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

Anabolic and anticatabolic agents used in burn care: What is known and what is yet to be learned

Major thermal injury induces profound metabolic derangements secondary to an inflammatory "stress-induced" hormonal environment. Several pharmacological interventions have been tested in an effort to halt the hypermetabolic response to severe burns. Insulin, insulin growth factor 1, insulin growth factor binding protein 3, metformin, human growth hormone, thyroid hormones, testosterone, oxandrolone, and propranolol, among others, have been proposed to have anabolic or anticatabolic effects. The aim of this broad analysis of pharmacological interventions was to raise awareness of treatment options and to help establishing directions for future clinical research efforts. A PubMed search was conducted on the anabolic and anticatabolic agents used in burn care. One hundred and thirty-five human studies published between 1999 and 2017 were included in this review. The pharmacological properties, rationale for the treatments, efficacy considerations and side effect profiles are summarized in the article. Many of the drugs tested for investigational purposes in the severely thermally injured are not yet gold-standard therapies in spite of their potential benefit. Propranolol and oxandrolone have shown great promise but further evidence is still needed to clarify their potential use for anabolic and anticatabolic purposes.

[Evolutionary endocrinology: a pending matter]

Twenty years have passed since the foundational article of what is now known as evolutionary medicine (EM) was published. This young medical discipline examines, following Darwinian principles, susceptibility to certain diseases and how we react to them. In short, EM analyzes the final cause of the disease from a historical perspective. Over the years, EM has been introduced in various medical areas in very different ways. While it has found a role in some fields such as infectious diseases and oncology, its contribution in other areas has been quite limited. In endocrinology, EM has only gained prominence as a basis for the so-called "diseases of civilization", including diabetes mellitus and obesity. However, many experts suggest that it may have a much higher potential. The aim of this paper is to provide a view about what evolutionary medicine is. Some examples of how EM may contribute to progress of our specialty are also given. There is no doubt that evolution enriches medicine, but medicine also offers knowledge to evolution.

Changes within the growth hormone/insulin-like growth factor I/IGF binding protein axis during critical illness

Interest in the somatotropic axis,with its complex network of interactions, during critical illness arose only a few decades ago. Te distinguishing neuroendocrine features of prolonged critical illness were not differentiated from those during the acute phase until the early 1990s. This incomplete understanding of the somatotropic axis contributed to some disastrous results, such as the multicenter growth hormone trial. The goal of stimulating the somatotropic axis without a proper preceding neuroendocrine diagnosis should be held obsolete. Moreover, the fascinating link between regulators of carbohydrate metabolism, such as insulin and insulin-like growth factor I, and the somatotropic axis may lead to future therapeutic possibilities.

Pharmacological approaches to ameliorating catabolic conditions

PURPOSE OF REVIEW

Nutritional debilitation is among the most devastating and life-threatening aspect of various diseases. It arises from a complex interaction between the illness and the host. This process includes cytokine production, release of lipid-mobilizing and proteolysis-inducing factors, and alterations in intermediary metabolism. As a result, many patients develop cachexia with progressive body fat and muscle tissue wasting with associated worsening of their clinical status and a lower quality of life. In this review, up-to-date information about different approaches to pharmacologic management of cachexia will be addressed.

RECENT FINDINGS

Until recently, the two major options for pharmacological therapy were either progestational agents or corticosteroids. Knowledge of the mechanisms of cachexia, however, has led to newer therapeutic interventions for treating several aspects of the syndrome. These include antiserotonergic agents, branched-chain amino acids, eicosapentaenoic acid, cannabinoids, melatonin, and thalidomide--all of which act on the feeding-regulatory circuitry to increase appetite and inhibit illness-derived catabolic factors.

SUMMARY

Information from this review will guide health care providers in limiting weight loss and improving performance status of cachectic patients through pharmacological therapy, with the hope that such therapy will extend patients' survival and improve their qualities of life.

Changes within the GH/IGF-I/IGFBP axis in critical illness

Interest in the somatotropic axis, with its complex network of interactions, during critical illness started only a few decades ago. The distinguished neuroendocrine features of prolonged critically ill patients were not differentiated from those during the acute phase until the 1990s. This incomplete understanding of the somatotropic axis has contributed to some disastrous results. Aiming to stimulate the somatotropic axis without a proper preceding neuroendocrine diagnosis should be held obsolete, because recent data indicate that the patient with the best anabolic parameters may not necessarily be the most favored to survive the ICU stay. Moreover, the fascinating link between regulators of carbohydrate metabolism, such as insulin and insulin-like growth factor 1, and the somatotropic axis may lead to future therapeutic possibilities.

Protective effects of recombinant human growth hormone on cirrhotic rats

AIM: To investigate the effects and molecular mechanisms of recombinant human growth hormone (rhGH) on protecting liver function and alleviating portal hypertension of liver cirrhotic rats.

METHODS: Liver cirrhosis of male Sprague-Dawley rats was induced by administration of thioacetamide. The rats with or without liver cirrhosis were randomly divided into four groups. Group A consisted of the normal rats was treated with normal saline (NS), group B consisted of the normal rats was treated with rhGH, group C consisted of cirrhotic rats was treated with NS, and group D consisted of cirrhotic rats was treated with rhGH. The rats of different groups were subcutaneously injected with 0.5 mL of NS or 333 ng/kg of rhGH daily for 7 d. After treatments, the following parameters were examined, including GH-binding capacity (R_T) by ¹²⁵I-hGH binding, growth hormone receptor mRNA(GHR mRNA) expression by RT-PCR, relative content of collagen (RCC) by histomorphomertry, and level of malon-dialdehyde (MDA) and superoxide dismutase (SOD) in liver tissue by thiobarbituric acid reaction and pyrogallic acid self-oxidation, respectively. Serum albumin (ALB), alanine transaminase (ALT) and portal vein pressure (PVP) were also examined.

RESULTS: rhGH up-regulated both the GH-binding capacity (R_T) and the expression of GHR mRNA in vivo. R_T in group A (72 ± 12 fmol/mg protein) was significantly higher than that in group C (31 ± 4 fmol/mg protein) (P < 0.05). R_T in group B (80 ± 9 fmol/mg protein) increased markedly compared to group A (P < 0.05). R_T in group D (40 ± 7 fmol/mg protein) raised remarkably compared with group C (P < 0.05), but less than that in group A, and there was no significant GH binding affinity contrast (Kd) change. The GHR mRNA level (iOD, pixel) in group A (29 ± 3) was significantly higher than that in group C (23 ± 3) (P < 0.05). GHR mRNA levels were significantly raised in group B (56 ± 4) and group D (42 ± 8) compared with groups A and C (29 ± 3 and 23 ± 3, respectively) (P < 0.05). Compared with the normal liver, MDA level was higher and SOD level was lower in cirrhotic livers. After rhGH treatment, MDA level was significantly declined to 12.0 ± 2.2 nmol/mg protein and SOD was raised to 1029 ± 76 U/mg protein in group D (P < 0.05). ALB levels in groups B and D (42 ± 7 g/L and 37 ± 7 g/L, respectively) were significantly raised compared with those in groups A and C (35 ± 5 g/L and 29 ± 4 g/L, respectively) (P < 0.05). ALT level was markedly lower in group D (69 ± 7 U/L) compared to group C (89 ± 15 U/L) (P < 0.05), and close to group A (61 ± 10 U/L). RCC in group C (22.30% ± 3.86%) was significantly higher than that in group A (1.14% ± 0.21%) and group D (14.70% ± 2.07%) (P < 0.05). In addition, rhGH markedly alleviated portal hypertension in liver cirrhotic rats (group D vs C, 9.3 ± 1.5 cmH₂O vs 14.4 ± 2.0 cmH₂O) (P < 0.05).

CONCLUSION: Pharmacological doses of rhGH can increase R_T and GHR mRNA expression, ameliorate liver functions, repress fibrosis and decline portal hypertension, suggesting it has potentially clinical usage as a hepatotropic factor.

Regulation of the somatotropic axis by intensive insulin therapy during protracted critical illness

The catabolic state of critical illness has been linked to the suppressed somatotropic GH-IGF-binding protein (IGFBP) axis. In critically ill patients it has been demonstrated that, compared with the conventional approach, which only recommended insulin therapy when blood glucose levels exceeded 12 mmol/liter, strict maintenance of blood glucose levels below 6.1 mmol/liter with intensive insulin therapy almost halved intensive care mortality, acute renal failure, critical illness polyneuropathy, and bloodstream infections. Poor blood glucose control in diabetes mellitus has also been associated with low serum IGF-I levels, which can be increased by insulin therapy. We hypothesized that intensive insulin therapy would improve the IGF-I axis, possibly contributing to the clinical correlates of anabolism. Therefore, this study of 363 patients, requiring intensive care for more than 7 d and randomly assigned to either conventional or intensive insulin therapy, examines the effects of intensive insulin therapy on the somatotropic axis. Contrary to expectation, intensive insulin therapy suppressed serum IGF-I, IGFBP-3, and acid-labile subunit concentrations. This effect was independent of survival of the critically ill patient. Concomitantly, serum GH levels were increased by intensive insulin therapy. The suppression of IGF-I in association with the increased GH levels suggests GH resistance induced by intensive insulin therapy, which was reflected by the decreased serum GH-binding protein levels. Intensive insulin therapy did not affect IGFBP-3 proteolysis, which was markedly higher in protracted critically ill patients compared with healthy controls. Also, intensive insulin therapy did not suppress the urea/creatinine ratio, a clinical correlate of catabolism. In conclusion, our data suggest that intensive insulin therapy surprisingly suppressed the somatotropic axis despite its beneficial effects on patient outcome. GH resistance accompanied this suppression of the IGF-I axis. To what extent and through which mechanisms the changes in the GH-IGF-IGFBP axis contributed to the survival benefit under intensive insulin therapy remain elusive.

Hormonal fountains of youth

Any hope of a fountain of youth to stop people from getting older is a long way off, with science just beginning to understand the complex genetic, physical, and hormonal causes of aging. Clearly, modem research has demonstrated that the concept of a hormonal fountain of youth is predominantly mythology. The best evidence supporting use of hormonal replacement is vitamin D and estrogen replacement to prevent hip fractures. Other than that, treatment should be limited to hormone replacement in persons who have endocrine disease.

Growth hormone modulation of the rat hepatic bile transporter system in endotoxin-induced cholestasis

Treatment with high dose human GH, although an effective anabolic agent, has been associated with increased incidence of sepsis, inflammation, multiple organ failure, and death in critically ill patients. We hypothesized that GH might increase mortality by exacerbating cholestasis through modulation of bile acid transporter expression. High dose GH was continuously infused over 4 d into rats, and on the final day lipopolysaccharides were injected. Hepatic bile acid transporter expression was measured by Northern analysis and immunoblotting and compared with serum markers of cholestasis and endotoxinemia. Compared with non-GH-treated controls, GH increased endotoxin-induced markers of cholestasis and liver damage as well as augmented IL-6 induction. In endotoxinemia, GH treatment significantly induced multidrug resistance-associated protein 1 mRNA and protein and suppressed organic anion transporting polypeptides, Oatp1 and Oatp4, mRNA, suggesting impaired uptake of bilirubin and bile acids at the basolateral surface of the hepatocyte, which could contribute to the observed worsening of cholestasis by GH. This study of endotoxinemia may thus provide a mechanistic link between GH treatment and exacerbation of cholestasis through modulation of basolateral bile acid transporter expression in the rat hepatocyte.

Expression of growth hormone receptor and its mRNA in hepatic cirrhosis

AIM: To investigate the expression of growth hormone receptor (GHR) and mRNA of GHR in cirrhotic livers of rats with the intension to find the basis for application of recombinant human growth hormone (rhGH) to patients with liver cirrhosis.

METHODS: Hepatic cirrhosis was induced in Sprague-Dawley rats by administration of thioacetamide intraperitoneally for 9-12 weeks. Collagenase IV was perfused in situ for isolation of hepatocytes. The expression of GHR and its mRNA in cirrhotic livers was studied with radio-ligand binding assay, RT-PCR and digital image analysis.

RESULTS: One class of specific growth hormone-binding site, GHR, was detected in hepatocytes and hepatic tissue of cirrhotic livers. The binding capacity of GHR (R_T, fmol/mg protein) in rat cirrhotic liver tissue (30.8 ± 1.9) was significantly lower than that in normal control (74.9 ± 3.9) at the time point of the ninth week after initiation of induction of cirrhosis (n = 10, P < 0.05), and it decreased gradually along with the accumulation of collagen in the process of formation and development of liver cirrhosis (P < 0.05). The number of binding sites (× 10⁴/cell) of GHR on rat cirrhotic hepatocytes (0.86 ± 0.16) was significantly lower than that (1.28 ± 0.24) in control (n = 10, P < 0.05). The binding affinity of GHR among liver tissue, hepatocytes of various groups had no significant difference (P > 0.05). The expression of GHR mRNA (riOD, pixel) in rat cirrhotic hepatic tissues (23.3 ± 3.1) was also significantly lower than that (29.3 ± 3.4) in normal control (n = 10, P < 0.05).

CONCLUSION: The growth hormone receptor was expressed in a reduced level in liver tissue of cirrhotic rats, and lesser expression of growth hormone receptors was found in a later stage of cirrhosis. The reduced expression of growth hormone receptor was partly due to its decreased expression on cirrhotic hepatocytes and the reduced expression of its mRNA in cirrhotic liver tissue.

Catabolic response to stress and potential benefits of nutrition support

The catabolic response to sepsis, severe injury, and burn is characterized by whole-body protein loss, mainly reflecting increased breakdown of muscle proteins, in particular myofibrillar proteins. Glucocorticoids and various proinflammatory cytokines are important regulators of muscle proteolysis in stressed patients. There is evidence that breakdown of proteins by the ubiquitin-proteasome pathway plays an important role in muscle cachexia, although other mechanisms may participate, such as calcium- and calpain-dependent release of myofilaments from the sarcomere. Three types of treatments have been used to reduce or prevent the catabolic response to injury and sepsis: 1). nutritional, 2). hormonal, and 3). pharmacologic. With regard to nutrition support, it is generally believed that enteral feeding is superior to parenteral feeding and that early feeding is better than late feeding. Although "immune-enhancing" enteral nutrition has been shown in several recent studies to improve outcome in critically ill patients, the specific effects of these treatments on the catabolic response in muscle are not known. In addition to nutrition support, various hormones, including insulin, growth hormone, and insulin-like growth factor-1, may blunt the catabolic response in patients with stress. Experimental studies have indicated that other treatments may become available in the future, including cytokine antibodies, calcium antagonists, and induction of heat shock response. Methods to prevent or reduce the catabolic response to stress are important considering the significant clinical consequences of muscle cachexia.

Orexigenic and anabolic agents

Anorexia and weight loss represent a major cause of morbidity and mortality. At present in the United States two effective anorectic agents are commonly used, namely, megestrol acetate and dronabinol. These two agents are compared in Table 1. In persons with a large excess cytokine production. megestrol acetate should be tried at a does of 800 mg per day for no longer than 3 months. Megestrol acetate should be administered with testosterone in men. It should be avoided in persons who are bed-bound because of the risk of deep vein thrombosis. Dronabinol should be used for most anorectic patients. Dronabinol should initially be given in a low dose (2.5 mg) in the evening. The dose should be increased to 5 mg per day if no improvement in appetite is seen after 2 to 4 weeks. Dronabinol can be continued indefinitely. It seems to have a particularly good profile for persons with anorexia who are at the end of life. In persons with depression and anorexia. mirtazapine seems to be the antidepressant of choice. In addition, the use of taste enhancers can be considered in persons who complain that the food does not taste good. The appropriate use of anabolic agents in older persons with weight loss is controversial. Certainly all older men who are losing weight should have bioavailable testosterone measured and, if the testosterone level is low, should receive testosterone replacement therapy. Women who are losing weight may benefit from the use of low-dose testosterone (eg, Estratest). Anabolic agents, such as oxandrolone, should be reserved for those who have profound cachexia. An approach to the management of anorexia and weight loss in older persons is given in Fig. 1. Thomas et al have provided a more complex algorithm the management of weight loss in nursing home residents.

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.