulin as a biomarker for the presence and severity of micro vascular complications among Egyptian patients with type 2 diabetes mellitus

Objective

The increasing prevalence of type 2 diabetes mellitus (T2DM) calls for evolving a concomitant screening strategies for early disease detection and prediction of the complications. Progranulin (PRGN) was recently introduced as a biomarker of inflammation in T2DM. However, little data have been published as regarding progranulin in relation to diabetic micro angiopathy among Egyptian patients with T2DM. The aim of this study was therefore to investigate and evaluate serum progranulin as a biomarker for the presence and severity of micro vascular complications among Egyptian patients with T2DM.

Methods

A total of 90 age and sex matched participants were included in this cross sectional study. They were divided into group 1 included 30 non diabetic healthy controls and group 2 included 60 patients with type 2 diabetes mellitus. Furthermore, diabetic patients were categorized into two subgroups depending on the presence or absence of microvascular complications. Evaluation for diabetic nephropathy, neuropathy and retinopathy were determined. Furthermore, laboratory investigations were performed and serum progranulin levels were measured by a quantitative sandwich enzyme linked immune sorbent assay.

Results

The mean serum PRGN levels were significantly elevated in type 2 diabetic patients (20.90 ± 6.38 ng/ml) compared to control group (9.20 ± 1.41 ng/ml) (p < 0.001). Moreover,the serum PRGN levels were increased parallel to the severity of diabetic nephropathy (DN) and diabetic retinopathy (DR) with significantly highest detectable values were in macro albuminuric group of diabetic nephropathy as well as proliferative diabetic retinopathy (PDR) groups (P < 0.001). Besides, it worth mentioning that, the level of Serum progranulin started to increase significantly in stage 2 DN in spite of normal level of albuminuria. There were highly significant positive correlation between serum PRGN and disease duration, body mass index (BMI),fasting blood sugar (FBS), HbA1c, Total cholesterol (TC),triglyceride (TG), serum creatinine, ACR (r = 0.918, 0.623, 0.430, 0.539,0.910,0.842,0.759, 0.903, resp., P < 0.001) and a significant positive correlation with low density lipoprotein (LDL) (r = 0.344),but there was a highly significant negative correlation between serum PRGN and eGFR (r = -0.866, P < 0.001) in the studied diabetic patients.

Conclusion

Progranulin might be considered as a biomarker for diabetic micro angiopathy and its severity. In addition, there is a group of diabetic patients with decreased eGFR but without albuminuria in which serum PRGN level was indicated to be used as an early biomarker of diabetic nephropathy.

The complex effects of adipokines in the patients with kidney disease

Kidney diseases are categorized as the highest prevalent ones with worldwide noticeable incidence. They cause accelerated cardiovascular diseases and noticeable mortalities. Adipose tissue and its messengers, adipokines, are reported to have the highest relationship with end-stage renal diseases or chronic kidney diseases. Over recent years, with shifting of scientists’ mindset from a simple overview of adipose tissue as a fat store to the complex paradigm of this issue as a multipotential secretory organ, the importance of studies on this tissue has emerged.

Biomarkers of diabetic kidney disease

Diabetic kidney disease (DKD) remains one of the leading causes of reduced lifespan in diabetes. The quest for both prognostic and surrogate endpoint biomarkers for advanced DKD and end-stage renal disease has received major investment and interest in recent years. However, at present no novel biomarkers are in routine use in the clinic or in trials. This review focuses on the current status of prognostic biomarkers. First, we emphasise that albuminuria and eGFR, with other routine clinical data, show at least modest prediction of future renal status if properly used. Indeed, a major limitation of many current biomarker studies is that they do not properly evaluate the marginal increase in prediction on top of these routinely available clinical data. Second, we emphasise that many of the candidate biomarkers for which there are numerous sporadic reports in the literature are tightly correlated with each other. Despite this, few studies have attempted to evaluate a wide range of biomarkers simultaneously to define the most useful among these correlated biomarkers. We also review the potential of high-dimensional panels of lipids, metabolites and proteins to advance the field, and point to some of the analytical and post-analytical challenges of taking initial studies using these and candidate approaches through to actual clinical biomarker use.

Pediatric endocrine and metabolic diseases and proteomics

The principles of Predictive, Preventive and Personalized Medicine (PPPM) dictate the need to recognize individual susceptibility to disease in a timely fashion and to offer targeted preventive interventions and treatments. Proteomics is a state-of-the art technology- driven science aiming at expanding our understanding of the pathophysiologic mechanisms that underlie disease, but also at identifying accurate predictive, diagnostic and therapeutic biomarkers, that will eventually promote the implementation of PPPM. In this review, we summarize the wide spectrum of the applications of Mass Spectrometry-based proteomics in the various fields of Pediatric Endocrinology, including Inborn Errors of Metabolism, type 1 diabetes, Adrenal Disease, Metabolic Syndrome and Thyroid disease, ranging from neonatal screening to early recognition of specific at-risk populations for disease manifestations or complications in adult life and to monitoring of disease progression and response to treatment.

SIGNIFICANCE

Proteomics is a state-of-the art technology- driven science aiming at expanding our understanding of the pathophysiologic mechanisms that underlie disease, but also at identifying accurate predictive, diagnostic and therapeutic biomarkers that will eventually lead to successful, targeted, patient-centric, individualized approach of each patient, as dictated by the principles of Predictive, Preventive and Personalized Medicine. In this review, we summarize the wide spectrum of the applications of Mass Spectrometry-based proteomics in the various fields of Pediatric Endocrinology, including Inborn Errors of Metabolism, type 1 diabetes, Adrenal Disease, Metabolic Syndrome and Thyroid disease, ranging from neonatal screening, accurate diagnosis, early recognition of specific at-risk populations for the prevention of disease manifestation or future complications.

Preoperative levels of urinary uromodulin predict acute kidney injury after pediatric cardiopulmonary bypass surgery

BACKGROUND

Acute kidney injury (AKI) is a common complication of cardiopulmonary bypass surgery (CPB) in children. Several promising postoperative AKI biomarkers have been identified, but no preoperative biomarkers are available. We evaluated the association of urinary uromodulin (uUMOD) with postoperative AKI.

METHODS

One hundred and one children undergoing CPB were enrolled. Urine was collected prior to CPB, and AKI was defined as ≧50% increase in serum creatinine from preoperative baseline within 48 h of surgery.

RESULTS

Forty-seven patients (47%) developed AKI, and 92% of participants in the lowest quartile of preoperative uUMOD concentrations developed AKI compared with 8% in the highest quartile. Patients with preoperative uUMOD levels in the lowest quartile had 132.3× increased risk of postoperative AKI versus the highest quartile. Raw uUMOD levels were significantly lower in patients with AKI vs. no AKI. Significance was unchanged after correcting uUMOD levels for urinary creatinine. Receiver operating characteristic analysis showed preoperative uUMOD strongly predicted postoperative AKI, with area under the curve (AUC) 0.90. Stepwise logistic regression analysis revealed a model combining uUMOD, and bypass time predicted AKI at p<0.001. Neither Risk Adjustment for Congenital Heart Surgery 1 (RACHS) score nor age improved the model's ability to predict AKI. Independent analysis demonstrated that while bypass time was associated with AKI, the predictive ability of bypass time (AUC 0.77) was less than that of preoperative uUMOD levels (AUC 0.9).

CONCLUSIONS

Children with lowest preoperative levels of uUMOD have greatly increased risk of AKI post-CPB. If uUMOD were used to risk-stratify patients undergoing CPB, clinical measures could be taken to minimize AKI development.

Quantitative GC-MS assay of citric acid from humans and db/db mice blood serum to assist the diagnosis of diabetic nephropathy

The early diagnosis of diabetic nephropathy (DN) is rather challenging. Our previous study suggested that citric acid is a potential marker for the early diagnosis of diabetic nephropathy in db/db mice. For the first time, in this study, a surrogate analyte of ¹³C₆-citric acid was employed to generate calibration curves for the quantitative measurement of the endogenous citric acid in the sera of db/db mice and diabetic nephropathy patients by GC/MS after the analytes were extracted, methoximated and trimethylsilylated. The constant response factor of ¹³C₆-citric acid versus citric acid over the linear range indicated the identical ionization efficiency of these two compounds. The full validation assessments suggested that the method is sensitive, specific, reliable, reproducible and has acceptable parameters. Statistical analysis revealed cut-off citric acid concentrations of 29.24 μg/mL with a 95% confidence interval between 32.75 and 39.16 μg/mL in the diabetic nephropathy patients and 16.74 and 22.57 μg/mL in the normal controls. The areas under the receiver operating characteristic curves indicated accuracies of over 90% for the diagnoses of early diabetic nephropathy in both humans and db/db mice, which suggests that the serum citric acid level is potentially a biomarker that could assist in the diagnosis of diabetic nephropathy.

Urinary Uromodulin and Risk of Urinary Tract Infections: The Cardiovascular Health Study

BACKGROUND

Laboratory studies suggest that urinary uromodulin, the most common protein in the urine of healthy adults, may protect against urinary tract infection (UTI). Epidemiologic studies evaluating this relationship in humans are lacking.

STUDY DESIGN

Prospective longitudinal cohort study.

SETTING & PARTICIPANTS

953 participants enrolled in the Cardiovascular Health Study.

PREDICTOR

Uromodulin assayed using enzyme-linked immunosorbent assay in spot urine samples.

OUTCOMES

Composite of outpatient UTI events or UTI-related hospitalizations and each of them individually identified using International Classification of Diseases, Ninth Revision (ICD-9) codes using negative binomial regression with robust standard errors adjusted for age, race, sex, body mass index, diabetes, estimated glomerular filtration rate, and urinary albumin and urinary creatinine excretion.

RESULTS

Median uromodulin level was 25.9 (IQR, 17.3-38.9) μg/mL, mean age of participants was 78 years, 61% were women, and 15% were black. There were 331 outpatient UTI events and 87 UTI-related hospitalizations among 186 participants during a median 9.9 years of follow-up. Persons in the highest quartile (>38.93μg/mL) of uromodulin concentration had a significantly lower risk for the composite outcome (incidence rate ratio [IRR], 0.47; 95% CI, 0.29-0.79) compared with those in the lowest quartile (≤17.26μg/mL). This association remained significant for outpatient UTI events (highest vs lowest quartile even after excluding those with prior UTI: IRR, 0.42; 95% CI, 0.23-0.77). The direction of association with UTI hospitalization was similar, but not statistically significant (IRR, 0.78; 95% CI, 0.39-1.58).

LIMITATIONS

Use of ICD-9 codes to identify outcomes and lack of generalizability to younger populations.

CONCLUSIONS

High urinary uromodulin levels are associated with lower risk for UTI in older community-dwelling adults independent of traditional UTI risk factors. This finding supports prior laboratory data indicating a protective role of uromodulin against UTI. Further research is needed to understand if this may lead to new treatments to prevent or treat UTI.

Effect of UMOD genotype on long-term graft survival after kidney transplantation in patients treated with cyclosporine-based therapy

The genetic rs12917707-G>T variant in uromodulin (UMOD) has been associated with renal function, chronic kidney disease and hypertension with the minor T-allele showing a protective effect. Hypertension and nephrotoxicity are adverse effects of chronic cyclosporine treatment. We tested whether UMOD rs12917707-T in donor kidneys associates with long-term graft survival in 393 Caucasian patients with stable graft function for more than 10 weeks after kidney transplantation treated with a cyclosporine-based maintenance therapy (mean graft survival 9 years). Presence of the donor T-allele had no effect on blood pressure, serum creatinine 1 year after transplantation, and on number of acute graft rejections during the first year. No significant effect on overall graft survival was observed in Kaplan-Meier analysis (P=0.65). In death-censored adjusted multivariate analysis, presence of donor T-allele associated with a significant lower hazard ratio of 0.67 (95% confidence interval: 0.46-0.97, P=0.05) for graft loss. This protective effect of the donor T-allele on graft loss observed in multivariate adjusted analysis justifies further investigations including patients treated with similar or other immunosuppressive regimens.

Association of Preoperative Urinary Uromodulin with AKI after Cardiac Surgery

BACKGROUND AND OBJECTIVES

AKI is a serious complication after cardiac surgery. Although high urinary concentrations of the tubular protein uromodulin, a marker of tubular health, are associated with less AKI in animal models, its relationship in humans is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A post hoc analysis of a prospective cohort study of 218 adults undergoing on-pump cardiac surgery between 2004 and 2011 was conducted. Multivariable logistic and linear regression analyses were used to evaluate the associations of preoperative urinary uromodulin-to-creatinine ratio with postoperative AKI (defined as a rise in serum creatinine of >0.3 mg/dl or >1.5 times baseline); severe AKI (doubling of creatinine or need for dialysis) and peak postoperative serum creatinine over the first 72 hours.

RESULTS

Mean age was 68 years, 27% were women, 95% were white, and the median uromodulin-to-creatinine ratio was 10.0 μg/g. AKI developed in 64 (29%) patients. Lower urinary uromodulin-to-creatinine ratio was associated with higher odds for AKI (odds ratio, 1.49 per 1-SD lower uromodulin; 95% confidence interval, 1.04 to 2.13), which was marginally attenuated after multivariable adjustment (odds ratio, 1.43; 95% confidence interval, 0.99 to 2.07). The lowest uromodulin-to-creatinine ratio quartile was also associated with higher odds for AKI relative to the highest quartile (odds ratio, 2.94; 95% confidence interval, 1.19 to 7.26), which was slightly attenuated after multivariable adjustment (odds ratio, 2.43; 95% confidence interval, 0.91 to 6.48). A uromodulin-to-creatinine ratio below the median was associated with higher adjusted odds for severe AKI, although this did not reach statistical significance (odds ratio, 4.03; 95% confidence interval, 0.87 to 18.70). Each 1-SD lower uromodulin-to-creatinine ratio was associated with a higher adjusted mean peak serum creatinine (0.07 mg/dl per SD; 95% confidence interval, 0.02 to 0.13).

CONCLUSIONS

Lower uromodulin-to-creatinine ratio is associated with higher odds of AKI and higher peak serum creatinine after cardiac surgery. Additional studies are needed to confirm these preliminary results.

Serum and Urinary Progranulin in Diabetic Kidney Disease

Progranulin has been recognized as an adipokine related to obesity, insulin resistance and type 2 diabetes mellitus (T2DM). There are scarce data regarding progranulin and kidney disease, but there are some data linking diabetic kidney disease (DKD) and increased progranulin levels. We aimed to better describe the relationship between serum and urinary progranulin levels and DKD in T2DM. This is a case-control study including four groups of subjects: 1) Advanced DKD cases: T2DM patients with estimated glomerular filtration rate (eGFR) <60 mL/min/1.73m²; 2) Albuminuric DKD cases: T2DM patients with urinary albumin excretion (UAE) ≥30 mg/g creatinine and eGFR ≥60 mL/min/1.73m²; 3) Diabetic controls: T2DM patients with UAE <30 mg/g creatinine and eGFR ≥60 mL/min/1.73m²; and 4) Non-diabetic controls: individuals without T2DM. Progranulin was determined by enzyme-linked immunosorbent assay. One hundred and fourteen patients were included (23 advanced DKD cases, 25 albuminuric DKD cases, 40 diabetic controls and 26 non-diabetic controls). Serum progranulin was increased in advanced DKD compared to other groups [70.84 (59.04–83.16) vs. albuminuric cases 57.16 (42.24–67.38), diabetic controls 57.28 (42.08–70.47) and non-diabetic controls 44.54 (41.44–53.32) ng/mL; p<0.001]. Urinary progranulin was decreased in advanced DKD cases compared to albuminuric cases [10.62 (6.30–16.08) vs. 20.94 (12.35–30.22); diabetic controls 14.06 (9.88–20.82) and non-diabetic controls 13.51 (7.94–24.36) ng/mL; p = 0.017]. There was a positive correlation between serum progranulin and body mass index (r = 0.27; p = 0.004), waist circumference (r = 0.25; p = 0.007); body fat percentage (r = 0.20; p = 0.042), high-sensitive C reactive protein (r = 0.35; p<0.001) and interleukin-6 (r = 0.37; p<0.001) and a negative correlation with eGFR (r = -0.22; p = 0.023). Urinary progranulin was positively associated with albuminuria (r = 0.25; p = 0.010). In conclusion, progranulin is affected by a decrease in eGFR, being at a higher concentration in serum and lower in urine of DKD patients with T2DM and eGFR <60 mL/min/1.73m². It is also associated with markers of obesity and inflammation.

Proteomics for prediction of disease progression and response to therapy in diabetic kidney disease

The past decade has resulted in multiple new findings of potential proteomic biomarkers of diabetic kidney disease (DKD). Many of these biomarkers reflect an important role in the (patho)physiology and biological processes of DKD. Situations in which proteomics could be applied in clinical practice include the identification of individuals at risk of progressive kidney disease and those who would respond well to treatment, in order to tailor therapy for those at highest risk. However, while many proteomic biomarkers have been discovered, and even found to be predictive, most lack rigorous external validation in sufficiently powered studies with renal endpoints. Moreover, studies assessing short-term changes in the proteome for therapy-monitoring purposes are lacking. Collaborations between academia and industry and enhanced interactions with regulatory agencies are needed to design new, sufficiently powered studies to implement proteomics in clinical practice.

Will the future lie in multitude? A critical appraisal of biomarker panel studies on prediction of diabetic kidney disease progression

Diabetic kidney disease is diagnosed and staged by albuminuria and estimated glomerular filtration rate. Although albuminuria has strong predictive power for renal function decline, there is still variability in the rate of renal disease progression across individuals that are not fully captured by the level of albuminuria. Therefore, research focuses on discovering and validating additional biomarkers that improve risk stratification for future renal function decline and end-stage renal disease in patients with diabetes, on top of established biomarkers. Most studies address the value of single biomarkers to predict progressive renal disease and aim to understand the mechanisms that underlie accelerated renal function decline. Since diabetic kidney disease is a disease encompassing several pathophysiological processes, a combination of biomarkers may be more likely to improve risk prediction than a single biomarker. In this review, we provide an overview of studies on the use of multiple biomarkers and biomarker panels, appraise their study design, discuss methodological pitfalls and make recommendations for future biomarker panel studies.

A Systems Biology Overview on Human Diabetic Nephropathy: From Genetic Susceptibility to Post-Transcriptional and Post-Translational Modifications

Diabetic nephropathy (DN), a microvascular complication occurring in approximately 20-40% of patients with type 2 diabetes mellitus (T2DM), is characterized by the progressive impairment of glomerular filtration and the development of Kimmelstiel-Wilson lesions leading to end-stage renal failure (ESRD). The causes and molecular mechanisms mediating the onset of T2DM chronic complications are yet sketchy and it is not clear why disease progression occurs only in some patients. We performed a systematic analysis of the most relevant studies investigating genetic susceptibility and specific transcriptomic, epigenetic, proteomic, and metabolomic patterns in order to summarize the most significant traits associated with the disease onset and progression. The picture that emerges is complex and fascinating as it includes the regulation/dysregulation of numerous biological processes, converging toward the activation of inflammatory processes, oxidative stress, remodeling of cellular function and morphology, and disturbance of metabolic pathways. The growing interest in the characterization of protein post-translational modifications and the importance of handling large datasets using a systems biology approach are also discussed.

Urinary uromodulin, kidney function, and cardiovascular disease in elderly adults

Urinary uromodulin (uUMOD) is the most common secreted tubular protein in healthy adults. However, the relationship between uUMOD and clinical outcomes is still unclear. Here we measured uUMOD in 192 participants of the Cardiovascular Health Study with over a 30% decline in estimated glomerular filtration rate (eGFR) over 9 years, 54 with incident end-stage renal disease (ESRD), and in a random subcohort of 958 participants. The association of uUMOD with eGFR decline was evaluated using logistic regression and with incident ESRD, cardiovascular disease, heart failure, and mortality using Cox proportional regression. Mean age was 78 years and median uUMOD was 25.8 μg/ml. In a case-control study evaluating eGFR decline (192 cases and 231 controls), each 1-s.d. higher uUMOD was associated with a 23% lower odds of eGFR decline (odds ratio 0.77 (95% CI 0.62-0.96)) and a 10% lower risk of mortality (hazard ratio 0.90 (95% CI 0.83-0.98)) after adjusting for demographics, eGFR, albumin/creatinine ratio, and other risk factors. There was no risk association of uUMOD with ESRD, cardiovascular disease, or heart failure after multivariable adjustment. Thus, low uUMOD levels may identify persons at risk of progressive kidney disease and mortality above and beyond established markers of kidney disease, namely eGFR and the albumin/creatinine ratio. Future studies need to confirm these results and evaluate whether uUMOD is a marker of tubular health and/or whether it plays a causal role in preserving kidney function.

Diabetic Nephropathy: New Risk Factors and Improvements in Diagnosis

Diabetic nephropathy is the leading cause of end-stage renal disease. Patients with diabetic nephropathy have a high cardiovascular risk, comparable to patients with coronary heart disease. Accordingly, identification and management of risk factors for diabetic nephropathy as well as timely diagnosis and prompt management of the condition are of paramount importance for effective treatment. A variety of risk factors promotes the development and progression of diabetic nephropathy, including elevated glucose levels, long duration of diabetes, high blood pressure, obesity, and dyslipidemia. Most of these risk factors are modifiable by antidiabetic, antihypertensive, or lipid-lowering treatment and lifestyle changes. Others such as genetic factors or advanced age cannot be modified. Therefore, the rigorous management of the modifiable risk factors is essential for preventing and delaying the decline in renal function. Early diagnosis of diabetic nephropathy is another essential component in the management of diabetes and its complications such as nephropathy. New markers may allow earlier diagnosis of this common and serious complication, but further studies are needed to clarify their additive predictive value, and to define their cost-benefit ratio. This article reviews the most important risk factors in the development and progression of diabetic nephropathy and summarizes recent developments in the diagnosis of this disease.

Quantitative Differences in the Urinary Proteome of Siblings Discordant for Type 1 Diabetes Include Lysosomal Enzymes

Individuals with type 1 diabetes (T1D) often have higher than normal blood glucose levels, causing advanced glycation end product formation and inflammation and increasing the risk of vascular complications years or decades later. To examine the urinary proteome in juveniles with T1D for signatures indicative of inflammatory consequences of hyperglycemia, we profiled the proteome of 40 T1D patients with an average of 6.3 years after disease onset and normal or elevated HbA1C levels, in comparison with a cohort of 41 healthy siblings. Using shotgun proteomics, 1036 proteins were identified, on average, per experiment, and 50 proteins showed significant abundance differences using a Wilcoxon signed-rank test (FDR q-value ≤ 0.05). Thirteen lysosomal proteins were increased in abundance in the T1D versus control cohort. Fifteen proteins with functional roles in vascular permeability and adhesion were quantitatively changed, including CD166 antigen and angiotensin-converting enzyme 2. α-N-Acetyl-galactosaminidase and α-fucosidase 2, two differentially abundant lysosomal enzymes, were detected in western blots with often elevated quantities in the T1D versus control cohort. Increased release of proteins derived from lysosomes and vascular epithelium into urine may result from hyperglycemia-associated inflammation in the kidney vasculature.

The role of progranulin in diabetes and kidney disease

Progranulin (PGRN) is a cysteine rich secreted protein, expressed in epithelial cells, immune cells, neurons, and adipocytes. It was first identified for its growth factor-like properties, being involved in early embryogenesis and tissue remodeling, acting as an anti-inflammatory molecule. In the central nervous system, PGRN has neurotrophic and neuroprotective actions. There is also evidence of PGRN effects on cancer, contributing to tumor proliferation, invasion and cell survival. Recently, PGRN was recognized as an adipokine related to obesity and insulin resistance, revealing its metabolic function and pro-inflammatory properties. In obesity and type 2 diabetes mellitus, PGRN levels are increased. In renal disease, there is a relevant association, however, it is not known if it could contribute to kidney damage or if it is only a route of PGRN elimination. PGRN is an emerging molecule which demands studies in different fields. Possibly, it plays distinct functions in different tissues/cells and metabolic conditions. Here, we discuss potential mechanisms and recent data of PGRN pro-inflammatory actions, regarding obesity, insulin resistance, type 2 diabetes mellitus and kidney disease.

Quantitative mass spectrometry of urinary biomarkers

The effectiveness of treatment of renal diseases is limited because the lack of diagnostic, prognostic and therapeutic markers. Despite the more than a decade of intensive investigation of urinary biomarkers, no new clinical biomarkers were approved. This is in part because the early expectations toward proteomics in biomarkers discovery were significantly higher than the capability of technology at the time. However, during the last decade, proteomic technology has made dramatic progress in both the hardware and software methods. In this review we are discussing modern quantitative methods of mass-spectrometry and providing several examples of their applications for discovery and validation of renal disease biomarkers. We are optimistic about future prospects for the development of novel of specific clinical urinary biomarkers.

Biomarkers in diabetic nephropathy: Present and future

Diabetic nephropathy (DN) is the leading cause of end stage renal disease in the Western world. Microalbuminuria (MA) is the earliest and most commonly used clinical index of DN and is independently associated with cardiovascular risk in diabetic patients. Although MA remains an essential tool for risk stratification and monitoring disease progression in DN, a number of factors have called into question its predictive power. Originally thought to be predictive of future overt DN in 80% of patients, we now know that only around 30% of microalbuminuric patients progress to overt nephropathy after 10 years of follow up. In addition, advanced structural alterations in the glomerular basement membrane may already have occurred by the time MA is clinically detectable.Evidence in recent years suggests that a significant proportion of patients with MA can revert to normoalbuminuria and the concept of nonalbuminuric DN is well-documented, reflecting the fact that patients with diabetes can demonstrate a reduction in glomerular filtration rate without progressing from normo-to MA. There is an unmet clinical need to identify biomarkers with potential for earlier diagnosis and risk stratification in DN and recent developments in this field will be the focus of this review article.

Quantitative proteomics reveals novel therapeutic and diagnostic markers in hypertension

Hypertension is a prevalent disorder in the world representing one of the major risk factors for heart attack and stroke. These risks are increased in salt sensitive individuals. Hypertension and salt sensitivity are complex phenotypes whose pathophysiology remains poorly understood and, remarkably, salt sensitivity is still laborious to diagnose.

Here we present a urinary proteomic study specifically designed to identify urinary proteins relevant for the pathogenesis of hypertension and salt sensitivity. Despite previous studies that underlined the association of UMOD gene variants with hypertension, this work provides novel evidence showing different uromodulin protein level in the urine of hypertensive patients compared to healthy individuals. Notably, we also show that patients with higher level of uromodulin are homozygous for UMOD risk variant and display a decreased level of salt excretion, highlighting the essential role of UMOD in the regulation of salt reabsorption in hypertension. Additionally, we found that urinary nephrin 1, a marker of glomerular slit diaphragm, may predict a salt sensitive phenotype and positively correlate with increased albuminuria associated with this type of hypertension.

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We identified urinary proteins differently excreted in hypertensive patients.

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Nephrin 1 might predict salt sensitive phenotype and glomerular complications.

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Uromodulin impacts salt homeostasis in hypertension.

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We provide new insights into the pathogenesis of hypertension and salt sensitivity.

Proteome-wide remodeling of protein location and function by stress

Protein location and function can change dynamically depending on many factors, including environmental stress, disease state, age, developmental stage, and cell type. Here, we describe an integrative computational framework, called the conditional function predictor (CoFP; http://nbm.ajou.ac.kr/cofp/), for predicting changes in subcellular location and function on a proteome-wide scale. The essence of the CoFP approach is to cross-reference general knowledge about a protein and its known network of physical interactions, which typically pool measurements from diverse environments, against gene expression profiles that have been measured under specific conditions of interest. Using CoFP, we predict condition-specific subcellular locations, biological processes, and molecular functions of the yeast proteome under 18 specified conditions. In addition to highly accurate retrieval of previously known gold standard protein locations and functions, CoFP predicts previously unidentified condition-dependent locations and functions for nearly all yeast proteins. Many of these predictions can be confirmed using high-resolution cellular imaging. We show that, under DNA-damaging conditions, Tsr1, Caf120, Dip5, Skg6, Lte1, and Nnf2 change subcellular location and RNA polymerase I subunit A43, Ino2, and Ids2 show changes in DNA binding. Beyond specific predictions, this work reveals a global landscape of changing protein location and function, highlighting a surprising number of proteins that translocate from the mitochondria to the nucleus or from endoplasmic reticulum to Golgi apparatus under stress.

Urine haptoglobin levels predict early renal functional decline in patients with type 2 diabetes

Diabetic nephropathy is the leading cause of end-stage renal disease. The urinary albumin to creatinine ratio is used as a predictor for the development of nephropathy but it is neither sensitive nor specific. Here we used liquid chromatography/mass spectrometry on urine of eight normoalbuminuric patients with type 2 diabetes from the VA Diabetes Trial to identify candidate markers for loss of renal function. Initial verification of seven markers (agrin, haptoglobin, mannan-binding lectin serine protease 2, LAMP-2, angiotensinogen, NGAL, and uromodulin) in the urine of an additional 30 patients showed that haptoglobin was the best predictor of early renal functional decline. We then measured this in the urine of 204 patients with type 2 diabetes who did not yet have significant kidney disease (estimated glomerular filtration rate stage 2 or better and an albumin to creatinine ratio <300 mg/g). In comparing the highest to lowest tertiles, the odds ratio for having early renal function decline was 2.70 (CI: 1.15, 6.32) using the haptoglobin to creatinine ratio compared with 2.50 (CI 1.14, 5.48) using the albumin to creatinine ratio after adjusting for treatment group and use of ACE inhibitors. Addition of the haptoglobin to creatinine ratio to a model using the albumin to creatinine ratio to predict early renal function decline resulted in improved predictive performance. Thus, the haptoglobin to creatinine ratio may be useful to predict patients with type 2 diabetes at risk of nephropathy before the development of macroalbuminuria or reduced glomerular filtration rate.

Serum levels of the adipokine progranulin depend on renal function

OBJECTIVE

Progranulin has recently been introduced as a novel adipokine inducing insulin resistance and obesity. In the current study, we investigated renal elimination, as well as association of the adipokine with markers of the metabolic syndrome.

RESEARCH DESIGN AND METHODS

Progranulin serum levels were quantified by enzyme-linked immunosorbent assay and correlated to anthropometric and biochemical parameters of renal function and glucose and lipid metabolism, as well as inflammation, in 532 patients with stages 1-5 of chronic kidney disease (CKD).

RESULTS

Median serum progranulin levels adjusted for age, sex, and BMI were significantly different between CKD stages with highest values detectable in stage 5 (stage 1, 58.3 µg/L; stage 2, 63.0 µg/L; stage 3, 65.4 µg/L; stage 4, 68.8 µg/L; and stage 5, 90.6 µg/L). Furthermore, CKD stage was the strongest independent predictor of circulating progranulin in our cohort. In addition, high-sensitivity interleukin-6 and adiponectin remained significantly and independently correlated with the adipokine.

CONCLUSIONS

We demonstrate that progranulin serum levels increase with deteriorating renal function. These findings are in accordance with the hypothesis that renal clearance is a major elimination route for circulating progranulin. Furthermore, the adipokine is positively and independently associated with markers of inflammation and adiponectin.