Pharmacokinetics of mycophenolic acid (MPA) and determinants of MPA free fraction in pediatric and adult renal transplant recipients. German Study group on Mycophenolate Mofetil Therapy in Pediatric Renal Transplant Recipients

Dosage guidelines for mycophenolate mofetil (MMF), an ester prodrug of the immunosuppressant mycophenolic acid (MPA), are still preliminary in children. This study compares the pharmacokinetics of MPA and its major metabolite MPA glucuronide (MPAG) in pediatric renal transplant recipients receiving 600 mg MMF/m2 body surface area twice a day to those of adults on the currently recommended oral dose of 1 g of MMF twice a day. Concentration-time profiles of 18 children (age, 10.7+/-0.72 yr; range, 5.9 to 15.3 yr) and 10 adults were investigated 1 and 3 wk after transplantation. Plasma concentrations of MPA and MPAG were measured by reverse-phase HPLC. Because MPA is extensively bound to serum albumin and only the free fraction is presumed to be pharmacologically active, the MPA free fraction was also analyzed by HPLC after separation through ultrafiltration. The areas under the concentration-time curves (AUC0-12) of total and free MPA throughout the 12-h dosing interval in children were, in general, comparable to the corresponding data in adult patients. The mean AUC0-12 of MPA and free MPA did not change significantly over the first 3 wk after transplantation, but there was substantial intra- and interindividual variation. MPAG-AUC0-12 values in children with primary renal transplant dysfunction were threefold higher than in those with functioning transplants. Renal impairment had no consistent effect on total MPA-AUC0-12 values, but the MPA free fraction in children (median, 1.65%; range, 0.40 to 13.8%) was significantly (r2=0.46) modulated by renal transplant function and serum albumin levels. In conclusion, concentration-time profiles of pediatric renal transplant recipients administered 600 mg MMF/m2 body surface area twice a day are comparable to those in adults on 1 g MMF twice a day in the first 3 wk after transplantation. Renal impairment and decreased serum albumin levels led to an increase in the free fraction of MPA and the free MPA-AUC0-12 values. Because the pharmacologic activity of MPA is a function of unbound drug concentration, these findings might be relevant for the pharmacodynamic effects of MPA.

Inappropriate elevation of serum leptin levels in children with chronic renal failure. European Study Group for Nutritional Treatment of Chronic Renal Failure in Childhood

Decreased spontaneous nutrient intake is a frequent clinical problem in patients with chronic renal failure (CRF). Leptin, the recently characterized gene product of the obese gene, is produced by adipocytes and is thought to act as an afferent satiety signal on the appetite and satiety centers of the brain. Serum leptin levels were investigated in 134 pediatric patients in different stages of CRF to evaluate a possible relationship between leptin, GFR, and spontaneous energy intake. Serum leptin levels, measured by a specific RIA, were elevated above the 50th percentile of the normal range in 78% of CRF patients and above the 95th percentile in 45% of patients. Gel chromatography of CRF sera yielded only one single immunoreactive peak at 16 kD, indicating that the increase of immunoreactive leptin levels in CRF serum was not due to accumulation of leptin degradation products. Multiple stepwise regression analysis revealed the percentage of body fat as assessed from skinfold measurements (r = 0.79, P < 0.0001) and GFR (r = -0.17, P < 0.005) as independent predictors of serum leptin levels, accounting for 66% of total statistical variability. There was an inverse linear correlation between standardized leptin levels (leptin z-score) and the spontaneous energy intake quantified from written dietary diaries (r = -0.36, P < 0.001). These data suggest that the percentage of body fat remains the main determinant of serum leptin in CRF patients, but their levels increase with declining GFR, presumably by reduced renal clearance. Leptin levels in CRF serum that are inappropriately elevated in relation to the percentage of body fat might lead to a dysregulation of the normal peripheral-central leptin feedback loop, thereby contributing to decreased nutrient intake in uremia.

Metabolic effects of long-term growth hormone treatment in prepubertal children with chronic renal failure and after kidney transplantation. The German Study Group for Growth Hormone Treatment in Chronic Renal Failure

To evaluate the metabolic effects of long-term treatment with recombinant human (rh) GH in short children with chronic renal failure (CRF), annual oral glucose tolerance tests (oGTT) during rhGH therapy for up to 5 y in 53 prepubertal children with CRF on conservative treatment, dialysis, and after renal transplantation were compared with that of 12 age-matched children treated with rhGH for idiopathic short stature. At the start of rhGH treatment, fasting values of glucose, insulin, glycosylated Hb A (HbA1C), triglycerides, cholesterol, glucose, and insulin responses during oGTT were significantly elevated in all patient groups compared with control subjects (p < 0.001). In the total population, fasting and 2-h postprandial glucose concentrations were inversely correlated with GFR and positively with age and methylprednisolone dosage in transplanted patients. Fasting insulin levels were positively correlated with body mass index and inversely with GFR. RhGH treatment was not associated with a change in fasting or stimulated glucose concentrations in any treatment group throughout the observation period. In contrast, serum insulin levels increased during the first treatment year in all groups, resulting in a more marked elevation of integrated insulin levels in transplant (1402 +/- 179 pM) and dialysis (1025 +/- 114 pM) patients compared with conservatively treated patients (829 +/- 94 pM), and control subjects (719 +/- 89 pM) (p < 0.01). Hyperinsulinemia persisted in all treatment groups for up to 5 y of follow-up. In conclusion, age, renal function, and obesity are the major independent predictors of glucose tolerance in children with CRF. Long-term rhGH treatment does not affect glucose tolerance, but aggravates the preexisting hyperinsulinemia in children with end-stage renal disease. In concert with the dyslipidemia of uremia, the rhGH-promoted hyperinsulinemia may contribute to the long-term risk for premature atherosclerosis in patients with childhood onset CRF.

Effects of insulin-like growth factor I on the renal juxtamedullary microvasculature

To characterize the effects on the rat renal preglomerular microvasculature of insulin-like growth factor I (IGF-I), experiments were performed using the in vitro blood-perfused juxtamedullary nephron preparation. IGF-I induced a reversible vasodilation of pre- but not postglomerular microvessels in a dose-dependent manner (10(-9)-10(-7) M). The IGF-I-induced vasodilation was similar in all preglomerular vascular segments: interlobular artery, 11.5 +/- 1.2% of control (n = 16); mid-afferent arterioles, 11.6 +/- 1.7% (n = 24); and juxtaglomerular afferent segments, 16.1 +/- 2.8% (n = 19). Renal autoregulatory capacity was not reduced by IGF-I. Pretreatment with the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (10(-4) M) completely inhibited the vasodilatory response to IGF-I. IGF-I induced a rapid increase of NO concentration in intact renal microvessels, monitored by a NO-selective voltametric microelectrode. Pretreatment with the cyclooxygenase inhibitor indomethacin (10(-5) M) not only abrogated the IGF-I-induced dilation, but, moreover, IGF-I elicited a small but significant (approximately 10%) vasoconstriction in all preglomerular vessels. These results indicate that the renal vascular effects of IGF-I involve activation of two endogenous vasodilators (NO and vasodilatory prostaglandins). In addition, IGF-I may also release an undefined vasoconstrictor.

Factors affecting growth and strategies for treatment in children after renal transplantation

Growth failure is a frequent side effect of long-term high-dose glucocorticoid therapy in children. Pharmacological doses of glucocorticoids interfere at different levels with the integrity of the somatotropic hormone axis. The majority of patients on chronic corticosteroid medication present with overt GH hyposecretion, apparently due to enhancement of hypothalamic somatostatin release. Glucocorticoids also inhibit IGF bioactivity by the induction of IGF inhibitors and stimulate the production of certain IGFBPs. In addition, glucocorticoids inhibit growth directly at the tissue level by suppressing local growth factors and skeletal tissue matrix production. In children post renal transplantation, concomitant treatment with cyclosporin A for immunosuppression allows low-dose glucocorticoid medication. Reduction of glucocorticoids, in particular when given as alternate-day therapy, improves growth in some but not all children. The new glucocorticoid deflazacort appears to have fewer side effects regarding steroid-induced osteopenia and cushingoid appearance. A beneficial effect on longitudinal growth has not been clearly established. Recent experimental and clinical data indicate that the catabolic and growth-depressing effects of glucocorticoids can be counterbalanced by concomitant anabolic treatment with rhGH. The potential role of rhIGF-I is less well investigated. Treatment with rhGH is able to antagonize several side effects of long-term glucocorticoid administration, such as growth failure, protein-wasting and osteoporosis. If catch-up growth cannot be achieved by an alternate-day steroid regimen and discontinuation of glucocorticoids appears to be an intolerable risk for graft survival, rhGH therapy may be initiated. However, rhGH therapy in this setting must still be considered experimental, because the possible interference of rhGH with the immunosuppressive action of glucocorticoids in children after organ transplantation is still incompletely defined.

Interactions between glucocorticoids and the growth hormone-insulin-like growth factor axis

Glucocorticoids in pharmacological doses interfere with the integrity of the somatotropics hormone axis. However, the apparent discrepancies between the in vitro and in vivo studies, short-term vs. long-term exposure, and species-specific changes complicate a clear assessment of these interactions. The growth-depressing effects of glucocorticoids are multifactorial and involve suppression of pituitary GH release by stimulating hypothalamic somatostatin tone, down-regulation of hepatic GH receptors, inhibition of GH bioactivity by the induction of IGF inhibitors, complex alteration of the IGFBP serum profile, and a direct suppressive effect on tissue matrix production and synthesis of local growth factors.

Insulin-like growth factors (IGFs) and IGF binding proteins, serum acid-labile subunit and growth hormone binding protein in nephrotic children

We hypothesized that the increased glomerular permeability to serum proteins in the nephrotic syndrome might lead to alterations of the somatotropic hormone axis, thereby contributing to growth failure and catabolism in the nephrotic state. The insulin-like growth factors (IGF)-I and -II and the IGF binding proteins (IGFBP)-1, -2 and -3 were analyzed in serum and urine of 21 children with the nephrotic syndrome and normal glomerular filtration rate. Mean age-related serum IGF-I levels by RIA (-0.53 +/- 0.34 SD) were slightly, but significantly (P < 0.05) decreased compared with the reference population, whereas mean age-related serum IGF-II levels (0.68 +/- 0.21 SD) were slightly, but significantly (P < 0.005) increased. The urinary excretion rate of both peptides was enhanced fivefold. By RIA, mean age-related serum IGFBP-1 (2.05 +/- 0.19 SD) and, even more pronounced, IGFBP-2 (5.97 +/- 0.65 SD) were clearly elevated despite a 12-fold and 2-fold increase of the respective urinary excretion rate. There was a tight and specific correlation between age-related serum IGFBP-2 levels and the degree of the nephrotic syndrome, as estimated by serum albumin levels (r = -0.78, P < 0.0001). Serum immunoreactive IGFBP-3 levels were also elevated (1.79 +/- 0.33 SD) in nephrotic serum, due to an increase of low-molecular weight IGFBP-3 fragments. By FPLC analysis, there was a decrease of the 150 kDa IGFBP ternary complex in nephrotic serum, which in the presence of normal concentrations of the acid-labile subunit by RIA appears to be due to a reduction of intact IGFBP-3. Serum levels of the high-affinity GH binding protein that presumably reflects GH receptor status in tissues were normal. In summary, total serum IGFs in children with the nephrotic syndrome are normal, but the binding of IGFs to IGFBPs in the circulation is altered with a shift from the 150 kDa IGFBP complex to an excess of low molecular weight IGFBPs. Because increased unsaturated high-affinity IGFBPs in nephrotic serum have the ability to inhibit IGF action on target tissues by competing with the type 1 IGF receptor for IGF binding, this alteration is likely to contribute to growth failure and tissue catabolism in the nephrotic state.

Impaired postprandial regulation of insulin-like growth factor binding protein-1 in children with chronic renal failure

Patients with chronic renal failure (CRF) have elevated plasma levels of insulin-like growth factor-1 (IGFBP-1). We sought to determine the dynamics of plasma IGFBP-1 in response to an endogenous insulin pulse during an oral glucose tolerance test (oGTT) in 12 prepubertal children with advanced CRF [glomerular filtration rate (GFR) 12.5 +/- 4 mL/min/1.73 m2] and in 9 age-, gender-, and body size-matched controls with normal renal function. Glucose and insulin responses to oGTT were significantly elevated in CRF (P < 0.01), indicating decreased sensitivity to the hypoglycemic action of insulin. Fasting plasma IGFBP-1 levels in CRF (235 +/- 40 ng/mL) were 2.5-fold increased compared with controls (94 +/- 11.6 ng/mL, P < 0.0001). In controls, plasma IGFBP-1 levels rapidly decreased with time by 52%, to a level of 45 +/- 6.7 ng/mL 180 min after the oral glucose load. In contrast, plasma IGFBP-1 levels in CRF patients slowly decreased with time by 25%, to a level of 176 +/- 28 ng/mL (P < 0.001 vs. controls) 180 min after the oral glucose load. For the group as a whole, the percent decrease in IGFBP-1 at 180 min was positively correlated with GFR (r = 0.85, P < 0.0001). Plasma GH concentrations were not statistically different at baseline, but showed a paradoxical increase in CRF patients thereafter. Plasma IGF-I concentrations at baseline were comparable in CRF patients and controls and similarly decreased by about 10% (P < 0.01) after the oral glucose load. In summary, our study shows that the decline of plasma IGFBP-1 in response to an oral glucose load is impaired in children with CRF despite increased insulin levels. This impaired postprandial decline of plasma IGFBP-1 might interfere with glucose homeostasis by blocking insulin-like activity of free IGFs in vivo and thereby contribute to glucose intolerance in uremia.

Reduced concentration of serum growth hormone (GH)-binding protein in children with chronic renal failure: correlation with GH insensitivity. The European Study Group for Nutritional Treatment of Chronic Renal Failure in Childhood. The German Study Group for Growth Hormone Treatment in Chronic Renal Failure

Growth retardation in children with chronic renal failure (CRF) despite normal or elevated GH levels indicates a peripheral insensitivity to the action of GH. One possible molecular mechanism is a reduced density of GH receptors in GH target organs. In humans, the circulating high affinity GH binding protein (GHBP) is thought to reflect GH receptor expression, because it is derived from the extra-cellular domain of the GH receptor by proteolytic cleavage. We, therefore, analyzed serum GHBP levels by ligand-mediated immunofunctional assay in 126 children with CRF compared to reference values obtained by analysis of 773 healthy children. In 77% of CRF patients, serum GHBP concentrations were below the mean for age- and gender-matched controls. The decrease in serum GHBP levels was related to the degree of renal dysfunction. In advanced CRF (glomerular filtration rate, < 35 mL/min.1.73 m2), mean age- and gender-adjusted GHBP levels were -1.40 +/- 0.18 SD score; 36% of patients had GHBP levels below the normal range (< -2 SD score). Children with end-stage renal disease (n = 26) had the lowest GHBP levels (-2.25 +/- 0.22 SD score). Multiple linear regression analysis revealed that body mass index, rather than glomerular filtration rate, is the prevailing determinant of serum GHBP levels in CRF. GHBP levels correlated with both the spontaneous growth rate ( r = 0.44; P < 0.0001) and the growth response to GH therapy (r = 0.48; P < 0.005), indicating decreased sensitivity to both endogenous and exogenous GH. Subcutaneous GH therapy did not consistently affect serum GHBP levels after 3 months of treatment. It is suggested that low GHBP levels in children with CRF represent a quantitative tissue GH receptor deficiency as one of the molecular mechanisms of GH insensitivity.

Derangements of the somatotropic hormone axis in chronic renal failure

Recent evidence indicates that disturbances of the somatotropic hormone axis play an important pathogenic role for growth retardation and catabolism in children with chronic renal failure (CRF). Whereas the growth hormone (GH) secretion rate in CRF is variable between patients and studies, a prolonged half-life of GH as a result of a reduced renal metabolic clearance rate is a consistent finding. Accordingly, the serum GH levels in children with CRF are normal or elevated depending on the extent of renal failure. The apparent discrepancy between normal or elevated GH levels and diminished longitudinal growth in CRF has led to the concept of GH insensitivity, which is caused by multiple alterations in the distal components of the somatotropic hormone axis. Serum insulin-like growth factor (IGF)-I and IGF-II levels are normal in preterminal CRF, while in end-stage renal disease (ESRD) IGF-I levels are slightly decreased and IGF-II levels slightly increased. In view of the prevailing elevated growth hormone levels in ESRD, these serum IGF-I levels appear as inadequately low. Indeed, there is both clinical and experimental evidence for a decreased hepatic IGF-I production rate in CRF. This hepatic insensitivity to the action of GH may be partially the consequence of a reduced GH receptor expression in liver tissue. The action and metabolism of IGFs are modulated by specific high-affinity IGF binding proteins (IGFBPs), which bind approximately 99% of circulating IGF. IGFBP-1, IGFBP-2, and low molecular weight IGFBP-3 fragments are increased in CRF serum in relation to the degree of renal dysfunction. Both decreased renal filtration, in particular of low molecular weight IGFBP-3 fragments, and increased hepatic production of IGFBP-1 and -2 contribute to high IGFBP serum levels. Experimental and clinical evidence suggests that these excessive high-affinity IGFBPs in CRF serum inhibit IGF action on target tissues by competition with the type 1 IGF receptor for IGF binding.

Decreased hepatic insulin-like growth factor (IGF)-I and increased IGF binding protein-1 and -2 gene expression in experimental uremia

The imbalance between normal insulin-like growth factor-I (IGF-I) and markedly increased IGF binding protein (IGFBP) plasma levels plays a pathogenic role for growth retardation and catabolism in children with chronic renal failure. To investigate the mechanism of these alterations, experiments were performed in an experimental model of uremia in rats (5/6 nephrectomy) and in pair-fed and ad libitum-fed sham-operated controls Using a specific solution hybridization/RNase protection assay, we observed a marked reduction of hepatic IGF-I messenger RNA (mRNA) abundance at steady state in uremic animals (37 +/- 5% of control) compared both with pair-fed (65 +/- 10%) and ad libitum-fed controls (100 +/- 11%) (P < 0.001). Reduced IGF-I gene expression was clearly organ-specific; it was most pronounced in liver (significant vs., pair-fed controls) and lung and muscle tissue (significant vs., ad libitum-fed controls); no change was observed in kidney and heart tissue. To determine a potential mechanism of reduced hepatic IGF-I gene expression in uremia, the hepatic GH receptor gene expression in the same experimental animals was analyzed by specific solution hybridization/RNase protection assay. Uremic animals had a 20-30% reduction of hepatic GH receptor mRNA abundance compared with controls. Hepatic GHBP expression in uremia was decreased in parallel. Despite the reduction of hepatic IGF-I mRNA abundance, plasma IGF-I levels in uremia were not different from ad libitum-fed controls. This discrepancy is explained by an increased concentration of IGFBPs in uremic plasma. By RIA, plasma IGFBP-1 levels in uremia were increased 4-fold; by Western immunoblot, plasma IGFBP-2 levels were increased 7-fold and plasma IGFBP-4 levels were increased 2-fold compared with both control groups. Intact IGFBP-3 (M(r), approximately 48 kDa) and low molecular IGFBP-3 fragments were not significantly different among the three groups. By Northern blot analysis, hepatic IGFBP-1 mRNA levels in uremia were 2-fold higher than in controls. IGFBP-2 mRNA abundance in liver tissue was increased 4-fold, whereas in kidney there was a significant reduction of IGFBP-2 mRNA (30% of control). IGFBP-4 mRNA was increased by 50% in kidney but not in liver. Plasma insulin and corticosterone levels were not different among the groups. Our study shows that hepatic IGF-I gene expression was specifically reduced in uremia, partially as the consequence of a reduced hepatic GH receptor gene expression. One of the mechanisms contributing to increased IGFBP levels in uremia is increased hepatic gene expression of IGFBP-1 and IGFBP-2. The imbalance between reduced hepatic IGF-I production and increased hepatic IGFBP-1 and 2 production is likely to play a pathogenic role for catabolism and growth failure in CRF.

Predictors of the response to growth hormone in short prepubertal children post-renal transplant. German Study Group for Growth Hormone Treatment in Children Post Renal Transplantation Study Group Members

The growth response to recombinant human growth hormone (rhGH) in post-renal transplantation children is variable. We sought to determine predictive factors of this variable effect of rhGH by analysis of a homogeneous group of 16 prepubertal children with a median age of 12.4 years (range 7.7-18.0 years). rhGH was given at 30 i.u./m2/week for at least one year. All children remained prepubertal during the study period. Height velocity increased from 2.5 +/- 0.4cm/year to 7.4 +/- 0.5cm/year after one year of treatment (p < 0.001). The growth response to rhGH (height velocity after one year of rhGH) was not significantly correlated with the dose of prednisolone administered (range 2.3-9.1mg/m2/day), graft function as estimated by creatinine clearances (range 19-88ml/min/1.73m2), the degree of stunting at baseline, baseline height velocity, or chronological age. However, a relatively tight inverse correlation was found between the growth response to rhGH and the degree of bone age delay (r = 0.73, p < 0.005). Hence, the degree of bone age delay appears to be a helpful clinical predictor of response to rhGH in short prepubertal children post-renal transplantation.

Serum insulin-like growth factors and their binding proteins in children with end-stage renal disease

Serum levels of insulin-like growth factor-I (IGF-I), IGF-II, and IGF binding protein-1 (IGFBP-1), IGFBP-2, and IGFBP-3 were measured in 54 children with end-stage renal disease (ESRD). The results were compared with their respective age-dependent normal ranges. IGFs and IGFBPs were quantified by specific radioimmunoassay. Serum IGF-I in children with ESRD tended to cluster in the low-normal range. Mean age-related serum IGF-I levels were slightly, but significantly decreased (-1.08 +/- 0.17 SDS). In view of the prevailing elevated growth hormone levels in ESRD, these serum IGF-I levels must be interpreted as inadequately low. In contrast to IGF-I, individual serum IGF-II levels were either in the upper-normal range or clearly elevated. Mean age-related IGF-II (1.09 +/- 0.15 SDS) was slightly, but significantly elevated. Mean age-related IGFBP-1 serum levels (2.20 +/- 0.10 SDS) were moderately increased, while mean age-related serum IGFBP-2 (5.65 +/- 0.36) and IGFBP-3 levels (3.60 +/- 0.19) were markedly elevated. Affinity cross-linking of 125iodine-IGF-II to sera from patients with ESRD and immunoprecipitation with a specific antiserum showed that low molecular weight IGFBP-3 fragments in ESRD serum are capable of binding IGF. In patients with ESRD, a rapid and persistent decline of immunoreactive IGFBP-3 in response to restoration of renal function by renal transplantation was observed. This finding indicates that renal dysfunction contributes to high immunoreactive IGFBP-3 levels in ESRD. In conclusion, the imbalance between normal total IGF levels and the excess of IGFBPs in ESRD is likely to play a role in growth failure in these children.

Growth promoting effects of growth hormone and IGF-I are additive in experimental uremia

Exogenous growth hormone (GH) stimulates the endogenous production of IGF-I and improves growth in uremia. We investigated whether exogenous IGF-I is also able to improve uremic growth failure in rats and whether the growth promoting effects of GH and IGF-I are additive. In female 150 g uremic (subtotal nephrectomy, NX) Sprague-Dawley rats, both rhGH in doses from 2 X 1.25 to 2 X 10 IU/kg bid s.c. and rhIGF-I in doses from 2 X 0.5 to 2 X 4.0 mg/kg bid s.c. caused a dose-dependent increase in weight gain and length gain. However, endogenous production of GH was suppressed by both agents. Peptide hormone treatment did not affect cumulative food intake, but significantly increased food efficiency ratio (weight gain/food intake). Concomitant s.c. treatment with maximally effective doses of rhGH (12 X 5 IU/kg bid) and of rhIGF-I (2 X 2 mg/kg bid) resulted in additive growth promoting effects in NX and pair-fed control (CO) animals during the observation period of 12 days. Cumulative length gain was 3.2 +/- 0.5 cm in solvent-treated NX-animals, 4.1 +/- 0.5 cm with rhGH (+ 28% above solvent), 4.2 +/- 0.6 cm with rhIGF-I (+ 31%) and 4.9 +/- 0.5 cm with both peptides (+ 53%). The food efficiency ratio was 0.16 +/- 0.05 in solvent NX, 0.33 +/- 0.04 with rhGH (+ 106% above solvent), 0.23 +/- 0.02 with rhIGF-I (+ 44%), and 0.38 +/- 0.02 with both peptides (+ 138%). Histomorphometric analysis and measurements of length gain by fluorescence microscopy in the upper tibial metaphysis confirmed the growth promoting effects of both peptide hormones. The serum concentrations of IGF binding protein (BP)-4 (Western ligand blotting analysis) and of IGFBP-2 (immunoblot) were increased in uremic animals whereas IGFBP-3 was unchanged. Treatment with IGF-I and/or rhGH increased serum concentration of IGF-I but did not change the IGFBP pattern. rhIGF-I lowered blood glucose levels within one to two hours after injection. The effect was most pronounced during the first treatment day and declined thereafter. Concomitant treatment with rhGH attenuated the glucose lowering effect of rhIGF-I (glucose serum concentration at day one: 120 +/- 11 mg% in solvent NX, 50 +/- 21 mg% with rhIGF-I, 80 +/- 24 mg% with both peptides). It is concluded that: (i) IGF-I is able to stimulate growth in NX animals but suppresses endogenous GH production in the long run; (ii) the concomitant treatment with IGF-I and GH has additive effects on growth; and (iii) concomitant treatment with rhGH prevents hypoglycemia that is noted with rhIGF-I alone.

Recombinant human growth hormone for children with renal failure

The pathogenesis of growth retardation in children with chronic renal failure (CRF) is clearly multifactorial. A major breakthrough in the understanding of the pathogenesis of uremic growth failure was achieved only recently by a more detailed analysis of the growth hormone (GH)/insulinlike growth factor (IGF) axis. Uremia is characterized by an insensitivity to the somatotropic action of GH. The mechanisms that account for this insensitivity include reduced hepatic GH receptor expression, decreased production of IGF-I, and inhibition of IGF bioactivity by increased binding of IGFs to their specific binding proteins. Recombinant human growth hormone (rhGH) in supraphysiological doses is able to overcome the partial GH resistance and to stimulate longitudinal growth under both experimental and clinical conditions. One possible mechanism of action of rhGH in uremia is the restoration of circulating IGF bioactivity, which results from the differential regulatory effect of rhGH on circulating IGF-I and IGFBP-3 concentrations. RhGH has proven to be an effective, safe, and well-tolerated new treatment modality for growth-retarded children at all stages of CRF. There is strong evidence that final height will increase in these children. Other than a modest chronic stimulation of insulin secretion, no frequent side effects have been observed; in particular, no acceleration in loss of residual renal function has been seen in children treated before the onset of end-stage renal failure. In children after transplantation, rhGH is also effective, but the potential risk of interference with graft function is not yet sufficiently defined.

Growth hormone as a new treatment modality for short children with chronic renal failure. The German Study Group for Growth Hormone Treatment in Chronic Renal Failure

Recombinant human growth hormone (rhGH) has become a new treatment modality for short children with chronic renal failure (CRF) and after renal transplantation. The rationale for high-dose rhGH treatment is the insensitivity of the uremic organism to GH. As the insensitivity to GH is expressed more in end-stage renal failure than in earlier stages of CRF, patients on dialysis respond less to rhGH. In transplanted children, rhGH can counterbalance the growth-depressing effects of corticosteroids. In prepubertal children, rhGH improves the height standard deviation score by a mean of +2 within 5 years. The effect of rhGH treatment on final height remains to be studied.

Serum insulin-like growth factors (IGFs) and IGF binding proteins 1, 2, and 3 in children with chronic renal failure: relationship to height and glomerular filtration rate. The European Study Group for Nutritional Treatment of Chronic Renal Failure in Childhood

Serum levels of insulin-like growth factor I (IGF-I), IGF-II, and IGF binding protein 1 (IGFBP-1), IGFBP-2, and IGFBP-3 were measured in 94 children with chronic renal failure (CRF). The results were compared with their respective age-dependent normal ranges, and the relationship with height and residual glomerular filtration rate (GFR) was examined. Each IGF and IGFBP was quantified by specific RIA. Serum IGF-I and IGF-II levels were in the normal range throughout their entire childhood in the vast majority of cases. The mean age-related IGF-I (0.07 +/- 0.14 SD score) and IGF-II levels (0.06 +/- 0.11 SD) were similar. Age-related IGF-II but not IGF-I levels showed a weak inverse linear correlation with residual GFRs (r = -0.24, P < 0.02). Mean age-related IGFBP-1 serum levels (1.04 +/- 0.09 SD) were slightly elevated, whereas mean age-related serum IGFBP-2 levels (3.25 +/- 0.20 SD) and serum IGFBP-3 levels (2.61 +/- 0.12 SD) were markedly elevated. Significant inverse correlations were found between GFRs and age-related IGFBP-1 (r = -0.42, P < 0.001), IG-FBP-2 (r = -0.56, P < 0.001), and IGFBP-3 (r = -0.28, P < 0.005), but the increase in IGFBP-2 with declining GFR was relatively more pronounced than the respective increase in IGFBP-1 and IGFBP-3. The correlation between age-related IGF-I and relative height in prepubertal children with CRF (n = 54, r = 0.43, P < 0.001) was lower than in prepubertal controls (n = 68, r = 0.67, P < 0.001), and the slope of the regression line was significantly less steep, indicating that the normal relationship between IGF-I and height is disturbed in CRF. The normal relationship between IGFBP-3 and height was disrupted in CRF. Forward stepwise regression analysis revealed that height in CRF is correlated with IGF-I and inversely correlated with IGFBP-2. We conclude that the imbalance between normal IGFs and excessive IGFBP serum levels in CRF plays a pathogenic role in the growth failure of these children.

Quantification of urinary insulin-like growth factors (IGFs) and IGF binding protein 3 in healthy volunteers before and after stimulation with recombinant human growth hormone

We examined excretion of urinary insulin-like growth factors I and II (IGF-I and IGF-II) and their major binding protein IGFBP-3 in comparison to their respective serum concentration in nine healthy female volunteers (median age 25 years, range 22-27) under baseline conditions and after stimulation with recombinant human growth hormone (rhGH), 4.5 IU twice daily subcutaneously for a period of 3 days. The IGFs were measured in unconcentrated urine by use of recently developed, highly sensitive radioimmunoassays. The IGFBP-3 was measured by a specific radioimmunoassay. The mean (+/- SD) urinary concentrations of IGF-I (0.08 +/- 0.07 micrograms/l), IGF-II (1.02 +/- 0.47 micrograms/l) and IGFBP-3 (19.1 +/- 6.9 micrograms/l) were two to three orders of magnitude lower than in serum. The ratio of IGF-II over IGF-I concentration in urine (13:1) was five times higher than in serum (2.5:1), and the ratio of IGFBP-3 over the sum of IGF-I and IGF-II in urine (17:1) was four times higher than in serum (4:1). Urinary excretion was 63.3 +/- 46.6 ng.m-2.24h-1 for IGF-I, 1002 +/- 598 ng.m-2.24h-1 for IGF-II and 18039 +/- 4983 ng.m-2.24h-1 for IGFBP-3. Using fast protein liquid exclusion chromatography, only immunoreactive IGFBP-3 components of less than 60 kD were detected in urine, with a major peak at 20 kD. Urinary IGFBP-3 excretion correlated with serum IGFBP-3 (r = 0.61, p < 0.01) and the glomerular filtration rate (r = 0.56, p < 0.05) measured by steady-state inulin infusion clearances.(ABSTRACT TRUNCATED AT 250 WORDS)