Nephrotic range proteinuria as a strong risk factor for rapid renal function decline during pre-dialysis phase in type 2 diabetic patients with severely impaired renal function.

BACKGROUND: Proteinuria is an established risk factor for progression of renal disease, including diabetic nephropathy. The predictive power of proteinuria, especially nephrotic range proteinuria, for progressive renal deterioration has been well demonstrated in diabetic patients with normal to relatively preserved renal function. However, little is known about the relationship between severity of proteinuria and renal outcome in pre-dialysis diabetic patients with severely impaired renal function. METHODS: 125 incident dialysis patients with type 2 diabetes were identified. This study was aimed at retrospectively evaluating the impact of nephrotic range proteinuria (urinary protein-creatinine ratio above 3.5 g/gCr) on renal function decline during the 3 months just prior to dialysis initiation. RESULTS: In total, 103 patients (82.4 %) had nephrotic range proteinuria. The median rate of decline in estimated glomerular filtration rate (eGFR) in this study population was 0.98 (interquartile range 0.51-1.46) ml/min/1.73 m(2) per month. Compared to patients without nephrotic range proteinuria, patients with nephrotic range proteinuria showed significantly faster renal function decline (0.46 [0.24-1.25] versus 1.07 [0.64-1.54] ml/min/1.73 m(2) per month; p = 0.007). After adjusting for gender, age, systolic blood pressure, serum albumin, calcium-phosphorus product, hemoglobin A1c, and use of an angiotensin-converting enzyme inhibitor or an angiotensin II receptor blocker, patients with nephrotic range proteinuria showed a 3.89-fold (95 % CI 1.08-14.5) increased risk for rapid renal function decline defined as a decline in eGFR ≥0.5 ml/min/1.73 m(2) per month. CONCLUSION: Nephrotic range proteinuria is the predominant renal risk factor in type 2 diabetic patients with severely impaired renal function receiving pre-dialysis care.

[Case of a focal segmental glomerulosclerosis collapsing variant associated with a hypertrophic column of Bertin].

A 59-year-old Japanese man admitted to our hospital complaining of anasarca, body weight gain, and elevation of blood pressure. Serum creatinine(Cre), albumin(Alb), cholesterol(chol), and urinary protein were 1.3 mg/dL, 2.5 g/dL, 527 mg/dL, and 10 g/gCr, respectively. An abdominal echography showed a renal mass, which was diagnosed to be a hypertrophic column of Bertin by enhanced CT. His serum Cre and Alb had worsened to 1.6 mg/dL and 1.7 g/dL, respectively, and a renal biopsy was performed. The results showed a segmental sclerotic lesion associated with hypertrophy and proliferation of podocytes in several glomeruli, hence we diagnosed a focal segmental glomerulosclerosis collapsing variant. After steroid pulse therapy and LDL apheresis, his serum Cre level had decreased to 1.1 mg/dL and the urinary protein level to 2.5 g/gCr. Patients with a focal segmental glomerulosclerosis collapsing variant are poor responders to standard therapies, and have a very poor prognosis. For this case, combined steroid pulse and LDL apheresis therapy was effective.

[Case of lupus vasculopathy associated with lupus nephritis class IV-G (A)].

Various renal vascular lesions are complicated with systemic lupus erythematosus (SLE), and are often overlooked in the actual renal biopsy specimen. We report a case of biopsy-proven lupus vasculopathy, with lupus nephritis class IV-G (A). She developed SLE at 15 years of age, and was treated with prednisolone(PSL) and cyclophosphamide (CTX). Sometimes she experienced a flare-up clinically or serologically, requiring a dose increase of oral PSL. At 40 years of age, she visited our hospital after discontinuation of hospital visits for about 4 months. Oral PSL at 30 mg per day was not effective for urinary abnormalities, increase of anti double-stranded DNA (ds-DNA) antibody titer and decrease in complement components. On admission she had hypertension (180/92 mmHg) and signs of microangiopathic hemolytic anemia. Renal biopsy findings showed the glomerular changes of lupus nephritis, WHO class IV-G (A), and lupus vasculopathy, which is marked luminal narrowing or total occlusion by abundant subendothelial accumulation of immunoglobulins and complement components. In addition to PSL, intravenous pulse CTX promptly achieved clinical remission. When lupus vasculopathy is complicated, CTX may be useful.

Amino terminal cleavage of PTH(1-84) to PTH(7-84) is regulated by serum calcium concentration via calcium-sensing receptor in hemodialysis patients.

BACKGROUND: Secondary hyperparathyroidism is one of the critical complications of end-stage renal disease patients. Conventionally intact parathyroid hormone (iPTH) was used to assess secondary hyperparathyroidism, but this assay measures both PTH(1-84) (full-length parathyroid hormone) and PTH(7-84) (amino (N)-terminal-cleaved parathyroid hormone). PTH(7-84) is biologically inactive or antagonistic for PTH. In this study, we examined the relationship between serum calcium concentration and PTH(7-84)/PTH(1-84) ratio and the effect of calcimimetics on the ratio in hemodialysis (HD) patients. METHODS: Ionized-calcium (iCa), iPTH, and whole PTH (wPTH) were measured at the start of HD sessions on HD patients. Patients were divided into four groups by presence (+) or absence (-) of vitamin D (VD) and calcimimetics (CM). RESULT: PTH(7-84)/PTH(1-84) ratios of the four groups [VD(-)CM(-), VD(+)CM(-), VD(-)CM(+) and VD(+)CM(+)] were 0.735, 0.799, 0.844, and 1.156, respectively. In VD(-)CM(-) and VD(+)CM(-) groups, iCa and PTH(7-84)/PTH(1-84) ratio showed equilateral correlation (r = 0.634, p < 0.001 and r = 0.360, p < 0.01, respectively). In calcimimetics-treated group, iCa and PTH(7-84)/PTH(1-84) ratio did not show correlation. CONCLUSION: Whereas in the absence of calcimimetics cleavage of N-terminal PTH was regulated by serum calcium concentration, this regulation was abolished in the presence of calcimimetics. This suggests that cleavage of N-terminal PTH is regulated by calcium concentration via a calcium-sensing receptor and that calcimimetics may have a novel effect to reduce PTH level.

[Comparison between serum cystatin C and estimation of GFR by the MDRD study equation for chronic kidney disease].

Glomerular filtration rate(GFR) can be estimated from serum (s-) creatinine using the modification of diet in renal disease (MDRD). However, its calculation is sometimes cumbersome in clinical use. Cystatin C is less influenced by age, gender and muscle mass than serum creatinine, and it has been proposed as an alternative marker for estimating GFR (eGFR). The comparison of s-cystatin C with MDRD-eGFR from 245 Japanese outpatients with chronic kidney disease (CKD)resulted in the equation of eGFR = 82.8/s-cystatin C - 10.7 (r = 0.85, n = 245). Based on this equation, there were 22 patients above + SD, which was the high-group in which s-cystatin C levels were higher than the corresponding eGFR, and there were 21 patients below -SD, which was the low-group in which s-cystatin C levels were lower than the corresponding eGER. Between the two groups there was no significant difference in age, gender, weight, and body mass index. The high-group included 1 case of hyperthyroidism and 7 cases of steroid user. The low-group included 4 cases of hypothyroidism and 1 case of steroid user. In healthy individuals, MDRD-eGFR is unsuitable for estimating GFR. Thyroid dysfunction or glucocorticoid excess are known to influence s-cystatin C levels. An improved eGFR equation was provided from 144 cases excluding 88 with normal renal function (eGFR > 90 mL/min/1.73 m2), 5 with thyroid dysfunction and 8 steroid users. eGFR = 86.1/s-cystatin C - 13.6 (r = 0.94, n = 144). Each GFR estimation provided from males or from females yielded nearly the same results as this equation. The prediction of eGFR using s-cystatin C may be convenient and useful in clinical practice, and the comparison of s-cystatin C with creatinine-based eGFR may reveal some factors that affect s-cystatin C or s-creatinine levels independent of GFR.

Expression of CCN1 (CYR61) in developing, normal, and diseased human kidney.

CCN1 (cysteine-rich protein 61; Cyr61) is an extracellular matrix-associated signaling molecule that functions in cell migration, adhesion, and differentiation. We previously reported that CCN1 is induced at podocytes in rat anti-Thy-1 glomerulonephritis, a well-known model of reversible glomerular injury, but its expression and significance in the human kidney remain totally unknown (Sawai K, Mori K, Mukoyama M, Sugawara A, Suganami T, Koshikawa M, Yahata K, Makino H, Nagae T, Fujinaga Y, Yokoi H, Yoshioka T, Yoshimoto A, Tanaka I, Nakao K. J Am Soc Nephrol 14: 1154-1163, 2003). Here we report that, in the human kidney, CCN1 expression was confined to podocytes in normal adult and embryonic glomeruli from the capillary loop stage. Podocyte CCN1 expression was decreased in IgA nephropathy, diabetic nephropathy, and membranous nephropathy, whereas it remained unchanged in minimal change disease and focal segmental glomerulosclerosis. Downregulation of CCN1 was significantly greater in diseased kidneys with severe mesangial expansion. CCN1 protein was also localized in the thick ascending limb of Henle's loop, distal and proximal tubules, and collecting ducts, which was not altered in diseased kidneys. In vitro, recombinant CCN1 protein enhanced endothelial cell adhesion, whereas it prominently inhibited mesangial cell adhesion. CCN1 also completely suppressed mesangial cell migration, suggesting its role as a mesangial-repellent factor. In cultured podocytes, CCN1 markedly induced the expression of cyclin-dependent kinase inhibitor p27(Kip1) as well as synaptopodin in a dose-dependent manner and suppressed podocyte migration. These data indicate that CCN1 is expressed in podocytes, can act on glomerular cells to modulate glomerular remodeling, and is downregulated in diseased kidneys, suggesting that impairment of CCN1 expression in podocytes may contribute to the progression of glomerular disease with mesangial expansion.

Redistribution of connexin43 expression in glomerular podocytes predicts poor renal prognosis in patients with type 2 diabetes and overt nephropathy.

BACKGROUND: Significance of podocyte injury in the progression of diabetic nephropathy is not well-understood. In this study, we examined whether alteration of gap junction protein connexin43 (Cx43) expression in podocytes is associated with the progression of overt diabetic nephropathy. METHODS: We recruited 29 type 2 diabetic patients with overt nephropathy who underwent renal biopsy. Nephrectomized kidney samples obtained from seven subjects with localized neoplasm and biopsy specimens from five patients diagnosed as minor glomerular abnormalities were used as controls. Cx43 staining on paraffin-embedded kidney sections were studied by immunohistochemistry. RESULTS: In controls, Cx43 was expressed at podocytes in a linear pattern along the glomerular basement membrane. In contrast, downregulation and loss of uniformly linear staining of Cx43 (Cx43 heterogeneity) in podocytes were observed in diabetic nephropathy. Cx43 intensity correlated with current renal function (R = 0.647, P < 0.005), whereas the magnitude of Cx43 heterogeneity correlated well with the degree of future decline in renal function (R = -0.705, P < 0.001). CONCLUSIONS: Alteration of Cx43 expression in podocytes was closely associated with the progression of overt diabetic nephropathy. These results indicate that change in Cx43 expression at podocytes represents a progressive stage in overt diabetic nephropathy and that it may be a convenient way to predict future decline in renal function.

Role of p38 mitogen-activated protein kinase activation in podocyte injury and proteinuria in experimental nephrotic syndrome.

Podocytes play an important role in maintaining normal glomerular function and structure, and podocyte injury leads to proteinuria and glomerulosclerosis. The family of mitogen-activated protein kinases (MAPK; extracellular signal-regulated kinase [ERK], c-Jun N-terminal kinase, and p38) may be implicated in the progression of various glomerulopathies, but the role of MAPK in podocyte injury remains elusive. This study examined phosphorylation of p38 MAPK in clinical glomerulopathies with podocyte injury, as well as in rat puromycin aminonucleoside (PAN) nephropathy and mouse adriamycin (ADR) nephropathy. The effect of treatment with FR167653, an inhibitor of p38 MAPK, was also investigated in rodent models. In human podocyte injury diseases, the increased phosphorylation of p38 MAPK was observed at podocytes. In PAN and ADR nephropathy, the phosphorylation of p38 MAPK and ERK was marked but transient, preceding overt proteinuria. Pretreatment with FR167653 (day -2 to day 14, subcutaneously) to PAN or ADR nephropathy completely inhibited p38 MAPK activation and attenuated ERK phosphorylation, with complete suppression of proteinuria. Electron microscopy and immunohistochemistry for nephrin and connexin43 revealed that podocyte injury was markedly ameliorated by FR167653. Furthermore, early treatment with FR167653 effectively prevented glomerulosclerosis and renal dysfunction in the chronic phase of ADR nephropathy. In cultured podocytes, PAN or oxidative stress induced the phosphorylation of p38 MAPK along with actin reorganization, and FR167653 inhibited such changes. These findings indicate that the activation of MAPK is necessary for podocyte injury, suggesting that p38 MAPK and, possibly, ERK should become a potential target for therapeutic intervention in proteinuric glomerulopathies.

Prevention and reversal of renal injury by leptin in a new mouse model of diabetic nephropathy.

Diabetic nephropathy is the leading cause of end-stage renal disease, for which effective therapy to prevent the progression at advanced stages remains to be established. There is also a long debate whether diabetic glomerular injury is reversible or not. Lipoatrophic diabetes, a syndrome caused by paucity of adipose tissue, is characterized by severe insulin resistance, dyslipidemia, and fatty liver. Here, we show that a genetic model of lipoatrophic diabetes (A-ZIP/F-1 mice) manifests a typical renal injury observed in human diabetic nephropathy that is associated with glomerular hypertrophy, diffuse and pronounced mesangial widening, accumulation of extracellular matrix proteins, podocyte damage, and overt proteinuria. By crossing A-ZIP/F-1 mice with transgenic mice overexpressing an adipocyte-derived hormone leptin, we also reveal that leptin completely prevents the development of hyperglycemia and nephropathy in A-ZIP/F-1 mice. Furthermore, continuous leptin administration to A-ZIP/F-1 mice by minipump beginning at 40 weeks of age significantly alleviates the glomerular injury and proteinuria. These findings demonstrate the therapeutic usefulness of leptin at least for a certain type of diabetic nephropathy. The model presented here will serve as a novel tool to analyze the molecular mechanism underlying not only the progression but also the regression of diabetic nephropathy.

Reduction in connective tissue growth factor by antisense treatment ameliorates renal tubulointerstitial fibrosis.

Connective tissue growth factor (CTGF/CCN2) is one of the candidate factors mediating fibrogenic activity of TGF-beta. It was shown previously that the blockade of CTGF by antisense oligonucleotide (ODN) inhibits TGF-beta-induced production of fibronectin and type I collagen in cultured renal fibroblasts. The in vivo contribution of CTGF in renal interstitial fibrosis, however, remains to be clarified. With the use of a hydrodynamics-based gene transfer technique, the effects of CTGF antisense ODN are investigated in rat kidneys with unilateral ureteral obstruction (UUO). FITC-labeled ODN injection via the renal vein showed that the ODN was specifically introduced into the interstitium. At day 7 after UUO, the gene expression of CTGF, fibronectin, fibronectin ED-A, and alpha1(I) collagen in untreated or control ODN-treated obstructed kidneys was prominently upregulated. CTGF antisense ODN treatment, by contrast, markedly attenuated the induction of CTGF, fibronectin, fibronectin ED-A, and alpha1(I) collagen genes, whereas TGF-beta gene upregulation was not affected. The antisense treatment also reduced interstitial deposition of CTGF, fibronectin ED-A, and type I collagen and the interstitial fibrotic areas. The number of myofibroblasts determined by the expression of alpha-smooth muscle actin was significantly decreased as well. Proliferation of tubular and interstitial cells was not altered with the treatment. These findings indicate that CTGF expression in the interstitium plays a crucial role in the progression of interstitial fibrosis but not in the proliferation of tubular and interstitial cells during UUO. CTGF may become a potential therapeutic target against tubulointerstitial fibrosis.

Angiogenic protein Cyr61 is expressed by podocytes in anti-Thy-1 glomerulonephritis.

Dynamic recovery of glomerular structure occurs after severe glomerular damage in anti-Thy-1 glomerulonephritis (Thy-1 GN), but its mechanism remains to be investigated. To identify candidate genes possibly involved in glomerular reconstruction, screening was performed for genes that are specifically expressed by podocytes and are upregulated in glomeruli of Thy-1 GN. Among them, cysteine-rich protein 61 (Cyr61 or CCN1), a soluble angiogenic protein belonging to the CCN family, was identified. By Northern blot analysis, Cyr61 mRNA was markedly upregulated in glomeruli of Thy-1 GN from day 3 through day 7, when mesangial cell migration was most prominent. By in situ hybridization and immunohistochemistry, Cyr61 mRNA and protein were expressed by proximal straight tubules and afferent and efferent arterioles in normal rat kidneys and were intensely upregulated at podocytes in Thy-1 GN. Platelet-derived growth factor-BB (PDGF-BB) and transforming growth factor-beta1 (TGF-beta1), of which the gene expression in the glomeruli of Thy-1 GN was upregulated in similar time course as Cyr61, induced Cyr61 mRNA expression in cultured podocytes. Furthermore, supernatant of Cyr61-overexpressing cells inhibited PDGF-induced mesangial cell migration. In conclusion, it is shown that Cyr61 is strongly upregulated at podocytes in Thy-1 GN possibly by PDGF and TGF-beta. Cyr61 may be involved in glomerular remodeling as a factor secreted from podocytes to inhibit mesangial cell migration.