Reduced hepatic growth hormone (GH) receptor gene expression and increased plasma GH binding protein in experimental uremia

Growth Hormone Treatment for Non-GHD Disorders: Excitement Tempered by Biology

The success of growth hormone (GH) replacement in children with classical GH deficiency has led to excitement that other causes of short stature may benefit similarly. However, clinical experience has shown less consistent and generally less dramatic effects on adult height, perhaps not surprising in light of increased understanding of GH and growth plate biology. Nonetheless, clinical demand for GH treatment continues to grow. Upon the 20th anniversary of the US Food and Drug Administration's approval of GH treatment for idiopathic short stature, this review will consider the factors underlying the expansion of GH treatment, the biological mechanisms of GH action, the non-GH-deficient uses of GH as a height-promoting agent, biological constraints to GH action, and future directions.

Growth Hormone and Insulin-Like Growth Factor Dysregulation in Pediatric Chronic Kidney Disease

Poor growth is a common finding in children with chronic kidney disease (CKD) that has been associated with poor long-term outcomes. The etiology of poor growth in this population is multifactorial and includes dysregulation of the growth hormone (GH) and insulin-like growth factor (IGF) axis. In this review, we describe the data on GH resistance or insensitivity and inappropriate levels or reduced bioactivity of IGF proposed as contributing factors of growth impairment in children with CKD. Additionally, we describe the theorized negative effect of metabolic acidosis, another frequent finding in pediatric CKD, on the GH/IGF axis and growth. Last, we present the current and potential therapies for the treatment of short stature in pediatric CKD that target the GH/IGF hormonal axis.

The Role of Growth Hormone in Chronic Kidney Disease

Growth hormone (GH) has become a critical therapy for treating growth delay and failure in pediatric chronic kidney disease. Recombinant human GH treatment is safe and significantly improves height and height velocity in these growing patients and improved growth outcomes are associated with decreased morbidity and mortality as well as improved quality of life. However, the utility of recombinant human GH in adults with chronic kidney disease and end-stage renal disease for optimization of body habitus and reducing frailty remains uncertain. Semin Nephrol 41:x-xx © 2021 Elsevier Inc. All rights reserved.

Growth Hormone and Malnutrition in Dialysis Patients

Objective

To review the normal function of the growth hormone (GH) insulin-like growth factor (IGF) axis, how it is altered in end-stage renal failure, how this may contribute to malnutrition in dialysis patients, and how therapy with recombinant human growth hormone (rHuGH) and recombinant human IGF-I (rHuIGF-1)might be used to treat malnutrition in these patients.

Data Sources

Studies in the literature dealing with the GH-IGF endocrine axis and its role in uremic malnutrition.

Study Selection

Eight studies in which uremic adults were treated with either rHuGH or rHuIGF-I.

Data Extraction

Data were abstracted from all of these studies.

Results

The review shows that there are marked abnormalities of the GH-IGF axis in uremic patients and that these lead to a state of GH resistance, which can be overcome by pharmacological doses of rHuGH. A small number of clinical studies in uremic adults suggests that both rHuGH and rHuIGF-I have dramatic beneficial effects on nutritional status in these patients.

Conclusions

rHuGH and rHuIGF-I have both been shown to have a beneficial effect on nutritional status in shortterm studies on small numbers of patients. Further studies need to be done for longer periods in larger groups of patients. Areas for additional research are suggested.

Growth Hormone and Malnutrition in Dialysis Patients

Objective

To review the normal function of the growth hormone (GH) insulin-like growth factor (IGF) axis, how it is altered in end-stage renal failure, how this may contribute to malnutrition in dialysis patients, and how therapy with recombinant human growth hormone (rHuGH) and recombinant human IGF-I (rHuIGF-1)might be used to treat malnutrition in these patients.

Data Sources

Studies in the literature dealing with the GH-IGF endocrine axis and its role in uremic malnutrition.

Study Selection

Eight studies in which uremic adults were treated with either rHuGH or rHuIGF-I.

Data Extraction

Data were abstracted from all of these studies.

Results

The review shows that there are marked abnormalities of the GH-IGF axis in uremic patients and that these lead to a state of GH resistance, which can be overcome by pharmacological doses of rHuGH. A small number of clinical studies in uremic adults suggests that both rHuGH and rHuIGF-I have dramatic beneficial effects on nutritional status in these patients.

Conclusions

rHuGH and rHuIGF-I have both been shown to have a beneficial effect on nutritional status in shortterm studies on small numbers of patients. Further studies need to be done for longer periods in larger groups of patients. Areas for additional research are suggested.

[Somatotropic axis and molecular markers of mineral metabolism in children undergoing chronic peritoneal dialysis]

Growth failure is one of the most relevant complications in children with chronic kidney disease (CKD). Among others, growth hormone (GH) resistance and bone mineral disorders have been identified as the most important causes of growth retardation.

OBJECTIVES

1. To characterize bone mineral metabolism and growth hormone bio-markers in CKD children treated with chronic peritoneal dialysis (PD). 2. To evaluate height change with rhGH treatment.

PATIENTS AND METHOD

A longitudinal 12-month follow-up in prepuberal PD children.

EXCLUSION CRITERIA

Tanner stage >1, nephrotic syndrome, genetic disorders, steroids, intestinal absorption disorders, endocrine disturbances, treatment with GH to the entry of the study. Demographic and anthropometric data were registered. FGF23, Klotho, VitD, IGF-1, IGFBP3, and GHBP were measured to evaluate mineral and growth metabolism.

RESULTS

15 patients, 7 male, age 6.9 ± 3.0 y were included. Time on PD was 14.33 ± 12.26 months. Height/age Z score at month 1 was -1.69 ± 1.03. FGF23 and Klotho: 131.7 ± 279.4 y 125.9 ± 24.2 pg/ml, respectively. 8 patients were treated with GH during 6-12 months, showing a non-significant increase in height/age Z-score during the treatment period. Bivariate analysis showed a positive correlation between Klotho and delta ZT/E, and between GHBP vs growth velocity index (p < .05).

CONCLUSIONS

FGF23 values were high and Klotho values were reduced in children with CKD in PD, comparing to healthy children. Somatotropic axis variables were normal or elevated. rhGH tends to improve height and there is a positive correlation of GHBP and growth velocity in these children.

Impaired phosphorylation of JAK2-STAT5b signaling in fibroblasts from uremic children

BACKGROUND

Chronic kidney disease (CKD) in children is characterized by severe growth failure. The growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis in uremic animals shows a post-receptor impaired phosphorylation of Janus kinase 2/signal transducer and activator of transcription (JAK-STAT) proteins. The objective of our study was to characterize the intracellular phosphorylation of JAK-STAT signaling in fibroblasts from children with CKD on chronic peritoneal dialysis (PD).

METHODS

Serum GH-binding protein (GHBP), IGF-1 and IGFBP3 were measured in 15 prepubertal CKD stage-5 children on PD. Cytoplasmic JAK2, cytoplasmic/nuclear STAT5b and nuclear IGFBP3, acid-labile subunit (ALS) and IGF-1 mRNA expression were quantified in fibroblasts obtained from skin biopsies before and after stimulation with 200 ng/ml recombinant human growth hormone (rhGH). Phosphorylation activity at both the cytoplasmic and nuclear level was expressed as the ratio phosphorylated (p)/total (t) abundance of the product (p/t) at 30 and 60 min. Fifteen healthy children were recruited as the control group. Values were expressed in arbitrary units (AU) and normalized for comparison. Significance was defined as p < 0.05.

RESULTS

Thirty minutes after rhGH stimulus, the cytoplasmic (p/t) JAK2 ratio was significantly lower in patients than in controls [median and interquartile range (IQR): 7.4 (4.56) vs. 20.5 (50.06) AU]. At 60 min after rhGH stimulation, median JAK2 phosphorylation activity was still significantly lower in the patients [7.14 (IQR 3.8) vs. 10.2 (IQR 29.8) AU; p < 0.05]. The increase in the cytoplasmic (p/t) STAT5b/β-actin ratio was lower at both measurement points in the patients compared to the controls, without reaching statistical significance between groups. Median IGFBP3 mRNA abundance was significantly decreased in fibroblasts from uremic patients 24 h after rhGH stimulation compared to the healthy controls [1.27 (IQR 0.83) vs. 2.37 (IQR 0.80) AU]. Median ALS and IGF-1 mRNA expression changed in response to rhGH stimuli at 24 and 48 h.

CONCLUSION

In this study, children with CKD undergoing PD therapy showed an impaired phosphorylation of JAK2/STAT5b signaling in fibroblasts after GH stimulation, as well as impaired IGFBP3 mRNA abundance. Both impairments may be partially responsible for the observed resistance to the growth-promoting actions of GH in chronic kidney failure.

Growth hormone, insulin-like growth factor-1, and the kidney: pathophysiological and clinical implications

Besides their growth-promoting properties, GH and IGF-1 regulate a broad spectrum of biological functions in several organs, including the kidney. This review focuses on the renal actions of GH and IGF-1, taking into account major advances in renal physiology and hormone biology made over the last 20 years, allowing us to move our understanding of GH/IGF-1 regulation of renal functions from a cellular to a molecular level. The main purpose of this review was to analyze how GH and IGF-1 regulate renal development, glomerular functions, and tubular handling of sodium, calcium, phosphate, and glucose. Whenever possible, the relative contributions, the nephronic topology, and the underlying molecular mechanisms of GH and IGF-1 actions were addressed. Beyond the physiological aspects of GH/IGF-1 action on the kidney, the review describes the impact of GH excess and deficiency on renal architecture and functions. It reports in particular new insights into the pathophysiological mechanism of body fluid retention and of changes in phospho-calcium metabolism in acromegaly as well as of the reciprocal changes in sodium, calcium, and phosphate homeostasis observed in GH deficiency. The second aim of this review was to analyze how the GH/IGF-1 axis contributes to major renal diseases such as diabetic nephropathy, renal failure, renal carcinoma, and polycystic renal disease. It summarizes the consequences of chronic renal failure and glucocorticoid therapy after renal transplantation on GH secretion and action and questions the interest of GH therapy in these conditions.

Insulin-like growth factors in normal and diseased kidney

This article reviews the physiology of the insulin-like growth factor (IGF) system in the kidney and the changes and potential role of this system in selected renal diseases. The potential therapeutic uses of recombinant human IGF-I for the treatment of acute and chronic kidney failure are briefly discussed.

Amino acid and protein metabolism in the human kidney and in patients with chronic kidney disease

The progressive loss of kidney function in patients with chronic kidney disease (CKD) is associated with a number of complications, including cardiovascular diseases, anemia, hyperparathyroidism, inflammation, metabolic acidosis, malnutrition and protein-energy wasting. The excess cardiovascular risk related to CKD is due in part to a higher prevalence of traditional atherosclerotic risk factors, in part to non-traditional, emerging risk factors peculiar to CKD. While even minor renal dysfunction is an independent predictor of adverse cardiovascular prognosis, nutritional changes are more often observed in an advanced setting. In addition, factors related to renal-replacement treatment may be implicated in the pathogenesis of heart disease and protein-energy wasting in dialysis-treated patients. Progressive alterations in kidney metabolism may cause progressive effects on cardiovascular status and nutrition. Altered kidney amino acid/protein metabolism and or excretion may be a key factor in the homeostasis of several vasoactive compounds and hormones in patients with more advanced disease. In this discussion recent research regarding the kidney handling of amino acids and protein turnover and their potential link with cardiovascular disease, progressive kidney dysfunction and nutritional status are reviewed.

A review of the effects of growth hormone changes on symptoms of frailty in the elderly with chronic kidney disease

The incidence and prevalence of chronic kidney disease (CKD) is increasing worldwide, especially in the elderly. Recently, functional impairment and frailty have been recognized as factors affecting the quality of life, and outcomes in elderly patients with CKD and therapeutic interventions to improve function and reduce frailty are therefore being considered. Growth hormone (GH) levels decrease with age and GH actions are impaired in CKD patients. GH stimulates protein synthesis, bone, and glucose metabolism, and affects body composition by reducing body fat and increasing lean body mass. An increase in lean body mass may reduce frailty and thus avoid functional impairment. Thus, providing GH to elderly CKD patients could potentially improve outcomes and quality of life by lowering the risk of frailty and associated functional impairment. There are few studies assessing the long-term effects of GH administration on symptoms of frailty in elderly patients with CKD. In this review we will try to shed some light on the trials assessing the administration of GH to elderly subjects and to patients with CKD and focus on the possible role GH administration may play to improve frailty and quality of life in those patients.

The growth hormone-insulin-like growth factor-I axis in chronic kidney disease

Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are important physiologic regulators of growth, body composition, and kidney function. Perturbations in the GH-IGF-I axis are responsible for many important complications seen in chronic kidney disease (CKD), such as growth retardation and cachectic wasting, as well as disease progression. Recent evidence suggests that CKD is characterized by abnormalities in GH and IGF-I signal transduction and the interaction of these pathways with those that involve other molecules such as ghrelin, myostatin, and the suppressor of cytokine signaling (SOCS) family. Further understanding of GH/IGF pathophysiology in CKD may lead to the development of therapeutic strategies for these devastating complications, which are associated with high rates of mortality and morbidity.

Circulating growth hormone binding protein levels and mononuclear cell growth hormone receptor expression in uremia

BACKGROUND

Resistance to growth hormone (GH) in end-stage renal disease (ESRD) causes growth retardation and muscle wasting. In humans, circulating GH binding protein (GHBP), the extracellular domain of the GH receptor that is shed into the circulation and is believed to reflect tissue GH receptor levels, is reduced in uremia and suggests that cellular GH receptor levels are correspondingly reduced. If true, this could be a cause of GH resistance. We set out to establish whether serum GHBP levels reflect cellular GH receptor levels and whether changes in serum GHBP levels are related to nutritional or inflammatory status.

METHODS

GH receptor protein expression in peripheral blood mononuclear cells (PBMC) from 21 ESRD and 14 normal subjects were analyzed by fluorochrome flow cytometry.

RESULTS

The GH receptor density and percent total PBMCs expressing the GH receptor were similar in the 2 groups, and there was no difference in percent GH receptor positive T or B cells or monocytes. In contrast, serum GHBP levels were 80% lower in ESRD. GHBP levels did not correlate with serum albumin, body mass index, or muscle mass but seemed to be partly related to the log serum C-reactive protein levels.

CONCLUSIONS

Serum GHBP levels are markedly reduced in ESRD; this seems to occur independent of nutritional status and may in part be caused by inflammation. Because GH receptor expression on PBMC of ESRD and control subjects was similar, our findings argue against a reduction in GH receptor as a cause of GH resistance and the use of serum GHBP levels as a reliable marker of specific tissue GH receptor levels.

Impaired growth plate chondrogenesis in children with chronic illnesses

In mammals, statural growth is primarily accomplished by endochondral ossification, which takes place at the growth plate. Growth plate chondrocyte proliferation, hypertrophy/differentiation, apoptosis, and cartilage matrix synthesis all contribute to chondrogenesis or cartilage formation, a process tightly coupled to the simultaneous remodeling of the cartilage into bone at the metaphyseal border of the growth plate. Growth plate chondrogenesis is regulated by the complex interaction of molecular signals acting systemically as well locally within the growth plate. This network is often dysregulated during chronic illnesses, thus resulting in impaired growth plate chondrogenesis and, in turn, growth failure. The principal events responsible for altered growth plate chondrogenesis in chronic illness are inflammation, protein/calorie deprivation, uremia/metabolic acidosis, glucocorticoids, and impaired GH/IGF-I axis.

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.

Insuficiência renal crônica e hormônio de crescimento: efeitos no eixo GH-IGF e na leptina

OBJETIVO: Avaliar as alterações de IGF-1, IGFBP-3, leptina e insulina após o uso de doses de reposição de hormônio de crescimento recombinante humano (rhGH) em crianças baixas pré-púberes com insuficiência renal crônica (IRC). CASUÍSTICA E MÉTODOS: Em 11 crianças (3F:8M), com idade média de 9,6 anos, em uso de rhGH (0,23mg/Kg/semana) por 12 meses, foram dosados (antes, 6 e 12 meses após o início do tratamento com rhGH) leptina, insulina, glicemia, IGF-1 e IGFBP-3. RESULTADOS: As concentrações séricas de leptina, insulina e glicemia não variaram significativamente no decorrer do uso do rhGH, sendo observado o padrão de leptina e glicemia normais, com hiperinsulinemia. Houve aumento significativo da IGF-1 e IGFBP-3 durante o uso do rhGH. CONCLUSÕES: O uso de doses de reposição de rhGH durante 12 meses em um grupo selecionado de crianças com IRC propiciou aumento significativo da concentração sérica de IGF-1 e IGFBP-3, com leptinemia normal e resistência insulínica.

Growth hormone resistance in uremia, a role for impaired JAK/STAT signaling

Resistance to growth hormone (GH) is a significant complication of advanced chronic renal failure. Thus while the circulating GH levels are normal or even elevated in uremia, resistance to the hormone leads to stunting of body growth in children and contributes to muscle wasting in adults. Insensitivity to GH is the consequence of multiple defects in the GH/insulin-like growth factor-1 (IGF-1) system. Expression of the GH receptor may be reduced, although this is not a consistent finding, GH activation of the Janus kinase 2-signal transducer (JAK2) and activator of transcription (STAT) signal transduction pathway is depressed and this leads to reduced IGF-1 expression, and finally there is resistance to IGF-1, a major mediator of GH action. We review these various defects with an emphasis on the GH-activated JAK2-STAT5 pathway, since this pathway is essential for normal body growth and there has been recent progress in our understanding of the perturbations that occur in uremia.

Growth hormone/insulin-like growth factor system in children with chronic renal failure

Disturbances of the somatotropic hormone axis play an important pathogenic role in growth retardation and catabolism in children with chronic renal failure (CRF). The apparent discrepancy between normal or elevated growth hormone (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 levels of IGF-I and IGF-II 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 GH levels in ESRD, these serum IGF-I levels appear inadequately low. Indeed, there is both clinical and experimental evidence for decreased hepatic production of IGF-I in CRF. This hepatic insensitivity to the action of GH may be partly the consequence of reduced GH receptor expression in liver tissue and partly a consequence of disturbed GH receptor signaling. The actions and metabolism of IGFs are modulated by specific high-affinity IGFBPs. CRF serum has an IGF-binding capacity that is increased by seven- to tenfold, leading to decreased IGF bioactivity of CRF serum despite normal total IGF levels. Serum levels of intact IGFBP-1, -2, -4, -6 and low molecular weight fragments of IGFBP-3 are elevated in CRF serum in relation to the degree of renal dysfunction, whereas serum levels of intact IGFBP-3 are normal. Levels of immunoreactive IGFBP-5 are not altered in CRF serum, but the majority of IGFBP-5 is fragmented. Decreased renal filtration and increased hepatic production of IGFBP-1 and -2 both contribute to high levels of serum IGFBP. Experimental and clinical evidence suggests that these excessive high-affinity IGFBPs in CRF serum inhibit IGF action in growth plate chondrocytes by competition with the type 1 IGF receptor for IGF binding. These data indicate that growth failure in CRF is mainly due to functional IGF deficiency. Combined therapy with rhGH and rhIGF-I is therefore a logical approach.

Malnutrition in Patients Undergoing Hemodialysis: Is Intradialytic Parenteral Nutrition the Answer?

Patients with end-stage renal disease often experience malnutrition as a result of decreased dietary intake; inadequate dialysis; loss of nutrients into the dialysate; abnormal protein, carbohydrate, and lipid metabolism; and concomitant diseases, which may contribute to an increase in morbidity and mortality. Intradialytic parenteral nutrition (IDPN) is being used to improve nutritional status, in conjunction with other methods of nutritional supplementation. The biggest advantage of IDPN is probably its convenience since it is administered during dialysis treatment and thus does not require additional clinic visits or prolonged dialysis time. Although IDPN has several disadvantages, its ability to improve nutritional status and reduce morbidity and mortality in patients with end-stage renal disease is promising. Well-designed, large-scale, prospective studies are required to confirm its beneficial effects.

Chondromodulin-I expression in the growth plate of young uremic rats

BACKGROUND

Growth retardation of chronic renal failure is associated with alterations in the growth plate suggestive of a disturbed chondrocyte maturation process and abnormal vascular invasion at the chondro-osseous interphase. Chondromodulin I (ChM-I) is a potent cartilage-specific angiostatic factor. Its pattern of expression in the uremic rat growth plate is unknown. Persistence of ChM-I synthesis and/or imbalance between ChM-I and vascular endothelial growth factor (VEGF) expressions might play a role in the alterations of uremic growth plate.

METHODS

Growth cartilage ChM-I expression was investigated by immunohistochemistry, in situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) in growth-retarded young uremic rats (UREM), control rats, fed ad libitum (SAL) or pair-fed with the UREM group (SPF), and uremic rats treated with growth hormone (UREM-GH). VEGF expression was analyzed by immunohistochemistry.

RESULTS

ChM-I and ChM-I mRNA were confined to the proliferative and early hypertrophic zones of growth cartilage. A similar number of chondrocytes per column was positive for ChM-I in the 4 groups. In accordance with the elongation of the hypertrophic stratum in uremia, the distance (X+/-SEM, microm) between the extracellular ChM-I signal and the metaphyseal end of growth cartilage was higher (P < 0.003) in UREM (236 +/- 40) and UREM-GH (297 +/- 17) than in SAL (92 +/- 7) and SPF (113 +/- 6). No differences in ChM-I expression were appreciated by RT-PCR. Similar VEGF positivity was observed in the hypertrophic chondrocytes of all groups.

CONCLUSION

In experimental uremia, expansion of growth cartilage does not result from increased or persistent expression of ChM-I or from reduced VEGF expression at the cartilage-metaphyseal bone interphase. GH treatment does not modify ChM-I and VEGF expressions.

Growth hormone therapy influences endothelial function in children with renal failure

Endothelial dysfunction, an early step in atherogenesis, is prevalent in children with renal insufficiency. Endothelial dysfunction in growth hormone deficiency is reversed by growth hormone (rhGH) therapy. Renal failure induces growth hormone resistance at the receptor and post-receptor level, which can be overcome by rhGH therapy. This study investigates the influence of rhGH therapy in children with renal failure on flow-mediated dilation (FMD) of the brachial artery, a marker of endothelial function. We studied 8 patients, who were on rhGH for at least 6 months, and 8 healthy children for comparison. FMD of the brachial artery was measured non-invasively as the percentage increase in diameter during post-ischemic hyperemia. Patients were studied at baseline, after 4 weeks interruption of rhGH therapy, and 4 weeks after resumption of therapy. FMD was significantly lower in patients (4.7%) than healthy controls (13.8%) ( P=0.01). During the administration of rhGH, FMD was significantly higher (3.9%) than during interruption of the treatment (1.4%) ( P=0.04). Our data support the theory that a disturbance in the GH-IGF axis contributes to the endothelial dysfunction of renal failure. Treatment with rhGH not only improves growth but may also favorably influence the risk for atherogenesis.

Special aspects of renal osteodystrophy in children

Renal osteodystrophy represents a spectrum of skeletal lesions that range from high-turnover to low-turnover bone disease. Similar factors are involved in the pathogenesis of renal osteodystrophy in adult and pediatric patients with chronic kidney disease (CKD). However, growth retardation and the development of bone deformities are specific complications that occurred in pediatric patients with CKD. Metabolic acidosis, renal osteodystrophy, malnutrition, and disturbances in the insulin growth factor (IGF)/growth hormone (GH) are among the main factors involved and they are discussed briefly in this article. In addition to disturbances in bone remodeling, longitudinal bone growth occurs at the growth plate cartilage by endochondral ossification. Although young rats with experimental CKD have growth retardation, the characteristics of the growth plate are markedly different between animals with severe secondary hyperparathyroidism and those with calcium-induced adynamic osteodystrophy. These disturbances may suggest potential molecular mechanisms by which endochondral bone formation may be altered in renal failure, consequently leading to growth retardation.

End-stage renal disease: endocrine aspects of treatment

End-stage renal disease (ESRD) is a deadly disease unless supportive treatment is administered in the form of haemodialysis, peritoneal dialysis or kidney transplantation. Although marked improvements have occurred in the efficiency of dialysis and in overall care, patients with ESRD still have poor long-term survival. The outcome is largely dependent on age, nutritional status, efficiency of dialysis and underlying reason for renal failure. As a consequence of renal failure, these patients experience a number of endocrine and metabolic disorders that may affect their well being and overall outcome. Disturbances in the somatotropic axis have been documented at several different levels, including an end-organ resistance to both growth hormone (GH) and insulin-like growth factor-I (IGF-I). A consequence seen in childhood is reduced growth velocity and short final height that may be overcome by long-term GH treatment, and it is possible that metabolism and nutritional status in adults with ESRD may be influenced by these abnormalities. Although a few small trials of GH treatment in adults with ESRD suggest that nutritional status may improve, long-term trials are needed to demonstrate other benefit of such treatment. This review will give a brief description of endocrine problems in adult patients with ESRD with a focus on the somatotropic axis, and it will review the experience reported in published trials of GH treatment in this patient group.

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.

Effects of thyroparathyroidectomy, exogenous calcium, and short-term calcitriol therapy on the growth plate in renal failure

Several factors have been implicated in the development of adynamic bone, including the use of calcium-containing phosphate binding agents, aggressive calcitriol therapy, and parathyroidectomy. To evaluate the effects of these interventions on the growth plate, weanling rats underwent sham nephrectomy (Control, n = 10) and 5/6 nephrectomy (Nx). In the nephrectomized group, animals underwent (a) thyroparathyroidectomy (Nx-TPTX, n = 7), (b) received exogenous calcium (Nx-Calcium, n = 10), (c) received short-term calcitriol therapy (Nx-D, n = 10), or (d) nephrectomized control (Nx-Control, n = 10). Higher serum calcium and lower PTH levels were demonstrated in Nx-Calcium and Nx-D animals. A decline in growth was demonstrated in Nx-Calcium and Nx-TPTX accompanied by shorter tibial lengths. The width of the growth plate was wider in Nx-Calcium animals due to an increase in the width of the hypertrophic zone and a decrease in the proliferative zone; these changes were accompanied by an impairment of chondroclastic resorption, lower gelatinase B/MMP-9 activity, decline in insulin-like growth factor-I (IGF-I) receptor, and lower histone-4 mRNA expression. Such findings in the growth plate, may partially contribute to the diminution of growth in these animals. Although growth was impaired in the Nx-TPTX animals, there were no significant changes demonstrated in the growth plate cartilage. Histone-4 transcripts, IGF-I receptor expression, and histochemical staining for chondroclasts were decreased in Nx-D animals. Thus, treatments used in the management of secondary hyperparathyroidism in renal failure have diverse effects on the growth plate of the young skeleton, and concurrent use of these interventions needs further evaluation.

The growth hormone and insulin-like growth factor axis: its manipulation for the benefit of growth disorders in renal failure

Renal failure is associated with dramatic changes in the growth hormone/insulin-like growth factor (GH/IGF) axis. In children, this results in growth retardation, which is treated with injections of recombinant human GH (rhGH). Given the many recent advances in the knowledge of the components of the GH/IGF axis, it is timely to review the role of GH in renal failure and to discuss likely new treatments for growth failure. Renal failure is not a state of GH deficiency but a state of GH and IGF resistance, making other approaches to manipulating the GH axis more logical than treatment with rhGH alone. Although in children rhGH is safe, in critically ill adults it can be lethal. As the mechanisms of these lethal actions of rhGH are unknown, caution is advised when using rhGH outside approved indications. In renal failure, an optimal balance between safety and efficacy for growth may be achieved with the use of the combination of rhGH and rhIGF-I, as animal studies have shown synergistic growth responses. However, inhibition of the GH axis, with the use of GH antagonists, is likely to be tested clinically given the beneficial effects of GH antagonists on renal function in animal models of renal disease. Manipulating IGF-I by either administering rhIGF-1 or its binding proteins or increasing IGF-I bioavailability with the use of IGF displacers could prove to be a safer and more effective alternative to the use of rhGH in renal failure. In the future, both rhGH and rhIGF-1 likely will be included in growth-promoting hormone cocktails tailored to correct specific growth disorders.

Impaired JAK-STAT signal transduction contributes to growth hormone resistance in chronic uremia

Chronic renal failure (CRF) is associated with resistance to the growth-promoting and anabolic actions of growth hormone (GH). In rats with CRF induced by partial renal ablation, 7 days of GH treatment had a diminished effect on weight gain and hepatic IGF-1 and IGFBP-1 mRNA levels, compared with sham-operated pair-fed controls. To assess whether GH resistance might be due to altered signal transduction, activation of the JAK-STAT pathway was studied 10 or 15 minutes after intravenous injection of 5 mg/kg GH or vehicle. Hepatic GH receptor (GHR) mRNA levels were significantly decreased in CRF, but GHR protein abundance and GH binding to microsomal and plasma membranes was unaltered. JAK2, STAT1, STAT3, and STAT5 protein abundance was also unchanged. However, GH-induced tyrosine phosphorylation of JAK2, STAT5, and STAT3 was 75% lower in the CRF animals. Phosphorylated STAT5 and STAT3 were also diminished in nuclear extracts. The expression of the suppressor of cytokine signaling-2 (SOCS-2) was increased twofold in GH-treated CRF animals, and SOCS-3 mRNA levels were elevated by 60% in CRF, independent of GH treatment. In conclusion, CRF causes a postreceptor defect in GH signal transduction characterized by impaired phosphorylation and nuclear translocation of GH-activated STAT proteins, which is possibly mediated, at least in part, by overexpression of SOCS proteins.

Collagen metabolism is markedly altered in the hypertrophic cartilage of growth plates from rats with growth impairment secondary to chronic renal failure

Skeletal growth depends on growth plate cartilage activity, in which matrix synthesis by chondrocytes is one of the major processes contributing to the final length of a bone. On this basis, the present work was undertaken to ascertain if growth impairment secondary to chronic renal insufficiency is associated with disturbances of the extracellular matrix (ECM) of the growth plate. By combining stereological and in situ hybridization techniques, we examined the expression patterns of types II and X collagens and collagenase-3 in tibial growth plates of rats made uremic by subtotal nephrectomy (NX) in comparison with those of sham-operated rats fed ad libitum (SAL) and sham-operated rats pair-fed with NX (SPF). NX rats were severely uremic, as shown by markedly elevated serum concentrations of urea nitrogen, and growth retarded, as shown by significantly decreased longitudinal bone growth rates. NX rats showed disturbances in the normal pattern of chondrocyte differentiation and in the rates and degree of substitution of hypertrophic cartilage with bone, which resulted in accumulation of cartilage at the hypertrophic zone. These changes were associated with an overall decrease in the expression of types II and X collagens, which was especially marked in the abnormally extended zone of the hypertrophic cartilage. Unlike collagen, the expression of collagenase-3 was not disturbed severely. Electron microscopic analysis proved that changes in gene expression were coupled to alterations in the mineralization as well as in the collagen fibril architecture at the hypertrophic cartilage. Because the composition and structure of the ECM have a critical role in regulating the behavior of the growth plate chondrocytes, results obtained are consistent with the hypothesis that alteration of collagen metabolism in these cells could be a key process underlying growth retardation in uremia.

Insulin-like growth factor-I (IGF-I), insulin-like growth factor binding proteins (IGFBP) and insulin-like growth factor type I receptor in children with various status of chronic renal failure

Chronic renal failure in childhood causes severe growth retardation. The aim of the study was to identify whether changes in the IGF system could account for the growth retardation observed in children with chronic renal failure. Insulin-like growth factor (IGF-I) serum concentrations, insulin-like growth factor binding proteins (IGFBP) and/or IGF-I binding to erythrocyte type I receptor of IGF were analysed in 69 children (mean age 11.6 +/- 4.3 years) with chronic renal failure and growth retardation (mean height -2.6 +/- 1.8 SD). The study population was separated into three groups, according to their renal status, children on conservative treatment (CRF group: n = 30), on haemodialysis (ESRD group: n = 26) and those transplanted (RT group: n = 13). Nineteen of these children, some from each of the three groups, received recombinant growth hormone therapy (rhGH). Mean basal IGF-I serum concentrations were -0.7 +/- 1.2 SD in the CRF group, + 2.1 +/- 3 SD in the ESRD group and + 1.1 +/- 2 SD in the RT group. Under rhGH therapy, as height velocity improved, mean IGF-I concentrations increased up to + 3.1 +/- 0.6 SD in the CRF group, to + 6.9 +/- 2.8 SD in the ESRD group and to + 3.9 +/- 2 SD in the RT group. Basal IGFBP-3 levels, studied by Western Ligand Blot were low in the CRF group and high in the ESRD and normal in the RT groups, whereas IGFBP-2 and a 30-32 kDa IGFBP were always high in all cases. Western immunoblot analysis showed that this 30-32 kDa IGFBP was mostly composed of IGFBP-1 and IGFBP-6 in all three groups, but IGFBP-6 was particularly abundant in the ESRD group. IGFBP-6 concentrations assessed by RIA were moderately increased in CRF children (392 +/- 177 ng/mL) and very high in children on ESRD (2094 +/- 1525 ng/mL) when compared to normal values (131 +/- 42 ng/mL). Binding studies of IGF type I receptor showed that there was no particular difference in IGF-I binding between renal failure patients and normal children. In poorly growing children, especially in ESRD children and to a lesser extent in RT children, high concentrations of IGF-I and IGFBP-1, 2, 3 and 6, suggest a resistance mainly by a sequestration mechanism. Moreover, in the CRF group, especially in the younger children, low levels of IGF-I and IGFBP-3 are evocative of an associated resistance at the GH receptor level.

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.

[Physiopathology of the somatotropin axis in chronic renal insufficiency]

Many factors contribute to the growth failure of chronic renal failure: water and electrolytes disturbances, hypertonicity, phosphate or calcium wasting, secondary hyperparathyroidism, anemia, hypertension, metabolic acidosis, and malnutrition. In addition, the pubertal growth spurt is usually stunted. Growth hormone (GH) resistance is observed with low GH binding protein (GHBP) level, and normal or low IGF I levels despite elevated GH level. Elevated IGFBP levels may contribute to a reduced IGF activity, especially in dialysed patients. Glucocorticoid therapy in transplanted patients further contribute to poor growth and inhibited IGF I activity. As conventional treatments have a limited effect to improve growth, adult height is often far below -2 SD. GH therapy has proved to be successful, especially in young children, overpassing the hormonal resistance so that an adult height within the normal range may be reached.

[Critical evaluation of growth hormone treatment in children with chronic renal insufficiency]

Growth failure remains a major complication of chronic renal insufficiency in children, which greatly affects their quality of life. Based upon the data published in the literature it appears that growth hormone therapy improves growth in these children, with little secondary effects. However, some uncertainties persist concerning the safety and efficacy of this therapy, so that careful evaluations must continue.

Insulin-like growth factor system components in hyperparathyroidism and renal osteodystrophy

BACKGROUND

The insulin-like growth factor (IGF) system plays a key role in regulation of bone formation. In patients with renal osteodystrophy, an elevation of some IGF binding proteins (IGFBPs) has been described, but there is no study measuring serum levels of both IGF-I and IGF-II as well as IGFBP-1 to -6 in different forms of renal osteodystrophy and hyperparathyroidism.

METHODS

In a cross-sectional study, we investigated 319 patients with mild (N = 29), moderate (N = 48), preuremic (N = 37), and end-stage renal failure (ESRF; N = 205). The ESRF group was treated by hemodialysis (HD; N = 148), peritoneal dialysis (PD; N = 27), or renal transplantation (RTX; N = 30). As controls without renal failure, we recruited age-matched healthy subjects (N = 87) and patients with primary hyperparathyroidism (pHPT; N = 25). Serum levels of total and free IGF-I, IGF-II, IGFBP-1 to -6, and biochemical bone markers including intact parathyroid hormone (PTH), bone alkaline phosphatase (B-ALP), and osteocalcin (OSC) were measured by specific immunometric assays. IGF system components and bone markers were correlated with clinical and bone histologic findings. Mean values +/- SEM are given.

RESULTS

With declining renal function a significant increase was measured for IGFBP-1 (range 7- to 14-fold), IGFBP-2 (3- to 8-fold), IGFBP-3 (1.5- to 3-fold), IGFBP-4 (3- to 19-fold), and IGFBP-6 (8- to 25-fold), whereas IGFBP-5 levels tended to decrease (1.3- to 1. 6-fold). In contrast, serum levels of IGF-I, free IGF-I, and IGF-II remained constant in most patients. Compared with renal failure patients, pHPT patients showed a similar decline in IGFBP-5 levels and less elevated levels of IGFBP-1 (3.5-fold), IGFBP-2 (2-fold), IGFBP-3 (1.2-fold), and IGFBP-6 (4-fold) but no elevation of IGFBP-4 levels. In all subjects, free and total IGF-I levels showed significant negative correlations with IGFBP-1, IGFBP-2, and IGFBP-4 (that is, inhibitory IGF system components) and significant positive correlations with IGFBP-3 and IGFBP-5 (that is, stimulatory IGF system components). A positive correlation was observed between IGF-II and IGFBP-6. ESRF patients with mixed uremic bone disease and histologic evidence for osteopenia revealed significantly (P < 0.05) higher levels of IGFBP-2 and IGFBP-4 but lower IGFBP-5 levels. Histologic parameters of bone formation showed significant positive correlations with serum levels of IGF-I, IGF-II, and IGFBP-5. In contrast, IGFBP-2 and IGFBP-4 correlated positively with indices of bone loss. Moreover, dialysis patients with low bone turnover (N = 24) showed significantly (P < 0.05) lower levels of IGFBP-5, PTH, B-ALP, and OSC than patients with high bone turnover.

CONCLUSION

Patients with primary and secondary hyperparathyroidism showed lower levels of the putative stimulatory IGFBP-5 but higher levels of IGFBP-1, -2, -3, and -6, whereas total IGF-I and IGF-II levels were not or only moderately increased. The marked increase in serum levels of IGFBP-4 appeared to be characteristic for chronic renal failure. IGFBP-5 correlated with biochemical markers and histologic indices of bone formation in renal osteodystrophy patients and was not influenced by renal function. Therefore, IGFBP-5 may gain significance as a serological marker for osteopenia and low bone turnover in long-term dialysis patients.

Clinical use of growth factors in chronic renal failure

Erythropoietin has been demonstrated to improve the quality of life in patients with chronic renal failure, and growth hormone has been approved for use in children with chronic renal failure and short stature as a growth promoting agent. Growth factors also have great therapeutic potential to improve glomerular function in the setting of chronic renal failure. Further studies are required to delineate the role of insulin-like growth factor I in the setting of end-stage chronic renal failure.

Growth retardation in children with chronic renal failure

Growth retardation is a major obstacle to full rehabilitation of children with chronic renal failure (CRF). Several factors have been identified as contributors to impaired linear growth and they include protein and calorie malnutrition, metabolic acidosis, growth hormone resistance, anemia, and renal osteodystrophy. Although therapeutic interventions such as the use of recombinant human growth hormone, recombinant human erythropoietin, and calcitriol have made substantial contributions, the optimal therapeutic strategy remains to be defined. Indeed, growth failure persists in a substantial proportion of children with renal failure and those treated with maintenance dialysis. In addition, the increasing prevalence of adynamic lesions of renal osteodystrophy and its effect on growth have raised concern about the continued generalized use of calcitriol in children with CRF. Recent studies have shown the critical roles of parathyroid hormone-related protein (PTHrP) and the PTH/PTHrP receptor in the regulation of endochondral bone formation. The PTH/PTHrP receptor mRNA expression has been shown to be down-regulated in kidney and growth plate cartilage of animals with renal failure. Differences in the severity of secondary hyperparathyroidism influence not only growth plate morphology but also the expression of selected markers of chondrocyte proliferation and differentiation in these animals. Such findings suggest potential molecular mechanisms by which cartilage and bone development may be disrupted in children with CRF, thereby contributing to diminished linear growth.

Growth plate cartilage formation and resorption are differentially depressed in growth retarded uremic rats

To characterize the modifications of growth plate in individuals with growth impairment secondary to chronic renal failure, young rats were made uremic by subtotal nephrectomy (NX) and, after 14 d, their tibial growth plates were studied and compared with those of sham-operated rats fed ad libitum (SAL) or pair-fed with NX (SPF). NX rats were growth retarded and severely uremic. Growth plate height (mean +/- SD) was much greater (P<0.05) in NX (868.4+/-85.4 microm) than SAL (570.1+/-93.5 microm) and SPF (551.9+/-99.7 microm) rats as a result of a higher (P<0.05) hypertrophic zone (661.0+/-89.7 versus 362.8+/-71.6 and 353.0+/-93.9 microm, respectively). The increased size of the growth plate was associated with a greater number of chondrocytes and modifications in their structure, particularly in the hypertrophic zone adjacent to bone. In this zone, chondrocytes of NX animals were significantly (P<0.05) smaller (12080.4+/-1158.3 microm3) and shorter (34.1+/-2.5 microm) than those of SAL (16302.8+/-1483.4 microm3 and 37.8+/-2.0 microm) and SPF (14465.8+/-1521.0 microm3 and 36.3+/-1.8 microm). The interface between the growth plate cartilage and the metaphyseal bone appeared markedly irregular in NX rats. Kinetics of chondrocytes was also modified (P<0.05) in the NX rats, which had lower cell turnover per column per day (5.4+/-0.9), longer duration of hypertrophic phase (89.0+/-15.2 h), and reduced cellular advance velocity (7.4+/-2.2 microm/h) compared with SAL (8.0+/-1.6, 32.1+/-6.7 h, and 11.3+/-2.7 microm/h) and SPF (7.2+/-1.1, 34.8+/-5.1 h, and 10.1+/-2.5 microm/h). Cell proliferation was no different among the three groups. Because the growth plates of SPF and SAL rats were substantially not different, modifications observed in the NX rats cannot be attributed to the nutritional deficit associated with renal failure. These findings indicate that chronic renal failure depresses both the activity of the growth plate cartilage by altering chondrocyte hypertrophy and the replacement of cartilage by bone at the metaphyseal end. The two processes are differentially depressed since cartilage resorption is more severely lowered than cartilage enlargement and this leads to an accumulation of cartilage at the hypertrophic zone.

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.

Hepatic expression of growth hormone receptor/binding protein and insulin-like growth factor I genes in uremic rats. Influence of nutritional deficit

The molecular basis for GH resistance in chronic renal failure is unknown. It may partly reside in a decreased number of hepatic GH receptors and subsequently reduced IGF-I synthesis. To investigate the hepatic expression of GH receptor/binding protein (GHBP) and IGF-I genes in chronic renal failure, mRNA levels and the concentrations of its splicing variants were measured by Northern Blot in male 5/6 nephrectomized rats (NX, n = 9), aged 26 +/- 1 days, and three groups of sham-operated rats: (1) fed ad libitum (SAL, n = 9); (2) pair-fed with NX (SPF, n = 7); and (3) pair-fed with NX in terms of protein ingestion but calorically supplemented up to the intake of SAL (SPF+, n = 8). NX rats had severe renal failure, serum urea nitrogen 106 +/- 11 mg/dl (mean +/- SEM), and were growth retarded. GH receptor/GHBP gene expression was detected as two bands of 4.7 and 1.2 kb, respectively. The amount of mRNA was lower (P < 0.0001) in NX than SAL, either when both bands were considered together or separately. No differences were found between NX, SPF, and SPF+. Serum GHBP concentrations were higher (P < 0.01) in NX rats than the other groups. For the IGF-I gene, two bands of 7.5 and 1.8-0.8 kb were identified. Expression of IGF-I gene was reduced (P < 0.05) in NX in comparison with SAL, this reduction being more marked for the 7.5 kb transcript (amount of mRNA equal to 56.6 +/- 2.6 vs 84.8 +/- 6.2% of values found in SAL rats). There were no differences between NX and SPF. Normalization of caloric intake in SPF+ resulted in partial recovery of the 7.5-kb band and did not modify the 1.8-0.8 kb mRNAs. Circulating IGF-I levels were no different among the four groups. These data confirm that expression of liver GH receptor/GHBP and IGF-I genes is markedly decreased in uremic rats. Nutritional deficiency and not uremia itself seems to be the main causal factor, with protein deficit playing a major role.

High dosage growth hormone treatment and post-ischemic acute renal failure in the rat

The positive effect of insulin-like growth factor I (IGF-I) on the outcome of experimental acute renal failure has gained much attention in recent years. However, the potential positive effects of GH have been less intensively studied. Therefore, a study was designed in which rats suffering from post-ischemic renal failure were treated with high dosage growth hormone (GH). Forty-six rats were subjected to bilateral renal ischemia for 45 min. Following reperfusion the animals were treated with either human recombinant GH in a dosage of 2 mg/day given as subcutaneous injection or placebo. The animals were monitored daily for body weight, s-creatinine, s-urea and B-glucose. S-IGF levels were determined at the start of the experiment and at days 3 and 7. IGF-I and GH receptor mRNA were measured in the kidney and the liver of the surviving animals at the end of the experiment. Survival in the GH-treated rats was 42.9% as compared to 32.0% in the control group (not significant). Both groups of animals lost body weight in the initial phase. The loss in body weight was less pronounced for the GH-treated animals and the difference was significant at day 2 (P<0.05). The s-creatinine levels tended to be lower in the GH-group at all times studied, but the difference was not significant. The s-urea levels were significantly reduced by GH-treatment at day 2 (P<0.05). GH treatment caused no adverse effects on carbohydrate metabolism as studied by daily B-glucose determinations. The serum IGF-I levels were identical in both the groups at day zero. At day 3 the serum IGF-I levels had increased by approximately 30% in both groups. At day 7 the serum IGF-I level was 1600 ng/ml in the GH-treated group as compared to 1400 ng/ml in the placebo group (not significant). When placebo-treated uremic rats were compared to normal sham-operated animals GH-rec mRNA was down-regulated in the kidney and liver, while IGF-I mRNA was down-regulated only in the liver (P<0.05). GH treatment partly restored the GH-rec and IGF-I mRNA levels in both organs. The data are compatible with a severe GH resistance syndrome in acute renal failure.

Excessive dietary protein and suboptimal caloric intake have a negative effect on the growth of children with chronic renal disease before and during growth hormone therapy

Although diet and nutrition are an integral part of the management of individuals with chronic renal failure (CRF), little has been written on the effect of nutrition on the growth response to growth hormone (GH) in CRF. We studied the GH axis and nutritional status of 31 prepubertal children aged 8.7 +/- 0.5 years with a height standard deviation score (SDS) of -3.2 +/- 0.2 (mean +/- SEM) with CRF. Sixteen CRF patients on hemodialysis and 15 on peritoneal dialysis were studied. Forty-four age-matched normal short children without GH deficiency served as controls. Spontaneous 12-hour GH and stimulated GH values were significantly higher and GH binding protein (GHBP) was significantly lower in the CRF patients than in the normal short children. Both before the initiation of GH therapy and after the first year of treatment, the growth velocity (SDS) was inversely correlated with dietary protein intake and positively correlated with caloric intake. GH was administered at a dosage of 28 and 21 IU/m2/wk to the CRF group and the normal short children, respectively, divided into seven daily doses. The growth response of the normal short children was significantly greater than that of the CRF patients. GH therapy induced a smaller increment in GHBP and IGF-I in the CRF patients versus the normal short children (8.8 +/- 2.2 and 10.2 +/- 2.7 v 24.8 +/- 1.3 and 27.6 +/- 2.5 nmol/L, respectively, P < .01). The 1-year growth velocity of the CRF children was most closely correlated with dietary protein and caloric intake. The nutritional status of CRF patients is concluded to be a major factor in growth both before and during GH therapy.

Expression of GH receptor, IGF-I receptor and IGF-I mRNA in the kidney and liver of rats recovering from unilateral renal ischemia

The role of the growth-hormone (GH), insulin-like growth factor-I (IGF-I) axis in the kidney has been extensively studied in recent years. To further elucidate the role for GH and IGF-I in renal regeneration, the expression of the GH-rec, IGF-I-rec and IGF-I mRNA was studied in the post-ischemic regenerating kidney and in the liver of the same rats, using a solution hybridization assay. Rats were subjected to 90 min of unilateral renal ischemia followed by reperfusion. The kidneys and livers were collected 1, 3 and 7 days after injury. Five animals were operated on in each group. An additional five animals were sham-operated and killed on day 4. In the kidney, significant alterations were found in the expression of mRNAs for the GH-rec and the IGF-rec. The GH-rec mRNA decreased significantly at day 1 (P < 0.01) to less than one-fifth of the initial value, and normalized at days 3 and 7. The IGF-rec mRNA levels increased more than three-fold at day 3 (P < 0.01) and more than five-fold at day 7 (P < 0.01). In the kidneys there was no significant alteration in the IGF-I mRNA level. In the liver, significant alteration in the level of the GH-rec mRNA was found, while the levels of IGF-rec and the IGF-I mRNA did not change significantly. The levels of GH-rec mRNA increased two-fold at day 3 (P < 0.05), while the levels were unchanged at days 1 and 7. In the early phase of renal regeneration, there is a sharp decrease in the expression of GH-rec mRNA in the kidney. This suggests that there are no direct effects on renal tissue mediated by GH in this situation. There is a significant increase in the intrarenal IGF-I-rec mRNA levels from day 3, suggesting an increased need for IGF-I during regeneration. In the liver, the concentration of GH-mRNA is increased significantly at day 3. These data show on alterations that suggest a role for these factors in renal regeneration.

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.

Moderate food restriction affects skeletal muscle and liver growth hormone receptors differently in pigs

The present study was conducted to determine the influence of food restriction on growth hormone receptor (GHR) in porcine skeletal muscle (longissimus dorsi and trapezius) and liver in relationship to plasma growth hormone binding protein (GHBP). At 76 d of age, pigs were allotted to one of three groups. In Group R100kg-196d, pigs were fed 70% of control food intake and slaughtered at 100 kg. Control pigs had free access to food and were slaughtered either at the same weight (Group C100kg-161d) or at the same age (Group C130kg-196d) as R100kg-196d pigs. Plasma insulin-like growth factor-I concentrations tended to be lower in food-restricted pigs than in control pigs at 40 kg (P < 0.1) and 70 kg (P < 0.05). At slaughter, there were no significant differences among the three groups. In liver, 125I-labeled bovine GH specific binding was higher (P < 0.05) in food-restricted pigs than in control pigs, and GHR mRNA level was higher (P < 0.05) in food-restricted pigs than in C100kg-161d pigs. In trapezius, 125I-labeled bovine GH specific binding was lower (P < 0.05) in food-restricted pigs than in C130kg-196d pigs, and the level of GHR mRNA was higher (P < 0.01) in food-restricted pigs than in control pigs. The levels of GHR in longissimus dorsi were not affected by food restriction. The level of plasma GHBP was lower (P < 0.05) in food-restricted pigs than in C130kg-196d pigs. These data indicate that nutritional status regulates GHR in a tissue-specific manner and that there is no simple relationship between plasma GHBP and hepatic GHR in pigs.