Effects of Reducing L-Carnitine Supplementation on Carnitine Kinetics and Cardiac Function in Hemodialysis Patients: A Multicenter, Single-Blind, Placebo-Controlled, Randomized Clinical Trial.

L-carnitine (LC) supplementation improves cardiac function in hemodialysis (HD) patients. However, whether reducing LC supplementation affects carnitine kinetics and cardiac function in HD patients treated with LC remains unclear. Fifty-nine HD patients previously treated with intravenous LC 1000 mg per HD session (three times weekly) were allocated to three groups: LC injection three times weekly, once weekly, and placebo, and prospectively followed up for six months. Carnitine fractions were assessed by enzyme cycling methods. Plasma and red blood cell (RBC) acylcarnitines were profiled using tandem mass spectrometry. Cardiac function was evaluated using echocardiography and plasma B-type natriuretic peptide (BNP) levels. Reducing LC administration to once weekly significantly decreased plasma carnitine fractions and RBC-free carnitine levels during the study period, which were further decreased in the placebo group (p < 0.001). Plasma BNP levels were significantly elevated in the placebo group (p = 0.03). Furthermore, changes in RBC (C16 + C18:1)/C2 acylcarnitine ratio were positively correlated with changes in plasma BNP levels (ß = 0.389, p = 0.005). Reducing LC administration for six months significantly decreased both plasma and RBC carnitine levels, while the full termination of LC increased plasma BNP levels; however, it did not influence cardiac function in HD patients.

Asymmetric dimethylarginine accumulates in the kidney during ischemia/reperfusion injury.

Ischemia/reperfusion injury is the leading cause of acute tubular necrosis. Nitric oxide has a protective role against ischemia/reperfusion injury; however, the role of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, in ischemia/reperfusion injury remains unclear. ADMA is produced by protein arginine methyltransferase (PRMT) and is mainly degraded by dimethylarginine dimethylaminohydrolase (DDAH). Here we examined the kinetics of ADMA and PRMT and DDAH expression in the kidneys of ischemia/reperfusion-injured mice. After the injury, DDAH-1 levels were decreased and renal and plasma ADMA values were increased in association with renal dysfunction. Renal ADMA was correlated with 8-hydroxy-2'-deoxyguanosine, a marker of oxidative stress. An antioxidant, N-acetylcysteine, or a proteasomal inhibitor, MG-132, restored these alterations. Infusion of subpressor dose of ADMA exacerbated renal dysfunction, capillary loss, and tubular necrosis in the kidneys of ischemia/reperfusion-injured wild mice, while damage was attenuated in DDAH transgenic mice. Thus, ischemia/reperfusion injury-induced oxidative stress may reduce DDAH expression and cause ADMA accumulation, which may contribute to capillary loss and tubular necrosis in the kidney.

Experimental diabetic nephropathy is accelerated in matrix metalloproteinase-2 knockout mice.

BACKGROUND: Matrix metalloproteinase-2 (MMP-2) is responsible for the degradation of various types of extracellular matrix (ECM) proteins such as type IV collagen. Decreased MMP-2 expression and activity has been generally thought to contribute to increased accumulation of ECM at the advanced stage of diabetic nephropathy. However, the kinetics and role of MMP-2 in the early phase of diabetic nephropathy remain unclear. To address this issue, we examined whether streptozotocin (STZ)-induced early diabetic nephropathy was accelerated in MMP-2 knockout (KO) mice. METHODS: Diabetes was induced by the injection of STZ in 6-week-old control and MMP-2 KO mice. Animals were killed after 16 weeks of diabetes of after observation alone. RESULTS: Compared with non-diabetic control mice, renal MMP-2 expression and activity were increased in 16-week old diabetic mice. Serum levels of blood urea nitrogen and creatinine and urinary excretion levels of albumin and N-acetyl-ß-D-glucosaminidase were significantly elevated in diabetic MMP-2 KO mice when compared with wild-type diabetic littermates. Further, accumulation of ECM in the glomeruli and atrophy and fibrosis in the tubulointerstitium were exacerbated, and renal α-smooth muscle actin expression was enhanced in diabetic MMP-2 KO mice. CONCLUSIONS: Our present study suggests that renal expression and activity of MMP-2 are increased as a compensatory mechanism in the early phase of diabetic nephropathy. Since MMP-2 could play a protective role against the progression of diabetic nephropathy, further enhancement of MMP-2 expression and/or activity in the kidney may be a therapeutic target for the treatment of early diabetic nephropathy.

Proteinuria elevates asymmetric dimethylarginine levels via protein arginine methyltransferase-1 overexpression in a rat model of nephrotic syndrome.

AIMS: Proteinuria is an independent risk factor for cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). Asymmetric dimethylarginine (ADMA) is a mediator of endothelial dysfunction and is associated with proteinuria in CKD patients. Thus, ADMA can partially account for the increased risk of CVD in CKD patients presenting proteinuria. However, a causal relationship between proteinuria and ADMA remains to be demonstrated. MAIN METHODS: We first investigated whether and how proteinuria might increase ADMA levels in adriamycin (ADR)-treated rats. Next, we examined the effects of human serum albumin (HSA) on ADMA production by human renal proximal tubular epithelial cells (RPTECs) cultured in vitro. KEY FINDINGS: Proteinuria was associated with ADMA levels in ADR treated rats. Although ADR treatment did not affect the expression levels of the dimethylarginine dimethylaminohydrolase (DDAH)-1 or -2 enzymes that degrade ADMA, it significantly increased the expression levels of protein arginine methyltransferase-1 (PRMT-1) that facilitates the production of ADMA. HSA increased the generation of reactive oxygen species in RPTECs, which was blocked by the anti-oxidant N-acetylcysteine (NAC) or an inhibitor of NADPH oxidase. Furthermore, HSA increased ADMA generation by RPTECs in a dose- and time-dependent manner and induced gene expression of PRMT-1 but not DDAHs, which were also suppressed by NAC. SIGNIFICANCE: Our data suggest that proteinuria might enhance ADMA generation in tubular cells, at least in part via the overexpression of PRMT-1 triggered by oxidative stress. Our findings thereby propose a mechanistic link between proteinuria and ADMA levels in CKD patients.

A new vasculitis activity score for predicting death in myeloperoxidase-antineutrophil cytoplasmic antibody-associated vasculitis patients.

BACKGROUND/AIMS: Myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-positive microscopic polyangiitis patients with renal involvement have been shown to have a progressive clinical course. In this study, we compared the clinical utility of the Japanese Vasculitis Activity Score (JVAS) with the Birmingham Vasculitis Activity Score (BVAS) for predicting death in patients with MPO-ANCA-associated renal involvement. METHODS: Sixty-nine patients with MPO-ANCA-associated vasculitis with renal involvement (22 males and 47 females, age 69.8 ± 8.7 years) were enrolled in this study. We retrospectively investigated which score was better for predicting the poor prognosis of patients. RESULTS: The mortality rate of the patients within 2 years after disease onset was 33% (23/69). JVAS was not correlated with BVAS. Univariate logistic regression analysis for death showed that the odds ratio (OR) of JVAS was statistically significant (OR 1.76, 95% confidence interval, CI, 1.29-2.41, p < 0.001), while that of BVAS was not (OR 1.07, 95% CI 0.98-1.16, p = 0.14). Moreover, a multivariate model showed that JVAS was an independent determinant of death (OR 1.59, 95% CI 1.12-2.25, p = 0.009). The area under the receiver operating characteristic curve for JVAS was 0.778, which was significantly larger (p = 0.02) than that for BVAS (0.586). The estimated optimal cut-off point of JVAS for the prediction of death was 5. At this point, the sensitivity was 82.6% and the specificity was 60.9%. CONCLUSION: We demonstrated that compared with BVAS, JVAS was a simpler and more reliable measure for predicting death in patients with MPO-ANCA-associated vasculitis with renal involvement.

Interstitial Foxp3-positive T cells may predict renal survival in patients with myeroperoxidase anti-neutrophil cytoplasmic antibody-associated glomerulonephritis.

1. Regulatory T cells (T(reg)) and cytotoxic T cells (CTL) are involved in various immune diseases. However, the prognostic impact of T(reg) and CTL in patients with myeroperoxidase anti-neutrophil cytoplasmic antibody-associated glomerulonephritis (MPO-ANCA-GN) is not well known. Therefore, in the present study, we examined the relationship between expression of forkhead box P3 (Foxp3) and T cell intracytoplasmic antigen (TIA)-1, T(reg) and CTL markers and renal survival in patients with MPO-ANCA-GN. 2. Forty patients with MPO-ANCA-GN and 10 patients with minimal change nephrotic syndrome (MCNS) underwent physical examination, determination of blood chemistry and renal biopsy. Immunohistochemical staining for Foxp3 and TIA-1 was performed on paraffin-embedded renal sections. 3. Although almost all patients received standard immunosuppressive treatment for 6 months, seven MPO-ANCA-GN patients needed maintenance haemodialysis (HD), whereas 33 patients did not (non-HD). Both Foxp3- and TIA-1-positive cells were detected in the interstitium and glomeruli of MPO-ANCA-GN patients, whereas they were rarely detected in patients with MCNS. The total crescent rate was significantly higher in the HD group than in the non-HD group (35.9 +/- 3.5 vs 65.8 +/- 7.4, respectively). In the interstitium, the age-adjusted Foxp3/TIA-1 ratio was significantly higher in the non-HD group than in the HD group (0.016 +/- 0.016 vs 0.004 +/- 0.008, respectively; P < 0.05). The Foxp3/TIA-1 ratio, but not the Foxp3/CD3 ratio, remained significantly higher in the non-HD group than in the HD group even after adjustment for crescent rate. Age- and total crescent rate-adjusted renal survival rates were higher in patients with a Foxp3/TIA-1 ratio > or = 0.06 than in patients with a Foxp3/TIA-1 ratio < 0.06 (P = 0.02). 4. The results of the present study suggest that T(reg) could play a protective role against MPO-ANCA-GN and that a decreased Foxp3/TIA-1 ratio in interstitial areas may predict future renal failure in patients with MPO-ANCA-GN.