Growth hormone, insulin-like growth factor and the kidney

Recent advances in diagnosis, treatment, and outcome of congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is an autosomal-recessive disease causing cortisol deficiency, aldosterone deficiency and hyperandrogenism. Diagnosis of 21-OHD is confirmed by steroid analysis in newborn screening or later on. Standard medical treatment consists of oral glucocorticoid and mineralocorticoid administration in order to suppress adrenal androgens and to compensate for adrenal steroid deficiencies. However, available treatment is far from ideal, and not much is known about the long-term outcome in CAH as trials in patients in adulthood or old age are rare. Here we briefly describe the pathophysiology, clinical picture, genetics and epidemiology of 21-OHD. This is followed by a comprehensive review of the recent advances in diagnosis, treatment and outcome. Novel insights have been gained in the fields of newborn screening, specific steroid measurement utilizing mass spectrometry, genetics, glucocorticoid stress dosing, additive medical therapy, prenatal treatment, side-effects of medical treatment, adrenomedullary involvement, metabolic morbidity, fertility and gender identity. However, many issues are still unresolved, and novel questions, which will have to be answered in the future, arise with every new finding.

Nutrition and Metabolism in Kidney Disease

Nutritional and metabolic derangements are highly prevalent in patients with chronic kidney disease (CKD) and patients on renal replacement therapy. These derangements, which can be termed uremic malnutrition, significantly affect the high morbidity and mortality rates observed in this patient population. Uremic malnutrition clearly is related to multiple factors encountered during the predialysis stage and during chronic dialysis therapy. Several preliminary studies suggested that interventions to improve the nutritional status and metabolic status of uremic patients actually may improve the expected outcome in these patients, although their long-term efficacy is not well established. It therefore is important to emphasize that uremic malnutrition is a major comorbid condition in CKD and renal replacement therapy patients, and that all efforts should be made to try to understand better and treat these conditions effectively to improve not only mortality but also the quality of life of chronically uremic patients. In this article we review the current state of knowledge in the field of nutrition and metabolism in all stages of CKD and renal replacement therapy, including kidney transplant. We also address questions that face investigators in this field and suggest where future research might be headed.

Protein and energy nutrition among adult patients treated with chronic peritoneal dialysis

Protein-energy malnutrition (PEM) in adult patients treated with chronic peritoneal dialysis (CPD), which is highly prevalent and frequently severe in its manifestation, poses a significant therapeutic dilemma. The causes of PEM include inflammation, low nutrient intake, nutrient losses during dialysis, metabolic acidemia, coexisting illnesses, and possibly the endocrine disorders of uremia. Treatment strategies for PEM in CPD patients include the following: attempt to treat the potentially reversible causes of anorexia, increase nutrient intake (by nutritional counseling, oral food supplements, consideration of appetite stimulants and intraperitonial amino acid solutions), and the correction of metabolic acidosis. Coexisting illnesses engendering PEM should be treated. Experimental evidence suggests that such agents as anabolic steroids, human growth hormone, insulin-like growth factor-I, and L-carnitine may engender positive protein balance in these individuals. Finally, the use of anti-inflammatory agents to improve the nutritional status of malnourished CPD patients remains to be defined. There is a need to carry out clinical trials that examine whether an improvement in the nutritional status of CPD patients is associated with an improvement in their mortality, morbidity and/or quality of life.

PTH ameliorates acidosis-induced adverse effects in skeletal growth centers: the PTH-IGF-I axis

BACKGROUND

Chronic metabolic acidosis (CMA) exerts profound adverse effects on bone metabolism thereby leading to impaired skeletal linear growth. We have recently shown that CMA in vitro causes distinct morphological changes in skeletal growth centers along with inhibition of endochondral differentiation. In addition, CMA causes an end organ resistance to the anabolic effects of growth hormone (GH) and locally produced insulin-like growth factor-I (IGF-I) in skeletal growth centers. Given the effects of parathyroid hormone (PTH) and PTH related protein (PTHrP) on the development of cartilaginous bone, we sought to determine whether PTH has any effects on the changes induced by CMA in skeletal growth centers. The interaction between PTH and IGF-I in growth centers during neutral or acidic conditions were studied specifically.

METHODS

An in vitro organ culture system using the murine mandibular condyle was employed as a model for endochondral active growth center. Condyles from six-day-old mice were cultured in BGJb medium of either neutral pH (pH approximately 7.4) or acidic pH (pH approximately 7.15) in the presence or absence of 10-10 mol/L [1-34] PTH. After 24, 48, 72 and 96 hours of culture, the condyles were washed, fixed in formaldehyde, and processed for paraffin embedding. Histologic markers of the growth center were assessed. In addition, the protein level and mRNA expression for various markers of cartilage differentiation were evaluated by immunohistochemistry and in situ hybridization, respectively. The abundance and expression levels of IGF-I and IGF-I receptor (IGF-I-R) were assessed also.

RESULTS

Following incubation for 72 hours in acidic conditions, there was a marked attenuation of the chondroblastic zone, suggesting a defect in the process of cellular differentiation. Acidosis also down-regulated endochondral differentiation markers (cartilage specific proteoglycans, collagen type II). This was accompanied by a reduction in the expression of IGF-1, IGF-1 receptor and PTH receptors. PTH (10-10 mol/L) added to acidic cultures prevented the adverse effects of CMA on endochondral differentiation and increased the overall condylar growth, when compared to acidic conditions without PTH. PTH also up-regulated its own receptor in control as well as during acidic conditions, and increased the expression levels of IGF-1 and IGF-1 receptor in the acidotic condyle. Acidosis increased the expression of IGF-I binding protein-4 (IGFBP-4, an inhibitor of IGF-I activity), whereas coincubation with PTH during acidic conditions abrogated the up-regulation of IGFBP-4. Addition of a neutralizing antibody to IGF-I-R during PTH treatment under acidic conditions resulted in the abrogation of the ameliorative effect of PTH on endochondral differentiation. The protein kinase C (PKC) signaling pathway was modulated negatively by CMA. However, PTH activated PKC-alpha under both control and acidic conditions. The phorbol ester, PMA (phorbol 12-myristate 13-acetate), a PKC activator, mimicked the effect of PTH on chondrocyte differentiation.

CONCLUSION

Parathyroid hormone at low concentration stimulates the differentiation and proliferation of cartilage cells and prevents the suppressive effect of acidosis on endochondral bone differentiation and on the IGF-I/IGF-I-R system in skeletal growth centers. Increased local production of IGF-I by PTH, which takes place even during acidotic conditions, mediates, at least in part, the ameliorative effect of PTH. Protein kinase C is probably one of the signaling pathways mediating the salutary effects of PTH on chondrocyte differentiation in growth centers. This study lends further credence to the notion that under certain conditions, PTH or PTHrP can exert anabolic effects in the skeleton. These findings may be of clinical-therapeutic significance in children and patients with CMA.

Effects of growth hormone treatment on the pituitary expression of GHRH receptor mRNA in uremic rats

BACKGROUND

A decreased ability of pituitary cells to secrete growth hormone (GH) in response to growth hormone releasing hormone (GHRH) stimulation has been shown in young uremic rats. The aim of the current study was to examine the effect of uremia and GH treatment on pituitary GHRH receptor expression.

METHODS

Pituitary GHRH receptor mRNA levels were analyzed by RNase protection assay in young female rats made uremic by subtotal nephrectomy, either untreated (UREM) or treated with 10 IU/kg/day of GH (UREM-GH), and normal renal function animals fed ad libitum (SAL) or pair-fed with the UREM group (SPF). Rats were sacrificed 14 days after the second stage nephrectomy.

RESULTS

Renal failure was confirmed by concentrations (X +/- SEM) of serum urea nitrogen (mmol/L) and creatinine (micromol/L) in UREM (20 +/- 1 and 89.4 +/- 4.5) and UREM-GH (16 +/- 1 and 91.4 +/- 6.9) that were much higher (P < 0.001) than those of sham animals (SAL, 3 +/- 0 and 26.5 +/- 2.2; SPF, 4 +/- 0 and 26.5 +/- 2.1). UREM rats became growth retarded as shown by a daily longitudinal tibia growth rate below (P < 0.05) that observed in SAL animals (156 +/- 3 vs. 220 +/- 5 microm/day). GH treatment resulted in significant growth rate acceleration (213 +/- 6 microm/day). GHRH receptor mRNA levels were no different among the SAL (0.43 +/- 0.03), SPF (0.43 +/- 0.08) and UREM (0.44 +/- 0.04) groups, whereas UREM-GH rats had significantly higher values (0.72 +/- 0.07).

CONCLUSIONS

The status of pituitary GHRH receptor is not modified by nutritional deficit or by severe uremia causing growth retardation. By contrast, the growth promoting effect of GH administration is associated with stimulated GHRH receptor gene expression.

Why is management of patients with classical congenital adrenal hyperplasia more difficult at puberty?

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is an autosomal recessive condition in which deletions or mutations of the cytochrome P450 21-hydroxylase gene cause glucocorticoid and often mineralocorticoid deficiency. Despite optimal substitution therapy, control of classical CAH is often inadequate at puberty, and the problems encountered relate to hypocortisolism and/or hyperandrogenism. A number of physiological alterations in the endocrine milieu at puberty, which include alterations in the growth hormone/insulin-like growth factor axis, insulin sensitivity, as well as the activity of enzymes participating in cortisol metabolism and adrenal steroidogenesis, may account for the documented hypocortisolism and elevated androgen production, and may explain the difficulty in maintaining adequate adrenocortical suppression in pubertal patients with classical 21-hydroxylase deficiency.

Exacerbated inflammatory response induced by insulin-like growth factor I treatment in rats with ischemic acute renal failure

In agreement with recent studies showing a deleterious effect of growth hormone treatment in critically ill patients, preliminary data showed that insulin-like growth factor I (IGF-I) administration increased the mortality rate of rats with ischemic acute renal failure (ARF). The present study was designed to investigate the mechanism responsible for this unexpected effect. Male rats with ischemic ARF were given subcutaneous IGF-I, 50 microg/100 g at 0, 8, and 16 h after reperfusion (ARF+IGF-I, n = 5) or were untreated (ARF, n = 5). A group of 5 sham-operated rats were used as controls. Rats were killed 48 h after declamping, and the following studies were performed: in serum, creatinine and urea nitrogen; and in kidneys, histologic damage score, cellular proliferation by bromodeoxyuridine labeling, apoptosis by morphologic criteria, macrophage infiltration by immunohistochemistry using a specific antibody against ED-1, neutrophil infiltration by naphthol AS-D chloroacetate esterase staining, and levels of IGF-I and IGF-I receptor mRNA by RNase protection assay. ARF and ARF+IGF-I groups had a severe and similar degree of renal failure. Kidney damage was histologically more evident in ARF+IGF-I (1.9 +/- 0.1) than in ARF (1.3 +/- 0.2) rats, and the number of neutrophils/mm(2) of tissue was significantly greater in ARF+IGF-I than in ARF rats at the corticomedullary junction (52.3 +/- 5.2 versus 37.2 +/- 4.1) as well as at the renal medulla (172.5 +/- 30.0 versus 42.1 +/- 9.6). No other differences between the groups were found. It is concluded that IGF-I treatment enhanced the inflammatory response in rats with ischemic ARF. Cell toxicity derived from increased neutrophil accumulation might play a key role in the greater mortality risk of critically ill patients that are treated with growth hormone.

Resting energy expenditure in pre-dialysis diabetic patients

BACKGROUND

The metabolic derangements of diabetes mellitus (DM) associated with those of chronic renal failure (CRF) may interfere with the energy and protein balance of patients with both diseases. The aim of this study was to verify whether the resting energy expenditure (REE) of non-dialysis chronic renal failure diabetic patients differs from that of chronic renal failure patients without DM.

METHODS

REE was measured by indirect calorimetry in 24 CRF diabetic patients (CRF diabetes group), matched for age, gender, and degree of renal impairment to 24 CRF patients without DM (CRF control group).

RESULTS

The CRF diabetes group had a significantly higher REE (1538+/-230 kcal/day) than the CRF control group (1339+/-315 kcal/day, P = 0.009). This difference was maintained even when the REE was adjusted for lean body mass (LBM; 30.3+/-4.3 vs 26.3+/-5.4 kcal/kg LBM/day, P = 0.004). Mean protein intake was significantly higher in the CRF diabetes than in the CRF control group (0.89+/-0.20 vs 0.76+/-0.25 g/kg/day, P = 0.02). Mean protein equivalent of nitrogen appearance (PNA) was also significantly higher in the CRF diabetes patients (1.21+/-0.31 vs 1.03+/-0.22 g/kg/day, P = 0.02), reflecting a higher protein intake and/or elevated protein breakdown. Accordingly, REE was directly correlated with PNA mainly in the CRF diabetes group (r = 0.57, P < 0.003).

CONCLUSION

Metabolic disturbances of poorly controlled DM may account for the higher REE observed in the CRF diabetes group. The role of the apparently higher protein breakdown in this increased REE remains to be clarified.

Effect of metabolic acidosis on the growth hormone/IGF-I endocrine axis in skeletal growth centers

BACKGROUND

Chronic metabolic acidosis (CMA) adversely affects bone metabolism and skeletal growth. Given the cardinal role played by the local growth hormone (GH)/insulin-like growth factor-I (IGF-I) in promoting cell proliferation and differentiation in growth plates, we tested the effect of CMA on the GH/IGF-I axis in a skeletal growth center.

METHODS

We employed an in vitro organ culture system using the murine mandibular condyle as a model for endochondral active growth center. Condyles from six-day-old ICR mice were cultured in BGJb medium of either neutral pH (pH approximately 7.4) or acidic pH (pH approximately 7.15). After 24, 48, 72, and 96 hours of culture, the condyles were washed, fixed in formaldehyde, and processed for paraffin embedding. We assessed histologic markers of the growth center. In addition, the protein level and mRNA expression for the different components of the GH/IGF-I axis were evaluated by immunohistochemistry and in situ hybridization, respectively. Finally, we evaluated the effect of acidosis on the biological functions mediated by GH and IGF-I (namely, proliferation and differentiation of cartilage cells in the active growth center).

RESULTS

Following three to four days in acidic conditions, there was a marked reduction in the size of young chondrocytic population, suggesting a defect in the process of endochondral differentiation. Immunohistochemistry and in situ hybridization analyses revealed a marked reduction in the expression of the IGF-I receptor, as well as in the GH receptor. These changes were already evident after 48 hours of incubation in acidic conditions. At 48 hours of acidosis, there was also a marked reduction in the expression of IGF-I both under basal conditions (nonstimulated) and following stimulation with GH. The expression of IGF binding protein 2 (IGFBP-2) and IGFBP-4, which serve as negative modulators of IGF-I, was enhanced in CMA. IGF-I markedly stimulated chondrocytic proliferation (assessed by BrdU incorporation into DNA) and differentiation (assessed as cartilage specific proteoglycan expression). These responses were markedly attenuated in acidic conditions.

CONCLUSION

CMA exerts an anti-anabolic effect in bone growth centers, which is partly related to a state of resistance to GH and IGF-I, created by CMA. This phenomenon may underlie the disturbance in longitudinal bone growth in CMA (that is, renal tubular acidosis) and may contribute to renal osteodystrophy in patients suffering from chronic renal failure.

The growth hormone-insulin-like growth factor axis in kidney re-revisited

The use of renal allotransplantation to treat ESRD in the US is limited by lack of organ availability. A possible solution is the transplantation of developing kidneys (metanephric allograft or xenografts). We have conducted studies that demonstrate the feasibility of such a strategy and have shown that IGF I may be useful to accelerate the growth and development of these transplanted organs. The rationale for the use of IGF I in this setting grew from a basic understanding of the role that the growth factor plays in kidney development. ARF in humans is the most costly kidney-related disease requiring hospitalization. Its incidence is increasing. Despite many advances in dialytic therapy, the mortality rate for patients with ARF has not changed in the last several decades. Strategies for treatment of ARF are directed toward supportive care to permit renal regeneration to occur. There exists a need for new therapeutic approaches that can speed recovery and reduce mortality. Although IGF I may not prove to be the 'magic bullet' for ARF, its proposal and testing as a potential therapeutic agent has provided a paradigm for the development of treatment modalities to accelerate renal regeneration based upon a basic understanding of the injury/repair process. The basis for development of a 'growth factor' therapy for ARF will probably evolve, at least in part, out of the testing and use of IGF I in rat models and in humans. The use of GH to treat ESRD was proposed shortly after its isolation and the demonstration of its action in increasing the rate of glomerular filtration. Later, it was discovered that the actions of GH on kidney are mediated by IGF I, and the means by which IGF I enhances glomerular filtration was elucidated. We have shown that humans with ESRD are not resistant to the actions of IGF I in enhancing the GFR, establishing the potential for use of IGF I as a pharmacological agent for ESRD. There is no effective drug therapy to enhance renal function in ESRD. Although much work remains to be done, and clearly caution is advised, our observations establish the potential for the use of IGF I as a therapeutic agent in this setting and justify continued study of IGF I as a medical therapy to delay the need for dialysis.

Response to growth hormone therapy in experimental ischemic acute renal failure

In acute renal failure (ARF), the gene and peptide expression of insulin-like growth factor-I (IGF-I) falls. Because IGF-I is regulated by growth hormone (GH) and because kidney GH receptor expression is also attenuated in ARF, the impaired IGF-I expression may partly reflect local GH resistance. Because IGF-I treatment accelerates recovery from ARF, we determined whether high-dose GH therapy could overcome this putative GH resistance, stimulate IGF-I production, and enhance recovery. Rats with ARF were given 2.5 mg GH or vehicle (V) over 2 days, beginning 24 hours before the onset of ARF. GH prevented weight loss but did not modify the course of ARF. Next we determined whether the failure of GH to modify kidney recovery could reflect a failure to stimulate renal IGF-I gene expression. Rats were treated with GH or V over an 18-hour period beginning 1 day after the induction of ARF. Hepatic IGF-I mRNA and serum IGF-I peptide levels rose significantly with GH treatment, but the low kidney IGF-I mRNA levels did not respond. We conclude that the failure of GH to enhance recovery from ARF is caused by impaired GH-stimulated renal IGF-I production, while the maintenance of body weight likely reflects the systemic effects of the increase in hepatic IGF-I production.

Muscle amino acid metabolism and the control of muscle protein turnover in patients with chronic renal failure

Malnutrition is frequently observed in patients with end-stage renal disease. Studies indicate that poor nutritional status plays a major role among factors adversely affecting patients outcome. Therefore prevention and treatment of malnutrition in renal patients is a major issue. In this article the potential mechanisms for alterations in muscle protein metabolism in uremia are explored. Malnutrition has been mainly attributed to inadequate intake of nutrients, superimposed illnesses, or both. However, both clinical and experimental evidence show that uremia per se may adversely affect the control of muscle protein and amino acid metabolism. Available evidence suggests that catabolic factors appear to be distinct for patients at different stages of chronic renal failure and require different modalities of treatments. Both nutritional requirements and the prevalence of malnutrition increase as end-stage renal disease progresses. Muscle protein degradation is increased by metabolic acidosis, which is often found in uremic patients. Another relevant, but less proven cause for increased protein degradation is insulin resistance. Furthermore, specific defects in muscle amino acid metabolism, resistance to growth hormone, insulin-like growth factor 1, or a very low protein intake can reduce muscle protein synthesis. Finally, the hemodialytic procedure per se can stimulate protein breakdown or reduce protein synthesis. All these factors may potentiate the effects of concurrent catabolic illnesses, anorexia, and physical inactivity often found in uremic patients.

L-arginine-induced vasodilation in healthy humans: pharmacokinetic-pharmacodynamic relationship

AIMS

Administration of L-arginine by intravenous infusion or via oral absorption has been shown to induce peripheral vasodilation in humans, and to improve endothelium-dependent vasodilation. We investigated the pharmacokinetics and pharmacokinetic-pharmacodynamic relationship of L-arginine after a single intravenous infusion of 30 g or 6 g, or after a single oral application of 6 g, as compared with the respective placebo, in eight healthy male human subjects.

METHODS

L-arginine levels were determined by h.p.l.c. The vasodilator effects of L-arginine were assessed non-invasively by blood pressure monitoring and impedance cardiography. Urinary nitrate and cyclic GMP excretion rates were measured as non-invasive indicators of endogenous NO production.

RESULTS

Plasma L-arginine levels increased to (mean +/- s.e.mean) 6223+/-407 (range, 5100-7680) and 822+/-59 (527-955) micromol l(-1) after intravenous infusion of 30 g and 6 g L-arginine, respectively, and to 310+/-152 (118-1219) micromol l(-1) after oral ingestion of 6 g L-arginine. Oral bioavailability of L-arginine was 68+/-9 (51-87)%. Clearance was 544+/-24 (440-620), 894+/-164 (470-1190), and 1018+/-230 (710-2130) ml min(-1), and elimination half-life was calculated as 41.6+/-2.3 (34-55), 59.6+/-9.1 (24-98), and 79.5+/-9.3 (50-121) min, respectively, for 30 g i.v., 6 g i.v., and 6 g p.o. of L-arginine. Blood pressure and total peripheral resistance were significantly decreased after intravenous infusion of 30 g L-arginine by 4.4+/-1.4% and 10.4+/-3.6%, respectively, but were not significantly changed after oral or intravenous administration of 6 g L-arginine. L-arginine (30 g) also significantly increased urinary nitrate and cyclic GMP excretion rates by 97+/-28 and 66+/-20%, respectively. After infusion of 6 g L-arginine, urinary nitrate excretion also significantly increased, (nitrate by 47+/-12% [P<0.05], cyclic GMP by 67+/-47% [P= ns]), although to a lesser and more variable extent than after 30 g of L-arginine. The onset and the duration of the vasodilator effect of L-arginine and its effects on endogenous NO production closely corresponded to the plasma concentration half-life of L-arginine, as indicated by an equilibration half-life of 6+/-2 (3.7-8.4) min between plasma concentration and effect in pharmacokinetic-pharmacodynamic analysis, and the lack of hysteresis in the plasma concentration-versus-effect plot.

CONCLUSIONS

The vascular effects of L-arginine are closely correlated with its plasma concentrations. These data may provide a basis for the utilization of L-arginine in cardiovascular diseases.

The phylogeny of the insulin-like growth factors

The insulin-like growth factors are major regulators of growth and development in mammals and their presence in lower vertebrates suggests that they played a similarly fundamental role throughout vertebrate evolution. While originally perceived simply as mediators of growth hormone, on-going research in mammals has revealed several hierarchical layers of complexity in the regulation of ligand bioavailability and signal transduction. Our understanding of the biological role and mechanisms of action of these important growth factors in mammals patently requires further elucidation of the IGF hormone system in the simple model systems that can be found in lower vertebrates and protochordates. This review contrasts our knowledge of the IGF hormone system in mammalian and nonmammalian models through comparison of tissue and developmental distributions and gene structures of IGF system components in different taxa. We also discuss the evolutionary origins of the system components and their possible evolutionary pathways.

IGF-I and insulin amplify IL-1 beta-induced nitric oxide and prostaglandin biosynthesis

The inflammatory cytokine interleukin-1 beta (IL-1 beta) induces both cyclooxygenase-2 (Cox-2) and the inducible nitric oxide synthase (iNOS) with concomitant release of PGs and nitric oxide (NO) by glomerular mesangial cells. In our current studies, we determine whether insulin and IGF-I are involved in the signal transduction mechanisms resulting in IL-1 beta-induced NO and PGE2 biosynthesis in renal mesangial cells. We demonstrate that both insulin and IGF-I increase IL-1 beta-induced Cox-2 and iNOS protein expression, which in turn enhance PGE2 and NO production. Our data also indicate that both insulin and IGF-I enhance IL-1 beta-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation and SAPK activation. These findings implicate the possible role of the MAPK pathway in mediating the effects of insulin and IGF-I on the upregulation of cytokine-stimulated NO and PG biosynthesis. Together, our results indicate that IGF-I and insulin may function to modulate the renal inflammatory process.

Effects of recombinant human growth hormone on muscle protein turnover in malnourished hemodialysis patients

To assess the effect of recombinant human growth hormone (rhGH) on muscle protein metabolism in uremic patients with malnutrition, forearm [3H]phenylalanine kinetics were evaluated in six chronically wasted (body weight 79% of ideal weight) hemodialysis (HD) patients in a self-controlled, crossover study. Forearm protein dynamics were evaluated before, after a 6-wk course of rhGH (5 mg thrice weekly) and after a 6-wk washout period. After rhGH: (a) forearm phenylalanine net balance--the difference between phenylalanine incorporation into and phenylalanine release from muscle proteins--decreased by 46% (-8+/-2 vs. -15+/-2 nmol/min x 100 ml at the baseline and -11+/-2 after washout, P < 0.02); (b) phenylalanine rate of disposal, an index of protein synthesis, increased by 25% (25+/-5 vs. 20+/-5 at the baseline and 20+/-4 after washout, P < 0.03); (c) phenylalanine rate of appearance, an index of protein degradation, was unchanged (33+/-5 vs. 35+/-5 at the baseline and 31+/-4 after washout); (d) forearm potassium release declined (0.24+/-0.13 vs. 0.60+/-0.15 microeq/min at the baseline, and 0.42+/-0.20 microeq/min after washout P < 0.03); (e) changes in the insulin-like growth factor binding protein (IGFBP)-1 levels and insulin-like growth factor-I (IGF-I)/IGFBP-3 ratios accounted for 15.1% and 47.1% of the percent variations in forearm net phenylalanine balance, respectively. Together, these two factors accounted for 62.2% of variations in forearm net phenylalanine balance during and after rhGH administration. These data indicate: (a) that rhGH administration in malnourished hemodialysis patients is followed by an increase in muscle protein synthesis and by a decrease in the negative muscle protein balance observed in the postabsorptive state; and (b) that the reduction in net protein catabolism obtained with rhGH can be accounted for by the associated changes in circulating free, but not total, IGF-I levels.

Nitric oxide may mediate the hemodynamic effects of recombinant growth hormone in patients with acquired growth hormone deficiency. A double-blind, placebo-controlled study

We studied the effects of recombinant growth hormone on systemic nitric oxide (NO) formation and hemodynamics in a double-blind, placebo-controlled trial in adult patients with acquired growth hormone deficiency. 30 patients were randomly allocated to either recombinant human growth hormone (r-hGH; 2.0 IU/d) or placebo for 12 mo. In the subsequent 12 mo, the study was continued with both groups of patients receiving r-hGH. In months 1, 3, 6, 9, and 12 of each year, urine and plasma samples were collected for the determination of urinary nitrate and cyclic GMP as indices of systemic NO production, and of plasma IGF-1 levels. Cardiac output was measured in months 1, 12, and 24 by echocardiography. r-hGH induced a fourfold increase in plasma IGF-1 concentrations within the first month of treatment. Urinary nitrate and cyclic GMP excretion rates were low at baseline in growth hormone-deficient patients (nitrate, 96.8+/-7.4 micromol/mmol creatinine; cyclic GMP, 63.6+/-7.1 nmol/mmol creatinine) as compared with healthy controls (nitrate, 167.3+/-7.5 micromol/mmol creatinine; cyclic GMP, 155.2+/-6.9 nmol/mmol creatinine). These indices of NO production were significantly increased by r-hGH, within the first 12 mo in the GH group, and within the second 12 mo in the placebo group. While systolic and diastolic blood pressure were not significantly altered by r-hGH, cardiac output significantly increased by 30-40%, and total peripheral resistance decreased by approximately 30% in both groups when they were assigned to r-hGH treatment. In the second study year, when both groups were given r-hGH, there were no significant differences in plasma IGF-1, urinary nitrate, or cyclic GMP excretion, or hemodynamic parameters between both groups. In conclusion, systemic NO formation is decreased in untreated growth hormone-deficient patients. Treatment with recombinant human growth hormone normalizes urinary nitrate and cyclic GMP excretion, possibly via IGF-1 stimulation of endothelial NO formation, and concomitantly decreases peripheral arterial resistance. Increased NO formation may be one reason for improved cardiovascular performance of patients with acquired hypopituitarism during growth hormone therapy.

Nutrition in end-stage renal disease

In summary, it is evident that malnutrition is highly prevalent in ESRD patients. This is clearly related to multiple factors encountered during the pre-dialysis stage, as well as during maintenance dialysis therapy. A body of evidence highlights the existence of relationship between malnutrition and outcome in this patient population. Several preliminary studies suggest that interventions to improve the poor nutritional status of the ESRD patients may actually improve the expected outcome in these patients, although their long-term efficacy is not well established. It is therefore important to emphasize that malnutrition is a major co-morbid condition in the ESRD population and that the nutritional status and the treatment parameters of these patients should be altered to improve not only the mortality outcome of ESRD patients but also their quality of life.

Effects of recombinant human growth hormone on plasma and dialysate amino acid profiles in CAPD patients

Protein and calorie malnutrition is common in chronic dialysis patients. Several interventions have been proposed to prevent and/or to treat malnutrition including the use of recombinant human growth hormone (rhGH) as an anabolic agent. We have previously reported a significant decrease in net urea nitrogen appearance along with modest but statistically significant decrements in several blood chemistries including serum potassium, phosphorus, albumin and a small increase in creatinine concentration during rhGH administration in CAPD patients. In order to evaluate the underlying mechanism of these changes, we systematically evaluated the plasma and dialysate amino acid profiles in blood and dialysate samples of the same patients during their participation in the study. The design of the study was prospective, cross-over with the patients serving as their own controls. There were three study periods: baseline (preGH), treatment (Tx), and follow-up (PostGH). During the seven days Tx period, patients self-administered 5 mg/day s.c of rhGH. Compared to PreGH period, administration of rhGH resulted in a significant decrease in essential amino acids (EAA), in both plasma (935 +/- 243 mumol/liter vs. 801 +/- 186 mumol/liter; P < 0.05) and dialysate (623 +/- 244 mumol/liter vs. 415 +/- 122 mumol/liter; P < 0.05). This decrease was evident in 8 out of 10 individual EAA, and the extent of decrease ranged from 15% to 28% for plasma EAA and from 30% to 45% for dialysate EAA. On the other hand, plasma non-essential AA levels increased significantly during treatment (2537 +/- 776 mumol/liter vs. 3177 +/- 1259 mumol/liter; P < 0.05). All changes returned to baseline values after discontinuation of rhGH. Our findings suggest that the net anabolic processes induced by rhGH reflect a shift in AA metabolism towards peripheral muscle tissues.

Chronic renal failure and human growth hormone treatment do not modify endothelium-dependent reactions in the rat aorta in vitro

1. Growth hormone (GH) increases glomerular filtration rate and renal plasma flow and decreases renal vascular resistance. Sustained GH-induced hyperfiltration might be undesirable in children with chronic renal failure (CRF) who are receiving recombinant human GH (rhGH) therapy. 2. In order to determine the effect of CRF on vascular reactivity and the modifications induced by rhGH administration, two endothelium-dependent effects, acetylcholine relaxation and decrease of contractile response to noradrenaline, were studied in aorta segments of various groups of male Sprague-Dawley rats: CRF rats (CRF, n = 8) with serum urea nitrogen (SUN) 68 +/- 16 mg dl-1 (mean +/- SEM), CRF rats treated with intraperitoneal rhGH at 10 IU kg-1 day-1 for 13 days (CRFGH, n = 6, SUN = 88 +/- 15 mg dl-1), sham operated rats (SHAM, n = 8, SUN: 21 +/- 1 mg dl-1) and control rats (CONTROL, n = 8, SUN 20 +/- 1 mg dl-1), housed in identical conditions but without undergoing surgical intervention or manipulation. CRF was induced by 5/6 two stage nephrectomy. 3. Rats were sacrificed and a segment of thoracic aorta was immediately removed, cut into spirals, and suspended in organ baths according to standard procedures. First, dose-response curves to noradrenaline and acetylcholine relaxation, in strips previously exposed to noradrenaline, were determined. Then, the endothelium was removed and both dose-response curves were repeated. Acetylcholine induced a greater relaxation, P < 0.05, in the aorta of CONTROL rats (82.6 +/- 6.1%) as compared with SHAM (60.3 +/- 4.7%), CRF (60.0 +/- 6.8%) and CRFGH (54.8 +/- 8.2%) rats. 4. Endothelium removal only caused a greater contractile response to noradrenaline (10(-9) and 3 x 10(-9)M) in the CONTROL group, P < 0.05. 5. No differences to acetylcholine and noradrenaline responses were found among the SHAM, CRF and CRFGH groups. 6. These results suggest that the endothelium-dependent vascular reactivity was modified by the experimental protocol to induce chronic renal failure but no further changes resulted from uraemia and rhGH treatment.