Detection of an earlier tubulopathy in diabetic nephropathy among children with normoalbuminuria.

INTRODUCTION: Diabetic nephropathy is a major cause of morbidity and mortality among young adults with type 1 diabetes mellitus (DM). Albuminuria, the gold standard for early diagnosis, cannot always detect early diabetic nephropathy. We aimed at evaluating the level of urine neutrophil gelatinase-associated lipocalin (NGAL) as a marker of tubulointerstitial damage in children and adolescents with type 1 DM in relation to the level of albuminuria and other parameters. MATERIALS AND METHODS: Fifty children with type 1 DM for more than 5 years were included in this study (mean age, 13.8 ± 4.0 years), and 18 healthy children served as controls. Patients with overt albuminuria (> 300 mg/g creatinine) or inflammatory states were excluded. Urine NGAL, microalbuminuria, and urine albumin-creatinine ratio were measured in patients and controls as well as other parameters. RESULTS: Urine NGAL was significantly higher in microalbuminuric in comparison with normoalbuminuric patients and controls, and correlated positively with urine albumin-creatinine ratio. A positive urine NGAL was observed in 12 of 38 normoalbuminuric patients (31.6%) compared to 9 of 12 microalbuminuric patients (75%). A positive correlation was reported between urine NGAL and both Hemoglobin A1c and duration of DM, but not with estimated glomerular filtration rate or hypertension. CONCLUSIONS: Diabetic children, even some normoalbuminurics, showed increased urine NGAL. This finding may support the hypothesis of a "tubular phase" of diabetic disease preceding overt diabetic nephropathy, and hence, the use of urine NGAL measurement for early evaluation of renal involvement.

The effect of on-line hemodiafiltration on improving the cardiovascular function parameters in children on regular dialysis.

The cardiovascular disease is an important cause of morbidity and accounts for almost 50% of deaths in patients undergoing maintenance dialysis. Many harmful molecules of the uremic milieu, such as the middle molecules, are difficult to remove by conventional hemodialysis (HD). On-line hemodiafiltration (OL-HDF) can achieve a considerable clearance of middle molecules and, together with its sterile ultrapure infusate, may have favorable effects on inflammation and cardiovascular complications. We aimed in this study to assess the effect of OL-HDF on improving the chronic inflammatory state associated with chronic kidney disease and the possible impact of these changes on myocardial function in chronic HD children. Thirty pediatric patients [12 (40%) males and 18 (60%) females with a mean age of 11.3 ± 3.2 years] on conventional HD for at least six months were switched to OL-HDF for six months. Variables for comparison at the end of each period included the levels of serum C-reactive protein and Kt/V as well as electrocardiography and echocardiographic measurements, including left ventricular mass index (LVMI). On changing from HD to OL-HDF, there was a significant decrease in hs-CRP (from 7.9 ± 8.9 to 3.4 ± 3 µ g/mL) (P = 0.01) and frequency of diastolic dysfunction (P = 0.04), while systolic function (FS and EF) improved significantly (P = 0.007 and 0.05, respectively), while LVMI did not change. We conclude that OL-HDF was well tolerated in children with improvement of the systolic function of the myocardium and the overall frequency of diastolic dysfunction.

Clinical utility of chitotriosidase enzyme activity in nephropathic cystinosis.

BACKGROUND: Nephropathic cystinosis is an inherited autosomal recessive lysosomal storage disorder characterized by the pathological accumulation and crystallization of cystine inside different cell types. WBC cystine determination forms the basis for the diagnosis and therapeutic monitoring with the cystine depleting drug (cysteamine). The chitotriosidase enzyme is a human chitinase, produced by activated macrophages. Its elevation is documented in several lysosomal storage disorders. Although, about 6% of Caucasians have enzyme deficiency due to homozygosity of 24-bp duplication mutation in the chitotriosidase gene, it is currently established as a screening marker and therapeutic monitor for Gaucher's disease. METHODS: Plasma chitotriosidase activity was measured in 45 cystinotic patients, and compared with 87 healthy controls and 54 renal disease patients with different degrees of renal failure (CKD1-5). Chitotriosidase levels were also correlated with WBC cystine in 32 treated patients. Furthermore, we incubated control human macrophages in-vitro with different concentrations of cystine crystals and monitored the response of tumor necrosis factor-alpha (TNF-α) and chitotriosidase activity. We also compared plasma chitotriosidase activity in cystinotic knocked-out (n = 10) versus wild-type mice (n = 10). RESULTS: Plasma chitotriosidase activity in cystinotic patients (0-3880, median 163 nmol/ml/h) was significantly elevated compared to healthy controls (0-90, median 18 nmol/ml/h) and to CKD patients (0-321, median 52 nmol/ml/h), P < 0.001 for both groups. Controls with decreased renal function had mild to moderate chitotriosidase elevations; however, their levels were significantly lower than in cystinotic patients with comparable degree of renal insufficiency. Chitotriosidase activity positively correlated with WBC cystine content for patients on cysteamine therapy (r = 0.8), P < 0.001. In culture, human control macrophages engulfed cystine crystals and released TNF-α into culture supernatant in a crystal concentration dependent manner. Chitotriosidase activity was also significantly increased in macrophage supernatant and cell-lysate. Furthermore, chitotriosidase activity was significantly higher in cystinotic knocked-out than in the wild-type mice, P = 0.003. CONCLUSIONS: This study indicates that cystine crystals are potent activators of human macrophages and that chitotriosidase activity is a useful marker for this activation and a promising clinical biomarker and therapeutic monitor for nephropathic cystinosis.

Decreasing intra-dialytic morbid events and assessment of dry weight in children on chronic hemodialysis using non-invasive changes in hematocrit.

Achieving dry weight after hemodialysis (HD) is critical as chronic fluid over-load can result in left ventricular hypertrophy, while small fluid shifts may result in intra-dialytic morbid events (IME). In the pediatric population, estimating dry weight can be difficult due to growth while on dialysis. Continuous non-invasive monitoring of the hematocrit (NIVM) has been proposed as a more accurate method of estimating dry weight. Fifteen pediatric patients on chronic HD (6 males and 9 females; mean age 11.4 ± 2.28 years) were included in an uncontrolled prospective study involving three phases. In phase 1, patients were observed for one month for their dry weight and frequency of IME. Phase 2 consisted of using NIVM-guided ultrafiltration algorithm for rate of blood volume (BV) reduction and post-dialysis refill, recommending an intra-dialytic reduction in BV of 8% in the first hour and <4% per hour thereafter and without significant post-dialytic vascular refill. Phase 3 comprised a one month period for comparing the results. IME decreased from 33 episodes per 180 sessions in phase 1 to 4 per 180 sessions during phase 3 (P = 0.04), without a significant difference in pre-systolic or post-systolic or mean BP before and after the intervention (all P >0.1). In phase 1, 40% of patients experienced no IME, 33% experienced one or two IME while 27% experienced more than two IME; during phase 3, 80% experienced no IME, 20% experienced one or two IME while no one experienced more than two IME. NIVM can serve as an objective method for determining dry weight as well as predicting and preventing IME in the pediatric population on maintenance HD.

Effect of high-flux versus low-flux dialysis membranes on parathyroid hormone.

INTRODUCTION. Hyperparathyroidism is a common finding in patients with renal insufficiency and parathyroid hormone (PTH) is considered a uremic toxin responsible for many of the abnormalities of the uremic state and bone disease. The aim of this study was to investigate the influence of permeability of low-flux versus high-flux dialysis membranes on intact PTH during hemodialysis in children. MATERIALS AND METHODS. Forty-four children aged between 4 and 13 years old on regular hemodialysis were enrolled in a prospective study. Low-flux polysulfone membranes were used for at least 6 months and then the patients were switched to use high-flux polysulfone membranes for 3 months. Serum electrolytes and intact PTH before and after dialysis were compared before and after changes in dialysis membrane. RESULTS. At the end of the 3-month use of high-flux filters, predialysis intact PTH level (49.40 ± 19.64 ng/dL) showed a highly significant decline (P < .001) compared to the predialysis intact PTH (21.67 ± 4.85 ng/dL) with low-flux membranes at the start of the study. Intact PTH level correlated negatively with serum ionized calcium and positively with serum phosphorus levels only in the predialysis samples with the use of low-flux but not high-flux filters. CONCLUSIONS. In children, high-flux dialysis membranes are more efficient in removal of intact PTH, one of the middle-sized uremic toxins, than low-flux membranes.