Impact of overweight on effectiveness of treatment with human growth hormone in growth hormone deficient children: analysis of German KIGS data

BACKGROUND

We hypothesized that overweight children with growth hormone deficiency (GHD) demonstrate a lower response to growth hormone (GH) as a result of a misclassification since obesity is associated with lower GH peaks in stimulation tests.

METHODS

Anthropometric data, response, and responsiveness to GH in the first year of treatment were compared in 1.712 prepubertal children with GHD from the German KIGS database according to BMI (underweight=group A, normal weight=group B, overweight=group C) (median age: group A, B, C: 7.3, 7.28, and 8.4 years).

RESULTS

Maximum GH levels to tests (median: group A, B, C: 5.8, 5.8, and 4.0 µg/ml) were significantly lower in group C. IGF-I SDS levels were not different between the groups. Growth velocity in the first year of GH treatment was significantly lower in the underweight cohort (median: group A, B, C: 8.2, 8.8, and 9.0 cm/yr), while the gain in height was not different between groups. The difference between observed and predicted growth velocity expressed as Studentized residuals was not significantly different between groups. Separating the 164 overweight children into obese children (BMI>97th centile; n=71) and moderate overweight children (BMI>90th to 97th centile, n=93) demonstrated no significant difference in any parameter.

CONCLUSIONS

Overweight prepubertal children with idiopathic GHD demonstrated similar levels of responsiveness to GH treatment compared to normal weight children. Furthermore, the IGF-I levels were low in overweight children. Therefore, a misclassification of GHD in overweight prepubertal children within the KIGS database seems unlikely. The first year growth prediction models can be applied to overweight and obese GHD children.

Differential regulation of RGS-2 by constant and oscillating PTH concentrations

PTH has diverse effects on bone metabolism: anabolic when given intermittently, catabolic when given continuously. The cellular mechanisms underlying the varying target cell response are not clear yet. PTH induces RGS-2, a member of the Regulator of G-protein Signaling protein family, via cAMP/PKA, and inactivates PKC-mediated signaling. To investigate intracellular signaling pathways with different PTH concentration-time patterns, we treated UMR 106-01 osteoblast-like cells in a perfusion system. PTH was administered intermittently (4 min/h, 10(-7) M) or continuously at an equivalent cumulative dose (6.6 x 10(-9) M). cAMP was measured using radioimmunoassay, mRNA levels using real-time rtPCR and ribonuclease protection assay, and protein levels using Western immunoblotting. A single PTH pulse transiently increased cAMP levels by 2000% +/- 1200%. In contrast to continuous PTH exposure, cAMP induction remained unchanged with intermittent PTH, ruling out desensitization of the PTH receptor. In continuously perfused cells, RGS-2 abundance was three to five times higher than in cells intermittently exposed to PTH for up to 12 h. MKP-1 and -3 were significantly less induced with pulsatile PTH; exposure-mode-dependent differences in MMP-13 and IGFBP-5 were small. Pulsatile but not continuous PTH administration prevents PTHrP receptor desensitization and accumulation of RGS-2 in osteoblasts, which should preserve PKC-dependent signaling.

Growth hormone treatment in short children with chronic kidney disease

Growth hormone (GH) has been used for treatment of impaired growth in children with chronic kidney disease (CKD) for nearly 17 years. Controlled and open-label studies have shown that GH is highly effective in improving growth velocity and adult height. The growth response is negatively correlated with age and height at start and time spent on dialysis treatment; it is positively correlated with dose and duration of treatment and the primary renal disease (renal hypodysplasia). In children with renal transplants, corticosteroid treatment is an additional factor negatively influencing spontaneous growth rates. However, GH treatment is able to compensate corticosteroid-induced growth failure. GH treatment improved final height by 0.5-1.7 standard deviation score (SDS) in various studies, whereas the control group lost about 0.5 SDS in comparable time intervals. These variable results are explained in part by the factors mentioned above. The adverse events are comparable to those in non-CKD children treated with GH.

CONCLUSION

GH treatment is safe and highly effective in improving growth and final height of short children with all stages of CKD. The highest treatment success is obtained if treatment is started at an early age and with relatively well-preserved residual renal function and continued until final height.

Pediatric renal transplantation and the dysfunctional bladder

We retrospectively reviewed our long-term experience with pediatric renal transplantation into a dysfunctional lower urinary tract to evaluate graft survival, function, and special urological complications. Between 1967 and March 2000, a total of 349 renal transplantations were performed in children younger than 18 years. Malformations of the lower urinary tract were the reasons for end-stage renal failure in 66 children (18.6%). The cause of urinary tract disorders included: meningomyelocele connected with neuropathic bladder (n = 4 transplantations); prune belly syndrome (n = 5 transplantations); VATER association (n = 2 transplantations); posterior urethral valves (n = 27 transplantations); and vesico-uretero-renal reflux (n = 28 transplantations). The majority of the patients underwent surgical interventions to preserve renal function or to prepare renal transplantation. The 1- and 5-year graft survival rate was evaluated with special reference to the underlying disease. The 1-year graft survival rate in all children with lower urinary tract malformations was 83.3%, compared with 88% for all children. In those children with vesico-ureteral reflux, it was 92.8% and in the children with Vater association and prune belly syndrome, it was 85.7%. One graft was lost in the children who had neurogenic bladder, so the 1-year graft survival rate was 75%. The worst 1-year graft survival rate was obtained for boys who had posterior urethral valves (1-year graft survival rate: 74%; 5-year graft survival rate: 62.9%). Concerning the 5-year graft survival rate, it was 70% for all children with malformations of the urinary tract. The best rate was obtained for children with reflux in the native kidneys (78.5%), followed by those with VATER association and prune belly syndrome. As an additional child with neurogenic bladder lost his graft, the 5-year graft survival rate was 50%. Pediatric renal transplantation into a dysfunctional bladder can be connected with high urological complication rates which may contribute to worse graft survival. The 1- and 5-year graft survival rate in children with malformations of the lower urinary tract is worse than in children without bladder dysfunction. We regarded a striking difference between graft survival and the urological disorders which led to renal insufficiency. We obtained the worst graft survival rates in children with posterior urethral valves which are usually connected with bladder emptying problems and dysfunctional voiding. Potential pediatric transplant recipients must be classified according to pathophysiological as well as anatomical abnormalities of the urinary tract and all urological problems have to be solved prior to transplantation. At our center, living donors are favored to plan transplantation of these children properly.

Survival in nephroblastoma treated according to the trial and study SIOP-9/GPOH with respect to relapse and morbidity

BACKGROUND

Recent Wilms' tumor (WT) trials and studies have tried to determine the minimal therapy needed for cure. The goal was survival without morbidity.

PATIENTS AND METHODS

From January 1989 to March 1994 the German Society of Pediatric Oncology and Hematology registered 440 patients (median age 2.9 years; 231 male, 209 female) with WTs (preoperative chemotherapy 362) for therapy according to the International Society of Pediatric Oncology Trial and Study 9. Therapy for relapse depended on site of relapse and therapy already received. Follow-up included inquiries for morbidity. Prognostic factors for relapse and death were evaluated.

RESULTS

Five-year survival of WTs was 89.5%; 98.2% (385 of 392) of survivors had a follow-up of 5 years (range 0.8-12.6; median 8). In non-anaplastic WTs, young age (<2 years) was of significance (P = 0.026) for a better survival. Non-anaplastic WTs (407 patients) had a 5-year survival of 92.3%, versus 48.5% in anaplastic WTs (33 patients), and a 5-year relapse-free survival of 87.6% versus 42.4%. Survival after relapse was significantly worse for anaplastic than for non-anaplastic WTs (residual 3-year survival 11.8% versus 54.3%; P <0.0001). In preoperatively treated WTs, anaplasia was a strong prognostic factor for death [relative risk (RR) 4.7], followed by poor response to preoperative therapy (RR 3.6), stage IV (RR 3.2) and abdominal stage III (RR 2.2). Low abdominal stages (<III) dominated (280 versus 82). In the 334 unilateral stage I-IV WTs (median age 3.2 years), diffuse anaplasia (21 patients) had a 5-year relapse-free survival of 38.1%, versus 58.4% in blastemal WTs (25 patients); survival was 42.9% in diffuse anaplasia versus 84% in blastemal WTs. None of 46 patients (median age 1.9 years; 91.3% stages I or II) with differentiated WTs (nine epithelial, 37 stromal) relapsed despite their non-response; two died (one therapy related, one due to bilaterization). In the 25 non-anaplastic bilateral WTs, differentiated cases (one epithelial, eight stromal, 33.3% abdominal stage III) were more frequent (P = 0.048) than in unilateral WTs (one stromal, abdominal stage III relapsed). In all, 52.9% of the 5-year survivors had received adriamycin (250-400 mg/m(2)), 25.7% radiation, 6.4% ifosfamide (24-30 g/m(2)) and 6.7% carboplatin plus etoposide. Abnormal parameters according to the National Cancer Institute score were seen in 18.9% during follow-up, but only 6.4% were treated for morbidity at the end of follow-up. Three WTs developed renal failure due to Drash syndrome, but none due to tumor therapy. After adriamycin 1.9% of WTs (9% of those receiving 400 mg/m(2)) required therapy for cardiac toxicity.

CONCLUSIONS

Initial therapy should be more individualized, taking the above risk groups (age in non-anaplastic WTs, poor response, anaplasia, etc.) into account, as morbidity even after relapse therapy with ifosfamide, carboplatin and etoposide was not high. Milder therapy in low stages of differentiated and of well responding WTs should be tested.

1,25(OH)2D3 and dihydrotestosterone interact to regulate proliferation and differentiation of epiphyseal chondrocytes

Growth plate chondrocytes are affected by 1,25(OH)2D3 and androgens, which may critically interact to regulate proliferation and differentiation during the male pubertal growth spurt. We investigated possible interactions of 1,25(OH)2D3 and the non-aromatizable androgen dihydrotestosterone (DHT) in primary chondrocyte cultures from young male rats. DHT and 1,25(OH)2D3 independently stimulated DNA synthesis and cell proliferation in a dose-dependent manner with maximally effective doses of [10(-8) M] and [10(-12) M], respectively. Both DHT and 1,25(OH)2D3 stimulated the expression and release of IGF-I, and the proliferative effects of each hormone were prevented by an IGF-I antibody. DHT and 1,25(OH)2D3 increased messenger RNAs (mRNAs) of their cognate receptors and of IGF-I receptor mRNA (IGF-I-R). 1,25(OH)2D3 also stimulated mRNA of the androgen receptor (AR), whereas DHT did not affect mRNA of the vitamin-D receptor (VDR). Coincubation with both steroid hormones did not stimulate receptor mRNAs more than either hormone alone. The proliferative effects of DHT and 1,25(OH)2D3 were completely inhibited by simultaneous incubation with both hormones, despite potentiation of IGF-I synthesis. In contrast, both hormones synergistically stimulated cell differentiation as judged by alkaline phosphatase activity, collagen X mRNA, and matrix calcification in long-term experiments. We conclude that DHT and 1,25(OH)2D3 interact with respect to chondrocyte proliferation and cell differentiation. The proliferative effects of both hormones are mediated by local IGF-I synthesis. Simultaneous coincubation with both hormones blunts the proliferative effect exerted by either hormone alone, in favor of a more marked stimulation of cell differentiation.

Vitamin D and dexamethasone inversely regulate parathyroid hormone-induced regulator of G protein signaling-2 expression in osteoblast-like cells

The PTH/PTHrP receptor stimulates both adenylate cyclase- and phospholipase C-dependent signaling pathways via different G proteins. The biological actions of PTH on bone are modified by steroid hormones. PTH induces expression of regulator of G protein signaling (RGS)-2, a putative preferential inhibitor of G(q)-mediated phospholipase C activation. We investigated whether steroid hormones interfere with PTH signaling by modulating PTH-induced RGS-2 expression in osteoblast-like UMR 106-01 cells. PTH (1-34) rapidly and transiently induced expression of RGS-2 mRNA and protein via the cAMP/protein kinase A pathway within 30 min, with maximal protein abundance after 2 h. PTH-induced RGS-2 preferentially bound to Galpha(q), compared with Galpha(s) protein. 1,25-(OH)(2)D(3) pretreatment enhanced PTH-induced RGS-2 mRNA and protein accumulation, whereas dexamethasone preincubation had an attenuating effect. These effects were due to modulation of the RGS-2 gene transcription rate, which increased by 35% with 1,25-(OH)(2)D(3) and decreased by 63% with dexamethasone pretreatment. RGS-2 mRNA half-life was not affected by either steroid. The transcriptional effects of dexamethasone and 1,25-(OH)(2)D(3) were independent of PTH/PTHrP receptor activation and were not explained by effects on cAMP accumulation, cAMP response element-binding protein expression or phosphorylation, or the abundance of the osteoblast-specific transcription factor core-binding factor alpha (CBFa1/Runx2), a known activator of RGS-2 expression. In conclusion, glucocorticoids and 1,25-(OH)(2)D(3) inversely modulate PTH-induced RGS-2 gene transcription. Regulation of RGS-2 may constitute a novel mechanism by which steroids modulate signaling via the PTH/PTHrP receptor and other G protein-coupled receptors in bone.

Mycophenolate mofetil in pediatric renal transplantation

Since mycophenolate mofetil (MMF), an ester prodrug of the immunosuppressant mycophenolic acid (MPA), has been approved for maintenance immunosuppressive therapy also in children after renal transplantation it has become an important part of immunosuppressive protocols. By inhibiting inosine monophosphate dehydrogenase, the key enzyme in the de novo purine biosynthesis of proliferating T and B lymphocytes, MMF acts as a relatively specific inhibitor of human lymphocyte proliferation. MMF is more effective than azathioprine in combination with cyclosporin A (CsA) and corticosteroids and distinctly reduces the incidence of acute rejection episodes in the 1st year post-transplant in adults as well as in children. Beneficial effects on steroid-resistant rejection and chronic allograft dysfunction have been shown. In general, MMF is well tolerated. Major adverse events in pediatric renal transplant recipients include leukopenia, infections and gastrointestinal problems. Pharmacokinetic monitoring of MPA can help to optimise MMF therapy after renal transplantation, as associations between the risk of acute rejection episodes and MPA-AUC values and MPA predose levels have been demonstrated. The incidence of MMF-related side effects such as leukopenia and/or infections, however, is associated with pharmacokinetic parameters of free MPA. Reference data of relevant pharmacokinetic parameters are available. The possible steroid-sparing potential of MMF is an important issue in pediatric renal transplantation. Preliminary data demonstrate improved longitudinal growth, less cushingoid habitus and lower blood pressure after steroid-withdrawal in pediatric renal transplant recipients under MMF and CsA therapy.

Adult height after GH therapy in 188 Ullrich-Turner syndrome patients: results of the German IGLU Follow-up Study 2001

OBJECTIVES

We aimed to evaluate the factors influencing true adult height (HT) after long-term (from 1987 to 2000) GH treatment in Ullrich-Turner syndrome (UTS) based on modalities conceived in the 1980s.

DESIGN

Out of 347 near-adult (>16 Years) patients from 96 German centres, whose longitudinal growth was documented within KIGS (Pharmacia International Growth Database), 188 (45, X=59%; bone age >15 Years) were available for further anthropometric measurements.

RESULTS

At a median GH dose of 0.88 (10th/90th percentiles: 0.47/1.06) IU/kg per week, a gain of 6.0 (-1.3/+13) cm above the projected adult height was recorded. Variables were recorded at GH start, after 1 Year GH, puberty onset, and last visit on GH therapy. At these visits, the median ages were 11.7, 12.7, 14.2, 16.6 and 18.7 Years; and median heights, 0.4, 1.1, 1.7, 1.7 and 1.3 SDS (UTS) respectively. Height gain (DeltaHT) after GH discontinuation was 1.5 cm. Total DeltaHT correlated (P<0.001) negatively with bone age and HT SDS at GH start, but positively with DeltaHT after the first Year, DeltaHT at puberty onset, and GH duration. Final HT correlated (P<0.001) positively with HT at GH start, first-Year DeltaHT, and HT at puberty onset. Body mass index increased slightly (P<0.05), with values at start and adult follow-up correlating highly (R=0.70, P<0.001). No major side effects of GH occurred.

CONCLUSIONS

GH dosages conceived in the 1980s are safe but too low for most UTS patients. HT gain and height are determined by age and HT at GH start. Height gain during the first Year on GH is indicative of overall height gain. After spontaneous or induced puberty, little gain in height occurs.

Renal transplantation in small children--a comparison between surgical procedures

OBJECTIVES

Renal transplantation is the therapy of choice for patients with end-stage renal failure. From the surgical point of view, small children remain a challenging patient group.

METHODS

We report our experience with 61 consecutive kidney transplantations in small children aged < or =6 years. Outcome and graft survival rates were presented with special reference to the surgical procedure used to perform the renal transplantation.

RESULTS

Of the 31 renal grafts, placed into the fossa iliaca (group 1), 8 grafts were lost shortly after transplantation due to a vascular complication (5 venous thromboses and 3 arterial thromboses). Six allografts were lost because of acute rejection. All in all, the 1- and 5-year graft survival rate in this group was 55.8% (p = 0.0106)/51.6% (p = 0.0134), respectively. Thirty grafts were placed retroperitoneally, using the aorta and the distal caval vein to perform end-to-side anastomoses (group 2). One graft was lost because of a venous thrombosis 6 weeks following transplantation, 3 further grafts were lost during the 1st year after transplantation due to acute rejection. The 1- and 5-year graft survival rate in that group was 86.6% (p = 0.0106)/83.3% (p = 0.0134), respectively. Comparing the 1-year graft survival rates of the two patient groups with special reference to vascular complications, we observed a 1-year graft survival rate of 74.2% (group 1) versus 96.6% (group 2; p = 0.026).

CONCLUSIONS

Our results on kidney transplantation in small children have considerably improved with the consistent use of the aorta and the distal caval vein to perform vascular anastomoses. The number of vascular complications following renal transplantation decreased, and especially for very small children the retroperitoneal placement of the graft is a safe, feasible surgical procedure that should be performed whenever possible.

Long-term treatment with growth hormone in short children with nephropathic cystinosis

OBJECTIVE

The objective was to assess the efficacy and safety of growth hormone (GH) treatment in severely growth retarded children with nephropathic cystinosis during conservative treatment and during renal replacement therapy.

STUDY DESIGN

The design was an open-labeled prospective trial with a run-in period of 1 year.

RESULTS

A total of 74 children with cystinosis (age 3.0 to 18 years) were treated with GH over a mean period of 3.1 years (range 1 to 10 years); 52 patients were receiving conservative treatment (mean age 7.1 years), 7 were receiving dialysis (12.5 years), and 15 had received a renal transplant (14.8 years). The mean standardized height (SD score) was -4.0 in the conservative treatment group, -4.4 in the dialysis group, and -4.9 in the renal transplant group. During the first treatment year, height velocity doubled in the conservative treatment group, increased by 80% in the dialysis group, and increased by 45% in renal transplant group. Within 3 years the height SD score increased by +1.6 (P <.001) in prepubertal patients receiving conservative treatment, and percentile parallel growth was maintained thereafter. These effects of GH were less expressed in peripubertal patients receiving renal replacement therapy. No major side effects were observed.

CONCLUSION

Long-term GH treatment is safe and effective in young children with nephropathic cystinosis. GH treatment should be started early in the course of the disease if adequate nutrition and cysteamine treatment do not prevent growth retardation.

Impact of ACE I/D gene polymorphism on congenital renal malformations

To investigate the role of the angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism on prevalence and progression of disease in children with chronic renal failure (CRF), we determined the ACE I/D genotype in 95 children with CRF due to renal malformations (hypo-/dysplasia, obstructive uropathy, reflux nephropathy; n = 59), other congenital or hereditary diseases (n = 23), or acquired glomerular disorders (n = 13), who had been followed prospectively over a 2-year period. CRF progression rate was followed in each individual by linear regression analysis of estimates of glomerular filtration rate (GFR) obtained every 2 months. Actuarial renal 'survival' analysis was performed, using a GFR loss of 10 ml/min per 1.73 m2 as a cutoff point. The distribution of the ACE genotype did not differ among the disease groups. There was also no difference in ACE genotype distribution between the patients and a control group of healthy Caucasian children (n = 163). Among the children with renal malformations, the 2-year renal survival was significantly lower in those with the DD genotype (61%) than in patients with ID or II genotype (89%, P < 0.01). In the other disease groups, the ACE I/D genotype was not predictive of CRF progression. In a multivariate analysis of risk factors, the adverse effect of the DD genotype (risk ratio 10.2, P < 0.05) was independent of and additive to those of arterial hypertension (RR 13.2, P < 0.001) and gross proteinuria (RR 4.7, P < 0.05). We conclude that the ACE DD genotype is a significant risk factor for children with congenital renal malformations to develop progressive CRF. The effect of the ACE polymorphism in this patient group is independent of hypertension and proteinuria.

The interaction of glucocorticoids with the growth hormone-insulin-like growth factor axis and its effects on growth plate chondrocytes and bone cells

Glucocorticosteroids interfere with the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis at different levels, and while low-dose corticosteroids may have permissive effects, high-dose, long-term treatment with corticosteroids may lead to growth disturbance. The mechanism involved is not clearly understood. The Janus kinase (JAK)-2/signal transducers and activators of transcription (STAT)-5 pathway is the means by which the corticosteroid interacts with the target-cell GH receptors. The production of local IGF-I is lowered by the corticosteroid via IGF-I transcription inhibition, and the rate of apoptosis is also increased, both in growth plate chondrocytes and osteoblast cell lines. GH in vitro and in vivo can partly counterbalance the negative effects of glucocorticoids on growth. GH has been seen to normalize growth rates in corticosteroid-treated rats as well as in children receiving glucocorticoids for immunosuppression following kidney transplantation.

Effect of growth hormone treatment on the adult height of children with chronic renal failure. German Study Group for Growth Hormone Treatment in Chronic Renal Failure

BACKGROUND

Growth hormone treatment stimulates growth in short children with chronic renal failure. However, the extent to which this therapy increases final adult height is not known.

METHODS

We followed 38 initially prepubertal children with chronic renal failure treated with growth hormone for a mean of 5.3 years until they reached their final adult height. The mean (+/-SD) age at the start of treatment was 10.4+/-2.2 years, the mean bone age was 7.1+/-2.3 years, and the mean height was 3.1+/-1.2 SD below normal. Fifty matched children with chronic renal failure who were not treated with growth hormone served as controls.

RESULTS

The children treated with growth hormone had sustained catch-up growth, whereas the control children had progressive growth failure. The mean final height of the growth hormone-treated children was 165 cm for boys and 156 cm for girls. The mean final adult height of the growth hormone-treated children was 1.6+/-1.2 SD below normal, which was 1.4 SD above their standardized height at base line (P< 0.001). In contrast, the final height of the untreated children (2.1+/-1.2 SD below normal) was 0.6 SD below their standardized height at base line (P<0.001). Although prepubertal bone maturation was accelerated in growth hormone-treated children, treatment was not associated with a shortening of the pubertal growth spurt. The total height gain was positively associated with the initial target-height deficit and the duration of growth hormone therapy and was negatively associated with the percentage of the observation period spent receiving dialysis treatment.

CONCLUSIONS

Long-term growth hormone treatment of children with chronic renal failure induces persistent catch-up growth, and the majority of patients achieve normal adult height.

No difference in intestinal strontium absorption after oral or IV calcitriol in children with secondary hyperparathyroidism. The European Study Group on Vitamin D in Children with Renal Failure

BACKGROUND

Oral and intravenous calcitriol bolus therapy are both recommended for the treatment of secondary hyperparathyroidism, but it has been claimed that the latter is less likely to induce absorptive hypercalcemia. The present study was undertaken to verify whether intravenous calcitriol actually stimulates intestinal calcium absorption less than oral calcitriol and whether it is superior in suppressing parathyroid hormone (PTH) secretion.

METHODS

Twenty children (16 males, age range of 5.1 to 16.9 years, mean creatinine clearance 21.9 +/- 11.5 mL/min/1.73 m2, range of 7.4 to 52.7) with chronic renal failure (CRF) and secondary hyperparathyroidism [median intact PTH (iPTH), 327 pg/mL; range 143 to 1323] received two single calcitriol boli (1.5 mg/m2 body surface area) orally and intravenously using a randomized crossover design. iPTH and 1,25(OH)2D3 levels were measured over 72 hours, and intestinal calcium absorption was measured 24 hours after the calcitriol bolus using stable strontium (Sr) as a surrogate marker. Baseline control values for Sr absorption were obtained in a separate group of children with CRF of similar severity.

RESULTS

The peak serum level of 1,25(OH)2D3 and area under the curve baseline to 72 hours (AUC0-72h) were significantly higher after intravenous (IV) calcitriol (AUC0-72h oral, 1399 +/- 979 pg/mL. hour vs. IV 2793 +/- 1102 pg/mL. hour, P < 0.01), but the mean intestinal Sr absorption was not different [SrAUC0-240min during the 4 hours after Sr administration 2867 +/- 1101 FAD% (fraction of the absorbed dose) vs. 3117 +/- 1581 FAD% with oral and IV calcitriol, respectively]. The calcitriol-stimulated Sr absorption was more then 30% higher compared with control values (2165 +/- 176 FAD%). A significant decrease in plasma iPTH was noted 12 hours after the administration of the calcitriol bolus, which was maintained for up to 72 hours without any differences regarding the two routes of administration.

CONCLUSIONS

These results demonstrate that under acute conditions, intravenous and oral calcitriol boli equally stimulate calcium absorption and had a similar efficacy in suppressing PTH secretion.

Calcitriol pulse therapy is not more effective than daily calcitriol therapy in controlling secondary hyperparathyroidism in children with chronic renal failure. European Study Group on Vitamin D in Children with Renal Failure

Calcitriol oral pulse therapy has been suggested as the treatment of choice for secondary hyperparathyroidism, but its efficacy and safety are still under discussion. The present randomized multicenter study compares the effect of an 8-week course of daily versus intermittent (twice weekly) calcitriol therapy on parathyroid hormone (PTH) suppression in 59 children (mean age 8.4+/-4.7 years) with chronic renal insufficiency (mean Ccr 22.4+/-11.6 ml/min per 1.73 m2) and secondary hyperparathyroidism. After a 3-week washout period, the patients were randomly assigned to treatment with daily oral calcitriol (10 ng/kg per day) or intermittent oral calcitriol (35 ng/kg given twice a week). The calcitriol dose was not changed throughout the study period of 8 weeks. At start of the study, the median intact PTH (iPTH) level was 485 pg/ml (range 83-2032) in the daily group (n=29) and 315 pg/ml (range 93-1638) in the intermittent group (n=30). After 8 weeks, the respective median iPTH concentrations were 232 pg/ml (range 63-1614) and 218 pg/ml (range 2-1785) (ns). The mean iPTH decrease from baseline was 19.2+/-57.8% and 13.7+/-46.7% respectively (not significant). Calcitriol reduced the iPTH concentration in 23/29 patients in the daily group and in 21/30 in the intermittent group. One episode of hypercalcemia (>11.5 mg/dl) was observed in both groups and a single episode of hyperphosphatemia (>7.5 mg/dl) was observed in the daily group. It is concluded that oral calcitriol pulse therapy does not control secondary hyperparathyroidism more effectively than the daily administration of calcitriol in children with chronic renal failure prior to dialysis.

Serum insulin-like growth factor binding protein (IGFBP)-4 and IGFBP-5 in children with chronic renal failure: relationship to growth and glomerular filtration rate. The European Study Group for Nutritional Treatment of Chronic Renal Failure in Childhood. German Study Group for Growth Hormone Treatment in Chronic Renal Failure

Growth retardation in children with chronic renal failure (CRF) is partly due to an inhibition of insulin-like growth factor (IGF) activity by an excess of high-affinity IGF-binding proteins (IGFBPs). The aim of this study was to analyze the serum levels and forms of IGFBP-4 and IGFBP-5 in CRF patients using specific, recently developed radioimmunoassays (RIAs) and immunoblot analysis. We examined 89 children [age 11.5 (2.8-19.0) years] with CRF [glomerular filtration rate 26.6 (7.0-67.4) ml/min per 1.73 m2], nine of them with end-stage renal disease undergoing peritoneal dialysis. Serum-immunoreactive IGFBP-4 levels were fourfold increased in CRF (prepubertal 1080+/-268 ng/ml; pubertal 989+/-299 ng/ml) compared to healthy prepubertal controls (265+/-73 ng/ml). In contrast, serum IGFBP-5 levels were not significantly increased neither in prepubertal (361+/-120 ng/ml vs 282+/-75 ng/ml in controls) nor pubertal CRF children (478+/-165 ng/ml vs 491+/-80 ng/ml in controls). Immunoblot analysis showed the presence of intact as well as fragmented IGFBP-4 and IGFBP-5. Serum IGFBP-4, but not IGFBP-5, levels were inversely correlated with GFR (r=-0.39, P<0.001). In prepubertal children, IGFBP-4 levels were inversely correlated with standardized height (r=-0.40; P<0.005). In contrast, IGFBP-5 levels were positively correlated both with standardized height (r=0.32, P<0.02) and baseline height velocity (r=0.45, P<0.005). A 3-month therapy with rhGH stimulated serum IGFBP-5 levels by 43% (P<0.01); there was no consistent effect on IGFBP-4 levels. There was a positive correlation between IGFBP-4 and IGFBP-2 (r=0.46, P<0.001); IGFBP-5 was positively correlated with IGF-I (r=0.59, P<0.001), IGF-II(r=0.42, P<0.001)and IGFBP-3 (r=0.47, P<0.001) and inversely correlated with IGFBP-1 (r=-0.41, P<0.001). In summary, serum IGFBP-4 is fourfold elevated in children with CRF in relation to the degree of renal dysfunction and contributes to the marked increase in IGF-binding capacity in CRF serum. The inverse correlation of serum IGFBP-4 with standardized height is consistent with its role as another inhibitor of the biological action of the IGFs on growth plate cartilage. In contrast, serum IGFBP-5 is not elevated in CRF serum and circulates mainly as proteolysed fragments. The positive correlation of serum IGFBP-5 with growth and its increase during GH therapy indicate that IGFBP-5 is a stimulatory IGFBP in patients with CRF, either by enhancing IGF activity through better presentation of TGF to its receptor or by an IGF-independent effect through activation of a specific, recently described putative IGFBP-5-receptor.

Growth hormone receptor abundance in tibial growth plates of uremic rats: GH/IGF-I treatment

BACKGROUND

Children with chronic renal failure (CRF) exhibit growth retardation and a disturbed growth hormone/insulin-like growth factor-I (GH/IGF-I) axis. Treatment of children with CRF with GH or GH/IGF-I can partially restore linear growth. The molecular basis for decreased longitudinal growth is not known but may involve an impaired action of GH.

METHODS

We used the growth-retarded uremic rat model to determine the abundance and distribution of GH receptors (GHRs) in the tibial epiphyseal growth plate and the influence of GH, IGF-I, or combined GH/IGF-I treatment. Pair-fed rats were used as the control.

RESULTS

While all treatment regimes increased body length and weight in both rat groups, only GH/IGF-I treatment increased the total growth plate width. This involved an increase in cell number in the hypertrophic zone, which could also be induced by IGF-I alone. Immunohistochemical analysis showed that uremic rats had decreased abundance of GHRs in the proliferative zone, and only GH/IGF-I therapy could overcome this decrease. These data thus suggest that growth retardation in uremic rats is, at least in part, due to a decrease in GHR abundance in chondrocytes of the proliferative zone of the tibial growth plate. This decreased GHR abundance can be overcome by combined GH/IGF-I therapy, thus enhancing generation and proliferation of hypertrophic zone chondrocytes and increasing growth-plate width.

CONCLUSION

These studies point to a mechanism for the growth retardation seen in children with CRF, and suggest that combined GH/IGF-I treatment may provide more effective therapy for these patients than GH alone.

Daily but not pulse calcitriol therapy improves growth in experimental uremia

Calcitriol (C) pulse therapy is widely used to suppress secondary renal hyperparathyroidism. However, high C serum concentrations may have an antiproliferative effect on growth cartilage cells and may suppress growth rate. The study was designed to evaluate whether daily C and pulse C therapy have differential effects on growth in uremic rats. Female Sprague-Dawley rats (150 g, n=5-10 per group) underwent two-stage subtotal nephrectomy (U). The duration of uremia was 14-18 days. The animals were fed a standard diet or a diet with a low-calcium content. Rats on a low-calcium diet were randomized for recombinant human growth hormone (rhGH) treatment (2.5 IU/kg per day) or solvent. C was injected subcutaneous twice daily (15 pmol/day) or intraperitoneal (105 pmol) twice per week. Weight gain and length gain was determined weekly. After sacrifice, total body calcium was determined by total body neutron activation analysis. Bone micromorphometric analysis of third lumbar vertebra and double staining with tetracycline for determination of mineralization rate were performed. Whereas daily C significantly increased total body length gain within 2 weeks, pulse C did not (U solvent 4.0+/-0.3 cm, UC bolus 4.3+/-0.4 cm, UC daily 5.3+/-0.3 cm, P<0.05). A low-calcium diet reduced and rhGH increased basal length gain and weight gain; regardless of these preconditions, daily but not bolus C increased length gain significantly. C both daily and in bolus form reduced bone osteoid content, but daily C improved mineral apposition rate more than C bolus. Total body calcium corrected for body weight decreased with a low-calcium diet, was lowest with concomitant rhGH treatment, and was not improved by C. In conclusion, daily but not bolus C treatment improves growth in uremic rats.

Assessment of body composition in children with chronic renal failure

In children with chronic renal failure treated conservatively by dialysis or by transplantation, various alterations of the nutritional, metabolic and fluid homeostasis may occur that may critically affect the patients' acute and chronic well-being. In the past, the assessment of body composition in children was hampered by insufficient precision, standardization and/or availability of appropriate anthropometric tools. Recently, there have been several methodological advances that may facilitate close and precise monitoring of body composition in this population. Specifically, the use of body mass index (BMI) data in children has become possible by the introduction of pediatric reference values processed for the calculation of standard deviation scores accounting for the skewed distribution of BMI. Skewness-adapted reference data have also been provided for percentage fat mass as assessed by multisite skinfold measurements. In addition, bioelectrical impedance analysis has been validated in healthy children as well as in pediatric dialysis and renal transplant populations. This novel auxological technique provides a highly reproducible, non-invasive and inexpensive way of assessing changes in total body water content in dialysed patients, as well as changes in fat and fat-free mass prior to dialysis and after renal transplantation.

Suppression of growth plate chondrocyte proliferation by corticosteroids

Growth depression is a side effect of high-dose glucocorticoid therapy in childhood. It is partially mediated by alterations of the somatotropic hormone axis and partially by direct local effects on growth plate chondrocytes. The mechanisms of interaction of corticosteroids and somatotropic and calciotropic hormones at the cellular level were recently investigated in more detail, using experimental models of primary cultures of growth plate chondrocytes. In proliferative chondrocytes, growth hormone (GH) and the calciotropic hormones parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D [1alpha,25(OH)2D3] increase cell proliferation via stimulation of paracrine insulin-like growth factor-I (IGF-I) secretion. Corticosteroids decreased GH, and PTH or 1alpha,25(OH)2D3 stimulated cell growth in a dose-dependent manner. Corticosteroids in high doses reduced the expression of the GH receptor and type 1 IGF receptor. But the main antiproliferative molecular effect of corticosteroid was the reduction in basal and hormone-stimulated IGF-I secretion. The in vitro results are in accordance with the observation in animal experiments and in children treated with corticosteroids, demonstrating that the growth-depressing effect of corticosteroids can be compensated for by supraphysiological doses of GH or IGF-I.

Experience with deflazacort in children and adolescents after renal transplantation

Deflazacort (DFZ) has been proposed as an alternative drug for immunosuppression after renal transplantation (TX), with fewer side effects than conventional glucocorticoids. We investigated renal function, body growth, body fat, and bone mineral density (BMD) after switching from oral methylprednisolone (MPR) to equivalent doses of DFZ 1-9 years after TX in 20 patients aged 5-20 years, selected because of severe adverse effects from previous steroid therapy. At conversion the patients received a mean dose of 7.4 +/- 2.4 mg DFZ/m2 per day. The drug was continued for a mean of 3.7 (1.2-5.5) years. Under DFZ, the glomerular filtration rate dropped slightly (NS). A single rejection episode occurred. Growth velocity significantly improved in the 1st year on DFZ treatment and height standard deviation score (SDS) increased steadily after introduction of DFZ (from -2.64 to -1.96 after 4 years, P = 0.06). However, in 10 prepubertal children the height gain (+0.20 SDS in 2 years on DFZ) was not significant and the overall mean annual growth rate after TX was similar to that in 10 matched prepubertal TX children on continued MPR treatment. Relative obesity, estimated from mean body mass index corrected for height, was reduced from +1.11 SDS at the start of DFZ to +0.71 SDS after 2 years (P = 0.03) and to +0.39 SDS after 4 years (NS). BMD-SDS of the lumbar spine (L2-4) increased after 1 year on DFZ (P = 0.005). In conclusion, DFZ is well tolerated and safe in pediatric patients after TX. It improves relative obesity and bone mineralization. However, body growth is not significantly influenced pre puberty.

Intermittent administration of parathyroid hormone (1-37) improves growth and bone mineral density in uremic rats

BACKGROUND

Parathyroid hormone (PTH) is secreted in a pulsatile fashion. Continuous infusion of PTH(1-84) resulted in a net decrease in trabecular bone volume. Differential effects have been reported following an intermittent application of PTH. We investigated the effects of a continuous infusion and of an intermittent (2 times daily subcutaneously) administration of PTH(1-37) on growth and bone mineral density (BMD) in healthy and uremic rats.

METHODS

Two-stage subtotal nephrectomy was performed on 130 g female Sprague-Dawley rats. PTH(1-37) or solvent was administered through minipumps in sham-operated and uremic rats (60 microg/kg x day for 2 weeks). The effect of intermittent administration was tested with a subcutaneous injection of solvent: 30 microg/kg PTH(1-37) two times per day, 100 pmol calcitriol (C)/kg two times per day, or both. The length (snout-tailtip) and BMD were measured at the start of uremia and at sacrifice. BMD was measured by peripheral quantitative computer tomography at the proximal tibia, 6 and 12 mm distal of the kneejoint space. Femur bone morphology was assessed by x-rays, and calcium content was measured by atomic absorption spectrophotometry.

RESULTS

Length gain was not altered by the continuous infusion of PTH. In contrast, it was significantly increased by intermittent PTH (control solvent 5.35 +/- 0.37 cm vs. control PTH 6.19 +/- 0.47 cm; uremia solvent 4.78 +/- 0.20 cm vs. uremia PTH 6.17 +/- 0.36 cm; P < 0.05). Intermittent PTH but not C increased BMD in uremic rats (Delta total BMD 134 + 13.3 vs. 76.3 +/- 11.5 mg/mL; P < 0.05). X-rays revealed increased bone mass following treatment with PTH but not with C. Uremia decreased bone calcium content (64 +/- 0.3 vs. 73. 3 +/- 2.5 mg/mL), which was normalized by PTH (80 +/- 3.6 mg/mL, P < 0.05) but not by C (69 +/- 1.9 mg/mL).

CONCLUSION

Pulsatile administration of PTH does not adversely affect, but improves longitudinal growth independent of concomitant treatment with C. At the same time PTH increases BMD and the calcium content of bone.

Effects of recombinant human growth hormone in catabolic adults with chronic renal failure

Growth hormone (GH) has been used for the treatment of catabolism in a few pilot studies and in two placebo-controlled studies of 6 months duration. Treatment with GH in doses of 2-4 IU/m2/day (0.67-1.33 mg/m2/day) resulted in clear anabolic effects and a significant change in body composition. Lean body mass increased by more than 3 kg within 6 months, whereas fat mass was decreased by the same amount, resulting in a constant total body weight. As there were no major side-effects, controlled long-term studies are justified.

Long-term outcome of paediatric patients with hereditary tubular disorders

BACKGROUND

An increasing number of children with hereditary tubular disorders (HTD) reach adult life due to diagnostic and therapeutic advances which results in growing need to manage these patients by adult centres. Data on the prevalence and the late clinical problems of these patients are limited.

METHODS

We observed 177 paediatric patients with isolated or complex HTD between 1969 and 1994. The median age at the time of diagnosis was 3 (range 0-18) years and the median observation period 10 (range 1-43) years. The long-term outcomes with respect to renal function, bone disease, and body growth were analyzed.

RESULTS

The prevalence of HTD was 3.2% of all patients observed in our renal unit and 14% of those patients with chronic renal failure and/ or end-stage renal disease. The three most frequent disorders observed were nephropathic cystinosis (n = 34), X-linked hypophosphataemic rickets (n = 26), and idiopathic hypercalciuria (n = 17). At the last observation, 12% of the patients with isolated HTD and 30% of those with complex HTD had developed preterminal chronic renal failure; end-stage renal disease was observed in 5 and 25%, respectively (p < 0.001). Progressive disease occurred mainly in patients having cystinosis, primary hyperoxaluria, the syndrome of hypomagnesaemia/hypercalciuria, primary Fanconi syndrome, Fanconi-Bickel syndrome, and methylmalonic aciduria. Nephrocalcinosis was found in 42%, urolithiasis in 14%, bone deformities and/or fractures in 28%, and other extrarenal alterations in 29% of all patients. The median body height at last observation was 2.0 SD below the normal mean (range from -10.4 to +2. 6), and the adult height was subnormal in 48% of 67 grown-up patients. Growth retardation was more severe in complex than in isolated HTD. The mortality decreased from 17% in 1969-1981 to 12% in 1982-1994.

CONCLUSION

Although HTD are rare nephropathies, their frequently progressive course associated with extrarenal complications requires the attention of nephrologists beyond the paediatric age.

Improved survival in renal replacement therapy in Europe between 1975 and 1992. An ERA-EDTA Registry study

BACKGROUND

The prevalence of Renal Replacement Therapy (RRT) is rising steadily, worldwide and in Europe. One reason for this is an increasing number of patients starting RRT, but improving survival on RRT may also be contributing.

MATERIAL AND METHODS

In an ERA-EDTA Registry study we have examined survival of patients with Standard Primary Renal Disease, or Diabetes, aged 20 to 75 years, who started RRT with haemodialysis (HD) or peritoneal dialysis (PD) between 1975 and 1992. Altogether close to a quarter of a million patients were included in the analysis which included conventional survival analysis of comparable subgroups of the whole cohort as well as Cox regression.

RESULTS

After accounting for age, mode of initial treatment, and diagnosis, an improvement in survival of RRT patients was evident. From Cox regression it was calculated the risk for death decreased by about 5% annually during the time period 1975 1992. Patients who started RRT using PD experienced a higher mortality than those starting with HD. According to Cox regression the relative risk ratio for death was 1.25 for the whole period. The difference in survival between patients starting with PD or HD diminished during the observation period (1975-1992).

DISCUSSION

The survival prospects of a patient presenting with end stage renal disease were considerably better in the early 1990s compared to the mid 1970s. This is reassuring despite the fact that mortality on RRT remains high. The higher mortality of RRT patients who started with PD is probably an 'historical' observation as the techniques of this treatment modality have improved considerably since the 1980s which was the time period from which came most of the data for the analysis.

No difference in intestinal strontium absorption after an oral or an intravenous 1,25(OH)2D3 bolus in normal subjects. For the European Study Group on Vitamin D in children with renal failure

It has been suggested that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) stimulates intestinal calcium absorption less via the intravenous (iv) than the oral route, because the first avoids direct contact of the drug with the enterocytes. However, no study has addressed the issue directly. This investigation was designed to measure the effect of a single oral or iv dose of 1,25(OH)2D3 on calcium absorption, using stable strontium (Sr) as a surrogate for calcium, and measuring the Sr fractional absorbed dose (FAD%) over 240 minutes after Sr administration. In 10 healthy volunteers, five tests were performed in a cross-over design, with a wash-out period between two consecutive tests: Sr absorption without 1,25(OH)2D3 (test A); Sr absorption immediately after either oral (test B) or iv (test C) 1,25(OH)2D3 (1.5 microg/m2 of body surface area [BSA]); Sr absorption (24 hr after either oral (test D) or iv (test E) 1, 25(OH)2D3 (1.5 microg/m2 BSA). The concurrent administration of 1, 25(OH)2D3 and Sr (tests B and C) did not significantly change the area under the Sr FAD%-time curve with respect to test A (test A: 4090 +/- 345; test B: 4510 +/- 345; test C: 4210 +/- 345), whereas Sr absorption was significantly increased (p < 0.001) when Sr was given 24 hr after either oral or iv 1,25(OH)2D3 (test D: 5710 +/- 345; test E: 5510 +/- 345). It was concluded that 1,25(OH)2D3 is likely to influence calcium absorption significantly only via its genomic effect, independent of its administration route.

Area under the plasma concentration-time curve for total, but not for free, mycophenolic acid increases in the stable phase after renal transplantation: a longitudinal study in pediatric patients. German Study Group on Mycophenolate Mofetil Therapy in Pediatric Renal Transplant Recipients

Mycophenolate mofetil, an ester prodrug of the immunosuppressant mycophenolic acid (MPA), is widely used for maintenance immunosuppressive therapy in pediatric renal transplant recipients. However, little is known about the pharmacokinetics of MPA in this patient population in the stable transplant phase, and dosage guidelines are preliminary. The authors therefore compared the pharmacokinetics of MPA, free MPA, and the renal metabolite MPA glucuronide (MPAG) in the initial (sampling at 1 and 3 weeks) and stable phases (sampling at 3 and 6 months) posttransplant in 17 children (age, 12.0 +/- 0.77 years; range, 5.9 to 15.8 years), receiving the currently recommended dose of 600 mg MMF/m2 body surface area (BSA) twice a day. Plasma concentrations of MPA and MPAG were measured by reverse phase HPLC. Because MPA is extensively bound to serum albumin and only the free drug is presumed to be pharmacologically active, the authors also analyzed the MPA free fraction by HPLC after separation by ultrafiltration. The intraindividual variability of the area under the concentration-time curves (AUC0-12) of MPA throughout the 12-hour dosing interval was high in the immediate posttransplant period, but declined in the stable phase, whereas the interindividual variability remained unchanged. The median MPA-AUC0-12 values increased 2-fold from 32.4 (range, 13.9 to 57.0) mg x h/L at 3 weeks to 65.1 (range, 32.6 to 114) mg x h/L at 3 months after transplantation, whereas the median AUC0-12 values of free MPA did not significantly change over time. This discrepancy can be attributed to a 35% decline of the MPA free fraction from 1.4% in the initial phase posttransplant to 0.9% (p < 0.01) in the stable phase. In conclusion, pediatric renal transplant recipients given a fixed MMF dose exhibit a 2-fold increase of the AUC0-12 of total MPA in the stable phase posttransplant and a 35% decrease of the MPA free fraction, whereas the AUC0-12 of free MPA remains unchanged over time. Because the latter pharmacokinetic variable is theoretically best predictive of the clinical immunosuppressive efficacy of MMF, these findings may have consequences for the dosing recommendations of MMF in renal transplant recipients.

Deaths within 90 days from starting renal replacement therapy in the ERA-EDTA Registry between 1990 and 1992

BACKGROUND

Patients who die within 90 days of commencing renal replacement therapy (RRT) may be recorded by some centres and not others, and hence data on mortality and survival may not be comparable. However, it is essential to compare like with like when analysing differences between modalities, centres and registries. It was decided, therefore, to look at the incidence of deaths within 90 days in the ERA-EDTA Registry, and to try to define the characteristics of this group of patients.

METHODS

Between 1 January 1990 and 31 December 1992, 78 534 new patients started RRT in 28 countries affiliated to the ERA-EDTA Registry. Their mean age was 54 years and 31% were over 65 years old. Eighty-two per cent of the patients received haemodialysis (HD), 16% peritoneal dialysis (PD) and 2% had preemptive transplantation as first mode of treatment.

RESULTS

From January 1990 to March 1993 the overall incidence of deaths was 19% and 4% of all patients died within 90 days from the start of RRT. Among those dying within 90 days 59% were over 65 years compared to 53% over 65 years in those dying beyond this time (P<0.0001). The modality of RRT did not influence the distribution of deaths before and after 90 days. Vascular causes and malignancy were more common in those dying after 90 days, while there were more cardiac and social causes among the early deaths. Mortality from social causes was twice as common in the elderly, who had a significantly higher chance of dying from social causes within 90 days compared to those aged under 65 years. The overall incidence of deaths within 90 days was 3.9% but there was a wide variation between countries, from 1.8% to 11.4%. Finally, patient survival at 2 years was markedly influenced in different age groups when deaths within 90 days were taken into account.

CONCLUSIONS

The incidence of deaths within 90 days from the start of RRT was 3.9%, with a marked variation between countries ranging from 1.8% to 11.4%, which probably reflects mainly differences in reporting these deaths, although variable selection criteria for RRT may contribute. Deaths within 90 days were significantly more frequent in elderly patients with more early deaths resulting from cardiac and social causes, while vascular causes of death and malignancy were more common in those dying after 90 days. Patient survival analyses should take into account deaths within 90 days from the start of RRT, particularly when comparing results between modalities, countries and registries.

Soluble transferrin receptor is correlated with erythropoietin sensitivity in dialysis patients

BACKGROUND

Iron deficiency is the most common cause of erythropoietin (EPO) resistance in dialyzed patients with renal anemia. Subclinical or functional iron deficiency is difficult to diagnose in these patients. The soluble transferrin receptor (sTf-R) is considered as a sensitive and specific indicator of bone marrow iron availability.

PATIENTS AND METHODS

To evaluate the clinical usefulness of this novel marker, we investigated relationships between EPO requirements and various hematological and biochemical parameters of erythropoiesis in 27 pediatric end-stage renal failure patients treated by hemodialysis (HD, n = 11) or chronic peritoneal dialysis (PD, n = 16). Iron was substituted intravenously once or twice per week in HD, and by daily oral administration to PD patients. Serum sTf-R concentrations were measured by an enzyme-linked immunosorbent assay. Serum ferritin and transferrin concentrations were determined using nephelometric assays. Hemoglobin and iron levels were estimated by automated procedures.

RESULTS

While neither transferrin saturation nor serum ferritin concentrations were indicative of EPO requirements, a highly significant correlation between the EPO efficacy index (EPO dose divided by hemoglobin concentration) and sTf-R was observed (r = 0.65, p = 0.001). The intravenous iron substitution in HD patients was associated with higher ferritin concentrations compared to the orally substituted PD patients (280+/-100 ng/ml vs. 124+/-83 ng/ml, p<0.002). In contrast, sTf-R concentrations were similar in both treatment groups (25.7+/-7.7 nM vs. 27+/-10.8 nM, n.s.), as were hemoglobin concentrations and EPO requirements.

CONCLUSION

Our results suggest that sTf-R is a more sensitive indicator of functional iron deficiency and impaired EPO responsiveness than serum ferritin or transferrin saturation in dialyzed patients. Intensified iron substitution to patients with elevated sTf-R concentrations may considerably improve the cost efficacy of EPO treatment.

Hypoglycemic effects of insulin-like growth factor-1 in experimental uremia: can concomitant growth hormone administration prevent this effect?

The risk of hypoglycemia limits the clinical application of insulin-like growth factor-1 (IGF-1). Our studies aimed to evaluate the mode of occurrence as well as the prevention of this side effect. Acute administration (i.v. infusion) of IGF-1 in subtotal nephrectomized uremic (U), sham-operated ad libitum fed control (C) and sham-operated pair-fed control (P) rats led to hypoglycemia, though more expressed in P. Serum glucose levels decreased within 60 min after the IGF-1 administration by 40% in U, by 45% in C and by 52% in P (p < 0.05, U vs. P). Chronic administration (7 days) of 1, 4 and 8 mg/kg/day IGF-1 in U rats led to hypoglycemia in an increasing manner as the dose of IGF-1 increased. On the first day, 2 h after injection, serum glucose levels were 116.5 +/- 8.6, 110.4 +/- 12.4, 60,3 +/- 19.2 and 50.6 +/- 18.3 mg/dl, respectively (p < 0. 01). One week later, IGF-1 therapy proved to be less hypoglycemic in all the groups. On day 7, 2 h after injection the serum glucose levels were 118.9 +/- 23.8, 89.0 +/- 23.9 and 66.0 +/- 32.0, respectively (in comparison to day 1 for 4 and 8 mg/kg/day IGF-1 p < 0.05). The combined effect of 4 mg/kg/day IGF-1 and 10 IU/kg/day growth hormone (GH) was also studied in U and P animals. Two hours after the first injections of IGF-1 serum glucose levels decreased in U from 120.0 +/- 11.3 to 49.2 +/- 21.6 mg/dl, while IGF-1 plus GH decreased the glucose level from 122.0 +/- 15.5 to 81.3 +/- 24.7 mg/dl (p < 0.05 IGF-1 vs. IGF-1 + GH). The hypoglycemic effect of IGF-1 was less expressed by long-term treatment and simultaneous administration of GH overcame the glucose-lowering effect of IGF-1 (serum glucose levels on day 11 one hour after the injections: 73.7 +/- 15.3 mg/dl with IGF-1, and 111.0 +/- 7.8 mg/dl with IGF-1 + GH). Methylprednisolone (MP) did not significantly alter the former effects of IGF-1 and GH. In summary, IGF-1 leads to hypoglycemia in control and uremic rats in a dose-dependent manner. This effect becomes less expressed after prolonged administration. GH attenuates the hypoglycemic effect of IGF-1. This suggests that the combined GH and IGF-1 treatment is more effective and less dangerous in correcting uremic growth failure.

Peritoneal transport properties and dialysis dose affect growth and nutritional status in children on chronic peritoneal dialysis. Mid-European Pediatric Peritoneal Dialysis Study Group

To evaluate a possible effect of peritoneal transport properties and dialysis dose on the physical development of children on chronic peritoneal dialysis, a cohort of 51 children was prospectively followed for 18 mo. Peritoneal transport characteristics were assessed by serial peritoneal equilibration tests (PET), dialysis efficacy by dialysate and residual renal clearance measurements, and growth and nutritional status by the longitudinal changes (delta) of height SD score (SDS), body mass index (BMI) SDS, and serum albumin. delta height SDS was negatively correlated with the creatinine equilibration rate observed in the initial PET (r = -0.31, P < 0.05). Multiple regression analysis confirmed the negative effect of the high transporter state (partial r2 = 0.07), and disclosed an additional positive effect of dialytic C(Cr) (partial r2 = 0.11) and a weak negative effect of daily dialysate volume (partial r2 = 0.04) on delta height SDS. delta BMI SDS was strongly age-dependent (r = -0.48, P < 0.001); while relative body mass gradually increased below 4 yr of age, it remained stable in older children. Positive changes in BMI SDS were associated with rapid PET creatinine equilibration rates (univariate r = 0.35, P < 0.05) and/or large dialysate volumes (multivariate partial r2 = 0.11), suggesting a role of dialytic glucose uptake in the development of obesity. The change in serum albumin concentrations was positively correlated with dialysate volume (partial r2 = 0.14), and negatively affected by dialytic protein losses (partial r2 = 0.06). In conclusion, the peritoneal transporter state is a weak but significant determinant of growth and body mass gain in children on chronic peritoneal dialysis. Rapid small solute equilibration contributes to impaired growth but enhanced acquisition of body mass. Dialytic small solute clearance has a weak positive effect on statural growth independent of the transporter state, but does not affect body mass gain.