Renal antifibrotic effect of N-acetyl-seryl-aspartyl-lysyl-proline in diabetic rats.

BACKGROUND AND AIM: Diabetic nephropathy is the main cause of end-stage renal disease. N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), a physiological tetrapeptide hydrolyzed by the angiotensin-converting enzyme (ACE), has antifibrotic effects in the cardiovascular system and in the kidney in experimental models of hypertension, heart failure and renal disease. The aim of the study was to evaluate the effect of Ac-SDKP in diabetic nephropathy and the potential additive effect of Ac-SDKP, when compared to ACE inhibitors alone, on the development of renal fibrosis. METHOD: Diabetes was induced in 28 Sprague-Dawley rats by a single intraperitoneal injection of streptozotocin. Control rats (n = 10) received only buffer solution. An ACE inhibitor (ramipril, 3 mg/kg/day) was administered to 11 diabetic rats. After 2 months, Ac-SDKP (1 mg/kg/day) was administered by osmotic minipumps for 8 weeks to 7 diabetic rats and to 6 diabetic rats treated with ramipril. Osmotic minipumps delivered saline solution in the corresponding sham-treated rats (diabetic rats, n = 10, and ramipril-treated diabetic rats, n = 5). RESULTS: Diabetic rats showed a significant increase in blood glucose level, urinary albumin excretion and renal fibrosis, and a reduction of glomerular nephrin expression with respect to control rats. Ac-SDKP administration significantly reduced renal fibrosis in diabetic rats, without significantly reducing urinary albumin excretion. Ramipril treatment caused a significant decrease in albuminuria and renal fibrosis and restored glomerular nephrin expression. Administration of Ac-SDKP, in addition to ramipril, further reduced renal fibrosis with respect to ramipril alone, while it did not improve the antiproteinuric effect of ramipril. CONCLUSION: Ac-SDKP administration reduces renal fibrosis in diabetic nephropathy. Addition of Ac-SDKP to ACE inhibition therapy improves the reduction of renal fibrosis with respect to ACE inhibition alone, suggesting a beneficial effect of this pharmacological association in diabetic nephropathy.

Computerized management of peritoneal dialysis.

The importance of the evaluation of dialytic adequacy is well known in peritoneal dialysis. It is necessary to be able to quantify and individualize the substitution treatment. In 15 patients we compared five quantitative approaches by using original software: Teehan's dialysis index (DI); Diaz-Buxo's liters/week (LW); Keshaviah's the quantity of dialysis prescribed (wKt/V); and Boen and Twardowski's weekly creatinine clearance (WC). All patients were treated by continuous ambulatory peritoneal dialysis (CAPD) according to the peritoneal equilibration test (PET). Peritoneal solute clearances for urea, creatinine, uric acid, and phosphorus were adequate, but there was disagreement between adequacy indexes. According to the DI, 40% of our patients were underdialyzed, 33% were adequate, and 27% received excessive dialytic dose, while according to LW and wKt/V, about 50% were adequate, 10% underdialyzed, and 40% received excessive doses. According to WC, 74% were overdialyzed and 26% were adequate. In two patients only (13%) all the indexes indicated underdialysis. We think that the DI is too severe an adequacy index, probably because residual renal clearances have a great weight in the formula, while WC may lead to an overestimate of the actual dose of therapy in patients with significant residual renal clearance. Prospective, randomized and clinical studies are needed to better assess the optimal index for individualization of targeted peritoneal dialysis prescription.

The sigmoidal parathyroid hormone-ionized calcium curve and the set point of calcium in hemodialysis and continuous ambulatory peritoneal dialysis.

A high incidence of adynamic bone disease not related to aluminum intoxication has been reported in continuous ambulatory peritoneal dialysis (CAPD). Since reduced parathyroid hormone (PTH) secretion may predispose to adynamic bone, we investigated whether parathyroid gland sensitivity may be depressed in CAPD in comparison with hemodialysis (HD). Thus we determined parathyroid function by the evaluation of the PTH-ionized calcium (ICa) relationship, which was obtained inducing hypocalcemia and hypercalcemia in 19 CAPD and 18 HD patients with biochemical and histological evidence of mild (MILD) or severe (OF) hyperparathyroidism, but negative stainable bone aluminum. Either CAPD or HD patients with OF showed a shift to the right of the sigmoidal PTH-ICa curve in comparison with patients with MILD, greater set point of calcium, and maximal PTH stimulation and inhibition. The PTH-ICa curve and the other parathyroid function parameters were not different in CAPD and HD patients within the same bone histological group. In conclusion, our data document that parathyroid gland activity is stimulated either in CAPD and HD patients with OF, but is not depressed in CAPD patients in comparison with HD patients.

Calcium mass transfer and kinetics in CAPD using calcium-free solutions.

In 12 continuous ambulatory peritoneal dialysis (CAPD) patients we evaluated peritoneal calcium mass transfer (CaMT), serum and effluent dialysate ionized calcium (iCa) changes, and the variations of the dialysate-to-plasma (D/P) ratio for calcium throughout 6-hour dwell exchanges with zero calcium, 1.25 mmol/L calcium (1.25 Ca), and 1.75 mmol/L calcium (1.75 Ca) peritoneal solutions. The infused ionized and total calcium were, respectively, 1.28 +/- 0.04 and 1.77 +/- 0.04 mmol/L with 1.75 Ca and 0.89 +/- 0.03 and 1.28 +/- 0.04 mmol/L with 1.25 Ca solutions. During CaMT studies, the ultrafiltration rate was 250 mL on average, and serum iCa 1.24 mmol/L. Calcium was gained by the patients (+0.41 +/- 0.6 mmol/L) using standard solutions. CaMT was -0.67 +/- 0.4 mmol/L with 1.25 Ca and -2.4 +/- 0.4 mmol/L with zero Ca solutions. Throughout the exchanges the D/P ratio for iCa decreased from 0.97 +/- 0.03 at 0 minutes to an equilibrium value (at about 240 minutes) of 0.84 +/- 0.03 with 1.75 Ca solutions, while it increased from 0.75 +/- 0.04 to 0.83 +/- 0.05 with 1.25 Ca solutions. After a 6-hour exchange with zero Ca, the D/P ratio for iCa was 0.76 +/- 0.04, significantly lower than the D/P ratio for urea (0.97 +/- 0.02), creatinine (0.89 +/- 0.06), and bicarbonate (0.98 +/- 0.02). In conclusion, dialysate and serum iCa are in equilibrium at a D/P ratio of about 0.84. Thus calcium is gained by the patients using 1.75 Ca solutions, and it is lost (both by diffusion and ultrafiltration) using 1.25 Ca solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of CAPD and hemodialysis on parathyroid function.

UNLABELLED: A high incidence of low turnover bone disease (LTBD) has been reported in predialysis and dialysis uremic patients, despite parathyroid hormone (PTH) levels two- to four-fold the upper normal limit. The aim of this study was to evaluate the trend of PTH in uremic patients after admission to continuous ambulatory peritoneal dialysis (CAPD) or hemodialysis (HD). Thus, we evaluated 53 patients (27 CAPD and 26 HD) of 73 consecutive uremic patients starting CAPD or HD from 1992, who had at least one year follow-up on dialysis. HD and CAPD patients were comparable for age, nephropathy, and duration of uremia. All the patients had been treated with calcium carbonate (CaCO3) as the sole phosphate binder during the predialysis period. At the time of admission to dialysis PTH was > 260 pg/mL (fourfold above the upper normal limit) in 12 CAPD and 9 HD patients, between 130 and 260 pg/mL in 6 CAPD and 5 HD patients, and < 130 pg/mL in 9 CAPD and 12 HD patients. Bone biopsy, performed in 22 patients, showed LTBD in 10 of 12 patients with PTH < 130 pg/mL and high bone turnover in 8 patients with PTH > 260 pg/mL. Patients were treated with a dialysate calcium (Ca) of 1.75 mmol/L and were given CaCO3 to maintain serum phosphate < 5 mg/dL. Oral calcitriol was given if they developed hypocalcemia (< 9 mg/dL). Hypercalcemia (> 10.5 mg/dL) occurred in 13 CAPD and 17 HD patients, and was managed by discontinuation of calcitriol and reduction of dialysate Ca to 1.25-1.5 mmol/L. A significant decrease in PTH and alkaline phosphatase was observed in both groups after six and 12 months of treatment. After one year of CAPD, PTH was > 260 pg/mL in 3 patients, between 130 and 260 pg/mL in 4 (all on calcitriol), and < 130 pg/mL in 20 patients (17 on calcitriol, but only 2 mild hypercalcemic). After one year of HD, PTH was > 260 pg/mL in 3 patients, 130-260 pg/mL in 5 (all on calcitriol), and < 130 pg/mL in 18 (11 on calcitriol, 1 mild hypercalcemic). IN CONCLUSION: (1) about 40% of predialysis patients treated with CaCO3 showed PTH levels suggestive of LTBD; (2) the proportion of patients with low PTH increases after one year on CAPD or HD, even though calcemia was maintained within the normal range; (3) suppressed PTH levels are associated with calcitriol therapy rather than dialysis modality; and (4) secondary hyperparathyroidism improves in most patients after one year on CAPD or HD.

[Acute renal failure and thrombotic microangiopathy (TM)]. / Insufficienza renale acuta e microangiopatia trombotica.

BACKGROUND: Thrombotic microangiopathy (TM) is a disorder characterized by fibrin formation and platelet aggregation in the small arteries and capillaries. Two main clinical settings are reported in association with this disorder: hemolitic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Both conditions share common findings such as microangiopathic anemia and thrombocytopenia. HUS is more frequent in children and is mainly characterized by renal symptoms, whereas PTT is dominated by neurologic abnormalities. However, in many patients, the clinical distinction between HUS and PTT is not clear; therefore, some authors consider the two syndromes as manifestations of the same entity. In children, the most common cause of HUS is an enteric infection caused by cytotoxin-producing bacteria (mainly Escherichia coli with serotype O157:H7). This toxin--the Shiga toxin--can bind to glomerular endothelial cells and stimulate the production of cytokines and the secretion of von Willebrand factor (vWf). TM may be caused by drugs such as cyclosporin, tacrolimus, mytomicin C, ticlopidine, quinine, and oral contraceptives. It may be associated with disorders of pregnancy (severe pre-eclampsia and postpartum HUS) or with systemic disorders such as systemic lupus erythematosus (SLE), antiphospholipid syndrome, systemic sclerosis, and human immunodeficiency virus (HIV) infection. Abnormalities of the gene of complement factor H have been found in familial HUS and in some sporadic cases of HUS not associated with diarrhea. Factor H abnormalities induce an uncontrolled complement activation that can activate the coagulation cascade. In familial PTT, genetic abnormalities of the cleaving metalloproteinase of fWf ADAMTS 13 have been identified. In other patients with TTP, antibodies inhibiting this enzyme have been found. As a consequence of plasma ADAMTS 13 deficiency, unusually large vWf multimers are produced. This abnormality, in the presence of an increased shear stress, stimulates platelet adhesion and aggregation. CONCLUSIONS: Knowledge of the type of causative abnormality is relevant to a therapeutic approach. Children with diarrheal HUS usually do not benefit from plasma infusion or exchange, whereas in patients with factor H or ADAMTS 13 deficiency procedures that include the administration of the lacking product and removal of the inhibiting or toxic factors, such as ultralarge vWfs, are mandatory. Potentially renal transplantation candidates should be screened for genetic defects to avoid the recurrence of TM in the graft.

Evaluation of the impact of a new synthetic vitamin E-bonded membrane on anemia and rHuEPO requirement in ESRD patients with central venous catheters: a pilot study.

In the last years, the number of hemodialysis (HD) patients with erythropoietin (rHuEPO) resistance is increasing. Probably, central venous catheters (CVCs) contribute to this resistance by inducing inflammation and oxidative stress. This study was aimed to compare vitamin E-bonded dialyzer (PSVE) versus polyethersulfone membrane. Sixteen subjects with CVCs were included in a prospective two-arm crossover 12-month study. The primary endpoints were the rHuEPO requirement and the erythropoiesis-stimulating agents (ESA) index, which was defined by the ratio between weekly EPO dosage (IU/kg/week) and Hb levels (g/dl). The mean dosages of rHuEPO to maintain hemoglobin between 10.5 and 12 g/dl were 135 ± 59 and 101 ± 57 IU/kg/week with polysulfone and PSVE, respectively (P = 0.14). The ESA indexes were 12.1 ± 5.2 and 8.7 ± 5.2 (P < 0.0001) with polysulfone and PSVE, respectively. A trend towards consensual changes in protein glycoxidation, antioxidant, and inflammatory markers was observed. In conclusion, the study suggests a role for PSVE in the reduction of ESA index in HD patients with CVCs.

Efficient detection of leukemia-related fusion transcripts by multiplex PCR applied on a microelectronic platform.

The identification of prognostically relevant fusion genes is required in the routine diagnostic process of most advanced clinical protocols for leukemia patients, either for risk stratification, target-specific treatments, and/or as markers for monitoring Minimal Residual Disease during treatment. However, there is emerging need to implement diagnostics and patient classification based on other biological features, such as expression levels of specific genes or genomic polymorphisms and/or mutations. This advancement would ideally be pursued in a diagnostic laboratory by an unique platform capable of different diagnostic purposes. We developed a rapid, accurate and reproducible assay to screen for the most common fusion gene transcripts in human leukemia, which combines a multiplex RT-PCR approach with the electronic hybridization and fluorescent detection on the Nanogen NanoChip Molecular Biology Workstation. This study demonstrates, as a proof-of-principle, that this microelectronic device, highly effective in detecting single base mutations, is also efficient in the analysis of gene expression, thus providing as a multi-purpose platform for relevant comprehensive diagnostics of hemato-oncology patients.

Calcium balance and serum ionized calcium fluctuations in on-line haemodiafiltration in relation to ultrafiltration rate and dialysate calcium concentration.

The use of high ultrafiltration rates in haemodiafiltration (HDF) has been suggested for improving the clearance of small and large molecules. This strategy has become economically applicable with the development of safe techniques for on-line production of sterile infusate from dialysate, which enables us to infuse large substitution fluid volumes without further increasing the cost of sessions. The effect of increasing the ultrafiltration rate in HDF on electrolyte balance has not yet been evaluated. The aim of this study was to evaluate the effects of variations of the ultrafiltration rate on calcium kinetics in HDF using three different dialysate calcium concentrations. Since the increase in ultrafiltration rate augments the convective calcium loss, variations of intrasession calcium balance could result from modifications of the ultrafiltration rate. In the present study we found no significant variations in calcium balance and serum ionized calcium (iCa) levels during on-line HDF treatment when increasing the mean ultrafiltration rate from 60 to 100 ml/min in the presence of an adequate and corresponding increase in the infusion rate (from 2.5 to 5 l/h). During the balance studies, pretreatment serum iCa was on the average 1.32 mmol/l and weight loss 3.2 kg. Mean calcium loss during treatment was 2.8 and 3.3 mmol at infusion rates of 2.5 and 5 l/h with 1.63 mmol/l of calcium in both the dialysate and infusate; calcium loss rose to 5.9 and 11.2 mmol at infusion rates of 2.5 l/h and to 5.7 and 14.2 mmol at infusion rates of 5 l/h when the dialysate and infusate calcium was reduced respectively to 1.5 and 1.25 mmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

High-dose oral calcitriol and zero calcium peritoneal solutions in CAPD patients with refractory secondary hyperparathyroidism.

We evaluated the effect of pulse oral calcitriol (4 micrograms three times weekly for 6 months) on parathyroid function in nine CAPD patients with hyperparathyroidism refractory to conventional low-dose oral calcitriol. Zero calcium peritoneal solutions were used to prevent the development of hypercalcaemia. The peritoneal loss of calcium increased from 168 +/- 40 to 417 +/- 48 mg/day using zero calcium solutions. Pulse oral calcitriol resulted in a significant decrease in PTH (from 617 +/- 272 to 382 +/- 299 pg/ml) by the 15th day of therapy, while serum iCa did not change from baseline. During the first month of therapy the mean PTH levels remained significantly reduced compared to baseline, thereafter PTH increased in four of nine patients. Hyperphosphataemia was not satisfactorily controlled in four patients, despite large amounts of binders used; seven of nine patients developed hypercalcaemia and required either the substitution of calcium acetate for calcium carbonate or reduction of calcitriol dose. Three patients showed a progressive increase in PTH. In conclusion our data suggest that in most CAPD patients with severe hyperparathyroidism oral calcitriol pulse therapy is not effective in maintaining a permanent suppression in PTH levels.

Adequacy of haemodiafiltration.

In this study we have evaluated the influence of blood and ultrafiltration flow rate on the performance of five different high-flux membrane dialysers during haemodiafiltration. On the basis of clearance data we optimised the haemodiafiltration schedule of six uraemic patients to maintain an adequate midweek blood urea nitrogen concentration, while reducing the treatment time from 285 +/- 23 min to 210 min. After a follow-up of 6 months, we observed no difference in the clinical tolerance or in the biochemical parameters, compared to those found during the preceding haemodialysis period. Our data confirm the suggestions of other authors that haemodiafiltration is an effective alternative to conventional haemodialysis.

Protein nitrogen appearance in CAPD patients: what is the best formula?

BACKGROUND: The protein equivalent of nitrogen appearance is an indirect index commonly used to assess dietary protein intake in patients on CAPD. Moreover it has been suggested that the ratio between nitrogen appearance and dietary nitrogen intake (fractional urea synthesis) can predict nitrogen balance in uraemic patients. Several formulae to directly calculate the protein equivalent of nitrogen appearance have been published. It has not been established, however, what formulae give the most appropriate estimate of protein intake and nitrogen appearance. STUDY DESIGN: Nitrogen balance studies were carried out in seven stable patients on CAPD. All of the patients were receiving a diet whose protein content (1.2 g/kg/body wt/day) and calorie content (35 kcal/kg/body wt/day) were rigorously controlled. Six formulae for calculating protein equivalent of nitrogen appearance and nitrogen appearance were tested and the agreement of the estimating formulae was evaluated by means of the Bland and Altman method. RESULT: Net nitrogen balance was 1.68 +/- 0.9 g/N day, protein intake (g/day) 81 +/- 19, protein intake (g/kg) 1.05 +/- 0.17. Differences in protein equivalent of nitrogen appearance of up to about 20% were found. The smallest differences between protein equivalent of nitrogen appearance and protein intake were obtained by the formulae of Bergstrom (1 +/- 7 g, limits of agreement -12 and +15 g) and Blumenkrantz (-2 +/- 5 g, limits of agreement -11 and +7 g). The formula of Bergstrom most closely estimated nitrogen appearance (-0.35 +/- 0.89 g). Using such formula, the fractional urea synthesis was 54 +/- 12%, giving evidence of positive nitrogen balances. CONCLUSION: For the routine monitoring of protein equivalent of nitrogen appearance in CAPD patients, we recommend Bergstrom's formula with the determination of dialysate protein losses.

Long-term effects of intravenous calcitriol therapy on the control of secondary hyperparathyroidism.

Although high-dose intravenous calcitriol has been shown to be effective in suppressing parathyroid hormone (PTH) secretion in dialysis patients with secondary hyperparathyroidism, an increasing number of patients is refractory to treatment. Only a few studies have evaluated the factors that can predict a favorable response to calcitriol, but contrasting results have been reported. This study was performed to evaluate the effect of high-dose intravenous calcitriol on parathyroid function and to investigate the factors that can predict a favorable response to treatment. Thirty-five dialysis patients were selected for intravenous calcitriol treatment (2 microg after dialysis for 12 months) because of increased PTH levels (>325 pg/mL). Before starting the treatment, the set point of calcium and the PTH-ionized calcium (ICa) curve was evaluated in each patient by inducing hypocalcemia and, 1 week later, hypercalcemia to maximally stimulate or inhibit PTH secretion. Parathyroid glands were assessed by high-resolution color Doppler ultrasonography. Throughout the study, calcium carbonate or acetate dosage was modified to maintain serum phosphate less than 5.5 mg/dL. Hypercalcemia was managed by reducing dialysate calcium to 5 mg/dL and, if necessary, calcitriol dose. The therapeutic goal was to reduce PTH levels below 260 pg/mL while maintaining normocalcemia. The patients who achieved the therapeutic goal were considered responders. Taking the data from the 35 patients together, we observed a significant decrease (P < 0.01) in alkaline phosphatase (from 252 +/- 106 IU/L to 194 +/- 81 IU/L) and PTH (from 578 +/- 231 pg/mL to 408 +/- 291 pg/mL), and a significant increase in serum ICa (from 5.1 +/- 0.2 mg/dL to 5.3 +/- 0.2 mg/dL; P < 0.001) after calcitriol therapy. PTH changes after therapy were not correlated to serum ICa changes, serum phosphate levels during treatment, and calcitriol dose. The response to therapy was heterogeneous because PTH levels markedly decreased over the treatment period in 18 responsive patients, whereas they increased or remained unchanged in 14 of 17 nonresponders. In three additional refractory patients, there was a decline in PTH of 20% to 35%, but this decline was associated with hypercalcemia. Pretreatment parathyroid gland size, serum ICa, PTH, maximal PTH induced by hypocalcemia, minimal PTH induced by hypercalcemia, the set point of ICa, and the ICa levels at which maximal PTH secretion and inhibition occurred were higher in the 17 refractory patients than in the 18 responsive patients. However, logistic regression analysis showed that among these parathyroid function parameters, the only significant predictors of a favorable response to calcitriol therapy were the parathyroid gland size and the set point of ICa. Throughout the study, serum phosphate and calcitriol dose were comparable in the two groups. In conclusion, the response to intravenous calcitriol therapy in dialysis patients with secondary hyperparathyroidism is heterogeneous, consisting of patients who are either responsive or refractory to treatment; refractoriness can be predicted by parathyroid volume and calcium set point.

Different effects of calcitriol and parathyroidectomy on the PTH-calcium curve in dialysis patients with severe hyperparathyroidism.

BACKGROUND: The PTH-calcium sigmoidal curve is shifted to the right, the slope of the curve is steeper, and the set point of calcium is increased in dialysis patients with secondary hyperparathyroidism, compared to patients with low-turnover bone disease. These findings could be related to increased parathyroid cell mass and increased sensitivity of parathyroid cells to serum calcium variations in these patients. Calcitriol therapy has been documented to reduce PTH levels by shifting the curve to the left and downward. The effect of a surgical reduction of parathyroid gland mass on the PTH-calcium curve has not yet been investigated. In this study we compared the effects of calcitriol and subtotal parathyroidectomy (PTH) on the dynamics of PTH secretion in response to acute changes of serum calcium in two groups of dialysis patients with severe hyperparathyroidism. METHODS: Fourteen dialysis patients treated for 6 months with high-dose i.v. calcitriol (1-2 micrograms thrice weekly, and 10 dialysis patients who underwent subtotal PTx were studied. The PTH-calcium relationship obtained by inducing hypo- and hypercalcaemia means of low and high calcium dialysis was evaluated before and 2-6 months after treatment. RESULTS: Both calcitriol and subtotal PTx significantly decreased PTH (respectively from 797 +/- 595 to 380 +/- 244 and from 1036 +/- 250 to 70 +/- 34 pg/ml), as well as maximal PTH response to hypocalcaemia (PTHmax), and maximal PTH suppression during hypercalcaemia ( PTHmin). When the PTH-calcium curves were constructed using PTHmax as 100% to factor for differences in absolute PTH levels and to provide an assessment of individual parathyroid cell function, a shift of the sigmoidal curve to the left and downward, and a significant decrease in the set point of ionized calcium (from 1.31 +/- 0.05 to 1.26 +/- 0.05 and from 1.36 +/- 0.09 to 1.22 +/- 0.07 mmol/l) was documented with both treatments. However, the slope of the PTH-calcium curve increased after subtotal PTx indicating that the sensitivity of the parathyroid cell to serum calcium changes increased with PTx, while on the contrary it decreased with calcitriol. CONCLUSIONS: PTH secretion decreases proportionally more with calcitriol than with surgery for a given decrease in the functional mass of parathyroid cells. The change in the PTH-ICa sigmoidal curve induced by subtotal PTx is due to the removal of a large mass of parathyroid tissue with advanced hyperplasia.