Urinary serum- and glucocorticoid-inducible kinase SGK1 reflects renal injury in patients with immunoglobulin A nephropathy.

AIM: Serum- and glucocorticoid-inducible kinase SGK1 functions as an important regulator of transepithelial sodium transport by activating epithelial sodium channel in renal tubules. Considerable evidence demonstrated that SGK1 was associated with hypertension and fibrosing diseases, such as diabetic nephropathy and glomerulonephritis. The present study was performed to evaluate the role of SGK1 played in immunoglobulin A (IgA) nephropathy. METHODS: Seventy-six patients of biopsy-proven IgA nephropathy and 33 healthy volunteers were enrolled in this study. All patients and healthy volunteers' urinary and serum samples were tested for SGK1 expression by indirect enzyme-linked immunosorbent assay. Meanwhile all patients' renal tissues were semi-quantified for SGK1 expression by immunohistochemistry assay. The relationships between SGK1 expressions and clinical or pathological parameters were also assessed. RESULTS: SGK1 expression was upregulated in urine and renal tubules in patients of Oxford classification T1 and T2, whereas its expression in serum did not increase significantly. Relationship analysis indicated that urinary and tissue SGK1 expressions were associated with heavy proteinuria and renal insufficiency in patients with IgA nephropathy. On the other hand, RAS blockades would reduce the SGK1 levels both in urine and renal tissues. CONCLUSION: These results suggested that urinary SGK1 should be a good indicator of tubulointerstitial damage in patients of IgA nephropathy. SGK1 expressions in urine and renal tissues were associated with the activity of renin-angiotensin-aldosterone system.

A novel accurate rapid ELISA for detection of urinary connective tissue growth factor, a biomarker of chronic allograft nephropathy.

BACKGROUND: Chronic allograft nephropathy (CAN) is a leading cause of kidney graft failure. The latest evidence suggests that connective tissue growth factor (CTGF) may be a biomarker of CAN. Detection of urinary CTGF levels is a potential noninvasive strategy to predict the early onset of CAN. Compared to the traditional "sandwich" enzyme-linked immunosorbent assay (ELISA), we established a novel, accurate, faster, one-step competitive indirect ELISA (Ci-ELISA) to estimate the urinary CTGF concentrations in humans, rats, and mice. MATERIALS AND METHODS: We used recombinant human CTGF, which is an 11.2 kDa protein of 98 amino acid residues containing the C-terminal portion of the full-length CTGF protein having 96% and 94% homology with rats and mice, as the coating antigen and standard competitor. We then applied polyclonal antibody against the CTGF C-terminal portion, secondary antibody conjugated with horseradish peroxidase (HRP), and urine samples to establish one-step Ci-ELISA. Rat kidney allograft recipients were sacrificed at 4, 8, or 12 weeks posttransplantation. We harvested serum, urine, and transplanted kidneys. Hematoxylin-eosin (H&E), periodic acid-Schiff (PAS), and Masson trichrome stains were used to estimate the histopathologic changes according to the Banff schema. Serum creatinine (SCr) levels were measured to represent renal function. CTGF in kidney was detected by immunohistochemistry. Urinary CTGF concentrations were measured using the one-step Ci-ELISA. RESULTS: The whole one-step Ci-ELISA test can be accomplished within 2 hours. The detection limit of the assay was 0.16 ng/mL CTGF. The time-dependent elevated recipient concentration of urinary CTGF was positively correlated with SCr, histologic changes, and CTGF in the kidney after transplantation. The 95% confidence intervals of urinary CTGF concentrations in control rats were 24.4 to 35.2 ng/mL; at 4, 8, and 12 weeks posttransplantation they were 139.4 to 395.6, 826.7 to 1429.5, and 3206.0 to 4448.2 ng/mL, respectively. CONCLUSIONS: A rapid one-step Ci-ELISA was successfully established to detect the CTGF levels in urine. These results further indicated that detection of urinary CTGF is a potential noninvasive strategy to predict the early onset of CAN.

Connective tissue growth factor and susceptibility to renal and vascular disease risk in type 1 diabetes.

OBJECTIVE: We explored the relevance and significance of connective tissue growth factor (CTGF) as a determinant of renal and vascular complications among type 1 diabetic patients. METHODS AND RESULTS: We measured the circulating and urinary levels of CTGF and CTGF N fragment in 1050 subjects with type 1 diabetes from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) Study cohort. We found that hypertensive diabetic subjects have significantly higher levels of plasma log CTGF N fragment relative to normotensive subjects (P = 0.0005). Multiple regression analysis showed a positive and independent association between CTGF N fragment levels and log albumin excretion rate (P < 0.0001). In categorical analysis, patients with macroalbuminuria had higher levels of CTGF N fragment than diabetic subjects with or without microalbuminuria (P < 0.0001). Univariate and multiple regression analyses demonstrated an independent and significant association of log CTGF N fragment with the common and internal carotid intima-media thickness. The relative risk for increased carotid intima-media thickness was higher in patients with concomitantly elevated plasma CTGF N fragment and macroalbuminuria relative to patients with normal plasma CTGF N fragment and normal albuminuria (relative risk = 4.76; 95% confidence interval, 2.21-10.25; P < 0.0001). CONCLUSION: These findings demonstrate that plasma CTGF is a risk marker of diabetic renal and vascular disease.

Urinary connective tissue growth factor excretion correlates with clinical markers of renal disease in a large population of type 1 diabetic patients with diabetic nephropathy.

OBJECTIVE: Levels of connective tissue growth factor (CTGF; CCN-2) in plasma are increased in various fibrotic disorders, including diabetic nephropathy. Recently, several articles have reported a strong increase of urinary CTGF excretion (U-CTGF) in patients with diabetic nephropathy. However, these studies addressed too small a number of patients to allow general conclusions to be drawn. Therefore, we evaluated U-CTGF in a large cross-sectional study of patients with type 1 diabetes. RESEARCH DESIGN AND METHODS: Subjects were 318 type 1 diabetic patients and 29 normoglycemic control subjects. U-CTGF was measured by sandwich enzyme-linked immunosorbent assay. Groups were compared by Kruskal-Wallis and Mann-Whitney analysis. The relation between U-CTGF and markers of diabetic nephropathy was determined by regression analysis. RESULTS: U-CTGF in patients with diabetic nephropathy (n = 89, median 155 pmol/24 h [interquartile range 96-258]) was significantly higher than in microalbuminuric (n = 79, 100 [65-78]) and normoalbuminuric (n = 150, 85 [48-127]) patients and control subjects (n = 29, 100 [78-114]). U-CTGF correlated with urinary albumin excretion (UAE) (R = 0.31) and glomerular filtration rate (R = -0.38) in patients with diabetic nephropathy. A standardized increase in U-CTGF was associated with diabetic nephropathy (odds ratio 2.3 [95% CI 1.7-3.1]), which was comparable with the odds ratios for diabetic nephropathy of increased HbA(1c) (2.0 [1.5-2.7]), and blood pressure (2.0 [1.5-2.6]). CONCLUSIONS: This is the first large cross-sectional study addressing U-CTGF in human type 1 diabetes. The observed association of U-CTGF with UAE and glomerular filtration rate might reflect a role of CTGF as progression promoter in diabetic nephropathy.

Reduction of urinary connective tissue growth factor by Losartan in type 1 patients with diabetic nephropathy.

BACKGROUND: Connective tissue growth factor (CTGF) is an important profibrotic cytokine implicated in development of diabetic glomerulosclerosis. Urinary CTGF is reported to be significantly increased in patients with diabetic nephropathy. The present study aimed to investigate the short- and long term effects of angiotensin II receptor blockade by Losartan on urinary CTGF levels in hypertensive type 1 diabetic patients with diabetic nephropathy. METHODS: Seventy-one hypertensive type 1 diabetic patients with diabetic nephropathy were included in the study. After a washout period of 4 weeks, the patients received Losartan 50 mg, 100 mg, and 150 mg once daily in treatment periods each lasting 2 months. Thereafter, patients were followed prospectively during treatment with Losartan 100 mg o.d. with a total mean follow-up time of 36 months. At baseline, after 2, 4, and 6 months and then biannually, urinary and plasma CTGF levels [enzyme linked immunosorbent assay (ELISA) fibroGen], albuminuria (Turbidimetry), glomerular filtration rate (GFR) [51-creatinine ethylenediaminetetraacetic acid ((51)Cr-EDTA plasma clearance)] and 24 hours blood pressure (TM2420)) were determined. RESULTS: Baseline levels of urinary and plasma CTGF were 7076 (5708 to 8770) ng/24 hours [geometric mean (95% CI)] and 12.7 (7.3) ng/mL [mean (SD)], respectively. Albuminuria, GFR, and arterial blood pressure at baseline were 1152 (937 to 1416) mg/24 hours, 88 (24) mL/min/1.73 m(2), and 153/80 (17/9) mm Hg, respectively. Losartan significantly reduced urinary CTGF by 21% (9 to 31) (95% CI) initially (P < 0.05 vs. baseline), with no further reduction after increasing dose. The sustained reduction in urinary CTGF was 22% (12 to 32) (P < 0.05 vs. baseline). Rate of decline in GFR during the study was 3.2 (-1.6 to 15.9) mL/min/year [median (range)]. Reduction in urinary CTGF was correlated with a lower rate of decline in GFR (r= 0.23, P= 0.05). Plasma CTGF remained unchanged throughout the study. CONCLUSION: Our 3-year study demonstrates that Losartan persistently reduces urinary CTGF excretion, which is associated with a slower rate of decline in GFR.

Biologic markers for the early detection of acute kidney injury.

PURPOSE OF REVIEW: This review discusses the current status of several biomarkers as potential diagnostic tools in patients with acute kidney disease. RECENT FINDINGS: Although the term "acute renal failure" has generally been used to describe acute kidney dysfunction that runs the spectrum from mild prerenal azotemia with no renal pathologic changes and no functional failure to severe oliguric renal dysfunction associated with tubular necrosis with failure of function, this spectrum is better described by the term "acute kidney injury." The mortality rate of hospitalized patients with severe acute kidney disease has not decreased significantly over the past 50 years despite advances in supportive care. The absence of sensitive and specific biomarkers for detecting injury early, grading the severity of the injury, and monitoring the response to therapy has impaired progress in the field and has had a very detrimental effect on the design and outcome of clinical trials in acute kidney disease. As a result of reliance on serum creatinine as a marker for injury and diagnosis, the institution of therapy is markedly delayed. SUMMARY: The search for new biomarkers for acute kidney injury is evolving rapidly with advancement in modern technologies. With better biomarkers we will have the ability to detect injury earlier, identify subclinical injury, provide prognostic information on the course of renal impairment, identify the nephron segments most affected, provide a rationale for segmentation of patients for clinical studies, guide timing of therapy, assess response to therapy, and screen patients at risk for renal injury.

Urinary CCN2 (CTGF) as a possible predictor of diabetic nephropathy: preliminary report.

BACKGROUND: It is currently impossible to reliably predict which diabetic patients will develop nephropathy and progress to kidney failure. Microalbuminuria, often regarded as a predictor of overt diabetic renal disease is, in fact, an indicator of established glomerular damage. We have shown that glomerular expression of the prosclerotic cytokine CCN2 (CTGF) is greatly up-regulated early in experimental and in human diabetes and mesangial cell exposure to CCN2 increases its production of extracellular matrix (ECM) molecules responsible for glomerulosclerosis. As an early marker, we therefore investigated the presence of CCN2 in urine and the relationship to diabetes and/or renal disease in an experimental model of diabetes and in a limited patient population. METHODS: Urine samples from (1) healthy rats, (2) rats made diabetic by streptozotocin (STZ), (3) healthy human volunteers, (4) diabetic patients with renal disease, and (5) diabetic patients without renal disease were examined by Western blotting and/or enzyme-linked immunosorbent assay (ELISA) for qualitative and quantitative analysis of the of CCN2. RESULTS: Low levels of urinary CCN2 were present in healthy, control rats, but were increased approximately sevenfold overall in STZ-diabetic animals. CCN2 levels were the highest at week 3 of diabetes, then decreased with time, but remained significantly elevated over controls even after 32 weeks. Consistently low levels of urinary CCN2 were also detected in healthy volunteers (mean value, 7.1 CCN2/mg creatinine). However, levels were elevated approximately sixfold in the majority of diabetic patients with nephropathy. A small number of the diabetic patients not yet exhibiting evidence of renal involvement demonstrated CCN2 urinary levels that were ninefold greater than controls. The remaining normoalbuminuric diabetic patients demonstrated CCN2 levels indistinguishable from those of healthy volunteers. Analysis by Western blotting confirmed the identity of the urinary CCN2. A molecular species equivalent to full-length CCN2 (37/39 kD doublet) was present in healthy controls. In contrast, the nephropathic group demonstrated multiple CCN2 bands. CONCLUSION: These findings support our hypothesis that CCN2 is up-regulated early in the evolution of glomerulosclerosis, including that of diabetes. We contend that urinary CCN2 may both stage nephropathy and predict those patients who are destined for progressive glomerulosclerosis and end-stage renal disease (ESRD). Cross-sectional and prospective studies of larger, well-defined diabetic patients groups will be required to prove this hypothesis, and are ongoing.

Early detection of cysteine rich protein 61 (CYR61, CCN1) in urine following renal ischemic reperfusion injury.

BACKGROUND: Acute renal failure (ARF) has a high morbidity and mortality. Many therapies have worked in animals but were unsuccessful in clinical trials. The inability to diagnose ARF early may have impaired the success of these trials. METHOD: We screened a subtraction library to search for potential disease markers that would be induced rapidly after renal injury. Mice and rats were subjected to 30 to 40 minutes of bilateral ischemia. RESULTS: mRNA for Cyr61, a secreted growth factor-inducible immediate early gene, was markedly up-regulated at two hours in the kidney but not other organs following renal ischemia. In situ hybridization studies suggested Cyr61 was synthesized in the proximal straight tubule. Cyr61 protein was analyzed by capture with heparin beads followed by Western blotting. Induction of Cyr61 protein could be detected in the kidney within one hour, peaked at four to eight hours, and remained elevated for at least 24 hours following ischemia. Cyr61 protein was detected in urine at three to six hours and peaked at six to nine hours after renal injury. Cyr61 was not detected after volume depletion, which is often difficult to differentiate from ARF. CONCLUSIONS: The secreted, cysteine-rich, heparin binding protein Cyr61 is rapidly induced in proximal straight tubules following renal ischemia, and excreted in the urine where it might serve as an early biomarker of renal injury.

Proteínas urinárias de baixo peso molecular como biomarcadores de efeitos nefrotóxicos precoces: ß²-microglobulina (ß²-m) e proteína transportadora do retinol (RBP) / Urinary protein as early biomarkers of nephrotocity: ß²-microglobulin, retinol-binding protein

Uma das características dos rins é a habilidade em compensar os eventuais danos renais provocados por xenobióticos, de modo que os testes clássicos de função renal se mostram inadequados para detectar precocemente as alterações orgânicas, uma vez que são pouco sensíveis, apresentando-se alterados, apenas tardiamente.A prevenção e o dignóstico precoce de alterações tóxicas renais causadas por xenobióticos presentes no meio ocupacional ou ambiental só é possível através do uso de parâmetros bioquímicos que revelam alterações, em suas fases iniciais, denominados biomarcadores precoces de nofrotoxidade. Um dos parâmetros que pode estar alterado desde o início de uma ação tóxica ao niível renal é a proteinúria. O uso de proteínas urinárias específicas como biomarcadores de nefrotoxidade, com especial arenção à utilização da ß²-microglobulina e da proteína transportadora do retinol, são enfocados no presente trabalho