Resistance of nitrogen metabolism to growth hormone treatment in the early phase after injury of patients with multiple injuries

Frequent intravenous pulses of growth hormone together with alanylglutamine supplementation in prolonged critical illness after multiple trauma: effects on glucose control, plasma IGF-I and glutamine

OBJECTIVE

We aim to demonstrate that low dose growth hormone (GH) administered in i.v. pulses every 3h is able to normalize IGF-I levels in subjects with prolonged critical illness, after multiple trauma. We also ask whether it is possible to control glycaemia during such a treatment and how alanylglutamine (AG) supplementation influences plasma glutamine concentration.

METHODS

We used a prospective double-blind (group 1 vs. 2), randomized trial with an open-label control arm (group 3). Thirty multiple trauma patients (median age: 36, 42, 46 years) were randomized on day 4 after trauma to receive (group 1, n=10) i.v. AG supplementation (0.3 g/kg day from day 4 till 17) and i.v. GH (0.05 mg/kg day divided into 8 boluses, maximum dose at 3 AM, administered on days 7-17) or AG and placebo (group 2, n=10). Group 3 (n=10) received isocaloric isonitrogenous (proteins 1.5 g/kg day) nutrition without AG. Glycaemia was controlled by i.v. insulin infusion according to a routine protocol.

RESULTS

GH treatment caused an increase of IGF-I (from median 169 on day 4 to 493 ng/ml on day 17), IGFBP-3 (from 2.4 to 3.2 microg/ml) and a fall in IGFBP-1 (from 11.5 to 3.1 microg/ml), whilst in both groups 2 and 3 these indices remained unchanged. At the end of the study (day 17) IGF-I and IGFBP-1 differed significantly among groups (p=0.008 resp. p=0.010, Kruskal-Wallis). Plasma glutamine remained below the normal range through the study in all groups (median: 0.18-0.30 mM), but had a tendency to rise in group 2 in contrast with a fall in groups 1 and 3 (NS). Group 1 required more insulin (p<0.01) than did the control group but median glycaemia was only 0.4-0.5 mM higher in group 1 (6.5 mM) than in groups 2 and 3 (6.1 resp. 6.0 mM).

CONCLUSIONS

GH (0.05 g/kg day) administered in i.v. pulses is able to normalize IGF-I levels in subjects with prolonged critical illness after trauma. During this treatment, the standard dose of AG prevents worsening of plasma glutamine deficiency and glucose control is possible using routine algorithms, but it requires higher insulin doses.

Systemic metabolic effects of combined insulin-like growth factor-I and growth hormone therapy in patients who have sustained acute traumatic brain injury

OBJECT

Hypermetabolism, hypercatabolism, refractory nitrogen wasting, hyperglycemia, and immunosuppression accompany traumatic brain injury (TBI). Pituitary dysfunction occurs, affecting growth hormone (GH) and plasma insulin-like growth factor-I (IGF-I) concentrations. The authors evaluated whether combination IGF-I/GH therapy improved metabolic and nutritional parameters after moderate to severe TBI.

METHODS

The authors conducted a prospective, randomized, double-blind study comparing combination IGF-I/GH therapy and a placebo treatment. Ninety-seven patients with TBI were enrolled in the study within 72 hours of injury and were assigned to receive either combination IGF-I/GH therapy or placebo. All patients received concomitant nutritional support. Insulin-like growth factor-I was administered by continuous intravenous infusion (0.01 mg/kg/hr), and GH (0.05 mg/kg/day) was administered subcutaneously. Placebo control group patients received normal saline solution in place of both agents. Nutritional and metabolic monitoring continued throughout the 14-day treatment period. The two groups did not differ in energy expenditure, nutrient intake, or use of insulin treatment. The mean daily serum glucose concentration was higher in the treatment group (123 +/- 24 mg/dl) than in the control group (104 +/- 11 mg/dl) (p < 0.03). A positive nitrogen balance was achieved within the first 24 hours in the treatment group and remained positive in that group throughout the treatment period (p < 0.05). This pattern was not observed in the control group. Plasma IGF-I concentrations were above 350 ng/ml in the treatment group throughout the study period. Overall, the mean plasma IGF-I concentrations were 1003 +/- 480.6 ng/ml in the treatment group and 192 +/- 46.2 ng/ml in the control group (p < 0.01).

CONCLUSIONS

The combination of IGF-I and GH produced sustained improvement in metabolic and nutritional endpoints after moderate to severe acute TBI.

Changes of biological functions of dipeptide transporter (PepT1) and hormonal regulation in severe scald rats

AIM: To determine the regulatory effects of recombinant human growth hormone (rhGH) on dipeptide transport (PepT1) in normal and severe scald rats.

METHODS: Male Sprague-Dawley rats with 30% total body surface area (TBSA)IIIdegree scald were employed as the model. In this study rhGH was used at the dose of 2 IU.kg^-1d^-1. An everted sleeve of intestine 4 cm long obtained from mid-jejunum was securely incubated in Kreb’s solution with radioactive dipeptide (³H-glycylsarcosine, ³H-Gly-Sar, 10 μCi/ml) at 37 °C for 15 min to measure the effects of uptake and transport of PepT1 of small intestinal epithelial cells in normal and severe scald rats.

RESULTS: Abundant blood supply to intestine and mesentery was observed in normal and scald rats administered rhGH, while less supply of blood to intestine and mesentery was observed in rats without rhGH. Compared with controls, the transport of dipeptide in normal rats with injection of rhGH was not significantly increased (P = 0.1926), while the uptake was significantly increased (P = 0.0253). The effects of transport and uptake of PepT1 in scald rats with injection of rhGH were significantly increased (P = 0.0082, 0.0391).

CONCLUSION: Blood supply to intestine and mesentery of rats was increased following injection of rhGH. The effects of uptake and transport of dipeptide transporters in small intestinal epithelial cells of rats with severe scald were markedly up-regulated by rhGH.

Hormonal regulation of dipeptide transporter (PepT1) in Caco-2 cells with normal and anoxia/reoxygenation management

AIM: To determine the regulation effects of recombinant human growth hormone (rhGH) on dipeptide transporter (PepT1) in Caco-2 cells with normal culture and anoxia/reoxygenation injury.

METHODS: A human intestinal cell monolayer (Caco-2) was used as the in vitro model of human small intestine and cephalexin as the model substrate for dipeptide transporter (PepT1). Caco-2 cells grown on Transwell membrane filters were preincubated in the presence of rhGH in the culture medium for 4 d, serum was withdrawn from monolayers for 24 h before each experiment. The transport experiments of cephalexin across apical membromes were then conducted; Caco-2 cells grown on multiple well dishes (24 pore) with normal culture or anoxia/reoxygenation injury were preincubated with rhGH as above and uptake of cephalexin was then measured.

RESULTS: The transport and uptake of cephelaxin across apical membranes of Caco-2 cells after preincubation with rhGH were significantly increased compared with controls (P = 0.045, 0.0223). Also, addition of rhGH at physiological concentration (34 nM) to incubation medium greatly stimulates cephalexin uptake by anoxia/reoxygenation injuried Caco-2 cells (P = 0.0116), while the biological functions of PepT1 in injured Caco-2 cells without rhGH were markedly downregulated. Northern blot analysis showed that the level of PepT1 mRNA of rhGH-treated injured Caco-2 cells was greatly increased compared to controls.

CONCLUSION: The present results of rhGH stimulating the uptake and transport of cephalexin indicated that rhGH greatly upregulates the physiological effects of dipeptide transporters of Caco-2 cells. The alteration in the gene expression may be a mechanism of regulation of PepT1. In addition, Caco-2 cells take up cephalexin by the Proton-dependent dipeptide transporters that closely resembles the transporters present in the intestine. Caco-2 cells represent an ideal cellular model for future studies of the dipeptide transporter.

Dangers of growth hormone therapy in critically ill patients

Prolonged length of stay is the major challenge for modern intensive care because of the associated morbidity and the impact on resource utilization. Severe trauma or infection is associated with a catabolic response, which is characterized by increased protein turnover and negative nitrogen balance. Severe catabolism leads to end-organ dysfunction and muscular weakness, prolonging the need for mechanical ventilation. Catabolism cannot be prevented with standard parenteral or enteral nutritional formulas. In order to prevent the complications of catabolism in intensive care patients, recombinant growth hormone has been applied as an experimental therapy for two decades in patients requiring parenteral nutrition and in patients with respiratory failure. Administration of recombinant growth hormone has resulted in positive nitrogen balance, and studies in mechanically ventilated patients suggest that it may shorten the need for ventilatory support. In contrast to the results of these relatively small studies, a recent multinational randomized controlled trial revealed that the administration of recombinant growth hormone (with doses 10-20 times higher than used for replacement therapy) increases mortality of critically ill patients. The excessive mortality in patients treated with recombinant growth hormone was related to infections and development of multiple organ failure, leading to the conclusion that administration of high doses of recombinant growth hormone cannot be recommended for critically ill patients. This review reinforces that conclusion.

Management of catabolism in metabolically stressed patients: a literature survey about growth hormone application

In the effort to improve the long-term outcome in critically ill patients, the utilization of anabolic agents, such as human recombinant growth hormone, has been proposed in order to reduce catabolism and improve nutritional status. A recent multicentre study regarding the use of human recombinant growth hormone in intensive care unit patients showed an unexpected increase in the mortality rate in human recombinant growth hormone-treated patients. This finding is in contrast with previous literature data reporting either no differences or an even lower mortality rate with the administration of human recombinant growth hormone. This review evaluates the possible reasons for this dramatic difference in outcomes between the multicentre study and the existing literature. Articles dealing with human recombinant growth hormone administration either in intensive care unit patients (n=26) or in postoperative patients (n=16) have been reviewed. Our analysis suggests that the low caloric intake given to patients enrolled in the multicentre study might have been inadequate to compensate for the hypermetabolism of these patients, and could not support the prolonged and delayed administration of high doses of human recombinant growth hormone. Whether the beneficial metabolic effects of human recombinant growth hormone translate into better clinical outcomes deserves further investigation. In addition, the careful selection of patients to be treated, and close monitoring of both the adequacy of caloric support and modality of human recombinant growth hormone administration would favour the safety of human recombinant growth hormone utilization in critical care settings.

Growth hormone together with glutamine-containing total parenteral nutrition maintains muscle glutamine levels and results in a less negative nitrogen balance after surgical trauma

BACKGROUND

Muscle protein catabolism, reflected by a decrease in glutamine (GLN), a decrease in muscle protein synthesis, and a negative nitrogen balance can be reduced by either administration of GLN or growth hormone (GH). In this study, the effects of a combination of GH and GLH were studied.

METHODS

Patients (n = 16) undergoing abdominal operation were given total parenteral nutrition (TPN) containing either GLN alone or GLN together with GH (GH/GLN) during 3 postoperative days. The amino acid concentration and protein synthesis in muscle tissue and the nitrogen balance were measured.

RESULTS

GH/GLN reduced nitrogen losses compared with GLN alone (-5.8 +/- 1.4 g nitrogen versus -10.6 +/- 1.1 g nitrogen, P <.05). GH/GLN maintained muscle GLN at preoperative levels compared with a 47.5% +/- 6.3% decline in the GLN group. A similar decrease was seen in the fractional synthesis rate of muscle protein postoperatively in both groups.

CONCLUSIONS

GH has an additive effect given together with GLN on muscle amino acid metabolism, preventing the decrease in the GLN concentration in skeletal muscle and diminishing the loss of whole body nitrogen. However, the improvements in muscle amino acid concentrations and nitrogen loss were not associated with differences between the groups in muscle protein synthesis postoperatively.

Stimulation of human albumin synthesis and gene expression by growth hormone treatment

BACKGROUND AND AIMS

In this study the effects of acute (5 h) and short-term (5 days) GH treatment on albumin synthesis rates in man were investigated and related to changes in the availability of hepatic albumin mRNA.

METHODS

30 patients undergoing elective laparoscopic cholecystectomy were randomized into controls (n=10) or GH-treatment (12 U/dose) for 5 h or 5 days (n=10 in each group). Albumin mRNA levels (in liver biopsy specimens) were measured employing a quantitative polymerase chain reaction assay developed specifically for this purpose, whereas albumin synthesis was measured using [(2)H(5)]phenylalanine.

RESULTS

The fractional synthesis rate of albumin was 6.0+/-0.9 %/day in the control group and 8.0+/-1.8 %/day and 8.3+/-1.7 %/day in the GH-treated groups, respectively (P<0.05 vs controls in both cases). The corresponding values for the concentration of albumin mRNA were 2.6+/-1.1 ng/microg total RNA, 2.9+/-0.8 ng/microg total RNA (NS) and 4.7+/-1.8 ng/microg total RNA in the "GH 5" group (P<0.01 vs controls). The changes in albumin synthesis were only partly explained by the differences in hepatic albumin mRNA levels (r=0.5, P<0.01).

CONCLUSION

These results suggest that GH may induce a quick, gene expression-independent increase in albumin synthesis, which is sustained by a later-occurring increase in albumin gene expression.

Regulation of protein and energy metabolism by the somatotropic axis

The somatotropic axis plays a key role in the co-ordination of protein and energy metabolism during postnatal growth. This review discusses the complexity of the regulation of protein and energy metabolism by the somatotropic axis using three main examples: reduced nutrition, growth hormone (GH) treatment and insulin-like growth factor-1 (IGF-1) treatment. Decreased nutrition leads to elevated GH secretion, but it reduces hepatic GH receptor (GHR) number and plasma levels of IGF-1; it also changes the relative concentrations of IGF binding proteins (IGFBPs) in plasma. GH treatment improves the partitioning of nutrients by increasing protein synthesis and decreasing protein degradation and by modifying carbohydrate and lipid metabolism. However, these well-established metabolic responses to GH can change markedly in conditions of reduced nutritional supply or metabolic stress. Short-term infusion of IGF-1 in lambs reduces protein breakdown and increases protein synthesis. However, long-term IGF-1 administration in yearling sheep does not alter body weight gain or carcass composition. The lack of effect of IGF-1 treatment can be explained by activation of feedback mechanisms within the somatotropic axis, which lead to a reduction in GH secretion and hepatic GHR levels. The somatotropic axis has multiple levels of hormone action, with complex feedback and control mechanisms, from gene expression to regulation of mature peptide action. Given that GH has a much wider range of biologic functions than previously recognized, advances in research of the somatotropic axis will improve our understanding of the normal growth process and metabolic disorders.

Recombinant human growth hormone for reconditioning of respiratory muscle after lung volume reduction surgery

OBJECTIVE

To investigate the effects of recombinant human growth hormone (rHGH) as a "rescue treatment" in an end-stage chronic obstructive pulmonary disease patient after prolonged weaning failure.

DESIGN

Descriptive case report.

SETTING

Fifteen-bed intensive care unit in a university hospital.

PATIENT

A 62-year-old man with end-stage chronic obstructive pulmonary disease and pulmonary emphysema after lung reduction surgery and prolonged weaning failure after long-term mechanical ventilation.

INTERVENTIONS

After 42 days of unsuccessful weaning from the respirator, rHGH (27 IU/day, 0.3 IU/kg body weight/day) was administered for 20 days through a subcutaneous injection in addition to standard intensive care.

MEASUREMENTS AND MAIN RESULTS

In addition to daily routine laboratory studies, the visceral proteins prealbumin, retinol-binding protein, and transferrin, and nitrogen balance were measured twice a week, as were the thyroid hormones triiodothyronine, thyroxine, and thyroid-stimulating hormone, plasma insulin levels, and the insulin-like growth factor (IGF)-1 binding proteins IGF-BP1 and IGF-BP3. IGF-1 was measured from day 1 to day 4 of rHGH administration. Nutritional support was guided by indirect calorimetry. Additionally, weaning variables such as peak expiratory flow rate and expiratory tidal volume were measured noninvasively. T-piece weaning trials were carried out daily until respiratory muscle fatigue occurred. IGF-1 increased in response to rHGH stimulation, from 103 to 230 microg/mL, within 4 days. The carrier protein IGF-BP3 increased from 126 to 283 mg/L at the end of the study period, and the inhibiting IGF-BP1 decreased initially from 19 to 14 mg/L and then increased until the end of the study to 31 mg/L. Nitrogen balance increased initially from 4.6 to 13.6 g/24 hrs and thereafter decreased until the end of rHGH treatment to 8.3 g/24 hrs. Resting energy expenditure increased from 1800 to 2300 kcal/24 hrs. Peak expiratory flow rate increased from 0.69 to 0.88 L/sec. The expiratory tidal volume showed a slight increase during the study period during the daily decrease of pressure support on the ventilator setting. Respiratory muscular strength increased beginning 10 days after rHGH therapy was started. From this point, T-piece weaning trials could be prolonged almost daily. The patient was extubated successfully on postoperative day 75.

CONCLUSIONS

This case report shows that after a prolonged catabolic state and long-term mechanical ventilation, administration of rHGH not only enhances the response of protein metabolism but improves respiratory muscular strength. Therefore, it may reduce the duration of mechanical ventilation in selected patients.

Parenteral amino acid intake alters the anabolic actions of insulin-like growth factor I in rats

The anabolic properties of insulin-like growth factor (IGF) I are attenuated by oral diets that are low in protein. However, it is not known whether parenteral nutrition (PN) providing a low amino acid (AA) input will influence IGF-I action. With the use of a rat model, this study examined the interaction between AA input (1.27 and 0.62 g N. kg body wt(-1). 24 h(-1), AA and 1/2AA groups, respectively) and recombinant human IGF-I (rhIGF-I, 2.5 mg. kg body wt(-1). 24 h(-1)) infusion on the composition of the carcass and organs and on plasma insulin, IGF-I, IGF-binding protein 1 (IGFBP-1), and acid-labile subunit (ALS) concentrations. Carcass protein deposition only occurred in the AA groups (P < 0.003) and was not influenced by administration of rhIGF-I. However, visceral protein loss persisted in the AA group but was prevented by rhIGF-I infusion. The changes in water content of the carcass and the organs were generally in the expected proportion of normal lean tissue. The accumulation of lipid that follows the infusion of the AA-deficient PN was prevented by rhIGF-I infusion, which may indicate an improved energy utilization. Neither serum insulin nor ALS concentrations were influenced by the level of AA infusion but were reduced by rhIGF-I administration. However, plasma IGF-I levels were elevated by higher AA infusion and by IGF-I administration. Also, IGFBP-1 concentrations were reduced by the higher AA infusion and increased with rhIGF-I administration. Interestingly, there was a significant interaction effect between both of these influences. It is concluded that free IGF-I concentration, which may be regulated by IGFBP-1 through a direct effect of AAs on the liver, may have an important role in regulating anabolism in visceral and possibly skeletal tissue during PN.

The stressful condition as a nutritionally dependent adaptive dichotomy

The injured body manifests a cascade of cytokine-induced metabolic events aimed at developing defense mechanisms and tissue repair. Rising concentrations of counterregulatory hormones work in concert with cytokines to generate overall insulin and insulin-like growth factor 1 (IGF-1), postreceptor resistance and energy requirements grounded on lipid dependency. Salient features are self-sustained hypercortisolemia persisting as long as cytokines are oversecreted and down-regulation of the hypothalamo-pituitary-thyroid axis stabilized at low basal levels. Inhibition of thyroxine 5'-deiodinating activity (5'-DA) accounts for the depressed T3 values associated with the sparing of both N and energy-consuming processes. Both the liver and damaged territories adapt to stressful signals along up-regulated pathways disconnected from the central and peripheral control systems. Cytokines stimulate liver 5'-DA and suppress the synthesis of transthyretin (TTR), causing the drop of retinol-binding protein (RBP) and the leakage of increased amounts of T4 and retinol in free form. TTR and RBP thus work as prohormonal reservoirs of precursor molecules which need to be converted into bioactive derivatives (T3 and retinoic acids) to reach transcriptional efficiency. The converting steps (5'-DA and cellular retinol-binding protein-I) are activated by T4 and retinol, themselves operating as limiting factors of positive feedback loops. Healthy adults with normal macrophage functioning and liver parenchymal integrity, who submitted to a stress of medium severity, are characterized by TTR-RBP plasma levels reduced by half and an estimated ten-fold increase in free ligand disposal to target cells during the days ensuing injury. This transient hyperthyroid and hyperretinoid climate creates a second defense line strengthening and fine-tuning the effects primarily initiated by cytokines. The suicidal behavior of thyroxine-binding globulin (TBG), corticosteroid-binding globulin (CBG), and IGFBP-3 allows the occurrence of peak endocrine and mitogenic influences at the site of inflammation. The production rate of TTR by the liver is the main determinant of both the hepatic release and blood transport of holoRBP, which explains why poor nutritional status concomitantly impairs thyroid- and retinoid-dependent acute-phase responses, hindering the stressed body to appropriately face the survival crisis. The prognostic significance of low TT4 blood levels may be assigned to the exhaustion of extrathyroidal hormonal pools normally stored in liver and plasma but markedly shrunken in protein-depleted states. These data offer new insights into the mechanisms whereby preexisting malnutrition and stressful complications are interrelated, emphasizing the pivotal role played by TTR in that context.

GH insensitivity induced by endotoxin injection is associated with decreased liver GH receptors

Sepsis induces a state of growth hormone (GH) resistance associated with a decrease of circulating insulin-like growth factor (IGF) I, a GH-dependent anabolic hormone mainly produced by the liver. To address the mechanisms that might trigger GH insensitivity in sepsis, we investigated the regulation of liver GH receptor (GHR) and its gene expression by endotoxin. Endotoxin injection in rats decreased serum IGF-I and liver GH-binding sites after 10 h. In contrast to liver GHR, circulating GH-binding protein (GHBP) levels were not significantly reduced after endotoxin injection. The parallel decrease in IGF-I and GHR and in their corresponding liver mRNAs suggests that decreased serum IGF-I and liver GHR were likely to result from decreased liver synthesis. Although GH administration in control animals significantly enhanced serum IGF-I, it did fail to prevent the decline in serum IGF-I and liver GH-binding sites in endotoxemic rats. In this study, we showed that endotoxin injection induces a state of GH insensitivity associated with decreased liver GHR. This decline in GHR, which cannot be prevented by exogenous GH, might contribute to the GH insensitivity observed in sepsis.

Thirty-day monitoring of insulin-like growth factors and their binding proteins in intensive care unit patients

This study investigates the regulation of the insulin-like growth factors (IGFs) and their regulatory proteins in 14 critically ill patients during the 30-day period following admission to an intensive care unit (ICU). Levels of IGF-I, IGF-II, IGF binding protein-3 (IGFBP-3) and acid-labile subunit (ALS) were low on admission, and in the 8 patients whose serum IGF-I levels failed to increase over 30 days, levels of the other proteins also remained low, while IGFBP-3 proteolytic activity increased. Of these proteins, ALS correlated best with serum levels of nutritional indicators, particularly prealbumin. IGFBP-2 and IGFBP-6 levels tended to be high in critically ill patients, but showed little change over the 30-day period. In contrast, IGFBP-1 levels were high on admission, correlated with early changes in nitrogen balance, and fell rapidly during the first week. By demonstrating that the IGF-I response in ICU patients is related to changes in the IGF regulatory proteins, this study may be of value in planning therapeutic intervention using growth hormone or IGF-I.

Growth hormone and insulinlike growth factor 1 promote intestinal uptake and hepatic release of glutamine in sepsis

OBJECTIVE

To study the effects of growth hormone (GH) and insulinlike growth factor 1 (IGF-1) on whole body and gastrointestinal (GI), hepatic, femoral, and renal glutamine (GLN) uptake and release in septic piglets.

SUMMARY BACKGROUND DATA

The GI metabolism of GLN is impaired during sepsis, and this may contribute to a breakdown of the gut's mucosal barrier. GH treatment has produced increased GI GLN uptake in surgical stress. Little is known about the effects of GH and IGF-1 in sepsis.

METHODS

Twenty-four piglets were randomized to three groups of eight each: a GH group received a bolus of 16 IU of Genotropin; an IGF-1 group received a continuous infusion of 1.3 mg/hour of IGF-1; and a control group received saline. After surgical preparation, sepsis was induced with live Escherichia coli bacteria. Using isotope technique, whole body turnover and organ-specific absolute uptake and release were measured before and 4 hours after sepsis.

RESULTS

After sepsis, both GH and IGF-1 treatment increased GI GLN uptake compared with controls and induced hepatic release of GLN. GLN release from skeletal muscle was diminished in all groups after sepsis. Whole body GLN turnover was increased in the GH and IGF-1 groups compared with the controls, before and after sepsis.

CONCLUSIONS

GH and IGF-1 treatment induced increased GI net uptake of GLN. GH and IGF-1 treatment also promoted absolute and net release of GLN from the liver. This release might facilitate increased GI uptake despite reduced hindleg release in the early phase of sepsis.

Nutrient pharmacotherapy for gut mucosal diseases

The use of nutrients for pharmacotherapy is a recent advance in the treatment of gastrointestinal disorders or alterations of gut function and structure. Nutrients may have a direct effect on the gut, or may enhance the response to medications. Alternatively, pharmacologic agents may improve the absorption of nutrients. Potentially, pharmacotherapy may be an adjunct to the traditional approach used in the treatment of compromised patients.

Anabolic agents in trauma and sepsis: repleting body mass and function

Both growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are potent anabolic agents. Exogenous GH improves nitrogen metabolism in patients undergoing surgery; however, the anabolic effects of GH in cases of multiple injury, burn, and sepsis are equivocal. Moreover, few data are available concerning the effects of GH in organ failures. Exogenous IGF-1 attenuates catabolism in animal trauma models. A clinical trial, however, did not confirm the anabolic actions of IGF-1. Further knowledge of the interaction between the GH/IGF-1 axis in critical illness is essential for GH and IGF-1 therapy. Theoretically, the improved nitrogen metabolism achieved with exogenous anabolic agents may provide functional benefits. However, only a few studies have confirmed the beneficial effects of GH on body function in trauma and sepsis. GH treatment decreases the postoperative depression of hand grip strength. GH also stimulates wound healing. Both GH and IGF-1 exert their effects on immune system, suggesting that these anabolic agents are potentially beneficial for the prevention and treatment of sepsis. On the contrary, inhibition of polymorphonuclear neutrophil apoptosis and the potentiation of PMNs by GH may have harmful effects on the systemic responses. Further studies are required to determine the safety and clinical benefits of GH administration in critical illness.

Systemic and splanchnic metabolic response to exogenous human growth hormone

BACKGROUND

Evidence exists indicating that growth hormone (GH) resistance in some disease states such as hypercatabolic conditions may limit the metabolic benefit associated with recombinant human growth hormone (rhGH) administration. It was the purpose of this study to compare the systemic and splanchnic effects of rhGH in patients with sepsis exhibiting systemic inflammatory response syndrome (SIRS) with the response observed in normal volunteers. Because insulin-like growth factor I (IGF-I) is believed to be the dominant factor responsible for the anabolic effects of rhGH, particular attention was given to this secondary effector.

METHODS

The systemic and splanchnic effects of rhGH (0.15 mg/kg/day) were studied in normal volunteers (n = 5), critically ill patients with sepsis exhibiting SIRS (n = 6), and patients with sepsis exhibiting SIRS while receiving total parenteral nutrition (n = 6). Basal and end study IGF-I, urinary urea excretion, hepatic blood flow, hepatic venous oxygen content, and splanchnic oxygen exchange were measured after a 48-hour course of rhGH.

RESULTS

Fasting basal IGF-I concentrations were reduced by 75% to 83% in patients with sepsis/SIRS relative to normal control subjects. After 48 hours of rhGH, peak IGF-I concentrations were 74% and 76% lower in patients in the Sepsis/SIRS and Sepsis/SIRS + Nutrition groups, respectively, compared with normal control subjects. Despite the attenuated IGF-I rise in patients, urea excretion declined by a similar magnitude in all three groups. Hepatic blood flow remained unaffected, but rhGH administration increased splanchnic oxygen consumption in all groups (control, +57%*; Sepsis/SIRS, +13%; Sepsis/SIRS + Nutr +42%*; *p < 0.05 relative to corresponding basal) resulting in a decline of basal to end therapy hepatic venous oxygen saturation (control, 67 +/- 4% to 62 +/- 11%; Sepsis/SIRS, 51% +/- 14% to 43% +/- 14%*; Sepsis/SIRS + Nutr, 62% +/- 11% to 55% +/- 16%; *p < 0.05 relative to corresponding control value), suggesting that rhGH may induce centrilobular hepatic hypoxia, which may contribute to the diminished IGF-I response.

CONCLUSIONS

Although critically ill patients exhibit an IGF-I increase in response to exogenous rhGH, the rise is markedly attenuated compared with healthy volunteers, indicating the presence of GH resistance. Unexpectedly, the changes in the anabolic hormone IGF-I did not appear to be related to the reduction in urea excretion. This may provide some additional evidence for IGF-I resistance. Finally, rhGH is associated with an augmented splanchnic oxygen consumption but no corresponding increase in regional blood flow. As a result, regional tissue hypoxia may arise and contribute to the impaired or suboptimal IGF-I response pattern.

Intravenous insulin-like growth factor-I (IGF-I) in moderate-to-severe head injury: a Phase II safety and efficacy trial

The purpose of this study was to determine the effect of insulin-like growth factor-I (IGF-I) on the catabolic state and clinical outcome of head-injured patients. Thirty-three patients between the ages of 18 and 59 years with isolated traumatic head injury and Glasgow Coma Scale (GCS) scores of 4 to 10 were randomized to one of two groups. All patients received standard neurosurgical intensive care plus aggressive nutritional support; the patients in the treatment group also received intravenous therapy with continuous IGF-I (0.01 mg/kg/hour).

During the 14-day dosing period, the control patients lost weight, whereas treated patients gained weight despite a significantly higher measured energy expenditure and lower caloric intake (p = 0.02). Daily glucose concentrations and nitrogen outputs were greater in control patients (p = 0.03) throughout the study period. During Week 1, only treated patients achieved positive nitrogen balance. Fifteen of 17 treated and 13 of 16 control patients survived the 1st week. No deaths occurred in patients whose serum IGF-I concentrations were higher than 350 ng/ml. Dichotomized Glasgow Outcome Scale scores for patients with baseline GCS scores of 5 to 7 improved from poor to good for eight of 12 treated patients but for only three of 11 control patients (p = 0.06). Eight of 11 treated patients with serum IGF-I concentrations that were at least 350 ng/ml achieved moderate-to-good outcome scores at 6 months, compared to only one of five patients with lower concentrations (p < 0.05). These findings indicate that pharmacological concentrations of IGF-I may improve clinical outcome and nitrogen utilization in patients with moderate-to-severe head injury.

Intravenous insulin-like growth factor-I (IGF-I) in moderate-to-severe head injury: a phase II safety and efficacy trial

The purpose of this study was to determine the effect of insulin-like growth factor-I (IGF-I) on the catabolic state and clinical outcome of head-injured patients. Thirty-three patients between the ages of 18 and 59 years with isolated traumatic head injury and Glasgow Coma Scale (GCS) scores of 4 to 10 were randomized to one of two groups. All patients received standard neurosurgical intensive care plus aggressive nutritional support; the patients in the treatment group also received intravenous therapy with continuous IGF-I (0.01 mg/kg/hour). During the 14-day dosing period, the control patients lost weight, whereas treated patients gained weight despite a significantly higher measured energy expenditure and lower caloric intake (p = 0.02). Daily glucose concentrations and nitrogen outputs were greater in control patients (p = 0.03) throughout the study period. During Week 1, only treated patients achieved positive nitrogen balance. Fifteen of 17 treated and 13 of 16 control patients survived the 1st week. No deaths occurred in patients whose serum IGF-I concentrations were higher than 350 ng/ml. Dichotomized Glasgow Outcome Scale scores for patients with baseline GCS scores of 5 to 7 improved from poor to good for eight of 12 treated patients but for only three of 11 control patients (p = 0.06). Eight of 11 treated patients with serum IGF-I concentrations that were at least 350 ng/ml achieved moderate-to-good outcome scores at 6 months, compared to only one of five patients with lower concentrations (p < 0.05). These findings indicate that pharmacological concentrations of IGF-I may improve clinical outcome and nitrogen utilization in patients with moderate-to-severe head injury.

Inhibition by interleukin-1 beta and tumor necrosis factor-alpha of the insulin-like growth factor I messenger ribonucleic acid response to growth hormone in rat hepatocyte primary culture

The cytokines are the putative mediators of the catabolic reaction that accompanies infection and trauma. Evidence suggests that their catabolic actions are indirect and potentially mediated through changes in hormonal axis such as the hypothalamo-pituitary-adrenal axis. Insulin-like growth factor I (IGF-I) is a GH-dependent growth factor that regulates the protein metabolism. To determine whether cytokines can directly inhibit the production of IGF-I by the liver, we investigated the regulation of IGF-I gene expression by interleukin (IL)-1 beta, IL-6, and tumor necrosis factor (TNF)-alpha (10 ng/ml) in a model of rat primary cultured hepatocytes. Hepatocytes were isolated by liver collagenase perfusion and cultured on Matrigel 48 h before experiments. Each experiment was performed in at least three different animals. In the absence of GH, IL-1 beta and TNF-alpha did not affect the IGF-I messenger RNA (mRNA) basal levels, whereas IL-6 increased it by a factor of 2.5 after 24 h (P < 0.05). GH (500 ng/ml) alone stimulated the IGF-I gene expression markedly (5-to 10-fold increase) after 24 h (P < 0.001). IL-1 beta, and TNF-alpha to a lesser extent, dramatically inhibited the IGF-I mRNA response to GH (IL-1 beta: -82%, P < 0.001 and TNF-alpha: -47%, P < 0.01). The half-maximal inhibition of the IGF-I mRNA response to GH was observed for a concentration of IL-1 beta between 0.1 and 1 ng/ml. Moreover, IL-1 beta abolished the IL-6-induced IGF-I mRNA response. In contrast, IL-6 did not impair the IGF-I mRNA response to GH. To determine the potential role of the GH receptor (GHR) and the GH-binding protein (GHBP) in this GH resistance, we assessed the GHR and GHBP mRNAs response to these cytokines. GH alone did not affect the GHR/GHBP mRNA levels. IL-1 beta markedly decreased the GHR and GHBP mRNA levels (respectively, -68% and -60%, P < 0.05). Neither TNF-alpha nor IL-6 affected the GHR/GHBP gene expression. In conclusion, our results show that IL-1 beta, and TNF-alpha to a lesser extent, blunt the IGF-I mRNA response to GH. The resistance to GH induced by IL-1 beta might be mediated by a decrease of GH receptors, as suggested by the marked reduction of GHR mRNA. These findings suggest that decreased circulating IGF-I, in response to infection and trauma, may be caused by a direct effect of cytokines at the hepatocyte level.

Serum insulin-like growth factor binding protein-3 responds differently to trauma in men and women

OBJECTIVES

Insulin-like growth factor-1 (IGF-1) has been studied as a marker of nutrition in critical illness, but there is little research on IGF-binding protein-3, which regulates the bioactivity of IGF-1. The objectives of the present study were to measure serum IGF-binding protein-3 concentrations in trauma patients and to determine whether factors such as age, gender, and severity of injury should be considered when evaluating serum IGF-binding protein-3 concentrations as a marker of nutritional or clinical status.

DESIGN

Prospective, randomized, descriptive study.

SETTING

Emergency room of a university hospital.

PATIENTS

One hundred eight trauma patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In this diverse group of patients, Injury Severity Score ranged from 1 to 45 (11.5 +/- 10.3 [SD]), age ranged from 18 to 77 yrs (35 +/- 15.3), and 68% were male. A venous blood sample was collected at the time of admission into the study and was analyzed for serum IGF-binding protein-3 concentration (by radioimmunoassay), serum osmolality, IGF-1 concentration, and C-reactive protein concentration. Relationships between variables were tested using Pearson's correlation coefficients and multiple regression analysis. Age, Injury Severity Score, serum osmolality, time since injury, and gender were not significant predictors of serum IGF-binding protein-3 concentrations when all patients were analyzed together. However, when men and women were analyzed separately, notable gender differences were observed. In women, serum IGF-binding protein-3 concentrations were increased with increasing severity of injury (beta = 0.52, R2 = .33, p < .01). In men, the opposite relationship was observed (beta = -0.29, R2 = .17, p < .01). Other predictors in the model (age, serum osmolality, and time since injury) were not significant. Variability in IGF-binding protein-3 concentration could not be explained by differences in body mass index or acute-phase response (serum C-reactive protein). Serum IGF-1 concentrations changed coordinately with IGF-binding protein-3 concentrations in females and males (r = .62, p < .001 and r = .54, p < .001, respectively). IGF-binding protein-3 concentration at the time of admission into the study could not predict mortality, but this value was correlated with length of hospitalization in women (r = .37, p < .05).

CONCLUSIONS

Determination of the specificity and sensitivity of IGF-binding protein-3 as an index of nutrition or anabolism requires knowledge of its relationship to nonnutritional factors. These factors are most discernible before the confounding effects of treatments, absence of feeding, and complications. The present study demonstrated that gender and severity of injury must be considered when interpreting serum IGF-binding protein-3 concentrations in trauma patients. In a much wider context, the present findings suggest that the study of the metabolic response to stress requires separate analyses, based on gender.

Insulin-like growth factor bioactivity and its modification in growth hormone resistant states

Acquired growth hormone (GH) resistance is an increasingly recognized feature of catabolic states. Low circulating levels of the insulin-like growth factors (IGF-I and II) have been shown to be associated with changes in the IGF binding proteins (IGFBP-1 to -6) that may significantly impact on IGF bioactivity. IGFBP-3 binds IGF and a third glycoprotein, the acid labile subunit (ALS), to form a stable 150 kDa ternary complex that serves as an intravascular store for IGFs and prolongs IGF half-life. IGFBP-1 is present at much lower concentration in serum but levels fluctuate acutely, suggesting regulation of IGF bioactivity in response to short-term metabolic changes. The function of IGFBP-2 remains unclear, but studies suggest that this protein may act as an alternative carrier for IGF when IGFBP-3 levels are low. Multiple regulatory influences on circulating IGFBP levels have been identified but three appear prominent. Nutritional influences, in particular substrate availability, appear to be a central regulatory influence on IGFBP levels in catabolic states. Low substrate availability increases IGFBP-1 levels acutely and decreases IGFBP-3 and IGFBP-2 levels in the intermediate term, with each of these changes likely to further limit IGF bioactivity. End organ failure, particularly of liver and kidney significantly affects production and clearance rates of the circulating IGFBPs and may contribute to the catabolism frequently seen in these states. Severe protein catabolism often accompanies malignancy and chronic sepsis and it is likely that additional ill-defined factors influence IGF bioactivity in this setting. Recent studies have identified post-translational modifications to the IGFBPs such as proteolysis and phosphorylation, which appear to further impact on IGF bioactivity. The relative contributions of these changes to the overall impairment of IGF bioactivity in GH-resistant states remains to be fully elucidated.